Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BARRIER WITH INTEGRATED SELF-COOLING SOLID STATE LIGHT SOURCES
REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application claims priority to United States Nonprovisional
Patent Application
Serial No. 14/071,636, filed November 4, 2013, and United States
Nonprovisional Patent
Application Serial No. 14/071,630, filed November 4, 2013, the entireties of
which are
incorporated herein by reference.
BACKGROUND
[0002] Installing lighting in rooms, industrial spaces, suspended ceilings,
walls, etc. has been
problematic due the weight of the light sources and the need to penetrate the
barriers creating
these enclosed illuminated spaces. Solid state light sources have offered the
promise of more
light weight lighting fixtures however that promise has not been fully
fulfilled. LEDs unlike
conventional light sources such as incandescent bulbs cannot effectively cool
themselves.
[0003] As such additional appended heatsinks or cooling means are required
to prevent
overheating. This increases the cost of not only the light sources due to
shipping costs and
materials costs but also the fixtures that use those light sources. It also
results in heavy light
source fixtures. In general, the need exists for articles and means which
allow LEDs to be used
without the need for additional heatsinking means. These appended heatsinks
due to the size
and unattractive appearance are typically hidden in the barrier or other side
of the barrier
(ceiling, wall, etc.)
[0004] It is desirable to minimize the temperature difference between the
junction or active
region of the semiconductor device and the ambient atmosphere to effectively
cool small
semiconductor devices. It is also desirable to minimize the surface area
needed to dissipate the
heat generated by the semiconductor devices to the ambient atmosphere. While
high thermal
conductivity materials can be used to spread the heat out over a very large
area, these high
thermal conductivity materials come with the addition of significant weight
and cost. In
conventional LED devices several layers of interconnect exist between the LED
die and the final
light source. This approach is used because the lighting fixture manufacturers
have historically
not been required or had the capability to wirebond, flip chip attach or even
solder components
into their fixtures. Also the need to regularly replace light sources such as
incandescent bulbs has
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led to a wide range of quick change interconnects like sockets and pin based
connector.
[0005] Lightweight self cooling solid state light sources would offer
significant benefits to
fixture manufacturers. Incandescent bulbs for instance are very lightweight
generating over 1000
lumens while weighing only 50 grams and as such can be easily held in place
using even simple
pins and sockets. For the typical LED sources, this is not the case. The added
weight of the
heatsink and the need for a low resistance thermal connection between the LED
package and the
heatsink necessitates the use of complex multiple level interconnects. The
need exists for LED
light sources which are lightweight and easily incorporated into a wide range
of lighting fixtures
without the need for additional heatsinking or cooling means.
[0006] Historically, light sources have cooled themselves as stated
earlier. In the case of
incandescent and fluorescent tubes, the glass envelope surrounding the
sources, and the filament
or arc itself transfers the excess heat generated via convection and
radiation. An incandescent
bulb glass envelope can exceed 1500 C and a halogen's quartz envelope may
exceed several
hundred degrees Celsius. Radiative power scales as the fourth power of the
temperature. A
naturally convectively cooled surface with a surface temperature of 500 C in a
250 C ambient
will transfer only about 5% of its energy to the surrounding ambient
radiatively. A naturally
convectively cooled surface with a surface temperature of 1000 C can transfer
20% of its energy
to the surrounding ambient radiatively. The typical LED junction temperature
for high powered
devices can be over 1200 C and still maintain excellent life and efficiency.
For surfaces with
temperatures less than 1200 C the majority of the radiated energy is in the
infrared with a
wavelength greater than 8 microns.
[0007] Heat generated within the LEDs and phosphor material in typical
prior art solid state
light sources is transferred via conduction means to a much larger heatsink
usually made out of
aluminum or copper. The temperature difference between the LED junction and
heatsink can be
40 to 500 C. The temperature difference between ambient and heatsink
temperature is typically
very small given the previously stated constraints on the junction
temperatures of LEDs. This
small temperature difference not only eliminates most of the radiative cooling
but also requires
that the heatsink be fairly large and heavy to provide enough surface area to
effectively cool the
LEDs. This added weight of the heatsink increases costs for shipping,
installation and poses a
safety risk for overhead applications. For example lighting in a typical
industrial or office
building will use troffers. These troffers which are typically 2 foot by 4
foot house fluorescent
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tubes and weigh as much as 30 pounds including the electronic ballasts. The
four foot
fluorescent tubes by themselves weigh 200 grams each. These troffers have to
be separately
rigged and supported independent of the suspended ceiling. They pose a safety
hazard in the
event of a severe earthquake. They also typically pose a fire hazard as the
diffusing elements
which interface to the occupant side of the room are made out of flammable
materials (e.g.
plastic). In newer installations light emitting diode (LED) based solid state
troffers are being
use to replace fluorescent troffers. These solid state troffers however still
require large and
heavy appended heatsinks to dissipate the excess heat from the LEDs. They also
use large
plastic diffusers to spread the light out over a larger surface.
[0008] Surprisingly, much like conventional incandescent, halogen and
fluorescent light
sources, conventional solid-state light source are not typically flame
resistant or even conform to
Class 1 or Class A building code requirements. There are two types of fire
hazards indirect
(where lamp/fixture is exposed to flames) and direct (where the lamp/fixture
creates the flames).
Conventional solid-state lamps and fixtures can pose both indirect and direct
fire threats because
they use large quantities of organic materials that can burn.
[0009] Even though the LED die are made using inorganic material such as
nitrides or
AlinGaP which are not flammable, these LED die are typically packaged using
organic materials
or mounted in fixtures which contain mostly organic materials. Organic LEDs or
OLEDs not
only are mostly organic but also contain toxic materials like heavy metals
like ruthenium which
can be released if burned. Smoke generated from the burning of these materials
is not only toxic
but one of the leading causes of death in fires due to smoke inhalation.
Incandescent and
fluorescent lighting fixtures typically are composed of sheet metal parts and
use glass or flame
retardant plastics designed specifically to meet building code requirements.
It is therefore
advantageous that solid state light sources be constructed of non-flammable
and non-toxic
materials especially in commercial applications like suspended ceilings. This
is for the benefit of
both for occupants and firefighters. Organic materials containing heavy metals
and nanoparticles
such as quantum dots are especially problematic.
[0010] As an example, solid-state panel lights typically comprise acrylic
or polycarbonate
waveguides which are edge lit using linear arrays of LEDs. A couple of pounds
of acrylic can be
in each fixture. Integrating these fixtures into a ceiling can actually lead
to increased fire hazard.
Other troffer designs rely on large thin organic films to act as diffusers and
reflectors as seen in
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recent LED troffer designs. During a fire these organic materials pose a
significant risk to
firefighters and occupants due to smoke and increased flame spread rates. In
many cases, the
flame retardant additives typically used to make polymers more flame retardant
that were
developed for fluorescent and incandescent applications negatively impacts the
optical properties
of waveguides and light transmitting devices. Class 1 or Class A standards
cannot be met by
these organic materials. As such a separate standard for optical transmitting
materials UL94 is
used in commercial installations. The use of large amounts of these organic
materials in
conventional solid-state light sources greatly increases the risks to
firefighters and occupants due
to their high smoke rate and tendency to flame spread when exposed to the
conditions
encountered in a burning structure. A typical commercial installation with a
suspended ceiling
contains 10% of the surface area as lighting fixtures. The ceiling tiles are
specifically designed
to act as a fire barrier between the occupants and the plenum above the
suspended ceiling. The
lighting fixtures compromise the effectiveness of this fire barrier by
providing a pathway for
flames to bypass the ceiling tiles. For this reason even incandescent and
fluorescent fixtures are
typically required to have additional fire resistant covers on the plenum side
of the ceiling.
These fire enclosures increases costs and eliminates the ability to
effectively cool the light fixture
from the plenum side of the ceiling. Given that most solid state troffers
depend on backside
cooling these fire enclosures lead to higher operating temperatures on the LED
die and actually
increase the direct fire hazard for solid state light sources. The large
amount of organics in the
solid state light fixtures can directly contribute to the flame spread once
exposed to flames either
indirectly or directly. The need therefore exists for solid state lighting
solutions which are Class
1 rated which can reduce the risks to occupants and firefighters during fires
and minimize the
direct fire hazard associated with something failing with the solid state
light bulbs.
[0011]
The recent recalls of solid-state light bulbs further illustrate the risks
based on the
solid-state light sources themselves being a direct fire hazard.
In the recalls, the drive
electronics over-heated, which then ignited the other organic materials in the
light source. The
need exists for solid state light sources which will not burn or ignite when
exposed to high heat
and even direct flames. Existing incandescent and fluorescent lighting
fixtures have over the last
several decades found that the ideal solution is to construct the majority of
the fixture using
inorganic materials and to maximize the lumens per gram of the source. A
typical incandescent
source emits greater than 30 lumens per gram and the source is self cooling
based on both
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convective cooling and radiative cooling. A conventional solid-state light
bulb emits less than 5
lumens per gram and requires heatsinking means to transfer the heat generated
by the LEDs and
drive electronics to the surrounding ambient. The heatsink surfaces must be
exposed to the
ambient. In many cases such as recessed can lights the heatsink surfaces are
enclosed which
dramatically reduces the heat that can be transferred to the ambient. The high
lumen per gram in
the incandescent and fluorescent bulbs also translates directly into less
material to burn both
indirectly and directly. Also, in solid-state light bulbs the drive
electronics and light source have
the same cooling path and therefore heat generated in the drive electronics is
added to the heat
generated by the LEDs. The added heat from the LEDs elevates the temperature
of the drive
electronics and vice versa. In the recalls this has led to catastrophic
results igniting the organic
materials used in the solid state light sources.
The coupling of the heat from the drive
electronics and the LEDs combined with the large quantity of organic materials
used creates a
direct fire hazard when components like polymer capacitors and organic coated
wiring overheat
and burn. Based on years of effort the incandescent and fluorescent sources
have moved away
from organic based materials for exactly the reasons illustrated above. The
solid state lighting
industry needs to develop high lumen per gram solid state light sources which
not only improve
efficiency but also do not represent a fire hazard either indirectly or
directly.
[0012]
Commercial light applications are also subject to seismic, acoustic, and
aesthetic
requirements. Seismic standards require that suspended ceilings withstand
earthquake conditions
and more recently these same requirements are being used to address terrorist
attacks. In
general, lighting fixtures must be separately suspended from the overhead deck
in suspended
ceiling applications because of their weight and size. The need exists for
solid state lighting
solutions which can be integrated and certified with suspended ceilings.
Regarding acoustics
the suspended ceiling dampens noise levels by forming a sound barrier in a
manner similar to the
fire barrier previously discussed. The lighting fixtures again compromise the
barrier created by
the ceiling tiles because they cannot be directly integrated into the ceiling
tiles or grid work. The
need exists for solid state lighting sources which do not degrade the acoustic
performance of the
ceilings.
Lastly, lighting is aesthetic as well as functional. Market research indicates
that
troffers while functional are not desirable from an aesthetic standpoint. The
need therefore exists
for solid state lighting sources which provide a wider range of aesthetically
pleasing designs.
[0013]
Suspended ceiling represent a large percentage of the commercial, office and
retail
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space. In this particular application 2 ft x 2 ft and 2 ft x 4 ft grids are
suspended from the ceiling
and acoustic/decorative tiles are suspended by the t shaped grid pieces.
Lighting has typically
been 2 x 2 or 2 x 4 troffers which similarly are suspended on the t shaped
grid pieces. The
troffers are wired to the AC bus lines above the suspended ceiling. Each
troffer comprises of a
sheet metal housing, driver, light sources, and reflective and diffusive
elements. In the case of
solid state troffers additional heatsinking means or cooling means may also be
incorporated into
each troffer. To comply with building codes most fixtures require additional
fire containment
housings which isolate the lighting fixture from the plenum space above the
suspended ceiling.
In general a standard troffer requires a minimum volume of 1 cubic foot for a
2 x 2 and 2 cubic
feet for a 2 x 4. The typical lumen output is 2000 lumens for a 2 x 2 troffer
and 4000 lumens for
a 2 x 4. In many instances the location of the light fixtures are put on a
regular spacing even
though uniform lighting throughout the area may not be required or desirable.
This is driven by
the difficulty and costs associated with relocating the troffers once
installed. This leads to excess
lighting with its associated energy losses. The need exists for lightweight
diffuse and directional
lighting fixtures for suspended ceilings that can be relocated easily and
upgraded or changed as
technology advances.
[0014] Recently Armstrong World Industries has introduced its 24 VDC DC
FlexZoneTM grid
system. The T-shaped grid pieces provide 24 VDC connections on both the top
and bottom of
the grid pieces. The availability of 24 VDC eliminates the need for a separate
drivers and
ballasts for solid state lighting. The elimination or simplification of the
driver allows for very
lightweight and low volume light fixtures especially for the cases where self
cooling solid state
light sources are employed. Lightweight and low volume, translate directly
into reduced raw
material usage, fixture cost, warehousing costs, and shipping costs. By
eliminating fixed metal
housings and replacing them with modular and interchangeable optical and
lighting elements that
directly attach to an electrical grid system like Armstrong's DC FlexZone
system costs can be
reduced not only for the fixture itself but also for the cost associated with
changing the lighting.
Close to 2 billion square feet of commercial and retail suspended ceiling
space is remodeled or
created each year. The need exists for more flexibility in how this space can
be reconfigured.
[0015] Present fixtures require addition support to the deck of the
building due to weight and
size constraints per seismic building codes. The need exists for field
installable and user
replaceable lighting fixtures that can be seismically certified with the grid
so that the end user
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can adjust and reposition fixtures as the need arises. Under the present
requirements, any
changes to the lighting require that the ceiling panels be removed and at a
minimum additional
support wires must be installed to the building deck before the fixture can be
repositioned. This
may also require a reinspection of the ceiling in addition to the added cost
for the change. The
need exists for lightweight, robust lighting that can be easily adjusted by
the end user without the
need for recertification and outside labor.
[0016] In evaluating the weight of light modules it is useful to utilize
the concept of lumens
per gram. The lumens per gram of light fixtures can have a major impact on
manufacturing
costs, shipping costs, and storage costs due to reduce materials costs and
handling costs. It could
also allow for fixtures which can be directly attached to the grid of a
suspended ceiling and still
meet seismic standards without requiring additional support structures which
are commonly
needed for existing troffer type light sources
[0017] The need also exists for aesthetically pleasing high lumen per gram
light fixtures. For
many applications, the lighting should be present but not draw attention to
itself. This is not the
case with troffers which immediately draw attention away from the other parts
of the ceiling.
Therefore, there is a need for lightweight and compact lighting fixtures which
address the above
needs in suspended ceiling applications. Again the thickness of the lighting
module has a direct
impact on the aesthetics of the installation. Existing linear solid state
sources require large light
mixing chambers to spread the light emitted by the LEDs. This dramatically
increases the depth
of these light sources. In order for light panel modules to have a an emitting
surface close to the
plane of the ceiling and not to protrude into the room or office space below,
the major portion of
the light source module must be recessed into the suspension ceiling. The need
exists for low
profile, or thin lighting panels with thicknesses under 10 mm, which are
attachable to the
electrified grids. Ideally these lighting panels would be field replaceable
from the office space
side of the installation by end users (and not require custom installers) and
present an
aesthetically pleasing and monolithic and uniform appearance. Essentially the
ideal suspension
ceiling lighting system would "disappear" into the ceiling from an aesthetic
standpoint.
[0018] Finally the need exists for solid state lighting source which can
meet or exceed Class
1 or Class A standards, meet seismic requirements, meet acoustic standards, be
field adjustable,
and be easily integrated in an aesthetically pleasing manner into commercial
lighting
applications.
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[0019] Intelligent lighting allows for integration of lighting and sensors
into the lighting
system. Lighting is required for all occupied areas and active control of
lighting via light
harvesting and occupancy actually can lead to larger energy savings than the
conversion from
incandescent to solid state lighting. Presently lighting is a separate market
and supply chain
from security, point of sale, and HVAC. As intelligent systems permeate into
retail, offices,
manufacturing, and homes existing lighting suppliers may well be replaced by
network suppliers.
The need exists for lighting solutions which enable the integration of sensors
and networking in a
wide range of installations.
[0020] As a large portion of the lighting market is based on upgrades, the
need exists for
retrofit systems that can be attached, mounted or otherwise adhered to a wide
range of barriers or
barrier surfaces. Incandescent and halogen lighting require thermal isolation
from combustible
surfaces, fluorescent requires high voltage operation and is susceptible to
overheating and cold
temperature issues. Existing solid state solutions either have limited lumen
output or require
heatsinking or other cooling means such as fans to operate. Alternately panel
based solid state
lighting uses waveguide or led array approaches to create distributed light
sources. Waveguides
are inherently flammable and represent a significant flame spreading issue
along with high cost
and weight. LED arrays transfer the heat generated into the mounting surface,
which can present
a significant fire hazard. The need exist for retrofittable solid state light
sources which overcome
the deficiencies listed above.
[0021] In general, integration of lighting into intelligent digital
networks is beginning to
occur. There is a need for an intelligent solid state element which also emits
light thereby
bypassing the conventional lighting supply chain and enabling network
companies the ability to
use the lighting grid, which must be in virtually every occupied area, as the
network grid. This
solid state element needs to be aesthetically pleasing, lightweight, low cost,
and compatible with
both active and passive electronics as well as emit light. Ideally this solid
state element would be
movable, retrofittable, and upgradable as well as emit light. The network
companies use
technology which is almost entirely direct current power. As such solid state
lighting and
network based technology such as wireless, RFID, data, IR, and optical links
have similar power
needs. Unlike incandescent, fluorescent, and halogen light sources the power
requirements of
solid state lighting can utilize low voltage power effectively.
[0022] Historically, lighting has been integrated into barriers or
partition systems like
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suspended ceilings, walls, etc. as separate lighting fixtures. In suspended
ceilings these are
typically 2 foot by 4 foot troffers which are built to accommodate 4 foot long
fluorescent tubes.
The troffers emit 3000 to 4000 lumens and weigh several kilograms each. As
such the troffers
must be supported by separate support wires to the deck above the suspended
ceiling because the
suspended ceiling cannot support the weight of the troffers using only the
support grid itself. In
addition, troffers because their supports are independently wired to the deck
and cannot be
integrated into the suspended ceiling they are typically set on a regular a
spaced interval
regardless of the lighting needs of the room. As such many rooms are overlit
leading to
significant unnecessary energy usage. The troffers severely limit the
aesthetic look of the
suspended ceiling. Existing troffers and conventional lighting also require
certified electricians
for installation and maintenance. The need exists for barrier or partition
systems which have
integrated lighting where the light sources can be easily removed,
retrofitted, and redistributed
on the barrier to adjust for changes in light needs.
[0023] This invention discloses how these needs can be met with self
cooling solid state light
sources which enable lower cost lighter weight barrier or partition systems
for ceilings, walls,
and floors.
SUMMARY
[0024] This invention discloses a barrier or partition to form suspended
ceilings, ceilings,
floors, and walls etc. containing integrated solid state lighting. Most
preferably low voltage grid
systems based on self cooling light sources are integrated into the partitions
disclosed. The self
cooling light sources are based on LEDs and other semiconductor elements
mounted onto or
within light transmitting thermally conductive elements such that the light
emitting and cooling
surfaces are substantially the same surfaces. The self cooling light source
have common light
emitting and cooling surfaces which eliminates the need for additional
heatsinking means.
Appended heatsinks increases weight and costs of not only the light fixture
but the other
structures needed to support the light fixture (e.g. supporting grid). The
heat generated in the self
cooling light sources is dissipated through the light emitting surface into
the illuminated space of
the installation. The light weight of the self cooling light sources enable
lighter weight and lower
cost suspension grids compared to conventional troffers and lighting fixtures.
Because the light
emitting surface and cooling surfaces are substantially the same the self
cooling light sources can
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be mounted and integrated into a wide range of barrier elements and or
surfaces including those
which may be considered combustible such as painted surfaces, wood,
wallpapered surfaces and
ceiling tiles. The self cooling light sources are constructed of non-flammable
materials being
substantially all inorganic such as alumina. The barriers may or may not
contain separate
barriers elements like ceiling tiles, panels, floor tiles or other
construction materials. Barrier as
used in this disclosure refers to panels, partitions, ceilings, floors, walls,
etc.
[0025]
This invention discloses a barrier with integrated lighting incorporating a
non-
flammable light recycling cavity light source comprising, at least one
reflector element and at
least one light transmitting thermally conductive element wherein at least one
light emitting
diode (LED) is within the light recycling cavity and in thermal contact with
and cooled by at
least one light transmitting thermally conductive element and optionally at
least one wavelength
conversion element is also within the light recycling cavity formed by at
least one reflector
element and at least one light transmitting thermally conductive element.
These light recycling
cavity solid state light sources are cooled using substantially the same
surfaces as the light
emitting surfaces. These light sources are particularly well suited for
suspended ceiling
applications where the majority of the heat is dissipated into the occupant or
office side of the
suspended ceiling installation. Using this approach a substantially contiguous
fire barrier can be
maintained in the suspended ceiling especially for the cases where fire
resistant ceiling tiles are
used. This eliminates the need for additional fire resistant shrouding.
[0026]
The elimination of appended external heatsinks reduces weight and cost of all
the
components within the suspended ceiling or barrier. The light recycling cavity
light sources may
be mounted onto the barrier supports (e.g. supporting grid for a ceiling) or
and integrated directly
into the barrier element (e.g. ceiling tile). Using this approach self cooling
light sources
outputting more than 30,000 lumens weigh less than 1 Kilogram.
This compares to a
conventional solid state troffer which may weigh more than 5 Kilograms and
output only 4000
lumens. Waveguide based troffers or light panels weigh even more and also
contain highly
flammable plastic materials which may increase flame spread and greatly
increase smoke
generation during fires. These conventional lighting sources must be
separately suspended from
the deck by support wires in suspended ceilings due to seismic and fire
requirements. The
lightweight self cooling nature of the light sources enables the direct
integration of the lighting
into ceilings, suspended ceilings, walls, and floors without the need for
additional support wires
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or cooling means. A preferred embodiment is that the light sources connect to
a distributed DC
grid, however remote power sources may also be used to power the light source.
The light
sources may also be configured for direct AC input using anti-parallel or
internal power
converters.
[0027] The light recycling cavity light typically comprises of a light
recycling envelope
formed using at least one strongly scattering light transmitting thermally
conductive element, at
least one LED in thermal contact with the at least one strongly scattering
light transmitting
thermally conductive element wherein at least one wavelength conversion
element and at least
one interconnect for the at least one LED are within the recycling cavity
envelope.
[0028] Alternately or simultaneously a substantially contiguous acoustical
barrier suspended
ceiling may be formed comprising light recycling cavity light sources which
dissipate the
majority of their heat into the office side of the installation. The active
control of the acoustics
including but not limited to noise blanking, background noise, and ambience
noise within the
office side of the suspended ceiling may be integrated into the recycling
cavity light source in the
form of an embedded speaker. In particular, low profile piezoelectric speakers
can be integrated
into the light source. Alternately, alerts, music, and fire warnings can be
integrated as well.
Lightweight self cooling solid state light sources with surface temperatures
less than the building
code of 900 C are disclosed. These sources enable designers to move away from
standard 2 foot
x 2 foot or 2 foot x 4 foot grid patterns dictated by fluorescent troffers and
eliminates the need
for additional support wires. The lightweight self cooling light sources may
be movable and
remounted by the end user as required when used in conjunction with a low
voltage power
distribution system.
[0029] In another aspect, the invention may be a suspended ceiling system
comprising: a
support grid support comprising a plurality of intersecting struts that form a
plurality of grid
openings, the support grid supported within an internal space of a building; a
plurality of ceiling
tiles mounted to the support grid and positioned in the grid openings to
collectively form a
barrier, each of the ceiling tiles comprising a front surface facing an
occupant portion of the
internal space of the building and a rear surface opposite the front surface;
at least one solid state
light source comprising: at least one reflector element; at least one light
emitting diode (LED); at
least one light transmitting thermally conductive element, the light
transmitting thermally
conductive element providing a common light emitting and cooling surface to
dissipate a
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majority of the heat from the solid state light source, the common light
emitting and cooling
surface facing the occupant portion of the internal space; and the solid state
light source at least
partially embedded in and supported by one of the ceiling tiles.
[0030] In yet another aspect, the invention may be an integrated ceiling panel
and lighting
apparatus comprising: a ceiling tile comprising: a front surface; a rear
surface opposite the front
surface; a side edge extending between the front and rear surfaces of the
ceiling tile; a recess
formed into the front surface of the ceiling tile, the recess defined by a
recess sidewall and a
recess floor surface, the recess sidewall extending from the front surface of
the one of the ceiling
tiles to the recess floor surface; at least one solid state light source
comprising: at least one
reflector element; at least one light emitting diode (LED); at least one light
transmitting
thermally conductive element, the light transmitting thermally conductive
element providing a
common light emitting and cooling surface to dissipate a majority of the heat
from the solid state
light source, the common light emitting and cooling surface facing the
occupant portion of the
internal space; and the solid state light source disposed within the recess
and mounted to the
ceiling tile.
[0031] In a further aspect, the invention may be a suspended ceiling system
comprising: a
support grid comprising a plurality of intersecting struts that form a
plurality of grid openings,
the support grid supported within an internal space of a building; a plurality
of ceiling tiles
mounted to the grid support and positioned in the grid openings to
collectively form a barrier,
each of the ceiling tiles comprising a front surface facing an occupant
portion of the internal
space of the building and a rear surface opposite the front surface, the front
surfaces of the
ceiling tiles defining a reference plane, the occupant portion of the internal
space located below
the reference plane; at least one solid state light source comprising: at
least one reflector element;
at least one light emitting diode (LED); at least one light transmitting
thermally conductive
element, the light transmitting thermally conductive element providing a
common light emitting
and cooling surface to dissipate a majority of the heat from the solid state
light source, the
common light emitting and cooling surface facing the occupant portion of the
internal space; and
the solid state light source mounted to one of the struts so that at least a
portion of the solid state
light source is located above the reference plane.
[0032] Disclosed are barriers with both lambertian and directional light
recycling light sources
wherein the light emission surface and cooling surfaces are substantially the
same.
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BRIEF DESCRIPTION OF DRAWINGS
[0033] FIGS. lA and 1B depict side views of prior art vertical and flip
chip mounted LED
packages and thermal schematics where the optical emission is substantially in
the opposite
direction of the heat removal.
[0034] FIGS. 2A, 2B and 2C depict side views of self-cooling solid state
light sources using
luminescent thermally conductive luminescent elements and interconnects with
thermal
schematics of the present invention.
[0035] FIGS. 3A, 3B and 3C depict side views of a self-cooling solid state
light source with
multiple die of the present invention.
[0036] FIGS. 4A, 4B and 4C depict side views of printed electrical
interconnects on
luminescent thermally conductive elements for various LED die types of the
present invention.
[0037] FIGS. 5A, 5B, 5C and 5D depict side views of various shapes of
wavelength
conversion elements of the present invention.
[0038] FIGS. 6A and 6B depict a side view of two different mountings for
LEDs on
wavelength conversion elements of the present invention.
[0039] FIGS. 7A, 7B and 7C depict side views of printed interconnects on
LED die of the
present invention.
[0040] FIGS. 8A, 8B, 8C and 8D depict side views of various environmental
seals for self
cooling light sources of the present invention.
[0041] FIGS. 9A and 9B depict side views of die shaping for enhanced dual
sided extraction
of the present invention.
[0042] FIGS. 10A and 10B depict a side view and a graph of blue and red die
in wavelength
conversion elements of the present invention.
[0043] FIG. 11 depicts a top view of a three pin self cooling light source
of the present
invention.
[0044] FIG. 12 depicts a top view of a self cooling light source with an
integrated driver of
the present invention.
[0045] FIGS. 13A and 13B depict a side view and a perspective view of a
self cooling light
source with additional cooling means of the present invention.
[0046] FIG. 14 depicts a top view of a self cooling light source with
thermally isolated
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sections of the present invention.
[0047] FIG. 15 depicts a top view of a self cooling light source with
separate drive scheme
for blue and red die of the present invention.
[0048] FIGS. 16A and 16B depict graphs of subtractive red phosphor and
additive red LED
of the present invention.
[0049] FIG. 17 depicts a graph of the spectrum from a self cooling light
source with cyan and
yellow LEDs of the present invention.
[0050] FIGS. 18A and 18B depict a side view and a perspective view of
various shapes with
luminescent coatings of the present invention.
[0051] FIGS. 19A and 19B depict side views of optics for self cooling light
source of the
present invention.
[0052] FIGS. 20A, 20B, and 20C depict side views of means of modifying the
far field
optical patterns of self cooling light sources of the present invention.
[0053] FIGS. 21A, 21B, and 21C depict side views of a light emitting patch
source and its
use with waveguiding materials of the present invention.
[0054] FIG. 22 depicts a side view of a prior art light strip.
[0055] FIG. 23 depicts a side view of a prior art waveguide light panel.
[0056] FIG. 24 depicts a side view of a self cooling light strip where
emitting surface and
cooling surface substantially the same.
[0057] FIG. 25 depicts a graph showing die temperature versus thermal
conductivity of
emitting/cooling surface.
[0058] FIG. 26 depicts a side view of a suspended ceiling installation.
[0059] FIG. 27 depicts a side view of a self cooling non-flammable light
strip attached to
suspended ceiling grid.
[0060] FIG. 28A depicts a side view of a self cooling non-flammable light
panel integrated
into ceiling tile of a suspended ceiling.
[0061] FIG. 28B depicts a side view of an embedded self cooling light
source with the scrim
of the ceiling tile taking the place of the reflector to form the light
recycling cavity.
[0062] FIG. 28C depicts a side view of a holey light transmitting thermally
conductive
element.
[0063] FIG. 29 depicts a side view of a suspended self cooling panel light.
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[0064] FIG. 30 depicts a side view of a seismic installation of self
cooling light strip in
suspended ceiling.
[0065] FIG. 31A is a schematic of a suspended ceiling system according to
an embodiment of
the present invention.
[0066] FIG. 31B is a perspective view of an integrated ceiling panel and
lighting apparatus
removed from the suspended ceiling system of FIG. 31 A in an exploded state;
[0067] FIG. 31 C is a cross-sectional view of integrated ceiling panel and
lighting apparatus
of FIG. 31B according to an embodiment of the present invention.
[0068]
[0069] FIG. 32A depicts a side view of a light recycling self cooling light
source with a light
transmitting thermally conductive translucent element 3202 and a direct attach
LED die 3204.
[0070] FIG. 32B depicts a side view of a light recycling cavity with a
light transmitting
thermally conductive element combined with a reflector 3224.
[0071] FIG. 32C depicts a side view of a light recycling cavity with a
light redirecting
reflector.
[0072] FIG. 32D depicts a side view of a light recycling self cooling light
source with an
additional waveguiding element that more or less fills the light recycling
cavity.
[0073] FIG. 33 depicts a graph showing efficiency versus reflectivity in
recycling self
cooling light sources.
[0074] FIG. 34 depicts a side view of decorative overlays on self cooling
light sources.
[0075] FIG. 35A depicts a side view of a light recycling self cooling light
source with a
reflector, a thermally conductive translucent element and a LED die.
[0076] FIG. 35B depicts a side view of a light recycling self cooling light
source with a light
transmitting thermally conductive luminescent element.
[0077] FIG. 35C depicts a side view of a separate wavelength conversion
coating/element
formed on a thermally conductive translucent element.
[0078] FIG. 35D depicts a side view of a self cooling light source without
a light recycling
cavity.
[0079] FIG. 36 depicts a side view of a push pin connector and self cooling
light source.
[0080] FIG. 37 depicts a side view of a scrim overlay for self cooling
light source.
[0081] FIG. 38 depicts a side view of a modular rail based field
replaceable linear sources.
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[0082] FIG. 39 depicts a side view of a magnetic connector for modular rail
or grid system.
[0083] FIG. 40 depicts a side view of a ceiling tile with recycling cavity.
[0084] FIG. 41 depicts a perspective view of a ceiling tile modular system
with integrated
recycling cavity.
[0085] FIG. 42 depicts a side view of a suspended ceiling grid for field
replaceable self
cooling light sources.
[0086] FIG. 43 depicts a side view of a snap fit linear source for grids,
undercounter, aircraft,
and ceiling lighting.
[0087] FIG. 44 depicts a side view of a self cooling lambertian solid state
light source with
thermal insulation barrier.
[0088] FIG. 45A depicts a side view of a connector for self cooling light
sources with a
reflector.
[0089] FIG. 45B depicts a side view of split reflectors with integral
contacts.
[0090] FIG. 45C depicts a side view of a recycling cavity formed of side
clips, a reflector
4564 and a translucent thermally conductive element.
[0091] FIG. 46A depicts a side view of a recycling light source with a
light transmitting
thermally conductive element and interconnects.
[0092] FIG. 46B depicts a side view of a flex circuit version of the self
cooling light source.
[0093] FIG. 47A depicts a side view of a plurality of light sources
connected together to form
linear, shaped or large planar area light sources.
[0094] FIG. 47B depicts a side view of a plurality of light sources with
connectors
comprising of at least one pin connector and at least one socket connector.
[0095] FIG. 48 depicts a side view of a retrofit system for suspended
ceilings.
[0096] FIG. 49A depicts a perspective view of a barrier utilizing a
retrofit wall or floor
installation of the light sources.
[0097] FIG. 49B depicts a side view of a power input means covered by cover
layer.
[0098] FIG. 50 depicts a perspective view of a removable modular wall
system with
integrated low voltage power grid.
[0099] FIG. 51 depicts a side view of a self supporting panel light.
[00100] FIG. 52 depicts a perspective view of an integrated low voltage
retrofittable power
grid.
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[00101] FIG. 53A depicts a side view of a light recycling cavity with an
integrated reflective
grid.
[00102] FIG. 53B depicts a side view of a light transmitting thermally
conductive element
with associated elements.
[00103] FIG. 54A depicts a side view of a recycling light source with a holey
light
transmitting thermally conductive element.
[00104] FIG. 54B depicts a side view of a recycling light source with a holey
light
transmitting thermally conductive element and a reflector.
[00105] FIG. 54C depicts a side view of a recycling light source with a holey
light
transmitting thermally conductive element and a reflector.
[00106] FIG. 55 depicts a side view of a shaped light transmitting thermally
conductive
element which can be attached to a flat or non-flat reflective mounting
surface.
[00107] FIG. 56 depicts a side view of a gimbaled self cooling light source.
[00108] FIG. 57 depicts a side view of a centrally support barrier system with
barrier
elements.
[00109] FIG. 58 depicts a perspective view of a strip light made of multiple
light transmitting
elements and single reflector.
[00110] FIG. 59A depicts a side view of a light recycling cavity source with
the light emitting
surface also being the cooling surface.
[00111] FIG. 59B depicts a side view of another light recycling cavity source
with the light
emitting surface also being the cooling surface.
[00112] FIG. 59C depicts a side view of a self-cooling light recycling source
with the LED
package mounted within the recycling cavity but not on the inner surface of
the light emitting
portion of the holey recycling cavity element.
[00113] FIG. 59D depicts a side view of a holey light recycling cavity element
with LED
package mounted onto a circuit board.
[00114] FIG. 59E depicts a side view of a light recycling cavity light source
with two or more
translucent light transmitting thermally conductive elements and reflectors.
[00115] FIG. 60 depicts a side view of a shaped self-cooling light source.
[00116] FIG. 61A depicts a side view of a self-cooling recycling light source
with thermal heat
transfer elements within the recycling cavity.
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[00117] FIG. 61B depicts a side view of a substantially contiguous thermal
transfer element
surrounded by reflective interconnects.
DETAILED DESCRIPTION
[00118] This invention relates to a solid state light sources based on LEDs
mounted on or
within thermally conductive luminescent elements. The thermally conductive
luminescent
elements provide a substantial portion of the cooling of the LEDs using both
convective and
radiative cooling from the light emitting surfaces of the thermally conductive
luminescent
elements. At least one thermally conductive luminescent element and at least
one reflector
element form a recycling cavity which contains at least one LED, at least one
interconnect, a
contact means, and optionally at least one wavelength conversion means. The
light source is
structured such that light emitted by the LED is emitted into the recycling
cavity, bounces around
within the recycling cavity and passes through and exits the light source
through the at least one
thermally conductive luminescent element. The recycling within the light
source creates a very
uniform emission from the surface of the at least one thermally conductive
luminescent element.
Wavelength conversion if used may occur within the recycling cavity, within or
on a surface of
the at least one thermally conductive luminescent element, or external to the
light source.
Recycling allows for the use of lower cost, lower in-line transmission
materials such as white
body color alumina while still maintaining high efficiency. The recycling
creates an efficient
white body color volume emitter which luminesces uniformly while also
providing sufficient
cooling to operate at high light output levels. The recycling combined with a
strongly scattering
thermally conductive luminescent element allows for the formation of thin
lightweight
distributed light sources. Specifically, white body color thermally conductive
luminescent
elements like alumina with in-line transmissions less than 50% (1mm thickness)
are preferred to
enhance intensity uniformity, enable large area light sources with thicknesses
less than lOmm,
and provide sufficient thermal spreading to enable natural convection and
radiative cooling of
sources emitting more than 100 lumens per square inch off the light emitting
surface alone. Even
more preferred is a strongly scattering thermally conductive luminescent
element with an in-line
transmission less than 20% (1mm thickness). Body color refers to the visual
appearance of the
light source when the LEDs are not emitting.
[00119] In general, this invention discloses an efficient, lightweight,
thin, self cooling solid
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state light source based on strongly scattering light transmitting elements
which are used to form
a recycling cavity around at least one LED. The strongly scattering light
transmitting elements
form a partially transmitting aperture, which increases the optical
pathlengths of the rays within
the recycling cavity. Further the strongly scattering light transmitting
elements provide thermal
spreading for the heat generated by the at least one LED, any wavelength
conversion losses,
electrical resistance heating, or optical absorption and transfers that heat
to the surrounding
ambient environment via convection, conduction, fluid transport, and/or
radiative means. This
creates a self cooling light source in which substantially all the heat
generated in the light source
is dissipated using the light emitting surface. By using the recycling cavity
approach and low
optical loss elements, low cost materials like alumina can form light sources
with greater than
70% efficiency (LED optical watts to light source output optical watts) while
simultaneously
providing substantially all the cooling for the light source.
[00120] Electrical interconnect of the LEDs and other semiconductor devices
are based on
opaque and/or transparent conductors to create low cost self-cooling solid
state light sources. The
low cost self-cooling solid state light sources can have printed thick film
printed silver
conductors with a reflectivity greater than 30%. The light emitted by the LEDs
and/or LED
packages is redirected by optical elements including but not limited to
reflectors, reflective
diffuse elements, and other thermally conductive luminescent elements. For
clarity it should be
noted that luminescence is defined as allowing the emission of light. This can
be based on
simple transmission of the light emitted from the LEDs or LED packages,
wavelength
conversion of the light emitted from the LEDs or LED packages or some
combination of both
transmission or wavelength conversion. However, it is noted that virtually all
materials exhibit
some level of wavelength conversion to UV and blue wavelengths. As an example,
standard
alumina (A1203) typically has chromium doping which when exposed to 450nm blue
light emits
narrowband red light. This in fact formed the basis of the first laser, which
was chromium doped
sapphire (ruby). A key attribute of this invention is the formation of
efficient recycling cavities
as disclosed in Zimmerman U.S. Patent No. 7,040,774 included by reference.
[00121] In recycling optical cavities multiple bounces or reflections are
purposefully caused
to occur. If the cavity is formed using materials with low enough optical
absorption losses, the
efficiency can be very high even though the material may be strongly
scattering. This invention
discloses the formation of recycling optical cavities in which at least a
portion of the recycling
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cavity is constructed of translucent thermally conductive elements. This is
based on the
recognition that even materials typically considered opaque can be used to
form efficient emitters
if optical absorption is minimized. The importance of this discovery is that
low cost materials
such as white body color alumina can now function as translucent thermally
conductive emitters
with or without wavelength conversion. The ability to form white body color or
even off-white
body color light sources is important from both an aesthetic and marketing
standpoint.
Consumers prefer white body color or off-white body color light sources for
mainly applications
due to their familiarity with incandescent and fluorescent lamps. As such
thermally conductive
luminescent elements with white or off-white body colors when they are not
emitting light from
the LEDs and/or LED packages are preferred. This can be further extended to
include a wide
range of body colors and patterns when non-homogenous thermally conductive
luminescent
elements are used such as reflectors with arrays of holes. The use of texture
and other outer
surface treatments to create various aesthetic looks is also disclosed. In
particular, the creation of
thermally conductive luminescent elements which match or are aesthetically
similar to ceiling
tiles is disclosed. In general, the ability to create a wide range of body
colors for the thermally
conductive luminescent element is a preferred embodiment of this invention.
[00122] In this configuration the light emitting surfaces also function as the
cooling surfaces.
As an example, alumina, TPA, or single crystal sapphire are all A1203 with
simply different
crystal structures. Alumina because of scatter elements (porosity and crystal
size) is not
considered an optical material due to its low in-line transmission and is
generally considered
opaque. However because of it usage in substrate materials it is available in
high volume for less
than 10 cents per square inch in thickness ranging from hundreds of microns to
a couple mm. At
these thicknesses in-line transmission is typically less than 20% (1mm
thickness). TPA is a
polycrystalline version that requires significantly different firing
conditions and material purity
and a host of filings exist on how to make this material economically
especially for halogen and
metal halide lamps. In similar thicknesses to alumina TPA has in-line
transmission greater than
80%. Sapphire is still another form of A1203 based on single crystal growth
which is even more
expensive than TPA and orders of magnitude more expensive than alumina. In
line transmission
for sapphire is similarly greater than 80% again for similar thickness. Using
the recycling cavity
approach disclosed in this invention overall light source efficiency using
alumina is greater than
70% with TPA and sapphire being only 5% higher at 75% even though there is a
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in-line transmission efficiency. This is due to the understanding that scatter
does not necessarily
lead to an absorption loss if recycling is allowed to occur. It should be
noted that the intensity
uniformity is very poor for the TPA and sapphire specifically because there is
very little
recycling occurring compared to the strongly scattering alumina when identical
source
geometries are used.
[00123] Also disclosed is a self cooling light source of the invention, which
comprises at least
one light-emitting diode (LED) die and at least one thermally conductive
luminescent element. In
this case the at least one thermally conductive luminescent element forms an
envelope around the
at least one light emitting LED. The luminescent element includes an
electrical interconnect and
can perform multiple functions: as a wavelength converter, converting at least
a portion of the
light emitted by said LED die to a different wavelength range, as an optical
waveguide for light
emitted by said LED die, and as a heat spreading element, spreading heat
generated by said LED
die over a greater cross-sectional area. Finally the luminescent element
provides a high
emissivity layer, for optimal coupling of emitted light from the light source.
[00124] The thermally conductive luminescent element can be used to completely
or partially
eliminate the need for any additional heatsinking means by efficiently
transferring and spreading
out the heat generated in LED and luminescent element itself over an area
sufficiently large
enough such that convective and radiative means can be used to cool the
device. In other words,
the surface emitting light also convectively and radiatively cools the device.
The thermally
conductive luminescent element can also provide for the efficient wavelength
conversion of at
least a portion of the radiation emitted by the LEDs.
[00125] The present invention may also be defined as a self cooling solid
state light source
comprising at least one light-emitting diode (LED) die and at least one
thermally conductive
luminescent element bonded to the at least one LED die; wherein heat is
transmitted from the
light source in basically the same direction as emitted light. More
specifically, light is emitted
from the LED die principally in a direction through the at least one
luminescent element, and
heat generated in the light source is transmitted principally in the same
direction as the direction
of light emission. Heat is dissipated from the light source by a combination
of radiation,
conduction and convection from the at least one luminescent element, without
the need for a
device heatsink.
[00126] Optionally, the luminescent thermally conductive element can provide
light spreading
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of at least a portion of the radiation from the LEDs and/or radiation
converted by the thermally
conductive luminescent elements via waveguiding. A thermally conductive
luminescent element
acts as a waveguide with alpha less than 10 cm-1 for wavelengths longer than
550 nm. In this
case, the LEDs with emission wavelengths longer than 550 nm can be mounted and
cooled by
the thermally conductive luminescent elements and also have at least a portion
of their emission
efficiently spread out via waveguiding within the thermally conductive
luminescent element as
well.
[00127] Thermally conductive luminescent elements with wavelength conversion
elements
used with InGaN and AlInGaP LEDs can convert at least a portion of the InGaN
spectrum into
wavelengths between 480 and 700 nm. Single crystal, polycrystalline, ceramic,
and/or
flamesprayed Ce:YAG, Strontium Thiogallate, or other luminescent materials
emitting light
between 480 and 700 nm and exhibiting an alpha below 10 cm-1 for wavelengths
between 500
nm and 700 nm can be a thermally conductive solid luminescent light spreading
element.
[00128] The mounting of InGaN and AlInGaP LEDs can form solid state extended
area light
sources with correlated color temperatures less than 4500 K and efficiencies
greater than 50 L/W
and optionally color rendering indices greater than 80 based on these
thermally conductive light
spreading luminescent elements.
[00129] One embodiment of this invention is a luminescent thermally conductive
translucent
element having a thermal conductivity greater than 1 W/mK comprising of one or
more of the
following materials, alumina, ALN, Spinel, zirconium oxide, BN, YAG, TAG,
composites, porous
metal reflectors and YAGG. Optionally, electrical interconnects maybe formed
on at least one
surface of the luminescent thermally conductive translucent element to provide
electrical
connection to the LED.
[00130] The luminescent thermally conductive element can have a thermal
conductivity
greater than 1 W/mK and have an emissivity greater than 0.2. A self cooling
solid state light
source can have at least one luminescent thermally conductive element with a
thermal
conductivity greater than 1 W/mK and an emissivity greater than 0.2. A self
cooling solid state
light source can have an average surface temperature greater than 500 C and a
luminous
efficiency greater than 50 L/W. Optionally, a self-cooling solid state light
source can have an
average surface temperature greater than 500 C and a luminous efficiency
greater than 50 L/W
containing at least one luminescent thermally conductive element with a
thermal conductivity
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greater than 1 W/mK and an emissivity greater than 0.2. A self-cooling solid
state light source
can dissipate greater than 0.3 W/cm2 via natural convection cooling and
radiation cooling.
[00131] Luminescent thermally conductive elements can be formed via the
following methods:
casting, metal forming, laser cutting, stamping, crystal growth, sintering,
coating, fusible coating,
injection molding, flame spraying, sputtering, CVD, plasma spraying, melt
bonding, and
pressing. Pressing and sintering of oxides with substantially one phase will
improve translucency
based on a luminescent powder. Alternately, a translucent element with a
thermal conductivity
greater the 1 W/mK and an alpha less than 10 cm-1 can be coated with a
luminescent layer
formed during the sintering process or after the sintering process. Single
crystal or
polycrystalline materials, both luminescent and non-luminescent, can be the
thermally
conductive luminescent element. Specifically TPA (transparent polycrystalline
alumina), Spinel,
cubic zirconia, quartz, and other low absorption thermally conductive
materials with a
luminescent layer can be formed during or after fabrication of these
materials. Techniques such
as pressing, extruding, and spatial flame spraying can form near net shape or
finished parts.
Additional luminescent layers can be added to any of these materials via dip
coating, flame
spraying, fusing, evaporation, sputtering, CVD, laser ablation, or melt
bonding. Controlled
particle size and phase can improve translucency. In the case of metal films
with holes the size
of the hole and spacing can be uniform or non-uniform. Non-homogenous
thermally conductive
luminescent elements may comprise metal foils with highly reflective inner
surfaces with holes.
A non-homogenous array of holes, where the open hole area represents 20% of
the surface area
is roughly equivalent to a piece of alumina with an in-line transmission of
20%. The higher
thermal conductivity of the metal foils allow for much thinner thickness while
still retaining
reasonable lateral thermal conductivity.
[00132] Coatings can improve the environmental and/or emissivity
characteristics of the self-
cooling light source, particularly if the coating is a high emissivity coating
with and without
luminescent properties. Single crystal, polycrystalline, ceramic, coating
layers, or flame sprayed
can be used both as a coating and as the bulk material Ce:YAG, with a high
emissivity or
environmental protective coating. In particular, polysiloxanes, polysilazanes
and other
transparent environmental overcoats can be applied via dip coating,
evaporative, spray, or other
coating methods, applied either before or after the attachment of the LEDs.
Additional
luminescent materials can be added to these overcoats such as but not limited
to quantum dots,
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luminescent dyes (such as Eljen wavelength shifter dyes), and other
luminescent materials. A
wide range of the coatings for aesthetic and improved radiation are possible
with non-
homogenous thermally conductive luminescent elements, because the inner and
outer surfaces of
the element are isolated from each other. It is preferred that the non-
homogenous thermally
conductive luminescent elements have a high reflectivity surface for the
surface, which forms the
inner walls of the recycling cavity. The outer surface of the non-homogenous
thermally
conductive luminescent elements can be any color up to and including black.
[00133] Wireless power transfer elements, power conditioning element, drive
electronics, power
factor conditioning electronics, infrared/wireless emitters, and sensors can
be integrated into the
self-cooling solid state light source.
[00134] A self-cooling solid-state light source can have a luminous efficiency
greater than 50
L/W at a color temperature less than 4500K and a color rendering index greater
than 70. The
self-cooling solid-state light source can have a surface temperature greater
than 400 C,
convectively and radiatively cooling more than 0.3 W/cm2 of light source
surface area, and
having a luminous efficiency greater than 50 L/W.
[00135] A self-cooling solid-state light source can have a luminous efficiency
greater than 50
L/W at a color temperature less than 4500K and a color rendering greater than
85 containing
both blue and red LEDs. At least one luminescent thermally conductive element
with an alpha
less than 10 cm-1 for wavelengths longer than 500 nm is used in the self
cooling solid state light
source containing at least one blue and at least one LED with emission
wavelengths longer than
500 nm. Additional luminescent materials in the form of coatings and/or
elements including, but
not limited, to phosphor powders, fluorescent dies, wavelength shifters,
quantum dots, and other
wavelength converting materials, can further improve efficiency and color
rendering index.
[00136] Aspect ratios and shapes for the solid state light source can be,
including but not limited
to, plates, rods, cylindrical rods, spherical, hemispherical, oval, and other
non-flat shapes. Die
placement can mitigate edge effects and form more uniform emitters. Additional
scattering,
redirecting, recycling, and imaging elements can be attached to and/or in
proximity to the solid
state light source designed to modify the far field distribution. Additional
elements can be
attached to the solid state light source with a thermally conductivity greater
than 0.1 W/mK such
that additional cooling is provided to the solid state light source via
conduction of the heat
generated within the solid state light source to the additional element and
then to the surrounding
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ambient. An external frame can provide mechanical support, can be attached to
the solid state
light source, and/or can provide an external electrical interconnect. Multiple
solid state sources
arranged with and without additional optical elements can generate a specific
far field
distribution. In particular, multiple solid state sources can be arranged non-
parallel to each other
such that surface and edge variations are mitigated in the far field. A
separation distance between
solid state light sources faces of greater than 2 mm is preferred to
facilitate convective cooling.
Mounting and additional optical elements can enhance convective cooling via
induced draft
effects.
[00137] In this invention, thermally conductive luminescent elements on to
which
semiconductor devices are mounted are used to effectively spread the heat out
over a sufficient
area with a low enough thermal resistance to effectively transfer the heat
generated by the
semiconductor devices and the thermally conductive luminescent element itself
to the
surrounding ambient by both convection and radiative means. In this invention,
the surface
emitting light convectively and radiatively cools the device.
[00138] The thermally conductive luminescent element can also provide for the
efficient
wavelength conversion of at least a portion of the radiation emitted by the
LEDs. Optionally, the
luminescent thermally conductive element can provide light spreading of at
least a portion of the
radiation from the LEDs and/or radiation converted by the thermally conductive
luminescent
elements. The thermally conductive luminescent elements act as waveguides with
alpha less than
cm-1 for wavelengths longer than 550 nm. In this case the LEDs with emission
wavelengths
longer than 550 nm can be mounted and cooled by the thermally conductive
luminescent
elements and also have at least a portion of their emission efficiently spread
out via waveguiding
within the thermally conductive luminescent element as well.
[00139] Disclosed is a self cooling solid state light source containing an
optically transmitting
thermally conductive element with a surface temperature greater than 500 C and
a surface area
greater than the semiconductor devices mounted on the optically transmitting
thermally
conductive element. Even more preferably a self cooling solid state light
source containing at
least one optically transmitting thermally conductive element with a surface
temperature greater
than 1000 C and a surface area greater than the surface area of the mounted
semiconductor
devices. The optically transmitting thermally conductive element may be
coupled with a
reflector to form a recycling cavity. In this case at least one LED is mounted
to the optically
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transmitting thermally conductive element such the heat generated by the LED
is distributed
laterally by the optically transmitting thermally conductive element and
thereby transmitted off
the surface of the optically transmitting thermally conductive element to the
surrounding
ambient. Optionally, a wavelength conversion element is also used within the
recycling cavity
formed by the optically transmitting thermally conductive element and
reflector to convert at
least a portion of the emission generated by the LED also within the recycling
cavity to a
different wavelength range. The emission from the LEDs and any optional
wavelength
conversion element exits the recycling cavity through the optically
transmitting thermally
conductive element and the heat generated within the light source is
dissipated to the office side
of the installation off the surface of the optically transmitting thermally
conductive element. The
formation of reflective interconnects for providing power to the LEDs on the
optically
transmitting thermally conductive element is also disclosed. Silver is a
preferred material for the
reflective interconnect. It should be noted that by using a recycling cavity
approach and high
reflectivity materials within the recycling cavity, what would typically be
considered opaque
materials like alumina can be used in thicknesses up to 1 mm for the optically
transmitting
thermally conductive element because multiple reflections are possible without
significant
losses. As an example, 500 micron 96% alumina substrates have an in-line
transmission of less
than 20% but when used as an aperture to a recycling cavity light source has
an efficiency of
over 70%. Even though only 20% is transmitted each time rays impinge on the
alumina within
the recycling cavity if the absorption losses are minimized by having a highly
reflective reflector
(such as AlanodTm), reflective interconnect traces, reflective LEDs, low loss
wavelength
conversion elements, and low loss alumina lOs if not 100s bounces can occur
within the
recycling cavity. This approach not only creates high efficiency solid state
light sources, it also
improves the brightness uniformity of the source, allows for indirect
positioning of the LEDs,
lower color temperature for a given amount of wavelength conversion material,
and the ability to
generate a wide range of external body colors.
[00140] Also preferred is a self cooling solid state light source containing
at least one optically
transmitting thermally conductive luminescent element with an average thermal
conductivity
greater than 1 W/mK. As an example, YAG doped with 2% Cerium at 4 wt % is
dispersed into an
alumina matrix using spray drying. The powders are pressed into a compact and
then vacuum
sintered at 15000 C for 8 hours, followed by hot isostatic pressing at 16000 C
for 4 hours under
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argon. The material is diamond saw diced into 1 mm thick pieces which are 1/2
inch x 1 inch in
area. The parts are laser machined to form interconnect trenches into which
silver paste is screen
printed and fired. The fired silver traces are then lapped to form smooth
surface to which direct
die attach LED die are soldered. Pockets are cut using the laser such that two
pieces can be
sandwiched together thereby embedding the direct die attach LED die inside two
pieces of the
ceramic Ce:YAG/alumina material. In this manner, a self cooling light source
is formed. The
direct die attached LED(s) are electrically interconnected via the silver
traces and thermally
connected to the ceramic Ce:YAG/alumina material. The heat generated within
the LEDs and the
ceramic Ce:YAG/alumina material is spread out over an area greater than the
area of the LEDs.
In this example, power densities greater than 1 W/cm2 can be dissipated while
maintaining a
junction temperature less than 1200 C and surface temperature on the ceramic
Ce:YAG/alumina
material of 80 to 900 C based on natural convection and radiative cooling. As
such a 1/4 inch x
1/2 inch solid state light source can emit over 100 lumens without any
additional heatsinking or
cooling means.
[00141] Materials with emissivities greater than 0.3 are preferred to enhance
the amount of heat
radiated of the surface of the solid state light source. Even more preferable
is an emissivity
greater than 0.7 for surface temperatures less than 2000 C. A naturally
convectively cooled
surface with a natural convection coefficient of 20 W/m2/k with a surface
temperature of 500 C
in a 250 C ambient will transfer about 25% of its energy to the surrounding
ambient radiatively if
the surface emissivity is greater than 0.8 and can dissipate approximately
0.08 W/cm2 of light
source surface area. A similar naturally convectively cooled surface with a
surface temperature of
1000 C can transfer 30% of its energy to the surrounding ambient radiatively
and dissipate
greater than 0.25 watts/cm2 of surface area. A similar naturally convectively
cooled surface with
a surface temperature of 1500 C can transfer 35% of the heat radiatively and
dissipate greater
than 0.4 watts/cm2. Given that solid state light sources can approach 50%
electrical to optical
conversion efficiency and that the typical spectral conversion is 300
lumens/optical watt, using
this approach a self cooling solid state light source can emit 75 lumens for
every 1.0 cm2 of light
source surface area. As an example, a 1/4 inch x1/2 inch x2 mm thick self
cooling light stick can
generate more than 150 lumens while maintaining a surface temperature less
than 1000 C. The
typical LED junction temperature for high powered devices can be over 1200 C
and still
maintain excellent life and efficiency. For surfaces with temperatures less
than 1200 C, the
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majority of the radiated energy is in the infrared with a wavelength greater
than 8 microns. As
such, high emissivity coatings, materials, and surfaces which are
substantially transparent in the
visible spectrum are preferred embodiments of self cooling light sources.
[00142] The emissivity of the materials in the infrared varies between 0 and
1. Glass has an
emissivity of approximately 0.95 while aluminum oxide may be between 0.5 and
0.8. Organics
such as polyimides can have fairly high emissivity in thick layers. This
however will negatively
affect the transfer of heat due to the low thermal conductivity of organics.
As such high thermal
conductivity high emissivity materials and coating are preferred. High
emissivity/low visible
absorption coatings are described in J. R. Grammer, "Emissivity Coatings for
Low-Temperature
Space Radiators", NASA Contract NAS 3-7630 (30 Sep. 1966). Various silicates
are disclosed
with emissivity greater than 0.85 and absorptions less than 0.2.
[00143] In order to maximize heat transfer to the ambient atmosphere, the need
exists for
luminescent thermally conductive materials which can effectively spread the
heat generated by
localized semiconductor and passive devices (e.g. LEDs, drivers, controller,
resistors, coils,
inductors, caps etc.) to a larger surface area than the semiconductor die via
thermal conduction
and then efficiently transfer the heat generated to the ambient atmosphere via
convection and
radiation. At the same time, these luminescent thermally conductive materials
must efficiently
convert at least a portion of the LED emission to another portion of the
visible spectrum to create
a self cooling solid state light source with high L/W efficiency and good
color rendering.
Conventional wavelength converters in both solid and powder form are
substantially the same
size as the LED die or semiconductor devices. This minimizes the volume of the
luminescent
material but localizes the heat generated within the luminescent element due
to Stokes losses and
other conversion losses. In present day solid state light sources
approximately 50% of the heat
generated is within the luminescent material. By using a thermally conductive
luminescent
element with low dopant concentration which also acts as a waveguide to the
excitation light
emitted by the LEDs the heat generated by the luminescent conversion losses
can be spread out
over a larger volume. In addition a more distributed light source can be
generated rather
localized point sources as seen in conventional LED packages. In this manner
the need for
addition diffusing and optical elements can be eliminated or minimized. As
such the use of
luminescent thermally conductive elements with surface area greater than the
semiconductor
devices mounted on the luminescent elements is a preferred embodiment.
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[00144] Heat generated within the LEDs and phosphor material in typical solid
state light
sources is transferred via conduction means to a much larger heatsink usually
made out of
aluminum or copper. The temperature difference between the LED junction and
heatsink can be
40 to 500 C. The temperature difference between ambient and heatsink
temperature is typically
very small given that significant temperature drop occurs from the LED
junction and the heatsink
surfaces. This small temperature difference not only eliminates most of the
radiative cooling but
also requires that the heatsink be fairly large and heavy to provide enough
surface area to
effectively cool the LEDs. The larger the heatsink, the larger the temperature
drop between the
LED junction and the surface of the heatsink fins. For this reason, heatpipes
and active cooling is
used to reduce either the temperature drop or increase the convective cooling
such that a smaller
heatsink volume can be used. In general, the added weight of the heatsink
and/or active cooling
increases costs for shipping, installation, and in some cases poses a safety
risk for overhead
applications.
[00145] Ideally, like incandescent, halogen, sodium, and fluorescent light
sources, the emitting
surface of the solid-state light source would also be used to cool the source.
Such a cooling
source would have an emitting surface that was very close to the temperature
of the LED
junctions to maximize both convective and radiative cooling. The emitting
surface should be
constructed of a material that exhibited sufficient thermal conductivity to
allow for the heat from
small but localized LED die to be spread out over a sufficiently large enough
area to effectively
cool the LEDs. In this invention this is accomplished by spreading the heat
generated within the
luminescent element out over a larger volume, using a thermal conductivity
luminescent element
that spreads the heat generated in the semiconductor devices used via
conduction over a larger
surface area than the semiconductor devices, and maximizing the radiative and
convective
cooling by high emissivity coatings, increased surface area, and higher
surface temperatures
created by efficient coupling of the heat to the surface of the self cooling
light source.
[00146] As stated earlier, the need exists for non-flammable solid state light
sources. The
techniques to reduce the fire hazard of organics not only can not meet Class 1
or Class A
requirements due to flame spread and smoke but also degrade optical properties
of the materials.
This disclosure cites inorganic materials and their use in self cooling solid
state lights sources
which are non-flammable. Not only do these light sources not contribute to the
spread of flames
and increase smoke during a fire they also enable the maintenance of a
contiguous fire, acoustic,
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and aesthetic suspended ceiling by eliminating and/or reducing the number of
breaks in the
ceiling. The lightweight nature of the sources defined by high lumens per gram
allow for direct
attachment, suspension, and embedding of the light sources on, from, or in the
suspended ceiling.
This allows for seismic certification with the suspended ceiling and
eliminates the need for
additional support wires. The elimination of support wires enables the user
within the office
space the ability to change, alter, replace, or otherwise move the lighting as
needed. This is also
enabled by the use of magnetic, clip and other releasable forms of electrical
and physical
connectors to the grid, ceiling tiles, or power grids attached to or embedded
in to the grid and/or
ceiling tiles.
[00147] The use of the ceiling tile outer layer or scrim to form recycling
cavities or depressions
which can then be used in conjunction with self-cooling light sources wherein
the emitting
surface and cooling surface is substantially the same is also disclosed. In
general the self cooling
solid state light fixtures disclosed transfer the majority of their heat to
the office space side not
the plenum side because the emitting/cooling surface is directly exposed the
ambient within the
office space. Electrical and physical connections to drivers in the plenum
space can occur via
push pin connects, embedded traces, surface traces, and other interconnect
means. In general,
the use of this approach to create thin, lightweight solid state light sources
which aesthetically
blend into suspended ceilings wherein the surface which emits also provides
the cooling for the
light source is a preferred embodiment of this invention.
[00148] FIG 1A depicts a prior art vertical LED die 3 mounted on a substrate
4. The vertical
LED die 3 is typically coated with an inorganic/organic matrix 7 comprising of
phosphor powder
such as, but not limited to, Ce:YAG in a silicone resin material. The wire
bond 2 is used to
electrically connect vertical LED die 3 to interconnect 5, which is then
coated with the
inorganic/organic matrix 7. The other side of vertical LED die 3 is contacting
interconnect 6
usually via eutectic solder or conductive adhesives. A lens 1 is further
attached to substrate 4 to
environmentally seal the assembly, enhance light extraction from vertical LED
die 3, and modify
the far field optical pattern of the light emitted by the device. In this
case, emitted rays 9 are
substantially traveling in the opposite direction of the heat ray 8.
[00149] As shown in the thermal schematic in FIG. 1A, cooling of the
inorganic/organic matrix
7 occurs almost exclusively via thermal conduction through the vertical LED
die 3 and into the
substrate 4 via interconnect 6. The heat generated within inorganic/organic
matrix 7 due to
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Stokes losses and scattering absorption is thermally conducted to the vertical
LED die 3 at a rate
determined by the thermal resistance determined by the bulk thermal
conductivity of the
inorganic/organic matrix 7. As shown in the simplified thermal schematic, the
average
temperature of the inorganic/organic matrix 7 is determined by the thermal
resistance
R(phosphor/encapsulant) and T2 the average temperature of the vertical LED die
3. In order for
heat generated within the inorganic/organic matrix 7 to be dissipated to the
ambient, it must
move the thermal resistance of LED die 3 (RLED) and substrate 4 (RPackage)
before it can be
dissipated to the ambient. This is a simplified thermal schematic which lumps
bulk and interface
thermal resistances and spatial variations within the device. But in general,
heat generated within
the inorganic/organic matrix 7 must be dissipated mainly through the vertical
LED die 3 due to
low thermal conductivity of the other materials (e.g. Lens) which surround
inorganic/organic
matrix 7. Additional heatsinking means can further increase the surface area
using metal,
composite, or ceramic elements to enhance the dissipation of heat to ambient
but the flow of heat
is still basically the same. The lens 1 acts as an extraction element for the
emitted light rays 9 but
also acts as a barrier to thermal rays 8. Typically constructed of silicone or
epoxy resins with
thermal conductivity less than 0.1 W/mK, Lens 1 acts as a thermal insulator.
Lens 1 also can
limit thermal radiation from vertical LED 3 and inorganic/organic matrix 7 due
to low emissivity.
In general this design requires that approximate 50% of the isotropic emission
from the active
region within vertical LED 1 must be reflected off some surface within the
device and that the far
field output of the device be substantially directional or lambertian in
nature. Even with the use
of highly reflective layers, this represents a loss mechanism for this
approach. These extra losses
are associated with the added pathlength that the optical rays must go through
and multiple
reflections off the back electrodes. This added pathlength and reflections,
which are required to
extract the light generated in the active region of vertical LED 1,
fundamentally reduces the
efficiency of the LED based on the absorption losses of the LED itself. A
significant portion of
the light generated within the inorganic/organic matrix 7 must also pass
through and be reflected
by vertical LED 1. Since vertical LED 1 is not a lossless reflector, the added
pathlength of these
optical rays also reduce overall efficiency.
[00150] FIG. 1B depicts a prior artchip mounted LED 15. Solder or
thermocompression bonding
attaches flip chip mounted LED 15 via contacts 16 and 21 to interconnects 17
and 18
respectively on substrate 19. Luminescent converter 14 may be an
inorganic/organic matrix as
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discussed in FIG. lA or solid luminescent element such as a Ce:YAG ceramic,
single crystalline
Ce:YAG, polycrystalline Ce:YAG or other solid luminescent materials as known
in the art. In
either case, the same cooling deficiency applies with this design. Virtually
all the cooling of the
luminescent converter 14 must be through the flip chip mounted LED 15. Again,
emission rays
12 travel in a direction substantially opposite to thermal rays 13 and once
again approximately
50% the isotropic emission of the active region of the flip chip mounted LED
15 must to
redirected within the device requiring the use of expensive metals like Ag,
specialized coating
methods and even nanolithography as in the case of photonic crystals.
[00151] The formation of contacts which are both highly reflective over a
large portion of the
LED die area and still forms a low resistivity contact has been a major
challenge for the industry
due to reflectivity degradation of Ag at the temperature typically required to
form a good ohmic
contact. This high light reflectivity and low electrical resistivity leads to
added expense and
efficiency losses. Because both the contacts must be done from one side
typically an underfill 20
is used to fill in the voids created by the use of flip chip contacts. Lens 11
forms a barrier to heat
flow out of the device from both convectively and radiatively. The luminescent
converter 14 is
typically attached after the flip chip mounted die 15 is mounted and
interconnected to substrate
19. A bonding layer 23 between the flip chip mounted die 15 and luminescent
element 14 further
thermally isolates the luminescent element 14. Typically, InGaN power LED
UV/Blue chips
exhibit efficiencies approaching 60% while White InGaN power LED packages are
typically
40%. The loss within the luminescent converter 14 therefore represents a
substantial portion of
the total losses within the device. In the case of an inorganic/organic matrix
luminescent
converter of FIG. 1A, the conversion losses are further localized within the
individual phosphor
powders due to the low thermal conductivity of the silicone or epoxy matrix.
The solid
luminescent converter 14 has more lateral spreading due to the higher thermal
conductivity of the
solid material. Both cases are typically Cerium doped YAG with an intrinsic
thermal
conductivity of 14 W/mK. However since the silicone matrix has a thermal
conductivity less than
0.1 W/mK and surrounds substantially all the phosphor powders, the
inorganic/organic matrix
has a macro thermal conductivity roughly equivalent to the silicone or epoxy
by itself. Very high
loading levels of phosphor powder can be used but lead to efficiency losses
due to higher scatter.
[00152] There is simply nowhere for the heat generated in luminescent
converter 14 to go
except be thermally conducted into the flip chip mounted LED 15 via the
bonding layer 23. In
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most cases, solid luminescent converters 14 must have an additional leakage
coating 22 that
deals with blue light that leaks out of the edge of the flip chip mounted LED
15. An
inorganic/organic matrix suffers from the same issues in FIG. 1A. In both
FIGS. lA and 1B, the
emission surfaces are substantially different from the cooling surfaces. The
thermal schematic for
FIG. 1B is similar to FIG. lA in that heat generated within the luminescent
converter 14 is
substantially dissipated through the flip chip mounted LED 15. With the advent
of high powered
LEDs, a substantially portion of the heat generated within the device can be
localized within
luminescent converter 14. This localization has led to a variety of solutions
including the use of
remote phosphors. In general, luminescent converter 14 efficiency reduces as
its average
temperature T4 increases. In the prior art the luminescent converter 14
dissipates the majority of
its heat through the flip chip mounted LED 15 with an average temperature of
T5. This is an
inherently higher temperature than the ambient. The need exists for techniques
whereby the heat
generated within luminescent converter 14 can be reduced for higher efficiency
devices.
[00153] FIG 2A depicts a vertical LED 24 of the present invention in which the
optical
emission rays 26 travel substantially in the same direction as the thermal
rays 27. A thermally
conductive luminescent element 25 provides wavelength conversion for at least
a portion of the
light emitted by vertical LED 24 and acts as an optical and thermal spreading
element, extraction
means, and a substrate for the electrical interconnect. In FIG. 2A, overcoat
30 may be reflective,
transparent, partially reflective and exhibit reflectivity which is wavelength
and/or polarization
dependent.
[00154] Wire bond 29 connects interconnect 28 to contact pad 33 with contact
34 attached via
conductive ink or eutectic solder to interconnect 31. A
transparent/translucent bonding layer 32
maximizes optical and thermal coupling into thermally conductive luminescent
element 25 and
eventually out of the device. The transparent/translucent bonding layer 32 may
comprise, but is
not limited to, glass fit, polysiloxane, polysilazane, silicone, and other
transparent/translucent
adhesive materials. Transparent/translucent bonding layer 32 has a thermal
conductivity greater
than 0.1 W/mK and even more preferably greater than 1 W/mK. Thermally
conductive
luminescent element 25 may comprise, but is not limited to, single crystal
luminescent materials,
polycrystalline luminescent materials, amorphous luminescent materials,
thermally conductive
transparent/translucent materials such as Sapphire, TPA, Nitrides, Spinel,
cubic zirconia, quartz,
and glass coated with a thermally conductive luminescent coating, and
composites of thermally
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conductive transparent/translucent material and thermally conductive
luminescent materials.
[00155] In FIG. 2A a high emissivity layer 35 may be applied to the thermally
conductive
luminescent element 25 to enhance radiative cooling. In addition, high
emissivity layer 35 may
also provide enhanced extraction efficiency by acting as an index matching
layer between the
surrounding air and the thermally conductive luminescent element 25,
especially in the case
where extraction elements are used to increase extraction from the thermally
conductive
luminescent element 25. Unlike the previous prior art thermal schematic, the
flow of heat
generated in the thermally conductive luminescent element 25 is directly
coupled to the ambient
via convective and radiative cooling off the surface of the thermally
conductive luminescent
element 25 itself. This direct coupling approach can only be effectively
accomplished if the bulk
thermal conductivity of the thermally conductive luminescent element 25 is
high enough to
effectively spread the heat out over an area sufficiently large enough to
effective transfer the heat
to the surrounding ambient. As such, a thermally conductive luminescent
element has a surface
area greater than the attached LED with an average bulk thermal conductivity
greater than 1
W/mK wherein the heat generated within the Vertical LED 24 and thermally
conductive
luminescent element 25 are substantially transferred to the surrounding
ambient via convection
and radiation off the surface of thermally conductive luminescent element 25.
High emissivity
layer 35 most preferably has an emissivity greater than 0.8 at 1000 C and an
absorption less than
0.2 throughout the visible spectrum. Alternately, the emissivity of the
thermally conductive
luminescent element 25 may be greater than 0.8 at 1000 C and have absorption
less than 0.2
throughout the visible spectrum.
[00156] FIG 2B depicts a flip chip mounted LED 36 mounted on thermally
conductive
luminescent element 42 via a transparent/translucent bonding layer 43 and
electrically connected
via contacts 41 and 40 to interconnects 44 and 45 on thermally conductive
luminescent element
25. Interconnects 44 and 45 are thick film silver conductors formed via screen
printing, inkjet
printing, lithographic means, or combinations of these other methods. As an
example, thermally
conductive luminescent element 42 may contain a laser cut trench approximately
5 micron deep
into which silver paste is screen printed and fired. The surface of conductive
luminescent
element 42 is then optionally lapped to create a smooth surface for
interconnect 44 and 45. The
resulting surface is now smooth enough for thermo compression bonded die,
direct die attach die
with integral eutectic solders, and other direct attach bonding methods.
Interconnects 44 and 45
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are typically fired at a temperature greater than 4000 C. Interconnects 44 and
45 are thick film or
inkjet silver traces with line widths less than or greater than the width of
the flip chip mounted
LED 36. Optical losses within the device can be minimized by minimizing the
amount of silver
used, minimizing the width of the interconnect traces and maximizing the
reflectivity of the
silver traces. Alternately, the thermal resistance between flip chip mounted
LED 36 and the
thermally conductive luminescent element 42 may be minimized by increasing
amount of silver
thickness or area. Overcoat 37 may comprise, but is not limited to, glass
frit, polysiloxane,
polysilazanes, flame sprayed ceramics, and evaporative/CVD coatings. A highly
reflective layer
in overcoat 37 is optional. In this manner, a compact directional light source
can be formed.
Transparent/translucent bonding layer acts as an environmental and shorting
barrier for the
device. The reflector in overcoat 37 can be applied after all the high
temperature processing
thereby maximizing reflectivity of the layer. The thermal schematic shown in
FIG. 2B again
shows that there is a much different thermal conduction path than FIG. 1
devices. Thermally
conductive luminescent element 42 provides the cooling surfaces for the device
as well as
conversion of light from LED 36. The emitting surface of the device is also
the cooling surface
of the device.
[00157] FIG 2C depicts a lateral LED 53 mounted onto thermally conductive
luminescent
element 46. As in FIG. 2A and FIG. 2B, the optical emission 50 and thermal
rays 51 travel in
substantially the same direction. In this configuration, a
transparent/translucent overcoat 48
couples thermal rays 56 and optical emission 57 out the backside of the
device. Optical emission
50 and optical emission 57 may be the same or different from each other
regarding emission
spectrum, intensity, or polarization. Additives, coatings, and combinations of
both can affect the
emission spectrum, intensity and polarization within overcoat 48. Interconnect
49 and 54 may
comprise, but are not limited to, electrically conductive materials in a
dielectric matrix. A silver
flake thick film paste screen can be printed and fired at greater than 4000 C
with a reflectivity
greater than 50% to form an electrically conductive material in a dielectric
matrix. Wire bond 47
and 52 connect LED contacts 56 and 55 to interconnect 49 and 54 respectively.
Gold wire is
preferred but the wire bond can be silver, silver coated gold, and aluminum in
wire, foil, and tape
form. The thermal schematic illustrates the flow of heat through the device to
ambient.
Transparent/translucent overcoat 48 may also contain luminescent materials. As
an example,
transparent/translucent overcoat 48 may comprise inorganic/organic matrix
material such as but
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not limited to HT 1500 Polysilazane (Clariant Inc.) containing at least one
luminescent materials
such as, but not limited to, Eljen EJ-284 fluorescent dye for conversion of
green and yellow
emission into red. Luminescent coatings can be applied via dip coating,
spraying, inkjet, and
other deposition techniques to form transparent/translucent overcoat 48 on a
light emitting device
containing at least one thermally conductive luminescent element 46.
[00158] FIG 3A depicts a self cooling light source comprising of a single
thermally conductive
luminescent element 60 attached both thermally and optically onto at least one
LED 61. LED 61
may comprise InGaN, GaN, AlGaN, AlinGaP, ZnO, AN, and diamond based light
emitting
diodes. Both blue and red light emitting diodes such as, but not limited to,
InGaN and AlinGaP
LEDs are attached optically and thermally to at least one thermally conductive
luminescent
element 60. Heat 59 and emission 58 generated by the LED 61 and the thermally
conductive
luminescent element 60 are spread out over a substantially larger area and
volume than the LED
61. In this manner the heat generated can be effectively transferred to the
surrounding ambient.
[00159] Ce:YAG in single crystal, polycrystalline, ceramic, and flame sprayed
forms are
preferred materials choices for thermally conductive luminescent element 60.
Various alloys and
dopants may also be used comprising of but not limited to gadolinium, gallium,
and terbium. The
thermally conductive luminescent element 60 can be single crystal cerium doped
YAG grown via
EFG with a cerium dopant concentration between 0.02% and 2%, preferably
between 0.02% and
0.2% with a thickness greater than 500 microns. Alternatively, the thermally
conductive
luminescent element 60 can be flamesprayed Ce:YAG with an optional post
annealing. The
thermally conductive luminescent element 60 can be formed by flame spraying,
HVOF, plasma
spraying under a controlled atmosphere directly onto the LED 61. This approach
maximizes both
thermal and optical coupling between the thermally conductive luminescent
element and LED 61
by directly bonding to LED 61 rather than using an intermediary material to
bond the LED 61 to
thermally conductive luminescent element 60. Alternately, the thermally
conductive luminescent
element 60 maybe formed using at least one of the following methods; hot
pressing, vacuum
sintering, atmospheric sintering, spark plasma sintering, flame spraying,
plasma spraying, hot
isostatic pressing, cold isostatic pressing, forge sintering, laser fusion,
plasma fusion, and other
melt based processes. Thermally conductive luminescent element 60 may be
single crystal,
polycrystalline, amorphous, ceramic, or a melted composite of inorganics. As
an example, 100
grams alumina and Ce doped Yag powder which have been mixed together are
placed into a
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container. The powders are melted together using a 2 Kw fiber laser to form a
molten ball within
the volume of the powder. In this manner the powder acts as the crucible for
the molten ball
eliminating any contamination from the container walls. The use of the fiber
laser allows for
formation of the melt in approximately 4 seconds depending on the beam size.
While still in a
molten state the ball may optionally be forged between SiC platens into a
plate. Most preferably
the molten ball is greater than 10 mm in diameter to allow sufficient working
time as a molten
material for secondary processing The plate may be further processed using
vacuum sintering,
atmospheric sintering, or hot isostatic pressing to form a translucent
thermally conductive
luminescent element 60. The use of fiber laser based melt processing is a
preferred method for
the formation of luminescent oxides, nitrides, and oxynitrides as a method of
reducing energy
costs compared to hot pressing or vacuum sintering. The use of controlled
atmospheres including
vacuum, oxygen, hydrogen, argon, nitrogen, and ammonia during the laser based
melting
processes is disclosed. While fiber lasers are preferred the use of localized
actinic radiation to
form a molten mass within a powder mass to form thermally conductive
luminescent element 60
is disclosed.
[00160] FIG 3B depicts a self cooling light source comprising of at least two
thermally
conductive luminescent elements 62 and 63 attached to at least one LED 64. In
this case, both
thermal emission 64 and optical emission 65 can be spread out and extracted
from both sides of
LED 64. In all cases, multiple LEDs allow for parallel, series, anti-parallel,
and combinations of
all three with the appropriate electrical interconnect. In this case, optical
emission 65 can be
substantially similar or different on the two sides of the devices. As an
example, thermally
conductive luminescent element 62 can be 1 mm thick single crystal Ce doped
YAG formed via
EFG bottle which is then sliced into 19 mm×6 mm wafers. The sliced
surface enhances
extraction of the Ce:YAG emission out of the high index of refraction Ce:YAG
material.
Alternately, thermally conductive luminescent element 63 may be a pressed and
sintered
translucent polycrystalline alumina with a thermally fused layer of Mn doped
Strontium
Thiogallate and a layer of Eu doped Strontium Calcium Sulfide within a glass
frit matrix. In this
manner, a wide range of optical emission spectrums can be created.
[00161] In this particular case, the two sides of the devices will emit
slightly different
spectrums. In general, unless an opaque reflector is placed between thermally
conductive
luminescent elements 62 and 63 there will be significant spectral mixing
within this device. This
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configuration can be used for quarter lights, wall washers, chandeliers, and
other light fixtures in
which a substantial portion of the optical emission 65 is required to occur in
two separate
directions. Directional elements such as BEF, microoptics, subwavelength
elements, and
photonic structures impart more or less directionality to the optical emission
65 of either thermal
conductive luminescent elements 62 and/or 63.
[00162] In another example, Cerium doped YAG is formed via flame, HVOF, or
plasma
spraying and then optionally annealed, spark plasma sintered, microwave
sintering, or HIP to
improve its luminescent properties for one or both thermally conductive
luminescent element 62
and/or 63. At least one InGaN LED and at least one AlInGaP LEDs are used for
at least one LED
64.
[00163] In yet another example, high purity aluminum oxide is flamesprayed
directly onto at
least one LED die 64 for thermally conductive luminescent element 62 forming a
translucent
reflector. The emissivity of flame sprayed aluminum oxide is typically 0.8
allowing for enhanced
radiative cooling from that surface. Thermally conductive luminescent element
63 is single
crystal Ce:YAG formed via skull melting and sliced into 0.7 mm thick wafers
0.5 inch x 1 inch in
area with a cerium doping concentration between 0.1% and 2%. In this case,
thermally
conductive luminescent element 62 does not necessarily contain a luminescent
material but acts
as diffuse reflector and thermal spreading element for the heat generated by
both LED 64 and
thermally conductive luminescent element 62. By embedding LED 64 directly into
thermally
conductive luminescent element 62 it is possible to eliminate pick and place,
die attachment
processes and materials, and maximize both thermal transfer 64 and optical
emission 65 by
eliminating unnecessary interfaces. Additional luminescent materials and
opaque reflectors can
be positioned within or coating onto either thermally conductive luminescent
elements 62 or 63.
Pockets or embedded die can recess the die such that printing techniques
including but not
limited to inkjet, silkscreen printing, syringe dispensing, and lithographic
means.
[00164] FIG 3C depicts two thermally conductive luminescent elements 72 and 74
providing
thermal conduction paths 74 and 79 to additional cooling means 71 and 73. In
this case,
thermally conductive luminescent elements 72 and 74 allow for thermal emission
76 and optical
emission 77 and also provide for thermal conduction paths 74 and 79.
Additional cooling means
71 and 73 may also provide for electrical connection to LED 75 via
interconnect means
previously disclosed in FIG. 2. One or more additional cooling means 71 and 73
further enhance
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the amount of heat that can be dissipated by the device. As an example, a
typical natural
convection coefficient is 20 W/m2/K and Ce:YAG has an emissivity of 0.8 near
room
temperature. A self cooling light source comprising of two 1/4 inch x 1/2 inch
x 1 mm thick
pieces of Ce:YAG 72 and 74 with four direct attach LEDs 75 soldered on silver
thick film
interconnect traces has a surface area of approximately 2.3 cm2. Using natural
convection and
radiative cooling approximately 500 milliwatts of heat can be dissipated off
the surface of the
self cooling light source if the surface temperature is approximately 1000 C
and the ambient is
250 C and the emissivity is 0.8. Of the 500 milliwatts, 350 milliwatts of heat
is dissipated via
natural convection cooling and 150 milliwatts are dissipated via radiation. A
typical 4000K
spectrum output has an optical efficiency of 300 lumens per optical watt. If
the solid state light
source has a electrical to optical conversion efficiency of 50%, 500
milliwatts of optical output is
generated for every 500 milliwatts of heat generated. Under these conditions a
1/4 inch x 1/2
inch solid state light source operating with a surface temperature of
approximately 1000 C can
output 150 lumens without the need for additional heatsinking means.
[00165] The use of additional cooling means 71 and 73 can be used to
significantly increase this
output level by increase the surface area that heat can be convectively and
radiatively transferred
to the ambient. As is easily seen in the example, increasing the surface area
is directly
proportional to amount of heat that can be dissipated. It is also clear that
the electrical to optical
conversion efficiency dramatically affects the amount of heat generated, which
is a key attribute
of this invention. Unlike conventional LED packages light generated within
this self cooling
solid state light source is extracted out of both sides of the device.
Isotropic extraction as shown
has a 20% theoretical higher efficiency than lambertian extraction. Also using
this approach, the
temperature difference between the LED 75 junction and the surfaces of
thermally conductive
luminescent elements 72 and 74 can be very low if the thermal conductivity is
greater than 10
W/mK and the LEDs 75 are attached such that there is low thermal resistance to
the surrounding
thermally conductive luminescent elements 72 and 74. In addition, cooling
means 71 and 73 may
be physically different to allow for the device to connect to different
external power sources
correctly. As an example, cooling mean 71 may be a pin and cooling means 73
maybe a socket
such that a keyed electrical interconnect is formed. Alternately, cooling
means 71 and 73 may
contain magnets, which allow for attachment of external power sources. Even
more preferably
the magnets have different polarity such that a keyed interconnect can be
formed. Additional
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cooling means 71 and 73 may include, but are not limited to, heatpipes,
metals, glass, ceramics,
boron nitride fibers, carbon fibers, pyrolytic graphite films, and thermally
conductive
composities. As an example, boron nitride nano tubes fibers, as provided by
BNNT Inc., are
pressed with exfoliated boron nitride flakes to form and thermally
interconnected skeleton matrix
using pressing, cold isostatic pressing, warm isostatic pressing, and/or hot
isostatic pressing to
form a solid sheet. The boron nitride nanotube fibers interconnect the boron
nitride flakes and
bond to the surface of the boron nitride flakes such that a continuous thermal
matrix is formed.
The resultant skeleton matrix may then be infused with polymeric or polymeric
ceramic
precursors including but not limited to polysilazane, polysiloxane, glasses,
silicones, and other
polymeric materials to form a composite.
[00166] Alternatively, The boron nitride nano tube fibers may be foamed into a
yarn and woven
into a cloth or felt and then infused with to form a thermally conductive
composite. Alternately,
high thermal conductivity carbon fibers and films may be used but boron
nitride is preferred due
to its low optical absorption compared to carbon based approaches.
Alternately, carbon based
additional cooling means 71 and 73 may include a reflective layer to reduced
absorption losses
and redirect light from the source as well as provide additional cooling.
Additional cooling
means 71 and 73 may also diffuse, reflect, or absorb optical emission 77
emitting between or
from the adjacent edge of thermally conductive luminescent element 72 or 74.
In this manner the
far field emission of the device can be adjusted both from an intensity and
spectral standpoint.
Doubling the surface cooling area using additional cooling means 71 and 73
approximately
doubles the lumen output as long as the thermal resistance of the additional
cooling means 71
and 73 is low.
[00167] FIG 4A depicts at least one LED 85 embedded within thermally
conductive
luminescent element 83. Thermally conductive luminescent element 83 may be
formed via press
sintering of aluminum oxide as known in the art to form a translucent
polycrystalline alumina
TPA with depressions sufficiently deep enough to allow for LED 85 to be
recessed. Luminescent
coating 84 may be substantially only in the pocket formed in thermally
conductive luminescent
element 83 or may cover substantially all the surfaces of thermally conductive
luminescent
element 83. Alternately, single crystal, polycrystalline or amorphous
phosphor, pieces, plates,
rods and particles can be fused or bonded into or onto thermally conductive
luminescent element
83. In this manner, the quantity of luminescent material can be minimized
while maintaining
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high thermal conductivity for the thermally conductive luminescent element 81.
[00168] As an example, single crystal Ce:YAG pieces 1 mm x 1 mm and 300
microns thick can
be fusion bonded into 1.1 mm x 1.1 mm x 500 micron deep pockets formed into
TPA press
sintered plates and then fired at 17000 C in a vacuum for 10 hours such that
the single crystal
YAG pieces are optical and thermally fused into the bottom of the TPA pockets.
LED 85 can then
be bonded into the remaining depth of pocket and be used to excite the single
crystal Ce:YAG
pieces locally. The combined optical emission from LED 85 and the single
crystal Ce:YAG
pieces would be spread out and extracted by the sinter pressed TPA while still
maintaining high
thermal conductivity.
[00169] Alternately, luminescent powders in glass frits, polysiloxane,
polysilazane, and other
transparent binders can be utilized in luminescent coating 84. In particular,
high temperature
binders in luminescent coating 84 such as polysilazane with luminescent
powders, flakes, rods,
fibers and in combination both pre-cured and as a bonding agent can be
positioned between
thermally conductive luminescent element 83 and at least one LED 85.
[00170] Materials with high visible spectrum transmission, lower refractive
index, high thermal
conductivity, and low processing costs for net and final shape are preferred
materials for
thermally conductive luminescent element 83. These materials include, but are
not limited to,
TPA, Spinel, Quartz, Glass, ZnS, ZnSe, ZnO, MgO, AlON, ALN, BN, Diamond, and
Cubic
Zirconia. In particular, Spinel and TPA formed via press sintering are low
cost of manufacture of
net shape parts. The use of techniques used to form TPA parts as seen in
transparent dental braces
as known in the art with luminescent elements either as coatings or bonded
elements can create
thermally conductive luminescent element 83.
[00171] With LED 85 recessed into thermally conductive luminescent element 83,
printing and
lithographic methods can be used to electrically interconnect at least one LED
83 to outside
power sources and/or other LEDs or devices. Unlike wirebonding, this approach
creates a low
profile method of interconnecting LEDs, which eases assembly of multiple
sticks and reduces
costs.
[00172] In one example, LED 85 is bonded into a pocket formed via laser
ablation in a 1 mm
thick wafer of Spinel to form thermally conductive luminescent element 83. In
this example the
Spinel may or may not include luminescent elements or properties. The majority
of the
wavelength conversion instead occurs locally around LED 85 via luminescent
coating 84 and/or
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additional luminescent coating 82. This minimizes the amount of luminescent
material necessary
yet still allows for a low thermal resistance to ambient for the luminescent
materials. While only
a single side is shown in FIG. 4, the light source may also be bonded to
another light source,
heatsink, another transparent/translucent thermally conductive element to
further enhance
cooling and optical distribution from LED 85 and any luminescent elements
within the light
source. LED 85 is bonded into the pocket using polysilazane containing 0.1% to
2% doped
Ce:YAG powder with a particle size below 10 microns.
[00173] Transparent/translucent dielectric layer 81 is inkjet-printed over at
least one LED 85
except contact pads 87 and 86. In the case where LED 85 uses TCO based
contacts, at least a
portion of the TCO is not covered by transparent/translucent dielectric 81 to
allow for electrical
contact. Optionally an additional luminescent coating 82 may be printed or
formed on at least
one LED 85 to allow for additional wavelength conversion and to create a more
uniform spectral
distribution from the device. Interconnects 80 and 88 may then be applied
either before or after
curing of transparent/translucent dielectric 81. Polysilazane, polysiloxane,
glass frit, spin-on
glasses, and organic coatings are examples of transparent/translucent
dielectric 81, preferably the
coatings can maintain transparency above 3000 C. Formulations containing
Polysilazane with
and without luminescent elements are preferred materials for additional
luminescent coating 82,
transparent/translucent dielectric 82 and luminescent coating 84. Preferred
luminescent elements
are powder phosphors, quantum dots, fluorescent dyes (example wavelength
shifting dyes from
Eljen Technologies) and luminescent flakes and fibers.
[00174] Electrical connection to LED 85 is via interconnects 80 and 88 for
lateral LED designs.
Precision inkjet printing of silver conductive inks and/or screen printing of
thick film silver inks
form interconnects 80 and 88. As an example thick film silver paste is screen
printed and fired
onto thermally conductive luminescent element 83 up to the pocket for LED 85.
Transparent/translucent dielectric 81 is inkjet printed such that only
contacts 87 and 86 are left
exposed and the transparent/translucent dielectric 81 covers the rest of the
exposed surface of
LED 85 and at least a portion of thermally conductive luminescent element 83
in a manner to
prevent shorting out LED 85 but still allowing access to the thick film silver
paste conductors
applied earlier. After or before curing of transparent/translucent dielectric
81 and optionally
additional luminescent coating 82, conductive ink is inkjet-printed connecting
the thick film
silver conductor applied previously to the contacts 86 and 87. Using this
approach, alignment
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issues can be overcome due to the availability of inkjet systems with image
recognition and
alignment features while still allowing for low resistance conductors. In
general, while inkjet
printing of conductors can be very accurate and be printed with line widths
under 50 microns, the
thickness is typically limited to under 10 microns which limits the current
carry capacity of long
lines. Using this approach, thick film silver conductors which can be over 50
microns thick can
be used to carry the majority of the current and then short inkjet-printed
traces can be used to
stitch connect between the thick film silver conductors and contacts 87 and
86. Using this
approach, gold wire bonding can be eliminated.
[00175] A transparent/translucent overcoat 89 may be applied over at least a
portion of
interconnects 80 and 89 and/or transparent/translucent dielectric 81,
additional luminescent
coating 82, and thermally conductive luminescent element 83 to environmentally
and/or
electrically isolate the device. Protective barrier layers on LED die 85 can
be formed during LED
fabrication to facilitate or even eliminate the need for
transparent/translucent dielectric layer 81
and allow for direct printing of interconnect 89 and 88 onto contacts 87 and
86 respectively.
Catalytic inks and/or immersion plating techniques allow for the formation of
thicker/lower
resistivity traces for interconnect 89 and 88, eliminate the need for thick
film printing and allow
for the use of inkjet printing for the entire interconnect. Preferred
materials for
transparent/translucent overcoat 89 include but are not limited to
polysilazane, polysiloxane,
spin-on glasses, organics, glass frits, and flame, plasma, HVOF coatings.
Planarization
techniques based on spin-on glasses and/or CMP can be used for
transparent/translucent overcoat
89. Luminescent elements including but not limited to powders, flakes, fibers,
and quantum dots
can be incorporated in transparent/translucent overcoat 89,
transparent/translucent dielectric 81,
and additional luminescent coating 82. Luminescent elements may be spatially
or uniformly
dispersed in these layers.
[00176] FIG 4B depicts a light source in which a luminescent layer 91 is
formed on a
transparent/translucent element 90 containing extraction elements.
Transparent/translucent
element 90 can be, but is not limited to, single crystalline materials such as
sapphire, cubic
zirconia, YAG (doped and undoped), ZnO, TAG (doped and undoped), quartz, GGG
(doped and
undoped), GaN (doped and undoped), AIN, oxynitrides (doped and undoped),
orthosilicates
(doped and undoped), ZnS (doped and undoped), ZnSe (doped and undoped), and
YAGG (doped
and undoped), polycrystalline materials, and amorphous materials such as
glass, ceramic YAG
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(doped and undoped), ALON, Spinel, and TPA. In general, single crystal
materials grown via
verneuil, EFG, HEM, Czochralski, CVD, hydrothermal, skull, and epitaxial means
can be the
transparent/translucent element 90.
[00177] Luminescent layer 91 may be formed directly one
transparent/translucent element 90 or
be formed separately and then bonded to transparent/translucent element 90.
Flamespraying,
plasma spraying, and HVOF techniques can form either or both luminescent layer
91 and
transparent/translucent element 90. The light source can have a
transparent/translucent element
90 with an alpha less than 10 cm-1 throughout the visible spectrum and a
luminescent layer 91
containing at least one luminescent element emitting between 400 nm and 1200
nm. The
luminescent layer 91 can exhibit a refractive index, which is not more than
0.2 different than
transparent/translucent element 90. LED 99 may be InGaN, AlInGaP, ZnO, BN,
Diamond, or
combinations of InGaN, AlInGaP, ZnO, BN, or diamond.
[00178] Both InGaN and AlInGaP LEDs can be used for LED 99 combined with a
transparent/translucent element 90 comprising of at least one of the following
materials;
sapphire, Spinel, quartz, cubic zirconia, ALON, YAG, GGG, TPA, or ZnO and
luminescent layer
91 and/or additional luminescent layer 98 containing Ce doped YAG. An
additional red phosphor
emitting between 585 and 680 nm can be used within luminescent layer 91 and/or
additional
luminescent layer 98. These elements form a self cooling light source which
emits an average
color temperature between 6500K and 1200K that lies substantially on the black
body curve is a
preferred embodiment of this invention. The self cooling light source can emit
an average color
temperature between 4000K and 2000K than lies substantially on the blackbody
curve.
[00179] Multiple self cooling light sources can be used within a fixture,
reflector, optic or
luminaire such that color and intensity variations are averaged out in the far
field. Three or more
self cooling light sources within a fixture, reflector, optic or luminaire
creates a uniform
illumination at a distance greater than 6 inches from the sources.
Transparent/translucent
dielectric layer 93 may be inkjet printed, silk screen printed, formed via
lithographic means and
exhibits an alpha less than 10 cm-1 throughout the visible spectrum.
Interconnect 95 and 94 may
be printed using inkjet, silkscreen, template, or lithographic means.
Catalytic inks and immersion
plating techniques increase conductor thickness and thereby reduce
resistivity. Silver traces with
a trace width less than 500 microns and a reflectivity greater than 50% for
interconnect 95 and
94 reduce absorption of the light generated within the light source. Contacts
96 and 97 on LED
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99 may be on one side only as in lateral devices or comprise one top contact
and one side contact
as previously disclosed in US Patent Application 20060284190, commonly
assigned and herein
incorporated by reference.
[00180] FIG 4C depicts a self-cooling light source with at least one vertical
LED 100 mounted
to or at least partially embedded in thermally conductive luminescent element
103. Composite,
layer, single crystal, polycrystalline, amorphous, and combinations as
described previously can
be used for the thermally conductive luminescent element 103. In this
particular example, one
vertical LED 100 is mounted such that interconnect 101 and 102 may be printed
via inkjet,
silkscreening, or lithographic means directly on thermally conductive
luminescent element 103
and in contact with a side of vertical LED 100. This embodiment eliminates the
need for an
additional dielectric and allows for the use of vertical LED devices which
inherently exhibit
lower Vf than lateral devices. A substrate free LED as described in US patent
application
20090140279 (commonly assigned and incorporated herein by reference) is a
preferred
embodiment for LED 100. Direct die attach and flip chip mounting
configurations may also be
used for LED 100. For the substrate free case, InGaN and/or AlinGaP vertical
LED 100 has TCO
contacts 104 and 105 for LED 100 wherein the interconnects 101 and 102 are
thick film silver
inks which form ohmic contact to the adjacent TCO contact 104 and 105. In this
manner,
absorption losses are minimized and the need for lithographic steps to
fabricate LED 100 is
eliminated or minimized. A self cooling light source contains at least one
vertical LED 100 with
TCO contacts 104 and 105 connected via thick film silver traces for
interconnect 101 and 102
directly bonded to TCO contacts 104 and 105 on a thermally conductive
luminescent element
103. Optionally, bonding layer 106 may be used to mount, improve extraction,
incorporate
additional luminescent materials or position LED 100 onto or within thermally
conductive
luminescent element 103.
[00181] FIG. 5 depicts various shapes of thermally conductive luminescent
elements. FIG. 5A
depicts a substantially flat luminescent element 107. Thickness is a function
of dopant
concentration but typically the thickness ranges from 200 micron to 2 mm for a
uniformly doped
Ce doped YAG with a Cerium doping concentration between 0.02% and 10%. In
order for
efficient thermal spreading to occur, the thermal conductivity of the
thermally conductive
luminescent element 107 needs to be greater than 1 W/mK to adequately handle
average power
densities greater than 0.1 W/cm2 of surface area on luminescent element 107.
If the thermal
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conductivity is to low there is insufficient thermal spreading of the heat
generated within the
device which decreases the ability of the flat luminescent element 107 to cool
itself via natural
convection and radiative means.
[00182] FIG 5B depicts a non-flat (hemispheric) luminescent element 108. In
this case, light
extraction can be enhanced for those rays which are waveguided within the
higher refractive
index of non-flat luminescent element 108. In addition, far field intensity
and wavelength
distributions can be modified. Multiple smaller self cooling light sources
with the same or
different shaped thermally conductive luminescent elements create uniform or
specific far field
intensity and wavelength distributions. The extraction of light generated
within a medium with a
refractive index greater than air is restricted by total internal reflection
per Snell's Law. Shaped
luminescent elements 108 can be used to reduce the average optical path length
of optical rays
required to escape the luminescent element 108. Since absorption losses are
directly proportional
to the optical path length for a given absorption coefficient (alpha),
reducing the average optical
path length directly translates into reduced absorption losses. The spatial
location of where the
optical rays are generated within luminescent element 108, the refractive
index of luminescent
element 108, absorption coefficient (alpha) of luminescent element 108, bulk
and surface
scattering within and on luminescent element 108, and the geometry of
luminescent element 108
can all be modeled as known in the art to optimize the extraction efficiency.
[00183] FIG 5C depicts a non-flat (curved) thermally conductive luminescent
element 109 with
a substantially uniform thickness. In this manner extraction can be enhanced
by maintaining a
uniform thickness of luminescent material. Extrusion, pressing, molding,
sawing, boring, and
flamespraying techniques as known in the art may be used to fabricate various
shapes of
thermally conductive luminescent elements.
[00184] FIG 5D depicts a non-flat (rectangular saw tooth) thermally conductive
luminescent
element 110 with additional surface elements to enhance convection cooling and
optionally to
modify or homogenize the emission output of the self-cooling light source.
Extrusion, pressing,
and molding techniques may be used to form thermally conductive luminescent
element 110.
[00185] FIG 6A depicts a partially embedded LED 108 within a depression in
thermally
conductive luminescent element 107 mounted via bonding layer 109. The
formation of the
depression may be by laser machining, electron beam machining, etching (both
chemical and
mechanical), plasma etching, molding, and machining means. Substrate-free LEDs
may be used
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for partially embedded LED 108 with a thickness less than 300 microns. By
embedding partially
embedded LED 108 in thermally conductive wavelength conversion element 107,
the thermal
resistance between the two elements can be reduced which lowers the junction
temperature of the
LED for a given drive level. Optionally, more of the emission from partially
embedded LED into
thermally conductive luminescent element 107 can be coupled thereby changing
the color
temperature of the self cooling light source.
[00186] FIG 6B depicts at least one LED 112 bonded onto thermally conductive
luminescent
element 110 via bonding layer 111. In this case, bonding layer 111 should
exhibit a thermal
conductivity greater than 1 W/mK and an alpha less than 10 cm-1 for the
emission wavelengths
of LED 112.
[00187] FIG 7 depicts various printed contacts for TCO contact based LEDs.
FIG. 7A depicts a
vertical LED comprising of a top silver paste contact 113 on TCO layer 114 on
p layer 117.
Active region 116 is between p layer 117 and n layer 115 with n layer 115
covered with TCO
contact 118 and bottom silver paste contact 119. A substrate free LED allows
dual sided growth
of TCO contact layers 114 and 118 on substrate free LED structures comprising
of p layer 117,
active layer 116 and n layer 115. Thick film high temperature silver paste
contacts 113 and 119
can be printed on LEDs with TCO contacts 114 and 118 and fired at temperatures
greater than
2000 C in various atmospheres to form a low optical absorption, low Vf, and
substantially
lithography free LED devices.
[00188] FIG 7B depicts a lateral device with printed/inkjet-printed contacts
120 and 125. In all
cases, ohmic contact to the n layer may include or not include an intermediary
TCO layer to form
reasonable ohmic contact. In FIG. 7B, TCO 122 is grown on p layer 123. Active
layer 124 is
between p layer 123 and n layer 125. TCO 122 is doped ZnO grown via CVD with a
resistivity
less than 0.003 ohm-cm and greater than 1000 Angstroms thick. Printed etch
masks allow for
etch of the step down to n layer 125. As an example, an AlInGaP LED epi may be
grown on
GaAs. The wafer can be etched and patterned to form the lateral device having
TCO 122 on the p
layer 123. Printed contacts 120 and 125 are formed on TCO 122 and n layer 125.
Optionally an
additional TCO layer maybe formed of n layer 125 to further reduce Vf. The
addition of a
eutectic solder layer to printed contact 120 and 125 to create a direct die
attach die is also
disclosed. In a preferred embodiment, the AlinGaP epi is removed via chemical
etching using a
sacrificial etching layer between the AlinGaP and GaAs substrate as known in
the art. The
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resulting direct attach die may be additionally wafer bonded to GaN substrates
as disclosed in
U.S. Pat. Nos. 7,592,637, 7,727,790, 8,017,415, 8,158,983, and 8,163,582, and
US Patent
Applications Publication Nos. 20090140279 and 20100038656, commonly assigned
as the
present application and herein incorporated by reference.
[00189] FIG 7C depicts a printed contact with a top contact 126 and side
contacts 132 and 130.
Again TCO 127 forms a low ohmic transparent contact to p layer 128 and the
active region 129
is between p layer 128 and n layer 130. Side contacts 131 and 132 contact the
side walls of n
layer 130. N layer 130 is greater than 10 microns of thickness. Even more
preferably, the
thickness of n layer 130 is greater than 50 microns but less than 250 microns.
[00190] FIG 8 depicts various methods of changing the far field distribution
of single self
cooling source. In FIG. 8A, the refractive indices, geometry, and spacing of
the LEDs 136, the
wavelength conversion elements 133 and 135, and the bonding material 137 will
determine the
far field distribution of the source. The far field distribution is determined
by where the optical
rays exit, how much of the optical rays, the direction of the optical rays and
the spectrum of
optical rays that exit a particular spatial point on the single self cooling
source. FIG. 8 illustrates
various reflectors, scattering elements, and diffusers which modify where, how
much, which way
and the spectrum of the light rays emitted from the source. One or more
wavelength conversion
elements for mounting LEDs 136 can be used although two wavelength conversion
elements 133
and 135 are depicted. Multiple LEDs 136 can be mounted on one or more surface
of the one
wavelength conversion element 133. Based on these parameters, radiation will
be emitted from
the structure or light guided within the source. Additionally, edge element
134 may also modify
the far field distribution out of the device. Edge element 134 and bonding
materials 137 may be
translucent, transparent, opaque, and/or luminescent. Luminescent powders
within a transparent
matrix for edge element 134 and bonding materials 137 can modify the emission
spectrum as
well as the far field intensity distribution.
[00191] FIG. 8B depicts a self cooling light source where the entire end of
the self cooling light
source is substantially covered with a scattering element 139 within a matrix
138. Additionally,
scattering element 139 and matrix 138 may extend to encompass not only edges
of the self
cooling light source but also substantial portions of the other surfaces of
the self cooling light
source. In this manner, light emitted from all the surface of the self cooling
light source can be
redirected to modify the far field intensity distribution. Luminescent
materials for scattering
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element 139 are excited by at least a portion of the spectrum emitted by the
self cooling light
source.
[00192] FIG 8C depicts edge turning element 140 comprising of metal, diffuse
scatterer,
dielectric mirror, and/or translucent material whereby at least a portion of
the light generated
within the LED or wavelength conversion elements are redirected as depicted in
ray 141.
[00193] FIG 8D depicts an outer coating 142 which may be translucent,
partially opaque,
polarized, and/or luminescent. The far field intensity, polarization, and
wavelength distribution
can be modified both in the near field and far field and spatial information
can be imparted onto
the self cooling light source. As an example, a self cooling light source with
a shape similar to a
candle flame may have a spectrally variable outer coating 142 such that red
wavelengths are
emitted more readily near the tip of the candle flame and blue wavelengths are
emitted more
readily near the base of the candle flame. In this fashion, the spatially
spectral characteristics of a
candle flame could be more closely matched. Using this technique a wide range
of decorative
light sources can be formed without the need for additional optical elements.
[00194] In another example, outer coating 142 may comprise a reflective
coating such as
aluminum into which openings are etched or mechanically formed. More
specifically, sunlight
readable indicator lights can be formed using this technique as warning,
emergency, or
cautionary indicators. The use of circular polarizers within outer coating 142
can enhance
sunlight readability. Alternately, outer coating 142 could be patterned to
depict a pedestrian
crossing symbol that could be either direct viewed or viewed through an
external optic thereby
creating a ultra compact warning sign for crosswalks and other traffic related
applications. In
another example, outer coating 142 may comprise spectrally selective
emissivity coating such
that the emissivity of the self cooling light source is enhanced for
wavelengths longer than 700
nm. By enhancing the infrared and far infrared emissivity of the self cooling
light source more
efficient light sources can be realized. As stated in the previous example of
FIG. 3 the radiation
cooling represents a significant percentage of the cooling in self cooling
light sources. It is
preferred that high emissivity coatings be used for outer coating 142 to
maximize cooling from
the surface of the self cooling light source. Most preferred is an outer
coating 142 with an
emissivity greater than 0.5. Depending on the maximum surface temperature the
radiative
cooling can represent between 20% and 50% of the heat dissipation of the
source.
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[00195] FIG 9A depicts the use of die shaping of optical devices within a
media 143. As an
example, LED 145 contains an active region 146 embedded within media 143.
Using ray tracing
techniques known in the art, there is an optimum angle 144 to maximize the
amount of radiation
transferred into media 143. Typically, semiconductor materials exhibit high
refractive index
which tends to lead to light trapping within the LED 145. In FIG. 9A the
optimum angle 144
subtends the active region 146 as shown in the figure.
[00196] Alternately, FIG. 9B depicts that surfaces 149, 148 and 147 may be non-
orthogonal
forming a non square or rectangular die. In both these cases, light trapped
within the LED 150
can more efficiently escape the die. The use of both forms of die shaping
together is preferred.
The use of non-rectangular shapes for LED 150 embedded within a wavelength
conversion
element to enhance extraction efficiency is a preferred embodiment of this
invention.
[00197] FIG 10A depicts different mounting methods for LEDs 152 and 154 within
wavelength
conversion element 151 and the use of bonding layers 153 and 155. Bonding
layers 153 and 155
thermally, optically, and mechanically attach LEDs 152 and 154 to at least one
surface of
wavelength conversion element 151. LED 152 is at least partially embedded
within wavelength
conversion element 151 which can allow for both edge and surface coupling of
radiation emitted
by the LED 152 into wavelength conversion element 151 using bonding layer 153.
Alternately,
LED 154 is substantially coupled to the surface of wavelength conversion
element 151 using
bonding layer 155. Bonding layers 55 and 153 may be eliminated where
wavelength conversion
element 151 is directly bondable to LEDs 154 and 152 using wafer boding,
fusion bonding, or
melt bonding.
[00198] FIG. 10B depicts a typical transmission spectrum 157 of wavelength
conversion
elements. Blue emission 156 is absorbed by the wavelength conversion element
and then
reemitted at longer wavelengths. Red emission 158 is typically not strongly
absorbed and
therefore behaves as if the wavelength conversion element 151 is simply a
waveguide. Virtually
any color light source can be realized by properly selecting the right
combination of blue and red
LEDs within the wavelength conversion element 151. While wavelength conversion
is a
preferred embodiment, FIG. 10B illustrates that self-cooling light sources do
not require that the
wavelength conversion element 151 be luminescent. In the case of a red self-
cooling light source,
wavelength conversion element 151 may be used to optically distribute and
thermally cool the
LEDS without wavelength conversion. Alternately, UV responsive luminescent
materials can be
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used for wavelength conversion element 162 with UV LEDs 164 or 165. The
transmission
spectrum 157 is shifted to shorter wavelength which allows for the formation
of self cooling light
sources which exhibit white body colors, as seen in fluorescent light sources.
This wavelength
shift however is offset by somewhat reduced efficiency due to larger Stokes
shift losses.
[00199] FIG 11 depicts a color tunable self-cooling light source containing at
least one
wavelength conversion element 162 with an electrical interconnect 168, at
least one blue LED
164, at least one red LED 163, and drive electronics 165, 166, and 167.
Electrical interconnect
168 is a thick film printed silver ink. Three separate pins 159, 160, and 161
to provide
independent control of blue led 164 from red LED 163. Pins 159, 160, and 161
can be physically
shaped to allow for keying thereby ensuring that the self-cooling light source
is properly
connected to external power sources. While pins 159, 160 and 161 are
substantially shown on the
same side of wavelength conversion element 162, the use of alternate pin
configurations are
anticipated by the inventors. In general, external electrical interconnect can
be accomplished via
pins 159, 160, and 161 as shown in FIG. 11 or via alternate interconnect means
including, but not
limited to, flex circuits, rigid elements containing electrical traces,
coaxial wires, shielded and
unshielded twisted pairs, and edge type connectors on or connected to
wavelength conversion
element 162 are embodiments of this invention. Additionally feedthroughs
within wavelength
conversion element 162 can be formed via mechanical, chemical etching, laser,
waterjet, or other
subtractive means to form external interconnects to any of the previous listed
electrical
interconnect elements in any plane of the wavelength conversion element 162.
[00200] Drive electronics 165, 166, and 167 may comprise both active and
passive elements
ranging from resistors, caps, and inductors. In this manner, a variety of
external drive inputs can
be used to excite the light source. As an example, a current source chip may
be mounted onto the
wavelength conversion element 162 and connected to an external voltage source
via pins
159,160, and 161. As known in the art, typical current source chips can also
have an external
resistor which sets the current which flows through the current source chip.
The external resistor
may be mounted on the wavelength conversion element 162 or be external to the
source and
connected to current source chip via pins 159, 160, and 161. As the
functionality within the light
source increases, the number pins may be increased. Integrated circuits can be
used for drive
electronics 165, 166, and/or 167. Wavelength conversion element 162 also
substantially cools the
drive electronics 165, 166, and 167 as well as LEDs 164 and 165. Pins 159,
160, and 161 may be
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used to remove heat from the heat generating elements of the light source.
Wavelength
conversion element 162 is luminescent and provides for optical diffusion and
cooling of the heat
generating elements within the self cooling light source In this case,
additional wavelength
emitters may be added including, but not limited to, UV, violet, cyan, green,
yellow, orange, deep
red, and infrared
[00201] FIG 12 depicts a self cooling light source with an embedded active
driver 172 capable
of driving multiple LEDs 171, all of which are mounted and cooled
substantially by wavelength
conversion element 169. Input pins 170 may provide power input to active
driver 172 but also
provide outputs including, but not limited to, light source temperature,
ambient temperature, light
output levels, motion detection, infrared communication links, and dimming
controls. As
previously disclosed, the transmission spectrum of the wavelength conversion
element 169
allows for low absorption of longer wavelengths. An infrared/wireless emitter
and receiver can
be integrated into embedded active driver 172 so that the self cooling light
source could also
serve as a communication link for computers, TVs, wireless devices within a
room, building, or
outside. This integration eliminates the need for additional wiring and
devices.
[00202] FIG 13A depicts the use of electrical contacts 174 and 175 as
additional thermal
conduction paths for extracting heat 178 out of the wavelength conversion
elements 173 and 174
additionally cooling paths for LED 177. LED 177 may be direct attach or flip
chip and may be a
lateral, vertical, or edge contact die. As an example, electrical contact 174
and 175 may comprise
0.3 mm thick Tin plated aluminum plates sandwiched between wavelength
conversion elements
173 and 174. In this manner both electrical input and additional cooling means
for wavelength
conversion elements 173 and 174 as well as LED 177 can be realized.
[00203] FIG 13B depicts a rod based light source with LEDs 180 within rod
shaped wavelength
conversion element 182 wherein heat 181 is additionally extracted via
conduction to contacts
178 and 179. Alternately, hemispherical, pyramidal, and other non-flat shapes
and cross-sections
maybe used for wavelength conversion element 182 to create a desired
intensity, polarization,
and wavelength distribution. Cross-section and other shapes, such as spheres
and pyramids,
maximize the surface area to volume ratio, so that convective and radiative
cooling off the
surface of the wavelength conversion element 182 is maximized while using the
least amount of
material possible. As an example, contacts 178 and 179 may comprise 2 mm
copper heatpipes
thermally bonded via a bonding method including but not limited to gluing,
mechanical,
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soldering, or brazing means to wavelength conversion element 182. In this
manner additional
cooling maybe realized. LEDs 180 may be mounted on the surface or inside of
wavelength
conversion element 182. As an example LEDs 180 may be mounted on the flat
surface of two
hemispherical wavelength conversion elements 182. The two hemispherical
wavelength
conversion elements 182 are bonded together to form a spherical self cooling
light source with
the LEDs 180 embedded within the wavelength conversion elements 182.
[00204] Alternately, the LEDs 180 may be mounted on the spherical surface of
the
hemispherical wavelength conversion element 182 such the light generated by
LED 180
generally is coupled into the hemispherical wavelength conversion element 182.
Optionally, the
flat surface of hemispherical wavelength conversion 182 may have additional
luminescent
coatings such that the light emitted by LEDs 180 is effectively coupled by the
hemispherical
wavelength conversion element 182 onto the luminescent bonding layer which
reflects,
transmits, converts or otherwise emits both the light emitted by the LEDs 180
and any
luminescent elements back out of the hemispherical wavelength conversion
element 182. The
advantage of this approach is that the LEDs 180 are mounted closer to the
cooling surface of the
wavelength conversion element, a high degree of mixing is possible, and the
angular distribution
of the source can be controlled by how well the bonding layer is index matched
to the
wavelength conversion element 182. Bonding two hemispherical wavelength
conversion
elements 182 together forms a spherical source with externally mounted LEDs
180.
[00205] FIG 14 depicts a self cooling light source with at least two thermally
and/or optically
separated zones. Waveguide 183 containing LEDs 184 is optically and/or
thermally isolated via
barrier 185 from waveguide 186 and LEDs 187. Dual colored light sources can be
formed.
Alternately, temperature sensitive LEDs such as AlInGaP can be thermally
isolated from more
temperature stable InGaN LEDs. Waveguide 183 and 186 may or may not provide
luminescent
conversion. LEDs 184 are AlInGaP (red) LEDs mounted to waveguide 183 made out
of sapphire.
LEDs 187 are InGaN blue LEDs mounted onto waveguide 186 which is single
crystal Ce:YAG.
The barrier 185 is a low thermal conductivity alumina casting material.
AlinGaP efficiency drops
by 40% for junction temperatures over 600 C while InGaN efficiency will drop
only by 10% for
a similar junction temperature. White light sources can be realized by
thermally isolating the
AlinGap from the InGaN high overall efficiency. Using this approach the two
sections operate at
different surface temperatures. The InGaN LED 187 and waveguide 186 operates
at a higher
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surface temperature while the AlInGaP LED 184 and waveguide 183 operates at a
lower surface
temperature.
[00206] FIG 15 depicts Blue LED 189 mounted to wavelength conversion element
188 and Red
LED 192 with driver 190. Power lines 191, 193, 194, and 195 and control line
196 are also
shown. Red LED 192 drive level is set via control line 196 by controlling the
voltage/current
flow available via power line input 191 and output 195. Typically driver 190
would be a constant
current source or variable resistor controlled via control line 196. As stated
earlier, blue LED 189
is typically InGaN with more stable regarding temperature, life and drive
levels than red LED
192 typically AlInGaP. As an example, TPA coated with europium doped strontium
thiogallate
singularly or as a multiphase with another gallate, such as Eu doped magnesium
gallate for
wavelength conversion element 188 is excited by 450 nm LED 189. 615 nm AlinGaP
red LED
192 is also mounted on the wavelength conversion element 188 along with driver
190. Heat is
spread out via wavelength conversion element 188 as well as the radiation
emitted by blue LED
189 and red LED 192. Control line 196 is used to adjust the color temperature
of the source
within a range by increasing the current to red LED 192 relative to the fixed
output of blue LED
189. Additional LEDs and other emission wavelengths can be used.
[00207] FIG 16 depicts a white light spectrum for a typical solid state light
source. FIG. 16A
illustrates high color temperature low CRI spectrum 197 typically created by
blue LEDS and
Ce:YAG phosphors. Additional phosphors are typically added to add more red
content in order to
lower the color temperature as shown in spectrum 198. This red addition
however requires that a
portion of the blue and in some cases some of the green be absorbed which
reduces overall
efficiency.
[00208] FIG 16B depicts the typical spectrum 199 from a blue LED, Ce:YAG
phosphor, and red
LED. The red LED spectrum is additive as shown in spectrum 200. In general,
both methods of
FIG. 16 are used to form self-cooling light source described in this
invention.
[00209] FIG 17 depicts a high CRI white light spectrum 201 formed by mixing
phosphor and
LED spectrums A, B, C, D, and E. Spectral ranges can be mixed, diffused and
converted within
the wavelength conversion elements disclosed in this invention in addition to
cooling,
mechanically mounting, environmentally protecting, and electrically
interconnecting the devices
needed to generate the spectrums depicted. As an example, spectrum B may be
derived from a
blue 440 nm emitting LED, a portion whose output is used to excite a single
crystal Ce:YAG
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luminescent element as previously disclosed to form spectrum A between 500 nm
and 600 nm.
Spectrum C may comprise a cyan quantum dot which also converts a portion of
output of the
blue 440 nm emitting LED into 490 to 500 nm wavelengths. Spectrum D maybe
produced by
using a wavelength shifter die such as Eljen-284 (Eljen Technologies Inc.) to
convert a portion of
Spectrum A into wavelengths between 580 nm and 700 nm and Spectrum E maybe a
AlinGap
red LED emitting between 600 and 800 nm. Infrared emitters or converters may
also be added
for communication links, security, and night vision applications.
[00210] FIG 18 depicts various shapes of waveguides and luminescent coatings.
FIG. 18A
depicts a textured thermally conductive waveguide 203 with a luminescent
coating 202. As an
example, a micro lens array may be press sintered out of TPA and coated with
Ce:YAG via flame
spraying. FIG. 18B depicts an EFG formed single crystal Ce:YAG rod 204 coated
with a high
emissivity coating 205 with a refractive index substantially equal to the
geometric mean of
Ce:YAG and air and a thickness greater than 300 angstroms. In the previous
example of FIG. 3
the importance of radiative cooling even at low surface temperatures is
disclosed. In this
example the radiative cooling can represent up to 30% of the total heat
dissipated as long as the
emissivity of the surface is above 0.8. Emissivity varies from very low (0.01)
for polished metals
to very high 0.98 for carbon black surfaces. The use of high emissivity
coatings 205 that are also
transparent in the visible spectrum are most preferred. These include but not
limited to silicates,
glasses, organics, nitrides, oxynitrides, and oxides. Even more preferred are
high emissivity
coatings 205 that also exhibit a thermal conductivity greater than 1 W/mK. The
high emissivity
coating 205 thickness is preferably between 1000 angstroms and 5 microns
thick. The emissivity
coating 205 may also be luminescent.
[00211] FIG 19A depicts a self cooling light source 206 and an optic 207.
Optic 207 may be
reflective, transparent, translucent or opaque. Both decorative and
directional means may be used
as an optic. Parabolic, elliptical, non-imaging and other optical
configuration as known in the art
may be used as an optic. In particular, the use of prismatic surface elements
on optic 207 wherein
a substantial portion of the light emitted by self cooling light source 206
are redirected in a
direction orthogonal to their original direction are embodiments of this
invention. Optic 207
redirects a portion of the light from light source 206 downward. The optic 207
may comprise, but
is not limited to, glass, single crystal, polymer or other
translucent/transparent materials. Colored
translucent/transparent materials create a specific decorative or functional
appearance. As an
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example a light source 206 may be embedded into an orange glass glob to form a
decorative
lamp. The elimination of the need for a heatsink greatly simplifies the
optical design and allows
for a wider range of reflectors and optical elements.
[00212] Alternately, FIG. 19B depicts an external movable reflector 209 which
slides 210 up
and down light source 208. Using this approach the percentage of downward
light can be
adjusted relative to the amount of diffuse lighting. Again the elimination of
heatsinks and the
formation of an extended source greatly simplifies the optical design of the
light fixture.
[00213] FIG 20 depicts methods of adjusting the far field distributions of
single light sources.
In FIG. 20A, the far field distribution both intensity and wavelength can be
adjusted by mounting
methods for the LEDs 214 and 216 within or onto wavelength conversion element
211. LED 214
depicts an embedded LED 214 in which a pocket or depression is formed in
wavelength
conversion element 211. This embedded LED changes the ratio of transmitted
rays 212 to
waveguided rays 213 relative to surface mounted LED 216 which has a
substantially different
ratio of transmitted rays 217 to waveguided rays 218.
[00214] In FIG. 20B an optic 220 extracts light off of more than one surface
of light source 219.
In this case, rays 221 are redirected substantially orthogonally to the
surface the rays were
emitted from and mixed with the rays from other surfaces of light source 219.
The optic 220 may
be a prism, lens, parabolic, elliptical, asperical, or free formed shape.
[00215] FIG. 20C depicts embedded LEDs 225 in embedded occlusions 226 with
edge-turning
elements 224 which were previously disclosed. Rays 227 and 223 can be directed
substantially
orthogonally out of the wavelength conversion element 222.
[00216] FIG. 21A depicts a LED die 230 bonded into a wavelength conversion
element
containing depressions or pockets 228 using a bonding layer 229, a electrical
interconnect layer
231 and protective dielectric layer 232. As an example, a 500 microns thick
Ce:YAG single
crystal wafer is laser drilled to have a pocket into which lateral LED die 230
is placed and
bonded using a polysilazane. The polysilizane is at least partially cured. The
polysilizane is
further coated using inkjet printing techniques to cover all but the metal
contact pads of lateral
LED die 230. Conductive ink is printed via, but not limited to, inkjet,
screenprinting, tampo, or
lithographic means such that the exposed metal contact pads of lateral LED die
230 are
interconnected electrically via electrical interconnect layer 231. Nanosilver,
silver paste, and
other highly reflective printable electrically conductive inks, pastes or
coatings are the preferred
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conductive ink. A protective dielectric layer 232 is applied via, but not
limited to, inkjet, spin
coating, dip coating, slot coating, roll coating and evaporative coating
means.
[00217] FIG 21B depicts LED 233 mounted to the surface of waveguide 234 most
of the rays
do not couple to the waveguide efficiently. FIG. 21C depicts embedded LED 235
within a pocket
in waveguide 236. Optically and thermally there is more coupling into
waveguide 236. In
addition the use of embedded LED 235 allows for simplified interconnect as
depicted in FIG.
21A. Further luminescent insert 237 may be used to convert at least a portion
of the spectrum
from LED 233 or 235. In this case lower cost materials may be used for
waveguide 234 and 236
respectively. As an example, single crystal Ce:YAG inserts 50 microns thick
with a Ce doping
concentration greater than 0.2% with substantially the same area as embedded
LED 235 can be
inserted into press sintered TPA waveguides. In this manner, the amount of
luminescent material
can be minimized while still realizing the benefit of a thermally conductive
element including,
but not limited to, waveguide, increased thermal cooling surface, and optical
spreading of the
light over an area larger than either luminescent insert 237 or LED 235.
Ceramic, polycrystalline,
amorphous, composite and pressed powders of luminescent materials may be used
for
luminescent insert 237. A waveguide 236 with a thermal conductivity greater
than 1 W/mK can
work with a luminescent insert 237. LED 235 comprises of one or more of the
LED which is an
InGaN, AlGaN, and/or AlInGaP based LED in waveguide 236 with a thermal
conductivity
greater than 1 W/mK with at least one luminescent insert 237.
[00218] FIG 22 depicts a prior art LED light strip. Enclosure 2202 contains
LED packages
which typically comprise a submount 2208, LED die 2206, and an encapsulating
lens 2204. The
inside of enclosure 2202 is reflective the light emitted by the LED die 2206
and a diffuser/lens
element 2200 is placed at distance sufficient for the light from the
individual LED packages to
mix and form a spatially uniform output on the output surface of the
diffuser/lens element 2200.
Heat is extracted from the LED packages through the enclosure 2202 to heatsink
2210. In
general the majority of the heat generated travels in the opposite direction
of the light emission
which is through diffuser/lens element 2200. From a practical standpoint the
distance between
the LED packages is the minimum distance the diffuser/lens element 2200 needs
to be away
from the LED packages to get uniformity. In this configuration the
diffuser/lens element 2200
typically is typically made of organic materials (plastic) and even the
enclosure 2202 and
heatsink 2210 may be filled with organic materials. For example the
diffuser/lens element 2200
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is typically acrylic or polycarbonate which is flammable under exposure to
flame.
[00219] Unfortunately, the techniques known in the art to reduce flame
spreading and smoke
adversely affect the optical transmission and optical absorption losses in
these materials. This
approach suffers from low lumens per gram due the weight of the heatsink,
typically less than 1
lumen/gram. Because the majority of the light emitted by the LEDs in this
configuration is
emanating from a point source, the LED 2206 of the light source uniformity
must be
accomplished within the diffuser/lens element 2200 in a single pass. The LEDs
in these prior art
light sources are directly viewable (imaged by the naked eye through the
diffuser/lens element)
due to the short optical path length between the LED and the diffuser.
Therefore, there is
minimal light bounces or recycling before emission from the light source.
Intensity, uniformity
and wavelength averaging all suffer due to the lack of mixing and averaging.
Also the thickness
of the source must be increased to allow for mixing to occur when the LEDs are
mounted in this
direct view configuration. This makes it difficult to achieve aesthetically
pleasing low profile
light sources.
[00220] FIG 23 depicts a prior art solid state waveguide based panel light
with a waveguide
2305 typically made of acrylic and polycarbonate. In this configuration the
amount of
flammable material is even larger with up to several pounds of organic
material that is used to
form a large waveguide as required in a 2 ft.x 2 ft. or 2 ft. x 4 ft troffer.
The required optical
properties such as transmission and low scatter or absorption losses are even
more strict in this
configuration. This makes it very difficult to use conventional flame
retardant techniques on
these elements. Light from the LED package 2313 is coupled to the waveguide
2305 using a
reflector 2308. Heat generated by the LED package 2313 is dissipated by
thermal conduction to
appended heatsink 2310 (typically an outer metal frame or bezel). A rear
reflector 2304,
extraction elements 2306, end reflector 2302, and top diffuser 2300 are used
to direct light within
the waveguide 2305 through the top diffuser 2300. Typically reflectors and
diffusers are all
organic and further enhance the flammability and toxic smoke generation upon
exposure to open
flames. In general, the use of large area organic materials in films,
diffusers, organic optical
waveguides, organic reflective films, and organic elements within LED packages
can pose an
increased risk to firefighters and occupants during a fire within a structure.
Many organics like
acrylic emit not only smoke but also toxic and noxious chemicals when burned.
The need exists
for non-flammable solid state light sources.
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[00221] This invention overcomes all of the aforementioned deficiencies by
indirectly mounting
the LEDs within a light recycling cavity formed by a reflector and an
optically reflective and
light transmitting thermally conductive element which functions as a
reflective exit aperture to
the light recycling cavity and simultaneously removes the heat generated by
the LEDs from the
light emitting surface of the light transmitting thermally conductive element.
[00222] FIG 24 depicts a non-flammable self cooling light source of the
present invention in
which the emitting and cooling surfaces are substantially the same. As an
example, the light
source contains at least one LED 2414, at least one reflector element 2412,
and at least one light
transmitting thermally conductive element 2400. The at least one light
transmitting thermally
conductive element 2400 has at least one exterior light emitting surface. The
at least one exterior
light emitting surface 2401 faces outward into the room or lighted area, while
the interior surface
2403 of at least one light transmitting thermally conductive element 2400
faces into the light
recycling cavity 2409 formed by the at least one light transmitting thermally
conductive element
2400 and at least one reflector element 2412. The at least one LED 2414 is
contained within the
light recycling cavity 2409 and in thermal contact with said at least one
light transmitting
thermally conductive element 2400 such that the heat from said at least one
LED 2414 is
transferred via thermal conduction from said at least one LED 2414 to the
exterior light emitting
surfaces 2401 of said at least one light transmitting thermally conductive
element 2400 and
wherein the heat is removed to ambient via convection and radiative cooling
from the exterior
light emitting surfaces 2401 of the at least one light transmitting thermally
conductive element
2400.
[00223] The light transmitting thermally conductive element 2400 has a thermal
conductivity
that is greater than 1 W/mK. More preferably the light transmitting thermally
conductive
element 2400 has a thermal conductivity that is greater than 10 W/mK. Most
preferably the light
transmitting thermally conductive element 2400 has a thermal conductivity that
is greater than 20
W/mK. In this particular embodiment at least one LED 2414 (this can be one of
the following: a
direct attach LED die, flip chip LED die, wire bonded LED die or other LED die
configuration
with or without wavelength conversion layer 2416 or an LED package with
integrated
wavelength conversion layer 2416) is soldered, wirebonded, adhesively bonded
or mechanically
attached to at least one light transmitting thermally conductive element 2400
either via or in
addition to being attached to interconnect 2402 (which is comprised of at
least one electrically
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conductive trace printed and fired on light transmitting thermally conductive
element 2400).
This electrical conductive interconnect is preferably highly reflective or
light transparent.
Interconnect 2402 may be conductive inks containing silver with either organic
or inorganic
binders. The binders are removed during firing resulting in a metal trace.
Light transmitting
thermally conductive element 2400 is typically composed of inorganic materials
such as but not
limited to alumina, sapphire, Yag, GGG, Spinel, and other inorganic high
thermal conductivity
materials which exhibit light absorption losses below 1 cm-1 throughout the
visible wavelength
range, a thermal conductivity greater than 1 W/mK, and are non-flammable when
exposed to a
flame. Alternately, glass composites and non-flammable inorganic/organic
composites may be
used such as polysilazane/hBN. Polysilazane as well as other siloxanes may be
used based on
their tendency to convert to non-flammable residues upon exposure to flames.
Alumina is
preferred due to its ready availability in thin layers, low cost, and
compatibility with high
temperature process like sintering of conductive inks and soldering. Alumina
has a thermal
conductivity of greater than 20 Watt/m-K.
[00224] Whereas materials with high light transmissivity (TPA, Spinel,
sapphire, etc.) may be
used as the light transmissive thermally conductive element 2400, these
materials are relatively
expensive. Lower cost ceramics tend to be more opaque and have low light
transmission and
higher reflectivity. However, it has been found by practicing the tenets of
this invention that high
net light extraction efficiency may be achieved with these materials. For
example commercial
grade Alumina (96% A1203) 500 micrometers thick has an optical transmission of
less than 16%
with a reflectivity of 84%. Visually it has a white body and appears opaque.
However, by
utilizing this highly reflective material (e.g. alumina) as the light
transmitting thermally
conductive element and forming a light recycling cavity 2409 with reflector
2412 greater than
70% of the light may be extracted from the light recycling cavity. Using these
more reflective
(84%) materials, light emitted from the LED(s) 2414 and optionally wavelength
converted,
impinges on the reflector 2412 of the light recycling cavity 2409 and is
reflected 2422 to the
light transmitting thermally conductive element 2400 where 16% would be
transmitted and
emitted 2424 from the outside surface 2401 of light transmitting thermally
conductive element
2400. However, the light not transmitted (84%) is reflected 2426 back to the
reflector 2412
where it again is reflected back to the light transmitting thermally
conductive element 2400 and
¨13.4% (16% of the 84% reflected light) is transmitted through and emitted
2428 from the
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outside surface 2401 of light transmitting thermally conductive element 2400.
This diminishing
cycle, for each reflection, continues until a very high percentage of the
original light emitted by
the LED(s) 2414 passes through the white reflective (almost opaque) alumina
and is emitted by
the light source. Remarkably, extraction efficiencies of greater than 70% have
been achieved
with alumina (A1203) elements that have less than 17% in line transmittance.
These efficiencies
are measured by measuring the raw lumen output of the LED(s) 2414 themselves
at a given
voltage and current and then measuring the output from the light recycling
cavity 2409 with the
LED(s) 2414 (enclosed within the closed cavity) driven at the same voltage and
current. The
very high number of reflections within the light recycling cavity 2409 and the
fact that the LED's
2414 light emitting surface faces away from the light transmitting thermally
conductive element
2400 combined with the highly reflective and white opaque appearance of the
light transmitting
thermally conductive element 2400 results in a very uniform and monolithic
appearance to the
light emitting surface of the light source 2401. This overcomes one of the
biggest complaints
about prior art solid state light sources: that the LEDs can be seen or
viewed, appearing as point
sources or hot spots when viewing the emitting surface of the light source.
[00225] Alumina is readily available in thin sheet form. However, a wide range
of additives are
used to form the material. For this application, additives which do not
introduce absorption
losses are preferred. Some additive or impurities such as iron can introduce
absorption in to the
final product and therefore are not preferred. In general, materials which
exhibit white body
color are preferred. However for applications such as red light sources a
wider range of body
colors can be used. As such, the most preferred light transmitting thermally
conductive element
2400 is one that exhibits low absorption losses over the wavelengths emitted
by the light source.
[00226] Heat generated by at least one LED 2414 and the wavelength conversion
layer 2416 is
conducted through the light transmitting thermally conductive element 2400 and
transferred to
the surrounding ambient without the need for additional heatsinking means. The
thickness of the
light transmitting thermally conductive element 2400 is between 100 microns
and 5 mm, with
500 microns to 1 mm preferred. If there is low level of scatter within the
light transmitting
thermally conductive element then the use of thicker light transmitting
thermally conductive
elements 2400 is preferred. However in this particular configuration highly
scattering light
transmitting thermally conductive elements 2400 such as 94% to 100% alumina
can be used if
the absorption losses are low. As such, sintering aids which do not color the
alumina are
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preferred. Also the at least one reflector 2412 should have a reflectivity
greater than 80% and
more preferably greater than 90%. The LED 2414 is preferably in direct thermal
contact to the
light transmitting thermally conductive element 2400. Alternatively, the LED
2414 may be
mounted or thermally in contact with the reflector or other thermally
conductive substrate as long
as the thermal impedance between the LED 2414 and the light transmitting
thermally conductive
element 2400 is minimized. While at least one LED 2414 may be thermally
attached to at least
one reflector 2412 to provide additional cooling surface area, it is preferred
and an embodiment
of this invention that the majority of the heat generated by at least one LED
2414 be transferred
to the at least one light transmitting thermally conductive element 2400. This
allows for the light
source to be mounted onto a wide range of surfaces which may or may not be
thermally
conductive such as ceilings, walls, sheet rock, ceiling tiles, glass and other
low thermal
conductivity surfaces which may be combustible or have maximum safe
temperature ranges.
[00227] In some cases it may even be advantageous to thermally isolate at
least one reflector
2412 from surfaces onto which it is mounted. This is possible because
substantially all the heat
generated within the light source can be dissipated off the exterior light
emitting surface(s) 2401
of the at least one light transmitting thermally conductive element 2400.
Preferably, heat
generated in the wavelength conversion layer 2416 is also transferred to at
least one light
transmitting thermally conductive element 2400 so that it may be dissipated
and cooled by the
exterior light emitting surface(s) 2401 of the light transmitting thermally
conductive element
2400 as well. In general, this invention discloses a light source with at
least one light
transmitting thermally conductive element 2400 with an external light emitting
surface 2401
whereby the same exterior light emitting surface 2401 also transfers the
majority of the heat
generated in the light source to ambient. This includes heat generated by the
at least one LED
2414, heat associated with absorption losses within the light recycling cavity
2409, and any heat
generated by losses (e.g. Stoke's shift) in the at least one wavelength
conversion layer 2416. At
least one reflector 2412 may additionally be used to transfer heat from either
the at least one
LED 2414 and/or wavelength conversion layer 2416 to at least one light
transmitting thermally
conductive element 2400. While at least one reflector 2414 could in principle
also contain all or
part of interconnect 2402 for at least one LED 2414. It should be noted
however that additional
dielectric layers (not shown) are required to integrate the interconnect 2402
into at least one
reflector 2412.
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[00228] It is important that all interior surfaces of the light recycling
cavity have high
reflectivity. For example reducing the reflectivity of the reflector 2412 from
95% to 90% will
reduce the extraction efficiency of the light recycling cavity by 20%. At
least one LED 2414
should preferably have a high reflectivity. However, it is not that critical
because the LED(s)
2414 will typically cover a very small percentage of the inside area of the
light recycling cavity.
The interconnect 2402 similarly also covers only a small fraction of the
inside area of the light
recycling cavity 2409. However, reactivities of greater 80% are achievable and
preferred for the
interconnect 2402. The at least one reflector should have a reflectivity
greater than 90%, and
more preferably greater than 95%. Also, the wavelength conversion layer 2416
preferably
should have low absorption losses. Scattering can be very high in these light
recycling systems
as long as the loss associated with each reflection is minimal. With the use
of mostly reflective
light transmitting thermally conductive element 2400 a light ray 2420 may as
many as 40
reflections before exiting the light recycling cavity 2409 through light
transmitting thermally
conductive element 2400. In a conventional light recycling cavity with a
physical exit aperture
the can only exit through the exit aperture. However, using a mostly
reflective and translucent
light transmitting thermally conductive element 2400 there is no defined
physical exit aperture.
Nevertheless, light does escape as described previously.
[00229] Optionally, a blocking layer 2404 may be used to prevent light from
the at least one
LED die 2414 and/or wavelength conversion layer 2416 from passing through the
light
transmitting thermally conductive element 2400 without first entering and
mixing in the light
recycling cavity. This will assure a high degree of mixing and minimize any
light "hotspots"
near the LED 2414. Alternately at least one LED 2414 may be an LED package
where blocking
layer 2404 is integrated into the LED package.
[00230] Power to at least one LED die 2414 is powered via interconnect 2402
which in turn
attaches to external power leads 2408 and 2406. While Fig. 24 is a two
dimensional view, it
should be noted that interconnect 2402 covers only a small amount of the
surface area of interior
surface 2403 of light transmitting thermally conductive element 2400. External
power leads
2408 and 2406 may be but not limited to flex circuits, pins, wires, insulated
wires, magnetic
contacts and other physical contacting means. At least one reflector 2412 is
preferred to be a
high reflectivity coated metal such as AlanodTM, but other materials both
diffuse and specular
with reflectivity greater than 90% may be used. It can't be seen in this cross
sectional view but
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the reflector 2412 forms five sides of the light recycling cavity 2409. The
reflector 2412 can be
easily manufactured using conventional sheet metal processes (e.g. stamping,
etc.). In general the
use of inorganic materials are preferred to create non-flammable recycling
cavity self cooling
light sources, but reflective polymers for the reflector 2412 may be used in
applications where
flammability is not an issue.
[00231] FIG 25 illustrates the temperature of the LED (sometimes referred to
as "die") versus
input watts to the LED (die) for two different thermal conductivities for the
light transmitting
thermally conductive translucent element 2400 previously discussed in FIG. 24.
The LED die
has a maximum operating temperature Tmax as depicted by the dashed line 2504.
If a low
thermal conductivity material such as glass with a thermal conductivity of 1
W/m-K is used as
the light transmitting thermally conductive translucent element 2400, the
LED's maximum
operating temperature Tmax is reached at very low input power (watts) even if
the thickness of
the glass is made very thin. This is depicted by graph line 2500 showing the
relationship
between input power of the LED in watts versus LED junction temperature TJ. In
this case to get
usable light output, requires the use of large numbers of LED die closely
spaced at low drive
levels. When the light transmitting thermally conductive element 2400 is
instead made of
materials with a thermal conductivity of 30 W/m-K (e.g. alumina), curve 2502
is attained in
which very high drive levels to the LED can be used while maintaining the LED
die temperature
below Tmax. This enables increased spacing between LED die and higher drive
levels for each
LED die without exceeding the LED's maximum temperature limit Tmax. This
results in higher
light output with fewer LEDs which lowers cost. In general, higher thermal
conductivity
materials are preferred for the light transmitting thermally conductive
element 2400 to spread the
heat out over a larger area.
[00232] FIG 26 depicts a typical suspended ceiling 2601. Ceiling tile 2606 is
suspended from
the deck 2600 via anchors 2602 and wires 2604 by grid 2603. Plenum space 2608
is the region
above the ceiling tile 2606 and below the deck 2600. The office space 2609 is
below the ceiling
tile 2606 and above the floor 2612. Occupants (or a firefighter) 2610
typically occupy the office
space 2609 below the ceiling 2601. A fire can propagate in either the plenum
space 2608 or
office space 2609. Duct work, electrical distribution, networks and fire
suppression typically is
in plenum space 2608. In general, it is desirable to minimize the number and
size of breaks in
the suspended ceiling for acoustic, aesthetic, and fire suppression. Existing
lighting fixtures
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such as troffers break the contiguous nature of the suspended ceiling 2601. In
most building
codes, troffers and can lights are required to be encased in fireproof
enclosures on the plenum
side 2608. Unfortunately most solid state light fixtures depend on cooling to
occur within the
plenum space 2608. The use of fireproof enclosures greatly hinders the
transfer of heat to the
plenum space 2608. It is highly desirable, from an aesthetic, fire, and
acoustical standpoint that
any lighting fixture not break the contiguous nature of the suspended ceiling
2601 and would
cool itself from or into the office space area 2609. Even more preferably an
ideal lighting fixture
would blend aesthetically into the grid 2603 and/or ceiling tile 2606 and be
lightweight enough
such that the lighting fixture can be seismically certified with the suspended
ceiling such that no
additional wires 2604 to support the light source are required. The use of
high lumens/gram self
cooling light sources of this invention provides a means of meeting these
simultaneous
requirements. Most preferable is that these lighting fixtures are non-
flammable thereby reducing
the risk to firefighters/occupants 2610 even further. In general the light
sources of this invention
may be installed on a wall, floor, ceiling or suspended ceiling of a room such
that substantially
all the heat generated by the light source is dissipated into the room or
office space side 2609.
The light source contains at least two external contacts that both
mechanically attach and
electrically interconnect said light source to a powered distributed grid 2603
contained on a
ceiling, wall or floor of a room wherein the light source can be easily
removed and attached to
different locations on the wall, floor or grid to adjust the lighting
distribution in the room. All of
this can be achieved without ever having to break or penetrate the ceiling
barrier. The light
source may be integrated into movable ceiling tiles 2606 as well.
[00233] FIG 27 depicts a self cooling recycling solid state light source 2704
attached to a 24
volt DC powered grid 2700 via magnetic contacts 2706. The conductors 2708 and
2709 are
attached to grid 2700 via dielectric 2710. External interconnects (not shown)
connect conductors
2708 and 2709 to a 24VDC power supply (not shown) as known in the art. A
typical example
would be Armstrong's FlexZone TM DC power grid ceiling. As the self cooling
light recycling
solid state light source 2704 can be adapted to run on AC or other DC
voltages, this embodiment
is not limited to 24VDC power grids. The self cooling recycling solid state
light source 2704
preferably has a thickness less than 5 mm such that the occupant or office
space side of the
ceiling tile 2702 can be essentially flush with the light emitting surface
2720 of the self cooling
light recycling solid state light source 2704. This creates a monolithic look
to the suspended
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ceiling. Even more preferable is that the lights off state body color of the
light emitting surface
2720 closely match the ceiling tile 2702 finished surface 2722 body color and
texture. The
suspended grid 2700 attaches to the deck 2712 via anchor 2714 and wire 2716.
[00234] FIG 28A depicts a self cooling solid state light source recessed into
a ceiling tile 2802.
In this embodiment, a direct attach LED die 2803 is attached to a light
transmitting thermally
conductive element 2808 and a light recycling cavity 2807 in fully enclosed
space formed by the
light transmitting thermally conductive element 2808 and reflector 2801. A
wavelength
conversion layer 2805 is applied to the direct attach LED die 2803 thereby
reducing the amount
of wavelength conversion material needed and minimizing the wavelength
conversion layer 2805
impact on the external body color. Because the ceiling tile is typically low
density and an
electrically insulating dielectric which is easily penetrated, lightweight
light sources can be
simply pinned on or otherwise attached without the need for additional
support. Push pins 2810
and 2811 act like pins in a cork board wherein they are pressed into the
relatively soft ceiling tile
and are able to support and secure the very light weight light sources of this
invention. The self
cooling solid state light source can be pushed into a recessed pocket in
ceiling tile 2802 such that
it is substantially flush with outer scrim layer 2800. The push pin contact
not only provides an
electrical connection but also attaches the self cooling solid state light
source to the ceiling tile
2802. On the plenum side of the ceiling tile 2802 clip 2804 further supports
the self cooling
solid state light source. In a manner similar to pierced earrings being held
in place the clip 2804
can be used not only to lock the source in place but also to provide
electrical input via power
leads 2806 an 2812. Because the majority of the heat is transferred by the
light emitting surface
2813 to the office (occupant) space, the self cooling solid state light source
can be cooled without
breaking the contiguous nature of the ceiling. This approach enables a wide
range of retrofittable
light sources wherein the lightweight and low surface temperature of the
surface in contact with
the mounting surface enables the mounting of the source to combustible
materials.
[00235] As a further example, push pin contacts 2810, 2811 may be robust
enough to pierce into
the surface of a piece of sheetrock or dry wall. Push pin contacts 2810, 2811
may protrude part
way or all the way through the sheetrock to allow for contact to electrical
connection to
conductors embedded in or behind the sheetrock sheet. Flat conductors as known
in the art,
which are typically used for audio applications, may also be utilized. Due to
the low current
nature of these sources even flat conductors mounted behind decorative
wallpaper can be used to
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provide power to the light sources disclosed in this invention. This is
possible because the light
sources disclosed are lightweight enough to allow for push pin mounting and
they do not require
additional heatsinking means. This is all made possible because substantially
all the heat
generated within the light source is dissipated by the light emitting surface
so that the mounting
surface does not require any thermal transfer for the light source to operate.
In general, the light
sources disclosed in this invention may be mounted to any surface via clips,
magnets, or other
mounting means while emitting light levels greater than 60 lumens per square
inch of emitting
surface independent of the size of the light source. This is possible because
the cooling area and
light emitting area are substantially the same. The sources may be easily
secured to virtually any
surface because they also emit greater than 30 lumens per gram. Lastly, the
light sources
disclosed are inherently distributed sources, which do not require any
additional fixturing
elements. Incandescent and halogen light sources require heat shields to
prevent overheating of
adjacent or nearby combustible materials. Fluorescent light sources require
additional optical
elements (reflectors, diffusers, etc.) to transform the tubular line of light
output into a larger flat
emitting source.
[00236] FIG 28B depicts an embedded self cooling light source wherein the
scrim or outside
layer 2828 of the ceiling tile takes the place of the reflector to form the
light recycling cavity. In
this case the light transmitting thermally conductive element 2822 to which
direct attach LED die
2824, wavelength conversion layer 2826, and push pin contacts 2832 are
attached simply cover
the cavity or depression formed in the ceiling tile 2820 and scrim layer 2828.
The push pin
contacts 2832 also can be connected and supported by clip 2818 with power
supplied via leads
2816 and 2814. In this case the scrim layer 2828 is preferably highly
reflective at least within
the region that forms the light recycling cavity of the self cooling solid
state light source. A
wide range of additional elements such as bezels and micro louvers can also be
attached to the
light emitting surface 2822 used to enhance the aesthetic and optical
performance of the sources.
This embodiment eliminates the need for a separate cavity reflector 2801 by
taking advantage of
the high reflectivity of the scrim layer 2828. Alternately, a scrim layer 2829
can be a surface
treatment on the thermally conductive translucent element 2822. Preferably,
scrim layer 2829
would be thermally conductive and light transmitting in nature with minimal
absorption to the
light emission from the light source. Even more preferably, the scrim layer
2829 enhances the
natural convection coefficient and/or radiative coefficient of the light
emitting surface 2823 of
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the light transmitting thermally conductive translucent element 2822 on
occupant or office side
of the light source. One means making such a scrim layer 2829, is the use of
flame spraying
alumina powders and/or fibers applied directly to an alumina light
transmitting thermally
conductive translucent element (e.g. alumina) 2822. Because the light
recycling cavity allows
for a wide range of translucency in the light transmitting thermally
conductive translucent
element, materials with in-line transmission less than 20% can be used and
still maintain
efficiency levels greater than 70%.
[00237] Alternatively, highly reflective totally opaque materials that have
arrays of holes or
openings representing a substantial percentage of the surface area can be used
for the light
transmitting thermally conductive element 2822. As an example, a metal core
board containing
an array of small holes through the metal core board may be used as the light
transmitting
thermally conductive element 2822. As long as the surfaces that make up the
recycling cavity
are highly reflective to allow for long optical pathlengths, large number of
light bounces, or a lot
of recycling either homogenous or in-homogenous materials may be used for the
light
transmitting thermally conductive translucent element 2822. It should be noted
that a holey
metal core board preferably also has high reflectivity within the holes
through the metal core
board. The holes in the holey metal core board most preferably are greater
than 10% of the
surface area of the holey metal core board. The hole may be uniformly
distributed or non-
uniformly distributed. Smaller holes are preferable with a range of 1 micron
to several
millimeters in diameter. The higher thermal conductivity of the metal core
allows for the
thermally conductive translucent element 2822 to thinner using this approach.
Additional
dielectric, diffusive elements, or imaging elements may be used to construct
composite thermally
conductive translucent element 2822. As an example, highly reflective porous
aluminum 100
microns thick with 20 micron diameter holes uniformly distributed across the
aluminum is
laminated with a 40 micron thick flexible zirconia sheet as know in the
industry. A silver thick
film interconnect is printed and fired on the 40 micron thick flexible
zirconia prior to lamination.
The resulting composite may be used as thermally conductive translucent
element 2822.
[00238] Optionally an additional scrim layer 2822 may be attached to the other
surface of the
aluminum to provide aesthetic, acoustical, or thermal benefits. In general,
the side of the holey
metal core board, which in not part of the recycling cavity may be painted,
printed, or otherwise
decorated to create a wide range of aesthetic looks. This approach is an
example of a non-
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homogeneous thermally conductive translucent element 2822. Also, the holey
metal core board
as thermally conductive translucent element 2822 can be used to allow for
enhanced heat transfer
to the office space side of the installation or even to allow for air flow
through the light source.
In the later case, the reflector also has a pathway for airflow. Most
preferably this approach is
used in porous metal ceiling tile applications. As an example a porous metal
ceiling tile is
patterned with a highly reflective dielectric layer and a highly reflective
interconnect to form
thermally conductive translucent element 2822. An optional scrim layer 2828
can be added for
aesthetic, thermal, or acoustic reasons. LED direct attach die 2824 with a
wavelength conversion
layer 2826 or LED packages with wavelength conversion already included can be
attached to the
highly reflective interconnect on the highly reflective dielectric which is on
the porous metal
ceiling tile which forms the thermally conductive translucent element 2822.
[00239] Reflector 2801 may or may not contain a pathway for air flow depending
on the
installation and desired optical output. In this example, the light source can
be the ceiling tile
not attached to the ceiling tile. Further, the scrim layer 2828 may be a light
transmitting
thermally conductive layer such that the light source blends into the ceiling
aesthetically but still
allows for light emission and thermal cooling of the light sources.
[00240] FIG 28C depicts a holey light transmitting thermally conductive
element 2861
comprising of at least three layers a metal core 2860, dielectric reflector
layer 2856, and
interconnect 2854. An optional fourth layer 2858 may be added as described
below. Metal core
2860 typically is made out of a metal including but not limited to aluminum,
copper, metal
alloys, and metal composites. Metal core most preferably has the thermal
conductivity greater
than 30 W/m-K and even more preferably greater than 100 W/m-K. Dielectric
reflector layer
2856 most preferably has a reflectivity greater than 90% and even more
preferably greater than
95%. The dielectric reflector 2856 may cover all or only a portion of inside
surface 2872.
Dielectric reflector layer 2856 electrically isolates interconnect 2854 from
the metal core 2860
allowing for power to be delivered to LED die 2852. LED die 2852 may further
be coated with
wavelength conversion layer 2850.
[00241] In general, a light recycling cavity reflector element 2870 reflects
2881 and redirects at
least a portion of the light emitted 2880 from the LED die 2852 and wavelength
conversion layer
2850 onto the inside surface 2872 of the holey light transmitting thermally
conductive element.
Some of those light rays are reflected 2882 off of surface 2872. Those light
rays which are not
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reflected off inside surface 2872 of dielectric reflector layer 2856, either
transmit light rays 2866
through the hole 2862 or the light rays 2864 may bounce of the sidewalls of
hole 2862 before
exiting. Holes 2862 may be perpendicular to the inside surface 2872 or tilted
such that the ratio
of light rays 2864 to light rays 2866 increases. It is important that the
inside sidewall 2876 of
hole 2862 is highly reflective to achieve high light extraction efficiency
from the light recycling
cavity formed by the holey light transmitting thermally conductive element
2861 and the
reflector 2870. Alternately, inside sidewall 2876 may be absorptive if it is
desirable to restrict
the angular output distribution of the light source. The inside sidewall 2876
may also be tapered
forming reflective optical elements which again can be used to modify the
output light
distribution from the light source. For example, if the opening of the holes
2885 is smaller than
the light output end of the holes 2886 the light rays reflected off the inside
of the holes will be
collimated. Because the light transmitting thermally conductive element
disclosed is not
homogenous, an optional outside layer 2858 may be added which can have a wide
range of
colors and/or finishes without negatively affecting the light recycling cavity
efficiency. Most
preferably outside layer 2858 is thermally conductive and exhibits a high
thermal emissivity as
previously described. Most preferred is an outside surface 2874 which has an
emissivity greater
than 0.3.
[00242] FIG 29 depicts a suspended self cooling light fixture 2916 within a
suspended ceiling.
Cables 2914 and 2918 attach to the grid 2920 and 2910 respectively, which
contain power leads
2912 and 2913 respectively. Cables 2914 and 2918 provide both physical support
and electrical
input to the suspended self cooling light recycling light source fixture 2916.
Alternately, the
power leads 2912 and 2913 can come through the ceiling tile 2908 with cables
2914 and 2918.
Because lumen per gram outputs are greater than 50 lumens per gram a 2000
lumen suspended
self cooling light source fixture 2916 weighs less than 40 grams which is well
within the safe
structural capacity for either the grid or the ceiling tiles to support. This
increases the flexibility
for the lighting designer. Unlike conventional large, heavy and fixed light
fixtures such as
troffers, virtually no falling or seismic hazard exists with this approach to
lighting. With prior art
heavy light source fixtures there is a significant risk especially for
firefighters/occupants 2924
during a fire where lighting fixtures can fall out of the suspended ceiling.
Aesthetically the
suspended ceiling supported by wires 2904, anchors 2902 to deck 2900 hides air
ducts, wiring,
and fire suppression means in the plenum space 2906. The
firefighters/occupants 2924 view is
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the office space defined by suspended ceiling, floor 2922, and walls. The
light source(s) 2916
of this invention use the combination of light weight and light output to
enable sufficient light in
a space such that the total weight of the light source divided by the square
footage of the
illuminated area or space is less than 1 gram per square foot while providing
over 30 foot candles
to the illuminated area.
[00243] FIG 30 depicts the use of self cooling solid state light recycling
cavity light sources
3012 and 3014 within a seismic suspended ceiling installation. During a
seismic event the deck
3000, floor 3006 and walls 3002 and 3004 move relative to each other which
stress the
suspended ceiling 3001 comprising of the grid 3034, the ceiling tile 3010
supported by wires
3032 anchored via anchors 3030 attached to the deck attachment 3008. The
suspended ceiling
3001 may also be attached to the walls 3004 and 3002 with supports 3020 and
3022 respectively.
Grid supported self cooling solid state light source 3012 is attached to grid
3034 while embedded
self cooling solid state light sources 3014 is attached to or embedded within
the ceiling tile 3010.
In either case the self cooling solid state light sources do not interfere
with the dampening and
supporting function of the either the grid 3034 or the ceiling tile 3010
because they have such
low thermal mass and because they do not form a break in the suspended
ceiling. The flexibility
of this approach permits a wide variety of suspended ceiling installations
without compromising
the structural integrity or the contiguous barrier of the suspended ceiling.
The lighting may be
easily configured or changed without compromising the safety of the occupants
in the event of a
seismic event.
[00244] FIG 31A depicts a suspended ceiling system 3101 supported by wires
3103 and 3104
anchored via anchors 3102 to the deck 3100 containing the self cooling solid
state light source
3112 of this invention embedded within a ceiling tile 3020 and containing the
self cooling solid
state light sources 3110 of this invention on the grid 3106. Using this
approach, the acoustical
response of the suspended ceiling is not compromised by the lighting fixtures.
In conventional
installations, large breaks in the noise dampening occurs because ceiling
tiles 3108 are replaced
by troffers with little to no acoustical treatment (e.g. dampening) or
capability. This increases the
noise level for the occupants 3114 as sound waves bounce between the floor
3116 and the
suspended ceiling. By virtually eliminating all breaks in the suspended
ceiling 3101 the noise
level within the office space can be reduced because the acoustically
functional ceiling tiles (e.g.
3108, 3120 and 3121) form a contiguous barrier between the plenum space 3105
and the
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occupant side 3107 of the suspended ceiling 3101. Also noise transmitted from
the plenum space
3105 (established by and between the suspended ceiling 3101 and the deck 3100)
is reduced to
the occupant or office space 3107 and the occupants 3114 with the more
contiguous suspended
ceiling enabled by the light sources of this invention. In general, the more
contiguous the
suspended ceiling the less acoustical noise and the lower the fire risk for
the occupants 3114.
[00245] Referring now to FIGS. 31A-C concurrently, the suspended ceiling
system 3101
generally comprises a support grid 3106 formed by a plurality of intersecting
struts 13100. The
support grid 3106 is supported within an internal space of a building. The
intersecting struts
13100 form a plurality of grid openings 13101. A plurality of ceiling tiles
3108, 3120 and 3121
are mounted to the support grid 3106 and positioned in the grid openings 13101
to collectively
form a barrier. Each of the ceiling tiles 3108, 3120 and 3121 comprises a
front surface 13102
and a rear surface 13103 opposite the front surface 13102. The front surfaces
13102 of the
ceiling tiles 3108, 3120 and 3121 facing an occupant portion 3107 of the
internal space of the
building. The front surfaces 13102 of the ceiling tiles 3108, 3120 and 3121
define a reference
plane A-A. The occupant portion 3107 of the internal space is located below
the reference plane
A-A.
[00246] The suspended ceiling system 3102 further comprises a plurality of
solid state light
sources 3112, 3110. The solid state light sources 3110 are mounted to the
struts 13100 of the
support grid 3106. The solid state light source 3112, however, is integrated
into the ceiling tile
3120, thereby collectively forming an integrated ceiling panel and lighting
apparatus 13500. The
solid state light sources 3112, 3110 can take the form of any of the solid
state light sources
discussed herein. For example, and as discussed in greater detail in this
application, the solid
state light sources 3112, 3110 generally comprise a reflector element 3200, a
light emitting diode
(LED), such as LED die 3204, and a light transmitting thermally conductive
element 3202. The
light transmitting thermally conductive element 3202 provides a common light
emitting and
cooling surface 3205 to dissipate a majority of the heat from the solid state
light source 3112.
The common light emitting and cooling surface 3205 faces the occupant portion
3107 of the
internal space. As can be seen, the solid state light source 3112 is at least
partially embedded in
and supported by the ceiling tile 3120.
[00247] The reflector element 3200 and the light transmitting thermally
conductive element
3202 collectively form a light recycling cavity 3203. The LED 3204 is mounted
on the light
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transmitting thermally conductive element 3202 in the light recycling cavity
3203. Light emitted
by the LED 3204 is redirected within the light recycling cavity 3203 by the
reflector element
3200 and passes through and exits from the solid state light source 3112 via
the light transmitting
thermally conductive element 3202 through the common light emitting and
cooling surface 3205.
The common light emitting and cooling surface 3205 of the light transmitting
thermally
conductive element 3202 acts as the primary heat dissipation means of the LED,
and the light
source 3112.
[00248] Each of the ceiling tiles 3108, 3120 and 3121 comprises a side edge
13104 extending
between the front and rear surfaces 13012, 13103 and having a profile that
engages the struts
13100 to support the entire weight of the ceiling tile 13012, 13103. Moreover,
the entire weight
of the solid state light source 3112 is supported by the ceiling tile 3120.
Thus, the entire weight
of the integrated ceiling panel and lighting apparatus 13500 is supported in
the support grid 3106
by the cooperation of the side edge 13104 of the ceiling panel 3120 and the
flange portion of the
struts 13100. The total weight of the solid state light source 3120 and all
heat sinking for the
solid state light source 3120 is less than one gram per square foot yet
provides greater than 30
lumens per square foot of illumination throughout an illuminated area of the
occupant portion
3107 of the internal space.
[00249] The ceiling tile 3120 comprises a recess 13105 formed into the front
surface 13102 of
the ceiling tile 3120. The recess 13105 is defined by a recess sidewall 13106
and a recess floor
surface 13107. The recess sidewall 13107 extends from the front surface 13102
of the ceiling
tile 3120 to the recess floor surface 13106. The solid state light source 3112
is disposed in the
recess 13105 and mounted to the ceiling tile 3120. In the exemplified
embodiment, the recess
sidewall 13107 circumferentially surrounds a side edge 13108 of the solid
state light source 3112
when mounted within the recess 13105. In one specific embodiment, the side
edge 13108 of the
solid state light source 3112 is in surface contact with the recess sidewall
13107 when the solid
state light source 3112 is mounted within the recess 13105. The solid state
light source 3112 also
comprises a rear surface 13109 opposite the common light emitting and cooling
surface 3205.
The rear surface 13109 of the solid state light source 3112, in certain
embodiments, is in surface
contact with the recess floor surface 13106 when the solid state light source
3112 is mounted
within the recess 13105. In the exemplified embodiment, the solid state light
source 3112 is
embedded in the ceiling tile 3120 so that the common light emitting and
cooling surface 320 of
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the light transmitting thermally conductive element 3202 is substantially
flush with the front
surface 13102 of the ceiling tile 3120.
[00250] The ceiling tile 3120 has a thickness ti measured from the front
surface 13102 to the
rear surface 1303. The recess 13105 has a depth dl measured from the front
surface 13102 to the
recess floor surface 13106. In one embodiment, the thickness ti is greater
than the depth dl.
[00251] In certain embodiment, each of ceiling tiles 3108, 3120 and 3121 may
comprise a core
13110 and a scrim 13111 (see FIG. 31C). The scrim 1311 may comprise the front
surface 13102
of the ceiling tiles 3108, 3120 and 3121. In certain arrangement, the recess
floor surface 13106
may be formed by a portion of the core 13110.
[00252] The core 13110 may be formed of a fibrous mat, such as those formed
from synthetic
fibers, such as mineral wool, fiberglass, polymer fibers (e.g., nylon fibers)
or metal fibers.
Alternatively, the core can be produced from recycled textile fiber such as
cotton, linen, and
wool. Vegetable fibers such as flax, hemp, kenaf, straw, waste paper, and wood
fiber can also be
used to produce the core. Fillers such as kaolin clay, calcium carbonate,
talc, mica, Wollastonite,
or inorganic flame retardant fillers are also used within the core 13110. The
core 13110 may also
be treated with fire retardant materials as is well understood in the art of
making ceiling tiles.
The scrim 13111 may be formed as discussed herein and is known in the art. For
example, the
scrim 13111 may be a light transmitting thermally conductive scrim. In certain
other
embodiments, discussed elsewhere herein, the light transmitting thermally
conductive scrim may
utilized so as to overlay the common light emitting and cooling surface 3205
of the light
transmitting thermally conductive element 3202 to optically conceal the solid
state light source
3112. Such a light transmitting thermally conductive scrim may comprise
alumina fibers.
[00253] In certain other arrangements (also discussed elsewhere herein), a
light transmitting
thermally conductive scrim may be applied to the common light emitting and
cooling surface
3205 of the light transmitting thermally conductive element 3202. In one such
arrangement, the
light transmitting thermally conductive scrim may have a color and texture
that matches the front
surface 13102 of the ceiling tile 3120. The light source 3112 may also
comprise push pin
contacts 3618, 3616 (also discussed herein elsewhere) that electrically couple
to the LED and
penetrate the ceiling tile 3120 to mounting the light source 3112 to the
ceiling tile 3120.
[00254] FIG. 32A depicts a light recycling self cooling light source 3201
comprising a light
transmitting thermally conductive translucent element 3202 to which a direct
attach LED die
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3204 is attached. (It should be noted that in most of the figures of the
individual light sources
herein the light emitting surface of the light source is depicted or shown
facing in an upward
direction. Of course, in ceiling installations the light emitting surfaces
would be facing
downward.) The direct attach led die 3204 further is coated with a wavelength
conversion layer
3206. The light recycling cavity 3203 is formed by the reflector element 3200
forming an
enclosure or cavity around the light transmitting thermally conductive element
3202. As
previously described, light rays generated and emitted by LED 3204 within the
light recycling
cavity are reflected and recycled by reflector 3200 to the light transmitting
thermally conductive
translucent element 3202 where they are reflected back into the cavity 3203 or
transmitted
through to the light emitting surface 3205 of the light transmitting thermally
conductive element
3202. Multiple reflections provide high uniformity to the light emitting
surface 3205.
Uniformity can be further enhanced with the addition of a turning element 3208
on reflector
3200 which redirects light rays emitted normal to the emitting face of the LED
3204 down the
length of the recycling cavity. In particular a conical, pyramidal, or cusp
shaped turning element
3208 can be used to increase the optical pathlength of light rays within the
light recycling cavity
which in turn increases spatial uniformity for the light rays exiting the
thermally conductive
translucent element 3202. The turning element 3208 may be a separate piece,
sheet, or formed
directly into the reflector 3200. A metal or reflective inorganic is preferred
for reflector 3200.
However, because the majority of the heat is transferred to the ambient via
the surface of the
light transmitting thermally conductive translucent element 3202 the reflector
3200 does not
need to be thermally conductive and therefore can be formed in virtually any
material including
multilayered reflectors like 3M's ESR films, metal coated films, diffuse
reflective films such as
polysilazane containing Hex-Boron-Nitride (hBN) flakes, and other inorganic
and/or organic
reflectors. Most preferred are reflectors with greater than 90% reflectivity.
Non-flammable
materials such as metals and ceramics are preferred.
[00255] FIG 32B depicts another embodiment of the light source of the present
invention
containing a light transmitting thermally conductive element 3220 combined
with reflector 3224,
which forms light recycling cavity 3227. Direct attach LED die 3228 emits blue
light which is
partially converted to longer wavelengths by wavelength conversion layer 3229.
The
wavelength conversion layer 3229 location is optional within the light
recycling cavity 3227.
Alternatively there may be no wavelength conversion layer. For example red,
green and/or blue
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LEDs may be used singly or together within the light recycling cavity 3227. A
tunable light
source is easily achieved with a high degree of mixing of the various colors
within the light
recycling cavity. Single color self cooling light sources and multicolored
self cooling light
sources may also be constructed using this approach. The use of direct attach
LEDs 3228 is
preferred. However, because the interconnect (not shown in this view but
previously described),
which is typically on the inside surface 3225 of the light transmitting
thermally conductive
element 3220, will accommodate direct attach, flip chip, wirebond or other
connection methods a
variety of LED die and LED packages can be used. In this embodiment scattering
elements 3226
are used to adjust the spatial uniformity of the light rays exiting the
thermally conductive
translucent element 3220.
[00256] FIG 32C depicts a light recycling cavity in which the reflector 3332
is formed to
redirect light out through the light transmitting thermally conductive element
3330. The direct
attach LED die 3336 and wavelength conversion layer 3338 emit light into the
light recycling
cavity 3335 formed by reflector 3332 and light transmitting thermally
conductive element 3330.
Additional scattering or turning elements 3334 and 3340 can be used to
spatially redirect light
within the recycling cavity out through the light transmitting thermally
conductive element 3330.
The turning element 3334 also depicts the ability to tune the uniformity after
assembly of the
recycling cavity by inserting turning elements 3334 through holes in the
reflector 3332. The
turning elements can be adjusted to present different reflective faces to the
light emanating from
the LED 3336 to alter the light distribution in the recycling cavity 3335.
Alternately, opaque or
translucent reflective elements can be spatially printed on the light
transmitting thermally
conductive element 3330 and used with or without turning element 3340 to
control the number
of reflections before the light rays escape the recycling cavity 3335. As an
example, highly
reflective small dots may be printed at the same time the silver thick film
interconnect is printed
on the light transmitting thermally conductive element 3330. These dots can be
patterned with
varying spatial density to alter the distribution of light emanating from the
light recycling cavity.
[00257] FIG 32D depicts a light recycling self cooling light source with an
additional
waveguiding element 3352 that more or less fills the light recycling cavity.
In this embodiment
the direct attach LED die 3356 and wavelength conversion element 3358 transfer
their heat to the
thermally conductive translucent element 3346. However light emanating from
the LED and
wavelength conversion element 3359 is coupled to the waveguide 3352 . Light
extraction from
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the waveguide 3352 occurs due to light extraction elements 3354, 3355 and
3357. Extraction
element(s) 3357 may be as simple as an index matching dot between waveguide
3352 and light
transmitting thermally conductive element 3346. The reflector 3350 is still
used to enhance the
recycling within the light source and it may be separate from or be formed on
the waveguide
3352 as a high reflectivity coated film.
[00258] FIG 33 depicts a graph illustrating the importance of reflectivity on
the efficiency of
light recycling cavities. Due to the large number of reflections that must
occur to convert a point
source like an LED die to a uniform and diffuse output, any losses in the
light recycling cavity
caused by the LED die, interconnect, reflector, and/or within the thermally
conductive
translucent element need to be minimized. It is preferable that all of these
components have high
reflectivity (e.g. > 80%). However, the LEDs are not as critical as they
represent a very small
portion of the inside surface of the recycling light cavity. The reflector
3200 as shown in Fig.
32A will typically represent over 60% of the inside surface area of the light
recycling
cavity3203. Therefore, it is preferred that the reflector 3200 has very high
reflectivity (e.g.
greater than 95%) The light transmitting thermally conductive elements
disclosed herein are
most preferably optically low absorption loss materials such as alumina,
sapphire, YAG, glass,
YSZ, GGG, and other optically low absorption materials. It should be noted
that in line
transmission number typically used are not a good indicator of optical losses.
Because recycling
cavity sources such as these allow for multiple bounces, highly scatter
materials such as alumina
which appear white or opaque can actually be very efficient windows. The
critical issue is not
in-line transmission but optical absorption losses. Alumina A1203 has very low
optical
absorption throughout the visible spectrum however if improper sintering aids
are used
absorption losses can be increased. Therefore, high purity materials are
preferred which may or
may not be amorphous, polycrystalline or single crystal in nature. The same is
true for organic
materials, Teflon films with high porosity have some of the highest diffuse
reflectivity numbers
that can be generated approaching 100%. This effect is due to the low optical
absorption
throughout the visible region for these materials. Composites can likewise be
low absorption as
is the case with polysilazane and hBN composites, which have been previously
disclosed, in the
referenced filings by the authors. In general, material with absorption losses
less than 0.1 cm-1
in their transparent state throughout the visible region are preferred for the
thermally conductive
translucent element.
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[00259] The use of organic materials to further enhance the reflectivity
inside the recycling light
cavity or to add aesthetic features to the outside of the light source is also
disclosed. Examples
of low optical absorption materials include spin-on glasses, polymers,
monomers, oligomers,
waxes, and oils. Other optically useful materials include composites and
mixtures including
inorganic/organic suspensions, polymers containing organometallics, and sol-
gels. These low
optical absorption materials can be formed, cured, crosslinked, or otherwise
densified using heat,
actinic radiation, pressure, shear, electron beam, mechanical or chemical
means to form a layer
or freestanding element.
[00260] Preferred optical materials include the following: Typical spin-on
glass materials
include methylsiloxane, methylsilsesquioxane, phenylsiloxane,
phenylsilsesquioxane,
methylphenylsiloxane, methylphenylsilsesquioxane, and silicate polymers. Spin-
on glass
materials also include hydrogensiloxane polymers of the general formula (H0-1
OSi01.5-2.0)x
and hydrogensilsesquioxane polymers, which have the formula (Hsi01.5)x, where
x is greater
than about 8. Also included are copolymers of hydrogensilsesquioxane and
alkoxyhydridosiloxane or hydroxyhydridosiloxane. Spin-on glass materials
additionally include
organohydridosiloxane polymers of the general formula (H0-1.0S i01.5-2.0)n(R0-
1.0S i01.5-
2.0)m, and organohydridosilsesquioxane polymers of the general formula
(HSi01.5)n(RSi01.5)m, where m is greater than 0 and the sum of n and m is
greater than about
8 and R is alkyl or aryl.
[00261] Typical polymer optical materials include halogenated polyalkylenes,
preferred
fluorinated an/or chlorinated polyalkylens, more preferred
chlorofluoropolyalkylens, and most
preferred are the fluorinated polyalkylenes among which are included:
polytetrafluoroethane
(ethylene), polytrifluoroethylene, polyvinylidene fluoride, polyvinylfluoride,
copolymers of
fluorinated ethylene or fluorinated vinyl groups with non-fluorinated
ethylenesor vinyl groups,
and copolymers of fluorinated ethylenes and vinyls with straight or
substituted cyclic
fluoroethers containing one or more oxygens in the ring. Also included in the
most preferred
polymers are poly(fluorinated ethers) in which each linear monomer may contain
from one to
four carbon atoms between the ether oxygens and these carbons may be
perfluorinated,
monofluorinated, or not fluorinated.
[00262] Also included in the most preferred polymer optical materials are
copolymers of wholly
fluorinated alkylenes with fluorinated ethers, partly fluorinated alkylenes
with wholly fluorinated
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ethers, wholly fluorinated alkylenes with partly fluorinated ethers, partly
fluorinated alkylenes
with partly fluorinated ethers, non-fluorinated alkylenes with wholly or
partly fluorinated ethers,
and non-fluorinated ethers with partly or wholly fluorinated alkylenes.
[00263] Also included among the most preferred polymer optical materials are
copolymers of
alkylenes and ethers in which one kind of the monomers is wholly or partly
substituted with
chlorine and the other monomer is substituted with fluorine atoms. In all the
above, the chain
terminal groups may be similar to those in the chain itself, or different.
[00264] Also among the most preferred polymer optical materials are
substituted polyacrylates,
polymethacrylates, polyitaconates, polymaleates, and polyfumarates, and their
copolymers, in
which their substituted side chains are linear with 2 to 24 carbon atoms, and
their carbon atoms
are fully fluorinated except for the first one or two carbons near the
carboxyl oxygen atom such
as Fluoroacrylate, Fluoromethacrylate and Fluoroitaconate.
[00265] Among the more preferred polymer optical materials, one includes
fluoro-substituted
polystyrenes, in which the ring may be substituted by one or more fluorine
atoms, or
alternatively, the polystyrene backbone is substituted by up to 3 fluorine
atoms per monomer.
The ring substitution may be on ring carbons No. 4, 3, 2, 5, or 6, preferably
on carbons No. 4 or
3. There may be up to 5 fluorine atoms substituting each ring.
[00266] Among the more preferred polymer optical materials, one includes
aromatic
polycarbonates, poly(ester-carbonates), polyamids and poly(esteramides), and
their copolymers
in which the aromatic groups are substituted directly by up to four fluorine
atoms per ring one by
one on more mono or trifluoromethyl groups.
[00267] Among the more preferred polymer optical materials, are fluoro-
substituted poly(amic
acids) and their corresponding polyimides, which are obtained by dehydration
and ring closure of
the precursor poly(amic acids). The fluorine substitution is effected directly
on the aromatic ring.
Fluoro-substituted copolymers containing fluoro-substituted imide residues
together with amide
and/or ester residues are included.
[00268] Also among the more preferred polymer optical materials are parylenes,
fluorinated and
non-fluorinated poly(arylene ethers), for example the poly(arylene ether)
available under the
trade name FLARETM from AlliedSignal Inc., and the polymeric material obtained
from phenyl-
ethynylated aromatic monomers and oligomers provided by Dow Chemical Company
under the
trade name SiLKTM, among other materials.
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[00269] In all the above, the copolymers may be random or block or mixtures
thereof.
[00270] In general, low optical absorption plastics are preferred (fluorinated
polymers,
polysiloxanes, polysilazanes, halogenated polymers, non-halogenated polymers,
polycarbonates,
acrylics, silicones, and inorganic/organic composites comprising low optical
absorption
organics). An example of a low absorption strongly scattering polymeric film
is WhiteOpticTM.
While this film exhibits low absorption losses and white body color it also
has very low thermal
conductivity. While this material can be used for parts of the recycling
cavity, which are not
used to cool the LED, materials with thermal conductivity higher than 1 W/mK
are preferred for
the light transmitting thermally conductive elements disclosed in this
invention. In general, all
unfilled organic materials exhibit low thermal conductivity (less than 1 W/mK
and typically less
than 0.1W/mK) cannot be used effectively to spread the heat generated in the
LEDs within the
light recycling cavity. While one could in theory operate the LEDs at such a
low level and use
hundreds of LEDS within the recycling cavity and use a lower thermal
conductivity material for
the light transmitting thermally conductive element the cost would be
excessive. In almost all
solid state light sources the LEDs typically represent 50% to 80% of the
overall cost.
[00271] The light source of this invention enables the minimum number of LEDs
while
eliminating the need for costly appended heatsinks. Based on experimental
results greater than 5
W/mK is preferred and greater than 20 W/mK is most preferred. In addition,
most unfilled
polymer systems, which exhibit low optical absorption have low use
temperatures typically
below 150 C and even below 1000 C. Therefore, strongly scattering organic
materials which can
withstand greater than 2000 C are preferred and even more preferred are
organic materials which
can withstand greater than 3000 C. High quality low resistance interconnects
compatible with
wirebonding and/or direct die attach fire at temperatures over 4000 C. Also
direct die attach
LEDs typically solder at greater than 3000 C. While lower temperature
interconnects and
conductive adhesive may be used there are significant tradeoff is performance
both electrically
and optically. Finally, most unfilled organic materials also are flammable. As
such inorganic
materials like alumina or porous metal foils are preferred. However
organic/inorganic
composites are possible.
[00272] As an example of thermally conductive inorganic/organic composite with
a thermal
conductivity over 5 W/mK capable of withstand greater than 3000 C, is boron
nitride filled
polysilazane may be used to form either a thermally conductive layer on the
porous flexible
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metal foils or inorganic light transmitting thermally conductive elements or
be used as a
freestanding element forming at least one face of the recycling light cavity.
Other polymeric
binders are also possible however the high temperature performance, optical
transparency and
compatibility of the polysilazanes with boron nitride make this
inorganic/organic composite a
preferred materials choice. Filled thermoplastic composites are especially
preferred.
[00273] FIG 34 depicts decorative overlay 3404 printed or otherwise formed on
light
transmitting thermally conductive element 3402. In this manner the visible
light emitting surface
3410 of the light transmitting thermally conductive element 3402 can be
modified aesthetically.
The light recycling cavity self cooling light source is again formed using a
reflector 3400 and a
light transmitting thermally conductive element 3402. Decorative overlay 3404
may include
paints, lacquers, fused glass, or other coatings that impart patterns,
textures and other aesthetic
elements. Because inorganic materials such as alumina is preferred for light
transmitting
thermally conductive element 3402 high temperature processing steps such as
glazing are
possible. These high temperature steps tend to also use materials like glass
and other inorganics,
which still have reasonable thermal conductivity. Texture may be imparted via
a coating on or
direct embossing of the light transmitting thermally conductive element 3402.
The decorative
element 3404 most preferably is thermally conductive such that when the
thermally conductive
decorative element 3404 is in thermal contact with the light transmitting
thermally conductive
element 3402 the majority of the heat is emitted from the exterior surface of
the thermally
conductive decorative element 3404. Like a lamp shade the decorative element
3404 may or
may not be transmissive to all wavelengths emitted by the light source.
Colored glasses in a
variety of patterns fused to the light transmitting thermally conductive
element 3402 is a
preferred embodiment of decorative element 3404.
[00274] FIG 35A depicts a light recycling self cooling light source with
reflector 3500 and
thermally conductive translucent element 3502 to which an LED die 3508 is
attached.
Wavelength conversion elements 3504 and 3506 maybe placed not in direct
contact with LED
3508 as shown. Light emitted by the LED 3508 is reflected and recycled in
light recycling cavity
3507 formed by reflector 3500 and light transmitting thermally conductive
element 3502. A
portion of the light is converted to longer wavelengths by the wavelength
conversion elements
3504 and 3506 before being transmitted to and emitted by the emitting surface
3503 of the light
transmitting thermally conductive element 3502. In this configuration a UV LED
die 3508 is
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preferred so that the phosphors used in wavelength conversion elements 3504
and 3506 can have
natural white body color. Alternately, the external body color of the light
source can be modified
by selecting phosphors, quantum dots, and other wavelength conversion
materials with a
particular body color. Body color is an important aesthetic attribute of light
sources when the
desire is to create a monolithic uniform look in installations like suspended
ceilings.
[00275] FIG 35B depicts a light recycling self cooling light source where the
light transmitting
thermally conductive element 3512 is also luminescent. As mentioned previously
a wide range
of materials can be used to form solid wavelength conversion elements in
ceramic, coated, and
single crystal form. The LED die 3514 attaches and is in thermal contact to
the light transmitting
thermally conductive element 3512 and the light recycling occurs due the
reflector 3510.
[00276] FIG 35C depicts a separate wavelength conversion coating/element 3524
formed on or
attached to thermally conductive translucent element 3522. The relative
position of these two
elements to the LED die 3526 may be switched or used as shown. Reflector 3520
and light
transmitting thermally conductive element 3522 form the recycling cavity.
[00277] FIG 35D depicts a self cooling light source without a light recycling
cavity. In this
embodiment the emission from the LED die 3532 which is attached to,
interconnected (not
shown) and cooled by thermally conductive translucent element 3530 only
partially illuminates
wavelength conversion layer 3534. A wide range of optical effects can be
formed using this
approach, which illustrates the flexibility of eliminating the heatsink by
integrating the cooling
and emission surfaces into one element.
[00278] FIG 36 depicts a push pin connector for ceiling tiles 3608. Self
cooling solid state light
source 3614 contains two substantially rigid pins 3618 and 3616. Because the
ceiling tile 3608 is
a dielectric and tends to be easily pierced the rigid pins 3618 and 3616 can
be simply pressed
through the scrim layer 3610 and ceiling tile 3608. Additional mounting
support can be via clips
3604 and 3606 which can additionally act as electrical connector to power
leads 3602 and 3600.
The ultra light weight of these light sources resulting in high lumens per
gram of these self
cooling solid state light source 3614 allows for this type of installation.
Aesthetic elements 3612
can be added as well. The use of non-flammable materials is preferred for
aesthetic elements
3612. Alternately, the scrim layer 3610 can be formed to create recesses for
the self cooling
solid state light source 3614. Optionally magnetic connectors 3632 and 3630
may be used to
allow for front side removal without removing the ceiling tile 3608.
Optionally magnetic push
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pins with their visible mating contacts coated to blend with the ceiling tile
may be used. In this
way Self cooling light sources with greater than 30 lumens per gram are
preferred and
embodiments of this invention.
[00279] FIG 37 depicts a self cooling solid state light source embedded within
a ceiling tile
3700 underneath the scrim layer 3708. In this configuration a translucent
scrim with a
reasonable porosity or thermal conductivity is preferred such that heat from
the thermally
conductive translucent element can be extracted to the ambient of the office
space. The heat
from the LED die 3706 and reflector 3702 are again used to create a light
recycling cavity as
previously disclosed. In this configuration the electrical interconnects 3710
and 3712 can be
embedded under the scrim layer 3708 as well. This creates an illuminated
ceiling tile that
replaces conventional light fixture.
[00280] FIG 38 depicts a modular rail self cooling light source, which is
field replaceable. In
order to be field replaceable several criteria must be met, including but not
limited to easy
installation, keyed installation or electrically/mechanically protected
installation, low voltage
operation, distributed power, light weight, and decorative elements to cover
unused areas.
Armstrong FlexDC TM suspended ceiling grid offers one example of a distributed
power system.
However, prior to this invention the lack of field replaceable light sources
due to weight and
thermal considerations restricted taking advantage of the full capability of
these new distributed
power grids. In this embodiment a light recycling cavity light source is
integrated into a modular
grid system 3800. In this case the reflector 3814 in previous examples is
integrated into the grid
along with DC input strips 3804 and 3802 to form a light recycling cavity
modular grid system
3800 such that only the light transmitting thermally conductive element 3806
with attached
LEDs and/or LED packages 3812, an interconnect (not shown), and an attachment
/contact
means 3810 and 3806 are required by the end user to create self cooling linear
light sources.
This is enabled by the basic nature of this design wherein substantially most
of the heat from the
light source is transferred to the occupant 3816 side or office space 3818
from the light emitting
surface 3813 of the light transmitting thermally conductive element 3806. The
office space 3818
is that area below the ceiling 3814 in which the occupants 3816 work. In this
configuration, the
light recycling cavity is formed once the translucent thermally conductive
element 3806 with its
associated LEDs and/or LED packages 3812 and contacts 3808 and 3810 are
mounted into the
reflective receptacle 3819 of the modular grid system 3800. While magnetic
contacts are
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preferred for contacts 3810 and 3808, other methods are may be used including
but not limited to
conductive VelcroTM, snaps, push pins, clips, and other mechanical/adhesive
means. The
lightweight and long life nature of this approach eliminates the need for
expensive locking means
to support the field replaceable light source.
[00281] The use of standard steel grid, which allows for magnetic contacts
3808 and 3810 to
make contact to DC strips 3804 and 3802 is preferred. This approach minimizes
the weight of
the light source itself, which in turn reduces the cost of shipping and
storage. A distributed
power grid with an integrated reflector 3819 is an embodiment of this
invention. The ceiling
3814 may be a suspended ceiling, cloud, or other aesthetic/acoustical element.
While ceilings
are shown, similar installations in walls and floors may also be utilized for
this invention.
Walls, sheetrock, brick, mortar, wood and other elements may be used in a
similar manner as a
receptacle for the self cooling light source. The ability to transfer the heat
into the office space
using substantially only the light emitting surface enables the use of
temperature sensitive
materials including but not limited to wallpaper and paint on any mounting
surface as well. In
general, the light sources disclosed herein may be installed on a wall, floor,
ceiling or suspended
ceiling of a room such that substantially all the heat generated by the light
source is dissipated
into the room. The room being defined as the illuminated area or space in to
which the light
emitted by the light sources is emitted.
[00282] FIG 39 depicts a magnetic connector with self centering for modular
rail or grid
system. In this case the recycling cavity modular grid system 3900 has a
recycling cavity shaped
to self center the linear light source 3906. By beveling the sides of the
recycling cavity and
using angled magnetic contacts 3908 and 3910, electrical contact to DC strips
3904 and 3902 and
mechanically self centering the linear light source 3906 can occur at the same
time. Other
mechanical, magnetic and adhesive means and elements, which support and center
the linear
light source 3906 in the recycling modular grid system 3900 can also be used.
[00283] FIG. 40 depicts ceiling tile 4000 with in-situ recycling cavity 4002.
In this
configuration the self cooling light panel comprising of a light transmitting
thermally conductive
4008 containing LED packages 4010 with contact pins 4004 and 4006 can be
easily attached to
the ceiling tile 4000 by the end user. The contact pins 4004 and 4006 can make
electrical contact
to embedded interconnects, slip-on contacts, or other contact means as
previously described.
This approach allows for reconfiguration of the lighting within a suspended
ceiling. In general it
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is preferred that in-situ light recycling cavity 4002 has the highest
reflectivity possible but a
reflectivity greater than 90% is preferred, with greater than 95% most
preferred. White paint,
polymeric coatings, metal foils, and combinations of both may be used for in-
situ recycling
cavity 4002.
[00284] FIG 41 depicts suspended ceiling modular system with in-situ light
recycling cavity
grid 4100 and light emitting units 4106 and dummy units 4102. Light emitting
units 4106
contain LEDs and/or LED packages 4108 and contacts 4110 on the light
transmitting thermally
conductive element 4103. An interconnect and any additional active elements as
previously
disclosed (not shown) are also included. Dummy unit(s) 4102 will typically
only comprise light
transmitting thermally conductive element(s) 4109 and contacts 4104. These
dummy units serve
as spacers and/or decorative elements. However additional components providing
additional
functions including but not limited to power conditioning, electrical
filtering, sensors, detectors,
emitters, antennas, and other active and passive may also be incorporated into
these dummy light
sources.
[00285] FIG 42 depicts a self cooling solid state light source with
reflector/thermal barrier
4206. By making the reflector 4206 out of a low thermal conductivity material
such as a
polymer, porous ceramic, or glass material with a thermal conductivity less
than 1 W/mK the self
cooling light sources can be attached to surfaces which are thermally
sensitive. The thermal
isolation may be created using porosity, low thermal conductivity materials,
heat shields and
other thermal barrier means. In the case of polymers the reflector 4206 can be
formed via blow
molding, injection molding, thermal forming, and other fabrication techniques
known in the art.
As previously stated high reflectivity is preferred. Most preferably the
reflectivity of the
reflector/thermal barrier 4206 should be greater than 95%. Also the use of non-
flammable or low
flammability materials is preferred for the reasons previously stated.
Contacts 4204 and 4202
can be molded in or pressed into the molded reflector/thermal barrier 4206.
Translucent light
transmitting thermally conductive element 4200 provides cooling and physical
support to LEDs
and/or LED packages 4210 and interconnect 4208 as previously disclosed. The
use of this
approach allows for a higher temperature operation point for the translucent
thermally
conductive element 4200 than those approaches disclosed which allow for
greater thermal
transfer to the reflector/thermal barrier 4206. This increases the lumens
output per surface area
and also increases the lumens per gram. It should be apparent that
reflector/thermal barrier 4206
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should be made of material compatible with the temperatures created by this
approach. Again in
this embodiment the emitting surface and cooling surface are both
substantially the same.
[00286] FIG 43 depicts snap fit linear light sources for grids, undercounter,
aircraft, and ceiling
lighting. Housing 4300 provides mounting of the self cooling light source
4310. The self cooling
light source 4310 is constructed as previously described wherein the emitting
surface(s) 4312 is
the heatsink. As shown the housing 4300 contains two housing contacts 4302 and
4304 which
form an electrical connection with light source contacts 4308 an 4306 which
provide power to
self cooling light source 4310. Housing 4300 may be made out of a wide range
of materials
including polymers, metals and ceramics. Thermally insulative materials are
preferred to
thermally isolate the self cooling light source 4310 from any wood, paper,
drywall or other heat
sensitive materials to which the housing 4300 is mounted. Housing 4300 may be
mounted using
screws, adhesives, pins, snaps or other mechanical or chemical means. Because
the self cooling
light source 4310 does not require additional heatsinking to dissipate its
heat, housing 4310 may
be made out of any material which can handle the surface temperatures of the
self cooling light
source 4310. Housing 4310 may also include additional support in the form of
rails, clips,
Velcro, magnets, or springs which secure and/or position the self cooling
light source 4310 with
the housing 4310. Housing contacts 4302 and 4304 and light source 4308 and
4306 may include
spring loaded contacts, snap fit, conductive Velcro, magnetic, or locking
means to ensure
electrical contact.
[00287] FIG 44 depicts a thermally insulated lambertian self cooling light
source with an
integral thermal barrier 4400, which additionally acts as a mounting fixture.
Mounting elements
4410 and 4414 can include but are not limited to tabs, rails, spring loaded
elements, clips, Velcro,
adhesive strips, magnets or other mechanical/chemical means of attachment
and/or alignment.
Optionally additional reflective layer 4402 may be used to enhance the
reflectivity of the integral
thermal barrier 4400 such that the recycling cavity 4408 will efficiently
spread the light from at
least one LED 4404 throughout the light recycling cavity 4408. Again the light
transmitting
thermally conductive element 4406 allows for both efficient emission of the
light from the at
least one LED 4404 and removing the heat generated by at least one LED 4404.
[00288] FIG 45 depicts various connector arrangements for a self cooling light
source with a
reflector. FIG 45A depicts two overlapping reflector elements 4506 and 4512,
which are
electrically isolated by dielectric layer 4510. The reflectors 4506 and 4512
have optional
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contacts 4502 and 4508 respectively. Electrical power is provided through the
overlapping
reflectors 4506 and 4512 to the translucent thermally conductive element 4500
through board
contacts 4514 and 4516 which may include conductive epoxies, clips, solder
joints, through
holes, wires, and/or other connection means. The electrical power is
distributed to the at least
one LED 4504 as previously disclosed via an interconnect means (not shown).
[00289] FIG 45B depicts another version of split reflectors 4538 and 4540 both
of which have
integral contacts which mechanically and electrically contact translucent
thermally conductive
element 4542 which contains at least one LED 4544. Optionally, reflector
contacts 4532 and
4534 may be used to improve the electrical contact to an external power
source. Insulating
bridge element 4530 serves not only to electrically isolate the split
reflectors 4538 and 4540 but
also to provide support for the overall assembly.
[00290] FIG 45C depicts the use of side clips 4562 and 4560, which
mechanically hold
reflector 4564 and translucent thermally conductive element 4568 together and
thereby form the
recycling cavity around at least one LED 4566. In this configuration the side
clips 4562 and
4560 also serve as the electrical contact to the external power supply (not
shown). Also in this
configuration reflector 4564 is most preferred to be electrically insulating.
Alternatively, the
side clips 4506, 4562 may have a dielectric or insulating layer on their
inside surfaces 4561 and
4563 where they contact the reflector 4564. The clips may also allow for
differing thermal
expansion between reflector and light transmitting thermally conductive
element. The use of
any of these connection means to form light sources with multiple translucent
light transmitting
thermally conductive elements 4568 is also an embodiment of this invention. In
general, robust
large contact area connections are preferred. Multiple contact points are
preferred to single point
connections for improved reliability. The use of corrosion resistant coatings
such as tin alloys,
carbon based contact, and other environmentally stable layers to enable
reliable electrical
connections are also embodiments of this invention.
[00291] FIG. 46A depicts another embodiment of a light recycling cavity 4600
comprising a
strongly light scattering and light transmitting thermally conductive element
4616 one which
interconnects 4620 and 4618 are formed as previously disclosed. It should be
noted that while
the side view shows interconnects 4620 and 4618 covering the inner surface of
strongly
scattering light transmitting thermally conductive element 4616 with only a
small gap 4629, in
most application standard line widths of typically 100 micron wide and 5
microns thick would be
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used such that the amount of conductive material used is minimized. Therefore,
the interconnect
only covers a small fraction of the total area of the inward facing surface
4603 of the light
transmitting thermally conductive element 4616. The width and thickness of the
interconnect
can be adjusted as would be appropriate for the at least one LED or
semiconductor device 4622
based on maximum drive current and the length of the traces. Most preferred
are interconnects
4620 and 4618 which are thin traces due to the cost of the metal materials
used. Most preferred
is low surface roughness silver thick film pastes with a RMS roughness less
than 5 microns. An
example is Heraeus silver thick film paste CL80-9364 which enables the use of
direct attach
LED die 2810 such as DA-500 die produced by Cree. Direct attached die and/or
soldered LED
packages are preferred devices for at least one LED or semiconductor device
4622 due to the
elimination of wirebonding costs. In general, high reflectivity and high
conductivity materials
are preferred for interconnects 4620 and 4618.
[00292] Additional wavelength conversion elements 4624 may be placed on the at
least one
LED or semiconductor device 4622 or elsewhere within the light recycling
cavity 4600. For
example on the surfaces which make up the light recycling cavity: reflectors
4612 and 4614, flex
layer 4602, interconnects 4620 and 4618, and strongly scattering thermally
conductive element
4616. External contacts 4610 and 4608 may attach to the reflective flex
circuit comprising
reflectors 4614 and 4604 respectively and optionally to flex layer 4602 using
conductive epoxy,
soldering, ultrasonic bonding, tab bonding, mechanical means, and other
connection means
known in the art. Adhesive insulators 4604 and 4606 are optionally used to
support external
contacts 4608 and 4610 respectively. Similarly reflector 4612 and 4614 may
make electrical
contact with interconnects 4620 and 4618 respectively using but not limited to
conductive epoxy,
soldering, ultrasonic bonding, tab bonding, mechanical means and other
connection means
known in the art. A single layer reflective flex circuit is shown comprising
reflectors 4612 and
4614 and flex layer 4602. However, additional layers of interconnect as
practiced in the flex
circuit industry may be used.
[00293] Unlike interconnects 4620 and 4618, it is most preferred that
reflectors 4614 and 4612
cover the majority of flex layer 4602. In addition it is most preferred that
reflectors 4614 and
4612 have reflectivity greater than 90%. The resulting reflective flex circuit
and its use in light
recycling cavities is an embodiment of this invention. External contacts 4610
and 4608 are
disclosed as pins however other means including but not limited to clips,
pads, strips, and other
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mechanical contact means may also be used. A preferred embodiment is
continuation of
interconnects 4618 and 4620 outside inner surfaces of the light recycling
cavity 4600 such that
external contacts 4610 and 4608 may be moved to edge of the light source (not
shown). These
approaches and the dimensional properties of interconnects 4618 and 4616 are
common to the
other embodiments in this disclosure. The use of adhesives, clips, solders,
mechanical means,
and fusion processes to bond the various pieces of the light source together
are also disclosed.
[00294] Once formed this embodiment can create a wide range of colors when lit
(by using
different color LEDs or wavelength conversion elements), while still
maintaining a substantially
white body color because of the strongly scattering nature of the strongly
scattering light
transmitting thermally conductive element 4616. In addition, the reflectors
4614 and 4612 as
well as other elements within the light recycling cavity 4600 contribute to
the body color of the
light source. Especially in the case of ceiling tiles and grid applications,
the ability to create thin
lightweight solid state light source with body colors which closely match the
white tiles is a
benefit. The desire is to essentially conceal the lighting in the ceiling
structure so that unlike
conventional troffers and can lights the lighting does not draw attention to
itself in the eyes of the
occupants but instead presents a monolithic uniform ceiling even though
lighting fixtures are
present. In addition the ability to distribute the lighting throughout the
ceiling tiles and grid
actually makes the lighting more efficient. Light can be positioned anywhere
in the ceiling as
needed unlike standard troffers which are typically placed on very regular
intervals but in
concentrated clumps which results in the need to over light some areas to meet
minimum
required lighting levels between the troffers. As previously disclosed
additional semiconductor
devices and elements may be incorporated within and/or on light recycling
light cavity envelope
4600 besides just LEDs. In addition interconnects 4620 and 4618 and reflective
flex circuit
comprising reflectors 4614 and 4612 and flex layer 4602 may be used to form
antennas for RFID
and other communication and sensor applications.
[00295] Alumina especially can be used for the strongly scattering light
transmitting thermally
conductive element 4616. The flex circuit may also be used to create inductive
or capacitive
couplers to external modulated energy source eliminating the need for external
contacts 4610 and
4608. Additional functions which can be incorporated into these self cooling
light sources are
but not limited to RFID sensing, smoke detection, ambient temperature
detection, RF emitters,
strobe sources, optical data links, motion sensors, and wireless
communications. As lighting is
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required in virtually all occupied spaces it is only natural that sensor,
communication, and
security functions be integrated into the light sources. The ability to use
commercial grade low
cost alumina provides an ideal substrate for integrating these extra
electrical components into
the light source. The strongly scattering white body color of these light
sources allow for the
concealment of security functions such as cameras and sensors. As an example a
piezo-electric
speaker can be placed within, built into or otherwise attached to the light
source. Audio and
other low frequency modulation may be brought into via the external contacts
4608 and 4610 or
separate leads. Audio modulation in particular can be run in parallel,
separately, or filtered off
the DC input or be brought in on separate inputs. The benefit of this approach
is elimination of
speakers within the ceiling and the added benefit of enhanced cooling of the
light source based
on surface boundary interruption created by vibrations from the integrated
speaker. Internal
speakers can also move air into and out of the light recycling cavity 4600.
This approach also
allows for easy repositioning of audio speakers in a ceiling. The use of this
approach to noise
blank, create audio ambience, create background noise, act as an audio fire
warning, acoustical
source for motion detection, create a distributed speaker system, create a
distributed music
system. In general, this approach allows field installable, field replaceable,
and field adaptable
audio systems integrated into the lighting.
[00296] As an example, a store owner could buy a light source based on this
disclosure, which
queried RFID tags at the exit from the story while an externally identical
light source could be
detecting motion elsewhere in the store. In this manner, lighting and security
become the same
element reducing cost, concealing the security, and improving the aesthetics.
Interconnects 4618
and 4620 may be single circuits as shown or multiple circuits. The extra
functions may be
powered separately and in tandem with at least one LED or semiconductor device
4622. Light
recycling cavity 4600 may be air, a gas, a liquid, a phase change material, an
optical transmitting
solid, or combinations of both. Most preferred is air. In the case where non-
homogenous
materials are used to make strongly scattering thermally conductive element
4616 air may flow
into light recycling cavity 4600. An outer porous scrim layer may optionally
be used to further
modify the external body color of the source. FIG. 46B further depicts a flex
circuit version of
the self cooling light source. Light recycling cavity 4662 is formed by inner
reflector element
4660 and translucent thermally conductive element 4664 as previously
disclosed. In this case
inner reflector element 4660 is electrically insulated by adhesive layer 4658
from conductive
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strips 4656 and 4657. In this manner conductive strips 4656 and 4657 can be
used to make
connection to interconnect 4670. Solder coated copper ribbon as used in the
solar industry is a
preferred material for conductive strips 4656 and 4657. Again LEDs and/or
semiconductor
devices 4668 and 4666 and interconnected using interconnect 4670. Additional
electrical
isolation may be provided using underfill 4672 and overcoat 4674. Paralyene
and other
transparent dielectric environmental coating are preferred materials for
overcoat 4674. It should
be noted that alumina and other materials while strongly scattering in the
visible region are
almost transparent in the infrared and therefore imaging at these longer
wavelengths is possible
from within the light recycling cavity 4662. The ability to hide detection,
security, acoustical,
and other sensor functions within the self cooling light sources or dummy
elements as previously
disclosed in FIG.41 is a preferred embodiment of this invention.
[00297] In general, the light sources disclosed may be used to attach, mount
or otherwise
adhere to a variety of surfaces. While halogen and incandescent sources can
have surface
temperatures exceeding 1500 C it is preferred that the sources disclosed in
this invention operate
below 900 C. Even more preferably the sources disclosed herein operate below
700 C.
Typically building codes limit direct contact to combustible surfaces such as
wallpaper to less
than 900 C. As such incandescent and halogen sources must be thermally
isolated from these
materials. Based on the higher efficiency of solid state light sources, with
the light emitting
surface being the cooling surface, the efficiency of this invention, and the
thermal spreading of
the light transmitting thermally conductive element; 4 inch x 4 inch panel
lights based on this
invention can emit in excess of 1000 lumens without exceeding the 900 C
surface temperatures
in contact with any mounting surfaces. As such the light sources disclosed can
emit a useful
level of output directly mounted on wallpaper and other combustible surfaces
unlike
incandescent and halogen sources. This allow for a wide range of applications.
The non-
flammable nature of the materials used in this invention do not allow for
flame spread even up to
10000 C unlike prior art organic based waveguide approaches. If even higher
lumen outputs are
required the thermal barrier 4650 may further thermally isolate the heat
generated in the light
source from coupling to any surface to which the light source is attached. The
thermal barrier
4650 may comprise polymers, fiberglass, ceramics, or metals. The thermal
barrier 4650 may
also be decorative, supportive, or even form a hermetic or environmental seal
for the light
source.
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[00298] FIG 47 depicts multiple or plurality of light sources and/or dummy
elements connected
together to form linear, shaped or large planar area light sources. FIG. 47A
depicts light
transmitting thermally conductive elements 4712 and 4714 on which an
electrical interconnect
means 4710 and 4708 is formed. Reflector 4704 may be separate reflectors for
each segment of
the light source or a single larger reflector that bridges the translucent
light transmitting
thermally conductive elements 4712 and 4714. Jumper 4702 may comprise but not
limited to
flex circuits, wires, pins, mechanical clips, ribbon, or other electrical
connecting means. Jumper
4702 may further have a contact 4700 which may comprise but not limited to
magnets, pins,
clips, or other contact means known in the art. While not shown reflector 4704
has sides as
previously disclosed which form a light recycling cavity 4706 as also
previously described.
Jumper 4702 may be within the recycling cavity 4706 or outside the recycling
cavity 4706
formed by reflector 4704 and the translucent thermally conductive elements
4712 and 4714.
Jumper 4702 may or may not be physically attached to reflector 4704. Reflector
4704 may or
may not be part of the electrical connections used to provide power to the LED
die or packages
(not shown) within the light recycling cavity 4706. While a two dimensional
rendering is shown,
it is disclosed that interconnect means 4708 and 4710 cover a small portion of
the surface area of
translucent light transmitting thermally conductive elements 4714 and 4712
respectively. This
allows for high transmission of the light through translucent light
transmitting thermally
conductive elements 4714 and 4712 as previously disclosed.
[00299] FIG 47B depicts multiple or plurality of light sources or dummy
elements which are
connected via connectors comprising of at least one pin connector 4724 and at
least one socket
connector 4722 which attach to interconnect means 4730 on translucent
thermally conductive
element 4734 and interconnects means 4728 on translucent thermally conductive
element 4732
respectively. Again reflector element 4720 forms a light recycling cavity 4726
along with
translucent light transmitting thermally conductive elements 4734 and 4732.
Using these
techniques multiple or a plurality of light sources may be interconnected
electrically and
physically to form long linear, shaped or large area low profile light sources
without the need
for heatsinks or other cooling means. In general, the techniques listed above
allow for light
sources, which emit greater than 30 lumens per gram. This high lumen output to
weight ratio
and the ability to cool using substantially only the light emitting surface is
fundamental to this
invention as it reduces the material costs of lighting fixtures, allows for
direct application of solid
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state lighting to suspended ceilings and a wide variety of surfaces, and in
many cases eliminates
the need for additional fixture elements. As an example a 1000 square foot
room requires
30,000 lumens to provide adequate lighting levels for general usage. Using the
light sources of
this invention the entire lighting for the room will weigh less than 1 kg.
This allows for direct
attachment to suspended ceilings without the need for additional support wires
to the deck. It
also reduces shipping costs and storage costs. Unlike incandescent or
fluorescent bulbs the low
profile and low voltage characteristics of these solid state light sources
eliminate in many cases
the need for additional fixture elements further reducing costs.
[00300] In particular the use of these light sources embedded in, attached to,
or mounted to
sheetrock, ceiling tiles, wood paneling, painted surfaces, metal surfaces,
trim elements, brick,
stone, tile or other construction materials to provide lighting or intelligent
lighting in homes,
offices, restrooms, manufacturing, or other lighting applications is an
embodiment of this
invention. Intelligent lighting is also a preferred embodiment allowing for
the integration of
color tuning, light harvesting, security, motion detection, or other sensor
functions into the
lighting modules. As lighting is required in virtually all locations where
humans work, reside, or
occupy; the integration of sensors into the lighting system is preferred.
[00301] The lighting system disclosed in this invention enables a low cost,
simple architecture
for implementing intelligent lighting. Not only are the light sources
disclosed lightweight,
efficient, and cost effective they are also (especially in the cases where
alumina is used for the
translucent light transmitting thermally conductive elements 4734 and 4732 )
completely
compatible with multi-chip module technologies such as thick film and
lithographic based
electronic packaging. The key component of the light source which acts as both
the light
emitting and cooling element also is compatible with thick film and
lithography based
interconnect means. This permits the light emitter to also simultaneously act
as a substrate for
multi-chip elements, passive elements, or active elements and is a preferred
embodiment of this
invention. Alumina is a preferred material due to its high scatter yet low
optical absorption,
white body color to external light, nearly linear optical absorption across
the visible spectrum,
high transmission in the IR, high emissivity, reasonable thermal conductivity,
low cost,
availability in thin sheet form, volume manufacturing, compatibility with high
temperature thick
film processing , low thermal expansion coefficient, insulative properties,
non-flammability, low
moisture uptake, vacuum tightness, and dielectric properties allowing for high
frequency
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elements. While other materials may be used the above properties all effect
final product
performance and must to be taken into account.
Other materials disclosed such as
organic/inorganic composites offer advantage of lower density and wider range
of body color but
lower operation temperatures. Holey metal approaches require the use of
dielectric layers but
allow for a wide range of aesthetic finishes since the outer surface no longer
effects the light
recycling cavity performance.
[00302] FIG 48 depicts a means to form a contiguous barrier with lighting with
a retrofit system
based on self cooling light sources disclosed in this invention. This approach
overcomes the
need to replace the existing grid in a suspended ceiling. This is field
installable unlike the DC
FlexZone system described previously which requires the existing grid to be
removed and
replaced. In this embodiment the existing grid 4812 is attached the deck 4800
via suspension
wire 4804 and mount 4802. Ceiling tiles 4804 and 4818 are suspended via the
existing grid
4812. Clip on power rail 4814 attaches to existing grid 4812 via but not
limited to one of the
following means, clips, adhesive, magnets, screws, snaps, or other mechanical
means. Power
leads 4808 and 4806 attach to contacts 4816 and 4814 respectively. Power leads
4808 and 4806
may or may not be integrated into clip on power rail 4814. Power leads 4808
and 4806 further
attach to at least one external power source (not shown) and deliver power to
the contacts 4816
and 4814 respectively. The light source 4826 contains contacts 4822 and 4824
which mate with
contacts 4816 and 4820 respectively. Contact 4822 and 4824 may also provide
mechanical,
magnetic, adhesive, Velcro, or other physical attachment means to hold light
source 4826 to clip
on power rail 4814 which in turn is attached to existing grid 4812.
[00303] The advantage of this approach is that existing grids and ceiling
tiles can be used,
lighting and intelligent lighting functions can be added only where needed,
the existing grid can
be cosmetically covered, the retrofit system can be installed by the end
customer (especially for
low voltage (less than 30VDC)), it is easily removed, moved, upgraded, or
otherwise changed,
and the lightweight nature of the approach does not degrade seismic
performance of the ceiling.
Alternately, the light source 4826 may be integrated in the ceiling tiles 4818
and/or 4810 instead
or as well as the existing grid 4812. In the case where the light source 4840
is mounted or
embedded in ceiling tile 4818, wires 4842 (only one wire shown) would contact
power leads
4808 and 4806 using contact means 4844 and 4850 as previously described. In
this case both
positive and negative inputs could be on one or each side of the existing grid
4812 and two or
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more contacts 4844 would be used to provide power to the light source 4840.
Again the main
advantage is the light weight (greater than 30 lumens per gram) and the self
cooling nature of
this invention. Ceiling tiles 4818 are typically composed of recycled paper
and as such contain
combustible materials. They also are specifically designed to have low thermal
conductivity to
isolate the plenum side 4832 from the occupant side 4834 to enhance the work
environment for
the occupants 4830. As previously state the high lumen per gram (greater than
30 lumens per
gram) enables the delivery of over 30,000 lumens into a room with less than 1
Kg of additional
weight to the suspended ceiling from the light sources 4826.
[00304] The light sources 4826 also cools itself substantially using the light
emitting surface
dissipating the heat it generates into the occupant side 4834 of the
installation. Light source
4840 similarly dissipates its heat into the occupant side 4834 of the
installation while
maintaining a maximum surface temperature against the ceiling tile 4818 of
less than 900 C and
even more preferably less than 700 C. Both light source 4822 and 4840 can
deliver greater than
100 lumens of diffuse substantially lambertian light per square inch of
emitting surface while
maintaining these surface temperature constraints. Unlike conventional solid
state lighting this
approach minimizes the amount of material required to create a high lumen
output distributed
substantially lambertian solid state source, minimizes the amount of weight
required to generate
1000s of lumens of output and does this in a package this is less than 1 cm
thick and even more
preferably less than 5 mm thick. This thin package enables the formation of a
nearly monolithic
suspended ceiling wherein ceiling tiles 4818 and 4810 can be tegular as shown.
Light source
4826 because of its thinness (less than 1 cm more preferably less than 5 mm)
can have its
emitting surface 4850 substantially flush with the occupant side 4852 of
ceiling tile 4818. This
creates a more pleasing and aesthetic look for the occupant 4830. In general,
30,000 lumens can
be delivered into a room using less than 1Kg of light sources 4826 while
dissipating less than
500 watts. A 1000 square foot room would be illuminated with greater than 30
lumens per
square foot while maintain a maximum surface temperature of less than 900 C
and even more
preferably less than 700 C. The low thermal resistance of the approach also
maintains the LED
junction temperatures within light source 4826 to be only a few degrees higher
than the emitting
surface 4850. Further still, the high lumens per gram output of light source
4826 enables clip,
snap, mechanical, Velcro, adhesive and magnetic suspension and mounting to the
ceiling.
Typically the existing grid 4812 is steel as such magnets can be used to not
only hold contacts
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4816 and 4820 to contacts 4822 and 4824 respectively, magnets may be used to
hold light source
4826 in place.
[00305] FIG 49A depicts a means to form a barrier 4900 of this invention
utilizing a retrofit
wall or floor installation of the light sources 4902. Because additional
elements such as
heatsinks, diffusers, or frames are not needed with the disclosed light
sources 4902 for use as a
fixture, light source 4902 can be mounted onto any surface which contains some
power input
means 4904 and 4906. Power input means 4904 and 4906 may include but not
limited to
embedded wires, tape based conductors, TCO based conductors, inductive
coupling means,
capacitive coupling means and radiative coupling means. As previously stated
because the
preferred embodiment is alumina for the emitting and cooling surfaces a wide
range of active
and passive elements can be easily incorporated into the light source 4902. As
an example
power input means 4902 and 4906 may be simply two copper conductors embossed,
trenched
into, or otherwise embedded into wall or floor barrier 4900.
[00306] As shown in FIG. 49B power input means 4904 can be covered by cover
layer 4912
which may include but not limited to wallpaper, spackle, paint or other
coverings. Because light
sources 4902 can deliver over 500 lumens in an area of less than 10 square
inches, weigh less
than 20 grams, in a package less than 5 mm thick, and still maintain a surface
temperature less
than 900 C while dissipating substantially all the heat generated into the
room via the light
emitting surface, it is possible to simply mount the light sources 4902 to the
wall or floor 4900
using mechanical means such as but not limited to screws, pins, staples,
magnets, Velcro,
adhesives and other attachment methods. As shown in FIG. 49B the support pin
4908 may also
act as an electrical connection between light sources 4902 and power input
means 4094, even
piercing cover layer 4912. Essentially the lightweight nature of these light
sources 4902 can be
tacked on to wall or floor 4900 if the proper power input means 4904 and 4906
are provided
either within, on, behind, in front of, or attached to wall of floor 4900.
While two leads are
shown for power input means 4904 and 4906 multiple lines may be used for
control and even
digital or RF inputs. Again light emitting and dummy units can be used in
floor and wall
applications as well. The light sources disclosed are applicable for indoor,
outdoor, underwater,
hazardous environment, space, and pressurized installations. Low voltage (less
than 30VDC) are
preferred due to elimination of shock hazards however AC and higher voltages
are disclosed with
the addition of dielectric protection and other safety features known in the
industry. Low voltage
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drive is also preferred due to elimination of AC to DC conversion losses for
intelligent lighting
functions which usually operate using DC. Using this approach wall wart power
supplies and
direct attachment to solar and other renewable resources are envisioned and
preferred.
[00307] FIG 50 depicts a means of forming a barrier of this invention
utilizing modular
sheathing units with integrated low voltage conductors to form a low voltage
power grid for
existing walls and floors. Sheathing unit 5000 contains at least two
conductors 5016 and 5014.
Sheathing unit 5000 may comprise but not limited to composite, paneling,
sheetrock, and other
construction materials. Sheathing unit 5000 most preferably is not permanently
affixed to
underlying walls and floors 5020 and is substantially self supporting. In a
manner similar to
modular flooring which snap together sheathing unit 5000 is intended to be
removable such that
the modular system can be taken with the owner when they move. The modular
nature also
allow for easy remodeling and redecorating without disturbing the underlying
walls and floors
5020. While attachment to underlying walls and flooring is possible it is not
preferred. This
enables the end user to easily reconfigure the room as required. As such
sheathing unit 500 has
sufficient structural integrity to support itself substantially over the
typical 8 foot floor to ceiling
distance with attachment only at the top and bottom to underlying walls and
floor 5020. Most
preferably sheathing unit 5000 has an integral or non-integral locking system
which allows the
multiple sheathing units 5000 to be linked together . The multiple sheathing
units 5000 may or
may not contain at least two conductors 5016 and 5014 in each unit. At least
two conductors
5016 and 5014 are shown with contact leads 5006 and 5004 respectively, which
connect to a
main low voltage power distribution system (not shown). The main low voltage
power
distribution system may be hidden within trim molding, wainscoting, or other
covering means
which may also be attached or mounted to the assembled sheathing units 5000
after installation.
[00308] Contact leads 5006 and 5004 may also be attachment means for securing
sheathing
units 5000 to the underlying floors and walls 5020. The sheathing units 5000
may also extend to
ceilings or be freestanding elements as well. Connector means 5010 and 5008
are meant to
electrically connect to at least two conductors 5016 and 5014 to provide power
to panel light
5002. Connector means 5010 and 5008 may optionally provide for attachment
means of panel
light 5002 to the sheathing unit 5000 as well. The lightweight, elimination of
heatsink, and
thinness of the panel light 5002 disclosed previously enables the use of this
type of independent
modular low voltage power grid. In conventional solid state lighting the
underlying walls and
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floors 5020 would be drilled or otherwise punctured to allow for electrical
wiring or recess
mounting of the heatsink or other cooling means. This not only means that any
changes such as
moving a light source results in have to patch or otherwise repair the
underlying walls and floors
5020 but it also means that underlying walls and floors 5020 no longer provide
a continuous
barrier which compromises the thermal and fire performance of the room. By
creating an outer
modular sheath comprising of multiple sheathing units 5000 which contain
integral low voltage
power grids the end user can change, remove, take with, or otherwise modify
any room. While
the approach can be extended to the ceiling as previously disclosed the
sheathing units 5000 may
require addition support or mounting elements to prevent warping. Sheathing
units 5000 may
also be used to connect, distribute or otherwise connect the low voltage power
grid between the
floor, ceiling, or walls. In this manner, a single power supply may be used to
provide power to
multiple lighting source or other devices such as but not limited to audio,
air movement,
displays, floor lamps, kitchen appliances, or tools.
[00309] An example, of additional support or mounting elements for ceiling
mounting would be
but not limited to the suspended grid, attachment to rafters, or other methods
consistent with
mounting of ceiling tiles, paneling, or sheetrock. Sheathing units 5000 may
also be spaced out
from underlying walls and floors and be acoustically permeable such that
additional noise
dampening can be created compared to hard mounted approaches. Sheathing units
5000 spaced
a distance from underlying walls and floors 5020 may also provide air channels
for HVAC. Hot
air may be routed to closer to the floor and cold air may be routed to the
ceiling using the space
between the sheathing units 5000 and the underlying walls and floors 5020 to
create more
efficient heating and cooling. Alternately, radiant heating and/or cooling
units may be
incorporated into sheathing units 5000,between sheathing units 5000 and
underlying walls and
floors 5020, and/or attached to underlying walls and floors 5020 such that
sheathing units 5000
act to not only hide the radiant heating and/or cooling units but also serve
to enhance air
circulation by forming induced draft air channels. In general, a preferred
embodiment is a semi-
rigid substantially freestanding modular system based on multiple connected
sheathing units
5000 where at least one sheathing unit 5000 contains at least one low voltage
power distribution
grid.
[00310] FIG 51 depicts at least one panel light 5112 mounted to at least one
modular sheathing
unit comprising of an inner dielectric layer 5104, at least one inner
conductor layer 5102, and at
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least one outer dielectric layer 5100. In this embodiment the modular
sheathing unit is shown
against wall, floor, or ceiling 5106. As previously stated the at least one
modular sheathing unit
is preferably substantially freestanding such that the power grid can be
easily reconfigured,
replaced, changed and moved to a new location. In the figure outer dielectric
layer 5110 is
pierced by contact probe 5110 to electrically connect the panel light 5112 to
the inner conductor
layer 5102. Multiple contact probes 5110 would be used to provide power to
panel light 5112.
Alternately, outer dielectric layer 5100 may be removed via mechanical,
chemical, or abrasive
means to expose inner conductor 5102 to enable electrical contact to panel
light 5112.
Alternately, inductive and capacitive means may be used to transfer power
between inner
conductor 5102 and the panel light 5112. In the wireless power transfer case a
transmitting
element would be additional incorporated into the sheating unit and receiving
unit would be
incorporated into the panel light 5112 as previously disclosed. Additional
mounting means 5114
may include but not limited to screws, adhesive, clips, nails, tape, magnets,
Velcro, or other
mounting means. The light weight of the disclosed panel lights 5112 enables
the use of this
approach without the need for additional support via attachment walls, floor,
or ceiling 5106.
Additional trim, reflectors or optical elements both functional and decorative
may be further
attached to the outer dielectric layer 5100 and/or panel light 5112. The panel
light 5112 emits
both light and heat to the ambient environment 5108.
[00311] FIG 52 depict a room comprising wall 5202, ceiling 5220, and floor
5228 with low
voltage devices 5218, 5204, 5210, 5214, and 5216 all power using power legs
5226, 5222, 5206,
5208, 5212,and 5224 off the main low voltage power grid 5200. In some cases
the power leg
directly attaches the low voltage device to the low voltage power grid 5200.
In other cases,
multiple power legs which are 3 dimensionally oriented relative to each other
are used to supply
power to the low voltage device. An example is low voltage device 5218 which
is connected to
the main low voltage power grid 5200 via power legs 5222 and 5218. Low voltage
devices
5218, 5204, 5210, 5214, and 5216 may comprise but not limited to panel lights,
smoke detectors,
motion sensors, light sensors, temperature sensors, DC to AC converters, DC to
DC converters,
data links, security sensors, RFID sensors, audio devices, video devices,
entertainment devices,
tools, kitchen appliances, and timers. In this embodiment sheathing units
containing low voltage
power grids are interconnected substantially orthogonally as shown however non-
orthogonal
interconnects between sheathing units is also envisioned. In general, it is
disclosed that
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substantially freestanding modular system of sheathing units containing low
voltage power grids
are interconnected such that substantially only openings 5230 are not covered
by the sheathing
units. Openings 5230 may include windows, doors, central vacuum outlets, and
HVAC
openings. This box within a box allows for a high degree of flexibility and
allows for HVAC,
radiant heating, and cosmetic issues to be easily covered and/or hidden. As an
example, an
apartment with an unfinished concrete block wall can be retrofitted with wood
paneling with an
embedded low voltage power grid which can be removed by the tenant at the end
of the lease
using this approach in a manner very similar to how snap and lock floating
flooring can be
reused. This minimizes material waste associated with redecorating and
renovation. Low
voltage power grids do not require electrician installations, this coupled
with light weight self
cooling panel lights enables the reusable modular sheathing approach
disclosed.
[00312] FIG. 53A depicts a reflective grid comprising of a grid element 5304
and reflector
element 5306 which form part of the light recycling cavity. In this embodiment
the end user
installs the light transmitting thermally conductive element 5300. The light
transmitting
thermally conductive element 5300 may be attached to the grid element 5304 to
form the light
recycling cavity using but not limited to at least one of the following
elements, clips, pins,
magnets, adhesives, Velcro, or other mechanical means. The translucent
thermally conductive
element 5300 may further contain at least one of the following associated
elements 5308, a
semiconductor device, passive element, and/or light source. The translucent
thermally
conductive element 5300 may also be a dummy unit designed to provide a
particular aesthetic
look. This embodiment is enabled because the heat is removed and dissipated
using the
substantially only the translucent thermally conductive element 5300. This
allows the reflector
element 5306 be a wide range of materials including but not limited to
reflective plastics,
reflective metals, and other reflective coatings which may be attached or
applied to the grid
element 5304. This embodiment further reduces the weight of the light source
which must be
provided to the end user. Greater than 100 lumens per gram is possible when
only the
translucent thermally conductive element 5300 and any associated elements 5308
are all that is
required to be shipped to the end user. This embodiment further reduces the
cost of shipping and
stocking. In addition this embodiment allows the end user access to the
associated elements
5308 for upgrades and retrofits. As an example, wireless data links could be
added or upgraded
simply by replacing associated elements 5308 as required. This user
adaptability is an
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embodiment and benefit of this invention. Given the long life (greater than 10
years) of solid
state lighting this approach if standardized would allow for the end user to
take their lighting to a
new location as well as reconfigure the present location. FIG. 53B depicts a
light transmitting
thermally conductive element 5322 with associated elements 5324 which may
include but not
limited to light sources, active semiconductor elements, passive electronic
elements, and
microwave and RF elements. The light transmitting thermally conductive element
5322 forms
the aperture element for a recycling cavity by attaching the light
transmitting thermally
conductive element 5322 to mounting surface 5320 which may include but not
limited to a
ceiling tile, wall, floor, ceiling, wood element, plastic element, sheetrock,
painted panel, glass
sheet, or other surface. The mounting surface most preferably has a
reflectivity to light or
radiation emitted from associated elements 5324 greater than 90%. The
attachment may be via
pins, wires, adhesives, mechanical means, nails, screws, clips, or other
attachment means.
[00313] FIG. 54A depicts a light recycling light source with holey light
transmitting thermally
conductive element 5402. The reflector 5400 forms the light recycling cavity.
The lens elements
5403 are aligned to the holes with the holey light transmitting thermally
conductive element
5402 such that the solid angle of the light emitted from the light recycling
light source is reduced
to less than lambertian. This can be used to reduce glare and/or form a
directive light source.
[00314] FIG 54B depicts a recycling light source comprising a holey light
transmitting
thermally conductive element 5422 and a reflector 5420 where the holes in the
holey light
transmitting thermally conductive element 5422 are not perpendicular to the
light emitting
surface of the holey light transmitting thermally conductive element 5422.
FIG. 54C depicts a
recycling light source comprising of a holey light transmitting thermally
conductive element
5432 and a reflector 5430. Additional turning element 5434 may be formed when
the holes are
formed in the holey light transmitting thermally conductive element 5432 or be
attached or
adhered such that the holes within holey light transmitting thermally
conductive element 5432
are substantially aligned with additional turning element 5434.
[00315] FIG. 55 depicts a compound shaped light transmitting thermally
conductive element
5504 which can be attached to a flat or non-flat reflective mounting surface.
The mounting
surface 5500 may be reflective and may or may not be ferromagnetic or
magnetic. Optional
reflective layer 5502 may be used to enhance the efficiency of the light
recycling cavity 5518. .
Because the shaped light transmitting thermally conductive element 5504
dissipates substantially
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all the heat generated by LED package 5506 there is no need for further
heatsinking means.
Interconnect 5510 and 5512 formed on the shaped light transmitting thermally
conductive
element 5504 make contact to conductors 5514 and 5516 respectively. Conductors
5514 and
5516 may be metals, TC0s, or other conductive materials. If the mounting
surface 5500 is
ferromagnetic or magnetic, magnetic mounts 5520 and 5522 may be used to not
only bring
interconnect 5510 and 5512 together with conductors 5514 and 5516 but also
hold the light
source physically to the mounting surface 5500. Alternately, electrical
connection may be via
pins, clips, conductive Velcro, springs, screws, nails or other mechanical
means. A preferred
material for conductor 5514 and 5516 is patterned ITO or other TCO with low
optical absorption
to the light emitted by LED package 5506 such that the light recycling cavity
5518. The
reflective layer 5502 may be a glass sheet with patterned ITO or other TCO on
the surface
forming the inner surface of the light recycling cavity 5518 with a reflective
coating on the glass
surface against the mounting surface 5500.
[00316] FIG. 56 depicts a gimbal 5604 supporting a self cooling lightweight
recycling light
source 5606 suspended from a ceiling 5600 or some other mounting surface using
a mount 5602.
In this case the gimbal 5604 and mount 5602 are greatly simplified and can be
much lighter due
the lightweight nature of the self cooling lightweight recycling light source
5606. The patient
5608 on the table 5610 can be more easily examined. The light source may be
mounted to a
variety of surfaces including the floor 5612. In general, the lightweight
greater than 50 lumens
per gram and high output level of this approach allows for the delivery of
lighting into a number
of weight critical lighting applications including but not limited to, mobile,
aircraft, automobile,
motorcycle, bicycle, and other applications in which weight is critical. The
substantially
inorganic construction of this approach also provides benefits associated with
environmental
resistance, color fastness, and non-flammability. Unlike substantially organic
approaches such as
troffer with large plastic diffusers and polymeric waveguides approach are
intrinsically heavy
and susceptible to photochemical degradation from both sunlight and the
UV/blue portion of the
light emitted from the LEDs themselves.
[00317] FIG. 57 depicts a barrier comprising of at least one support grid
element 5712
supporting at least one central attachment point devices 5724 to the walls
5702 and 5704. The at
least one support grid element 5712 may alternately be attached to the deck
5700 or floor 5722
as well depending on the orientation of the barrier. The barrier assembly may
additionally have
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support wire 5706 which is anchored to the deck 5700 using mount 5708 and
attached to either a
central attachment point device 5724 or a support grid element 5712. The
reduced weight
associated with the use of self cooling lighting sources 5720 allows for the
use of substantially
centrally supported barrier elements 5714. Using a substantially central
mounting approach it
becomes possible to layer or stack the barrier elements 5714, 5716, and 5718.
Layering allows
lighting to be hidden behind barrier elements as shown in barrier elements
5716 and light source
5726. The layered or stacked ceiling tiles 5714, 5716, and 5718 can be used to
conceal lighting
and other functions previously disclosed. As long as there is sufficient air
gap allowed between
barrier elements 5714, 5716, and 5718, air can flow between occupant side 5730
and plenum
side 5732. The centrally supported barrier elements 5714, 5716, and 5718 may
attach to central
attachment point device 5724 via Velcro, mechanical means, clips, screws,
snaps or locking
mechanisms. Most preferably, centrally supported barrier elements 5714, 5716,
and 5718 are
attached using a mounting means which is not visible from occupant side 5730.
This
embodiment can be used as a very effective acoustical dampening ceiling due to
sound waves
being trapped in the plenum side 5732.
[00318] Alternately, centrally supported barrier elements 5714, 5716 and 5718
may be
substantially in the same plane such that a monolithic surface is formed. The
centrally supported
barrier elements 5714, 5716, and 5718 may also have edges which interlock,
snap together or
otherwise attach to each other. In general, the lightweight nature of the self
cooling light sources
5720 and 5726 enables support grid element 5712, central attachment point
device 5724, and
centrally supported barrier elements 5714, 5716, and 5718 to be lighter weight
and lower cost
materials. As previously disclosed the self cooling light sources 5720 and
5726 are light
recycling cavity light sources or light recycling cavity elements which are
integrated into
centrally supported barrier elements 5714 and 5716 respectively.
[00319] FIG. 58 depicts a strip light based on the previously described
techniques of this
invention containing multiple translucent light transmitting thermally
conductive elements 5800,
5802, 5804, and 5806 attached to a larger reflector 5808 that form light
recycling cavity 5805.
This allows for thermal expansion difference and a degree of flexing of the
strip light. As an
example, translucent light transmitting thermally conductive elements 5800,
5802, 5804 and
5806 may be 500 micron thick alumina pieces which are 1 inch x 6 inches. The
larger and
longer reflector 5808 may be coated aluminum, which is less than 300 microns
thick. The large
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reflector 5808 is used to hold the multiple translucent light transmitting
thermally conductive
elements 5800, 5802, 5804 and 5806 such that a substantially contiguous 24
inch x 1 inch self
cooling strip light is formed. The large reflector 5808 being aluminum is more
flexible than the
alumina pieces allowing the strip to flex. This slightly flexible nature
allows the strip light to
connect to surfaces which are not perfectly flat like suspended ceiling grids.
Wall and floor
mountings may also require a less than rigid strip light due to non-flat
surfaces.
[00320] FIGS. 59A-E depicts a variety of self cooling recycling cavity light
sources in which
the light emitting and cooling surfaces are substantially the same. FIG. 59A
depicts a translucent
light transmitting thermally conductive element 5900 and a reflector 5918
which forms a light
recycling cavity 5907 in which at least one LED package 5912 is mounted to the
translucent
thermally conductive element 5900 along with an interconnect 5908 and 5910. An
LED package
typically contains an LED mounted to a substrate with a phosphor or wavelength
conversion
element covering the LED. A preferred LED package for use in this light source
is one with a
small ceramic (alumina) substrate that is surface mountable. The at least one
LED package 5912
generates heat which is transferred by thermal conduction to the light
transmitting thermally
conductive element 5900 and spread out as depicted by heat ray 5904 over an
area greater than
the area of the at least one LED package 5912 and transferred to the
surrounding ambient via
convective and/or radiative ray 5902. Also the light emitted depicted by ray
5914 is emitted
from the at least one LED 5912, is reflected off the reflector 5918 as
reflected ray 5916 one or
more times and impinges on the translucent light transmitting thermally
conductive element 5900
where it is either further reflected off the interior surface 5903 of the
translucent light
transmitting thermally conductive element 5900 or becomes transmitted ray 5906
which exits the
recycling cavity 5907 from exterior surface 5901 of translucent light
transmitting thermally
conductive element 5900. Transmitted ray 5906 and heat ray 5904 travel
substantially in the
same direction and are emitted from the same exterior light emitting surface
5901 of translucent
light transmitting thermally conductive element 5900. As in other embodiments
of this invention
the light emitted rays 5916 on average experience a large number of
reflections before exiting the
recycling light cavity 5907. This creates a more uniform brightness
distribution on exterior
surface 5901 of light transmitting thermally conductive element 5900. In
general, materials
which exhibit less than 20% in line transmission are preferred to generate
high uniformity. Most
preferred is alumina.
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[00321] FIG. 59B depicts another light recycling cavity source in which the
light emitting
surface also is the cooling surface. In this case the at least one LED die
5936 is mounted on a
holey metal recycling cavity 5930. In this embodiment the interconnect 5934
may also require a
dielectric layer 5932 to electrically isolate the interconnect 5934. Holes
5931 in holey metal
recycling cavity 5930 allow for light rays to eventually exit the holey
recycling cavity 5930.
While there may be additional thermal resistance from the dielectric layer
5932, the higher
thermal conductivity of metals such as aluminum can more effectively spread
the heat generated
by the at least one LED package 5936 even with holes 5931. Alternately, the
holey metal
recycling cavity may be sinter metals, porous ceramics, porous composites, and
other thermally
conductive materials which also have holes 5931 which are either random or
combinations of
holes and translucent materials such as metal/glass composites. The basic
requirement is that
heat is transferred to the same surfaces which also emit light. The heat
generated by elements
within the recycling cavity 5933 may be transferred to the light emitting
surface by conduction,
convection, and radiation or combinations of these cooling means.
[00322] FIG. 59C depicts a self cooling light recycling source is which LED
package 5962 is
mounted within the recycling cavity 5951 but not on the inner surface 5955 of
the light emitting
portion of the holey recycling cavity element 5952. Heat is conducted to
exterior surface 5951
by thermal conduction ray 5966 and transferred to the surrounding ambient via
convection
and/or radiative means 5950. The LED package 5962 is mounted on interconnect
5960 which in
turn is isolated from the holey recycling cavity element 5952 using dielectric
layer 5958 as in
FIG. 59B. In this configuration, there is an additional thermal resistance
associated with moving
the heat via thermal conduction ray 5966. Thermal insulator 5954 may be used
in this
configuration to thermally isolate the holey recycling cavity element 5952
from the mounting
surface 5959. Building codes require that combustible surfaces not be exposed
to temperatures
greater than 90 C. By using thermal insulator 5954 the exterior surface 5951
portion of the holey
recycling cavity element 5952 can be greater than 90 C and yet the light
source can still be
mounted on combustible surfaces by limiting the convection and/or radiative
means 5950 to
substantially only the light emitting portion of exterior surface 5951 of
holey recycling cavity
element 5952.
[00323] FIG. 59D depicts a holey light recycling cavity element 5970 in which
LED package
5974 is mounted onto circuit board 5976. The light ray 5972 is still recycled
multiple times
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within the holey light recycling cavity element 5970 but heat from the LED
package 5974 is
conducted first through the circuit board 5976 then transferred to holey light
recycling cavity
element 5970 via conduction. The heat is then conducted again to the light
emitting portion of
the holey light recycling cavity element 5970. Circuit board 5976 may be a
flex circuit, printed
circuit board, multi-chip module, and interconnect means. In this
configuration a low thermal
resistance thermal conduction path within the circuit board 5976 and a low
thermal resistance
interface between circuit board 5976 and holey light recycling cavity element
is required to move
the heat generated by LED package 5974 to the cooling surface and light
emitting surface 5973
of the holey light recycling cavity element 5970. In these configurations the
intent is to provide
a low thermal resistance path to the light emitting surfaces so that
substantially most of the heat
generated within the light recycling light source is transferred to the
surrounding ambient using
substantially the same surface as which light is emitted from the light
recycling light source. In
general and from a practical standpoint the light emitting surfaces face the
space or area to be
illuminated. With the light sources of this invention all emitting surfaces
are exposed to
ambient. Therefore with the light sources diffuse and/or directly viewable all
the light emitting
surfaces can be used for convection and radiative cooling as well as light
emission. All other
surfaces of the disclosed light sources not exposed to ambient can be used for
external
interconnect, mounting, and can be thermally isolated from the mounting
surface if needed.
This greatly increases where, how, and on what surfaces or structures the
light sources can be
used because substantially all the cooling from the light emitting surfaces
are in convective
contact with the ambient space occupied by the end users.
[00324] FIG. 59E depicts a light recycling cavity light source in which two or
more translucent
light transmitting thermally conductive elements 5986 and 5988 and reflectors
5996 and 5984
form the light recycling cavity 5991. The LED packages 5990 and 5986 are
mounted within the
light recycling cavity 5991. Rays 5994, 5992, and 5982 are emitted from the
light recycling
cavity 5991 through the two or more light transmitting thermally conductive
elements 5986 and
5988. The reflectors 5996 and 5984 may be holey, solid, or substantially
porous. The reflectors
5996 and 5984 may also be thermally insulated as discussed in FIG. 59C. In
general,
combinations of light emitting surfaces which are also cooling surfaces such
as two or more light
transmitting thermally conductive elements 5986 and 5988 may be combined with
opaque
reflectors such as reflector 5996 and 5984 which may or may not contain
thermal barriers or
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other thermal isolation means to allow for safe mounting of the disclosed
light sources to
combustible surfaces. This allows for high lumen output light sources to be
integrated into or
attached to but not limited to ceiling tiles (even if those ceiling tiles are
thermally insulating and
constructed of combustible materials like recycled paper), sheet rock with
paper outer surfaces,
wallpapered surfaces, painted surfaces, fabrics, plastic surfaces, and wood
surfaces. Most
preferred is the mounting of the LED packages 5990 and 5986 on light emitting
surfaces such
that the minimum thermal resistance can be achieved between the LED packages
5990 and 5986
and outer light emitting surfaces of two or more light transmitting thermally
conductive 5988 and
5986. However, as described above LED packages 5990 and 5986 may be mounted
anywhere
within the light recycling cavity 5991 as long as the LED packages 5990 and
5986 are thermally
connected to the two or more light transmitting thermally conductive elements
5988 and 5986.
[00325] FIG. 60 depicts a light recycling self cooling light source. In this
embodiment a porous
thermally conductive element 6000 contains an array of holes 6002. Alternately
array of holes
6002 may be transmitting elements, porosity, and sintered metals. The porous
thermally
conductive element 6000 may be shaped in a variety of three dimensional shapes
including but
not limited to hemispheres, cylinders, cubes, and free form shapes to create a
desired aesthetic
look. The shape of porous thermally conductive element 6000 shape and
distribution of an array
of holes 6002 may also be used to create a desired far field pattern as well.
As previously
disclosed the use of materials with reflectivity greater than 90% for inner
surface 6016 of porous
thermally conductive element 6000 is preferred to maximize the efficiency of
the light recycling
cavity 6006. Concurrently, the porous thermally conductive element 6000 most
preferably
exhibits a thermal conductive of greater than 1 W/m/K and even more preferably
greater than 30
W/m/K such that heat generated by LED package 6004 can be spread efficiently
to the light
emitting side of exterior surface 6018 of porous thermally conductive element
6000 and be
transferred to the same ambient environment as illuminated by the light
source. In this
embodiment LED package 6004 is mounted onto flex circuit 6014, which contains
at least two
conductors 6012 and 6010. At least two conductors 6012 and 6010, in additional
to providing
power to LED package 6004 also provides a thermal conduction path through
dielectric layer
6008 to the porous thermally conductive element 6000. This embodiment can also
be realized
using translucent light transmitting thermally conductive elements for porous
thermally
conductive element 6000. However, the higher thermal conductivity, ease of
forming and low
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cost of metals such as aluminum are most preferred. In addition, the use of
reflectivity enhanced
aluminum like AlanodTM with an array of holes 6002 for porous thermally
conductive element
6000 allows for the exterior surface 6018 to be painted and otherwise modified
to create a wide
range of aesthetic looks. Most preferably, any coating on the exterior surface
6018 should
exhibit a thermal conductivity greater than 1 W/mK and an emissivity greater
than 0.3 to
enhance convective and radiative heat transfer to the surrounding ambient
environment 6020. In
this case, light emitted from the LED package 6004 exits from the array of
holes 6002 while the
heat is mostly emitted off the exterior surface 6018. Some convective heat
transfer can occur as
air from the surrounding ambient environment 6020 passes through the array of
holes 6002 and
into the recycling cavity 6006. In this case, even LED package 6004 and the
inner surfaces 6016
of porous thermally conductive element 6000 may enhance heat transfer to the
surrounding
ambient environment 6020. In addition, the array of holes 6002 allow for
additional radiative
heat transfer to the surrounding ambient environment 6020 in a manner very
similar to how the
light emitted from LED package 6004 exits the light recycling cavity 6006.
[00326] FIG. 61A depicts self cooling recycling light sources with thermal
transfer elements
6106. The thermal transfer elements may include glasses, metals, ceramics,
amorphous
materials, polycrystalline materials and single crystalling materials with or
without luminescent
materials. The heat generated by LED package 6102 is transferred through
reflector 6104
through thermal transfer elements 6106 to the light transmitting thermally
conductive element
6100 via conduction. The thermal transfer elements 6106 may be light
transmitting, wavelength
converting, opaque, and/or translucent but most preferably the thermal
transfer element 6106
exhibit low optical losses because they are within the light recycling cavity
6108.
[00327] FIG. 61B depicts a substantially contiguous thermal transfer element
6128 surrounded
by reflective interconnects 6122 and 6124. LED die or package 6126 is in
thermal contact with
the thermal transfer element 6128 which in turn transfer the heat generated
for LED die or
package 6126 to the light transmitting thermally conductive element 6120. In
this embodiment
thermal transfer element acts as an embedded waveguide element as well as a
thermal transfer
element.
[00328] While the invention has been described in conjunction with specific
embodiments and
examples, it is evident to those skilled in the art that many alternatives,
modifications and
variations will be evident in light of the foregoing descriptions.
Accordingly, the invention is
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intended to embrace all such alternatives, modifications and variations that
fall within the spirit
and scope of the appended claims.
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