Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED THIN-FILM COATINGS, ELECTRO-OPTIC ELEMENTS
AND ASSEMBLIES INCORPORATING THESE ELEMENTS
BACKGROUND OF THE INVENTION
[0001] Electro-optic elements are becoming commonplace in a number of
vehicular and
architectural applications. Various electro-optic element configurations
provide variable
transmittance and or variable reflectance for windows and mirrors.
SUMMARY OF THE INVENTION
[0002] The present invention relates to various thin-film coatings,
electro-optic elements
and assemblies incorporating these elements.
[0003] In accordance with one aspect of the present invention, there is
provided a
vehicular rearview assembly including a mirror element having transflective
and opaque
areas, the mirror element comprising a first substantially transparent
substrate, a lower
reflecting layer disposed on the first substantially transparent substrate,
the lower
reflecting layer covering the transflective area, an opacifying layer disposed
outside the
transflective area and adjacent to the lower reflecting layer, and an upper
reflecting layer
extending over the opacifying layer and the transflective area of the EC-
element, the
upper reflecting layer and the lower reflecting layer having a common surface
over at
least a portion of the transflective area.
[0004] In accordance with another aspect of the present invention, there
is provided a
vehicular rearview assembly including a mirror element having transflective
and opaque
areas and a transition area therebetween, the EC-element comprising a
substantially
transparent substrate, an opacifying layer disposed on the substantially
transparent
substrate outside the transflective area of the EC-element, and an upper
reflecting layer
extending over the opacifying layer and the transflective area of the EC-
element, wherein
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at least one of the opacifying layer and upper reflecting layer has a
thickness which
gradually changes in a transition area between a first thickness value
corresponding to
the opaque area and a second thickness value corresponding to the
transflective area,
thereby causing at least one of the reflectance and transmittance of ambient
light by the
EC-element to change gradually between the opaque and transflective areas.
BRIEF DESCRIPTION OF THE FIGURES
[0005] Fig. 1 depicts an airplane having variable transmittance windows;
[0006] Figs. 2a and 2b depict a bus and a train car, respectively, having
variable
transmittance windows;
[0007] Fig. 3 depicts a building having variable transmittance and or
variable reflectivity
windows;
[0008] Fig. 4 depicts a vehicle having variable transmittance windows and
variable
reflectance rearview mirrors;
[0009] Figs. 5a-5e depict various views of exterior rearview mirror
assemblies and
related variable reflectance elements;
[0010] Figs. 6a-6d depict various views of interior rearview mirror
assemblies and related
variable reflectance elements;
[0011] Fig. 7 depicts a profile view of a cross section of a variable
reflectance element;
[0012] Figs. 8a-8d depict profile views of cross sections of various
elements;
[0013] Figs. 9a-9j depict various electrical contacts for various
elements;
[0014] Fig. 10 depicts an electrical control schematic for multiple
elements;
[0015] Figs. 11a-11c depict various electrical control schematics;
[0016] Fig. 12 depicts a graph of element wrap v. oxygen flow for various
argon process
gas pressures utilized in an element manufacturing process;
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[0017] Fig. 13 depicts a graph of thin film bulk resistance v. oxygen flow
for various
process gas pressures utilized in an element manufacturing process;
[0018] Fig. 14 depicts a graph of thin film thickness v. oxygen flow for
various
process gas pressures utilized in an element manufacturing process;
[0019] Fig. 15 depicts a graph of thin film sheet resistance v. argon flow
for various
process gas pressures utilized in an element manufacturing process;
[0020] Fig. 16 depicts a graph of thin film bulk resistance v. argon flow
for various
process gas pressures utilized in an element manufacturing process;
[0021] Fig. 17 depicts a graph of thin film absorption v. oxygen flow for
various
process gas pressures utilized in an element manufacturing process;
[0022] Fig. 18 depicts a graph of element wrap v. oxygen flow for various
process
gas pressures utilized in an element manufacturing process;
[0023] Fig. 19 depicts a graph of element wrap v. thin film absorption for
various
process gas pressures utilized in an element manufacturing process;
[0024] Fig. 20 depicts a graph of element wrap v. thin film transmittance
for various
process gas pressures utilized in an element manufacturing process;
[0025] Figs. 21-32 depict various thin film surface morphologies;
[0026] Figs. 33a and 33b depict thin film peak-to-peak surface roughness;
[0027] Fig. 34 depicts a graph of sputtering yield v. ion energy for
various thin film
materials;
[0028] Fig. 35 depicts a graph of sputter yield v. sputter gas mass/target
mass;
[0029] Figs. 36 and 37 depict enlarged ion-milling results;
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[0030] Fig. 38 depicts a graph of thin film surface roughness v. inverse of
line
speed;
[0031] Fig. 39 depicts a graph of thin film reflectance v. ion beam
current;
[0032] Fig. 40 depicts a graph of thin film reflectance v. inverse of line
speed;
[0033] Fig. 41 depicts a graph of thin film b* v. inverse of line speed;
[0034] Fig. 42 depicts a graph of thin film reflectance v. ion beam
residence time;
[0035] Fig. 43 depicts a graph of thin film reflectance v. thickness;
[0036] Fig. 44 depicts a graph of thin film reflectance v. wavelength;
[0037] Fig. 45 depicts a graph of thin film transmission v. wavelength;
[0038] Fig. 46 depicts a graph of thin film reflectance v. thickness;
[0039] Fig. 47 depicts a graph of thin film transmission v. reflectance;
[0040] Figs. 48a-53c depict various graphs of thin film reflectance and or
transmission v. wavelength; and
[0041] Figs. 54-62 depict various embodiments of elements having graded
thin-film
coatings.
DETAIL DESCRIPTION OF THE INVENTION
[0042] Figs. 1, 2a and 2b depict multi-passenger vehicles 102, 202a, 202b
employing variable transmittance windows 110, 210a, 210b. Multi-passenger
vehicles employing variable transmittance windows 110, 210a, 210b include, for
example, aircraft 102, buses 202a, and trains 202b. It should be appreciated
that
other multi-passenger vehicles, some of which are described in more detail
elsewhere herein, may employ variable transmittance windows 110, 210a, 210b.
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The multi-passenger vehicles generally illustrated in Figs. 1, 2a and 2b also
include window control systems (not shown in figs 1 - 2b, however, shown and
described with reference to Fig. 10) for controlling the variable
transmittance
windows. Commonly assigned U.S. Patent 6,567,708 and U.S. Patent
7,990,603 describe various details related to variable transmittance windows.
[0043] Another application of variable transmittance windows is depicted in
Fig. 3.
Architectural windows 302 of buildings 301 may advantageously incorporate
variable transmission functionality. It should be understood that these
variable
transmission architectural windows may be included in residential, commercial
and industrial facilities.
[0044] Fig_ 4 depicts a controlled vehicle 400 comprising various variable
transmittance and variable reflectance elements. As one example, an interior
rearview mirror assembly 415 is depicted, in at least one embodiment, the
assembly 415 comprises a variable reflectance mirror element and an automatic
vehicle exterior light control system. Detailed descriptions of such automatic
vehicle exterior light control systems are contained in commonly assigned U.S.
Patent numbers 5,837,994, 5,990,469, 6,008,486, 6,130,448, 6,130,421,
6,049,171, 6,465,963, 6,403,942, 6,587,573, 6,611,610, 6,621,616, 6,631,316,
6,774,988, 7,565,006, 7,683,326, 6,861,809 and 8,045,760. The
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controlled vehicle is also depicted to include a driver's side outside
rearview
mirror assembly 410a, a passenger's side outside rearview mirror assembly
410b,
a center high mounted stop light (CHMSL) 445, A-pillars 450a, 450b, B-pillars
455a, 455b and C-pillars 460a, 460b; it should be understood that any of these
locations may provide alternate locations for an image sensor, image sensors
or
related processing and, or, control components. It should be understood that
any,
or all, of the rearview mirrors may be automatic dimming electro-optic mirrors
(i.e.
variable reflectance mirror elements). In at least one embodiment, a
controlled
vehicle may comprise variable transmittance windows 401, 402. The controlled
vehicle is depicted to include a host of exterior lights including headlights
420a,
420b, foil weather lights 430a, 430b, front turn indicator/hazard lights 435a,
435b,
tail lights 425a, 425b, rear turn .indicator lights 426a, 426b, rear hazard
lights
427a, 427b and backup lights 440a, 440b. It should be understood that
additional
exterior lights may be provided, such as, separate low beam and high beam
headlights, integrated lights that comprise multipurpose lighting, etc. It
should
also be understood that any of the exterior lights may be provided with
positioners (not shown) to adjust the associated primary optical axis of the
given
exterior light. In at least one embodiment, at least one exterior mirror
assembly is
provided with pivoting mechanisms to allow pivoting in directions 4101, 410a2,
410b1, 410b2. It should be understood that the controlled vehicle of Fig. 4 is
generally for illustrative purposes and that suitable automatic dimming
rearview
mirrors, such as those disclosed in the patents and patent applications
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mentioned herein, may be employed along with other features described herein
and
within disclosures mentioned herein.
[0045] Preferably, the controlled vehicle comprises an inside rearview
mirror of unit
magnification. Unit magnification mirror, as used herein, means a plane or
flat
mirror with a reflective surface through which the angular height and width of
an
image of an object is equal to the angular height and width of the object when
viewed directly at the same distance with the exception for flaws that do not
exceed normal manufacturing tolerances. A prismatic day-night adjustment
rearview mirror wherein at least one associated position provides unit
magnification is considered herein to be a unit magnification mirror.
Preferably,
the mirror provides a field of view with an included horizontal angle measured
from the projected eye point of at least 20 degrees and a sufficient vertical
angle
to provide a view of a level road surface extending to the horizon beginning
at a
point not greater than 61 m to the rear of the controlled vehicle when the
controlled vehicle is occupied by a driver and four passengers or the
designated
occupant capacity, if less, based on an average occupant weight of 68 kg. It
should be understood that the line of sight may be partially obscured by
seated
occupants or by head restraints. The location of the driver's eye reference
points
are preferably in accordance with regulation or a nominal location appropriate
for
= any 95th percentile male driver. In at least one embodiment the
controlled vehicle
comprises at least one outside mirror of unit magnification. Preferably, the
outside mirror provides a driver of a controlled vehicle a view of a level
road
surface extending to the horizon from a line, perpendicular to a longitudinal
plane
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tangent to the driver's side of the controlled vehicle at the widest point,
extending
2.4 m out from the tangent plane 10.7 m behind the driver's eyes, with the
seat in
the rearmost position. It should be understood that the line of sight may be
partially obscured by rear body or fender contours of the controlled vehicle.
Preferably, the locations of the driver's eye reference points are in
accordance
with regulation or a nominal location appropriate for any 95th percentile male
driver. Preferably, the passenger's side mirror is not obscured by an unwiped
portion of a corresponding windshield and is preferably adjustable by tilting
in
both horizontal and vertical directions from the driver's seated position. In
at least
one embodiment, the controlled vehicle comprises a convex mirror installed on
the passenger's side. Preferably, the mirror is configured for adjustment by
tilting
in both horizontal and vertical directions. Preferable, each outside mirror
comprises not less than 126 cm of reflective surface and is located so as to
provide the driver a view to the rear along an associated side of the
controlled
vehicle. Preferably, the average reflectance of any mirror, as determined in
accordance with SAE Recommended Practice J964, 0CT84, is at least 35
percent (40% for many European Countries). In embodiments where the mirror
element is capable of multiple reflectance levels, such as with electro-optic
mirror
elements in accordance with the present invention, the minimum reflectance
level
in the day mode shall be at least 35 (40 when for European use) percent and
the
minimum reflectance level in the night mode shall be at least 4 percent. It
should
be understood that various embodiments of the present invention are equally
applicable for motorcycle windscreens and rearview mirrors.
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[0046] Turning now to Figs. 5a and 5b, various components of an outside
rearview
mirror assembly 510a, 510b are depicted. As described in detail herein, an
electro-optic mirror element may comprise a first substrate 521b secured in a
spaced apart relatidnship with a second substrate 522b via a primary seal 523b
to form a chamber there between. In at least one embodiment, at least a
portion
of the primary seal is left void to form at least one chamber fill port 523b1.
An
electro-optic medium is enclosed in the chamber and the fill port(s) are
sealingly
closed via a plug material 523b2. Preferably, the plug material is a UV
curable
epoxy or acrylic material. In at least one embodiment a spectral filter
material
545a, 545b is located proximate a second surface of a first substrate, near
the
periphery of the mirror element. Electrical connectors 525b1, 525b2 are
preferably secured to the element, respectively, via first adhesive material
526b1,
526b2. The mirror element is secured to a carrier plate 575b via second
adhesive
material 570b. Electrical connections from the outside rearview mirror to
other
components of the controlled vehicle are preferably made via a connecter 585b.
The carrier is attached to an associated housing mount 585b via a positioner
580b. Preferably, the housing mount is engaged with a housing 515a, 515b and
secured via at least one fastener 534b4. Preferably the housing mount
comprises
a swivel portion configured to engage a swivel mount 533b. The swivel mount is
preferably configured to engage a vehicle mount 530b via at least one fastener
531b. Additional details of these components, additional components, their
interconnections and operation is provided herein.
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[0047] = VVith further reference to Figs. 5a and 5b, an outside rearview
mirror
assembly 510a is oriented such that a view of the first substrate 521b is
shown
with a spectral filter material 524b positioned between the viewer and the
primary
seal material 523b. A blind spot indicator 550a, a keyhole illuminator 555a, a
puddle light 560a, a supplemental tum signal 540a, or 541a, a photo sensor
565a,
anyone thereof, a subcombination thereof or a combination thereof may be
incorporated within the rearview mirror assembly such that they are positioned
behind the element with respect to the viewer. Preferably, the devices 550a,
555a, 560a, 540a, or 541a, 565a are configured in combination with the mirror
element to be at least partially covert as discussed in detail herein and
within
various references mentioned herein. Additional details of these components,
additional
components, their interconnections and operation are provided herein.
[0048] Turning now to Figs. 5c-5e, a discussion of additional features in
accordance
with the present invention is provided. Fig. 5c depicts a rearview mirror
element
500c viewed from the first substrate 502c with a spectral filter material 596c
positioned between the viewer and a primary seal material 578c. A first
separation area 540c is provided to substantially electrically insulate a
first
conductive portion 508c from a second conductive portion 530c. A perimeter
material 560c is applied to the edge of the element. Fig. 5d depicts a
rearview
mirror element 500d viewed from the second substrate 512d with a primary seal
material 578d positioned between the viewer and a spectral filter material
596d.
A second separation area 586d is provided to substantially electrically
insulate a
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third conductive portion 518d from a fourth conductive portion 587d. A
perimeter
material 560d is applied to the edge of the element. Fig. 5e depicts a
rearview
mirror element 500e viewed from a section line Fig. 5e-Fig. 5e of either the
element of Fig. 5c or 5d. A first substrate 502e is shown to be secured in a
spaced apart relation via a primary seal material 578e with a second substrate
512e. A spectral filter material (in at least one embodiment referred to
herein as
"chrome ring") 596e is positioned between a viewer and the primary seal
material
578e. First and second electrical clips 563e, 584e, respectively, are provided
to
facilitate electrical connection to the element. A perimeter material 560e is
applied to the edge of the element. It should be understood that the primary
seal
material may be applied by means commonly used in the LCD industry such as
by silk-screening or dispensing. U.S. Patent number 4,094,058, to Yasutake et
al.,
describes applicable methods. Using these techniques the primary seal material
can be applied to an individually cut to shape substrate or it can be applied
as
multiple primary seal shapes on a large substrate. The large substrate with
multiple primary seals applied may then be laminated to another large
substrate
and the individual mirror shapes may be cut out of the laminate after at least
partially curing the primary seal material. This multiple processing technique
is a
commonly used method for manufacturing LCD's and is sometimes referred to as
an array process. Electro-optic devices in accordance with the present
invention
may be made using a similar process. All coatings such as the transparent
conductors, reflectors, spectral filters and in the case of solid state
electro-optic
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devices the electro-optic layer or layers may be applied to a large substrate
and
patterned if necessary. The coatings may be patterned using a number of
techniques such as by applying the coatings through a mask, by selectively
applying a patterned soluble layer under the coating and removing it and the
coating on top of it after coating application, laser ablation or etching.
These
patterns may contain registration marks or targets used to accurately align or
position the substrates throughout the manufacturing process. This is usually
done optically for instance with a vision system using pattern recognition
technology. The registration marks or targets may also be applied to the glass
directly such as by sand blasting, laser or diamond scribing if desired.
Spacing
media for controlling the spacing between the laminated substrates may be
placed into the primary seal material or applied to 6 substrate prior to
lamination.
The spacing media or means may be applied to areas of the laminate that will
be
,
cut away from the finished singulated mirror assemblies. The laminated arrays
can be cut to shape before or after filling with electro-optic material and
plugging
the fill port if the devices are solution phase electro-optic mirror elements.
[0049] Turning now to Figs. 6a and 6b, there is shown an inside rearview
mirror.
assembly 610a, 610b as viewed looking at the first substrate 622a, 622b with a
spectral filter material 645a or a bezel 645b positioned between a viewer and
a
primary seal material (not shown). The mirror element is shown to be
positioned
within a movable housing 675a, 675b and optionally combined with a stationary
housing 677a on a mounting structure 681a (w/stationary housing) or 681b (w/o
stationary housing). A first indicator 686a, a second indicator 687a, operator
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interfaces 691a, 691b and a first photo sensor 696a are positioned in a chin
portion of the movable housing. A first information display 688a, 688b, a
second
information display 689a and a second photo sensor 697a are incorporated
within the assembly such that they are behind the element with respect to the
viewer. As described with regard to the outside rearview mirror assembly, it
is
preferable to have devices 688a, 688b, 689a, 697a at least partially covert as
described in detail herein. In at least one embodiment an interior rearview
mirror
assembly may comprise at least one or more illumination assemblies 670b at
printed circuit board 665b, at least one microphone, a sub-combination
thereof, a
combination thereof, or other combinations along with aforementioned devices.
It
should be understood that aspects of the present invention may be individually
or
collectively incorporated in electro-optic windows or mirrors in a multitude
of
combinations.
[0050] Fig. 6c depicts a plan view of a second substrate 612c comprising a
stack of
materials on a third, fourth or both third and fourth surfaces. In at least
one
embodiment, at least a portion 620c1 of a stack of materials, or at least the
substantially opaque layers of a stack of materials, are removed, or masked,
beneath the primary seal material. At least a portion 620c2 of at least a
layer of
the stack of materials extends substantially to the outer edge of the
substrate or
extends to an area to facilitate electrical contact between the third surface
stack
and an element drive circuit (not shown in fig. 6c). Related embodiments
provide
for inspection of the seal and or plug viewing and or plug curing from the
rear of
the mirror or window element subsequent to element assembly. In at least one
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embodiment, at least a portion of an outer edge 620c1 of a stack of materials
620c is located between an outer edge 678c1 and an inner edge 678c2 of a
primary seal material 678c. In at least one embodiment, the portion 620c1 of a
stack of materials, or at least the substantially opaque layers of a stack of
materials, are removed, or masked, beneath the primary seal material between
approximately 2mm and approximately 8mm wide, preferably approximately
5mm wide. At least a portion 620c2 of at least a layer of the stack of
materials
extends substantially to the outer edge of the substrate or extends to an area
to
facilitate electrical contact between the third surface stack and an element
drive
circuit (not shown) between approximately 0.5mm and approximately 5mm wide,
preferably approximately 1mm. It should be understood that any of the first,
second, third and fourth surface layers or stacks of materials may be as
disclosed herein or within the references mentioned elsewhere herein.
[0051] Fig. 6d depicts a plan view of a second substrate 612d comprising a
third
surface stack of materials. In at least one embodiment, at least a portion of
an
outer edge 620d1 of a third surface stack of materials 620d is located between
an outer edge 678d1 and an inner edge 678d2 of a primary seal material 678d.
In at least one related embodiment, a conductive tab portion 682d extends from
an edge of the second substrate inboard of an outer edge 678d1 of a primary
seal material 678d. In at least one related embodiment, a conductive tab
portion
682d1 overlaps with at least a portion of a third surface stack of materials
beneath a primary seal material 678d. In at least one embodiment, a
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substantially transparent conductive layer (not shown individually), such as a
conductive metal oxide, of a third surface stack of materials extends beyond
an
outer edge 620d1 of a remainder of the third surface stack as depicted in Fig.
8b
to provide external electrical connection to the third surface. It should be
understood that a conductive tab may be deposited along any'of the substrate
peripheral areas as shown in Figs. 9c-91. In at least one embodiment, a
conductive tab portion comprises chrome. It should be understood that the
conductive tab portion improves conductivity over the conductive electrode; as
long as a conductive electrode layer is provided with sufficient conductivity,
the
conductive tab portion is optional. In at least one embodiment, the conductive
electrode layer imparts the desired color specific characteristics of the
corresponding reflected light rays in addition to providing the desired
conductivity.
Therefore, when the conductive electrode is omitted, color characteristics are
controlled via the underlayer material specifications. It should be understood
that
any of the first, second, third and fourth surface layers or stacks of
materials may
be as disclosed herein or within the references mentioned herein.
[0052] Fig. 7 depicts rearview mirror element 700 which is an enlarged view
of the
element depicted in Fig. 5e to provide greater detail. Element 700 comprises a
first substrate 702 having a first surface 704 and a second surface 706. A
first
conductive electrode portion 708 and a second conductive electrode portion 730
applied to the second surface 706 are substantially electrically insulated
from one
another via a first separation area 740. As can be seen, in at least one
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embodiment the separation area is located such that the spectral filter
material
796 and a corresponding adhesion promotion material 793 are also substantially
electrically insulated to define first and second spectral filter material
portions 724,
736, respectively, and first and second adhesion promotion material portions
727,
739, respectively. A portion of the first separation area 740, 540c, 540d,
540e is
shown to be extending parallel within a portion of the primary seal material
778
located near the center thereof. It should be understood that this portion of
the
separation area 740 may lie such that a viewer would not readily perceive a
line
within the spectral filter material; for example, a portion of the separation
area
may be substantially aligned with an inboard edge 797 of spectral filter
material
596. lt should be understood that when any portion of the separation area 740
is
located inboard of the primary seal material, as is described in more detail
elsewhere herein, a discontinuity in the electro-optic material coloring and,
or,
clearing may be observed. This operational characteristic may be manipulated
to
derive a subjectively visually appealing element.
[0053] With further reference to Fig. 7, the element 700 is depicted to
comprise a
second substrate 712 having a third surface 715 and a fourth surface 714. It
should be noted that the first substrate may be larger than the second
substrate
to create an offset along at least a portion of the perimeter of the mirror.
Third
and fourth conductive electrode portions 718, 787, respectively, are shown
proximate the third surface 715 substantially electrically insulated via
second
separation area 786. A portion of the second separation area 786, 586c, 586d,
586e is shown to be extending parallel within a portion of the primary seal
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material 778 located near the center thereof. It should be understood that
this
portion of the separation area 786 may lie such that a viewer would not
readily
perceive a line within the spectral filter material; for example, a portion of
the
separation area may be substantially aligned with an inboard edge 797 of
spectral filter material 796. As further shown in Fig. 7, a reflective
material 720
may be applied between an optional overcoat material 722 and the third
conductive electrode portion 718. It should be understood that any of the
materials as disclosed in commonly assigned U.S. Patents 6,111,684,
6,166,848, 6,356,376, 6,441,943, 6,700,692, 5,825,527, 6,111,683, 6,193,378,
6,816,297, 7,084,882, 7,688,495 and 7,324,261 may be employed to define a
unitary surface coating, such as a hydrophilic coating on a first surface, or
a
composite stack of coatings, such as conductive electrode material, spectral
filter
material, adhesion promotion material, reflective material, overcoat material
applied to the first, second, third and fourth surfaces. It should be
additionally
understood that a hydrophobic coating, such as, a fluorinated alkyl saline or
polymer, a silicone containing coating or a specially textured surface may be
applied to the first surface. Either a hydrophilic or hydrophobic coating will
alter
the contact angle of moisture impinging upon the first surface relative to
glass
with no such coating and will enhance rear vision when moisture is present. It
should be understood that both third surface and fourth surface reflector
embodiments are within the scope of the present invention. In at least one
embodiment, the materials applied to the third surface and, or, fourth surface
are
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configured to provide a partially reflective/partially transmissive
characteristic for
at least a portion of the corresponding surface stack. In at least one
embodiment,
the materials applied to the third surface are integrated to provide a
combination
reflector/conductive electrode. It should be understood that additional "third
surface" materials may extend outboard of the primary seal, in which case, it
should be understood that the corresponding separation area extend through the
additional materials. Having at least a portion of the primary seal visible
from the
fourth surface, as depicted in Fig. 6c for example, facilitates inspection and
UV
curing of plug material. In at least one embodiment, at least a portion of a
stack
of materials 620c, or at least the substantially opaque layers of a stack of
materials, are removed, or masked, beneath the primary seal material to
provide
for inspection of at least 25% of the primary seal width around at least a
portion
of the perimeter. It is more preferred to provide for inspection of 50% of the
primary seal width around at least a portion of the perimeter. It is most
preferred
to provide for inspection of at least 75% of the primary seal width around at
least
a portion of the perimeter. Various embodiments of the present invention will
incorporate portions of a particular surface having a coating or stack of
coatings
different from other portions; for example, a "window" in front of a light
source,
information display, a photo sensor, or a combination thereof may be formed to
selectively transmit a particular band of light ray wavelengths or bands of
light ray
wavelengths as described in many of the references mentioned herein.
[0064] With further reference to Figs. 6a-6b and 7, the first separation
area 740
cooperates with a portion of the primary seal material 775 to define the
second
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conductive electrode portion 730, the second spectral filter material portion
736
and the second adhesion promotion material portion 739 substantially
electrically
insulated from the first conductive electrode portion 708, the first spectral
filter
material portion 724 and first adhesion promotion material portion 727. This
configuration allows for placement of an electrically conductive material 748
such
that the first electrical clip 763 is in electrical communication with the
third
conductive electrode portion 718, the reflective material 720, the optional
overcoat 722 and the electro-optic medium 710. It should be apparent,
particularly in embodiments wherein the electrically conductive material 748
is
applied to the element prior to placement of the first electrical clip 769,
that
electrically conductive material may at least partially separate the
interfaces 757,
766, 772, 775. Preferably, the material, or composition of materials, forming
the
third conductive electrode portion 718, the first electrical clip 763 and the
electrically conductive material 748 are chosen to promote durable electrical
communication between the clip and the materials leading to the electro-optic
medium. The second separation area 786 cooperates with a portion of the
primary seal material 775 to define the fourth conductive electrode portion
787
substantially electrically insulated from the third conductive electrode
portion 718,
the reflective layer 720, the optional overcoat material 722 and the electro-
optic
medium 710. This configuration allows for placement of an electrically
conductive
material 790 such that the second electrical clip 784 is in electrical
communication with the first adhesion promotion material portion 727, the
first
spectral filter material portion 724, the first conductive electrode portion
708 and
=
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the electro-optic medium 710. It should be apparent, particularly in
embodiments
wherein the electrically conductive material 790 is applied to the element
prior to
placement of the first electrical clip 784, that electrically conductive
material may
at least partially separate the interfaces 785, 788, 789. Preferably, the
material,
or composition of materials, forming the first conductive electrode portion
708,
the first electrical clip 784, the adhesion promotion material 793, the
spectral filter
material 796 and the electrically conductive material 790 are chosen to
promote
durable electrical communication between the clip and the materials leading to
the electro-optic medium.
[0055] It is sometimes desirable to provide one or more optional flash over-
coat
layers 722 over reflective layer 720, such that it (and not the reflective
layer 720)
contacts the electrochromic medium. This flash over-coat layer 722 must have
stable behavior as an electrode, it must have good shelf life, it must bond
well to
the reflective layer 720, and maintain this bond when the seal member 778 is
bonded thereto. If optical properties from the underlayer(s) are to be visible
the =
cover layer it must be sufficiently thin, such that it does not completely
block the
reflectivity of layer(s) beneath 720. In accordance with another embodiment of
the present invention, when a very thin flash over-coat 722 is placed over the
highly reflecting layer, then the reflective layer 720 may be silver metal or
a silver
alloy because the flash layer protects the reflective layer while still
allowing the
highly reflecting layer 720 to contribute to the reflectivity of the mirror.
In such
cases, a thin (e.g., less than about 300 .ANG., and more preferably less than
about 100 .ANG.) layer of rhodium, ruthenium, palladium, platinum, nickel,
CA 02644218 2008-08-27
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tungsten, molybdenum or their alloys, is deposited over the reflective layer
720.
The thickness of the flash layer is dependent on the material selected. For
example, elements constructed with a third surface coating of chrome under
ruthenium under rhodium under silver coated with a flash layer of as little as
.ANG. of ruthenium showed improved resistance compared to elements
without the flash layer both to the formation of spot defects during
processing
and haze in the viewing area of the element when subjected to high temperature
testing. The initial reflectivity of the elements with the ruthenium flash
layer was
70-72%. When reflective layer 720 is silver, flash layer 722 may also be a
silver
alloy or an aluminum-doped zinc oxide. The flash layer or a thicker cover
layer
may also be a transparent conductor such as a transparent metal oxide. Cover
layer(s) may be chosen specifically to compliment the other layers for such
factors as barrier properties, advantageous interferential optics, balancing
of
compressive or tensile stresses and the like. It should be understood that the
flash layer as described above may be used in other embodiments described
elsewhere in this document.
[0056] Such cover layers when made from the aforementioned list of metals
or other
metals / alloys/ semi-metals found to be compatible with the electrochromic
system, when the metal or semi-metal layer(s) is thicker than 300 Angstroms
tend to allow little optical effect from the layers beneath it. If it is
considered more
desirable that the appearance of the metallic cover layer it may be
advantageous
to use such a thicker cover layer. Some description of such stacks is provided
in
commonly assigned European patent EP0728618A2 "Dimmable Rearview Mirror
21
CA 02644218 2012-08-03
for Motor Vehicles" Bauer, et al. When such thicker cover layer(s), which
could be used
in combination with glue layers and flash layers, and transparent conductive
layers, such
as indium doped tin oxide, aluminum doped zinc oxide, or indium zinc oxide are
used,
the conductivity benefits of having underlayers such as silver, silver alloys,
copper,
copper alloys, aluminum or aluminum alloys, would still be present. Layers
typically
thought of as insulators such as titanium dioxide, silicon dioxide, zinc
sulfide or the like,
may also be utilized in such a cover layer stack or interlayers and not negate
the
benefits of the more highly conductive layer(s) as long as their layer
thicknesses were
such that they still passed sufficient current from the more highly conductive
layers.
[0057] It is known in the electrochromic art that a mirror or window may
not darken
uniformly when an electrical potential is applied to the element. The non-
uniform
darkening results from local differences in electrical potential across the
solid
state EC materials, fluid or gel in an EC element. The electrical potential
across
the element varies with the sheet resistance of the electrodes, the bus bar
configuration, the conductivity of the EC medium, the concentration of the EC
medium, the cell spacing or distance between the electrodes, and the distances
from the bus bars. A commonly proposed solution to this problem is to make the
coatings or layers composing the electrodes thicker thus reducing their sheet
resistance and enabling a faster darkening element. As will be discussed below
there are practical penalties that are imparted that restrict this simplistic
approach
to solving the problem. In many instances the penalties make an EC element
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unsuitable for a given application. In at least one embodiment of the present
invention improved electrode materials, methods of manufacturing said
electrodes and bus bar configurations are described that solve problems that
arise with simply thickening the electrode layers and result in EC elements
with
faster, more uniform darkening characteristics.
[0058] In a typical inside mirror the bus bars run parallel to the long
dimension. This
is to minimize the potential drop across the part between the electrodes. The
mirror also typically consists of a high sheet resistance transparent
electrode and
a lower sheet resistance reflector electrode. The mirror will darken most
quickly
near the bus bar for the higher sheet resistance electrode and slowest at some
intermediate position between the two electrodes. Near the bus bar for the
lower
sheet resistance electrode will have a darkening rate between these two
values.
There is a variation in effective electrical potential as one moves between
the two
bus bars. In the case of two long parallel bus bars that have a relatively
short
distance between them (distance between the bus bars is less than half the
length of the bus bars) the mirror will darken in a "window shade" fashion.
This
means that the mirror darkens faster near one bus and the darkening appears to
move between the two bus bars in a gradual fashion. Typically, the darkening
rate is measured at the middle of the part and in the case of a mirror with a
width
to height ratio greater than 2, any non-uniformities in darkening rate are
relatively
minor.
[0059] As the size of the mirrors increases, and along with it the distance
between
the bus bars, the relative difference in the darkening rate across the parts
also
23
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WO 2007/100921 PCT/US2007/005494
increases. This can be exacerbated when the mirrors are designed for an
outside
application. The metals that can withstand the rigors of such an environment
typically have lower conductivity than metals such as silver or silver alloys
that
are suitable and common for inside mirror applications. A metal electrode for
an
outside application may therefore have a sheet resistance.up to 6 ohms/sq
while
an inside mirror may have a sheet resistance of <0.5 ohms/sq. In other outside
mirror applications the transparent electrode may be limited in thickness for
various optical requirements. The transparent electrode, such as ITO, is often
limited to a % wave thickness in the most common usage. This limitation is due
to properties of the ITO discussed herein but also due to the expense
associated
with making an ITO coating thicker. In other applications the coating is
limited to
80% of the '1/2 wave thickness. Both of these thickness constraints limit the
sheet
resistance of the transparent electrode to greater than about 12 ohm/sq for a
1/2
wave and up to 17-18 ohms/sq for a coating that is 80% of a '1/2 wave coating.
The higher sheet resistance of the metal and transparent electrodes results in
a
slower, less uniform darkening mirror.
[0060] The darkening rate may be estimated from an analysis of the EC
element in
terms of an electrical circuit. The discussion below pertains to coatings that
have
uniform sheet resistance across the element. The potential at any location
between parallel electrodes is simply a function of the sheet resistance of
each
electrode and the resistance of the EC medium. In Table 1 below the average
potential across the element between the electrodes is presented along with
the
difference between the maximum and minimum potential. This example is for an
24
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WO 2007/100921 PCT/US2007/005494
element with a 10 cm spacing between the parallel bus bars, a 180 micron cell
spacing, a 1.2 volt driving voltage and 100,000 Ohm*cm fluid resistivity. Six
combinations of top and bottom electrode sheet resistance are compared.
Table 1
Ex: 1 Ex: 2 Ex: 3 Ex: 4 Ex: 5
Ex: 6
Top Plate Sheet Resistance (ohm/sq) 17 17 12 12 9 9
Bottom Plate Sheet Resistance
(ohm/sq) 5 0.5 5 0.5 5 0.5
Distance Between Electrodes (cm) 10 10 10 10 10 10
Cell Spacing (um) 180 180 180 180 180 180
Fluid Resistivity (Ohrn*cm) 100000 100000 100000 100000
100000 100000
Driving Potential (V) 1.2 1.2 1.2 1.2 1.2 1.2
Finite Element Width (cm) 1 1 1 1 1 1
a_
Potential at Anode (V) 1.168 1.197 1.168 1.197 1.168
1.197
Potential at Cathode (V) 1.096 1.096 1.125 1.125 1.143
1.143
Average Potential (V) 1.131 1.145 1.146 1.160 1.155 1.169
[0061] The
speed of darkening is fastest at the electrical contact to the highest
sheet resistance electrode and is related to the effective potential at this
position.
The higher the effective potential adjacent to this electrical contact (or
elsewhere)
the faster the average darkening of the mirror will be. The fastest overall
darkening time will occur when the potential is as high as possible across the
part. This will drive the electrochemistry to darken at an accelerated rate.
The
sheet resistance of the coatings on both the top and bottom substrates plays a
role in determining the effective potential between the electrodes, but as can
be
seen from the table the high sheet resistance electrode plays a more critical
role.
In past electrochromic art the improvements were driven almost exclusively by
lowering the sheet resistance of the low resistance electrode. This was
because
CA 02644218 2008-08-27
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the use of materials such as silver gave substantive benefits and was
relatively
easy to implement.
[0062] It is known in the art that the overall rate can be increased as the
driving
potential is increased but the trends will be constant independent of the
driving
voltage. It is also known that the current draw at a given voltage influences
the
darkening uniformity. Uniformity can be improved by adjustments to cell
spacing,
concentration, or choice of EC materials, but often improvements in uniformity
using these adjustments can have a negative impact on darkening speed,
clearing speed or both darkening and clearing speed. For example, increasing
cell spacing and decreasing fluid concentration will decrease the current draw
and will thereby improve uniformity, but the clearing time will increase.
Therefore,
the sheet resistance of the layers must be appropriately set to attain both
speed
of darkening and uniformity of darkening. Preferably the sheet resistance of
the
transparent electrode should be less than 11.5 ohms/sq, preferably less than
10.5 ohms/sq and more preferably less than 9.5 ohms/sq and due to the optical
requirements discussed below, in some embodiments, the thickness of the
transparent electrode should be less than about a half wave optical thickness.
The reflector electrode should be less than about 3 ohms/sq, preferably less
than
about 2 ohms/sq and most preferably less than 1 ohm/sq. A mirror or EC element
so constructed will also have a relatively uniform darkening such that the
difference in darkening time between the fastest and slowest darkening rate is
less than a factor of 3, preferably less than a factor of 2 and most
preferably less
26
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than a factor of 1.5. Novel, high-performance, low-cost materials are
discussed
below that enable these fast, uniform darkening elements.
[0063] In other applications it may be impractical to have two relatively
parallel bus
bars. This may be due to an uneven shape common with outside mirrors. In other
circumstance it may be desirable to have a point contact to the low resistance
electrode. The point contact may enable the minimization or elimination of the
laser deletion line used in some applications. The use of a point contact
simplifies or is preferential for some aspects of the mirror construction but
it
makes it difficult to achieve a relative uniform potential across the part.
The
elimination of the relatively long bus along the low resistance reflector
electrode
effectively increases the resistance of the electrode_ Therefore, novel
combinations of bus bars and coating sheet resistance values are needed to
attain fast, uniform darkening.
[0064] As noted above one skilled in the art would have anticipated that it
would
require extremely low sheet resistance values on the metal reflector electrode
to
enable a point contact scheme. Unexpectedly it was discovered that it is
necessary to have a lower sheet resistance for the transparent electrode to
improve the uniformity. Table 2 shows the results of the uniformity
experiments.
In this test we made solution phase EC elements that were approximately 8
inches wide by 6 inches tall. The benefits of element designs discussed herein
pertain predominantly to large elements. A large element is defined as one
that
has the minimum distance from the edge of any point on the edge of the viewing
area to the geometric center is greater than approximately 5 cm. Lack of
uniform
27
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darkening becomes even more problematic when the distance is greater than
approximately 7.5 cm and even more problematic when the distance is greater
than approximately 10 cm. The sheet resistance of the transparent electrode
(ITO) and the metal reflector were varied as noted in Table 2. Contact was
made
to the metal electrode with a point contact. A clip contact such as the so
called J-
clip was used with an Ag paste line approximately 1" long to provide
electrical
contact to the metal reflector along one of the short length sides of the
mirror.
Electrical contact was made to the transparent electrode via an Ag paste along
the one side opposite the point contact and continuing down one third of the
distance along both long sides of the mirror. The darkening time (T5515) was
measured at three locations on the mirror. Position 1 is near the point
contact,
position 2 is at the edge of the transparent electrode bus opposite the point
contact and position 3 is at the center of the mirror. The T5515 time (in
seconds)
is the time it takes the mirror to go from 55% reflectance to 15% reflectance.
The
max reflectance is the maximum reflectance of the mirror. The delta T5515 is
the
time difference between either point 1 and point 2 or between point 2 and
point 3.
This is a measure of the difference in darkening rate between the fastest
position
and the other two locations on the mirror. As the darkening becomes more
uniform these numbers become closer together. The timing factor is the
darkening time at a given position divided by the time at the fastest
position. This
shows the relative scaling of time between the different locations independent
of
the absolute rate at any given location. As noted above, it is preferred to
have a
timing factor less than 3 and preferable less than 2 and most preferably less
than
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1.5. It can be seen from Table 2 that we do not attain a timing factor of 3
when
the ITO sheet resistance is at 14 ohms/sq for this particular mirror
configuration.
All three examples with an ITO with 9 ohms per square have timing factors less
than 3. The center of mirror reading is the location that deviates most from
the
fastest location. A statistical analysis was conducted on this data which
revealed
unexpectedly that the ITO sheet resistance was the sole factor that
contributed to
the timing factor. Using the statistical models an ITO sheet resistance of
less
than about 11.5 ohms/sq is needed to have a timing factor of 3.0 or less for
this
embodiment. Using the same statistical models the ITO must have a sheet
resistance of less than 7 ohms/sq for the timing factor to be less than 2.0
for this
mirror configuration. Even though the timing factor is not affected by the
sheet
resistance of the third surface reflector the overall darkening rate is
affected.
When the sheet resistance of said reflector is less than or equal to 2 ohms/sq
and the ITO is at approximately 9 ohms/sq the darkening rate for this mirror
is
less than 8 seconds in the center. This value corresponds approximately to a
,
mirror of similar size with a conventional bus arrangement. Therefore, by
lowering the sheet resistance of the ITO a point contact is enabled with a
relatively high sheet resistance reflector.
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WO 2007/100921 PCT/US2007/005494
Table 2
Reflector ITO Measurement Max T5515 delta timing
ohms/sq ohm/sq Position Reflectance T5515 factor
0.5 9 1 55.3 3.7 1.3 1.6
0.5 9 2 55.5 2_3
0.5 9 3 55.3 6.0 3.7 2.6
1 9 1 56.0 5.4 2.3 1.7
1 9 2 56.0 3.1
1 9 3 56.0 7.2 4.1 2.3
2 9 1 55.8 . 5.0 1.9 1.6
2 9 2 _ 55.9 3.1
2 9 3 55.9 7.8 4.6 2.5
0.5 14 1 56.5 5.6 2.8 2.0
0.5 14 2 56.6 2.9
0.5 14 3 56.5 10.2 7.3 3.6
1 14 1 57.6 6.8 3.4 2.0 ,
1 14 2 57.6 3.4
'1 14 3 57.5 12.2 8.8 3.6
2 14 1 57.3 8.4 4.4 2.1
2 14 2 57.5 4.0
2 14 3 57.4 14.0 9.9 3.5
[0065] The unexpected role of the sheet resistance of the ITO in the
uniformity and
speed of darkening was expanded on in another set of experiments. In these
experiments the length of bus bar contact to the higher sheet resistance
electrode, in this example ITO, was extended further down the sides of the
mirror
and even onto the bottom edge of the mirror in some cases. Table 3
demonstrates the effect on uniformity with changes in bus length. In these
tests
the element shape and configuration are the same as for Table 2 except where
noted. The contact percentage is a percentage comparison of the bus bar length
of the ITO contact compared to the total length of the perimeter. The bus bar
ratio is the length of the ITO contact relative to the small reflector contact
of
approximately 2 cm or less.
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[0066] The data from Table 3 depicts that increasing the bus length of the
higher
sheet resistance electrode significantly improves uniformity. For the 2
ohm/sq.
reflector, increasing the length of the bus contact from 40% to 85 % improves
the
timing factor from 2.4 to 1.7. For the 0.5 ohm/sq reflector, the same change
in
ITO bus length from 40 to 85% improves the timing factor from 3.2 to 1.2 and
significantly improves the darkening rate. It is noted that the element with
the
lower sheet resistance reflector is generally faster to darken than the
comparable
2 ohm/sq. case, but the uniformity of the 0.5 ohm case with a shorter ITO
contact
is actually worse as demonstrated by the timing factor. The increase bus
length
to the ITO is particularly helpful for the element with the 0.5 ohm/sq.
reflector.
[0067] When the contact percentage is increased, the position of the
fastest and
slowest darkening can change as well. In this example higher contact
percentage
significantly improves the darkening times at both positions 1 and 3 and the
corresponding timing factors.
=
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Table 3
Contact Bus Bar Reflector ITO Measurement Max
delta timing
Percentage Ratio ohms/sq ohm/sq Position Reflectance T5515 T5515 factor
85 20 2 9 1 57.0 2.9
85 20 2 9 2 57.0 3.7 0.8
1.3
85 20 2 9 3 , 57.3 4.8
1.9 , 1.7
58 13 2 9 1 56.6 3.4
58 13 , 2 9 , 2 57.2
3.5 2.2 1.0
58 13 2 9 3 57.5 5.6 2.2
1.6
40 9 2 9 1 56.9 8 4.6
2.4
40 9 2 9 2 57.3 3.4
40 9 2 9 3 57.4 8.2 4.8
2.4
85 20 0.5 9 1 . 56.0 3
85 20 0.5 9 2 56.2 3
_
85 20 0_5 9 3 56.1 3.5 0.5
1.2
-
58 13 0.5 9 1 55.8 4
1.5 , 1.6
58 13 0.5 9 2 56.1 2.5
58 13 0.5 9 3 56.0 3.5 1
1.4
40 9 0.5 9 1 55.5 8.2 5.6
3.2
. 40 9 0.5 9 2 55.8 2.6
40 9 0.5 9 3 56.0 4.9 2.3
1.9
[0068] These experiments demonstrate that when using a short bus with the
low
sheet resistance electrode it is beneficial to increase the bus length to the
opposite electrode to improve uniformity. Ideally, therefore for large mirrors
we
prefer the ratio of the lengths of the bus bars to be greater than 5:1,
preferably
greater than 9:1, even more preferably greater than 13:1 and most preferably
greater than 20:1 to attain a timing factor below 3. We also find that
independent
of the length of the smaller bus that uniformity improves by increasing the
length
of the bus to the higher sheet resistance electrode to acquire a contact
percentage preferably greater than approximately 58% and more preferably
greater than approximately 85%. Typical large EC mirrors have a contact
percentage less than 50%.
32
CA 02644218 2012-08-03
[0069] These findings are critical not only to mirrors with opaque
reflectors but they
are even more critical to mirrors employing transflective reflectors. In order
to
have a transflective coating the metals must be thinned to the point of
transparency. The thinner metals therefore have higher sheet resistance
values.
In at least one embodiment of the present invention an electro-optic element
comprises fast, uniform darkening with traditional bus bar arrangements with
the
optional point contact bus arrangements taught herein. Novel transflective
coatings are described below that are particularly well suited to complement
the
bus arrangements described above.
[0070] One may also pattern the conductivity underneath an opaque cover
layer or
stack of layers that are opaque, in order to enable an electrochromic mirror
to
darken more uniformly over its entire area or to darken from its center first
( where most headlight glare appears ) outward toward the top and bottom of
the
viewing area. U.S. Patent Application 20040032638A1 " Electrochromic devices
with thin bezel-covered edge" Tonar, et. al., mentions that" lower sheet
resistance
coating may be provided in an area proximate the associated electrical contact
or
around a perimeter area and allow the sheet resistance to increase as the
distance from
the electrical contact increases" and states that "this is particularly
applicable when point
contacts are utilized". One would typically want to provide contrast in ohms
without any,
or very minimal, visible contrast in the reflector when the electrochromic
element has no
voltage applied to it.
33
CA 02644218 2012-08-03
[0071] In order to obtain sufficient contrast between the more and less
highly
conductive areas of an electrochromic device to enable preferential darkening
of
certain areas, it may be necessary to include in the stack materials that are
not
metallic. This is because opaque layers or stacks of the more reflective
metals
and alloys tend to be conductive enough to provide acceptable darkening
characteristics in an automotive electrochromic mirror without the supplement
of
more highly conductive patterns underneath them. One example of such a
materials stack including semi-metals is one constructed similarly to those
described in U.S. Patent 5,535,056, "method for making elemental
semiconductor mirror for vehicles", where an opaque silicon layer would be
covered by
approximately one quarter wave optical thickness of Indium Tin Oxide covered
by 20 to
25 nanometers of Silicon, covered by approximately 20nm of Indium Tin Oxide.
Such a
coating stack, being opaque could have additional materials placed beneath it
in
patterns with minimal effect on its appearance from the front. This stack
would also be
sufficiently conductive throughout to not lose the advantages of that
patterning. In
addition, the ITO, if found to still be too conductive when deposited under
conditions that
usually yield approximately 12 ohms per square at about 1400 Angstroms
thickness,
can be made less conductive by adjusting process conditions or by changing the
indium
to tin ratio.
[0072] Elements constructed in accordance with the principles described in
US20040032638A1 with the geometry of Figs. 5f and 7, having conductive epoxy
along top, lower and left edge, and point contact made at approximately the
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WO 2007/100921 PCT/US2007/005494
middle of the right edge were made with different third surface coating stacks
and
conductivity patterns. When mention of the entire third surface is made that
will
refer to the surface prior to any lasering to create the insulating areas
necessary
for the constructions in accordance with commonly assigned U.S. Patent
Application 20040022638A1.
[0073] Elements with % ohm per square third surface reflectors over the
entirety of
the viewing area were contrasted with those that had % ohm per square in a
stripe of IA" or 1" or 2" across the center of the element covered by an
opaque
layer such that there was 4 Ohms per square conductivity in the remainder of
the
viewing area and yet fairly uniform appearance of the elements in the bright
state.
Upon darkening the elements there was a slight decrease in the tendency for
the
center of the element to lag in darkening when compared to the edges with the
contrasting regions of conductivity.
[0074] In order to have a higher level of conductivity contrast, elements
were made
similar in construction to those in the preceding paragraph but on the third
surface ITO of approximately 12 ohms and 40 ohms per square, respectively,
had a conductive stripe of silver of 2" placed across the center of the single
which
(for processing durability) then was covered with a flash layer of transparent
conductive oxide. After being made into full electrochromic devices, the
elements
were placed over a silvered piece of glass so that in evaluating the darkening
characteristics there would be a reflector of similar strength to the silver
stripe
behind the regions with 12 ohm/sq. and 40 ohm/sq. ITO, which are relatively
transparent. It was seen that the device with 40 Ohm/sq. to % ohm/sq.
CA 02644218 2008-08-27
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contrasting regions on the third surface had less of an iris effect when
darkening
than the element with 12 ohm/sq to 1h ohm/sq contrasting regions when viewed
under these conditions.
[0075] Elements were made per the preceding paragraph except that
additional
coatings were used on the third surface. Those coatings consisted of: an
additional flash layer of conductive oxide (put there for adhesion since the
processing involved vacuum breaks in the coating process), approximately 300
nm Silicon, approximately 60 nm ITO, another 20 nm Silicon and then 10 nm ITO.
The silicon layer may be prone to surface oxidation which may in certain EC
elements may form a surface oxide that then interferes with the uniformity and
consistency of darkening. The ITO or other TCO or another material described
herein as a flash layer or overlayer may be used to inhibit the formation or
negative effects of said oxide. Those elements which had started with the
initial
layer (per the preceding example) of 40 ohms per square had resulting third
surface conductivities that were about 24 ohms/ square in the top and bottom
regions (per Figs. 5f and 7), and <1 ohm /square in the center region as
measured by four point probe. The elements which had started with an initial
ITO
layer of 12 Ohms/ square had 10-12 ohms per square in the top and bottom
regions. As per the previous example the elements with higher ohmic contrast
had the least iris effect or the most tendency to center to edge darken. These
elements also had the following optical characteristics in the unpowered state
when using D65 2 degree observer,
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WO 2007/100921 PCT/US2007/005494
L* a* b* Y
Higher ohmic contrast ( 50 ohm base layer ) 76 -5 4 50
Lower ohmic contrast ( 12 ohm base layer) 75 -3 5 51
[0076] Preferential darkening of certain areas of the electrochromic device
may also
be obtained by means of thin deletion lines in the second surface transparent
conductor (stack) or third surface reflective (stack), as well as grading the
thickness of the coatings as described elsewhere herein. Using laser deletion
as
an example, in general, as one decreases the operating wavelength of a laser
it
is capable of creating a thinner laser line. 15 micron width deletion lines,
have
been produced using UV laser of wavelength 355nm. These lines are still
discernable but much less so than those produced by using longer wavelength
lasers. As shorter wavelength lasers continue to become more accessible one
may fairly anticipate that deletion lines that are not cosmetically
objectionable in
the viewing area under normal conditions for an automotive mirror will be
possible.
[0077] When at the lines or portions of the lines indicated across the
center of Figs.
5f and 7 there are deletions of the coating stack that will become the third
surface
of the element, and then elements are constructed in accordance with prior
techniques so that there is a relatively small contact at one edge of the part
and
conductive epoxy used on the other three sides of the element the darkening
characteristics are affected....
[0078] Patterns of deletion, by laser, were made for both the lines shown
interior to
the element as described in Figs. 5f and 7 on a % ohm per square reflector
electrode as follows:
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1) There was complete deletion of coating in a thin line extending form the
edge of
the glass to 15cm from the edge of the glass.
2) There was complete deletion of coating in thin lines in a repeating pattern
of
8mm deletion and 2mm unablated across the entire width of the part.
3) There was complete deletion of coating in a thin line extending from the
edge of
the glass to 14 cm from the edge and then deletion in a repeating pattern of
5mm
no oblation and 5mm deletion across the remainder of the part.
4) There was complete deletion of coating in a thin line extending from the
edge of
the glass to 15 cm from the edge with the exception of 2 unablated segments of
0.4mm at approximately 5 and 10 cm along the line.
[0079] When compared to similar parts without any deletion lines these
elements
exhibited some to substantially less "iris effect" when darkening. Pattern 4
being
the best for overall cosmetics and even darkening among those with deletion
patterns. Nonetheless all of these patterns would need adjustment for
acceptable
darkening cosmetics but movement towards a desired darkening characteristic
has been shown.
[0080] With reference to Fig. 8a, a profile view of a portion of a rearview
mirror
element is depicted comprising a first substrate 802a having at least one
layer
808a of a substantially transparent conductive material deposited on the
second
surface and a second substrate 812a having a stack of materials deposited on
the third surface secured in a spaced apart relationship with respect to one
another via a primary seal material 878a to define a chamber there between. In
at least one embodiment, an electro-optic medium 810a is located within said
chamber. In at least one embodiment, the third surface stack of materials
comprises an underlayer 818a, a conductive electrode layer 820a, a metallic
layer 822a and a conductive tab portion 882a having an overlap portion 883a
underneath the metallic layer and primary seal material. It should be noted
that
the conductive tab portion 882a could alternatively be deposited over the
metallic
38
CA 02644218 2012-08-03
coating 822a to create the overlap portion. In at least one embodiment, the
underlayer is titanium-dioxide. In at least one embodiment, the underlayer is
not
used. In at least one embodiment, the conductive electrode layer is indium-tin-
oxide _ In at least one embodiment, the conductive electrode layer is omitted.
In at
least one embodiment, the conductive electrode layer is omitted and the
underlayer is either a thicker layer of titanium-dioxide or some other
substantially
transparent material having a relatively high index of refraction (i.e. higher
index
of refraction than ITO), such as, silicon carbide. In at least one embodiment,
the
conductive tab portion comprises chrome. It should be understood that the
conductive tab portion may comprise any conductive material that adheres well
to glass and/or other stack layers or the epoxy depending on the layers
sequence and is resistant to corrosion under vehicular mirror testing
conditions.
As can be appreciated, when the third surface stack of materials, or at least
those layers within the stack that are susceptible to corrosion, are kept
within an
area defined by an outer edge of the primary seal material, the element will
be
substantially immune to problems associated with third surface corrosion. It
should be understood that the layer, or layers, susceptible to corrosion may
extend beyond the primary seal material provided a protective overcoat or
sealant is incorporated, such as, conductive epoxy or an overcoat layer. It
should
be understood that any of the first, second, third and fourth surface layers
or
stacks of materials may be as disclosed herein or within the references
mentioned elsewhere herein. It should be understood that the conductive
tab portion improves conductivity over the conductive electrode; as
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long as a conductive electrode layer is provided with sufficient conductivity,
the
conductive tab portion is optional. In at least one embodiment, the conductive
electrode layer imparts the desired color specific characteristics of the
corresponding reflected light rays in addition to providing the desired
conductivity.
Therefore, when the conductive electrode is omitted color characteristics are
controlled via the underlayer material specifications.
[0081] Turning to Fig. 8b, a profile view of a portion of a rearview mirror
element is
depicted comprising a first substrate 802b having at least one layer 808b of a
substantially transparent conductive material deposited on the second surface
and a second substrate 812b having a stack of materials deposited on the third
surface secured in a spaced apart relationship with respect to one another via
a
primary seal material 878b to define a chamber there between. In at least one
embodiment, an electro-optic medium 810b is located within said chamber. In at
least one embodiment, the third surface stack of materials comprises an
underlayer 818b, a conductive electrode layer 820b, a metallic layer 822b and
a
conductive tab portion underneath the primary seal material. In at least one
embodiment, a void area 883c is defined between the metallic layer and the
conductive tab portion, the conductive electrode provides electrical
continuity
there between. In at least one embodiment, the underlayer is titanium-dioxide.
In
at least one embodiment, the underlayer is not used. In at least one
embodiment,
the conductive electrode layer is indium-tin-oxide. In at least one
embodiment,
the conductive tab portion comprises chrome. It should be understood that the
conductive tab portion may comprise any conductive material that adheres well
CA 02644218 2012-08-03
to glass and/or other stack layers or the epoxy depending on the layers
sequence and is resistant to corrosion under vehicular mirror testing
conditions.
As can be appreciated, when the third surface stack of materials, or at least
those layers within the stack that are susceptible to corrosion, are kept
within an
area defined by an outer edge of the primary seal material, the element will
be
substantially immune to problems associated with third surface corrosion. It
should be understood that any of the first, second, third and fourth surface
layers
or stacks of materials may be as disclosed herein or within the references
mentioned elsewhere herein.
[0082] With reference to Fig. 8c, a profile view of a portion of a rearview
mirror
element is depicted comprising a first substrate 802c having at least one
layer
808c of a substantially transparent conductive material deposited on the
second
surface and a second substrate 812c having a stack of materials deposited on
the third surface secured in a spaced apart relationship with respect to one
another via a primary seal material 878c to define a chamber there between. In
at least one embodiment, an electro-optic medium 810c is located within said
chamber. In at least one embodiment, a first metallic layer 818c is deposited
over
substantially the entire third surface. In at least one embodiment, a second
metallic layer 820c is deposited over the first metallic layer such that an
outer
edge of the second metallic layer is located within an area defined by an
outer
edge of a primary seal material 878c. In at least one embodiment, the first
metallic layer comprises chrome. In at least one embodiment, the second
metallic layer comprises silver or a silver alloy. It should be understood
that any
41
CA 02644218 2012-08-03
of the first, second, third and fourth surface layers or stacks of materials
may be
as disclosed herein or within the references mentioned elsewhere herein.
[0083] Turning to Fig. 8d, a second substrate 812d is depicted comprising a
stack of
materials having an eyehole 822d1 substantially in front of a light sensor or
information display. In at least one embodiment, a first metallic layer 818d
is
provided with a void area in the eyehole area. In at least one embodiment, a
second metallic layer 820d is provided with a void area in the eyehole area.
In at
least one embodiment, a third metallic layer 822d is provided. In at least one
embodiment, only the third metallic layer is deposited in the eyehole area. In
at
least one embodiment, the first metallic layer comprises chrome. In at least
one
embodiment, the second metallic layer comprises silver or silver alloy. In at
least
one embodiment, the third metallic layer comprises a thin silver, chrome or
silver
alloy. It should be understood that any of the first, second, third and fourth
surface layers or stacks of materials may be as disclosed herein or within the
references mentioned elsewhere herein.
[0084] Turning to Figs. 9a-k there are shown various options for
selectively
contacting a particular portion of the second and third surface conductive
electrode portions 922, 908. As can be appreciated, the configuration of Fig.
7
results in the electrically conductive material contacting at least a portion
of each
the second and third surface conductive electrode portions. It should be
understood that the contact configurations as shown may be rotated about the
element in any fashion.
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CA 02644218 2012-08-03
[0085] The
element construction depicted in Fig. 9a comprises a first substrate 902a
having a second surface stack of materials 908a and a second substrate 912a
having a third surface stack of materials 922a. The third surface stack of
materials is shown to have an isolation area 983a such that a portion of the
third
surface stack of materials that is in contact with a conductive epoxy 948a is
isolated from the remainder of the third surface stack of materials. The first
and
second substrates are held in spaced apart relationship to one another via a
primary seal material 978a. It should be understood that another side of the
element may have a similar isolation area associated with the second surface
stack of materials for providing contact to the third surface stack of
materials
within the viewing area. It should be understood that either the second or
third
surface stack of materials may be a single layer of materials as described
elsewhere herein and within references mentioned herein by reference.
[0086] The element construction depicted in Fig. 9b comprises a first
substrate 902b
having a second surface stack of materials 908b and a second substrate 912b
having a third surface stack of materials 922b. The first and second
substrates
are held in a spaced apart relationship with respect to one another via a
primary
seal material 978b. An electrically conductive epoxy 948b is in contact with
the
third surface stack of materials and electrically insulated from the second
surface
stack of materials via the insulating material 983b. It should be understood
that
another side of the element may have a similar isolation area associated with
the
second surface stack of materials for providing contact to the third surface
stack
of materials within the viewing area. It should be understood that either the
43
CA 02644218 2012-08-03
second or third surface stack of materials may be a single layer of on
materials
as described elsewhere herein and within references mentioned herein.
[0087] The element of Fig. 9c comprises a first substrate 902c having a
second
surface stack of materials 908c and a second substrate 912c having a third
surface stack of materials 922c. The first and second substrates are held in
spaced apart relationship with respect to one another via a primary seal
material
978c. The second surface stack of materials extends toward the edge of the
first
substrate beyond the primary seal material such that it is in electrical
contact with
a first electrically conductive epoxy, or first solder, 948c1. The third
surface stack
of materials extends toward the edge of the second substrate beyond the
primary
seal material such that it is in electrical contact with a second electrically
conductive epoxy, or second solder, 948c2. It should be understood that
another
side of the element may have a similar isolation area associated with the
second
surface stack of materials for providing contact to the third surface stack of
materials within the viewing area. It should be understood that either the
second
or third surface stack of materials may be a single layer of on materials as
described elsewhere herein and within references mentioned herein.
[0088] Fig_ 9d depicts the second surface electrical contact 948d1 being
made on
an opposite side of the element from a third surface electrical contact 948d2.
Fig.
9e depicts the second surface electrical contact 948e1 being made on a side of
the element and the third surface electrical contact being made on an end of
the
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WO 2007/100921 PCT/US2007/005494
element. Fig. 9f depicts the second surface electrical contact 948f1 being
made
on one side and continuously with one end of the element and the third surface
electrical contact 948f2 being made on an opposite side and continuously with
an
opposite end of the element. Fig. 9g depicts the second surface electrical
contact
948g1 being made on opposite sides of the element and the third surface
electrical contact 948g2 being made on an end of the element. Fig. 9h depicts
the second surface electrical contact 948h1 being made on opposite sides of
the
element and the third surface electrical contact 948h2 being made on opposite
ends of the element. Fig. 91 depicts the second surface electrical contact
948i1
being made continuously on opposite ends and one side of the element and the
third surface electrical contact 948i2 being made on one side of the element.
Fig.
9j depicts the second surface electrical contact 948j1 being made continuously
on opposite ends, completely on one side and on at least one portion on the
second side and the third surface electrical contact 948j2 being made on one
side of the element. It should be understood that, in at least one embodiment,
the
longer electrical contact will correspond to the surface having the highest
sheet
resistance stack of materials. It should be understood that the electrical
contact
may be via electrical conductive epoxy, solder or an electrically conductive
adhesive.
[0089] Fig. 9k depicts an element comprising a first substrate 902k having
a second
surface stack of materials 908k and a second substrate 912k having a third
surface stack of materials 922k. The first and second substrates are held in
spaced apart relationship with respect to one another via perimeter first and
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second primary seals 948k1, 948k2. The first primary seal functions to make
electrical contact with the second surface stack of materials and the second
primary seal functions to make electrical contact with the .third surface
stack of
materials. The first and second primary seals hold the first and second
substrates
in a spaced apart relationship with respect to one another and preferably both
primary seals are substantially outside the edge of each substrate.
[0090] Another approach for establishing an electrical connection to an
electrode or
contact clip, such as a J clip or L clip, of an electro-optic element is
through a
solid phase welding process. Wire bonding is a welding process that is used in
the electronics industry to establish reliable interconnections between
electronic
components (usually IC chips and chip carriers). A wire bonding process is
described in Chapter A by Zonghe Lai and Johan Liu in Nordic Electronics
Packaging Guidelines. Electrical interconnections made by wire bonding employ
a metal wire or ribbon and a combination of heat, pressure and/or ultrasonic
energy to weld the wire or ribbon to an associated metal surface. Typically
the
wire or ribbon is welded using a special wedge or capillary bonding tool.
Typical
bonding processes use heat and or ultrasonic energy and generally fall into
three
major categories: thermocompression bonding, ultrasonic bonding and
thermosonic bonding. A wire being bonded may be terminated at the bond or
multiple bonds may be made with a continuous wire. Common forms of wire
bonds include a ball bond, wedge bond and stitch bond. Wires and ribbons made
of many different metals and alloys may be wire bonded including aluminum,
gold, silver, copper and alloys thereof. These wires may be bonded to a number
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of metals or substrates coated with metal layers including but not limited to
metal
layers of gold, silver, nickel, aluminum and alloys made with these metals. In
the
case of bonding to electrodes of electro-optic elements the preferred
substrate is
glass and the preferred metal deposition process is by a physical vapor
deposition process such as magnetron sputtering. A glue layer or layers such
as
of chrome, molybdenum, nichrome or nickel may be applied between the wire
bonded metal layer and glass to obtain acceptable adhesion. The deposited
metal layer thickness may be between 5 Angstroms to 1000 microns. More
preferably the metal layer thickness is between 100 Angstroms and 1 micron and
most preferably the metal layer thickness is between 200 and 1000 Angstroms.
The wire diameter or ribbon thickness may be between 10 and 250 microns with
diameters or thicknesses between 25 and 100 micron being preferred and
diameters or thickness between 50 and 75 microns being most preferred. In at
least one embodiment A continuous wire may be wedge or stitch bonded along a
perimeter edge of a substrate such as to a chrome ring on a second surface of
an electrochromic mirror. A wire or ribbon bus may be electrically connected
to a
clip such as a nickel J or L clip by welding the wire or ribbon to the clip
and then
looping the cup to the substrate and welding it to the associated electrode.
The
wire or ribbon may start at the metal clip and progress along the EC electrode
or
start along the EC electrode and loop to the clip and back to the electrode.
In at
least one embodiment, it is preferred to have redundant welded connections to
the associated electrode and/or from the EC electrode to the associated
electrical contact clip for reliability and uniform coloration of the device.
Multiple
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welded connections to the substrate may be made at spacings from every 0.005
inches to 10 inches with spacings of 0.040 inches to 2 inches being preferred
and with spacings between 0.100 and 0.50 inches being most preferred. A
welded wire or ribbon bus may be protected from damage by encapsulating the
wire and welds in a sealant. A preferred method is to protect the bus by
encapsulating the wire/ribbon and welded bonds in the perimeter seal of the
associated element. The metal wire/foil is chemically compatible with the EC
media enclosing the bus in the device (inside the perimeter seal) is
preferred. A
wire bus may also be used to supplement the conductivity of the associated
electrode inside the element. Wires with diameters of 75 microns or less are
not
readily apparent to the human eye. Welded wire bonding is attractive from a
manufacturing perspective because it is a room temperature or low temperature
process, there is no post cure or post processing operations required, the
technology is well established with proven reliability and the bonds may be
quickly (around 100 millisecond per bond) established.
[0091] Wire bonding may also be used to electrically connect electronic
components
to the substrate surfaces of an element. For example, many metals are
electrochemically stable when used as a cathode but not as an anode in an
element. It is desirable to provide protection such as by a diode to limit
operation
of the EC device when the polarity is reversed. (This is described in detail
below
with reference to Fig. 11a-c.) An electrical component such as a surface mount
diode may be attached to the substrate or the bus clip and electrically
connected
to the substrate and/or the clip by wire bonding. In another embodiment, light
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emitting diodes (LED's) that are part of a signaling or warning system may be
attached, for example in chip form, to an associated substrate and
electrically
connected to a circuit on the substrate formed by patterning metal coatings by
etching, masking or laser ablation. These LED's or other electrical components
may be mounted on or in the element on substrate surfaces one, two, three or
four. Often it is desirable to increase the drive voltage applied to a
solution phase
electrochromic device as the temperature increases to compensate for the
increased rates of diffusion of the electrochromic species and maintain good
device darkening properties over a wide temperature range. A thermistor and
electronic components required for a temperature modulated variable voltage
drive circuit may be mounted to an associated substrate surface and
electrically
connected to metal coatings on the substrate by wire bonding. Example:
Aluminum wires bonded to metal coatings on a glass substrate as follows:
[0092] Glass washed and vacuum sputter coated with approximately 400
Angstrom
thick layers comprising a first layer of chrome and second layer of nickel
(CN); a
first layer of chrome and second layer of ruthenium (CR); a first layer of
chrome,
a second layer of ruthenium and third layer of nickel (CRN). A 0.00125"
diameter
aluminum alloy wire containing 1% silicon (1-4% elongation, 19 to 21 grams
tensile strength) wire bonded to the metal coated glass substrates using a
Westbond Model 454647E wirebonder with the following settings:
Settings First Bond Second Bond
"CN" Power 175 150
Time 30 millisecond 30 millisecond
Force 26 grams 26 grams
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"CRN" Power 175 150
Time 30 milliseconds 30 milliseconds
Force 26 grams 26 grams
"CR" Power 150 125
Time 75 milliseconds 100 milliseconds
Force 26 grams 26 grams
Bond strength of the wire was evaluated by pulling off the wire after bonding
and
after 1 hour exposure to 300 degrees centigrade and measuring the force.
Wire Bond Mean Pull Strength:
After Bonding After 300C bake
"CN" 14.51 grams 9.02 grams
"CRN" 19.13 grams 8.2 grams
"CR" 12.42 grams 8.7 grams
[0093] Predominate failure after bonding was wire break at the end of first
welded
bond. After bake the predominate failure was wire break at mid span for "CN"
and
"CRN" groups and wire break at the end of first bond for the "CR" group. This
example demonstrates multiple reliable welded bonds may be made to typical
sputtered metal layers on glass.
[0094] Fig. 10 generally illustrates variable transmittance windows 1010
that may be
employed in multi-passenger vehicles, along with a window control system 1008
electrically coupled to the variable transmittance windows 1010 for
controlling the
transmittance state of the variable transmittance windows 1010. Window control
system 1008 includes a window control unit 1009 coupled to each of the
variable
transmittance windows 1010 for controlling the transmittance of 7 each of the
variable transmittance windows 1010. Each window control unit 1009 includes
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slave control circuitry 1070 for controlling the transmittance state of an
associated variable transmittance window 1010. Each window control unit 1009
is also shown having user input mechanism 1060 coupled to slave control
circuitry 1070 for providing a user input to slave control circuitry 1070 to
change
the transmittance state of the associated variable transmittance window 1010.
Each window control unit 1009 is also shown coupled to power and ground lines
1011 for providing power to slave control circuitry 1070, user input mechanism
1060, and variable transmittance window 1010. As shown, power is provided to
variable transmittance window 1010 via slave control circuitry 1070 from the
power and ground lines 1011.
[0095] Each window control unit 1009 is also shown coupled to a window
control
system bus 1013. Other devices also coupled to the window control system bus
1013 include master control circuitry 1090 and other electronic devices 1092.
.
Master control circuitry 1090 is configured to monitor signals provided on the
window control system bus 1013 by each of window control units 1009 and to
provide control signals on the bus to each of window control units 1009.
Master
control circuitry 1090 includes processing circuitry, including logic, memory,
and
bus interface circuitry, to permit master control circuitry 1090 to generate,
send,
receive, and decode signals on the window control system bus 1013. Slave
control circuitry 1070, included in each of window control units 1009, is
configured to receive a desired window transmittance state from user input
mechanism 1060, and provide electrical signals to variable transmittance
window
1010 to change the transmittance state of variable transmittance window 1010
to
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the state requested by the user via user input mechanism 1060. Slave control
circuitry 1070 is also configured to monitor various characteristics of
variable
transmittance window 1010, including the power consumed by variable
transmittance window 1010 and the transmittance state of variable
transmittance
window 1010. Slave control circuitry 1070 also includes circuitry for
receiving
signals from, and sending signals to, the window control system bus 1013.
[0096] Certain metal films can be less stable when configured as an anode
when
compared to transparent conductive oxides, such as, indium tin oxide films.
This
may be evidenced upon cycling in an electrochromic device by the metal
deplating from the anode or by chemical changes in the metal surface such as
oxidation, or by the surface becoming hazy from the mobile metal atoms
rearranging into a rougher surface. Some metals and metal thin film stacks and
thin film stacks containing metallic layers will be more resistant to these
effects
than others. Nonetheless it may be desirable to take steps to insure that the
third
surface reflector electrode is the cathode.
[0097] It is possible that in certain embodiments it might be preferable to
incorporate
materials into the second surface transparent electrode that are sensitive to
use
as an anode. In this case it may be preferable to drive the third surface
electrode
as the anode and the second surface electrode as the cathode in order to
protect
the second surface electrode.
[0098] For electrochromic mirrors on the exterior of a vehicle there may be
a power
source that is not directly tied to an associated drive circuit located in an
associated interior mirror which may to some degree minimize the risk of the
third
=
=
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surface reflector electrode being the anode on that mirror (i.e. the given
e)derior
mirror may comprise an independent drive circuit). However, it is common for
the
power of an exterior mirror (or mirrors) to be supplied via the interior
mirror.
There are oftentimes several connections between an interior mirror and
corresponding exterior mirror(s). The risk of the polarity of the power from
the
interior mirror to the exterior mirror being reversed, making the third
surface
reflector electrode of the device and anode, may be unacceptable when the
associated reflector/electrode is not sufficiently durable to function as an
anode.
[0099] With reference to Fig. 11a, a circuit 1101a having a diode in series
with an
exterior mirror element 1102a, prevents current flow with reversed polarity,
as
well as preventing electrochromic functionality. The device may have
compromised performance when operated in the correct polarity in that the
mirror
will darken upon application of the usual voltage however upon shorting of the
circuit at the inside mirror circuitry for clearing , the exterior mirror will
not be able
to discharge via that route. Therefore the exterior mirror element will mainly
discharge as the positive and negatively charged species neutralize each other
in
solution, however not as they discharge to the conductive surfaces of the
device.
This may result in a substantially slowed clearing speed for the device.
[0100] The circuit 1100b depicted in Fig. 11b comprises a diode 1101b in
parallel
across the leads near an exterior mirror element 1102b. A short circuit will
be
caused if the polarity of the current provided to that portion of circuit is
reversed.
Current will then flow through the diode and not the electrochromic element.
The
short is detected by the interior mirror circuitry 1103b and voltage is
automatically
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disconnected. Therefore, even though allowing proper operation of the mirror
when the polarity is correct, this circuit completely disables the
electrochromic
functionality of the mirror if the polarity is reversed.
[0101] However, when a diode 1101c is coupled with circuitry 1100c that
does not
initially cease to apply voltage when excessive current ( shorting) however
reverses voltage the mirror element 1102c remains operational and the proper
polarity is delivered to the element such that the reflector electrode
automatically
is reconnected as the cathode. In this circuit 1100c when excessive current is
detected two solid state switches 1104c1, 1104c2 are automatically
reconfigured
to redirect the current through the element 1102c in the opposite direction.
Should excessive current be detected in this configuration, the solid state
switches are reset and the drive to the element is discontinued since it is
likely
that some other fault is causing the excessive current draw.
[0102] Fig. 11d depicts an alternate configuration for an electro-optic
drive circuit
that provides automatic compensation for reverse polarity. Diodes 1101d1,
1101d2, 1101d3, 1101d4 define a rectifier bridge which provides a dual current
path. The actual path current flows will always have the desired orientation
of
anode and cathode of the electro-optic element 1102d.
[0103] The circuits 1100a, 1100b, 1100c, 1100d of Figs. 11a-11d are
depicted to a
single outside mirror. Should it be desirable to protect more than a single
exterior
mirror the desired circuitry may be so adapted.
[0104] In electro-optic elements similar to that shown in Figure 7, having
a fourth
surface reflector (not shown), when there is no electrical potential
difference
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between transparent conductors 708 and 718, the electrochromic medium in
chamber 710 is essentially colorless or nearly colorless, and incoming light
(lo)
enters through the front element 702, passes through the transparent coating
708, the electrochromic medium in chamber 710, the transparent coating 718,
the rear element 712, and reflects off the layer and travels back through the
device and out the front element 702. It should be understood that aspects of
the
present invention directed toward variable transmittance windows as described
above may not incorporate a reflective layer. In other embodiments a third
surface reflector/electrode may be employed. Typically, the magnitude of the
reflected image (IR) with no electrical potential difference is about 45
percent to
about 85 percent of the incident light intensity (lo). The exact value depends
on
many variables outlined below, such as, for example, the residual reflection
(11R)
from the front face of the front element, as well as secondary reflections
from the
interfaces between the front element 702 and the front transparent electrode
708,
the front transparent electrode 708 and the electrochromic medium, the
electrochromic medium and the second transparent electrode 718, and the
second transparent electrode 718 and the rear element 712. These reflections
are well known in the art and are due to the difference in refractive indices
between one material and another as the light crosses the interface between
the
two. When the front element and the back element are not parallel, the
residual
reflectance (I'R) or other secondary reflections will not superimpose with the
reflected image (IR) from mirror surface, and a double image will appear
(where
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an observer would see what appears to be double, or triple, the number of
objects actually present in the reflected image).
[0105] There are minimum requirements for the magnitude of the intensity of
the
reflected light depending on whether the electrochromic mirrors are placed on
the
inside or the outside of the vehicle. For example, according to current
requirements from most automobile manufacturers, inside mirrors preferably
have a minimum high end reflectivity of at least 40 percent, and outside
mirrors
must have a minimum high end reflectivity of at least 35 percent.
[0106] The electrode layers 708 and 718 are connected to electronic
circuitry, Figs.
10-11d for example, which is effective to electrically energize the
electrochromic
medium, such that when a potential is applied across the conductors 708 and
718, the electrochromic medium in chamber 710 darkens, such that incident
light
(l.) is attenuated as the light passes toward the reflector and as it passes
back
through after being reflected. By adjusting the potential difference between
the
transparent electrodes, a preferred device functions as a "gray-scale" device,
with continuously variable transmittance over a wide range. For solution-phase
electrochromic systems, when the potential between the electrodes is removed
or returned to zero, the device spontaneously returns to the same, zero-
potential,
equilibrium color and transmittance as the device had before the potential was
applied. Other materials are available for making electrochromic devices and
it
should be understood that aspects of the present invention are applicable
irrespectively of which electro-optic technology is employed. For example, the
electro-optic medium may include materials that are solid metal oxides, redox
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active polymers, and hybrid combinations of solution-phase and solid metal
oxides or redox active polymers; however, the above-described solution-phase
design is typical of most of the electrochromic devices presently in use.
[0107] Various attempts have been made to provide an electro-optic element
with a
second surface transparent conducting oxide with a relatively low sheet
resistance while maintaining low absorption. In the electrochromic mirrors
described above as well as in electrochromic windows or electro-optic devices
in
general, the transparent conductive layers 708, 718 are often made of indium
tin
oxide. Other attempts have focused on reducing the intrinsic stress of an ITO
layer as applied to an associated glass substrate to minimize bending or
warping
of the substrate. Still other attempts have been made to optimize the optical
properties such as the reflectance by adjusting the quarter and, or, half wave
thickness of the ITO layer(s), or to minimize the weight of the overall
associated
assembly. However, there has been little success in efforts to simultaneously
optimize all of the optical and physical properties noted above due to the
previously perceived physical limitations.
[0108] One such previous approach to optimizing the optical properties of a
given
electrochromic assembly has been to manipulate the composition of the
electrodes therein. Specifically, certain optical properties may be obtained
by
adjusting the reflectance of the reflective electrode of the assembly. More
specifically, by manipulating the material composition of the stacked layers
comprising the reflective electrode, the reflectivity thereof may be
increased,
thereby nullifying the relative absorption of the associated transparent
electrode.
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However, increasing the reflectivity of the reflective electrode typically
requires
the use of additional amounts of the metals used to construct the same, such
as
rhodium, ruthenium, chrome, silver, and the like. As many of these metals are
relatively expensive, adding additional amounts thereof to the electrochromic
element unacceptably raises the cost thereof. Moreover, many lower cost
metals,
while providing good reflective properties, are incompatible with
manufacturing
processes and/or with the harsh environmental conditions to which the overall
assembly will be subjected, such as, exterior mirror assemblies and exterior
window assemblies.
[0109] Other approaches, which utilize ITO electrodes, required the
balancing of
several optical and physical parameters that are non-complimentary to one
another. For example, increasing the thickness of a transparent ITO conductive
layer to achieve a lower sheet resistance may adversely effect the absorption
associated with that layer, the position of the quarter and, or, half wave
points,
and the bending of the substrate to which the ITO layer is applied, as is
discussed in detail below.
[0110] As known in the art, reducing the sheet resistance of an ITO layer
may be
accomplished by increasing the thickness of that layer. However, the increased
thickness of the ITO layer is accomplished with an undesirable increase in
light
absorption of that layer. Further, an increase in the thickness of the ITO
layer has
typically been restricted to quantums of half waves of a given wavelength
range
(typically centered at approximately 550 nm) so as to minimize the relative
reflectance from the outer surface of the ITO layer. Moreover, increasing the
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thickness of the ITO layer may increase the bending of the substrate to which
the
ITO layer is applied. As is known, the ITO layer includes an internal stress
that is
exerted on the substrate, which when applied to some thin substrates, may
result
in bending of such substrate. In many applications, the substrate comprises
relatively thin glass, so as to reduce absorption of the glass and the weight
associated therewith, such that unacceptable bending occurs as the thickness
of
the ITO layer is increased. This is particularly prevalent in large
applications,
such as large windows such as those used within aircraft or in buildings.
Bending
of the associated substrate may effect the distance between the two electrodes
within the overall assembly, thereby effecting clearing rates, color, relative
uniformity darkness or brightness of the assembly at varying points across the
surface thereof, and even causing optical distortions to the point of created
multiple reflected images rather than a single image. Previous approaches at
reducing the intrinsic stress of the ITO layer have focused on the methods
utilized to produce the electrochromic elements. One method known in the art
for
applying the ITO layer to an associated substrate includes magnetic
sputtering.
Heretofore, these attempts have only been moderately successful due to several
drawbacks, one of which is the physical limitations inherent in the approach,
an
example of which is the disruption of the laydown of the ITO layer at
increased
pressure, resulting in clustering of the ITO. Such clustered ITO layers
exhibit an
increase in sheet resistance, haze and absorption.
(0111] In at least one embodiment an electro-optic element is provided
utilizing an
ITO layer having reduced sheet resistance, reduced absorptivity, and low
stress,
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while attaining a uniform darkness or brightness of the overall assembly,
while
reducing the weight of the overall assembly, any sub combination or
combination
thereof.
[0112] In at least one embodiment an electro-optic element is provided
having a
relatively reduced sheet resistance while simultaneously providing a
relatively
reduced absorptivity, a relatively decreased bending of an associated
substrate
to which the associate ITO layer is applied, and provides a relatively uniform
darkness or brightness for the overall assembly while reducing the total
weight
thereof.
[0113] While mirror assemblies in general are utilized herein to describe
many
details of the present invention, it should be noted that embodiments of the
present invention is equally applicable to the construction of electro-optic
windows, as discussed elsewhere herein. The inside mirror assembly of Figs. 6a-
d and the outside rearview mirror assemblies of Figs. 5a-5f may incorporate
light-
sensing electronic circuitry of the type illustrated and described in Canadian
Patent No. 1,300,945, U.S. Patent No. 5,204,778, or U.S. Patent No. 5,451,822,
and other circuits capable of sensing glare and ambient light and supplying a
drive voltage to the electrochromic element.
[0114] As noted above, high performance electro-optic elements (either
mirrors or
windows) require that the electrode and or reflector on the third surface and
the
transparent conductive electrode 708 provide moderate to high conductivity to
provide even overall coloration, increased speeds of coloration and clearing,
etc.
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While improvements in mirror elements have been accomplished by employing a
third surface reflector/electrode, improvements with respect to the
transparent
electrode 708, 718 are desired. As also previously noted, simply increasing
the
overall thickness of an ITO transparent electrode 708, 718 while improving
conductivity by decreasing the sheet resistance, has detrimental effects on
other
optical and physical properties of the electrochromic element. Table 4 depicts
the
drop in reflectance of an EC element With changing ITO thickness for three ITO
coatings with different optical constants. The different ITO coatings in this
example have different imaginary refractive indices. The example element
construction consists of 1.7 mm glass, 50 nm Cr, 20 nm Ru, 140 microns of EC
fluid, varying ITO and 1.7 mm.of glass. The thickness of different ITO layers
is
shown in Table 4. In many side mirror applications the customer specifications
require that the reflectance is greater than 55%. The thickness is limited
depending on the properties of the ITO and therefore the viable sheet
resistance
is also limited. In a typical manufacturing process it is not always possible
to
operate a process at the lowest absorption levels. Therefore, the practical
upper
thickness and lower sheet resistance limits are constrained by the variation
in the
manufacturing process. Additionally, .it is common that ITO with lower
absorption
undesirably corresponds to higher sheet resistance. Thicker, low absorption,
ITO
may also correspond to one with a higher sheet resistance thereby limiting the
benefit of the thicker coating.
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Table 4
. Reflectance (%)
ITO ITO ITO ITO
Thickness RI=1.893 RI=1.868 RI=1.865
(nm) k=0.0057 K=0.0079 K=0.012
100 59.8 59.3 58.2
150 58.5 57.7 56.0
200 58.4 57.2 55.1
250 57.5 56.2 53.7
300 56.5 54.9 51.9
350 56.1 54.3 50.9
400 55.4 53.4 49.6
450 54.5 52.3 48.2
500 54.0 51.6 47.1
[0115] Another design attribute desirably for EC elements is to have a low
reflectance in the dark state. This results in a high contrast ratio for the
mirror
elements. Table 5 depicts the dark state reflectance values for an EC mirror
as a
function of the ITO thickness. In this example the EC fluid is set to be
substantially opaque. If the EC fluid is not completely opaque then the
reflected
light from the mirror coating will add to the reflectance in Table 5. As
depicted,
the dark state reflectance reaches a minimum at about 140 to 150 nm or a %
wave coating with a design wavelength of 550 nm. As the thickness deviates
from this half wave thickness, the dark state reflectance rises and the
contrast
ratio degrades. Therefore, ITO thickness cannot be set to an arbitrary
thickness
to attain a given sheet resistance value. The ITO thickness is constrained by
both
absorption of the coating and the dark state reflectance requirements.
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Table 5
ITO Dark State
Thickness Reflectance (%)
(nm)
70 9.4
80 9.2
90 8.6
100 7.7
110 6.7
120 5.8
130 5.1
140 4.9
150 5
160 5.5
170 6.2
180 7
190 7.7
200 8.2
210 8.5
[0116] In at least one embodiment, an electro-optic element includes at
least one
ITO transparent electrode 128 with reduced bulk resistance, thereby improving
conductivity, without simultaneously sacrificing other related optical and
physical
properties. Specifically, an electro-optic element is constructed via a
sputtering
process at relatively high pressures and relatively high oxygen flow rates.
Heretofore, traditional sputtering processes utilized for applying an ITO
layer to a
substrate have been limited to certain maximum pressures. Exceeding these
pressures has previously resulted in a poor quality layer of ITO, or
specifically a
clustered, non-uniform deposition exhibiting poor electrical and optical
properties.
[0117] In at least one embodiment, the ITO coatings were produced on a
vertical, in-
line sputtering coater. Cathodes were approximately 72" in length and either
two
or four cathodes were used to produce the coatings. The cathodes were
outfitted
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with ceramic ITO tiles commonly used in the industry. The conveyor speed was
adjusted as necessary to produce a targeted thickness of coating. The power
applied to the cathodes was 5 kilowatts unless otherwise noted. Each process
section has two pair of cathodes in an aligned facing configuration. Oxygen
gas
flows shown herein are for a process section consisting of four cathodes
unless
otherwise indicated. When two process sections are operated it is assumed that
an equivalent amount of oxygen is fed into both chambers and the total amount
of oxygen is double that used for four cathodes in one process chamber. Glass
substrates were preheated to approximately 300 degrees Celsius. The sputtering
gas was adjusted to attain a given pressure and oxygen was introduced at the
prescribed flow rate or as a percentage of the total gas fed to the system. It
should be understood, however, that the present invention is not limited by
the
exact flow rates and percentages described herein as one skilled in the art
will
know that different chambers have different pumping configurations, gas inlets
and manifolds, cathodes and powers and measure their pressure at different
points in the process. Rather, one skilled in the art will appreciate the
novelty of
the method used to produce the coatings and their resultant properties
including
bulk resistance, stress and morphology and will be able to readily scale or
adapt
the teachings herein to a different sputtering system without undo
experimentation. Though the majority of the work described herein was
conducted with a glass substrate temperature of 300 C the trends and findings
will be adaptable to higher and lower temperatures and will yield improvements
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over the standard conditions even if the absolute values described herein are
not
attained at the different temperatures.
[0118] In at least one embodiment of the present invention, increase in
process
pressure is offset by an increase in oxygen flow. As described particular
relation
of pressure to oxygen flow rate depends on several factors, including the
,
particular noble gas used during the sputtering process. Two noble gases,
krypton, and argon, are discussed in detail herein, however, other gases may
be
utilized with the particulars for the other gases being extrapolated from the
given
data.
[0119] With respect to krypton, a pressure of greater than or equal to 1
millitorr (mT)
with an oxygen percentage of 5%, is preferred, a pressure of greater than or
equal to 2 mT with an oxygen percentage of 4% is more preferred a pressure of
greater than or equal to 3mT with an oxygen percentage of 3% is even more
preferred, and a pressure of greater than or equal to 4.5 mT with an oxygen
flow
rate of 2% is most preferred.
[0120] With respect to argon, a pressure of greater than or equal to 2 mT
with an
oxygen percentage of 4% is preferred, a pressure of greater than or equal to
3mT with an oxygen percentage of 3% is more preferred, a pressure of greater
than or equal to 4.5 mT with an oxygen percentage of 2% is even more preferred
and a pressure of greater than or equal to 6 mT with an oxygen percentage of
1% is most preferred.
[0121] As noted above, other gases may also be utilized. For example, Neon
may
be used with expected higher pressures, preferably greater than or equal to 3
mT
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and more preferably greater than or equal to 7 or 8 mT. Further, Xenon allows
use of relatively low pressures as compared to krypton. One skilled in the art
will
also recognize that the preferred oxygen percentages may vary with the details
of the sputtering apparatus. The percentages listed above are meant to be
illustrative and non-limiting. The total flow of oxygen needed to obtain the
optimal
combination of material properties will generally increase with increased
pressure.
The needed amount of oxygen does not increase at the same rate as the
sputtering gas, therefore, the percentage of oxygen decreases with increased
pressure.
[01221 Typically, ITO is run at low pressures ¨ at or below 2 mT. Low
pressure,
however tends to result in the ITO coating having compressive stress. Stress
in
the ITO can be high enough to bend glass especially as the thickness of the
glass is reduced. As the thickness of the glass is reduced to make EC elements
lighter, deflection of glass due to the ITO stress increases. When the mirror
element or window size is large, deflection of the glass can be several
millimeters.
With traditional high volume production processing, as the thickness of the
ITO is
increased the deflection of the substrate typically increases.
[0123] Deflection of the glass can be expressed in various ways. One
way is to
consider the deflection of the glass is in terms of a lens. The magnification
value
then directly relates to the deflection of the glass and is independent of the
dimensions of the glass. The magnification values relate to a radius of
curvature
using the following formula: radius of curvature = (3124 mm)/(1-
1/magnification).
A perfectly flat piece of glass will have a magnification value of 1Ø Coated
glass,
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viewed from the coated side, when the coating is in compressive stress then
the
glass will become convex on the coated side. If the coating were in tensile
stress
the glass will be concave on the coated side. A compressive coating results in
a
warp or magnification value less than one and conversely if the coating is
tensile,
the magnification or warp values will be greater than 1. Warp values on the
order
of 0.85 are highly distorted from flat and glass. Warp values on this order
will
yield an EC mirror or window that may have double image since the reflectance
from the first and third surfaces may not overlap. Additionally, it is
difficult to
produce a viable seal with glass having unacceptable warp. Glass with warp
values as high as 0.97 can cause issues in manufacturing or with regard to
double image.
[0124] With reference to Fig. 12, labeled "Argon Pressure Tests," the warp
values
were measured for ITO coatings on 1.6 mm glass. The glass thickness plays a
significant role in deflection and warp when an ITO or other stressed coating
is
applied. The deflection amount generally varies inversely with the cube of the
thickness of the glass (assuming that the intrinsic stress in the coating is
constant
with thickness of the coating). Therefore, thinner glass will warp in a non-
linear
fashion relative to thick glass. Thinner glass will generally warp with
thinner ITO
coatings when compared to thicker glass. The amount of warp scales linearly
with the thickness of the coatings. In Fig. 12 the coatings were all
approximately
50 nm in thickness. To calculate the warp at other thickness values the
following
formula may be used: New warp = [1-(1-warp value)*new thickness/old
thickness]. Applying this formula to a value in Fig. 12 of 0.98, a warp value
of
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0.94 for an ITO coating 150 nm thick and a warp value of 0.74 for a coating
650
nm thick would be derived. If the glass were thinner these values would
deviate
from flat much more substantially.
[0125] Fig. 12 depicts several key findings. First, the warp values or
stress (y-axis)
in the ITO produced at 2.1 mT do not change substantially over the oxygen flow
rate range (x-axis) in this experiment. Over this range the ITO passes through
the minimum sheet resistance and bulk resistance values. It could be
incorrectly
concluded that it is not possible to simultaneously optimize both the
electrical and
stress properties, not to mention the other required optical properties. At
very
high oxygen flow rates, warp values start to deviate even more substantially
from
flat.
[0126] At the higher pressures (4.0 mT) a trend emerges. At low oxygen flow
rates
the stress in the ITO coating is reduced. But at higher pressures this
translates
into lower oxygen percentages in the overall sputtering environment. It is
common in the sputtering art to keep the oxygen percentage constant while
adjusting pressure. The trend and findings leading to one embodiment of the
present invention is therefore undiscovered when traditional experimentation
is
employed. At the higher Argon pressure of 4 mT depicted with line 1202 a
strong
trend emerges whereby the stress in the ITO is minimized at low oxygen flows
as
compared to line 1201. The lower stress is due to a unique microstructure or
morphology in the ITO coating that is described in detail below. At higher
oxygen
flow rates the warp values deviate from flatness, however at any particular
oxygen flow rate the warp values remain higher than those obtained at the
lower
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pressure. This trend continues for even higher pressures than those
demonstrated in this Fig. 12. The benefits continue at pressures in excess of
7
mT. Further improvements may also be attained at even higher pressures,
however, limitations in a particular sputtering chambers may restrict
experimentation at pressures beyond this value.
[0127] The graph of Fig. 13 illustrates the effects of a relative increase
in Argon
pressure and oxygen flow on bulk resistance. This particular test was
conducted
utilizing an argon as the sputtering gas. The 400 sccm argon case (line 1301)
yields a pressure of 3.7 mT, 550 sccm (line 1302) yields 5 mT, 700 sccm (line
1303) yields 6.2 mT and 850 sccm (line 1304) yields 7.4 mT. The oxygen flow
rate on the x-axis is in sccm. It is noted that significant improvements are
obtained with respect to bulk resistivity as Argon pressure and oxygen flow
increase. Additionally, the lower Argon pressure cases tend to have a minimum
at higher bulk resistance values relative to the higher pressure cases. For
reference, a comparable coating made at a pressure of 2 mT comprises a bulk
resistance value between about 180 and 200 micro-ohm cm. In a recently
published patent application, it was submitted by another manufacturer of
electrochromic devices that the current state of the art for ITO coatings in
EC
applications corresponds to a bulk resistance of 200 micro-ohm cm. This
indicates that the benefits and properties of ITO viable for EC applications
does
not anticipate the improved ITO coatings of the present invention. The higher
pressure cases described herein do not attain their minimum value at the range
of oxygen tested.
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[0128] The graph of Fig. 14 illustrates that higher pressures further
result in a
relatively thinner ITO coating on the substrate. This fact also contributes to
why
this embodiment of the present invention has not been previously attained. As
depicted, when oxygen flow and Argon pressure are increased, the thickness of
the ITO coating is decreased. The bulk resistance, an intrinsic measure of the
quality of the ITO's electrical properties, is the multiplication of the sheet
resistance and the thickness. It is common to only measure the sheet
resistance,
however, much information is lost when the coatings are not characterized in
detail. Because the coatings are getting thinner with the changes to the
process
gasses the sheet resistance does not follow the same trends as the bulk
resistance. The continued benefits to the bulk resistance obtained with the
higher
Argon pressures (line 1404 representing the highest relative to lines 1401,
1402
and 1403) and oxygen flows are shown in a comparable analysis of the sheet
resistance. If only sheet resistance is examined then one may conclude that
the
3.7 mT case is best and the preferred properties are attained at relatively
low
oxygen flow rates. Another benefit that comes with the lower bulk resistance
is
that the real part of the refractive index is reduced. A half wave coating
with a
lower refractive index is physically thicker than one with a higher refractive
index
resulting in even lower sheet resistance.
[0129] The graph of Fig. 15 illustrates the effect of utilizing an argon
gas in
conjunction with increased Argon pressure and increased oxygen flows, while
the
graph of Fig. 16 illustrates achieved ITO half wave bulk resistance. In order
to
attain 1/2 wave coating two process chambers were used. The 200 sccm case
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represents the standard in prior ITO coatings in the EC art. The half wave
coating
of the prior art had a sheet resistance of over 12.5 ohms/sq while higher
pressure
cases in accordance with at least one embodiment of the present invention
attained values lower then 12 ohms/sq and some even below 11 ohms/sq.
Substantial improvement in bulk resistance attained at higher pressures is
exemplified in Fig. 16. In this case oxygen was not optimized at the higher
pressures and the bulk resistance is seen to remain relatively constant with
argon flows from 400-800 SCCM.
[0130] Bulk resistance of the ITO is important, however, as mentioned
elsewhere
herein sheet resistance is the primary factor that affects darkening speed in
an
EC element. A bulk resistance of 200 micro-ohm cm equates to a sheet
resistance of 13.7 ohms/sq for a half wave coating, a bulk resistance of 180
equates to a sheet resistance of 12.4 ohms/sq and a bulk resistance of 140
equates to a sheet resistance of 9.6 ohms/sq. 9.6 ohms/square is a 30%
reduction compared to the 13.7 ohms/sq case and results in substantial
improvements in darkening times and will also enable novel bus configurations
as described elsewhere herein which also improve element darkening uniformity.
[0131] In the next example, coatings were produce in a different coater.
This coater
has a cathode that is approximately 27 inches long. The experiments were
conduced with both argon and krypton at a pressure of 2.73 millitorr. The
coatings were made in two passes past the cathode. The oxygen was varied as
depicted in the associated Figs. and tables. The resulting ITO coatings are
approximately 600 nm in thickness. In Fig. 17 the absorption (y-axis) in the
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coatings is plotted as a function of the oxygen flow rate (x-axis). As can be
seen
the samples made with Krypton (line 1701) are higher in absorption at a given
oxygen flow rate compared to the samples produced using argon (line 1702) as
the sputtering gas.
[0132] In Fig.18 warp in the glass (y-axis) is plotted as a function of
oxygen flow rate
(x-axis). It can be seen that the samples produced with Krypton (line 1801)
have
warp values closer to 1 which indicates that the krypton produced ITO coated
glass is flatter than argon (line 1802) produced glass. Fig. 18 illustrates
the data
presented earlier where the warp was shown to increase with increasing oxygen
flow rate.
[0133] In Fig. 19 warp of the glass (y-axis) is plotted versus the
absorption (x-axis).
The Krypton produced samples (line 1901) have more absorption when plotted
against oxygen flow rate, however, when the warp is compared against
absorption the Krypton produced samples are flatter than the argon produced
samples (line 1902).
[0134] Fig. 20 depicts warp (y-axis) versus transmittance (x-axis) for
Krypton (line
2001) and Argon (line 2002). Flatter glass is obtained for a given increased
transmittance value. Additional improvements are possible using Krypton or
Xenon, or even Argon, at higher pressures. Higher pressures enable the
simultaneous achievement of lower stress, higher transparency and lower sheet
resistance.
[0135] The morphology, or surface features, of the ITO coating also change
with
pressure and oxygen flow rate. There exists an interaction effect between
these
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values where different morphologies are attained at different oxygen flow
rates
when the pressure is changed. ITO coating samples depicted in Figs. 21-23 were
produced in a coater with 72" cathodes. All samples were made at 2.1 rnT, 5 kw
per target, 1 process chamber (2 targets/side) and a line rate of 32 ipm. The
oxygen flow rate was 2, 8 and 17 sccm for the samples in Figures 21, 22 and
23,
respectively. Samples of Fig. 21 and Fig. 23 illustrate the extremes in the
morphology. The sample of Fig. 21 has what we call a nodular 2101 morphology
while the sample of Fig. 23 has a platelet 2302 morphology. Examining the
sample of Fig. 21 reveals a background platelet 2102 structure. The sample of
Fig. 21 is considered to have a somewhat mixed morphology. The sample of Fig.
22, at the intermediate oxygen flow has very few nodules 2201 and an overall
dominant platelet 2202 morphology. The platelet morphology has been
correlated with a higher stress in the coatings while the nodular morphology
occurs in the coatings with less stress. Depending on the given process gas
pressure, the transition between these two different morphologies is either
abrupt
or gradual. The low oxygen nodular morphology is characterized by a large peak-
to-valley roughness (as described in detail with regard to Figs. 33a and 33b).
The
nodules rise substantially above the surface of the coating thus creating
large
peak to valley roughness. As the nodules transition into the platelet
microstructure the roughness of the surface decreases. The roughness is at a
minimum when the nodules have just vanished from the surface. At this point we
have a platelet microstructure with shallow "cliffs" 2103, 2203, 2303 or
regions
between the platelets. As the oxygen flow is further increased the height of
the
=
73
CA 02644218 2008-08-27
WO 2007/100921 PCT/US2007/005494
cliffs between the platelets increases, undesirably increasing the roughness
of
the surface.
[0136] The samples of Figs. 24-26 are made at comparable powers and line
rates
as with those of Figs. 21-23 and all at 2 sccm oxygen. The process gas
pressures were 3.7, 2.1 and 1.6 millitorr respectively. The morphology is
increasingly dominated by the nodular morphology as the pressure is increased.
The transition between the nodular 2401, 2501, 2601 and platelet morphologies
is more gradual at the higher pressures, thus, allowing a finer adjustment
between desirable optical and mechanical properties in the coating. The
platelet
2402 morphology is still present in the background of the 3.7 millitorr
sample,
however, in a much less dominant amount. As the pressure is further decreased
the nodule component is eventually eliminated leaving only the platelet
morphology.
[0137] Use of Krypton or other heavier sputtering process gas is similar in
some
regards to running at a higher pressure. Three SEM images of% wave ITO
samples are compared which were produced with Krypton as the process gas
and with varying oxygen flow rates as depicted in Figs. 27-29. These samples
are described in more detail with reference to Table 6. These samples were
made at 40 ipm line rate and 6.2 kw and using two process chambers (four
cathodes/side). The glass thickness was 1.1 mm. Oxygen flow rates are 8, 12
and 16 sccm for samples in Figs. 27, 28 and 29, respectively. The oxygen flow
rates are per process chamber. The surface of the sample depicted in Fig. 27,
produced at 8 sccm oxygen, has virtually no platelet component and is
extremely
74
CA 02644218 2008-08-27
WO 2007/100921 PCT/US2007/005494
stress free; the surface of this sample is predominantly nodules 2701. The
sample depicted in Fig. 27, and the other I/2 wave samples from Table 6, has
warp values that are essentially unity. The surface structure of the sample
depicted in Fig. 28 is generally comprised of nodules 2801 and has a very
minor
amount of platelet 2802 morphology with slight cliffs 2803. The sample of Fig.
29
is essentially all platelet 2902 surface structure with well defined cliffs
2903. The
samples have very low bulk resistance values of approximately 150 micro-ohm
cm. The absorption of these coatings is fairly low with the 12 sccm case
having
the best combination of flatness, resistivity and absorption. The low stress
values
for these coatings indicates that even some platelet morphology can be
utilized
with success when produced using higher pressures or with heavier sputtering
gasses.
[0138] Samples D, E and F as depicted in Figs. 30-32, respectively, are for
the 2-
wave ITO cases as tabulated in Table 7 and correspond to the 8, 12 and 16
=
sccm flow rates, respectively. The line rate was 7 ipm for these samples
otherwise the process conditions were equivalent to those of Table 6. These
coatings are approximately 5 times thicker than their half wave counterparts.
The
morphology of the coatings is somewhat different on these samples with the
nodular 3001, 3101, 3201 morphology of the thinner samples giving rise to a
more granular structure (sample D, Fig. 30). There are voids between the
grains
depicted in Fig. 30 which gives rise to undesirably high haze and a degraded
conductivity; this is exemplified by the relatively high bulk resistance value
of 200
micro-ohm-cm for this sample. Sample E, made with 12 sccm of oxygen has a
CA 02644218 2008-08-27
WO 2007/100921 PCT/US2007/005494
very low bulk resistance (131 micro-ohm cm) and a fine grain microstructure.
The
16 sccm case has a similar microstructure but in this case the platelet
morphology is not present as it is in the thinner coatings. The stress levels
of
these Krypton-produced coatings are relatively low. The warp values range from
essentially unity for the low oxygen case to 0.956 for the highest oxygen
case.
These samples were produced with 1.1 mm glass which is more susceptible to
warp compared to the thicker 1.6 mm glass described previously. Still, the
warp
values are very close to unity. This is with coatings that are over 10 times
thicker
than the 50 nm coatings originally discussed on 1.6 mm glass. Not only do
these
coatings have extremely low stress but they also have better bulk resistance
values and acceptable absorption values.
[0139] The peak-to-valley surface roughness (as defined in the discussion
below
with reference to Figs. 33a and 33b) for these coatings is preferably less
than or
equal to 200 A, more preferably less than 150 A, more preferably less than or
equal to about 100 A, even more preferably less than or equal to about 50 A,
and
most preferably less than or equal to about 25 A.
[0140] To illustrate additional features and advantages of an
electrochromic mirror,
constructed in accordance with at least one embodiment of the present
invention,
summaries of experimental results are provided below in tables 3 and 4. In
these
summaries, references are made to the spectral properties of elements of
electrochromic mirrors constructed in accordance with the parameters specified
in each example. In discussing colors, it is useful to refer to the Commission
Internationale de l'Eclairage's (CIE) 1976 CIELAB Chromaticity Diagram
76
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WO 2007/100921 PCT/US2007/005494
(commonly referred to a the L*a*b* chart). The technology of color is
relatively
complex, but a fairly comprehensive discussion is given by F.W. Billmeyer and
M.
Saltzman in Principles of Color Technology, 2"d Edition, J. Wiley and Sons
Inc.
(1981), and the present disclosure, as it relates to color technology and
terminology, generally follows that discussion. On the Ca*b*chart, L* defines
lightness, a* denotes the red/green value, and b* denotes the yellow/blue
value.
Each of the electrochromic media has an absorption spectra at each particular
voltage that may be converted to a three number designation, their Ca*b*
values.
To calculate a set of color coordinates, such as CA* values, from the spectral
transmission or reflectance, two additional items are required. One is the
spectral
power distribution of the source or illuminant. The present disclosure uses
CIE
Standard Illuminant A to simulate light from automobile headlamps and uses CIE
Standard Illuminant D65 to simulate daylight. The second item needed is the
spectral response of the observer. The present disclosure uses the 2 degree
CIE
standard observer. The illuminant/observer combination generally used for
mirrors is then represented as A/2 degree and the combination generally used
for
windows is represented as D65/2 degree. Many of the examples below refer to a
value Y from the 1931 CIE Standard since it corresponds more closely to the
spectral reflectance than L*. The value C*, which is also described below, is
equal to the square root of (a*)2+(b*)2, and hence, provides a measure for
quantifying color neutrality.
[0141] Tables 3 and 4 summarize experimental results for elements
constructed in
accordance with the present invention. Specifically, experiments were
conducted
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WO 2007/100921 PCT/US2007/005494
within a range of between 8 sccm and 16 sccm oxygen flow for both half and two
wave thicknesses with krypton as the sputtering gas and at a pressure of 3
mTorr.
Table 6 summarizes the results for a slightly less than half wave ITO
thickness,
while Table 7 summarizes the results for a slightly more than two wave ITO
thickness, the half wave thickness being applicable, for example, to mirror
applications and the two wave thickness being applicable, for example, to
window applications. Further, it is noted that these tables include results
for both
single layers and elements constructed of dual layers.
78
o
t.,
_ Table 6
-
,4z
Experiment
n.)
Rack Average Transmittance Singles
Cell
Oxygen ohms Oxygen Trial L* a* b* Y Haze
Singles L* a* b* Y Haze , Absorption Reflection
Absorption
8 1/2wv-8sccm-1/3 93.1 4.7 83.3 0.06
8 11.6 2.8 .5W 8-1 94.9
2.1 3.8 87.3 0.01 4.1 8.5 8.7
_ .5W 8-3 94.8
2.1 3.8 87.2 0.01 4.3 8.5
-
1/2wv-8sccm-2/4 92.9 5.7 82.8 0.01
2.6
.5W8-2 94,7 1.9 4.9 86.9 0.02 4.5 8.6 9.1 n
o
.5W 8-4 94.7 1.9 5.2 86.9 0.01 4.3 8.8
.
iv
m
10 1/2wv-10sccm-1/3 93.4
5.7 83.9 0.01 .i.
10.9 2.7 .5 W 10-1 95.0 2.1 5,0
87,5 0.02 3.5 8.9 7.6 .i.
iv
H
--.1 .5W 10-3 94.8
1.8 5.6 87.2 0.01 3.7 9.1 co
o
iv
1/2wv-10sccm-2/4 93.8
4.2 84,9 0,02 o
3.0 .5W 10-2 95.1
2.3 4.0 87.9 0.00 3.2 8.9 6.9 , o
m
o1
.5W 10-4 _ 95.1 2.3 2.9 88.0 0.01
3.2 8.8 co
_
1
12 1/2wv-12sccm-1/2 94.1
4.2 85.5 0.05 iv
12 10.6 3.1 .5W 12-1 95.2
2.4 3.9 88.2 0.01 2.9 8.9 6.3 . .--1
.5W 12-2 95.3 2.4 2.9 88.3 0.01 2.7 9.0
14 1/2wv-14sccm-2/4 94.3 4,1 85.9 0.05
14 11.1 3.1 .5W 14-2 95.3
2.4 3.5 88.3 0.01 2.7 9.1 5.8
.5W 14-4 95.3 2.5 3.1 88.4 _ 0.02 2,4 9,1
16 1/2wv-16sccm-1/2 94.3
4.8 85.9 0.15 IV
16 11.0 3.1 .5W 16-1 95.3
2.5 4.1 88.4 0.01 2.5 9.1 5.6 n
1-3
.5W 16-2 95.3 2.5 4.0 88.4 0.01 2.6 9.0
ci)
n.)
o
o
--.1
o
o
un
4=.
o
4=.
o
Table 6 (cont.)
=
Reflectance
o
---.1
1-,
Total
Bulk o
Oxygen Trial , V a* , IP` Y Haze
Singles V a* V Y Haze Bulk Thick roughness
Thickness Ohms/sq Resistance o
o
c.)
1/2wv-8sccm-1/3 33.9 6.1 .
7.9 0.06
8 12.4
.5W8-1 35.0 8.5 13.3 8,5 0.01 131.9 5.4 137.3 11.6 159.3
- .
SW 8-3 35.0 8.5 12.9 8.5 0.01
- - - ,
_ .
. _
1/2wv-8sccm-2/4 34.4 5.1 8.2 0.01
16.1 5W82 35.1 7.8 16.8 8.6 0.02
-
.5W8-4 35,6 , 7.5 17.4 8.8 _., 0.01
.
,
1/2wv-10sccm-1/3 34.9 5.2 8.4 0.01 _
17.0 .5 W 10-1 35.9 7.8 17.6 8.9 0.02 132.7
5.0 137.7 11.1 152.8 n
.
o
.5W 10-3 36.2 6.4 19.2 9,1 _ 0.01iv
.
.
m
1/2wv-10sccm-2/4 34.3 6.6 8.2 0.02 _
.i.
.i.
12.4 .5W 10-2 35.8 8.8
14.2 8.9 0.00 tv
.
H
Cie .
CO
0 SW 10-4 35.7
8.6 10.2 8.8 0.01 .
-
iv
o
1/2wv-12sccm-1/2 34.5 6.9 8.2 = 0.05 .
o
12 12.4 .5W 12-1 35.8
9.0 14.1 8.9 0.01 130.2 4.4 134.6 11 148.1
m
O-
.5W 12-2 36.0 8.9 10.5 9.0
0.01 m
1
F\)
1/2wv-14sccm-2/4 34.7 7.2 8.4 0.05 .
-A
14 12.3 .5W 14-2 36.1
9.1 12.9 9.1 0.01 127.6 5.1 132.7 11.7 155.3
.5W 14-4 36.2 9.2 11,1 9.1 0.02
. ..._
_
1/2wv-16sccm-1/2 34.9 7,2 8.5 0,15
16 14.9 .5W 16-1 36.1
9.3 15.0 9.1 0.01 126.7 3.6 130.3 11.45 149.2
-
.5W 16-2 36.0 9.3 14.8 9.0 0.01
1-0
n
,-i
cp
t..,
=
=
-..,
=
=
u,
.6.
,4z
.6.
Table 7
k
Transmittance
Singles 0
Cell
iµ.)
Oxygen Trial L" a* b* Y Haze Singles I..* a* b" Y Haze
Absorption Reflection Absorption o
o
--.1
2W81 89.0 0.9 3.8 74.2 1.48 17.5 8.3 27.0 = 1--,
o
2wv-8sccm-1/3 84.0 4.2 64.0 2.0
o
2.9 .
2W8-3 88.6 0.5 5.0 73.3 1.47 18.2 8.5 iµ.)
8 -
1--,
2wv-8sccm-2/4 84.2 2.8 64.4 1.9
2W 8-2 88.9 0.9 4.1 74.0 2.20 16.5 9.5 25.4
4.4 .
2W 8-4 88.6 0.2 5.0 73.3 1.87 16.2 10.5
_
2wv-10sccm-2/4 85.2 2.9 3.4 66.3 1.7
2W 10-2 89.5 0.6 3.5 75.3 1.54 15.3 9.4 24.3
_
2W 10-4 89.4 1.0 3.7 75.0 1.51 15.9 9.1
_
n
_
2W10-1 89.8 0.5 3.6 75.9 1.41 15.0 . 9.1 23.4
2wv-10sccm-1/3 85.6 3.3 67.1 1.8
o
2.6
2W 10-3 89.5 0.7 3.4 75.3 1.51
15.5 , 9.3 (3)
.i.
.i.
oe 2W 12-1 89.5
0.5 1.9 75.3 0.22 13.8 11.0 22.5 H
1--,
co
2wv-12sccm-1/2 84.5 2.5 2.4 65.0 0.1 _
n)
2W12-2 89.4 0.9 2.0 75.1 0.20 14.2 10.7 o
12
o
_ co
2W 12- -
3 89.6 1.1 23 75.4 0.23 12,6 12.0 35.5 O
2wv-12sccm-3/4 78.8 2.8 2.9 54.5 0.3
co
1
2W12-4 83.4 1.0 2.1 62.9 0.25 13.1 n)
---1
2wv-14sccm-1/3 85.3 2.6 1.8 66.7 0.3
2W 14-1 89.6 0.7 1.4 75.5 0.33 13.6 10.9 23.4
-
14
-
n
_
1-3
2W 16-1 89.7 1.1 2.2 75.8 0.63 10.8 13.4 18.8
2wv-16sccm-1/3 86.5 1.9 69.0 0.7
,
2.8 -
ci)
16
2W 16-3 90.3 1.3 1.0 77.0 0.63 11.0
12.0 o
o
2wv-16sccm-2/4 87.2 18 1.4 70.3 0.7
2W 16-2 90.5 1.3 1.2 77.4 0.53 10.8 11.8
18.8 o
o
- un
-6.
. 2W 16-4 90.5 1.2 1.0 77.4 0.58 103 11.9
-6.
Table 7 (cont.)
Reflectance
Data from center of Rack 0
Total
Bulk t=-)
Trial L* a* b* Y Haze Singles
LA a* , b* V _ Haze Bulk
Thick roughness Thickness Ohms Resistance Warp o
o
---.1
- -
2wv-8sccm-1/3 2.4 3.1 9.0 2.0 2W 8-1
34.6 1.9 3.2 8.3 1.48 758.5 21.4 779.9 2.6
202.8 0.996 1--,
o
_ 35.9
o
2W8-3 35.1 2.0 3.8 8.5
1.47 _ t=-)
1--,
2W 8-2 36.9 2.2 4.4 9.5 2.20
2wv-8sccm-2/4 38.3 10.3 1.9
.
2.7 5.3
2W 8-4 38.6 3.3 4.9 10.5 , 1.87 ,
2wv-10sccm-2/4 36.7 2.3 3.5 9.4 1.7
2W 10-2 36.8 3.1 2,1 9.4 1.54 740.9 16.1 757.0
1.95 147.6 0.984
2W 10-4 36.2 2.2 1,9 9.1 1.51
n
2W10-1 36.3 2.3 2.0 9.1 1.41
-
2wv-10sccm-1/3 36.9 9.5 1.8
o
3.1 2.9
n.)
o)
2W 10-3 , 36.5 1.7 2.5 _ 9.3
1.51 _ 11. r
.
N.)
2W 12-1 39.5 4.5 6.3 11.0 0.22 705.7 6.2 711.9
1.85 =. 131.7 0.972 H
cc 2wv- I 2sccm-1/2 42.1 5.8
9.0 12' CO 5 0.1
t=-)
n.)
2W12-2 39.1 2.8 6.4 10.7
0.20 _ o
o
m
O
2W 12-3 41.2 1.4 8 2 12.0 0.2 3 '
_
4.1 7.7
2wv-12sccm-3/4 37.8 10.0 0.3
m
1
2W12-4 42.9 5,4 7.2 13,1 0,25 n.)
---1
2wv-14sccm- I /3 37.6 2.9 6.4 9.9 0.3
2W 14-1 39.4 2.9 4.9 10.9 0,33 712.7 7.2 719.9 1.95
140.4 0.961
2W 14-3 39.6 3,4 _ 4.5 11.0 0.27
2W14-2 40.1 1.2 5.7 11.3 0.38
- 2wv-14sccm-2/4 37.1 9.6 0.3
3.6 6.1 - -
2W14-4 39.1 3.1 5.3 10.7 0.30 IV
.
n
2wv-16sccm-1/3 41.6 1.3 7.2 12'2 0.7
. .
2W 16-1 43.4 0.=8 5.9 13.4 0.63 716.5 8.9 725.4 2
145.1 0.956
t=-)
2W 16-3 41.2 0.7 3.5
12.0 0.63 o
.
o
2wv-16sccm-2/4 39.3
2W 16-2 40.9 0.. 6 3.7
11.8 0.53 =
0.7 o
1.3 5.0 10.9
- -
un
-6.
2W 16-4 41.0 0.7 3.3 11.9 0.58
-6.
CA 02644218 2008-08-27
WO 2007/100921 PCT/US2007/005494
[0142] Table 8 depicts the inter'-dependence between bulk resistance,
electron
mobility and electron carrier concentration. It is noted that there is a
continuum of
carrier concentration and mobility combinations that will yield a given bulk
resistance.
Table 8
Bulk. RI RI k
=
Resistance cc = mu
160 1.15E+21 34.0 1.776
0.0145
160 6.88E+20 56.7 1.8845
0.0054
160 4.91E+20 79.4 1.9295
0.0031
140 1.31E+21 34.0 1.7349
0.0168
140 7.86E+20 56.7 1.8616
0.0062
140 5.61E+20 79.4 1.9135
0.0034
120 1.53E+21 34.0 1.6791
0.0202
120 9.17E+20 56.7 1.8306
0.0072
120 6.55E+20 79.4 1.892 0.0039
[0143] The electron carrier concentration is preferably greater than or
equal to 40e2
electrons/cc, while the mobility is preferably greater than or equal to 25
cmA2N-s.
The carrier concentration and electron mobility, thickness and= surface
roughness
presented herein are derived from ellipsometric analysis of the coatings. The
electron concentration and mobility may vary from those determined using a
Hall
characterization method and one skilled in the art will recognize that an
offset
may exist between the measurement methods. As noted above there are a
continuum of carrier concentrations and mobility values that can attain a
given
bulk resistance. In an embodiment where a low refractive index is preferred
then
tuning of the deposition process to yield a higher carrier concentration will
be
83
CA 02644218 2008-08-27
WO 2007/100921 PCT/US2007/005494
preferred. In other embodiments where a low absorption is preferred then
tuning
of the deposition process to yield higher electron mobility will be preferred.
In
other embodiments one may desire an intermediate level of both carrier
concentration and mobility.
[0144] In at least one embodiment, an electro-optic element includes an
improved
ITO layer that simultaneously exhibits a reduced bulk resistance, reduced
absorption, decreasing bending or warping of the associated substrate to which
the ITO is applied, and maintaining a uniform darkness and brightness of the
overall assembly, and reduces the weight thereof.
[0145] Surface topology, morphology or roughness is typically not important
in non-
microscale electrical applications dealing with metal coatings. The surface
topology is of particular interest when metals are used in an optical
application.
When the surface roughness becomes too large the coating will have
appreciable non-specular reflectivity or haze. This degree of roughness, in
most
applications, is often the first to be addressed because it can have a
negative
impact on visual appearance but not necessarily on functionality. In the case
of
optical applications, such as many described herein, the presence of
objectionable haze is considered a worst case scenario. The surface roughness
may have other negative consequences at roughness levels much less than
those that result in objectionable haze. Surface roughness levels define
acceptable morphologies for metal films to allow them to function adequately
in
different optical applications. A penalty associated with not adequately
controlling
84
CA 02644218 2008-08-27
WO 2007/100921 PCT/US2007/005494
the surface morphology is often increased cost since larger quantities of
higher
priced metals with higher reflectivity are often needed overcome the problems
associated with improper surface morphology. The effects of different levels
of
morphology or surface roughness using thin film modeling techniques have been
analyzed. These techniques are accepted in the art of thin film technologies
and
have been proven to accurately describe real thin film or coating systems and
can therefore be used to predict the impact of different changes to a coating.
This
is advantageous because it may be expensive or time consuming to manufacture
or fabricate the large number of samples needed to show the effects. In this
case
a commercial thin film program called TFCalc supplied by Software Spectra,
Inc.
was used to perform the calculations.
[0146] The roughness, as used herein, is defined in terms of mean peak-to-
valley
distance. The Figs. 33a and 33b depict two different roughness scenarios. In
Fig.
33a large crystallites 3302a are represented. In Fig. 33b small crystallites
3302b
are represented. In both of these cases the peak-to-valley distance 3301a,
3301b
is depicted to be the same. Additionally, both examples have the same void to
bulk ratios. It should be understood that the valleys and peaks may not be at
the
same height. The mean peak-to-valley measurement, therefore, provides a more
representative quantifying value.
[0147] When the layer is thin it may be approximated by a single
homogeneous
layer with a uniform refractive index. There are several ways to approximate
the
refractive index of a mixed layer. These are called effective medium
CA 02644218 2008-08-27
WO 2007/100921 PCT/US2007/005494
approximations (EMA). Each different EMA has its strengths and weaknesses. In
these examples a Bruggeman EMA methodology was employed. When the
thickness of the layer becomes large the roughness is not approximated well if
a
single fixed refractive index is used. In these cases the roughness may be
approximated as several slices of different ratios of void and bulk material
to form
a graded index approximation.
[0148] Several metals are modeled herein to provide representative examples
of the
optical effect of surface roughness on reflectance. Tables 6, 7 and 8 show the
effect of roughness thickness on the reflectivity of the surface for Ag, Cr
and Rh,
respectively. The thickness of the layers is in nanometers and the Cap Y value
represents the reflectance from the coated surface. The reflectivity drops off
as
the thickness of the roughness increases for each of these metals. Depending
on
the application, the amount of acceptable roughness will vary. The roughness
should be less than 20 nm mean peak-to-valley, preferably less than 15 nm,
even more preferably less than 10 nm and even more preferably less than 5 nm
and most preferably less than 2.5 nm. These preferred ranges, as noted above,
depend on the application. For instance, in one embodiment, the thickness of a
flash layer, cover layer, barrier layer or adhesion layer (i.e., functional
layer) may
need to scale with the degree of roughness of the underlying surface. The
thickness of the functional layer necessitated by the roughness of the
underlying
surface may result in undesirable effects such as changes in optical
properties of
the resultant stack, higher costs or other negative effects. Means to smooth
the
86
CA 02644218 2008-08-27
WO 2007/100921 PCT/US2007/005494
surfaces prior to deposition of the functional layers are described below. It
should
be noted that there may be some embodiments where increased surface
roughness may be advantageous such as creating an effectively larger surface
area for better adhesion to a seal material.
[0149] The tables 6, 7 and 8 also include a value labeled as "% of
Theoretical
Maximum". This metric defines how close the reflectance of a coating with a
rough surface matches the reflectance of the ideal, perfectly smooth surface.
A
coating with a % of Theoretical Maximum value of 100% would have the
maximum reflectance theoretically attainable for that material. If the % of
Theoretical Maximum value was 85% then the reflectance attained would be only
85% of the value of the ideal smooth coating or reflectance of coating with
zero
- roughness times 0.85.
[0150] The reflectance of a metal or alloy coating is dependent on many
attributes of
the coating even one that is relatively smooth. The density of the coating,
presence or absence of internal voids, stress levels, etc all play a role in
how the
reflectance approaches some ideal maximum value. The theoretical maximum
reflectance defined herein pertains not to this ideal reflectance of an ideal
coating
but rather to the reflectance value of a smooth real world coating. In
practice the
Theoretical Maximum value is obtained through a combination of optical
analysis
and thin film modeling. By analyzing a real world coating that has surface
roughness using an optical technique such a Variable Angle Spectroscopic
Ellipsometry the refractive index versus wavelength and surface roughness can
87
CA 02644218 2008-08-27
WO 2007/100921 PCT/US2007/005494
be obtained. The refractive index versus wavelength can then be inputted into
a
thin film modeling program such as TFCalc or Essential Macleod and the
reflectance can be calculated. This calculated reflectance using measured
refractive index data is then the Theoretical Maximum reflectance value from
that
particular film or coating.
[0151] Preferably the reflectance of a coating is greater than 85% of the
Theoretical
Maximum, more preferably 90% of the Theoretical Maximum and most preferably
greater than 95% of the Theoretical Maximum.
Table 9: Effect of roughness thickness on reflectivity of Ag coatings
Silver
% of
Cap Theoretical
Bulk Roughness Y Maximum
350 0 98.5
350 5 95.2 97%
350 10 91.3 93%
350 15 87.1 88%
350 20 82.7 84%
350 25 78.4 80%
350 . 30 74.2 75%
350 35 70.4 71%
350 40 66.8 68%
350 45 63.6 65%
350 50 60.8 62%
350 55 58.3 59%
350 60 56.2 57%
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-
Table 10: Effect of roughness thickness on reflectivity of chrome coatings
Chrome
% of
Cap Theoretical
Bulk Roughness Y Maximum
40 0 65.9
40 5 64.6 98%
40 10 62.2 94%
40 15 59.0 89%
40 20 55.2 84%
40 25 51.3 78%
40 30 47.7 72%
40 35 44.5 68%
40 40 41.9 84% .
40 45 39.8 60%
40 50 38.3 58%
40 55 37.2 56%
40 60 36.5 55%
Table 11: Effect of roughness thickness on reflectivity of rhodium coatings
Rhodium
% of
Cap Theoretical
Bulk Roughness Y Maximum
40 0 , 76.9
40 5 74.8 97%
40 10 = 71.6 93%
40 15 67.2 87%
40 20 62.1 81%
40 25 56.4 73%
40 30 50.7 66%
40 35 45.2 59%
40 40 40.3 52%
40 45 36.0 47%
40 50 , 32.4 42%
. 40 55 , 29.6 38%
40 60 27.4 36%
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[0152] In some applications it is desirable to have high second surface
reflectance
where the reflectance is off of the metal layer when viewed through the glass.
In
this case buried void is of concern in addition to surface roughness. The
amount
of void (% relative to bulk) may vary and the thickness of the void layer may
vary
also. The general rules described above for surface roughness apply here as
well.
[0153] Often times when metallic layers comprise low sheet resistance
surface
roughness is of particular concern. A metal or other electrically conductive
material has an intrinsic property known as the bulk resistivity. The sheet
resistance of the coating is determined by dividing the bulk resistance number
by
the thickness of the coating. In principle, any sheet resistance value can be
obtained from any conductive material as long as the coating is thick enough.
The challenge or limitation in achieving low sheet resistance comes in when
other attributes are required in addition to the sheet resistance or
conductivity.
[0154] As the thickness of coatings is increased the surface roughness
typically also
increases which leads to a reduction in the specular reflectivity as described
previously. Coatings which are very thick often have reflectivity levels
significantly below those of a perfectly smooth surface. The amount of
roughness
a coating will develop is a function of a number of factors. The properties of
the
material itself are the major driving force but within boundaries the
deposition
process parameters (along with which deposition process is employed) can
modify the surface properties of the coating.
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[0155] Due to other considerations, the material with the best surface
roughness
can not always be selected for a given application. Other factors also play a
role.
Adhesion and cost, for instance, are critical issues which influence the
selection
of materials which go into a coating stack. Often it is impossible to select a
single
material to meet all of the requirements; therefore, multilayer coatings are
employed. Certain platinum group metals have high reflectivity such as
Rhodium,
Ruthenium, Iridium, etc but are very expensive. Therefore, an entire coating
with
a low sheet resistance produced with these materials would be cost
prohibitive.
When extreme adhesion to glass or other materials may be needed then these
materials may also be found to have weaker bond strengths than other
materials.
Silver based coatings may have insufficient stability as an anode and
depending
on the coating stack may also be problematic from an adhesion standpoint. A
metal such as chrome is relatively low in cost compared to some other metals
and is known to have very good adhesion. Chrome may, therefore, function as
an adhesion layer and may be built up to sufficient thickness to get the
desired
electrical properties.
[0156] Unfortunately, chrome is very reactive and this leads to an
intrinsic
predisposition to relatively large surface roughness values. The high
reactivity is
important in that as the coating is deposited, using Magnetron Sputter Vacuum
Deposition (MSVD) for example, the chrome atoms will tend to stick where they
first land. The rate of bond formation is very fast and this restricts the
atom's
ability to diffuse along the surface and find a low energy location.
Typically, a low
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=
energy stable location on the coating is onethat lends itself to less surface
roughness. This tendency to not go to a low energy state also contributes to a
degradation of the coating's bulk resistance. Therefore, a thicker layer is
needed
to attain the target sheet resistance and the surface roughness tends to
further
degrade. It is difficult to simultaneously attain the goal of low sheet
resistance
and high reflectivity because of these competing effects.
[0157] It is known that the reflectivity of a low reflectance metal may
be increased by
putting a thin layer of a higher reflectance metal above it. For instance, the
previously mentioned metals such as Rhodium or Ruthenium may be used. The
necessary thickness of these metals to attain a given reflectivity level will
be a
direct result of the surface roughness of the underlying chrome layer. Other
metals that could be used as the conductive layer include, but are not limited
to,
=
aluminum, cadmium, chromium, cobalt, copper, gold, iridium, iron, magnesium,
molybdenum, nickel, osmium, palladium, platinum, rhodium, ruthenium, silver,
tin
tungsten and zinc. Alloys of these metals with each other or with another
metal or
metals may be possible. The suitability of these materials in a given
application
will depend on the full list of requirements. For instance, Ruthenium may be
an
expensive metal in one application but in another application it may be low
cost
relative to another metal such as Rhodium and may therefore fall within the
spirit
of this invention. In other non-limiting embodiments a given metal or alloy
may
not be compatible with all of the other components in an application. In this
case,
the sensitive metal may be buried or otherwise isolated from components where
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there are interaction limitations. The layers deposited on top of the chrome
usually will pattern the roughness of the underlying layer. Therefore, a thin
layer
of a higher reflectance metal will also not have its ideal reflectivity
because of the
layer or layers underneath it. In most instances the preferred embodiment is
one
that has the higher reflectance metal oriented toward the observer. Many of
the
high conductivity metals listed above also have high reflectivity. These
metals
may need to be alloyed with other metals to have adequate chemical,
environmental or physical properties. The metals or alloys may then have an
unacceptable color or hue. The overall reflectance intensity may be adequate
for
the desired application but if the reflected color does not meet requirements
then
the metal or alloy is unsuitable. In this case, similar to the description
above, the
metal or alloy may be buried beneath a layer with lower intrinsic reflectivity
but
one that has a more preferable reflected color.
[0158] Reference samples were prepared to allow evaluation of the trade-off
.
between reflectance and sheet resistance for a chrome-ruthenium bi-layer
coating stacks. In these samples chrome was applied to get a target sheet
resistance value. The samples were then overcoated with Ruthenium of different
thicknesses. The following process conditions were employed:
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All of the coating were processed a 3.0 mTorr
Cr @ 4.0Kw (130) = approx 1000 angstroms
Cr @ 4.0Kw @ (130) X 9 = .7 ohms squ.
Cr @ 4.0Kw @ (130) X 3 = 1.5 ohms.squ.
Cr @ 4.0Kw @ (87) X 1 = 3 ohms squ.
Cr @ 4.0Kw (170) X 1 = 6 ohms squ.
Ru @ 1.7Kw @ (130) = 400 angstroms
Ru @ .85Kw @ (130) = 200 angstroms
Ru @ .43Kw @ (130) = 100 angstroms
Ru @ .43Kw @ (260) = 50 angstroms
Ru @ .43Kw @ (520) = 25 angstroms
[0159] The chrome samples were all deposited at 4 kw. The line speed (in
parenthesis ¨ arbitrary units) and number of passes (e.g. X 9) were varied to
adjust the thickness of the coating to hit sheet resistance targets. The
ruthenium
layers were produced with varying line speed and power to attain the target
thickness levels. The results of the matrix are tabulated in Table 12. The
reflectivity generally drops with increasing thickness and decreasing sheet
resistance. Several samples prepared which target 3 ohm/sq do not fit the
trends.
This is because they were made a different line speed than the other chrome
coatings. When the line speed is reduced the substrate moves at a slower
speed.
In a linear process this means that the initial nucleation layers are formed
predominantly with sputtered high angle deposition materials. As noted in the
description below, the high angle deposition results in inferior material
properties.
Shielding is often used to eliminate this high angle deposition. The 3 ohm/sq
chrome case in this study is an excellent example of how the high angle can
degrade the optical properties of the coating.
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Table 12: Chrome Ruthenium bi-layer results
Trial Ruthenium Ohms Y a* b* Haze (Specular
Excluded)
#1 .7 0 0.6 50.0 -0.9 0.0 0.13
#2 1.5 0 1.5 55.3 -0.7 -0.2 0.04
#3 3 0 2.9 54.4 -0.5 0.5 0.02
#6 6 0 5.1 60.9 -0.9 -0.2 0.02
#1 .7 25 25 0.6 50.7 -0.9 1.0 0.11
#2 1.5 25 25 1.6 54.2 -0.6 0.8 0.03
#3 3 25 25 3 53.0 -0.5 1.1 0.02
#4 6 25 25 5.9 58.8 -0.7 1.0 0.02
#1 .7 50 50 0.6 51.0 -0.9 1.6 0.12
#2 1.5 50 50 1.5 55.0 -0.6 1.2 0.03
#3 3 50 50 2_9 54.1 -0.5 1.2 0.03
#6 6 50 50 5.6 59.6 -0.6 1.2 0.02
#1 .7 100 100 0.6 52.7 -0.7 2.4 0.13
#2 1.5 100 100 1.5 56.6 -0.5 1.6 0.04
#3 3 100100 2.8 56.7 -0.4 1.3 0.03
#6 6 100 - 100 5 62.5 -0.4 1.2 0.02
#1 .7 200 200 0.5 54.7 -0.2 2.7 0.14
#2 1.5 200 200 1.4 60.1 -0.1 1.6 0.04
#3 3 200 200 2.5 63.1 0.0 1.3 0.03
-
#6 6 200 200 4.2 67.4 -0.1 0.9 0.03
#1 .7 400 400 0.6 56.5 0.2 2.6 0.15
#2 1.5 400 400 1.3 64.1 0.1 1.4 0.05
#3 3 400 400 2 67.5 0.0 1.2 0.03
#6 6 400 400 3 69.8 -0.1 0.8 0.03
[0160] As can be seen from Table 12, the chrome coating alone has
relatively low
reflectance values even at the 6 ohm/sq case. The reflectance was only about
61% for this sample. Chrome produced by other means or process conditions
should be able to attain values in excess of 65%. Therefore, even at this
modest
sheet resistance value the chrome reflectance has been compromised.
[0161] When a 3 ohm/sq coating is desired, 100 and 200 angstroms of
ruthenium on
top of the chrome is needed to attain even modest reflectance values. Ideally,
a
ruthenium coating should be able to attain a reflectance in excess of 72%.
Even
400 angstroms on top of the 6 ohm/sq chrome fall short of the theoretical
optimum by 2%. The lower ohm samples do not even come close to approaching
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the theoretically attainable reflectance values. Therefore, in cases where
both
low sheet resistance and high reflectance are needed a standard chrome-
ruthenium bi-layer does not meet the requirements. Other means must be
employed to solve this problem.
[0162] Deposition process parameters can be adjusted to minimize the
surface
roughness during the formation of the coating. In the case of metals, the
surface
roughness can be reduced and the reflectivity increased by running the process
at low pressure and preferably using neon or an argon-neon mixture as the
sputtering gas as described in detail below. These parameters contribute to
proper momentum and energy transfer in the deposition process with the result
in
less rough surfaces and lower bulk resistivities.
[0163] Table 13 depicts how the surface roughness, reflectivity and
electrical
properties vary as the process parameters are adjusted. The 3mT case is
provided as a reference. The thickness of the coating is about 600 angstroms.
This thickness is important because the coating is nearly opaque at this level
and
the sheet resistance is relatively low. As can be seen, lowering the pressure
reduces the roughness by about 17% and almost a 2% increase in reflectance is
achieved. Lowering the pressure and sputtering with a 50:50 mixture of argon
and neon results in further improvements. The roughness is about 20% lower
than the reference case and the reflectance is about 2.7% higher. The last
case
is with even higher amounts of neon ¨ approximately 70% of the sputtering gas
is
neon. Reflectance is about 3.5% higher than in the reference case and the
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roughness is reduced by about 24%. Thickness and roughness values are
determined by using variable angle spectroscopic ellipsometry.
Table 13: Chrome properties versus process settings
Chrome
Bulk
Sheet Resistance
Thickness Roughness Resistance Micro-ohm Reflectance
Process Conditions Angstroms Angstroms Ohms/sq cm %
3 mT Chrome 100% Ar 484 101 13.5 79
59.6
2 mT Chrome 100% Ar 494 84 12.6 72.8
61.7
2 mT Chrome 50:50 Ar:Ne 507 81 11 64.7
62.3
2 mT Chrome 10:24 Ar:Ne 506 77 11.3 65.9
63.1
[0164]
Results can be further improved by lowering the pressure and by increasing
the neon content in the sputtering gas. In addition, increasing the substrate
temperature also contributes to smoother coatings. Higher substrate
temperature
results in more surface mobility of the deposited atoms leading to a smoother
surface.
[0166] Table 13 also includes bulk resistance values for the chrome
coatings. The
theoretical minimum bulk resistance value for chrome is about 13 micro ohm cm.
The reference case made at a typical pressure of 3 mT in argon has a bulk
resistance value of more than 6 times the theoretical bulk resistance. By
improving the deposition properties bulk resistance values of less than 5
times
the theoretical minimum may be obtained. Preferably, the bulk resistance is
less
than 5 times the theoretical minimum, more preferably less than 4 times the
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theoretical minimum, more preferably less than 3 times the theoretical minimum
and most preferably less than 2 times the theoretical minimum.
[0166] The presence of oxygen (or water) in the system can be particularly
harmful
from a surface roughness perspective. Chrome is very reactive with oxygen and
tends to react immediately. This leads to additional roughness in the coating.
Therefore, a coating with less oxygen is recommended. Table 14 depicts the
effect of oxygen on roughness. The oxygen level in Table 14 refers to the
percentage in the sputtering gas. The pressure is in mT and the thickness is
in
angstroms. The amount of acceptable oxygen in the coating is less than 5
atomic
percent, preferable less than 2 atomic percent and ideally less than 1 atomic
percent.
Table 14: The effect of oxygen percentage in the sputtering atmosphere on the
roughness of chrome coatings
Oxygen level pressure thickness Roughness
1 2.00 493 105
2.00 438 130
2.00 370 162
[0167] The amount of acceptable roughness is dependent on the application.
When
high reflectance values are desired less roughness is also desirable. Where
reflectance requirements are not as stringent more roughness may be
acceptable. Generally, roughness should be less than about 200 angstroms,
preferable less than 100 angstroms, even more preferably less than 50
angstroms, even more preferably less than 25 angstroms and most preferably
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less than 15 angstroms. Roughness as the term is used herein refers to the
average peak-to-valley distance as determined using ellipsometry or atomic
force
microscopy.
[0168] Other means may be used either alone or together with each other or
the
previously mentioned methods to minimize surface roughness. For example, the
cathode may be shielded to minimize the grazing (high) angle deposition. Other
methods to get smoother surfaces include the use of ion assisted sputtering or
ion assisted deposition, plasma assisted sputtering and other means to
increase
surface mobility of atoms. The cathode type may be selected to facilitate
smoother coatings, such as, use of 'twin mags", unbalance magnetrons, rf
superimposed dc power, microwave assisted sputtering, high power pulse
deposition, AC sputtering or other such means.
[0169] Although Chrome was used in the examples above as the conductive
layer,
other metals, alloys or multilayer coating materials as described herein and
within
the references mentioned herein may be used within the spirit of the
invention.
Other materials may need other process conditions to attain smooth surfaces.
ITO for instance does not necessarily have smooth surfaces under conditions
which are preferred for metals. In the case of ITO, the surface morphology is
modified by a number of process variables. The case of controlling the surface
properties of ITO are even more challenging than that of a metal. ITO is not
always conductive like a metal and some process settings which may result in a
smooth coating for a metal may not result in a highly conductive coating with
ITO.
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Therefore, controlling the morphology in light of other properties of the
material is
quite challenging. In general, for high temperature coatings on glass or other
vitreous substrates, relatively smooth coatings may be obtained at high
pressures and relatively high oxygen settings as describe earlier in this
document.
Variation in process parameters to smooth a coating can be applied to other
materials as well such as TiO2 or multi-layers such as TiO2 and ITO taught in
transflective coating applications.
[0170] As noted above, the roughness generally increases with the thickness
of the
coatings. Often the process settings described above are insufficient to
result in
coatings with an acceptable roughness level. This is the case where extremely
low sheet resistance values are needed. In this scenario alternate means are
needed to attain coatings with relatively low surface roughness that
simultaneously have low sheet resistance values.
[0171J In commonly assigned US Patent application publication number
2006/0056003, an ion beam is introduced as a means to thin a coating in a
local
area on a coated substrate. As discussed at length herein, an ion beam may
also
be used to smooth (as depicted in Fig. 33a and 33b) a rough coating (as
depicted
in Fig. 37). An ion beam may be used either alone or in conjunction with other
methods taught herein to reduce the roughness of a coating and thus increase
the
reflectivity. Ion beam sources vary in design and function. For the purpose of
this
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discussion, any design capable of delivering fluxes of ions at the energy
ranges
described herein are suitable.
[0172] An ion beam is a relatively collimated group of energetic
positive.or negative
ions. The energy of the ions is a function of the operating potential of the
ion
beam. The current, or flux of ions, is a function of the operating potential
and the
amount of gas fed through the beam and the back ground pressure in the
chamber. Sufficient energy for the ions is desirable to etch, mill away and/or
smooth the coating material. An example of a related phenomenon is that of
billiards. Consider the incoming ion as the cue ball and the coating as the
rack of
balls at the start of the game. If the cue ball is shot at the rack with very
low
energy then the rack does not break apart. Conversely, if the cue ball is shot
with
high energy then the rack can be broken apart quite violently.
[0173] Fig. 34 depicts sputtering yield as a function of argon ion energy
for various
materials. There is a threshold energy whereby no or minimal sputtering
occurs.
As the energy is increased the sputtering yield increases. The ionized atom
may
also affect the sputtering rate. The preferred mass of sputtering ion to have
the
maximum sputtering yield will vary with the energy of the sputtering ion and
the
mass of the atoms to be sputtered. Fig. 35 depicts sputtering yield as a
function
of sputtering ion and sputtered atom mass at 500eV ion energy. The data
depicted in Fig. 35 was generated using a computer simulation program called
"Stopping and Range of Ions in Matter (SRIM)". As depicted there is a range of
optimal sputter gas ion masses which will produce acceptable sputtering yields
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for a given target atomic mass. In general, as the beam energy is increased
the
optimal mass of ions increases to maximize the sputter yield. To some extent,
the preferred ion will be dependent on the mass of the sputtering atom. For
optimal energy and momentum, transfer of the atoms should be of relatively
comparable mass. Fig. 34 depicts that the threshold energy is dependent on the
sputtered material. Some materials take more energy to release than others.
The
graph of Fig. 34 also depicts that at relatively high energy of the ion the
sputtering yields tend to plateau. At these relatively high energies, the
process
starts to move into the region of ion implantation rather than ion sputtering.
For
efficient sputtering or etching, the ion energy should be above 100 electron
volts,
preferably above 500 electron volts and most preferably above 1000 electron
volts.
[0174] The smoothing effect is illustrated with reference to Figs. 36 and
37. In Fig.
36 an ion is impinging on a smooth surface. When the ion hits the surface,
energy is transferred both parallel and perpendicular to the surface. Some of
the
energy which is transferred parallel to the surface may result in a component
perpendicular and away from the surface which results in an ejected atom. In
Fig.
37 the same ion impinges on a rough surface. As can be appreciated, it is much
more likely that an ion is ejected from the coating. The majority of the
energy
which is directed perpendicular to the surface may result in ejection of an
atom;
there is more surface area and are more directions which can release an atom.
As the ion milling process continues, the coating becomes more and more
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smooth. In these and other examples the ion beam is consisting of a single
atom.
In practice clusters of ions/atoms may be employed in lieu of single ions.
Known
methods to produce clusters may be employed in this situation also.
[0176] In a similar fashion, an ion beam impinging on the surface at an
angle may
have a substantially higher sputtering efficiency and smoothing effect. In
this
case the angled ion beam would have a high probability of ejecting material
laterally to the coating surface.
[0176] As noted below the reflectance, transmittance, absorption and sheet
resistance properties of a particular transflective coating were limited by
roughness in the layers. One relevant coating is Glass/ITO/Si/Ru herein
referred
to as "Option 4". The ITO is optimally a 3/4 or 5/4 wave coating, 2100 or 3600
angstroms, respectively. The Si layer is about 220 angstroms and the Ruthenium
layer is about 70 angstroms. Also as discussed below different variants of
this
stack are possible. The reflectance and transmittance of this stack is very
dependent on the surface and interface roughness. When multi-layer stacks such
as option 4 are considered that consist of dielectric, semiconducting layers,
transparent conduction oxides and metals then the interface roughness must be
considered as well as the roughness of the surface.
[0177] Table 15 depicts the effect of ion milling the surface of ITO ¨ one
of the tower
layers used in Option 4 stacks. The data was determined by using ellipsometry
to
characterize the coatings. Table 15 also depicts the initial properties of the
ITO
coating. The initial roughness for the sh and 5/4 wave coatings are 7.4 and
11.5
.
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nm, respectively. These values are relatively high. The samples were ion
milled
with a single beam (38 cm long beam) running at 270 mA current and 3000 volts
with argon feed at 20 sccm and the operating pressure in the chamber was 2.5
mT. The ion beam is a closed drift Hall-effect anode layer type design. The
line
speed for the 2B (two beam equivalent at 30 ipm) case was 15 ipm and the line
speed for the 4B (four beam equivalent at 30 ipm) was 7.5 ipm. The beam was
oriented perpendicular to the surface of the coated glass. The ion beam
removed
about 17 nm/beam equivalent at 30 ipm for the 3/4 wave ITO and about 11.1 nm/
beam equivalent at 30 ipm. The surface roughness drops dramatically in both
cases with the 3/4 wave ITO getting nearly perfectly smooth. The 5/4 wave ITO
did not get as smooth, however, because it started from a much more rough
initial state it may require a slower line speed or additional beams to attain
the
minimal roughness values.
Table 15: Ion milled ITO properties
Ion Milling Data
(Micro
=
Thickness (nm) (Ohms/sq)
ohm cm)
nm/Beam Average Sheet Bulk
Bulk Roughness Total Removed Resistance
Resistanc
3/4 wave ITO 233.0 7.4 240.4 5.9
141.0
3/4 wave ITO 2 beam 2030. 1.4 204.4 18.0 6.4
130.3
3/4 wave ITO 4 beam 177.2 0.2 177.4 15.8 6.8
121.0
5/4 wave ITO 369.0 11.5 380.5 4.0
150.3
5/4 wave ITO 2 beam 351.0 7.1 358.1 11.2 4.2
149.5
5/4 wave ITO 4 beam 331.1 4.9 336.0 11.1 4.4
147.8
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[0178] The key demonstration is the substantial increase in reflectance
with the ion
milling process. In Table 16a the ITO coatings described in Table 15 are
overcoated with approximately 22 nm of Si and 7 nm of Ru. The transmittance
generally decreases with ion milling due to the higher reflectance of these
coatings. More importantly the absorption of the ion milled ITO samples is
appreciably lower. This results in higher light output of associated light
sources
through the coating at the same reflectivity level. The differences are much
more
significant when all of these coatings are normalized to the same reflectance
level. In order to attain the same reflectance levels for the non-ion milled
parts
the thickness of the Ruthenium layer is substantially increased. This, in
turn,
further reduces the transmittance and increases the absorption which is
undesirable in some applications.
[0179] These coated lites, as tabulated in Table 16a, were incorporated
into electro-
optic mirror elements, as tabulated in Table 16b, to evaluate the optics in an
actual EC element. A number of 2"x5" cells were made and the transmittance
and reflectance (specular and non-specular) were measured. The increase in
reflectance of the assembled elements correlates with the results observed in
the
singles data. The transmitted color is very amber biased even though the
reflected color is quite neutral. This implies that this design, due to its
unique
materials of construction, transmits more red light than blue light. This can
be of
particular advantage when a red display, for example is positioned behind the
mirror element.
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[0180] Table 16b also depicts the specular excluded reflectance (Spec Ex)
data for
the sample elements. Ion milling smoothes the surface which substantially
reduces the scattered light. The resultant image is much clearer and crisp due
to
the lower amount of scattered light.
[0181] Many automotive companies have specifications dictating that the
reflectance must be above 55% for an outside mirror application. The non-ion
milled samples did not meet this specification with the initial amount of
roughness
on the ITO. The ion milled samples, even the 5/4 wave ITO parts, meet the
specification. The switching speed of a mirror element, particularly the
darkening
speed, is dependent on the sheet resistance of the coatings. By enabling the
use
of a 5/4 wave ITO or thicker, the ion beam milling allows for faster switching
times while simultaneously meeting the reflectance requirements. Also, some of
the % wave elements have reflectance values that significantly exceed the
minimum requirement. These coatings may be adjusted to have higher
transmittance values by decreasing the thickness of the Ruthenium or other
high
reflectance metal used as the top layer when overall design requirements
benefit
from this change. Without the ion beam smoothing method the useful range of
reflectance and transmittance options would be limited.
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-
Table 16a
Option 4 - Single Lite of Glass
Results Reflectance Transmittance
Absorption
Trial Y a* b* Y a* b* Y
3/4 wave ITO @ 3mT Pressure 66.3 0.6 0.8 9.9 2.3 19.6
23.9
3/4 wave ITO @ 3mT Pressure
and 2 beam equivalent 69.3 1.0 1.1 8.4 1.4 19.2
22.3
3/4 wave ITO @ 3mT Pressure
and 4 beam equivalent 70.8 0.7 2.2 8.1 _ 1.0 17.1
21.2
3/4 wave ITO @ 1.7mT Pressure 67.7 0.6 1.2 8.7 2.8 20.1
23.7
3/4 wave ITO @ 1.7mT Pressure
and 2 beam equivalent 70.0 1.1 1.4 7.7 1.9 19.6
22.3
3/4 wave ITO @ 1.7mT Pressure .
and 4 beam equivalent 71.1 0.9 2.3 7.5 1.4 17.3
21.3
5/4 wave ITO @ 3mT Pressure 62.9 -1.3 2.0 10.5 4.9 16.0
26.6
5/4 wave ITO @ 3mT Pressure
and 2 beam equivalent 65.7 1.0 1.5 8.9 1.5 17.9
25.4
5/4 wave ITO @ 3mT Pressure
and 4 beam equivalent 68.4 0.8 1.5 8.1 0.5 17.9
23.4
5/4 wave ITO p 1.7mT Pressure 64.2 -1.2 2.4 9.4 5.2 16.6
26.5
5/4 wave ITO @ 1.7mT Pressure
and 2 beam equivalent 66.4 1.0 1.9 8.2 1.9 18.3
25.5
5/4 wave ITO @ 1.7mT Pressure
and 4 beam equivalent 69.2 1.1 1.8 7.2 1.0 18.4
23.5
Table 16b: Cell data comparing ion milled parts properties
Sample ID Reflectance a* b* Transmittance a* b*
Spec Ex
3/4 wave 54.2 -1.5 2.3 11.5 2.9 21.7 0.7
3/4 wave 2B . 57.6 -0.2 3.1 10.4 0.9 21.6 0.2
3/4 wave 4B 59.3 -0.7 4.4 10.0 1.0 19.1 0.3
3/4 wave 4B 58.5 -0.4 3.6 10.3 0.7 20.5 0.3
5/4 wave 50.1 -2.0 4.0 10.8 3.9 18.2 1.1
5/4 wave 2B 52.9 -0.6 3.6 11.0 2.1 19.8 0.8
5/4 wave 2B 52.1 -0.6 3.6 11.5 2.0 19.7 0.8
5/4 wave 48 55.6 -0.3 3.9 10.0 0.1 20.4 0.5
5/4 wave 4B 55.3 0.0 3.2 10.2 0.6 20.8 0.6
[0182] In another application, use of ion milling to smooth an ITO for a
non-
.
transflective application was performed. In this case, the coating is =
Glass/ITO/Cr/Ru. The chrome and ruthenium are masked internal to the epoxy
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seal and the ITO is used to transfer electric current from the electrodes to
the EC
element interior. The ITO has some degree of roughness which is reduced by
treatment with an ion beam. Figure 38 shows decreased roughness with inverse
line speed at fixed beam current. In another example the line speed for the
glass
through the coater was 30 inches per minute (ipm). A single ion beam was used
and the current was adjusted to vary the ion milling rate. Fig. 39 depicts the
increase in reflectance versus beam current. A reflectance increase of 0.5% is
attained with even this modest ion milling condition. In these examples the
ITO
coating maintained its initial roughness to potentially facilitate increased
adhesion
of the ITO to the epoxy in the area of the seal while milling the ITO in the
viewing
area to attain improved optical properties.
[0183] In another application using the ion milling the color and
reflectance of a so-
called chrome ring type coating was investigated. In this application a multi-
layer
metal coating is applied on top of an ITO coating that is on glass. The ITO
coated
glass was ion etched in a ring around an element to thin the ITO coating in
this
location to improve the color and reflectance of the chrome ring stack while
enabling lower sheet resistance of the thicker ITO in the center of the part.
Fig.
40 depicts the reflectance of different conditions when viewed through the
glass.
The reflectance without ion milling is depicted as the bold line. The
reflectance
with several different line speeds are also depicted. As the speed is reduced,
the
residence time under the beam is increased and the roughness is reduced. This
results in an increase in reflectance. The reflectance appears to plateau,
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however, there was some arcing of the beam during these tests which may have
affected the results. The key result is that with ion milling, even in the
presence of
arcing, the reflectance is increased. Fig. 38 depicts the change in ITO
roughness
in these tests versus line speed under conditions without arcing.
[0184] Another set of tests in the same coater examined the color of
the chrome ring
with ion milling. The line speed was adjusted to alter the amount of ITO
removed.
The ITO started as a'Awave and the goal was to reduce the thickness to
approximately 80% of a 1/2 wave in other words from approximately 145 nm to
approximately 115 nm. Fig. 41 depicts the reflected b* of the chrome ring with
= line speed adjustments. The reflected b* is directly correlated with the
thickness
of the ITO as described in the priority document. The b* for a 1/2 wave ITO
coating is
about 16. As the line speed is lowered, the amount of etched material is
reduced. In at
least one embodiment an ideal match to the center viewing area a b* of about
2.5 is
desired. Therefore, the line speed should be about 12.5 ipm. When faster line
speeds
are required then more ion beams may be employed.
[0185] In another example where reduced sheet resistance values are
desired the
effect of ion milling on reflectance and material usage was investigated. As
noted
above, the roughness of a coating increases with thickness and the reflectance
decreases with roughness. In this example, a coating with 1.5 ohms/sq with a
layer structure of Glass/Chrome/Ruthenium was desired. The chrome thickness
was set to approximately 2500 angstroms to provide the majority of the
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contribution to the sheet resistance. The Ruthenium was initially set to 400
angstroms. In situations where the surfaces are perfectly smooth, the maximum
reflectance will be attained with as little as 180 to 200 angstroms of
Ruthenium. A
level of 400 angstroms was used to ensure that the Ruthenium was thick enough
to compensate somewhat for the rough surface of the chrome. The additional
Ruthenium increases the reflectance but the cost also increases.
[0186] Fig. 42 depicts the reflectance versus inverse line speed for an ion
beam
treatment of a chrome layer prior to the application of the Ruthenium layer.
The
beam current was set to about 250 mA. At a line speed of about 4"/minute the
coating attains its maximum reflectance of almost 70.5%. Further reductions in
the line speed did not result in additional increases in reflectance. If
faster line
speeds are desired then additional beams may be employed.
[0187] Fig. 43 depicts how reducing the amount of Ruthenium may be used in
the
coating due to the smoothing effect of the ion beam. The line speed was at
about
2.1 ipm and the beam current was comparable to the results in Fig. 42. As
little
as 160 angstroms of Ruthenium may be used to net the maximum reflectivity.
This results in substantial cost savings relative to the baseline case where
extra
Ruthenium was used to compensate for the roughness of the initial layers.
Additionally, a 1.5 ohm/sq coating of chrome and ruthenium with relatively
high
reflectance may not have even been practical without ion beam smoothing.
[0188] Typically roughness of a coating produced without any special
efforts to
make a smooth coating will vary between approximately 10 and 20% of the total
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thickness of the coating. Table 17 depicts the thickness of chrome/ruthenium
stacks needed to attain various sheet resistance values. The bulk resistance
of
the chrome layer is varied to demonstrate how the thickness of the chrome
layer
will vary to attain different sheet resistance values as the bulk resistance
changes. This may be used as an example of variations in chrome bulk
resistance properties or one could consider this as a means to demonstrate
what
happens when materials with different or varying bulk resistance values are
substituted for chrome.
[0189] The range of roughness is calculated in Table 17 as 10 and 20 % of
the bulk
thickness. The ruthenium is set at 200 angstroms which is just slightly above
the
thickness necessary to attain maximum reflectance for that material in an
ideal
application. If the chrome layer is smooth or has been smoothed by an ion beam
then this thickness demonstrates the optimal reflectance case. Table 17
depicts
the results of calculations where the thickness of the ruthenium is compared
to
the total thickness. The contribution of the roughness is considered to be the
average of the 10 and 20% cases. The percentage of the stack that is ruthenium
varies with the target sheet resistance of the stack and with the bulk
resistance of
the chrome or base layer. It is desirable that the ruthenium or other high
reflectance metal to be less than 50% of the total thickness if the sheet
resistance is greater than or equal to 6 ohm/sq. If the sheet resistance of
the
stack is approximately 2 ohms/sq then the ruthenium thickness should be less
than about 25% of the total thickness. The thickness percentage of the high
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reflectance layer will also vary with the bulk reflectance of this metal and
the
reflectance target. The appropriate high reflectance percentage of total
thickness
is a function of the desired reflectance of the stack, the desired sheet
resistance
of the stack and the bulk resistance of the different materials being used to
construct the stack. The percentage of the high reflectance material should be
less than 50% of the total thickness, preferable less than 25%, more
preferably
less than 15%, even more preferably less than 10% and most preferably less
than 7.5% of the total thickness. In this example chrome and ruthenium are
used
to demonstrate the benefits of one embodiment of the present invention. Other
metals can be substituted for the chrome layer as a means to provide the
majority of the sheet resistance. The so-called high reflectance metal is
defined
as a metal that is of higher reflectance relative to the layer that is
contributing to
the majority of the sheet resistance. In this example we discuss the role of
the
top most layer as having a higher reflectance relative to the electrical
conduction
layer. In other embodiments the electrical conduction layer or layers may have
an
unacceptable color or hue. The reflectance intensity may be acceptable but the
reflected color may be considered objectionable. In this embodiment the top
most,
high reflectance layer, may in fact function not to increase the reflectance
but
rather to provide an acceptable color. In one example the electrical
conduction
layer may be highly colored and a neutral reflected color is preferred. In
this case
the so called high reflectance layer would act to make the color more neutral.
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,
[0190] In
another embodiment, the electrical conduction layer may have a neutral
reflected color and a highly colored reflectance is preferred. Here the top,
high
reflectance metal may be selected to provide a non-neutral appearance. In yet
another embodiment, a multi-layer stack may be applied over the electrical
conduction layer such that the stack attains low sheet resistance while having
the
flexibility to adjust color via adjustments to the multi-layer stack placed
above the
electrical conduction layer. In this example, the multi-layer stack could
consist of
metals, dielectric layers, and/or semi-conductor layers. The selection of the
materials comprising the stack, their thicknesses, orientation relative to the
electrical conduction layer and neighboring medium will be determined by the
design criteria of a given application.
Table 17: Sheet Resistance Analysis
Minimum Maximum Bulk Sheet Bulk
Sheet Total
Chrome Chrome Chrome Resistance Resistance Ruthenium Resistance Resistance
Sheet
Thickness Roughness Roughness Chrome
Chrome Thickness Ruthenium Ruthenium Resistance Ruthenium %
496 50 99 57 10.00 200 30 15 _
6.00 26.0%
909 91 182 57 5.45 200 30 15 4.00
16.1%
2148 215 430 57 2.31 200 30 15 2.00
7.5%
4622 462 924 57 1.07 200 30 = 15 1.00
3.6%
9581 958 1916 57 0.52 200 30 15 0.50
1.8%
261 26 52 30 10.00 200 30 15 6.00
40.0%
478 48 96 30 5.46 200 30 15 4.00
26.7%
1130 113 226 30 2.31 200 30 15 2.00
13.3%
2433 243 487 30 1.07 200 30 15 1.00
6.7%
5040 504 1008 30 0.52 200 30 15 0.50
3.3%
130 13 26 15 10.00 200 30 15 6.00
57.1%
239 24 48 15 5.45 200 30 15 4.00
42.1%
565 57 113 15 2.31 200 30 15 2.00
23.5%
1217 122 243 15 1.07 200 30 15 1.00
12.5%
2522 252 504 15 0.52 200 30 15 0.50
6.5%
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[0191] As
the sheet resistance is lowered for various applications the thickness
must be increased and thus the surface roughness is increased and the
reflectance is decreased. The reflectance of the coating then will drop to a
low
value relative to the Theoretical Maximum value. The lower the sheet
resistance
value that is targeted then the lower the percentage of the Theoretical
Maximum
reflectance value that is attained. For a coating with a sheet resistance of
approximately 6 ohms per square or less the techniques described herein will
allow one to attain a reflectance greater than 90% of the Theoretical Maximum
and preferably greater than about 95% of the Theoretical Maximum. For a
coating with a sheet resistance of approximately 3 ohms per square or less the
techniques described herein will allow one to attain a reflectance greater
than
80% of the Theoretical Maximum and preferably greater than about 85% of the
Theoretical Maximum, more preferably greater than about 90% of the Theoretical
Maximum, and most preferably greater than about 95% of the Theoretical
Maximum. For a coating with a sheet resistance of approximately 1.5 ohms per
square or less the techniques described herein will allow one to attain a
reflectance greater than 75% of the Theoretical Maximum and preferably greater
than about 85% of the Theoretical Maximum, more preferably greater than about
90% of the Theoretical Maximum, and most preferably greater than about 95% of
the Theoretical Maximum. For a coating with a sheet resistance of
approximately
0.5 ohms per square or less the techniques described herein will allow one to
attain a reflectance greater than 70% of the Theoretical Maximum and
preferably
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greater than about 80% of the Theoretical Maximum, more preferably greater
than about 90% of the Theoretical Maximum, and most preferably greater than
about 95% of the Theoretical Maximum.
[0192] In commonly assigned US Patent application publication number
2006/0056003, various metal stacks are discussed for a "chrome ring" mirror
element.
A thin chrome adhesion layer is deposited onto ITO and a layer of a metal with
a
higher inherent reflectivity is deposited onto the chrome layer. Various
higher
reflectance metals were discussed. A second layer of chrome is described that
does not contribute to the appearance when the coating is viewed from the
glass
side, however, is applied to minimize the transmittance of visible and UV
light.
The reduction of visible light is to hide the seal material while the UV light
is
reduced to protect the seal material during exposure to sunlight. Chrome was
contemplated in this example as a low cost means to reduce the transmittance
of
the light, whether it be UV and/or visible. Other low cost metals may provide
the
same function provided they have good adhesion to the seal and to the higher
reflectance metal.
[0193] The thickness of the high reflectance metal may also be simply
increased to
also reduce the light transmittance but the high reflectance metals are often
relatively expensive and the sole use of these materials would result in a
higher
price of the coating.
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[0194] The ITO layer may be any transparent conducting oxide or other
transparent
electrode. The transparent conducting oxide or transparent electrode may
consist
of a single layer or multilayer. The layers in a multilayer may be selected to
modify the reflected color or appearance such that the "ring" has the
appropriate
optical properties. One such multilayer may include the use of color
suppression
layers placed between the glass substrate and the transparent conducting
oxide.
The use of this layer leads to more selections of color for the ring as the
ITO
layer thickness is adjusted.
[0195] Adhesion layer may be chrome, Ni, NiCr, of various compositions, Ti,
Si, or
silicon alloys, or other suitable adhesion enhancement layer. The "high
reflectance metals" are selected from metals and alloys that have bulk
reflectance values that are higher than chrome. Example metals include
aluminum, ruthenium, rhodium, iridium, palladium, platinum, cadmium, copper,
cobalt, silver, gold and alloys of these materials. In addition to alloys,
mixtures of
these metals with each other or with other metals may be employed. Multi-
layers
may also be used in place of the single layer shown in the schematic for the
high
reflectance metal. Similarly, the UV blocking layer may consist of a single
material, alloy, multi-layer or other combination which results in the
appropriate
reduction of transmittance.
[0196] The adhesion of materials, layer or coatings may also be improved by
use of
the ion beam treatment described herein. For example, ion beam treatment of an
ITO surface was performed using argon and then a mixture of argon and oxygen.
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These tests were compared to non-ion milled surfaces. The samples were
attached to a test piece of glass by an epoxy material to form a sealed
cavity. A
hole was drilled in the top lite of glass and the cavity is pressurized to
determine
the pressure value necessary for the cavity to fail. Failure mode may include
cohesive failure within the epoxy, adhesion of the epoxy to the coatings,
facture
of the glass or the coating may de-adhere from the substrate or there may be
intra-coating adhesion failures.
[0197] The ITO surface was either ion beam treated with argon,
argon/oxygen
mixture or had no treatment. The surface was then coated with a thin layer of
chrome about 50 angstroms thick followed by a ruthenium layer approximately
500 angstroms thick (so called Beta Ring). The coated glass was bonded to
another piece of glass with an epoxy typically used in EC elements and the
epoxy was then cured. Table 18 depicts the pressure values at failure and the
amount of metal lift from the ITO coating. The control parts have= trace
amounts
of metal lift. The argon beamed parts had substantial lift of metals but the
pressures at failure were essentially the same. The use of oxygen had again
similar pressure values at failure but the lift of metals from the ITO was
eliminated. The oxygen improves the adhesion of chrome to the ITO. The ion
beam will preferentially sputter oxygen which is a component which helps the
adhesion of chrome. The argon only case results in a minimization of critical
oxygen and a weaker bond. Adding oxygen into the beam, it is believed, "heals"
the ITO surface thus strengthening the bond and minimizing the metal lift. The
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pressure values at failure do not show a correlation because the glass is
fracturing during the test. This fracturing determines the pressure value at
failure
and thus dominates the test. In this example, the oxygen is necessary but
there
may be situations where other gases may be preferable or argon alone may be
the better choice.
[0198] In another example, where Ruthenium is deposited directly onto ITO a
dramatic change in the pressure values at failure and a change in failure mode
was observed. When the ion beam treatment is not used the pressure values at
failure are quite low, approximately 6-7 psi, and the coating lift was the
failure
mode; the glass does not fracture. When the ITO surface is treated with an
oxygen containing beam and ruthenium is then deposited on the surface the
pressure values at failure increase by over a factor of 2 and the glass
fracture is
the dominant failure mode. The coating still lifts from the ITO but the
adhesion
strength is dramatically increased.
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=
Table 18: Pressure values at failure and amount of metal lift from ITO
coating.
Blow Values (psi) Lift %
A B C A B C
10.8 11.8 11.5 trace 45 0
10.4 12.2 9.9 trace 40 0
10.6 11.6 12.2 5 trace 0
12 9.4 9.9 5 30 0
9 9.7 10.2 5 20 0
12.4 11.4 9.3 0 40 o
11.2 9.4 9.7 0 40 o
10.4 11 9.5= 0 60 . 0
9.7 . 11.6 11.1 5 20 0
11.8 8.9 11.5 0 40 0
9.7 10.4 9.5 5 20 o
11.5 9.4 11.8 trace 0 0
10.3 30
9.1 30
10.7 30
11.1 35
A - Beta Ring Controls
B - Beta Ring with Argon lon Milling
C - Beta Ring with Argon/Oxygen Ion Milling
[0199] A top layer, which may be used in some applications, may be an
electrical
conduction stabilizing material. Its role is to provide good electrical
conduction
between the ring metals and the bus bar or silver paste. The material may be
selected from the platinum group metals such as iridium, osmium, palladium, =
platinum, rhodium and ruthenium. Mixtures or alloys of these metals with each
other or with other suitable metals may be used.
[0200] The thickness and selection of the materials in the layers are
preferably
selected to provide the appropriate color and reflectance intensity as taught
in
the referenced patent application. The thickness of the layers should also be
selected to attain the necessary transmittance properties. The visible
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transmittance should be set so that the epoxy seal is not visible when viewed.
The visible transmittance should be less than 5%, preferably less than 2.5%,
even more preferably less than 1% and most preferably less than about 0.5%.
The UV transmittance may or may not correlate exactly with the visible
transmittance. In the case of the UV transmittance the appearance of the ring
is
not the issue but rather the protection of the seal is the principle concern.
This of
course presumes that the selected seal is sensitive to UV light. The amount of
allowable UV light is dependent on how susceptible the seal is to the UV
light.
Ideally, the coating should be designed such that the ring coating is opaque
to
UV light but unfortunately this level of UV transmittance may be cost
prohibitive.
Additionally, the adhesion of the layers may be compromised if the total
thickness becomes too large. The stresses which may be present in the layers
would result in a strain large enough to cause the layers to delaminate from
the
glass or other layers of the coating. For this reason one needs to contemplate
a
finite amount of UV transmittance. The UV transmittance should be less than
about 1%, preferable less than 0.5%,.more preferably less than 0.1% and most
preferably less than 0.05%.
pm] One feature/area that is gaining popularity is the use of the
exterior mirror to
display features such as turn signals, heater on/off indicators, door ajar
warnings
or warning to oncoming traffic that a door may be about to open. The mirror or
mirror housing is also being used to house puddle or approach lighting.
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[0202] The requirements are unique for an inside mirror when compared with
a
mirror for outside the vehicle. In at least one embodiment the specular
reflectance of an inside mirror is preferably 60% or higher and preferably has
ample transmittance in front of the display to pass an adequate amount of
light
through the associated mirror element. Furthermore, an inside mirror does not
have to withstand the harsh chemicals and environmental challenges
encountered in an outside mirror application. One challenge is to balance the
need to meet automotive specifications for a rearview mirror and the desire to
incorporate an aesthetically pleasing information center. Providing high
mirror
element light transmittance is one means to compensate for limited light
output
display technologies. Often times high transmittance results in circuitry and
other
hardware behind the mirror element being visible. An pacifier layer may be
applied on the fourth surface of the mirror element to combat this problem.
[0203] A supplemental turn signal as depicted in Fig. 5a is one example of
a display
feature desirable in an outside mirror assembly. One way to incorporate a
signal
feature behind an electrochromic mirror element is to laser ablate some of the
reflective material from the element to allow light to pass through. A desire
to
offer alternative styling and designs is motivation for employing
transflective
mirror element technologies. The transflective approaches of some embodiments
of the present invention allow features in the mirror with a much more
"stealthy"
(covert) appearance. Stealthy allows light to pass through the transflective
element while blocking the view of the source of the light. Stealthy may also
or
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alternatively mean that there is minimal contrast between the display area and
the main reflective area. In some instances there is a desire to clearly
indicate
the display or feature with a contrast in color or in reflectivity to give a
framing
effect so that the viewer has a clear indication of where to look for the
desired
information. Traditional materials utilized in outside mirror applications
typically
have low reflectivity, and or, high sheet resistance associated with achieving
an
appreciable transmittance level.
[0204] For example, ruthenium is often used in outside EC applications
because of
its relatively high reflectance and environmental durability. A 23 nm Ru
coating
as the reflector in an EC element would have a reflectance of approximately
57.5% a level that would meet most commercial mirror reflectance
specifications.
This coating would have a sheet resistance of approximately 20 ohms/sq and the
EC element would have a transmittance of approximately 2.5%. Neither the
transmittance nor the sheet resistance is viable for practical applications.
Other
environmentally durable metals may have slightly different reflectance,
transmittance and sheet resistance values but none will have the properties to
meet the requirements in an EC application.
[0205] A lower reflectivity requirement for OEC elements enables use of
different
configurations of materials including silver, silver alloys, chrome, rhodium,
ruthenium, rhenium, palladium, platinum, iridium, silicon, semiconductors,
molybdenum, nickel, nickel-chrome, gold and alloy combinations for the
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associated reflective and, or, transflective layer(s) stacks with fewer
difficulties in
meeting the preferred reflectance, durability and electrochromic performance
characteristics. Some of these materials have an advantage over silver or
silver
alloys in that silver and silver alloys are susceptible to damage in an
outside
mirror environment. Use of harder metals is advantageous for durability of the
mirror element in terms of manufacturing options and a more robust final
product.
Reflective and, or, transflective stacks may also be created with dielectric
materials which produce high enough reflectance levels for use in an OEC
element.
[0206] Ag based materials will generally gain approximately 1%
transmittance for
every percent of reflectance reduction in the mid-visible range. An advantage
associated with increased transmission is the ability to utilize lower cost,
lower
light output light sources, such as, displays or LED's. The outside mirror has
typically been used for indication type displays that generally use LED's that
can
be ordered with very high light outputs. Novel designs are disclosed herein
that
enable the use of Ag based transflective coatings in inside and outside mirror
applications. These novel designs preserve the unique optical properties and
benefits derived from the Ag layer while simultaneously addressing the
limitations
for using Ag based materials in outside applications. Different coating
options
may be considered when lower transmittance is part of the design criteria
using
stacks that have and do not have an Ag based layer. One big advantage to a
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lower transmittance is the reduction, or elimination, of the need for an
opacifier
layer.
[0207] In many markets the size of the mirror is increasing to allow for
more field of
view. The darkening time for larger mirrors is a challenge and is an important
consideration in the design options. Larger mirrors, generally associated with
outside mirrors, require increased or improved conductivity to maintain an
acceptable darkening and clearing speed. The previous limitations of a single
thin metal coating as described above are solved by the innovative use of a
Transparent Conductive Oxide (TCO) in the stack. The TCO provides a means
for achieving good conductivity while maintaining a high level of
transmittance.
Several of the following examples illustrate that satisfactory levels of
transmittance for outside mirrors can be achieved with relatively thick Indium
Tin
Oxide (ITO. ITO is one specific example of the broader TCO class of materials.
Other TCO materials include F:Sn02, Sb:Sn02, Doped ZnO, IZO, etc. The TCO
layer is overcoated with a metal coating that may consist of a single metal or
alloy or a multilayer metal coating. The use of multiple metal layers may be
needed, for instance, to facilitate adhesion between different materials. In
another embodiment a semiconductor layer may be added in addition or in lieu
of
the metal layers. The semiconductor layer provides some unique properties that
will be discussed below. When the thickness of the ITOTTCO layer(s) is
increased to improve conductivity the effects of coating roughness need to be
considered. The increased roughness can lead to lower reflectance which in
turn
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requires increased metal thickness which can lower transmittance. Increased
roughness can also lead to unacceptable haze as described elsewhere. The
roughness issue can be solved by either modifying the deposition process for
the
ITO and/or implementing ion beam smoothing after the ITO deposition and
before the deposition of subsequent layers. Both methods were discussed above
in detail. In addition, improved ITO materials discussed above may be employed
in this embodiment to lower the sheet resistance of the overall transflective
coating.
[0208] The semiconductor layer may comprise Silicon or doped silicon. Small
amounts of an additional element or elements may be added to alter the
physical
or optical properties of the Silicon to facilitate its use in different
embodiments.
The benefit of a semiconductor layer is that it enhances the reflectivity with
less
absorption compared to a metal. Another benefit of many semiconductor
materials is that they have a relatively low band gap. This equates to an
appreciable amount of absorption in the blue to green wavelengths of the
visible
spectrum. The preferential absorption of one or more bands of light lends the
coating to have relatively pure transmitted color. The high transmitted color
purity
equates to having certain portions of the visible or near infrared spectra
with
transmittance values greater than 1.5 times the transmittance of the lower
transmitting regions. More preferably the transmittance in the high
transmitting
region will be greater than 2 times the transmittance in the low transmitting
region
and most preferably greater than 4 times the transmittance in the low
transmitting
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=
region_ Alternately, the transmitted color of the transflective stack should
have a
C* value [sqrt(a*2+b*2)] greater than about 8, preferably greater than about
12
and most preferably greater than about 16. Other semiconductor materials that
result in transflective coatings with relatively high purity transmitted color
include
SiGe, InSb, InP, InGa, InAlAs, InAI, InGaAs, HgTe, Get GaSb, AlSb, GaAs and
AIGaAs. Other semiconductor materials that would be viable would be those that
have a band gap energy at or below about 3.5 eV. In an application where
stealthy characteristics are desired and a red signal is used then a material
such
as Ge or an SiGe mixture may be preferred. Ge has a smaller band gap
compared to Si and this results in a greater wavelength range that have
relatively
low transmittance levels. This can be preferred because the lower
transmittance
at wavelengths different from the display are more effective at hiding any
features behind the mirror. If a uniform transmittance is needed then it would
be
advantageous to select a semiconductor material that has a relatively high
band
gap.
[02091 A display area may be stealthy in nature such that an observer
may not
perceive that the mirror has a display until the display it is activated or
back lit.
Stealthyness is achieved when the reflectivity of the display area is
relatively
similar to the remaining viewing area and the color or hue contrast is
minimal.
This feature is very advantageous because the display area does not reduce the
viewing area of the mirror as discussed above.
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[0210] A small amount of transmitted light can make features behind the
mirror
visible such as circuit boards, LED arrays, shrouds and heater terminals. Use
of
a light blocking (opacifying) layer may be used to avoid this problem. An
opaque
layer is often applied on the fourth surface of the mirror using a variety of
materials such as paints, inks, plastics, foams, metals or metal foils. The
challenge of applying this layer is complicated in an outside mirror. Most
outside
mirrors have a convex or aspheric shape which makes application of a film or
coating more difficult.
[0211] An opacifying layer may be incorporated into the third surface stack
of the
element. The transflective area may be masked and an appropriate stack such
as ruthenium, rhodium or other single or multi-layer stack (metals,
metal/dielectrics and or dielectrics) which provide the appropriate
reflectance and
color (opaqueness) may be applied over the remaining surface. The stealthy
appearance is achieved when desired color and reflectance match or
mismatches are maintained. In one preferred embodiment the display area and
the main viewing area of the mirror element are virtually indistinguishable.
In
other embodiments one may want the transflective area to have a different
color
with an aesthetically pleasing contrast.
[0212] Another option is to maintain high transmittance levels in one part
of the
visible spectrum with low overall transmittance to obtain a stealthy
appearance.
Use of a narrow spectral band pass filter may also be employed to obtain the
stealthy effect.
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[0213] Inserting a relatively opaque layer (whether of the same material or
one
different than those in adjacent layers) into an otherwise transflective third
surface coating stack maybe be incorporated to help hide electronics that are
behind the mirror element in without, or in addition to, use of a coating or
tape or
other opacifying material on the rear surface of the element. Addition of this
layer
may affect the reflectance in the area where it is inserted. Reflectance in
this
area might then be adjusted, through choice of materials and their
thicknesses,
such that the difference between A display area and the relatively opaque
areas
of the mirror element are hardly noticeable, thereby preserving the unity of
the
appearance of the device.
[0214] It may also be advantageous to purposely offset the reflectivity
and/or hue of
the display area to give a visual cue as to where the display will be when it
is
active and give some indication that a display function is included in the
mirror
even when the display is off. When a conductive material is used to add
opacity
the conductivity of the relatively opaque portion of the display is now
greater and
there is a correspondingly smaller voltage drop across the majority of the
Viewing
area providing a faster coloring speed. Additional opacifying layer(s) may be
such that the reflectivity from the back of that area is substantially less
than
without the opacifying layer(s), thereby, lessening the effect of multiple
reflections
that may otherwise occur from stray light. One such device demonstrating the
aforementioned principles includes a third surface coating stack of
approximately
400 angstroms TiO2 followed by 200 angstroms of ITO over substantially all of
the
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entirety of the third surface followed by approximately 90 angstroms of chrome
except for an area roughly over the display followed by approximately 320
angstroms of 7% gold 93% silver alloy over substantially the entire third
surface.
[0215] The opening for the display on this particular model of inside
automotive
mirror is too small for measuring reflectance with some sphere based
spectrophotometers, therefore, elements were made with different portions of
the
stack over their entire viewing surface in order to facilitate measurement of
reflectance of the different portions of the stack_ Transmission and
reflectance
measurements were taken from both the front and back of the elements.
[0216] Tables 19 and 20 along with the graphs of Figs. 44 and 45,
respectively,
depict the resulting measurements
Table 19
Measurements in an Element
A illuminant 10 Degree
Observer Reflectance
values
L* a* b*
Comments
400A Ti02/200A ITO/90A Chrome Front 36.8 67.2 -3.5 -1.7
400A TiO2/200A ITO/90A Chrome Back 10.8 39.3 -4.5 -23.6
400A Ti02/200A ITO/90A Chrome/320A 7Au93Ag Front 79.3 91.4 -1.9
2.9 as in the more opaque area
400A TiO2/200A ITO/90A Chrome/320A 7Au93Aq Back 24.9 57.0 -3.4 -
17.0 as in the more opaque area
400A TiO2/200A ITO/320A 7Au93Aq Front 74.7 89.3 -1.0 4.0 as
in the display area
400A 1102/200A ITO/320A 7Au93Ag Back 76.3 90.0 -0.2 2.3 as
in the display area
Table 20
Measurements in an element
A illuminant 10 Degree
Observer Reflectance
values
Y L* a* b* Comments
400A Ti02/200A ITO/90A Chrome Front 24.5 56.6 1.4 5.2
400A TiO2/200A ITO/90A Chrome/320A
7Au93Ag Front 3.7 22.8 -0.1 -0.9 as in the
more opaque area
400A Ti02J200A ITO/320A 7Au93Ag Front 13.5 43.5 -4.4 -4.9 as in
the display area
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[0217] It can be seen that for this particular example, the addition of
chrome to the
stack adds opacity and lowers reflectance from the back of the element. If in
order to achieve opacity the thickness of the silver alloy were increased in
the
non-display areas it would not yield the reduction in reflectance from the
back of
the element as seen in this example but would increase further the already
relatively high reflectance seen from the back of the element if the chrome
were
omitted. It can also be seen that the display area of this design when
compared
to the area with the chrome layer included, has a difference in hue that is
relatively small as is the difference in brightness, even though the
transmission is
sufficient in the display area to serve as a transflector.
[0218] It should also be noted in the preceding example that by increasing
or
decreasing the thickness of the silver alloy layer in the transflective
region, a
greater or lesser "blue bias" will be obtained, respectively, in the
transmission
characteristics of this display region. Using an RGB video display behind this
region may benefit by adjusting the relative intensity of the red, green and
blue
emitters in order to maintain better color rendering. For example, in the case
of
transmission that was greater for the blue region of the spectrum and lesser
for
the red region it may be desirable to decrease the intensity of the blue
emitter
and increase the intensity of the red emitter. This type of adjustment would
be
appropriate in this and other transflective designs whether the spectral bias
of the
transmission is a gentle slope or one with more distinct bands of
transmission.
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[0219] When the display is intended for use when the mirror element is
dimmed
intensity adjustments may be made to compensate for any spectral bias from the
coatings and, of, the activated electrochromic medium. The intensity
adjustment,
may be a function of the operating voltage of the device, and or, other
feedback
mechanism to match the relative RGB intensities appropriately for a given
point
in the color excursion of the electrochromic element. When dyes are used, such
as those that might be used to create a "blue mirror" even when the
electrochromic species are not active, the intensity of the emitters may be
adjusted to have improved color rendering. As the mirror element decreases in
reflectivity, any spectral bias of first and /or second surface coatings will
become
more of a factor; the degree of compensation of the intensities of the
different
colors of the display may correspondingly be adjusted. UV absorbers and other
additives to the EC medium may also affect the visible absorption of the
element
intensity adjustments may be incorporated to improve color rendering of an
associated display.
[0220] It may be advantageous to design a transflective coating for both
displays
and signal or other indicator applications. When high output is necessary for
the
signals or indicators, the transmittance spectra of the transfiector may be
biased
to accentuate the transmittance in this region. An RGB display with equal
intensities in the red, green and blue parts of the spectrum would have
different
intensities after passing through the transflective layer (and other
components of
the mirror element). This offset in intensities may then be correspondingly
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compensated by adjusting= the output of the individual RGB colors to get
proper
color rendering.
[0221] There may be situations where the reflectance match between the
opaque
and display areas is more desirable than the example in Tables 19 and 20.
Additionally, there may be benefits for having the reflectance match at a
range of
different reflectance values. In this manner, the transmittance of the display
area
may be adjusted without compromising the reflectance match between the
opaque viewing area and the display areas. Another design objective is to have
the color either match in the viewing and display areas or to be different in
an
aesthetically pleasing fashion. A color match may be beneficial when the least
perceptible difference between the two areas is desired. In other
circumstances it
may be beneficial to have a reflectance match but a color mismatch to help
guide
the viewer to where the display is located.
[0222] Other means may be employed to further reduce the reflectance in the
opaque area when viewed from the reverse direction independent of the first
surface reflectance. Another aspect of the invention relates to the perception
of
the display area relative to the opaque or viewing area. The viewer will see
only
reflected light in the viewing area while in the display area the viewer will
see a
combination of reflected and transmitted light. The addition of the
transmitted
light in this area may make the display area noticeable even though the
reflectance in both areas is identical. Therefore, the reflectance in the
display
area may be reduced to compensate for the added transmitted light.
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[0223j It should be noted that in the previous example the reflectance
match
between the opaque areas and the display areas is a function of the thickness
of
the layers. The thickness of the chrome and AgAu7x were optimized so that the
reflectance match was relatively close while still having a relatively low
transmittance. The change in reflectance and transmittance as a function of
the
chrome and AgAu7x thickness is shown in Table 21. The data in Table 21 is
modeled data for an Electrochromic element consisting of the identified stack,
0.14 microns of EC fluid, and a top plate with a 14 wave of ITO coating on the
2'd
surface. The reflectance difference between the opaque and display areas are
lower when the chrome layer is relatively thin and/or when the AgAu7x layer is
relatively thick. This approach provides for a means to make a mirror with an
opaque area and a display with a fairly good match in certain transmittance
and
reflectance ranges.
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Table 21: Optical properties of calculated stacks with and without pacifying
chrome layers
Transflective Examples
2 degree, 065
R Cap
Reflectance
Stack
a* b* Transmittance Difference
GIass/45 nm Ti02/18 nm ITO/ 0 nm Cr/ 15 nm AgAu7x 48.4 -3.8 0.4
42.1
Glass/45 nm Ti02/18 nm ITO/ 0 nm Cr/ 20 nm AgAu7x 58.1 _ -3.6
1.1 31.6
Glass/45 nm Ti02/18 nm ITO/ 0 nm Cr/ 25 nm AgAu7x 66.1 -3.4 2.1
22.9
Glass/45 nm Ti02/18 nm ITO/ 0 nm Cr/ 30 nm AgAu7x 72.3 -3.4 2.7
16.3
Glass/45 nm Ti02/18 nm ITO/ 0 nm Cr/ 35 nm AgAu7x 76.9 -3.3 2.9
11.3
Glass/45 nm Ti02/18 nm ITO/ 0 nm Cr/ 40 nm AgAu7x 80.2 -3.3 3.0
7.8
Glass/45 nm Ti02/18 nm ITO/ 10 nm Cr/ 15 nm AgAu7x 64.0 -3.8 1.6
13.1 15.6
Glass/45 nm Ti02/18 nm ITO/ 10 nm Cr/ 20 nm AgAu7x 70.3 -3.7 2.2
9.7 12.3
Glass/45 nm Ti02/18 nm ITO/ 10 nm Cr/ 25 nm AgAu7x 75.3 -3.6 2.5
6.9 9.2
Glass/45 nm Ti02/18 nm ITO/ 10 nm Cr/ 30 nm AgAu7x 79.0 -3.5 2.7
4.8 6.7
Glass/45 nm Ti02/18 nm ITO/ 10 nm Cr/ 35 nm AgAu7x 81.7 -3.4 2.8
3.4 4.8
Glass/45 nm Ti02/18 nm ITO/ 10 nm Cr/ 40 nm A. u7x 83.5 -3.3 2.8
2.3 3.3
Glass/45 nm Ti02/18 nm ITO/ 20 nm Cr/ 15 nm AgAu7x 70.3 -3.3 2.1
4.9 21.9
Glass/45 nm Ti02/18 nm ITO/ 20 nm Cr/ 20 nm AgAu7x 75.2 -3.3 2.5
3.5 17.2
Glass/45 nm Ti02/18 nm ITO/ 20 nm Cr/ 25 nm AgAu7x 78.9 -3.3 2.6
2.5 12.8
Glass/45 nm Ti02/18 nm ITO/ 20 nm Cr/ 30 nm AgAu7x 81.6 -3.2 2.7
1.7 9.3
Glass/45 nm Ti02/18 nm ITO/ 20 nm Cr/ 35 nm AgAu7x 83.5 -3.2 2.7
1.2 6.6
Glass/45 nm Ti02/18 nm ITO/ 20 nm Cr/ 40 nm A=Au7x 84.8 -3.2 2.7
0.8 4.6
Glass/45 nm Ti02/18 nm ITO/ 30 nm Cr/ 15 nm AgAu7x 72.1 -2.9 2.1
1.9 23.7
Glass/45 nm Ti02/18 nm ITO/ 30 nm Cr/ 20 nm AgAu7x 76.6 -3.0 2.4
1.4 18.5
Glass/45 nm Ti02/18 nm ITO/ 30 nm Cr/ 25 nm AgAu7x 79.9 -3.1 2.6
1.0 13.8
Glass/45 nm Ti02/18 nm ITO/ 30 nm Cr/ 30 nm AgAu7x 82.3 -3.1 2.6
0.7 10.0
Glass/45 nm Ti02/18 nm ITO/ 30 nm Cr/ 35 nm AgAu7x 84.0 -3.1 2.6
0.5 7.1
Glass/45 nm Ti02/18 nm ITO/ 30 nm Cr/ 40 nm AgAu7x 85.1 -3.2 2.6
0.3 4.9
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[0224] A means is desirable to attain a reflectance match over a broad
range of
desired reflectance values while maintaining opacity in the viewing area and
higher transmittance in the display area. This is attained in at least one
embodiment by adding an additional layer to the stack described in the example
of Table 21. This preferred third surface stack is Ti02/ITO/AgAu7x/Cr/AgAu7x.
. By splitting the AgAu7x the ability to achieve a reflectance match over
a brOad
intensity range and have the ability to simultaneously control the
transmittance of
the stack in the opaque area is attained. The transmittance in the display
area is
limited to the values previously described for AgAu7x stacks.
[0225] The chrome layer is masked in the area of the display while the
other layers
may be present over substantially the entire surface or, at a minimum, in the
area
of the display. This example uses a Ti02/ITO net quarter wave bi-layer (the so-
called GTR3 base layer) to neutralize the color of the transflective silver or
silver
alloy layer in the area of the display. Other transflective color
neutralization layers
may be substituted in the display area and are within the scope of this
embodiment. The chrome layer which splits the AgAu7x layer has the novel
property in this application of not only providing an opaque character for the
stack but it also optically isolates the lower layers from the top AgAu7x
layer. Fig.
46 shows how the reflectance varies with the thickness of the chrome layer. As
can be seen, at a thickness slightly greater than 5 nm the thin chrome layer
effectively isolates the bottom silver gold alloy layer from contributing to
the
reflectance. This isolation results with such a thin layer of chrome which
allows
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the chrome thickness to be tuned to attain a range of transmittance values
while
not having any applicable effect on the overall reflectance of the stack.
[0226] One benefit of this approach extends to the display area. Since only
a thin
chrome layer is needed to isolate the bottom AgAu7x layer from contributing to
the reflectance the thickness of the bottom AgAu7x layer may be varied to
attain
other design goals. For example, the desire to have the reflectance match in
the
opaque area and in the display area as previously expressed may be achieved.
In the examples wherein a transflective mirror element has regions of
relatively
high transmittance and low transmittance the term "opaque" is meant to
indicate
that the transmittance level is sufficiently low to hide the appearance of
components behind the fourth surface without the addition of opacifying
materials
on the fourth surface. In certain embodiment the transmittance should be less
than 5%, preferably less than 2.5% and even more preferably less than 1% and
most preferably less than 0.5%. Since the AgAu7x is isolated in the opaque
area,
the thickness may be adjusted as needed to attain the desired reflectance in
the
display area. The AgAu7x top layer will have a higher reflectivity when it is
deposited onto Cr versus Ti02/ITO (as present in the display area). The bottom
AgAu7x thickness may be set such that the display area matches the reflectance
of the opaque area. The reflectance value for the mirror element may be as low
as the reflectance value of the chrome layer alone up to the reflectance of a
thick
AgAu7x layer. The reflectance can be tuned to any desired value over this
range
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=
and the transmittance can be adjusted as well. A desirable reflectance match
between the display area and the viewing area is also attainable.
[0227] The silver containing layers may be other alloys or combinations of
alloys
aside from 7%Au93%Ag. For example, it may be advantageous to have a higher
amount of gold in the alloy above the opacifying layer(s) than under the
layer(s).
This may be for reasons associated with obtaining a more durable interface
between the opacifying layer and the upper silver bearing layer, color desires
or
durability of the upper silver bearing layer during processing or when in
contact
with the electrochromic medium. If the two silver bearing layers contain
different
levels of materials that easily diffuse through the silver such as gold,
platinum,
palladium, copper, indium or the like, the transflective area where the silver
layers no longer have one or more intervening opacifying layers will likely
become after processing or time, an alloy that is the weighted average of the
upper and lower alloys. For example if silver-palladium alloy were used as the
upper silver bearing layer and silver-gold alloy for the lower layer, then the
transflective region would likely become a silver-gold-palladium ternary alloy
layer. Similarly if equal thicknesses of 7% gold in silver and 13% gold in
silver
were used as the two silver bearing layers, the resulting layer in the
transflective
region would likely be a layer with essentially uniform distribution of gold
at 10%
in silver.
[0228] The opacifying layer may be separate layers combined in the
transflective
region where one, or both or all layers might not contain silver. For example,
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silver alloy over silicon may be employed in the transflective region, or
ruthenium
over silicon, among many possible combinations.
[0229] Flash overcoat layers of materials mentioned in US patent 6,700,692,
as useful for flash layers, which include among other materials, indium tin
oxide, other
conductive oxides, platinum group metals and their alloys, nickel, molybdenum
and their
alloys, may also be incorporated into the above described designs. Depending
on the
thickness and optical properties of the materials chosen for the flash
layer(s)
adjustments may be needed to the underlying stack to maintain a similar degree
of match or mismatch between the relatively opaque region and the
transflective
region(s).
[0230] As noted above the transmittance attainable in the "opaque" area is
dependent on both the silver based layer and the chrome or "opacifying" layer.
The thicker the chrome layer the lower the transmittance at a given
reflectance
level. The chrome layer can be thinned to a desired level to approach the
transmittance of the display area. It is often difficult to control the
thickness of a
very thin layer if higher transmittance levels are needed. Thicker layers may
be
used if the metal opacifying layer is partially oxidized. A thicker layer may
be
needed to attain the higher transmittance relative to a thin pure metal layer.
Fig.
47 depicts the relationship between transmittance and reflectance for the
stacks
from Table 21 above and the case of using a CrOx layer as the opacifying
layer.
Fig. 47 depicts transmittance versus reflectance for different opacifying
layers
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and thicknesses. The symbols in the chart represent different thickness AgAu7x
layers. The thicker layers are to the right and the thinner layers are to the
left.
[0231] As can be seen, as the thickness of the AgAu7x layer is thinned the
reflectance approaches the value of the chrome or opacifying layer. The
thickness of the opacifying layer will affect the low end reflectance of the
mirror
element. For instance, when the Cr layer is 10 nm thick the low end
reflectance is
41.7%, 20 nm it is 50.5% and 30 nm it is 52.7%. The low end reflectance
approaches a constant value as the opacifying layer is increased in thickness
however, for thin layers there will be a drop in reflectance when the layer
gets too
thin. This can be an advantage or disadvantage depending on the design
criteria
for a given application. The limitations between reflectance and transmittance
for
a chrome layer can be overcome by replacing the chrome layer entirely with a
different material or by adding additional layers.
[0232] With reference to US patent 6,700,692 different metals,
semiconductors,
nitrides or oxides are taught above or below the Ag containing layer. These
layOrs and materials are selected to provide improvements to the stack. A base
layer below the reflector is taught which may be a conductive metal, metal
oxide,
metal nitride or alloy. There may also be an intermediate layer or layers
between
the base layer and the reflective material. These metals and materials may be
selected such that there are no galvanic reactions between the layers and/or
to
improve adhesion to the substrate and to the reflector or other layer(s).
These
layers may be deposited on the substrate or there may be additional layers
below
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the previously mentioned base layers that provide additional desirable
characteristics. For example, a dielectric pair comprising TiO2 and ITO with
an
effective odd quarter wave optical thickness may be present. The thickness of
the TiO2 and ITO layers may be adjusted as needed to meet specific
conductivity
and optical requirements.
[0233] When a metal layer is deposited under the silver comprising
layer it may be
selected from the group consisting of chromium, stainless steel, silicon,
titanium,
= nickel, molybdenum, and alloys of chromium/molybdenum/nickel,
nickel/chromium, molybdenum, and nickel-based alloys, Inconel, indium,
palladium, osmium, tungsten, rhenium, iridium, molybdenum, rhodium, ruthenium,
stainless steel, silicon, tantalum, titanium, copper, nickel, gold, platinum,
and
alloys whose constituents are primarily those aforementioned materials, any
other platinum group metals, and mixtures thereof. In addition the layer under
the
reflector layer may be an oxide or metal oxide layer such as chromium oxide
and
zinc oxide.
[0234] An optional metal layer over the silver comprising layer may be
chosen from
the group consisting of rhodium, ruthenium, palladium, platinum, nickel,
tungsten,
tantalum, stainless steel, gold, molybdenum or their alloys.
[0235] The present disclosure contemplates opacifying layers in
conjunction with
transflective portions of the mirror or optical element. This presents new or
additional design criteria be included which affect the selection of metals
which
act to reduce the transmittance in certain areas of the element or mirror.
Table 22
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below shows the reflectance and color of various suitable base or opacifying
layer metals on a Ti02/ITO dielectric layer stack in an EC cell. The thickness
of
all of the metal layers is 30 nm. The color and reflectance will vary with the
thickness of the metal layers. Table 22 depicts the relative differences in
color
and reflectivity of various suitable metal opacifying layers on the low end
reflectance when the opacifying metal is relatively thick and the AgAu7x or
other
Ag comprising top layer is absent. As is known in the art, alloys of these
metals
with each other or with other metals will have differing optical properties.
In some
cases the alloys will behave as do mixtures of the individual metals, however
in
other cases the alloys do not have reflective properties which are simply the
interpolation of the individual metals. The metals or alloys can be selected
for
their galvanic properties, reflectivity, color or other properties as needed.
[0236] In silver containing reflective layer stack's the reflectivity and
color will vary
when deposited onto these different metals or alloys. Table 23 depicts metal
containing stacks with 20 nm of AgAu7x on top. The color and reflectance of
the
20 nm Ag containing layer stack is altered by the properties of the metal used
as
with the opacifying layer. The transmittance of the different stacks is also
shown.
As shown above for chrome, the transmittance, reflectance and color can be
altered by changing the thickness of the opacifying metal. It is clear from
these
examples that a desired color, transmittance and reflectivity may be attained
by
altering the properties of the opacifying metal layer or layers.
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Table 22: Reflectance and color of various metals in an EC cell on top of a
Ti02/ITO base layer system.
Stack RCapY a* b*
Glass/45 nm Ti02/18 nm ITO/ 30 nm Mo/ 0 nm AgAu7x 45.9 -2.2
1.6
Glass/45 nm Ti02/18 nm ITO/ 30 nm Au/ 0 nm AgAu7x 50.8 1.3
16.6
Glass/45 nm Ti02/18 nm ITO/ 30 nm NiCr (80/20)/ 0 nm AgAu7x 52.8 -2.1
4.4
Glass/45 nm Ti02/18 nm ITO/ 30 nm Si/ 0 nm AgAu7x 36.9 -0.8 -
3.4
Glass/45 nm Ti02/18 nm ITO/ 30 nm Pd/ 0 nm AgAu7x 55.8 -2.2
4.0
Glass/45 nm Ti02/18 nm ITO/ 30 nm Os/ 0 nm AgAu7x 37.4 -0.9 -
9.8
Glass/45 nm Ti02/18 nm ITO/ 30 nm W/ 0 nm AgAu7x 39.3 -0.2
4.8
Glass/45 nm Ti02/18 nm ITO/ 30 nm Rh/ 0 nrriAgAu7x = 63.9 -1.3
2.2
,Glass/45 nm Ti02/18 nm ITO/ 30 nm Rid 0 nm AgAu7x 60.3 -2.3
1.1
Glass/45 nm Ti02/18 nm ITO/ 30 nm Ir/ 0 nm AgAu7x 56.0 -2.9
3.7
Glass/45 nm Ti02/18 nm ITO/ 30 nm Cu/ 0 nm AgAu7x 48.4 -2.1
7.4
Glass/45 nm Ti02/18 nm ITO/ 30 nm Pt/0 nm AgAu7x 51.2 -1.8
5.4
Table 23: Reflectance and color of various metals and AgAu7x in an EC cell on
top of a
Ti02/ITO base layer system. =
Table 23
Stack R Cap Y a b*
Transmittance
Glass/45 nm Ti02/18 nm ITO/ 30 nm Mo/ 20 nm AgAu7x 73.2 -2.8 3.8
2.1
Glass/45 nm Ti02/18 nm ITO/ 30 nm Au/ 20 nm AgAu7x 78.4 -3.0 8.4
6.3
Glass/45 nm Ti02/18 nm ITO/ 30 nm NiCr (80/20)/ 20 nm AgAu7x 77.3 -
3.1 4.2 1.9
Glass/45 nm Ti02/18 nm ITO/ 30 nm Si/ 20 nm AgAu7x 62.7 -2.0 0.5
15.8
Glass/45 nm T102/18 nm ITO/ 30 nm Pd/ 20 nm AgAu7x 78.8 -3.0 3.9
2.1
Glass/45 nm Ti02/18 nm ITO/ 30 nm Os/ 20 nm AgAu7x 66.6 -1.0 -0.5
7.3
Glass/45 nm 1102/18 nm ITO/ 30 nm W/20 nm AgAu7x 70.4 -2.5 6.1
3.8
Glass/45 nm Ti02l18 nm ITO/ 30 nm Rh/ 20 nm AgAu7x 80.9 -2.6 2.9
0.9
Glass/45 nm Ti02/18 nm ITO/ 30 nm Ru/ 20 nm AgAu7x 78.5 -3.0 2.6
0.4
Glass/45 nm TiO2/18 nm ITO/ 30 nm Ir/ 20 nm AgAu7x 78.3 -3.2 3.8
1.4
Glass/45 nm Ti02/18 nm ITO/ 30 nm Cu/ 20 nm AgAu7x 76.4 -3.2 5.5
3.1
Glass/45 nm Ti02/18 nm ITO/ 30 nm Pt/ 20 nm AgAu7x 76.8 . -3.0 4.7
2.2
Glass/45 nm Ti02/18 nm ITO/ 30 nm Cr/ 20 nm AgAu7x 76.6 -3.0 2.4
1.4
[0237] The
ability to color and reflectance tune in the viewing area may be further
augmented or enhanced by combining the metal opacifying layers with dielectric
layers additionally described in the US patent 6,700,692: The dielectric
layers
may modify both the color and reflectance, often without having a substantial
effect on the absorption in the stack.
=
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[0238] In order to match the color and reflectance in the display area the
previously
described bi-layer base layer under the silver containing reflecting layer may
be
employed. Table 24 depicts how the reflectance and color varies with changes
to
the ITO and TiO2 thickness for a fixed AgAu7x layer. As can be seen the
thickness of the bi-layers not only affects the reflectance, but, the color
can also
be tuned. These layers may then be adjusted as needed to get both the desired
reflectance and color. The adjustability of the color and reflectance may be
further expanded by adjusting the thickness of the AgAu7x, or silver
containing
reflecting layer_ Additional color and reflectance changes may be obtained by
adding additional dielectric or metal layers as part of the display stack
either
above or below the silver containing layer or by changing the refractive
indices of
the dielectric layers.
[0239] Table 24: Color and reflectance changes with variations in the TiO2
and ITO
thickness of the base layer in the display area for a fixed silver containing
layer
thickness.
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Table 24
Reflectance
TiO2 ITO AgAu7x (cell) a* b*
20 15 20 46.2 3 4.8
30 15 20 50.1 0.6 -1.2
40 15 20 56.2 -2.2 -1.2
50 15 20 61.5 -3.7 1.5
20 25 20 50.3 1 0.7
30 25 20 56 -1.8 -0.6
40 25 20 61.6 -3.4 1.4
50 25 = 20 65.4 -4.2 4.7
20 35 20 55.1 -1.1 0.5
30 35 20 60.8 -3.1 1.7
40 35 20 65 -4 4.6
50 35 20 67.3 -4.7 8.8
20 45 20 59.3 -2.6 2.3
30 45 20 63.9 -3.9 4.9
40 45 20 66.7 -4.7 8.9
50 45 20 67.6 -5.5 14.4
[0240] For example, when the color in the viewing area is yellow, blue,
green or red
biased by choice of metal under the silver reflecting layer or due to the
silver
reflecting layer itself or by a combination of the layers then a color and/or
a
reflectance match may be achieved by adjusting the layers in the display area.
One benefit of this approachis that layers can be applied over substantially
the
entire surface, however because of the unique optical shielding properties of
the
opacifying layer or layers, these lower layers do not contribute to the
reflectance
and color in the viewing or opaque area but are fully functional in the
display area
where the opacifying layer or layers are masked. The present invention is not
limited to having the layers which function in the display area cover the
entire
part. This is particularly applicable to layers under the opacifying layer.
These
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layers may be deposited as necessary only in the general area of the display
should the manufacturing process warrants this approach.
[0241] In some situations it might be advantageous for the reflector and or
transflector to be bluish in reflected hue. It could also be advantageous to
combine an opaque bluish reflector region and a bluish transflective region in
the
same element for a stealthy appearance.
[0242] It is known to make blue electrochromic elements that have a blue
hue to
them even when there is no potential applied to them through the use of dyes
such as in U.S. Patent 5278693. There are also practical methods using third
surface
coating stacks to make such a device that meets the typical requirements of
outside
automotive electrochromic devices. These techniques could also possibly be
used in
combination. Such a device must, at present, have a reflectance value above
35% in the United States and 40% in Europe. Preferably in at least one
embodiment reflectance values above 50% or 55% are preferred. Whatever third
surface stack is utilized needs to be durable, both chemically and physically
and
electrically in an electrochromic device.
[0243] One can obtain a bluish Electrochromic device by depositing a layer
of
chrome on glass that is essentially opaque and then depositing approximately
900 A of ITO over the top of that and afterwards completing the construction
of
an electrochromic device. A coating stack made and used in such a fashion had
color values shown in Table 25 and a reflectance spectrum shown in Fig. 53.
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Table 25 and Fig. 53 show values when the coating is on a single lite of glass
and after incorporation into an EC element.
[0244] There will be a substantial reflectance drop when the coating on
glass
measured in air is compared to the reflectance in the completed device. To
compensate one might think that an opaque layer of silver or silver alloy
could be
used instead of or in addition to the chrome layer with a similar top layer or
layers.
However the optics of silver are such that it is more difficult to obtain a
high
reflectance bluish coating over a silver based material. This is partly due to
the
slightly yellow spectral bias of silver and also due to the fact that as there
is little
one can do to interferentially boost the reflectivity of silver in any portion
of the
spectrum to give it significant color since the reflectance is already so
close to
100% over the visible spectrum.
[0245] If one however places a translucent layer of silver or silver alloy
between the .
chrome and ITO in the stack above, one can still boost the reflectivity a
significant amount, maintain a bluish color and increase the conductivity of
the
third surface reflector electrode. =
[0246] With a translucent layer of silver present one could make a region
that is
transflective by the addition of color neutralizing underlayer(s) and
"splitting" the
silver and masking an opening in the chrome, in accordance with teachings
contained in this document.
[0247] For example a reflective stack of approximately 40nm of Ti02, 20nm
of ITO,
14 nm Silver, 50nm Chrome, 10nm Silver and 90nm ITO models as being similar
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in hue and brightness to the same stack without the Chrome layer. Without the
chrome layer the transmission of the stack is calculated as being adequate for
use as a display or light sensor region. Therefore one could mask the chrome
during the deposition of that layer and make an electrochromic element with
similar bluish hue and brightness (i.e. stealthy) in both the opaque and
transflective portions of the device.
[0248] One might also boost the reflectivity of the Chrome\ITO stack
through the
insertion of a low index layer between the chrome and the ITO or by multiple
alternating low and high index layers. However most=low index oxide and
fluoride
materials in sufficient layer thicknesses to have the appropriate optical
effect will
also be electrical insulators. Silver itself is however a low index material
and this
does explain in part its benefit when placed between the chrome and ITO_
Table 25
Illuminant A 10 degree observer Chrome with about 900 Angstroms ITO as single
and as the 3rd Surface reflector electrode
L*
Single 49.571 75.805 -13.526 -15.323
element 44.315 72.439 -7.339 -7.896
[0249] Another feature beneficial in the area of display windows and
transflective
coatings is an anti-reflection feature from the reverse direction. Often
displays put
out a substantial amount of stray light which bounces or scatters around the
back
of the mirror element and eventually make its way out in the area of the
display.
By having the elements have a relatively low reflectance from the reverse
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direction this stray light can be reduced. Attaining lower reflectance without
additional layers on the fourth surface has the added benefit of reduced cost.
[0250] CriTi02/ITO/AgAu7x/Cr/AgAu7x is provided in the opaque or viewing
area
while having Ti02/ITO/AgAu7x/AgAu7x in the display area. The first chrome
layer is thin, about 2 to 15 nm thick, preferable about 5-10 nm thick and is
masked in the display area. The second chrome is also masked in the display
area and its thickness is adjusted to get the desired transmittance in the
viewing
area. The Ti02/ITO bi layer covers the entire surface and is adjusted to get
the
anti-reflectance effect from the reverse direction in the viewing area while
providing the proper color in the display area from the front of the part.
[0251] Table 26 depicts the reflectance from the reverse direction, or from
the fourth
surface. The first case is the reference case. This is the stack described
above
for the opaque or viewing area of the mirror element. As can seen the
reflectance
from the back is quite high at about 61%. In the second case a thin chrome
layer
(-5nm) is added below the dielectric layers. The addition of this thin layer
in the
viewing area reduces the reflectance to approximately 6% at 10 fold decrease
in
intensity. In this manner the scattering of any stray light will be reduced.
This
reflectance value, and its color, may be adjusted by the thickness of the
chrome
layer and the dielectric layers. Approximately 4% of the 6.2% reflectance
arises
from the uncoated fourth surface of the glass. If further reductions in
reflectance
are desired an additional traditional anti-reflection layer may be added. The
reflectance value of 6.2% could be reduced to values below 2.5%.
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=
Table 26: Reflectance from reverse direction (fourth surface) with and without
anti-reflection layer in the view area. These are assembled element values.
Stack R Cap
Y
Glass/35 nm Ti02/18 nm ITO/ 14 nm AgAu7x/ 25 nm Cr/ 8.5 nm AgAu7x 61_4
Glass/5Cr/ 35 nm Ti02/ 18 nm ITO/ 14 nm AgAu7x/ 25 nm Cr/ 8.5 nm AgAu7x 6.2
[02521 The amount of reflectance reduction and its absolute value are
dependent on
the properties.of the first *silver containing layer and the subsequent chrome
layer.
As described above these layers are adjusted to tune not only the
transmittance
but also the reflectance toward the viewer. As these layers are adjusted to
meet
varying design goals or targets, the dielectric layers and/or the base chrome
layer may be adjusted to achieve the optimal anti-reflection effects.
[0253] Other metals or absorbing layers other than chrome may be used as
the anti-
reflection layer. Materials such as tungsten, chrome, tantalum, zirconium,
vanadium and other similar metals will also provide a broad anti-reflection
property. Other metals may result in a higher, more colored reflectance.
Additionally, the chrome or other metal layer may be doped with small amounts
of oxygen or nitrogen to alter the optical properties of the metal to adjust
the anti-
reflection properties.
[0254] The usefulness of an alternating set of a layer of high and low
refractive
index or multiple sets of such layers to modify the optical properties of a
surface
or thin film stack has been mentioned elsewhere in this document. Materials
that
are typically thought of as being low refractive index that are metal oxides,
nitrides, oxynitrides, fluorides tend to be poor conductors. Typically, the
greater
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the difference in indices of refraction between adjacent materials the greater
the
optical effect. This is why a material with an index of refraction of about
1.6 or
less is usually used as the low index material. However, beneficial effects
arise
with materials of higher index, such as transparent conductive oxides, when
the
material to which the TCO is coupled has sufficiently higher index of
refraction
and results in a high-low index pair. In particular, when titanium dioxide is
used
as a relatively high index material coupled with indium tin oxide as a
relatively
low index material benefits are obtained optically and electrically. In
particular
titianium dioxide is a relatively high index of refraction material that is
not a
sufficiently good insulator at optical thicknesses to isolate more conductive
thin
films placed above or below it such as ITO, another TCO or a metal or
semimetal
layer or layers. When -1;02 is applied as an optical thin film between layers
that
are much more conductive, such as Indium Tin Oxide, the -1102 will not
insulate
the ITO layers from one another in an electrochromic element and the desired
optical effect of a high-low-high stack is achieved. In other words, most of
the
cumulative conductivity benefits of the total thickness of ITO in the thin
film is
retained along with obtaining the optical benefits of the high and low index
layers.
The following examples will illustrate the benefits of this principle in
general and
these materials in particular. All base layers were deposited and measured on
soda lime glass (n approximately 1.5 in the visible spectrum).
[0255] Base layer A= half wave optical thicknes ITO of approximately 145 nm
physical thickness and 23 ohms /square sheet resistance (produced under
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conditions less than ideal for conductivity). Base layers B = approximately 40
nm
titanium dioxide under approximately 20 nm ITO with sheet resistance between
about 110 and 150 ohms / square. Base layers C= Base layer A + base layers B
with a sheet resistance of approximately 16 ohms / square (the lower than
expected sheet resistance may be due to the fact that capping the ITO layer of
A
before vacuum break and cooling may have enhanced the conductivity compared
with layer A alone). Base layers D= approximately 42.5 nm titanium dioxide,
42.5nm ITO, 42.5 nm titanium dioxide, 42.5nm ITO with a sheet resistance of
about 40 ohms / square. Fig. 54a depicts the reflectance spectra of these base
layers on glass in air (without additional coatings and prior to assembly into
electrochromic elements).
[0256] Samples from the same coating runs (note that there will be some
variation
even within a run) as the samples of Fig. 54a were given an additional coating
of
approximately 25 nm of 6% Au 94% Ag (referred to as 6x) alloy and assembled
into electrochromic elements in accordance with principles outlined elsewhere
in
this document. Half wave optical thickness ITO with approximately 12 ohms /
square on glass was used as the second surface coating for these elements.
Spectrophotometric measurements were then taken as depicted in Figs. 54b and
54c. The results are tabulated in Table 27.
Table 27
Reflected Color Values Ilium L. a* b Illum L a
tr=
Element with 6x and base layer C 1365 85.183 -5.628 7.707
66.366 A 85.076 -3.044 6.241 66.158
Element with 6x and base layer B 065 85.921 -2.895 3.187
67.83 A 85.815 -1.824 2.358 67.618
Element with 6x and base layer D D65 84.769 -7.573 -1.199
65.555 A 83.838 -6.109 -3.781 63.754
Element with 6x and base layer A D65 82.573 2.453 15.379
61.362 A 83.845 5.064 16.813 63.768
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[0257] As mentioned previously, it is often useful to mask the silver alloy so
that it is,
for the most part, not deposited under the seal area As a consequence, if that
option is chosen the electrical contact for the element is made to the
underlayer
(s ) on the third surface. In such an instance lower sheet resistance for the
underlayers becomes more important than if the silver or silver alloy is taken
all
the way to the point of electrical contact via buss bar or conductive epoxy or
other means.
[0258] Resistance measurements on the base layers described were taken with a
four
point probe that can give misleading results as to the surface conductivity if
the
probes break through insulating layers. Therefore elements were constructed
with just the base layer(s) as the third surface coatings and compared for
coloring and clearing characteristics. The performance of the elements was
consistent with sheet resistance measurements taken via the four point probes.
[0259] In one embodiment of the present invention a color and reflectivity
match
between the viewing area and the display area may be desired. In some
examples mentioned above there may be two different metal stacks in the two
areas and if the same metal is the top layer the thickness of the layer may be
different or other metals may or may not be below the top metal layer. As
singles,
before being laid up into EC elements, the reflectance of the two areas may be
adjusted to be substantially ,the same. After lay up, when the medium in
contact
with the metals changes from air to that of the EC fluid the reflectivity may
be
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different in the two areas. This is because each stack interacts with the new
incident medium in different ways.
[0260] For example, Ruthenium as the top layer in one design (Glass/TiO2
45nm/ITO 18nm/Ru14nm) and AgAu7x in another (GlassiTiO2 45nm/ITO
18nm/AgAu7x19nm) both are adjusted to have a reflectance as single of 70.3%
then when assembled into an element the Ru side will drop to 56.6% reflectance
while the AgAu7x side will drop to 58.3%.
[0261] Another example TiO2 40nm/ITO 18nm/Cr 25nm/AgAu7x 9nm has a
reflectance of 77.5% as a single and 65.5% when assembled in an element while
TiO2 40nm/ITO 18nm/AgAu7x 23.4nm has a reflectance of 77.5% as a single
and 66% when assembled in an element. The difference in this case is not as
dramatic as the earlier example, however it shows that even buried layers can
influence the reflectance drop going from a single to an element. This is to
illustrate that when reflectance matches are desired in an element a
reflectance
mismatch may be needed for the coatings as singles.
[0262] The methods described above to attain good reflectance and color
matches
in the two areas of the mirror presume that the appearance in the two areas is
due virtually entirely by the reflectance. However, the viewer perceives not
only
the reflectance but, in the display area, also the transmitted light. In the
viewing
or opaque area the viewer only perceives the reflectance since the
transmittance
is relatively low. The amount of transmitted light is a function of the
transmittance
in the display area and the reflectance of components behind or in contact
with
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the fourth surface of the mirror. The amount of light perceived by the viewer
increases as the transmittance of the coating in the display area increases.
Similarly, as the reflectance of the components behind the mirror increases
the
light perceived by the viewer also increases. This may add a substantial
amount
of light and the viewer would perceive this as the display area being brighter
than
the viewing area. This may result in the display area appearing brighter even
if
the two areas have identical reflectance. This effect may be mitigated by
producing an element with components having low reflectance and/or by having
the transmittance in the viewing area set to a relatively low level. If the
output
brightness of the display is relatively limited, or low, then reducing the
transmittance can substantially dim the display.
[0263] For yet another example, an EC element consisting of
40nmTi02/18nm
ITO/EC fluid/140nm ITO/Glass having a reflectance of 8.1%. a 5 nm Ruthenium
layer is deposited on the fourth surface to simulate a display behind the
mirror
(i.e. 5nm Ru/Glass/40nmTi02/18nm ITO/EC fluid/ITO/Glass) the reflectance
rises to 22.4%. An EC element consisting of Glass/40nmTi02/18nm IT0/22nm
AgAu7x/EC fluid/ITO/Glass has a reflectance of 61.7%. The stack with the 5 nm
of Ruthenium has a reflectance of 63.5% - approximately a 2% increase in
reflectance. This amount of reflectance is quite perceptible by the viewer. As
noted above the actual reflectance increase will be dependent on the
reflectance
of the components behind the mirror and the transmittance of the EC element.
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[0264] In order to reduce the perceived brightness differences in the two
areas the
relative reflectance may be adjusted in the two areas to compensate for the
transmitted light component. Therefore, to achieve a net 2 percent brighter
area
in the display section of the mirror either preferentially increase the
reflectance in
the viewing area or decrease the reflectance in the display area. The amount
of
adjustment is dependent on the particular circumstances of the system.
Example la
[0265] In this example, the third surface of a 2.2mm glass substrate is
coated with
approximately 400A TiO2 followed by approximately 180A of ITO and finally with
approximately 195A of silver-gold alloy (93% silver/7% gold by weight). The
titanium dioxide and ITO are preferably applied substantially to the edge of
the
glass and the silver alloy is preferably masked inboard of at least the
outboard
side of the associated seal. In at least one embodiment the second surface
comprises a 1/2 wave (HW) layer of ITO. The associated element reflectance and
transmission model is illustrated Figs. 48a and 48b, lines 4801a and 4801b
respectively. The model reflection is approximately 57% @ approximately 550nm
and transmittance is approximately 36.7%.
Example lb
[0266] This Example is configured similar to Example la except with a
chrome/metal tab along at least a portion of a perimeter area of the third
surface
extending beneath the seal to improve the conductivity between an associated
clip contact area and the silver alloy. The appearance remains the same
however,
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the darkening speed is improved. This feature may be applied to a number of
the
following examples to improve electrical conductivity from the third surface
to the
associated electrical contacts. As can be seen from Figs. 48a and 48b, the
reflectance associated with the element of Example la while the transmission
of
each is dramatically different; this represents one of the advantages of the
present invention.
Example lc
[0267] Example lc is configured similar to Example 1a, however, a display
area is
initially masked and a stack consisting of Cr/Ru is deposited over
substantially
the entire surface, subsequent to removing the mask (i.e. resulting in only
the
Cr/Ru on the glass in the display area. The Cr/Ru opacifying stack may be
replaced by a number of combinations. The reflectance and transmission results
are depicted in Figs. 48a and 48b by lines 4802a and 4802b, respectively. The
opacifying stack preferably has a low contrast for both reflectivity and
color,
relative the display area. Another advantage in this example is that the
metals
generally used in the opacifying layer may extend to the edge of the glass to
bridge between an associated electrical connection clip and the third surface
silver-gold alloy. The model reflection is approximately 56.9% @ approximately
550nm in the viewing area and approximately 57% reflection in the display
region
with transmittance <10, <5% preferred, <1% even more preferred, and <0.1%
most preferred design goal (this applies to all comparable designs) in the
viewing
area and transmittance in the display region of approximately36.7%. It should
be
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understood that a light sensor may be located behind the "display area" in
addition to, or in lieu of, a display or other light source.
Example 2a
[0268] In this Example, the third surface of a mirror element is coated
with
approximately 2000A of ITO followed by approximately 50% transmission
chrome and finally with approximately 170A of silver-gold alloy. Preferably
the
ITO and chrome are coated substantially to the edge of the glass and the
silver
alloy is masked inboard of at least the outboard side of the seal. The Cr
thickness is preferably adjusted so that the ITO plus Cr layer measures 50%
transmittance through the back plate only. In at least one embodiment the
second surface preferably comprises a HWITO layer. The reflectance and
transmission of the element is illustrated in Figs. 49a-49d lines 4901a and
4901b
respectively. The Cr layer may be adjusted (thicker or thinner) to adjust the
final
transmittance of the transflective element. As the Cr layer is thickened the
transmittance will drop, when the Cr layer is thinned the transmittance will
increase. An added advantage of the Cr layer is that the stack is relatively
color
stable for normal vacuum sputter deposition process fluctuations in the base
ITO=
layer. The physical thickness of the chrome layer is preferably between
approximately 5 A and 150 A, more preferably between 20 and 70 A and most
preferably between 30 and 60 A. The model reflection is approximately 57% @
approximately 550nm and the transmittance is approximately 21.4%.
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Example 2b:
[0269] Example 2b is similar to Example 2a except with chrome/ruthenium
combination stack coated to obtain a transmittance of 50% when measuring the
back plate only (i.e. prior to incorporation in a mirror element). Addition of
the Ru
layer provides improved stability during curing of the epoxy seal. The ratio
of the
Ru and chrome thickness may be adjusted and there is some design latitude.
Chrome is incorporated primarily to improve the Ru adherence to the ITO. The
Ru has preferred bonding to the Ag or Ag alloy. Other metal or metals may be
placed between the Cr and Ru layers so long as the proper material and
physical
properties are maintained. The reflectance and transmission characteristics
are
depicted in Fig. 49c, lines 4901c and 4902c, respectively.
Example 2c
[0270] Example 2c is similar to Examples 2a and 2b except a display area is
initially
masked and a Cr/Ru (or other pacifier) layer deposited over substantially the
entire third surface subsequent to removing the mask. Transmission and
reflectance results are illustrated in Figs. 49a and 49b, lines 4902a and
4902b,
respectively. The associated advantages are similar to those of Example lc.
Example 3a
[0271] In this Example, the third surface of an EC element is coated
approximately
400A of T102 followed by approximately 180A of ITO followed by approximately
195A of silver and finally with approximately 125A of lzo-Tco.
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[0272] This Example is similar to example la, the TiO2 and ITO are coated
substantially to the edge of the glass and the silver is masked inboard of at
least
the outboard side of the seal and a layer of Indium-Zinc-Oxide (IZO) or other
TCO is subsequently applied over the silver as a protective barrier from the
EC
fluid. Alternatively, the IZOTTCO layer may extend substantially to the edge
of the
glass. In at least one embodiment, the second surface preferably comprises a
HWITO layer. The element reflectivity and transmission is illustrated in Figs.
50a
and 50b, lines 5001a and 5001b, respectively. The model reflection is
approximately 57% @ approximately 550nm and the transmittance is
approximately 36%.
Example 3b
= [0273] Example 3b is configured similar to Example 3a except a
display area is
masked and a stack consisting of Cr/Ru is deposited over substantially the
entire
unmasked area of the third surface. The Cr/Ru opacifying stack may be replaced
by a number of combinations of materials. The reflectance and transmission
results are depicted in figs. 50a and 50b by lines 5002a and 5002b,
respectively.
An advantage in this example is that the metals generally used in the
pacifying
layer may extend substantially to the edge of the glass and provide a bridge
between an associated electrical contact clip and the silver alloy. Related
reflectance and transmission measured data is depicted in Fig. 50c, lines
5001c.
5002c, respectively.
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Example 4a
[0274] In this Example, the third surface of an EC element is coated with
approximately 2100A of ITO followed by approximately 225A of silicon and
finally
with approximately 70A of Ru or Rh.
[0275] All of the layers may be coated substantially to the edge of the
glass.
Alternatively the glass may be processed in sheets and cut subsequently into
singles for incorporation into a mirror element. The Ru or Rh layer may be
replaced by one of several highly reflective metals or alloys. In at least one
embodiment the second surface is preferably coated with HWITO. This example
illustrates the advantage of increased transmittance at different wavelengths.
The
base ITO layer may be replaced having layers with different thicknesses. In
some
embodiments it is preferred that the ITO is an odd multiple of % wave. In
these
cases the reflectance will be slightly enhanced by the ITO. This effect is
diminished somewhat as the ITO gets thicker. The benefit of the thicker ITO is
generally lower sheet resistance which will result in faster element darkening
times. The model reflection is approximately 57% g approximately 550nm'and
the transmittance is approximately 11.4%. The modeled reflectance and
transmission is depicted in Figs. 51a and 51b, respectively. The measured
reflectance and transmission is depicted in Fig. 51c, lines 5101c, 5102c,
respectively.
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=
Example 5
[0276] In this Example, the third surface of an EC element is coated with
approximately 2100A of ITO followed by approximately 50A of chrome followed
by approximately 75A of Ru and finally, optionally, with approximately 77A of
Rh.
[0277] All of the layers may be coated substantially to the edge of the
glass or the
glass may be processed in sheets and subsequently cut into singles for
incorporation into mirror elements. The Ru layer may be replaced by one of
several highly reflective metals or alloys or additional layer(s) may be added
such
as rhodium. The metal layers may be adjusted to obtain a higher or lower
reflectivity/transmittance balance. In at least one embodiment, the second
surface is preferably coated with a HWITO layer. One benefit of the thicker
ITO is
lower sheet resistance which will result in faster element darkening times.
Thicker ITO may increase the third surface stack roughness which may result in
lower reflectivity. This effect is observed when comparing the model
transmission
and reflectance of Figs. 52a and 52b, respectively to the transmission and
reflectance obtained from the. experiments (lines 5201c1 and 5201c2,
respectively of Fig. 52c). The model reflection is approximately 57% a
approximately 550nm and the transmittance is approximately 7.4%.
Example 6a Opacifier laver on third surface
[0278] In this Example an pacifier layer is incorporated into the third
surface
coating stack. A base layer stack of approximately 600A of chrome followed by
approximately 600A of ITO is deposited onto a glass substrate either with a
display area masked during the deposition process of the base layer stack or
the
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base layer stack is subsequently laser deleted in the display area.
Subsequently
layers of approximately 700A of ITO and (approximately 180A of silver-alloy Ag-
X
where X indicates the option for an alloy of Ag) are applied. This approach is
substantially opaque in the viewing area and transflective in the display
area.
[0279] The alloy may be masked relatively far away from the seal to improve
the life
of the element in harsh environments. The model reflection is approximately
52%
@ approximately 550nm and the transmittance is approximately 41%.
Example 6b
[0280] Example 6b is similar to Example 6a. In this Example the third
surface is
initially coated with a base layer stack of approximately 600A of chrome
followed
by approximately 100A of ITO followed by approximately sooA of TiO2 and
finally
by approximately 50A chrome other than in a display area. Substantially the
entire third surface is subsequently coated with approximately 150A of TiO2
followed by approximately 500A of ITO and finally by approximately 180A of
silver-gold alloy. The model reflection is approximately 54% g approximately
550nm and the transmittance is approximately 41%.
[0281] An electrochromic mirror, may have limited reflectance (R) if a high
transmittance (T) level is desired or alternatively limited transmittance if
high
reflectivity is required. This may be described by the relationship R+T+A=1
assuming the absorption (A) remains constant. In some display, or light
sensor,
mirror applications it may be desirable to have a high level of transmitted
light or
(luminance) to adequately view an associated display or transmit adequate
light,
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through the mirror element. Often this results in a mirror with less than
desirable
reflectance.
[02821 Solutions to deal with the mentioned limitations have been discussed
in other
examples herein where the thickness of the metal layer or layers are adequate
for reflectance in the viewing area and are thinner over the display area
only.
Other examples employ layers of differing metals or coating stacks over the
= display area in an attempt to match color and or reflectivities of the
different
regions. Often times an abrupt change in reflectivity or color is
objectionable to
an observer. Referring to Figs. 55 and 56a, for example, the boundary (C)
between the two regions is abrupt. Region (A) has a higher transmittance than
region (B). Boundary (C) delineates the two regions. In Fig. 63 the boundary
at
the start of the transition between high and lower reflectance region is also
abrupt. The slope of the reflectance change per unit distance approaches
infinity
as one transitions between the regions.
[0283] In at least one embodiment a transition in the metal layer thickness
is gradual
in manner. A gradual change in reflectance and or transmittance in a
transition
region is more difficult for the human eye to detect. Two regions still have
distinct
reflectance and transmittance values, however, the boundary between the two
regions is graded. The gradation eliminates the abrupt discontinuity and
replaces
it with a gradual transition. The human eye is not as drawn to the interface
when
it is graded. The grade may be linear, curvilinear or other forms of
transition
illustrated in Figs. 56b-56d. The distance over which the grade takes place
may
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=
vary. In at least one embodiment the distance is a function of the reflectance
difference between the two regions. When the reflectance between the two
regions is relatively low, the distance of the grading may be relatively
short.
When the reflectance difference is large, a longer grade may be desired to
minimize visibility of the transition. In at least one embodiment length of
the
grade is a function of the application and intended use, observers, lighting,
etc.
[0284] In at least one embodiment, shown in Fig. 56e, the transmittance may
be
reduced to near zero in one or more portions. The reflectance may be the same
or different in other cases described herein. The "stealthy" embodiments
described elsewhere herein may be employed to keep the reflectance relatively
constant while allowing the transmittance to be tuned in various portions of
the
mirror element as desired.
[0285] The present invention is not limited to having two or more regions
of constant
transmittance or reflectance. One embodiment is illustrated in Fig. 56f.
Region
has a relatively low transmittance that may be zero. This may be desired if
one of
the design goals is to have region B block the light coming from objects
placed
behind the transflective.coated substrate. The coating stack may have a
gradual
transition from region B via grade C. Region A may have another gradient
within
itself. There are potential benefits to this that will be discussed below.
[0286] In certain applications sufficient length may not be available to
attain a dual
plateau situation. In these cases, it is advantageous to use a continuous
grade
across the area where transflective properties are desired, as illustrated in
Fig.
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57a. The change in reflectance is gradual and the benefits of higher
transmittance are attained; there is no abrupt interface between the regions.
[0287] The grade between the two zones may take on various forms. In the
broadest sense an element may comprise regions of distinct and uniform
transmittance and reflectance. In the examples shown in Figs. 57a-57c, there
are
not regions of constant reflectance and transmittance. These cases have a
gradual and continuous change in optical properties. Advantages to this
approach are illustrated in Fig. 58.
[0288] When a viewer looks at a display through a mirror element or coated
glass
substrate there is a continuum of path lengths and angles in relation to a
closer
portion of the display relative to a far portion of the display. Depending on
the
orientation of the mirror element display, the size of the element, distance
from
the observer, etc., the effective angle relativeof incidence will change. This
results in a different amount of transmittance through the glass at various
portions of a display area. The different amount of transmittance in turn
leads to
a change in brightness of the display. When a constant output of light from
all
regions of the display is desirable the transflective coating may be varied to
take
into account the loss of transmittance arising from the viewing angle and path
difference through the glass. If the effective angle of viewing changes from
about
45 degrees to 60 degrees the transmittance through the glass will vary by
about
6%. Thus, having a graded transflective coating in the region of the display
may
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compensate somewhat for this effect and therefore can result in a more equal
perceived light intensity across the display.
[0289] A graded transition zone may be used for a display such as a rear
camera or
a traditional compass temperature display. In some of the "stealthy" examples
discussed elsewhere herein a so called "split Ag" stack is provided where an
opacifying layer is placed between two Ag layers to help match the appearance
between the areas of transfiective and opaque properties. In another
embodiment of a stealthy display an Ag layer is placed above an opacifying
layer.
Both of these embodiments may benefit from a graded transition between the
regions. The opacifying layer or Ag layer or all layers may be graded. In at
least
one embodiment the opacifying layer may be graded to minimize the abruptness
of the transition between the regions.
[0290] Many methods may be employed for varying the material thickness in
the
layer or layers to create transition regions, including but not limited to,
masking;
motion or speed variations on either the substrate or coating source; magnetic
field variations in a magnetron, or layer reduction techniques such; as ion
beam
etching as described herein or other suitable means.
[0291] Fig. 59 illustrates an example of an electrochromic mirror
construction having
a back plate 5914 of glass, layer 5972 including a sub layer of titanium
dioxide of
approximately 440A and a sub layer of ITO of about 200A, a layer 5978 of
6Au94Ag where one region has a thicknesses of about 140A another region has
a thickness of about 235A, and a third region between the first two regions
where
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the thickness gradually transitions between the two, an electrochromic
fluid/gel
5925 having a thickness of approximately 140 microns, a layer 5928 of
'approximately 1400A of ITO, and a glass plate 5912 of 2.1 mm. The resulting
reflectance of the element ranges from about 63% in the majority of the mirror
to
about 44% in the area in front of the display.
[0292] A similar electrochromic device to that described above was
constructed
where the thickness of layer 5978 was varied in a manner similarly described
and
illustrated in Fig. 57c using a combination of masking techniques and magnetic
manipulation of the deposition source. The method of choice will depend on the
exact features required in the finished element and what processing methods
are
available. Figs. 60 and 61 depict the corresponding reflectance data as a
function
of the position on a mirror. A display is placed behind the region of low
reflectance, high transmittance in this instance.
[0293] Another application of graded transitions is in electrochromic
elements
having a second surface reflector that hides the epoxy seal; a reflectance and
color match between the "ring" and the reflector positioned on the third or
fourth
surfaces may be achieved. The best match is when the reflected intensity of
the
ring matches the reflector reflected intensity. In at least one embodiment the
reflectance of the reflector is further increased while not altering the ring.
This
may occur because of durability, manufacturing or other considerations. A
means
to maintain the match between the reflector and the ring may be obtained when
the reflectance of the reflector is graded as discussed above. When a gradual
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change in reflectance occurs, the reflectance of the reflector may be tuned to
match the reflectance of the ring near the ring and then gradually increase
moving away from the ring. In this manner the reflectance in the center of the
viewing area is relatively high, as seen in Fig. 62.
[0294] In a similar manner the ITO may be gradually changed from the ring
area to
the center of the viewing area to preserve the thickness range necessary for
acceptable color while allowing a relatively high reflectance in the center of
the
element. In this manner, the mirror will darken relatively quickly compared to
the
case where the ITO coating is relatively thin across the element.
[0295] The same concepts may be extended to the metal reflector electrode.
In this
case grading may be employed such that the sheet resistance of the coating
varies gradually with position. This method compliments various bus
configurations and results in faster and more uniform darkening. Fig. 63
illustrates an embodiment of a mirror element in accordance with the state of
the
art prior to the present invention.
[0296] It should be understood that the detail descriptions provided herein
are
intended to allow one of ordinary skill in the art to make and use the best
mode of
various embodiments of the present invention. In no way should these
descriptions be construed as limiting the scope of the appending claims. The
claims, as well as, each individual claim limitation shall be construed as
encompassing all equivalents.
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