Note: Descriptions are shown in the official language in which they were submitted.
` 2155~72
s50413-shf
GR 94P5539 US
IN THE UNITED STATES PATENT AND TRADEMARK OFFICE
"METAL-HALIDE HIGH-PRESSURE DISCHARGE LAMP"
Reference to related patents, assigned to the assignee of the
present application, the disclosures of which are hereby
incorporated by reference:
U.S. 5,138,227, Heider et al.
U.S. 5,323,085, Genz.
* * * * * * * *
FIELD OF THE INVENTION.
The present invention relates to metal-halide high-pressure
discharge lamps, and more particularly to such lamps which are
suitable for general service illumination as well as for higher
power use, and which provide color temperatures between about
4000 K and 7000 K, with a color rendition index Ra equal to or
above 90, and which have an extended lifetime of, on the average,
at least about 1000 hours.
BACKGROUND.
Metal-halide high-pressure discharge lamps have the
advantage that they have good to excellent color rendition, that
is, color rendition indices Ra of 90 and above, with color
temperatures in the range of between about 4000 K and 7000 K.
The light efficiency, i.e. light output per power consumed is
high, and light yield values of over 70 lm/W are obtainable.
These lamps, thus, are suitable for general service illumination
- 2156472
use, as well as for special illumination applications. Such
special illumination applications are projection technology,
highlighting and special effects illuminations, stage
illumination, and illumination for photographic, film and
television studios. The electrical power ratings can vary
widely, between about 35 W to 5000 W. For general service use,
typical power ratings are between about 150 W and 400 W. Special
effects and special applications require, usually, higher power
lamps, typically of 575 W and above.
Usually, the lamps have discharge vessels which are double-
ended, that is, are sealed at two ends by meanSof pinch or press
seals or melt seals. They are usually surrounded by an outer
envelope or outer bulb. Single-ended lamps are also known and
sometimes used.
Lamps for special effects, and special illumination
applications, are frequently used with optical reflectors. To
obtain high efficiency of the system lamp - reflector, short-arc
lengths are desirable. The electrode spacings, between which the
arc is established, thus may be only a few millimeters, typically
less than 10 mm. The power ratings, thus, result in very high
arc power, typically between about 50 W and lO0 W per millimeter
of arc length. The high arc power per mm results in high wall
loading on the vessel confining the arc, which may lead to
premature devitrification of the discharge vessel. Frequently,
the lifetime of special-purpose high-power lamps may be only a
few lO0 hours.
General service illumination requires a long lifetime,
typically 6000 hours. The power ratings per arc length of
general service lamps are usually much less than for special-
effect lamps, typically between about 10 W and 20 W permillimeter.
The referenced U.S. Patent 5,138,227, Heider et al., the
disclosure of which is hereby incorporated by reference,
215~47~
describes a metal-halide high-pressure discharge lamp without an
outer bulb, useful for optical applications, but also for outdoor
illumination. The power ratings are between about 1000 W and
4000 W, with wall loadings in the order of between about 30 W and
60 W per cm2 of the wall surface of the discharge vessel.
Specific arc power is about 67 W/ ~. The discharge vessel
retains a fill of argon (Ar) and mercury (Hg) as well as, per
cubic centimeter of discharge volume, halides of rare-earth
metals. The relative quantities, per cm3, are also given in mol.
The rare-earth metal halides are 1 ~mol dysprosium bromide
(DyBr3) and 0.5 ~mol thulium bromide (TmBr3); further, per cubic
centimeter, the fill contains 1 ~mol thallium bromide (TlBr),
2 ~mol cesium bromide (CsBr) and 0.5 ~mol thorium iodide (ThI4).
The thorium (Th) can be replaced by hafnium (Hf). A lamp with
such a fill provides light at a color temperature of 5600 K with
a color rendition index Ra of 92. A lifetime of about 2000 hours
is disclosed.
U.S. Patent 5,323,085, Genz, the disclosure of which is
hereby incorporated by reference, describes a metal-halide high-
pressure discharge lamp for optical use. Typical power ratings
are 400 W, 575 W and 4000 W, with arc power of between about 95 W
and 200 W per m~. gThe fill includes, besides Ar, Hg and Cs, the
halogens iodine (I) and bromine (Br) as well as the metals
hafnium (Hf) or zirconium (Zr). With a fill of this kind, color
temperatures of between 5200 K and 6200 K can be obtained, with
color rendition indices of Ra = 95 and 97, respectively.
Lamps of this type, particularly at the higher power
ratings, have a limited lifetime of only about 300 h. Another
fill system can be used, utilizing cobalt (Co) and at least one
of: dysprosium (Dy) and gadolinium (Gd), or both, dysprosium and
gadolinium. The lifetime of such a lamp can be extended, but
only up to about 500 hours.
.
.
- 2156~72
THE INVENTION.
It is an object to improye the lifetime of metal-halide
high-pressure discharge lamps, which have a color temperature of
between 4000 K and 7000 K, a color rendition index of Ra of 90 or
S more, and a lifetime of at least 1000 hours, and preferably
without using thulium (Tm), which is rare and expensive.
Briefly, the lamp which otherwise can be of conventional
construction, contains a fill which, besides having at least one
inert gas and mercury, includes halides formed of thallium (Tl),
cesium (Cs), and at least one of: hafnium (Hf) and zirconium
(Zr), or both hafnium and zirconium; and at least one of the
rare-earth metals dysprosium (Dy) and gadolinium (Gd), or both,
Dy and Gd.
The hafnium may, in whole or in part, be replaced by the
zirconium; also, both, or only one, of the rare-earth metals,
dysprosium and gadolinium, may be present. The halogen for the
formation of the halide is preferably iodine or bromine, or both.
The inert gas, for example argon, is included in the fill of up
to about 40 kPa; it is used to ignite the arc or the discharge.
The desired discharge arc voltage is determined by the mercury.
Typically, between about 4 mg and 25 mg per cubic centimeter
volume of the discharge vessel is used, to provide arc voltages
between 120 V and 95 V.
The fill in accordance with the present invention has an
advantage over the fill of the Heider et al Patent S,138,227 in
that it does not use thulium (Tm), while having essentially as
good a color rendition index (Ra equal to or above 90), while
providing a lifetime of about 1500 hours and above. In
comparison to the lamp described in the referenced Patent
5,323,085, Genz, this results in at least doubling of the
lifetime with light efficiency of about 80 lm/W. These
advantages are obtained by targeting an increase of the hafnium
or zirconium portions of the fill. This increase surprisingly
- 2156~72
prevents premature devitrification and thus increases the
lifetime of the lamp while, additionally, and unexpectedly,
improving the color rendition index.
The mol relationship between the hafnium and zirconium
portion of the fill on the one hand and the sum of the portion of
the fill of the rare earth parts, dysprosium and/or gadolinium on
the other, is at least 0.35. Lamps having high specific arc
power, typically above 60 W per mm arc length, which result in
very high wall loadings, preferably use such a mol relationship
in a range of between 0.5 and 1.5. With respect to the other
fill components, thallium (Tl) and cesium (Cs), the mol
relationship as follows have been found suitable:
Hf (Zr, respectively) : Tl at least ~ . For high wall
loadings, preferably in a range of from about 1 and 2.5.
Hf (Zr, respectively) : Cs at least 0.35. For high wall
loadings, preferably in a range of from about between 0.5 and 1.
The mol relationship between the fill component
Hf (Zr, respectively) on the one hand, and the sum of the rare
earth portions, that is, Dy and/or Gd, as well as Tl and Cs, on
the other hand, is at least 0.14, and for high wall loadings,
preferably in the range of between about 0.2 and 0.5.
With respect to the volume of the discharge vessel, per
cubic centimeter, the quantity of the fill, in mol, of Hf or Zr,
respectively, is in the region between about 0.005 ~mol and
35 ~mol, preferably in the range between about 0.05 ~mol and
5 ~mol. The fill quantity, per cubic centimeter of volume of the
discharge vessel, for Cs, is up to about 30 ~mol; for Tl up to
about 15 ~mol; for Dy up to about 30 ~mol, and for Gd up to about
0.6 ~mol.
In a preferred form of the invention, the discharge vessel
is located within an outer envelope or bulb which, for
particularly good color rendition, is evacuated. The lifetime
can be increased if the outer bulb contains a gas fill, for
- 215647~
example up to about 70 kPa nitrogen (N2) or up to about 40 kPa
carbon dioxide (CO2). Use of carbon dioxide, which is cheap,
slightly decreases the color rendition index.
DRAWINGS:
Fig. 1 is a highly schematic side view of a double-based,
double-ended high-pressure discharge lamp, having a power rating
of 150 ~;
Fig. 2 is a highly schematic side view of a single-based
high-pressure discharge lamp having a double-ended discharge
vessel, with a power rating of 400 W; and
Fig.3is a highly schematic side view, partly in section, of
a single-based high-pressure discharge lamp retaining a double-
ended discharge vessel, with a power rating of 575 W.
DETAILED DESCRIPTION.
The invention will first be described using a double-ended,
double-based 150 W high-pressure discharge lamp 1 as an example.
As shown in Fig. 1, the discharge lamp 1 has a double-sided pinch
sealed discharge vessel 2 made of quartz glass, which is
surrounded by a double-based evacuated outer envelope 3.
Electrodes 4, 5, spaced 10 mm from each other, are retained by
molybdenum foils 6, 7, melt-sealed gas-tightly in the discharge
vessel 2. Current supply leads 8, 9 connected electrically with
molybdenum foils 10, 11 within the outer envelope 3 are
connected, via short connecting stubs, to bases of ceramic base
elements 12, 13, forming a ceramic base of the type R7s. The
pinch seal of the outer envelope 3 additionally retains a getter
14, secured to a small metal plate and retained by a small wire
which is unconnected and carries no voltage, melt-sealed in the
pinch seal of the outer envelope 3. The ends 15, 16 of the
discharge vessel 2 are coated with a heat reflecting coating.
The volume of the discharge vessel is about 1.8 cm3.
The fill retains, basically, 23 mg mercury and argon as a
starting gas, with a cold fill pressure of 14 kPa. In addition,
2156472
the discharge vessel 2 retains the metal halides shown in Table
la. The resulting relationships in mol between Hf and Zr,
respectively, on the-one hand, and Cs, Tl and Dy, as well as the
sum of the portions Cs,`Tl and Dy on the othe~, are shown in
Table lb. The specific-arc power and arc voltage are 15 W per mm
arc length, and 105 ~. The light values obtained are listed in
Table lc. Two illustrative different fills are shown in Tables
la and lb. The light values obtained in Table lc are comparable.
21~6~17~
Components in mg Fill I Fill II
Csl 0~6 0.6
Tll 0;42 0.42
DyI3 1.23 1~23
HfI4 0.6
ZrI4 - 0.52
able la: Two metal-halide compositions 'for the lamp
of Fig. 1
Mol relationships Fill I Fill II
Hf( or Zr):Cs 0.38 0.43
Hf( or Zr):TI 0.69 0.79
Hf( or Zr):Dy 0.39 0.44
Hf (or Zr):(Cs,TI~Dy~ 0~15 0~17
able lb: Mol relationships of Hf and Zr, resp.,
with respect to other main components of
the metal-halide compositions of Table la
Li'ght flux in lm 11200
Light'yield in lm/W 75
Color temperature in K 5200
Ra 95
Rg 90 -
Lifetime ~ h 6000
Table lc: Light values obtained with the fills
of Table la
21~6472
Embodiment of Fiq. 2:
A 400 W lamp 201 is shown schematically, which is surrounded
by a C~lni~rii6ca~revsainug~eed-based envelope 203 of hard glass. The
discharge vessel 2 is double-ended and pinch-sealed. One end of
the hard-glass envelope 203 is formed with a rounded cap 17, the
other end is constructed in form of a screw base 12. A mount 18
retains the discharge vessel 2 within the envelope 203 in axially
aligned position. The mount 18, as well known, includes two
supply leads. One supply lead 18a is coupled to the proximate
- lead 8 from the discharge vessel 2. The other connection from
the base 12 includes a solid metal support wire 18b which extends
along the discharge vessel 2 to the distal current supply lead 9.
A guide element 15a is located close to the proximate end 15 of
the discharge vessel. The guide element ~ preferably is a
punched sheet-metal structure, suitably supported, for example on
the solid supply lead 18b. The distal end of the supply lead 18b
is bent in the vicinity of the cap 17 in a partial circle 18c, to
bear against the inside of the hard glass of the envelope 203.
The ends 15, 16 of the discharge vessel 2 are coated with heat-
reflective coatings.
The volume of the discharge vessel 2 is approximately
14.5 cm3. The electrodes, not shown, within the discharge vessel
2 are spaced from each other by 30 mm. The arc power is 15 W/mm
of arc length; the arc voltage is l20 V.
The fill retains 60 mg mercury and 8 kPa argon as a base
gas. In addition, the discharge vessel 2 contains the metal
halides shown in Table 2a. The resulting relationships, in mol,
between Hf on the one hand, and Cs, Tl and Dy, as well as the sum
of the components of Cs, Tl and Dy, on the other, are shown in
Table 2b. The light values are shown in Table 2c.
~15647
Components in mg
CsI 2.27
TII 1.58
DyI3 4~65
~IfI4 2.27
Table 2a: Metal-halide composition of
the lamp of Fig. 2
Mol relationships
Hf:Cs 0.38
Hf:TI 0.69
Hf:Dy 0.39
Hf:(Cs,Tl,Dy) 0. 15
Table 2b:. Mol relationships of Hf to other main components
of the metal-halide composition of Table 2a
.Light flux in lm 32400
Light yield in lm/W 81
.Color temperature in K 5200
Ra 96
Rg 91
Lifetime ~ h . 6000
Table 2c: Light values obtained with the fill
of TabIe 2a
10
21S~472
Embodiment of Fiq. 3:
The lamp 301, schematically illustrated in Fig. 3, is a
575 W lamp, which has a double-ended sealed discharge vessel 302
of quartz glass surrounded by a cylindrical single-based
evacuated envelope 303. One end of the envelope 303 is formed
with a rounded cap 317; the other end includes a pinch seal which
is cemented in a two-pin base 19. The electrodes 4, 5 are spaced
7 mm from each other and are gas-tightly melt-sealed in the
discharge vessel 302 by molybdenum foils~ The current supply
leads 8, 9 are connected with first ends of two solid massive
supply wires*~nd furthcr ~hort currcnt ^upply lc~ds conncct th~
~cnno~tion load~ 20, 21 with electrical terminals 24, 25 in the
base 19. A mica plate 26, located between the terminals 24, 25,
additionally proves electrical insulation.
The volume of the discharge vessel is about 3.5 cm3. The
electrode spacing of the electrodes 4, 5 is about 7 mm. Arc
power is 82 W per mm arc length, and arc voltage is 95 V.
The discharge vessel 302 retains 60 mm mercury and 22 kPa Ar
as a base gas. Additionally, the discharge vessel 302 includes
the metal halides shown in Table 3a, which illustrates two
possible fills having effectively the same light output. The
respective mol relationships of Hf to Cs and, Tl, as well as the
mol relationships of Hf to the sum of the rare-earth (RE)
components Dy and Gd as well as the sum of the components of Cs
and Tl and the rare-earth components RE, Dy and/or Gd are shown
in Table 3b. In Table 3b, the rare-earth components Dy and/or Gd
are commonly identified by the abbreviation RE.
* 321, 320 whose second ends are connected via sealing foils 22, 23 in the
pinch seal of the outer envelope 303 and further short current supply leads
11
2156~7~7
components in mg Fill I Fill ~
CsI 0.8 0.88
TII 0.4 0.39
DyI3 1.5 1.~6
GdI3 - 0~16
HfBr4 - 1.16
Htl4 1.3
HgI2 - 1~63
HgB r2 3.6 0.52
Table 3a: Two metal-halide compositions of the
lamp of Fig. 3
II
Hf:Cs 0.62 0.69
Hf:TI 1.57 1.98
Hf:~RE ` 0.69 0.89
Hf:(Cs,Tl,RE) 0.27 0.32
Table 3b: Mol relationships of Hf to other main
components of the metal-halide
compositions of Table 3a
Fill I Fill
.Light flux in lm 49000 47500
Light yield in lm/W 85 83
Color temperature in K5600 6000
Ra 92 go
Rg >50 >50
Lifetime in h 1500 1500
Table 3c: Light values obtained with the fills
of Table 3a
