Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Reexamination Certificate
2000-06-15
2002-03-19
Group, Karl (Department: 1755)
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
C501S066000, C501S067000, C501S070000, C313S025000, C313S636000
Reexamination Certificate
active
06358873
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a glass suitable for manufacturing high temperature lamp envelopes such as tungsten-halogen lamp envelopes, as well as glass suitable for manufacturing high temperature glass filters and glass filter lenses, such as those used with tungsten-halogen lamps. More specifically, the present invention relates to Nd
2
O
3
containing glass compositions that provide tungsten-halogen lamps with a higher correlated color temperature (CCT), thereby making the emitted light whiter, which can aid illuminated surroundings contrast.
BACKGROUND OF THE INVENTION
In the automotive industry there is a continued need for automobile headlights which provide better illumination of the surrounding environment. In recent years tungsten-halogen lamps have gained popularity over conventional incandescent sealed beam lamps due to several advantages which include: a whiter light emitted; a smaller size lamp produces an equivalent or even greater quantity of light; the intensity of the illumination remains virtually constant over the life of the lamp; and, the service life is significantly longer. In spite of these advantages, however, tungsten-halogen lamps can be improved especially with respect to illumination and contrast performance. This may be achieved, for example, by manufacturing the lamp envelopes out of glass that gives the tungsten-halogen lamp a higher CCT.
Because tungsten-halogen lamps operate at high temperatures, generally between about 500-700° C., suitable glasses for these lamp envelopes must be thermally stable (resist devitrification) and withstand thermal deformation at high temperatures. Additionally, the glass must permit a seal to the molybdenum leads while maintaining integrity through lamp operation. The glass must also be able to be economically formed into good quality tubing or pressed into filters and lens filter shapes.
Hence, much research has been concentrated upon alkaline earth aluminosilicate glasses because such are suitable for mass production of tungsten-halogen lamp envelopes, while concurrently manifesting the properties necessary for lamp operation.
U.S. Pat. No. 3,496,401 (Dumbaugh) describes the basic mechanism underlying the operation of tungsten-halogen incandescent lamps with specific reference to tungsten-iodide lamps. U.S. Pat. No. 3,496,401 discloses alkaline earth metal aluminosilicate glass compositions suitable as envelopes for such lamps, wherein the glass compositions consist essentially, expressed in weight percent on the oxide basis, of 10-25% alkaline earth metal oxide, 13-25% Al
2
O
3
, 55-70% SiO
2
, 0-10% B
2
O
3
, and less than 0.1% alkali metal oxide.
U.S. Pat. No. 3,978,362 (Dumbaugh et al.) discloses glasses designed for tungsten-bromine lamp envelopes displaying strain points greater than 700° C., liquidus viscosities of at least 100,000 poises, operable melting temperature no higher than 1550° C., liquidus temperature less than 1200° C., and coefficients of thermal expansion between 48-55×10
−7
/° C., the glass composition consisting essentially, in weight percent, of 14-21% CaO, 0-5% MgO, 0-7% BaO, the total CaO+MgO+BaO being at least 19%, 13-16% Al
2
O
3
, 0-10% SrO and/or La
2
O
3
and 58-63% SiO
2
.
U.S. Pat. No. 4,060,423 (Thomas) described another group of glass compositions particularly designed for use envelopes for tungsten-halogen lamps. Those glasses are characterized as exhibiting a liquidus temperature no greater than 1250° C., a strain point of at least 725° C., and a coefficient of expansion of about 42-48×10
−7
/° C. The compositions therefor consist essentially, expressed in terms of weight percent on the oxide basis, of 55-68% SiO
2
, 15-18% Al
2
O
3
, 6-13% CaO, and 6-16% BaO, wherein the weight ratio Al
2
O
3
:CaO+BaO is about 0.6:1 to 1:1.
U. Pat. No. 4,255,198 (Danielson et al.) discloses glasses suitable for sealing to molybdenum metal, in tungsten-halogen lamps, and having a strain point in excess of 730° C., a liquidus temperature of at least 40,000 poises, axial compression at room temperature not exceeding 350 PPM and axial compression or tension not exceeding 150 PPM at 500° C., a coefficient of thermal expansion between 43-48×10
−7
/° C. The glasses have a composition consisting essentially, in terms of weight percent on the oxide basis, of: 62-64% SiO
2
, 14-16% Al
2
O
3
, 10-13% CaO, and 7-9% SrO.
U.S. Pat. No. 4,302,250 (Danielson) discloses glasses for use as envelopes for tungsten-halogen lamps displaying strain points higher than 750° C., liquidus viscosities of at least 40,000 poises, liquidus temperatures below 1300° C. and coefficients of thermal expansion between 48-55×10
−7
/° C., consisting essentially, in weight percent, of 11-14% CaO, 2-6.5% SrO+BaO, consisting essentially of 0-4% SrO and 0-5% BaO, 16.5-18.5% Al
2
O
3
, and 64-68% SiO
2
.
U.S. Pat. No. 4,605,632 (Elmer) discloses a high silica glass for the production of envelopes for tungsten-halogen lamps, consisting essentially, by weight, of 1-2.5% Al
2
O
3
, 0.25-1% CaO, 0.1-0.25 Na
2
O and/or K
2
O, 2.5-3.5% B
2
O
3
, 0.15-0.3% F., and the remainder SiO
2
.
U.S. Pat. No. 4,394,453 (Dumbaugh) describes a glass composition suitable for tungsten-halogen lamps, consisting essentially, expressed in weight percent on the oxide basis, of 60±1.5% SiO
2
, 17.0±1% Al
2
O
3
, 5.0±0.8% B
2
O
3
, 11.4±0.8% CaO, and 7.5±0.8% MgO. The physical properties of the disclosed glasses are a strain point of at least 670° C., a coefficient of thermal expansion of 42-45×10
−7
/° C., a liquidus temperature below 1100° C., and a liquidus viscosity greater than 20,000 poises.
U.S. Pat. No. 4,409,337 (Dumbaugh) discloses glasses for tungsten-halogen lamps which exhibit a strain point in excess of 665° C., a liquidus temperature no higher than 1125° C., a liquidus viscosity of at least 50,000 poises, and a coefficient of thermal expansion between about 42-46×10
−7
/° C., the composition consisting essentially, in terms of weight percent on the oxide basis, of 56-59% SiO
2
, 16-17% Al
2
O
3
, 4.5-5.25% B
2
O
3
, 7.5-9.25% CaO, 5.5-6.25% MgO, and 5-9% MgO, wherein the sum of SiO
2
+Al
2
O
3
, will not exceed about 75%, the weight ratio SiO
2
:Al
2
O
3
is maintained between about 3.1-3.7 and the weight ratio CaO:MgO is held between about 1.2-2.0.
U.S. Pat. No. 4,693,987 (Danielson) discloses a glass for use as envelopes for tungsten-halogen lamps especially where molybdenum metal wires are used, the glass having strain points between 718°-725° C., liquidus viscosities of at least 50,000 poises, liquidus temperatures below 1145-1180° C. and coefficients of thermal expansion between 46.2-50.1×10
−7
/° C., consisting essentially, in weight percent, of 10.7-11.9% CaO, 9.1-13.1% BaO, 14.6-15.1% Al
2
O
3
, and 60.5-62.4% SiO
2
.
Correlated Color Temperature (CCT), also referred to herein as lamp color temperature, is used in the lighting industry to describe and compare the color appearance of lamps. CCT refers to the temperature of a blackbody radiator whose perceived color most closely resembles that of a given light source. As the temperature of a blackbody is raised, its color changes from a dull red to bright red, then orange, yellow, white and finally blue. Thus, lower temperatures imply longer wavelengths and “warmer” colors; higher temperatures imply shorter wavelengths and “cooler” colors. In particular, typical automotive tungsten-halogen lamps are warm in color and show CCT ranging from 2800-3200K; a value given by the fact that tungsten-halogen lamps produce much of their light output in the yellow to red wavelength region of the spectrum between 560-700 nm and less in the blue to green wavelength region of the spectrum between 400-560 nm. One method of raising the CCT in tungsten-halogen lamps is to selectively absorb a small percentage of visible radiation in the longer wavelength region (yellow to red) while fully transmitting in the shorter wavelength region (bl
Corning Incorporatedc
Gheorghiu Anca C.
Group Karl
Schaeberle Timothy M.
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