Compositions: ceramic – Ceramic compositions – Glass compositions – compositions containing glass other than...
Reexamination Certificate
1999-12-22
2001-09-04
Sample, David R (Department: 1755)
Compositions: ceramic
Ceramic compositions
Glass compositions, compositions containing glass other than...
C501S066000, C501S068000, C501S069000, C501S070000, C313S636000, C313S025000
Reexamination Certificate
active
06284686
ABSTRACT:
TECHNICAL FIELD
This invention relates to borosilicate glass compositions and lamps containing same. More particularly, it relates to ultraviolet (UV) absorbing, tungsten-sealing, borosilicate glass compositions for use in the manufacture of electric arc discharge lamps.
BACKGROUND ART
UV absorbing borosilicate glass compositions for electric arc discharge lamps such as high intensity discharge (HID) lamps, typically contain either lead and arsenic oxides or lead and cerium oxides. One conventional lead and arsenic containing borosilicate glass is SG772. SG772 has physical properties which enables it be used for both outer envelope and lamp stem applications. However, both lead and arsenic are toxic materials and it would be very advantageous to be able to manufacture acceptable glasses without using these materials. Arsenic oxide is generally employed in glass compositions as a fining agent for glasses which are difficult to fine (i.e., removal of bubbles). Ceria (>0.15 wt. %) has been used as an acceptable substitute for arsenic oxide for fining glasses, and providing UV absorption. However, ceria-containing borosilicate glasses will solarize under UV irradiation when lead oxide is not in the composition.
Solarization produces light absorbing color centers that darken the outer envelope and seriously reduce light output.
Lead and arsenic free borosilicate glass compositions have been developed to exclude these toxic components. One such lead and arsenic free borosilicate glass (designated SG773) is described in commonly assigned, copending U.S. application Ser. No. 09/085,989, filed May 5, 1998 which is incorporated herein by reference. SG773 glass is typically manufactured in a glass melter equipped with a bubbler system. Bubblers improve convection, and control the flow of glass through the melter. Large bubbles are introduced at the bottom of the melter which rise to the surface. The convective mixing which develops with bubbling brings cold bottom glass up to the melt surface for additional melting. This increases the average glass temperature and melting rate. Without bubbling, the radiative heat transfer in SG773 glass must be enhanced to make up for the decrease in convective mixing. Thus, it would be an advantage to make this glass more suitable for use in glass melters which are not equipped with bubblers.
SUMMARY OF THE INVENTION
It is an object of the invention to obviate the disadvantages of the prior art.
It is another object of the invention to provide a lead and arsenic free borosilicate glass for use in the outer envelopes and stems of electric discharge lamps.
It is still another object of the invention to provide a more suitable lead and arsenic free borosilicate glass composition for use in glass melters not equipped with bubblers.
In accordance with one object of the invention, there is provided a lead and arsenic free borosilicate glass having a composition containing 13.5 to 16.8 weight percent B
2
O
3
, 2.0 to 4.0 weight percent Al
2
O
3
, 2.0 to 5.0 weight percent Na
2
O, 1.3 to 4.0 weight percent K
2
O, from 0 to 0.30 weight percent Li
2
O, 0 to 2.0 weight percent CaO, 0 to 2.0 weight percent MgO, 0.04 to 0.17 weight percent Fe
2
O
3
, 0.005 to 0.12 weight percent CeO
2
, 0.005 to 0.30 weight percent TiO
2
, and the balance SiO
2
, and wherein the sum of the amounts of Fe
2
O
3
and CeO
2
comprise no greater than 0.19 weight percent, the sum of CaO and MgO comprise no greater than 2.0 weight percent, and the sum of the amounts of Na
2
O, K
2
O and Li
2
O comprise no greater than 7.5 weight percent.
In accordance with another object of the invention, there is provided an electric arc discharge lamp having an arc discharge light source which emits both visible and ultraviolet radiation, the light source being enclosed within an outer envelope comprising a lead and arsenic free borosilicate glass having a composition containing 13.5 to 16.8 weight percent B
2
O
3
, 2.0 to 4.0 weight percent Al
2
O
3
, 2.0 to 5.0 weight percent Na
2
O, 1.3 to 4.0 weight percent K
2
O, from 0 to 0.30 weight percent Li
2
O, 0 to 2.0 weight percent CaO, 0 to 2.0 weight percent MgO, 0.04 to 0.17 weight percent Fe
2
O
3
, 0.005 to 0.12 weight percent CeO
2
, 0.005 to 0.30 weight percent TiO
2
, and the balance SiO
2
, and wherein the sum of the amounts of Fe
2
O
3
and CeO
2
comprise no greater than 0.19 weight percent, the sum of CaO and MgO comprise no greater than 2.0 weight percent, and the sum of the amounts of Na
2
O, K
2
O and Li
2
O comprise no greater than 7.5 weight percent.
In accordance with still another object of the invention, the outer envelope and the stem of the electric discharge lamp are made of the same lead and arsenic free borosilicate glass.
REFERENCES:
patent: 3531677 (1970-09-01), Loughridge
patent: 3984252 (1976-10-01), Kiefer
patent: 4806268 (1989-02-01), Kiss et al.
patent: 4925814 (1990-05-01), Fine
patent: 5182237 (1993-01-01), Brix
patent: 5557171 (1996-09-01), Marlor et al.
patent: 5599753 (1997-02-01), Watzke et al.
patent: 5849649 (1998-12-01), Poole
patent: 5885915 (1999-03-01), Bako et al.
patent: 6118216 (2000-09-01), Marlor
patent: 0 588 000 A (1994-03-01), None
patent: 0603933A1 (1994-06-01), None
patent: 0699636A1 (1996-03-01), None
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patent: 0 749 150 A (1996-12-01), None
patent: 06-056467 (1994-03-01), None
patent: 08-012369 (1996-01-01), None
JP 08 012369, Patent Abstracts of Japan, vol. 96, No. 5, (May 31, 1996).
Abstract, RU 2035414 C (May 20, 1995).
Clark Robert F.
Osram Sylvania Inc.
Sample David R
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