Glass envelopes for tungsten-halogen lamps
AssigneeCorning Glasss Works
InventorPaul S. Danielson
Life of this patent
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Abstract
The instant invention is concerned with glass envelopes for tungsten-halogen lamps. The glasses exhibit a strain point higher than 750.degree. C., a coefficient of thermal expansion (0.degree.-300.degree. C.) between 42-44.times.10.sup.-7 /.degree.C., a liquidus temperature below 1300.degree. C., a viscosity at the liquidus of at least 40,000 poises, and consist essentially, in weight percent on the oxide basis, of 64-68% SiO.sub.2, 11-14% CaO, 16.5-18.5% Al.sub.2 O.sub.3, and 2-6.5% SrO+BaO consisting of 0-4% SrO and 0-5% BaO. The preferred glasses demonstrate a viscosity of less than 1000 poises at temperatures no higher than 1520.degree. C. and contain at least 3% total of SrO+BaO, those components being present in a molar ratio SrO:BaO ranging from 2:1-1:2.
Claims2
A glass composition suitable as an envelope for a tungsten-halogen lamp and for sealing to molybdenum metal, said glass exhibiting a strain point higher than 750.degree. C., a coefficient of thermal expansion (0.degree.-300.degree. C.) between 42-44.times.10.sup.31 7 /.degree.C., a liquidus temperature below 1300.degree. C., a viscosity at the liquidus of at least 40,000 poises, a viscosity of less than 1000 poises at temperatures no higher than 1520.degree. C., and consisting essentially, expressed in terms of weight percent on the oxide basis, of 64-68% SiO.sub.2, 11-14% CaO, 16.5-18.5% Al.sub.2 O.sub.3, and 3-6.5% SrO+BaO, consisting of 0-4% SrO and 0-5% BaO, those latter two components being present in a molar ratio SrO:BaO ranging from 2:1-1:2.
Dependencies are inferred from the claim text.