High index ophthalmic glasses

Details High index ophthalmic glasses High index ophthalmic glasses

C - Chemistry, Metallurgy

03

C

261/17, 88/42

C03C 3/10 (1980.01)

Patent

CA 1041558

HIGH INDEX OPHTHALMIC GLASSES Abstract of the Disclosure This invention relates to soft, low expansion, high durability, high refractive index glasses especially suitable for the production of segments or buttons for multifocal ophthalmic lenses and, in particular, photo- chromic ophthalmic lenses. The glasses demonstrate refrac- tive indices between about 1.58-1.71, softening points between about 630°-675°C., strain points between about 450°-500°C., good chemical durability, and coefficients of thermal expansion (25°-300°C.) between about 45-60 x 10-7/°C. The glasses consist essentially, by weight on the oxide basis, of about 3-7% B2O3, 3-8% Al2O3, 30-60% PbO, and 30-55% SiO2.

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