High index ophthalmic glasses

Details High index ophthalmic glasses High index ophthalmic glasses

1975-11-07

1976-08-10

Douglas, Winston A.

Compositions: coating or plastic

Coating or plastic compositions

Metal-depositing composition or substrate-sensitizing...

106 47Q, C03C 310, C03C 330, C03C 308

Patent

active

039739767

ABSTRACT:
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, photochromic ophthalmic lenses. The glasses demonstrate refractive indices between about 1.58-1.71, softening points between about 630.degree.-675.degree.C., strain points between about 450.degree.-500.degree.C., good chemical durability, and coefficients of thermal expansion (25.degree.-300.degree.C.) between about 45-60 .times. 10.sup.-.sup.7 /.degree.C. The glasses consist essentially, by weight on the oxide basis, of about 3-7% B.sub.2 O.sub.3, 3-11% Al.sub.2 O.sub.3, 30-60% PbO, and 27-55% SiO.sub.2.

REFERENCES:
patent: 3303399 (1967-02-01), Hoogendoorn et al.
patent: 3369961 (1968-02-01), Dalton et al.
patent: 3653933 (1972-04-01), Tsunekawa
patent: 3801336 (1974-04-01), Upton
patent: 3888692 (1975-06-01), Kuwayama

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