High index ophthalmic glasses

Details High index ophthalmic glasses High index ophthalmic glasses

1979-03-09

1980-07-08

Vertiz, O. R.

Compositions: coating or plastic

Coating or plastic compositions

Metal-depositing composition or substrate-sensitizing...

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

Patent

active

042115698

ABSTRACT:
This invention is concerned with the production of glasses suitable for use as segments in multifocal ophthalmic lenses and, especially, as segments in multifocal photochromic ophthalmic lenses. The glasses have refractive indices between about 1.58-1.71, softening points between 620.degree.-645.degree. C., strain points between 445.degree.-480.degree. C., coefficients of thermal expansion (0.degree.-300.degree. C.) between 60-66.times.10.sup.-7 /.degree.C., excellent chemical durability, and consist essentially, in weight percent on the oxide basis, of 0-2% Li.sub.2 O and/or 0-3% Na.sub.2 O, 1-4% Li.sub.2 O+Na.sub.2 O, 4-9% BaO, 25-50% PbO, 4-8% B.sub.2 O.sub.3, 4-7% Al.sub.2 O.sub.3, 30-50% SiO.sub.2, and 0.5-3% TiO.sub.2.

REFERENCES:
patent: 3973976 (1976-08-01), Boyd

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