Claims
- 1. An ophthalmic glass exhibiting a refractive index between about 1.58-1.71, a softening point between about 630.degree.-675.degree.C., a strain point between about 450.degree.-500.degree.C., a coefficient of thermal expansion (25.degree.-300.degree.C.) between about 45-60 .times. 10.sup.-.sup.7 /.degree.C., and no surface imperfection with a weight loss of no more than about 0.03 mg/cm.sup.2 after immersion into a 10% by weight aqueous solution of HCl for 10 minutes at 25.degree.C. consisting 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.
- 2. A glass according to claim 1 also containing up to 6% La.sub.2 O.sub.3, up to 10% BaO, up to 3% Li.sub.2 O and/or Na.sub.2 O, and up to 3% TiO.sub.2, the sum of all such additions constituting no more than 10% of the total composition.
REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of my co-pending application Ser. No. 475,665, filed June 3, 1974, now abandoned.
US Referenced Citations (5)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
475665 |
Jun 1974 |
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