Patent US3973976A successfully refreshed from Google Patents.
US3973976A
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High index ophthalmic glasses
Assignee: Corning Glass Works
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Filing: 1975-11-07
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Granted: 1976-08-10
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Expires: 1995-11-07
Abstract
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°-675°C., strain points between about 450°-500°C., good chemical durability, and coefficients of thermal expansion (25°-300°C.) between about 45-60 × 10 - 7 /°C. The glasses consist essentially, by weight on the oxide basis, of about 3-7% B 2 O 3 , 3-11% Al 2 O 3 , 30-60% PbO, and 27-55% SiO 2 .
Inventors
- 👤 David C. Boyd
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 08:14
CPC Classifications
C; C03; C03C; C03C3/00; C03C3/04; C03C3/076; C03C3/102; C03C3/062; C03C3/07; C03C3/072; C03C3/12
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
97 words
An ophthalmic glass exhibiting a refractive index between about 1.58-1.71, a softening point between about 630°-675°C., a strain point between about 450°-500°C., a coefficient of thermal expansion (25°-300°C.) between about 45-60 × 10 - 7 /°C., and no surface imperfection with a weight loss of no more than about 0.03 mg/cm 2 after immersion into a 10% by weight aqueous solution of HCl for 10 minutes at 25°C. consisting essentially, by weight on the oxide basis, of about 3-7% B 2 O 3 , 3-11% Al 2 O 3 , 30-60% PbO, and 27-55% SiO 2 .
Claim 2
Dependent Claim
97 words
An ophthalmic glass exhibiting a refractive index between about 1.58-1.71, a softening point between about 630°-675°C., a strain point between about 450°-500°C., a coefficient of thermal expansion (25°-300°C.) between about 45-60 × 10 - 7 /°C., and no surface imperfection with a weight loss of no more than about 0.03 mg/cm 2 after immersion into a 10% by weight aqueous solution of HCl for 10 minutes at 25°C. consisting essentially, by weight on the oxide basis, of about 3-7% B 2 O 3 , 3-11% Al 2 O 3 , 30-60% PbO, and 27-55% SiO 2 .
Claim 3
Dependent Claim
52 words
A glass according to claim 1 also containing up to 6% La 2 O 3 , up to 10% BaO, up to 3% Li 2 O and/or Na 2 O, and up to 3% TiO 2 , the sum of all such additions constituting no more than 10% of the total composition.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-08-10 | 1980-02-09 | 1980-08-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-08-10 | 1984-02-09 | 1984-08-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-08-10 | 1988-02-09 | 1988-08-10 | $7700.00 | Window Closed / Lapsed |