High index ophthalmic glasses
US4211569A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 9, 1979 |
| Grant date | Jul 8, 1980 |
| Priority date | — |
| Expiry date | Mar 9, 1999 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S501/90
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.