High strength ophthalmic lens
US4012131A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 20, 1975 |
| Grant date | Mar 15, 1977 |
| Priority date | — |
| Expiry date | Aug 20, 1995 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S501/903
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
An ophthalmic glass lens can be prepared by exposing an alkali metal silicate glass to an ion exchange process in which the glass is chemically strengthened by an exchange of potassium ions for sodium ions in the surface layer of the lens at a temperature either above or below the strain point of the glass. The glasses prepared are essentially free of alumina, have adequate strength and substantially increased depth of pentration of the neutral zone even when up to about 6 percent lime is utilized in the preparation of the glass. The effect of lime as a diffusion-retarding agent during the ion exchange process can be overcome (1) by use of an appropriate amount of zinc or magnesium oxide or mixtures thereof so as to maintain an adequate rate of diffusion during ion exchange or (2) by preparation of the glass essentially free of alumina.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.