Preparation of photochromic gradient lenses of cosmetically improved color
US4080051A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 18, 1976 |
| Grant date | Mar 21, 1978 |
| Priority date | — |
| Expiry date | Mar 18, 1996 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S501/903
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
Glass lenses, or lens blanks, containing all the ingredients necessary to produce phototropic, or photochromic, behavior, are treated in a conventional production furnace to produce a locally variable heat treatment, wherein at least one portion thereof is raised to a temperature exceeding the glass strain point but not the softening point, and other portions are heated to variable temperature decreasing from the strain point. The treatment causes development of phototropic, or photochromic, behavior only in those portions of the lenses, or lens blanks, exposed to the temperature above the strain point. The lenses resulting are characterized by trichromatic coefficients, x=0.306 and y=0.307, in the unactivated state and x=0.324 and y=0.321, in an activated state and including a small but effective quantity of cobalt oxide.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.