Colored photochromic glasses and method
US4537612A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 17, 1984 |
| Grant date | Aug 27, 1985 |
| Priority date | — |
| Expiry date | Sep 17, 2004 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC03C23/007
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
This invention is directed to a method for modifying the coloration produced in a silver halide-containing photochromic glass when heat treating the glass at a temperature not exceeding 450.degree. C. under reducing conditions. The method comprises subjecting such a glass having a base composition which contains at least 1% by weight Li.sub.2 O, at least 2% by weight Na.sub.2 O, and at least 6% by weight Li.sub.2 O+Na.sub.2 O+K.sub.2 O to an ion exchange reaction, wherein lithium ions, and potassium ions, when the latter are present in the composition, in the glass surface are exchanged with sodium ions from an external source, prior to the reduction heat treatment.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.