Very fast fading photochromic glass
US4407966A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 16, 1982 |
| Grant date | Oct 4, 1983 |
| Priority date | — |
| Expiry date | Sep 16, 2002 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC03C3/093
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
The present invention is directed to the preparation of photochromic glasses exhibiting a darkened luminous transmittance at 40.degree. C. below 35% and a five-minute fading rate at 40.degree. C. of at least 40 units of transmittance and a darkened transmittance at 25.degree. C. below 25% and a five-minute fading rate at 25.degree. C. of at least 35 units of transmittance. The glasses consist essentially, by weight, of: ______________________________________ SiO.sub.2 56-60 Al.sub.2 O.sub.3 6-9 B.sub.2 O.sub.3 18-21 Li.sub.2 O >2.5-3.5 Na.sub.2 O 0.5-2.5 K.sub.2 O 5-7 ZrO.sub.2 3.75-5 PbO 0.1-0.15 Ag >0.15-0.25 Cl 0.2-0.35 Br 0.075-0.15 CuO 0.004-0.02 CeO.sub.2 0-0.5 ______________________________________ wherein the levels of Ag, Br, Cl, and CuO represent values as analyzed in the glass.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.