Fast fading photochromic glass
US4746633A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 10, 1986 |
| Grant date | May 24, 1988 |
| Priority date | — |
| Expiry date | Feb 10, 2006 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC03C3/118
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
This invention is directed to transparent photochromic glasses that can darken to a comfort range, i.e., between about 35-60%, or to a dark range, i.e., below 35%, depending upon glass composition, and will exhibit a faded transmittance after five minutes' removal from actinic radiation higher than 70%. The base compositions of the glasses consist essentially, in weight percent, of about ______________________________________ SiO.sub.2 46-60 MgO 0-3.5 B.sub.2 O.sub.3 16-28 CaO 0-6 Al.sub.2 O.sub.3 4-11 SrO 0-6 ZrO.sub.2 2-6 BaO 0-6 Al.sub.2 O.sub.3 + ZrO.sub.2 6-13 MgO + CaO + SrO + BaO 0-7 Li.sub.2 O 2-5 P.sub.2 O.sub.5 0-5 Na.sub.2 O 0-4 TiO.sub.2 0-3 K.sub.2 O 2.5-9 ______________________________________ For a comfort glass the photochromic elements consist essentially, as analyzed, of ______________________________________ Ag 0.13-0.18 Br 0.08-0.14 Cl 0.16-0.34 CuO 0.001-0.004 ______________________________________ For a dark glass the photochromic elements consist essentially, as analyzed, of ______________________________________ Ag 0.15-0.3 Br 0.07-0.14 Cl 0.2-0.45 CuO 0.004-0.016 ______________________________________
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.