Photochromic boro-silicate glass
US4290813A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 18, 1978 |
| Grant date | Sep 22, 1981 |
| Priority date | — |
| Expiry date | May 18, 1998 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S501/903
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
Fast-response photochromic boro-silicate glasses which have a half-fading time of not more than 145 secs, have silver halide crystals dispersed throughout the glass and are free from barium, comprise, in weight percentages: PA1 SiO.sub.2 --31 to 59% PA1 B.sub.2 O.sub.3 --18 to 28% PA1 Al.sub.2 O.sub.3 --8 to 20% PA1 R.sub.2 O--6 to 16% wherein R.sub.2 O represents one or more of Li.sub.2 O, Na.sub.2 O and K.sub.2 O in amounts within the ranges 0 to 3% Li.sub.2 O, 0 to 8% Na.sub.2 O and 0 to 16% K.sub.2 O, and where the content of silver, expressed as Ag.sub.2 O, lies within the range 0.05 to 0.4% by weight, while the content of halide lies within the range 0.13 to 1% by weight of the glass. Further optional constituents are MgO (up to 2.6%) and P.sub.2 O.sub.5 (up to 12%). Refractive index n.sub.D can be corrected to the standard ophthalmic value of 1.523 by additions of ZrO.sub.2, TiO.sub.2 and/or PbO.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.