Photochromic boro-silicate glass
US4102693A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 31, 1977 |
| Grant date | Jul 25, 1978 |
| Priority date | — |
| Expiry date | Jan 31, 1997 |
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 silver halide crystals dispersed throughout the glass and are free from barium, comprise, in weight percentages: ______________________________________ SiO.sub.2 31 to 59% B.sub.2 O.sub.3 18 to 28% Al.sub.2 O.sub.3 8 to 20% R.sub.2 O 6 to 16% ______________________________________ Where 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.