Alumino:phosphate glass with rapid photochromic response - obtd. by addn. of silver halide, chromic oxide, antimony tri:oxide and arsenic tri:oxide

摘要

The glass contains dispersed silver halide crystals; a chromium oxide imparting a green colour; and an oxide of Sb and/or As. When the glass is transformed from its fully darkened state to its completely light state, at least 25% of the total variation in optical density (TVOD) occurs within 16 seconds. The pref. glass contains by wt. 8.5-22% SiO2, 13-36.5% Al2O3, 7.5-33.5% P2O5, 7-28% B2O3, 7-20.5% R20, where R is Na, K, or Li. The amt. of Li2O is max. 5%; and the glass contains min. 16% SiO2 when the B2O3 is below 8%. The photochromic addns. added to 100% of the above are:- 0.05% min. Ag20; 0.2-2% Cl + Br; plus Cr2O3 and Sb2O3 and/or As 2O3.