Patent ID: 9527769
Filing Date: 2016-12-27
CPC Classification: C03C

Claim Text:
1. A photochromic borosilicate glass composition comprising (in weight %) 66-76% SiO 2 , 0-8% Al 2 O 3 , 10-18% B 2 O 3 , 0-4% Li 2 O, 0-12% Na 2 O, 0-12% K 2 O, 1-1.5% Ag, 1.5-2.5% Cl − and 0.01-0.06% of a summed amount of CuO and NiO, wherein the glass composition is bleachable upon exposure to ultraviolet irradiation from a stable state color or shade to a lighter color or shade.