Patent ID: 6037283
Filing Date: 2000-03-14
Classification: C03C

Abstract:
An ophthalmic lens of photochromic glass, having a plus power, having a center thickness greater than 2 mm., and having a composition consisting essentially of: SiO.sub.2 54-58% Ag -0.20-0.33% B.sub.2 O.sub.3 18-22% Cl 0.30-0.50% Al.sub.2 O.sub.3 7-8% Br 0.04-0.14% Li.sub.2 O 3.75-4.5% CuO 0.007-0.012% Na.sub.2 O 0-1% PbO 0-0.08% TiO.sub.2 0-2% Sb.sub.2 O.sub.3 0-0.20% ZrO.sub.2 2-4.5% K.sub.2 O 5.5-7.5%  and wherein the mole ratio of Li.sub.2 O:Na.sub.2 O is =>9:1.