Patent ID: 6187702
Filing Date: 2001-02-13
Classification: C03C,Y10S

Abstract:
Ophthalmic and optical glasses having the following composition in weight percent:SiO.sub.2 4.5-9.5% B.sub.2 O.sub.3 10-19.5% Al.sub.2 O.sub.3 0-3% GeO.sub.2 0-5% La.sub.2 O.sub.3 18-less than 23% Gd.sub.2 O.sub.3 0.3-less than 2% TiO.sub.2 5.5-13.5% ZrO.sub.2 0-7.5% Nb.sub.2 O.sub.5 15-21% Ta.sub.2 O.sub.5 0-1.5% WO.sub.3 0.3-5%with the proviso that (Ta.sub.2 O.sub.5 +WO.sub.3)/B.sub.2 O.sub.3 is 0.5 or below in the ratio in terms of weightZnO 2.1-10% MgO 0-5% CaO 7-12.5% SrO 0-5% BaO 0-4% Li.sub.2 O + Na.sub.2 O + K.sub.2 O .gtoreq.0.1% in which Li.sub.2 O 0-1% Na.sub.2 O 0-1% K.sub.2 O 0-1% As.sub.2 O.sub.3 0-0.5% Sb.sub.2 O.sub.3 0-0.5%and having a specific gravity of 4.1 or below.