OPTICAL GLASS AND PREFORMS FOR PRECISION PRESS MOLDING AND OPTICAL ELEMENTS MADE BY USING THE GLASS

摘要

The invention aims at providing an optical glass for precision pressing which has optical characteristics of high refractive index and low dispersion, low molding temperature, high devitrification resistance, excellent moldability, and a small specific gravity. An optical glass characterized by comprising by mass in term of oxide B2O3: 10 to 20%, SiO2: 0.5 to 12%, La2O3: 25 to 50%, Gd2O3: 0 to 20%, Y2O3: 0 to 20%, with the proviso that La2O3 + Gd2O3 + Y2O3: 35 to 60%, ZnO: 5 to 20%, Li2O: 0.2 to 3%, ZrO2: 0 to 0.5%, Ta2O5: 3 to 18%, and WO3: 3 to 20% and exhibiting optical constants of refractive index nd of 1.84 to 1.86 and Abbe value ?d of 37 to 42 and a glass transition temperature (Tg) of 630°C or below.