OPTICAL GLASS, PREFORM FOR PRECISION PRESS MOLDING USING THE OPTICAL GLASS, AND OPTICAL ELEMENT USING THE OPTICAL GLASS

摘要

Disclosed is an optical glass comprising, by mass based on the following oxides, B2O3: 18 to 30%, SiO2: 3 to 12%, La2O3: 15 to 30%, Gd2O3: 20.5 to 30%, ZnO: 20 to 30%, Li2O: 0.1 to 2%, and ZrO2: 0.1 to 5% as indispensable components, the total contents of ZnO and Li2O being 20 to 30%. The optical glass has a refractive index (nd) of 1.73 to 1.76, an Abbe number (νd) of 48 to 51, and a glass transition temperature (Tg) of 580°C or below. By virtue of the above constitution, the optical glass has optical properties of a high refractive index and a low dispersibility, is less likely to cause devitrification, has excellent preform moldability, has a low molding temperature, and has excellent press moldability.