| 摘要 |
PROBLEM TO BE SOLVED: To obtain an optical glass for mold pressing having desired optical coefficients, a low glass transition point (Tg) and a lower devitrifying temperature than the melt temperature for providing the viscosity suitable for molding a preform material. SOLUTION: This optical glass for mold pressing comprises a lanthanum borosilicate-based glass having optical coefficients of 1.65-1.73 refractive index and 50-60 Abbe's number, the Tg within the range of 480-580 deg.C and a devitrifying temperature below the melt temperature when the viscosityηis longη=2.5. The optical glass comprises a composition containing 10-20 wt.% of SiO2, 23-35 wt.% of B2O3, 10-21 wt.% of La2O3, 5-15 wt.% of Y2O3, 0-10 wt.% of Gd2O3, 1-10 wt.% of Ta2O5, 0-8 wt.% of ZrO2, 5-20 wt.% of CaO, 0-10 wt.% of ZnO, 0-20 wt.% of SrO, 0-20 wt.% of BaO, 2.5-8 wt.% of Li2O and 0-1 wt.% of Sb2O3.
|
