| 摘要 |
A high-refractivity low-dispersion optical glass that gives press-molding preforms excellent in high-temperature shapability and suitable for precision press-molding, including an optical glass comprising B2O3, La2O3, Gd2O3 and ZnO as essential components, substantially containing none of lead and fluorine, having a refractive index (nd) of 1.72 to 1.83, an Abbe's number ( nu d) of 45 to 55 and a glass transition temperature (Tg) of 630 DEG C or lower and having a viscosity of at least 0.6 Pa.s at its liquidus temperature, and an optical glass comprising, by mol%, 45 to 65 % of B2O3, 5 to 22 % of La2O3, 1 to 20 % of Gd2O3, provided that the total content of La2O3 and Gd2O3 is 14 to 30 %, 5 to 30 % of ZnO, 0 to 10 % of SiO2, 0 to 6.5 % of ZrO2 and 0 to 1 % of Sb2O3, substantially containing none of lead and fluorine, and having a refractive index (nd) of 1.72 to 1.83 and an Abbe's number ( nu d) of 45 to 55. |
