| 摘要 |
A method for manufacturing optical glass and prefoam for fine press forming is provided to secure a low temperature softening property and excellent glass stability. Optical glass comprises 40-75mole% of B2O3, 0-15mole% of SiO2, 1-10mole% of Li2O, 0-15mole% of ZnO, 5-22mole% of La2O3, 3-20mole% of Gd2O3, 0-1mole% of Y2O3, 0-10mole% of ZrO2, 0-5mole% of MgO, 0-5mole% of CaO and 0-5mole% of SrO. The optical glass has less than 0.365 of a mole ratio represented by (La2O3+Gd2O3+Y2O3)/(B2O3+SiO2) and 0-0.2 of a mole ratio represented by Y2O3/(La2O3+Gd2O3+Y2O3). The total contents of B2O3, SiO2, Li2O, ZnO, La2O3, Gd2O3, ZrO2, MgO, CaO and SrO are 97mole% or greater.
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