| 摘要 |
PROBLEM TO BE SOLVED: To provide a phosphate optical glass suitable for precise press molding having a refractive index of 1.57 to 1.62, an Abbe number of 65 to 70 and a small thermal expansion coefficient.SOLUTION: There is provided a phosphate optical glass which contains 32 to 50 mol% of PO, 3 to 20 mol% of BO, 12 to 25 mol% of BaO, 0 to 20 mol% of SrO, 0 to 8 mol% of AlO, more than 0 mol% and 15 mol% or less of LiO, more than 0 mol% and 11 mol% or less of MgO, 0 to 15 mol% of CaO, 0 to 5 mol% of GdO, 0 to 5 mol% of LaOand 0 to 0.5 mol% of SbOand no ZnO. There can be provided a phosphate optical glass having a thermal expansion coefficient at 20 to 300°C of less than 110×10/°C and a transition temperature of less than 520°C by rationally distributing the content of each component. |
