Patent ID: 7560405

Claim:
An optical glass for precision press molding which comprises, by mol %, 15 to 40% of B 2 O 3 , 3 to 25% of SiO 2 , 12 to 32% of a total of La 2 O 3 and Gd 2 O 3 , 2 to 35% of ZnO, 0.5 to 15% of Li 2 O, 0.5 to 15% of ZrO 2 , 0.2 to 10% of Ta 2 O 5 , 0 to 12% of WO 3 , 0 to 7% of Y 2 O 3 , and 0 to 1.65% of Yb 2 O 3 , substantially containing none of PbO and Lu 2 O 3 , having a B 2 O 3 , SiO 2 , La 2 O 3 , Gd 2 O 3 , ZnO, Li 2 O, ZrO 2 , Ta 2 O 5 , WO 3 , Y 2 O 3 and Yb 2 O 3 total content of 95 mol % or more, having a glass transition temperature of 630° C. or lower, and having a refractive index nd and an Abbe's number νd which satisfy all of the following relational expressions, 1.80<nd≦1.90 35<νd≦50, and nd≧ 2.025−(0.005 ×νd ).