Patent ID: 7655585

Claim:
An optical glass that is for use as a glass material for precision press-molding and comprises B 2 O 3 , ZnO, La 2 O 3 and ZrO 2 , the optical glass comprising, by mol %, 0 to less than 0.5% of Li 2 O, 20 to 50% of B 2 O 3 , 0 to 20% of SiO 2 , 22 to 42% of ZnO, 5 to 24% of La 2 O 3 , 0 to 20% of Gd 2 O 3 , provided that the total content of La 2 O 3 and Gd 2 O 3 is 10 to 24%, 0.5 to 10% of ZrO 2 , 0 to 15% of Ta 2 O 5 , 0 to 20 % of WO 3 , 0 to 15% of Nb 2 O 5 , 0 to 20% of TiO 2 , 0 to 10% of Bi 2 O 3 , 0 to 10% of GeO 2 , 0 to 10% of Ga 2 O 3 , 0 to 10% of Al 2 O 3 , 0 to 10% of BaO, 0 to 10% of Y 2 O 3 and 0 to 10% of Yb 2 O 3 , and the glass is essentially free of tellurium, the optical glass having an Abbe's number (νd) of at least 35 but less than 40.