Patent ID: 8741795

Claim:
An optical glass comprising, by mol %, 0.1 to 40% of SiO 2 , 10 to 50% of B 2 O 3 , 0 to 10% of total of Li 2 O, Na 2 O and K 2 O, 0 to 10% of total of MgO, CaO, SrO and BaO, 0.5 to 22% of ZnO, 5 to 50% of La 2 O 3 , 0.1 to 25% of Gd 2 O 3 , 0.1 to 20% of Y 2 O 3 , 0 to 20% of Yb 2 O 3 , 0 to 25% of ZrO 2 , 0 to 25% of TiO 2 , 0 to 20% of Nb 2 O 5 , 0 to 7% of Ta 2 O 5 , over 0.1% but not more than 20% of WO 3 , 0 to less than 3% of GeO 2 , 0 to 10% of Bi 2 O 3 , and 0 to 10% of Al 2 O 3 , the mass ratio of the content of SiO 2 to the content of B 2 O 3 , SiO 2 /B 2 O 3 , being 1 or less, the optical glass having a refractive index nd of 1.86 to 1.95, an Abbe's number νd of (2.36−nd)/0.014 or more but less than 38, and a glass transition temperature of equal to or greater than 640° C.