Patent ID: 7468338

Claim:
An optical glass comprising, by mol %, 45 to 65% of B 2 O 3 , 5 to 22% of La 2 O 3 , 1 to 20% of Gd 2 O 3 , provided that the total content of La 2 O 3 and Gd 2 O 3 is 14 to 30%, 5 to 30% of ZnO, 0 to 10% of SiO 2 , 0 to 6.5% of ZrO 2 and 0 to 1% of Sb 2 O 3 , substantially containing none of lead and fluorine, and having a refractive index (nd) of 1.72 to 1.83, an Abbe's number (νd) of 45 to 55, a glass transition temperature (Tg) of 630° C. or lower and having a viscosity of at least 0.6 Pa·s at its liquidus temperature.