Patent ID: 7700507
Filing Date: 2010-04-20
Classification: C03C

Abstract:
1. An optical glass comprising B 2 O 3 and SiO 2 as essential components and having a B 2 O 3 and SiO 2 total content (B 2 O 3 +SiO 2 ) of 45 to 70 by mol % and an SiO 2 content/B 2 O 3 content molar ratio (SiO 2 /B 2 O 3 ) of from 0.1 to 0.5, the optical glass further comprising, by mol %, 5 to 15% of La 2 O 3 , 0.1 to 8% of Gd 2 O 3 , provided that the total content of La 2 O 3 and Gd 2 O 3 is 8% or more, 0 to 10% of Y 2 O 3 , 3 to 18% of Li 2 O, provided that the molar ratio of the content of Li 2 O to the total content of B 2 O 3 and SiO 2 [Li 2 O/(B 2 O 3 +SiO 2 )] is over 0 but not more than 0.2, 0.1 to 15% of ZnO, 2 to 20% of CaO, 0 to 5% of BaO, provided that the content of BaO is smaller than the content of ZnO, 0 to 5% of SrO, 0 to 5% of MgO, provided that the molar ratio of the total content of MgO, CaO, SrO and BaO to the total content of B 2 O 3 and SiO 2 [(MgO+CaO+SrO+BaO)/(B 2 O 3 +SiO 2 )] is from 0.1 to 0.4, and 0 to 5% of ZrO 2 , and having a refractive index (nd) of 1.71603 or less, the refractive index and an Abbe's number (νd) which satisfy the equation (1),