Patent ID: 7501369
Filing Date: 2009-03-10
Classification: C03C,Y10S

Abstract:
1. An optical glass which is a borosilicate glass comprising at least one selected from La 2 O 3 , Gd 2 O 3 , Y 2 O 3 or Yb 2 O 3 and at least one selected from ZrO 2 , Ta 2 O 5 or Nb 2 O 5 , and 0 to 1% by weight WO 3 , wherein the weight ratio of the total content of La 2 O 3 , Gd 2 O 3 , Y 2 O 3 and Yb 2 O 3 to the total content of SiO 2 and B 2 O 3 is from 2 to 4, the weight ratio of the total content of ZrO 2 , Ta 2 O 5 and Nb 2 O 5 to the total content of SiO 2 and B 2 O 3 is from 1 to 2, and the total content of SiO 2 , B 2 O 3 , GeO 2 , ZnO, La 2 O 3 , Gd 2 O 3 , Y 2 O 3 , Yb 2 O 3 , ZrO 2 and Ta 2 O 5 to over 95% by weight, and the weight ratio of ZnO/(SiO 2 +B 2 O 3 ) is more than 0 but less than 2, said optical glass having a refractive index nd of at least 1.875, an Abbe's number νd of at least 39.5 and a glass transition point Tg of 700° C. or lower.