Patent ID: 6753281
Filing Date: 2004-06-22
Classification: C03C

Abstract:
An optical glass consisting of:optical constants which are a refractive index (nd) in a range of 1.70 to 1.75 and an Abbe number (&ngr;d) in a range of 45.0 to 54.0; a glass transformation temperature (Tg) in a range of 500 to 580Â° C.; more than 5 to 15 mass % of SiO2; 20 to less than 30 mass % of B2O3; a total amount of SiO2+B2O3 being more than 25 to 40 mass %; more than 21 to less than 30 mass % of La2O3; more than 5 to 15 mass % of Y2O3; 0 to less than 10 mass % of Gd2O3; 1 to 8 mass % of ZrO2; 0.1 to 5 mass % of Nb2O5; more than 5 to 12 mass % of Ta2O5; a total amount of ZrO2+Nb2O5+Ta2O5 being 7 to 20 mass %; 0 to 10 mass % of ZnO; 0 to 10 mass % of CaO; 0 to 5 mass % of SrO; 0 to 10 mass % of BaO; a total amount of ZnO+CaO+SrO+BaO being 5 to 15 mass %; 1 to 8 mass % of Li2O; 0 to 1 mass % of Sb2O3; and 0 to 1 mass % of As2O3; wherein devitrification is not generated when the optical glass is kept at a temperature of 920Â° C. for two hours.