Patent ID: 6797659
Filing Date: 2004-09-28
Classification: C03C

Abstract:
An optical glass having optical constants of a refractive index (nd) within a range from 1.75 to 1.85 and Abbe number (&ngr;d) within a range from 35 to 45 comprising, said optical glass being free of Yb2O3 and Y2O3 in mass % on the basis of the oxides:SiO2 + B2O316.5-less than 30%in which SiO2â€ƒâ€‰1-7.5%B2O315.5-25%La2O3â€‰â€‚25-40%ZrO2â€‚1.5-10%Nb2O5â€ƒâ€‰1-15%Ta2O5â€ƒâ€‰1-10%WO3â€ƒâ€‰1-10%ZnO15.5-30%Li2Oâ€‚1.8-5%Sb2O3â€‰â€‚0-1%said optical glass having a transition point (Tg) within a range from 500Â° C. to 590Â° C. and a yield point (At) within a range from 530Â° C. to 630Â° C., and being free from devitrification in a devitrification test conducted under a condition of 950Â° C./2 hours.