US Patent 7582579 Phosphate optical glass

The object of the present invention is to provide an optical glass which has optical constants such as a refractive index of from 1.45 to 1.65 and an Abbe number of at least 65 and which is yet excellent in chemical durability. A phosphate optical glass comprising, as glass components by mass %, from 73 to 85 of P2O5, from 14 to 26 of Al2O3, from 1 to 12 of K2O+Li2O, from 0 to 12 of SiO2, from 0 to 12 of B2O3, from 0 to 12 of Na2O, from 0 to 12 of Y2O3, from 0 to 12 of La2O3, from 0 to 12 of MgO+CaO+SrO+BaO, from 0 to 10 of ZrO2+TiO2+Gd2O3, from 0 to 10 of Ta2O5+GeO2+Ga2O3+Nb2O5+WO3+TeO2, from 0 to 2 of Sb2O3, and from 0 to 12 of ZnO+PbO.