Patent ID: 7598189

Claim:
Phosphate optical glass having an Abbé number, νd, of greater than 59 and less than 70, comprising the following components, denoted as mass percentages: P 2 O 5 : 18 to 70 percent, where 70 percent is excluded; B 2 O 3 : 0 to 34 percent, where 0 percent is excluded; Al 2 O 3 : 0 to 8 percent; Li 2 O: 0 to 20 percent, where 0 percent is excluded; Na 2 O: 0 to 18 percent; K 2 O: 0 to 15 percent; MgO: 0 to 25 percent, where 0 percent is excluded; CaO: 0 to 18 percent, where MgO+CaO>4 percent; SrO: 0 to 20 percent; BaO: 0 to 40 percent, where SrO+BaO>1 percent and BaO/B 2 O 3 , as a mass percentage ratio, is 0 to 15; ZnO: 0 to 14 percent, where the ratio of ΣR″O/ΣR′O as a mass percentage ratio is less than 23, where ΣR″O═MgO+CaO+SrO+BaO+ZnO and ΣR′0═Li 2 O+Na 2 O+K 2 O; Gd 2 O 3 : 0 to 18 percent; Sb 2 O 3 : 0 to 1 percent; wherein any other component besides those listed above has a content lower than the content of B 2 O 3 as well as lower than the content of Li 2 .