| 摘要 |
880,323. Optical glass compositions. LEITZ G.m.b.H., ERNST. Sept. 3, 1959 [Sept. 19, 1958], No. 30100/59. Class 56. An optical crown glass, smelted from a mix free of any significant amount of beryllium and containing not more than 12% by weight of lanthanum, barium or aluminium oxides, comprises at least one oxide of calcium or magnesium, at least one oxide of zinc or cadmium and boric acid in the following proportions: 12.5 to 36% by weight of CaO and/or MgO; 10 to 42% by weight of ZnO and/or CdO; 19 to 50 % by weight of B 2 O 3 , the balance, if any, consisting of other compatable constituents. The bivalent oxides are preferably supplied to the mix at least in part as metaborates, and may be in part as silicates, there being not more than 20% by weight of silicic acid in the mix. In addition the mix may contain up to 12% by weight of zirconium oxide or of strontium oxide, and small amounts of alkaline oxides, and arsenic acid or nitrate. |
