| 摘要 |
PROBLEM TO BE SOLVED: To provide glass having no defects characteristic of the conventional glass, having excellent transmissibility and a high refractive index in which variation is reduced, and also having low specific gravity. SOLUTION: The lead-free and arsenic-free optical lanthanum flint glass having a refractive index satisfying 1.73n<SB>d</SB>≤1.82 and an Abbe's number satisfying 43≤v<SB>d</SB>≤53, and also having satisfactory chemical resistance and stability to crystallization is produced with the composition of, by weight, 0.1 to 5.5% SiO<SB>2</SB>, 27 to 35% B<SB>2</SB>O<SB>3</SB>, 42 to 48% La<SB>2</SB>O<SB>3</SB>. 0 to 5% BaO, 0.5 to 5% ZnO, 6 to 12% Y<SB>2</SB>O<SB>3</SB>, 0 to 4% TiO<SB>2</SB>, 4 to 10% ZrO<SB>2</SB>, 0 to 5% Nb<SB>2</SB>O<SB>5</SB>and 0 to 5% WO<SB>3</SB>. COPYRIGHT: (C)2005,JPO&NCIPI
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