| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical glass for precision press molding hardly causing the quality degradation due to the generation of a decomposed layer such as cloudiness and scorching on the surface and to provide a preform for precision press molding and a glass element consisting of the optical glass. SOLUTION: In the optical glass containing B<SB>2</SB>O<SB>3</SB>, La<SB>2</SB>O<SB>3</SB>and ZnO and used for a glass raw material for the precision press molding, the optical glass contains, by mol%, 20-60% B<SB>2</SB>O<SB>3</SB>, 0-20% SiO<SB>2</SB>, 22-42% ZnO, 5-24% La<SB>2</SB>O<SB>3</SB>, 0-20% Gd<SB>2</SB>O<SB>3</SB>, (wherein, the sum amount of La<SB>2</SB>O<SB>3</SB>and Gd<SB>2</SB>O<SB>3</SB>is 10-24%), 0-10% ZrO<SB>2</SB>, 0-10% Ta<SB>2</SB>O<SB>5</SB>, 0-10% WO<SB>3</SB>, 0-10% Nb<SB>2</SB>O<SB>5</SB>, 0-10% TiO<SB>2</SB>, 0-10% Bi<SB>2</SB>O<SB>3</SB>, 0-10% GeO<SB>2</SB>, 0-10% Ga<SB>2</SB>O<SB>3</SB>, 0-10% Al<SB>2</SB>O<SB>3</SB>, 0-10% BaO, 0-10% Y<SB>2</SB>O<SB>3</SB>and 0-10% Yb<SB>2</SB>O<SB>3</SB>, and also the glass has an Abbe number (ν<SB>d</SB>) of≥40 and does not substantially contain lithium, and the preform for the precision press molding and the glass element are composed of the optical glass. COPYRIGHT: (C)2006,JPO&NCIPI
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