| 摘要 |
PROBLEM TO BE SOLVED: To provide optical glass having high thermal stability while keeping desired refractive index (n<SB>d</SB>) and Abbe's number (ν<SB>d</SB>) and a preform for precision press molding and an optical element, which are obtained by using the optical glass. SOLUTION: The optical glass includes 10.0-70.0 mass% Bi<SB>2</SB>O<SB>3</SB>component, 1.0-30.0 mass% GeO<SB>2</SB>component and 1.0-40.0 mass% La<SB>2</SB>O<SB>3</SB>component in terms of oxides on the basis of the total mass of the optical glass. The optical element is obtained by subjecting the optical glass to precision press molding. Since the optical glass includes the Bi<SB>2</SB>O<SB>3</SB>component, the glass transition point (Tg) becomes much lower in comparison with the crystallization starting temperature (Tx) to make higher the thermal durability of the optical glass. Since the optical glass includes all of the Bi<SB>2</SB>O<SB>3</SB>component, the GeO<SB>2</SB>component and the La<SB>2</SB>O<SB>3</SB>component by the contents, the refractive index/light transmissivity of the optical glass can be made higher/improved. COPYRIGHT: (C)2010,JPO&INPIT
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