| 摘要 |
PROBLEM TO BE SOLVED: To provide optical glass which has a high index of refraction and low dispersibility and can give a preform for press forming having excellent high temperature formability and suitable for precision press forming. SOLUTION: The optical glass contains, as essential components, by mol, 25-45% B<SB>2</SB>O<SB>3</SB>, 2-20% SiO<SB>2</SB>, 5-22% La<SB>2</SB>O<SB>3</SB>, 2-20% Gd<SB>2</SB>O<SB>3</SB>, 15-29% ZnO, 1-10% Li<SB>2</SB>O and 0.5-8% ZrO<SB>2</SB>, with the proviso that the molar ratio of B<SB>2</SB>O<SB>3</SB>to SiO<SB>2</SB>is 2-5.5, the total content of La<SB>2</SB>O<SB>3</SB>and Gd<SB>2</SB>O<SB>3</SB>is 12-24%, and the total content of ZnO and Li<SB>2</SB>O is 25-30%, and has an index of refraction (nd) of 1.75-1.85 and an Abbe's number (μd) of 40 to 55. Alternatively, the optical glass contains, as essential components, B<SB>2</SB>O<SB>3</SB>, SiO<SB>2</SB>, La<SB>2</SB>O<SB>3</SB>, Gd<SB>2</SB>O<SB>3</SB>, ZnO, Li<SB>2</SB>O, and ZrO<SB>2</SB>, and has viscosity at a liquid phase temperature of≥6 dPa s, a glass transition temperature (Tg) of≤600°C, an index of refraction (nd) of 1.75 to 1.85 and an Abbe's number (μd) of 40-55. COPYRIGHT: (C)2007,JPO&INPIT
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