| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical glass which is excellent in low temperature softening properties even if it has a refractive index (nd) of 1.75 to 1.87 and an Abbe's number (νd) of 30 to 45, and does not comprise Ta<SB>2</SB>O<SB>5</SB>, and which can be obtained at a reduced cost. SOLUTION: The optical glass contains, by mol, 30 to 45% B<SB>2</SB>O<SB>3</SB>, 2 to 15% SiO<SB>2</SB>, 10 to 20% La<SB>2</SB>O<SB>3</SB>, 1 to 10% TiO<SB>2</SB>, 10 to 30% ZnO, 2 to 15% Li<SB>2</SB>O, >0 to 10% WO<SB>3</SB>, 0 to 15% Nb<SB>2</SB>O<SB>5</SB>and 0 to 10% ZrO<SB>2</SB>, wherein the total content of the components mentioned above is >95%. The optical glass has a refractive index (nd) within a range of 1.75 to 1.87, and an Abbe's number (νd) within a range of 30 to 45. A preform for precision press forming and an optical element are formed of the optical glass. A method for producing the preform for precision press forming comprises forming the preform for precision press forming, formed of the optical glass. A method for producing the optical element uses the preform for precision press forming. COPYRIGHT: (C)2007,JPO&INPIT
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