| 摘要 |
An optical glass which has an Abbe's number (&ngr;d) of 50 to 59, has the property of not easily reacting with a press mold, a low-temperature softening property, excellent glass stability and high refractivity, and is suitable for precision press-molding. The optical glass comprising B2O3 and SiO2 as essential components and having a B2O3 and SiO2 total content (B2O3+SiO2) of 45 to 70 by mol % and an SiO2 content/B2O3 content molar ratio (SiO2/B2O3) of from 0.1 to 0.5, the optical glass further comprising, by mol %, 5 to 15% of La2O3, 0.1 to 8% of Gd2O3, provided that the total content of La2O3 and Gd2O3 is 8% or more, 0 to 10% of Y2O3, 3 to 18% of Li2O, provided that the molar ratio of the content of Li2O to the total content of B2O3 and SiO2 [Li2O/(B2O3+SiO2)] is over 0 but not more than 0.2, 0.1 to 15% of ZnO, 2 to 20% of CaO, 0 to 5% of BaO, provided that the content of BaO is smaller than the content of ZnO, 0 to 5% of SrO, 0 to 5% of MgO, provided that the molar ratio of the total content of MgO, CaO, SrO and BaO to the total content of B2O3 and SiO2 [(MgO+CaO+SrO+BaO)/(B2O3+SiO2) is from 0.1 to 0.4, and 0 to 5% of ZrO2, and having a refractive index (nd) and an Abbe's number (&ngr;d) which satisfy the equation (1), &ngr;d≧308.5−150×nd (in which 50≦̸&ngr;d≦̸59)  (1).
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