| 摘要 |
A high-refractivity high-dispersion optical glass for producing an optical element, which requires no machining, such as polishing or lapping, of an optical-function surface after precision press molding, containing B<SUB>2</SUB>O<SUB>3</SUB>, SiO<SUB>2</SUB>, La<SUB>2</SUB>O<SUB>3</SUB>, Gd<SUB>2</SUB>O<SUB>3</SUB>, ZnO, Li<SUB>2</SUB>O, ZrO<SUB>2 </SUB>and Ta<SUB>2</SUB>O<SUB>5 </SUB>as essential components, containing 0 to 1 mol % of Sb<SUB>2</SUB>O<SUB>3 </SUB>as an optional component, substantially containing none of PbO and Lu<SUB>2</SUB>O<SUB>3</SUB>, having a glass transition temperature of 630° C. or lower, and (1) having a refractive index nd and an Abbe's number nud which satisfy all of the following relational expressions, 1.80<nd<=1.90, 35<=nud<=50, and nd>=2.025-(0.005xnud) or (2) having an nd of greater than 1.85 and a nud of greater than 35.
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