| 摘要 |
An optical glass having a remarkably high refractive index and excellent stability can be give without being based on PbO, and the optical glass contains, as essential components, at least one oxide selected from La<SUB>2</SUB>O<SUB>3</SUB>, Gd<SUB>2</SUB>O<SUB>3</SUB>, Y<SUB>2</SUB>O<SUB>3</SUB>, Yb<SUB>2</SUB>O<SUB>3</SUB>, TiO<SUB>2</SUB>, Nb<SUB>2</SUB>O<SUB>5 </SUB>or WO<SUB>3</SUB>, at least one oxide selected from MgO, CaO, SrO or BaO and B<SUB>2</SUB>O<SUB>3 </SUB>and optionally containing SiO<SUB>2</SUB>, wherein on the basis of mass, the total content of B<SUB>2</SUB>O<SUB>3 </SUB>and SiO<SUB>2 </SUB>is from 1 to 25%, the ratio of (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>+Y<SUB>2</SUB>O<SUB>3</SUB>+Yb<SUB>2</SUB>O<SUB>3</SUB>+TiO<SUB>2</SUB>+Nb<SUB>2</SUB>O<SUB>5</SUB>+WO<SUB>3</SUB>) is from 0.05 to 0.3 and the ratio of (MgO+CaO+SrO+BaO)/(La<SUB>2</SUB>O<SUB>3</SUB>+Gd<SUB>2</SUB>O<SUB>3</SUB>+Y<SUB>2</SUB>O<SUB>3</SUB>+Yb<SUB>2</SUB>O<SUB>3</SUB>+TiO<SUB>2</SUB>+Nb<SUB>2</SUB>O<SUB>5</SUB>+WO<SUB>3</SUB>) is from 0.1 to 0.4, the optical glass having a refractive index (nd) of 2.000 or more and an Abbe's number (vd) of 27 or less.
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