| 摘要 |
An optical glass for precision press molding that has desired optical constants, a low glass transformation point (Tg), and a devitrification temperature that is lower than a temperature of a glass melt, at which a viscosity suitable for forming of a preform material is obtained, is provided. The optical glass for precision press molding has a lanthanum borosilicate system glass having optical constants of refractive index (nd) within a range from 1.65 to 1.73 and Abbe number (nud) within a range from 50 to 60, a Tg within a range of 480-580° C. The optical glass for precision press molding has a devitrification temperature that is lower than a temperature of the glass melt when the glass melt has a viscosity eta (poise) of log eta=2.5. The optical glass for precision press molding has a specific composition range of SiO2-B2O3-La2O3-Y2O3-Ta2O5-CaO-Li2O system composition.
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