Optical glass

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PROBLEM TO BE SOLVED : To provide optical glass having a low glass transition temperature (Tg), optical constants in which the refractive index (nd) ranges from 1.60 to 1.80 or less and the Abbe number (νd) ranges from 30 to 60, and a low rare-earth content. SOLUTION : Optical glass has a refractive index (nd) in the range of 1.60 to 1.80, an Abbe number (νd) in the range of 30 to 60, a glass transition temperature (Tg) of 600°C or less, and in terms of oxide-based mass%, a total amount of Ln2O3 (Ln being one or more types selected from La, Y, Yb, and Gd), Bi2O3, Ta2O5, GeO2, and WO3 of 20% or less, and a Nb2O5 content of 20% or less. Preferably, in addition to the above, in terms of oxide-based mass%, the optical glass contains 10% to 50% of SiO2, 30% or less of B2O3, more than 0% and 20% or less of TiO2, and 10% or more and 60% or less of RO (R is one or more types selected from Mg, Ca, Zn, Sr, and Ba). COPYRIGHT : (C)2014, JPO&INPIT