| 摘要 |
PROBLEM TO BE SOLVED: To provide optical glass having a low glass transition temperature (Tg), optical constants in which the refractive index (n) ranges from 1.60 to 1.80 or less and the Abbe number (&ngr;) ranges from 30 to 60, and a low rare-earth content.SOLUTION: Optical glass has a refractive index (n) in the range of 1.60 to 1.80, an Abbe number (&ngr;) 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 LnO(Ln being one or more types selected from La, Y, Yb, and Gd), BiO, TaO, GeO, and WOof 20% or less, and a NbOcontent of 20% or less. Preferably, in addition to the above, in terms of oxide-based mass%, the optical glass contains 10% to 50% of SiO, 30% or less of BO, more than 0% and 20% or less of TiO, and 10% or more and 60% or less of RO (R is one or more types selected from Mg, Ca, Zn, Sr, and Ba). |
