| 摘要 |
Optical glass has a refractive index of 1.83 or above and an Abbe number of 26 or less and contains SiO2, TiO2, Nb2O5 and Na2O as its essential constituents in such proportions on a final oxide basis that the amounts of its oxide constituents as expressed on a mass percentage basis may satisfy the relationship: (TiO2+Nb2O5)/(Na2O+K2O)=3.0 to 4.0.
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