| 摘要 |
PROBLEM TO BE SOLVED: To obtain optical glass free from PbO and As2 O3 that require the cost for the protection of environment, having superior chemical durability and homogeneity, suitable for use as glass for mold pressing and having prescribed optical constants by providing a compsn. contg. specified amts. of SiO2 , B2 O3 , ZrO2 , Nb2 O5 , etc. SOLUTION: This optical glass has a compsn. consisting of, by weight, 20-50% SiO2 , 6-20% B2 O3 (SiO2 /B2 O3 <=6), 0.5-15% ZrO2 , 31-50% Nb2 O5 , 0-4% Al2 O3 , 0-5% GeO2 , 0-5% Y2 O3 , 0-5% La2 O3 , 0-5% Gd2 O3 , 0-5% Yb2 O3 , 0-15% Ta2 O5 , 0-10% WO3 , 0-14% ZnO, 0-7% MgO, 0-7% CaO, 0-14% SrO, 0-14% BaO, 0-10% Li2 O, 0-15% Na2 O, 0-15% K2 O and 0-1% Sb2 O3 . This glass has a refractive index (nd) of 1.65-1.80 and an Abbe's number (υd) of 28-42 as optical constants.
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