| 摘要 |
PROBLEM TO BE SOLVED: To provide a low density lead-free optical glass good in melting and processing property and also good in chemical resistance and stability against crystallization, the index of refraction nd of which is 1.65-1.80, the Abbe no.νd of which is 21-33. SOLUTION: The lead-free optical glass, the index of refraction nd of which is 1.65-1.80 and Abbe no.νd of which is 21-33, is composed of SiO2 of 27-40, B2 O3 of 0-<0.5, Al2 O3 of 0-6, Na2 O of 7-18, K2 O of 1-10, BaO of 1-10, SrO of 0-3, CaO of 0.5-5, MgO of 0-3, in wt.% in terms of oxide, wherein, BaO+SrO+ CaO+MgO<15, TiO2 of 21-37, ZrO2 of 0-7, Nb2 O5 of 5-17, WO3 of 0.1-7, and as an optional ingredient of ordinary amount of refined agent may be used.
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