| 摘要 |
A low-dispersion optical glass suitable for producing a quality preform from a molten glass and suitable for precision press-molding, which is a fluorophosphate glass containing, as essential cationic components, P 5+ , Al 3+ , at least two members selected from Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ as divalent cationic components (R 2+ ) and Li + and containing, by cationic %,
10 to 45 % of P 5+ ,
5 to 30 % of Al 3+ ,
0 to 20 % of Mg 2+ ,
0 to 25 % of Ca 2+ ,
0 to 30 % of Sr 2+ ,
0 to 33 % of Ba 2+ ,
1 to 30 % of Li + ,
0 to 10 % of Na + ,
0 to 10 % of K + ,
0 to 5 % of Y 3+ ,
and 0 to 15 % of B 3+ ,
the molar ratio of the content of F - to the total content of F - and O 2- , F - /(F - + O 2- ), being 0.25 to 0.85,
the optical glass having a refractive index (N d ) of 1.40 to 1.58 and an Abbe's number (½ d ) of 67 to 90. |
