The invention provides an optical glass which comprises, in terms of % by mass on the basis of oxides, 35-45% of SiO 2 , 12-20% of B 2 O 3 , 2-7% of Li 2 O, 0.1-10% of ZnO, 2-15% of Al 2 O 3 , 10-40% of BaO, 0-5% of K 2 O, 0-10% of Na 2 O, and 0-20% of Gd 2 O 3 , wherein SiO 2 +B 2 O 3 is 47-58% and Li 2 O+Na 2 O+K 2 O is 5-14%.
1. An optical glass which consists of, in terms of % by mass on the basis of oxides,
37-45% of SiO 2 ,
12-20% of B 2 O 3 ,
2-7% of Li 2 O,
0.1-10% of ZnO,
2-15% of Al 2 O 3 ,
25-30.7% of BaO,
0-5% of K 2 O,
0-10% of Na 2 O,
0-20% of Gd 2 O 3 ,
optionally at least one selected from the group consisting of 0-10% of MgO, 0-5% of CaO, and 0-5% of SrO, such that BaO+MgO+CaO+SrO is 25-40%, and
optionally at least one selected from the group consisting of 0.01-1% of Sb 2 O 3 , 0.01-1% of SnO 2 , and 0.01-1% of As 2 O 3
wherein
SiO 2 +B 2 O 3 is 47-58%;
Li 2 O+Na 2 O+K 2 O is 6-14%; and
the optical glass has an Abbe number v d of 58-65.
2. The optical glass of claim 1 , which has a refractive index n d of 1.55-1.65.
3. The optical glass of claim 1 , which has a yield point Ts of 590° C. or lower.
4. The optical glass of claim 1 , which shows a decrease in transmittance of less than 20% after being held for 100 hours in an environment having a temperature of 60° C. and a relative humidity of 90%.
5. The optical glass of claim 1 , which comprises 37-43% of SiO 2 .
6. The optical glass of claim 1 , which comprises 12.5-16% of B 2 O 3 .
7. The optical glass of claim 1 , wherein SiO 2 +B 2 O 3 is 48-55.5%.
8. The optical glass of claim 1 , which comprises 3-6.5% of Li 2 O.
9. The optical glass of claim 1 , which comprises 1-6% of ZnO.
10. The optical glass of claim 1 , which comprises 3-10% of Al 2 O 3 .
11. The optical glass of claim 1 , which comprises 25-30% of BaO.
12. The optical glass of claim 1 , which comprises 0-3% of K 2 O.
13. The optical glass of claim 1 , which comprises 0.1-8% of Na 2 O.
14. The optical glass of claim 1 , wherein Li 2 O+Na 2 O+K 2 O is 7-14%.
15. The optical glass of claim 1 , which comprises 0-10% of Gd 2 O 3 .
16. The optical glass of claim 1 , which has a refractive index n d of 1.57-1.63.
17. The optical glass of claim 1 , which has an Abbe number v d of 58-63.
18. A method of making an optical glass, the method comprising
melting a mixture of raw material powders; and
producing the optical glass of claim 1 .