Optical glass, precision press molding preform, and optical element and method of manufacturing the same
The optical glass is described that may be an oxide glass including, denoted as cation %, a total of 5 to 60% of B 3+ and Si 4+ (with 5 to 50% of B 3+ ), a total of equal to or higher than 5% of Zn 2+ and Mg 2+ , a total of 10 to 50% of La 3+ , Gd 3+ , Y 3+ , and Yb 3+ , and a total of 6 to 45% of Ti 4+ , Nb 5+ , Ta 5+ , W 6+ , and Bi 3+ (a total content of Ti 4+ and Ta 5+ being higher than 0% and a content of W 6+ being higher than 5%).
1. Optical glass, which is oxide glass comprising, denoted as cation %,
a total of 5 to 60% of B 3+ and with 5 to 50% of B 3+ ,
a total of equal to or higher than 5% of Zn 2+ and Mg 2+ ,
a total of 10 to 50% of La 3+ , Gd 3+ , Y 3+ , and Yb 3+ , and
a total of 6 to 45% of Ti 4+ , Nb 5+ , Ta 5+ , W 6+ , and Bi 3+ , with a total content of Ti 4+ and Ta 5+ being higher than 0% and a content of W 6+ being higher than 5%;
wherein a cation ratio of a content of Si 4+ to a content of B 3+ , Si 4+ /B 3+ , is equal to or lower than 0.70;
a cation ratio of a content of Ta 5+ to a total content of Ti 4+ and Ta 5+ , Ta 5+ /(Ti 4+ +Ta 5+ ), is equal to or higher than 0.23;
a cation ratio of a content of W 6+ to a total content of Nb 5+ and W 6+ , W 6+ /(Nb 5+ +W 6+ ), is equal to or higher than 0.30;
a cation ratio of a total content of Ti 4+ , Nb 5+ , Ta 5+ , W 6+ , and B 3+ to a total content of B 3+ and Si 4+ , (Ti 4+ +Nb 5+ +Ta 5+ +W 6+ +B 3+ )/(B 3+ +Si 4+ ), is higher than 0.37 but equal to or lower than 3.00;
a cation ratio of a total content of Zn 2+ , Mg 2+ , and Li + to a total content of La 3+ , Gd 3+ , Y 3+ , and Yb 3+ , (Zn 2+ +Mg 2+ +Li + )/(La 3+ +Gd 3+ +Y 3+ +Yb 3+ ), is equal to or higher than 0.40; and
which has a refractive index nd ranging from 1.90 to 2.00 and an Abbé number νd satisfying the following equation (1):
25≦ν d <(3.91− nd )/0.06 (1).
2. The optical glass according to claim 1 , which has a glass transition temperature of equal to or lower than 650° C.
3. The optical glass according to claim 1 , wherein a content of Ge is less than 5.0 mass % as a content of GeO 2 in a glass composition based on oxides, and a cation ratio of a content of Te 4+ to a total content of Zn 2+ and Mg 2+ , Te 4+ /(Zn 2+ +Mg 2+ ), is lower than 1.
4. The optical glass according to claim 1 , which comprises equal to or higher than 8 cation % of Zn 2+ and Mg 2+ combined.
5. The optical glass according to claim 1 , wherein a content of Yb is lower than 2.0 mass % as a content of Yb 2 O 3 in a glass composition based on oxides.
6. A precision press molding preform, which is comprised of the optical glass according to claim 1 .
7. An optical element, which is comprised of the optical glass according to claim 1 .
8. A method of manufacturing an optical element, which comprises heating and precision press molding with a pressing mold the precision press molding preform according to claim 6 to obtain an optical element.
9. The method of manufacturing an optical element according to claim 8 , which comprises heating the precision press molding preform together with a pressing mold after introducing the precision press molding preform into the pressing mold.
10. The method of manufacturing an optical element according to claim 8 , which comprises heating the precision press molding preform and then introducing into a pressing mold to conducting the precision press molding.