Optical glass, preform for press-molding and optical element formed from preform
View Patent ↗The present invention relates to an optical glass including, in terms of mass % on the basis of oxides, B 2 O 3 : 10% to 20%, SiO 2 : 0.5% to 12%, ZnO: 5% to 19%, Ta 2 O 5 : 3% to 17%, Li 2 O: 0.2% to 3%, ZrO 2 : 0.6% to 4.9%, WO 3 : 6.1% to 20%, La 2 O 3 : 32.5% to 50%, and Y 2 O 3 : 0.2% or more and less than 1.5%, in which a mass fraction (La 2 O 3 /Y 2 O 3 ) of a content of La 2 O 3 to a content of Y 2 O 3 in terms of mass % is 40 or higher, and the optical glass has optical constants of a refractive index n d of 1.83 to 1.88 and an Abbe's number υ d of 39 to 42.
1. An optical glass comprising, in terms of mass % on a basis of oxides:
B 2 O 3 : 10% to 20%,
SiO 2 : 0.5% to 12%,
ZnO: 5% to 19%,
Ta 2 O 5 : 3% to 17%,
Li 2 O: 0.2% to 3%,
ZrO 2 : 0.6% to 4.9%,
WO 3 : 6.1% to 20%,
La 2 O 3 : 32.5% to 50%, and
Y 2 O 3 : 0.2% or more, and
wherein a mass fraction of a content of La 2 O 3 to a content of Y 2 O 3 in terms of mass % is 40 or higher, and
wherein the optical glass has a refractive index n d of 1.83 to 1.88 and an Abbe's number υ d of 39 to 42.
2. The optical glass according to claim 1 , having a liquidus temperature T L of 1,100° C. or lower.
3. The optical glass according to claim 2 , wherein the liquidus temperature T L of the glass is from greater than 1,000 to 1,100° C. and wherein said mass fraction of a content of La 2 O 3 to a content of Y 2 O 3 in terms of mass % is 42 or higher.
4. The optical glass according to claim 3 , wherein
a devitrification start time of said glass in molten form at 1000° C. as measured by a hot-thermocouple method is 750 seconds or longer.
5. The optical glass according to claim 3 , wherein
a devitrification start time of said glass in molten form at 1000° C. as measured by a hot-thermocouple method is 1000 seconds or longer.
6. The optical glass according to claim 3 , wherein
a devitrification start time of said glass in molten form at 1000° C. as measured by a hot-thermocouple method is 1250 seconds or longer.
7. The optical glass according to claim 3 , comprising, in terms of mass % on a basis of oxides: ZnO: 5% to 13.1%.
8. The optical glass according to claim 7 , further comprising, in terms of mass % on a basis of oxides: Gd 2 O 3 : 2% to 13%.
9. The optical glass according to claim 1 , wherein a total content of Ta 2 O 5 and La 2 O 3 is greater than 45 mass %.
10. The optical glass according to claim 1 , wherein a devitrification start time of said glass in molten form at 1000° C. as measured by a hot-thermocouple method is 500 seconds or longer.
11. A preform for press-molding, comprising:
the optical glass according to claim 1 .
12. An optical element obtained by a process comprising press-molding the preform according to claim 11 .
13. The optical glass according to claim 1 , comprising, in terms of mass % on a basis of oxides: ZnO: 5% to 13.1%.
14. The optical glass according to claim 1 , further comprising, in terms of mass % on a basis of oxides: Gd 2 O 3 : 0% to 15%.
15. The optical glass according to claim 1 , further comprising, in terms of mass % on a basis of oxides: Gd 2 O 3 : 2% to 13%.