Optical glass and preforms for precision press molding and optical elements made by using the glass
View Patent ↗An object of the invention is to provide an optical glass for precision press having optical properties of a high refractive index and a low dispersion property and having a low molding temperature, a high devitrification resistance, an excellent molding property, and a small specific gravity. The optical glass of the invention contains, in terms of % by mass on the basis of oxides, respective components of B 2 O 3 : 10 to 20%, SiO 2 : 0.5 to 12%, La 2 O 3 : 25 to 50%, Gd 2 O 3 : 0 to 20%, Y 2 O 3 : 0 to 20%, provided that La 2 O 3 +Gd 2 O 3 +Y 2 O 3 : 35 to 60%, ZnO: 5 to 20%, Li 2 O: 0.2 to 3%, ZrO 2 : 0 to 0.5%, Ta 2 O 5 : 3 to 18% and WO 3 : 3 to 20%, and has optical constants of a refractive index n d of 1.84 to 1.86 and an Abbe number v d of 37 to 42 and a glass transition point (T g ) of 630° C. or lower.
1. An optical glass comprising, in terms of % by mass on the basis of oxides, respective components of
B 2 O 3 : 10 to 20%,
SiO 2 : more than 2 to 12%,
La 2 O 3 : 25 to 50%,
Gd 2 O 3 : 0 to 20%,
Y 2 O 3 : 1 to 20%,
provided that La 2 O 3 +Gd 2 O 3 +Y 2 O 3 : 35 to 60%,
ZnO: 5 to 20%,
Li 2 O: 0.2 to 3%,
ZrO 2 : 0 to 0.5%,
Ta 2 O 5 : 3 to 18% and
WO 3 : 3 to 20%, and
having optical constants of a refractive index n d of 1.84 to 1.86 and an Abbe number v d of 37 to 42, and a glass transition point (T g ) of 630° C. or lower.
2. The optical glass according to claim 1 , wherein the total content of Gd 2 O 3 and Ta 2 O 5 is 25% or less in terms of % by mass on the basis of oxides.
3. The optical glass according to claim 2 , having a specific gravity of 5.34 or less.
4. The optical glass according to claim 1 , having a specific gravity of 5.34 or less.
5. A preform for precision press molding comprising the optical glass according to claim 1 .
6. An optical element obtained by precision press molding of the optical glass according to claim 1 .
7. The optical glass according to claim 1 , wherein B 2 O 3 is present in the optical glass in an amount of from 13 to 18 mass %, relative to the entire mass of the oxides.
8. The optical glass according to claim 1 , wherein ZnO is present in the optical glass in an amount of from 6 to 18 mass %, relative to the entire mass of the oxides.
9. The optical glass according to claim 1 , wherein La 2 O 3 is present in the optical glass in an amount of from 30 to 46 mass %, relative to the entire mass of the oxides.
10. The optical glass according to claim 1 , wherein Gd 2 O 3 is present in the optical glass in an amount of from 2 to 16 mass %, relative to the entire mass of the oxides.
11. The optical glass according to claim 1 , wherein Li 2 O is present in the optical glass in an amount of from 0.5 to 2 mass %, relative to the entire mass of the oxides.
12. The optical glass according to claim 1 , wherein Y 2 O 3 is present in the optical glass in an amount of from 2 to 10 mass %, relative to the entire mass of the oxides.
13. The optical glass according to claim 1 , having a refractive index n d of 1.845 to 1.855 and a glass transition point (T g ) of 600° C. or lower.
14. An optical glass comprising, in terms of % by mol on the basis of oxides, respective components of:
B 2 O 3 : 20 to 40%,
SiO 2 : 10 to 30%,
La 2 O 3 : 10 to 25%,
ZnO: 10 to 35%,
Ta 2 O 5 : 1 to 8%,
Li 2 O: 0.5 to 15%,
WO 3 : 1 to 15%,
Gd 2 O 3 : 0 to 10%,
Y 2 O 3 : 1.1 to 15%, and
ZrO 2 : 0 to 0.5%,
wherein the content of La 2 O 3 +Gd 2 O 3 +Y 2 O 3 is 15 to 30%, and having a refractive index n d of 1.84 to 1.86, an Abbe number v d of 37 to 42, and a glass transition point (T g ) of 630° C. or lower.
15. The optical glass according to claim 14 , wherein B 2 O 3 is present in the optical glass in an amount of from 26.2 to 33.4 mol %, relative to the entire moles of the oxides.
16. The optical glass according to claim 14 , wherein ZnO is present in the optical glass in an amount of from 14.8 to 25.3 mol %, relative to the entire moles of the oxides.
17. The optical glass according to claim 14 , wherein La 2 O 3 is present in the optical glass in an amount of from 14.9 to 18.8 mol %, relative to the entire moles of the oxides.
18. The optical glass according to claim 14 , wherein Gd 2 O 3 is present in the optical glass in an amount of from 1 to 10 mol %, relative to the entire moles of the oxides.
19. The optical glass according to claim 14 , wherein Li 2 O is present in the optical glass in an amount of from 2.3 to 6.8 mol %, relative to the entire moles of the oxides.
20. The optical glass according to claim 14 , wherein Y 2 O 3 is present in the optical glass in an amount of from 1.1 to 5.0 mol %, relative to the entire moles of the oxides.