Optical glass, precision press-molding preform, process for production thereof, optical element and process for the production thereof

• US 20050164864A1
• Filed: 01/21/2005
• Published: 07/28/2005
• Est. Priority Date: 01/23/2004
• Status: Active Grant

• Current Assignee: Hoya Corporation
• Original Assignee: Hoya Corporation
• Inventors: Zou, Xuelu, Kasuga, Yoshiko
• Granted Patent: US 7,351,675 B2
• Time in Patent Office: Days
• US Class Current: 501/78
• CPC Class Codes: C03B 11/08 for making solid articles, e.g. lenses
• CPC Class Codes: C03B 11/122 Heating
• CPC Class Codes: C03B 7/12 Cutting-off or severing a free-hanging glass stream , e.g. by the combination of gravity and surface tension forces
• CPC Class Codes: C03C 3/068 containing rare earths
• CPC Class Codes: Y02P 40/57 Improving the yield, e-g- reduction of reject rates
• CPC Class Codes: Y10S 501/903 having refractive index less than 1.8 and ABBE number less than 70

Abstract

An optical glass taking account of meltability and the moldability of a preform, having optical constants including a refractive index (nd) of at least 1.57 but less than 1.67 and an Abbe'"'"'s number (νd) of over 55 but not more than 65, having the property of softening at a low temperature and being suitable as a glass for precision press-molding, the optical glass including an optical glass containing B₂O₃, SiO₂, La₂O₃, Gd₂O₃, an alkali metal oxide and an alkaline earth metal oxide as essential components, having a B₂O₃ and SiO₂ total content of 52% by weight or more and having an SiO₂/B₂O₃ content ratio of from 0.38 to 1.2, and an optical glass wherein the relationship of the refractive index (nd) and the Abbe'"'"'s number (νd) satisfies the equation (1),
νd>260−126×nd  (1).

Claims

1. An optical glass having a refractive index (nd) of at least 1.57 but less than 1.67 and an Abbe'"'"'s number (ν

d) of over 55 but not more than 65,

the optical glass containing B₂O₃, SiO₂, La₂O₃, Gd₂O₃, an alkali metal oxide and an alkaline earth metal oxide as essential components, having a B₂O₃ and SiO₂ total content of 52% by weight or more and having an SiO₂/B₂O₃ content ratio of from 0.38 to 1.2.

2. The optical glass of claim 1, which contains, as glass components and by mol %, to 50% of B₂O₃, to 40% of SiO₂,

over 0% but not more than 5% of La₂O₃,

over 0% but not more than 5% of Gd₂O₃,

2 to 20% of Li₂O,

0 to 10% of Na₂O,

0 to 5% of K₂O, and

over 0% but not more than 15% of BaO.

3. The optical glass of claim 2, which contains, as glass components and by mol %,

0 to 5% of Y₂O₃,

0 to 5% of Al₂O₃,

0 to 15% of SrO,

0 to 15% of CaO,

0 to 15% of MgO,

0 to 8% of ZnO, and

0 to 3% of ZrO₂.

5. The optical glass of claim 1, which is used as a glass material for precision press-molding.

6. A precision press-molding preform, which is formed of the optical glass recited claim 5.

7. An optical element formed of the optical glass recited in claim 1.

8. A process for the production of a precision press-molding preform, which comprises separating a molten glass gob having a predetermined weight from a molten glass that flows out of a flow pipe, and shaping the molten glass gob into the preform,

wherein the preform is shaped which consists of the optical glass recited in claim 5 and has a weight equivalent to said predetermined weight.

9. A process for the production of an optical element, which comprises softening a precision press-molding preform, formed of an optical glass, under heat and precision press-molding the preform,

wherein said preform is the preform recited in the claim 6 or the preform produced by the process recited in claim 8.

10. The process for the production of an optical element as recited in claim 9, wherein the preform is introduced into a press mold and said press mold and the preform are heated together to carry out the precision press-molding.

11. The process for the production of an optical element as recited in claim 9, wherein the press mold and the preform are separately pre-heated, and the pre-heated preform is introduced into said press mold to carry out the precision press-molding.

4. An optical glass having a refractive index (nd) of at least 1.57 but less than 1.67 and an Abbe'"'"'s number (ν

d) of over 55 but not more than 65, wherein the relationship of the refractive index (nd) and the Abbe'"'"'s number (ν

d) satisfies the equation (1),

ν

d>

260−

126×

nd 

 

(1).