Lens and process for the production thereof

• US 20070225147A1
• Filed: 03/23/2007
• Published: 09/27/2007
• Est. Priority Date: 03/27/2006
• Status: Active Grant

• Current Assignee: Hoya Corporation
• Original Assignee: Hoya Corporation
• Inventors: Hayashi, Kazutaka, Shiraishi, Koichiro, Satou, Kouichi
• Granted Patent: US 8,357,624 B2
• Time in Patent Office: Days
• US Class Current: 501/50
• CPC Class Codes: C03B 11/08 for making solid articles, e.g. lenses
• CPC Class Codes: C03B 2201/50 doped with alkali metals
• CPC Class Codes: C03B 2215/12 Ceramics or cermets, e.g. cemented WC, Al2O3 or TiC
• CPC Class Codes: C03B 2215/24 Carbon, e.g. diamond, graphite, amorphous carbon
• CPC Class Codes: C03B 2215/46 Lenses, e.g. bi-convex
• CPC Class Codes: C03B 2215/47 Bi-concave
• CPC Class Codes: C03B 2215/48 Convex-concave
• CPC Class Codes: C03B 2215/66 Means for providing special atmospheres, e.g. reduced pressure, inert gas, reducing gas, clean room
• CPC Class Codes: C03B 2215/72 Barrel presses or equivalent, e.g. of the ring mould type
• CPC Class Codes: C03C 3/15 containing rare earths

Abstract

A lens formed of a high-refractivity low-dispersion glass and free of fogging and scorching on its optical-function surface, which is obtained by precision press-molding of an optical glass having a refractive index (n_d) of over 1.83, an Abbe'"'"'s number (ν_d) of 40 or more and a glass transition temperature (T_g) of 640° C. or lower and containing no Li₂O and has one form of a meniscus form, a biconcave form or a plano-concave form.

Claims

1. A lens formed of an optical glass having a refractive index (n_d) of over 1.83, an Abbe'"'"'s number (ν

_d) of 40 or more and a glass transition temperature (T_g) of 640°

C. or lower and containing no Li₂O and obtained by precision press-molding and the lens having one form of a meniscus form, a biconcave form or a plano-concave form.

2. The lens of claim 1, wherein the optical glass contains, as essential components, B₂O₃, La₂O₃ and ZnO and has contents of said components determined to give an refractive index (n_d) of over 1.83, an Abbe'"'"'s number (ν

_d) of 40 or more and a glass transition temperature (T_g) of 640°

C. or lower.

3. The lens of claim 2, wherein the optical glass contains, by mol %, 20 to 45% of B₂O₃, 5 to 24% of La₂O₃ and 22 to 42% of ZnO.

4. The lens of claim 1, which has a concave meniscus form or a biconcave form.

5. A process for the production of a lens by heating and precision press-molding a glass material, which comprises introducing a glass material formed of an optical glass having a refractive index (n_d) of over 1.83, an Abbe'"'"'s number (ν

_d) of 40 or more and a glass transition temperature (T_g) of 640°

C. or lower and containing no Li₂O into a press mold and precision press-molding the glass material to produce a lens having one form of a meniscus form, a biconcave form or a plano-concave form.

6. The process for the production of a lens as recited in claim 5, which uses, as the glass material, an optical glass containing B₂O₃, La₂O₃ and ZnO as essential components and having contents of said components determined to give an refractive index (n_d) of over 1.83, an Abbe'"'"'s number (ν

_d) of 40 or more and a glass transition temperature (T_g) of 640°

C. or lower.

7. The process for the production of a lens as recited in claim 6, wherein said glass material is formed of an optical glass containing, by mol %, 20 to 45% of B₂O₃, 5 to 24% of La₂O₃ and 22 to 42% of ZnO.

8. The process for the production of a lens as recited in claim 5, wherein a lens having a concave meniscus form or a biconcave form is obtained by the precision press-molding.

9. The process for the production of a lens as recited in claim 5, which comprises the steps of

softening the glass material by heating and pressing the glass material with a mold comprising a first mold member whose molding surface for forming an optical-function surface of a lens to be obtained is a concave surface or a flat surface and a second mold member whose molding surface is a convex surface,

cooling said mold until said glass material in said mold comes to have a temperature of a glass transition temperature (T_g) or lower, and

taking said glass material cooled out of said mold,

the cooling being carried out in said step of cooling the mold in a manner that the temperature of the first mold member reaches the glass transition temperature (T_g) of said glass material before the temperature of the second mold member.

10. The process for the production of a lens as recited in claim 5, which comprises the pressing step of softening the glass material by heating and pressing the glass material with a mold comprising a first mold member whose molding surface for forming an optical-function surface of a lens to be obtained has a relatively large curvature radius or paraxial curvature radius and a second mold member whose molding surface has a relatively small curvature radius or paraxial curvature radius,

the cooling step of cooling said mold until said glass material in said mold comes to have a temperature of the glass transition temperature (T_g) or lower, and

the step of taking said glass material cooled out of said mold,

the cooling being carried out in said cooling step in a manner that the temperature of the first mold member reaches the glass transition temperature (T_g) of said glass material before the temperature of the second mold member, thereby to produce a biconcave lens.