# US 7,745,361 B2 · Optical glass, preform for precision press molding and method of manufacturing thereof, optical element and method of manufacturing thereof

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- Number: US 7,745,361 B2
- Document ID: US7745361B2
- Status: Granted
- Kind: B2
- Application number: 11/723,468
- Filed: 2007-03-20
- Published: 2007-10-25
- Granted: 2010-06-29
- Earliest claimed: 2006-03-24
- Assignees: Hoya Corporation
- Inventors: Yoshiko Kasuga; Yasuhiro Fujiwara; Xuelu Zou
- Web page: https://patentgrep.com/patent/US7745361B2

## CPC

- C03C 3/068: containing rare earths
- C03C: CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS

## Abstract

The present invention relates to an optical glass having a refractive index (nd) of greater than or equal to 1.65 and an Abbé number (ν (nu)d) of greater than or equal to 50 for use in precision press molding. The glass exhibits that a ratio α (alpha)1/α (alpha)2 is less than 17 when temperature denoting maximum value of differential in amount of elongation of glass relative to temperature differential DELTAT (where DELTAT denotes a constant value of 1° C. or less) over a temperature range from glass transition temperature (Tg) to sag temperature (Ts) is denoted as T1, average coefficient of linear expansion over a range from T1−5° C. to T1+5° C. is denoted as alpha1, and average coefficient of linear expansion over a range from the glass transition temperature (Tg)−160° C. to the glass transition temperature (Tg)−140° C. is denoted as alpha2.

## Claims

### Claim 1

An optical glass comprising:
a glass wherein
(i) SiO2, B2O3, La2O3 and Gd2O3 are contained as essential components;
(ii) the combined quantity of SiO2 and B2O3 ranges from 50 to 72 mole percent;
(iii) the mole ratio (SiO2/B2O3) of the SiO2 content to the B2O3 content is in a range that exceeds 0.5 but does not exceed 0.90;
(iv) the quantity of La2O3 ranges from 4.87 to 10 mole percent; and
(v) the quantity of Gd2O3 ranges from 3.30 to 8 mole percent,
wherein said glass has a refractive index (nd) within the range of 1.65 to 1.70 and an Abbé number (ν (nu)d) of greater than or equal to 50 for use in precision press molding, exhibiting that a ratio α (alpha)1/α (alpha)2 is less than 17 when temperature denoting maximum value of differential in amount of elongation of glass relative to temperature differential DELTAT (where DELTAT denotes a constant value of 1° C. or less) over a temperature range from glass transition temperature (Tg) to sag temperature (Ts) is denoted as T1, average coefficient of linear expansion over a range from T1−5° C. to T1+5° C. is denoted as alpha1, and average coefficient of linear expansion over a range from the glass transition temperature (Tg)−160° C. to the glass transition temperature (Tg)−140° C. is denoted as alpha2.

### Claim 2

An optical glass comprising:
a glass wherein
(i) SiO2, B2O3, La2O3 and Gd2O3 are contained as essential components;
(ii) the content of SiO2 ranges from 11 to 18 mole percent;
(iii) the content of La2O3 ranges from 5 to 15 mole percent;
(iv) the content of Gd2O3 ranges from 1 to 12 mole percent;
(v) the combined quantity of SiO2 and B2O3 ranges from 50 to 72 mole percent;
(vi) the mole ratio (SiO2/B2O3) of the SiO2 content to the B2O3 content ranges from 0.1 to 0.90, and
wherein said glass has a refractive index (nd) that exceeds 1.70 and an Abbé number (ν (nu)d) of greater than or equal to 50 for use in precision press molding, exhibiting that a ratio α (alpha)1/α (alpha)2 is less than 17 when temperature denoting maximum value of differential in amount of elongation of glass relative to temperature differential DELTAT (where DELTAT denotes a constant value of 1° C. or less) over a temperature range from glass transition temperature (Tg) to sag temperature (Ts) is denoted as T1, average coefficient of linear expansion over a range from T1−5° C. to T1+5° C. is denoted as alpha1, and average coefficient of linear expansion over a range from the glass transition temperature (Tg)−160° C. to the glass transition temperature (Tg)−140° C. is denoted as alpha2.

### Claim 3 (depends on 1)

A preform for precise press molding comprised of an optical glass of claim 1.

### Claim 4 (depends on 1)

An optical element comprised of an optical glass of claim 1.

### Claim 5 (depends on 3)

A method of manufacturing an optical element comprising heating a preform of claim 3 and precision press molding the heated preform with a precision pressing mold to manufacture an optical element.

### Claim 6 (depends on 2)

A preform for precise press molding comprised of an optical glass of claim 2.

### Claim 7 (depends on 2)

An optical element comprised of an optical glass of claim 2.

### Claim 8 (depends on 6)

A method of manufacturing an optical element comprising heating a preform of claim 6 and precision press molding the heated preform with a precision pressing mold to manufacture an optical element.