Silica glass containing TiO2 and process for its production

• US 20050272590A1
• Filed: 07/05/2005
• Published: 12/08/2005
• Est. Priority Date: 04/03/2003
• Status: Active Grant

• Current Assignee: AGC, Inc.
• Original Assignee: Asahi Glass Company, Limited (AGC, Inc.)
• Inventors: Koike, Akio, Iwahashi, Yasutomi
• Granted Patent: US 7,429,546 B2
• Time in Patent Office: Days
• US Class Current: 501/55
• CPC Class Codes: C03B 19/1415 Reactant delivery systems
• CPC Class Codes: C03B 19/1461 for doping the shaped article with flourine
• CPC Class Codes: C03B 2201/12 doped with fluorine C03B2201/14 takes precedence
• CPC Class Codes: C03B 2201/42 doped with titanium
• CPC Class Codes: C03C 2201/12 containing fluorine C03C2201/14 takes precedence
• CPC Class Codes: C03C 2201/23 containing hydroxyl groups
• CPC Class Codes: C03C 2201/42 containing titanium
• CPC Class Codes: C03C 2203/40 Gas-phase processes
• CPC Class Codes: C03C 2203/54 in a dopant containing atmosphere
• CPC Class Codes: C03C 3/06 with more than 90% silica by weight, e.g. quartz C03C3/045 takes precedence

Abstract

A silica glass containing TiO₂, which has a fictive temperature of at most 1,200° C., a F concentration of at least 100 ppm and a coefficient of thermal expansion of 0±200 ppb/° C. from 0 to 100° C.

A process for producing a silica glass containing TiO₂, which comprises a step of forming a porous glass body on a target quartz glass particles obtained by flame hydrolysis of glass-forming materials, a step of obtaining a fluorine-containing porous glass body, a step of obtaining a fluorine-containing vitrified glass body, a step of obtaining a fluorine-containing formed glass body and a step of carrying out annealing treatment.

Claims

1. A silica glass containing TiO₂, which has a fictive temperature of at most 1,200°

C., a F concentration of at least 100 ppm and a coefficient of thermal expansion of 0±

200 ppb/°

C. from 0 to 100°

C.

3. The silica glass containing TiO₂ according to claim 1, which has a coefficient of thermal expansion of 0±

150 ppb/°

C. from 0 to 100°

C.

4. The silica glass containing TiO₂ according to claim 1, which has a F concentration of at least 1,000 ppm.

5. The silica glass containing TiO₂ according to claim 1, of which the fluctuation of the refractive index (Δ

n) is at most 2×

10<sup>−

4</sup> within an area of 30 mm×

30 mm in at least one plane.

2. A silica glass containing TiO₂, which has a fictive temperature of at most 1,200°

C., a F concentration of at least 500 ppm and a coefficient of thermal expansion of 0±

200 ppb/°

C. from 0 to 100°

C.

6. A process for producing a silica glass containing TiO₂, which comprises:

(a) a step of forming a porous glass body by depositing and growing on a target quartz glass particles obtained by flame hydrolysis of glass-forming materials;

(b) a step of holding the porous glass body in a fluorine-containing atmosphere to obtain a fluorine-containing porous glass body;

(c) a step of heating the fluorine-containing porous glass body to a vitrification temperature to obtain a fluorine-containing vitrified glass body;

(d) a step of heating the fluorine-containing vitrified glass body to a temperature of at least the softening temperature and forming it in a desired shape to obtain a fluorine-containing formed glass body; and

(e) a step of carrying out annealing treatment wherein the formed glass body is held at a temperature exceeding 500°

C. for a predetermined time, and then, the temperature is lowered to 500°

C. at an average cooling rate of at most 10°

C./hr, or a step of carrying out annealing treatment wherein the formed glass body at a temperature of at least 1,200°

C. is cooled to 500°

C. at an average cooling rate of at most 10°

C./hr.

7. A process for producing a silica glass containing TiO₂, which comprises:

(a) a step of forming a porous glass body by depositing and growing on a target quartz glass particles obtained by flame hydrolysis of glass-forming materials;

(b) a step of holding the porous glass body in a fluorine-containing atmosphere to obtain a fluorine-containing porous glass body;

(c) a step of holding the fluorine-containing porous glass body in an atmosphere containing oxygen at from 300 to 1,300°

C. for a predetermined time and then heating it to a vitrification temperature to obtain a fluorine-containing vitrified glass body;

(d) a step of heating the fluorine-containing vitrified glass body to a temperature of at least the softening temperature and forming it in a desired shape to obtain a fluorine-containing formed glass body; and

(e) a step of carrying out annealing treatment wherein the formed glass body is held at a temperature exceeding 500°

C. for a predetermined time, and then, the temperature is lowered to 500°

C. at an average cooling rate of at most 10°

C./hr, or a step of carrying out annealing treatment wherein the formed glass body at a temperature of at least 1,200°

C. is cooled to 500°

C. at an average cooling rate of at most 10°

C./hr.