# US 12,006,242 B2 · Opaque quartz glass and method of manufacturing the same

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- Number: US 12,006,242 B2
- Document ID: US12006242B2
- Status: Granted
- Kind: B2
- Application number: 17/594,885
- Filed: 2019-06-03
- Published: 2022-08-11
- Granted: 2024-06-11
- Earliest claimed: 2019-06-03
- Assignees: Tosoh Quartz Corporation
- Applicants: Tosoh Quartz Corporation
- Inventors: Chiemi Ito; Takeshi Mutou; Minoru Kuniyoshi; Mutsumi Asano; Atsushi Ando
- Web page: https://patentgrep.com/patent/US12006242B2

## CPC

- C03B 19/066: {for the production of quartz or fused silica articles (other processes specially adapted for the production of quartz or fused silica articles C03B20/00)}
- B02C 17/20: Disintegrating members
- C03B 19/10: Forming beads
- C03B 19/1005: {Forming solid beads (chemical aspects C03C12/00)}
- C03B 2201/02: Pure silica glass, e.g. pure fused quartz
- Y02P 40/57: Improving the yield, e-g- reduction of reject rates
- C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- B02C: CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN ({household tools and machines for pulverising foodstuffs, e.g. coffee and spice mills A47J42/00; pharmaceutical mortars A61J3/02; mechanical processing of refuse and garbage B03B9/06; dressing mould materials by grinding B22C5/04}; obtaining metallic powder by crushing, grinding or milling B22F9/04; {recovery of plastics by disintegrating B29B17/00; crushing raw materials in starch making C08B30/02; beaters for papermaking D21D1/02; crushing devices specially for transport in mines E21F13/002; slag crushing devices F23J1/00; fuel milling devices in combustion apparatus F23K1/00; household devices for crushing coal F24B15/02; ice disintegrating devices F25C5/02})
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A large sized opaque quartz glass ingot having an excellent heat ray shielding property, an outstanding light blocking property, high mechanical strength and small roughness of a baked finished smooth surface. The shape of bubbles inside the quartz glass are almost complete spheres and the average particle size of the bubbles is 1 μm or less, such that the strength of the opaque quartz glass ingot is increased as the stress concentration at the edges of the bubbles is eliminated and an increase of surface roughness caused by baking is alleviated.

## Claims

### Claim 1

An opaque quartz glass wherein an average diameter of bubbles contained therein is 1 μm or less, a density is 2.16 to 2.19 g/cm3, a whiteness is 90% or more at a thickness of 10 mm, and a reflectance of light of wavelength from 0.2 to 3 μm at a thickness of 3 mm is above 85%, wherein the average diameter of the bubbles is determined by cutting a sample of the opaque quartz glass to provide a cut surface, observing at least 20 bubbles on the cut surface by using a scanning electron microscope, processing obtained images from the scanning electron microscope of the at least 20 bubbles and measuring an area “A” of each bubble wherein an average value “D” of the bubbles is determined by the following equation (1):
D
=
(
4
×
A
/
π
)
1
/
2
.
(
1
)

### Claim 2 (depends on 1)

The opaque quartz glass according to claim 1, wherein a bending strength of the opaque quartz glass is equal to or above 75 MPa.

### Claim 3 (depends on 1)

The opaque quartz glass according to claim 1, wherein the opaque quartz glass has a baked finished surface, and a surface roughness Ra of the baked finished surface is equal to or less than 0.5 μm.

### Claim 4

A method of manufacturing an opaque quartz glass, comprising the steps of:
preparing a silica powder slurry having a silica powder concentration of 45 to 75 wt %;
subjecting the silica powder slurry to wet pulverization by applying one or a combination of two or more methods selected from beads mill pulverization, ball mill pulverization, vibration mill pulverization and attritor pulverization;
subjecting the silica powder slurry to spray dry granulation for forming substantially spherical granulated silica particles each having a mean particle diameter of 2 to 8 μm, a standard deviation of the particle size of the granulated silica particles of 3 to 7 μm and a BET specific area of 2 to 9 m2/g, to make a prepared slurry;
subjecting the prepared slurry to spray drying to obtain dried granulated silica particles; and
press-molding and firing the dried granulated silica particles.

### Claim 5 (depends on 4)

The method of manufacturing an opaque quartz glass according to claim 4, wherein one or more type of beads is used for the wet pulverization, the beads being selected from the group consisting of quartz glass beads, zirconia beads, silicon carbide beads and alumina beads having an average particle size of 0.1-3 mm.