# US 2022/0033299 A1 · Chemically strengthened glass, and method for manufacturing the same

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- Number: US 2022/0033299 A1
- Document ID: US20220033299A1
- Status: Published application
- Kind: A1
- Application number: 17/388,494
- Filed: 2021-07-29
- Published: 2022-02-03
- Earliest claimed: 2020-07-31
- Assignees: AGC Inc.
- Applicants: AGC Inc.
- Inventors: Kaname SEKIYA; Yusuke FUJIWARA
- Web page: https://patentgrep.com/patent/US20220033299A1

## CPC

- C03C 21/002: {to perform ion-exchange between alkali ions (C03C21/005 takes precedence)}
- C03C 3/083: containing aluminium oxide or an iron compound
- C03C 3/095: containing rare earths
- C03C 4/18: for ion-sensitive glass
- C03C 2204/00: Glasses, glazes or enamels with special properties
- 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 a chemically strengthened glass having a thickness of t [mm], and having a profile of a stress value CSx [MPa] at a depth x [μm] from a surface of the glass, the stress value being measured by a scattered-light photoelastic stress meter, in which a second-order differential value CSx″ of the stress value CSx in the profile satisfies the following expression within a range of CSx≥0: 0<CSx″≤0.050.

## Claims

### Claim 1

A chemically strengthened glass having a thickness of t [mm], and having a profile of a stress value CSx [MPa] at a depth x [μm] from a surface of the glass, the stress value being measured by a scattered-light photoelastic stress meter,
wherein a second-order differential value CSx″ of the stress value CSx in the profile satisfies the following expression within a range of CSx≥0:
0<CSx″≤0.050.

### Claim 2 (depends on 1)

The chemically strengthened glass according to claim 1, wherein a tensile stress value CT2 [MPa] satisfies the following expression using the thickness t [mm]:
CT2≤−120t+164.

### Claim 3 (depends on 1)

The chemically strengthened glass according to claim 1, wherein a tensile stress value CT2 [MPa] satisfies the following expression using the thickness t [mm]:
−120t+150≤CT2.

### Claim 4 (depends on 1)

The chemically strengthened glass according to claim 1, wherein a stress value CS50 at a depth of 50 [μm] from the surface of the glass satisfies the following expression using the thickness t [mm], the tensile stress CT2 [MPa] and a depth DOL [mm] of a compressive stress layer:
CS50/(CT2×(t−2×DOL))/t≥4.90.

### Claim 5 (depends on 1)

The chemically strengthened glass according to claim 1, wherein a first-order differential value CSx′ of the stress value CSx [MPa] in the profile is −5.3 or more.

### Claim 6 (depends on 1)

The chemically strengthened glass according to claim 1, wherein the chemically strengthened glass is a chemically strengthened glass that has been chemically strengthened at two or more stages, and
the tensile stress value CT2 [MPa] of the chemically strengthened glass is a value as large as 50% to 93% of a tensile stress value CT1 [MPa] of the chemically strengthened glass that has been chemically strengthened at the first stage of the two or more stages.

### Claim 7 (depends on 1)

The chemically strengthened glass according to claim 1, wherein a base composition of the chemically strengthened glass comprises, by mol % in terms of oxides:
52 to 75% of SiO2;
8 to 20% of Al2O3;
5 to 16% of LiO2; and
8% or lower of NaO2.

### Claim 8

A method of manufacturing a chemically strengthened glass, the method comprising:
immersing a lithium-containing glass into a first molten salt composition comprising sodium ions and potassium ions to thereby perform first ion exchange; and
immersing the lithium-containing glass into a second molten salt composition comprising potassium ions to thereby perform second ion exchange,
wherein in the first molten salt composition, a concentration of potassium nitrate is higher than a concentration of sodium nitrate, and
in the second molten salt composition, a concentration of potassium nitrate is 85 mass % or higher, and a mass ratio of sodium ions to lithium ions is 0 or higher and 15 or lower.

### Claim 9 (depends on 8)

The method of manufacturing a chemically strengthened glass according to claim 8, wherein the concentration of potassium nitrate in the first molten salt composition is higher than 50 mass %.

### Claim 10 (depends on 8)

The method of manufacturing a chemically strengthened glass according to claim 8, wherein the second molten salt composition comprises sodium nitrate whose concentration is higher than 0 mass % and 5 mass % or lower.

### Claim 11 (depends on 8)

The method of manufacturing a chemically strengthened glass according to claim 8, wherein the second molten salt composition comprises lithium ions whose concentration is 0.1 mass % or higher and 10 mass % or lower.

### Claim 12 (depends on 8)

The method of manufacturing a chemically strengthened glass according to claim 8, wherein in the first ion exchange, the first molten salt composition has a temperature of 380° C. or higher and 450° C. or lower.

### Claim 13 (depends on 12)

The method of manufacturing a chemically strengthened glass according to claim 12, wherein in the first ion exchange, the lithium-containing glass is immersed in the first molten salt composition for 0.5 hours or more and 8 hours or less.

### Claim 14 (depends on 8)

The method of manufacturing a chemically strengthened glass according to claim 8, wherein in the second ion exchange, the second molten salt composition has a temperature of 380° C. or higher and 450° C. or lower.

### Claim 15 (depends on 14)

The method of manufacturing a chemically strengthened glass according to claim 14, wherein in the second ion exchange, the lithium-containing glass is immersed in the second molten salt composition for an immersion time t2 [min] satisfying the following expression using a temperature T [° C.] of the second molten salt composition:
−0.38T+173<t2<−1.4T+650.

### Claim 16 (depends on 8)

The method of manufacturing a chemically strengthened glass according to claim 8, wherein the chemical strengthening is performed so that a tensile stress value CT2 [MPa] of the chemically strengthened glass after the second ion exchange is a value corresponding to 50% to 93% of a tensile stress value CT1 [MPa] of the chemically strengthened glass after the first ion exchange.

### Claim 17 (depends on 8)

The method of manufacturing a chemically strengthened glass according to claim 8, wherein a tensile stress value CT1 [MPa] of the chemically strengthened glass after the first ion exchange satisfies the following expression using a thickness t [mm] of the chemically strengthened glass:
CT1>−120t+164.

### Claim 18 (depends on 8)

The method of manufacturing a chemically strengthened glass according to claim 8, wherein the lithium-containing glass comprises, by mol % in terms of oxides:
52 to 75% of SiO2;
8 to 20% of Al2O3;
5 to 16% of LiO2; and
8% or lower of NaO2.

### Claim 19 (depends on 8)

The method of manufacturing a chemically strengthened glass according to claim 8, wherein the second molten salt composition comprises silicic acid.

### Claim 20 (depends on 8)

The method of manufacturing a chemically strengthened glass according to claim 8, wherein the second molten salt composition comprises carbonate.