# US 10,308,549 B2 · Chemically strengthened glass and method for producing same

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- Number: US 10,308,549 B2
- Document ID: US10308549B2
- Status: Granted
- Kind: B2
- Application number: 15/000,719
- Filed: 2016-01-19
- Published: 2016-05-12
- Granted: 2019-06-04
- Earliest claimed: 2013-07-19
- Assignees: AGC Inc.
- Applicants: AGC Inc.
- Inventors: Izuru Kashima; Yusuke Fujiwara; Kiyoshi Tamai; Yuichi Suzuki; Daisuke Kobayashi; Yoichi Sera; Taku Yamada; Noriko Tanabe
- Web page: https://patentgrep.com/patent/US10308549B2

## CPC

- C03C 21/002: {to perform ion-exchange between alkali ions (C03C21/005 takes precedence)}
- C03C 3/085: containing an oxide of a divalent metal
- C03C 3/087: containing calcium oxide, e.g. common sheet or container glass
- C03C 3/091: containing aluminium
- C03C 15/00: Surface treatment of glass, not in the form of fibres or filaments, by etching (etching or surface-brightening compositions, in general C09K13/00)
- C03C 21/006: {to perform an exchange of the type Xn+ ----> nH+}
- C03C 23/0075: {Cleaning of glass (specially adapted to plate glass B08B11/00)}
- G01B 5/28: for measuring roughness or irregularity of surfaces
- 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
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS

## Abstract

A chemically strengthened glass having a compressive stress layer formed in a surface layer thereof according to an ion exchange method, in which a surface of the glass has polishing flaws, the glass has a texture direction index (Stdi) of 0.30 or more, a hydrogen concentration Y in a region to a depth X from an outermost surface of the glass satisfies the following relational equation (I) at X=from 0.1 to 0.4 (μm), and a surface strength F (N) measured by a ball-on-ring test is (F≥1400×t2) relative to a sheet thickness t (mm) of the glass: Y=aX+b (I) in which meanings of respective symbols in the equation (I) are as follows: Y: hydrogen concentration (as H2O, mol/L), X: depth from the outermost surface of the glass (μm), a: −0.300 or more, and b: 0.220 or less.

## Claims

### Claim 1

A glass sheet, having a compressive stress layer formed in a surface layer thereof according to an ion exchange method,
wherein a surface of the glass sheet has polishing flaws,
the glass sheet has a texture direction index (Stdi) of 0.30 or more,
a surface strength F (N) of the glass sheet measured by a ball-on-ring test is at least a value of (1400×t2), wherein t (mm) is a thickness of the glass sheet, and
a hydrogen concentration Y in a region to a depth X from a surface of the glass sheet satisfies relational equation (I) at X=from 0.1 to 0.4 (μm):
Y=aX+b (I)
wherein:
Y is the hydrogen concentration measured as H2O, (mol/L);
X is the depth from the surface of the glass sheet (μm);
a is −0.300 or more; and
b is 0.220 or less,
wherein the ball-on-ring test is conducted by:
placing the glass sheet on a stainless ring whose diameter is 30 mm and whose contact part has a roundness with a curvature radius of 2.5 mm;
applying a load on a center of the ring by the ball under a static loading condition, while a steel ball having a diameter of 10 mm is kept in contact with the glass sheet; and
measuring a BOR surface strength which is a fracture load (unit: N) at which the glass sheet is fractured and determining an average value of twenty measured values of the BOR surface strength as the surface strength F, provided that in a case where a fracture origin of the glass sheet is apart from a loading point of the ball by 2 mm or more, the obtained value is excluded from data for calculating the average value.

### Claim 2 (depends on 1)

The glass sheet according to claim 1, wherein the glass sheet is made of an aluminosilicate glass, an aluminoborosilicate glass or a soda-lime glass.

### Claim 3 (depends on 1)

The glass sheet according to claim 1, wherein the glass sheet has a texture aspect ratio (Str20) of 0.10 or more.

### Claim 4 (depends on 1)

The glass sheet according to claim 1, wherein a thickness of the glass sheet is 5 mm or less.

### Claim 5 (depends on 1)

A method for producing the glass sheet as defined in claim 1, the method comprising:
polishing a surface of a glass sheet comprising sodium;
bringing the glass sheet into contact with an inorganic salt comprising potassium nitrate, thereby performing ion exchange of a Na ion in the glass sheet with a K ion in the inorganic salt, after the polishing;
washing the glass sheet after the ion exchange;
subjecting the glass sheet to an acid treatment after the washing; and
subjecting the glass sheet to an alkali treatment after the acid treatment,
wherein the inorganic salt further comprises at least one salt selected from the group consisting of K2CO3, Na2CO3, KHCO3, NaHCO3, K3PO4, Na3PO4, K2SO4, Na2SO4, KOH and NaOH.

### Claim 6 (depends on 5)

The method according to claim 5, wherein the inorganic salt has an Na concentration of 500 ppm by weight or more.

### Claim 7 (depends on 5)

The method according to claim 5, wherein the inorganic salt contains K2CO3 in an amount of 0.1 mol % or more.

### Claim 8 (depends on 5)

The method according to claim 5, further comprising washing the glass sheet after the acid treatment.

### Claim 9 (depends on 5)

The method according to claim 5, further comprising washing the glass sheet after the alkali treatment.

### Claim 10 (depends on 5)

The method according to claim 5, wherein a solution having a pH of less than 7 is used in the acid treatment.

### Claim 11 (depends on 10)

The method according to claim 10, wherein the solution having the pH of less than 7 is a weak acid.

### Claim 12 (depends on 10)

The method according to claim 10, wherein the solution having the pH of less than 7 is a strong acid.

### Claim 13 (depends on 5)

The method according to claim 5, wherein the acid treatment is performed at a temperature of 100° C. or lower.

### Claim 14 (depends on 5)

The method according to claim 5, wherein a time for performing the acid treatment is from 10 seconds to 5 hours.

### Claim 15 (depends on 10)

The method according to claim 10, wherein the solution having the pH of less than 7 has an acid concentration of from 0.1 wt % to 20 wt %.

### Claim 16 (depends on 5)

The method according to claim 5, wherein a solution having a pH of more than 7 is used in the alkali treatment.

### Claim 17 (depends on 16)

The method according to claim 16, wherein the solution having the pH of more than 7 is a weak base.

### Claim 18 (depends on 16)

The method according to claim 16, wherein the solution having the pH of more than 7 is a strong base.

### Claim 19 (depends on 5)

The method according to claim 5, wherein the alkali treatment is performed at a temperature of from 0 to 100° C.

### Claim 20 (depends on 5)

The method according to claim 5, wherein a time for performing the alkali treatment is from 10 seconds to 5 hours.

### Claim 21 (depends on 16)

The method according to claim 16, wherein the solution having the pH of more than 7 has an alkali concentration of from 0.1 wt % to 20 wt %.