# US 11,078,106 B2 · Two-step method for strengthening glass

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- Number: US 11,078,106 B2
- Document ID: US11078106B2
- Status: Granted
- Kind: B2
- Application number: 16/295,685
- Filed: 2019-03-07
- Published: 2019-07-04
- Granted: 2021-08-03
- Earliest claimed: 2010-08-26
- Assignees: Corning Incorporated
- Applicants: Corning Incorporated
- Inventors: Sinue Gomez; Lisa Ann Lamberson; Robert Michael Morena
- Web page: https://patentgrep.com/patent/US11078106B2

## CPC

- C03C 3/097: containing phosphorus, niobium or tantalum
- C03C 3/091: containing aluminium
- C03C 3/095: containing rare earths
- C03C 4/18: for ion-sensitive glass
- C03C 21/002: {to perform ion-exchange between alkali ions (C03C21/005 takes precedence)}
- C03C 2204/00: Glasses, glazes or enamels with special properties
- Y10T 428/2495: Thickness [relative or absolute]
- Y10T 428/315: Surface modified glass [e.g., tempered, strengthened, etc.]
- 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
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A method of strengthening an alkali aluminoborosilicate glass. A compressive layer extending from a surface of the glass to a depth of layer is formed by exchanging larger metal cations for smaller metal cations present in the glass. In a second step, metal cations in the glass are exchanged for larger metal cations to a second depth in the glass that is less than the depth of layer and increase the compressive stress of the compressive layer. Formation of the compressive layer and replacement of cations with larger cations can be achieved by a two-step ion exchange process. An alkali aluminoborosilicate glass having a compressive layer and a crack indentation threshold of at least 3000 gf is also provided.

## Claims

### Claim 1

A method, the method comprising:
a. contacting an alkali aluminoborosilicate glass with a first ion exchange bath to form a compressive layer extending from a surface of the glass to a depth of layer, wherein the compressive layer is under a compressive stress, wherein the alkali aluminoborosilicate glass prior to the contacting with the first ion exchange bath comprises: 5-20 mol % B2O3; and 2-8.3 mol % Li2O; and
b. contacting the alkali aluminoborosilicate glass with a second ion exchange bath to replace at least a portion of the alkali metal cations in the compressive layer with a larger alkali metal cation to a second depth that is less than the depth of layer, wherein replacing the alkali metal cations in the compressive layer with the larger alkali metal cation increases the compressive stress, wherein the alkali aluminoborosilicate glass after the contacting with the second ion exchange bath has a crack initiation threshold of at least 6000 gf upon indentation with a Vickers indenter and wherein the surface has a compressive stress of at least 711 MPa, wherein the glass is a glass sheet having a thickness of up to 2 mm.

### Claim 2 (depends on 1)

The method of claim 1, wherein contacting the alkali aluminoborosilicate glass with a first ion exchange bath comprises replacing lithium cations with sodium cations to the depth of layer of the glass.

### Claim 3 (depends on 2)

The method of claim 2, wherein the first ion exchange bath comprises a sodium salt.

### Claim 4 (depends on 3)

The method of claim 3, wherein the first ion exchange bath further comprises a potassium salt.

### Claim 5 (depends on 1)

The method of claim 1, wherein contacting the alkali aluminoborosilicate glass with a second ion exchange bath comprises replacing at least one of sodium cations and lithium cations with potassium cations within the second depth.

### Claim 6 (depends on 5)

The method of claim 5, wherein the second ion exchange bath comprises a potassium salt.

### Claim 7 (depends on 1)

The method of claim 1, wherein the alkali aluminoborosilicate glass prior to the contacting with the first ion exchange bath comprises: 50-70 mol % SiO2; 5-15 mol % Al2O3; 0-20 mol % Na2O; and 0-10 mol % K2O.

### Claim 8 (depends on 7)

The method of claim 7, wherein the alkali aluminoborosilicate glass further comprises at least one of: 0-10 mol % P2O5; 0-5 mol % MgO; 0-1 mol % CeO2; and 0-1 mol % SnO2.

### Claim 9 (depends on 1)

The method of claim 1, wherein the alkali aluminoborosilicate glass after the contacting with the second ion exchange bath has a depth of layer of at least 50 μm.

### Claim 10 (depends on 9)

The method of claim 9, wherein the depth of layer is in a range from 70 μm up to 290 μm.

### Claim 11 (depends on 1)

The method of claim 1, wherein the second depth is in a range from 5 μm up to 20 μm.

### Claim 12 (depends on 1)

The method of claim 1, wherein the alkali aluminoborosilicate glass prior to the contacting with the first ion exchange bath has a crack initiation threshold of at least 1000 gf upon indentation with a Vickers indenter.

### Claim 13

A method, the method comprising:
a. contacting an alkali aluminoborosilicate glass with a first ion exchange bath to form a compressive layer extending from a surface of the glass to a depth of layer, wherein the compressive layer is under a compressive stress, wherein the alkali aluminoborosilicate glass prior to the contacting with the first ion exchange bath comprises: 5-20 mol % B2O3; and 2-8.3 mol % Li2O; and
b. contacting the alkali aluminoborosilicate glass with a second ion exchange bath to replace sodium cations and lithium cations in the compressive layer with potassium cations to a second depth that is less than the depth of layer, and wherein replacing the lithium cations and the sodium cations in the compressive layer with the potassium cations increases the compressive stress, wherein the alkali aluminoborosilicate glass after the contacting with the second ion exchange bath has a crack initiation threshold of at least 6000 gf upon indentation with a Vickers indenter and wherein the surface has a compressive stress of at least 711 MPa, wherein the glass is a glass sheet having a thickness of up to 2 mm.

### Claim 14 (depends on 13)

The method of claim 13, wherein the first ion exchange bath comprises a sodium salt.

### Claim 15 (depends on 14)

The method of claim 14, wherein the first ion exchange bath further comprises a potassium salt.

### Claim 16 (depends on 13)

The method of claim 13, wherein the second ion exchange bath comprises a potassium salt.

### Claim 17 (depends on 13)

The method of claim 13, wherein the alkali aluminoborosilicate glass prior to the contacting with the first ion exchange bath comprises: 50-70 mol % SiO2; 5-15 mol % Al2O3; 0-20 mol % Na2O; and 0-10 mol % K2O.

### Claim 18 (depends on 17)

The method of claim 17, wherein the alkali aluminoborosilicate glass further comprises at least one of: 0-10 mol % P2O5; 0-5 mol % MgO; 0-1 mol % CeO2; and 0-1 mol % SnO2.

### Claim 19 (depends on 12)

The method of claim 12, wherein the alkali aluminoborosilicate glass after the contacting with the second ion exchange bath has a depth of layer of at least 50 μm.

### Claim 20 (depends on 19)

The method of claim 19, wherein the depth of layer is in a range from 70 μm up to 290 μm.

### Claim 21 (depends on 13)

The method of claim 13, wherein the second depth is in a range from 5 μm up to 20 μm.

### Claim 22 (depends on 13)

The method of claim 13, wherein the alkali aluminoborosilicate glass prior to the contacting with the first ion exchange bath has a crack initiation threshold of at least 1000 gf upon indentation with a Vickers indenter.