# US 11,306,019 B2 · Ion exchangeable glasses with high crack initiation threshold

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- Number: US 11,306,019 B2
- Document ID: US11306019B2
- Status: Granted
- Kind: B2
- Application number: 15/625,264
- Filed: 2017-06-16
- Published: 2017-10-05
- Granted: 2022-04-19
- Earliest claimed: 2013-09-13
- Assignees: Corning Incorporated
- Applicants: Corning Incorporated
- Inventors: Qiang Fu; Xiaoju Guo
- Web page: https://patentgrep.com/patent/US11306019B2

## CPC

- C03C 3/091: containing aluminium
- C03C 21/002: {to perform ion-exchange between alkali ions (C03C21/005 takes precedence)}
- 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

Alkali boroaluminosilicate glasses with high resistance to crack initiation and damage due to sharp impact are provided. The glass compositions have melting and forming temperatures that allow forming the glass into sheets via float-based processes while still allowing for the glass to be efficiently ion exchanged. The glass compositions contain MgO, and when ion exchanged, have a Vickers indentation crack initiation load of at least about 10-15 kgf.

## Claims

### Claim 1

A glass composition comprising:
from 65 to 72 mol % SiO2
from 8 to 13 mol % Al2O3
from 9 to 15 mol % B2O3
from 3 to 10 mol % MgO
from 8 to 12 mol % Na2O and
from 8 to 12 mol % M2O wherein M2O is Li2O, Na2O, K2O, Rb2O, and Cs2O
wherein said glass composition is capable of being formed into sheets via a float process and has a Vickers indentation crack initiation load of at least about 12 kgf after ion exchange.

### Claim 2 (depends on 1)

The glass composition of claim 1, comprising:
from 65 to 69 mol % SiO2
from 9 to 12 mol % Al2O3
from 10 to 14 mol % B2O3
from 3 to 7 mol % MgO
from 9 to 12 mol % Na2O.

### Claim 3 (depends on 1)

The glass composition of claim 1, wherein the glass is substantially free of phosphate or CaO.

### Claim 4 (depends on 1)

The glass composition of claim 1, wherein the glass has a strain point from about 500° C. to about 575° C.

### Claim 5 (depends on 1)

The glass composition of claim 1, wherein the glass has a viscosity of less than 104 Poise at 1300° C.

### Claim 6 (depends on 1)

The glass composition of claim 1, wherein the glass has a density of from about 2.320 g/cm3 to about 2.380 g/cm3.

### Claim 7 (depends on 1)

The glass composition of claim 1, wherein the glass has a coefficient of thermal expansion, CTE20-300° C. of from about 55 to about 75×10−7/° C.

### Claim 8 (depends on 1)

The glass composition of claim 1, wherein the glass is ion exchanged to a depth of layer of at least about 10 μm.

### Claim 9 (depends on 8)

The glass composition of claim 8, wherein the glass has a compressive layer extending from a surface of the glass to the depth of layer, and wherein the compressive layer is under a compressive stress of at least about 300 MPa.

### Claim 10 (depends on 1)

The glass composition of claim 1, wherein glass has a Vickers indentation crack initiation load of at least about 15 kgf.