# US 9,517,968 B2 · Strengthened glass with deep depth of compression

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- Number: US 9,517,968 B2
- Document ID: US9517968B2
- Status: Granted
- Kind: B2
- Application number: 14/530,155
- Filed: 2014-10-31
- Published: 2015-08-27
- Granted: 2016-12-13
- Earliest claimed: 2014-02-24
- Assignees: Corning Incorporated
- Applicants: Corning Incorporated
- Inventors: Jaymin Amin; Benedict Osobomen Egboiyi; Jonathan David Pesansky; Kevin Barry Reiman; Rostislav Vatchev Roussev; Brian Paul Strines
- Web page: https://patentgrep.com/patent/US9517968B2

## CPC

- C03C 21/002: {to perform ion-exchange between alkali ions (C03C21/005 takes precedence)}
- C03C 3/04: containing silica
- 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 3/093: containing zinc or zirconium
- C03C 3/095: containing rare earths
- C03C 3/097: containing phosphorus, niobium or tantalum
- C03C 4/18: for ion-sensitive glass
- C03C 21/00: Treatment of glass, not in the form of fibres or filaments, by diffusing ions or metals in the surface
- G06F 1/1637: {Details related to the display arrangement, including those related to the mounting of the display in the housing}
- C03C 2204/00: Glasses, glazes or enamels with special properties
- G06F 2200/1634: Integrated protective display lid, e.g. for touch-sensitive display in handheld computer
- H04B 1/3827: Portable transceivers
- 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
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)
- H04B: TRANSMISSION
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Chemically strengthened glass articles having at least one deep compressive layer extending from a surface of the article to a depth of at least about 45 μm within the article are provided. In one embodiment, the compressive stress profile includes a single linear segment extending from the surface to the depth of compression DOC. Alternatively, the compressive stress profile includes two linear portions: the first portion extending from the surface to a relatively shallow depth and having a steep slope; and a second portion extending from the shallow depth to the depth of compression. The strengthened glass has a 60% survival rate when dropped from a height of 80 cm in an inverted ball drop test and an equibiaxial flexural strength of at least 10 kgf as determined by abraded ring-on-ring testing. Methods of achieving such stress profiles are also described.

## Claims

### Claim 1

A glass article having a thickness t, the glass article comprising:
a compressive layer having a compressive stress CS in a range from about 500 MPa up to about 1200 MPa at a surface of the glass article, wherein:
a. the compressive layer extends from the surface to a depth of compression DOC, wherein DOC≧0.1·t when t<0.5 mm and DOC≧50 μm when t≧0.5 mm, and wherein the compressive layer has a compressive stress profile; and
b. the compressive stress profile comprises:
i. a first portion h extending from the surface to a depth db and having an average slope mb, wherein 3 μm≦db≦15 μm and −40 MPa/μm≧mb≧−200 MPa/μm and wherein the first portion b is linear such that

σ
″
⁡
(
x
)

<

2
⁢
σ
′
⁡
(
x
)
d
b

where σ″(x) is the second derivative of the stress profile in the first portion h with respect to depth x and σ′(x) is the first derivative of the stress profile in the first portion b with respect to depth x;
ii. a second portion c extending from db to the DOC and having an average slope mc, wherein −2 MPa/μm≧mc≧−8 MPa/μm and wherein the second portion c is linear such that

σ
″
⁡
(
x
)

<

2
⁢
σ
′
⁡
(
x
)
D
⁢
⁢
O
⁢
⁢
C

where σ″(x) is the second derivative of the stress profile in the second portion e with respect to depth x and σ′(x) is the first derivative of the stress profile in the second portion c with respect to depth x.

### Claim 2 (depends on 1)

The glass article of claim 1, wherein −40 MPa/μm≧mb≧−120 MPa/μm.

### Claim 3 (depends on 1)

The glass article of claim 1, wherein thickness t is in a range from about 0.15 mm up to about 2.0 mm.

### Claim 4 (depends on 1)

The glass article of claim 1, wherein the glass article comprises an alkali aluminosilicate glass.

### Claim 5 (depends on 4)

The glass article of claim 4, wherein the alkali aluminosilicate glass further comprises up to about 10 mol % Li2O.

### Claim 6 (depends on 1)

The glass article of claim 1, wherein the glass article has at least about a 60% survival rate when subjected to an inverted ball drop test with a 4.2 g stainless steel ball having a diameter of 10 mm from a height of about 80 cm onto a 30 grit sandpaper disposed on the surface of the glass, wherein the survival rate is based on testing at least 5 samples.

### Claim 7 (depends on 1)

The glass article of claim 1, wherein the glass article has an equibiaxial flexural strength in a range from about 10 kgf up to about 50 kgf as determined by abraded ring-on-ring testing.

### Claim 8 (depends on 1)

The glass article of claim 1, wherein DOC≧0.11·t when t<0.5 mm and 55 μm≦DOC≦100 μm when t≧0.5 mm.

### Claim 9 (depends on 4)

The glass article of claim 4, wherein the alkali aluminosilicate glass is lithium-free.

### Claim 10 (depends on 1)

The glass article of claim 1, wherein thickness t is in a range from about 0.15 mm up to about 1.0 mm.

### Claim 11 (depends on 1)

The glass article of claim 1, wherein the DOC≦0.2t.

### Claim 12 (depends on 1)

The glass article of claim 1, wherein the second portion e is linear such that

σ
″
⁡
(
x
)

<

σ
′
⁡
(
x
)
D
⁢
⁢
O
⁢
⁢
C

.

### Claim 13 (depends on 12)

The glass article of claim 12, wherein the first portion b is linear such that

σ
″
⁡
(
x
)

<

σ
′
⁡
(
x
)
d
b

.

### Claim 14 (depends on 1)

An electronic device comprising the glass article of claim 1.

### Claim 15 (depends on 14)

The electronic device of claim 14, wherein the glass article is a cover plate, window, or display.