Strengthened glass with deep depth of compression

Patent metadata

Field	Value
Publication number	US-9517968-B2
Application number	US-201414530155-A
Country	US
Kind code	B2
Filing date	Oct 31, 2014
Priority date	Feb 24, 2014
Publication date	Dec 13, 2016
Grant date	Dec 13, 2016

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.

First claim

The invention claimed is:

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 d b and having an average slope m b , wherein 3 μm≦d b ≦15 μm and −40 MPa/μm≧m b ≧−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 d b to the DOC and having an average slope m c , wherein −2 MPa/μm≧m c ≧−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.

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

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

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

5. The glass article of claim 4 , wherein the alkali aluminosilicate glass further comprises up to about 10 mol % Li 2 O.

6. 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.

7. 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.

8. 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.

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

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

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

12. The glass article of claim 1 , wherein the second portion e is linear such that



σ
″

⁡

(
x
)



<



σ
′

⁡

(
x
)

D
⁢

⁢
O
⁢

⁢
C



.

13. The glass article of claim 12 , wherein the first portion b is linear such that



σ
″

⁡

(
x
)



<



σ
′

⁡

(
x
)

d
b



.

14. An electronic device comprising the glass article of claim 1 .

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

Assignees

• Corning Inc

Inventors

• Amin Jaymin
• Egboiyi Benedict Osobomen
• Pesansky Jonathan David
• Reiman Kevin Barry
• Roussev Rostislav Vatchev
• Strines Brian Paul

Classifications

• C03C4/18 Primary

  for ion-sensitive glass · CPC title

• Y10T428/315

  Surface modified glass [e.g., tempered, strengthened, etc.] · CPC title

• C03C3/087

  containing calcium oxide, e.g. common sheet or container glass · CPC title

• C03C21/002 Primary

  to perform ion-exchange between alkali ions (C03C21/005 takes precedence) · CPC title

• C03C3/085

  containing an oxide of a divalent metal · CPC title