Strengthened glass with deep depth of compression
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 a peak load at failure of at least 10 kgf as determined by abraded ring-on-ring testing. Methods of achieving such stress profiles are also described.
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 . 15 ·t, and wherein the compressive layer has a compressive stress profile; and
b. the compressive stress profile comprises:
i. a first portion b extending from the surface to a depth d b and having a an average slope m b , wherein −40 MPa/μm≥m b ≥−200 MPa/μm,
ii. a second portion c extending from a depth d c to the DOC and having an average slope m c , and
iii. a transition region extending from d b to d c having a slope that transitions from slope m b to slope m c .
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, wherein the alkali aluminosilicate glass further comprises up to about 10 mol % Li 2 O.
6. The glass article of claim 1 , wherein the first portion b is linear such that
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where σ″(x) is the second derivative of the stress profile in the first portion b 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.
7. The glass article of claim 6 , wherein the first portion b is linear such that
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.
8. The glass article of claim 1 , wherein the glass article has at least 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 positioned above the surface of the glass so there is a 100 μm air gap between the sandpaper and the surface of the glass, wherein the survival rate is based on testing at least 5 samples.
9. The glass article of claim 1 , wherein the thickness t is in a range from about 0.15 mm to about 2.0 mm and wherein the glass article that has had a surface sandblasted with abrasive material at a load of 15 psi for 5 seconds has a peak load at failure of at least about 10 kgf as determined by abraded ring-on-ring testing wherein a ratio of a diameter of a loading ring D 1 to a diameter of a support ring D 2 is about 0.5.
10. The glass article of claim 9 , wherein the peak load at failure is at least about 20 kgf.
11. An electronic device comprising the glass article of claim 1 .
12. The electronic device of claim 11 , wherein the glass article is a cover plate, window, or display.
13. 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 b extending from the surface to a depth d b and having an average slope m b , wherein −40 MPa/μm≥m b ≥−200 MPa/μm,
ii. a second portion c extending from a depth d c to the DOC and having an average slope m c , and
iii. a transition region extending from d b to d c having a slope that transitions from slope m b to slope m c ,
wherein the first portion b is linear such that
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where σ″(x) is the second derivative of the stress profile in the first portion b 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.
14. The glass article of claim 6 , wherein the first portion b is linear such that
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