Ion exchanged glasses via non-error function compressive stress profiles
First Claim
1. A glass having a surface and a thickness t, in a range from 0.05 mm to 1.3 mm, the glass comprising:
- a first region under a compressive stress, the first region extending from the surface to a depth of layer DOL in the glass, wherein the compressive stress CS has a maximum CS1 at the surface and varies with distance d from the surface according to a function other than a complementary error function; and
a second region under a tensile stress CT, the second region extending from the depth of layer into the glass, wherein the glass has a frangibility limit CTlimit, expressed in MPa, greater than −
37.6ln(t)(MPa)+48.7(MPa).
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Accused Products
Abstract
Glasses with compressive stress profiles that allow higher surface compression and deeper depth of layer (DOL) than is allowable in glasses with stress profiles that follow the complementary error function at a given level of stored tension. In some instances, a buried layer or local maximum of increased compression, which can alter the direction of cracking systems, is present within the depth of layer. Theses compressive stress profiles are achieved by a three step process that includes a first ion exchange step to create compressive stress and depth of layer that follows the complimentary error function, a heat treatment at a temperature below the strain point of the glass to partially relax the stresses in the glass and diffuse larger alkali ions to a greater depth, and a re-ion-exchange at short times to re-establish high compressive stress at the surface.
84 Citations
17 Claims
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1. A glass having a surface and a thickness t, in a range from 0.05 mm to 1.3 mm, the glass comprising:
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a first region under a compressive stress, the first region extending from the surface to a depth of layer DOL in the glass, wherein the compressive stress CS has a maximum CS1 at the surface and varies with distance d from the surface according to a function other than a complementary error function; and a second region under a tensile stress CT, the second region extending from the depth of layer into the glass, wherein the glass has a frangibility limit CTlimit, expressed in MPa, greater than −
37.6ln(t)(MPa)+48.7(MPa). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An ion exchanged glass having a surface and a thickness t, in a range from 0.05 mm to 1.3 mm, the glass comprising a first region under a compressive stress CS and extending to a depth of layer DOL in the glass and second region under a tensile stress CT, the second region extending from the depth of layer into the glass, wherein the glass has a frangibility limit CTlimit, expressed in MPa, greater than −
- 37.6ln(t)(MPa)+48.7(MPa), the first region comprising a first segment in which the compressive stress CS varies according to a first error function, the first segment having a maximum compressive stress CS1 at the surface and extending from the surface to a first depth d1, wherein the depth d1 is less than the depth of layer DOL, and a second segment in which the compressive stress CS varies according to a second function, the second segment extending from the first depth d1 up to the depth of layer DOL, wherein the first error function is different than the second function.
- View Dependent Claims (11, 12, 13, 14, 15)
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16. A method of providing a glass with a compressive stress in a layer extending from a surface of the glass to a depth of layer in the glass and a tensile region extending from the depth of layer into the glass, the method comprising:
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ion exchanging the glass with a salt comprising first cations to a first compressive stress and a first depth of layer, wherein the first compressive stress varies with distance in the glass according to a complementary error function; relaxing stresses within the glass and diffusing the first cations deeper into the glass; and re-ion exchanging the glass with a salt comprising the first cations to a second compressive stress at the surface, wherein the compressive stress has a maximum value at the surface and varies with distance according to a function other than the complementary error function, wherein the glass has a thickness t in a range from 0.05 mm to 1.3 mm and a frangibility limit CTlimit, expressed in MPa, greater than −
37.6ln(t)(MPa)+48.7(MPa). - View Dependent Claims (17)
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Specification