Non-fracturable stress profile with high stress area for improved fracture resistance

Abstract

In one or more embodiments, a chemically strengthened glass article comprises a first main surface and an opposite second main surface defining the thickness t of the glass article, a stress profile σ(x) extending through the thickness t of the glass article, a first compressive stress layer extending to a first depth DOC1 greater than about 0.15t, a second compressive stress layer extending from the second main surface to a second compressive depth DOC2 less than or equal to DOC1, and a central tension zone positioned between the first and second compressive stress layers and including a peak tension PT and a tension zone width BTZ extending from DOC1 to t-DOC2. In embodiments, the following criteria apply: [1], where DOC = DOC1, [2] is the slope of the stress profile σ(x) at DOC, [3], and [4], where TA is the tension area defined by [5]. [Math 1] TIFF2026513507000280.tif54114

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 450,276, filed on March 6, 2023, entitled “Non-Frangible Stress Profiles With High Stress Area For Improved Fracture Resistance,” the entirety of which is incorporated herein by reference.

[0002] This specification generally relates to chemically strengthened glass articles, and more specifically to non-fracturable chemically strengthened glass articles. [Background technology]

[0003] Chemically strengthened glass is widely used as cover glass for mobile devices, touch-enabled displays, and other applications. Generally, non-fracturable ion-exchange glass is preferred as cover glass for touchscreen devices to reduce the risk of user injury from small glass particles that can be scattered during self-accelerating, highly fragmented fracture, a characteristic of high-fracturability stress conditions. Such conditions are often generated as a result of balancing excessive compressive stress in the surface layer of the glass article with excessive tensile stress in the central tension zone of the glass article. There is a continuing need for glass articles with desired stress profiles, imparted through strengthening, that provide glass with good mechanical and fracture properties for use in a variety of applications, including cover glass applications. [Overview of the Initiative]

[0004] Many electronic devices, such as smartphones, tablets, portable media players, personal computers, and cameras, incorporate cover glass that can function as a display cover and incorporate touch functionality. Cover glass for electronic devices is provided with significantly enhanced fracture resistance through strengthening processes, such as ion exchange processes. Such strengthening processes provide the cover glass with a layer of compressive stress extending from the outer surface to a limited compression depth (DOC). The compressive stress within the compressive stress layer is balanced by a central tension zone positioned between the compressive stress layers.

[0005] There are two main modes of failure for the cover glass when a portable device falls onto a hard surface. One mode is flexural failure, which is caused by the bending of the glass when the device is subjected to a dynamic load from impact with a hard surface. The other mode is sharp contact failure, which is caused by the introduction of damage to the glass surface. Impact of glass with rough, hard surfaces such as asphalt or granite can result in sharp indentations on the glass surface. These indentations become points of failure on the glass surface, from which cracks may emerge and propagate.

[0006] Generally, the deeper the DOC (Depth of Condensation) and the greater the compressive stress within the compression layer, the more resistant the cover glass will be to drops onto hard surfaces, especially rough surfaces. This is because scratches introduced to the surface of the cover glass are less likely to penetrate through the compressive stress layer into the central tension zone, where cracks can propagate and negatively impact the device's use. However, given that in some situations surface scratches may penetrate through the compressive stress layer, it is preferable for the cover glass to be non-fracturable, particularly to reduce the risk of user injury from small glass particles that may be scattered during self-accelerated, highly fragmented fracture that can occur under high-fracturable stress conditions. Furthermore, since the fracturability of the cover glass is determined in part by the magnitude and distribution of tensile stress within the central tension zone, care must be taken when designing the compressive stress layer so that the balanced central tension zone does not have a fracturable stress profile. Therefore, there is a continuing need for chemically strengthened glass-based articles that exhibit both improved fracture resistance and non-fracturability.

[0007] One driving factor for fracture is the tensile strain energy (TSE) of glassy articles. To avoid fracture while simultaneously generating a deep compressive stress layer, it has been found that the tensile stress integrated through the thickness of the central tension zone must be maximized for an acceptable level of TSE. An acceptable level of TSE is determined based on the fracture toughness of the glassy article, and the actual TSE is proportional to the squared tensile stress integrated through the thickness of the central tension zone. Since TSE is proportional to the depth integral of the squared tensile stress, and the tensile stress area, i.e., the force balancing the compressive forces in the compression layer, is the depth integral of only the tensile stress (not the squared), a more uniform distribution of tensile stress within the central tension zone maximizes the tensile stress area for a given TSE (set according to the acceptable level considered above).

[0008] This disclosure provides non-fracturable, chemically strengthened glass articles with improved fracture resistance by incorporating a compressive stress layer having both high DOC and high stress magnitude into the depth of the compressive stress layer. This disclosure focuses on increasing the level of deep compressive stress for any fixed material parameter (e.g., fracture toughness) so that the performance improvements generated in connection with this disclosure can be added to any performance improvements based on advances in material properties. Furthermore, it should be understood that the concepts disclosed herein regarding non-fracturable stress profiles can be implemented in articles of various thicknesses, various numbers, and assemblages of phases (e.g., completely amorphous glass or glass with precipitated crystalline phases), and various compositions (e.g., Li-free). Finally, although the glass articles considered herein are generally planar, the concepts considered can also be applied to non-planar articles.

[0009] According to a first aspect of this disclosure, a chemically strengthened glass article comprises: a first main surface and an opposite second main surface defining the thickness t of the glass article; a stress profile σ(x) where x extends through the thickness t of the glass article in a direction perpendicular to the first and second main surfaces; a first compressive stress layer extending from the first main surface to a first compressive depth DOC1 which is greater than approximately 0.15t; a second compressive stress layer extending from the second main surface to a second compressive depth DOC2 which is less than or equal to DOC1; and a central tension zone located between the first and second compressive stress layers and including a peak tension PT and a tension zone width (BTZ) extending from DOC1 to t-DOC2.

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[0010] The second aspect may include the first aspect and relating to a chemically strengthened glass-based article.

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[0011] The third aspect may include any of the prior aspects and relating to a chemically strengthened glass-based article.

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[0012] The fourth embodiment may include any of the preceding embodiments, wherein the peak tension PT for the chemically strengthened glass-based article is greater than 90 MPa.

[0013] The fifth embodiment may include any of the prior embodiments, wherein the peak tension PT for a chemically strengthened glass-based article is

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[0014] The sixth embodiment may include any of the prior embodiments, wherein the thickness t of the chemically strengthened glass-based article is 0.4 mm to 0.77 mm.

[0015] The seventh embodiment may include any of the preceding embodiments, wherein the composition of the chemically strengthened glass article contains less than 3 mol% Li2O, and the fracture toughness of the glass article is KIC is the position x within the central tension zone corresponding to the peak tension PT ピーク at which

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[0016] The eighth aspect may include any one of the first to sixth aspects, the composition of the chemically strengthened glass article contains Li2O in an amount ranging from about 3.0 mol% to about 7.5 mol%, and the fracture toughness K of the glass article IC is the position x within the central tension zone corresponding to the peak tension PT ピーク at which

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[0017] The ninth aspect may include any one of the first to fifth aspects, the composition of the chemically strengthened glass article contains Li2O in an amount ranging from about 7.5 mol% to about 11 mol%, and the fracture toughness K of the glass article IC is the position x within the central tension zone corresponding to the peak tension PT ピーク at which

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[0018] The tenth aspect may include any one of the first to fifth aspects, the composition of the chemically strengthened glass article contains Li2O in an amount ranging from about 11 mol% to about 13 mol%, and the fracture toughness K of the glass article IC is the position x within the central tension zone corresponding to the peak tension PT ピーク at which

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[0019] The eleventh embodiment may include any of the first to fifth embodiments, wherein the composition of the chemically strengthened glass article contains more than about 13 mol% Li2O, and the fracture toughness of the glass article is K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク In

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[0020] The twelfth embodiment may include any of the preceding embodiments, when the stress profile σ(x) in the central tension zone conforms to Equation I,

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[0021] The 13th embodiment may include any of the preceding embodiments, wherein the force coefficient p does not exceed 20.

[0022] The 14th embodiment may include any of the prior embodiments, wherein the chemically strengthened glass article is 2.1 × K IC Crushing coefficient K not exceeding t Includes K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク This is the fracture toughness of glass articles in [location].

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[0023] The 15th aspect may include any of the prior aspects, K t ≤1.97 × K IC That is the case.

[0024] The sixteenth embodiment may include any of the prior embodiments, wherein the DOC is 0.190t or more.

[0025] The seventeenth embodiment may include any of the preceding embodiments, wherein the chemically strengthened glass-based article includes surface compressive stress CS on each of the first and second main surfaces, relating I:

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[0026] The 18th embodiment may include any of the preceding embodiments, wherein the stress profile σ(x) of a chemically strengthened glass-based article exhibits spikes on the first and second main surfaces, and the spike depth DOL SP Knee stress CS k However, Relationship II:

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[0027] The 19th embodiment may include any of the prior embodiments, wherein the following criteria are met for a chemically strengthened glass article: 0≦DOL sp ≦DOL ul , In the formula, D.O.L. ul However, it is the larger of 4 μm and 0.01 t.

[0028] The 20th embodiment may include any of the preceding embodiments, wherein the stress profile σ(x) of a chemically strengthened glass-based article is such that the spikes on the first and second main surfaces, as well as the spike depth DOL SP Knee stress CS k This indicates DOL SP A portion of the stress profile σ(x) between and DOC contains a negative second derivative.

[0029] According to a first aspect of this disclosure, a chemically strengthened glass article comprises: a first main surface and an opposite second main surface defining the thickness t of the glass article; a stress profile σ(x) where x extends through the thickness t of the glass article in a direction perpendicular to the first and second main surfaces; a first compressive stress layer extending from the first main surface to a first compressive depth DOC1 which is greater than approximately 0.15t; a second compressive stress layer extending from the second main surface to a second compressive depth DOC2 which is less than or equal to DOC1; and a central tension zone located between the first and second compressive stress layers and including a peak tension PT and a tension zone width (BTZ) extending from DOC1 to t-DOC2.

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[0030] The second aspect may include the first aspect and relating to a chemically strengthened glass-based article.

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[0031] The third embodiment may include any one of the prior embodiments and relating to a chemically strengthened glass article.

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[0032] The fourth embodiment may include any one of the prior embodiments, wherein the peak tension PT for the chemically strengthened glass-based article is greater than 90 MPa.

[0033] The fifth embodiment may include any one of the prior embodiments, wherein the peak tension PT for a chemically strengthened glass-based article is

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[0034] The sixth embodiment may include any one of the prior embodiments, wherein the thickness t of the chemically strengthened glass-based article is 0.4 mm to 0.77 mm.

[0035] The seventh embodiment may include any one of the prior embodiments, wherein the composition of the chemically strengthened glass article contains less than 3 mol% Li2O, and the fracture toughness of the glass article is K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク In

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[0036] The eighth aspect may include any one of the first to sixth aspects, wherein the composition of the chemically strengthened glass article contains Li2O in an amount ranging from about 3.0 mol% to about 7.5 mol%, and the fracture toughness of the glass article is K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク In

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[0037] The ninth aspect may include any one of the first to sixth aspects, wherein the composition of the chemically strengthened glass article contains Li2O in an amount ranging from about 7.5 mol% to about 11 mol%, and the fracture toughness of the glass article is K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク In

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[0038] The tenth embodiment may include any one of the first to sixth embodiments, wherein the composition of the chemically strengthened glass article contains Li2O in an amount ranging from about 11 mol% to about 13 mol%, and the fracture toughness of the glass article is K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク In

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[0039] The eleventh embodiment may include any one of the first to sixth embodiments, wherein the composition of the chemically strengthened glass article contains more than about 13 mol% Li2O, and the fracture toughness of the glass article is K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク In

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[0040] The twelfth embodiment may include any one of the preceding embodiments, when the stress profile σ(x) in the central tension zone conforms to Equation I,

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[0041] The 13th embodiment may include any one of the preceding embodiments, wherein the force coefficient p does not exceed 20.

[0042] A fourteenth aspect may include any one of the prior aspects, wherein the chemically strengthened glass article is 2.1 × K IC Crushing coefficient K not exceeding t Includes K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク This is the fracture toughness of glass articles in [location].

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[0043] The 15th aspect may include any one of the prior aspects, K t ≤1.97 × K IC That is the case.

[0044] The sixteenth embodiment may include any one of the prior embodiments, wherein the DOC is 0.190t or more.

[0045] The 17th embodiment may include any one of the preceding embodiments, wherein the chemically strengthened glass-based article includes surface compressive stress CS on each of the first and second main surfaces, relating I:

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[0046] The 18th embodiment may include any one of the preceding embodiments, wherein the stress profile σ(x) of a chemically strengthened glass-based article exhibits spikes on the first and second main surfaces, and the spike depth DOL SP Knee stress CS k However, Relationship II:

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[0047] The 19th embodiment may include any one of the prior embodiments, wherein the following criteria are met for a chemically strengthened glass article: 0≦DOL sp ≦DOL ul , In the formula, D.O.L. ul However, it is the larger of 4 μm and 0.01 t.

[0048] The 20th embodiment may include any one of the preceding embodiments, wherein the stress profile σ(x) of a chemically strengthened glass-based article is such that the spikes on the first and second main surfaces, as well as the spike depth DOL SP Knee stress CS k This indicates DOL SP A portion of the stress profile σ(x) between and DOC contains a negative second derivative.

[0049] According to a 21st aspect of this disclosure, a chemically strengthened glass article comprises: a first main surface and an opposite second main surface defining the thickness t of the glass article; a stress profile σ(x) where x extends through the thickness t of the glass article in a direction perpendicular to the first and second main surfaces; a first compressive stress layer extending from the first main surface to a first compressive depth DOC1 which is greater than approximately 0.15t; a second compressive stress layer extending from the second main surface to a second compressive depth DOC2 which is less than or equal to DOC1; and a central tension zone located between the first and second compressive stress layers and including a peak tension PT and a tension zone width (BTZ) extending from DOC1 to t-DOC2.

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[0050] The 22nd embodiment may include the 21st embodiment, wherein the peak tension PT is greater than 90 MPa.

[0051] The 23rd embodiment may include the 21st embodiment, wherein the peak tension PT is greater than 115 MPa.

[0052] The 24th embodiment may include the 21st embodiment, wherein the peak tension PT is greater than 125 MPa.

[0053] The 25th aspect may include any one of the 21st to 24th aspects.

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[0054] The 26th aspect may include the 25th aspect,

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[0055] The 27th aspect may include the 25th aspect,

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[0056] The 28th embodiment may include any one of the 21st to 27th embodiments, wherein the thickness t of the glass-based article is 0.4 mm to 0.77 mm.

[0057] The 29th embodiment may include any one of the 21st to 27th embodiments, wherein the thickness t of the glass-based article is 0.43 mm to 0.68 mm.

[0058] The 30th aspect may include any one of the 21st to 29th aspects, wherein the composition of the glass-based article contains less than 3 mol% Li2O, and the fracture toughness of the glass-based article is K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク In

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[0059] The 31st aspect may include any one of the 21st to 29th aspects, wherein the composition of the glass-based article contains an amount of Li2O in the range of about 3.0 mol% to about 7.5 mol%, and the fracture toughness of the glass-based article is K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク In

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[0060] The 32nd aspect may include any one of the 21st to 29th aspects, wherein the composition of the glass-based article contains an amount of Li2O in the range of about 7.5 mol% to about 11 mol%, and the fracture toughness of the glass-based article is K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク In

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[0061] The 33rd aspect may include any one of the 21st to 29th aspects, wherein the composition of the glass-based article contains Li2O in an amount in the range of about 11 mol% to about 13 mol%, and the fracture toughness of the glass-based article is K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク In

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[0062] The 34th aspect may include any one of the 21st to 29th aspects, wherein the composition of the glass-based article contains more than about 13 mol% Li2O, and the fracture toughness of the glass-based article is K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク In

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[0063] The 35th aspect may include any one of the 21st to 34th aspects, when the stress profile σ(x) in the central tension zone conforms to Equation I,

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[0064] The 36th aspect may include the 35th aspect, wherein the best fit value of the force coefficient p exceeds 2.75.

[0065] The 37th aspect may include the 35th aspect, wherein the best fit value of the force coefficient p exceeds 3.2.

[0066] The 38th aspect may include any one of the 35th to 37th aspects, wherein the force coefficient p does not exceed 20.

[0067] The 39th aspect may include any one of the 21st to 38th aspects, 2.1 × K IC Crushing coefficient K not exceeding t It further includes K IC However, the position x within the central tension zone corresponding to the peak tension PT ピーク This is the fracture toughness of glass-based articles in [location].

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[0068] The 40th aspect may include the 39th aspect, K t ≤1.97 × K IC That is the case.

[0069] The 41st aspect may include any one of the 21st to 40th aspects, wherein the DOC is 0.190t or more.

[0070] The 42nd aspect may include any one of the 21st to 40th aspects, wherein the DOC is 0.200t or more.

[0071] The 43rd embodiment may include any one of the 21st to 40th embodiments, wherein the DOC is 0.210t or more.

[0072] The 44th embodiment may include any one of the 21st to 43rd embodiments, wherein the surface compressive stress CS on each of the first and second main surfaces is greater than 110 MPa.

[0073] The 45th embodiment may include any one of the 21st to 44th embodiments, wherein the stress profile σ(x) shows spikes on the first and second main surfaces, and the spike depth DOL SP Knee stress CS k However, Relationship II:

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[0074] The 46th aspect may include the 45th aspect, spike depth DOL SP Knee stress CS k but,

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[0075] The 47th aspect may include the 45th aspect, spike depth DOL SP Knee stress CS k but,

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[0076] The 48th aspect may include any one of the 45th to 47th aspects. 0≦DOL sp ≦DOL ul , In the formula, D.O.L. ul However, it is the larger of 4 μm and 0.01 t.

[0077] The 49th aspect may include any one of the 21st to 48th aspects, wherein the stress profile σ(x) is such that the spikes on the first and second main surfaces and the spike depth DOL SP Knee stress CS k This indicates DOL SP A portion of the stress profile σ(x) between and DOC contains a negative second derivative.

[0078] The 50th aspect may include any one of the 21st to 49th aspects.

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[0079] The 51st aspect may include any one of the 21st to 49th aspects.

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[0080] The 52nd aspect may include any one of the 21st to 49th aspects.

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[0081] The 53rd aspect may include any one of the 21st to 52nd aspects.

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[0082] The 54th aspect may include any one of the 21st to 52nd aspects.

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[0083] The 55th aspect may include any one of the 21st to 52nd aspects.

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[0084] The 56th aspect may include any one of the 21st to 55th aspects.

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[0085] The 57th aspect may include any one of the 21st to 55th aspects.

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[0086] The 58th aspect may include any one of the 21st to 55th aspects.

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[0087] The 59th embodiment may include any one of the 21st to 58th embodiments, wherein the surface compressive stress CS on each of the first and second main surfaces is greater than 550 MPa.

[0088] The 60th embodiment may include any one of the 21st to 58th embodiments, wherein the surface compressive stress CS on each of the first and second main surfaces is greater than 725 MPa.

[0089] The 61st aspect may include any one of the 21st to 60th aspects, wherein the chemically strengthened glass article includes an amorphous microstructure that is substantially free of crystals or microcrystals.

[0090] The 62nd aspect may include any one of the 21st to 61st aspects, wherein the chemically strengthened glass-based article is

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[0091] The 63rd embodiment may include any one of the 21st to 60th embodiments, wherein the chemically strengthened glass-based article is a glass-ceramic material comprising an amorphous phase and a crystalline phase.

[0092] The 64th aspect may include any one of the 21st to 60th aspects or the 63rd aspect, wherein the chemically strengthened glass-based article is

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[0093] The 65th embodiment may include any one of the 21st to 64th embodiments, wherein a chemically strengthened glass-based article is formed by subjecting a glass-based substrate to an ion exchange treatment, and the glass-based substrate contains 50 mol% to 75 mol% of SiO2, 10 mol% to 25 mol% of Al2O3, 1 mol% to 11 mol% of B2O3, 1 mol% to 10 mol% of Na2O, and 5 mol% to 15 mol% of Li2O, wherein the molar concentration of Li2O in the glass-based substrate is higher than the molar concentration of Na2O in the glass-based substrate.

[0094] The 66th embodiment may include any one of the 21st to 65th embodiments, wherein a chemically strengthened glass-based article is formed by subjecting a glass-based substrate to an ion exchange treatment, and the glass-based substrate contains Li2O in an amount of 7.0 to 15.0 mol%.

[0095] The 67th embodiment may include any one of the 21st to 66th embodiments, wherein a chemically strengthened glass-based article is formed by subjecting a glass-based substrate to an ion exchange treatment, and the glass-based substrate contains a Li2O to Na2O molar ratio of 2.0 or higher.

[0096] According to the 68th aspect of this disclosure, a chemically strengthened glass-based article comprises: a first main surface and an opposite second main surface defining the thickness t of the glass-based article, wherein the thickness t is 0.52 mm or less; a stress profile σ(x) where x extends through the thickness t of the glass-based article in a direction perpendicular to the first and second main surfaces; a first compressive stress layer extending from the first main surface to a first compressive depth DOC1 greater than approximately 0.15 t; a second compressive stress layer extending from the second main surface to a second compressive depth DOC2 less than or equal to DOC1; and a central tension zone positioned between the first and second compressive stress layers and including a peak tension PT and a tension zone width BTZ extending from DOC1 to t-DOC2.

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[0097] The 69th aspect may include the 68th aspect, wherein the peak tension PT is greater than 115 MPa.

[0098] The 70th aspect may include the 68th aspect, wherein the peak tension PT is greater than 125 MPa.

[0099] The 71st aspect may include any one of the 68th to 70th aspects, when the stress profile σ(x) in the central tension zone conforms to Equation I,

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[0100] The 72nd aspect may include any one of the 68th to 70th aspects, when the stress profile σ(x) in the central tension zone conforms to Equation I,

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[0101] Aspect 73 may include any one of Aspects 68 - 72, and the stress profile σ(x) includes spikes at the first and second major surfaces, and the knee stress CS SP at the depth of layer (DOL) k is shown, and a portion of the stress profile σ(x) between DOL SP and the depth of compression (DOC) includes a negative second derivative.

[0102] Aspect 74 may include any one of Aspects 68 - 73, and DOC is 0.190t or more.

[0103] Aspect 75 may include any one of Aspects 68 - 73, and DOC is 0.200t or more.

[0104] Aspect 76 may include any one of Aspects 68 - 73, and DOC is 0.210t or more.

[0105] According to Aspect 77 of the present disclosure, a chemically strengthened glass - based article includes a first major surface and an opposite second major surface that define the thickness t of the glass - based article, where the thickness t is from about 0.43 mm to about 0.68 mm, the first major surface and the opposite second major surface, a stress profile σ(x) where x extends through the thickness t of the glass - based article in a direction perpendicular to the first major surface and the second major surface, a first compressive stress layer extending from the first major surface to a first depth of compression (DOC1) greater than about 0.19t, a second compressive stress layer extending from the second major surface to a second depth of compression (DOC2) less than or equal to DOC1, a central stress zone positioned between the first compressive stress layer and the second compressive stress layer and including a peak tension PT and a tension zone width (BTZ) extending from DOC1 to t - DOC2, and the peak tension PT is greater than 95 MPa, and when the stress profile σ(x) in the central stress zone conforms to Equation I,

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[0106] Aspect 78 may include aspect 77, and the thickness t is 0.52 mm or less.

[0107] Aspect 79 may include aspect 77 or 78, and the peak tension PT is greater than 103 MPa.

[0108] According to the 80th aspect of this disclosure, a method for producing a chemically strengthened glass article comprises exposing a glass substrate to a molten salt bath to form a chemically strengthened glass article, wherein the temperature of the molten salt bath is 110°C or less lower than the strain point of the glass substrate, the strain point of the glass substrate is determined by fiber stretching, the chemically strengthened glass article comprises a first main surface defining the thickness t of the glass article and a second main surface on the opposite side, and the ion exchange treatment time is such that the chemically strengthened glass article has a stress profile σ(x), where x However, it is selected to include a stress profile σ(x) extending through the thickness t of the glass-based article in a direction perpendicular to the first and second main surfaces, a first compressive stress layer extending from the first main surface to a first compressive depth DOC1 greater than approximately 0.15t, a second compressive stress layer extending from the second main surface to a second compressive depth DOC2 less than or equal to DOC1, and a central tension zone positioned between the first and second compressive stress layers and including a peak tension PT and a tension zone width BTZ extending from DOC1 to t-DOC2.

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[0109] The 81st embodiment may include the 80th embodiment, wherein the temperature of the molten salt bath is 455°C to 490°C.

[0110] The 82nd embodiment may include the 80th or 81st embodiment, wherein the ion exchange treatment time is 2 to 4 hours.

[0111] The 83rd embodiment may include any one of the 80th to 82nd embodiments, wherein the glass substrate contains 50 mol% or more and 75 mol% or less of SiO2, 10 mol% or more and 25 mol% or less of Al2O3, 1 mol% or more and 11 mol% or less of B2O3, 1 mol% or more and 10 mol% or less of Na2O, and 5 mol% or more and 15 mol% or less of Li2O, wherein the molar concentration of Li2O in the glass substrate is higher than the molar concentration of Na2O in the glass substrate.

[0112] The 84th embodiment may include any one of the 80th to 83rd embodiments, wherein the glass substrate contains Li2O in an amount of 7.0 to 15.0 mol%.

[0113] The 85th embodiment may include any one of the 80th to 84th embodiments, wherein the glass substrate contains a Li2O to Na2O molar ratio of 2.0 or higher.

[0114] Additional features and advantages of the chemically strengthened glass articles disclosed herein are described in the following detailed description and will be readily apparent to those skilled in the art from that description, or will be recognized by practicing the embodiments described herein, including the following detailed description, claims, and accompanying drawings.

[0115] It should be understood that both the foregoing summary and the following detailed description of the invention are intended to describe various embodiments and provide an overview or framework for understanding the nature and characteristics of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, are incorporated herein, and constitute a part of this specification. The drawings illustrate the various embodiments described herein and, together with the description, serve to explain the principles and operations of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0116] [Figure 1] A schematic cross-sectional view of a chemically strengthened glass-based article. [Figure 2a] 1) A strengthened glass-based article showing a frangible behavior upon fragmentation, and 2) a strengthened glass-based article showing a non-frangible behavior upon fragmentation are schematically shown. [Figure 2b] A strengthened glass-based article showing a non-frangible behavior upon fragmentation is schematically shown. [Figure 3] A plot showing the stress profile for a glass-based article approximated as a force profile having different force coefficients p, where the tension (y-axis) is plotted as a function of depth (x-axis). [Figure 4] Stress profile attributes with respect to the force coefficient p (x-axis)

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[0117] Herein, various embodiments are referred to in more detail, some of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used throughout the drawings to refer to the same or similar parts.

[0118] Herein, various embodiments of reinforced glass articles having a non-fracturable stress profile are referred to in detail. Various embodiments of chemically reinforced glass articles and methods for manufacturing them are referred to herein with specific reference to the attached drawings.

[0119] Generally, referring to the drawings, and in particular to Figure 1, it will be understood that the illustrative diagrams are for the purpose of illustrating specific embodiments and are not intended to limit the scope of this disclosure or the appended claims. The drawings are not necessarily to scale, and certain features and figures of the drawings may be exaggerated in scale or schematic for clarity and conciseness.

[0120] Before describing some exemplary embodiments, it should be understood that this disclosure is not limited to the details of the configuration or process steps expressed herein. Other embodiments of the disclosure provided herein are possible and can be practiced or implemented in various ways.

[0121] This disclosure relates to a chemically strengthened glass-based article comprising: a first main surface and an opposite second main surface defining the thickness t of the glass-based article; a stress profile σ(x) where x extends through the thickness t of the glass-based article in a direction perpendicular to the first and second main surfaces; a first compressive stress layer extending from the first main surface to a first compressive depth DOC1 greater than approximately 0.15t; a second compressive stress layer extending from the second main surface to a second compressive depth DOC2 less than or equal to DOC1; and a central tension zone positioned between the first and second compressive stress layers and including a peak tension PT and a tension zone width BTZ extending from DOC1 to t-DOC2.

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[0122] While we do not wish to be bound by theory, it is believed that chemically strengthened glass articles described herein, having the above-described combination of stress profile attributes, exhibit improved fracture toughness while avoiding fragility. This is achieved by modifying the stress profile in the central tension zone to achieve an increase in the tension area for a given tensile strain energy, selected considering the fracture toughness of the glass article in order to avoid making the glass article fragile. The increase in the tension area TA allows for deep DOC and high levels of compressive stress in the compression layer while keeping the glass article non-fragile. However, this disclosure also describes chemically strengthened glass articles having stress profiles modified for the above-described combination of stress profile attributes, for example, taking into account variations in the composition and thickness of the glass article, and similarly aiming to improve fracture toughness while avoiding fragility.

[0123] Throughout this specification, any reference to “one embodiment,” “a particular embodiment,” “various embodiments,” “one or more embodiments,” or “a certain embodiment” means that the specific features, structures, materials, or properties described in relation to that embodiment are included in at least one embodiment of this disclosure. Therefore, the appearance of phrases such as “in one or more embodiments,” “a particular embodiment,” “various embodiments,” “in one embodiment,” or “in a certain embodiment” in various places throughout this specification does not necessarily refer to the same embodiment or only one embodiment. Furthermore, specific features, structures, materials, or properties may be combined in any preferred manner in one or more embodiments.

[0124] In the following description, similar reference signs represent similar or corresponding parts across several diagrams shown in the figures. Unless otherwise specified, terms such as “upper,” “lower,” “outward,” and “inward” are for convenience only and should not be interpreted as limiting terms. In addition, whenever a group is described as containing at least one of a group of elements and combinations thereof, it is understood that the group may contain, essentially consist of, or consist of any number of those elements listed, individually or in combination with each other. Similarly, whenever a group is described as containing at least one of a group of elements and combinations thereof, it is understood that the group may consist of any number of those elements listed, individually or in combination with each other. Unless otherwise specified, when a range of values ​​is listed, it includes both the upper and lower bounds of the range, as well as any range between them.

[0125] As used herein, the indefinite articles "a," "an," and the corresponding definite article "the" mean "at least one" or "one or more" unless otherwise specified. It is also understood that the various features disclosed herein and in the drawings may be used in any and all combinations.

[0126] Where used herein, the term “approximately” means that quantities, sizes, formulations, parameters, and other quantities and characteristics are not and do not need to be exact, and may be approximate and / or greater or less, as desired, to reflect tolerances, conversion factors, rounding, measurement errors, and other factors known to those skilled in the art. Where the term “approximately” is used when describing values ​​or endpoints of a range, this disclosure should be understood to include the specific values ​​or endpoints being referenced. Whether or not the numerical values ​​or endpoints of a range in the specification indicate “approximately,” the numerical values ​​or endpoints of a range are intended to include two embodiments: those modified by “approximately” and those not modified by “approximately.” It will be further understood that each endpoint of a range is significant, whether in relation to other endpoints or independently of other endpoints.

[0127] Definitions and measurement techniques The terms “glass-based article” and “glass-based substrate” are used to include any object made entirely or partially from glass, including glass-ceramics (including amorphous and crystalline phases). As used herein, “glass-based substrate” refers to a formed substrate that can be subjected to a strengthening process to form a “glass-based article.” Glass-based substrates according to one or more embodiments may be selected from soda-lime silicate glass, alkali-aluminosilicate glass, alkali-containing borosilicate glass, alkali-containing aluminoborosilicate glass, and alkali-containing glass-ceramics.

[0128] "Glass-ceramics" include materials produced through the controlled crystallization of glass. One or more nucleating agents, such as titanium dioxide (TiO2), zirconium oxide (ZrO2), sodium oxide (Na2O), and phosphorus oxide (P2O5), can be added to glass-ceramic compositions to promote homogeneous crystallization. In some embodiments, the glass-based articles described herein may exhibit an amorphous microstructure and may be substantially free of crystals or microcrystals. In other words, in some embodiments, the glass-based articles described herein may exclude glass-ceramic materials. In some embodiments, the glass-based articles described herein may include glass-ceramic materials. Therefore, the terms "glass-based articles" and "multiple glass-based articles" are used in their broadest sense to include any objects made entirely or partially from glass.

[0129] The “base composition” is the chemical composition of the substrate before any ion exchange (IOX) treatment. That is, the basic composition is undoped with any ions from the IOX. The central composition of the IOX-treated glass-based article is close to or the same as the base composition, provided that the IOX treatment conditions are such that the ions supplied to the IOX do not diffuse to the center of the substrate. In one or more embodiments, the central composition of the glass-based article includes the base composition. The “base composition” may also be referred to herein as the “glass composition.”

[0130] It should be noted that the terms “substantially” and “about” may be used herein to express the degree of inherent uncertainty that may arise from any quantitative comparison, value, measurement, or other expression. These terms are also used herein to express the extent to which a quantitative expression may vary from the described reference without altering the fundamental function of the subject matter in question. For example, a “substantially MgO-free” glass article means that MgO is not actively added to or batched into the glass article, but may be present as a contaminant in very small amounts (e.g., <0.1 mol%).

[0131] Unless otherwise specified, all compositions are expressed in mole percent (mol%). The terms "0 mol%" and "free of" are used to describe the concentration and / or absence of a particular constituent in the glass composition and the resulting glass-based article, meaning that the constituent is not present in the glass composition and the resulting glass-based article.

[0132] As used herein, the term "fracture toughness (K IC )" represents the ability of a glass-based article to withstand fracture. Fracture toughness is measured on an unstrengthened glass-based article, such as measurement of the K IC value prior to ion exchange (IOX) treatment of the glass-based article, thereby characterizing the glass-based substrate prior to ion exchange. The fracture toughness test method described herein is not suitable for glass exposed to ion exchange treatment. However, fracture toughness measurements performed as described herein on the same glass (e.g., a glass-based substrate) prior to ion exchange treatment are correlated with the fracture toughness after ion exchange treatment and are thus used as such. The chevron-notch short bar (CNSB) method utilized to measure the K IC value is disclosed in Reddy, K.P.R. et al, "Fracture Toughness Measurement of Glass and Ceramic Materials Using Chevron-Notched Specimens," J. Am. Ceram. Soc., 71[6], C-310-C-313 (1988), provided that Y* mHowever, this is calculated using Equation 5 from Bubsey, RT et al., “Closed-Form Expressions for Crack-Mouth Displacement and Stress Intensity Factors for Chevron-Notched Short Bar and Short Rod Specimens Based on Experimental Compliance Measurements,” NASA Technical Memorandum 83796, pp.1-30 (October 1992). IC The double-torsion method and fixation device used to measure the values ​​are described in Shyam, A. and Lara-Curzio, E., “The double-torsion testing technique for determination of fracture toughness and slow crack growth of materials: A review,” J.Mater.Sci., 41, pp.4093-4104, (2006). The double-torsion measurement method generally yields slightly higher K values ​​than the chevron notched short bar method. IC The values ​​were generated. Unless otherwise specified, all fracture toughness values ​​were measured by the chevron-notched short bar (CNSB) method.

[0133] As described herein, the modulus of elasticity (also known as Young's modulus) and shear modulus of glass articles are provided in gigapascals (GPa) and measured according to ASTM C623. As described herein, Poisson's ratio is also measured according to ASTM C623.

[0134] As used herein, the term “strain point” refers to a glass composition whose viscosity is 1 × 10⁻⁶ when measured according to ASTM C598. 14.68 It refers to a certain temperature.

[0135] As used herein, the term “annealing point” or “effective annealing temperature” refers to a glass composition whose viscosity, as measured according to ASTM C598, is 1 × 10⁻⁶. 13.18 It refers to a certain temperature.

[0136] As used herein, the term "softening point" refers to the point at which the viscosity of the glass composition reaches 1 × 10⁻⁶. 7.6 This refers to the temperature at which the Poise core is formed. The softening point is expressed as a function of temperature, similar to ASTM C1351M, as 10⁻¹⁰. 7 ~10 9 The viscosity of inorganic glass is measured according to the parallel plate viscosity method.

[0137] As used herein, the term “melting point” refers to the temperature at which the viscosity of a glass composition is 200 poise, as measured according to ASTM C338.

[0138] Where used herein, the terms “linear thermal expansion coefficient” and “CTE” may be measured according to ASTM E228-85 over a temperature range of 25°C to 300°C, and “×10 -6 Expressed in units of " / °C". As used herein, the term "low-temperature CTE" or "LTCTE" refers to the CTE of a glass composition measured at a specific temperature in the range of 50°C to 500°C. As used herein, the term "high-temperature CTE" or "HTCTE" refers to the CTE of a glass composition measured at 10°C. 11 Viscosity of Poise (T 11 This refers to the CTE of a glass composition at its lowest temperature (temperature). CTE is measured by a digital image correlation method that determines the thermal expansion and instantaneous thermal expansion coefficient of a glass composition as it cools through a glass transition zone at a cooling rate of 2°C / second.

[0139] Where described herein, density is measured by the buoyancy method of ASTM C693-93.

[0140] Where used herein, the refractive index is measured according to ASTME 1967.

[0141] A "stress profile" is a plot of stress as a function of depth over the thickness of a glass-based article. The compressive stress region, where the article is under compressive stress, extends from the first surface of the article to the depth of compression (DOC). The central tension zone extends from DOC and includes the region where the glass-based article is under tensile stress.

[0142] As used herein, the terms “DOC” and “DOC” refer to the depth at which the stress within the glass changes from compressive to tensile stress. At DOC, the stress crosses from positive (compressive) stress to negative (tensile) stress and therefore has a value of zero. However, when used in conjunction with the term “tensile,” the stress in the central tension zone may be expressed as a positive value.

[0143] A "surface spike" refers to a region in the stress profile where the compressive stress decreases rapidly from its maximum value at the surface to a depth of approximately 15-20 μm below the surface, and then does not decrease as rapidly until the point where the stress transitions from compressive to tensile stress.

[0144] The "knee" of a stress profile is the region of an article with surface spikes where the slope of the stress profile transitions from a steep (spike region) to a gentler (deeper region). The steep portion of the stress profile extending from the surface into the glass-like article is called a "spike." The knee can refer to the transition region over a depth span where the slope changes. Knee compressive stress (CS) k ) is the deeper part of the CS profile, spike depth (DOL sp It is defined as the value of the compressive stress extrapolated to ). sp This refers to the depth of the knee joint and can be measured by a surface stress meter using known methods (see U.S. Patent No. 11 / 402,366, entitled "Methods of Characterizing Ion-Exchanged Chemically Strengthened Gasses Containing Lithium").

[0145] A non-zero metal oxide concentration that varies from a first surface to the layer depth (DOL) or along at least a substantial portion of the article thickness (t) indicates that stress has been generated in the article as a result of ion exchange. The variation in metal oxide concentration may be referred to herein as a metal oxide concentration gradient. A metal oxide concentration that is non-zero and varies from a first surface to the DOL or along a portion of the thickness may be described as indicating stress has been generated in a glass-based article. The metal oxide concentration gradient or variation arises from the chemical strengthening of the glass-based substrate, where multiple first metal ions in the glass-based substrate are exchanged for multiple second metal ions.

[0146] Where used herein, the terms “exchange depth,” “layer depth” (DOL), “chemical depth of layer,” and “depth of chemical layer” can be used interchangeably to describe the depth to which ion exchange facilitated by an ion exchange process (IOX) occurs for a particular ion. DOL refers to the depth within a glassy article (i.e., the distance from the surface of the glassy article to its interior region) to which ions of a metal oxide or alkali metal oxide (e.g., metal ions or alkali metal ions) diffuse into the glassy article, where the ion concentration is minimized, if determined by glow discharge emission spectroscopy (GD-OES). In some embodiments, DOL is given as the exchange depth of the slowest diffusing or largest ion introduced by the ion exchange (IOX) process.

[0147] Figure 1 shows a schematic cross-sectional view of a chemically strengthened glass-based article. The glass-based article 100 has a thickness t, a first surface 110, and a second surface 112. Although the embodiment shown in Figure 1 shows the glass-based article 100 as a flat, planar sheet or plate, the glass-based article may have other configurations, such as a three-dimensional shape or other non-planar configurations. The glass-based article 100 has a first compressive stress layer 120 extending from the first surface 110 to a compressive depth DOC1 in most of the glass-based article 100. In the embodiment shown in Figure 1, the glass-based article 100 also has a second compressive stress layer 122 extending from the second surface 112 to a second compressive depth DOC2. In the embodiment, DOC2 is less than or equal to DOC1. The glass-based article 100 also has a central tension zone 130 extending from DOC1 to DOC2. The central tension CT refers to the tensile stress midway through the central tension zone 130, which coincides with 0.5 × t when DOC1 and DOC2 are equal. The peak tension PT refers to the maximum tensile stress within the central tension zone 130. While it is very common for CT and PT to be the same, this is not mandatory.

[0148] The tensile stress in the central tension zone 130 balances or weakens the compressive stress in stress layers 120 and 122. The compression depths DOC1 and DOC2 of the first and second compressive stress layers 120 and 122 protect the glass-based article 100 from the propagation of scratches introduced by sharp impacts to the first and second surfaces 110 and 112 of the glass-based article 100, while the magnitude of the compressive stress minimizes the possibility of scratches penetrating through the depths DOC1 and DOC2 of the first and second compressive stress layers 120 and 122.

[0149] CT and PT values ​​can be measured using a scattered light polarizer (SCALP), such as the SCALP-05 portable scattered light polarizer. Near-field (RNF) or SCALP may be used to measure stress profiles and compression depth (DOC). When the RNF method is used to measure stress profiles, the peak tension PT value provided by SCALP is used in the RNF method. Specifically, the stress profile measured by RNF is force-balanced and calibrated to the peak tension PT value provided by the SCALP measurement. The RNF method is described in U.S. Patent No. 8,854,623, titled "Systems and methods for measuring a profile characteristic of a glass sample," which is incorporated herein by reference in its entirety. Specifically, the RNF method includes positioning a glass object adjacent to a reference block, generating a polarization-switched light beam that switches between orthogonal polarizations at a speed of 1 Hz to 50 Hz, measuring the power amount in the polarization-switched light beam, and generating a polarization-switched reference signal, where the measured power amount in each orthogonal polarization is within 50% of the other. This method further includes transmitting the polarization-switched light beam to the glass object at various depths through the glass object and the reference block, and then relaying the transmitted polarization-switched light beam to a signal photodetector using a relay optical system, where the signal photodetector generates a polarization-switched detector signal. This method also includes dividing the detector signal by the reference signal to form a normalized detector signal, and determining the profile characteristics of the glass object from the normalized detector signal.

[0150] As used herein, CS refers to the peak compressive stress in a glassy article, which, in many embodiments, is the surface compressive stress, i.e., the compressive stress on the first and second surfaces 110, 112. Therefore, unless otherwise specified, CS refers to the surface compressive stress. However, in embodiments, the chemical strengthening process may be designed so that the peak compressive stress CS is embedded within the glassy article rather than on its surface. The relationship between the peak compressive stress CS and the peak tension PT is approximated in some embodiments by the following equation.

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[0151] In various sections of this disclosure, peak tension PT and maximum compressive stress CS are expressed in megapascals (MPa), thickness t is expressed in either microns (μm) or millimeters (mm), and compression depth DOC is expressed in microns (μm).

[0152] Surface compressive stress CS, compressive depth DOC (for non-lithium glass), and spike depth DOL SPThe stress profile attributes of the compressive stress layer, including the surface stress, can be measured using means known in the art. Such means include, but are not limited to, thin-film stress measurement (FSM) using commercially available instruments such as the FSM-6000 stress meter manufactured by Luceo Co., Ltd. (Tokyo, Japan), etc. Methods for measuring compressive stress and compression depth are described in ASTM 1422C-99, titled "Standard Specification for Chemically Strengthened Flat Glass," and ASTM 1279.19779, "Standard Test Method for Non-Destructive Photoelastic Measurement of Edge and Surface Stresses in Annealed, Heat-Strengthened, and Fully-Tempered Flat Glass," the contents of which are incorporated herein by reference in their entirety. Surface stress measurement relies on the accurate measurement of the stress optical coefficient (SOC) related to the birefringence of the glass. Subsequently, SOC was measured by methods known in the art, such as the fiber and four-point bending method described in ASTM standard C770-98 (2008) entitled "Standard Test Method for Measurement of Glass Stress-Optical Coefficient," as well as by the bulk cylinder method, the contents of which are incorporated herein by reference in their entirety.

[0153] The stress profile attributes of the compressive stress layer can be measured using a prism-coupled instrument similar to the FSM-6000, as described in U.S. Patent No. 11,448,595 issued on September 20, 2022, entitled "Prism-Coupling Systems and Methods with Improved Intensity Transition Position Detection and Tilt Compensation," which is incorporated herein by reference in its entirety, but may be used with additional options for operating wavelengths that provide a preferred measurement window.

[0154] For tempered glass articles where the compressive stress layer extends to greater depths within the glass, the FSM technique may suffer from contrast problems that affect the observed DOC value. At deeper DOC values, insufficient contrast exists between the transverse electric field (TE) spectrum and the transverse magnetic field (TM) spectrum, thus making the calculation of the difference between the TE and TM spectra and the determination of the DOC more difficult. Furthermore, the FSM technique cannot determine the compressive stress profile (i.e., the variation in compressive stress as a function of depth within the glass). In addition, the FSM technique cannot determine layer depths resulting from ion exchange of certain elements, such as lithium.

[0155] The techniques described below have been developed to more accurately determine the depth of compression (DOC) and compressive stress profiles of reinforced glass-based articles.

[0156] U.S. Patent Application No. 13 / 463,322, filed on May 3, 2012, by Rostislav V. Roussev et al., entitled “Systems And Methods for Measuring the Stress Profile of Ion-Exchanged Glass” (hereinafter referred to as “Roussev I”), and claiming priority to U.S. Provisional Patent Application No. 61 / 489,800, filed on May 25, 2011, entitled “The Same,” discloses two methods for extracting a detailed and precise stress profile (stress as a function of depth) of tempered or chemically strengthened glass. Spectra of coupled optical modes for TM and TE polarization are collected via a prism coupling technique, and the whole is used to obtain a detailed and precise TM and TE refractive index profile n TM (z) and n TE (z) is obtained. The contents of the above-mentioned applications are incorporated herein by reference in their entirety.

[0157] In one embodiment, a detailed refractive index profile can be obtained from the mode spectrum by using the inverse Wentzel-Kramers-Brillouin (IWKB) method.

[0158] In another embodiment, a detailed refractive index profile is obtained by fitting a measured mode spectrum to a numerically calculated spectrum in a predetermined functional form that describes the shape of the refractive index profile, and obtaining the functional parameters from the best fit. A detailed stress profile S(z) is calculated from the difference between the recovered TM refractive index profile and TE refractive index profile using a known value of the stress optical coefficient (SOC).

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[0159] Because the SOC value is small, birefringence n at any depth z TM (z)-n TE (z) is the refractive index n TM (z) and n TEThis is the smaller of either (z) (typically around 1%). To obtain a stress profile that is not significantly distorted by noise in the measured mode spectrum, it is necessary to determine the mode effective refractive index with an accuracy of about 0.00001 RIU. The method disclosed in Roussev I further includes techniques applied to the raw data to ensure such high accuracy for the measured mode refractive index despite noise and / or insufficient contrast in the collected TE and TM mode spectra or images of the mode spectrum. Such techniques include noise averaging, filtering, and curve fitting to find the location of the extrema corresponding to the mode at subpixel resolution.

[0160] Similarly, U.S. Patent Application No. 14 / 033,954 (hereinafter referred to as "Roussev II"), filed on September 23, 2013, by Rostislav V. Roussev et al., under the title "Systems and Methods for Measuring Birefringence in Glass and Glass-Ceramics," claiming priority to U.S. Provisional Application No. 61 / 706891, filed on September 28, 2012, under the same title, discloses apparatus and methods for optically measuring birefringence on the surfaces of glass and glass-ceramics, including opaque glass and glass-ceramics. Unlike Roussev I, where separate mode spectra are identified, the method disclosed in Roussev II relies on a meticulous analysis of the angular intensity distribution of TM and TE light reflected by the prism-sample interface in a prism-coupled configuration of measurement. The contents of the aforementioned applications are incorporated herein by reference in their entirety.

[0161] Therefore, the precise distribution of reflected light intensity with respect to angle is considerably more important than conventional prism-coupled stress measurements, which can only determine the positions of distinct modes. For this purpose, the methods disclosed in Roussev1 and RoussevII include techniques for normalizing the intensity spectrum, including normalization with respect to a reference image or signal, correcting for detector nonlinearity, averaging multiple images to reduce image noise and speckle, and applying digital filtering to further smooth the intensity angular spectrum. In addition, one method includes forming a contrast signal, which is further normalized to compensate for fundamental differences in shape between the TM and TE signals. The aforementioned methods rely on achieving two signals that are nearly identical and determining their relative displacement at sub-pixel resolution by comparing portions of the signals that contain the steepest gradient regions. Birefringence is proportional to the relative displacement, and the coefficient is determined by the apparatus design, including the geometry and refractive index of the prism, the focal length of the lens, and the pixel spacing on the sensor. Stress is determined by multiplying the measured birefringence by a known stress optical coefficient.

[0162] Alternatively, the derivatives of the TM and TE signals are determined after applying several combinations of the aforementioned signal conditioning techniques. The position of the maximum derivative of the TM and TE signals is obtained at sub-pixel resolution, and the birefringence is proportional to the interval between the two maximum values, with coefficients determined by the instrument parameters as previously mentioned.

[0163] In relation to the requirements for accurate intensity extraction, the apparatus may include several enhancements such as a light scattering surface (static diffuser) adjacent to or on the prism incident surface to improve the angular uniformity of illumination, a moving diffuser for speckle reduction when the light source is coherent or partially coherent, and light-absorbing coatings on parts of the input and output facets of the prism as well as on the sides of the prism to reduce parasitic background that tends to distort the intensity signal. In addition, the apparatus may include an infrared light source to enable measurement of opaque materials.

[0164] Furthermore, Roussev II discloses the wavelength and attenuation coefficient ranges of the studied samples that can be measured by the described methods and instrument enhancements. This range is α s λ < 250πσ s Defined by, α s α is the optical attenuation coefficient at the measurement wavelength λ, and s This represents the expected stress value measured with the precision typically required for practical applications. This broad range makes it possible to obtain practically important measurements at wavelengths where large optical attenuation has previously made existing measurement methods unusable. For example, Roussev II discloses a successful measurement of stress-induced birefringence of opaque white glass-ceramics at a wavelength of 1550 nm, where the attenuation is over approximately 30 dB / mm.

[0165] In embodiments, the stress profiles of chemically strengthened glass articles disclosed herein may be measured using a scattered light photoelastic stress meter (SLP), or an SLP in combination with a fsymmetric photometer (FSM). Commercial SLP meters include the SLP-1000 and SLP-2000 manufactured by Orihara Industrial Co., Ltd. However, stress profile attributes may also be measured using custom measurement systems. In some cases, custom measurement systems may be able to provide more accurate measurements than commercially available systems.

[0166] When measuring the stress profile attributes of glass-based articles using commercial-grade equipment, it should be noted that it may be necessary to perform several measurements, for example 10 measurements, and average the retardation data for subsequent analysis and extraction of the attributes of various objects, which will be discussed in more detail below.

[0167] Base composition of glass-based articles In the embodiments of the glass-based articles disclosed herein, SiO2 is the largest component and, therefore, the main component of the glass network formed from the glass-based substrate composition. Pure SiO2 has a relatively low CTE and does not contain alkali. However, pure SiO2 has a high melting point. Therefore, if the concentration of SiO2 in the glass-based substrate composition is too high, the higher the concentration of SiO2, the greater the difficulty of melting the glass, which adversely affects the moldability of the glass and can reduce the moldability of the glass composition. In embodiments, the glass-based substrate composition may contain 50.0 to 75.0 mol% of SiO2. In embodiments, the glass-based substrate composition may contain 50.0 to 70.0 mol% of SiO2. In embodiments, the glass-based substrate composition may contain 55.0 to 65.0 mol% of SiO2. In embodiments, the glass-based substrate composition may contain 57.0 to 63.0 mol% of SiO2. In the embodiment, the concentration of SiO2 in the glass substrate composition is 50.0-70.0 mol%, 50.0-67.0 mol%, 50.0-65.0 mol%, 50.0-63.0 mol%, 50.0-60.0 mol%, 55.0-70.0 mol%, 55.0-67.0 mol%, 55.0-65.0 mol%, 55.0-64.0 mol%, 55.0-63.0 mol%, 55.0-62.0 mol%, 55.0-61.0 mol%, 55.0-60.0 mol%, 55.0-59.0 mol%, 56.0-70.0 mol%, 56.0-67.0 mol%, 56.0-65.0 mol%, 56. The ranges may be 0-64.0 mol%, 56.0-63.0 mol%, 56.0-62.0 mol%, 56.0-61.0 mol%, 56.0-60.0 mol%, 56.0-59.0 mol%, 57.0-70.0 mol%, 57.0-67.0 mol%, 57.0-65.0 mol%, 57.0-64.0 mol%, 57.0-63.0 mol%, 57.0-62.0 mol%, 57.0-61.0 mol%, 57.0-60.0 mol%, 57.0-59.0 mol%, or 65.0-75.0 mol%, or any subrange formed from any of these endpoints.

[0168] The base compositions or glass-based articles described herein may further contain Al2O3. Al2O3, like SiO2, can act as a glass network-forming agent. Due to its tetrahedral coordination in the glass melt formed from the glass-based substrate composition, Al2O3 can increase the viscosity of the glass-based substrate composition. If the amount of Al2O3 is too high, the moldability of the glass-based substrate composition may decrease. However, when the concentration of Al2O3 balances the concentration of SiO2 and the concentration of alkali oxides in the glass-based substrate composition, Al2O3 can reduce the liquidus temperature of the glass melt. Reducing the liquidus temperature increases the liquidus viscosity, improving the compatibility of the glass-based substrate composition with certain forming processes, such as fusion forming processes. In embodiments, the glass-based substrate composition may contain 10.0 to 25.0 mol% of Al2O3. In embodiments, the glass-based substrate composition may contain 14.0 to 20.0 mol% of Al2O3. In the embodiment, the glass substrate composition may contain 15.0 to 19.0 mol% Al2O3.In the embodiment, the concentration of Al2O3 in the glass substrate composition is 10.0-25.0 mol%, 10.0-23.0 mol%, 10.0-20.0 mol%, 10.0-19.0 mol%, 10.0-18.0 mol%, 12.0-25.0 mol%, 12.0-23.0 mol%, 12.0-20.0 mol%, 12.0-19.0 mol%, 12.0-18.0 mol%, 13.0-25.0 mol%, 13.0-23.0 mol%, 13.0-20.0 mol%, 13.0-19.0 mol%, 13.0-18.0 mol%, 14.0-25.0 mol%, 14.0-23.0 mol%, 14.0-20.0 mol%, 14 The ranges may be 0.0-19.0 mol%, 14.0-18.0 mol%, 15.0-25.0 mol%, 15.0-23.0 mol%, 15.0-20.0 mol%, 15.0-19.0 mol%, 15.0-18.0 mol%, 16.0-25.0 mol%, 16.0-23.0 mol%, 16.0-20.0 mol%, 16.0-19.0 mol%, 16.0-18.0 mol%, 17.0-25.0 mol%, 17.0-23.0 mol%, 17.0-20.0 mol%, 17.0-19.0 mol%, or 17.0-18.0 mol%, or any subrange formed from any of these endpoints. In the embodiment, the concentration of Al2O3 in the glass substrate composition may be 10.0 mol% or more, 11.0 mol% or more, 12.0 mol% or more, 13.0 mol% or more, 14.0 mol% or more, 15.0 mol% or more, 16.0 mol% or more, or 17.0 mol% or more.

[0169] The glass substrate composition may further contain B2O3. B2O3 is added to the glass substrate composition as a mesh molded body, thereby reducing the meltability and moldability of the glass substrate. In embodiments, the glass substrate composition may contain 1.0 to 11.0 mol% of B2O3. In embodiments, the glass substrate composition may contain 2.0 to 10.0 mol% of B2O3, 3.0 to 9.0 mol% of B2O3, 4.0 to 8.0 mol% of B2O3, or 5.0 to 7.0 mol% of B2O3. In embodiments, the concentration of B2O3 in the glass substrate composition may be 0.5 mol% or more, 1.0 mol% or more, 1.5 mol% or more, 1.0 mol% or more, 2.0 mol% or more, 2.0 mol% or more, 2.5 mol% or more, 3.0 mol% or more, 3.5 mol% or more, or 4.0 mol% or more.

[0170] The glass substrate composition may further contain Li2O. The potential effect of Li2O on fracture toughness is discussed above. Furthermore, the addition of lithium to the glass allows for better control of the ion exchange process and further reduces the softening point of the glass. In embodiments, the glass substrate composition may contain 5.0 to 15.0 mol% of Li2O. In embodiments, the glass substrate composition may contain 5.0 to 10.0 mol% of Li2O. In embodiments, the glass substrate composition may contain 6.0 to 9.0 mol% of Li2O. In the embodiment, the concentration of Li2O in the glass substrate composition is 5.0-15.0 mol%, 5.0-10.0 mol%, 5.0-9.0 mol%, 5.0-8.5 mol%, 5.0-8.0 mol%, 6.0-15.0 mol%, 6.0-10.0 mol%, 6.0-9.0 mol%, 6.0-8.5 mol%, 6.0-8.0 mol%, 6.0-7.5 mol%, 6.0-7.0 mol%, 6.5-15.0 mol%, and 6.5-10.0 mol%. The concentration can be in the range of 1%, 6.5-9.0 mol%, 6.5-8.5 mol%, 6.5-8.0 mol%, 7.0-15.0 mol%, 7.0-10.0 mol%, 7.0-9.0 mol%, 7.0-8.5 mol%, 7.0-8.0 mol%, 7.5-15.0 mol%, 7.5-10.0 mol%, 7.5-9.0 mol%, or 7.5-8.5 mol%, or any subrange formed from any of these endpoints. In embodiments, the concentration of Li2O in the glass substrate composition can be 15.0 mol% or less, 10.0 mol% or less, 9.5 mol% or less, 9.0 mol% or less, 8.5 mol% or less, or 8.0 mol% or less. In the embodiment, the glass substrate contains 9 mol% Li2O or more, 10 mol% Li2O or more, 10.5 mol% Li2O or more, 11 mol% Li2O or more, 11.5 mol% Li2O or more, or 12 mol% Li2O or more.

[0171] The glass substrate compositions described herein may further contain alkali metal oxides other than Li2O, such as Na2O. Na2O assists in the ion exchange properties of the glass substrate composition, increases its melting point, and improves its moldability. However, if Na2O is added in excess to the glass substrate composition, the CTE may become too low and the melting point may become too high. Therefore, in the embodiments, the concentration of Li2O present in the glass substrate composition is higher than the concentration of Na2O present in the glass substrate composition. In the embodiments, the glass substrate composition may contain 0.5 to 15.0 mol% of Na2O. In the embodiments, the glass substrate composition may contain 1.0 to 10.0 mol% of Na2O. In the embodiments, the glass substrate composition may contain 1.0 to 2.0 mol% of Na2O. In the embodiments, the glass substrate composition may contain 1.0 to 3.0 mol% of Na2O.

[0172] The glass substrate compositions described herein may further contain alkali metal oxides other than Li2O and Na2O, such as K2O. K2O promotes ion exchange and increases DOC. However, the addition of K2O may result in an excessively low CTE and an excessively high melting point. In embodiments, the glass substrate composition may contain 0.0 to 1.0 mol% of K2O. In embodiments, the glass substrate composition may contain 0.0 to 0.5 mol% of K2O. In embodiments, the glass substrate composition may contain 0.0 to 0.4 mol% of K2O. In embodiments, the concentration of K2O in the glass substrate composition may be in the range of 0.0 to 1.0 mol%, 0.0 to 0.5 mol%, 0.0 to 0.4 mol%, 0.0 to 0.3 mol%, 0.0 to 0.2 mol%, or 0.0 to 0.1 mol%, or any subrange formed from any of these endpoints. In the embodiment, the glass substrate composition may contain 1.0 mol% or less of K2O, 0.5 mol% or less of K2O, 0.4 mol% or less of K2O, 0.3 mol% or less of K2O, 0.2 mol% or less of K2O, or 0.1 mol% or less of K2O.

[0173] The glass substrate compositions described herein may further contain MgO. MgO can lower the viscosity of the glass, thereby increasing its formability, strain point, and Young's modulus, and improving its ion exchange properties. However, excessive addition of MgO to the glass substrate composition increases the density and CTE of the glass substrate composition. In the embodiments, the MgO concentrations in the glass substrate composition are 0.0-5.0 mol%, 0.0-4.5 mol%, 0.0-4.0 mol%, 0.0-3.5 mol%, 0.0-3.0 mol%, 0.0-2.5 mol%, 0.0-2.0 mol%, 0.0-1.5 mol%, 0.5-5.0 mol%, 0.5-4.5 mol%, 0.5-4.0 mol%, 0.5-3.5 mol%, and 0.5-3.0 mol%. The MgO concentration can be in the range of %, 0.5-2.5 mol%, 0.5-2.0 mol%, 0.5-1.5 mol%, 1.0-5.0 mol%, 1.0-4.5 mol%, 1.0-4.0 mol%, 1.0-3.5 mol%, 1.0-3.0 mol%, 1.0-2.5 mol%, 1.0-2.0 mol%, or 1.0-1.5 mol%, or any subrange formed from any of these endpoints. In embodiments, the MgO concentration is 5.0 mol% or less, 4.5 mol% or less, 4.0 mol% or less, 3.5 mol% or less, 3.0 mol% or less, 2.5 mol% or less, 2.0 mol% or less, or 1.5 mol% or less. In the embodiment, the concentration of MgO in the glass substrate composition may be greater than 0.0 mol% to 3.0 mol%, greater than 0.0 mol% to 2.5 mol%, greater than 0.0 mol% to 2.0 mol%, or greater than 0.0 mol% to 1.5 mol%.

[0174] The glass substrate compositions described herein may further contain CaO. CaO can lower the viscosity of the glass, thereby increasing its formability, strain point, and Young's modulus, and improving its ion exchange properties. However, if CaO is added in excess to the glass substrate composition, the density and CTE of the glass substrate composition will increase. In the embodiment, the concentration of CaO in the glass substrate composition is 0.0-5.0 mol%, 0.0-4.0 mol%, 0.0-3.5 mol%, 0.0-3.0 mol%, 0.0-2.5 mol%, 0.0-2.0 mol%, 0.0-1.5 mol%, 0.0-1.0 mol%, 0.0-0.5 mol%, 0.0-0.1 mol%, 0.5-5.0 mol%, 0.5-4.0 mol%, 0.5-3.5 mol%, 0.5-3.0 mol%, 0.5-2.5 mol%, 0.5-2.0 mol%, 0.5-1.5 mol%, 0.5-1.0 mol%, 1.0-5.0 mol%, 1.0-4.0 mol%, 1.0 The concentration can be ~3.5 mol%, 1.0~3.0 mol%, 1.0~2.5 mol%, 1.0~2.0 mol%, 1.5~5.0 mol%, 1.5~4.0 mol%, 1.5~3.5 mol%, 1.5~3.0 mol%, 1.5~2.5 mol%, 1.5~2.0 mol%, 2.0~5.0 mol%, 2.0~4.0 mol%, 2.0~3.5 mol%, 2.0~3.0 mol%, 2.0~2.5 mol%, 2.5~5.0 mol%, 2.5~4.0 mol%, 2.5~3.5 mol%, or 2.5~3.0 mol%, or any sub-range formed from any of these endpoints. In embodiments, the concentration of CaO in the glass substrate composition may be 0.1 mol% or less. In the embodiment, the concentration of CaO in the glass substrate composition may be greater than 0.0 mol% and less than 0.1 mol%. In the embodiment, the glass substrate composition may be substantially free of CaO or may not contain CaO at all.

[0175] The glass substrate compositions described herein may further contain ZnO. In the embodiments, the concentration of ZnO in the glass substrate composition may be greater than 0.0 mol% and less than or equal to 3.0 mol%.

[0176] The glass substrate compositions described herein may further comprise one or more clarifying agents. In embodiments, the clarifying agent may comprise, for example, SnO2. In embodiments, the concentration of SnO2 in the glass substrate composition may be 0.0 to 1.0 mol%, 0.0 to 0.5 mol%, 0.0 to 0.4 mol%, 0.0 to 0.3 mol%, 0.0 to 0.2 mol%, or 0.0 to 0.1 mol%, or any sub-range formed from any of these endpoints. In embodiments, the concentration of SnO2 in the glass substrate composition may be 0.1 mol% or less. In embodiments, the concentration of SnO2 in the glass substrate composition may be in the range of greater than 0.0 mol% to 0.1 mol%, greater than 0.0 mol% to 0.5 mol%, or greater than 0.0 mol% to 1.0 mol%. In embodiments, the glass substrate composition may be substantially free of or omit SnO2.

[0177] The base compositions for glass-based articles disclosed herein may, specifically, contain additional elements and / or oxides as necessary for desired properties. For example, TiO2 may be added to improve the UV absorbance of the glass-based substrate composition. Those skilled in the art will understand that additional components may be added to the composition without departing from the concepts disclosed herein in relation to the stress profile imparted to the glass-based article through the strengthening process.

[0178] In this embodiment, the glass substrate may contain 50 mol% or more and 75 mol% or less of SiO2, 10 mol% or more and 25 mol% or less of Al2O3, 1 mol% or more and 11 mol% or less of B2O3, 1 mol% or more and 10 mol% or less of Na2O, and 5 mol% or more and 15 mol% or less of Li2O, wherein the molar concentration of Li2O in the glass substrate is less than the molar concentration of Na2O in the glass substrate.

[0179] In the embodiment, the glass substrate contains a Li2O to Na2O molar ratio of 1.0 or more, 1.5 or more, 2.0 or more, 2.5 or more, 3.0 or more, 3.5 or more, 4.0 or more, 4.5 or more, 5.0 or more, 5.5 or more, 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, 8.5 or more, 9.0 or more, 9.5 or more, or 10.0 or more.

[0180] Ion exchange treatment As described above, glass articles can be chemically strengthened by ion exchange treatment. In this process, ions on or near the surface of the glass are replaced or exchanged with larger ions having the same valence or oxidation state. In embodiments of glass articles containing, essentially consisting of, or consisting of alkali aluminosilicate glass, ions in the surface layer of the glass and larger ions are replaced with Li + (If present in glass), Na + , K + , Rb + , and Cs + These are monovalent alkali metal cations. Alternatively, monovalent cations in the surface layer include Ag + These can be replaced with monovalent cations other than alkali metal cations.

[0181] The ion exchange process is typically carried out by immersing a glass article in a molten salt bath containing larger ions to be exchanged for smaller ions in the glass. Parameters for the ion exchange process, including but not limited to the bath composition and temperature, immersion time, number of immersions of the glass in the salt bath (or multiple baths), use of multiple salt baths, annealing, and washing, are generally determined based on the glass composition, as well as the desired layer depth and compressive stress of the glass resulting from the strengthening operation, as will be understood by those skilled in the art. As an example, ion exchange of alkali metal-containing glass can be achieved by immersion in at least one molten bath containing salts such as nitrates, sulfates, and chlorides of larger alkali metal ions, but not limited to those listed above. The temperature of the molten salt bath is typically in the range of about 380°C to a maximum of about 450°C, or about 460°C, while the immersion time is in the range of about 15 minutes to a maximum of about 40 hours. However, different temperatures and immersion times than those described above may also be used. For example, those skilled in the art will understand that the thickness of the glass substrate subjected to ion exchange treatment may be taken into consideration when selecting the temperature of the molten salt bath and the immersion time for the ion exchange treatment.

[0182] In addition, non-limiting examples of ion exchange processes in which glass is immersed in multiple ion exchange baths, with washing and / or annealing steps performed between immersions, include U.S. Patent No. 8,561,429, published on 22 October 2013 by Douglas C. Allan et al., entitled “Glass with Compressive Surface for Consumer Applications,” claiming priority to U.S. Provisional Patent Application No. 61 / 079,995 filed on 11 July 2008, which describes how glass is strengthened by immersion in multiple successive ion exchange treatments in salt baths of different concentrations, and U.S. Patent No. 8,561,429, published on 20 November 2012 by Christopher M. Lee et al., entitled “Dual Stage Ion Exchange for Chemical Strengthening of U.S. Patent No. 8,312,739, claiming priority from U.S. Provisional Patent Application No. 61 / 084,398, filed July 29, 2008, describes how glass is strengthened by ion exchange in a first bath diluted with efferent ions, followed by immersion in a second bath having a lower concentration of efferent ions than the first bath. The contents of U.S. Patents No. 8,561,429 and No. 8,312,739 are incorporated herein by reference in their entirety.

[0183] Compressive stress is generated by chemically strengthening a glass-based article, for example, by an ion exchange process previously described herein, in which a plurality of first metal ions in the outer region of the glass-based article are exchanged for a plurality of second metal ions, such that the outer region contains a plurality of second metal ions. Each of the first metal ions has a first ionic radius, and each of the second alkali metal ions has a second ionic radius. The second ionic radius is larger than the first ionic radius, and the presence of larger second alkali metal ions in the outer region generates compressive stress in the outer region.

[0184] At least one of the first and second metal ions is an alkali metal ion. The first ion may be lithium, sodium, potassium, or rubidium. The second metal ion may be one of sodium, potassium, rubidium, or cesium, provided that the second alkali metal ion has a larger ionic radius than the first alkali metal ion.

[0185] As used herein, the term “sodium ion penetration depth after ion exchange” refers to the depth within the glass article (i.e., the distance from the surface of the glass article to its interior region) to which sodium ions introduced by the ion exchange process diffuse into the glass article and reach the minimum concentration of sodium ions determined by glow discharge emission spectroscopy (GD-OES).

[0186] As used herein, the term “potassium ion penetration depth after ion exchange” refers to the depth within the glass article (i.e., the distance from the surface of the glass article to its interior region) to which potassium ions introduced by the ion exchange process diffuse into the glass article and reach the minimum potassium ion concentration determined by GD-OES.

[0187] As stated above, this disclosure relates to chemically strengthened glass articles that are strengthened to satisfy the requirement of non-fractureness while achieving deep DOC and high levels of compressive stress in the compression layer. However, several obstacles must be overcome to obtain a stress profile for a strengthened glass article that achieves these characteristics. For example, since the desired ion exchange diffusivity often depends on the concentration of outward-diffusing ion species, the ability to induce a stress profile with high DOC may be hindered by the limited concentration of outward-diffusing ions. Thus, the limited concentration of outward-diffusing ion species may limit the ability to induce stress in the glass. Exemplary ion exchange treatment methods that overcome some of these challenges are discussed in more detail herein.

[0188] Non-crushing As discussed above, the strength of a glass-based article subjected to tensile stress strongly depends on the depth of sharp scratches extending from the surface into the glass.

[0189] During practical use, the cover glass of electronic devices may be subjected to contact events with rough surfaces, leading to the formation of scratches of various depths, including considerable depths close to and even exceeding 100 micrometers (μm). For critical protection against fracture due to relatively deep scratches, it is desirable to maximize the density of contact (DOC). In addition, during drop events, considerable stress can be induced in the cover glass, particularly near the point of contact. Compressive stress within the compression layer can weaken the tensile stress generated during a drop event. Therefore, a higher magnitude of compressive stress within the compression layer can further increase the level of protection. Thus, to provide cover glass with improved protection against breakage, there is a need for reinforced glass-based articles with deep DOC and high levels of compressive stress in the compression layer.

[0190] The glass articles described herein are non-shatterable glass articles. It is becoming increasingly common for manufacturers of electronic devices having cover glasses to require that the cover glasses be non-shatterable. The non-shatterable glass articles described herein do not exhibit shatterable behavior (also referred to herein as "shatterable").

[0191] Fracturable behavior is a result of sufficiently accumulated strain energy within an article, causing a glassy article to fracture into multiple parts (e.g., more than three) with several branching points. In thermally tempered, laminated, or chemically strengthened (e.g., strengthened by ion exchange) glassy articles, fracturable behavior can occur when sufficient energy is provided to cause crack branching accompanied by the scattering, ejection, or "throwing" of small glass particles from the article, by balancing the compressive stress in the surface or outer regions of the glassy article with tensile stress in the center of the article. The rate at which such scattering occurs is a result of the amount of high tensile energy within the glassy article.

[0192] Fragile behavior can be characterized by at least one of the following: fracture of a reinforced glass article (e.g., a plate or sheet) into multiple small pieces (e.g., ≤1 mm); the number of fragments formed per unit area of ​​the glass article; multiple cracks branching from the initial crack of the glass article; severe scattering of at least one fragment to a certain distance (e.g., about 5 cm or about 2 inches) from its original position; and any combination of the aforementioned fracture (size and density), crack formation, and scattering behavior. As used herein, the terms “fragile behavior” and “fragility” refer to those modes of severe or strong fragmentation of a reinforced glass article without any external constraints such as coatings, adhesive layers, etc. Coatings, adhesive layers, etc. may be used in conjunction with the reinforced glass articles described herein, but such external constraints are not used in determining the fragility or fragile behavior of the glass article.

[0193] Non-fracturable glass articles can be made from a glass composition strengthened by one or more strengthening processes configured to impart a desired stress profile to the glass composition, such as the glass compositions and strengthening processes disclosed herein. In some embodiments, the strengthening process may include one or more ion exchange processes. In such embodiments, the glass composition from which the non-fracturable glass article is made is an ion-exchangeable glass composition. As used herein, “ion-exchangeable” means that the glass composition, or a glass article containing the composition, can exchange a first cation located on or near the surface of a substrate for a second cation of the same valence. The first cation may be a sodium ion. The second cation may be one of potassium, rubidium, and cesium ions, provided that the second cation has a larger ionic radius than the first cation. The first cation exists in the glass composition as its oxide (e.g., Na₂O). As used herein, “ion-exchanged glass article” or “chemically strengthened glass article” means that the glass article has undergone at least one ion-exchange process in which cations located on or near the surface of the glass are exchanged with cations of the same valence. In some embodiments, the strengthening process may include one or more thermal tempering processes. In some embodiments, the strengthening process may include one or more annealing processes.

[0194] Examples of the fracturing and non-fracturing behavior of reinforced glass articles during point impact with a sharp indenter are shown in Figures 2a and 2b. The point impact test used to determine the fracturing behavior involves a device that delivers a force to the surface of the glass article with just enough force to release the internally stored energy present within the reinforced glass article. That is, the point impact force is sufficient to induce at least one new crack on the surface of the reinforced glass sheet and to cause the crack to extend through the compressive stress layer into a region under tension. The impact energy required to induce or activate a crack in the reinforced glass sheet depends on the compressive stress in the compressive stress layer and the compression depth DOC of the article, and therefore depends on the conditions under which the sheet was reinforced (i.e., the conditions used to reinforce the glass by ion exchange). Otherwise, each ion-exchanged glass plate shown in Figures 2a and 2b received contact with a sharp dart indenter (e.g., a SiC indenter) sufficient for the crack to propagate into the inner region of the plate (the inner region is under tensile stress). The force applied to the glass plate is just enough to reach the starting point of the inner region; therefore, the energy propelling the crack originates from the tensile stress within the inner region, rather than from the force of the dart impact on the outer surface. The degree of scattering can be determined, for example, by centering the glass sample on a grid, impacting the sample, and using the grid to measure the scattering distance of individual pieces.

[0195] Referring to Figure 2a, glass plate a can be classified as fragile. Specifically, glass plate a fragmented into multiple small pieces, generating fragments with a significant degree of crack branching from the initial crack. Approximately 50% of the fragments were less than 1 mm in size, and it is estimated that about 8 to 10 cracks branched from the initial crack. The glass fragments also scattered about 5 cm from the original glass plate a, as seen in Figure 2a. Glass-based articles exhibiting any of the three criteria described herein (i.e., multiple crack branching, scattering, and extreme fragmentation) are classified as fragile. For example, if glass exhibits excessive branching alone but does not exhibit scattering or extreme fragmentation as described above, the glass is still characterized as fragile.

[0196] Glass plates b, c (Figure 2b) and d (Figure 2a) are classified as non-fracturable. In each of these samples, the glass sheet fractures into a few large pieces. Glass plate b (Figure 2b) fractures into two large pieces without crack branching, for example; glass plate c (Figure 2b) fractures into four pieces with two cracks branching from the first crack; and glass plate d (Figure 2a) fractures into four pieces with two cracks branching from the first crack. Based on the absence of scattered fragments (i.e., no glass fragments violently scattered beyond 2 inches from their original position), the absence of visible fragments smaller than 1 mm in size, and the minimal amount of observed crack branching, samples b, c, and d are classified as non-fracturable or substantially non-fracturable.

[0197] Stress profile for compressive stress layer The chemically strengthened glass articles of this disclosure exhibit improved fracture resistance and non-fracture properties by having a stress profile (induced through a specific chemical strengthening process) with certain attributes that are thought to result in these mechanical properties. These attributes are described in detail below.

[0198] In glass-based articles exhibiting surface spikes, the surface spikes occupy a significant portion of the compressive stress area, protecting the glass-based article from relatively low penetration. However, this results in lower compressive stress levels (for the same compressive stress area) in the deeper parts of the compressive stress layer where the tip of a deep scratch may reside. Therefore, the protective effect of surface spikes is not very useful for protecting against damage resulting from deep scratches. This is especially true when the near-surface facets of a crack (e.g., a scratch) do not separate during bending events that impose externally applied tensile stresses, due to the concentration of surface compressive stress.

[0199] The two compression layer parameters of the glass-based article according to the embodiments of this disclosure are, excluding surface spikes, the deep compressive stress area (CSA) in the compression region. 深部 ) and mean deep compressive stress

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[0200] These two parameters in the deep compressive stress region are defined as follows:

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[0201] Compared to previously known glass-based articles, a more refined parameter of strengthening, which can be a good predictor of improved fracture resistance on rough surfaces, is the stress strength coefficient K. R And,

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[0202] Specifically, K corresponds to a scratch depth c equal to DOC. R The value of is

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[0203] Set the crack shape coefficient to 1.12, input the above Green function approximation, and then calculate the stress strength coefficient K. R teeth,

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[0204] Due to the generally continuous and almost monotonic nature of the stress profiles obtained by diffusion, these three parameters (CSA 深部 ,

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[0205] The parameters described above, representing different stress profile attributes in the deep compression region, have been found to allow for an effective comparison of the different occurrences of high DOC stress profiles for any selected specific thickness with respect to the predicted fracture resistance during drops onto a rough surface. This is mainly because the DOC is substantially maximized for thicknesses below approximately 0.8 mm, resulting in nearly the same DOC / thickness ratio for Li glass profiles (the force balance sets the maximum DOC for conventional chemical strengthening of Li-based glass). This DOC is typically around 20% of the thickness, but in some cases, it may be slightly lower or slightly higher, depending on the characteristics of the process (single or double ion exchange), the interaction with the glass composition and its concentration dependence of its diffusion coefficient, and the degree of stress relaxation. Furthermore,

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[0206] Glass with higher fracture toughness has a higher peak tension zone (p<2), higher PT, and therefore, advantageously,

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[0207] In the embodiment, when the composition of the glass-based article contains less than 3 mol% Li2O, the fracture toughness K of the glass-based article is IC This corresponds to position x within the central tension zone 130, which is the peak tension PT. ピーク In

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[0208] In this embodiment, the fracture toughness K of the glass-based article IC teeth,

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[0209] With respect to glass-based articles that have been ion-exchanged to have surface spikes, in at least three cases of the subject, DOL sp It is recognized that efforts should be made to increase the level of deep compressive stress between the DOC and the cover glass: (i) a cover glass with high fracture toughness and reduced thickness (mainly 0.4 mm to 0.6 mm, more generally up to 0.65 mm or 0.7 mm, and as low as about 0.35 mm or 0.30 mm), (ii) a cover glass with a geometred edge (2.5D geometred edge) that has locally reduced or further reduced thickness, and (iii) a 3D geometred cover glass, in particular having reduced thickness (e.g., 0.4 mm to 0.6 mm).

[0210] For thin or 3D-shaped cover glass, the importance of higher deep compressive stress increases due to the tendency for more localized bending upon contact, and therefore higher localized bending stress. For glass articles with 2.5D-shaped edges, the stress profile may have higher levels of deep compressive stress over a thicker and wider area of ​​the sheet in order to achieve higher levels of deep compressive stress at the 2.5D edge of the sheet with at least one relevant stress component, thus reducing the risk of fracture when a contact event occurs on the 2.5D edge.

[0211] As discussed above, increasing the level of deep compressive stress beyond the most advanced technology is difficult to achieve without making the glass fragile, and the increased deep compressive stress occurs in conjunction with an increase in tensile stress within the central tension zone 130 due to the force balance between the integrated compressive and integrated tensile stresses. Such an increase in tensile stress would result in a reinforced glass article that is fragile unless the glass-based substrate has substantially higher fracture toughness. Transparent glass-ceramics with substantially better fracture toughness than typical cover glasses have been invented and have actually entered the market, but the cost of glass-ceramic covers is currently significantly higher than that of glass covers due to the extra processing steps for glass-ceramics and generally more expensive processing (e.g., more expensive polishing). This disclosure focuses on increasing the level of deep compressive stress with respect to any fixed material strength parameter such as fracture toughness, so that the resulting performance improvement is additive with respect to any performance improvement based on advanced material mechanical properties such as fracture toughness.

[0212] Stress profile for the central tension zone While the primary ultimate goal of this disclosure is to increase the level of deep compressive stress within a compression region, a key aspect of this disclosure relates to increasing the average tension within the tension area and / or tension zone without increasing the tensile stress energy. This is driven by the importance of tensile stress energy as a driving factor for shatter resistance. Therefore, one key aspect of the reinforced glass articles of this disclosure is to intentionally shape the stress distribution in the tension zone to achieve a more uniform distribution for a particular target DOC (e.g., greater than 15% or substantially greater than 15% of the thickness). One ultimate goal of this disclosure is to enhance the shatter resistance of modern cover glasses of low to medium thickness. Such cover glasses generally need to have a high DOC-to-thickness ratio.

[0213] Relative uniformity of the tensile stress distribution is desirable because the tensile strain energy (TSE) is proportional to the depth integral of the squared tensile stress across the central tension zone, whereas the tension area TA (equal to the compressive stress area by force balance) is only the depth integral of the tensile stress across the central tension zone. Therefore, a less uniform stress distribution increases the TSE for a fixed TA, and vice versa. Since fragility imposes an upper limit on the TSE, this disclosure attempts to increase TA by improving the uniformity of the tensile stress distribution in the tension zone. Another reason for focusing on the tension zone first is that it is relatively easy to measure the stress distribution in the deeper interior of Li-based glass using scattered light polarization (SLP). In fact, measuring the stress distribution in the tension zone of Li-based glass is usually much more accurate than in the compression region, as the compression region is closer to the surface and strong surface scattering impairs the data collected for the near-surface region. A second reason for a more accurate extraction of stress within the tension zone is the finite resolution of the scattered light polarization method, which results in reduced accuracy in regions where the profile tends to have high second derivatives by absolute value. Li glass stress profiles typically have higher second derivatives by absolute value in the compression region, both at the bottom of the spike and at some deeper locations.

[0214] The tension zone stress profile attribute is particularly applicable to Li-based glasses, but can be used similarly for Na-based glasses. However, for Na-based glasses, the Inverse Wentzel-Kramers-Brillouin (IWKB) method discussed above provides an alternative method for directly obtaining the accurate stress distribution in the compression region, provided the glass surface is flat and the profile is not excessively deep, allowing for the correct resolution of fringes in the prism-coupled spectra corresponding to deep modes and obtaining their effective indices with high accuracy.

[0215] It is counterintuitive to pursue a profile with more uniform tension in the tension zone in order to increase the level of deep compression while avoiding fracturing. In fact, prior art profiles with the most uniform tension zone, such as conventional one-step profiles in sodium aluminosilicate (Gorilla® glass 1, 2, and 3) with DOC / t < 0.08 and in most cases DOC / t < 0.06, have a substantially flat tension zone and average tension

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[0216] The tension area (TA) of the stress profile is the depth integral of the tensile stress across the tension zone of the glass-based article. The central tension zone 130 is defined by the space extending from the DOC of the compressive stress layer on one side of the glass-based article to the DOC of the compressive stress layer on the opposite side of the glass-based article. The tension area TA is calculated according to the following formula:

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[0217] One way to ensure non-fractureness in chemically strengthened glass-based articles is to consider the fracture toughness of the glass-based substrate undergoing chemical strengthening, and then determine the tension zone fracture coefficient K. t The objective is to limit the crushability coefficient K. t It is defined as follows:

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[0218] In the embodiment, the glass-based article is 2.1 × K IC Crushing coefficient K not exceeding t It may have, K IC This corresponds to position x within the central tension zone 130, which is the peak tension PT. ピーク This is the fracture toughness of a glass article in . In the embodiment, the glass article has a fracture toughness of 1.97 × K. IC Crushing coefficient K not exceeding t It may have.

[0219] It has been found that the maximum non-fracture PT varies approximately in proportion to the reciprocal of the square root of the thickness. Therefore, in embodiments, the PT of a glassy article induced by chemical strengthening can be set based on the inverse square root of the thickness. In embodiments, the peak tension PT of a glassy article is

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[0220] In the embodiment, the glass-based article has a peak tension PT of over 90 MPa, over 92 MPa, over 95 MPa, over 100 MPa, over 103 MPa, over 108 MPa, over 110 MPa, over 113 MPa, or over 115 MPa. In the embodiment, the glass-based article has a peak tension PT of over 105 MPa. In the embodiment, the glass-based article has a peak tension PT of over 120 MPa, over 125 MPa, or over 130 MPa.

[0221] In the embodiment, the thickness t of the glass-based article may be in the range of about 0.4 mm to about 0.77 mm or about 0.43 mm to about 0.68 mm. In the embodiment, the thickness t of the glass-based article may be 0.40 mm or more or 0.43 mm or more. In the embodiment, the thickness t of the glass-based article may be 0.77 mm or less or 0.68 mm or less. In the embodiment, the thickness t of the glass-based article is 0.52 mm or less.

[0222] The shape of the stress profile within the tension zone can be approximated by the force shape profile as follows:

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[0223] It illustrates how to improve stress profile attributes using a suitable model of stress distribution in the tension zone, enabling accurate measurement of stress profile attributes even when the measured retardation is relatively noisy, and K t and

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[0224] In the embodiment, the stress profile of the glass-based article has a best-fit value of force coefficient p that is 2.75 or greater, 2.8 or greater, 2.85 or greater, 2.9 or greater, 3.0 or greater, 3.1 or greater, or 3.2 or greater when conforming to Equation 14. In the embodiment, the stress profile of the glass-based article has a best-fit value of force coefficient p that is not greater than 20 when conforming to Equation 14. In the embodiment, the stress profile of the glass-based article has a best-fit value of force coefficient p that is greater than 2.35, greater than 2.4, greater than 2.45, greater than 2.5, greater than 2.55, greater than 2.6, greater than 2.65, or greater than 2.7 when conforming to Equation 14.

[0225] Average tension within the tension zone

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[0226] The degree of uniformity of the tensile stress distribution can be evaluated using several different attributes of the stress profile. Some of the most generally applicable attributes (regardless of the shape of the distribution) include ratios.

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[0227] Figure 4 shows the dimensionless stress profile attributes with respect to the force coefficient p (x axis).

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[0228] Other ratios related to improving the stress profile under non-fracture limits include the tension zone fracture coefficient K. t and

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[0229] As each of the stress profile attributes shown above increases, an increase in the amount of compression in the compressive stress layer is permitted for a given level of tensile strain energy.

[0230] Figure 5 shows the dimensionless stress profile attributes shown in Equation 19, where the force coefficient p varies from 1 to 20. For a fixed tension zone width (e.g., fixed DOC), profiles with higher p have a higher stress area.

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[0231] Furthermore, recognizing the importance of high DOC for fracture resistance on rough surfaces, this disclosure defines stress profile parameters that indicate an increased level of deep compressive stress, which also explicitly describes the improved DOC.

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[0232] The improved DOC is explicitly explained, and TA vs K t or

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[0233] The evaluation of the stress profile attributes described above is not as concentrated for the flat portions of the glass-based article away from the edges. Furthermore, for 2.5D geometry, due to the importance of reinforcing the 2.5D edge area, the ratio of the flat (and thicker) portions of the sheet away from the 2.5D edge is important.

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[0234] In the embodiment, the DOC of the glass-based article may be 0.150t or more, 0.160t or more, 0.170t or more, 0.180t or more, 0.190t or more, or 0.200t or more. In the embodiment, the DOC of the glass-based article may be 0.205t or more or 0.210t or more.

[0235] The slope at high DOC for the diffusion-generated stress profile signifies high compressive stress in the region of the compression layer closest to DOC. Therefore, the slope of the stress profile at DOC is incorporated into another set of tension zone stress profile attributes that are more directly related to the deepest stress levels within the compression region. The slope at DOC can be calculated as follows:

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[0236] Figure 6 shows the stress profile attributes with respect to the force coefficient p (x axis).

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[0237] The stress profile attributes combining DOC and / or thickness, as well as the slope in DOC, include the following:

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[0238] In the embodiment, for glass-based articles

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[0239] In embodiments in which the glass-based article includes compression spikes on its surface, the knee compressive stress CS k (Deeper parts of the CS profile spike depth (DOL sp The value of the compressive stress (extrapolated to ) may be 100 MPa or more or 110 MPa or more. In embodiments in which the glass-based article includes compression spikes on its surface, the compressive stress CS of the knee k teeth,

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[0240] In embodiments in which the glass-based article includes compression spikes on its surface, the spike depth is DOL SP is zero or greater and has an upper limit of DOL ul The following may be true, DOL ul This is the larger of 4 μm and 0.01 t.

[0241] In embodiments in which the glass-based article includes compression spikes on its surface, DOL SP A portion of the stress profile between and DOC may contain negative curvature. While obtaining very high ratios of DOC / t (such as above 0.19 and 0.20), p and

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[0242] From here,

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[0243] Furthermore, for the case of the subject matter of the present disclosure, the condition DOL SP <<DOC holds, so the condition

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[0244] Higher CS k This is strongly associated with higher fracture resistance during system drop tests on rough surfaces (such as sandpaper), at least when DOC is already nearly maximized. The stress profile of the present invention in this disclosure is associated with a high level of CS kThis tends to be characterized by a high slope in the DOC resulting from the targeted shaping of the central tension zone. At the same time, a particularly preferred profile of the present invention is

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[0245] In the embodiment

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[0246] TA vs K t or

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[0247] K t or

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[0248] Specifically, the parameters of the stress profile attribute can be obtained directly from the retardation curve as follows: ●TA is proportional to the difference between the highest and lowest values ​​of retardation in the retardation curve, for example, the difference in retardation between two points where the stress profile crosses zero. ●PT is proportional to the maximum slope of the retardation curve between the minimum retardation position and the maximum retardation position. ●BTZ is the difference in depth between the minimum retardation point and the maximum retardation point. ●DOC is the distance from the surface to the nearest minimum or maximum retardance. ●

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[0249] TA, PT, and

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[0250] In the formula, Φ(x) is the retardation measured in radians, degrees, or nanometers as a function of depth x.

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[0251] Experimental retardation curves often contain noise, which affects the measured quantity, particularly retardation (PT and

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[0252] SLP-2000 Stress Profile Characterization Method Based on the above considerations, the stress profile attributes of the embodiments described herein can be measured using the SLP-2000 stress profile characterization method. The SLP-2000 stress profile characterization method utilizes a commercial SLP-2000 manufactured by Orihara Industrial Co., Ltd., which uses a 405 nm operating source (laser) wavelength. To address laser speckle noise in the spatial distribution of light intensity in the image of the laser beam, which by default may be too high to allow for precise determination of the essential profile shape in a single measurement, the SLP-2000 stress profile characterization method involves performing 10 measurements in which the glass specimen is rotated or linearly shifted between each measurement. Each of the 10 measurements generates a different speckle-noise pattern that propagates a different retardation-noise pattern on the retardation curve. After all 10 measurements are completed and the retardation curves are saved, an average retardation curve is obtained, characterized by significantly reduced noise compared to the retardation noise of the individual retardation curves.

[0253] If the glass specimen is rotated between each measurement, different retardation noise patterns can be achieved by covering a cumulative angular range of 180 degrees of rotation with approximately equal angular intervals between consecutive orientations, e.g., about 20 degrees per rotation. However, larger cumulative angular ranges of rotation and / or different rotation increments can be implemented, however, multiple measurements may not be taken correctly in the same location and orientation of the specimen, which may result in the same noise pattern persisting even after averaging. If the glass specimen is linearly shifted between each measurement, it should be shifted by about 100 μm (the diameter of a laser of about 405 nm) between each measurement, so that 10 measurements result in a cumulative linear shift of about 1 mm. However, as with the specimen rotation method, larger cumulative linear shifts and / or different linear shift increments can be implemented, however, multiple measurements may not be taken correctly in the same location and orientation of the specimen.

[0254] To ensure the accuracy of the measured retardation curve, the SLP-2000 must be calibrated according to the calibration procedure provided by the manufacturer. This involves providing the SLP-2000 software with accurate values ​​for the prism refractive index (provided by the manufacturer) and the measured glass refractive index at the measurement wavelength, as well as accurate values ​​for the stress optical coefficient (SOC) of the measured glass at the measurement wavelength. It is also important to supply the SLP-2000 software with the correct calibration coefficients for each calibration specimen at the measurement wavelength when using depth calibration specimens ("depth standard glass") and stress calibration specimens ("stress standard glass") provided by the manufacturer. There are three calibration coefficients provided in the 2018 version of the SLP-2000 software: the first is for depth correction ("DOL_zero"), and the second is for stress correction, surface stress correction, and deep stress correction ("CS correction" and "deep stress correction," respectively). For the retardation curve in the central tension zone to accurately represent the depth integral of the stress profile in the tension zone, the deep stress correction calibration coefficient must be equal to or approximately equal to the surface stress correction calibration coefficient. Otherwise, the stress profile will be distorted by the application of the deep stress correction calibration coefficient. It is also true that if the deep stress correction calibration coefficient is not set to the same value as the surface stress correction calibration coefficient, the shape of the resulting stress profile will vary depending on the depth referenced by the deep stress correction (the deep stress correction value is assumed to be applied to a specific depth). Therefore, to avoid unexpected distortion of the profile, it is best to keep the deep stress correction calibration coefficient the same as the surface stress correction calibration coefficient (i.e., "deep stress correction" = "CS correction").

[0255] For the SLP-2000 instrument used by the inventors, depth calibration using depth calibration specimens yielded a depth correction coefficient very close to 1, typically between 0.99 and 1.0; therefore, the inventors kept the depth correction coefficient value at 1. Surface compressive stress calibration, applied multiple times over many days, had an average value in the range of approximately 1.038 to 1.048. Each of these calibration values ​​was obtained after measuring the calibration specimen 10 times and averaging 10 surface compressive stress values ​​representing the calibration measurement. The inventors set the surface stress correction calibration coefficient to 1.04. Furthermore, since the retardation curve yielded a relatively symmetrical stress profile, the deep stress correction calibration coefficient was set to the same value as the surface stress correction calibration coefficient.

[0256] The SLP-2000 stress profile characterization method described herein enables accurate and reproducible measurement of averaged retardation curves for glass specimens, to which the following post-processing steps are applied to extract the attributes of the corresponding stress profiles of the glass specimens. Therefore, in addition to the measurement techniques and calibration procedures described above, the SLP-2000 stress profile characterization method involves the following post-processing steps to extract the attributes of the corresponding stress profiles of the glass specimens.

[0257] Figure 7 presents the average retardation curve for Example 7 and is referenced below to facilitate consideration of the post-processing procedure used by the SLP-2000 stress profile characterization method. The horizontal axis in Figure 7 represents spatial coordinates along the depth dimension for the glass specimen and is approximately equal to the depth measured from the surface with an accuracy that identifies the precise location of the glass specimen surface on the retardation curve (typically comparable to a DOC accuracy specification of ±5 μm). The vertical axis shows the measured retardation (phase difference) in degrees between the transverse electric field polarization state and the transverse magnetic field polarization state. The solid line represents the average retardation for 10 measurements. Two dashed lines, one near a local peak of retardation and the other near a local trough, represent local quartic polynomial fits, which are used to determine the more precise location of the retardation peaks and troughs at sub-pixel resolution. The quartic polynomial fit is based on retardation data spanning between 32 microns on the outside (i.e., within the corresponding compressive stress layer) and 51 microns on the inside (i.e., within the central tension region). Peak and trough locations were obtained from the local minimum / maximum values ​​of the corresponding quartic local polynomial fit and evaluated on a dense depth grid with a depth spacing of 0.05 microns.

[0258] The obtained x-coordinates, or the maximum and minimum x-positions of the retardation curve, represent the positions where the stress changes sign, for example, from compressive stress to tensile stress, or vice versa. When measured relative to the nearest surface of the specimen, these positions represent the corresponding depth of compression (DOC) relative to that nearest surface. The tension zone width BTZ is determined as the difference between the x-positions corresponding to the maximum (peak) and minimum (trough) values ​​of the retardation curve.

[0259] It should be noted that when the incident angle of the laser beam within the specimen is measured perpendicular to the large surface of the specimen and exceeds approximately 80 degrees, a small deviation may exist between the position of the peaks and troughs of the retardation curve and the position where the stress changes sign. Therefore, at very high beam angles, especially angles substantially above 80 degrees, the slightly different beam bending effects on transverse electric and magnetic fields may lead to the need for more complex analysis to maintain a high degree of accuracy in measuring the stress profile (see Siim Hodemann et al., “Gradient scattered light method for non-destructive stress profile determination in chemically strengthened glass”, J.Mater.Sci., 51:5962-5978 (2016)).

[0260] The peak tension PT was determined by fitting each of the 10 individual retardation curves with a sixth-order polynomial fit provided by the SLP-2000 software, excluding the outermost 70-80 micrometers on both sides of the glass specimen to limit the fitting area to the interior of the glass specimen. The peak tension PT for each measurement was determined by calculating the maximum slope of the sixth-order polynomial fit between the minimum and maximum retardation positions. Despite relatively high retardation noise in individual measurements, averaging the peak tension PT of 10 measurements with different specimen orientations yielded values ​​nearly identical to those obtained after averaging the retardation data for the 10 retardation curves and then performing a sixth-order fit on the averaged retardation curves to calculate the peak tension PT. Therefore, for the purpose of determining the peak tension PT of the stress profile, it is sufficient to use the sixth-order polynomial fitting utility of the SLP-2000 software, as described above, and average the peak tension PT of 10 measurements with slightly different orientations or locations.

[0261] Next, the averaged retardation curve is decomposed into symmetric and antisymmetric components, and the decomposition plane (symmetric plane) is selected as the midpoint between the peak and trough positions of the retardation curve (see Figure 7). When a retardation model is obtained to fit the retardation curve using a symmetric stress model, the retardation model generates an antisymmetric retardation with respect to the thickness axis centered on that midpoint or midpoint plane (centered on that point / plane means that the zero value of the axis is located on the midpoint plane). This decomposition is performed because, even after performing the averaging of the individual retardation curves described above to reduce noise in the retardation data, obtaining a precise fit to the improved retardation can still be limited by certain strains in the retardation curve that may be caused by systematic errors in the measurement setup, asymmetry in the actual stress profile, and / or some warping in the glass specimen. For more information regarding retardation curve decomposition, see U.S. Patent No. 11,105,561, issued on 31 August 2021, entitled "Hybrid Systems and Methods for Characterizing Stress in Chemically Strengthened Transparent Substrates," which is incorporated herein by reference in its entirety (see column 32, rows 33-67).

[0262] Next, the nonlinear fitting of the antisymmetric component of the averaged retardation curve is performed based on the integral equation of the force model provided in Equation 14, using the tension zone width BTZ and peak tension PT as model input parameters and restricting the region of adaptation to a sub-region inside the glass specimen. The sub-region includes the entire tension zone, and at least the outermost 50 microns on both sides of the specimen are excluded, as it is well understood that the retardation at the outermost 50 microns is not a direct and accurate representation of the depth integral of the stress profile due to various strain effects beyond the scope of this consideration. Furthermore, depending on the specimen-prism interface oil (liquid, fluid), specimen-back-cover-interface oil, and the scattering intensity of refractive index mismatch between the oil and glass, between the oil and the prism, and between the surface roughness of the glass specimen and the prism, the beam focusing conditions, the rate of change of stress with respect to depth, the rate of change of stress gradient with respect to depth, and the thickness of the specimen, there is some negligible difference between the retardation in the depth range of 50 to 110 microns and the hypothetical perfect retardation that is exactly proportional to the depth integral of the stress up to the corresponding depth within that range. The difference (or error) typically decreases with increasing depth and is usually small enough at a depth of 110 microns unless the surface roughness is very large and does not cause very bright surface scattering, thus damaging the retardation signal corresponding to relatively large depths. Fitting the retardation signal at depths significantly smaller than the compression depth does not improve the accuracy of the fit in representing retardation in the tension region. Therefore, to ensure accurate measurement of important aspects of the tension zone stress profile, such as shape, it is preferable to rely on fitting only the small portion of the compression zone closest to the compression depth and on the tension zone. To obtain a more precise value for the slope in the DOC, the fitted region extends at least 15 microns into the compressive stress layers on both sides of the central tension zone.

[0263] The antisymmetric integral of the symmetric stress-force profile model used to fit the antisymmetric component of the experimental retardation curve is given with respect to the optimization parameters b1 and b2 in the following equation:

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[0264] The nonlinear fitting routine used with the force model for tensile zone stress was the function "nlinfit," available in the Matlab and Octave software engines for scientific numerical calculations. Figure 9 shows the integrated force profile model of Equation 14 fitted to the antisymmetric component of the averaged retardation curve for Example 7, with the vertical dashed line indicating the boundary of the fitted region. Figure 11 shows the residual between the antisymmetric component of the averaged retardation and its fitted force profile model, the residual not exceeding 1.5 degrees in absolute value. From Figures 9 and 11, it can be seen that the force profile provided by Equation 14 accurately represents the stress profile in the central tension zone of the chemically strengthened glass-based article of this disclosure. The relevant stress profile of the fitted force model for Example 7 is shown in Figure 13, with the vertical dashed line indicating the boundary of the fitted region. The fitted force model is then used to determine the slope in the tension area TA, DOC.

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[0265] The thickness of the glass specimen is measured in micrometers. For stress profiles that are symmetrical about the central plane of the glass specimen, DOC1 and DOC2 are assumed to be equal (DOC1=DOC2=DOC), and DOC is determined by using micrometers to measure the thickness of the glass specimen, subtracting the tension zone width BTZ from the thickness, and dividing by 2. However, for substantially asymmetric stress profiles, DOC1 and DOC2 can be determined using SLP-2000 data.

[0266] Method for evaluating the characteristics of compressive stress layers As described herein, the stress profile attributes of the compressive stress layer in the embodiments described herein may be measured using a prism-coupled instrument similar to the FSM-6000, as described in U.S. Patent No. 11,448,595 issued on September 20, 2022, entitled "Prism-Coupling Systems and Methods with Improved Intensity Transition Position Detection and Tilt Compensation," which is incorporated herein by reference in its entirety, but may be used with additional options for operating wavelengths that provide a preferred measurement window. The compressive stress layer characterization method of this disclosure is performed in accordance with U.S. Patent Nos. 11,448,595 and 11,703,500 issued on July 18, 2023, entitled "Methods of characterizing ion-exchanged chemically strengthened glasses containing lithium," which are incorporated herein by reference in their entirety. This method allows for the measurement of the compressive knee stress CS k , spike depth DOL SP This enables the measurement of surface compressive stress CS. k When performing the measurement, the wavelength must be selected so that there are no resonances close to the TIR transition for both TE and TM polarization.

[0267] The surface compressive stress CS is obtained using the fringe spectrum at 365 nm and by extrapolating the surface refractive index, based on the assumption that the refractive index profile within the spike is linear from the surface to the depth (transition point) of the second mode (fringe). In this approximation, the surface refractive index is equal to the effective refractive index of the first mode plus 1.317 times the effective refractive index interval between the first and second modes.

[0268] This disclosure presents, above, numerous stress profile attributes that help characterize the properties of stress profiles imparted through ion exchange treatment(s). While we do not wish to be bound by theory, the stress profile attributes and associated limits and ranges described herein are considered to result in glass articles exhibiting improved fracture resistance while avoiding fracturing. The following portions of this disclosure provide exemplary ion exchange treatment methods that may be used to achieve the desired stress profile attributes described herein. Following the exemplary ion exchange treatment methods are examples of chemically strengthened glass articles of this disclosure.

[0269] Exemplary ion exchange methods: Regarding sodium-based glass: Method 1: Ion exchange in a potassium ion-rich bath to increase the surface concentration of K2O in the glass to at least 5 mol%, preferably higher or significantly higher. Ion exchange is continued until the target DOC / t ratio is approached. The surface concentration is selected so that the glass approaches the fracturing limit when the DOC / t ratio is approached. Then, a heat treatment of a moderate time is performed to further increase the DOC and slightly decrease the tension-strain energy, as this increases the DOC and decreases the uniformity of the tension zone. Then, if necessary, short spike steps are performed in a K-rich bath to finish the profile with a high surface CS.

[0270] Second method (for even higher p and higher slope at DOC): Ion exchange in a K-rich bath is performed to increase the surface concentration of K2O to above 5 mol%, preferably significantly higher. Ion exchange is performed until the target ratio DOC / t approaches, allowing the glass to enter a fragile space, but with great care to avoid breaking the part during chemical strengthening. Then, heat treatment is performed for a moderate time to increase DOC to the target, thereby slightly reducing the force coefficient p and slightly decreasing the slope at DOC. If a buried peak is desired, the heat treatment may proceed with short ion exchange in a bath with a mixture of Na and K ions so that the surface concentration of K2O decreases and results in a buried peak. In some cases, it may be acceptable to omit the heat treatment step before such a K2O reduction ion exchange step. After any such combination of heat treatment and K reduction step, the glass-based article should be in a non-fragile state. Finally, if a surface spike is desired, short ion exchange is performed in a K-rich bath to increase the surface concentration and surface CS. The size of the spikes needs to be adapted to the amount of tensile energy to avoid crushing.

[0271] Third method: Ion exchange is performed at a high temperature in the first K-rich bath. The temperature is high enough to allow strong stress relaxation. In this way, the deepening of the profile is prevented from raising its tensile energy to the fracturing limit, at least while the DOC is not too close to the target. Then, optionally, a short to moderate heat treatment is performed to further advance the DOC to reach the target DOC. Then, a short ion exchange is performed in the second K-rich bath to increase the surface concentration and surface CS. The heat treatment step may not be necessary if the first K-rich bath provides a substantially low increase in K2O concentration at the surface compared to the second K-rich bath. The selection of whether to use the heat treatment step depends on the goal of maximizing the optimization of the profile.

[0272] Regarding Li2O-containing glass having a relatively high Li2O content (for example, more than 7 mol% Li2O, preferably more than 8 or 9 mol% Li2O): First method: Ion exchange is performed at a temperature sufficient to significantly activate stress relaxation in the compression region within the glass having a high Li2O content (preferably more than 8 mol%). If the fracture toughness of the glass substrate is relatively high and a somewhat limited surface stress is required to prevent excessive stress fracture of shallow scratches, a single-step ion exchange can be used in a mixed bath (KNO3 and NaNO3). When the DOC is sufficient, the ion exchange is stopped. The temperature is selected so that stress relaxation is just enough to raise the DOC while the uniformity of the tension zone has not yet deteriorated (e.g., while p is still higher than 2.4), but not so high that the tension energy is unnecessarily lowered far below the fracturing limit. An ion exchange bath suitable for a 0.55 mm thick glass substrate having composition 1 (see Table 1) may contain 8-9.5 wt% NaNO3 and 90.5-92 wt% KNO3. Glass substrates should be properly preheated before ion exchange, which should be performed at approximately 470°C for approximately 2.5–2.75 hours. This ion exchange procedure produces a stress profile with a DOC similar to that produced using a 0.7 wt% LiNO3 / 9 wt% NaNO3 / 90.3 wt% KNO3 bath composition at a bath temperature of 450°C and a processing time of 5 hours. If the glass becomes slightly fragile, a small amount of LiNO3 can be added to the bath (0.1–0.3 wt%) to reduce the TSE. The final profile, when non-fragile, has a higher stress area than the process-of-record conditions used for mass production. The progressively higher functional enhancement of the stress profile attributes discussed above can be achieved by further increasing the IOX temperature, shortening the processing time, and slightly increasing the NaNO3 content of the bath at the expense of KNO3 and LiNO3. For example, for a 0.55 mm thick glass substrate having composition 1, it may be advantageous to use a bath containing 9-11 wt% NaNO3, less than 0.3 wt% LiNO3, and the remainder KNO3, with an IOX temperature of 480°C and a processing time of 2.05-2.25 hours. At 490°C, the appropriate time is 1.7-1.87 hours, and it may be necessary to further slightly increase the NaNO3 content of the bath.

[0273] A first method, based on activating an appropriate amount of stress relaxation, increasing the NaNO3 content of the bath, and shortening the processing time, may work well for several glasses having a similar composition to composition 1, which has suitable nonlinear diffusion properties for enabling a high content of Li2O (10.7 mol%), as well as very high PT and DOC profiles. However, this method has limited usefulness for glasses with lower levels of Li2O (about 8 mol%), and may have a more modest Li2O / Na2O ratio that is not as favorable for achieving very high PT and very high DOC.

[0274] Second method: The second method utilizes a multi-step ion exchange process, in which the first step provides a Na2O composition near the surface so that the glass becomes fragile in the first ion exchange step when the DOC is close to the target DOC. Then, in the second step, a surface spike is formed with KNO3, and the influx of Na ions in the second step is strongly or completely suppressed, or even reversed (by adding an appropriate amount of Li ions to the bath in the second step). Thus, in the second step, the TSE of the profile is reduced (almost always along with PT), while the DOC is slightly increased, and the knee stress CS is reduced. k This is reduced very significantly. The second step is short enough that the slope at DOC is reduced only slightly compared to the slope after the first step. An optional short-duration heat treatment step may be inserted between the first and second steps, as long as it is small enough to avoid the heat treatment step significantly reducing the slope at DOC and decreasing the p-parameter of the profile (e.g., significantly reducing the uniformity of tension within the tension zone).

[0275] Third method: This method involves a two-step ion exchange process in which stress relaxation is enhanced in the first step. In this case, the IOX temperature in step 1 is raised to a degree that activates significant stress relaxation (e.g., somewhere between 100°C and 20°C below the glass strain point). The ion exchange in step 1 is carried out until the DOC approaches the target DOC (but does not reach very close to the target DOC). After step 1, the glass is slightly above or very close to the fracturing limit. Step 2 provides little or no influx of Na ions into the glass and mainly forms a spike. If necessary, step 2 can extract some Na ions from the glass by supplying a suitable and relatively low level of Li ions to the bath to exchange for Na ions. As in the second method described above, the majority of cations in the bath in step 2 are K ions. For glasses with low levels of Li2O (approximately 8 mol%) in the substrate glass and equivalent molar concentrations of Li2O and Na2O, performing the first step at a higher temperature may allow for a concentration distribution that enables higher DOC in order to mitigate some undesirable aspects of nonlinear diffusion.

[0276] Fourth Method: In the fourth method, the part of the process that develops the deep portion of the stress profile that generates high tensile area and high DOC is divided into two steps. The first of the two steps is a short ion exchange at a very high temperature with strong stress relaxation. In this step, the weight increase is kept to less than about 65% of the total weight increase. The remainder of the ion exchange (surface CS, DOC, and CS) k Depending on the required combination, one or two additional steps are performed at significantly lower temperatures to limit further stress relaxation. [Examples]

[0277] Table 1 below provides exemplary compositions of glass substrates that can be chemically strengthened to satisfy one or more of the purposes of this disclosure, and hereafter referred to as “Composition 1”. [Table 1]

[0278] The properties of a glass substrate having composition 1 are shown in Table 2 below. [Table 2]

[0279] The stress profiles of the present invention in Examples 1 to 8 of this disclosure were obtained using glass substrates having Composition 1. The glass substrates having Composition 1 were manufactured on a roller manufacturing platform and polished for high surface quality. As a result, the virtual temperature of the glass is substantially higher than that of annealed glass of the same composition, but the virtual temperature difference with respect to the annealed glass is not as high as the virtual temperature difference between the fused-formed glass sheet and the annealed glass sheet of the same composition. The elevated virtual temperature of the roller-formed glass sheet having Composition 1 (compared to annealed glass) is related to a higher diffusivity of alkali ions involved in ion exchange for chemical strengthening, a slightly higher stress relaxation rate, and a slightly reduced network expansion coefficient (e.g., reduced expansion and stress per ion exchange unit). Therefore, when applying the method for implementing the stress profile of the present invention as described herein to an annealed version of glass, or to glass of a similar composition produced by the float method, moderate adjustments to the IOX procedure may be necessary, such as increasing the diffusion time to compensate for the lower diffusion rate of the annealed glass, and / or adding some LiNO3 to the bath to reduce the central tension of the annealed glass to prevent the annealed glass from becoming brittle. If the diffusion time is not increased, the desired high DOC may not be achieved in the annealed glass.

[0280] An alternative adjustment for annealed glass and float glass is to raise the ion exchange temperature by approximately 8°C to 20°C, depending on the magnitude of the difference between the virtual temperature of the roller sheet and the virtual temperature of the annealed glass. In most cases, this method requires raising the temperature by approximately 10°C to 15°C. The advantages of this method are that (i) stress relaxation is accelerated with higher diffusivity at higher temperatures, and (ii) the diffusivity of K ions increases more significantly than that of Na ions, thus shortening the ion exchange processing time and guiding all stress profile attributes in the right direction to suit the mounting of the roller glass. Naturally, a combination of moderate temperature increases and the addition of small amounts of LiNO3 to the bath is also an acceptable method for mounting the target profile without making the annealed glass fragile. In the following description, the specific times and temperatures used for glass substrates having composition 1 were applicable to the virtual temperature of the roller glass.

[0281] Examples 1-8 of this disclosure were produced by performing single-step ion exchange (SIOX) on a glass substrate having composition 1. One important aspect of SIOX-based packaging is the use of a mixed bath providing both Na and K ions, where Na ions are for controlling the compressive stress profile in the deeper portions of the compressive stress layer, and K ions are for controlling the compressive stress profile in the spikes of the compressive stress layer. Another important aspect of SIOX-based packaging is a relatively high bath temperature to activate a non-negligible amount of stress relaxation during ion exchange. Furthermore, another important aspect of SIOX-based packaging is maintaining the ion exchange treatment time within a very narrow time frame that does not substantially alter the Na concentration in the deepest portions of the specimen around the midplane, allowing for high DOC in combination with stress relaxation, but achieving a high force coefficient p in the stress profile despite the high DOC.

[0282] Regarding the activation of stress relaxation, the strain point and annealing point of the glass are relevant, as is the virtual temperature. The strain point of the glass used in the embodiments of the present invention in this disclosure is approximately 563°C, measured by the fiber stretching method of ASTM C336-71 (2015), or approximately 567°C, estimated by beam bending viscosity (BBV) measurement. The annealing point is approximately 607°C by fiber stretching and approximately 612°C by BBV. The embodiments of the present invention in this disclosure used ion exchange temperatures of at least 455°C and about 490°C. It should be noted that further embodiments of the present invention can be generated at even higher ion exchange temperatures, the ion exchange time is further shortened, and the bath is shifted toward a higher Na / K ratio. The resulting profiles then still feature the combination of properties of the present invention in the tension zone and deep compression region, the main difference being that the surface compressive stress CS is slightly smaller than in the embodiments at ion exchange temperatures in the range of 455°C to 490°C.

[0283] In embodiments, the ion exchange temperature for implementing the stress profile of the present invention must be above a temperature corresponding to about 110°C below the strain point of glass (measured by the fiber stretching method of ASTM C336-71 (2015)), preferably above a temperature corresponding to about 107°C below the strain point of glass. If an increase in negative curvature in the compression region is particularly desirable, the ion exchange temperature should be significantly increased to a range corresponding to 40-90°C below the strain point, and it should be understood that (i) as the difference from the strain point decreases, it is necessary to increase the Na / K ratio of the bath to achieve a high integral of compressive stress, and (ii) the surface compressive stress CS decreases. If it is also extremely important that the application has a high surface compressive stress CS, a two-step process may be required to enable the combination of a higher negative second derivative in the deeper parts of the profile, a high stress area, and a high surface stress all at the same time.

[0284] Furthermore, when the target product thickness is substantially small, such as 0.3-0.4 mm, it can be useful to use an ion exchange temperature that is even closer to the strain point, less than 40°C from the strain point. In fact, in some cases, it is particularly important to achieve the highest possible integral value of compressive stress while maximizing the DOC in such thin glass. The short diffusion time required for small thicknesses can work very effectively with a high stress relaxation rate. Since thinner glass is usually more fragile with respect to peak tension, the combination of small thickness and high ion exchange temperature usually requires an increase in the Na / K ratio in the ion exchange bath as well.

[0285] In the embodiments of this disclosure, the ion exchange time was selected to ensure that the central composition of the glass article was not substantially or completely altered by ion exchange, and furthermore, high DOCs were achieved, exceeding 19% of the thickness in all cases, exceeding 20% ​​of the thickness in most cases, and in some cases exceeding 21% of the thickness. The relatively narrow range of diffusion times that achieve this condition is identified through optimization after the diffusion properties of the glass for alkali ion exchange have been determined at the target temperature, where (i) the target temperature is selected to activate sufficient stress relaxation.

[0286] Example 9 of this disclosure was produced by performing a double-step ion exchange (DIOX) on a glass substrate having Composition 1, which was fabricated on a rolling production platform and had a thickness of 0.502 mm after polishing and before ion exchange. In step 1, a preheated specimen was ion-exchanged at 500°C for 0.67 hours in a bath containing 20 wt% NaNO3 and 80 wt% KNO3 with a standard addition of 0.5% silica. Then, in step 2, the specimen was ion-exchanged at 460°C for 0.8 hours in a bath containing approximately 9% NaNO3 and 91% KNO3 with a standard addition of 0.5% silica. After this process, the specimen had a central tension of 130.8 MPa, a tension zone width of approximately 104 microns or 20.7% of the thickness, a surface compressive stress CS of 750 MPa, and a DOL of approximately 4.2 μm. SP , CS obtained at 405 nm with a pressure of approximately 256 MPak It has a tensile area of ​​approximately 28.7 MPa* mm and a p-factor of approximately 3.2 profile shape.

number

[0287] Although the temperatures in both Step 1 and Step 2 of this two-step embodiment were within 110°C of the strain point, the additional flexibility gained by extending to two-step ion exchange allows for the implementation of embodiments of the present invention having a sub-region with a negative second derivative of the CS profile, even at lower temperatures, without substantial activation of stress relaxation. In this method, the negative second derivative is obtained by strictly limiting the influx of Na ions in the second step compared to the first step by using a second-step bath with a much lower Na / K ratio than the first-step bath, for example, the molar ratio of NaNO3 / (NaNO3+KNO3) in the second step is 10 times, or even more than 10 times, lower than the molar ratio in the first bath. The design space for the ion exchange process in this case can be reduced compared to the case of high ion exchange temperatures, if it is required that the glass be non-fracturable after both the first and second steps to avoid glass fragments entering the ion exchange equipment during accidental breakage of the specimen being produced.

[0288] Here, an ion exchange procedure for composition 2 enabling the stress profile of the present invention is provided. The strain point of composition 2 is very high at 592°C. The fracture toughness of composition 2 is

number

[0289] A two-step ion exchange can be used to obtain the stress profile of the present invention having a surface compressive stress CS higher than 600 MPa, including the use of temperatures lower than 490°C. For example, for a 0.6 mm material, step 1 of ion exchange is performed by immersion at 460°C for 1 hour in a bath containing 20 wt% NaNO3 / 80 wt% KNO3, followed by step 2 of 0.3 hours at 430°C in a bath containing 4 wt% NaNO3 and 96 wt% KNO3.

[0290] For glass of the same composition formed on a rolling platform with a slightly higher virtual temperature, the NaNO3 content of the salt bath must be increased from the range of 8-20% for the one-step process to the range of 12-25%, and the ion exchange time must be reduced by 2 / 3 so that the ion exchange time is 0.4-0.5 hours at 490°C. For the two-step process, the NaNO3 content of the bath in step 1 is increased to 25%, and the KNO3 is reduced to 75%. The ion exchange time in step 1 is reduced to 70% of the ion exchange time for the annealed glass, or 0.7 hours at 460°C. In order to maintain a high surface compressive stress CS, step 2 uses 4% NaNO3 / 96% KNO3 for 0.2 hours at 430°C.

[0291] Despite significant differences in the percentages of the different components, the bath composition and ion exchange temperature range for composition 2 are very similar to those for composition 1. However, because composition 2 has a higher diffusivity than composition 1, the ion exchange treatment time is significantly shorter than that of composition 1.

[0292] Table 3 provides IOX treatment parameters for Examples 1 to 8, each of which is a chemically strengthened glass article produced by subjecting a glass substrate having composition 1 to a chemical strengthening process according to the method described herein. [Table 3]

[0293] Table 4 provides the thickness and stress profile attributes for Examples 1 to 8. [Table 4-1] [Table 4-2] [Table 4-3] [Table 4-4] [Table 4-5]

[0294] The stress profile attributes for the chemically strengthened glass articles of Examples 1-8 provided in Table 4 above exhibit a uniform tensile stress distribution in the central tension zone, which allows for an increase in compressive stress in the compressive stress layer while also avoiding fracturing. To illustrate the difference between the stress profiles of the present invention and stress profiles that do not employ the teachings, i.e., strengthened glass articles found in the prior art, the averaged retardation curve, force model fit, residuals for the force model, and the stress profile corresponding to the fitted force model are shown as comparative examples in Figures 8, 10, 12, and 14, respectively. By comparing the stress profile of Example 7 of the present invention shown in Figure 13 with the stress profile of the comparative example shown in Figure 14, the increase in tension area provided by the uniform tensile stress distribution of Example 7 can be observed. Furthermore, as described above, a uniform tensile stress distribution is desirable because the tensile strain energy (TSE) is proportional to the depth integral of the squared tensile stress across the central tension zone, whereas the tension area TA (equal to the compressive stress area by force balance) is only the depth integral of the tensile stress (not squared) across the central tension zone. Therefore, a smaller uniform stress distribution results in an increase in TSE for a fixed TA. Since fragility imposes an upper limit on TSE, the increase in TA in the embodiments described herein allows for an increase in the level of compressive stress within the compressive stress layer while maintaining non-fragility for chemically strengthened glassy articles.

[0295] Those skilled in the art will see that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Therefore, this specification is intended to encompass such modifications and variations, provided that they fall within the scope of the appended claims and their equivalents.

Claims

1. Chemically strengthened glass-based articles, A first main surface defining the thickness t of the glass-based article and a second main surface on the opposite side, A stress profile σ(x) where x extends through the thickness t of the glass-based article in a direction perpendicular to the first main surface and the second main surface, From the first main surface, a first compression depth DOC of approximately 0.15 t or more １ The first compressive stress layer extends to, From the second main surface, DOC １ The following is the second compression depth DOC ２ A second compressive stress layer extends to, Positioned between the first compressive stress layer and the second compressive stress layer, and with peak tension PT and DOC １ from t-DOC ２ A central tension zone, including a tension zone width BTZ that extends over a certain distance, [Math 1] And, In the formula, DOC=DOC １ And, [Math 2] However, this is the slope of the stress profile σ(x) in DOC, [Math 3] And, [Math 4] And, During the ceremony, TA, [Math 5] A chemically strengthened glass-based article whose tensile area is defined by [a specific factor / method].

2. The chemically strengthened glass article according to claim 1, wherein the peak tension PT is greater than 90 MPa.

3. The chemically strengthened glass article according to claim 1, wherein the peak tension PT is greater than 115 MPa.

4. The chemically strengthened glass article according to claim 1, wherein the peak tension PT is greater than 125 MPa. [Request Item 5] [Number 6] And, In the ceremony, K ＩＣ However, the position x within the central tension zone corresponding to the peak tension PT ピーク The fracture toughness of the glass-based article in any one of claims 1 to 4, a chemically strengthened glass-based article. [Request Item 6] [Number 7] The chemically strengthened glass-based article according to claim 5. [Request Item 7] [Number 8] The chemically strengthened glass-based article according to claim 5.

8. A chemically strengthened glass-based article according to any one of claims 1 to 7, wherein the thickness t of the glass-based article is 0.4 mm to 0.77 mm.

9. The chemically strengthened glass-based article according to any one of claims 1 to 7, wherein the thickness t of the glass-based article is 0.43 mm to 0.68 mm.

10. The composition of the glass-based article contains less than 3 mol% of Li ２ O and The fracture toughness K of the glass-based article ＩＣ However, the position x within the central tension zone corresponding to the peak tension PT ピーク In [Number 9] The above is the chemically strengthened glass article according to any one of claims 1 to 9.

11. The composition of the glass-based article contains an amount of Li in the range of about 3.0 mol% to about 7.5 mol%. ２ Including O, The fracture toughness K of the glass-based article ＩＣ However, the position x within the central tension zone corresponding to the peak tension PT ピーク In [Number 10] The above is the chemically strengthened glass article according to any one of claims 1 to 9.

12. The composition of the glass-based article contains an amount of Li in the range of about 7.5 mol% to about 11 mol%. ２ Including O, The fracture toughness K of the glass-based article ＩＣ However, the position x within the central tension zone corresponding to the peak tension PT ピーク In [Math 11] The above is the chemically strengthened glass article according to any one of claims 1 to 9.

13. The composition of the glass-based article contains an amount of Li in the range of about 11 mol% to about 13 mol%. ２ Including O, The fracture toughness K of the glass-based article ＩＣ However, the position x within the central tension zone corresponding to the peak tension PT ピーク In [Math 12] The above is the chemically strengthened glass article according to any one of claims 1 to 9.

14. The composition of the glass-based article contains more than 13 mol% Li ２ Including O, The fracture toughness K of the glass-based article ＩＣ However, the position x within the central tension zone corresponding to the peak tension PT ピーク In [Number 13] The above is the chemically strengthened glass article according to any one of claims 1 to 9.

15. When the stress profile σ(x) in the central tension zone conforms to equation I, [Number 14] 2. It has the best-fit value for the force coefficient p greater than 2.4, x ピーク The chemically strengthened glass article according to any one of claims 1 to 14, wherein the position is within the central tension zone corresponding to the peak tension PT.

16. The chemically strengthened glass-based article according to claim 15, wherein the best-fit value of the force coefficient p exceeds 2.

75.

17. The chemically strengthened glass-based article according to claim 15, wherein the best-fit value of the force coefficient p is greater than 3.

2.

18. A chemically strengthened glass-based article according to any one of claims 15 to 17, wherein the force coefficient p does not exceed 20.

19. 2.1 × K ＩＣ Crushing coefficient K not exceeding ｔ It further includes K ＩＣ However, the position x within the central tension zone corresponding to the peak tension PT ピーク The fracture toughness of the glass-based article in the above case, [Number 15] And, A chemically strengthened glass-based article according to any one of claims 1 to 18, wherein σ is the stress profile σ(x) in the formula.

20. K ｔ ≤ 1.97 × K ＩＣ The chemically strengthened glass article according to claim 19.

21. A chemically strengthened glass-based article according to any one of claims 1 to 20, wherein the DOC is 0.190 t or more.

22. A chemically strengthened glass-based article according to any one of claims 1 to 20, wherein the DOC is 0.200 t or more.

23. A chemically strengthened glass-based article according to any one of claims 1 to 20, wherein the DOC is 0.210 t or more.

24. A chemically strengthened glass-based article according to any one of claims 1 to 23, wherein the surface compressive stress CS on each of the first and second main surfaces is greater than 110 MPa.

25. The stress profile σ(x) indicates spikes on the first and second main surfaces, and the spike depth DOL ＳＰ Knee stress CS ｋ However, relation II: [Number 16] A chemically strengthened glass-based article according to any one of claims 1 to 24, satisfying the following conditions.

26. The spike depth DOL ＳＰ The knee stress CS in ｋ but, [Number 17] The following is a chemically strengthened glass-based article according to claim 25.

27. The spike depth DOL ＳＰ The knee stress CS in ｋ but, [Number 18] The following is a chemically strengthened glass-based article according to claim 25.

28. 0 ≤ DOL ｓｐ ≤DOL ｕｌ And, In the ceremony, D.O.L. ｕｌ A chemically strengthened glass article according to any one of claims 25 to 27, wherein the thickness is the greater of 4 μm and 0.01 t.

29. The stress profile σ(x) is the spike on the first and second main surfaces, and the spike depth DOL ＳＰ Knee stress CS ｋ This indicates DOL ＳＰ A chemically strengthened glass-based article according to any one of claims 1 to 28, wherein a portion of the stress profile σ(x) between and DOC includes a negative second derivative. [Request Item 30] [Number 19] A chemically strengthened glass-based article according to any one of claims 1 to 29. [Request Item 31] [Number 20] A chemically strengthened glass-based article according to any one of claims 1 to 29. [Request Item 32] [Number 21] A chemically strengthened glass-based article according to any one of claims 1 to 29. [Request Item 33] [Number 22] A chemically strengthened glass-based article according to any one of claims 1 to 32. [Request Item 34] [Number 23] A chemically strengthened glass-based article according to any one of claims 1 to 32. [Request Item 35] [Number 24] A chemically strengthened glass-based article according to any one of claims 1 to 32. [Request Item 36] [Number 25] A chemically strengthened glass-based article according to any one of claims 1 to 35. [Request Item 37] [Number 26] A chemically strengthened glass-based article according to any one of claims 1 to 35. [Request Item 38] [Number 27] A chemically strengthened glass-based article according to any one of claims 1 to 35.

39. A chemically strengthened glass-based article according to any one of claims 1 to 38, wherein the surface compressive stress CS on each of the first and second main surfaces is greater than 550 MPa.

40. A chemically strengthened glass-based article according to any one of claims 1 to 38, wherein the surface compressive stress CS on each of the first and second main surfaces is greater than 725 MPa.

41. The chemically strengthened glass article according to any one of claims 1 to 40, wherein the chemically strengthened glass article comprises an amorphous microstructure that is substantially free of crystals or microcrystals.

42. The aforementioned chemically strengthened glass-based article, [Number 28] A chemically strengthened glass-based article according to any one of claims 1 to 41, comprising the following fracture toughness:

43. The chemically strengthened glass-based article according to any one of claims 1 to 40, wherein the chemically strengthened glass-based article is a glass-ceramic material comprising an amorphous phase and a crystalline phase.

44. The aforementioned chemically strengthened glass-based article, [Number 29] A chemically strengthened glass-based article according to any one of claims 1 to 40 or 43, comprising the fracture toughness described above.

45. The aforementioned chemically strengthened glass-based article is formed by subjecting a glass-based substrate to ion exchange treatment, and the glass-based substrate is SiO₂ with a concentration of 50 mol% or more and 75 mol% or less ２ and, Al content of 10 mol% or more and 25 mol% or less ２ O ３ and, B is 1 mol% or more and 11 mol% or less. ２ O ３ and, Na: 1 mol% or more and 10 mol% or less ２ O and, Li 5 mol% or more and 15 mol% or less ２ O and Li in the glass substrate ２ The molar concentration of O is equal to the Na concentration in the glass substrate. ２ A chemically strengthened glass-based article according to any one of claims 1 to 44, having a molar concentration higher than that of oxygen.

46. The chemically strengthened glass article according to any one of claims 1 to 45, wherein the chemically strengthened glass article is formed by subjecting a glass substrate to an ion exchange treatment, and the glass substrate contains Li2O in an amount of 7.0 to 15.0 mol%.

47. The aforementioned chemically strengthened glass-based article is formed by subjecting a glass-based substrate to ion exchange treatment, wherein the glass-based substrate contains 2.0 or more Li ２ O to Na ２ A chemically strengthened glass-based article according to any one of claims 1 to 46, including the molar ratio of O.

48. Chemically strengthened glass-based articles, A first main surface and an opposite second main surface that define the thickness t of the glass-based article, wherein the thickness t is 0.52 mm or less, A stress profile σ(x) where x extends through the thickness t of the glass-based article in a direction perpendicular to the first main surface and the second main surface, From the first main surface, a first compression depth DOC of approximately 0.15 t or more １ The first compressive stress layer extends to, From the second main surface, DOC １ The following is the second compression depth DOC ２ A second compressive stress layer extends to, Positioned between the first compressive stress layer and the second compressive stress layer, and with peak tension PT and DOC １ from t-DOC ２ A central tension zone, including a tension zone width BTZ that extends over a certain distance, [Number 30] And, In the formula, DOC=DOC １ And, [Number 31] However, this is the slope of the stress profile σ(x) in DOC, [Number 32] And, [Number 33] And, During the ceremony, TA, [Number 34] A chemically strengthened glass-based article whose tensile area is defined by [a specific factor / method].

49. The chemically strengthened glass article according to claim 48, wherein the peak tension PT is greater than 115 MPa.

50. The chemically strengthened glass article according to claim 48, wherein the peak tension PT is greater than 125 MPa.

51. When the stress profile σ(x) in the central tension zone conforms to equation I, [Number 35] 2. It has the best-fit value for the force coefficient p greater than 2.4, x ピーク The chemically strengthened glass article according to any one of claims 48 to 50, wherein the position is within the central tension zone corresponding to the peak tension PT.

52. When the stress profile σ(x) in the central tension zone conforms to equation I, [Number 36] 2. It has the best-fit value for the force coefficient p greater than 2.75, x ピーク The chemically strengthened glass article according to any one of claims 48 to 50, wherein the position is within the central tension zone corresponding to the peak tension PT.

53. The stress profile σ(x) is the spike on the first and second main surfaces, and the spike depth DOL ＳＰ Knee stress CS ｋ This indicates DOL ＳＰ A chemically strengthened glass-based article according to any one of claims 48 to 52, wherein a portion of the stress profile σ(x) between and DOC includes a negative second derivative.

54. A chemically strengthened glass-based article according to any one of claims 48 to 53, wherein the DOC is 0.190 t or more.

55. A chemically strengthened glass-based article according to any one of claims 48 to 53, wherein the DOC is 0.200 t or more.

56. A chemically strengthened glass-based article according to any one of claims 48 to 53, wherein the DOC is 0.210 t or more.

57. Chemically strengthened glass-based articles, A first main surface and an opposite second main surface that define the thickness t of the glass-based article, wherein the thickness t is approximately 0.43 mm to approximately 0.68 mm, A stress profile σ(x) where x extends through the thickness t of the glass-based article in a direction perpendicular to the first main surface and the second main surface, From the first main surface, a first compression depth DOC greater than approximately 0.19 t １ The first compressive stress layer extends to, From the second main surface, DOC １ The following is the second compression depth DOC ２ A second compressive stress layer extends to, Positioned between the first compressive stress layer and the second compressive stress layer, and with peak tension PT and DOC １ from t-DOC ２ A central tension zone, including a tension zone width BTZ that extends over a certain distance, The aforementioned peak tension PT is greater than 95 MPa, When the stress profile σ(x) in the central tension zone conforms to equation I, [Number 37] 2. The best-fit value for the force coefficient p is greater than 4, and in the formula, DOC = DOC １ and x ピーク However, this is a position within the central tension zone corresponding to the peak tension PT, The stress profile σ(x) indicates spikes on the first and second main surfaces, and the spike depth DOL ＳＰ Knee stress CS ｋ However, relation II: [Number 38] It satisfies, In the formula, DOC=DOC １ And, [Number 39] However, the slope of the stress profile σ(x) in DOC is a chemically strengthened glass-based article.

58. The chemically strengthened glass-based article according to claim 57, wherein the thickness t is 0.52 mm or less.

59. The chemically strengthened glass article according to claim 57 or 58, wherein the peak tension PT is greater than 103 MPa.

60. A method for producing a chemically strengthened glass-based article, the method comprising exposing a glass-based substrate to a molten salt bath to form the chemically strengthened glass-based article, The temperature of the molten salt bath is 110°C or less lower than the strain point of the glass substrate, and the strain point of the glass substrate is determined by fiber stretching. The ion exchange treatment time is such that the chemically strengthened glass-based article A stress profile σ(x) where x extends through the thickness t of the glass-based article in a direction perpendicular to the first main surface and the second main surface, From the first main surface, a first compression depth DOC of approximately 0.15 t or more １ The first compressive stress layer extends to, From the second main surface, DOC １ The following is the second compression depth DOC ２ A second compressive stress layer extends to, Positioned between the first compressive stress layer and the second compressive stress layer, and with peak tension PT and DOC １ from t-DOC ２ A central tension zone, including a tension zone width BTZ, is selected to be provided, [Number 40] And, In the formula, DOC=DOC １ And, [Number 41] However, this is the slope of the stress profile σ(x) in DOC, [Number 42] And, [Number 43] And, During the ceremony, TA, [Number 44] A method that defines the tensile area by [a specific method].

61. The method according to claim 60, wherein the temperature of the molten salt bath is 455°C to 490°C.

62. The method according to claim 60 or 61, wherein the ion exchange treatment time is 2 to 4 hours.

63. The glass substrate, SiO₂ with a concentration of 50 mol% or more and 75 mol% or less ２ and, Al content of 10 mol% or more and 25 mol% or less ２ O ３ and, B is 1 mol% or more and 11 mol% or less. ２ O ３ and, Na: 1 mol% or more and 10 mol% or less ２ O and, Li 5 mol% or more and 15 mol% or less ２ O and Li in the glass substrate ２ The molar concentration of O is equal to the Na concentration in the glass substrate. ２ The method according to any one of claims 60 to 62, wherein the molar concentration is higher than that of O.

64. The method according to any one of claims 60 to 63, wherein the glass substrate contains Li₂O in an amount of 7.0 to 15.0 mol%.

65. The glass-based substrate contains a molar ratio of Li ２ ２ O to Na ２ ２ O according to any one of claims 60 to 64.

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