Stress profile of glass-based articles with improved drop performance

Abstract

Glass-based articles include a stress profile for providing improved drop performance. A glass-based substrate includes: a glass transition temperature (T g ), a liquid fragility index (m), and a fictive temperature (T f ), wherein T g is less than or equal to 650 °C, T f minus T g is greater than or equal to -30 °C, and m is greater than or equal to 25. The stress relaxation rate is greater than or equal to 10%, 20%, or more. The article can include a lithium-based aluminosilicate composition and a fracture toughness greater than or equal to 0.75 MPa*m 0.5 . The stress profile includes: a spike region extending from the first surface to an inflection point; and a tail region extending from the inflection point to a center of the glass-based article, the tail region including: a negative curvature region, wherein a second derivative of stress as a function of depth is negative; a depth of compression (DOC) greater than or equal to 0.22t, and a parabolic region originating at the DOC and extending to the center of the glass-based article.

Description

[0001] This application claims priority under 35 U.S.C. § 119 to U.S. Provisional Application No. 63 / 083,267, filed September 25, 2020, the contents of which are relied upon and incorporated herein by reference in their entirety.

[0002] BACKGROUND TECHNICAL FIELD

[0003] The present specification generally relates to stress profiles of glass-based articles suitable as cover glasses for electronic devices. More specifically, the present specification relates to improved stress profiles of lithium alumino silicate glasses that provide improved drop performance and methods. BACKGROUND

[0004] The mobile nature of portable devices (e.g., smart phones, tablet computers, portable media players, personal computers, and cameras) makes these devices particularly susceptible to being accidentally dropped on a hard surface (e.g., the ground). These devices often include a cover glass that can be damaged after impacting a hard surface. In many of these devices, the cover glass serves as a display cover plate and can incorporate touch functionality, and when the cover glass is damaged, the use of the device is negatively impacted.

[0005] There are two main modes of breakage for the cover glass when the associated portable device is dropped on a hard surface. One of the modes is flexural breakage, which is caused by the bending of the glass when the device is subjected to a dynamic load impacting a hard surface. The other mode is sharp contact breakage, which is caused by damage to the glass surface. Impact of the glass by a rough hard surface (e.g., asphalt, granite, etc.) can result in sharp indentations in the glass surface. These indentations become sites of breakage in the glass surface from which cracks can initiate and propagate.

[0006] Chemical treatment is a strengthening method used to impart a desired and / or designed stress profile with one or more of the following parameters: compressive stress (CS), depth of compressive (DOC), and maximum central tension (CT). Many glass-based articles, including those with a designed stress profile, have a compressive stress that is highest or peaked at the surface of the glass and decreases from the peak as one moves away from the surface, and there is zero stress at some interior location of the glass article before the stress of the glass article becomes tensile. Chemical strengthening by ion exchange (IOX) of alkali-containing glasses is an effective method in this field.

[0007] Glass-based articles, particularly glass, can be made more resistant to bend fracture by traditional ion exchange techniques, which can involve inducing compressive stress in the glass surface. However, ion exchanged glass can still be susceptible to dynamic sharp contact, due to high stress concentrations caused by localized indentations in the glass from the sharp contact.

[0008] Glass manufacturers and handheld device manufacturers continue to strive to improve the resistance of handheld devices to sharp contact breakage. Solutions range from cover glass to bezel to prevent the cover glass from directly impacting a hard surface when the device is dropped on the hard surface. However, due to limitations of aesthetic and functional requirements, it is difficult to completely prevent the cover glass from impacting the hard surface.

[0009] There is a need for improved stress profiles to produce superior drop performance. SUMMARY

[0010] Aspects of the disclosure relate to glass-based articles and methods of making the same.

[0011] In an aspect, a glass-based article includes: a composition including a lithium-based aluminosilicate and a fracture toughness greater than or equal to 0.75 MPa*m 0.5 a first surface and a second surface defining a thickness (t); and a stress profile including: a spike region extending from the first surface to an inflection point; and a tail region extending from the inflection point to a center of the glass-based article, the tail region including: a negative curvature region in which a second derivative of a function of stress versus depth is negative; a depth of compression (DOC) greater than or equal to 0.22t, and a parabolic region originating at the DOC and extending to the center of the glass-based article.

[0012] In embodiments, the composition at the center of the glass-based article includes a lithium oxide (Li20) content greater than 8 mol%. In embodiments, the composition at the center of the glass-based article includes a molar ratio of sodium oxide (Na20) to lithium oxide (Li20) less than 1.0. In embodiments, the molar ratio of sodium oxide (Na20) to lithium oxide (Li20) is less than or equal to 0.63. In embodiments, the lithium-based aluminosilicate composition includes potassium oxide (K20) and phosphorous pentoxide (P205) in an amount less than 2 mol% of the composition. In embodiments, the average compressive stress (CS) included in the negative curvature region is greater than or equal to 50 MPa to less than or equal to 120 MPa.

[0013] In embodiments, the composition at the center of the glass-based article comprises: from 50 mol% to 69 mol% Si02; from 12.5 mol% to 25 mol% AI2O3; from 0 mol% to 8 mol% B203; from greater than 0 mol% to 4 mol% CaO; from greater than 0 mol% to 17.5 mol% MgO; from 0.5 mol% to 8 mol% Na20; from 0 mol% to 2.5 mol% La203; and from greater than 8 mol% to 18 mol% Li20.

[0014] In embodiments, the stress profile further comprises: a peak central tension (CT) * thickness (t) value in a parabolic region in a range from greater than or equal to 80 MPa to less than or equal to 160 MPa. 最大 ).

[0015] In embodiments, the stress profile further comprises: a peak central tension (CT) * thickness (t) value in a parabolic region in a range from greater than or equal to 80 MPa to less than or equal to 160 MPa.

[0016] In embodiments, t is in a range from greater than or equal to 0.02 millimeters to less than or equal to 2 millimeters.

[0017] In embodiments, the glass-based article further comprises an alkali metal present in a non-zero varying concentration extending from the first and / or second surface of the glass-based article to a depth of the glass-based article. In embodiments, the alkali metal is selected from the group consisting of potassium (K), sodium (Na), lithium (Li), rubidium (Rb), cesium (Cs), francium (Fr), and combinations thereof.

[0018] In embodiments, the glass-based article further comprises a retained strength of greater than or equal to 170 MPa as measured after impacting with 30 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm.

[0019] In embodiments, the glass-based article further comprises a retained strength of greater than or equal to 170 MPa as measured after impacting with 80 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm.

[0020] In one aspect, a glass-based article comprises: opposing first and second surfaces defining a thickness (t); and a first retained strength of greater than or equal to 170 MPa as measured after impacting with 30 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm, and a second retained strength of greater than or equal to 170 MPa as measured after impacting with 80 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm.

[0021] In embodiments, the first retained strength differs from the second retained strength by ± 5 MPa. In embodiments, the glass-based article comprises: a composition comprising a lithium-based aluminosilicate and a fracture toughness greater than or equal to 0.75 MPa*m 0.5 In embodiments, the glass-based article comprises: a stress profile comprising: a spike region extending from the first surface to an inflection point; and a tail region extending from the inflection point to a center of the glass-based article, wherein the tail region comprises: a negative curvature region, wherein a second derivative of stress as a function of depth is negative; a depth of compression (DOC) greater than or equal to 0.22t, and a parabolic region originating at the DOC and extending to the center of the glass-based article.

[0022] Yet another aspect is a consumer electronic product comprising: a housing having a front surface, a back surface, and side surfaces; electronic components disposed at least partially within the housing, the electronic components including at least a controller, a memory, and a display, the display disposed at the front surface of the housing or adjacent to the front surface; and a cover disposed over the display; wherein a portion of at least one of the housing and the cover comprises the glass-based article of any aspect or embodiment described herein.

[0023] Another aspect is a method of making a glass-based article comprising the steps of: ion exchanging a glass-based substrate having opposing first and second surfaces defining a substrate thickness (t) and a lithium-based aluminosilicate composition to form a glass-based article, the ion exchanging comprising: a first molten salt bath and a second molten salt bath; wherein the glass-based article comprises: a fracture toughness greater than or equal to 0.75 MPa*m 0.5 In embodiments, the glass-based article comprises: a stress profile comprising: a spike region extending from the first surface to an inflection point; and a tail region extending from the inflection point to a center of the glass-based article, wherein the tail region comprises: a negative curvature region, wherein a second derivative of stress as a function of depth is negative; a depth of compression (DOC) greater than or equal to 0.22t, and a parabolic region originating at the DOC and extending to the center of the glass-based article.

[0024] In embodiments, the method further comprises an annealing step after the ion exchanging.

[0025] In embodiments, the lithium-based aluminosilicate composition comprises a lithium oxide (Li20) content greater than 8 mol%. In embodiments, the composition at the center of the glass-based article comprises a molar ratio of sodium oxide (Na20) to lithium oxide (Li20) less than 1.0. In embodiments, the molar ratio of sodium oxide (Na20) to lithium oxide (Li20) is less than or equal to 0.63. In embodiments, the lithium-based aluminosilicate composition comprises potassium oxide (K20) and phosphorous pentoxide (P205) in an amount less than 2 mol% of the composition. In embodiments, the negative curvature region comprises an average compressive stress (CS) greater than or equal to 50 MPa and less than or equal to 120 MPa. In embodiments, the composition comprises: 50 to 69 mol% Si02; 12.5 to 25 mol% AI2O3; 0 to 8 mol% B203; greater than 0 to 4 mol% CaO; greater than 0 to 17.5 mol% MgO; 0.5 to 8 mol% Na20; 0 to 2.5 mol% La203; and greater than 8 to 18 mol% Li20. In embodiments, the stress profile further comprises a maximum compressive stress (CSmax) greater than or equal to 150 MPa. 最大

[0026] Additional features and advantages will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of various embodiments that will be realized as the description proceeds. It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are intended to provide further explanation of the principles of the claimed subject matter.

[0027] It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are intended to provide further explanation of the principles of the claimed subject matter. As such, this detailed description is included to provide a complete understanding of certain embodiments of the claimed subject matter and is not intended in any way to limit the broader concepts.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings are included to provide a further understanding of the various embodiments described herein and are incorporated in and constitute a part of this specification, illustrate embodiments described herein, and together with the description serve to explain the principles of the claimed subject matter.

[0030] FIG. 1 schematically illustrates a cross-section of a glass having a compressive stress layer on a surface thereof according to embodiments described and illustrated herein;

[0031] FIG. 2 is a generalized schematic stress profile plot of stress (MPa) versus normalized position from the surface (z / thickness) for embodiments of glass-based articles;​

[0032] FIG. 3A A plan view of an exemplary electronic device incorporating any glass article disclosed herein;

[0033] FIG. 3B for FIG. 3A A perspective view of an exemplary electronic device;

[0034] FIG. 4 A graph showing the relationship between stress (MPa) and depth (micrometers) from the surface for embodiments and comparative examples of glass-based articles;

[0035] FIG. 5 A graph showing the relationship between sodium dioxide (Na2O) concentration and depth for the embodiments;

[0036] FIG. 6 A graph showing the relationship between applied fracture stress (MPa) and particle size for embodiments of glass-based articles;

[0037] FIG. 7 A graph showing the relationship between stress (MPa) and depth (micrometers) from the surface for embodiments and comparative examples of glass-based articles;

[0038] FIG. 8 for FIG. 6 The second derivative of the stress distribution curve is plotted.

[0039] FIG. 9 This is an excerpt of the stress distribution curve according to an embodiment of a glass-based article;

[0040] FIG. 10 A schematic diagram of a device that damages glass products by utilizing the impact of an impacting object.

[0041] FIGS. 11-14 The stress relaxation rate according to the embodiment of the glass substrate; and

[0042] FIG. 15 For T g Minimum fragility (m) and measures to ensure resistance to temperatures less than or equal to 500°C. IOX The minimum T with sufficient stress relaxation f -T g The image. Detailed Implementation

[0043] Before describing several exemplary embodiments, it should be understood that this disclosure is not limited to the details of the construction or processing steps described below. The disclosures provided herein can have other embodiments and can be practiced or performed in various ways.

[0044] References throughout this specification to "one implementation", "certain implementations", "various implementations", "one or more implementations" or "implementation" mean that a particular feature, structure, material, or characteristic is included in at least one implementation of the disclosure. Thus, appearances of such phrases in various places throughout this specification are not necessarily intended to refer to the same implementation or to only one implementation. Furthermore, a particular feature, structure, material, or characteristic can be combined in any suitable manner in one or more implementations.

[0045] Definitions and Measurement Techniques

[0046] The terms "glass-based article" and "glass-based substrate" are used to include any object that is made, at least partially, of glass (e.g., a glass or glass-ceramic material). Laminated glass-based articles include laminates of glass with non-glass materials and laminates of glass with crystalline materials.

[0047] The "base composition" is the chemical composition of the substrate prior to any ion exchange (IOX) treatment. That is, the base composition is not doped with any ions from the IOX. When the IOX treatment conditions are such that the ions supplied by the IOX do not diffuse to the center of the substrate, the composition at the center of the glass-based article after the IOX treatment is typically the same as the base composition. In one or more implementations, the central composition at the center of the glass article comprises the base composition.

[0048] It should be noted that the terms "substantially" and "about" can be used herein to represent the inherent degree of uncertainty that can be attributed to any quantitative comparison, value, measurement, or other representation. These terms can also be used herein to represent the degree by which a quantitative representation can vary from a stated reference, and at the same time be considered to fall within the scope of the subject matter at issue. Thus, for example, a glass-based article that is "substantially free of MgO" is one to which MgO has not been intentionally added or formulated into the glass-based article, but can be present in very small amounts as a contaminant. The term "about" as used herein means that the amount, size, formula, parameter, and other quantities and characteristics are not exact, and are not necessarily precise, but can be approximated and / or larger or smaller, as desired, to reflect typical tolerances, conversion factors, rounding off, measurement error and the like, as well as other factors that those skilled in the art will recognize. When the term "about" is used in relation to a range of values or endpoints, the disclosure should be understood to encompass the specific values or endpoints. Whether the numerical values or endpoints of a range are set forth in the specification, the values or endpoints are intended to include both what is specifically stated and what is understood within the art to which the disclosure pertains, given the overall context of this specification. It is further understood that each endpoint of a range is independently associated with each other endpoint to thereby form a generic disclosure of a range of values that can be used in each instance when the term "about" is used.

[0049] All compositions described herein are expressed in mole percent (mol%) on an oxide basis, unless otherwise specified.

[0050] A "stress profile" is a function of stress across the thickness of a glass-based article. The compressive stress region extends from the first surface to a depth of compression (DOC) of the article and is the region of the article under compressive stress. The central tension region extends from the DOC to include the region of the article under tensile stress.

[0051] As used herein, the depth of compression (DOC) refers to the depth within a glass-based article where the stress changes from compressive to tensile. At the DOC, the stress crosses from a positive (compressive) stress to a negative (tensile) stress and thus exhibits a zero stress value. According to the convention commonly used in the mechanical arts, compression is represented as a negative (<0) stress while tension is represented as a positive (>0) stress. However, in this specification, a positive value of stress is a compressive stress (CS), which is represented as positive or absolute value (i.e., CS = |CS| as described herein). Further, a negative value of stress is a tensile stress. But using the term "tensile", the stress or central tension (CT) can be represented as a positive value (i.e., CT = |CT|). The central tension (CT) refers to the tensile stress in the central region or central tension region of the glass-based article. The maximum central tension (maximum CT or CT 最大 ) can exist in the central tension region (e.g., nominally at 0.5-t) where t is the article thickness, which allows for variation from the exact center of the location of maximum tensile stress. The peak tension (PT) refers to the maximum tension measured and can or can not be in the center of the article.

[0052] An "inflection point" of a stress profile is the depth of the article where the slope of the stress profile changes from steep to shallow. The inflection point can refer to the transition region of the span of depths where the slope changes. The inflection point stress CS k is defined as the value of the compressive stress at which the deeper portion of the CS profile extrapolates to the depth of ligament (DOL k ). k is measured by surface stress meter by known methods. FIG. 2 A schematic of a stress profile including the inflection point stress is provided.

[0053] A non-zero metal oxide concentration that varies from the first surface to a depth of layer (DOL) or along at least a substantial portion of the thickness (t) of the article indicates that stress has been created in the article as a result of ion exchange. The variation in the metal oxide concentration can be referred to herein as a metal oxide concentration gradient. A metal oxide concentration that is non-zero and varies from the first surface to the DOL or along a portion of the thickness can be described as creating stress in the glass-based article. The concentration gradient or variation in the metal oxide is created by chemically strengthening the glass-based substrate, in which a plurality of first metal ions are exchanged with a plurality of second metal ions in the glass-based substrate.

[0054] As used herein, the terms “exchange depth,” “depth of layer” (DOL), “chemical depth of layer,” and “chemical layer depth” can be used interchangeably and generally describe the depth facilitated by ion exchange processing (IOX) for a particular ion. The DOL refers to the depth within a glass-based article (i.e., the distance from a surface of the glass-based article to an interior region thereof) in which ions of a metal oxide or alkali metal oxide (e.g., metal ions or alkali ions) have diffused into the glass-based article, where the ion concentration reaches a minimum value as determined by a glow discharge optical emission spectrometer (GD-OES). In some embodiments, the DOL is given by the slowest diffusing or maximum ion exchange depth introduced by the ion exchange (IOX) process. The DOL for potassium (DOL K ) is the depth of the potassium content of the glass article to the potassium content of the underlying substrate. The DOL for sodium (DOL Na ) is the depth of the sodium content of the glass article to the sodium content of the underlying substrate.

[0055] Unless otherwise specified, CT and CS are expressed herein in megaPascals (MPa), thickness is expressed in millimeters, and DOC and DOL are expressed in micrometers (pm).

[0056] Compressive stress (including surface / peak CS, CS 最大 ) and DOL sp are measured by a surface stress meter (FSM) using a commercially available instrument such as the FSM-6000 manufactured by Orihara Industrial Co., Ltd. (Japan). Surface stress measurement depends on the accurate measurement of the stress-optical coefficient (SOC) associated with the birefringence of the glass. SOC is then measured according to Procedure C (Glass Disk Method) described in the procedures of ASTM Standard C770-16 entitled “Standard Test Method for Measurement of Glass Stress-Optical Coefficient,” the contents of which are incorporated herein by reference in their entirety.

[0057] Maximum center tension (CT) or peak tension (PT) and stress retention values are measured using a scattered light polariscope (SCALP) technique known in the art. The refracted near field (RNF) method or SCALP can be used to measure the stress profile curve versus depth of compression (DOC). When the RNF method is used to measure the stress profile curve, the maximum CT value provided by SCALP is used in the RNF method. More specifically, the stress profile curve measured by RNF is force balanced and calibrated to the maximum CT value provided by SCALP measurements. The RNF method is described in U.S. Patent 8,854,623 entitled "Systems and methods for measuring a profile characteristic of a glass sample," which is incorporated herein by reference in its entirety. More specifically, the RNF method includes placing a glass article adjacent to a reference block, generating a polarization-switched light beam that is switched between orthogonal polarizations at a rate of 1 Hz to 50 Hz, measuring an amount of power in the polarization-switched light beam, and generating a polarization-switched reference signal, wherein the measured amount of power for each of the orthogonal polarizations is within 50% of each other. The method further includes transmitting the polarization-switched light beam through the glass sample and the reference block at different depths into the glass sample, then relaying the transmitted polarization-switched light beam to a signal photodetector using a relay optical system, wherein the signal photodetector generates a polarization-switched detector signal. The method also includes dividing the detector signal by the reference signal to form a normalized detector signal, and determining a profile characteristic of the glass sample from the normalized detector signal.

[0058] Fracture toughness (K 1C ) represents the ability of a glass composition to resist fracture. Fracture toughness is measured on non-strengthened glass articles (e.g., K 1C values are measured prior to ion exchange (IOX) treatment of the glass article), and thereby represent characteristics of the glass substrate prior to IOX. The fracture toughness test methods described herein are not applicable to glass that has been IOX treated. However, fracture toughness measurements made as described herein prior to IOX treatment for the same glass (e.g., glass substrate) are relevant to fracture toughness after IOX treatment, and are used accordingly. K 1CThe chevron notched short bar (CNSB) method for measuring K m values is described 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), with the difference that Y* is calculated using Bubsey, R.T., 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). 1C The double torsion method for measuring K 1C values is 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 K r values that are slightly higher than the CNSB method. Unless otherwise noted, all fracture toughness values were measured by the CNSB method.

[0059] The measured relaxation stress (σ o) of the stress relaxation ratio (SR) refers to the ratio of the measured relaxed stress after IOX to the theoretical non-relaxed stress as predicted from the stress profile based on the ideal diffusion condition of complementary error function (erfc(x)). SR has a value less than 1 and greater than 0. The stress relaxation rate of a substrate or article is the percentage decrease of the theoretical non-relaxed stress. For example, for a theoretical non-relaxed stress (σ o ) of 100 MPa and a measured relaxed stress (σ r ) of 90 MPa, the stress relaxation rate is 10%, or 1 minus SR multiplied by 100.

[0060] The theoretical non-relaxed stress (σ o ) is determined from the ion concentration measured through the thickness of the IOX treated article and is input into the following linear elastic equation.

[0061]

[0062] where z is the position, T is the thickness through the article, C is the concentration, B is the linear lattice expansion coefficient, E is the Young’s modulus, and v is the Poisson’s ratio. Based on the ion radii of Li+(0.08 nm), Na+(0.102 nm), and K+(0.0138 nm), 1 mol% Li+→ Na+ IOX causes about 60% more expansion than 1 mol% Na+→ K+, so B uses a value of 0.6 ppk / mol% Li+→ Na+. For the glasses discussed, E typically ranges from greater than or equal to 60 and less than or equal to 90 GPa; v typically ranges from greater than or equal to 0.2 and less than or equal to 0.24.

[0063] The measured relaxed stress (σ r ) is determined from surface stress measurements by, for example, the refracted near-field (RNF) method and does not include any sharp or steep surface profile.

[0064] Melted glass has a different structure at different temperatures. Depending on the thermal history experienced by the glass, this structure can be frozen into a solidified (or solid) glass. The fictive temperature (T f ) of a solid glass, as used herein, is the temperature of a melted glass having the same structure as the structure of the solid glass. For example, a discussion of fictive temperature can be found in Mauro et al., J. Am. Ceram. Soc., 2009, 92:75-86, “Fictive Temperature and the Glassy State,” the contents of which are incorporated herein by reference in their entirety. According to the present disclosure, the calculation of fictive temperature associated with the thermal history of a particular glass composition and glass properties can follow established methods. T fThe Guo method, described in Guo et al.'s "Unified approach for determining enthalpic fictive temperature of glasses with arbitrary thermal history" in the Journal of Non-Crystalline Solids. 357 (2011) 3230-3236, is incorporated herein by reference in its entirety. The Guo method uses differential scanning calorimetry (DSC) at a DSC upscan rate of 10 K / min to generate the first and second upscans of the heat capacity versus temperature curve. The three-step procedure includes: (a) First, using area matching, calculating the hypothetical temperature T of the recycled glass in the second upscan. f2 (b) Next, the area between the scan curves on the two DSCs is calculated, given the difference in enthalpy between the formed glass (H1) and the recycled glass (H2); and (c) Finally, the hypothetical temperature T of the formed glass is determined by area matching using equation (A). f1 .

[0065]

[0066] Unless otherwise stated, all T f The values ​​are all determined by the Guo method.

[0067] The glass transition temperature (T) of the materials used in this article g ) for having 10 12 The equilibrium viscosity at temperature (Pa-s). Unless otherwise specified, all T values ​​are... g Values ​​are determined in accordance with ASTM C1350M-96 (2019) ("Standard Test Method for Measurement of Viscosity of Glass Between Softening Point and Annealing Range (Approximately 10 8 Pa·s to Approximately 10 13 Pa·s) by Beam Bending” (measured by bending beam between the softening point and the annealing range (approximately 10) 8 Pa·s to approximately 10 13 The viscosity is determined by the viscosity versus temperature curve generated by the standard test method for glass viscosity (Pa·s).

[0068] The liquid brittleness index (m) of the material used in this paper is the glass transition temperature (T). gThe rate of change of viscosity with temperature for composition (x) is defined as the liquid fragility index (m) of composition (x). The liquid fragility index (m) of composition (x) is defined as the slope of the log(viscosity) versus 1 / T curve at T = T

[0069]

[0070] The viscosity versus temperature curve is generated using one or more viscometers. The value of the liquid fragility index (m) is the slope of the log(viscosity) versus 1 / T curve at T = T g All m values are determined from viscosity versus temperature curves generated according to the following test method combinations unless otherwise noted: ASTM C-965-96(2017) (“Standard Practice for Measuring Viscosity of Glass Above the Softening Point”) (Standard Practice for Measuring Viscosity of Glass Above the Softening Point); ASTM C1351M-96(2017) (“Standard Test Method for Measurement of Viscosity of Glass Between 10 4 Pa·s and 10 8 Pa·s by Viscous Compression of a Solid Right Cylinder”) (Standard Test Method for Measurement of Viscosity of Glass Between 10 4 Pa·s and 10 8 Pa·s by Viscous Compression of a Solid Right Cylinder”) (Standard Test Method for Measurement of Viscosity of Glass Between 10 8 Pa·s and 10 13 Pa·s by Beam Bending”) (Standard Test Method for Measurement of Viscosity of Glass Between Softening Point and Annealing Range (Approximately 10 8 Pa·s to Approximately 10 13 Pa·s by Beam Bending”) (Standard Test Method for Measurement of Viscosity of Glass Between Softening Point and Annealing Range (Approximately 10

[0071] The glass transition temperature (T g) and the composition's brittleness can be expressed as extensions employing empirically determined fitting coefficients. Such extensions are discussed in detail in co-pending and commonly assigned U.S. Patent Application 12 / 896,355, filed October 1, 2010, entitled "METHODS AND APPARATUS FOR PREDICTING GLASS PROPERTIES," the contents of which are incorporated herein by reference in their entirety.

[0072] Overview of Properties of Glass-Based Articles

[0073] The glass-based articles described herein are designed to have improved drop performance for high damage resistant glasses. The glass-based articles described herein are designed to have compositions and properties that utilize stress relaxation. This results in a stress profile that is S-shaped prior to the depth of compression (DOC) and parabolic-shaped after the DOC.

[0074] The glass-based substrates are designed herein to achieve the desired S-shaped profile at reasonable ion exchange (10X) processing times and below a selected 10X processing temperature. In one or more embodiments, the glass stress-based substrates achieve a stress relaxation rate of greater than or equal to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or more. The compositions for suitable glass-based substrates are correspondingly designed to include the desired combination of the glass transition temperature (T g ), the liquid brittleness index (m), and the fictive temperature (T f ). In one or more embodiments, for a 10X processing temperature of less than or equal to 500 °C, T g is less than or equal to 650 °C, T f is less than or equal to 650 °C, T g is less than or equal to 650 °C, the difference between T f and T g is greater than or equal to -30 °C, and m is greater than or equal to 25.

[0075] In one or more embodiments, the articles herein include a lithium-based aluminosilicate composition and a fracture toughness of greater than or equal to 0.75 MPa*m 0.5 The stress profile includes a spike region extending from the first surface to an inflection point, and a tail region extending from the inflection point to the center of the glass-based article, the tail region including a negative curvature region where the second derivative of the stress as a function of depth is negative, a DOC of greater than or equal to 0.22t, and a parabolic region originating at the DOC and extending to the center of the glass-based article.

[0076] Under ideal conditions, the shape and value of the stress profile in ion exchanged glass is expected to follow the classical diffusion equation. The solution to this equation indicates that, in the case of a single boundary where ions diffuse without restriction, the stress profile should be a complementary error function (erfc(x)). As used herein, the terms "error function" and "erf" refer to a function that is twice the integral of the normalized Gaussian function between 0 and x / σ√2. The term "complementary error function" and "erfc" is equal to 1 minus the error function; that is, erfc(x) = 1 - erf(x). For the boundary condition (e.g., ions diffusing from opposite surfaces to the center of the glass), the diffusion of the strengthening cations follows the complementary error function until the ions meet in the center of the glass, after which the entire diffusion profile can be better approximated by a parabolic shape profile of the ion distribution. The stress profile is directly related to the ion distribution within the glass. Therefore, the stress profile should resemble the ion distribution, whether the ion distribution follows the complementary error function or the parabolic function.

[0077] Some glasses can exhibit a difference between the expected and observed stress profile. This can be due to stress relaxation present in the glass as well as additional annealing effects. In the presence of stress relaxation, an S-shaped profile is achieved with a region of negative curvature where the second derivative of the stress as a function of depth is negative. In the region of negative curvature, the slope of the stress profile in the compressive layer between the surface and the depth of compression (DOC) includes at least one region where the slope value changes sign, indicating that the slope (S) of the stress profile is not a monotonically increasing or decreasing function. Rather, the slope (S) changes from a decreasing mode to an increasing mode, or vice versa, thus defining the S-shaped region of the stress profile.

[0078] The stress profile herein has an S-shape before the DOC and a parabolic shape after the DOC. During the ion exchange (IOX) process, stress relaxation occurs simultaneously with ion diffusion. When diffusion is fast, the amount of time at the IOX temperature limits the stress relaxation to a very low level, and an almost linear decay profile from the surface to the depth of the sample is expected. A favorable glass composition will have a reasonably slow diffusion rate to enhance stress relaxation to achieve the profile herein. However, slower diffusion requires longer IOX times and higher IOX temperatures. When the IOX temperature is increased, the time for the IOX can be reduced. However, increasing the IOX temperature results in higher processing costs and undesirable oxide gases that can be released. In some glass compositions, the optimization between the IOX temperature and the diffusion rate is more easily achieved than in other glasses.

[0079] In general, the stress profile herein is not fragile, and thus a glass composition suitable for a high fragility limit is desired. Accordingly, a suitable glass composition as used herein has a high fragility limit greater than or equal to 0.75 MPa*m0.5 a fracture toughness of greater than or equal to 0.75 MPa*m 0.5 ; preferably greater than or equal to 0.8 MPa*m 0.5 . In particular, suitable glass compositions used herein have a fracture toughness of greater than or equal to 0.75 MPa*m 0.5 a fracture toughness of greater than or equal to 0.75 MPa*m 0.5 ; preferably greater than or equal to 0.8 MPa*m 0.5 ; preferably greater than or equal to 0.85 MPa*m From a glass composition perspective, the presence of K2O and P2O5 reduces the brittle limit. In one or more embodiments, the total amount of potassium oxide (K2O) and phosphorous pentoxide (P2O5) in the glass composition is less than 2 mole% (e.g., K2O + P2O5 < 2 mole%). Glass compositions containing Li2O have higher fracture toughness relative to glasses containing only Na2O. In one or more embodiments, the Li2O content is greater than the Na2O. In other words, in one or more embodiments, the molar ratio of sodium oxide (Na2O) to lithium oxide (Li2O) at the center of the glass-based article is less than 1.0. High fracture toughness can also be associated with improved damage resistance (lower damage depth for the same force).

[0080] The glass-based articles herein are advantageous in that they are designed to have excellent resistance to deep damage performance and their stress profiles are not fragile by utilizing stress where it is needed. The profiles herein are suitable for many glass styles, including 2.5D designs, where the glass thickness tapers down to much lower thicknesses at the edges. Without being bound by theory, it is understood that by moving the tension away from the edges, over a longer diffusion duration, the performance of the glass can be improved. The methods described herein are advantageous in that they are feasible for large scale manufacturing using existing equipment and can be completed within a reasonable timeframe. The use of longer diffusion durations herein is expected to provide good performance in 2.5D configurations.

[0081] Lithium aluminosilicate glasses will now be described in detail according to various embodiments. Alkali aluminosilicate glasses have good ion exchangeability, and high strength and high toughness have been achieved in alkali aluminosilicate glasses using chemical strengthening methods. Sodium aluminosilicate glasses are highly ion exchangeable glasses with high glass formability and quality. Lithium aluminosilicate glasses are highly ion exchangeable glasses with high glass quality. The substitution of Al2O3into the silicate glass network increases the interdiffusivity of monovalent cations during ion exchange. Through chemical strengthening in a molten salt bath (e.g., KNO3or NaNO3), glasses with high strength, high toughness, and high indentation crack resistance can be achieved. The stress profile achieved by chemical strengthening can have various shapes, increasing the drop performance, strength, toughness, other properties, and improved scratch resistance of the glass article.

[0082] Accordingly, lithium aluminosilicate glasses with good physical properties, chemical durability, and ion exchangeability have attracted attention as cover glasses. Greater central tension (CT), depth of compression (DOC), and compressive stress (CS) can be achieved through different ion exchange processes. The stress profiles described herein provide increased drop performance for lithium-containing glass articles.

[0083] In embodiments of the glass compositions described herein, the concentrations of the constituent components (e.g., SiO2, Al2O3, Li2O, etc.) are given in mole percent (mol%) on an oxide basis unless otherwise specified. It should be understood that any one of the various recited ranges for one component can be combined with any one of the various recited ranges for any other component, individually.

[0084] Ion exchange methods and stress profiles for lithium aluminosilicate glass compositions are disclosed herein. The stress profile presents scratch resistance. Referring to FIG. 1 , the glass has a thickness t, a first region (e.g., FIG. 1 of the first and second compressive stress layers 120, 122 of ) in compressive stress extending from a surface of the glass to a depth of compression (DOC), and a second region (e.g., FIG. 1 of the central region 130 of ) in tensile stress or central tension (CT) extending from the DOC to a center or interior region of the glass.

[0085] The compressive stress (CS) has a maximum or peak value that generally occurs at the surface of the glass (but this is not necessarily the case, as the peak can occur at a depth from the surface of the glass), and the CS varies as a function of distance d from the surface. Again referring to FIG. 1, the first compressive stress layer 120 extends from the first surface 110 to a depth dl, and the second compressive stress layer 122 extends from the second surface 112 to a depth d2. Together, these segments define the compressive or CS of the glass 100.

[0086] The compressive stresses of the two compressive stress layers FIG. 1 120, 122 are balanced by the tension stored by the central region (130) of the glass.

[0087] FIG. 2 A schematic showing a generalized stress profile curve that includes a spike region extending proximate to a surface to an inflection point and a tail region extending from the inflection point to a deeper portion of the glass toward the center. The stress values in this generalized plot are not absolute, as indicated by the inclusion of "y" in the non-zero y-axis values. The stress profile curve includes: a compressive stress CS at the surface, a depth of layer (DOL sp ) of the spike region (related to the diffusion depth of ions proximate to the spike), a stress CS k at the inflection point (stress at the asymptotic extrapolation of the spike to the deep profile curve region), a depth of compression (DOC) (the location where the stress first goes to zero inside the glass and the sign changes from compressive to tensile), and a central tension (CT) (the stress at the center of the glass). In the spike region, there is a region of negative curvature, where the second derivative of the function of stress versus depth is negative. In the tail region, there is a region of positive curvature, where the second derivative of the function of stress versus depth is positive. FIG. 2 In general, for purposes of illustration, compressive stress is conventionally referred to as positive, while tension is negative.

[0088] In one or more embodiments, the shape of the stress profile curve deeper than the DOC in the central tension (CT) region (where the stress is in a state of tension) can be approximated by an equation. In some embodiments, the stress profile along the CT region can be approximated by equation (B):

[0089] Stress(x) = max CT - (((max CT • (n + l)) / 0.5 n ) • |(x / t) - 0.5| n (B)

[0090] In equation (B), stress(x) is the stress value at position x. Stress is positive (tension) here. max CT is the maximum central tension in MPa, which is a positive value. Value x is the position along the thickness (t) in microns, where the range is from 0 to t; x = 0 is one surface (e.g., 110 in FIG. 1), x = 0.5t is the center of the glass article, where stress(x) = max CT, and x = t is the opposite surface (e.g., 112 in FIG. 1), and x = 0.5t is the center of the glass article, where stress(x) = max CT, and x = t is the opposite surface (e.g., 112 in FIG. 1). Value n is a positive number that is less than 0.5, and value t is the thickness of the glass article in microns. FIG. 1 FIG. 1 ​The maximum CT for equation (B) can range from about 50 MPa to about 350 MPa (e.g., 60 MPa to about 300 MPa, or about 70 MPa to about 270 MPa), and the fitting parameter n is 1.5 to 5 (e.g., 2 to 4, 2 to 3, or 1.8 to 2.2), where n = 2 can provide a parabolic stress profile curve, and exponents that deviate from n = 2 provide stress profile curves that are close to parabolic stress profile curves. The "parabolic shape" profile curves referred to herein include both the parabolic equation and the near-parabolic equation.

[0091] In the glass-based article, there is a non-zero concentration of alkali metal oxide that varies between one or both of the first surface and the second surface and the depth of layer (DOL). A stress profile curve results from the non-zero concentration of metal oxide that varies from the first surface. The non-zero concentration can vary along a portion of the thickness of the article. In some embodiments, the concentration of alkali metal oxide is not zero and varies along a thickness range from about 0-t to about 0.3-t. In some embodiments, the concentration of alkali metal oxide is not zero and varies along a thickness range from about 0-t to about 0.35-t, from about 0-t to about 0.4-t, from about 0-t to about 0.45-t, from about 0-t to about 0.48-t, or from about 0-t to about 0.50-t. The variation in concentration can be continuous along the thickness range described above. The variation in concentration can include a change in metal oxide concentration of about 0.2 mol% or more along a thickness segment of about 100 microns. The change in metal oxide concentration along a thickness segment of about 100 microns can be about 0.3 mol% or more, about 0.4 mol% or more, or about 0.5 mol% or more. The change can be measured by methods known in the art, including microprobe.

[0092] In some embodiments, the variation in concentration can be continuous along a thickness segment in a range from about 10 microns to about 30 microns. In some embodiments, between the first surface and the second surface, the concentration of alkali metal oxide decreases from the first surface to a value, then increases to the value at the second surface.

[0093] The concentration of alkali metal oxide can include more than one metal oxide (e.g., a combination of Na20 and K20). In some embodiments, where two metal oxides are used and the radii of the ions differ from each other, at shallower depths, the concentration of the ion with the larger radius is greater than the concentration of the ion with the smaller radius, and at deeper depths, the concentration of the ion with the smaller radius is greater than the concentration of the ion with the larger radius.

[0094] In one or more embodiments, the alkali metal oxide concentration gradient extends through a majority of the thickness t of the article. In some embodiments, the concentration of the metal oxide along the entire thickness of the first and / or second segment can be about 0.5 mol% or more (e.g., about 1 mol% or more) and is greatest at the first surface and / or second surface 0 · t and decreases substantially uniformly to a value between the first surface and the second surface. At this value, the concentration of the metal oxide along the entire thickness t is a minimum; however, the concentration at this point is not zero either. In other words, the non-zero concentration of this particular metal oxide extends along a majority of the thickness t (as described herein) or the entire thickness t. The total concentration of the particular metal oxide in the glass-based article can be in the range from about 1 mol% to about 20 mol%.

[0095] The concentration of the alkali metal oxide can be determined by the baseline amount of the metal oxide in the glass-based substrate ions that are exchanged to form the glass-based article.

[0096] In one or more embodiments, the glass-based article comprises: a lithium-based aluminosilicate composition. In one or more embodiments, the lithium-based aluminosilicate composition comprises potassium oxide (K2O) and phosphorous pentoxide (P2O5) in an amount less than 2 mol% of the composition, less than 1.9 mol%, less than 1.8 mol% of the composition, less than 1.7 mol%, less than 1.6 mol% of the composition, or less than 1.5 mol%, less than 1.4 mol% of the composition, less than 1.3 mol% of the composition, less than 1.2 mol% of the composition, less than 1.1 mol%, less than 1.0 mol% of the composition, less than 0.9 mol%, less than 0.8 mol% of the composition, less than 0.7 mol%, less than 0.6 mol% of the composition, or less than 0.5 mol% of the composition, and / or greater than or equal to 0.01 mol%, and including all values and sub-ranges therebetween. In one or more embodiments, the lithium-based aluminosilicate composition comprises a total amount of potassium oxide (K2O) and phosphorous pentoxide (P2O5) that is: greater than or equal to 0 mol% and less than 2 mol%, greater than or equal to 0.01 mol% and less than 1.5 mol%, or greater than or equal to 0.5 mol% and less than 1 mol%, and including all values and sub-ranges therebetween.

[0097] In one or more embodiments, the lithium-based aluminosilicate composition comprises a lithium oxide (Li20) content greater than 8 mol%, greater than 8.5 mol%, greater than 9 mol%, greater than 9.5 mol%, greater than 10 mol%, greater than or equal to 10.5 mol%, greater than or equal to 11 mol%, greater than or equal to 11.5 mol%, greater than or equal to 12 mol%, greater than or equal to 12.5 mol%, greater than or equal to 13 mol%, greater than or equal to 13.5 mol%, greater than or equal to 14 mol%, or greater than or equal to 15 mol%, and / or less than or equal to 18 mol%. In one or more embodiments, the lithium-based aluminosilicate composition comprises a lithium oxide (Li20) content greater than or equal to 8 mol% and less than or equal to 18 mol%, greater than or equal to 9 mol% and less than or equal to 16 mol%, or greater than or equal to 10 mol% and less than or equal to 14 mol%, and including all values and sub-ranges therebetween.

[0098] In one or more embodiments, the composition at the center of the glass-based article comprises: 50 to 69 mol% Si02; 12.5 to 25 mol% Al203; 0 to 8 mol% B203; greater than 0 to 4 mol% CaO; greater than 0 to 17.5 mol% MgO; 0.5 to 8 mol% Na20; 0 to 2.5 mol% La203; and greater than 8 to 18 mol% Li20. The glass composition is characterized by a molar ratio of (Li20 + Na20 + MgO) / Al203of 0.9 to less than 1.3; and Al203+ MgO + Li20 + Zr02+ La203+ Y203of greater than 23 mol% and less than 50 mol%.

[0099] The glass-based articles shown herein comprise lithium aluminosilicate glass compositions that exhibit high fracture toughness (K 1C ) values. In some embodiments, the lithium aluminosilicate glass compositions are characterized by a K 0.5 fracture toughness value of at least 0.75 MPa*m 1C as measured by the chevron notched short bar (CNSB) method.

[0100] In some embodiments, the glass compositions exhibit a K 1Cvalues greater than or equal to 0.75 and less than or equal to 1.00 (e.g., greater than or equal to 0.76 and less than or equal to 0.99, greater than or equal to 0.77 and less than or equal to 0.98, greater than or equal to 0.78 and less than or equal to 0.97, greater than or equal to 0.79 and less than or equal to 0.96, greater than or equal to 0.80 and less than or equal to 0.95, greater than or equal to 0.81 and less than or equal to 0.94, greater than or equal to 0.82 and less than or equal to 0.93, greater than or equal to 0.83 and less than or equal to 0.92, greater than or equal to 0.84 and less than or equal to 0.91, greater than or equal to 0.85 and less than or equal to 0.90, greater than or equal to 0.86 and less than or equal to 0.89, or greater than or equal to 0.87 and less than or equal to 0.88, and all ranges and sub-ranges between the foregoing values). 1C values greater than or equal to 0.75 and less than or equal to 1.00 (e.g., greater than or equal to 0.76 and less than or equal to 0.99, greater than or equal to 0.77 and less than or equal to 0.98, greater than or equal to 0.78 and less than or equal to 0.97, greater than or equal to 0.79 and less than or equal to 0.96, greater than or equal to 0.80 and less than or equal to 0.95, greater than or equal to 0.81 and less than or equal to 0.94, greater than or equal to 0.82 and less than or equal to 0.93, greater than or equal to 0.83 and less than or equal to 0.92, greater than or equal to 0.84 and less than or equal to 0.91, greater than or equal to 0.85 and less than or equal to 0.90, greater than or equal to 0.86 and less than or equal to 0.89, or greater than or equal to 0.87 and less than or equal to 0.88, and all ranges and sub-ranges between the foregoing values).

[0101] In one or more embodiments, the composition of the center of the glass-based article comprises a molar ratio of sodium oxide (Na20) to lithium oxide (Li20) that is less than 1.0 and / or greater than or equal to 0.1, including less than or equal to 0.99, less than or equal to 0.9, less than or equal to 0.85, less than or equal to 0.8, less than or equal to 0.75, less than or equal to 0.7, less than or equal to 0.65, less than or equal to 0.63, less than or equal to 0.6, less than or equal to 0.55, less than or equal to 0.5, less than or equal to 0.45, less than or equal to 0.4, less than or equal to 0.35, less than or equal to 0.3, less than or equal to 0.25, less than or equal to 0.2, less than or equal to 0.15, and all values and sub-ranges therebetween. In one or more embodiments, the composition at the center of the glass-based article comprises a molar ratio of sodium oxide (Na20) to lithium oxide (Li20) that is greater than or equal to 0.1 and less than 1.0, greater than or equal to 0.15 and less than or equal to 0.9, or greater than or equal to 0.2 and less than or equal to 0.85, and all values and sub-ranges therebetween.

[0102] In one or more embodiments, the glass-based article comprises a depth of compression (DOC) greater than or equal to 0.22t, greater than or equal to 0.225t, greater than or equal to 0.23t, greater than or equal to 0.235t, greater than or equal to 0.24t, greater than or equal to 0.245t, or greater than or equal to 0.25t, and / or less than or equal to 0.30t, less than or equal to 0.29t, less than or equal to 0.28t, less than or equal to 0.27t, or less than or equal to 0.26t, and including all values and sub-ranges therebetween. In one or more embodiments, the glass-based article comprises a depth of compression (DOC) greater than or equal to 0.22t and less than or equal to 0.30t, greater than or equal to 0.225t and less than or equal to 0.29t, or greater than or equal to 0.23t and less than or equal to 0.8t, and including all values and sub-ranges therebetween.

[0103] In one or more embodiments, the glass-based article comprises a depth of compression (DOC) greater than or equal to 150 microns, greater than or equal to 155 microns, greater than or equal to 160 microns, greater than or equal to 165 microns, greater than or equal to 170 microns, and including all values and sub-ranges therebetween.

[0104] In one or more embodiments, the glass-based article comprises a t greater than or equal to 0.02 mm and / or less than or equal to 2 mm, including: a t less than or equal to 1 mm, less than or equal to 0.8 mm, less than or equal to 0.75 mm, less than or equal to 0.73 mm, less than or equal to 0.70 mm, less than or equal to 0.65 mm, less than or equal to 0.6 mm, less than or equal to 0.55 mm, and / or greater than or equal to 0.1 mm, or greater than or equal to 0.5 mm, and including all values and sub-ranges therebetween. In one or more embodiments, the glass-based article comprises a t greater than or equal to 0.02 mm and less than or equal to 2 mm, greater than or equal to 0.55 mm and less than or equal to 1 mm, greater than or equal to 0.7 mm and less than or equal to 0.8 mm, and including all values and sub-ranges therebetween.

[0105] Maximum compressive stress (CS 最大 ) is desired value is related to the application of the glass-based article. The conditions of IOX are factors that affect CS 最大 . In some embodiments, a spike is introduced to increase CS 最大 . In some embodiments, no spike is introduced. In one or more embodiments, the maximum compressive stress (CS 最大greater than or equal to 150 MPa, greater than or equal to 300 MPa, greater than or equal to 350 MPa, greater than or equal to 400 MPa, greater than or equal to 450 MPa, greater than or equal to 500 MPa, greater than or equal to 550 MPa, greater than or equal to 600 MPa, greater than or equal to 650 MPa, greater than or equal to 700 MPa, greater than or equal to 750 MPa, greater than or equal to 800 MPa, greater than or equal to 850 MPa, greater than or equal to 900 MPa, greater than or equal to 950 MPa, greater than or equal to 1000 MPa, greater than or equal to 1050 MPa, greater than or equal to 1100 MPa, greater than or equal to 1150 MPa, or greater than or equal to 1200 MPa, and all values and sub-ranges therein. In one or more embodiments, the maximum compressive stress (CS) included by the glass-based article is greater than or equal to 150 MPa and less than or equal to 1200 MPa, greater than or equal to 250 MPa and less than or equal to 1100 MPa, greater than or equal to 350 MPa and less than or equal to 1000 MPa, and all values and sub-ranges therein. 最大 greater than or equal to 150 MPa and less than or equal to 1200 MPa, greater than or equal to 250 MPa and less than or equal to 1100 MPa, greater than or equal to 350 MPa and less than or equal to 1000 MPa, and all values and sub-ranges therein.

[0106] In one or more embodiments, the average compressive stress (CS) included by the negative curvature region is greater than or equal to 50 MPa and less than or equal to 120 MPa, greater than or equal to 55 MPa and less than or equal to 115 MPa, or greater than or equal to 60 MPa and less than or equal to 110 MPa, and all values and sub-ranges therein.

[0107] In one or more embodiments, the peak central tension (CT) in the parabolic region ranges from greater than or equal to 100 MPa and less than or equal to 200 MPa, or greater than or equal to 125 MPa and less than or equal to 175 MPa, and all values and sub-ranges therein.

[0108] In one or more embodiments, the value of the peak central tension (CT) * thickness (t) in the parabolic region ranges from greater than or equal to 80 MPa and less than or equal to 160 MPa, or greater than or equal to 90 MPa and less than or equal to 155 MPa, and all values and sub-ranges therein.

[0109] In one or more embodiments, the glass-based article comprises a retained strength greater than or equal to 170 MPa as measured after an impact with a 30 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm. In one or more embodiments, the glass-based article comprises a retained strength greater than or equal to 170 MPa as measured after an impact with an 80 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm. In one or more embodiments, the glass-based article comprises a first retained strength greater than or equal to 170 MPa as measured after an impact with a 30 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm, and a second retained strength greater than or equal to 170 MPa as measured after an impact with an 80 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm. In one or more embodiments, the first retained strength differs from the second retained strength by ± 5 MPa.

[0110] In one or more embodiments, the glass-based article comprises a retained strength greater than or equal to 170 MPa and less than or equal to 200 MPa, greater than or equal to 175 MPa and less than or equal to 195 MPa, or greater than or equal to 180 MPa and less than or equal to 190 MPa, as measured after an impact with a 30 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm, and including all values and sub-ranges therebetween.

[0111] In one or more embodiments, the glass-based article comprises a retained strength greater than or equal to 170 MPa and less than or equal to 200 MPa, greater than or equal to 175 MPa and less than or equal to 195 MPa, or greater than or equal to 180 MPa and less than or equal to 190 MPa, as measured after an impact with an 80 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm, and including all values and sub-ranges therebetween.

[0112] In one or more embodiments, the glass-based article comprises a retained strength greater than or equal to 170 MPa and less than or equal to 200 MPa, greater than or equal to 175 MPa and less than or equal to 195 MPa, or greater than or equal to 180 MPa and less than or equal to 190 MPa, as measured after an impact with a 30 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm and independently measured after an impact with an 80 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm, and including all values and sub-ranges therebetween.

[0113] Design of Glass-Based Substrates

[0114] In one or more embodiments, the glass stress-based substrate achieves a stress relaxation rate that is (100*(1-relaxed stress (σ r ) to initial stress (σ o )) that is greater than or equal to 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or greater, and / or less than or equal to 100%, less than or equal to 90%, less than or equal to 85%, and all values and sub-ranges therebetween. In one or more embodiments, the stress relaxation rate of the glass stress-based substrate is greater than or equal to 10% and less than or equal to 100%, greater than or equal to 20% and less than or equal to 90%, greater than or equal to 25% and less than or equal to 80%, and all values and sub-ranges therebetween. The composition for the suitable glass-based substrate is accordingly designed to include the desired combination of glass transition temperature (T g ), liquid fragility index (m), and fictive temperature (T f ).

[0115] In one or more embodiments, T g is greater than or equal to 550°C or less than or equal to 650°C, and all values and sub-ranges therebetween. In one or more embodiments, T g is greater than or equal to 550°C and less than or equal to 650°C, and all values and sub-ranges therebetween.

[0116] In one or more embodiments, the value of T f minus T g is greater than or equal to -30°C or less than or equal to 100°C, and all values and sub-ranges therebetween. In one or more embodiments, the value of T f minus T g is greater than or equal to -30°C and less than or equal to 100°C, greater than or equal to 0°C and less than or equal to 95°C, or greater than or equal to 30°C and less than or equal to 90°C, and all values and sub-ranges therebetween.

[0117] In one or more embodiments, m is greater than or equal to 25 or less than or equal to 60, and all values and sub-ranges therebetween. In one or more embodiments, m is greater than or equal to 25 and less than or equal to 60, greater than or equal to 30 and less than or equal to 55, greater than or equal to 35 and less than or equal to 50, and all values and sub-ranges therebetween.

[0118] The viscosity of the glass-based substrate contributes to the stress relaxation rate. For a glass in a non-equilibrium state, the viscosity at the time of measurement is very high. The desired ion exchange (IOX) treatment temperature (T IOX ) and the glass transition temperature are preferably in the following ranges: Tg -200 °C < T < 200 °C IOX < T < 200 °C g -50 °C. The upper limit is established to ensure that ion exchange stress is still retained, not that all of the stress is relaxed.

[0119] Stress relaxation is a common phenomenon for glasses under stress. As long as stress is present, stress relaxation occurs in the glass. Stress relaxation follows a stretched exponential equation, as shown in equation (1).

[0120]

[0121] where σ r is the relaxed stress, σ0is the initial stress, t is the physical time, τ is the characteristic relaxation time, and β is the stretch exponent. Stress relaxation according to equation (1) is a property of the base glass substrate and does not need to be accounted for when using the substrate. It is expected that if a glass experiences significant stress relaxation under the thermal conditions typically used for IOX, then a glass article that has undergone IOX under such thermal conditions will also experience significant stress relaxation. Thus, stress relaxation according to equation (1) is a way to predict the stress relaxation performance of an IOX glass. In the typical IOX temperature range, the relaxation time can be approximated by the Arrhenius equation (2):

[0122]

[0123] where τ0is the relaxation time as temperature T approaches infinity, and E is the activation energy.

[0124] The relaxation time is directly related to viscosity by the Maxwell equation (3):

[0125]

[0126] where η is the viscosity, and G is the shear modulus. From the laboratory stress relaxation data, the shear modulus is different than the shear modulus measured in the laboratory. The stress relaxation measurements are discussed in Marcel Potuzak, Roger C. Welch, and John C. Mauro, J. of Chem. Phys. 135, 214502 (2011), entitled "Topological origin of stretched exponential relaxation in glass," which is incorporated herein by reference. In order to best fit the laboratory measured stress relaxation, G is approximately 100 MPa.

[0127] According to the MAP non-equilibrium viscosity model of Mauro et al. (J.C. Mauro, D.C. Allan, M. Potuzak, Phys. Rev. B 80, 094204 (2009)) and the composition-dependent viscosity model of Guo et al. (X.J. Guo, J.C. Mauro, D.C. Allan, M.M. Smedskjaer, J. Am. Ceram. Soc. 2018; 101 : 1169-1179), the expression for the composition dependence of the non-equilibrium glass viscosity is given by:

[0128] log 10 η(T,T f ,x) = y(T,T f ,x)log 10 η eq (T f ,x) + [(1 - y(T,T f ,x)]log 10 η ne (T,T f ,x), (4)

[0129] where

[0130]

[0131] In the viscosity model of equation (4), η eq and η ne are given by equations (6) and (7), respectively. We assume that A(x) = A(x ref ) and ΔΗ(χ) = ΔΗ(χ ref ) are constant over the composition range of interest, i.e., the composition dependence of η ne (T,T f ,x) is contained in the last term of equation (7).

[0132]

[0133] where T g is the glass transition temperature (10 12 Pa s isoincric temperature) and m is the liquid fragility index:

[0134]

[0135] and η ∞ = 10 -2.9 Pa s is the infinite temperature limit of the liquid viscosity (a universal constant independent of composition for silicate liquids).

[0136]

[0137] where A is a constant related to the attempt frequency, AH is the dominant activation enthalpy of isokinetic flow, and S is the configurational entropy ∞ at the infinite temperature limit.

[0138] In accordance with previous enthalpy landscape modeling by Mauro, there is an exponential number of configurational microstates for more brittle systems, each with an exponential number of possible transition states. Thus, we assume S ∞ As brittleness exhibits an exponential change,

[0139]

[0140] Examples herein demonstrate use of this model.

[0141] In one or more embodiments, a method of making a glass-based article includes the steps of: preparing a glass composition; treating the glass composition to form a glass-based substrate comprising: a glass transition temperature (T g ), a liquid brittleness index (m), and a fictive temperature (T f ), where T g is less than or equal to 650 °C, T f is greater than or equal to 650 °C, the difference between T g is greater than or equal to -30 °C, and m is greater than or equal to 25; subjecting the glass-based substrate to ion exchange conditions at less than or equal to 550 °C, including less than or equal to 500 °C, to form the glass-based article such that a stress relaxation rate is greater than or equal to 10%.

[0142] Glass-Based Substrates

[0143] Examples of materials that can be used to form the glass-based substrate include glass and glass-ceramic materials. Exemplary glasses that can be used as the substrate can include alkali aluminosilicate glass compositions or alkali-containing aluminoborosilicate glass compositions, although other glass compositions are also contemplated. Specific examples of glass substrates that can be used include, but are not limited to, alkali aluminosilicate glass, alkali-containing borosilicate glass, alkali aluminoborosilicate glass, alkali-containing lithium aluminosilicate glass, or alkali-containing phosphate glass. The glass-based substrate has a base composition that can be characterized as ion exchangeable. As used herein, “ion exchangeable” means that a substrate comprising the composition is capable of exchanging cations located at or near the surface of the substrate with cations of the same valence that are larger or smaller in size.

[0144] In one or more embodiments, the glass-based substrate can include a lithium-containing aluminosilicate.

[0145] In embodiments, the glass-based substrate can be formed from any composition capable of forming a stress profile. In some embodiments, the glass-based substrate can be formed from the glass compositions described in U.S. Application 16 / 202,691, filed November 28, 2018, entitled “Glasses with Low Excess Modifier Content,” the entire contents of which are incorporated herein by reference. In some embodiments, the glass article can be formed from the glass compositions described in U.S. Application 16 / 202,767, filed November 28, 2018, entitled “Ion-Exchangeable Mixed Alkali Aluminosilicate Glasses,” the entire contents of which are incorporated herein by reference.

[0146] The glass-based substrate can be characterized by the manner in which it is formable. For example, the glass-based substrate can be characterized as being float-formable (i.e., formed by a float process), down-drawable, and more specifically fusion-formable or slot-drawable (i.e., by a down-draw process such as a fusion draw process or a slot draw process). In embodiments, the glass-based substrate can be roll-formed. For glass-ceramics, a ceramming step can be included. Other forming methods can be used for glasses and glass-ceramics.

[0147] Some embodiments of the glass-based substrates described herein can be formed by a down-draw process. Down-draw processes produce glass-based substrates having a uniform thickness of the original surface. Since the average flexural strength of a glass article is controlled by the number and size of surface flaws, the original surface, which has minimal contact, has a higher initial strength. In addition, down-drawn glass articles have very flat and smooth surfaces that can be used in final applications without the need for expensive grinding and polishing.

[0148] Some embodiments of the glass-based substrates can be described as fusion formable (i.e., can be formed using a fusion draw process). The fusion process uses a draw container with a trough for receiving a molten glass feedstock. The weir of the trough is open at the top along the length of the trough on both sides of the trough. When the trough is filled with the molten material, the molten glass overflows the weir. Due to gravity, the molten glass flows down the outside surfaces of the draw container as two flowing glass films. These outside surfaces of the draw container extend downward and inward to join at an edge below the draw container. The two flowing glass films join together at this edge to fuse and form a single flowing glass article. The advantage of the fusion draw method is that neither of the outside surfaces of the resulting glass article is in contact with any part of the apparatus as the two flowing glass films from the overflow of the trough fuse together. Thus, the surface properties of the fusion drawn glass article are not affected by such contact.

[0149] Some embodiments of the glass-based substrates described herein can be formed by a slot draw process. The slot draw process is different from the fusion draw method. In the slot draw process, a molten feedstock glass is provided to a draw container. The bottom of the draw has an open slot with a nozzle extending along the length of the slot. The molten glass flows through the slot / nozzle and is drawn downward as a continuous glass article into an annealing region.

[0150] In one or more embodiments, the base composition comprises: 50 to 69 mole percent Si02; 12.5 to 25 mole percent Al203; 0 to 8 mole percent B203; greater than 0 to 4 mole percent CaO; greater than 0 to 17.5 mole percent MgO; 0.5 to 8 mole percent Na20; 0 to 2.5 mole percent La203; and greater than 8 to 18 mole percent Li20. The glass composition is characterized by: (Li20 + Na20 + MgO) / Al203of 0.9 to less than 1.3; and Al203+ MgO + Li20 + Zr02+ La203+ Y203of greater than 23 mole percent and less than 50 mole percent.

[0151] In one or more embodiments, the glass-based substrates described herein can exhibit an amorphous microstructure and can be substantially free of crystalline or microcrystalline. In other words, in some embodiments, the glass-based substrates do not include glass-ceramic materials.

[0152] In one or more embodiments, an annealing step is performed after ion exchange. That is, the annealing step is optional. Annealing at a temperature of, for example, 500 °C ± 50 °C for a duration of about 15 to 60 minutes can be used to achieve a deeper depth of compression (DOC) and / or a stress relaxation rate.

[0153] Ion Exchange (IOX) Treatment

[0154] Chemical strengthening of a glass-based substrate having a base composition is accomplished by placing the ion-exchangeable glass-based substrate in an ion exchange medium. In embodiments, the ion exchange medium can be a molten bath containing cations (e.g., K+, Na+, Ag+, etc.) that diffuse into the glass, while smaller alkali metal ions (e.g., Na+, Li+) of the glass diffuse into the molten bath. Replacing the smaller cations with larger cations creates compressive stress near the surface of the glass. Tensile stress is created in the interior of the glass to balance the near-surface compressive stress.

[0155] Ion exchange processes can be standalone thermal diffusion processes or electrodiffusion processes. Non-limiting examples of ion exchange processes that involve immersing the glass in multiple ion exchange baths with cleaning and / or annealing steps in between immersions are described in U.S. Patent 8,561,429 entitled "Glass with Compressive Surface for Consumer Applications" to Douglas C. Allan et al., issued October 22, 2013, claiming priority from U.S. Provisional Patent Application No. 61 / 079,995, filed July 11, 2008, in which the glass is strengthened by performing multiple successive ion exchange processes by immersing in salt baths of different concentrations; and U.S. Patent 8,312,739 entitled "Dual Stage Ion Exchange for Chemical Strengthening of Glass" to Christopher M. Lee et al., issued November 20, 2012, claiming priority from U.S. Provisional Patent Application No. 61 / 084,398, filed July 29, 2008, in which the glass is strengthened by performing ion exchange with a first bath that is diluted with effluent ions, followed by immersing in a second bath having a lower concentration of effluent ions than the first bath. The contents of U.S. Patents 8,561,429 and 8,312,739 are incorporated herein by reference in their entirety.

[0156] After performing the ion exchange process, it is understood that the composition at the surface of the glass article can be different from the composition of the as-formed glass-based substrate (i.e., the glass-based substrate prior to performing the ion exchange process). This is due to one of the alkali metal ions (e.g., Li + or Na + ) in the as-formed glass being replaced by a larger alkali metal ion (e.g., Na + or K +) substituted. However, in embodiments, the glass composition at or near the center of the depth of the glass article still has the composition of the as-formed glass-based substrate.

[0157] In one or more embodiments, the potassium salt comprises: KNO3, K2CO3, K3PO4, K2SO4, K3BO3, KCl, or combinations thereof.

[0158] In one or more embodiments, the sodium salt comprises: NaNO3, Na2CO3, Na3PO4, Na2SO4, Na3BO3, NaCl, or combinations thereof.

[0159] In one or more embodiments, the lithium salt comprises: LiNO3, Li2CO3, Li3PO4, Li2SO4, Li3BO3, LiCl, or combinations thereof.

[0160] In one or more embodiments, the potassium salt comprises KNO3, the sodium salt comprises NaNO3, and the lithium salt comprises LiNO3.

[0161] Following the IOX treatment, an optional annealing step as described above can be applied.

[0162] In one or more embodiments, a method of making a glass-based article, comprising the steps of: subjecting a glass-based substrate having opposing first and second surfaces defining a substrate thickness (t) and a lithium-based aluminosilicate composition to an ion exchange treatment to form a glass-based article, the ion exchange treatment comprising: a first molten salt bath and a second molten salt bath; wherein the glass-based article comprises: a fracture toughness greater than or equal to 0.75 MPa*m 0.5 ; and a stress profile comprising: a spike region extending from the first surface to an inflection point; and a tail region extending from the inflection point to a center of the glass-based article, the tail region comprising: a negative curvature region, wherein a second derivative of stress as a function of depth is negative; a depth of compression (DOC) greater than or equal to 0.22t, and a parabolic region originating at the DOC and extending to the center of the glass-based article.

[0163] End Products

[0164] The glass-based articles disclosed herein can be incorporated into another article (e.g., an article having a display (or display article) (e.g., a consumer electronic product, including a mobile phone, a tablet computer, a computer, a navigation system, etc.), a building article, a transportation article (e.g., a vehicle, a train, an aircraft, a watercraft, etc.), an appliance article, or any article that requires some transparency, scratch resistance, wear resistance, or combinations thereof). FIG. 3A and FIG. 3B Exemplary articles incorporating any of the glass articles disclosed herein are illustrated. In particular,FIG. 3A and FIG. 3B The illustrated consumer electronic device 200 includes: a housing 202 having a front surface 204, a rear surface 206, and a side surface 208; electrical components (not shown) at least partially or entirely located inside the housing, including at least a controller, memory, and a display 210 at or near the front surface of the housing; and a cover 212 located at or on the front surface of the housing to cover the display. In some embodiments, at least a portion of at least one of the cover 212 and / or the housing 202 may include any glasswork disclosed herein.

[0165] Example

[0166] The various implementation methods will be further clarified through the following examples. In these examples, before strengthening, the example is referred to as a "substrate". After strengthening, the example is referred to as an "article" or "glass-based article".

[0167] In the following examples, glass substrates according to composition A or B are subjected to ion exchange, and the resulting articles are tested. Compositions A and B, and the glass substrates produced therefrom, have the following properties.

[0168] Composition A: 17.83 mol% Al₂O₃, 6.11 mol% B₂O₃, 4.41 mol% MgO, 1.73 mol% Na₂O, 58.39 mol% SiO₂, 0.08 mol% SnO₂, 0.18 mol% K₂O, 0.02 mol% Fe₂O₃, 0.58 mol% CaO, and 10.66 mol% Li₂O (0.00 mol% SrO, 0.00 mol% ZnO, and 0.00 mol% P₂O₅); and the molar ratio of Na₂O / Li₂O is 0.16. The glass substrate according to composition A has a strength of 0.85 mPa / MPa*m. 0.5 Fracture toughness; T at approximately 660℃ f T, approximately 617℃ g T f With T g The difference between them is approximately 43°C; the liquid brittleness index (m) is 35.

[0169] Composition B: 12.88 mol% Al203, 1.84 mol% B203, 2.86 mol% MgO, 2.39 mol% Na20, 70.96 mol% Si02, 0.07 mol% Sn02, 0.02 mol% Fe203, 8.13 mol% Li20, and 0.85 mol% ZnO (0.00 mol% K20, 0.00 mol% CaO, 0.00 mol% SrO, and 0.00 mol% P205); and a molar ratio of Na20 / Li20 of 0.29. A glass substrate according to Composition B has a fracture toughness of 0.8 mPa MPa*m 0.5

[0170] The stress profile curves of the experimental examples herein were measured via the Refracted Near Field (RNF) method, where the CT matches the measurement of CT provided by the Scattering Polarimetry method by using SCALP-5 manufactured by Glasstress Co. in Estonia. Moreover, due to the limitations of RNF in providing accurate information in the first ~2 pm of the stress profile curve caused by the size of the beam used in this measurement technique, the RNF data was extrapolated to the surface to find the stress at the surface, thus also matching the measurement by FSM-6000LE by OZ Optics in Japan to measure the estimated stress at the surface. Thus, the total stress profile curve matches the CT at the center of the sample measured by the SCALP instrument using a 365 nm light source and the CS at the surface measured by the FSM-6000LE instrument to provide an accurate representation of the entire stress profile curve from the surface to the center of the sample.

[0171] The term "retained strength" as used herein refers to the strength of a glass article after damage has been introduced by an impact force when the article is flexed to apply a tensile stress. The damage is introduced according to the "Surface Impact Test" method described in U.S. Patent Publication No. 2019 / 0072469 Al, which is incorporated herein by reference. For example, the apparatus used for impact testing of glass articles is described in U.S. Patent Publication No. 2019 / 0072469 Al, which is incorporated herein by reference. FIG. 10 ​A device 1100 is shown as an assembly symbol 1100. The device 1100 includes a pendulum 1102 that includes a bob 1104 attached to a pivot 1106. As used herein, the term "bob" on a pendulum is a weight suspended by an arm and connected to a pivot. Thus, the bob 1104 shown is connected to the pivot 1106 by an arm 1108. The bob 1104 includes a base 1110 for receiving a glass article, and the glass article is secured to the base. The device 1100 further includes an impact object 1140 positioned such that a surface of the bob 1104 contacts the impact object 1140 when the bob 1104 is released from a position at an angle greater than zero from an equilibrium position. The impact object includes an abrasive sheet having an abrasive surface to contact an outer surface of the glass article. The abrasive sheet can comprise sandpaper, and can have a grit size in a range of 30 grit to 400 grit, or 100 grit to 300 grit (e.g., 30 or 80 grit).

[0172] For the purposes of this disclosure, the impact object is in the form of a 6 mm diameter 30 grit or 80 grit sandpaper disc secured to the device. A glass article having a thickness of about 600.0 μιη is secured to the bob. A new sandpaper disc is used for each impact. The glass article is damaged at an impact force of about 470 N by swinging the arm of the device to an angle of about 90°. About 10 samples of each glass article are impacted.

[0173] After the damage is introduced for 12 hours or more, the glass article is fractured under four-point bend (4PB). The damaged glass article is placed on support bars (support span) with the damaged site between the bottom (i.e., tension side) and the loading path (loading span). For the purposes of this disclosure, the loading span is 18 mm and the support span is 36 mm. The radius of curvature of the loading and support bars is 3.2 mm. A screw-driven testing machine (Instron®) is used to load at a constant displacement rate of 5 mm / min until the glass breaks. The 4PB test is performed at a temperature of 22°C + 2°C and a RH (relative humidity) of 50% + 5%.

[0174] The applied fracture stress (or applied breakage stress) σ app .

[0175]

[0176] where P is the maximum break load, L (= 36 mm) is the distance between the support bars (support span), a (= 18 mm) is the distance between the loading bars (loading span), b is the width of the glass sheet, h is the thickness of the glass sheet, and v is the Poisson's ratio of the glass composition. The (1 / (1-v 2 )) term in equation (C) accounts for the stiffening effect of the sheet. In four-point bending, the stress is constant under the loading span, and thus, the damage site is under mode I uniaxial tensile stress loading. The stress rate estimate for the 4-point bend test of the sample is between 15 and 17 MPa per second. The retained strength of the glass composition is the highest applied fracture stress at which breakage does not occur.

[0177] Example 1-2 vs. A-B (comparative)

[0178] Table 1 provides an overview of the double ion exchange (DIOX) conditions using nitrates of potassium (K) and sodium (Na) as indicated for Example 1-2. Substrates according to Composition A were used with a thickness of 800 microns. The DIOX conditions included a pre-heat at 380 °C for 10 minutes and were the same as for Example 1-2. Table 1 also shows the following data: percent weight gain, compressive stress (CS), depth of layer at the inflection point (DOL k ), and central tension (CT). Both Step I and Step II included the addition of 0.5 wt% silicic acid to the IOX bath. Between Step I and Step II, the substrates were cleaned to remove excess salt.

[0179] Table 1

[0180]

[0181] *Step I and Step II each included the addition of 0.5 wt% silicic acid.

[0182] Example 1-2 was annealed at 500 °C after DIOX. Table 2 provides the CT data and DOC (pm).

[0183] Table 2

[0184]

[0185] Table 3 provides an overview of the single ion exchange (SIOX) conditions using nitrates of potassium (K), sodium (Na), and lithium (Li) as indicated for Examples A-B (comparative). Example A used 800 micron thick substrates of Composition A. Example B used 800 micron thick substrates of Composition B. Table 3 also shows the following data: compressive stress (CS), compressive stress at the inflection point (CS k ), depth of layer at the inflection point (DOL k ), central tension (CT), and depth of compression (DOC) values. The IOX step included the addition of 0.5 wt% silicic acid to the IOX bath.

[0186] Table 3

[0187]

[0188] *Includes addition of 0.5 wt% silicic acid.

[0189] FIG. 4 Stress profile curves (stress (MPa) vs. depth (microns)) are provided for Examples 1-2 and A-B (comparative). FIG. 4 Negative curvature region is shown: for Example 1, the negative curvature region includes a depth of about 20 to about 140 microns, and for Example 2, the negative curvature region includes a depth of about 10 to about 160 microns. FIG. 5 Graph of sodium dioxide (Na2O) concentration vs. depth measured by GD-OES for Example 1. The solid line is a linear fit of the Na2O profile. The surface CS as a result of force balance is equal to CS = BEAC / (1-v), where AC = CO-C ave The surface Na2O concentration is subtracted from the average Na2O concentration through the thickness, B is the linear lattice expansion coefficient, E is the Young's modulus, and v is the Poisson's ratio. According to FIG. 5 , CO = 10.2, and C ave = 5.1. Thus, the theoretical unrelaxed stress (σ o ) is about 300 MPa more than the measured relaxed stress (σ r ) assuming B is about 0.6 ppk / mole%. (As published by Tandia et al. in Journal of Non-Crystalline Solids, 358 (2012) 316-320). In the paper cited here, the authors discuss Na+→ K+ IOX, the coefficient B is about 1 ppk / mole%. According to the ionic radii of Li+(0.08 nm), Na+(0.102 nm), and K+(0.0138 nm), 1 mole% Li+→ Na+ IOX would cause about 60% more growth than 1 mole% Na+→ K+, thus, B uses a value of 0.6 ppk / mole% for Li+→ Na+. E is 83 GPa, and v is 0.22. FIG. 4 The measured stress profile curve of Example 1 shows a surface stress of about 115 MPa (measured relaxed stress (σ r )) when ignoring the surface steep profile curve. Thus, the stress relaxation in this example is about 60% (e.g., (300-115) / 300).

[0190] The retained strength of the article of Example 1 was determined in 4-point bend (4PB) by surface impact testing after damage introduction according to the method described above. In a first set of experiments, a first retained strength was determined relative to damage impact with 30 grit sandpaper. In a second, independent set of experiments, a second retained strength was determined relative to damage impact with 80 grit sandpaper.

[0191] FIG. 6 A plot of applied fracture stress (MPa) versus grit size for Example 1 is provided, where the first retained strength averaged 185 MPa for 30 grit, and the second retained strength averaged 189 MPa for 80 grit. Sandpaper of 30 grit generally causes deeper damage than sandpaper of 80 grit. Unexpectedly, for Example 1, the second retained strength after impact with 30 grit was found to be statistically equivalent (e.g., within 5 MPa) to the first retained strength after impact with 80 grit.

[0192] Example 3

[0193] Table 4 provides a summary of the double ion exchange (DIOX) conditions indicated for Example 3 using nitrate salts of potassium (K) and sodium (Na). A substrate according to Composition A was used with a thickness of 800 microns. The DIOX conditions included a pre-heat at 380 °C for 10 minutes. Table 4 also shows the following data: compressive stress (CS) after Step II, depth of layer (DOL k , and central tension (CT). After Step I, the CS was 540.0 MPa, and the DOL k was 6.50 μιη. Both Step I and Step II included the addition of 0.5 wt% silicic acid to the IOX bath. Between Step I and Step II, the substrate was cleaned to remove excess salt.

[0194] Table 4

[0195]

[0196] * Each of Step I and Step II included the addition of 0.5 wt% silicic acid.

[0197] FIG. 7 A smoothed stress profile (stress (MPa) versus depth (microns)) for Example 3 after Step II is provided. In this example, to account for variability in the measurements, the stress versus depth data was smoothed according to the following equation: y = 9E-13x 6 - 1 E-09x 5 + 6E-07x 4 - 0.0001x 3 + 0.0084x 2 - 0.0475x + 113.15; R2= 0.9998. FIG. 8A plot of the second derivative of the stress profile curve for FIG. 7 From a depth of about 50 microns, the second derivative remains negative except for some positive values in the range of 63 to 64 microns, until about the center of the article (400 microns). The range of the absolute value of the second derivative is 0.03 to 0.70 in the depth range of 50 microns to 202 microns (DOC).

[0198] Example 3 was annealed at 500°C after DIOX. Table 5 provides the CT data.

[0199] Table 5

[0200]

[0201] FIG. 9 A snippet of the stress profile curve for Example 3 after annealing to show the parabolic region fits the following equation:

[0202] Stress (x) = 2.317E-03x 2 - 2.099E+00x + 3.403E+02, where R 2 = 9.987E-01.

[0203] Examples 5-8

[0204] The T g (x) and m(x) composition dependence is based on experimentally determined values and the range is evaluated using modeling resulting from equations (1) to (7). For these examples, the range of T g is 550°C to 650°C and the range of the fragility index is 25 to 35. The T f was investigated in the following range: 30°C < T f < T g < 70°C. Table 6 provides a summary of the combinations.

[0205] Table 6

[0206]

[0207] FIGS. 10-13 The stress relaxation rate at 1 hour of T IOX (IOX temperature) was plotted against T f < T g (e.g., the difference between T f and T g ). The stress relaxation rate of the glass-based substrate was calculated according to equation (1).

[0208] Stress relaxation rates greater than or equal to 10% (e.g., a range of 20% to 80%, and all values and sub-ranges therebetween) and IOX treatment temperatures less than 550°C (including less than 500°C) are desired. With respect to FIGS. 11-15 , for a T IOX temperature of 500°C, a correlation between T g , minimum brittleness m m , and minimum fictive temperature (T f - T g ) can be determined, as shown in Table 7 based on FIG. 15 . For T IOX less than or equal to 500°C to achieve a desired stress relaxation, a combination of T g less than or equal to 650°C, T f greater than or equal to 30°C, a difference between T g and T f (T g - T 0.5 ), and m greater than or equal to 25 can be used, as shown in Table 7 based on FIG. 15 .

[0209] Table 7

[0210]

[0211] All composition ingredients, relationships, and ratios described in this specification are provided in mole % unless otherwise specified. All ranges disclosed herein include any and all ranges and subranges between the endpoints, whether or not explicitly disclosed.

[0212] While the foregoing is directed to various embodiments, other and further embodiments can be devised without departing from the basic scope of the application, which is determined solely by the claims that follow. For example, features of the disclosed embodiments can be combined into any and all combinations, as to be apparent to those of ordinary skill in the art. For example, the following embodiments are set forth:

[0213] Embodiment 1 : A glass-based article comprising: a composition comprising a lithium-based aluminosilicate and a fracture toughness greater than or equal to 0.75 MPa*m 0.5 ; opposing first and second surfaces defining a thickness (t); and a stress profile comprising: a spike region extending from the first surface to an inflection point; and a tail region extending from the inflection point to a center of the glass-based article, the tail region comprising: a negative curvature region, wherein a second derivative of stress as a function of depth is negative; a depth of compression (DOC) greater than or equal to 0.22t, and a parabolic region originating at the DOC and extending to the center of the glass-based article.

[0214] Embodiment 2: The glass-based article of Embodiment 1, wherein the composition at the center of the glass-based article comprises a lithium oxide (Li20) content greater than 8 mole percent.

[0215] Embodiment 3: The glass-based article of any one of Embodiments 1 or 2, wherein the composition at the center of the glass-based article comprises a molar ratio of sodium oxide (Na20) to lithium oxide (Li20) less than 1.0.

[0216] Embodiment 4: The glass-based article of the previous embodiment, wherein the molar ratio of sodium oxide (Na20) to lithium oxide (Li20) is less than or equal to 0.63.

[0217] Embodiment 5: The glass-based article of Embodiment 1, wherein the lithium-based aluminosilicate composition comprises potassium oxide (K20) and phosphorous pentoxide (P205) in an amount less than 2 mole percent of the composition.

[0218] Embodiment 6: The glass-based article of Embodiment 1, wherein the negative curvature region comprises an average compressive stress (CS) greater than or equal to 50 MPa and less than or equal to 120 MPa.

[0219] Embodiment 7: The glass-based article of any one of Embodiments 1 to the previous embodiment, wherein the composition at the center of the glass-based article comprises: 50 to 69 mole percent Si02; 12.5 to 25 mole percent Al203; 0 to 8 mole percent B203; greater than 0 to 4 mole percent CaO; greater than 0 to 17.5 mole percent MgO; 0.5 to 8 mole percent Na20; 0 to 2.5 mole percent La203; and greater than 8 to 18 mole percent Li20.

[0220] Embodiment 8: The glass-based article of any one of Embodiments 1 to the previous embodiment, wherein the stress profile further comprises: a maximum compressive stress (CS 最大 ) greater than or equal to 150 MPa.

[0221] Embodiment 9: The glass-based article of any one of Embodiments 1 to the previous embodiment, wherein the stress profile further comprises: a value of peak central tension (CT)*thickness (t) in a parabolic region in a range greater than or equal to 80 MPa and less than or equal to 160 MPa.

[0222] Embodiment 10: The glass-based article of any one of Embodiments 1 to the previous embodiment, wherein t is in a range greater than or equal to 0.02 millimeter and less than or equal to 2 millimeters.

[0223] Embodiment 11 : The glass-based article of any one of embodiments 1 to the preceding embodiment, further comprising an alkali metal present in a non-zero varying concentration extending from the first and / or second surface of the glass-based article to a depth of the glass-based article.

[0224] Embodiment 12: The glass-based article of the preceding embodiment, wherein the alkali metal is selected from the group consisting of potassium (K), sodium (Na), lithium (Li), rubidium (Rb), cesium (Cs), francium (Fr), and combinations thereof.

[0225] Embodiment 13: The glass-based article of any one of embodiments 1 to the preceding embodiment, comprising a retained strength greater than or equal to 170 MPa as measured after an impact with a 30 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm.

[0226] Embodiment 14: The glass-based article of any one of embodiments 1 to the preceding embodiment, comprising a retained strength greater than or equal to 170 MPa as measured after an impact with an 80 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm.

[0227] Embodiment 15: A glass-based article comprising: opposing first and second surfaces defining a thickness (t); and a first retained strength greater than or equal to 170 MPa as measured after an impact with a 30 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm, and a second retained strength greater than or equal to 170 MPa as measured after an impact with an 80 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm.

[0228] Embodiment 16: The glass-based article of embodiment 15, wherein the first retained strength and the second retained strength differ by ± 5 MPa.

[0229] Embodiment 17: The glass-based article of embodiment 15, comprising: a composition comprising a lithium-based aluminosilicate and a fracture toughness greater than or equal to 0.75 MPa*m 0.5 .

[0230] Embodiment 18: The glass-based article of embodiment 15, comprising: a stress profile comprising: a spike region extending from the first surface to an inflection point; and a tail region extending from the inflection point to a center of the glass-based article, wherein the tail region comprises: a negative curvature region, wherein a second derivative of stress as a function of depth is negative; a depth of compression (DOC) greater than or equal to 0.22t, and a parabolic region originating at the DOC and extending to the center of the glass-based article.

[0231] Embodiment 19: A consumer electronic product comprising: a housing having a front surface, a back surface, and side surfaces; electronic components disposed at least partially within the housing, the electronic components comprising at least a controller, a memory, and a display, the display disposed at the front surface of the housing or adjacent to the front surface; and a cover disposed over the display; wherein a portion of at least one of the housing and the cover comprises the glass-based article of any one of Embodiments 1 to the immediately preceding embodiment.

[0232] Embodiment 20: A method of making a glass-based article comprising the steps of: ion exchanging a glass-based substrate having opposing first and second surfaces defining a substrate thickness (t) and a lithium-based aluminosilicate composition to form a glass-based article, the ion exchanging comprising: a first molten salt bath and a second molten salt bath; wherein the glass-based article comprises: a fracture toughness greater than or equal to 0.75 MPa*m 0.5 ; and a stress profile comprising: a spike region extending from the first surface to an inflection point; and a tail region extending from the inflection point to a center of the glass-based article, the tail region comprising: a negative curvature region, wherein a second derivative of stress as a function of depth is negative; a depth of compression (DOC) greater than or equal to 0.22t, and a parabolic region originating at the DOC and extending to the center of the glass-based article.

[0233] Embodiment 21 : The method of the immediately preceding embodiment, further comprising an annealing step after the ion exchanging.

[0234] Embodiment 22: The method of Embodiment 20, wherein the lithium-based aluminosilicate composition comprises a lithium oxide (Li20) content greater than 8 mol%.

[0235] Embodiment 23: The method of Embodiment 20, wherein the composition at the center of the glass-based article comprises a molar ratio of sodium oxide (Na20) to lithium oxide (Li20) less than 1.0.

[0236] Embodiment 24: The method of the immediately preceding embodiment, wherein the molar ratio of sodium oxide (Na20) to lithium oxide (Li20) is less than or equal to 0.63.

[0237] Embodiment 25: The method of Embodiment 20, wherein the lithium-based aluminosilicate composition comprises potassium oxide (K20) and phosphorous pentoxide (P205) in an amount less than 2 mol% of the composition.

[0238] Embodiment 26: The method of Embodiment 20, wherein the negative curvature region comprises an average compressive stress (CS) greater than or equal to 50 MPa and less than or equal to 120 MPa.

[0239] Embodiment 27: The method of any one of embodiments 20-26, wherein the composition has: 50-69 mole percent Si02; 12.5-25 mole percent AI2O3; 0-8 mole percent B2O3; greater than 0-4 mole percent CaO; greater than 0-17.5 mole percent MgO; 0.5-8 mole percent Na20; 0-2.5 mole percent La203; and greater than 8-18 mole percent Li20.

[0240] Embodiment 28: The method of any one of embodiments 20-26, wherein the stress profile further comprises: a maximum compressive stress (CS 最大 ) greater than or equal to 150 MPa.

[0241] Those skilled in the art will appreciate that various modifications and changes can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Accordingly, it is intended that the disclosure cover all modifications and alterations of the various embodiments provided herein, whether expressly described or not.

Claims

1. A glass-based article comprising: The composition comprises lithium-based aluminum silicate and a pressure greater than or equal to 0.75 MPa*m 0.5 fracture toughness; The opposing first and second surfaces define a thickness t; as well as Stress distribution curves, which include: The peak region extends from the first surface to the inflection point; as well as The tail region, extending from the inflection point to the center of the glass-based article, includes: Negative curvature regions, where the second derivative of the stress as a function of depth is negative; Depth of compression (DOC) greater than or equal to 0.22t; and The parabolic region originates from the compression depth and extends to the center of the glass substrate, wherein, based on 100 mol% of the composition, the composition contains less than 1 mol% of P2O5, and the composition contains a molar ratio of Na2O to Li2O greater than or equal to 0.1 and less than or equal to 0.

4.

2. The glass-based article of claim 1, wherein the composition at the center of the glass-based article contains more than 8 mol% Li2O.

3. The glass-based article of claim 1, wherein the negative curvature region extends to the center of the glass-based article.

4. The glass-based article as claimed in claim 1, wherein the compression depth is greater than or equal to 0.25t.

5. The glass-based article as claimed in claim 1, wherein the fracture toughness is greater than or equal to 0.8 MPa*m. 0.5 .

6. The glass-based article of claim 1, wherein the average compressive stress (CS) contained in the negative curvature region is greater than or equal to 50 MPa and less than or equal to 120 MPa.

7. The glass-based article of claim 1, wherein the composition at the center of the glass-based article comprises: 50 mol% to 69 mol% SiO2; 12.5 mol% to 25 mol% Al2O3; 0 mol% to 8 mol% B2O3; greater than 0 mol% to 4 mol% CaO; greater than 0 mol% to 17.5 mol% MgO; 0.5 mol% to 8 mol% Na2O; 0 mol% to 2.5 mol% La2O3; and greater than 8 mol% to 18 mol% Li2O.

8. The glass-based article according to any one of claims 1-6, wherein the stress distribution curve further includes: a maximum compressive stress (CS) greater than or equal to 150 MPa. 最大 ).

9. The glass-based article according to any one of claims 1-6, wherein the stress distribution curve further comprises: the value of peak center tension (CT) * thickness (t) in the parabolic region, the value being greater than or equal to 80 MPa * mm and less than or equal to 160 MPa * mm.

10. The glass-based article according to any one of claims 1-6, wherein the range of t is greater than or equal to 0.02 mm and less than or equal to 2 mm.

11. The glass-based article according to any one of claims 1-6, wherein the stress distribution curve further includes a peak center tension (CT) value in the parabolic region within the range of greater than or equal to 100 MPa and less than or equal to 200 MPa.

12. The glass-based article according to any one of claims 1-6, wherein the composition contains less than 2 mol% of the total amount of K2O and P2O5 in the composition.

13. The glass-based article of claim 1, wherein the total amount of K2O and P2O5 is less than or equal to 1.4 mol%.

14. The glass-based article according to any one of claims 1-6, comprising a retained strength greater than or equal to 170 MPa measured after impacting an article having a thickness of 600.0 μm with 30-grit sandpaper with a force of 470.0 N.

15. The glass-based article as claimed in any one of claims 1-6, comprising a retained strength of greater than or equal to 170 MPa measured after impacting an article having a thickness of 600.0 μm with 80-grit sandpaper with a force of 470.0 N.

16. The glass-based article of any one of claims 1-6, comprising: a first retention strength of greater than or equal to 170 MPa measured after impacting an article having a thickness of 600.0 μm with 30-grit sandpaper with a force of 470.0 N; and a second retention strength of greater than or equal to 170 MPa measured after impacting an article having a thickness of 600.0 μm with 80-grit sandpaper with a force of 470.0 N.

17. The glass-based article of claim 16, wherein the first retention strength differs from the second retention strength by ±5 MPa.

18. A consumer electronic product comprising: The housing has a front surface, a rear surface, and side surfaces; An electronic component, at least partially disposed within the housing, the electronic component including at least a controller, memory, and a display, the display being disposed on or adjacent to the front surface of the housing; as well as A cover plate is mounted on the display; A portion of at least one of the housing and the cover plate comprises a glass-based article as described in any one of claims 1-6.

19. A method for manufacturing a glass-based article, comprising the following steps: An ion exchange treatment is performed on a glass substrate having opposing first and second surfaces with a defined substrate thickness t and a lithium-based aluminosilicate composition to form a glass article. The ion exchange treatment includes a first molten salt bath and a second molten salt bath. The glass-based product includes: Greater than or equal to 0.75 MPa*m 0.5 fracture toughness; and Stress distribution curve, the stress distribution curve including: The peak region extends from the first surface to the inflection point; and The tail region, which extends from the inflection point to the center of the glass-based article, includes: Negative curvature regions, where the second derivative of the stress as a function of depth is negative; Depth of compression (DOC) greater than or equal to 0.22t; and The parabolic region originates from the compression depth and extends to the center of the glass-based article, wherein, based on 100 mol% of the composition, the lithium-based aluminosilicate composition contains less than 1 mol% of P2O5, and the composition contains a molar ratio of Na2O to Li2O greater than or equal to 0.1 and less than or equal to 0.

4.

20. The method of claim 19, wherein the compression depth is greater than or equal to 0.25t.

21. The method of claim 19, further comprising an annealing step following the ion exchange treatment performed using the first molten salt bath and the second molten salt bath.

22. The method of claim 19, wherein the lithium-based aluminum silicate composition contains more than 8 mol% Li2O.

23. The method of claim 19, wherein the negative curvature region extends to the center of the glass-based article.

24. The method of claim 19, wherein the stress distribution curve further includes, in the parabolic region, a peak central tension (CT) value in the range of greater than or equal to 100 MPa and less than or equal to 200 MPa.

25. The method of claim 19, wherein the amount of K2O and P2O5 contained in the lithium-based aluminosilicate composition is less than 2 moles of the composition.

26. The method of claim 19, wherein the average compressive stress (CS) contained in the negative curvature region is greater than or equal to 50 MPa and less than or equal to 120 MPa.

27. The method of any one of claims 19 to 26, wherein the composition comprises: 50 mol% to 69 mol% SiO2; 12.5 mol% to 25 mol% Al2O3; 0 mol% to 8 mol% B2O3; greater than 0 mol% to 4 mol% CaO; greater than 0 mol% to 17.5 mol% MgO; 0.5 mol% to 8 mol% Na2O; 0 mol% to 2.5 mol% La2O3; and greater than 8 mol% to 18 mol% Li2O.

28. The method of any one of claims 19 to 26, wherein the stress distribution curve further comprises: a maximum compressive stress (CS) greater than or equal to 150 MPa. 最大 ).

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