Stress profile for glass-based articles with improved drop performance

Abstract

The glass-based article includes a stress profile for providing improved drop performance. A glass-based substrate includes a glass transition temperature (Tg), a liquid brittleness index (m), and a hypothetical temperature (Tf), where Tg is less than or equal to 650 DEG C, a value obtained by subtracting Tg from Tf is greater than or equal to-30 DEG C, and m is greater than or equal to 25. The stress relaxation rate is greater than or equal to 10%, 20% or greater. An article may 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 a center of the glass-based article, the tail region comprising: a negative curvature region in which a second derivative of a function of stress and depth is negative; a depth of compression (DOC) greater than or equal to 0.22 t, and a parabolic region originating at the DOC and extending to a center of the glass-based article.

Description

[0001] Divisional Application Instructions

[0002] This application is a divisional application of the invention patent application filed on September 8, 2021, with national application number 202180077447.7, entitled "Stress distribution curve of glass-based article with improved drop performance".

[0003] This application claims priority to U.S. Provisional Application No. 63 / 083,267, filed September 25, 2020, pursuant to 35 USC § 119, the contents of which are incorporated herein by reference in their entirety. background Technical Field

[0004] This specification generally relates to stress distribution profiles of glass substrate articles suitable as cover glass for electronic devices. More specifically, this specification relates to providing improved stress distribution profiles and methods for lithium-containing aluminosilicate glasses with improved drop performance. Background Technology

[0005] The mobile nature of portable devices (such as smartphones, tablets, portable media players, personal computers, and cameras) makes them particularly vulnerable to accidental drops onto hard surfaces (such as the ground). These devices often include a glass cover, which can be damaged upon impact with a hard surface.

[0006] In many of these devices, the cover glass serves as a display cover and can be combined with touch functionality; however, damage to the cover glass negatively impacts the device's usability.

[0007] When a portable device is dropped onto a hard surface, the glass covering exhibits two main breakage modes. One mode is flexural breakage, caused by the glass bending when the device is subjected to a dynamic load from an impact with the hard surface. The other mode is sharp-contact breakage, caused by damage to the glass surface. Impacts to glass from rough, hard surfaces (e.g., asphalt, granite, etc.) can result in sharp indentations on the glass surface. These indentations become breakage sites on the glass surface, from which cracks can originate and propagate.

[0008] Chemical treatment is a strengthening method used to impart a desired and / or designed stress profile having one or more of the following parameters: compressive stress (CS), depth of compression (DOC), and maximum central tension (CT). Many glass-based articles, including those having a designed stress profile, have a compressive stress at the glass surface that is the highest or peak 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.

[0009] Glass-based articles, particularly glass, can be made more resistant to flexural breakage by conventional 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 the high stress concentration caused by the localized indentation in the glass induced by the sharp contact.

[0010] 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 the limitations of aesthetic and functional requirements, it is difficult to completely prevent the cover glass from impacting the hard surface.

[0011] There is a need for improved stress profiles to produce superior drop performance. SUMMARY

[0012] Aspects of the disclosure relate to glass-based articles and methods of making the same.

[0013] In one aspect, a 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 a first surface and a second surface 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 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.

[0014] In embodiments, the composition at the center of the glass-based article 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 to less than or equal to 120 MPa.

[0015] 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% Al203; from 0 mol% to 8 mol% B203; greater than 0 mol% to 4 mol% CaO; 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 greater than 8 mol% to 18 mol% Li20.

[0016] In embodiments, the stress profile further comprises: a maximum compressive stress (CS 最大 ).

[0017] In embodiments, the stress profile further comprises: a peak central tension (CT) * thickness (t) value in a parabolic region in a range greater than or equal to 80 MPa and less than or equal to 160 MPa.

[0018] In embodiments, t is in a range greater than or equal to 0.02 millimeters and less than or equal to 2 millimeters.

[0019] 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.

[0020] In embodiments, the glass-based article further comprises a retained strength 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.

[0021] In embodiments, the glass-based article further comprises a retained strength greater than or equal to 170 MPa as measured after an impact with 80 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm.

[0022] In an aspect, a glass-based article includes: 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 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 80 grit sandpaper at a force of 470.0 N for an article having a thickness of 600.0 pm.

[0023] 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.

[0024] 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.

[0025] 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 0.5a 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 a function of stress versus depth is negative; a depth of compression (DOC) that is 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.

[0026] In embodiments, the method further comprises an annealing step after the ion exchange treatment.

[0027] 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 an amount of potassium oxide (K20) to phosphorous pentoxide (P205) 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 ).

[0028] 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 intended that the following detailed description together with the drawings will be considered to provide a full and complete understanding of various embodiments, and be considered as comprising a part of the application for patent.

[0029] It is to be understood that both the foregoing general description and the following detailed description are exemplary and intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments described herein, and, together with the description, serve to explain principles and operations of the claimed subject matter. BRIEF DESCRIPTION OF DRAWINGS

[0030] Several embodiments are described below in conjunction with the accompanying drawings, which are incorporated in and form part of this specification.

[0031] FIG. 1 The schematic diagram shows a cross-section of glass having a compressive stress layer on its surface according to the embodiments described and illustrated herein;

[0032] FIG. 2 A generalized schematic stress distribution curve of stress (MPa) versus normalized position (z / thickness) from the surface for an embodiment of a glass-based article.

[0033] FIG. 3A A plan view of an exemplary electronic device incorporating any glass article disclosed herein;

[0034] FIG. 3B for FIG. 3A A perspective view of an exemplary electronic device;

[0035] 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;

[0036] FIG. 5 A graph showing the relationship between sodium dioxide (Na2O) concentration and depth for the embodiments;

[0037] FIG. 6 A graph showing the relationship between applied fracture stress (MPa) and particle size for embodiments of glass-based articles;

[0038] 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;

[0039] FIG. 8 for FIG. 6 The second derivative of the stress distribution curve is plotted.

[0040] FIG. 9 This is an excerpt of the stress distribution curve according to an embodiment of a glass-based article;

[0041] FIG. 10 A schematic diagram of a device that damages glass products by utilizing the impact of an impacting object.

[0042] FIGS. 11-14 The stress relaxation rate according to the embodiment of the glass substrate; and

[0043] FIG. 15 For T gminimum fragility (m) and for ensuring that the T IOX minimum T f -T g of the graph. DETAILED DESCRIPTION

[0044] Before several exemplary embodiments are described, it is to be understood that the disclosure is not limited to the details of construction or process steps set forth herein. The disclosure provided herein can have other embodiments and can be practiced or carried out in various ways.

[0045] Reference throughout this specification to "one embodiment", "certain embodiments", "various embodiments", "one or more embodiments" or "an embodiment" means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as "in one or more embodiments", "in certain embodiments", "in various embodiments", "in one embodiment", or "in an embodiment" in various places throughout this specification are not necessarily referring to the same embodiment or to only one embodiment. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments.

[0046] Definitions and Measurement Techniques

[0047] The terms "glass-based article" and "glass-based substrate" are used to include any object that is made wholly or partly 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.

[0048] 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 embodiments, the central composition at the center of the glass article comprises the base composition.

[0049] It should be noted that the terms "substantially" and "about" can be used herein to indicate an amount that is close to an expected value, but not necessarily identical to it. These terms also can be used to indicate an amount that is close to a stated reference amount, but not necessarily identical to it. For example, a glass-based article that is "substantially free of MgO" is one where 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 with reference to an amount, dimension, formulation, parameter, and other quantity or characteristic, is not precise and need not be precise, but can be approximate and / or larger or smaller, as appropriate, to reflect tolerances, conversion factors, rounding off, measurement error, and the like, as well as other factors known to those of skill in the art. When the term "about" is used in reference to a range of values or endpoints, the disclosure should be understood to include the specific values or endpoints in question. Whether or not the numerical values or endpoints of a range in the specification are prefaced with "about," the numerical values or endpoints are intended to include both implementations, one modified by "about" and one not modified by "about." It can further be understood that each endpoint of a range is implicitly dependent on the other endpoint to the extent that the range is used in the specification.

[0050] Unless otherwise indicated, all compositions described herein are in terms of mole percent on an oxide basis (mol%).

[0051] 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.

[0052] 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 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. However, when the term "tensile" is used, 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 a glass-based article. The maximum central tension (maximum CT or CTmax) refers to the maximum tensile stress in the central region or central tension region of a glass-based article. 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 tensile stress measured and can or can not be in the center of the article.

[0053] The "knee" of the stress profile is the depth of the article where the slope of the stress profile changes from steep to shallow. The knee can refer to the transition region of the span of depths where the slope changes. The knee 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 the onset of the peak (DOL k ). The reported DOL k is measured by surface stress meter by known methods. FIG. 2 A schematic of a stress profile including the knee stress is provided.

[0054] A non-zero metal oxide concentration that varies from a first surface to a depth of layer (DOL) or along at least a substantial portion of the thickness (t) of the metal oxide relative to the metal oxide indicates that a stress has been created in the article as a result of ion exchange. A change in the concentration of the metal oxide can be referred to herein as a metal oxide concentration gradient. A metal oxide that is not zero in concentration and varies from the first surface to the DOL or along a portion of the thickness can be described as creating a stress in the glass-based article. The concentration gradient or change in the metal oxide is created by a chemically strengthened glass-based substrate in which a plurality of first metal ions are exchanged with a plurality of second metal ions.

[0055] The terms "exchange depth," "depth of layer" (DOL), "chemical depth of layer of the layer," and "chemical layer depth" as used herein can be used interchangeably and generally describe the depth facilitated by an ion exchange process (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 internal region thereof) in which ions of a metal oxide or alkali metal oxide (e.g., metal ions or alkali ions) diffuse into the glass-based article where the ion concentration reaches a minimum as determined by a glow discharge optical emission spectrometer (GD-OES). In some embodiments, the DOL is given by the slowest diffusing or maximum exchanged depth of ions introduced by an 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.

[0056] 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).

[0057] Compressive stress (including surface / peak CS, CS 最大 ) and DOL sp measured by using a surface stress meter (FSM) of a commercially available instrument, such as FSM-6000 manufactured by Orihara Industrial Co., Ltd (Japan). The surface stress measurement depends on the accurate measurement of the stress optical coefficient (SOC) associated with the birefringence of the glass. The SOC is then measured according to Procedure C (Glass Disc Method) described in the procedure 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.

[0058] The maximum central tension (CT) or peak tension (PT) and the stress retention values are measured using the 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 and the depth of compression (DOC). When the RNF method is used to measure the stress profile curve, the maximum CT value provided by SCALP 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 the SCALP measurement. The RNF method is described in U.S. Patent No. 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 switching 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 switching light beam, and generating a polarization switching 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 switching light beam through the glass sample and the reference block at different depths into the glass sample, then relaying the transmitted polarization switching light beam to a signal photodetector using a relay optical system, wherein the signal photodetector generates a polarization switching 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.

[0059] Fracture toughness (K 1Crepresents the ability of the 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, thereby representing characteristics of the glass substrate prior to IOX. The fracture toughness test method described herein is not applicable to glass that has been subjected to IOX treatment. However, fracture toughness measurements as described herein for the same glass (e.g., glass substrate) prior to IOX treatment are correlated to fracture toughness after IOX treatment and are used accordingly. The Chevron Notch Short Bar (CNSB) method for measuring K 1C 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 exception that Y m 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). 1CThe double-torsion method and fixtures for values are described in "The double-torsion testing technique for determination of fracture toughness and slow crack growth of materials: A review" by Shyam, A. and Lara-Curzio, E., J. Mater. Sci., 41, pp. 4093-4104, (2006). The double-torsion method generally produces K 1C values that are slightly higher than the chevron notched short bar method. Unless otherwise noted, all fracture toughness values were measured by the chevron notched short bar (CNSB) method.

[0060] The measured relaxation stress (σ r ) in the glass that has been IOX treated and the theoretical non-relaxation stress (σ o ) are used to determine the stress relaxation ratio (SR) of the measured relaxation stress after IOX to the theoretical non-relaxation stress as predicted by the stress profile based on ideal diffusion conditions of the complementary error function (erfc(x)). The 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-relaxation stress. For example, for a theoretical non-relaxation stress (σ o ) of 100 MPa and a measured relaxation stress (σ r ) of 90 MPa, the stress relaxation rate is 10%, or 1 minus the SR multiplied by 100.

[0061] The theoretical non-relaxation 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.

[0062]

[0063] 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 would cause 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.

[0064] The measured relaxation 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 profiles.

[0065] Melted glass has a different structure at different temperatures. Depending on the thermal treatment 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 "Fictive Temperature and the Glassy State" by Mauro et al., J. Am. Ceram. Soc., 2009, 92:75-86, 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 f may be determined according to the Guo method of "Unified approach for determining enthalpic fictive temperature of glasses with arbitrary thermal history" by Guo et al., Journal of Non-Crystalline Solids. 357 (2011) 3230-3236, the contents of which are incorporated herein by reference in their entirety. The Guo method uses differential scanning calorimetry to produce first and second upscans of the heat capacity versus temperature curve at a DSC upscan rate of 10 K / min. The three-step procedure includes: (a) first, the fictive temperature of the rejuvenated glass, T f2 , is calculated using area matching; (b) second, the area between the two DSC upscan curves is calculated, given the difference between the enthalpy of the as-formed glass (H1) and the rejuvenated glass (H2); and (c) finally, area matching is performed by using equation (A) to determine the fictive temperature of the as-formed glass, T f1 .

[0066] (A)

[0067] Unless otherwise stated, all T f values are determined by the Guo method.

[0068] The glass transition temperature (T g ) of a material, as used herein, is the temperature at which the material changes from a glassy state to a rubbery state, as determined by dynamic mechanical analysis (DMA) at a frequency of 1 Hz. The glass transition temperature (T 12temperature of the equilibrium viscosity of Pa-s. Unless otherwise specified, all T g values were determined from viscosity versus temperature curves generated according to 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”). 8 Pa-s to Approximately 10 13 Pa-s) by Beam Bending”).

[0069] The liquid fragility index (m) of a material used herein is a function of the rate of change of viscosity with temperature at the glass transition temperature (T g ) of the composition (x). The liquid fragility index (m) of a composition (x) is defined as:

[0070]

[0071] The viscosity versus temperature curves were 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 Unless otherwise specified, all m values were determined from viscosity versus temperature curves generated according to the following test method combinations: ASTM C-965-96 (2017) (“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”). 4 Pa-s and 10 8Standard 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”). 8 Pa·s to Approximately 10 13 Pa·s) by Beam Bending”).

[0072] The glass transition temperature (T g ) and the brittleness of the compositions can be expressed as extensions using 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 by reference in their entirety.

[0073] Overview of Properties of Glass-Based Articles

[0074] 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 before the depth of compression (DOC) and parabolic after the DOC.

[0075] The glass-based substrates are designed herein to achieve the desired S-shaped profile at reasonable ion exchange (IOX) processing times and below a selected IOX 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 an IOX processing temperature of less than or equal to 500°C, T g is less than or equal to 650°C, T fT g values (e.g., the difference between T f and T g ) is greater than or equal to -30°C, while m is greater than or equal to 25.

[0076] In one or more embodiments, the articles herein comprise a lithium-based aluminosilicate composition and a fracture toughness greater than or equal to 0.75 MPa*m 0.5 The stress profile comprises: a peak 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 comprising: a negative curvature region, wherein the second derivative of the function of stress versus depth is negative; a 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.

[0077] Under ideal conditions, the shape and values of the stress profile in ion exchanged glass are 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 the function of twice the integral of the normalized Gaussian function between 0 and x / σ√2. The term "complementary error function" or "erfc" is equal to 1 minus the error function; that is, erfc(x) = 1 - erf(x). For boundary conditions where ions diffuse from opposite surfaces to the center of the glass, the diffusion of the strengthening cations follows a complementary error function until the ions meet at 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 inside the glass. Therefore, the stress profile should resemble the ion distribution, whether the ion distribution is according to a complementary error function or a parabolic function.

[0078] Certain glasses can exhibit a difference between the expected and observed stress profiles. This can be due to stress relaxation and additional annealing effects present in the glass. In the presence of stress relaxation, an S-shaped profile is achieved with a negative curvature region, where the second derivative of the function of stress versus depth is negative. In the negative curvature region, 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 pattern to an increasing pattern, or vice versa, thus defining an S-shaped region of the stress profile.

[0079] The stress profiles herein have an S-shape before the DOC and a parabolic shape after the DOC. During the ion exchange (IOX) treatment, 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 depth of the sample is expected. Advantageous glass compositions will have a reasonably slow diffusion rate to enhance stress relaxation to achieve the profiles herein. However, slower diffusion requires longer IOX times and higher IOX temperatures. As the IOX temperature is increased, the time for the IOX can be reduced. However, increasing the IOX temperature results in higher processing costs and potentially undesirable oxide gases being released. In some glass compositions, it is easier to achieve an optimization between the IOX temperature and the diffusion rate than in other glasses.

[0080] In general, the stress profiles herein are not fragile and thus glass compositions suitable for high fragility limits are desired. Accordingly, suitable glass compositions for use herein have a fracture toughness greater than or equal to 0.75 MPa*m 0.5 ; more preferably greater than or equal to 0.8 MPa*m 0.5 ; and more preferably greater than or equal to 0.85 MPa*m 0.5 . In particular, suitable glass compositions for use herein have a fracture toughness greater than or equal to 0.75 MPa*m 0.5 ; more preferably greater than or equal to 0.8 MPa*m 0.5 ; and more preferably greater than or equal to 0.85 MPa*m 0.5 as measured by the chevron notched bar method. From a glass composition perspective, the presence of K2O and P2O5 reduces the fragility 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 glass-based article has a molar ratio of sodium oxide (Na2O) to lithium oxide (Li2O) at the center of the glass-based article that is less than 1.0. High fracture toughness can also be associated with improved damage resistance (lower damage depth for the same force).

[0081] The glass-based articles herein are advantageous in that they are designed to have excellent damage resistance to deep scratches 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 a much lower thickness at the edge. Without being bound by theory, it is understood that by moving the tension away from the edge, 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.

[0082] 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. Aluminosilicate sodium glasses are highly ion exchangeable glasses with high glass formability and quality. Aluminosilicate lithium glasses are highly ion exchangeable glasses with high glass quality. The substitution of Al203into the silicate glass network increases the interdiffusivity of monovalent cations during ion exchange. Glasses with high strength, high toughness, and high indentation crack resistance can be achieved by chemical strengthening in a molten salt bath (e.g., KNO3or NaNO3). 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.

[0083] 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.

[0084] 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 is 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.

[0085] Ion exchange methods and stress profiles for lithium aluminosilicate glass compositions are disclosed herein. The stress profiles exhibit scratch resistance. Referring to FIG. 1 , the glass has a thickness t, a first region under compressive stress (e.g., a compressive layer) extending from the surface to a depth of compression (DOC) in the glass, FIG. 1The first and second compressive stress layers 120, 122) and the second region extending from the DOC to the center or inner region of the glass under tensile stress or central tension (CT) (e.g., FIG. 1 The central area is 130).

[0086] Compressive stress (CS) typically has a maximum or peak value at the surface of the glass (but this is not always the case, as the peak value may occur at a depth of some distance from the surface), and CS varies with the distance d from the surface according to a function. See again... FIG. 1 The first compressive stress layer 120 extends from the first surface 110 to a depth d1, while the second compressive stress layer 122 extends from the second surface 112 to a depth d2. These sections together define the compression or CS of the glass 100.

[0087] Two compressive stress layers ( FIG. 1 The compressive stress of 120, 122) is balanced by the tension stored in the central region (130) of the glass.

[0088] FIG. 2 This diagram illustrates the generalized stress distribution curve, which includes a peak region extending near the surface to the inflection point and a tail region extending deeper into the glass towards the center. The stress values ​​in this generalized curve are not absolute; this is indicated by the inclusion of "y" in the non-zero y-axis values. The stress distribution curve includes: the compressive stress CS at the surface, and the layer depth (DOL) of the peak region. sp (Related to the diffusion depth of ions near the peak), stress CS at the inflection point k (Stress at the asymptotic extrapolation points of the peak and depth distribution curve regions), Depth of Compression (DOC) (the location where stress first becomes zero on the inner side of the glass and its sign changes from compression to tension), and Center Tension (CT) (stress at the center of the glass). In the peak region, there exists a region of negative curvature where the second derivative of stress as a function of depth is negative. FIG. 2 In Chinese, for illustrative purposes, compressive stress is conventionally considered positive, while tension is considered negative.

[0089] In one or more embodiments, the shape of the stress distribution curve deeper than the DOC in the central tension (CT) region (where the stress is under tension) can be approximated by an equation. In some embodiments, the stress distribution along the CT region can be approximated by equation (B):

[0090] Stress (x) = Maximum CT – (((Maximum CT • (n+1)) / 0.5 n •|(x / t)-0.5| n(B) In equation (B), stress (x) is the stress value at position x. Here, stress is positive (tension). Maximum CT is the maximum center tension expressed in MPa as a positive value. The value x is the position along the thickness (t) expressed in micrometers, ranging from 0 to t; x = 0 represents a surface (e.g., FIG. 1 In the case of 110), x = 0.5t is the center of the glass-based article, where stress (x) = maximum CT, and x = t is the relative surface (e.g., FIG. 1 (112 in the text). The maximum CT used 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), while n is a fitting parameter of 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 distribution curve, and exponents deviating from n=2 provide a stress distribution curve with a near-parabolic stress distribution curve. The "parabolic shape" distribution curve mentioned herein includes the distribution curves fitted to the parabolic equation and the near-parabolic equation.

[0091] In glass-based articles, alkali metal oxides with a non-zero concentration are present, the non-zero concentration of which varies between one or both of the first and second surfaces and the depth of layer (DOL). A stress distribution profile is generated due to the non-zero concentration of the metal oxides, which varies starting from the first surface. The non-zero concentration can vary along a portion of the article thickness. In some embodiments, the concentration of the alkali metal oxides is not zero and varies along a thickness range of about 0.t to about 0.3.t. In some embodiments, the concentration of the alkali metal oxides is not zero and varies along thickness ranges of about 0.t to about 0.35.t, about 0.t to about 0.4.t, about 0.t to about 0.45.t, about 0.t to about 0.48.t, or about 0.t to about 0.50.t. The concentration variation can be continuous along the aforementioned thickness ranges. The concentration variation can include a change of about 0.2 mol% or more in the metal oxide concentration along a thickness segment of about 100 micrometers. The change in the concentration of metal oxide along a thickness segment of approximately 100 micrometers can be approximately 0.3 mol% or more, approximately 0.4 mol% or more, or approximately 0.5 mol% or more. This change can be measured by methods known in the art (including microprobes).

[0092] In some embodiments, the concentration variation can be continuous along a thickness range of about 10 micrometers to about 30 micrometers. In some embodiments, between the first surface and the second surface, the concentration of the alkali metal oxide decreases to a value at the first surface and then increases 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 are different 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, while 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 segments can be about 0.5 mol% or more (e.g., about 1 mol% or more) and is greatest at 0 • t at the first surface and / or the second surface 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 a range from about 1 mol% to about 20 mol%.

[0095] The concentration of alkali metal oxide can be determined by the baseline amount of the metal oxide in the glass-based substrate ion 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 (K20) and phosphorous pentoxide (P205) 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 (K20) and phosphorous pentoxide (P205) 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: from 50 mol% to 69 mol% Si02; from 12.5 mol% to 25 mol% Al203; 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. The glass composition is characterized by a molar ratio of (Li20 + Na20 + MgO) / Al203from 0.9 to less than 1.3; and Al203+ MgO + Li20 + Zr02+ La203+ Y203greater than 23 mol% and less than 50 mol%.

[0099] The glass-based articles shown herein comprise lithium aluminosilicate glass compositions exhibiting high fracture toughness (K 1C 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 Notch Short Beam (CNSB) method.

[0100] In some embodiments, the glass compositions exhibit a K 1Cvalues of at least 0.75 (e.g., at least 0.76, at least 0.77, at least 0.78, at least 0.79, at least 0.80, at least 0.81, at least 0.82, at least 0.83, at least 0.84, at least 0.85, at least 0.86, at least 0.87, at least 0.88, at least 0.89, at least 0.90, at least 0.91, at least 0.92, at least 0.93, at least 0.94, at least 0.95, or at least 0.96). In embodiments, the glass composition exhibits a K 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] The desired value of the maximum compressive stress (CS 最大 ) is related to the application of the glass-based article. The conditions of IOX are factors that affect the CS 最大 . In some embodiments, a spike is introduced to increase the CS 最大 . In some embodiments, no spike is introduced. In one or more embodiments, the glass-based article comprises a 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 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) comprised 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 (100*(1 - (relaxed stress (σ r ) / (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 ) is preferably in the range of Tg -200℃<T IOX <T g -50℃. This upper limit is established to ensure that ion exchange stress is still maintained, rather than all stress being mostly relaxed.

[0119] Stress relaxation is a common phenomenon in glass under stress. As long as stress exists, glass will undergo stress relaxation. Stress relaxation follows the stretching exponent equation, as shown in equation (1).

[0120] (1)

[0121] Where σ r Let σ0 be the relaxation stress, σ0 be the initial stress, t be the physical time, τ be the characteristic relaxation time, and β be the stretching exponent. The stress relaxation based on equation (1) is a characteristic of the base glass substrate, which does not require ion exchange (IOX) during use. It is expected that if the glass undergoes significant stress relaxation under the thermal conditions typically used for IOX, then glass products subjected to IOX under such thermal conditions will also undergo significant stress relaxation. Therefore, stress relaxation based on equation (1) is a way to predict the stress relaxation performance of IOX glass. Within the typical IOX temperature range, the relaxation time can be approximated by the Arrhenius equation (2):

[0122] (2)

[0123] Where τ0 is the relaxation time as temperature T approaches infinity, and E is the activation energy.

[0124] Relaxation time is directly related to viscosity via Maxwell's equation (3):

[0125] (3)

[0126] Where η is viscosity and G is shear modulus. The shear modulus differs from laboratory-measured shear modulus based on laboratory stress relaxation data. The paper titled “Topological origin of stretched exponential relaxation in glass” by Potuzak et al. (Marcel Potuzak, Roger C. Welch, and John C. Mauro, J. of Chem. Phys. 135, 214502 (2011)) discusses stress relaxation measurements and is incorporated herein by reference. For best fit to 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 determined as:

[0128] (4)

[0129] where

[0130] (5)

[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 ΔH(x) = ΔH(x 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] (6)

[0133] where T g is the glass transition temperature (10 12 Pa s isothermally) 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] (7)

[0137] where A is a constant related to the attempt frequency, ΔH is the primary activation enthalpy for structural flow, and S ∞ is the configurational entropy at the infinite-temperature limit.

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

[0139] (7)

[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; processing the glass composition to form a glass-based substrate comprising: a glass transition temperature (T g ), a liquid fragility index (m), and a hypothetical temperature (T f ), wherein T g is less than or equal to 650 °C, T f is greater than or equal to 550 °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 substrates 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 ion exchangeable in character. 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 draw formable (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 being fusion-formable (i.e., can be formed using a fusion draw process). The fusion process uses a draw container having 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, becoming two flowing sheets of glass. These outside surfaces of the draw container extend downward and inward, joining at an edge below the draw container. The two flowing sheets of glass join together at this edge to fuse and form a single flowing glass article. The advantage of the fusion draw method is that neither outside surface of the resulting glass article comes into contact with any part of the apparatus, as the two sheets of glass flowing from the overflow 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 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 polarization method by using SCALP-5 manufactured by Glasstress Co., Estonia. Moreover, due to the limitation 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-6000 LE by OZ Optics, Japan, which was done 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 light source of 365 nm and the CS at the surface measured by the FSM-6000 LE 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. 10A 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 purposes of the present 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. Damage to the glass article is caused 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 12 hours or more of damage introduction, 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 (load span). For purposes of the present disclosure, the load span is 18 mm and the support span is 36 mm. The loading and support bars have a radius of curvature of 3.2 mm. The loading is performed using a screw drive testing machine (Instron®, Norwood, Massachusetts, USA) at a constant displacement rate of 5 mm / minute 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) in four point bend (4PB) is calculated from equation (C) .

[0175] (C)

[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 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. Item 2 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. Table 1

[0179]

[0180] *Step I and Step II each included the addition of 0.5 wt% silicic acid.

[0181] Example 1-2 was annealed at 500 °C after DIOX. Table 2 provides the CT data and DOC (pm). Table 2

[0182]

[0183] 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. Table 3

[0184]

[0185] *includes addition of 0.5 wt% silicic acid.

[0186] FIG. 4 Stress profile curves (stress (MPa) vs. depth (microns)) for Examples 1-2 and A-B (comparative) are provided. FIG. 4 Negative curvature region is shown: for Example 1, the negative curvature region includes depths of about 20 to about 140 microns, and for Example 2, the negative curvature region includes depths of about 10 to about 160 microns. FIG. 5 A plot of sodium oxide (Na20) concentration vs. depth measured by GD-OES for Example 1. The solid line is a linear fit of the Na20 profile. The surface CS, which is a result of force balance, is equal to where The surface Na20 concentration minus the average Na20 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 , C0= 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 ) when stress relaxation is ignored, 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, and 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+, so B is using 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 (measured relaxed stress (σ r )) of about 115 MPa when the surface steep profile curve is ignored. Thus, the stress relaxation in this example is about 60% (e.g., (300-115) / 300).

[0187] 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.

[0188] FIG. 6The graph shows the relationship between applied fracture stress (MPa) and grit size for Example 1, where the average first retention strength is 185 MPa for 30 grit and the average second retention strength is 189 MPa for 80 grit. 30 grit sandpaper typically causes deeper damage compared to 80 grit sandpaper. Surprisingly, for Example 1, the second retention strength after impact with 30 grit was found to be statistically equivalent (e.g., within 5 MPa) to the first retention strength after impact with 80 grit.

[0189] Example 3

[0190] Table 4 provides a summary of the dual ion exchange (DIOX) conditions for the potassium (K) and sodium (Na) nitrates indicated in Example 3. A substrate of composition A with a thickness of 800 micrometers was used. The DIOX conditions included preheating at 380°C for 10 minutes. Table 4 also shows the following data: compressive stress (CS) after step II, inflection point layer depth (DOL). k ) and central tension (CT). After step I, CS was 540.0 MPa, while DOL k The thickness is 6.50 μm. Both Step I and Step II involve adding 0.5% by weight of silica to the IOX bath. Between Step I and Step II, the substrate is cleaned to remove excess salt. Table 4

[0191]

[0192] *Steps I and II each include the addition of 0.5% by weight of silica.

[0193] FIG. 7 Provides a smoothed stress distribution curve (stress (MPa) versus depth (micrometers)) for Example 3 following step II. In this example, to account for measurement variability, the stress and depth data are smoothed according to the following equation: y = 9E-13x 6 -1E-09x 5 +6E-07x 4 -0.0001x 3 +0.0084x 2 -0.0475x+113.15; R² = 0.9998. FIG. 8 for FIG. 7 The stress distribution curve is plotted as a graph of the second derivative. Starting from a depth of approximately 50 micrometers, the second derivative remains negative, except for some positive values ​​in the range of 63 to 64 micrometers, until approximately the center of the workpiece (400 micrometers). In the depth range of 50 to 202 micrometers (DOC), the absolute value of the second derivative ranges from 0.03 to 0.70.

[0194] Example 3 was annealed at 500°C after DIOX. Table 5 provides the CT data. Table 5

[0195]

[0196] FIG. 9 The following is an excerpt of the stress distribution curve for Example 3 after annealing, to demonstrate that the parabolic region conforms to the following equation:

[0197] Stress (x) = 2.317E-03x 2 -2.099E+00x+3.403E+02, where R 2 =9.987E-01.

[0198] Example 5-8

[0199] T on glass substrate g The compositional dependence of (x) and m(x) is based on experimental measurements and is assessed using modeling derived from equations (1) through (7). For these instances, T g The temperature range is 550℃ to 650℃, and the brittleness index ranges from 25 to 35. f The study was conducted within the following range: 30℃ < T f -T g <70℃. Table 6 provides a summary of the combinations. Table 6

[0200]

[0201] FIGS. 10-13 Draw T IOX Stress relaxation rate at 1 hour (IOX temperature) and T f -T g (For example, T) f With T g The difference between them). The stress relaxation rate of the glass substrate is calculated according to equation (1).

[0202] The desired stress relaxation rate is greater than or equal to 10% (e.g., the range from 20% to 80%, and all values ​​and sub-ranges in between) and the IOX treatment temperature is below 550°C (including below 500°C). Regarding... FIGS. 11-15 For 500℃ T IOX Temperature, T can be determined g Minimum brittleness m m and minimum hypothetical temperature (T) f -T g The correlation between them, such as FIG. 15 As shown. For T values ​​less than or equal to 500℃ IOX To achieve the desired stress relaxation, such as based on FIG. 15T g greater than or equal to 30°C f the difference between T g T f -T g and m greater than or equal to 25. Table 7

[0203]

[0204] All composition ingredients, relationships, and ratios described in this specification are provided in mole percent, unless otherwise specified. All ranges disclosed herein are inclusive of the endpoints and subranges therebetween, whether explicitly disclosed or not.

[0205] Although the foregoing has been described in some detail for purposes of clarity, it is understood that certain changes and modifications can be made to the embodiments described above, with the scope of the disclosed embodiments being defined by the appended claims. For example, the features of the disclosed embodiments can be combined in any and all permutations.

[0206] 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 a first surface and a second surface 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.

[0207] 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.

[0208] 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.

[0209] 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.

[0210] Embodiment 5: The glass-based article of Embodiment 1, wherein the lithium-based aluminosilicate composition comprises potassium oxide (K2O) and phosphorous pentoxide (P2O5) in an amount less than 2 mol% of the composition.

[0211] 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.

[0212] Embodiment 7: The glass-based article of any one of Embodiments 1 to the preceding embodiment, wherein the composition at the center of the glass-based article comprises: 50 to 69 mol% SiO2; 12.5 to 25 mol% Al2O3; 0 to 8 mol% B2O3; greater than 0 to 4 mol% CaO; greater than 0 to 17.5 mol% MgO; 0.5 to 8 mol% Na2O; 0 to 2.5 mol% La2O3; and greater than 8 to 18 mol% Li2O.

[0213] Embodiment 8: The glass-based article of any one of Embodiments 1 to the preceding embodiment, wherein the stress profile further comprises: a maximum compressive stress (CS 最大 ).

[0214] Embodiment 9: The glass-based article of any one of Embodiments 1 to the preceding 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.

[0215] Embodiment 10: The glass-based article of any one of Embodiments 1 to the preceding embodiment, wherein t is in a range greater than or equal to 0.02 millimeter and less than or equal to 2 millimeters.

[0216] 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.

[0217] 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.

[0218] Embodiment 13: The glass-based article of any one of embodiments 1 to the immediately 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.

[0219] Embodiment 14: The glass-based article of any one of embodiments 1 to the immediately 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.

[0220] 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.

[0221] Embodiment 16: The glass-based article of embodiment 15, wherein the first retained strength and the second retained strength differ by ± 5 MPa.

[0222] 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 .

[0223] 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.

[0224] 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 including at least a controller, a memory, and a display, the display disposed at or adjacent to the front surface of the housing; 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.

[0225] 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 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.

[0226] Embodiment 21 : The method of the preceding embodiment, further comprising an annealing step after the ion exchanging.

[0227] Embodiment 22: The method of Embodiment 20, wherein the lithium-based aluminosilicate composition comprises a lithium oxide (Li20) content greater than 8 mol%.

[0228] 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.

[0229] Embodiment 24: The method of the preceding embodiment, wherein the molar ratio of sodium oxide (Na20) to lithium oxide (Li20) is less than or equal to 0.63.

[0230] 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.

[0231] 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.

[0232] Embodiment 27: The method of any one of Embodiments 20 to 26, wherein the composition has: 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.

[0233] Embodiment 28: The method of any one of embodiments 20-26, wherein the stress profile further comprises: a maximum compressive stress (CSmax) greater than or equal to 150 MPa. 最大 ).

[0234] 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, falling within the scope of the claims and their equivalents.

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 are defined with a thickness t greater than or equal to 0.02 mm and less than or equal to 2.0 mm. as well as Stress distribution curves, which include: Depth of compression (DOC) greater than or equal to 0.22t; and The negative curvature region, where the slope of the stress distribution curve changes sign in the compression layer between the first surface and the compression depth; A parabolic region, originating at the compression depth and extending to the center of the glass substrate, wherein the stress distribution curve within the parabolic region has a parabolic shape; and The value of peak center tension (CT) * thickness (t) in the parabolic region, which is greater than or equal to 80 MPa * mm and less than or equal to 160 MPa * mm. The composition, based on 100 mol% of the composition, contains greater than or equal to 8 mol% Li2O and less than 1 mol% P2O5 at the center of the glass-based article, and the composition contains a molar ratio of Na2O to Li2O of 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 comprises a Li2O content of greater than 8.5 mol%.

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 DOC 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 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 peak center tension in the parabolic region is greater than or equal to 100 MPa and less than or equal to 200 MPa.

10. The glass-based article of claim 9, wherein the peak center tension is 105 MPa to 175 MPa.

11. The glass-based article according to any one of claims 1-6, wherein the value of the peak center tension (CT) * thickness (t) in the parabolic region is in the range of greater than or equal to 90 MPa * mm and less than or equal to 155 MPa * mm.

12. The glass-based article according to any one of claims 1-6, wherein the molar ratio of Na2O to Li2O is greater than or equal to 0.1 and less than or equal to 0.

4.

13. The glass-based article according to any one of claims 1-6, wherein the thickness is greater than or equal to 0.55 mm and less than or equal to 1 mm.

14. The glass-based article according to any one of claims 1-6, wherein the composition comprises less than 2 mol% of the total amount of potassium oxide (K2O) and phosphorus pentoxide (P2O5) in the composition.

15. The glass-based article of claim 14, wherein the total amount of potassium oxide (K2O) and phosphorus pentoxide (P2O5) is less than or equal to 1.4 mol.

16. 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 at a force of 470.0 N.

17. The glass-based article of 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.

18. 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.

19. 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.

20. 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: Compression depth, which is greater than or equal to 0.22t; and The negative curvature region, where the slope of the stress distribution curve changes sign in the compression layer between the first surface and the compression depth; A parabolic region, originating at the compression depth and extending to the center of the glass substrate, wherein the stress distribution curve within the parabolic region has a parabolic shape; and The value of peak center tension (CT) * thickness (t) in the parabolic region, which is greater than or equal to 80 MPa * mm and less than or equal to 160 MPa * mm. The thickness of the substrate is greater than or equal to 0.02 mm and less than or equal to 2.0 mm; based on 100 mol% of the composition, the lithium-based aluminosilicate composition contains greater than or equal to 8 mol% of Li2O and less than 1 mol% of P2O5 at the center of the glass substrate, and the composition contains a molar ratio of Na2O to Li2O of less than or equal to 0.

4.

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

22. The method of claim 20, further comprising an annealing step following the ion exchange treatment performed using the first molten salt bath and the second molten salt bath.

23. The method of claim 20, wherein the lithium-based aluminum silicate composition contains a Li₂O content of greater than 8.5 mol%.

24. The method of claim 20, wherein the negative curvature region extends to the center of the glass-based article.

25. The method of claim 20, wherein the peak center tension in the parabolic region is greater than or equal to 100 MPa and less than or equal to 200 MPa.

26. The method of claim 25, wherein the value of the peak center tension is from 105 MPa to 175 MPa.

27. The method of claim 20, wherein the amount of potassium oxide (K₂O) and phosphorus pentoxide (P₂O₅) contained in the lithium-based aluminosilicate composition is less than 2 mol% of the composition.

28. The method of claim 20, wherein the average compressive stress contained in the negative curvature region is greater than or equal to 50 MPa and less than or equal to 120 MPa.

29. The method of any one of claims 20 to 28, wherein the value of the peak center tension (CT) * thickness (t) in the parabolic region is in the range of greater than or equal to 90 MPa * mm and less than or equal to 155 MPa * mm.

30. The method according to any one of claims 20 to 28, wherein the molar ratio of Na2O to Li2O is greater than or equal to 0.1 and less than or equal to 0.

4.

31. The method of any one of claims 20 to 28, 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.

32. The method of any one of claims 20 to 28, wherein the stress distribution curve further comprises: a maximum compressive stress (CS) greater than or equal to 150 MPa. 最大 ).

33. The method of any one of claims 20 to 28, wherein the thickness is greater than or equal to 0.55 mm and less than or equal to 1 mm.

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