Glass, chemically strengthened glass, and electronic equipment

Abstract

The present invention relates to a glass containing, in molar percentage with respect to oxide, 45-65% of SiO2, 18-30% of Al2O3, 7-15% of Li2O, 0-10% in total of at least one selected from among Y2O3 and La2O3, 0-10% of P2O5, 0-10% of B2O3, and 0-4% of ZrO2, wherein when the content of Al2O3 is [Al2O3], the content of P2O5 is [P2O5], the total content of alkali metal oxides is [R2O], and the total content of alkaline-earth metal oxides is [RO], [Al2O3]-[R2O]-[RO]-[P2O5]>0 is satisfied.

Description

Technical Field

[0001] The present invention relates to glass, chemically strengthened glass, and electronic devices.

Background Art

[0002] Chemically strengthened glass is used for cover glass of mobile terminals and the like. Chemically strengthened glass is a glass in which ion exchange occurs between alkali ions contained in the glass and alkali ions having a larger ionic radius contained in a molten salt by a method such as immersing the glass in a molten salt such as sodium nitrate, thereby forming a compressive stress layer in the surface layer portion of the glass.

[0003] Patent Document 1 discloses a method for obtaining a chemically strengthened glass having high surface strength and a large compressive stress layer depth by subjecting a lithium-containing aluminosilicate glass to a two-step chemical strengthening treatment.

[0004] Chemically strengthened glass tends to have higher strength as the surface compressive stress value and the compressive stress layer depth increase. On the other hand, when a compressive stress layer is formed on the glass surface, internal tensile stress is generated inside the glass according to the total amount of the compressive stress. When the value (CT) of the internal tensile stress exceeds a certain threshold value, the cracking manner when the glass breaks becomes violent. This threshold value is also called the CT limit.

[0005] Patent Document 2 discloses a high-strength glass having high crack resistance. This high-strength glass contains a large amount of Al2O3 and is manufactured by a special method called the containerless method, which is not suitable for mass production.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide glass having a high fracture toughness value and being easy to manufacture. Another object of the present invention is to provide chemically strengthened glass having high strength and being less likely to cause severe fracture.

Means for Solving the Problems

[0008] The present inventors studied the CT limit for chemically strengthened glass and found that the CT limit tends to increase as the fracture toughness value increases. Therefore, they considered that high strength can be achieved by chemical strengthening while preventing severe fracture if the glass has excellent chemical strengthening characteristics and a large fracture toughness value. In addition, the present inventors found glass that can be easily manufactured and simultaneously achieve a high fracture toughness value and transparency by adopting a composition capable of introducing an extremely fine phase separation structure into the glass structure, and thus arrived at the present invention.

[0009] That is, the present invention relates to glass containing, in terms of molar percentage based on oxides, 45 to 65% of SiO2, 18 to 30% of Al2O3, 7 to 15% of Li2O, a total of 0 to 10% of one or more selected from Y2O3 and La2O3, 0 to 10% of P2O5, 0 to 10% of B2O3 0 to 4% of ZrO2, and with respect to glass where the content of Al2O3, the content of P2O5, the total content of alkali metal oxides, and the total content of alkaline earth metal oxides are represented as [Al2O3], [P2O5], [R2O], and [RO] respectively in terms of molar percentage based on oxides, [Al2O3] - [R2O] - [RO] - [P2O5]>0.

[0010] The present invention relates to glass containing, in terms of molar percentage based on oxides, 45 to 65% of SiO2, 18 to 30% of Al2O3, 7 to 15% of Li2O, a total of 2 to 10% of one or more selected from Y2O3 and La2O3, 2 to 10% of P2O5, contains 0 to 4% of ZrO2, relates to a glass in which the ratio [Al2O3] / [P2O5] of the Al2O3 content to the P2O5 content is 2.5 to 13.

[0011] In one aspect of the glass of the present invention, when the content of Li2O in terms of molar percentage based on oxides is [Li2O] and the total content of alkali metal oxides is [R2O], it is preferable that [Li2O] / [R2O] is 0.7 to 1. In one aspect of the glass of the present invention, the fracture toughness value is 0.85 MPa·m 1 / 2 or more. In one aspect of the glass of the present invention, the interparticle distance of the particles present in the glass, determined from small-angle X-ray scattering (SAXS) measurement, is preferably 2 to 100 nm. In one aspect of the glass of the present invention, the ratio of the total number of 5-coordinate aluminum atoms and 6-coordinate aluminum atoms to the total number of aluminum atoms in the glass is preferably 1% or more and 15% or less. In one aspect of the glass of the present invention, the Young's modulus is preferably 85 GPa or more. In one aspect of the glass of the present invention, any oxide M other than SiO2, B2O3, Al2O3, Li2O, Na2O, K2O, and P2O5 x O y (where X and Y are positive integers) is contained, and when the content in terms of mol% of M x O y is [M x O y , and the ionic radius of M is r(M), when the sum of (2y / x) / r(M) × [M x O y × 2 / x is Σ, it is preferable that Z represented by the following formula (1) is 5 to 100. Z = Σ + [Al2O3] - [Li2O] - [Na2O] - [K2O] - [P2O5] ··· Formula (1) In one embodiment of the glass of the present invention, it is preferable that the devitrification temperature is 1500°C or lower. In one embodiment of the glass of the present invention, when the glass is chemically strengthened and the number of fractures is measured by the following method, it is preferable that the maximum absolute value of the internal tensile stress (CT) at which the number of fractures is 10 or less is 75 MPa or more. (Method for measuring the number of crushed pieces) A 15mm square, 0.7mm thick glass plate with a mirror finish is prepared as the test glass plate. The test glass plate is chemically strengthened under various conditions to prepare multiple test glass plates with different CT values. In this case, the CT value is measured using a scattered light photoelastic stress meter. Using a Vickers testing machine, a diamond indenter with a 90° angle at its tip is driven into the center of a test glass plate to break it, and the number of fragments is defined as the number of fragments. The test is started with a driving load of 3 kgf for the diamond indenter, and if the glass plate does not break, the driving load is increased by 1 kgf at a time, and the test is repeated until the glass plate breaks, and the number of fragments when it first breaks is counted.

[0012] The present invention relates to a chemically strengthened glass, wherein the base composition is expressed as a mole percentage based on oxides. SiO2 at 45-65%, Al2O3 at 18-30%, Li2O at 7-15% One or more types selected from Y2O3 and La2O3, totaling 0-10%. P2O5 at 0-10%, B2O3 0-10% It contains 0-4% ZrO2, Let [Al2O3] be the molar percentage content of Al2O3 based on oxides, [P2O5] be the content of P2O5, [R2O] be the total content of alkali metal oxides, and [RO] be the total content of alkaline earth metal oxides. Then, [Al2O3]-[R2O]-[RO]-[P2O5]>0. Compressive stress value at a depth of 50 μm from the glass surface (CS 50 This relates to chemically strengthened glass with a pressure of 150 MPa or higher.

[0013] The present invention relates to a chemically strengthened glass, wherein the base composition is expressed as a mole percentage based on oxides. SiO2 at 45-65%, Al2O3 at 18-30%, Li2O at 7-15% One or more types selected from Y2O3 and La2O3 make up a total of 2-10%. P2O5 at 2-10%, It contains 0-4% ZrO2, Compressive stress value at a depth of 50 μm from the glass surface (CS 50 ) is 150 MPa or higher. Regarding chemically strengthened glass.

[0014] In one embodiment of the chemically strengthened glass of the present invention, it is preferable that the interparticle distance of the particles present in the glass, as determined by small-angle X-ray scattering (SAXS) measurement, is 2 to 100 nm. In one embodiment of the chemically strengthened glass of the present invention, it is preferable that the depth at which the compressive stress value becomes zero (DOL) is 60 to 120 μm. In one embodiment of the chemically strengthened glass of the present invention, the surface compressive stress value (CS0) is preferably 600 to 900 MPa. In one embodiment of the chemically strengthened glass of the present invention, it is preferable that the internal tensile stress value (CT) is -70 MPa to -120 MPa. In one embodiment of the chemically strengthened glass of the present invention, the compressive stress value (CS) 50 Preferably, the compressive stress is 180 MPa or more, and the depth (DOL) at which the compressive stress value becomes 0 is 80 μm or more.

[0015] In one embodiment of the chemically strengthened glass of the present invention, it is preferable that the glass is in the form of a plate with a thickness of 2 mm or less. In one embodiment of the chemically strengthened glass of the present invention, it is preferable to have a curved portion with a radius of curvature of 100 mm or less.

[0016] The present invention relates to an electronic device containing the above-mentioned chemically strengthened glass. [Effects of the Invention]

[0017] According to the present invention, a chemically strengthened glass can be obtained that is easy to manufacture, exhibits excellent strength, and is resistant to severe shattering, while simultaneously satisfying high fracture toughness and transparency. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 shows the relationship between the internal tensile stress (CT) value and the number of fractures after chemical strengthening for two types of glass. [Figure 2] Figure 2 shows an example of the stress profile when this glass is chemically strengthened. [Figure 3] Figure 3 shows an example of an electronic device containing this glass. [Figure 4] Figure 4 shows an example of 27Al-NMR measurement results. [Figure 5] Figure 5 shows an example of small-angle X-ray scattering (SAXS) measurement results. [Modes for carrying out the invention]

[0019] In this specification, the symbol "~" indicating a numerical range includes the values ​​before and after it as the lower and upper limits. Unless otherwise specified, "~" will be used in the same sense hereafter in this specification.

[0020] In this specification, "chemically strengthened glass" refers to glass that has undergone chemical strengthening treatment, and "glass for chemical strengthening" refers to glass that has not undergone chemical strengthening treatment. In this specification, "matrix composition of chemically strengthened glass" refers to the glass composition of chemically strengthened glass. In chemically strengthened glass, except in cases of extreme ion exchange treatment, the glass composition at a depth of half the plate thickness t is the same as the matrix composition of the chemically strengthened glass.

[0021] In this specification, glass composition is expressed in molar percentages based on oxides unless otherwise specified, and mole percent is simply denoted as "%". Furthermore, in this specification, "substantially absent" means that the level is below the level of impurities contained in the raw materials, etc., that is, it is not intentionally included. Specifically, "substantially absent" means, for example, less than 0.1 mol%. In this specification, "light transmittance" refers to the average transmittance for light with wavelengths of 380 nm to 780 nm. "Haze value" is measured using a halogen lamp C light source in accordance with JIS K7136:2000. For this glass, the light transmittance and haze value are the same before and after chemical strengthening.

[0022] In this specification, "stress profile" refers to the compressive stress value expressed with respect to the depth from the glass surface. "Compressive stress layer depth (DOL)" is the depth at which the compressive stress value (CS) becomes zero. "Internal tensile stress value (CT)" refers to the tensile stress value at a depth of half the glass plate thickness t. In this specification, the tensile stress value is expressed as a negative compressive stress value.

[0023] The stress profiles described herein can be measured using a scattered light photoelastic stress meter (for example, the SLP-1000 manufactured by Orihara Seisakusho Co., Ltd.). Scattered light photoelastic stress meters may experience reduced measurement accuracy near the sample surface due to surface scattering. However, if compressive stress is generated solely by ion exchange between lithium ions in the glass and external sodium ions, for example, the compressive stress value expressed as a function of depth follows a complementary error function, allowing the surface stress value to be determined by measuring the internal stress value. If the compressive stress value expressed as a function of depth does not follow a complementary error function, the surface portion should be measured by another method (for example, by measuring with a surface stress meter).

[0024] In this specification, the CT limit is the maximum absolute value of CT at which the number of fragments measured by the following procedure is 10 or less. (Method for measuring the number of crushed pieces) For the test, a glass plate measuring 15 mm square with a thickness of 0.7 mm and having a mirror-finished surface will be prepared. The test glass plate will be chemically strengthened under various conditions to prepare multiple test glass plates with different CT values. In this case, the CT value will be measured using a scattered light photoelastic stress meter. Furthermore, the depth of the compressive stress layer (DOL) is estimated. If the DOL is too large relative to the thickness of the glass plate, the glass composition of the tensile stress layer may change, and the CT limit may not be evaluated correctly. Therefore, it is desirable to use glass plates with a DOL of 100 μm or less for the following tests.

[0025] Using a Vickers test machine, a diamond indenter with a 90° angle at its tip is driven into the center of a test glass plate to break it, and the number of fragments is recorded as the number of fragments. For example, if the glass plate breaks into two pieces, the number of fragments is 2. If very fine fragments are produced, the number of fragments that do not pass through a 1 mm sieve is counted and recorded as the number of fragments. However, if the number of fragments exceeds 50, the number of fragments may be considered 50. This is because if the number of fragments becomes too large, it becomes difficult to accurately count them, as most of the fragments will pass through the sieve, and in practice, it has little effect on the evaluation of the CT limit. In addition, the test should begin with a diamond indenter load of 3 kgf, and if the glass plate does not break, the load should be increased by 1 kgf at a time, and the test should be repeated until the glass plate breaks, and the number of fragments when it first breaks should be counted.

[0026] (Method for measuring CT limit) The number of fractures is plotted against the CT value of the test glass plate. The absolute value of the CT at which the number of fractures reaches 10 is read from the CT value where the number of fractures is 10 or less (as large as possible) and the CT value where the number of fractures is greater than 10 and as small as possible, and this is set as the CT limit. In this case, the largest possible value for the number of fractures of 10 or less is 8 or greater, and preferably 9 or greater. For points where the number of fractures is greater than 10, the number of fractures should be 40 or less, and more preferably 20 or less. The following is an example of CT limit measurement.

[0027] Figure 1 plots the CT value and the number of fragments for two glasses, A and B, with different glass compositions. Glass A is plotted as a white diamond, and glass B is plotted as a black circle. From Figure 1, it can be seen that for glasses of the same composition, the number of fragments increases as the absolute value of CT increases. Furthermore, it can be seen that once the number of fragments exceeds 10, the number of fragments increases rapidly with increasing CT.

[0028] The compositions of glass A and glass B are as follows: (Glass A) SiO2:70.4%, Al2O3:13.0%, Li2O:8.4%, Na2O:2.4%, B2O3:1.8%, MgO:2.8%, ZnO:0.9% (Glass B) SiO2:57%, Al2O3:22.5%, Li2O:9.9%, Na2O:0.2%, Y2O3:5.3%, P2O5:3.1%, ZrO2:2.0%

[0029] Table 1 shows the measured stress values ​​(CT values) and number of fractures for glass A and glass B. For glass A, the CT limit is determined to be 60 MPa from the stress value (CT value) of -57 MPa when the number of fractures was 8 and the stress value (CT value) of -63 MPa when the number of fractures was 13. For glass B, the CT limit is determined to be 88 MPa from the stress value (CT value) of -88 MPa when the number of fractures was 8 and the stress value (CT value) of -94 MPa when the number of fractures was 40.

[0030] [Table 1]

[0031] <Glass> When the glass according to the embodiment of the present invention (hereinafter also referred to as "this glass") is in the form of a plate, the plate thickness (t) is preferably, for example, 2 mm or less, more preferably 1.5 mm or less, even more preferably 1 mm or less, even more preferably 0.9 mm or less, particularly preferably 0.8 mm or less, and most preferably 0.7 mm or less, from the viewpoint of enhancing the chemical strengthening effect. Furthermore, in order to obtain sufficient strength, the plate thickness is preferably, for example, 0.1 mm or more, more preferably 0.2 mm or more, even more preferably 0.4 mm or more, and even more preferably 0.5 mm or more. The shape of the glass may be other than a flat plate, depending on the product and application to which it is applied. The glass plate may also have a rim shape with a different thickness on the outer edge. Furthermore, the shape of the glass plate is not limited to these. For example, the two main surfaces do not have to be parallel to each other, and one or both of the two main surfaces may be curved, in whole or in part. More specifically, the glass plate may be, for example, a flat glass plate without warping, or a curved glass plate with a curved surface.

[0032] The light transmittance of this glass is preferably 85% or higher when its thickness is 0.7 mm. A transmittance of 85% or higher is preferable because it makes the display screen easier to see when used as cover glass for a mobile phone display. A light transmittance of 88% or higher is preferable, and 90% or higher is more preferable. A higher light transmittance is preferable, but it is usually 91% or lower. The typical light transmittance of this glass when its thickness is 0.7 mm is 90.5%.

[0033] If the actual glass thickness is not 0.7 mm, the light transmittance for a 0.7 mm thickness can be calculated based on the measured value using the Lambert-Beer law. If a glass plate with thickness t [mm] has a total visible light transmittance of 100 × T [%] and a surface reflectance of 100 × R [%] on one side, then by applying the Lambert-Beer law, using a constant α, T = (1 - R) 2 There is a relationship of ×exp(-αt). From here, we can express α in terms of R, T, and t, and if we set t = 0.7 mm, then R does not change with plate thickness, so the total visible light transmittance T on a 0.7 mm basis is... 0.7 is T 0.7 = 100 × T 0.7 / t It can be calculated as / (1-R)^(1.4 / t-2)[%], where X^Y is X Y It represents. Surface reflectance can be calculated from the refractive index or measured directly. Furthermore, if the plate thickness t is greater than 0.7 mm, the plate thickness may be adjusted to 0.7 mm by polishing or etching before measuring the light transmittance.

[0034] Furthermore, the haze value of this glass is preferably 0.2% or less, more preferably 0.1% or less, even more preferably 0.08% or less, even more preferably 0.05% or less, and particularly preferably 0.03% or less, when the thickness is 0.7 mm. A smaller haze value is preferable, but it is usually 0.01% or more. When the thickness is 0.7 mm, the typical haze value of this glass is 0.02%.

[0035] Furthermore, if the total visible light transmittance of this glass with a thickness t [mm] is 100 × T [%] and the haze value is 100 × H [%], then by applying the Lambert-Beer law, using the constant α mentioned above, dH / dt ∝ exp(-αt) × (1-H). In other words, the haze value can be considered to increase proportionally to the internal linear transmittance as the thickness increases, so the haze value H for 0.7 mm is... 0.7 It can be calculated using the following formula. However, "X^Y" is "X Y This represents ". H 0.7 =100 × [1-(1-H)^{((1-R) 2 -T 0.7 ) / ((1-R) 2 -T)}][%] Furthermore, if the plate thickness t is greater than 0.7 mm, the plate thickness may be adjusted to 0.7 mm by polishing or etching before measurement.

[0036] The fracture toughness value of this glass is 0.85 MPa·m 1 / 2The above is preferable. Glass with a high fracture toughness value has a large CT limit, so even if a large surface compressive stress layer is formed by chemical strengthening, severe shattering is less likely to occur. The fracture toughness value is 0.86 MPa·m 1 / 2 The above is more preferable, 0.88 MPa·m 1 / 2 The above is even more preferable, 0.90 MPa·m 1 / 2 The above is even more preferable. The fracture toughness value of glass is typically 2.0 MPa·m. 1 / 2 The following is typical, usually 1.5 MPa·m 1 / 2 The following applies: Fracture toughness values ​​can be measured, for example, using the DCDC method (Acta metall.mater. Vol.43, pp.3453-3458, 1995).

[0037] In this glass, the aforementioned CT limit is preferably 70 MPa or higher, more preferably 73 MPa or higher, and even more preferably 75 MPa or higher. The CT limit of this glass is usually 95 MPa or lower.

[0038] This glass is lithium aluminosilicate glass. Specifically, this glass contains 40% or more SiO2, 18% or more Al2O3, and 5% or more Li2O. Since lithium aluminosilicate glass contains lithium ions, which are the alkali ions with the smallest ionic radius, chemical strengthening treatment using various molten salts for ion exchange can yield chemically strengthened glass with a desirable stress profile.

[0039] This glass is expressed in mole percentage based on oxides. SiO2 at 45-65%, Al2O3 at 18-30%, Li2O at 7-15% One or more types selected from Y2O3 and La2O3, totaling 0-10%. P2O5 at 0-10%, B2O3 0-10% ZrO2 0-4%, It is preferable to include it. The composition of this glass will be explained below.

[0040] In this glass, SiO2 is a component that constitutes the framework of the glass network structure and is a component that increases chemical durability. To obtain sufficient chemical durability, the SiO2 content is preferably 45% or more, more preferably 46% or more, even more preferably 47% or more, even more preferably 48% or more, and particularly preferably 50% or more. Furthermore, the SiO2 content is preferably 65% ​​or less, more preferably 63% or less, even more preferably 60% or less, and even more preferably 59% or less. To facilitate bending and other processes, the SiO2 content is preferably 58% or less.

[0041] Al2O3 is an essential component of this glass and contributes to its high strength. The Al2O3 content is preferably 18% or more, more preferably 19% or more, and even more preferably 20% or more, in order to obtain sufficient strength. The Al2O3 content is preferably 30% or less, more preferably 28% or less, even more preferably 26% or less, even more preferably 25% or less, and most preferably 24% or less, in order to increase meltability.

[0042] SiO2 and Al2O3 are components that make up the network of the glass. In order to include a sufficient amount of network components and improve the chemical durability and brittleness of the glass, the total amount of SiO2 + Al2O3 is preferably 60% or more, more preferably 62% or more, even more preferably 64% or more, and even more preferably 66% or more. Also, if there is too much network component, the Young's modulus of the glass will decrease, so the total amount of SiO2 + Al2O3 is preferably 90% or less, more preferably 87% or less, even more preferably 84% or less, even more preferably 83% or less, particularly preferably 82% or less, and most preferably 81% or less.

[0043] Li2O is an essential component of lithium aluminosilicate glass. The Li2O content is 5% or more, preferably 6% or more, more preferably 7% or more, even more preferably 8% or more, and even more preferably 9% or more, in order to increase the compressive stress layer depth (DOL) due to chemical strengthening. Furthermore, in order to suppress devitrification during the manufacturing or bending of glass, the Li2O content is preferably 15% or less, more preferably 14% or less, even more preferably 13% or less, and even more preferably 12% or less.

[0044] This glass may contain other alkali metal oxides to adjust its chemical strengthening properties or to improve the stability of the molten glass. Preferred alkali metal oxides include Na2O and K2O, with Na2O being more preferred. K2O may be substantially omitted. To increase the fracture toughness, the total content of other alkali metal oxides is preferably 10% or less, more preferably 8% or less, even more preferably 6% or less, even more preferably 5% or less, particularly preferably 4% or less, even more preferably 2% or less, especially preferably 1% or less, and most preferably 0.5% or less.

[0045] In the following, alkali metal oxides such as Li2O, Na2O, and K2O may be collectively referred to as R2O. R2O is a component that lowers the melting point of glass. In this glass, the ratio of the total content of Li2O to the total content of alkali metal oxides, [Li2O] / [R2O], is preferably 0.7 or higher, more preferably 0.75 or higher, even more preferably 0.8 or higher, and particularly preferably 0.85 or higher. Furthermore, [Li2O] / [R2O] is 1 or less, and more preferably 0.99 or less.

[0046] Neither Y2O3 nor La2O3 is essential, but it is preferable to include one or both to enhance solubility. The total content of these [Y2O3] + [La2O3] is preferably 0.5% or more, more preferably 1% or more, even more preferably 2% or more, even more preferably 3% or more, particularly preferably 4% or more, and even more preferably 5% or more. Furthermore, to maintain high strength, the [Y2O3]+[La2O3] content is preferably 10% or less, more preferably 8% or less, even more preferably 7% or less, even more preferably 6% or less, and particularly preferably 5% or less.

[0047] To enhance the solubility of this glass, it is more preferable to contain Y2O3. The Y2O3 content is preferably 0.5% or more, more preferably 1% or more, even more preferably 2% or more, even more preferably 3% or more, and even more preferably 5% or more. The Y2O3 content is preferably 10% or less, more preferably 8% or less, and even more preferably 6% or less, in order to increase the strength of the glass.

[0048] P2O5 is a component that forms a network in combination with Al2O3 in the glass. Furthermore, the glass may contain P2O5 to improve the ion diffusion rate during chemical strengthening treatment. The P2O5 content is preferably 0% or more, more preferably 1% or more, and even more preferably 2% or more. To achieve high chemical durability, the P2O5 content is preferably 10% or less, more preferably 9% or less, even more preferably 8% or less, even more preferably 6% or less, particularly preferably 4% or less, and most preferably 3% or less.

[0049] When this glass contains P2O5, the glass network is formed not only by SiO2 but also by a combination of P2O5 and Al2O3, resulting in high strength and a lower devitrification temperature. When this glass contains P2O5, the ratio of Al2O3 content to P2O5 content [Al2O3] / [P2O5] is preferably 2.5 or higher, more preferably 3 or higher, and even more preferably 4 or higher, in order to lower the devitrification temperature. This is because if there is too much P2O5, aluminum phosphate-based devitrification is likely to precipitate. Furthermore, in order to suppress the precipitation of aluminum silicate and other crystals during glass melting, the [Al2O3] / [P2O5] ratio is preferably 13 or lower, more preferably 10 or lower, and even more preferably 8 or lower.

[0050] ZrO2 is preferably included in order to increase the surface compressive stress of the chemically strengthened glass. If the glass contains ZrO2, the content is preferably 0% or more, more preferably 0.2% or more, even more preferably 0.5% or more, and particularly preferably 1% or more. Furthermore, in order to suppress devitrification during melting, the ZrO2 content is preferably 4% or less, more preferably 3.5% or less, even more preferably 3% or less, and still more preferably 2% or less.

[0051] TiO2, like ZrO2, tends to increase the surface compressive stress of chemically strengthened glass and may be included. When this glass contains TiO2, the content is preferably 0.1% or more. The TiO2 content is preferably 5% or less, more preferably 3% or less, even more preferably 1% or less, and particularly preferably 0.5% or less, in order to suppress devitrification during melting. Furthermore, the total content of TiO2 and ZrO2 (TiO2 + ZrO2) is preferably 5% or less, and more preferably 3% or less. The total content of TiO2 and ZrO2 is preferably 1% or more, and more preferably 1.5% or more.

[0052] Alkaline earth metal oxides such as MgO, CaO, SrO, BaO, and ZnO are not essential components but may be included. While these components all enhance the melting properties of the glass, they tend to reduce its ion exchange performance. The total content of MgO, CaO, SrO, BaO, and ZnO (MgO + CaO + SrO + BaO + ZnO) is preferably 10% or less, more preferably 5% or less, even more preferably 4% or less, and even more preferably 3% or less.

[0053] In alkaline earth metal oxides, the presence of MgO tends to enhance the chemical strengthening effect. When this glass contains MgO, the content is preferably 0.1% or more, more preferably 0.5% or more. Furthermore, the MgO content is preferably 10% or less, more preferably 5% or less, even more preferably 4% or less, and even more preferably 3% or less.

[0054] If this glass contains CaO, the CaO content is preferably 0.5% or more, and more preferably 1% or more. To improve ion exchange performance, the CaO content is preferably 5% or less, and more preferably 3% or less.

[0055] If this glass contains SrO, the content is preferably 0.5% or more, and more preferably 1% or more. To improve ion exchange performance, the SrO content is preferably 5% or less, and more preferably 3% or less.

[0056] If this glass contains BaO, the content is preferably 0.5% or more, more preferably 1% or more. To improve ion exchange performance, the BaO content is preferably 5% or less, more preferably 1% or less, and even more preferably substantially absent.

[0057] ZnO is a component that improves the meltability of glass, and this glass may contain ZnO. If this glass contains ZnO, the content is preferably 0% or more, more preferably 0.2% or more, and even more preferably 0.5% or more. In order to improve the weather resistance of the glass, the ZnO content is preferably 5% or less, and more preferably 3% or less.

[0058] B2O3 is not essential, but it can be added to improve meltability during glass manufacturing, etc. Furthermore, to enhance stability by reducing the slope of the stress profile near the surface of chemically strengthened glass during chemical strengthening, the B2O3 content is preferably 0.5% or more, more preferably 1% or more, even more preferably 2% or more, and still more preferably 3% or more. Since B2O3 is a component that facilitates stress relaxation after chemical strengthening, in order to further increase the surface compressive stress of chemically strengthened glass, the B2O3 content is preferably 10% or less, more preferably 8% or less, even more preferably 6% or less, even more preferably 5% or less, particularly preferably 4% or less, and most preferably 3% or less.

[0059] Nb2O5 and Ta2O5 may be included to suppress the shattering of chemically strengthened glass, etc. When this glass contains these components, the total content of Nb2O5 and Ta2O5 is preferably 0.2% or more, more preferably 0.5% or more, even more preferably 1% or more, particularly preferably 1.5% or more, and most preferably 2% or more. Furthermore, the total content of Nb2O5 and Ta2O5 is preferably 3% or less, and more preferably 2.5% or less.

[0060] When coloring glass, coloring components may be added insofar as they do not hinder the achievement of the desired chemical strengthening properties. Examples of coloring components include Co3O4, MnO2, Fe2O3, NiO, CuO, Cr2O3, V2O5, Bi2O3, SeO2, CeO2, Er2O3, and Nd2O3. These may be used individually or in combination. The total content of coloring components is preferably 7% or less. This suppresses devitrification of the glass. The content of coloring components is more preferably 5% or less, even more preferably 3% or less, and particularly preferably 1% or less. If high transparency of the glass is desired, it is preferable that these components are substantially absent.

[0061] Furthermore, this glass may appropriately contain SO3, chlorides, fluorides, etc., as clarifying agents during glass melting. It is preferable that this glass is substantially free of As2O3. If this glass contains Sb2O3, the Sb2O3 content is preferably 0.3% or less, more preferably 0.1% or less, and most preferably substantially free.

[0062] In this glass, aluminum atoms (hereinafter sometimes referred to as Al) can have oxygen coordination numbers ranging from 4 to 6. Of these, 4-coordinate Al improves the chemical durability of the glass. 5-coordinate and 6-coordinate Al improve fracture toughness and increase the strength of the glass. While general glass only contains 4-coordinate Al, this glass, by adjusting the coordination number of aluminum atoms, becomes a glass with an extremely small phase separation structure, as described later. This is presumed to result in a glass with high fracture toughness while maintaining transparency, thus obtaining superior properties.

[0063] The total number of 5-coordinate and 6-coordinate aluminum atoms to the total number of aluminum atoms in the glass is preferably 1% or more. This percentage is more preferably 2% or more, even more preferably 3% or more, and most preferably 4% or more. On the other hand, the total number of 5-coordinate and 6-coordinate aluminum atoms is preferably 15% or less, more preferably 14% or less, even more preferably 13% or less, even more preferably 12% or less, particularly preferably 11% or less, even more particularly preferably 10% or less, especially preferably 9% or less, and most preferably 8% or less, from the viewpoint of suppressing deterioration of acid resistance. The total number of 5-coordinate and 6-coordinate aluminum atoms to the total number of aluminum atoms in the glass can be adjusted to the desired range by adjusting the glass composition. Also, the coordination number of aluminum atoms is 27 This can be measured using Al-NMR. "The ratio of the total number of 5-coordinate and 6-coordinate aluminum atoms to the total number of aluminum atoms" means: 27 This refers to the percentage of 4-coordinate Al, 5-coordinate Al, and 6-coordinate Al calculated from the Al-NMR measurement results, and then summing the percentages of 5-coordinate Al and 6-coordinate Al. 27 Preferred conditions for Al-NMR measurement will be described later in the examples.

[0064] In this glass, the Al2O3 content is [Al2O3], the P2O5 content is [P2O5], the total alkali metal oxide content is [R2O], and the total alkaline earth metal oxide content is [RO], and the condition [Al2O3]-[R2O]-[RO]-[P2O5]>0 is met. The inventors believe that in order to produce a glass containing 5-coordinate and 6-coordinate Al, it is necessary to have fewer network modifiers (NWMs) than the network former (NWF) Al2O3. In other words, the total number of NWMs of oxides such as alkali metals and alkaline earth metals must be less than that of Al2O3. That is, if the above-mentioned "[Al2O3]-[R2O]-[RO]-[P2O5]" is greater than 0, at least one of 5-coordinate and 6-coordinate aluminum atoms can be present in the glass. This value is preferably 1 or greater, more preferably 2 or greater, even more preferably 3 or greater, and most preferably 4 or greater. The "[Al2O3]-[R2O]-[RO]-[P2O5]" is preferably 12 or less, more preferably 11 or less, even more preferably 9 or less, even more preferably 8 or less, particularly preferably 7 or less, even more preferably 6 or less, and most preferably 5 or less, from the viewpoint of suppressing the rise in devitrification temperature and facilitating sheet formation.

[0065] In this glass, it is preferable that the interparticle distance of the particles present in the glass, as determined by small-angle X-ray scattering (SAXS) measurement, is 2 to 100 nm. Since general glass is uniformly amorphous, internal scattering is not observed in SAXS measurements. This glass, however, is composed such that at least one of 5-coordinate and 6-coordinate Al is present, resulting in a glass containing extremely minute scattering. Glass in which scattering is observed is known as phase-splitting glass. Phase-splitting glass is generally cloudy. On the other hand, the inventors have found that this glass, by having an extremely minute phase-splitting structure, maintains transparency and exhibits high fracture toughness (KIC) that suppresses crack propagation. In this specification, transparency means, for example, that no cloudiness is observed by visual inspection, preferably a haze value of 0.2% or less, and more preferably a haze value of 0.1% or less.

[0066] The interparticle distance calculated from small-angle X-ray scattering measurements represents the distance between particles contained in the glass. It is thought that the smaller the interparticle distance, the more particulate structures are contained in the glass, which tends to increase scattering and decrease transmittance. From the viewpoint of suppressing increased scattering and improving transmittance, an interparticle distance of 2 nm or more is preferable. The interparticle distance is more preferably 5 nm or more, even more preferably 10 nm or more, and even more preferably 15 nm or more. From the viewpoint of greatly suppressing crack elongation and improving fracture toughness, an interparticle distance of 100 nm or less is preferable. An interparticle distance of 90 nm or less is more preferable, 80 nm or less is even more preferable, 70 nm or less is even more preferable, 60 nm or less is particularly preferable, 50 nm or less is even more preferable, 40 nm or less is even more preferable, 30 nm or less is particularly preferable, and 20 nm or less is most preferable.

[0067] This glass may contain one or more oxides selected from Li2O, Na2O, K2O, and P2O5. Furthermore, this glass may contain any oxide other than SiO2, B2O3, Al2O3, Li2O, Na2O, K2O, and P2O5. x O y (X and Y are positive integers) may contain two or more types of M x O y It may contain.

[0068] M x O y Examples include MgO, CaO, SrO, Y2O3, La2O3, TiO2, ZrO2, Nb2O5, Ta2O5, and WO3.

[0069] This glass, M x O y If it contains, the content of that oxide in mole percent should be expressed as [M x O y Let r(M) be the ionic radius of M, then (2y / x) / r(M) × [M x O y When the sum of ] × 2 / x is denoted as Σ, it is preferable that Z, expressed by the following formula (1), is between 5 and 100. Z=Σ+[Al2O3]-[Li2O]-[Na2O]-[K2O]-[P2O5]...Equation (1)

[0070] The Z represented by formula (1) above contributes to determining the coordination number of Al in the glass. Based on our diligent research to date, we believe that the influence of each component on the coordination number of Al is as follows.

[0071] The more cations with small ionic radii and high valency a substance contains, the easier it is for the coordination number of Al to increase. Furthermore, Al itself is a component that increases the coordination number when present in large quantities. Conversely, components such as alkali metal oxides and P2O5 are components that easily allow Al to form a 4-coordinate state.

[0072] Since the coordination number of Al has a preferred range for balancing chemical durability and strength, it is preferable that the value of Z represented by formula (1) be within such a range. From this perspective, the value of Z represented by formula (1) is preferably 5 or more, more preferably 6 or more, even more preferably 7 or more, even more preferably 8 or more, particularly preferably 9 or more, even more particularly preferably 10 or more, especially preferably 11 or more, and most preferably 12 or more. Also for similar reasons, the value of Z is preferably 100 or less. The value of Z is more preferably 80 or less, even more preferably 60 or less, even more preferably 40 or less, and most preferably 20 or less.

[0073] In this glass, boron atoms (hereinafter sometimes referred to as B) can have 3-coordinate or 4-coordinate oxygen atoms. In typical boron-containing glass, the oxygen coordination of boron is mainly 3-coordinate. While 4-coordinate boron is thought to have the effect of increasing Young's modulus, there is a concern that if the amount of 4-coordinate boron becomes too high, the acid resistance will decrease.

[0074] When this glass contains B2O3, the ratio of four-coordinate boron atoms to the total number of boron atoms is preferably 1% or more, more preferably 2% or more, and even more preferably 3% or more, from the viewpoint of improving Young's modulus. Furthermore, from the viewpoint of suppressing a decrease in acid resistance, this ratio is preferably 10% or less, more preferably 7% or less, and even more preferably 5% or less.

[0075] The oxygen coordination number of a boron atom 11 It can be measured by 1B-NMR. Also, "the ratio of the number of 4-coordinate boron atoms to the total number of boron atoms" is 11 This is the proportion of four-coordinate boron atoms calculated from the results of B-NMR measurements. 11 Preferred conditions for B-NMR measurement will be described later in the examples.

[0076] The devitrification temperature of this glass is preferably 1500°C or lower, more preferably 1450°C or lower, even more preferably 1430°C or lower, even more preferably 1400°C or lower, particularly preferably 1350°C or lower, even more particularly preferably 1300°C or lower, especially preferably 1275°C or lower, and most preferably 1250°C. Because the devitrification temperature of this glass is low due to the adjustment of its composition to a specific range, it is relatively easy to manufacture, and specifically, mass production by methods such as the float process is possible. The devitrification temperature of this glass is usually 1250°C or higher. Furthermore, the devitrification viscosity of this glass η L (Unit: dPa·s) is its logarithm logη L It is preferable that the ratio is 2 or higher. The high devitrification viscosity makes it easier to perform molding by methods such as the float method. Furthermore, the viscosity of this glass at 1650°C is 10 2 A value of dPa·s or less is preferable.

[0077] The softening point of this glass is preferably 1000°C or lower, and more preferably 950°C or lower. This is because a lower softening point of the glass allows for lower heat treatment temperatures during bending and other processes, resulting in less energy consumption and reduced equipment load. Glass with a softening point that is too low tends to have low strength because the stress introduced during chemical strengthening is easily relaxed; therefore, a softening point of 550°C or higher is preferred. A softening point of 600°C or higher is more preferable, and even more preferably 650°C or higher. The softening point can be measured using the fiber stretching method described in JIS R3103-1:2001. The glass softening point of this glass is easily below the temperature at which the surface of carbon-type glass begins to change under atmospheric conditions, making it easy to bend and form. The bending and forming method will be described later.

[0078] The glass transition temperature (Tg) of this glass is preferably 800°C or lower, more preferably 780°C or lower, and even more preferably 750°C or lower, from the viewpoint of glass plate manufacturing. Furthermore, the glass transition temperature is preferably 500°C or higher, more preferably 600°C or higher, and even more preferably 650°C or higher.

[0079] From the viewpoint of mold wear in the 3D molding machine, the 3D moldable temperature of this glass is preferably 820°C or lower, more preferably 800°C or lower, and even more preferably 770°C or lower. The 3D moldable temperature is preferably 500°C or higher, more preferably 600°C or higher, and even more preferably 650°C or higher. The 3D moldable temperature refers to the temperature at which 3D molding can be performed while maintaining transparency, and is a value measured by the method described in the examples.

[0080] Furthermore, because the composition of this glass is adjusted to a specific range, when heated and bent on a carbon mold, carbon transfer from the carbon mold is reduced, and haze deterioration is less likely to occur. Therefore, it is also suitable for curved cover glasses and the like, as described later.

[0081] The Young's modulus of this glass is preferably 85 GPa or higher, more preferably 87 GPa or higher, even more preferably 89 GPa or higher, even more preferably 91 GPa, preferably 93 GPa or higher, and most preferably 95 GPa or higher, from the viewpoint of rigidity. Furthermore, the Young's modulus is preferably 110 GPa or lower, more preferably 105 GPa or lower, and even more preferably 102 GPa or lower.

[0082] From the viewpoint of improving strength, the Poisson's ratio of this glass is preferably 0.22 or higher, more preferably 0.23 or higher, and even more preferably 0.24 or higher. There is no upper limit to the Poisson's ratio, but for example, 0.30 or lower is preferred, 0.29 or lower is more preferred, and 0.28 or lower is even more preferred.

[0083] This glass has a high fracture toughness value and is resistant to breakage, yet it is easy to manufacture, making it useful as a structural component such as window glass. Furthermore, this glass has a large CT limit when chemically strengthened, making it excellent as a glass for chemical strengthening.

[0084] <Chemically strengthened glass> The chemically strengthened glass according to this embodiment (hereinafter also referred to as "this chemically strengthened glass") is obtained by chemically strengthening the aforementioned glass. This chemically strengthened glass has a relatively large CT limit, resulting in a compressive stress value (CS) at a depth of 50 μm from the glass surface. 50 ) can be enlarged. CS 50 The pressure is preferably 150 MPa or higher, more preferably 180 MPa or higher, and even more preferably 200 MPa or higher. 50 It is usually below 250 MPa.

[0085] In this chemically strengthened glass, the depth at which the compressive stress value becomes zero (DOL) is preferably 60 μm or more, and more preferably 75 μm or more. A DOL of 80 μm or more is even more preferable, 85 μm or more is even more preferable, 90 μm or more is particularly preferable, and 100 μm or more is most preferable. If the DOL is too large relative to the plate thickness t, it will lead to an increase in CT, so a DOL of t / 4 or less is preferable, and t / 5 or less is more preferable. Specifically, for example, if the plate thickness t is 0.6 mm, a DOL of 150 μm or less is preferable, and 120 μm or less is more preferable.

[0086] This chemically strengthened glass is designed to suppress fracture due to bending and impact, with a compressive stress value of CS. 50 The compressive stress is preferably 150 MPa or more, more preferably 180 MPa or more, and even more preferably 200 MPa or more, and the depth DOL at which the compressive stress value becomes 0 is preferably 60 μm or more, more preferably 70 μm or more, more preferably 80 μm or more, more preferably 85 μm or more, and even more preferably 90 μm or more.

[0087] The surface compressive stress value (CS0) of this chemically strengthened glass is preferably 500 MPa or higher, more preferably 550 MPa or higher, and even more preferably 600 MPa or higher. To prevent chipping during impact, the CS0 is preferably 1000 MPa or lower, and more preferably 900 MPa or lower.

[0088] The surface compressive stress value CS0 can sometimes be measured using a photoelastic surface stress meter (for example, the FSM6000 manufactured by Orihara Seisakusho Co., Ltd.). However, measurement using a surface stress meter is difficult when the Na content in the glass before chemical strengthening is low.

[0089] In such cases, measuring the bending strength can sometimes be used to estimate the magnitude of the surface compressive stress. This is because a larger surface compressive stress tends to correlate with a greater bending strength. Bending strength can be evaluated, for example, by performing a four-point bending test using a strip-shaped test specimen measuring 10 mm x 50 mm, with the external support distance of the support being 30 mm, the internal support distance being 10 mm, and the crosshead speed being 0.5 mm / min. For example, 10 test specimens may be used.

[0090] The four-point bending strength of this chemically strengthened glass is preferably 500 MPa or higher, more preferably 550 MPa or higher, and even more preferably 600 MPa or higher. The four-point bending strength of this chemically strengthened glass is generally 1000 MPa or lower, and typically 900 MPa or lower.

[0091] The internal tensile stress (CT) of this chemically strengthened glass is preferably -70 MPa or less, more preferably -75 MPa or less, and even more preferably -80 MPa or less, in order to impart sufficient compressive stress to the glass surface. From the viewpoint of preventing explosive shattering in the event of damage, the CT is preferably -120 MPa or more, more preferably -110 MPa or more, and even more preferably -100 MPa or more.

[0092] The matrix composition of this chemically strengthened glass is the same as the glass composition of the original glass described above. That is, the glass composition of this chemically strengthened glass is the same as the glass composition of the original glass described above in the central part in the thickness direction of the plate. Furthermore, except for the difference in alkali metal ion concentration due to the chemical strengthening treatment, it is basically the same as the original glass overall, so the explanation is omitted. For example, the coordination number of Al and the interparticle distance in the original glass described above are thought to remain almost unchanged even after chemical strengthening.

[0093] <Chemically strengthened glass sheet> This chemically strengthened glass may also be in sheet form. The following describes sheet-shaped chemically strengthened glass (chemically strengthened glass sheets). The thickness (t) of the chemically strengthened glass plate is preferably 2 mm or less, more preferably 1.5 mm or less, even more preferably 1 mm or less, even more preferably 0.9 mm or less, particularly preferably 0.8 mm or less, and most preferably 0.7 mm or less. Furthermore, in order to obtain sufficient strength, the plate thickness (t) is preferably 0.1 mm or more, more preferably 0.2 mm or more, even more preferably 0.4 mm or more, and even more preferably 0.5 mm or more.

[0094] This chemically strengthened glass plate may be flat. This chemically strengthened glass plate may have a curved shape, for example, a curved portion with a radius of curvature of 100 mm or less. In recent years, curved cover glass has been required to improve the operability and visibility of display components. This chemically strengthened glass is suitable for such applications.

[0095] <Methods for manufacturing glass and glass sheets> This chemically strengthened glass is obtained by chemically strengthening the glass after it has been manufactured through ion exchange treatment. This glass can be manufactured, for example, by conventional methods. For instance, the raw materials for each component of the glass are mixed and heated and melted in a glass melting furnace. Then, the glass is homogenized by known methods, formed into a desired shape such as a glass plate, and slowly cooled.

[0096] When this chemically strengthened glass is in sheet form, it is formed into a sheet using methods such as the float method, press method, or downdraw method. Subsequently, the molded glass is ground and polished as needed to form a glass plate. When cutting the glass plate to a predetermined shape and size, or when chamfering the glass plate, it is preferable to perform the cutting or chamfering before applying the chemical strengthening treatment described later, because this will allow a compressive stress layer to be formed on the edge surface during the subsequent chemical strengthening treatment.

[0097] If the chemically strengthened glass sheet has a curved shape, it is preferable to manufacture a flat glass sheet, then bend and shape it before chemically strengthening it. The bending forming method can include self-weight forming, vacuum forming, press forming, etc. Furthermore, two or more bending forming methods may be used in combination.

[0098] Self-gravity molding is a method in which a glass plate is placed on a mold, then heated to soften it, and then molded by gravity. Vacuum forming is a method of bending a glass plate by placing it on a mold, sealing the edges of the glass plate, and then reducing the pressure in the space between the mold and the glass plate. In this case, the upper surface of the glass plate may also be pressurized. The press forming method involves placing a glass plate between the upper and lower dies of a mold, heating the glass plate, and applying a press load between the upper and lower dies to bend and form a predetermined shape. In all cases, carbon fiber molds are widely used as molding dies.

[0099] Chemical strengthening is carried out through ion exchange treatment. Chemical strengthening (ion exchange treatment) can be performed, for example, by immersing a glass plate in a molten salt such as potassium nitrate heated to 360-600°C for 0.1-500 hours. Preferably, the heating temperature of the molten salt is 375-500°C, and the immersion time of the glass plate in the molten salt is 0.3-200 hours.

[0100] Examples of molten salts used for chemical strengthening treatment include nitrates, sulfates, carbonates, and chlorides. Examples of nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, and silver nitrate. Examples of sulfates include lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, and silver sulfate. Examples of carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of chlorides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, and silver chloride. These molten salts may be used individually or in combination.

[0101] In the present invention, the processing conditions for the chemical strengthening treatment are not particularly limited, and appropriate conditions can be selected considering the composition (properties) of the glass, the type of molten salt, and the desired chemical strengthening properties.

[0102] Furthermore, in this invention, chemical strengthening treatment may be performed only once, or multiple chemical strengthening treatments (multi-stage strengthening) may be performed under two or more different conditions. For example, as the first stage of chemical strengthening treatment, chemical strengthening treatment may be performed under conditions in which DOL is large and CS is relatively small, and then as the second stage of chemical strengthening treatment, chemical strengthening treatment may be performed under conditions in which DOL is relatively small and CS is large. In this case, the CS of the outermost surface of the chemically strengthened glass can be increased while suppressing the internal tensile stress area (St), and as a result, the absolute value of the internal tensile stress (CT) can be suppressed.

[0103] <Electronic equipment> This chemically strengthened glass sheet is particularly useful as cover glass for mobile electronic devices such as mobile phones, smartphones, personal digital assistants (PDAs), and tablet devices. Furthermore, it is also useful as cover glass for electronic devices not intended for portability, such as televisions (TVs), personal computers (PCs), and touch panels. In addition, it is useful as building materials such as window glass, tabletops, and as cover glass for interiors of automobiles and airplanes.

[0104] Figure 3 shows an example of an electronic device that includes this chemically strengthened glass plate. The portable terminal 10 shown in Figure 3 has a cover glass 20 and a housing 30. The housing 30 has a side surface 31 and a bottom surface 32. This chemically strengthened glass plate is used for both the cover glass 20 and the housing 30. [Examples]

[0105] The present invention will be described below using examples, but the present invention is not limited thereto. Examples 1 to 44 are examples, and Examples 45 to 48 are comparative examples. In the table, blank spaces indicate that the measurement was not taken.

[0106] (Glassmaking) Glass (glass plates) Examples 1 to 48 were produced by mixing, melting, and polishing the glass raw materials to achieve the glass composition shown in Tables 2 to 5, expressed in molar percentages based on oxides. As glass raw materials, common glass raw materials such as oxides, hydroxides, and carbonates were appropriately selected and weighed to obtain 900g of glass. The mixed glass raw materials were placed in a platinum crucible, melted at 1700°C, and degassed. The resulting glass was poured onto a carbon board to obtain a glass block, which was then polished to obtain a plate-like glass with a thickness of 0.7 mm. All of the glasses from Examples 1 to 48 were visually inspected to show no cloudiness and were transparent.

[0107] (Fracture toughness value) Fracture toughness was measured using the DC-DC method on 6.5 mm × 6.5 mm × 65 mm samples of each type of glass. A 2 mm diameter through-hole was drilled into the 65 mm × 6.5 mm surface of the sample for evaluation.

[0108] (Young's modulus, Poisson's ratio) Young's modulus and Poisson's ratio were measured using ultrasound.

[0109] (Glass transition temperature (Tg)) A portion of the obtained glass was crushed in an agate mortar, and the glass transition temperature was measured using a differential scanning calorimeter (Bruker DSC3300SA). The sample amount used for DSC measurement was approximately 60 mg, and measurements were taken from room temperature to 1100°C at a heating rate of 10°C / min.

[0110] (CT limit) The CT limit was evaluated using the method described above.

[0111] (3D molding temperature) A 120mm x 60mm x 0.7mm thick glass plate was placed between the upper and lower molds of a carbon mold, and the entire structure was placed in a heating furnace and heated to a predetermined temperature between 500°C and 800°C. Next, a pressing load of 0.5 MPa was applied between the upper and lower molds and held for 90 seconds to form the mold. The shape was then measured visually or with a contact-type shape measuring device to determine whether the desired shape had been obtained (forming test). In addition, the presence or absence of devitrification was determined by observation with a polarizing microscope. The minimum temperature at which the desired shape can be obtained without devitrification was defined as the moldable temperature.

[0112] (Haze value) The haze value [unit: %] was measured using a haze meter (manufactured by Suga Test Instruments Co., Ltd.; HZ-V3) in accordance with JIS K7136:2000, with a halogen lamp C light source. Note that while the haze value was measured only for the glass in Example 2, the glass in the other examples showed similar values.

[0113] (light transmittance) Light transmittance was measured using a Hitachi UH410 spectrophotometer, with the average transmittance measured for light with wavelengths of 380 to 780 nm. Although the light transmittance was measured only for the glass in Example 2, the glass in the other examples showed similar values.

[0114] (Difference in haze before and after molding) The haze value was measured before and after the molding test described above. The haze value was measured using a haze meter (HZ-V3, manufactured by Suga Test Instruments Co., Ltd.) under a halogen lamp C light source in accordance with JIS K7136:2000. If the glass plate and carbon mold adhere during molding, the haze value of the glass plate may increase. The difference in haze value before and after molding (haze value after molding (%) - haze value before molding (%)) is shown in Tables 2-5 as "Haze degradation due to carbon (%)".

[0115] (devitrification temperature) A portion of the glass was crushed, and the glass particles were placed in a platinum dish and heat-treated for 17 hours in an electric furnace controlled to a constant temperature within the range of 1000°C to 1700°C. The devitrification temperature was estimated by observing the glass after heat treatment with a polarizing microscope to check for devitrification. Evaluations were performed at 10°C intervals around the devitrification temperature, and the highest temperature at which devitrification was observed was recorded as the devitrification temperature.

[0116] (devitrification viscosity) Devitrification viscosity was measured using a rotary high-temperature viscometer, while cooling from 1700°C to 1000°C (or until viscosity began to increase rapidly due to devitrification) at a rate of 10°C / min. The viscosity value at the devitrification temperature was defined as the devitrification viscosity logη.

[0117] (Interparticle distance) The interparticle distances in the glass were analyzed using small-angle X-ray scattering (SAXS). The measurement conditions are shown below. Equipment: Synchrotron radiation, beamline "BL8S3", small-angle X-ray scattering Location of the device: Aichi Synchrotron Radiation Center, Science and Technology Exchange Foundation, located within "Knowledge Hub Aichi," 250-3 Minami-Yamaguchi-cho, Seto City, Aichi Prefecture Energy (wavelength): 0.92Å Measurement detector: PILATUS Measurement time: 480sec Measurement camera length: 2180.9 mm An example of the results obtained from the above measurements is shown in Figure 5. From the obtained results, the interparticle distance I was calculated using the following formula. I = 2π / Qmax Qmax is the value of Q (scattering vector) corresponding to the peak in intensity of the SAXS data with a clear peak in Figure 5. A clear peak means, for example, when the peak intensity is 5 times or more compared to the baseline.

[0118] (Coordination number of Al) The coordination number of aluminum atoms in glass 27 Analysis was performed using Al-NMR. 27 The Al-NMR measurement conditions are shown below. Measurement equipment: JEOL Ltd. ECZ900 nuclear magnetic resonance spectrometer Resonance frequency: 900MHz Rotation speed: 20kHz Probe: 3.2mm for solids Flip angle: 30° Pulse repetition waiting time: 1.5 seconds Measurements were performed using the Single Pulse method with the aforementioned apparatus and conditions. α-Al2O3 was used as the secondary reference for the chemical shift, set to 16.6 ppm. The measurement results were then phase-corrected and baseline-corrected using the Delta NMR software from JEOL Ltd., followed by fitting using a Gaussian function to calculate the proportions of Al in 4-coordinate, 5-coordinate, and 6-coordinate states. While phase and baseline corrections are highly arbitrary, they were appropriately handled by subtracting the spectrum of an empty cell without the sample. Peak fitting is also highly arbitrary, but good fitting was obtained by setting the peak tops within the following ranges: 80 to 45 ppm for 4-coordinate, 45 to 15 ppm for 5-coordinate, and 15 to 5 ppm for 6-coordinate, and appropriately setting the peak widths (ensuring a maximum ratio of 1.5 times or less between each coordination number). 27 To quantitatively evaluate the coordination number of Al using Al MAS NMR spectroscopy, it is important to perform measurements in a high magnetic field (22.3 T or higher).

[0119] Here, in Figure 4 27 An example of Al-NMR measurement results is shown. Figure 4(a) shows the glass from Example 2. 27 This figure shows the Al-NMR spectrum, and Figure 4(b) shows the glass of Example 48. 27 This figure shows the Al-NMR spectrum. In Figure 4(a), peak a is assigned to 4-coordinate Al, peak b to 5-coordinate Al, and peak c to 6-coordinate Al. On the other hand, in Figure 4(b), peak a', which is assigned to 4-coordinate Al, was observed, but peaks assigned to 5-coordinate Al and 6-coordinate Al were not observed.

[0120] (Coordination number of B) The proportion of the coordination number of B atoms in the glass was measured using the ECAII-700, manufactured by JEOL Ltd. and owned by the RIKEN (National Research Institute). 11 (B-NMR measurement). The magnetic field strength of the ECAII-700 was 21.2T (proton resonance frequency of 700MHz), and a 3.2mm solid-state probe was used with a rotation speed of 15kHz. B2O3 was measured as a standard sample and used as a secondary reference for chemical shifts. All measurements were performed using the Single Pulse method. Measurement equipment: Nuclear magnetic resonance spectrometer ECAII-700 manufactured by JEOL Ltd. Resonance frequency: 700MHz Rotation speed: 15kHz Probe: 3.2mm for solids Flip angle: 90° Pulse repetition waiting time: 20 seconds The measurement results were subjected to phase correction and baseline correction using the NMR software Delta from JEOL Ltd., followed by fitting using a Gaussian function to calculate the proportions of 3-coordinate and 4-coordinate B atoms.

[0121] [Table 2]

[0122] [Table 3]

[0123] [Table 4]

[0124] [Table 5]

[0125] (Chemical strengthening treatment) Chemically strengthened glass plates with a thickness of 700 μm, consisting of the glass examples 1, 2, 45, and 46 shown in Tables 2 and 5, were obtained as chemically strengthened glass examples 51-54. Chemical strengthening was performed by ion exchange under the first conditions (strengthening salt, temperature, and processing time) shown in Table 6, followed by ion exchange under the second conditions also shown in Table 6. The obtained chemically strengthened glass examples 51-54 were processed into 0.3 mm × 20 mm pieces, and the stress profiles were measured using a birefringence stress meter (CRi's Abrio-IM birefringence imaging system). As an example, Figure 2 shows the stress profile of the chemically strengthened glass example 2. Furthermore, the number of fragments was measured for the chemically strengthened glass examples 51-54 using the method described above in the section on CT limit measurement method.

[0126] [Table 6]

[0127] The chemically strengthened glasses of Examples 51 and 52 (the glasses of Examples 1 and 2) not only had high surface compressive stress due to chemical strengthening, but also exhibited higher compressive stress at a depth of 50 μm compared to the comparative examples. Such chemically strengthened glasses are not only less prone to bending fracture, but also less prone to fracture due to impact. The chemically strengthened glass in Example 54 (the glass in Example 46), which has an excessively high Al2O3 content, is difficult to manufacture because it has a high devitrification temperature. Furthermore, the glass in Example 46 shows an increase in haze value after molding tests and has poor 3D moldability. In addition, the glass in Example 46 did not show a significant increase in DOL even after prolonged chemical strengthening treatment (Example 54). The conventional chemically strengthened glass, Example 53 (the glass in Example 45), has a relatively small CT limit. Therefore, increasing the surface compressive stress is expected to either decrease the compressive stress value at a depth of 50 μm or increase the number of fractures.

[0128] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2020-080385 filed on 30 April 2020, the contents of which are incorporated herein by reference. [Explanation of symbols]

[0129] 10 Mobile devices 20 Cover glass 30 cabinets 31 Side view 32 Bottom

Claims

1. Chemically strengthened glass, where the base composition is expressed as a mole percentage based on oxides, SiO ２ 45-65% Al ２ O ３ を18~30%、 Li ２ Oを7~15%、 Na ２ Oを0.2~4.3%、 Y ２ O ３ and La ２ O ３ One or more selected from the above in total 0 to 8%, P ２ O ５ 0-10%, B ２ O ３ 0-10% ZrO ２ 0-4%, ZnO at 3% or less, MgO content of 5% or less SiO ２ and Al ２ O ３ One or more of these will be selected in total from 66-79.5%, and TiO ２ It contains 3% or less of the following: Al expressed as a mole percentage based on oxides ２ O ３ The content of [Al ２ O ３ ], P ２ O ５ The content of [P ２ O ５ ], the total content of alkali metal oxides is [R ２ [O], with [RO] representing the total content of alkaline earth metal oxides, [Al ２ O ３ ]-[R ２ O]-[RO]-[P ２ O ５ ] > 0, Compressive stress value (CS) at a depth of 50 μm from the glass surface ５０ Chemically strengthened glass with a pressure of 180 MPa or higher.

2. The chemically strengthened glass according to claim 1, wherein the interparticle distance of particles present in the glass, as determined by small-angle X-ray scattering (SAXS) measurement, is 2 to 100 nm.

3. The chemically strengthened glass according to claim 1 or 2, wherein the depth at which the compressive stress value becomes zero (DOL) is 60 to 120 μm.

4. Surface compressive stress value (CS ０ A chemically strengthened glass according to any one of claims 1 to 3, wherein the pressure is 600 to 900 MPa.

5. A chemically strengthened glass according to any one of claims 1 to 4, wherein the internal tensile stress value (CT) is -70 MPa to -120 MPa.

6. The aforementioned compressive stress value (CS) ５０ A chemically strengthened glass according to any one of claims 1 to 5, wherein the compressive stress is 180 MPa or more, and the depth (DOL) at which the compressive stress value becomes 0 is 80 μm or more.

7. A chemically strengthened glass according to any one of claims 1 to 6, wherein the glass is in the form of a plate with a thickness of 2 mm or less.

8. The chemically strengthened glass according to claim 7, having a curved surface portion with a radius of curvature of 100 mm or less.

9. An electronic device comprising the chemically strengthened glass according to claim 7 or 8.

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