Chemically strengthened glass, cover glass, display, and solar cell module

Abstract

Provided is a chemically strengthened glass which has high crack strength.　This chemically strengthened glass has a plate thickness of 0.6 mm or less, a compressive stress of the outermost surface of 600 MPa or more, a compressive stress layer depth of 10-175 μm, and a value of X that is represented by formula (1) of 0 or more.　Formula (1): X = 2.05 × Em 0.5 + CS120 In formula (1), Em represents the Young's modulus at the in-plane central position of the chemically strengthened glass, and the unit of Em is GPa.　In formula (1), CS120 represents the value of the compressive stress at the depth of 120 μm, and the unit of CS120 is MPa.

Description

Chemically strengthened glass, cover glass, displays and solar cell modules

[0001] The present invention relates to chemically strengthened glass. The present invention also relates to a cover glass including the chemically strengthened glass. The present invention also relates to a display and a solar cell module including the cover glass.

[0002] In recent years, cover glass has been used for the purpose of protecting and enhancing the aesthetic appearance of display devices such as mobile phones, smartphones, and tablet terminals. Cover glass for these applications is required to have excellent strength to prevent breakage due to impact, etc. Furthermore, such cover glass is sometimes used to protect solar cell modules, etc.

[0003] Conventionally, a method for increasing the surface strength of glass by chemically strengthening the glass by immersing the glass in a potassium nitrate molten salt or the like has been known. For example, Patent Document 1 discloses that the surface strength of a glass plate is improved by chemically strengthening the glass by immersing the glass in a potassium nitrate molten salt. More specifically, it discloses that the strength of a glass plate is improved by chemically strengthening a Li-containing glass with a Na-containing molten salt and a K-containing molten salt in that order. It also discloses that the mechanism for strengthening the strength of a glass plate by such chemical treatment is due to compressive stress generated by alkali metal exchange.

[0004] International Publication No. 2022 / 004808

[0005] In recent years, there has been a demand for thinner cover glasses in order to reduce weight and improve visibility and transmittance, etc. The present inventors have studied chemically strengthened glass with a thinner plate thickness (for example, 0.6 mm or less) and found that the crack strength may be reduced, and therefore there has been a demand for increased crack strength.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide chemically strengthened glass with high fracture resistance. Another object of the present invention is to provide a cover glass. Another object of the present invention is to provide a display and a solar cell module.

[0007] As a result of extensive research into the above-mentioned problems, the inventors discovered that the crack resistance can be increased by adjusting parameters related to the compressive stress on the outermost surface, the depth of the compressive stress layer, Young's modulus, and the magnitude of the compressive stress at a predetermined depth, and thus arrived at the present invention.

[0008] That is, the present inventors have found that the above-mentioned problems can be solved by the following configuration: [1] Chemically strengthened glass having a plate thickness of 0.6 mm or less, a compressive stress of 600 MPa or more on the outermost surface, a compressive stress layer depth of 10 to 175 μm, and a value of X represented by the following formula (1) of 0 or more. Formula (1) X = 2.05 × E ｍ ０．５ +CS １２０ In formula (1), E ｍ is the Young's modulus at the in-plane center position of the chemically strengthened glass, and E ｍ The unit is GPa. In formula (1), CS １２０ is the value of compressive stress at a depth of 120 μm, and CS １２０ The unit of is MPa. [2] The chemically strengthened glass according to [1], wherein the Young's modulus at the in-plane central position of the chemically strengthened glass is 80 GPa or more. [3] The chemically strengthened glass according to [1], wherein the Young's modulus at the in-plane central position K ＩＣ However, 0.80 MPa m １／２ [4] The chemically strengthened glass according to any one of [1] to [3], wherein the glass does not break when the abrasive surface of #80 sandpaper, the abrasive of which is silicon carbide, is brought into contact with one side of the chemically strengthened glass and an impact of 0.003 J is applied from the side opposite the abrasive surface of the sandpaper. [5] The chemically strengthened glass according to any one of [1] to [3], wherein the composition at the center of the plate thickness, expressed in mole percentage on an oxide basis, is: SiO ２ 60 to 70% Al ２ O ３ 10 to 20% Li２ O 3-12% Na ２ O 1-5% K ２ O 0-3% MgO 0-10% CaO 0-10% SrO 0-5% ZnO 0-5% TiO ２ 0 to 3% ZrO ２ 0 to 3% SnO ２ 0 to 1% P ２ O ５ 0 to 1% B ２ O ３ 0 to 10% Y ２ O ３ Contains 0 to 3% of Li ２ O content, Na ２ The content of O and K ２ The total content of O, R, is 5 to 20%, and the ratio of Li to R is ２ The ratio of the content of O to the content of R is 0.5 to 0.8, ２ The ratio of the content of O and the content of Na relative to the above R ２ The ratio of the content of O and the content of K to the above R ２ [6] The chemically strengthened glass according to any one of [1] to [4], wherein the value of the product of the ratio of the content of SiO and the content of O is 0.003 to 0.03. [7] The chemically strengthened glass according to [5], wherein the Young's modulus at the center of the thickness of the glass is 85 GPa or more. [8] The composition at the center of the thickness of the glass, expressed in mole percentage on an oxide basis, is: SiO ２ 55 to 75% Al ２ O ３ 3 to 18% Li ２ O 17-30% Na ２ O 0-3% K ２ O 0-1% MgO 0-10% CaO 0-10% SrO 0-5% ZnO 0-5% TiO ２ 0 to 3% ZrO ２ 0 to 3% SnO ２ 0 to 1% P ２ O ５ 0 to 3% B ２ O ３ 0 to 10% Y ２ O ３ Contains 0 to 3% of Li２ O content, Na ２ The content of O and K ２ The total content of O, R, is 8 to 35%, and the ratio of Li to R is ２ The content of O is 0.85 to 0.99, and the ratio of Li to the R is ２ The content of O and the Na relative to the above R ２ The content of O and the ratio of K to the above R ２

[10] A chemically strengthened glass according to any one of [1] to [4], wherein the product of the content of 100% by the content of O is 0 to 0.003.

[11] The chemically strengthened glass according to [7], wherein the Young's modulus at the center of the plate thickness is 90 GPa or more.

[12] A cover glass comprising the chemically strengthened glass according to any one of [1] to [8].

[13] A display comprising the cover glass according to

[10] .

[14] A solar cell module comprising the cover glass according to

[10] .

[0009] According to the present invention, chemically strengthened glass having high fracture resistance can be provided. The present invention also provides a cover glass. The present invention also provides a display and a solar cell module.

[0010] 1 is a diagram showing a method for calculating various characteristic temperatures from a DSC curve of glass. ＩＣ 1 is an explanatory diagram of a sample used to measure fracture toughness value K by the DCDC method. ＩＣ The stress intensity factor K1 (unit: MPa m １／２ 1 is a diagram showing a K1-v curve showing the relationship between the crack propagation velocity v (unit: m / s) and the impact energy in the impact resistance test. FIG. 2 is a diagram showing a K1-v curve showing the relationship between the impact energy in the impact resistance test and the crack propagation velocity v (unit: m / s). FIG. 3 is a diagram showing a schematic diagram of a test device used in one embodiment of the impact resistance test and the impact resistance step in the impact resistance test. FIG. 4 is a plot showing the relationship between the impact energy in the impact resistance test and the maximum crack depth.

[0011] The chemically strengthened glass of the present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be arbitrarily modified and implemented within the scope of the present invention.

[0012] In this specification, "chemically strengthened glass" refers to glass after chemical strengthening treatment, and "glass for chemical strengthening" refers to glass before chemical strengthening treatment.

[0013] In this specification, the glass composition of chemically strengthened glass is sometimes referred to as the mother glass composition of chemically strengthened glass. In chemically strengthened glass, a compressive stress layer due to ion exchange is usually formed on the surface of the glass, so the glass composition of the non-ion-exchanged portion is identical to the mother glass composition of chemically strengthened glass. In this specification, the glass composition is expressed in mole percentage based on oxides, and mole percent is sometimes simply referred to as %. Furthermore, the symbol "to" indicating a numerical range is used to mean that the values ​​before and after it are included as the lower and upper limits.

[0014] In the glass composition, "substantially not containing" means that the glass does not contain any components except for unavoidable impurities contained in raw materials, etc., that is, the glass is not intentionally contained. Specifically, the content of components other than those described as the glass composition is preferably less than 0.1 mol%, more preferably 0.08 mol% or less, and even more preferably 0.05 mol% or less.

[0015] In this specification, the term "stress profile" refers to a pattern that expresses compressive stress values ​​with the depth from the glass surface as a variable. A negative compressive stress value indicates tensile stress. In this specification, the "stress profile" can be measured using a method that combines an optical waveguide surface stress meter and a scattered light photoelastic stress meter.

[0016] Optical waveguide surface stress meters can accurately measure the stress of glass in a short time. One example of an optical waveguide surface stress meter is the FSM-6000 manufactured by Orihara Seisakusho. However, in principle, optical waveguide surface stress meters can only measure stress when the refractive index decreases from the surface to the interior of the sample. In chemically strengthened glass, the layer obtained by replacing sodium ions inside the glass with external potassium ions has a refractive index that decreases from the surface to the interior of the sample, so stress can be measured with an optical waveguide surface stress meter. However, the stress of the layer obtained by replacing lithium ions inside the glass with external sodium ions cannot be accurately measured with an optical waveguide surface stress meter.

[0017] The method using a scattered light photoelastic stress meter can measure stress regardless of the refractive index distribution. An example of a scattered light photoelastic stress meter is the SLP1000 manufactured by Orihara Seisakusho Co., Ltd. However, scattered light photoelastic stress meters are susceptible to surface scattering and may not be able to accurately measure stress near the surface. For the above reasons, accurate stress measurement is possible by combining two types of measuring devices: an optical waveguide surface stress meter and a scattered light photoelastic stress meter.

[0018] In this specification, the compressive stress layer depth is the depth at which the compressive stress value becomes zero.

[0019] In this specification, "fracture toughness value K ＩＣ " is measured with reference to the DCDC method [Reference: M. Y. He, M. R. Turner and A. G. Evans, Acta Metall. Mater. 43 (1995) 3453.]. Specifically, using a sample having the shape shown in FIG. 2 and a SHIMADZU Autograph AGS-X5KN, the stress intensity factor K1 (unit: MPa m) as shown in FIG. 3 is measured. １／２ The K1-v curve, which shows the relationship between the stress intensity factor K1 at 0.1 m / s and the crack propagation velocity v (unit: m / s), was measured, and the obtained Region III data was regressed and extrapolated using a linear equation to determine the fracture toughness value K1. ＩＣ Let's say.

[0020] <Chemically Tempered Glass> The chemically tempered glass of the present invention has a thickness of 0.6 mm or less, a compressive stress at the outermost surface of 600 MPa or more, a compressive stress layer depth of 10 to 175 μm, and the value of X represented by formula (1) described below is 0 or greater. The mechanism by which the chemically tempered glass of the present invention, which satisfies the above requirements, exhibits increased fracture strength is not entirely clear, but the inventors speculate as follows. Because the chemically tempered glass of the present invention has the predetermined compressive stress at the outermost surface and compressive stress layer depth described above, the surface is less susceptible to scratches. Furthermore, in the chemically tempered glass of the present invention, the value of X represented by formula (1) above is 0 or greater. As can be seen from formula (1) described below, the value of X is a parameter related to the Young's modulus at the in-plane center position and the value of compressive stress at a depth of 120 μm. Consider the case where a scratch is made deep into the chemically tempered glass (e.g., a depth of 120 μm or greater). In this case, the glass having the composition at that depth is subjected to stress at that depth. At this time, depending on the balance between the stress at that depth and the Young's modulus, it is thought that the crack will spontaneously progress and the chemically strengthened glass will break. After extensive research, the present inventors have found that there is a high correlation between the value of X and the crack strength, and that adjusting the value of X to a predetermined value or more increases the crack strength.

[0021] Hereinafter, the conditions satisfied by the chemically strengthened glass of the present invention will be described.

[0022] [Thickness] The thickness of the chemically strengthened glass of the present invention is 0.6 mm or less. The lower limit of the thickness of the chemically strengthened glass of the present invention is often 0.1 mm or more, preferably 0.2 mm or more, more preferably 0.3 mm or more, and even more preferably 0.4 mm or more.

[0023] [Compressive stress] The compressive stress (CS) of the outermost surface of the chemically strengthened glass of the present invention ０ ) is 600 MPa or more. That is, the chemically strengthened glass of the present invention has a compressive stress layer on the surface layer. ０ The CS of the chemically strengthened glass of the present invention is preferably 700 MPa or more, and more preferably 750 MPa or more. ０The upper limit of the CS of the chemically strengthened glass of the present invention is preferably 1500 MPa or less, and more preferably 1200 MPa or less, from the viewpoint of making it easier to adjust the value of X described later within a predetermined range. ０ is measured by the optical waveguide surface stress meter described above.

[0024] The compressive stress (CS) at a depth of 30 μm of the chemically strengthened glass of the present invention ３０ ) is preferably −20 MPa or more, more preferably 50 MPa or more, and even more preferably 100 MPa or more, in that when another object collides with the chemically strengthened glass of the present invention, cracks are less likely to occur even with a larger impact. ３０ is often 500 MPa or less, and is preferably 300 MPa or less, more preferably 200 MPa or less, in that the value of X represented by formula (1) described later can be easily adjusted to a predetermined range.

[0025] The compressive stress (CS) at a depth of 50 μm of the chemically strengthened glass of the present invention ５０ ) is preferably −20 MPa or more, more preferably 50 MPa or more, and even more preferably 100 MPa or more, in that when another object collides with the chemically strengthened glass of the present invention, cracks are less likely to occur even with a larger impact. ５０ is often 300 MPa or less, and is preferably 200 MPa or less, more preferably 170 MPa or less, in that the value of X represented by formula (1) described later can be easily adjusted to a predetermined range.

[0026] The compressive stress (CS) at a depth of 90 μm of the chemically strengthened glass of the present invention ９０ ) is preferably −20 MPa or more, more preferably 10 MPa or more, and even more preferably 20 MPa or more, in that when another object collides with the chemically strengthened glass of the present invention, cracks are less likely to occur even with a larger impact. ９０ is often 200 MPa or less, and is preferably 100 MPa or less, more preferably 60 MPa or less, in that the value of X represented by formula (1) described later can be easily adjusted to a predetermined range.

[0027] The compressive stress at each depth can be calculated from the stress profile obtained by the above-mentioned method.

[0028] The above compressive stresses can be adjusted, for example, by the conditions of the chemical strengthening treatment described below.

[0029] [Compressive stress layer depth] The compressive stress layer depth of the chemically strengthened glass of the present invention is 10 to 175 μm. The compressive stress layer depth is preferably 150 μm or less, more preferably 120 μm or less, in order to increase the crack strength. The compressive stress layer depth is preferably 20 μm or more, more preferably 50 μm or more, and more preferably 70 μm or more, in order to make the chemically strengthened glass of the present invention less susceptible to cracking even with a larger impact when another object collides with it. The compressive stress layer depth can be adjusted, for example, by the conditions of the chemical strengthening treatment described below.

[0030] [Tensile stress] As described above, the chemically strengthened glass of the present invention has a compressive stress layer on the surface, and therefore a tensile stress that balances the compressive stress acts inside the chemically strengthened glass. The maximum value of the tensile stress (CT Ｍａｘ ) is preferably 200 MPa or less, more preferably 150 MPa or less, and even more preferably 130 MPa or less, in that fragments are less likely to scatter when the glass is broken. Ｍａｘ The lower limit of CT is not particularly limited, but is often 10 MPa or more. Ｍａｘ is determined from the stress profile and usually acts at the mid-thickness position.

[0031] The average value of the tensile stress of the chemically strengthened glass of the present invention (CT ａｖｅ ) is preferably 200 MPa or less, more preferably 150 MPa or less, and even more preferably 100 MPa or less, in that fragments are less likely to scatter when the glass is broken. ａｖｅ The lower limit of the stress profile is not particularly limited, but is often 10 MPa or more. The average value of the tensile stress is calculated by dividing the integral value of the tensile stress in the thickness direction in the depth region showing the tensile stress in the stress profile by the length of the tensile stress portion.

[0032] The integrated tensile stress (ICT) of the chemically strengthened glass of the present invention is often 50,000 Pa m or less, preferably 40,000 Pa m or less, and more preferably 30,000 Pa m or less. The lower limit of ICT is not particularly limited, but is often 10,000 Pa m or more. ICT is obtained by integrating the tensile stress in the depth region showing the tensile stress from the stress profile.

[0033] [Formula (1)] In the chemically strengthened glass of the present invention, the value of X represented by the following formula (1) is 0 or more. Formula (1) X = 2.05 × E ｍ ０．５ +CS １２０ In formula (1), E ｍ is the Young's modulus at the in-plane center position of the chemically strengthened glass, and E ｍ The unit is GPa. ｍ ０．５ " is E ｍ In formula (1), CS represents the 0.5th power (square root) of １２０ is the value of compressive stress at a depth of 120 μm, and CS １２０ The unit is MPa. When the compressive stress at a depth of 120 μm is a negative value (tensile stress), the negative value is used for the calculation. In the chemically strengthened glass of the present invention, the value of X is 0 or more, and is preferably 0.2 or more, more preferably 0.3 or more, in that the crack strength is greater. The value of X may be 1.0 or more, 2.0 or more, or 4.0 or more. The upper limit of the value of X is not particularly limited, but is often 50 or less, preferably 30 or less, and preferably 20 or less.

[0034] CS in the above formula (1) １２０ is not particularly limited as long as the value of X falls within a predetermined range, but is preferably −50 MPa or more, more preferably −30 MPa or more, and even more preferably −20 MPa or more. １２０ The upper limit of CS in the above formula (1) is not particularly limited, but may be, for example, 50 MPa or less, preferably 30 MPa or less, and more preferably 20 MPa or less. １２０ can be adjusted, for example, by the conditions of the chemical strengthening treatment described later.

[0035] [Young's modulus] The Young's modulus (E ｍ ) is preferably 80 GPa or more. The Young's modulus is more preferably 83 GPa or more, even more preferably 85 GPa or more, and particularly preferably 90 GPa or more. The Young's modulus at the in-plane central position of chemically strengthened glass refers to the Young's modulus measured at the central position in the in-plane direction of the plate-shaped chemically strengthened glass. The central position in the in-plane direction is the position of the center of gravity in the in-plane direction, and in the case of a square chemically strengthened glass, the central position is the position of the intersection of the diagonal lines. The Young's modulus can be adjusted by the composition (mother glass composition) of the glass used in the chemically strengthened glass (chemically strengthened glass), as well as by heat treatment conditions such as the heat treatment temperature, heat treatment time, cooling rate, and temperature profile of the chemically strengthened glass. For example, if the mother glass composition is a composition that can be turned into crystallized glass, the Young's modulus value is likely to change depending on the heat treatment conditions. In addition, in the chemically strengthened glass of the present invention, the Young's modulus at the center position of the sheet thickness is preferably 80 GPa or more, more preferably 83 GPa or more, even more preferably 85 GPa or more, and particularly preferably 90 GPa or more. The Young's modulus of the glass for chemical strengthening corresponds to the Young's modulus at the center position of the sheet thickness of the chemically strengthened glass. In this specification, the Young's modulus at the in-plane center position of the chemically strengthened glass and the Young's modulus at the center position of the sheet thickness are measured by an ultrasonic pulse method. A detailed measurement method for the Young's modulus follows the method shown in the examples below.

[0036] [Fracture toughness value] The fracture toughness value (K ＩＣ ) has a higher fracture strength, and is 0.75 MPa m １／２ More preferably, 0.80 MPa m １／２ More preferably, 0.85 MPa m １／２ The above is more preferable. ＩＣ is 2.00 MPa m １／２ In most cases, it is 1.80 MPa m １／２The following is preferable. The method for measuring the fracture toughness value at the center position of the sheet thickness of the chemically strengthened glass of the present invention follows the method for measuring the fracture toughness value in the examples described later. The fracture toughness rate of the glass for chemical strengthening corresponds to the fracture toughness value at the center position of the sheet thickness of the chemically strengthened glass. K ＩＣ can be adjusted in the same manner as the Young's modulus.

[0037] [Impact Resistance Test] The chemically strengthened glass of the present invention preferably does not break when subjected to the following impact resistance test. Specifically, the impact resistance test involves contacting one side of the chemically strengthened glass with the abrasive surface of #80 sandpaper, which uses silicon carbide as an abrasive, and applying an impact with an energy of 0.03 J from the side opposite the abrasive surface of the sandpaper to confirm whether or not breakage occurs. For more specific methods, see the methods in the Examples below.

[0038] [Composition] The chemically strengthened glass of the present invention is obtained by chemically strengthening a plate glass (glass for chemical strengthening) before chemical strengthening. A preferred composition of the glass for chemical strengthening (mother glass composition) will be described below. The mother glass composition coincides with the composition at the center of the plate thickness of the chemically strengthened glass. Hereinafter, a first embodiment and a second embodiment will be described as preferred mother glass compositions.

[0039] (First embodiment) The first embodiment of the mother glass composition is expressed in mole percentage based on oxides, and is: SiO ２ 60 to 72% Al ２ O ３ 10 to 20% Li ２ O 3-12% Na ２ O 0.5 to 5% K ２ O 0-3% MgO 0-10% CaO 0-10% SrO 0-5% ZnO 0-5% TiO ２ 0 to 3% ZrO ２ 0 to 3% SnO ２ 0 to 1% P ２ O ５ 0 to 1% B ２ O ３ 0 to 10% Y ２ O ３Contains 0 to 3% of Li ２ O content, Na ２ The content of O and K ２ The total content of O, R, is 5 to 20%, and the ratio of Li to R is ２ The content of O is 0.5 to 0.95, and the ratio of Li to R is ２ O content and Na relative to R ２ O content and K relative to R ２ The product of the content of SiO and the content of O is 0.001 to 0.03. Each component contained in the mother glass composition will be explained below. ２ The content expressed as mole percentage based on oxides is expressed as "[SiO ２ ]" may be written as follows.

[0040] SiO ２ is a component that forms the glass network. It also increases chemical durability and reduces the occurrence of cracks when the glass surface is scratched.

[0041] SiO ２ In order to improve chemical durability, the content of SiO is more preferably 60.0% or more, even more preferably 62.0% or more, particularly preferably 64.0% or more, and most preferably 66.0% or more. On the other hand, from the viewpoint of improving melting property, ２ The content is more preferably 70.0% or less, even more preferably 68.0% or less, particularly preferably 67.0% or less, and most preferably 66.0% or less.

[0042] Al ２ O ３ is a component that improves the ion exchange performance during chemical strengthening and increases the surface compressive stress after strengthening. ２ O ３ The content of Al is more preferably 10.0% or more, and even more preferably 11.0% or more, 11.5% or more, and 12.0% or more, in that order. On the other hand, there are also cases where it is required that crystals do not grow easily during melting, that devitrification defects do not occur easily, leading to a higher yield, and that the high-temperature viscosity of the glass is reduced to make it easier to melt. From these viewpoints, Al ２O ３ The content of is more preferably 15.0% or less, further preferably 14.0% or less, 13.5% or less, and 13.0% or less, in that order.

[0043] SiO ２ and Al ２ O ３ These are all components that stabilize the glass structure. ２ and Al ２ O ３ The total content of SiO is preferably 74.0% or more, more preferably 76.0% or more, and even more preferably 78.0% or more. ２ and Al ２ O ３ Both of these tend to increase the melting temperature of the glass. ２ and Al ２ O ３ The total content of is preferably 83.0% or less, more preferably 82.0% or less, even more preferably 81.0% or less, and particularly preferably 80.5% or less.

[0044] Li ２ O is a component capable of ion exchange and improves the melting property of the glass. ２ By containing O, Li ions on the glass surface are ion-exchanged with external Na ions to be incorporated into the glass, and the incorporated Na ions are then ion-exchanged with external K ions, which makes it easier to obtain a stress profile with a large surface compressive stress and a thick compressive stress layer. ２ The O content is more preferably 8.0% or more, and further preferably 9.0% or more, 9.5% or more, 10.0% or more, 10.2% or more, and 10.4% or more, in this order.

[0045] On the other hand, from the viewpoint of reducing the crystal growth rate during glass molding and making it difficult for quality degradation due to devitrification to occur, Li ２ The O content is more preferably 11.8% or less, further preferably 11.5% or less, and further preferably 11.0% or less, in that order.

[0046] Na ２ O and K ２ O is a component that improves the meltability of the glass and reduces the crystal growth rate during glass molding. It is also preferable to include a small amount of O in order to improve the ion exchange performance.

[0047] Na ２ O is a component that can be ion-exchanged in chemical strengthening treatment using potassium salts, and also a component that reduces the viscosity of glass. ２ The O content is preferably 1% or more, more preferably 1.5% or more, 2.5% or more, 3.0% or more, and 4.0% or more, in that order.

[0048] K ２ O is a component that suppresses the rise in devitrification temperature to suppress devitrification and also improves ion exchange performance. ２ The O content is more preferably 0.1% or more, further preferably 0.15% or more, particularly preferably 0.2% or more, and most preferably 0.5% or more.

[0049] Li ２ O content, Na ２ O content and K content ２ The total content of O, R, is more preferably 8% or more, and further preferably 9% or more, from the viewpoint of suppressing an increase in the devitrification temperature and reducing the crystal growth rate.

[0050] Li for the above R ２ The ratio of the content of O ([Li ２ O] / ([Li ２ O] + [Na ２ O] + [K ２ O]), hereinafter referred to as “Li ２ O / R ２ From the viewpoint of further improving the chemical strengthening properties against compressive stress in the deep layer portion, Li is more preferably 0.52 or more, and even more preferably 0.55 or more. ２ O / R ２ From the viewpoint of further enhancing chemical resistance, O is more preferably 0.90 or less, further preferably 0.85 or less, and particularly preferably 0.75 or less.

[0051] Na for the above R２ The ratio of the content of O ([Na ２ O] / ([Li ２ O] + [Na ２ O] + [K ２ O]), hereinafter referred to as “Na ２ O / R ２ From the viewpoint of further improving the chemical strengthening properties against compressive stress in the deep layer, Na is preferably 0.08 or more, more preferably 0.15 or more, and even more preferably 0.20 or more. ２ O / R ２ From the viewpoint of further enhancing chemical resistance, O is preferably 0.60 or less, more preferably 0.50 or less, even more preferably 0.40 or less, and particularly preferably 0.30 or less.

[0052] K for the above R ２ The ratio of the content of O ([K ２ O] / ([Li ２ O] + [Na ２ O] + [K ２ O]), hereinafter referred to as “K ２ O / R ２ From the viewpoint of further improving the electrical resistance of the glass, K is preferably 0.01 or more, more preferably 0.015 or more, even more preferably 0.02 or more, particularly preferably 0.08 or more, and most preferably 0.10 or more. ２ O / R ２ From the viewpoint of further enhancing the chemical strengthening properties against compressive stress near the surface, O is preferably 0.50 or less, more preferably 0.40 or less, even more preferably 0.30 or less, and particularly preferably 0.20 or less.

[0053] Also, Li ２ O / R ２ O and Na ２ O / R ２ O and K ２ O / R ２ From the viewpoint of suppressing an increase in the devitrification temperature, the product with O is more preferably 0.002 or more, further preferably 0.01 or more, and particularly preferably 0.02 or more. Moreover, from the viewpoint of improving chemical resistance, the product is more preferably 0.028 or less.

[0054] Al relative to the above R ２ O ３The ratio of the content of ([Al ２ O ３ ] / ([Li ２ O] + [Na ２ O] + [K ２ O]), hereinafter referred to as “Al ２ O ３ / R ２ Al is preferably 0.20 or more, more preferably 0.30 or more, even more preferably 0.40 or more, and still more preferably 0.50 or more. ２ O ３ / R ２ O is preferably 1.50 or less, more preferably 0.80 or less, even more preferably 0.75 or less, particularly preferably 0.70 or less, and most preferably 0.65 or less.

[0055] Also, Na ２ K content relative to O content ２ The ratio of the content of O ([K ２ O] / [Na ２ O]) is preferably 0.0 to 1.8. ２ O] / [Na ２ [O] is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.4 or more, and particularly preferably 0.5 or more, in that it improves the compressive stress near the surface layer and makes it easier to obtain chemically strengthened glass having a greater bending test strength. ２ O] / [Na ２ From the above viewpoints, [0] is preferably 1.0 or less, more preferably 0.9 or less, even more preferably 0.8 or less, and particularly preferably 0.7 or less.

[0056] [Al ２ O ３ ]-[Na ２ O]-[K ２ O] + [Li ２ The value represented by [0] is preferably from 10.0 to 22.0, more preferably from 10.0 to 20.0, and even more preferably from 12.0 to 18.0.

[0057] MgO may be contained to reduce viscosity during dissolution, etc. The MgO content is more preferably 0.05% or more, and even more preferably, in the following order, 0.1% or more, 0.2% or more, 0.9% or more, more than 0.9%, and 1.0% or more. On the other hand, in order to easily increase the compressive stress layer during chemical strengthening treatment, the MgO content is more preferably 8.0% or less, and even more preferably, in the following order, 7.5% or less, 5.0% or less, 4.0% or less, 3.8% or less, 3.0% or less, 2.0% or less, and 1.5% or less. By setting the MgO content to 4.0% or less, acid resistance can be improved.

[0058] Furthermore, by including MgO, it is possible to suppress the phase transition of the crystal phase from β-quartz solid solution to β-spodumene, and to suppress the precipitation of β-spodumene crystals. Therefore, in embodiment 2, it is preferable to include MgO. From the above viewpoint, it is preferable to include more than 0.5% and not more than 7.0% of MgO. The more preferable range is as described above.

[0059] CaO is a component that improves the meltability of glass and may be contained. The CaO content is more preferably 0.1% or more, and even more preferably 0.15% or more. On the other hand, in terms of the tendency to increase the compressive stress value during chemical strengthening treatment, the CaO content is more preferably 2.0% or less, even more preferably 1.0% or less, particularly preferably 0.8% or less, and most preferably 0.5% or less.

[0060] In order to increase the stability of the glass, it is more preferable to contain at least one of MgO and CaO, and even more preferable to contain MgO. The total content of MgO and CaO is preferably more than 0.1%, more preferably 0.2% or more, and even more preferably 0.5% or more. In order to further improve chemical strengthening properties, the total content of MgO and CaO is preferably 10.0% or less, more preferably 5.0% or less, 3.0% or less, 2.0% or less, and 1.0% or less, in that order.

[0061] SrO is a component that improves the meltability of glass and may be contained. The content of SrO is more preferably 0.1% or more, even more preferably 0.15% or more, and particularly preferably 0.5% or more. In order to facilitate increasing the compressive stress value during chemical strengthening treatment, the content of SrO is more preferably 3.0% or less, even more preferably 2.0% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. SrO may not be substantially contained.

[0062] BaO is a component that improves the meltability of glass and may be contained. When BaO is contained, the content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.5% or more. In order to make it easier to increase the compressive stress value during chemical strengthening treatment, the content of BaO is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and particularly preferably 0.5% or less. BaO may not be substantially contained.

[0063] ZnO is a component that improves the meltability of glass. The ZnO content is more preferably 0.1% or more, even more preferably 0.15% or more, and particularly preferably 0.5% or more. In order to facilitate increasing the compressive stress value during chemical strengthening treatment, the ZnO content is more preferably 3.0% or less, even more preferably 2.0% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. ZnO may not be substantially contained.

[0064] InW is a parameter that represents the degree of oxide mixing, calculated from the contents of alkali metal oxides, alkaline earth metal oxides, and zinc oxide contained in glass. InW is expressed by the following formula: InW = In(([Li ２ O] + [Na ２ O] + [K ２ O] + [MgO] + [CaO] + [SrO] + [BaO] + [ZnO])! / ([Li ２ O]! × [Na ２ O]! × [K ２O]! × [MgO]! × [CaO]! × [SrO]! × [BaO]! × [ZnO]!)) ... Formula (W1) In formula (W1), [Li ２ O], [Na ２ O], [K ２ O], [MgO], [CaO], [SrO], [BaO] and [ZnO] are LiO, ２ O, Na ２ O.K. ２ The formula represents the content of each component of O, MgO, CaO, SrO, BaO, and ZnO expressed as mole percentage based on oxide. The symbol ! indicates a factorial multiplication of a positive number. For example, [XO]! is the value of the mole percentage content of component XO expressed as oxide, rounded down to the nearest whole number, and then multiplied by the factorial. For example, Na ２ When O is 4.8 mol%, the calculation is made by factoring "4", that is, 4 x 3 x 2 x 1. The larger the value of lnW, the higher the degree of mixing of the above metal oxides, and the more effectively devitrification of the glass can be suppressed. From the above viewpoints, lnW is preferably 10 or more, more preferably 12 or more, even more preferably 13 or more, and particularly preferably 14 or more. lnW is preferably 20 or less, more preferably 18 or less, and even more preferably 17 or less.

[0065] TiO ２ is a component that is highly effective in suppressing solarization of glass and may be contained. ２ When TiO is contained, the content is preferably 0.02% or more, more preferably 0.03% or more, even more preferably 0.04% or more, particularly preferably 0.05% or more, and most preferably 0.06% or more. On the other hand, from the viewpoint of preventing the occurrence of devitrification and deterioration of the quality of the chemically strengthened glass, TiO ２ The content is preferably 2.0% or less, more preferably 1.0% or less, even more preferably 0.5% or less, particularly preferably 0.25% or less, and most preferably 0.15% or less.

[0066] ZrO ２ is a component that makes it easier to increase the surface compressive stress of chemically strengthened glass. ２The content of ZrO is more preferably more than 0%, and further preferably 0.1% or more, 0.15% or more, 0.2% or more, 0.25% or more, 0.3% or more, and 0.4% or more in the following order. On the other hand, in terms of suppressing the occurrence of devitrification defects and making it easier to increase the compressive stress value during chemical strengthening treatment, ZrO ２ The content is more preferably 2.0% or less, further preferably 1.5% or less, particularly preferably 1.0% or less, and most preferably 0.6% or less.

[0067] P ２ O ５ P tends to increase the compressive stress layer during chemical strengthening. ２ O ５ The content of P is more preferably 0.5% or more, further preferably 1.0% or more, and particularly preferably 2.0% or more. ２ O ５ The content of is more preferably 4.0% or less, and further preferably 2.0% or less. From the viewpoint of preventing the occurrence of striae during melting, it is also preferable that it is substantially not contained.

[0068] B ２ O ３ reduces the brittleness of the glass and improves the crack resistance, or improves the meltability of the glass. ２ O ３ The content of B is more preferably 0.5% or more, further preferably 1.0% or more, and particularly preferably 2.0% or more. ２ O ３ The content of B is preferably 8.0% or less. ２ O ３ The content of is more preferably 6.0% or less, further preferably 4.0% or less, and particularly preferably 2.0% or less. From the viewpoint of preventing the occurrence of striae during melting, it is also preferable that it is not substantially contained.

[0069] Y ２ O ３ is a component that makes it easier to increase the surface compressive stress of chemically strengthened glass while slowing down the crystal growth rate. ２ O ３The content of Y is more preferably more than 0%, and further preferably 0.1% or more, 0.2% or more, 0.5% or more, and 1.0% or more in the following order. ２ O ３ The content is more preferably 2.0% or less.

[0070] From the viewpoint of improving the initial solubility, ZrO ２ and Y ２ O ３ The total content of ZrO is preferably 4.0% or less, and more preferably 2.4% or less. ２ and Y ２ O ３ Although there is no particular lower limit for the total content, from the viewpoint of increasing the strength of the glass, the total content is more preferably 0.5% or more, further preferably 0.7% or more, 1.0% or more, and 1.2% or more, in that order.

[0071] ZrO ２ and Y ２ O ３ ZrO relative to the total content of ２ The ratio of the content of [ZrO ２ ] / ([ZrO ２ ]+[Y ２ O ３ ]) is more preferably 0.10 or more, further preferably 0.20 or more, and particularly preferably 0.25 or more. ２ ] / ([ZrO ２ ]+[Y ２ O ３ ]) is more preferably 0.60 or less, even more preferably 0.50 or less, particularly preferably 0.45 or less, and most preferably 0.40 or less.

[0072] ZrO ２ and Y ２ O ３ is known as a nucleating agent when added alone, but ZrO ２ and Y ２ O ３ By co-adding with ZrO ２ and Y ２ O ３Since a eutectic of [ZrO ２ ] / ([ZrO ２ ]+[Y ２ O ３ By setting [ZrO ] within the above range, the diffusion of ions in the glass is suppressed, the increase in the devitrification temperature is suppressed, and devitrification can be suppressed. ２ ] / ([ZrO ２ ]+[Y ２ O ３ By setting [ZrO ] within the above range, the glass is stabilized, and further, the temperature ranges where nucleation occurs and the temperature ranges where crystal growth occurs are separated without overlapping, suppressing an increase in the crystal growth rate, and thus suppressing the occurrence of defects. ２ ] / ([ZrO ２ ]+[Y ２ O ３ By setting the temperature range at which nucleation occurs to the lower side, the decrease in the crystallization initiation temperature is suppressed, and manufacturing characteristics can be improved.

[0073] From the viewpoint of reducing defects in the glass, 100×[ZrO ２ ]+63×[Y ２ O ３ The value represented by 100×[ZrO ２ ]+63×[Y ２ O ３ The lower limit of the value represented by the formula] is not particularly limited, but from the viewpoint of promoting nucleation, it is preferably 100 or more, more preferably 110 or more, even more preferably 125 or more, and particularly preferably 130 or more.

[0074] La ２ O ３ is not required, but Y ２ O ３ It can be contained for the same reasons as above. ２ O ３is preferably 0.1% or more, more preferably 0.2% or more, further preferably 0.5% or more, particularly preferably 0.8% or more. On the other hand, if the content is too high, it becomes difficult to increase the compressive stress layer during chemical strengthening treatment. ２ O ３ is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 2.0% or less, and particularly preferably 1.5% or less. ２ O ３ It is also preferable that the material is substantially free of

[0075] Nb ２ O ５、 Ta ２ O ５ , Gd ２ O ３ , CeO ２ is a component that has the effect of suppressing solarization of the glass and improving meltability, and may be contained. When these components are contained, the content of each is preferably 0.03% or more, more preferably 0.1% or more, even more preferably 0.5% or more, particularly preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, it is preferably 3.0% or less, more preferably 2.0% or less, and even more preferably 1.0% or less.

[0076] Fe ２ O ３ Since Fe absorbs heat rays, it has the effect of improving the meltability of glass, and is preferably contained when mass-producing glass using a large melting furnace. In this case, the content is preferably 0.002% or more, more preferably 0.005% or more, even more preferably 0.007% or more, and particularly preferably 0.01% or more, expressed in mass% on an oxide basis. On the other hand, Fe ２ O ３ Since an excessive content of causes coloration, from the viewpoint of enhancing the transparency of the glass, the content thereof, expressed as mass% on an oxide basis, is preferably 0.3% or less, more preferably 0.04% or less, even more preferably 0.025% or less, and particularly preferably 0.015% or less.

[0077] Furthermore, other coloring components may be added within a range that does not impede the achievement of the desired chemical strengthening properties. ３ O ４ , MnO ２ , NiO, CuO, Cr ２ O ３ , V ２ O ５ , Bi ２ O ３ , SeO ２ , Er ２ O ３ , Nd ２ O ３ The following are suitable examples.

[0078] SO is used as a fining agent when melting glass. ３ , chloride, fluoride, etc. may be contained as appropriate. ２ O ３ It is preferable that Sb is not contained. ２ O ３ When SnO is contained, it is preferably 0.3% or less, more preferably 0.1% or less, and most preferably not contained. ２ The content of SnO is more preferably 0.1% or more, further preferably 0.2% or more, and particularly preferably 0.3% or more. ２ In order to suppress the occurrence of defects, the content is preferably 1% or less, more preferably 0.8% or less, even more preferably 0.7% or less, and particularly preferably 0.5% or less.

[0079] Preferred physical properties of the glass having the mother glass composition of the first embodiment will be described below.

[0080] (Devitrification temperature) The glass for chemical strengthening having the mother glass composition of the first embodiment preferably has a devitrification temperature of 1300 ° C. or less. The devitrification temperature is more preferably 1280 ° C. or less, and even more preferably 1250 ° C. or less. Particularly preferred are 1240 ° C. or less, 1230 ° C. or less, 1220 ° C. or less, and 1210 ° C. or less, in the following order. The lower limit of the devitrification temperature is not particularly limited, but is usually 1100 ° C. or more.

[0081] A devitrification temperature of 1300°C or lower (preferably 1250°C or lower) allows the glass to be stably formed, improving manufacturing characteristics. Specifically, for example, when forming glass by the float process, if crystallization occurs before the molten glass is poured into the float bath, the crystals may erode the bricks that make up the float bath. A devitrification temperature of 1300°C or lower (preferably 1250°C or lower) can suppress brick erosion. The devitrification temperature of glass is the minimum temperature at which crystals do not precipitate on the surface or inside of the glass when crushed glass particles of 2 mm to 3 mm are placed in a platinum dish and heat-treated for 17 hours in an electric furnace controlled at a constant temperature, and then observed with an optical microscope after the heat treatment.

[0082] (Glass transition point Tg, crystallization onset temperature Tcs, crystallization peak temperature Tc) In this specification, measurement by differential scanning calorimetry (DSC) is carried out by grinding glass in an agate mortar, obtaining about 70 mg of powder with a uniform particle size of 106 to 180 μm, and heating the powder from room temperature to 1200° C. at a heating rate of 10° C. / min.

[0083] The chemically strengthened glass having the mother glass composition of the first embodiment preferably has a crystallization onset temperature Tcs measured by DSC of 790 ° C. or higher, more preferably 800 ° C. or higher, even more preferably 810 ° C. or higher, still more preferably 815 ° C. or higher, particularly preferably 820 ° C. or higher, and most preferably 825 ° C. or higher. The upper limit of the crystallization onset temperature is not particularly limited, but is usually 900 ° C. or lower.

[0084] By setting the crystallization onset temperature Tcs to 790°C or higher, manufacturing characteristics can be improved. Specifically, for example, in molding including a three-dimensional shape in which glass is molded into a plate and then heat-treated (for example, 2.5D or 3D molding, hereinafter also referred to as three-dimensional molding), the nucleation temperature is passed when the temperature is raised from room temperature to the molding temperature, and defects due to crystallization are likely to occur. By setting the crystallization onset temperature Tcs to 790°C or higher, molding can be performed without passing through the nucleation temperature when the temperature is raised from room temperature to the molding temperature, and the occurrence of defects can be suppressed.

[0085] Figure 1 shows a schematic diagram for explaining Tg, Tcs, and Tc in this specification. The glass transition temperature Tg in this specification is the intersection of an auxiliary line on a curve obtained by DSC, as shown in Figure 1. The crystallization onset temperature Tcs of glass in this specification refers to the temperature at the peak when the glass is heated at 10°C / min using DSC.

[0086] In the chemically strengthened glass having the mother glass composition of the first embodiment, the ratio of the crystallization onset temperature Tcs to the glass transition temperature Tg (Tcs + 273.15) / (Tg + 273.15) is preferably 1.10 or more, more preferably 1.15 or more, even more preferably 1.20 or more, and particularly preferably 1.25 or more. By having (Tcs + 273.15) / (Tg + 273.15) be 1.10 or more, the occurrence of defects in three-dimensional molding can be suppressed and molding characteristics can be improved. The upper limit of (Tcs + 273.15) / (Tg + 273.15) is not particularly limited, but from the viewpoint of glass moldability, it is usually preferably 1.6 or less. In addition, the units of Tcs and Tg in "(Tcs + 273.15) / (Tg + 273.15)" are "°C", and "(Tcs + 273.15) / (Tg + 273.15)" is the same as "Tcs / Tg" when the unit is "K".

[0087] The chemically strengthened glass having the mother glass composition of the first embodiment preferably has a value (Tcs-Tg) obtained by subtracting the glass transition point Tg from the crystallization onset temperature Tcs of 180 ° C. or higher, more preferably 200 ° C. or higher. It is even more preferably 210 ° C. or higher, even more preferably 215 ° C. or higher, particularly preferably 225 ° C. or higher, and most preferably 230 ° C. or higher. By having (Tcs-Tg) of 200 ° C. or higher, the occurrence of defects in three-dimensional molding can be suppressed and molding characteristics can be improved. The upper limit of (Tcs-Tg) is not particularly limited, but from the viewpoint of glass moldability, it is usually preferably 400 ° C. or lower. The chemically strengthened glass having the mother glass composition of the first embodiment preferably has a value (Tcs-Tg) obtained by subtracting the glass transition point Tg from the crystallization onset temperature Tcs of 180 ° C. or higher, more preferably 185 ° C. or higher.

[0088] From the viewpoint of reducing warpage after chemical strengthening, the glass transition temperature Tg is preferably 500° C. or higher, more preferably 520° C. or higher, and even more preferably 540° C. or higher. From the viewpoint of ease of float forming, the glass transition temperature Tg is preferably 750° C. or lower, more preferably 700° C. or lower, even more preferably 650° C. or lower, particularly preferably 600° C. or lower, and most preferably 580° C. or lower.

[0089] The chemically strengthened glass having the mother glass composition of the first embodiment preferably has a crystallization peak temperature Tc of 790 ° C or higher, more preferably 800 ° C or higher, and even more preferably 810 ° C or higher. When the crystallization peak temperature Tc is 790 ° C or higher, stable molding is possible. It is most preferable that no crystallization peak is observed. The upper limit of the crystallization peak temperature Tc is not particularly limited, but is usually 950 ° C or lower.

[0090] (Crystal Growth Rate) By containing MgO in the chemically strengthened glass having the mother glass composition of the first embodiment, the phase transition from β-quartz solid solution to β-spodumene can be suppressed, and the precipitation of β-spodumene crystals can be suppressed. Therefore, even if the chemically strengthened glass is held at 1000 ° C. for 30 minutes, the precipitation of β-spodumene is suppressed. Furthermore, the crystal growth rate can be further reduced. When the chemically strengthened glass having the mother glass composition of the first embodiment contains MgO, only β-quartz solid solution is the first precipitation phase, and the crystal growth rate of the β-quartz solid solution at 1000 ° C. is preferably 4000 μm / hr or less, more preferably 3800 μm / hr or less, even more preferably 3500 μm / hr or less, particularly preferably 3200 μm / hr or less, and most preferably 2700 μm / hr or less.

[0091] Crystallization in glass during the glass forming process can cause drawbacks. For example, when forming glass using the float method, crystallization occurs in the float bath where the temperature ranges for nucleation and crystal growth overlap because the glass is cooled from a high temperature.

[0092] In ordinary glass, the temperature range in which nucleation occurs and the temperature range in which crystal growth occurs do not overlap. ２ O ３and Li ２ In glasses containing a large amount of O, the temperature range in which nucleation occurs and the temperature range in which crystal growth occurs tend to overlap around 1000°C. Even if the nucleation and crystal growth rates overlap, this is not a drawback as long as the crystal growth rate is slow. Therefore, by setting the crystal growth rate of β-quartz solid solution at 1000°C to 600 μm / hr or less, crystallization during the molding process can be suppressed.

[0093] In this specification, the crystal growth rate of β-quartz solid solution at 1000°C is determined by holding a glass sample at 1000°C for 30 minutes, measuring the length of the crystals in the glass with a polarizing microscope, and calculating the average value. The crystal growth rate of β-spodumene at 1000°C is also determined in a similar manner.

[0094] The "β-OH value" is measured by the FT-IR method at a reference wavelength of 4000 cm －１ Transmittance X at １ (%), the absorption wavelength of the hydroxyl group is 3570 cm －１ Minimum transmittance X in the vicinity ２ The β-OH value can be calculated from the β-OH value (%) and the thickness t (unit: mm) of the glass plate using the formula (1): β-OH value = (1 / t) log １０ (X １ / X ２ ) (1) The β-OH value can be adjusted by the amount of water contained in the glass raw materials and the melting conditions.

[0095] The glass for chemical strengthening having the mother glass composition of the first embodiment has a β-OH value of 0.1 mm －１ It is preferable that the thickness is 0.15 mm or more. －１ More preferably, 0.2 mm or more －１ More preferably, 0.22 mm or more －１ More than 0.25 mm is particularly preferable. －１ The above is most preferable.

[0096] The β-OH value is an index of the amount of water in glass. Glass with a large β-OH value tends to have a lower softening point and be easier to bend. On the other hand, from the viewpoint of improving the strength of glass by chemical strengthening, as the β-OH value of glass increases, the surface compressive stress (CS) value after chemical strengthening tends to decrease. From this viewpoint, the β-OH value is 0.5 mm －１ Preferably less than 0.4 mm －１ More preferably, 0.3 mm or less －１ The following is even more preferred:

[0097] In a preferred embodiment described below, the glass for chemical strengthening having the mother glass composition of the first embodiment is subjected to a first-stage chemical strengthening with a Na salt, and then a second-stage chemical strengthening with a Li-K mixed salt. In order to improve the drop strength of the glass after chemical strengthening, K is incorporated into the glass. From the viewpoint of improving the drop strength of the glass after chemical strengthening, Na_DOL / K_DOL, which is the ratio of Na_DOL to K_DOL defined below, is preferably 26 or less, more preferably, in the following order: 25 or less, 24 or less, 23 or less, 22 or less, 21 or less, 20 or less. Further, after the first-stage chemical strengthening with a Na salt, from the viewpoint of preventing excessive K from being incorporated into the glass when performing the second-stage chemical strengthening with a Li-K mixed salt, Na_DOL / K_DOL is preferably 15 or more, more preferably, in the following order: 16 or more, 16.5 or more, 17 or more, 17.5 or more, 18 or more. K_DOL: compressive stress layer depth of chemically strengthened glass obtained by ion-exchanging glass using molten salt composed of 100% potassium nitrate Na_DOL: compressive stress layer depth of chemically strengthened glass obtained by ion-exchanging glass using molten salt composed of 100% sodium nitrate Here, the ion exchange time and temperature in calculating the above K_DOL and the above Na_DOL are the same conditions.

[0098] The glass for chemical strengthening having the mother glass composition of the first embodiment has a fracture toughness value (K ＩＣ ) is 0.80 MPa m １／２ It is preferable that the viscosity is 0.810 MPa m or more. １／２ More preferably, it is 0.82 MPa m or more. １／２More preferably, it is equal to or greater than 0.83 MPa m １／２ More than 0.84 MPa m １／２ The upper limit of the fracture toughness value is not particularly limited, but is typically 1.0 MPa m １／２ The following is the result.

[0099] The Young's modulus of the glass for chemical strengthening having the mother glass composition of the first embodiment is preferably 80 GPa or more, more preferably 85 GPa or more, even more preferably 90 GPa or more, and particularly preferably 95 GPa or more. The upper limit of the Young's modulus is not particularly limited, but is typically 120 GPa or less.

[0100] (Second embodiment) The second embodiment of the mother glass composition is expressed in mole percentage based on oxides, and is: SiO ２ 55 to 75% Al ２ O ３ 3 to 18% Li ２ O 17-30% Na ２ O 0-3% K ２ O 0-1% MgO 0-10% CaO 0-10% SrO 0-5% ZnO 0-5% TiO ２ 0 to 3% ZrO ２ 0 to 3% SnO ２ 0 to 1% P ２ O ５ 0 to 3% B ２ O ３ 0 to 10% Y ２ O ３ Contains 0 to 3% of Li ２ O content, Na ２ The content of O and K ２ The total content of O, R, is 8 to 35%, and the ratio of Li to R ２ The content of O is 0.85 to 0.99, and the ratio of Li to R is ２ O content and Na relative to R ２ O content and K relative to R ２ The product of this with the content of O is 0 to 0.003. Each component contained in the mother glass composition will be described below.

[0101] SiO ２ is a component that forms the glass network. It also increases chemical durability and reduces the occurrence of cracks when the glass surface is scratched.

[0102] SiO ２ In order to improve chemical durability, the content of SiO is more preferably 57.0% or more, even more preferably 58.0% or more, particularly preferably 59.0% or more, and most preferably 60.0% or more. On the other hand, from the viewpoint of improving melting property, ２ The content is more preferably 74.0% or less, even more preferably 72.0% or less, particularly preferably 69.0% or less, and most preferably 66.0% or less.

[0103] Al ２ O ３ is a component that improves the ion exchange performance during chemical strengthening and increases the surface compressive stress after strengthening. It also contributes to the formation of crystals containing Al and Li. From the viewpoint of obtaining the above effects, Al ２ O ３ The content of Al is more preferably 3.5% or more, and even more preferably 4.0% or more and 4.5% or more, in that order. On the other hand, there are also cases where it is required that crystals do not grow easily during melting, that devitrification defects do not occur easily, leading to a higher yield, and that the high-temperature viscosity of the glass is reduced to make it easier to melt. From these viewpoints, Al ２ O ３ The content of is more preferably 18.0% or less, and further preferably 15.0% or less, 12.0% or less, 9.0% or less, 7.0% or less, and 6.0% or less, in that order.

[0104] SiO ２ and Al ２ O ３ These are all components that stabilize the glass structure. ２ and Al ２ O ３ The total content of SiO is preferably 60.0% or more, more preferably 62.0% or more, and even more preferably 64.0% or more. ２ and Al ２ O３ Both of these tend to increase the melting temperature of the glass. ２ and Al ２ O ３ The total content of is preferably 80.0% or less, more preferably 75.0% or less, even more preferably 70.0% or less, and particularly preferably 68.0% or less.

[0105] Li ２ O is a component capable of ion exchange and improves the melting property of the glass. ２ By containing O, Li ions on the glass surface are ion-exchanged with external Na ions to be incorporated into the glass, and the incorporated Na ions are then ion-exchanged with external K ions, which makes it easy to obtain a stress profile with a large surface compressive stress and a thick compressive stress layer. ２ By including O, it is easy to obtain crystallized glass when a specific heat treatment is performed. ２ The O content is more preferably 17% or more, and further preferably 19% or more, 21% or more, and 22% or more, in that order.

[0106] On the other hand, in order to reduce the crystal growth rate during glass molding and to prevent deterioration of quality due to devitrification, Li ２ The O content is more preferably 30% or less, further preferably 28% or less, 26% or less, 24% or less, and 23% or less, in that order.

[0107] Na ２ O and K ２ O is a component that improves the meltability of the glass and reduces the crystal growth rate during glass molding. It is also preferable to include a small amount of O in order to improve the ion exchange performance.

[0108] Na ２ O is a component that can be ion-exchanged in chemical strengthening treatment using potassium salts, and also a component that reduces the viscosity of glass. ２The content of O is preferably 0.3% or more, more preferably 0.5% or more, 0.8% or more, 1.0% or more, 1.2% or more, 1.5% or more, and 1.8% or more, in the following order. On the other hand, from the viewpoint of maintaining the glass network and avoiding a decrease in the surface compressive stress (Na_CS) in the strengthening treatment with a sodium salt, Na ２ The O content is preferably 3.0% or less, more preferably 2.5% or less, and further preferably 2.3% or less.

[0109] K ２ O is a component that suppresses the rise in devitrification temperature to suppress devitrification and also improves ion exchange performance. ２ The content of O is more preferably 0.1% or more, even more preferably 0.15% or more, particularly preferably 0.2% or more, and most preferably 0.5% or more. On the other hand, from the viewpoint of avoiding a decrease in the surface compressive stress (K_CS) in the strengthening treatment using a sodium salt, K ２ The content of O is preferably 1.0% or less, and more preferably 0.8% or less. ２ O may not be substantially contained.

[0110] Li ２ O content, Na ２ O content and K content ２ The total content of O, R, is more preferably 10 to 30%, further preferably 15 to 28%, particularly preferably 18 to 25%, from the viewpoint of suppressing an increase in the devitrification temperature and reducing the crystal growth rate.

[0111] Li for the above R ２ The ratio of the content of O ([Li ２ O] / ([Li ２ O] + [Na ２ O] + [K ２ O]), hereinafter referred to as “Li ２ O / R ２ From the viewpoint of further improving the deep layer stress in the chemical strengthening characteristics, Li is more preferably 0.88 or more, and even more preferably 0.90 or more. ２ O / R ２From the viewpoint of further increasing the electrical resistance and chemical resistance of the glass, O is more preferably 0.98 or less, further preferably 0.95 or less, and particularly preferably 0.93 or less.

[0112] Na for the above R ２ The ratio of the content of O ([Na ２ O] / ([Li ２ O] + [Na ２ O] + [K ２ O]), hereinafter referred to as “Na ２ O / R ２ From the viewpoint of further improving the deep layer stress in the chemical strengthening characteristics, Na is preferably more than 0, more preferably 0.01 or more, even more preferably 0.03 or more, particularly preferably 0.05 or more, and most preferably 0.06 or more. ２ O / R ２ From the viewpoint of further improving chemical resistance, O is preferably 0.40 or less, more preferably 0.30 or less, even more preferably 0.20 or less, and particularly preferably 0.10 or less.

[0113] K for the above R ２ The ratio of the content of O ([K ２ O] / ([Li ２ O] + [Na ２ O] + [K ２ O]), hereinafter referred to as “K ２ O / R ２ From the viewpoint of further increasing the electrical resistance of the glass, K is preferably 0.05 or more, more preferably 0.08 or more, and even more preferably 0.10 or more. ２ O / R ２ From the viewpoint of increasing the compressive stress near the surface in chemical strengthening properties, O is preferably 0.50 or less, more preferably 0.40 or less, further preferably 0.30 or less, and particularly preferably 0.20 or less. ２ O / R ２ O may be 0.

[0114] Also, Li ２ O / R ２ O and Na ２ O / R ２ O and K ２ O / R ２From the viewpoint of suppressing an increase in the devitrification temperature and reducing the crystal growth rate, the product with O is more preferably 0.008 or more, even more preferably 0.01 or more, and particularly preferably 0.02 or more. Moreover, the product is more preferably 0.028 or less. The product may be 0.

[0115] Al relative to the above R ２ O ３ The ratio of the content of ([Al ２ O ３ ] / ([Li ２ O] + [Na ２ O] + [K ２ O]), hereinafter referred to as “Al ２ O ３ / R ２ Al is preferably 0.05 or more, more preferably 0.10 or more, even more preferably 0.15 or more, and even more preferably 0.20 or more. ２ O ３ / R ２ O is preferably 0.50 or less, more preferably 0.40 or less, even more preferably 0.30 or less, and particularly preferably 0.25 or less.

[0116] [Al ２ O ３ ]-[Na ２ O]-[K ２ O] + [Li ２ The value represented by [0] is preferably 15.0 to 35.0%, more preferably 20.0 to 30.0%.

[0117] MgO may be contained to reduce viscosity during dissolution, etc. The MgO content is more preferably 0.05% or more, and even more preferably 0.5% or more, 1.0% or more, 2.0% or more, 3.0% or more, and 4.0% or more, in the following order. On the other hand, in terms of making it easier to increase the compressive stress layer during chemical strengthening treatment, the MgO content is more preferably 9.0% or less, and even more preferably 8.0% or less, 7.0% or less, and 6.0% or less, in the following order.

[0118] Furthermore, by including MgO, it is possible to suppress the phase transition of the crystal phase from β-quartz solid solution to β-spodumene, and to suppress the precipitation of β-spodumene crystals. Therefore, in embodiment 2, it is preferable to include MgO. From the above viewpoint, it is preferable to include more than 0.5% and not more than 7.0% of MgO. The more preferable range is as described above. It is not necessary for MgO to be substantially included.

[0119] CaO is a component that improves the meltability of glass and may be contained. The CaO content is more preferably 0.1% or more, and even more preferably 0.15% or more. On the other hand, in terms of the tendency to increase the compressive stress value during chemical strengthening treatment, the CaO content is more preferably 2.0% or less, even more preferably 1.0% or less, particularly preferably 0.8% or less, and most preferably 0.5% or less. CaO may not be substantially contained.

[0120] In order to increase the stability of the glass, it is more preferable to contain at least one of MgO and CaO, and it is even more preferable to contain MgO. The total content of MgO and CaO is preferably more than 1.0%, more preferably 2.0% or more, even more preferably 3.0% or more, and particularly preferably 4.0% or more. In terms of further improving chemical strengthening properties, the total content of MgO and CaO is preferably 10.0% or less, more preferably 8.0% or less, 7.0% or less, and 6.0% or less, in that order.

[0121] SrO is a component that improves the meltability of glass and may be contained. The content of SrO is more preferably 0.1% or more, even more preferably 0.15% or more, and particularly preferably 0.5% or more. In order to facilitate increasing the compressive stress value during chemical strengthening treatment, the content of SrO is more preferably 3.0% or less, even more preferably 2.0% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. SrO may not be substantially contained.

[0122] BaO is a component that improves the meltability of glass and may be contained. When BaO is contained, the content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.5% or more. In order to make it easier to increase the compressive stress value during chemical strengthening treatment, the content of BaO is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and particularly preferably 0.5% or less. BaO may not be substantially contained.

[0123] ZnO is a component that improves the meltability of glass. The ZnO content is more preferably 0.1% or more, even more preferably 0.15% or more, and particularly preferably 0.5% or more. In order to facilitate increasing the compressive stress value during chemical strengthening treatment, the ZnO content is more preferably 3.0% or less, even more preferably 2.0% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. ZnO may not be substantially contained.

[0124] InW is a parameter that represents the degree of oxide mixing, calculated from the contents of alkali metal oxides, alkaline earth metal oxides, and zinc oxide contained in glass. InW is expressed by the following formula: InW = In(([Li ２ O] + [Na ２ O] + [K ２ O] + [MgO] + [CaO] + [SrO] + [BaO] + [ZnO])! / ([Li ２ O]! × [Na ２ O]! × [K ２ O]! × [MgO]! × [CaO]! × [SrO]! × [BaO]! × [ZnO]!)) ... Formula (W1) In formula (W1), [Li ２ O], [Na ２ O], [K ２ O], [MgO], [CaO], [SrO], [BaO] and [ZnO] are LiO, ２ O, Na ２ O.K. ２The formula represents the content of each component of O, MgO, CaO, SrO, BaO, and ZnO expressed as mole percentage based on oxide. The symbol ! indicates a factorial multiplication of a positive number. For example, [XO]! is the value of the mole percentage content of component XO expressed as oxide, rounded down to the nearest whole number, and then multiplied by the factorial. For example, Na ２ When O is 4.8 mol%, the calculation is made by factoring "4", that is, 4 x 3 x 2 x 1. The larger the value of lnW, the higher the degree of mixing of the above metal oxides, and the more effectively devitrification of the glass can be suppressed. From the above viewpoints, lnW is preferably 10 or more, more preferably 12 or more, even more preferably 13 or more, and particularly preferably 14 or more. lnW is preferably 20 or less, more preferably 18 or less, and even more preferably 17 or less.

[0125] TiO ２ is a component that is highly effective in suppressing solarization of glass and is a material that forms the nuclei of crystals, so it may be contained. ２ When TiO is contained, the content is preferably 0.05% or more, more preferably 0.1% or more, even more preferably 0.2% or more, particularly preferably 0.5% or more, and most preferably 0.8% or more. ２ has light absorption properties, so from the viewpoint of preventing color development of glass, TiO ２ The content of TiO is preferably 2.5% or less, more preferably 2.0% or less, further preferably 1.5% or less, and particularly preferably 1.0% or less. ２ may not be substantially included.

[0126] ZrO ２ is a component that makes it easier to increase the surface compressive stress of chemically strengthened glass. In addition, since it is a material that forms the nucleus of crystals, ZrO ２ It may contain ZrO ２ The content of is more preferably more than 0%, and further preferably 0.5% or more, 1.0% or more, 1.5% or more, 2.0% or more, and 2.5% or more, in the following order.

[0127] P ２ O ５P tends to increase the compressive stress layer during chemical strengthening. ２ O ５ The content of P is more preferably 0.5% or more, further preferably 1.0% or more, and particularly preferably 2.0% or more. ２ O ５ The content of is more preferably 2.0% or less. From the viewpoint of preventing the occurrence of striae during melting, it is also preferable that it is substantially not contained.

[0128] B ２ O ３ reduces the brittleness of the glass and improves the crack resistance, or improves the meltability of the glass. ２ O ３ The content of B is more preferably 0.5% or more, further preferably 1.0% or more, and particularly preferably 2.0% or more. ２ O ３ The content of B is preferably 8.0% or less. ２ O ３ The content of is more preferably 6.0% or less, further preferably 4.0% or less, and particularly preferably 2.0% or less. From the viewpoint of preventing the occurrence of striae during melting, it is also preferable that it is not substantially contained.

[0129] Y ２ O ３ is a component that makes it easier to increase the surface compressive stress of chemically strengthened glass while slowing down the crystal growth rate. ２ O ３ The content of Y is more preferably more than 0%, and further preferably 0.1% or more, 0.2% or more, 0.5% or more, and 0.8% or more in the following order. ２ O ３ The content is more preferably 2.0% or less, and further preferably 1.5% or less.

[0130] From the viewpoint of improving the initial solubility, ZrO ２ and Y ２ O ３ The total content of ZrO is more preferably 5.0% or less. ２ and Y ２ O３ Although the lower limit of the total content of is not particularly limited, from the viewpoint of increasing the strength of the glass, it is more preferably 0.5% or more, and further preferably 1.0% or more, 1.5% or more, 2.0% or more, 2.5% or more, and 3.0% or more, in the following order.

[0131] ZrO ２ and Y ２ O ３ ZrO relative to the total content of ２ The ratio of the content of [ZrO ２ ] / ([ZrO ２ ]+[Y ２ O ３ ]) is more preferably 0.50 or more, further preferably 1.00 or more, and particularly preferably 2.00 or more. ２ ] / ([ZrO ２ ]+[Y ２ O ３ ]) is more preferably 8.00 or less, even more preferably 7.00 or less, and particularly preferably 6.00 or less.

[0132] ZrO ２ and Y ２ O ３ is known as a nucleating agent when added alone, but ZrO ２ and Y ２ O ３ By co-adding with ZrO ２ and Y ２ O ３ Since a eutectic of [ZrO ２ ] / ([ZrO ２ ]+[Y ２ O ３ By setting [ZrO ] within the above range, the diffusion of ions in the glass is suppressed, the increase in the devitrification temperature is suppressed, and devitrification can be suppressed. ２ ] / ([ZrO ２ ]+[Y ２ O ３ By setting [ZrO ] within the above range, the glass is stabilized, and further, the temperature ranges where nucleation occurs and the temperature ranges where crystal growth occurs are separated without overlapping, suppressing an increase in the crystal growth rate, and thus suppressing the occurrence of defects.２ ] / ([ZrO ２ ]+[Y ２ O ３ By setting the temperature range at which nucleation occurs to the lower side, the decrease in the crystallization initiation temperature is suppressed, and manufacturing characteristics can be improved.

[0133] La ２ O ３ is not required, but Y ２ O ３ It can be contained for the same reasons as above. ２ O ３ is preferably 0.1% or more, more preferably 0.2% or more, further preferably 0.5% or more, particularly preferably 0.8% or more. On the other hand, if the content is too high, it becomes difficult to increase the compressive stress layer during chemical strengthening treatment. ２ O ３ is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 2.0% or less, and particularly preferably 1.5% or less. ２ O ３ It is also preferable that the material is substantially free of

[0134] Nb ２ O ５、 Ta ２ O ５ , Gd ２ O ３ , CeO ２ is a component that has the effect of suppressing solarization of the glass and improving meltability, and may be contained. When these components are contained, the content of each is preferably 0.03% or more, more preferably 0.1% or more, even more preferably 0.5% or more, particularly preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, it is preferably 3.0% or less, more preferably 2.0% or less, and even more preferably 1.0% or less.

[0135] Fe ２ O ３Since Fe absorbs heat rays, it has the effect of improving the meltability of glass, and is preferably contained when mass-producing glass using a large melting furnace. In this case, the content is preferably 0.002% or more, more preferably 0.005% or more, even more preferably 0.007% or more, and particularly preferably 0.01% or more, expressed in mass% on an oxide basis. On the other hand, Fe ２ O ３ Since an excessive content of causes coloration, from the viewpoint of enhancing the transparency of the glass, the content thereof, expressed as mass% on an oxide basis, is preferably 0.3% or less, more preferably 0.04% or less, even more preferably 0.025% or less, and particularly preferably 0.015% or less.

[0136] Furthermore, other coloring components may be added within a range that does not impede the achievement of the desired chemical strengthening properties. ３ O ４ , MnO ２ , NiO, CuO, Cr ２ O ３ , V ２ O ５ , Bi ２ O ３ , SeO ２ , Er ２ O ３ , Nd ２ O ３ The following are suitable examples.

[0137] SO is used as a fining agent when melting glass. ３ , chloride, fluoride, etc. may be contained as appropriate. ２ O ３ It is preferable that Sb is not contained. ２ O ３ When SnO is contained, it is preferably 0.3% or less, more preferably 0.1% or less, and most preferably not contained. ２ The content of SnO is more preferably 0.1% or more, further preferably 0.2% or more, and particularly preferably 0.3% or more. ２In order to suppress the occurrence of defects, the content is preferably 1% or less, more preferably 0.8% or less, even more preferably 0.7% or less, and particularly preferably 0.5% or less.

[0138] Preferred physical properties of the glass having the mother glass composition of the second embodiment will now be described.

[0139] (Devitrification Temperature) A preferred aspect of the devitrification temperature of the chemically strengthened glass having the mother glass composition of the second embodiment is the same as that of the chemically strengthened glass having the mother glass composition of the first embodiment, and therefore description thereof will be omitted.

[0140] (Glass transition point Tg, crystallization onset temperature Tcs, crystallization peak temperature Tc) The glass for chemical strengthening having the mother glass composition of the second embodiment preferably has a crystallization onset temperature Tcs measured by DSC of 500 ° C. or higher. The upper limit of the crystallization onset temperature is not particularly limited, but is usually 800 ° C. or lower.

[0141] When the crystallization onset temperature Tcs is within the above range, for example, by performing heat treatment at 500 to 600°C for 1 to 6 hours, followed by 0.5 to 6 hours at 600 to 800°C, crystals can be precipitated in the chemically strengthened glass, resulting in a chemically strengthened glass that is a crystallized glass. The heat treatment may be performed in three stages. For example, the glass may be held at 500 to 600°C for 1 to 6 hours, then at 550 to 650°C for 0.5 to 6 hours, and then at 600 to 800°C for 0.5 to 6 hours to obtain a chemically strengthened glass that is a crystallized glass.

[0142] From the viewpoint of reducing warpage after chemical strengthening, the glass transition temperature Tg is preferably 500° C. or higher, more preferably 520° C. or higher, and even more preferably 540° C. or higher. From the viewpoint of ease of float forming, the glass transition temperature Tg is preferably 750° C. or lower, more preferably 700° C. or lower, even more preferably 650° C. or lower, particularly preferably 600° C. or lower, and most preferably 580° C. or lower.

[0143] The glass for chemical strengthening having the mother glass composition of the second embodiment preferably has a crystallization peak temperature Tc of 600 ° C or higher, more preferably 650 ° C or higher, and even more preferably 700 ° C or higher. When the crystallization peak temperature Tc is 600 ° C or higher, stable molding is possible. It is most preferable that no crystallization peak is observed. The upper limit of the crystallization peak temperature Tc is not particularly limited, but is usually 950 ° C or lower.

[0144] The glass for chemical strengthening having the mother glass composition of the second embodiment has a β-OH value of 0.1 mm －１ It is preferable that the thickness is 0.15 mm or more. －１ More preferably, 0.2 mm or more －１ More preferably, 0.22 mm or more －１ More than 0.25 mm is particularly preferable. －１ The above is most preferable.

[0145] The β-OH value is an index of the amount of water in glass. Glass with a large β-OH value tends to have a lower softening point and be easier to bend. On the other hand, from the viewpoint of improving the strength of glass by chemical strengthening, as the β-OH value of glass increases, the surface compressive stress (CS) value after chemical strengthening tends to decrease. From this viewpoint, the β-OH value is 0.5 mm －１ Preferably less than 0.4 mm －１ More preferably, 0.3 mm or less －１ The following is even more preferred:

[0146] The glass for chemical strengthening having the mother glass composition of the second embodiment has a fracture toughness value (K ＩＣ ) is 0.80 MPa m １／２ It is preferable that the viscosity is 0.85 MPa m or more. １／２ More preferably, it is 0.90 MPa m or more. １／２ More preferably, it is equal to or greater than 1.0 MPa m １／２ More than 1.1 MPa m １／２ The upper limit of the fracture toughness value is not particularly limited, but is typically 1.6 MPa m １／２ The following is the result.

[0147] The glass for chemical strengthening having the mother glass composition of the second embodiment preferably has a Young's modulus of 80 GPa or more, more preferably 90 GPa or more, even more preferably 95 GPa or more, and most preferably 100 GPa or more. The upper limit of the Young's modulus is not particularly limited, but is typically 120 GPa or less.

[0148] (Manufacturing method) The glass for chemical strengthening (the mother glass composition of the first embodiment and the mother glass composition of the second embodiment) can be manufactured by a conventional method. For example, the raw materials of each component of the glass are mixed and heated and melted in a glass melting furnace. The glass is then homogenized by a known method, formed into a desired shape such as a glass plate, and slowly cooled.

[0149] Examples of glass sheet forming methods include the float method, press method, fusion method, and down-draw method. In particular, the float method, which is suitable for mass production, is preferred. Continuous forming methods other than the float method, such as the fusion method and down-draw method, are also preferred.

[0150] The glass for chemical strengthening having the mother glass composition of the second embodiment described above may be subjected to the heat treatment described above to form crystallized glass.

[0151] The molded glass is then ground and polished as necessary to form a glass substrate. When cutting or chamfering the glass substrate to a predetermined shape and size, it is preferable to cut or chamfer the glass substrate before performing the chemical strengthening treatment described below, because a compressive stress layer is formed on the end surface by the subsequent chemical strengthening treatment.

[0152] The shape of the glass for chemical strengthening may be a shape other than a plate shape depending on the product to which it is applied, its intended use, etc. The glass plate may also have a bordered shape with a different thickness around the periphery. The shape of the glass plate is not limited thereto; for example, the two main surfaces may not be parallel to each other, and one or both of the two main surfaces may be entirely or partially curved. More specifically, the glass plate may be, for example, a flat glass plate without warping, or a curved glass plate having a curved surface.

[0153] [Chemical Strengthening Treatment] The chemically strengthened glass of the present invention is obtained by subjecting a glass for chemical strengthening (the mother glass composition of the first embodiment and the mother glass composition of the second embodiment) to a chemical strengthening treatment. The chemical strengthening treatment can be performed by a known method. The chemical strengthening treatment is performed, for example, by contacting a glass sheet with a molten salt of a metal salt (e.g., potassium nitrate) containing a metal ion with a large ionic radius (typically, K ion). The contact between the glass sheet and the molten salt of the metal salt is performed, for example, by immersing the glass sheet in the molten salt of the metal salt. The contact between the glass sheet and the molten salt of the metal salt replaces metal ions with large ionic radii (typically, Na ions or Li ions) in the glass sheet with metal ions with large ionic radii (typically, K ions for Na ions, and Na ions or K ions for Li ions).

[0154] Chemical strengthening treatment, i.e., ion exchange treatment, can be performed by immersing a glass plate in a molten salt such as potassium nitrate heated to 360 to 600° C. for 0.1 to 500 hours. The heating temperature of the molten salt is preferably 375° C. or higher and 500° C. or lower. The immersion time of the glass plate in the molten salt is preferably 0.3 hours or longer and 200 hours or shorter.

[0155] Examples of metal salts contained in the molten salt for chemical strengthening treatment include nitrates, sulfates, carbonates, and chlorides. Nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, and silver nitrate. Sulfates include lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, and silver sulfate. Carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Chlorides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, and silver chloride. These metal salts may be used alone or in combination.

[0156] The stress profile can be adjusted by the treatment conditions of the chemical strengthening treatment. Specifically, the stress profile can be adjusted by the CS in the above-mentioned formula (1). １２０The processing conditions of the chemical strengthening treatment can be adjusted by, more specifically, the type and composition of the molten salt used in the chemical strengthening treatment, the temperature of the molten salt, and the contact time with the molten salt. The parameters can also be adjusted by the composition of the chemically strengthened glass used in the chemical strengthening treatment.

[0157] The chemical strengthening treatment may be performed only once, or multiple times (multi-stage strengthening) under two or more different conditions. The chemical strengthening treatment may be performed in one stage, but preferably in two or more stages. The chemical strengthening treatment preferably involves contacting the Li-containing chemically strengthened glass with a molten salt of a metal salt containing at least Na ions (first molten salt) and then with a molten salt of a metal salt containing at least K ions (second molten salt). The first molten salt preferably contains a metal salt containing Na ions and a metal salt containing K ions. When the first molten salt contains a metal salt containing Na ions and a metal salt containing K ions, the content of the metal salt containing Na ions is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, and particularly preferably 40% by mass or more, relative to the total mass of the first molten salt. The first molten salt may consist solely of a metal salt containing Na ions. The second molten salt preferably contains a metal salt containing K ions and a metal salt containing Li ions. The second molten salt may further include a metal salt containing Na ions.

[0158] <Applications> The chemically strengthened glass of the present invention is useful, for example, as a cover glass. The cover glass can also be suitably used for purposes such as surface protection of displays and solar cell modules. In particular, the chemically strengthened glass of the present invention is useful as a cover glass for mobile devices such as mobile phones, smartphones, personal digital assistants (PDAs), and tablet terminals. Furthermore, it is useful as a cover glass for non-portable display devices such as televisions (TVs), personal computers (PCs), and touch panels, as a cover glass for the surface of solar cell modules, as building materials such as elevator walls, walls (full-surface displays) of buildings such as houses and buildings, and window glass, as well as tabletops, interiors of automobiles and airplanes, etc. It is also useful as a cover glass for the above-mentioned items. Furthermore, it can be applied to applications such as housings having curved shapes by bending and bending forming.

[0159] The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, treatment details, and treatment procedures shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below. Examples 4, 5, 7, 8, 10, 11, 17, and 24 are working examples, and Examples 1 to 3, 6, 9, 12 to 16, 18 to 23, and 25 are comparative examples.

[0160] <Preparation of Chemically Tempered Glass> First, glass raw materials A to C and P were prepared by melting them in a platinum crucible to obtain the glass compositions shown in Table 1, expressed in mole percentages based on oxides. Specifically, commonly used glass raw materials such as oxides, hydroxides, carbonates, or nitrates were appropriately selected and weighed to obtain 1,000 g of glass. The mixed raw materials were then placed in a platinum crucible and placed in a resistance-heated electric furnace at 1,500 to 1,700 °C, where they were melted for approximately 3 hours, degassed, and homogenized to obtain molten glass. The resulting molten glass was poured into a mold and held at a temperature of glass transition point + 50 °C for 1 hour. It was then cooled to room temperature at a rate of 0.5 °C / min to obtain a glass block. The resulting glass block was then cut and ground to obtain plate glass. Both surfaces of the obtained glass plate were mirror-finished to finally obtain glass plates (glass for chemical strengthening) of 120 mm length x 60 mm width x 0.55 mm thickness or 120 mm length x 60 mm width x 0.7 mm thickness. On the other hand, the fracture toughness value (K ＩＣ ) and a sample piece for measuring Young's modulus were cut out. Regarding glass material B, after forming it into a plate glass, it was heated to 550°C, held for 2 hours, then heated to 720°C and held for 2 hours, and heat-treated under these conditions. Regarding glass material P, after forming it into a plate glass, it was heated to 540°C, held for 4 hours, then heated to 600°C, held for 4 hours, then heated to 710°C and held for 4 hours, and heat-treated under these conditions. Regarding glass material B, the same heat treatment as above was performed on a glass block, and the fracture toughness value (K ＩＣ ) and a sample piece for measuring Young's modulus were obtained.

[0161] Each of the chemically strengthened glasses (glass materials A to C and P) obtained by the above procedure was subjected to a chemical strengthening treatment under the conditions shown in Table 2, thereby obtaining chemically strengthened glasses of Examples 1 to 25.

[0162] <Measurement of Stress Profile> The stress profile of the chemically strengthened glass was obtained by the method described above.

[0163] <Measurement of Young's modulus> In the procedure for obtaining each of the above glass materials, the Young's modulus of the glass for chemical strengthening was measured using a cut sample piece. Specifically, the sample piece was used to perform measurement in accordance with JIS R 1602 by an ultrasonic pulse method. The Young's modulus of the glass for chemical strengthening corresponds to the Young's modulus at the center position of the plate thickness of the chemically strengthened glass. The Young's modulus at the in-plane center position of the chemically strengthened glass was measured using the same method as the sample piece, and was the same value as the value measured using the sample piece. Therefore, in the tables below, the Young's modulus at the in-plane center position is omitted.

[0164] <Measurement of fracture toughness value> Using the sample pieces cut out in the procedure for obtaining each of the above glass materials, the Young's modulus of the glass for chemical strengthening was measured. The fracture toughness value was measured by the above-mentioned DCDC method.

[0165] <Calculated Value> The value of X was calculated according to the above-mentioned formula (1).

[0166] <Impact Resistance Test> An impact resistance test was performed according to the following procedure. A schematic diagram of a test apparatus used in one embodiment of the impact resistance test is shown in FIG. 4. First, a glass plate 43 was attached and fixed to one surface of an iron block base 42 placed on a platform 41 using adhesive tape. Next, the glass plate 43 and sandpaper 44 were attached with adhesive tape so that the surface of the glass plate 43 opposite the fixed surface contacted the sand surface (abrasive surface) of the sandpaper 44. The abrasive of the sandpaper 44 was silicon carbide, and its grit size was #80. The adhesive tape was removable from the block base 42, the glass plate 43, and the sandpaper 44. The adhesive tape was attached at a position away from the position where the pendulum 45 would collide in the procedure described below. With the sandpaper 44 and the glass plate 43 fixed to the block base 42, the pendulum 45 was placed at a position where the stationary pendulum 45 would contact the side of the sandpaper 44 opposite the abrasive surface. The impact surface of the pendulum 45 (the side in contact with the sandpaper 44, the left side of the drawing in Figure 4) had a radius of curvature of 200 mm, and the mass of the pendulum 45 was 50 g. The swing length x of the pendulum 45 was 400 mm. The pendulum 45 was set so as to achieve the above state, and was then struck toward the block base 42 from the side opposite the abrasive surface of the sandpaper 44, thereby applying an impact to the glass 43. The swing height of the pendulum 45 was adjusted so that the impact energy was 0.03 J. After the impact, it was confirmed whether or not the glass 43 had been broken. Breakage refers to the progression of scratches caused by the impact of the pendulum, resulting in the glass being broken into two or more pieces.

[0167] <Evaluation> The average breaking stress was determined using the following procedure. First, the surface of the glass 43 was scratched using the apparatus shown in FIG. 4 . Specifically, similar to the impact resistance test described above, the swing height of the pendulum 45 was adjusted so that the applied impact was 0.03 J, and an impact was applied to the glass 43 in the same manner as in the impact resistance test described above. The surface of the glass 43 was scratched using the above procedure. Micro-scratches were generated on the surface of the glass 43 within a radius of approximately 5 mm, centered on the point where the weight of the pendulum 45 struck the surface via sandpaper 44. A bending test was then performed on the glass scratched using the above procedure. The bending test was a four-point bending test (4PB bending test) in accordance with JIS-R1601:2008. The four-point bending test device used was a Shimadzu Autograph AGS-10kNX desktop precision universal testing machine. In order to evaluate the entire damaged area, the bending test span was set to 20 mm on the upper side and 40 mm on the lower side. The crosshead moving speed was 5 mm / min. The cracking stress was calculated from the load measurement results until cracking occurred. The cracking stress was measured for five samples, and the arithmetic mean value of the measured cracking stresses was taken as the average cracking stress.

[0168] <Results> The composition of the glass for chemical strengthening used in the chemical strengthening treatment of each example, the conditions of the chemical strengthening treatment, the measurement results, and the evaluation results are shown in Tables 1 to 3 below. Tables 2 and 3 are listed in two parts, "Part 1" and "Part 2." In Table 2, Young's modulus and K ＩＣ (Fracture toughness value) indicates a value measured by the above-mentioned method using a sample piece for measurement. In Table 3, the descriptions in the stress profile column have the following meanings. The calculation method for each value is as described above or as shown below. K_CS ０ : Compressive stress of the outermost surface caused by potassium ions in chemically strengthened glass. ０" is typically the compressive stress of the outermost surface measured by an optical waveguide surface stress meter. K_DOL: Depth of the compressive stress layer caused by potassium ions in chemically strengthened glass. The "K_DOL" is typically the depth at which the compressive stress is 0 MPa in a stress distribution obtained using only an optical waveguide surface stress meter. On the other hand, if it is difficult to measure "K_DOL" using the optical waveguide surface stress meter, the potassium distribution in the plate thickness direction may be measured using an Electron Probe Micro Analyzer (EPMA), and the "K_DOL" may be determined from the potassium diffusion depth. CS ０ ~CS １２０ : Compressive stress at each depth (unit: μm) of the obtained chemically strengthened glass DOL: Compressive stress depth of the obtained chemically strengthened glass Na_DOL: Compressive stress layer depth due to sodium ions in the chemically strengthened glass The above "Na_DOL" is typically the depth at which the compressive stress is 0 MPa in a stress distribution obtained using only a scattered light photoelastic stress meter. CT Ｍａｘ : Maximum value of tensile stress CT ａｖｅ : Average value of tensile stress ICT: Average value of tensile stress In addition, in the impact resistance test column in Table 3, when an impact was applied with the above energy value, if no breakage occurred, it is recorded as "N", and if breakage occurred, it is recorded as "Y". In Table 3, the value of "X" in the calculated value column represents the value calculated by the above-mentioned method.

[0169]

[0170]

[0171]

[0172]

[0173]

[0174] From the results shown in Table 3, it was confirmed that chemically strengthened glasses (Examples 4, 5, 7, 8, 10, 11, 17, and 24) having a compressive stress of 600 MPa or more on the outermost surface, a compressive stress layer depth of 10 to 175 μm, and a value of X represented by the above formula (1) of 0 or more had a high average cracking stress and high cracking strength. On the other hand, in Examples 1 to 3, 6, 9, 12 to 16, 18 to 23, and 25 in which the value of X was less than 0, the average cracking stress was low and the cracking strength was poor.

[0175] In the impact resistance test, the swing height of the pendulum 45 was adjusted to change the impact energy, and the depth of cracks generated on the surface of the glass 43 was observed using an optical microscope. Specifically, the fracture initiation point on the outermost surface of the glass was first observed and confirmed using an optical microscope. Then, the fracture initiation point was removed with tweezers without applying a load, and the fracture surface was observed using an optical microscope. From the cross-sectional observation, the maximum crack depth of the glass 43 was determined, and the relationship between the maximum crack depth and the impact energy was plotted. This plot is shown in Figure 5. The maximum crack depth was determined by drawing a perpendicular line from the outermost surface of the glass to the deepest part of the crack when observing the fracture surface of the fracture initiation point, and measuring the distance between the outermost surface of the glass and the deepest part of the crack. The maximum crack depth was also the average value of the maximum crack depths generated in five pieces of glass 43. As can be seen from Figure 5, a correlation was observed between the impact energy and the maximum crack depth.

[0176] The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2023-206400, filed on December 6, 2023, are incorporated herein by reference as part of the disclosure of the present invention.

[0177] 41 Base 42 Block base 43 Glass 44 Sandpaper 45 Pendulum

Claims

1. A chemically strengthened glass having a plate thickness of 0.6 mm or less, a compressive stress of the outermost surface of 600 MPa or more, a compressive stress layer depth of 10 to 175 μm, and a value of X represented by the following formula (1) of 0 or more. Formula (1) X = 2.05 × E ｍ ０．５ +CS １２０ In formula (1), E ｍ is the Young's modulus at the in-plane center position of the chemically strengthened glass, and E ｍ The unit is GPa. In formula (1), CS １２０ is the value of compressive stress at a depth of 120 μm, and C １２０ The unit is MPa.

2. The chemically strengthened glass according to claim 1, wherein the chemically strengthened glass has a Young's modulus of 80 GPa or more at a central position in its plane.

3. Fracture toughness value K at the in-plane center position of the chemically strengthened glass ＩＣ However, 0.80 MPa m １／２ The chemically strengthened glass according to claim 1 or 2.

4. The chemically strengthened glass according to claim 1 or 2, which does not break when an abrasive surface of #80 sandpaper containing silicon carbide as an abrasive is brought into contact with one side of the chemically strengthened glass and an impact with energy of 0.003 J is applied from the side opposite to the abrasive surface of the sandpaper.

5. The composition at the center of the plate thickness is expressed as a mole percentage based on oxides: SiO ２ 60 to 72% Al ２ O ３ 10 to 20% Li ２ O 3-12% Na ２ O 0.5-5% K ２ O 0-3% MgO 0-10% CaO 0-10% SrO 0-5% ZnO 0-5% TiO ２ 0 to 3% ZrO ２ 0 to 3% SnO ２ 0 to 1% P ２ O ５ 0 to 1% B ２ O ３ 0 to 10% Y ２ O ３ Contains 0 to 3% Li ２ O content, Na ２ The content of O and K ２ The total content of O, R, is 5 to 20%, ２ The ratio of the content of Li to the content of R is 0.5 to 0.

95. ２ The ratio of the content of O to the content of Na ２ The ratio of the content of O to the content of K relative to R ２ The chemically strengthened glass according to claim 1 or 2, wherein the product of the ratio of the O content and the O content is 0.001 to 0.

03.

6. The chemically strengthened glass according to claim 5, wherein the Young's modulus at the center position of the plate thickness is 85 GPa or more.

7. The composition at the center of the plate thickness is expressed as mole percentage based on oxides: SiO ２ 55 to 75% Al ２ O ３ 3 to 18% Li ２ O 17-30% Na ２ O 0-3% K ２ O 0-1% MgO 0-10% CaO 0-10% SrO 0-5% ZnO 0-5% TiO ２ 0 to 3% ZrO ２ 0 to 3% SnO ２ 0 to 1% P ２ O ５ 0 to 3% B ２ O ３ 0 to 10% Y ２ O ３ Contains 0 to 3% Li ２ O content, Na ２ The content of O and K ２ The total content of O, R, is 8 to 35%, ２ The content of O is 0.85 to 0.99, and the ratio of Li to R is ２ The content of O and the Na content relative to R ２ The content of O and the ratio of K to R ２ The chemically strengthened glass according to claim 1 or 2, wherein the product value with the O content is 0 to 0.

003.

8. The chemically strengthened glass according to claim 7, wherein the Young's modulus at the center position of the plate thickness is 90 GPa or more.

9. A cover glass comprising the chemically strengthened glass according to claim 1 or 2.

10. A display comprising a cover glass according to claim 9.

11. A solar cell module comprising the cover glass of claim 9.

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