Glass and chemically strengthened glass

Abstract

The invention relates to glass and chemically strengthened glass. The present invention relates to a glass having a specific composition range and having a parameter M of 20 or less as determined by the following formula. M is equal to-1.15 * [SiO2] to 1.73 * [Al2O3] + 0.155 * [Li2O] + 0.74 * [Na2O] to 4.75 * [K2O] to 2.1 * [B2O3] to 2.17 * [P2O5] + 3.25 * [MgO] to 2.0 * [ZnO] to 13.3 * [ZrO2] to 0.80 * [Y2O3] + 120, and M is equal to-1.15 * [SiO2] to 1.73 * [Al2O3] + 0.155 * [Li2O] + 0.74 * [Na2O] to 4.75 * [K2O] to 2.1 * [B2O3] to 2.17 * [P2O5] + 3.25 * [MgO] to 2.0 * [ZnO] to 13.3 * [ZrO2] to 0.80 * [Y2O3] + 120.

Description

[0001] This application is a divisional application of the Chinese patent application with the application date of July 5, 2021, application number 202180048398.4, and invention name: Glass and Chemically Strengthened Glass. Technical Field

[0002] The present invention relates to glass and chemically strengthened glass. Background Art

[0003] In recent years, cover glass including chemically strengthened glass has been used to protect display devices such as mobile phones, smartphones, and tablet terminals and to improve their appearance.

[0004] Chemically strengthened glass tends to increase in strength as surface compressive stress (CS) and depth of compressive layer (DOL) increase. Meanwhile, to maintain balance with the surface compressive stress, internal tensile stress (CT) is generated within the glass. Therefore, increasing CS and DOL increases CT. When glass with a high CT breaks, the number of fragments increases, increasing the risk of fragmentation.

[0005] Patent Document 1 describes that a stress distribution represented by a curved line is formed by a two-step chemical strengthening process, thereby increasing the surface compressive stress (CS) while suppressing the internal tensile stress (CT).

[0006] Patent Document 2 discloses lithium aluminosilicate glass that can achieve relatively large surface compressive stress and compressive stress layer depth through a two-step chemical strengthening process. The two-step chemical strengthening process using sodium and potassium salts can increase CS and DOL while suppressing CT.

[0007] The two-step strengthening treatment generally combines the following treatments: a treatment for forming a deep compressive stress layer with a relatively small surface compressive stress value by ion exchange between sodium ions having a relatively small ionic radius and lithium ions in the glass; and a treatment for forming a large compressive stress near the surface by ion exchange between potassium ions having a relatively large ionic radius and sodium ions in the glass.

[0008] Patent Document 3 describes that a more complex stress distribution can be formed by three-step chemical strengthening.

[0009] This technology can be said to be a technology that, in addition to the usual two-step chemical strengthening, also performs a treatment to pull back alkali ions with large ionic radius in the glass through ion exchange with alkali ions with small ionic radius, or a treatment to relax the stress generated in the glass through heat treatment, thereby reducing the internal tensile stress CT while further increasing CS and DOL.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: U.S. Patent Application Publication No. 2015 / 0259244

[0013] Patent Document 2: Japanese Patent Application No. 2013-520388

[0014] Patent Document 3: Japanese Patent Application No. 2019-517985 Summary of the Invention

[0015] Problems to be solved by the invention

[0016] However, the three-step strengthening process is complex. The present invention aims to provide a chemically strengthened glass that can achieve high CS and DOL while suppressing CT through a relatively simple strengthening process. Another object of the present invention is to provide a chemically strengthened glass that can achieve high CS and DOL while suppressing CT through a relatively simple strengthening process.

[0017] Means used to solve problems

[0018] Potassium ions, which have a larger ionic radius, diffuse more slowly in glass than sodium ions, which have a smaller ionic radius. Therefore, when potassium ions are used for ion exchange treatment, the DOL typically decreases. However, the present inventors have discovered that by adjusting the glass composition, the diffusion rate of potassium ions can sometimes be increased relative to that of sodium ions. When ion exchange treatment is performed on glass with such a composition, a stress distribution different from that of conventional glass can be formed. Therefore, it is believed that a relatively simple two-step strengthening process can produce a more complex stress distribution with larger CS and DOL than conventional glass and suppressed CT, thereby completing the present invention.

[0019] The present invention provides a glass comprising, in terms of molar percentage based on oxides:

[0020] 52% to 70% SiO2,

[0021] 14% to 25% Al2O3,

[0022] 10% to 18% Li2O,

[0023] 1% to 7% Na2O,

[0024] 0.1% to 5% K2O,

[0025] 0-10% B2O3,

[0026] 0-5% P2O5,

[0027] 0-5% MgO,

[0028] 0-5% ZnO,

[0029] 0~2% ZrO2, and

[0030] 0~5% Y2O3, and

[0031] The parameter M obtained from the contents of SiO2, Al2O3, Li2O, Na2O, K2O, B2O3, P2O5, MgO, ZnO, ZrO2, and Y2O3 in mol% [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3] in accordance with the following formula is 20 or less.

[0032] M=-1.15×[SiO2]-1.73×[Al2O3]+0.155×[Li2O]+0.74×[Na2O]-4.75×[K2O]-2.1 ×[B2O3]-2.17×[P2O5]+3.25×[MgO]-2.0×[ZnO]-13.3×[ZrO2]-0.80×[Y2O3]+120

[0033] The parameter D of the glass of the present invention, which is obtained from [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3] according to the following formula, is preferably 1200 or greater.

[0034] D=-943×[SiO2]-859×[Al2O3]-998×[Li2O]-991×[Na2O]-1013×[K2O]-949×[ B2O3]-941×[P2O5]-687×[MgO]-956×[ZnO]-1516×[ZrO2]-823×[Y2O3]+95174

[0035] The glass of the present invention is preferably composed of [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3], and the parameter E calculated according to the following formula is preferably 500 or above.

[0036] E=539×[SiO2]+527×[Al2O3]+587×[Li2O]+467×[Na2O]+578×[K2O]+510×[B 2O3]+516×[P2O5]+442×[MgO]+502×[ZnO]+850×[ZrO2]+546×[Y2O3]-53476.

[0037] The present invention provides a glass comprising, in terms of molar percentage based on oxides:

[0038] 52% to 70% SiO2,

[0039] 14% to 25% Al2O3,

[0040] 10% to 18% Li2O,

[0041] 1% to 7% Na2O, and

[0042] 0.1% to 5% K2O,

[0043] When the glass having a thickness of 700 μm is immersed in NaNO 3 at 380° C. for 4 hours, the surface compressive stress value CS0(Na) generated is 500 MPa or more.

[0044] When the glass having a thickness of 700 μm is immersed in KNO 3 at 380° C. for 4 hours, the surface compressive stress value CS0(K) generated is 1200 MPa or more.

[0045] When the glass having a thickness of 700 μm is immersed in KNO3 at 380°C for 4 hours, the depth of the compressive stress layer DOL(K) generated is 3 μm or more, and

[0046] When the glass having a thickness of 700 μm is immersed in NaNO 3 at 380° C. for 4 hours, the ratio DOL(Na) / DOL(K) of the depth of the compressive stress layer generated to DOL(K) is 35 or less.

[0047] The compressive stress value CS at a depth of 50 μm from the surface of the glass of the present invention generated when the glass having a thickness of 700 μm is immersed in NaNO3 at 380°C for 4 hours is 50 (Na) is preferably 170 MPa or more.

[0048] The devitrification temperature of the glass of the present invention is preferably 1350° C. or lower.

[0049] The viscosity of the glass of the present invention reaches 10 2 The temperature T2 at dPa·s is preferably 1750° C. or lower.

[0050] The temperature of the DSC exothermic peak of the glass of the present invention measured by the following test method is preferably higher than the glass transition temperature by 150° C. or more.

[0051] (Test method)

[0052] About 70 mg of glass was pulverized and ground using an agate mortar, and the temperature was measured from room temperature to 1200° C. using a differential scanning calorimeter (DSC) at a heating rate of 10° C. / min.

[0053] The glass of the present invention preferably has an S value represented by the following formula of 0.4 or less.

[0054] S=-P Li ×log(P Li )-P Na ×log(P Na )-P K ×log(P K )

[0055] Here,

[0056] P Li =[Li2O] / ([Li2O]+[Na2O]+[K2O])

[0057] P Na =[Na2O] / ([Li2O]+[Na2O]+[K2O])

[0058] P K =[K2O] / ([Li2O]+[Na2O]+[K2O])

[0059] Here, [Li2O], [Na2O], and [K2O] represent the contents of Li2O, Na2O, and K2O in mole percentage, respectively.

[0060] The present invention provides a chemically strengthened glass having a surface compressive stress value of 400 MPa or more, wherein:

[0061] When the Na2O concentration distribution is obtained in the depth direction from the surface to the center of the plate thickness, the depth where the Na2O concentration reaches the maximum is 1 μm or more, and

[0062] The basic composition of the chemically strengthened glass comprises, in terms of molar percentage based on oxides:

[0063] 52% to 70% SiO2,

[0064] 14% to 25% Al2O3,

[0065] 10% to 18% Li2O,

[0066] 1% to 7% Na2O, and

[0067] 0.1% to 5% K2O.

[0068] The compressive stress value CS of the chemically strengthened glass of the present invention at a depth of 50 μm from the surface is 50 It is preferably 90 MPa or more.

[0069] The internal tensile stress value CT of the chemically strengthened glass of the present invention is preferably 70.6 MPa or less.

[0070] The surface compressive stress value CS0 of the chemically strengthened glass of the present invention is preferably 800 MPa or more.

[0071] The frequency hopping of the chemically strengthened glass of the present invention is preferably 10 2.5 above.

[0072] Effects of the Invention

[0073] According to the present invention, chemically strengthened glass having a complex stress distribution with large CS and DOL and suppressed CT can be obtained through a relatively simple strengthening process. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 This is a diagram showing an example of stress distribution in the chemically strengthened glass according to the embodiment of the present invention.

[0075] Figure 2 This is a diagram showing an example of stress distribution in the chemically strengthened glass according to the embodiment of the present invention.

[0076] Figure 3 A diagram showing an electrode pattern used for frequency hopping measurement. DETAILED DESCRIPTION

[0077] Hereinafter, the glass according to the embodiment of the present invention will be described in detail. However, the present invention is not limited to the following embodiment and can be implemented with arbitrary modifications without departing from the gist of the present invention.

[0078] In this specification, "chemically strengthened glass" refers to glass that has been subjected to a chemical strengthening treatment. In addition, "glass for chemical strengthening" refers to glass before being subjected to a chemical strengthening treatment.

[0079] In this specification, the glass composition of chemically strengthened glass is sometimes referred to as the basic composition of chemically strengthened glass. In chemically strengthened glass, a compressive stress layer caused by ion exchange typically forms on the glass surface. Therefore, the glass composition of the union-exchanged portion of the glass is consistent with the basic composition of the chemically strengthened glass. In chemically strengthened glass, the basic composition is defined as the glass composition at a depth of 1 / 2 the plate thickness t, except in cases where extreme ion exchange treatment has been performed.

[0080] In this specification, glass compositions are expressed as molar percentages based on oxides, and molar % may be expressed simply as %. In addition, “to” indicating a numerical range is used to include the numerical values described before and after it as the lower limit and the upper limit.

[0081] In the glass composition, “substantially free” means that it contains no impurities other than inevitable impurities contained in raw materials, etc., that is, it is not intentionally contained. Specifically, regarding components other than coloring components, the content is, for example, less than 0.1 mol %.

[0082] In this specification, "stress distribution" is a graph that represents the compressive stress value with the depth from the glass surface as a variable. Negative compressive stress values represent tensile stress.

[0083] In this specification, the property that glass fragments are easily scattered when broken may be referred to as "fragility".

[0084] In this specification, the “stress distribution” can be measured by a method using an optical waveguide surface stress meter and a scattered light photoelastic stress meter in combination, or by a method using a scattered light photoelastic stress meter.

[0085] It is known that optical waveguide surface stress gauges can accurately measure the stress of glass in a short time. An example of an optical waveguide surface stress gauge is the FSM-6000 manufactured by Orihara Seisakusho Co., Ltd. However, in principle, optical waveguide surface stress gauges can only measure stress when the refractive index decreases from the sample surface toward the interior. In chemically strengthened glass, the refractive index of the layer formed by replacing sodium ions in the glass with external potassium ions decreases from the sample surface toward the interior, making it possible to measure stress using an optical waveguide surface stress gauge. However, the stress of the layer formed by replacing lithium ions in the glass with external sodium ions cannot be accurately measured using an optical waveguide surface stress gauge.

[0086] The method using a scattered light photoelastic stress meter can measure stress regardless of the refractive index distribution. Examples of scattered light photoelastic stress meters include the SLP-1000 and SLP-2000 manufactured by Orihara Manufacturing Co., Ltd. However, scattered light photoelastic stress meters are susceptible to surface scattering, and may not accurately measure stress near the surface. Combining two measurement devices allows for accurate stress measurement.

[0087] <Glass>

[0088] The glass according to an embodiment of the present invention (hereinafter sometimes referred to as "the present glass") has a relatively deep diffusion depth of K ions, resulting from ion exchange between K ions intruding from the glass surface and Na ions in the glass, making chemical strengthening easier. Furthermore, the present glass easily achieves an appropriate stress distribution, making it suitable for chemically strengthened glass.

[0089] The surface compressive stress value CS0(Na) generated when the present glass having a plate thickness of 700 μm is immersed in NaNO3 at 380°C for 4 hours is preferably 500 MPa or more, more preferably 520 MPa or more, further preferably 550 MPa or more, and particularly preferably 600 MPa or more. When CS0(Na) is above the above value, it is easy to sufficiently increase the compressive stress when the present glass is subjected to a strengthening treatment using sodium ions. In order to prevent severe fracture, CS0(Na) is preferably 1000 MPa or less, more preferably 800 MPa or less. It should be noted that, herein, "the present glass having a plate thickness of 700 μm" refers to "the present glass when the plate thickness is set to 700 μm". That is, according to such a description, there is no restriction on the shape and thickness of the present glass. The specific preferred shape and thickness of the present glass will be described in detail later.

[0090] The surface compressive stress CS0(K) generated when a 700 μm thick glass is immersed in KNO3 at 380°C for 4 hours is preferably 1200 MPa or greater, more preferably 1230 MPa or greater, and even more preferably 1250 MPa or greater. A CS0(K) of at least these values facilitates sufficient increase in compressive stress during potassium ion strengthening treatment of the glass. To prevent severe fracture, CS0(K) is preferably 1800 MPa or less, more preferably 1600 MPa or less.

[0091] The compressive stress layer depth DOL(K) generated when the present glass having a thickness of 700 μm is immersed in KNO3 at 380°C for 4 hours is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 6.5 μm or more. When DOL(K) is above the above value, the diffusion depth of potassium ions during chemical strengthening of the present glass is easily sufficient. From the perspective of ease of designing stress distribution, DOL(K) is preferably 18 μm or less, more preferably 16 μm or less.

[0092] The ratio DOL(Na) / DOL(K) of the depth of the compressive stress layer DOL(Na) generated when the present glass having a thickness of 700 μm is immersed in NaNO3 at 380°C for 4 hours to the above-mentioned DOL(K) is preferably 35 or less, more preferably 30 or less, further preferably 25 or less, further preferably 20 or less, particularly preferably 18 or less, further particularly preferably 17 or less, further preferably 16 or less, and most preferably 15 or less. When DOL(Na) / DOL(K) is below the above-mentioned value, the diffusion rate of potassium ions becomes relatively large relative to the diffusion rate of sodium ions during chemical strengthening, and the balance becomes good, so that a complex stress distribution is easily obtained. From the viewpoint of increasing the diffusion of sodium ions, DOL(Na) / DOL(K) is preferably 5 or more, more preferably 7 or more, and particularly preferably 8 or more.

[0093] The compressive stress CS at a depth of 50 μm from the surface generated when the present glass with a thickness of 700 μm is immersed in NaNO3 at 380°C for 4 hours is 50 (Na) is preferably 170 MPa or more, more preferably 190 MPa or more, and even more preferably 200 MPa or more. 50 (Na) in the above range, when chemically strengthening the glass, it is easy to increase the compressive stress inside the glass and improve the strength. In order to prevent severe fracture, CS 50 (Na) is preferably 500 MPa or less, more preferably 400 MPa or less.

[0094] The compressive stress CS at a depth of 90 μm from the surface generated when the present glass with a thickness of 700 μm is immersed in NaNO3 at 380°C for 4 hours is 90 (Na) is preferably 0 MPa or more, more preferably 0.5 MPa or more, further preferably 5 MPa or more, further preferably 10 MPa or more, and particularly preferably 15 MPa or more. 90 (Na) in the above range, when chemically strengthening the glass, it is easy to increase the compressive stress inside the glass and improve the strength. In order to prevent severe fracture, CS 90 (Na) is preferably 200 MPa or less, more preferably 150 MPa or less, and even more preferably 100 MPa or less.

[0095] This glass is lithium aluminosilicate glass.

[0096] Specifically, the present glass preferably contains, in terms of molar percentage based on oxides:

[0097] 52% to 70% SiO2,

[0098] 14% to 25% Al2O3, and

[0099] 10% to 18% Li2O.

[0100] In addition, the present glass preferably contains:

[0101] 1% to 7% Na2O,

[0102] 0.1% to 5% K2O,

[0103] 0-10% B2O3,

[0104] 0-5% P2O5,

[0105] 0-5% MgO,

[0106] 0-5% ZnO,

[0107] 0~2% ZrO2, and

[0108] 0~5% Y2O3.

[0109] The contents of SiO₂, Al₂O₃, Li₂O, Na₂O, K₂O, B₂O₃, P₂O₅, MgO, ZnO, ZrO₂, and Y₂O₃ in the present glass in terms of mole percentage are as follows: [SiO₂], [Al₂O₃], [Li₂O], [Na₂O], [K₂O], [B₂O₃], [P₂O₅], [MgO], [ZnO], [ZrO₂], and [Y₂O₃], and the parameter M calculated according to the following formula is preferably 20 or less. The value of M is more preferably 18 or less, further preferably 17 or less, particularly preferably 16 or less, even more preferably 15 or less, further preferably 13 or less, and most preferably 11 or less.

[0110] M=-1.15×[SiO2]-1.73×[Al2O3]+0.155×[Li2O]+0.74×[Na2O]-4.75×[K2O]-2.1 ×[B2O3]-2.17×[P2O5]+3.25×[MgO]-2.0×[ZnO]-13.3×[ZrO2]-0.80×[Y2O3]+120

[0111] M is a parameter related to the ratio of the diffusion rate of Na ions to the diffusion rate of K ions. When the value of M is within the above range, the ratio of the diffusion rate of Na ions to the diffusion rate of K ions tends to decrease. In order to increase the compressive stress value CS at a depth of 50 μm from the surface, 50 The value of the parameter M is preferably greater than 2, more preferably greater than 5, and even more preferably greater than 7.

[0112] Furthermore, by having the aforementioned preferred composition range and parameter M being 20 or less, the present glass has a composition suitable for chemical strengthening, and the ratio of the diffusion rate of Na ions to the diffusion rate of K ions is adjusted to be within an appropriate range. Thus, chemically strengthened glass with high CS and DOL and suppressed CT can be easily obtained through relatively simple strengthening treatment.

[0113] The parameter D obtained by the following formula is preferably not less than 1200. The value of D is more preferably not less than 1230, further preferably not less than 1250, particularly preferably not less than 1300, further preferably not less than 1350, and most preferably not less than 1450.

[0114] D=-943×[SiO2]-859×[Al2O3]-998×[Li2O]-991×[Na2O]-1013×[K2O]-949×[B2O3]-941×[P2O5]-687×[MgO]-956×[ZnO]-1516×[ZrO2]-823× [Y2O3]+95174

[0115] D is a parameter related to the compressive stress generated by K ion diffusion. When the D value is within the above range, the diffusion rate of K ions tends to increase. To reduce CT, the D value is preferably 1950 or less, more preferably 1800 or less, and even more preferably 1600 or less.

[0116] The parameter E calculated from [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3] according to the following formula is preferably 500 or greater. The value of the parameter E is more preferably 520 or greater, further preferably 550 or greater, particularly preferably 570 or greater, further preferably 600 or greater, and most preferably 650 or greater.

[0117] E=539×[SiO2]+527×[Al2O3]+587×[Li2O]+467×[Na2O]+578×[K2O]+510×[B 2O3]+516×[P2O5]+442×[MgO]+502×[ZnO]+850×[ZrO2]+546×[Y2O3]-53476

[0118] E is a parameter related to the compressive stress value generated by Na ion diffusion. When the value of E is within the above range, the diffusion rate of Na ions tends to decrease. In order to reduce CT, the value of E is preferably 1000 or less, more preferably 800 or less.

[0119] Hereinafter, a preferred glass composition will be described.

[0120] SiO2 is a component that constitutes the network of glass. In addition, SiO2 is a component that improves chemical durability and is a component that reduces the generation of cracks when damage occurs on the glass surface.

[0121] To improve chemical durability, the SiO2 content is preferably 52% or more, more preferably 56% or more, further preferably 60% or more, even more preferably 63% or more, and particularly preferably 65% or more. To improve meltability during glassmaking, the SiO2 content is preferably 70% or less, more preferably 68% or less, and even more preferably 65% or less.

[0122] From the viewpoint of improving the ion exchange performance during chemical strengthening and increasing the surface compressive stress after strengthening, Al2O3 is an effective component.

[0123] To improve chemical durability and chemical strengthening properties, the Al2O3 content is preferably 14% or more, more preferably 16% or more, even more preferably 18% or more, and particularly preferably 20% or more. On the other hand, excessive Al2O3 content can sometimes lead to increased crystal growth during melting. To prevent yield reduction due to devitrification defects, the Al2O3 content is preferably 25% or less, more preferably 23% or less, and even more preferably 21% or less.

[0124] SiO2 and Al2O3 are components that stabilize the structure of glass. In order to reduce brittleness, the total content of SiO2 and Al2O3 is preferably 75% or more, more preferably 77% or more, and even more preferably 79% or more.

[0125] SiO2 and Al2O3 both have the tendency to improve the melting temperature of glass. Therefore, in order to make glass easy to melt, the total content of SiO2 and Al2O3 is preferably below 90%, more preferably below 87%, further preferably below 85%, and particularly preferably below 82%.

[0126] Li2O is a component that generates surface compressive stress through ion exchange and improves the meltability of glass. By incorporating Li2O into chemically strengthened glass (chemically strengthened glass), the Li ions on the glass surface are exchanged for Na ions, and then the Na ions are exchanged for K ions. This creates a stress distribution with high surface compressive stress and a high compressive stress layer.

[0127] In order to increase the surface compressive stress during chemical strengthening, the content of Li2O is preferably 10% or more, more preferably 11% or more, further preferably 13% or more, and particularly preferably 15% or more.

[0128] On the other hand, if the Li2O content is too high, the crystal growth rate during glass molding increases, and the problem of reduced yield due to devitrification defects may become more serious. In order to suppress devitrification during the glass manufacturing process, the Li2O content is preferably 18% or less, more preferably 16% or less, further preferably 14% or less, and particularly preferably 12% or less.

[0129] Neither Na2O nor K2O is essential, but both Na2O and K2O are components that improve the meltability of glass and reduce the crystal growth rate of glass. In order to improve ion exchange performance, the present glass preferably contains at least one of Na2O and K2O.

[0130] Na2O is a component that forms a surface compressive stress layer in a chemical strengthening treatment using potassium salt, and is a component that can improve the meltability of glass. In order to obtain this effect, the content of Na2O is preferably more than 1%, more preferably more than 2%, and further preferably more than 3%. On the other hand, when the content of Na2O is too much, it is difficult to increase the compressive stress of the deeper part from the surface by chemical strengthening. From such a viewpoint, the content is preferably less than 7%, more preferably less than 5%, and further preferably less than 3%.

[0131] In order to suppress devitrification in the glass manufacturing process, the present glass may contain K2O. When K2O is contained in the present glass, the content of K2O is preferably 0.1% or more, more preferably 0.15% or more, and particularly preferably 0.2% or more. In order to further prevent devitrification, the content of K2O is preferably 0.5% or more, more preferably 1.2% or more. On the other hand, if the glass contains a large amount of K, it sometimes becomes the main cause of the reduction in surface stress due to brittleness or reverse exchange during strengthening. From this point of view, the content of K2O is preferably 5% or less, more preferably 3% or less, further preferably 1% or less, and particularly preferably 0.5% or less.

[0132] To improve the meltability of the glass, the total content of Na2O and KO ([Na2O] + [KO]) is preferably 3% or more, more preferably 3.5% or more, even more preferably 4% or more, and particularly preferably 4.5% or more. Excessive ([Na2O] + [KO]) tends to reduce the surface compressive stress value, so ([Na2O] + [KO]) is preferably 10% or less, more preferably 8% or less, even more preferably 7% or less, and particularly preferably 6% or less.

[0133] Furthermore, the content of Na2O is preferably greater than that of K2O because K2O tends to increase the surface resistivity.

[0134] In order to reduce the surface resistivity, the ratio of Li2O content to the total content of Li2O, Na2O and K2O is P Li =[Li2O] / ([Li2O]+[Na2O]+[K2O]) is preferably 0.4 or more, more preferably 0.5 or more, and further preferably 0.6 or more. On the other hand, in order to suppress devitrification during glass melting, P Li It is preferably 0.9 or less, particularly preferably 0.8 or less.

[0135] In order to suppress devitrification, the ratio of the content of Na2O to the total content of Li2O, Na2O and K2O is P Na=[Na2O] / ([Li2O]+[Na2O]+[K2O]) is preferably 0.1 or more, more preferably 0.2 or more. In order to reduce the surface resistivity, P Na It is preferably 0.5 or less, and more preferably 0.4 or less.

[0136] In order to reduce the surface resistivity, the ratio of the content of K2O to the total content of Li2O, Na2O and K2O is P K =[K2O] / ([Li2O]+[Na2O]+[K2O]) is preferably 0.3 or less, more preferably 0.2 or less.

[0137] The parameter S value represented by the following formula is preferably 0.4 or less, more preferably 0.37 or less, further preferably 0.35 or less, and particularly preferably 0.34 or less.

[0138] S=-P Li ×log(P Li )-P Na ×log(P Na )-P K ×log(P K )

[0139] The smaller the S value, the more biased the content of Li₂O, Na₂O, and KO is. The smaller the S value, the more likely the glass's conductivity is to improve and its surface resistivity is to decrease. To facilitate ion exchange, the S value is preferably 0.15 or greater, and more preferably 0.2 or greater.

[0140] MgO, CaO, SrO, BaO, and ZnO are not essential. However, to improve glass stability, the present glass may contain one or more of these substances. When the present glass contains one or more of MgO, CaO, SrO, BaO, and ZnO, the total content ([MgO] + [CaO] + [SrO] + [BaO] + [ZnO]) is preferably 0.1% or more, more preferably 0.2% or more. To maintain a high CS, the total content of these substances is preferably 5% or less, preferably 2% or less, more preferably 1.5% or less, and even more preferably 1% or less.

[0141] The present glass may contain MgO to reduce viscosity during melting, for example. When the present glass contains MgO, the MgO content is preferably 1% or greater, more preferably 2% or greater, and even more preferably 3% or greater. On the other hand, excessive MgO content makes it difficult to increase compressive stress during chemical strengthening. The MgO content is preferably 5% or less, more preferably 4% or less, even more preferably 3% or less, and particularly preferably 2% or less.

[0142] CaO is a component that improves the meltability of glass. The present glass may contain CaO. When the present glass contains CaO, the CaO content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.5% or more. On the other hand, excessive CaO content makes it difficult to increase the compressive stress value during chemical strengthening treatment. The CaO content is preferably 5% or less, more preferably 3% or less, even more preferably 1% or less, and typically 0.5% or less.

[0143] ZnO is a component that improves the meltability of glass. The present glass may contain ZnO. When the present glass contains ZnO, the ZnO content is preferably 0.2% or greater, more preferably 0.5% or greater. To improve the weather resistance of the glass, the ZnO content is preferably 5% or less, more preferably 3% or less, and even more preferably less than 1%.

[0144] ZnO, SrO, and BaO tend to deteriorate chemical strengthening properties. To facilitate chemical strengthening of the glass, the combined content of [ZnO] + [SrO] + [BaO] is preferably 3% or less, more preferably less than 1%, and even more preferably 0.5% or less. It is particularly preferred that ZnO, SrO, and BaO be substantially absent.

[0145] The present glass may not contain ZrO2. On the other hand, from the perspective of increasing the surface compressive stress of chemically strengthened glass, the present glass preferably contains ZrO2. The ZrO2 content is preferably 0.1% or greater, more preferably 0.15% or greater, even more preferably 0.2% or greater, particularly preferably 0.25% or greater, and even more preferably 0.3% or greater. On the other hand, excessive ZrO2 content can easily cause devitrification defects, making it difficult to increase the compressive stress during chemical strengthening. The ZrO2 content is preferably 2% or less, more preferably 1.5% or less, even more preferably 1% or less, and particularly preferably 0.8% or less.

[0146] To increase the fracture toughness value, the present glass preferably contains a total of 0.2% or more of at least one of Y2O3, La2O3, and ZrO2. The combined content of Y2O3, La2O3, and ZrO2 is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 1.5% or more. Furthermore, to lower the liquidus temperature and suppress devitrification, the combined content is preferably 6% or less, more preferably 5% or less, and even more preferably 4% or less.

[0147] In order to lower the devitrification temperature and suppress devitrification, the total content of Y2O3 and La2O3 is preferably greater than the content of ZrO2, and more preferably the content of Y2O3 is greater than the content of ZrO2.

[0148] Y2O3 is not essential, but in order to increase the surface compressive stress of the chemically strengthened glass and reduce the crystal growth rate, the present glass preferably contains Y2O3.

[0149] When the present glass contains Y2O3, the Y2O3 content is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, and particularly preferably 1% or more. On the other hand, if the Y2O3 content is too high, it is difficult to increase the compressive stress value during chemical strengthening treatment. The Y2O3 content is preferably 5% or less, more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1.5% or less.

[0150] La2O3 is not essential, but for the same reasons as Y2O3, the present glass may contain La2O3. When the present glass contains La2O3, the La2O3 content is preferably 0.1% or more, more preferably 0.2% or more, even more preferably 0.5% or more, and particularly preferably 0.8% or more. On the other hand, excessive amounts of La2O3 make it difficult to increase the compressive stress during chemical strengthening. The La2O3 content is preferably 5% or less, more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1.5% or less.

[0151] TiO2 is a component that inhibits the solarization of glass. The present glass may contain TiO2. When the present glass contains TiO2, the TiO2 content is preferably 0.02% or greater, more preferably 0.03% or greater, even more preferably 0.04% or greater, particularly preferably 0.05% or greater, and even more preferably 0.06% or greater. On the other hand, if the TiO2 content exceeds 1%, devitrification is likely to occur, potentially reducing the quality of the chemically strengthened glass. The TiO2 content is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.25% or less.

[0152] B2O3 is not essential, but the present glass may contain B2O3 for the purpose of reducing the brittleness of the glass and improving the crack resistance or for the purpose of improving the meltability of the glass. When the present glass contains B2O3, the content of B2O3 is preferably 0.5% or more, preferably 1% or more, and more preferably 2% or more. On the other hand, when the content of B2O3 is too much, the acid resistance tends to deteriorate. The content of B2O3 is preferably 10% or less. The content of B2O3 is more preferably 6% or less, more preferably 4% or less, and particularly preferably 2% or less. From the viewpoint of preventing the problem of wave streaks during melting, the present glass more preferably does not contain substantially B2O3.

[0153] P2O5 is not essential, but may be included in the present glass to increase the compressive stress during chemical strengthening. When P2O5 is included, the P2O5 content is preferably 0.5% or greater, more preferably 1% or greater, and even more preferably 2% or greater. On the other hand, to improve acid resistance, the P2O5 content is preferably 5% or less, more preferably 4% or less, and even more preferably 2% or less. To prevent striae during melting, the present glass is preferably substantially free of P2O5.

[0154] The total content of B2O3 and P2O5 is preferably 0-10%, more preferably 1% or more, and even more preferably 2% or more. The total content of B2O3 and P2O5 is more preferably 6% or less, and even more preferably 4% or less.

[0155] Nb2O5, Ta2O5, Gd2O3, and CeO2 are components that inhibit the sun exposure of the glass and improve its meltability. The present glass may contain at least one of Nb2O5, Ta2O5, Gd2O3, and CeO2. When the present glass contains these components, the total content is preferably 0.03% or more, more preferably 0.1% or more, further preferably 0.5% or more, particularly preferably 0.8% or more, and further preferably 1% or more. On the other hand, when their content is too high, it is difficult to increase the compressive stress value during chemical strengthening treatment. Therefore, the total content is preferably 3% or less, more preferably 2% or less, further preferably 1% or less, and particularly preferably 0.5% or less.

[0156] Fe2O3 absorbs heat rays and therefore has the effect of improving the solubility of the glass. When large-scale glass production is carried out using large melting furnaces, the present glass preferably contains Fe2O3. In this case, the Fe2O3 content is preferably 0.002% or more, more preferably 0.005% or more, further preferably 0.007% or more, and particularly preferably 0.01% or more, as measured by weight % based on the oxide. On the other hand, excessive Fe2O3 can cause coloration. Therefore, from the perspective of improving the transparency of the glass, its content is preferably 0.3% or less, more preferably 0.04% or less, further preferably 0.025% or less, and particularly preferably 0.015% or less, as measured by weight % based on the oxide.

[0157] It should be noted that while all iron oxides in glass are described here as Fe2O3, in reality, oxidized Fe(III) and reduced Fe(II) are typically present as a mixture. Fe(III) produces a yellow color, while Fe(II) produces a blue color. The balance between the two produces a green color in the glass.

[0158] Furthermore, the present glass may contain coloring components within a range that does not hinder the achievement of the desired chemical strengthening properties. Suitable examples of coloring components include Co₃O₄, MnO₂, NiO, CuO, Cr₂O₃, V₂O₅, Bi₂O₃, SeO₂, CeO₂, Er₂O₃, and Nd₂O₃.

[0159] The total content of coloring components, calculated as a molar percentage based on oxides, is preferably 5% or less. If the content exceeds 5%, the glass may be susceptible to devitrification. The content of coloring components is preferably 3% or less, more preferably 1% or less. If the transmittance of the glass is to be increased, it is preferably substantially free of these components.

[0160] The present glass may contain sulfates, chlorides, fluorides, etc. as appropriate as clarifiers during glass melting. The present glass preferably does not contain As2O3. If the present glass contains Sb2O3, its content is preferably 0.3% or less, more preferably 0.1% or less, and most preferably, it is not contained.

[0161] The fracture toughness value of the present glass is preferably 0.70 MPa·m 1 / 2 More preferably, 0.75 MPa·m 1 / 2 More preferably, 0.80 MPa·m 1 / 2 Above, particularly preferably 0.83 MPa·m 1 / 2 In addition, the fracture toughness value is usually 2.0MPa·m 1 / 2 Below, typically 1.5 MPa·m 1 / 2 Due to the high fracture toughness value, even if a large surface compressive stress is introduced into the glass by chemical strengthening, it is not easy to cause severe breakage.

[0162] The fracture toughness value can be measured using, for example, the DCDC method (Acta Metall. Mater. Vol. 43, pp. 3453-3458, 1995).

[0163] To make the glass resistant to breakage, the Young's modulus of the present glass is preferably 80 GPa or higher, more preferably 82 GPa or higher, even more preferably 84 GPa or higher, and particularly preferably 85 GPa or higher. There is no particular upper limit on the Young's modulus, but a glass with a high Young's modulus may have reduced acid resistance. Therefore, for example, the Young's modulus is preferably 110 GPa or lower, more preferably 100 GPa or lower, and even more preferably 90 GPa or lower. The Young's modulus can be measured, for example, by the ultrasonic pulse method (JIS R1602:1995).

[0164] From the viewpoint of reducing warpage after chemical strengthening, the average linear thermal expansion coefficient (thermal expansion coefficient) of the present glass at 50°C to 350°C is preferably 95×10-7 / ℃ or less, more preferably 90×10 -7 / ℃ or less, more preferably 88×10 -7 / ℃ or less, particularly preferably 86×10 -7 / ℃ or less, and the most preferred is 84×10 -7 / °C or less. There is no particular restriction on the lower limit of the thermal expansion coefficient, but glass with a small thermal expansion coefficient may be difficult to melt. Therefore, the average linear thermal expansion coefficient (thermal expansion coefficient) of the present glass at 50°C to 350°C is preferably, for example, 60×10 -7 / ℃ or more, more preferably 70×10 -7 / ℃ or more, more preferably 74×10 -7 / ℃ or more, more preferably 76×10 -7 / ℃ or above.

[0165] From the perspective 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 perspective of ease of float forming, it 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.

[0166] In the present glass, the temperature of the DSC exothermic peak measured by the following test method is preferably higher than the glass transition temperature by 150°C or more.

[0167] Specifically, about 70 mg of glass was ground using an agate mortar, and the temperature was measured from room temperature to 1200° C. using a differential scanning calorimeter (DSC) at a heating rate of 10° C. / min.

[0168] The DSC exothermic peak temperature is preferably at least 120°C higher than Tg, and even more preferably at least 150°C higher. A DSC exothermic peak temperature above this value reduces the likelihood of crystallization when the glass is heated and formed. This facilitates, for example, 3D molding of the glass. The DSC exothermic peak temperature is typically below (Tg + 300°C), and more preferably below (Tg + 250°C).

[0169] Viscosity reaches 10 2The temperature (T2) at dPa·s is preferably 1750°C or lower, more preferably 1730°C or lower, further preferably 1700°C or lower, particularly preferably 1675°C or lower, and typically 1650°C or lower. Temperature (T2) is a standard temperature that serves as the melting point of glass. The lower T2, the easier it is to manufacture the glass. While there is no particular lower limit for T2, glasses with low T2 tend to have an excessively low glass transition temperature. Therefore, T2 is typically 1400°C or higher, preferably 1450°C or higher.

[0170] In addition, the viscosity reaches 10 4 The temperature (T4) at dPa·s is preferably 1350°C or lower, more preferably 1300°C or lower, even more preferably 1250°C or lower, and particularly preferably 1150°C or lower. Temperature (T4) is a standard temperature for forming glass into a sheet. Glass with a high T4 tends to increase the load on the forming equipment. While there is no particular lower limit for T4, glass with a low T4 tends to have an excessively low glass transition temperature. Therefore, T4 is typically 900°C or higher, preferably 950°C or higher, and more preferably 1000°C or higher.

[0171] When the devitrification temperature of the glass is 4 A temperature (T4) at dPa·s of 120°C or lower is preferred because devitrification is less likely to occur during float forming. The devitrification temperature is more preferably 100°C or lower than T4, even more preferably 50°C or lower than T4, and particularly preferably lower than T4. For example, when T4 is 1230°C, the devitrification temperature is preferably 1350°C or lower, more preferably 1330°C or lower, and even more preferably 1280°C or lower.

[0172] In addition, from the viewpoint of ease of production, the devitrification growth rate of the present glass is preferably 10000 μm / hour or less, more preferably 8000 μm / hour or less. The devitrification growth rate refers to the growth rate of crystals caused by the devitrification phenomenon and can be measured, for example, by the method described in the Examples.

[0173] The softening point of the present glass is preferably below 850°C, more preferably below 820°C, and even more preferably below 790°C. This is because the lower the softening point of the glass, the lower the heat treatment temperature during bending, the lower the energy consumption, and the smaller the load on the equipment. From the viewpoint of reducing the bending temperature, the lower the softening point, the better, but it is usually above 700°C in glass. Glass with an excessively low softening point tends to relax the stress introduced during chemical strengthening treatment and tends to become low in strength, so the softening point is preferably above 700°C. It is more preferably above 720°C, and even more preferably above 740°C. The softening point can be measured by the fiber elongation method described in JIS R3103-1:2001.

[0174] In the present glass, the crystallization peak temperature measured by the following measurement method is preferably higher than the softening point - 100° C. Furthermore, it is more preferable that no crystallization peak is observed.

[0175] Specifically, about 70 mg of glass was pulverized and ground using an agate mortar, and the temperature was measured from room temperature to 1200° C. using a differential scanning calorimeter (DSC) at a heating rate of 10° C. / min.

[0176] In order to reduce the amount of charge on the glass surface, the surface resistivity of the glass at 50°C is preferably 10 15 Ω / sq or less, more preferably 10 14.5 Ω / sq or less, more preferably 10 14 Ω / sq or less. In addition, glass with a small amount of charge tends to have poor devitrification characteristics during production, so the surface resistivity is preferably 10 8 Ω / sq or more, more preferably 10 9 Ω / sq or more. The lower the surface resistivity, the better the conductivity of the glass. The surface resistivity ρ is calculated by forming electrodes on the surface of a glass sheet and measuring the current I and voltage V using R=V / I to obtain the resistance R. The resistance R and the electrode coefficient r are then calculated using ρ=R×r.

[0177] When the present glass is in the form of a plate (glass plate), from the perspective of enhancing the effect of chemical strengthening, the plate thickness (t) is, for example, preferably 2000 μm or less, more preferably 1500 μm or less, further preferably 1000 μm or less, further preferably 900 μm or less, particularly preferably 800 μm or less, and most preferably 700 μm or less. Furthermore, from the perspective of obtaining a sufficient strength-enhancing effect through chemical strengthening treatment, the plate thickness is, for example, preferably 100 μm or more, more preferably 200 μm or more, further preferably 400 μm or more, and further preferably 500 μm or more.

[0178] The present glass may have a shape other than a plate, depending on the intended product, application, and other factors. Furthermore, the glass plate may have a rim with varying thicknesses around the perimeter. Furthermore, the shape of the glass plate is not limited to this. For example, the two principal surfaces may not be parallel to each other, or one or both principal surfaces may be curved, in whole or in part. More specifically, the glass plate may be, for example, a flat plate without warping, or a curved plate with a curved surface.

[0179] The glass according to the embodiments of the present invention can be manufactured by conventional methods. For example, the raw materials of the various glass components are mixed and melted in a glass melting furnace. The glass is then homogenized by known methods, formed into a desired shape such as a glass sheet, and slowly cooled.

[0180] Examples of glass sheet forming methods include the float process, press process, fusion process, and down-draw process. The float process, which is suitable for mass production, is particularly preferred. Continuous forming methods other than the float process, such as the fusion process and down-draw process, are also preferred.

[0181] The formed glass is then ground and polished as needed to form a glass substrate. It should be noted that when cutting a glass substrate into a predetermined shape and size or performing chamfering on the glass substrate, it is preferable to perform the cutting and chamfering before performing the chemical strengthening treatment described below, because the subsequent chemical strengthening treatment also forms a compressive stress layer on the end surface.

[0182] Chemically strengthened glass

[0183] The basic composition of the chemically strengthened glass according to the embodiment of the present invention (hereinafter also simply referred to as the present chemically strengthened glass) is the same as the glass composition of the present glass described above. Figure 1 and Figure 2 This is a diagram showing an example of stress distribution of the chemically strengthened glass. Figure 2 The stress distribution inside the chemically strengthened glass is measured using a scattered light photoelastic stress meter. Note that, here, the interior refers to, for example, a range of 30 μm or more in depth from the surface.

[0184] The surface compressive stress value CS0 of the present chemically strengthened glass is preferably 400 MPa or more, more preferably 600 MPa or more, further preferably 700 MPa or more, further preferably 800 MPa or more, and particularly preferably 850 MPa or more.

[0185] Higher surface compressive stress values increase strength. However, excessively high surface compressive stress can generate large tensile stresses within the chemically strengthened glass, potentially leading to fracture. Therefore, the surface compressive stress value CSO is preferably 1600 MPa or less, and more preferably 1500 MPa or less.

[0186] In the stress distribution of this chemically strengthened glass, the compressive stress value CS at a depth of 50 μm from the surface is 50 It is preferably 90 MPa or more, more preferably 110 MPa or more, further preferably 130 MPa or more, further preferably 140 MPa or more, particularly preferably 150 MPa or more, and most preferably 160 MPa or more. 50 The CS is large, so it is not easy to break when the chemically strengthened glass is damaged by falling from a high place. From the perspective of suppressing the large tensile stress generated inside the chemically strengthened glass and causing fracture, 50 It is preferably 300 MPa or less, more preferably 250 MPa or less, and even more preferably 200 MPa or less.

[0187] In this chemically strengthened glass, the tensile stress value at a depth of half the glass thickness t, i.e., the internal tensile stress value CT, is preferably 70.6 MPa or less, more preferably 62.1 MPa or less, even more preferably 61.8 MPa or less, and even more preferably 56.9 MPa or less. A low CT value reduces breakage. The internal tensile stress value CT is preferably 50 MPa or more, more preferably 53 MPa or more, and even more preferably 55 MPa or more. When the CT value is above these values, the compressive stress near the surface increases, thereby enhancing the strength.

[0188] When the distribution of Na2O concentration in the depth direction from the surface toward the center of the plate thickness is obtained, the depth at which the Na2O concentration of the present chemically strengthened glass reaches a maximum is preferably 0.01t or more.

[0189] The depth at which the Na2O concentration reaches its maximum is preferably 0.025t or greater, more preferably 0.045t or greater, even more preferably 0.055t or greater, and particularly preferably 0.0625t or greater. Furthermore, in the case of a typical thickness, the depth at which the Na2O concentration reaches its maximum is preferably 0.15t or less, more preferably 0.1t or less, and even more preferably 0.08t or less.

[0190] The depth at which the Na2O concentration reaches its maximum is preferably 1 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. To prevent breakage caused by strong impact, it is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 μm to 60 μm.

[0191] When the depth at which the Na2O concentration reaches its maximum is within the above range, it is easy to obtain glass having a large compressive stress inside the glass while suppressing CT.

[0192] The depth at which the Na2O concentration reaches a maximum can be determined by measuring the concentration distribution in the thickness direction of a cross section of chemically strengthened glass using an electron probe microanalyzer (EPMA).

[0193] The hopping frequency of the chemically strengthened glass measured by the following method is preferably 10 2.5 More than 10 3.0 More than 10 3.5 When the frequency hopping is too large, the glass may have poor devitrification characteristics or reduced fracture toughness. The frequency hopping is preferably 10 6.0 Below, more preferably 10 5.5 Below, more preferably 10 5.0 the following.

[0194] (Method for measuring frequency hopping)

[0195] The glass plate was processed into a 50 mm × 50 mm × 0.7 mm plate and a Figure 3 The electrode pattern shown.

[0196] The impedance at 20 MHz to 2 MHz was measured using an impedance analyzer to determine the complex admittance.

[0197] Assume K = -11.214, n1 = 0.995, n2 = 0.576, C∞ = 20.726, and calculate the hopping frequency ωp according to the following formula (13) (Almond-West formula) and the obtained complex admittance.

[0198] It should be noted that the following equation (13) is known as a model formula related to complex admittance Y*(ω) with frequency ω as a variable (Journal of Materials Science, Vol. 19, 1984: pp. 3236-3248).

[0199]

[0200] Here, A1, B1, A2, and B2 are as follows.

[0201]

[0202] The present chemically strengthened glass can be produced by chemically strengthening the present glass described above, followed by washing and drying. Preferred shapes for the present chemically strengthened glass are the same as those for the present glass. For example, it can be a flat glass plate without warping, a curved glass plate with a curved surface, or a shape other than a plate. In producing the present chemically strengthened glass, the chemical strengthening treatment can be performed on a flat glass plate. In the case of a curved glass plate, the chemical strengthening treatment can be performed on the curved glass plate. Furthermore, the chemical strengthening treatment can be performed on glass in shapes other than a plate.

[0203] Chemical strengthening treatment can be carried out by a known method. In the chemical strengthening treatment, the glass sheet is contacted with a melt of a metal salt (such as potassium nitrate) containing a metal ion with a large ionic radius by impregnation or the like. Thus, the metal ions with a small ionic radius in the glass sheet are replaced with metal ions with a large ionic radius. Here, the metal ions with a small ionic radius are typically Na ions or Li ions. The metal ions with a large ionic radius are typically K ions or Na ions, specifically, K ions for Na ions and Na ions or K ions for Li ions.

[0204] Chemical strengthening treatment (ion exchange treatment) can be performed, for example, by immersing the glass sheet in a molten salt such as potassium nitrate heated to 360° C. to 600° C. for 0.1 to 500 hours. The heating temperature of the molten salt is preferably 375° C. to 500° C., and the immersion time of the glass sheet in the molten salt is preferably 0.3 to 200 hours.

[0205] Examples of molten salts used for chemical strengthening include nitrates, sulfates, carbonates, and chlorides. Examples of nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, and silver nitrate. Examples of sulfates include lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, and silver sulfate. Examples of carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of chlorides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, and silver chloride. These molten salts may be used alone or in combination.

[0206] In this embodiment, the chemical strengthening treatment conditions can be appropriately selected in consideration of the properties and composition of the glass, the type of molten salt, and the desired chemical strengthening properties of the resulting chemically strengthened glass, such as the surface compressive stress and the depth of the compressive stress layer.

[0207] In this embodiment, a single chemical strengthening treatment may be performed, or multiple chemical strengthening treatments may be performed under two or more different conditions (multi-step strengthening). For example, as the first step of chemical strengthening, chemical strengthening is performed under conditions of a large DOL and a relatively small CS. Then, as the second step of chemical strengthening, chemical strengthening is performed under conditions of a small DOL and a relatively high CS. This can increase the CS of the outermost surface of the chemically strengthened glass, while simultaneously suppressing the internal tensile stress area (St) and keeping the internal tensile stress (CT) low.

[0208] This glass and this chemically strengthened glass are particularly useful as cover glass for mobile devices such as cell phones, smartphones, personal digital assistants (PDAs), and tablet computers. Furthermore, they are useful as cover glass for non-portable display devices such as televisions (TVs), personal computers (PCs), and touch panels; in applications such as elevator walls, walls of buildings (full-screen displays), window glass, and other building materials; in applications such as desktops, interiors of cars and airplanes, and their cover glass; and in applications such as housings with non-flat curved surfaces obtained through bending or forming.

[0209] Example

[0210] The present invention is illustrated below using examples, but the invention is not limited thereto. Examples 1 to 13, 21 to 37, and 39 are examples of the present glass, while Examples 14 to 20, 38, and 40 are comparative examples. It should be noted that for each measurement result in the table, "-" indicates that no evaluation was performed.

[0211] (Production of Chemically Strengthened Glass)

[0212] According to the glass compositions shown in Tables 1 to 3 in terms of the molar percentage of oxides, a glass plate was produced by melting in a platinum crucible. Commonly used glass raw materials such as oxides, hydroxides, carbonates or nitrates were appropriately selected and weighed to obtain 1000 g of glass. Next, the mixed raw materials were placed in a platinum crucible and melted in a resistance-heated electric furnace at 1500°C to 1700°C for about 3 hours to degas and homogenize. The resulting molten glass was poured into a mold, kept at a temperature of glass transition temperature + 50°C for 1 hour, and then cooled to room temperature at a rate of 0.5°C / min to obtain a glass block. The obtained glass block was cut and ground, and finally both sides were mirror-finished to obtain a plate glass (chemically strengthened glass) with a length of 50 mm × a width of 50 mm × a thickness of 0.8 mm. It should be noted that in Tables 1 to 3, R2O represents the total content of Li2O, K2O and Na2O.

[0213]

[0214]

[0215]

[0216] The physical properties of the obtained chemically strengthened glass were evaluated as follows. The results are shown in Tables 4 to 6. In Tables 4 to 6, the values shown in bold and italics are values estimated based on the glass composition.

[0217] Density (d)

[0218] Density is measured according to the liquid weighing method (JIS Z8807:2012 Solids - Determination of density and specific gravity). The unit is g / cm 3 .

[0219] Young's modulus

[0220] The Young's modulus (G) (unit: GPa) was measured by an ultrasonic pulse method (JIS R1602: 1995).

[0221] <Average Linear Thermal Expansion Coefficient α and Glass Transition Temperature (Tg)>

[0222] Average linear expansion coefficient (α) at temperatures of 50°C to 350°C (unit: 10 -7 The average linear expansion coefficient of glass (° C.) and the glass transition temperature (° C.) were measured in accordance with JIS R3102:1995 "Test method for average linear expansion coefficient of glass".

[0223] <T2, T4>

[0224] The viscosity was measured using a rotational viscometer (based on ASTM C 965-96) to a value of 10 2 dPa·s when the temperature T2 (℃) and viscosity reach 10 4 Temperature T4 (℃) at dPa·s.

[0225] Devitrification growth rate

[0226] The growth rate of crystals caused by devitrification was measured according to the following procedure.

[0227] The glass pieces were crushed and classified in a mortar, and the glass particles that passed a sieve with a mesh size of 3.35 mm and did not pass a sieve with a mesh size of 2.36 mm were washed with ion-exchanged water and dried before use in the test.

[0228] A glass particle is placed in each recess of an elongated platinum pool having multiple recesses, maintained at above 1350°C for more than 15 minutes, then taken out of the furnace and heated in an electric furnace at 700°C to 1300°C until the surface of the glass particle melts and becomes smooth.

[0229] Next, the glass is placed in a temperature gradient furnace maintained at a predetermined temperature and heat treated for a predetermined time (denoted as w). The glass is then taken out of the furnace and rapidly cooled to room temperature. This method allows for simultaneous heating of multiple glass particles by placing a long, narrow container within the temperature gradient furnace.

[0230] The heat-treated glass was observed using a polarizing microscope (Nikon Corporation: ECLIPSE LV100ND), and the diameter of the largest crystal among the observed crystals was measured (L μm). Observation was performed using a 10x eyepiece, a 5x to 100x objective, and both transmitted light and polarized light. Since crystals resulting from devitrification are believed to grow isotropically, the devitrification (crystal) growth rate is (L / 2) / w [unit: μm / hour].

[0231] The crystals to be measured are those that do not precipitate from the interface with the container. This is because the devitrification growth at the metal interface has a different tendency from the normal devitrification growth behavior occurring inside the glass or at the glass-atmosphere interface.

[0232] Devitrification temperature

[0233] The crushed glass particles were placed in a platinum dish and heat-treated for 17 hours in an electric furnace controlled at a constant temperature. The heat-treated glass was observed using a polarizing microscope, and the devitrification temperature was estimated by evaluating the presence of devitrification. For example, in the table, "1000°C-1025°C" indicates that devitrification occurred when heat-treated at 1000°C but not at 1025°C. In this case, the devitrification temperature is 1000°C or higher and less than 1025°C.

[0234] <DSC peak temperature>

[0235] The DSC peak temperature (°C) was measured by pulverizing approximately 70 mg of glass and grinding it in an agate mortar from room temperature to 1200°C using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min.

[0236] <CS0(Na),CS 50 (Na), CS 90 (Na), DOL (Na)>

[0237] Glass having a thickness of 700 μm was chemically strengthened by immersing it in NaNO 3 at 380° C. for 4 hours.

[0238] The surface compressive stress (value) (CS, DOL) of the obtained chemically strengthened glass was measured using a surface stress meter (FSM-6000 manufactured by Orihara Seisakusho Co., Ltd.). The internal CS and DOL were measured using a scattered light photoelastic stress meter (SLP-1000 manufactured by Orihara Seisakusho Co., Ltd.). 50 (Na), CS 90 (Na) and DOL (Na) are shown in the table.

[0239] <CS0(K), DOL(K)>

[0240] A glass sheet with a thickness of 700 μm was chemically strengthened by immersing it in KNO 3 at 380° C. for 4 hours.

[0241] The obtained chemically strengthened glass was measured for CS and DOL in the same manner as in the case of strengthening with NaNO 3. The CS0(K) and DOL(K) of each glass are shown in the table.

[0242]

[0243]

[0244]

[0245] Chemically Strengthened Properties

[0246] The glass of Example 9 was subjected to two-step chemical strengthening as follows. Specifically, as the first chemical strengthening treatment, the glass was immersed in a molten salt containing 70% by weight of KNO3 and 30% by weight of NaNO3 at 380°C for 90 minutes. Furthermore, as the second strengthening treatment, the glass was immersed in a molten salt containing 99% by weight of KNO3 and 1% by weight of LiNO3 at 380°C for 40 minutes.

[0247] The compressive stress value of the surface layer of the obtained chemically strengthened glass was measured using a surface stress meter (FSM-6000), and the CS and DOL of the interior were measured using a scattered light photoelastic stress meter (SLP-1000).

[0248] The CS0 of the obtained chemically strengthened glass is 818 MPa, CS 50 The K ion exchange depth was 3.3 μm and the DOL was 104 μm.

[0249] exist Figure 1The stress distribution of the obtained chemically strengthened glass is shown in FIG. Figure 2 The stress distribution inside the chemically strengthened glass measured using a scattered light photoelastic stress meter (SLP-1000) is shown. Note that the interior here refers to a range of 30 μm or more in depth from the surface.

[0250] according to Figure 2 The peak of the compressive stress caused by the diffusion of Na ions can be confirmed at a depth of approximately 33 μm from the surface of the glass. This suggests that since the depth at which the Na₂O concentration reaches its maximum is greater than 1 μm, the depth at which the Na₂O concentration reaches its maximum is also greater than 1 μm when the Na₂O concentration distribution in the depth direction from the surface of the present glass toward the center of the thickness is taken.

[0251] The parameter M of the glass of the embodiment is within the preferred range, so the value of DOL(Na) / DOL(K) is small. Therefore, the diffusion rate of potassium ions during chemical strengthening is relatively large compared to the diffusion rate of sodium ions. Therefore, the glass of the embodiment is obtained by a relatively simple strengthening process. Figure 1 The chemically strengthened glass shown has large DOL and CS in the compressive stress layer due to diffusion of Na ions at a depth of 50 μm from the surface and in the compressive stress layer due to diffusion of K ions in the surface layer, and has suppressed CT.

[0252] On the other hand, the glass of the comparative example has a large DOL(Na) / DOL(K) value, similar to conventional glass. Therefore, it is thought that it is difficult to obtain the complex stress distribution described above through simple strengthening treatment. Alternatively, the glass of the comparative example does not contain sufficient amounts of Li and Al to obtain compressive stress in the interior and surface layers, resulting in low compressive stress.

[0253] Although the present invention has been described in detail and with reference to specific embodiments, it is apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the present invention. This application is based on Japanese patent application (Japanese Patent Application No. 2020-119445) filed on July 10, 2020, the contents of which are incorporated herein by reference.

Claims

1. A lithium aluminosilicate glass, wherein: Calculated in mole percentage based on oxides, the lithium aluminosilicate glass contains: 56% to 70% SiO2, Al2O3 below 21%, Li2O below 16%, 0% to 2.5% Na2O, 0.1% to 3% K2O, 0% to 10% B2O3, 0% to 5% P2O5, Less than 5% CaO, 0% to 5% ZnO, 0% to 2% ZrO2, 0% to 5% Y2O3, and Less than 0.5% TiO2, and The content of Na2O is greater than that of K2O. The parameter M obtained from the contents of SiO2, Al2O3, Li2O, Na2O, K2O, B2O3, P2O5, MgO, ZnO, ZrO2, and Y2O3 in mol% [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3] according to the following formula is 2 or more and 20 or less, M=-1.15×[SiO2]-1.73×[Al2O3]+0.155×[Li2O]+0.74×[Na2O]-4.75×[K2O]-2.1× [B2O3]-2.17×[P2O5]+3.25×[MgO]-2.0×[ZnO]-13.3×[ZrO2]-0.80×[Y2O3]+120, P is represented by the following formula K The value is below 0.14, P K =[K2O] / ([Li2O]+[Na2O]+[K2O]) Here, [Li2O], [Na2O], and [K2O] represent the contents of Li2O, Na2O, and K2O in mole percentage, respectively.

2. The lithium aluminosilicate glass according to claim 1, wherein The value of S represented by the following formula is 0.37 or less, S=-P Li ×log(P Li )-P Na ×log(P Na )-P K ×log(P K ) Here, P Li =[Li2O] / ([Li2O]+[Na2O]+[K2O]) P Na =[Na2O] / ([Li2O]+[Na2O]+[K2O]) P K =[K2O] / ([Li2O]+[Na2O]+[K2O]) Here, [Li2O], [Na2O], and [K2O] represent the contents of Li2O, Na2O, and K2O in mole percentage, respectively.

3. The lithium aluminosilicate glass according to claim 1 or 2, wherein: P is represented by the following formula Na The value is 0.16 or above, P Na =[Na2O] / ([Li2O]+[Na2O]+[K2O]) Here, [Li2O], [Na2O], and [K2O] represent the contents of Li2O, Na2O, and K2O in mole percentage, respectively.

4. The lithium aluminosilicate glass according to claim 1 or 2, wherein: The parameter D obtained from the following formula of [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3] is 1200 or more. D=-943×[SiO2]-859×[Al2O3]-998×[Li2O]-991×[Na2O]-1013×[K2O]-949×[B 2O3]-941×[P2O5]-687×[MgO]-956×[ZnO]-1516×[ZrO2]-823×[Y2O3]+95174.

5. The lithium aluminosilicate glass according to claim 1 or 2, wherein: The parameter E obtained from the following formula of [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3] is 800 or less. E=539×[SiO2]+527×[Al2O3]+587×[Li2O]+467×[Na2O]+578×[K2O]+510×[B 2O3]+516×[P2O5]+442×[MgO]+502×[ZnO]+850×[ZrO2]+546×[Y2O3]-53476.

6. The lithium aluminosilicate glass according to claim 1 or 2, wherein: When the glass having a thickness of 700 μm is immersed in NaNO 3 at 380° C. for 4 hours, the surface compressive stress value CS0(Na) generated is 500 MPa or more. When the glass having a thickness of 700 μm is immersed in KNO 3 at 380° C. for 4 hours, the surface compressive stress value CS0(K) generated is 1200 MPa or more. When the glass having a thickness of 700 μm is immersed in KNO3 at 380°C for 4 hours, the depth of the compressive stress layer DOL(K) generated is 3 μm or more, and When the glass having a thickness of 700 μm is immersed in NaNO 3 at 380° C. for 4 hours, the ratio DOL(Na) / DOL(K) of the depth of the compressive stress layer generated to DOL(K) is 11.8 or less.

7. The lithium aluminosilicate glass according to claim 6, wherein: The compressive stress value CS at a depth of 50 μm from the surface generated when the glass with a thickness of 700 μm was immersed in NaNO3 at 380°C for 4 hours was 50 (Na) is 170 MPa or more.

8. The lithium aluminosilicate glass according to claim 1 or 2, wherein: The devitrification temperature of the lithium aluminosilicate glass is 1350° C. or lower.

9. The lithium aluminosilicate glass according to claim 1 or 2, wherein: The viscosity of the lithium aluminosilicate glass reaches 10 2 The temperature T2 at dPa·s is 1750° C. or lower.

10. The lithium aluminosilicate glass according to claim 1 or 2, wherein: The temperature of the DSC exothermic peak measured by the following test method is 150°C higher than the glass transition temperature. (Test method) 70 mg of glass was pulverized and ground using an agate mortar, and the temperature was measured from room temperature to 1200° C. using a differential scanning calorimeter (DSC) at a heating rate of 10° C. / min.

11. A chemically strengthened glass having a surface compressive stress value of 400 MPa or more, wherein: The chemically strengthened glass is lithium aluminosilicate glass, When the Na2O concentration distribution is obtained in the depth direction from the surface to the center of the plate thickness, the depth where the Na2O concentration reaches the maximum is 1 μm or more, and The basic composition of the chemically strengthened glass comprises, in terms of molar percentage based on oxides: 56% to 70% SiO2, Al2O3 below 21%, Li2O below 16%, 0% to 2.5% Na2O, 0.1% to 3% K2O, 0% to 10% B2O3, 0% to 5% P2O5, Less than 5% CaO, 0% to 5% ZnO, 0% to 2% ZrO2, 0% to 5% Y2O3, and Less than 0.5% TiO2, and The content of Na2O is greater than that of K2O. The parameter M obtained from the contents of SiO2, Al2O3, Li2O, Na2O, K2O, B2O3, P2O5, MgO, ZnO, ZrO2, and Y2O3 in mol% [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3] according to the following formula is 2 or more and 20 or less, M=-1.15×[SiO2]-1.73×[Al2O3]+0.155×[Li2O]+0.74×[Na2O]-4.75×[K2O]-2.1× [B2O3]-2.17×[P2O5]+3.25×[MgO]-2.0×[ZnO]-13.3×[ZrO2]-0.80×[Y2O3]+120, P is represented by the following formula K The value is below 0.14, P K =[K2O] / ([Li2O]+[Na2O]+[K2O]) Here, [Li2O], [Na2O], and [K2O] represent the contents of Li2O, Na2O, and K2O in mole percentage, respectively.

12. The chemically strengthened glass according to claim 11, wherein The value of S represented by the following formula is 0.37 or less, S=-P Li ×log(P Li )-P Na ×log(P Na )-P K ×log(P K ) Here, P Li =[Li2O] / ([Li2O]+[Na2O]+[K2O]) P Na =[Na2O] / ([Li2O]+[Na2O]+[K2O]) P K =[K2O] / ([Li2O]+[Na2O]+[K2O]) Here, [Li2O], [Na2O], and [K2O] represent the contents of Li2O, Na2O, and K2O in mole percentage, respectively.

13. The chemically strengthened glass according to claim 11 or 12, wherein: P is represented by the following formula Na The value is 0.16 or above, P Na =[Na2O] / ([Li2O]+[Na2O]+[K2O]) Here, [Li2O], [Na2O], and [K2O] represent the contents of Li2O, Na2O, and K2O in mole percentage, respectively.

14. The chemically strengthened glass according to claim 11 or 12, wherein The parameter D obtained from the following formula of [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3] is 1200 or more. D=-943×[SiO2]-859×[Al2O3]-998×[Li2O]-991×[Na2O]-1013×[K2O]-949×[B 2O3]-941×[P2O5]-687×[MgO]-956×[ZnO]-1516×[ZrO2]-823×[Y2O3]+95174.

15. The chemically strengthened glass according to claim 11 or 12, wherein The parameter E obtained from the following formula of [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3] is 800 or less. E=539×[SiO2]+527×[Al2O3]+587×[Li2O]+467×[Na2O]+578×[K2O]+510×[B 2O3]+516×[P2O5]+442×[MgO]+502×[ZnO]+850×[ZrO2]+546×[Y2O3]-53476.

16. The chemically strengthened glass according to claim 11 or 12, wherein: When the glass having a thickness of 700 μm is immersed in NaNO 3 at 380° C. for 4 hours, the surface compressive stress value CS0(Na) generated is 500 MPa or more. When the glass having a thickness of 700 μm is immersed in KNO 3 at 380° C. for 4 hours, the surface compressive stress value CS0(K) generated is 1200 MPa or more. When the glass having a thickness of 700 μm is immersed in KNO3 at 380°C for 4 hours, the depth of the compressive stress layer DOL(K) generated is 3 μm or more, and When the glass having a thickness of 700 μm is immersed in NaNO 3 at 380° C. for 4 hours, the ratio DOL(Na) / DOL(K) of the depth of the compressive stress layer generated to DOL(K) is 11.8 or less.

17. The chemically strengthened glass according to claim 11 or 12, wherein: The compressive stress value CS of the chemically strengthened glass at a depth of 50 μm from the surface is 50 Above 90MPa.

18. The chemically strengthened glass according to claim 11 or 12, wherein The chemically strengthened glass has an internal tensile stress value CT of 70.6 MPa or less.

19. The chemically strengthened glass according to claim 11 or 12, wherein The surface compressive stress value CS0 of the chemically strengthened glass is greater than or equal to 800 MPa.

20. The chemically strengthened glass according to claim 11 or 12, wherein The frequency hopping of the chemically strengthened glass is 10 2.5 above.

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