Glass and chemically strengthened glass

Abstract

The present invention pertains to a glass having a specific composition range and a parameter M of 20 or less which is obtained from equation. 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

Description

[Technical Field]

[0001] The present invention relates to glass and chemically strengthened glass. [Background technology]

[0002] BACKGROUND ART In recent years, cover glasses made of chemically strengthened glass have been used for the purpose of protecting display devices such as mobile phones, smartphones, and tablet terminals and improving their appearance.

[0003] In chemically strengthened glass, the strength tends to increase as the surface compressive stress (CS) and depth of compressive stress layer (DOL) increase. However, internal tensile stress (CT) occurs within the glass to maintain a balance with the surface compressive stress, so the greater the CS and DOL, the greater the CT. When glass with a high CT breaks, it breaks into more fragments, increasing the risk of the fragments scattering.

[0004] Patent Document 1 describes that a two-stage chemical strengthening treatment can form a stress profile represented by a bent line, thereby suppressing internal tensile stress (CT) while increasing surface compressive stress (CS).

[0005] Furthermore, Patent Document 2 discloses lithium aluminosilicate glass that can obtain a relatively large surface compressive stress and compressive stress layer depth through a two-stage chemical strengthening treatment. The lithium aluminosilicate glass can increase both CS and DOL while suppressing CT through a two-stage chemical strengthening treatment using sodium salts and potassium salts. The two-stage strengthening process generally combines a process in which sodium ions, which have a relatively small ionic radius, are exchanged with lithium ions in the glass to form a deep compressive stress layer with a relatively small surface compressive stress value, and a process in which potassium ions, which have a relatively large ionic radius, are exchanged with sodium ions in the glass to form a large compressive stress near the surface.

[0006] Patent Document 3 describes that a more complex stress profile can be formed by three-stage chemical strengthening. In addition to the typical two-stage chemical strengthening, this method involves a process of pulling back the large ionic radius alkali ions in the glass by ion exchange with alkali ions with a small ionic radius, or a process of relaxing the stress generated in the glass by heat treatment, thereby attempting to reduce the internal tensile stress CT while further increasing CS and DOL. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] US Patent Application Publication No. 2015 / 0259244 [Patent Document 2] Japan Special Publication No. 2013-520388 [Patent Document 3] Japan Special Publication No. 2019-517985 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the three-stage tempering process is complicated. The present invention aims to provide glass that can be obtained by a relatively simple tempering process, with chemically tempered glass having large CS and DOL and suppressed CT. Another object of the present invention is to provide chemically tempered glass that can be obtained by a relatively simple tempering process, with large CS and DOL and suppressed CT. [Means for solving the problem]

[0009] Potassium ions, which have a large ionic radius, diffuse more slowly in glass than sodium ions, which have a small ionic radius. Therefore, ion exchange treatment using potassium ions generally results in a smaller DOL. However, the inventors discovered that adjusting the glass composition can sometimes increase the diffusion rate of potassium ions relative to that of sodium ions. When ion exchange treatment is performed using glass with such a composition, a stress profile different from conventional ones can be formed. This led to the completion of the present invention, based on the idea that a relatively simple two-step tempering process can be used to obtain a more complex stress profile with larger CS and DOL and reduced CT than conventional ones.

[0010] The present invention provides, in terms of mole percentage based on oxides: SiO2 52-70%, Al2O3 14-25%, Li2O 10-18%, Na2O 1-7%, K2O 0.1 to 5%, B2O3 0-10% P2O5 0-5%, MgO 0-5% ZnO 0-5%, ZrO2 0-2%, Contains 0-5% Y2O3 Provided is glass in which the parameter M, calculated from the contents of SiO2, Al2O3, Li2O, Na2O, K2O, B2O3, P2O5, MgO, ZnO, ZrO2, and Y2O3 expressed in mole percent, [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3], is 20 or less according to the following formula: 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

[0011] In the glass of the present invention, it is preferable that the parameter D, calculated from [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3] using the following formula, is 1200 or more. D=-943×[SiO2]-859×[Al2O3]-998×[Li2O]-991×[Na2O]-1013×[K2O]-949×[ B2O3]-941×[P2O5]-687×[MgO]-956×[ZnO]-1516×[ZrO2]-823×[Y2O3]+95174

[0012] In the glass of the present invention, it is preferable that the parameter E, calculated from [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3] using the following formula, is 500 or more. 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

[0013] The present invention provides a glass comprising, in mole percentage on an oxide basis: SiO2 52-70%, Al2O3 14-25%, Li2O 10-18%, Na2O 1-7%, Contains 0.1 to 5% K2O, the surface compressive stress value CSO(Na) generated when the glass having a plate thickness of 700 μm is immersed in NaNO at 380° C. for 4 hours is 500 MPa or more, the surface compressive stress value CSO(K) generated when the glass having a plate thickness of 700 μm is immersed in KNO3 at 380 ° C for 4 hours is 1200 MPa or more, the compressive stress layer depth DOL (K) generated when the glass having a plate thickness of 700 μm is immersed in KNO at 380 ° C for 4 hours is 3 μm or more; The ratio of the compressive stress layer depth DOL(Na) that occurs when the above glass with a thickness of 700 μm is immersed in NaNO3 at 380 °C for 4 hours to the above DOL(K). Provided is a glass having a DOL(Na) / DOL(K) ratio of 35 or less.

[0014] The glass of the present invention has a compressive stress value CS at a depth of 50 μm from the surface, which is generated when the glass having a thickness of 700 μm is immersed in NaNO3 at 380° C. for 4 hours. 50 (Na) is preferably 170 MPa or more.

[0015] The glass of the present invention preferably has a devitrification temperature of 1350° C. or lower. The glass of the present invention has a viscosity of 10 2 The temperature T2 at which dPa·s is reached is preferably 1750°C or lower. The glass of the present invention preferably has a DSC exothermic peak temperature measured by the following test method that is 150° C. or more higher than the glass transition point. (Test Method) Approximately 70 mg of glass is crushed and ground in an agate mortar, and the temperature is measured using a differential scanning calorimeter (DSC) from room temperature to 1200°C at a heating rate of 10°C / min.

[0016] In the glass of the present invention, the value of S, represented by the following formula, is preferably 0.4 or less. S=-P Li ×log(P Li )-P Na ×log(P Na )-P K ×log(P K ) Here, P Li =[LiO] / ([LiO]+[NaO]+[KO]) P Na =[Na2O] / ([Li2O]+[Na2O]+[K2O]) P K =[KO] / ([LiO]+[NaO]+[KO]) Here, [Li2O], [Na2O], and [K2O] represent the contents of Li2O, Na2O, and K2O, respectively, expressed as mole percentages.

[0017] The present invention provides chemically strengthened glass having a surface compressive stress value of 400 MPa or more, When the Na2O concentration profile is taken in the depth direction from the surface to the center of the plate thickness, the depth at which the Na2O concentration is maximum is 1 μm or more, The base composition of the chemically strengthened glass is expressed as mole percentage based on oxides. SiO2 52-70%, Al2O3 14-25%, Li2O 10-18%, Na2O 1-7%, A chemically strengthened glass containing 0.1 to 5% K2O is provided.

[0018] The chemically strengthened glass of the present invention has a compressive stress value CS at a depth of 50 μm from the surface 50 It is preferable that the compressive strength is 90 MPa or more. The chemically strengthened glass of the present invention preferably has an internal tensile stress value CT of 70.6 MPa or less. The chemically strengthened glass of the present invention preferably has a surface compressive stress value CSO of 800 MPa or more. The chemically strengthened glass of the present invention has a hopping frequency of 10 2.5 It is preferable that this is equal to or greater than this. [Effects of the Invention]

[0019] According to the present invention, a chemically strengthened glass having a complex stress profile with large CS and DOL and suppressed CT can be obtained by a relatively simple strengthening treatment. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing an example of a stress profile of chemically strengthened glass according to an embodiment of the present invention. [Figure 2]FIG. 2 is a diagram showing an example of a stress profile of chemically strengthened glass according to an embodiment of the present invention. [Figure 3] FIG. 3 shows the electrode pattern used to measure the hopping frequency. DETAILED DESCRIPTION OF THE INVENTION

[0021] Glass according to an embodiment of the present invention will be described in detail below, but the present invention is not limited to the following embodiment and can be practiced with any modifications within the scope of the gist of the present invention.

[0022] 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.

[0023] In this specification, the glass composition of chemically strengthened glass may be referred to as the matrix 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 coincides with the matrix composition of chemically strengthened glass. In chemically strengthened glass, except in cases where extreme ion exchange treatment has been performed, the glass composition at a depth of 1 / 2 the plate thickness t is the matrix composition of chemically strengthened glass.

[0024] In this specification, glass compositions are expressed in mole percentages based on oxides, and mole % may be simply referred to as %. Furthermore, the symbol "to" indicating a range of values is used to mean that the values before and after it are included as the lower and upper limits.

[0025] In the glass composition, "substantially free" means that no components are contained except for unavoidable impurities contained in raw materials, etc., that is, that no components are intentionally contained. Specifically, the content of components other than coloring components is, for example, less than 0.1 mol %.

[0026] In this specification, the term "stress profile" refers to a pattern that expresses compressive stress values as a function of depth from the glass surface. A negative compressive stress value indicates tensile stress. In this specification, the property of glass to easily scatter fragments when broken is sometimes referred to as "friable." In this specification, the "stress profile" can be measured by a method using a combination of an optical waveguide surface stress meter and a scattered light photoelastic stress meter, or by a method using a scattered light photoelastic stress meter.

[0027] Optical waveguide surface stress meters are known to be able to accurately measure the stress in glass in a short time. One example of an optical waveguide surface stress meter is the FSM-6000 manufactured by Orihara Seisakusho Co., Ltd. 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 in 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.

[0028] The method using a scattered light photoelastic stress meter can measure stress regardless of refractive index distribution. Examples of scattered light photoelastic stress meters include the SLP-1000 and SLP-2000 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. Accurate stress measurement is possible by combining two types of measuring devices.

[0029] <Glass> The glass according to an embodiment of the present invention (hereinafter sometimes referred to as "the present glass") is easily chemically strengthened because the K ion diffusion depth due to ion exchange between K ions penetrating from the glass surface and Na ions in the glass is relatively deep. In addition, the present glass is suitable as a glass for chemical strengthening because an appropriate stress profile can be easily obtained.

[0030] The surface compressive stress value CSO(Na) generated when the present glass having a 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, even more preferably 550 MPa or more, and particularly preferably 600 MPa or more. CSO(Na) of the above value or more facilitates a sufficiently large compressive stress when the present glass is subjected to a tempering treatment using sodium ions. CSO(Na) is preferably 1000 MPa or less, more preferably 800 MPa or less, to prevent severe fracture. Here, "the present glass having a thickness of 700 μm" means "the present glass when the thickness is 700 μm." In other words, this description does not limit the shape or thickness of the present glass in any way. Specific preferred shapes and thicknesses of the present glass will be described in detail later.

[0031] The surface compressive stress CSO(K) generated when a 700 μm thick sheet of this glass is immersed in KNO3 at 380°C for 4 hours is preferably 1200 MPa or more, more preferably 1230 MPa or more, and even more preferably 1250 MPa or more. Having a CSO(K) of at least this value makes it easier to increase the compressive stress sufficiently when the glass is subjected to a tempering treatment using potassium ions. To prevent severe fracture, CSO(K) is preferably 1800 MPa or less, more preferably 1600 MPa or less.

[0032] The compressive stress layer depth DOL(K) generated when a 700 μm-thick glass plate 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. Having a DOL(K) of at least the above value facilitates sufficient diffusion of potassium ions during chemical strengthening of the glass. From the viewpoint of ease of stress profile design, DOL(K) is preferably 18 μm or less, more preferably 16 μm or less.

[0033] The ratio DOL(Na) / DOL(K), which is the depth of the compressive stress layer DOL(Na) generated when a 700 μm-thick glass plate is immersed in NaNO3 at 380°C for 4 hours, to the DOL(K), is preferably 35 or less, more preferably 30 or less, even more preferably 25 or less, even more preferably 20 or less, particularly preferably 18 or less, even more particularly preferably 17 or less, even more preferably 16 or less, and most preferably 15 or less. When DOL(Na) / DOL(K) is equal to or less than the above value, the diffusion rate of potassium ions relative to the diffusion rate of sodium ions during chemical strengthening is relatively large, resulting in a good balance, making it easier to obtain a complex stress profile. 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.

[0034] The compressive stress value CS at a depth of 50 μm from the surface that occurs when a 700 μm thick sheet of glass is immersed in NaNO3 at 380°C for 4 hours. 50 (Na) is preferably 170 MPa or more, more preferably 190 MPa or more, and even more preferably 200 MPa or more. 50 By ensuring that the (Na) content is within the above range, the compressive stress inside the glass can be increased when the glass is chemically strengthened, making it easier to improve the strength. 50 In order to prevent severe destruction, (Na) is preferably 500 MPa or less, more preferably 400 MPa or less.

[0035] The compressive stress value CS at a depth of 90 μm from the surface that occurs when a 700 μm thick sheet of glass is immersed in NaNO3 at 380°C for 4 hours. 90 (Na) is preferably 0 MPa or more, more preferably 0.5 MPa or more, even more preferably 5 MPa or more, even more preferably 10 MPa or more, and particularly preferably 15 MPa or more. 90 By ensuring that the (Na) content is within the above range, the compressive stress inside the glass can be increased when the glass is chemically strengthened, making it easier to improve the strength. 90 In order to prevent severe destruction, (Na) is preferably 200 MPa or less, more preferably 150 MPa or less, and even more preferably 100 MPa or less.

[0036] The glass is a lithium aluminosilicate glass. Specifically, this glass has the following oxide-based mole percentages: SiO2 52-70%, Al2O3 14-25%, It is preferable that the content of Li2O is 10 to 18%.

[0037] In addition, this glass is Na2O 1-7%, K2O 0.1 to 5%, B2O3 0-10% P2O5 0-5%, MgO 0-5% ZnO 0-5%, ZrO2 0-2%, It is preferable that the content of Y2O3 is 0 to 5%.

[0038] In the present glass, the parameter M, calculated by the following formula from the contents, expressed as mole percentages, of SiO2, Al2O3, Li2O, Na2O, K2O, B2O3, P2O5, MgO, ZnO, ZrO2, and Y2O3, [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3], is preferably 20 or less. The value of M is more preferably 18 or less, even more preferably 17 or less, particularly preferably 16 or less, even more particularly preferably 15 or less, even more preferably 13 or less, and most preferably 11 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 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 in the above range, the ratio of the diffusion rate of Na ions to the diffusion rate of K ions tends to be small. The value of the parameter M is related to the compressive stress value CS at a depth of 50 μm from the surface. 50 To increase the value, it is preferably 2 or more, more preferably 5 or more, and even more preferably 7 or more.

[0039] Furthermore, since the present glass has the above-described preferred composition range and the parameter M is 20 or less, it 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 an appropriate range. This makes it easy to obtain chemically strengthened glass with large CS and DOL and suppressed CT through a relatively simple strengthening treatment.

[0040] Furthermore, the parameter D calculated by the following formula is preferably 1200 or more. The value of D is more preferably 1230 or more, even more preferably 1250 or more, particularly preferably 1300 or more, even more preferably 1350 or more, and most preferably 1450 or more. D=-943×[SiO2]-859×[Al2O3]-998×[Li2O]-991×[Na2O]-1013×[K2O]-949×[ B2O3]-941×[P2O5]-687×[MgO]-956×[ZnO]-1516×[ZrO2]-823×[Y2O3]+95174 D is a parameter related to the compressive stress value due to the diffusion of K ions. When the value of D is within the above range, the diffusion rate of K ions tends to be high. In order to reduce CT, the value of D is preferably 1950 or less, more preferably 1800 or less, and even more preferably 1600 or less.

[0041] The parameter E, calculated from [SiO2], [Al2O3], [Li2O], [Na2O], [K2O], [B2O3], [P2O5], [MgO], [ZnO], [ZrO2], and [Y2O3] using the following formula, is preferably 500 or more. The value of parameter E is more preferably 520 or more, even more preferably 550 or more, particularly preferably 570 or more, even more preferably 600 or more, and most preferably 650 or more. E = 539 × [SiO2] + 527 × [Al2O3] + 587 × [Li2O] + 467 × [Na2O] + 578 × [K2O] + 510 × [B2O3] + 516 × [P2O5] + 442 × [MgO] + 502 × [ZnO] + 850 × [ZrO2] + 546 × [Y2O3] - 53476 E is a parameter related to the compressive stress value due to the diffusion of Na ions. When the value of E is within the above range, the diffusion rate of Na ions tends to be slow. In order to reduce CT, the value of E is preferably 1000 or less, and more preferably 800 or less.

[0042] A preferred glass composition will now be described.

[0043] SiO2 is a component that makes up the network of glass. SiO2 also increases chemical durability and reduces the occurrence of cracks when the glass surface is scratched. To improve chemical durability, the SiO content is preferably 52% or more, more preferably 56% or more, even more preferably 60% or more, even more preferably 63% or more, and particularly preferably 65% or more. To improve meltability during glass production, the SiO content is preferably 70% or less, more preferably 68% or less, and even more preferably 65% or less.

[0044] Al2O3 is an effective component from the viewpoint of improving the ion exchange performance during chemical strengthening and increasing the surface compressive stress after strengthening. 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, in order to improve chemical durability and chemical strengthening properties. On the other hand, if the Al2O3 content is too high, crystals may easily grow during melting. To prevent a decrease in yield due to devitrification defects, the Al2O3 content is preferably 25% or less, more preferably 23% or less, and even more preferably 21% or less.

[0045] Both SiO2 and Al2O3 are components that stabilize the glass structure. 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. Both SiO2 and Al2O3 tend to increase the melting temperature of glass, so in order to make glass more easily meltable, the total content of SiO2 and Al2O3 is preferably 90% or less, more preferably 87% or less, even more preferably 85% or less, and particularly preferably 82% or less.

[0046] Li2O is a component that forms surface compressive stress through ion exchange and improves the meltability of glass. When chemically strengthened glass (glass for chemical strengthening) contains Li2O, the Li ions on the glass surface are ion-exchanged with Na ions, and then the Na ions are ion-exchanged with K ions, resulting in a large stress profile for both the surface compressive stress and the compressive stress layer.

[0047] In order to increase the surface compressive stress during chemical strengthening, the Li2O content is preferably 10% or more, more preferably 11% or more, even more preferably 13% or more, and particularly preferably 15% or more. On the other hand, if the Li2O content is too high, the crystal growth rate during glass molding increases, which can exacerbate the problem of reduced yield due to devitrification defects. To suppress devitrification during the glass manufacturing process, the Li2O content is preferably 18% or less, more preferably 16% or less, even more preferably 14% or less, and particularly preferably 12% or less.

[0048] Although neither Na2O nor K2O is essential, they are components that improve the meltability of the glass and reduce the crystal growth rate of the glass. In order to improve the ion exchange performance, the present glass preferably contains at least one of Na2O and K2O.

[0049] Na2O is a component that forms a surface compressive stress layer in a chemical strengthening treatment using a potassium salt and can also improve the meltability of glass. To achieve this effect, the Na2O content is preferably 1% or more, more preferably 2% or more, and even more preferably 3% or more. On the other hand, if the Na2O content is too high, it becomes difficult to increase the compressive stress in a relatively deep portion from the surface by chemical strengthening. From this perspective, the content is preferably 7% or less, more preferably 5% or less, and even more preferably 3% or less.

[0050] The present glass may contain K2O for the purpose of suppressing devitrification during the glass manufacturing process, etc. When K2O is contained in the present glass, the content is preferably 0.1% or more, more preferably 0.15% or more, and particularly preferably 0.2% or more. To further prevent devitrification, the K2O content is preferably 0.5% or more, and more preferably 1.2% or more. On the other hand, a high K content in the glass may cause brittleness or a decrease in surface stress due to back-exchange during tempering. From this viewpoint, the K2O content is preferably 5% or less, more preferably 3% or less, even more preferably 1% or less, and particularly preferably 0.5% or less.

[0051] The total content of Na2O and K2O ([Na2O] + [K2O]) is preferably 3% or more, more preferably 3.5% or more, even more preferably 4% or more, and particularly preferably 4.5% or more in order to improve the meltability of the glass. If ([Na2O] + [K2O]) is too high, the surface compressive stress value is likely to decrease, so ([Na2O] + [K2O]) is preferably 10% or less, more preferably 8% or less, even more preferably 7% or less, and particularly preferably 6% or less.

[0052] Furthermore, it is preferable that the content of Na2O is larger than the content of K2O, because K2O tends to increase the surface resistivity.

[0053] Ratio of the Li2O content to the total content of Li2O, Na2O and K2O, P Li = [Li2O] / ([Li2O] + [Na2O] + [K2O]) is preferably 0.4 or more, more preferably 0.5 or more, and even more preferably 0.6 or more in order to reduce the surface resistivity. On the other hand, in order to suppress the occurrence of devitrification during glass melting, P Li is preferably 0.9 or less, and particularly preferably 0.8 or less.

[0054] Ratio of Na2O content to the sum of Li2O, Na2O and K2O contents, P Na = [Na2O] / ([Li2O] + [Na2O] + [K2O]) is preferably 0.1 or more, more preferably 0.2 or more, in order to suppress devitrification. Na is preferably 0.5 or less, more preferably 0.4 or less.

[0055] Ratio of K2O content to the total content of Li2O, Na2O and K2O, P K =[K2O] / ([Li2O]+[Na2O]+[K2O]) is preferably 0.3 or less, and more preferably 0.2 or less, in order to reduce the surface resistivity.

[0056] Furthermore, the value of parameter S, which is expressed by the following formula, is preferably 0.4 or less, more preferably 0.37 or less, even more preferably 0.35 or less, and particularly preferably 0.34 or less. S=-P Li ×log(P Li )-P Na ×log(P Na )-P K ×log(P K ) The smaller the value of the parameter S, the more uneven the content of Li2O, Na2O, and K2O. The smaller the value of S, the more likely the glass is to have good electrical conductivity and low surface resistivity. From the viewpoint of the ease of ion exchange, the value of S is preferably 0.15 or more, and more preferably 0.2 or more.

[0057] Although MgO, CaO, SrO, BaO, and ZnO are not essential, the present glass may contain one or more of these to enhance the stability of the glass. 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 is preferably 5% or less, more preferably 2% or less, more preferably 1.5% or less, and even more preferably 1% or less.

[0058] The present glass may contain MgO to reduce viscosity during melting, etc. When the present glass contains MgO, the content is preferably 1% or more, more preferably 2% or more, and even more preferably 3% or more. On the other hand, if the MgO content is too high, it becomes difficult to increase the compressive stress layer during chemical strengthening treatment. 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.

[0059] CaO is a component that improves the meltability of glass. The present glass may contain CaO. When the present glass contains CaO, the 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, if the CaO content is excessive, it becomes 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.

[0060] ZnO is a component that improves the meltability of glass. The present glass may contain ZnO. When the present glass contains ZnO, the content is preferably 0.2% or more, and more preferably 0.5% or more. 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%.

[0061] ZnO, SrO, and BaO tend to deteriorate chemical strengthening properties. To facilitate chemical strengthening of glass, the total content of these elements ([ZnO] + [SrO] + [BaO]) is preferably 3% or less, more preferably less than 1%, and even more preferably 0.5% or less. It is particularly preferable that ZnO, SrO, and BaO are substantially not contained.

[0062] The present glass does not necessarily contain ZrO2. On the other hand, from the viewpoint of increasing the surface compressive stress of chemically strengthened glass, the present glass preferably contains ZrO2. The ZrO2 content is preferably 0.1% or more, more preferably 0.15% or more, even more preferably 0.2% or more, particularly preferably 0.25% or more, and even more preferably 0.3% or more. On the other hand, if the ZrO2 content is too high, devitrification defects are likely to occur, making it difficult to increase the compressive stress value during chemical strengthening treatment. 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.

[0063] To increase the fracture toughness value, the present glass preferably contains at least one of Y2O3, La2O3, and ZrO2 in a total content of 0.2% or more. The total 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 total content of these elements is preferably 6% or less, more preferably 5% or less, and even more preferably 4% or less.

[0064] 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 the content of Y2O3 is more preferably greater than the content of ZrO2.

[0065] Although Y2O3 is not essential, it is preferable that the present glass contain Y2O3 in order to increase the surface compressive stress of the chemically strengthened glass while decreasing the crystal growth rate. When the present glass contains Y2O3, the 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 becomes difficult to increase the compressive stress layer 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.

[0066] Although La2O3 is not essential, the present glass may contain La2O3 for the same reasons as Y2O3. When the present glass contains La2O3, the 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, if the La2O3 content is too high, it becomes difficult to increase the compressive stress layer during chemical strengthening treatment. 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.

[0067] TiO2 is a component that suppresses solarization of glass. The present glass may contain TiO2. When the present glass contains TiO2, 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 even more preferably 0.06% or more. On the other hand, if the TiO2 content exceeds 1%, devitrification is likely to occur, and there is a risk of a decrease in 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.

[0068] Although B2O3 is not essential, the present glass may contain B2O3 for the purposes of reducing the brittleness of the glass and improving its crack resistance, or for the purposes of improving the meltability of the glass. When the present glass contains B2O3, the content is preferably 0.5% or more, preferably 1% or more, and more preferably 2% or more. On the other hand, if the B2O3 content is too high, the acid resistance tends to deteriorate. The B2O3 content is preferably 10% or less. The B2O3 content is more preferably 6% or less, even more preferably 4% or less, and particularly preferably 2% or less. From the viewpoint of preventing the problem of striae formation during melting, it is more preferable that the present glass does not substantially contain B2O3.

[0069] Although P2O5 is not essential, the present glass may contain P2O5 for the purpose of increasing the compressive stress layer during chemical strengthening. When the present glass contains P2O5, the content is preferably 0.5% or more, preferably 1% or more, and more preferably 2% or more. On the other hand, from the viewpoint of improving acid resistance, the content of P2O5 is preferably 5% or less, more preferably 4% or less, and even more preferably 2% or less. From the viewpoint of preventing the formation of striae during melting, it is more preferable that the present glass contains substantially no P2O5.

[0070] The total content of B2O3 and P2O5 is preferably 0 to 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.

[0071] NbO 5、 Ta2O5, Gd2O3, and CeO2 are components that suppress solarization of the glass and improve meltability. 5、At least one of Ta2O5, Gd2O3, and CeO2 may be contained. When the present glass contains these components, the total content 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 even more preferably 1% or more. On the other hand, if the content of these components is too high, it becomes difficult to increase the compressive stress value during chemical strengthening treatment, so the total content is preferably 3% or less, more preferably 2% or less, even more preferably 1% or less, and particularly preferably 0.5% or less.

[0072] Fe2O3 absorbs heat rays and thus has the effect of improving the meltability of glass. When mass-producing glass using a large melting furnace, it is preferable that the glass contain Fe2O3. 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, by weight percent based on the oxide. On the other hand, since excessive Fe2O3 content causes coloration, from the viewpoint of improving the transparency of the glass, the content 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, by weight percent based on the oxide.

[0073] Although all iron oxides in glass have been described as Fe2O3, in reality, a mixture of oxidized Fe(III) and reduced Fe(II) is usually present. Of these, Fe(III) produces a yellow color, while Fe(II) produces a blue color, and the balance between the two produces a green color in the glass.

[0074] Furthermore, the present glass may contain a coloring component, such as Co3O4, MnO2, NiO, CuO, Cr2O3, V2O5, Bi2O3, SeO2, CeO2, Er2O3, or Nd2O3, as long as the coloring component does not impede the achievement of the desired chemical strengthening properties.

[0075] The total content of the coloring components, expressed as mole percentage on an oxide basis, is preferably 5% or less. If it exceeds 5%, the glass may be prone to devitrification. The content of the coloring components is preferably 3% or less, and more preferably 1% or less. If high transmittance of the glass is desired, it is preferable that these components are substantially not contained.

[0076] The present glass may contain sulfates, chlorides, fluorides, etc. as appropriate as fining agents during glass melting. The present glass preferably does not contain As2O3. If the present glass contains Sb2O3, the content is preferably 0.3% or less, more preferably 0.1% or less, and most preferably zero.

[0077] The fracture toughness of this glass is 0.70 MPa m 1 / 2 It is preferable that the pressure is equal to or higher than 0.75 MPa m 1 / 2 More preferably, 0.80 MPa m 1 / 2 More preferably, 0.83 MPa m 1 / 2 The fracture toughness value is usually 2.0 MPa m 1 / 2 Typically, it is 1.5 MPa m 1 / 2 The high fracture toughness value makes it difficult for severe fracture to occur even when a large surface compressive stress is introduced into the glass by chemical strengthening.

[0078] The fracture toughness value can be measured, for example, by the DCDC method (Acta metall. mater. Vol. 43, pp. 3453-3458, 1995).

[0079] The Young's modulus of the present glass is preferably 80 GPa or more, more preferably 82 GPa or more, even more preferably 84 GPa or more, and particularly preferably 85 GPa or more, so that the glass is less likely to break. There are no particular limitations on the upper limit of Young's modulus, but since glasses with high Young's modulus may have low acid resistance, for example, it is preferably 110 GPa or less, more preferably 100 GPa or less, and even more preferably 90 GPa or less. Young's modulus can be measured, for example, by the ultrasonic pulse method (JIS R1602:1995).

[0080] The average linear thermal expansion coefficient (thermal expansion coefficient) of the present glass at 50 to 350°C is preferably 95×10 -7 / ℃ or less, more preferably 90×10 -7 / °C or less, more preferably 88 × 10 -7 / °C or less, particularly preferably 86 × 10 -7 / °C or less, most preferably 84 x 10 -7 / °C or less. Although there is no particular limitation on the lower limit of the thermal expansion coefficient, 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 from 50 to 350°C is, for example, 60 × 10 -7 / °C or more, and more preferably 70 × 10 -7 / °C or higher, and more preferably 74 × 10 -7 / °C or more, and even more preferably 76 × 10 -7 / ℃ or more.

[0081] From the viewpoint of reducing warpage after chemical strengthening, the glass transition point (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 point (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.

[0082] The present glass preferably has a DSC exothermic peak temperature measured by the following test method that is 150° C. or more higher than the glass transition point. That is, about 70 mg of glass is ground in an agate mortar and measured using a differential scanning calorimeter (DSC) from room temperature to 1200°C at a heating rate of 10°C / min. The DSC exothermic peak temperature is more preferably 120°C or more higher than Tg, and even more preferably 150°C or more higher. When the DSC exothermic peak temperature is above the above value, crystallization is less likely to occur when the glass is heated and molded, etc. This makes it easier to mold the glass into 3D shapes, for example. The DSC exothermic peak temperature is usually (Tg + 300°C) or less, and more preferably (Tg + 250°C) or less.

[0083] Viscosity is 10 2 The temperature (T2) at which the viscosity becomes dPa·s is preferably 1750°C or lower, more preferably 1730°C or lower, even more preferably 1700°C or lower, particularly preferably 1675°C or lower, and typically 1650°C or lower. The temperature (T2) is a guide to the melting temperature of the glass, and the lower the T2, the easier the glass tends to be to manufacture. There is no particular restriction on the lower limit of T2, but glass with a low T2 tends to have an excessively low glass transition point, so T2 is usually 1400°C or higher, preferably 1450°C or higher.

[0084] Also, the viscosity is 10 4 The temperature (T4) at which the viscosity becomes 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. The temperature (T4) is a guideline for the temperature at which glass is formed into a sheet, and glass with a high T4 tends to place a heavy load on the forming equipment. There is no particular restriction on the lower limit of T4, but glass with a low T4 tends to have an excessively low glass transition point, so T4 is usually 900°C or higher, preferably 950°C or higher, and more preferably 1000°C or higher.

[0085] The devitrification temperature of this glass is 4A temperature 120°C higher than the temperature (T4) at which the viscosity reaches dPa·s is preferred, as this makes it less likely for devitrification to occur during molding by the float method. The devitrification temperature is more preferably 100°C higher than T4 or lower, even more preferably 50°C higher than T4 or lower, and particularly preferably T4 or lower. 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.

[0086] From the viewpoint of ease of production, the devitrification growth rate of the present glass is preferably 10,000 μm / h or less, and more preferably 8,000 μm / h 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.

[0087] The softening point of the present glass is preferably 850°C or lower, more preferably 820°C or lower, and even more preferably 790°C or lower. This is because the lower the softening point of the glass, the lower the heat treatment temperature during bending, which not only reduces energy consumption but also the load on the equipment. From the perspective of lowering the bending temperature, a lower softening point is preferable, but for ordinary glass, the softening point is 700°C or higher. Glass with a softening point that is too low tends to easily relax the stress introduced during chemical strengthening treatment and result in low strength, so the softening point is preferably 700°C or higher. It is more preferably 720°C or higher, and even more preferably 740°C or higher. The softening point can be measured by the fiber drawing method described in JIS R3103-1:2001.

[0088] The present glass preferably has a crystallization peak temperature, measured by the following measurement method, that is higher than the softening point −100° C. It is more preferable that no crystallization peak be observed.

[0089] That is, about 70 mg of glass is crushed and ground in an agate mortar, and the temperature is measured from room temperature to 1200°C at a heating rate of 10°C / min using a differential scanning calorimeter (DSC).

[0090] The surface resistivity of this glass at 50°C is set to 1015 Ω / sq or less is preferable, and 10 14.5 Ω / sq or less is more preferable, and 10 14 Furthermore, since glass with a small amount of electrostatic charge tends to have poor devitrification characteristics during manufacturing, the surface resistivity is preferably 10 8 Ω / sq or more is preferable, 10 9 A surface resistivity of Ω / sq or higher is preferable. The lower the surface resistivity, the better the electrical conductivity of the glass tends to be. Surface resistivity ρ can be calculated by forming electrodes on the surface of the glass plate and measuring the current I and voltage V, using the equation R=V / I, where R is the resistance value R and r is the electrode coefficient, as follows: ρ=R×r.

[0091] When the present glass is in a plate form (glass plate), the plate thickness (t) is, for example, preferably 2000 μm or less, more preferably 1500 μm or less, even more preferably 1000 μm or less, still more preferably 900 μm or less, particularly preferably 800 μm or less, and most preferably 700 μm or less, from the viewpoint of enhancing the effect of chemical strengthening. Furthermore, the plate thickness is, for example, preferably 100 μm or more, more preferably 200 μm or more, even more preferably 400 μm or more, and even more preferably 500 μm or more, from the viewpoint of obtaining a sufficient strength improvement effect by chemical strengthening treatment.

[0092] The shape of the present glass 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 rim shape with a different thickness around the periphery. The shape of the glass plate is not limited thereto, and 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.

[0093] The glass according to the embodiment of the present invention can be produced by a conventional method. For example, raw materials for the glass components 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.

[0094] 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.

[0095] The molded glass is then ground and polished as necessary to form a glass substrate. When the glass substrate is cut to a predetermined shape and size or chamfered, it is preferable to perform the cutting or chamfering of the glass substrate before performing the chemical strengthening treatment described below, because a compressive stress layer is also formed on the end surface by the subsequent chemical strengthening treatment.

[0096] <Chemically strengthened glass> The chemically strengthened glass according to an embodiment of the present invention (hereinafter also referred to as the present chemically strengthened glass) has a matrix composition equal to the glass composition of the present glass described above. Figures 1 and 2 are diagrams showing an example of the stress profile of the present chemically strengthened glass. Note that Figure 2 shows the stress profile inside the chemically strengthened glass measured using a scattered light photoelastic stress meter. Note that the "inside" here refers to, for example, a range of 30 μm or more in depth from the surface.

[0097] The chemically strengthened glass preferably has a surface compressive stress value CSO of 400 MPa or more, more preferably 600 MPa or more, even more preferably 700 MPa or more, still more preferably 800 MPa or more, and particularly preferably 850 MPa or more. The greater the surface compressive stress value, the greater the strength, but if the surface compressive stress value is too high, large tensile stress will be generated inside the chemically strengthened glass, which may lead to fracture. Therefore, the surface compressive stress value CSO is preferably 1600 MPa or less, and more preferably 1500 MPa or less.

[0098] In the stress profile of this chemically strengthened glass, the compressive stress value CS at a depth of 50 μm from the surface 50is preferably 90 MPa or more, more preferably 110 MPa or more, even more preferably 130 MPa or more, still more preferably 140 MPa or more, particularly preferably 150 MPa or more, and most preferably 160 MPa or more. 50 The large CS makes chemically strengthened glass less likely to break when damaged by dropping, etc. 50 From the viewpoint of preventing a large tensile stress from occurring inside the chemically strengthened glass, which would lead to fracture, the compressive strength is preferably 300 MPa or less, more preferably 250 MPa or less, and even more preferably 200 MPa or less.

[0099] In this chemically strengthened glass, the tensile stress value at a depth of 1 / 2 the glass plate 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 small CT makes it less likely to fracture. 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 is above this value, the compressive stress near the surface increases, resulting in increased strength.

[0100] In the present chemically strengthened glass, when the Na2O concentration profile is taken in the depth direction from the surface toward the center of the plate thickness, the depth at which the Na2O concentration is maximum is preferably 0.01t or more. The depth at which the NaO concentration is maximum is preferably 0.025t or more, more preferably 0.045t or more, even more preferably 0.055t or more, and particularly preferably 0.0625t or more. In the case of a general thickness, the depth is preferably 0.15t or less, more preferably 0.1t or less, and even more preferably 0.08t or less.

[0101] The depth at which the NaO concentration is maximum is preferably 1 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. To prevent breakage due to strong impact, the depth is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 to 60 μm. When the depth at which the Na2O concentration reaches a maximum is within the above range, it is easy to obtain glass in which the CT is suppressed and the compressive stress inside the glass is large. The depth at which the Na2O concentration is 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).

[0102] The chemically strengthened glass preferably has a hopping frequency of 10 2.5 More than 10, preferably 3.0 More preferably, 10 3.5 If the hopping frequency is 10 or more, the glass is less likely to be charged. If the hopping frequency is too high, the glass may have poor devitrification characteristics or low fracture toughness. 6.0 The following is preferred: 10 5.5 The following is more preferable, 10 5.0 The following is even more preferred: (Method of measuring hopping frequency) A glass plate is processed into a plate of 50 mm x 50 mm x 0.7 mm, and an electrode pattern shown in Figure 3 is formed on one surface. The impedance is measured in the range of 20 MHz to 2 MHz using an impedance analyzer, and the complex admittance is calculated. With K=-11.214, n1=0.995, n2=0.576, and C∞=20.726, the hopping frequency ωp is calculated from the following equation (13) (Almond-West equation) and the obtained complex admittance. The following equation (13) is the complex admittance Y * This is known as a model equation for (ω) with frequency ω as a variable (Journal of Materials Science vol.19, 1984: 3236-3248).

[0103]

number

[0104] Here, A1, B1, A2, and B2 are as follows:

[0105]

number

[0106] The present chemically strengthened glass can be produced by subjecting the above-described present glass to a chemical strengthening treatment, followed by cleaning and drying. The preferred shape of the present chemically strengthened glass is the same as the preferred shape of the present glass. For example, it may be a flat glass plate without warping, a curved glass plate having a curved surface, or a shape other than a plate. In producing the present chemically strengthened glass, the chemical strengthening treatment may be applied to a flat glass plate, or if the present chemically strengthened glass is a curved glass plate, the chemical strengthening treatment may be applied to a curved glass plate. The chemical strengthening treatment may also be applied to glass having a shape other than a plate.

[0107] The chemical strengthening treatment can be performed by a known method. In the chemical strengthening treatment, a glass sheet is brought into contact with a melt of a metal salt (e.g., potassium nitrate) containing a metal ion with a large ionic radius by immersion or the like. This replaces the metal ions with a small ionic radius in the glass sheet 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.

[0108] The chemical strengthening treatment (ion exchange treatment) can be carried out, for example, by immersing the glass plate for 0.1 to 500 hours in a molten salt such as potassium nitrate heated to 360 to 600° C. The heating temperature of the molten salt is preferably 375 to 500° C., and the immersion time of the glass plate in the molten salt is preferably 0.3 to 200 hours.

[0109] Examples of molten salts used in chemical strengthening 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 molten salts may be used alone or in combination.

[0110] In this embodiment, the treatment conditions for the chemical strengthening treatment may be appropriately selected in consideration of the properties and composition of the glass, the type of molten salt, and the chemical strengthening properties, such as the surface compressive stress and the depth of the compressive stress layer, desired for the final chemically strengthened glass.

[0111] In this embodiment, the chemical strengthening treatment may be performed only once, or multiple times under two or more different conditions (multi-stage strengthening). For example, the first stage of chemical strengthening treatment is performed under conditions that increase the DOL and relatively decrease the CS. Then, the second stage of chemical strengthening treatment is performed under conditions that decrease the DOL and relatively increase the CS. This increases the CS of the outermost surface of the chemically strengthened glass, while suppressing the internal tensile stress area (St), thereby keeping the internal tensile stress (CT) low.

[0112] The present glass and the present chemically strengthened glass are particularly useful as cover glass for mobile devices such as mobile phones, smartphones, personal digital assistants (PDAs), tablet devices, etc. Furthermore, they are also useful as cover glass for non-portable display devices such as televisions (TVs), personal computers (PCs), and touch panels, elevator walls, walls (full-surface displays) of buildings such as houses and buildings, building materials such as window glass, tabletops, interiors of automobiles and airplanes, and cover glass for these, as well as for housings that have curved shapes other than flat shapes obtained by bending or forming. [Example]

[0113] The present invention will be described below with reference to examples, but is not limited to these. Examples 1 to 13, 21 to 37, and 39 are working examples of the present glass, while Examples 14 to 20, 38, and 40 are comparative examples. In the tables, "-" indicates that the measurement results were not evaluated.

[0114] (Production of chemically strengthened glass) Glass plates were prepared by melting in a platinum crucible to obtain the glass compositions shown in Tables 1 to 3, expressed in oxide-based mole percentages. Commonly used glass raw materials, such as oxides, hydroxides, carbonates, or nitrates, were appropriately selected and weighed to yield 1000 g of glass. The mixed raw materials were then placed in a platinum crucible and placed in a resistance-heated electric furnace at 1500–1700°C, where they were melted for approximately 3 hours, degassed, and homogenized. The resulting molten glass was poured into a mold and held at a temperature of glass transition point + 50°C for 1 hour. Then, it was cooled to room temperature at a rate of 0.5°C / min to obtain a glass block. The resulting glass block was cut and ground, and finally, both sides were mirror-finished to obtain a 50 mm long x 50 mm wide x 0.8 mm thick glass plate (glass for chemical strengthening). In Tables 1 to 3, R2O represents the total content of Li2O, KO, and Na2O.

[0115] [Table 1]

[0116] [Table 2]

[0117] [Table 3]

[0118] The physical properties of the obtained glass for chemical strengthening were evaluated as follows. The results are shown in Tables 4 to 6. In Tables 4 to 6, the values shown in bold and italic are estimated values from the glass composition.

[0119] <Density (d)> Density measurements were performed using the liquid weighing method (JIS Z8807:2012, Methods for measuring density and specific gravity of solids). The unit is g / cm. 3 is.

[0120] <Young's modulus> Young's modulus (G) (unit: GPa) was measured by the ultrasonic pulse method (JIS R1602:1995).

[0121] <Average coefficient of linear thermal expansion α and glass transition temperature (Tg)> Average linear expansion coefficient (α) at temperatures between 50 and 350°C (unit: 10 -7 The thermal expansion coefficient (°C) and glass transition point (°C) were measured in accordance with JIS R3102:1995 "Test method for average linear expansion coefficient of glass."

[0122] <T2、T4> The viscosity measured by a rotational viscometer (based on ASTM C 965-96) was 10 2 The temperature T2 (℃) at which the 4 The temperature T4 (°C) at which the viscosity becomes dPa·s was measured.

[0123] <Devitrification growth rate> The growth rate of crystals caused by the devitrification phenomenon was measured by the following procedure. The glass pieces were crushed in a mortar and classified. The glass particles that passed through a sieve with a mesh opening of 3.35 mm and did not pass through a sieve with a mesh opening of 2.36 mm were washed with ion-exchanged water and dried for use in the test.

[0124] One glass particle was placed in each recess of a long, narrow platinum cell with many recesses, and the cell was held at 1350°C or higher for 15 minutes or more. The cell was then removed from the furnace and heated in an electric furnace at 700-1300°C until the surface of the glass particle melted and became smooth.

[0125] The glass was then placed in a temperature-gradient furnace maintained at a predetermined temperature, and after heat treatment for a certain time (denoted as w), it was removed to room temperature and rapidly cooled. This method allows a large number of glass particles to be heat-treated simultaneously by placing a long, narrow container in the temperature-gradient furnace.

[0126] The heat-treated glass was observed with a polarizing microscope (Nikon Corporation: ECLIPSE LV100ND), and the diameter (L μm) of the largest crystal observed was measured. Observation was performed using an eyepiece of 10x magnification, an objective lens of 5x to 100x magnification, transmitted light, and polarized light. Since the crystals produced by devitrification can be considered to grow isotropically, the devitrification (crystal) growth rate is (L / 2) / w [unit: μm / h].

[0127] However, the crystals to be measured were selected to be crystals that had not precipitated at the interface with the container, because devitrification growth at a metal interface tends to differ from the general devitrification growth behavior that occurs inside the glass or at the glass-atmosphere interface.

[0128] <Devitrification temperature> Crushed glass particles were placed in a platinum dish and heat-treated for 17 hours in an electric furnace controlled at a constant temperature. After heat treatment, the glass was observed under a polarizing microscope, and the devitrification temperature was estimated using an evaluation method to determine whether or not devitrification occurred. For example, if the table states "1000-1025°C," this means that devitrification occurred when heat-treated at 1000°C, but not when heat-treated at 1025°C. In this case, the devitrification temperature is between 1000°C and 1025°C.

[0129] <DSC peak temperature> The DSC peak temperature (°C) was measured using a differential scanning calorimeter (DSC) from room temperature to 1200°C with a heating rate of 10°C / min after crushing about 70 mg of glass, grinding it in an agate mortar.

[0130] <CS0(Na), CS 50 (Na), CS 90 (Na), DOL(Na)> Glass with a thickness of 700 μm was immersed in NaNO3 at 380°C for 4 hours for chemical strengthening. For the obtained chemically strengthened glass, the surface compressive stress (value) (CS, DOL) was measured by a surface stress meter (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.). The CS0(Na), CS 50 (Na), CS 90 (Na), DOL(Na) are shown in the table.

[0131] <CS0(K), DOL(K)> Glass with a thickness of 700 μm was immersed in KNO3 at 380°C for 4 hours for chemical strengthening. For the obtained chemically strengthened glass, CS and DOL were measured in the same manner as in the case of strengthening with NaNO3. The CS0(K), DOL(K) of each glass are shown in the table.

[0132]

Table 4

[0133]

Table 5

[0134]

Table 6

[0135] <Chemical strengthening characteristics> The glass of Example 9 was subjected to two-stage chemical strengthening as follows: the first stage of chemical strengthening involved immersion in a molten salt containing 70 wt% KNO3 and 30 wt% NaNO3 at 380°C for 90 minutes, and the second stage of strengthening involved immersion in a molten salt containing 99 wt% KNO3 and 1 wt% LiNO3 at 380°C for 40 minutes. The compressive stress of the surface layer of the chemically strengthened glass was measured using a surface stress meter (FSM-6000), and the internal CS and DOL were measured using a scattered light photoelastic stress meter (SLP-1000).

[0136] The CS0 of the obtained chemically strengthened glass was 818 MPa, and the CS 50 The K ion exchange depth was 3.3 μm and the DOL was 104 μm.

[0137] The stress profile of the obtained chemically strengthened glass is shown in Figure 1. Furthermore, the stress profile inside the chemically strengthened glass measured using a scattered light photoelastic stress meter (SLP-1000) is shown in Figure 2. Note that the "inside" here refers to the range from the surface to a depth of 30 μm or more. Figure 2 shows that the compressive stress due to the diffusion of Na ions peaks at a depth of approximately 33 μm from the surface of the glass. This indicates that the depth at which the Na2O concentration reaches a maximum is 1 μm or more, and therefore when the Na2O concentration profile is taken in the depth direction from the surface of this glass toward the center of the plate thickness, the depth at which the Na2O concentration reaches a maximum is also thought to be 1 μm or more.

[0138] The glass of the example has a small DOL(Na) / DOL(K) value because the parameter M is within a preferred range. This means that the diffusion rate of potassium ions during chemical strengthening is relatively high compared to the diffusion rate of sodium ions. Therefore, a relatively simple strengthening process was used to obtain chemically strengthened glass, as shown in Figure 1, in which the CS of the compressive stress layer due to the diffusion of Na ions at a depth of approximately 50 μm from the surface and the DOL and CS of the compressive stress layer due to the diffusion of K ions in the surface layer are large, and the CT is suppressed. On the other hand, the comparative glass has a large DOL(Na) / DOL(K) value, as in conventional glasses, and therefore it is thought that it would be difficult to obtain such a complex stress profile by simple tempering.Also, the comparative glass had an insufficient amount of Li and Al required to obtain compressive stress in the interior and surface layers, resulting in low compressive stress.

[0139] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2020-119445) filed on July 10, 2020, the contents of which are incorporated herein by reference.

Claims

1. In mole percentage based on oxides, SiO ２ 52 to 70% Al ２ O ３ を14~21%、 Li ２ Oを10~18%、 Na ２ Oを1~7%、 K ２ O 0.1 to 2%, B ２ O ３ 0 to 10%, P ２ O ５ 0 to 5%, MgO 0 to 5%, ZnO 0 to 5%, ZrO ２ 0 to 2%, Y ２ O ３ Contains 0 to 5% of SiO ２ , Al ２ O ３ , Li ２ O, Na ２ O.K. ２ O, B ２ O ３ , P ２ O ５ , MgO, ZnO, ZrO ２ , Y ２ O ３ The content in mol% [SiO ２ ], [Al ２ O ３ ], [Li ２ O], [Na ２ O], [K ２ O], [B ２ O ３ ], [P ２ O ５ ], [MgO], [ZnO], [ZrO ２ ], [Y ２ O ３ ], the parameter M calculated by the following formula is 2 or more and 20 or less, The [SiO ２ ], [Al ２ O ３ ], [Li ２ O], [Na ２ O], [K ２ O], [B ２ O ３ ], [P ２ O ５ ], [MgO], [ZnO], [ZrO ２ ], [Y ２ O ３ ], the parameter D calculated by the following formula is 1200 or more, A parameter S represented by the following formula is equal to or greater than 0.2 and equal to or less than 0.34, Li ２ O, Na ２ O and K ２ Li relative to the total content of O expressed in mol% ２ The ratio of the content of O expressed in mole percent P Ｌｉ = [Li ２ O] / ([Li ２ O] + [Na ２ O] + [K ２ O]) is 0.6 or more and 0.8 or less. M=-1.15×[SiO ２ ]-1.73×[AS ２ O ３ ]+0.155×[L- ２ O]+0.74×[N ２ O]-4.75×[K ２ O]-2.1×[B ２ O ３ ]-2.17×[P ２ O ５ ]+3.25×[MO]-2.0×[ZﻎO]-13.3×[ZrO ２ ]-0.80×[Y ２ O ３ ]+120 D=-943×[SiO ２ ]-859×[AS ２ O ３ ]-998×[L- ２ O]-991×[N ２ O]-1013×[K ２ O]-949×[B ２ O ３ ]-941×[P ２ O ５ ]-687×[MgO]-956×[[[O]-1516×[ZrO ２ ]-823×[Y ２ O ３ ]+95174 S=-P Ｌｉ ×log(P Ｌｉ )-P Ｎａ ×log(P Ｎａ )-P Ｋ ×log(P Ｋ ) ここでP Ｌｉ =[LS ２ O] / ([L+ ２ O]+[N] ２ O]+[K ２ O]) P Ｎａ =[N ２ O] / ([L- ２ O]+[[ ２ O]+[K ２ O]) P Ｋ =[K ２ O] / ([L- ２ O]+[[ ２ O]+[K ２ O]) However, [Li ２ O], [Na ２ O], [K ２ O] are Li ２ O, Na ２ O.K. ２ The content of O is expressed as a mole percentage.

2. The [SiO ２ ], [Al ２ O ３ ], [Li ２ O], [Na ２ O], [K ２ O], [B ２ O ３ ], [P ２ O ５ ], [MgO], [ZnO], [ZrO ２ ], [Y ２ O ３ 2. The glass according to claim 1, wherein a parameter E calculated from the above formula (2) is 500 or more: E=539×[SiO ２ ]+527×[AS ２ O ３ ]+587×[L- ２ O]+467×[N ２ O]+578×[K ２ O]+510×[B ２ O ３ ]+516×[P ２ O ５ ]+442×[MgO]+502×[ZﻎO]+850×[ZrO ２ ]+546×[Y ２ O ３ ]-53476

3. A glass having, expressed as mole percentage on an oxide basis, SiO ２ 52 to 70% Al ２ O ３ を14~21%、 Li ２ Oを10~18%、 Na ２ Oを1~7%、 K ２ Contains 0.1 to 2% O, The glass plate having a thickness of 700 μm was heated at 380° C. with NaNO ３ The surface compressive stress CS generated when immersed in ０ (Na) is 500 MPa or more, The glass plate having a thickness of 700 μm is heated to 380° C. by KNO ３ The surface compressive stress CS generated when immersed in ０ (K) is 1200 MPa or more, The glass plate having a thickness of 700 μm is heated to 380° C. by KNO ３ The compressive stress layer depth DOL (K) generated when immersed in water for 4 hours is 3 μm or more, The glass plate having a thickness of 700 μm was heated at 380° C. with NaNO ３ The ratio of the compressive stress layer depth DOL (Na) generated when immersed in water for 4 hours to the DOL (K) DOL(Na) / DOL(K) is 35 or less, SiO ２ , Al ２ O ３ , Li ２ O, Na ２ O.K. ２ O, B ２ O ３ , P ２ O ５ , MgO, ZnO, ZrO ２ , Y ２ O ３ The content in mol% [SiO ２ ], [Al ２ O ３ ], [Li ２ O], [Na ２ O], [K ２ O], [B ２ O ３ ], [P ２ O ５ ], [MgO], [ZnO], [ZrO ２ ], [Y ２ O ３ ], the parameter M calculated by the following formula is 2 or more and 20 or less, The [SiO ２ ], [Al ２ O ３ ], [Li ２ O], [Na ２ O], [K ２ O], [B ２ O ３ ], [P ２ O ５ ], [MgO], [ZnO], [ZrO ２ ], [Y ２ O ３ ], the parameter D calculated by the following formula is 1200 or more, A parameter S represented by the following formula is equal to or greater than 0.2 and equal to or less than 0.34, Li ２ O, Na ２ O and K ２ Li relative to the total content of O expressed in mol% ２ The ratio of the content of O expressed in mole percent P Ｌｉ = [Li ２ O] / ([Li ２ O] + [Na ２ O] + [K ２ O]) is 0.6 or more and 0.8 or less. M=-1.15×[SiO ２ ]-1.73×[AS ２ O ３ ]+0.155×[L- ２ O]+0.74×[N ２ O]-4.75×[K ２ O]-2.1×[B ２ O ３ ]-2.17×[P ２ O ５ ]+3.25×[MO]-2.0×[ZﻎO]-13.3×[ZrO ２ ]-0.80×[Y ２ O ３ ]+120 D=-943×[SiO ２ ]-859×[AS ２ O ３ ]-998×[L- ２ O]-991×[N ２ O]-1013×[K ２ O]-949×[B ２ O ３ ]-941×[P ２ O ５ ]-687×[MgO]-956×[[[O]-1516×[ZrO ２ ]-823×[Y ２ O ３ ]+95174 S=-P Ｌｉ ×log(P Ｌｉ )-P Ｎａ ×log(P Ｎａ )-P Ｋ ×log(P Ｋ ) ここでP Ｌｉ =[LS ２ O] / ([L+ ２ O]+[N] ２ O]+[K ２ O]) P Ｎａ =[N ２ O] / ([L- ２ O]+[[ ２ O]+[K ２ O]) P Ｋ =[K ２ O] / ([L- ２ O]+[[ ２ O]+[K ２ O]) However, [Li ２ O], [Na ２ O], [K ２ O] are Li ２ O, Na ２ O.K. ２ The content of O is expressed as a mole percentage.

4. The glass plate having a thickness of 700 μm was heated at 380° C. with NaNO ３ The compressive stress value CS at a depth of 50 μm from the surface when immersed in ５０ The glass according to claim 3, wherein (Na) is 170 MPa or more.

5. 5. The glass according to claim 1, having a devitrification temperature of 1,350° C. or lower.

6. Viscosity is 10 ２ The glass according to any one of claims 1 to 5, wherein the temperature T2 at which the viscosity reaches dPa s is 1750°C or lower.

7. The glass according to any one of claims 1 to 6, wherein the temperature of a DSC exothermic peak measured by the following test method is 150°C or more higher than the glass transition point. (Test Method) Approximately 70 mg of glass is crushed and ground in an agate mortar, and the temperature is measured from room temperature to 1200° C. at a heating rate of 10° C. / min using a differential scanning calorimeter (DSC).

8. A chemically strengthened glass having a surface compressive stress value of 400 MPa or more, Na in the depth direction from the surface to the center of the plate thickness ２ When the O concentration profile was taken, Na ２ The depth at which the O concentration is maximum is 1 μm or more, The base composition of the chemically strengthened glass is expressed as mole percentage based on oxides. SiO ２ 52 to 70% Al ２ O ３ を14~21%、 Li ２ Oを10~18%、 Na ２ Oを1~7%、 K ２ Contains 0.1 to 2% O, In the base composition of the chemically strengthened glass, SiO ２ , Al ２ O ３ , Li ２ O, Na ２ O.K. ２ O, B ２ O ３ , P ２ O ５ , MgO, ZnO, ZrO ２ , Y ２ O ３ The content in mol% [SiO ２ ], [Al ２ O ３ ], [Li ２ O], [Na ２ O], [K ２ O], [B ２ O ３ ], [P ２ O ５ ], [MgO], [ZnO], [ZrO ２ ], [Y ２ O ３ ], the parameter M calculated by the following formula is 2 or more and 20 or less, The [SiO ２ ], [Al ２ O ３ ], [Li ２ O], [Na ２ O], [K ２ O], [B ２ O ３ ], [P ２ O ５ ], [MgO], [ZnO], [ZrO ２ ], [Y ２ O ３ ], the parameter D calculated by the following formula is 1200 or more, A parameter S represented by the following formula is 0.2 or more and 0.34 or less, and Li ２ O, Na ２ O and K ２ Li relative to the total content of O expressed in mol% ２ The ratio of the content of O expressed in mole percent P Ｌｉ = [Li ２ O] / ([Li ２ O] + [Na ２ O] + [K ２ Chemically strengthened glass, wherein [O] is 0.6 or more and 0.8 or less. M=-1.15×[SiO ２ ]-1.73×[AS ２ O ３ ]+0.155×[L- ２ O]+0.74×[N ２ O]-4.75×[K ２ O]-2.1×[B ２ O ３ ]-2.17×[P ２ O ５ ]+3.25×[MO]-2.0×[ZﻎO]-13.3×[ZrO ２ ]-0.80×[Y ２ O ３ ]+120 D=-943×[SiO ２ ]-859×[AS ２ O ３ ]-998×[L- ２ O]-991×[N ２ O]-1013×[K ２ O]-949×[B ２ O ３ ]-941×[P ２ O ５ ]-687×[MgO]-956×[[[O]-1516×[ZrO ２ ]-823×[Y ２ O ３ ]+95174 S=-P Ｌｉ ×log(P Ｌｉ )-P Ｎａ ×log(P Ｎａ )-P Ｋ ×log(P Ｋ ) ここでP Ｌｉ =[LS ２ O] / ([L+ ２ O]+[N] ２ O]+[K ２ O]) P Ｎａ =[N ２ O] / ([L- ２ O]+[[ ２ O]+[K ２ O]) P Ｋ =[K ２ O] / ([L- ２ O]+[[ ２ O]+[K ２ O]) However, [Li ２ O], [Na ２ O], [K ２ O] are Li ２ O, Na ２ O.K. ２ The content of O is expressed as a mole percentage.

9. Compressive stress value CS at a depth of 50 μm from the surface ５０ The chemically strengthened glass according to claim 8, wherein the compressive strength is 90 MPa or more.

10. The chemically strengthened glass according to claim 8 or 9, having an internal tensile stress value CT of 70.6 MPa or less.

11. Surface compressive stress value CS ０ The chemically strengthened glass according to any one of claims 8 to 10, wherein the compressive strength is 800 MPa or more.

12. Hopping frequency is 10 ２．５ The chemically strengthened glass according to any one of claims 8 to 11.

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