Chemically strengthened glass, method for manufacturing chemically strengthened glass

Abstract

Providing a novel type of chemically strengthened glass unlike anything previously available. [Solution] Chemically strengthened glass, wherein the absolute value of the maximum measured voltage in a charging test, in which a static honest meter device is used to generate a corona discharge with an applied voltage of 10kV and the chemically strengthened glass is charged for 30 seconds, is 800V or less.

Description

Technical Field

[0001] The present invention relates to chemically strengthened glass. The present invention also relates to a method for manufacturing chemically strengthened glass.

Background Art

[0002] In recent years, cover glass has been used for the purpose of protecting and enhancing the aesthetics of display devices such as mobile phones, smartphones, and tablet terminals. Cover glass for these applications is required to have excellent strength in order to suppress breakage due to impacts and the like. In addition, the cover glass as described above may be used for protecting solar cell modules and the like.

[0003] Conventionally, a technique for increasing the surface strength of glass by immersing the glass in a molten salt such as potassium nitrate and performing chemical strengthening treatment has been known. For example, Patent Document 1 discloses that the surface strength of a glass plate is improved by immersing the glass in a molten potassium nitrate salt and performing chemical strengthening treatment. More specifically, it is disclosed that the strength of a glass plate is improved by sequentially performing chemical strengthening treatment on glass containing Li with a molten salt containing Na and a molten salt containing K. Further, it is described that the mechanism for strengthening the strength of the glass plate by such chemical treatment is due to the compressive stress generated by the exchange of alkali metals.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, with the diversification of devices, novel glasses having various characteristics have been demanded.

[0006] This invention has been made in view of the above-mentioned problems, and aims to provide a novel chemically strengthened glass that is not available in the conventional range. Furthermore, the present invention also aims to provide a method for manufacturing chemically strengthened glass. [Means for solving the problem]

[0007] As a result of diligent research into the above-mentioned problems, the inventors of this invention discovered a chemically strengthened glass in which the voltage measured by a static honest meter device falls below a predetermined value, leading to the present invention.

[0008] In other words, the inventors found that the above problem could be solved by the following configuration. [1] Chemically strengthened glass, Chemically strengthened glass in which, in a charging test in which corona discharge is generated by applying a voltage of 10kV using a static honest meter device and the chemically strengthened glass is charged for 30 seconds, the absolute value of the maximum measured voltage is 800V or less. [2] The chemically strengthened glass according to [1], wherein the ratio of the measured voltage measured 2 seconds after stopping the corona discharge following the charging test to the maximum measured voltage is 0.200 or less. [3] A chemically strengthened glass as described in [1] or [2], having a Young's modulus of 90 GPa or more. [4] A chemically strengthened glass according to any one of [1] to [3], wherein the value of the compressive stress layer depth DOC is 0.16 times or more the thickness of the chemically strengthened glass. However, the unit of the compressive stress layer depth and the unit of the thickness of the chemically strengthened glass are μm. [5] Average value of tensile stress CT ave However, the chemically strengthened glass is 80 MPa or less, as described in any one of [1] to [4]. [6] A chemically strengthened glass according to any one of [1] to [5], wherein the K ion exchange depth is 1.8 μm or more. [7] Chemically strengthened glass as described in any one of [1] to [6], with a plate thickness of 1.0 mm or less. [8] A chemically strengthened glass that is a crystallized glass, as described in any one of [1] to [7]. [9] The chemically strengthened glass according to [8], wherein the crystallized glass comprises one or more crystals selected from the group consisting of lithium silicate crystals and lithium aluminosilicate crystals.

[10] The chemically strengthened glass according to [8] or [9], wherein the crystallized glass comprises one or more crystals selected from the group consisting of lithium disilicate crystals, β-spodumene crystals, β-quartz solid solution crystals, and petalite crystals.

[11] A method for manufacturing chemically strengthened glass, comprising bringing chemically strengthened glass into contact with a molten salt to perform a chemical strengthening treatment, The KNO3 content in the above molten salt is 60% by mass or more relative to the total mass of the above molten salt, and the NaNO3 content in the above molten salt is 20% by mass or more relative to the total mass of the above molten salt. A method for manufacturing chemically strengthened glass, wherein the temperature of the chemical strengthening treatment is 450°C or higher, and the duration of the chemical strengthening treatment is 6 hours or more.

[12] The method for manufacturing chemically strengthened glass according to

[11] , wherein the temperature of the chemical strengthening treatment is 450 to 480°C.

[13] The method for manufacturing chemically strengthened glass according to

[11] or

[12] , wherein the time of the chemical strengthening treatment is 6 to 24 hours.

[14] A method for manufacturing chemically strengthened glass according to any one of

[11] to

[13] , wherein the chemically strengthened glass is crystallized glass.

[15] The method for producing chemically strengthened glass according to

[14] , wherein the crystallized glass comprises one or more crystals selected from the group consisting of lithium silicate crystals and lithium aluminosilicate crystals.

[16] The method for producing chemically strengthened glass according to

[14] or

[15] , wherein the crystallized glass comprises one or more crystals selected from the group consisting of lithium disilicate crystals, β-spodumene crystals, β-quartz solid solution crystals, and petalite crystals. [Effects of the Invention]

[0009] According to the present invention, a novel chemically strengthened glass can be provided. Furthermore, the present invention provides a method for manufacturing chemically strengthened glass. [Brief explanation of the drawing]

[0010] [Figure 1] This is an explanatory diagram of the sample used for measuring the fracture toughness value KIC using the DCDC method. [Figure 2] This figure shows the K1-v curve, which illustrates the relationship between the stress intensity factor K1 (unit: MPa·m1 / 2) and the crack propagation rate v (unit: m / s), used in measuring the fracture toughness value KIC by the DCDC method. [Modes for carrying out the invention]

[0011] The chemically strengthened glass of the present invention will be described in detail below, but the present invention is not limited to the following embodiments and can be modified and implemented as desired without departing from the spirit of the invention.

[0012] In this specification, "chemically strengthened glass" refers to glass that has undergone chemical strengthening treatment. "Chemically strengthened glass" refers to glass that has not undergone chemical strengthening treatment.

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

[0014] In glass composition, "substantially absent" means that, excluding unavoidable impurities contained in the raw materials, etc., it means that the impurities are not intentionally included. Specifically, for components other than those listed in the glass composition, for example, less than 0.1 mol% is preferred, 0.08 mol% or less is more preferred, and 0.05 mol% or less is even more preferred.

[0015] In this specification, a "stress profile" is a pattern representing compressive stress values ​​with respect to the depth from the glass surface as a variable. Negative compressive stress values ​​indicate tensile stress. In this specification, the "stress profile" can be measured using a scattered light photoelastic stress meter.

[0016] The method using a scattered light photoelastic stress meter allows for stress measurement regardless of the refractive index distribution that occurs from the surface to the interior of chemically strengthened glass. An example of a scattered light photoelastic stress meter is the SLP2000 manufactured by Orihara Corporation.

[0017] In this specification, the compressive stress layer depth is defined as the depth to which the compressive stress value becomes zero.

[0018] In this specification, "fracture toughness value K" IC The stress intensity factor K1 (unit: MPa·m) is measured using the DCDC method [Reference: MY He, MR Turner and AG Evans, Acta Metall. Mater. 43 (1995) 3453.]. Specifically, using a sample with the shape shown in Figure 1 and a SHIMADZU Autograph AGS-X5KN, the stress intensity factor K1 (unit: MPa·m) is measured as shown in Figure 2. 1 / 2 The K1-v curve, which shows the relationship between stress and crack propagation rate v (unit: m / s), was measured, and the obtained data for Region III was regression and extrapolated using a linear equation. The stress intensity factor K1 of 0.1 m / s was used to determine the fracture toughness value K IC Let's assume that.

[0019] <Chemically strengthened glass> The chemically strengthened glass of the present invention exhibits a maximum absolute value of 800V or less in a charging test in which a corona discharge is generated using a static honest meter with an applied voltage of 10kV, and the chemically strengthened glass is charged for 30 seconds. The following describes the method for conducting the static charge test and the method for measuring the maximum measurement voltage.

[0020] [Maximum Measurable Voltage] In this invention, the static honest meter device uses a static honest meter (H0110-S4) manufactured by Shishido Electrostatics Co., Ltd. The measurement environment will be a temperature of 22-25°C and a relative humidity of 47-55%. The static honest meter device described above includes a turntable for holding the sample to be measured, an application unit connected to a high-voltage DC power supply for generating corona discharge, and a receiving unit for measuring the potential of the sample to be measured. The turntable has a specimen mounting frame that holds the sample to be measured so that a portion of the sample is exposed on the surface.

[0021] Next, cut out a 45mm x 45mm sample from the chemically strengthened glass and prepare it for measurement. The above measurement sample is fixed to the specimen mounting frame of the turntable. After fixing, the height of the application section is adjusted so that the distance from the frame surface of the specimen mounting frame to the tip of the needle electrode of the application section is 18 mm. Also, the height of the receiving section is adjusted so that the distance from the frame surface of the specimen mounting frame to the electrode of the receiving section is 13 mm. Afterward, the measurement sample is destaticized using a static eliminator.

[0022] Next, while rotating the turntable, a corona discharge is generated by applying a voltage of 10kV to charge the sample to be measured. The charging time is set to 30 seconds. The maximum voltage measured at the receiving section while the device is charged is recorded as the maximum measured voltage (in volts). Note that the maximum voltage refers to the value with the largest absolute value. The above measurement is performed on five measurement samples, and the arithmetic mean value of the maximum measured voltage obtained is taken as the maximum measured voltage of the chemically strengthened glass.

[0023] In the chemically strengthened glass of the present invention, the absolute value of the above maximum measured voltage is 800 V or less, preferably 700 V or less, may be 500 V or less, may be 300 V or less, may be 100 V or less, and may be 50 V or less. The absolute value of the maximum measured voltage is often 5 V or more. The absolute value of the above maximum measured voltage can be adjusted by the composition of the glass for chemical strengthening used in the production of the chemically strengthened glass and the chemical strengthening treatment conditions. Details will be described in detail later.

[0024] The chemically strengthened glass of the present invention is considered to have a small value of the above maximum measured voltage and be difficult to be charged on the surface. If the surface is difficult to be charged, the member using the chemically strengthened glass of the present invention is considered to be excellent in electrostatic resistance (ESD resistance). Further, the member using the chemically strengthened glass of the present invention is considered to be difficult for particles such as dust to adhere to the surface.

[0025] [Charge characteristics] The chemically strengthened glass of the present invention is for the above maximum measured voltage (hereinafter, also referred to as "V MAX "). After the above charging test is performed, the corona discharge is stopped, and the measured voltage measured 2 seconds after the corona discharge is stopped (hereinafter, also referred to as "V 2S "). The ratio of (hereinafter, also referred to as "V 2S / V MAX ") is preferably 0.200 or less. V 2S / V MAX is more preferably 0.100 or less, further preferably 0.070 or less, may be 0.040 or less, may be 0.010 or less, and may be 0.005 or less. V 2S / V MAX may be 0.000, and is often 0.001 or more. The method for measuring the voltage 2 seconds after stopping corona discharge involves performing the above-mentioned charging test to measure the maximum measurement voltage, then stopping only the corona discharge, and measuring the voltage of the sample after 2 seconds using the above-mentioned measuring device. The unit of the measured voltage obtained is V. The above measurement was performed on five measurement samples, and the absolute value of the arithmetic mean of the obtained measurement voltages was used to measure the measurement voltage (V) measured 2 seconds after the corona discharge was stopped. 2S )

[0026] V 2S The voltage is preferably 150V or less, more preferably 100V or less, even more preferably 50V or less, and may be 10V or less, 1V or less, or 0.1V or less. 2S This can be as low as 0.000V, but is often 0.001V or higher.

[0027] The above V 2S This can be adjusted by the composition of the chemically strengthened glass used in the manufacture of chemically strengthened glass, and by the chemical strengthening treatment conditions. Further details will be provided later.

[0028] [Compressive stress] The chemically strengthened glass of the present invention often has a compressive stress layer on the surface side where compressive stress acts. Preferred parameters related to compressive stress are described below.

[0029] The compressive stress (CS) at a depth of 50 μm of the chemically strengthened glass of the present invention 50 The CS of the chemically strengthened glass of the present invention is preferably 30 MPa or higher, more preferably 40 MPa or higher, and even more preferably 50 MPa or higher, in that it makes the chemically strengthened glass of the present invention less prone to cracking even with greater impacts when other objects collide with it. 50 From the standpoint of not exceeding the glass's CT limit, the pressure is often 300 MPa or less, preferably 200 MPa or less, and preferably 150 MPa or less.

[0030] The compressive stress (CS) at a depth of 100 μm of the chemically strengthened glass of the present invention 100) is preferably -10 MPa or higher, more preferably 0 MPa or higher, and even more preferably 5 MPa or higher, in that when another object collides with the chemically strengthened glass of the present invention, cracking is less likely to occur even with a greater impact. 100 From the viewpoint of not exceeding the CT limit of the glass, the pressure is often 150 MPa or less, preferably 100 MPa or less, more preferably 50 MPa or less, even more preferably 20 MPa or less, and particularly preferably 15 MPa or less. The compressive stress at each of the depths mentioned above can be calculated by determining the stress profile using the method described above and then determining the stress profile from that profile.

[0031] The compressive stress layer depth DOC of the chemically strengthened glass of the present invention is preferably 60 μm or more, more preferably 80 μm or more, and even more preferably 100 μm or more. The compressive stress layer depth DOC of the chemically strengthened glass of the present invention is preferably 180 μm or less, more preferably 160 μm or less, and even more preferably 140 μm or less.

[0032] Furthermore, regarding the compressive stress layer depth DOC of the chemically strengthened glass of the present invention, it is preferable that the value of the compressive stress layer depth DOC is 0.16 times or more the thickness of the chemically strengthened glass of the present invention, and more preferably 0.17 times or more. However, the unit of the compressive stress layer depth DOC and the unit of the thickness of the chemically strengthened glass are μm. That is, it is also preferable that the value obtained by dividing the DOC (unit: μm) of the chemically strengthened glass of the present invention by the thickness (unit: μm) is 0.16 or more, and more preferably 0.17 or more. The value of the compressive stress layer depth DOC is often 0.25 times or less the thickness of the chemically strengthened glass of the present invention.

[0033] [Tensile stress] The chemically strengthened glass of the present invention often has a compressive stress layer on its surface, but in this case, a tensile stress that balances it acts inside the chemically strengthened glass. The following describes preferred parameters for tensile stress.

[0034] The maximum tensile stress (CT) of the chemically strengthened glass of the present inventionMax The pressure is preferably 20 MPa or higher, more preferably 30 MPa or higher, even more preferably 40 MPa or higher, and particularly preferably 50 MPa or higher. Furthermore, the CT of the chemically strengthened glass of the present invention Max The pressure is often 200 MPa or less, preferably 150 MPa or less, more preferably 100 MPa or less, and even more preferably 70 MPa or less. CT Max This is determined from the stress profile and typically acts at the center of the plate thickness.

[0035] Average value of tensile stress (CT) of the chemically strengthened glass of the present invention ave The pressure is preferably 10 MPa or higher, more preferably 20 MPa or higher, and even more preferably 30 MPa or higher. Furthermore, the CT of the chemically strengthened glass of the present invention ave The pressure is often 140 MPa or less, preferably 100 MPa or less, and more preferably 60 MPa or less. The average value of tensile stress can be obtained by dividing the integral of tensile stress in the thickness direction of the plate by the length of the tensile stress region in the depth region of the stress profile that exhibits tensile stress.

[0036] The integral tensile stress (ICT) of the chemically strengthened glass of the present invention is often 40,000 Pa·m or less, preferably 30,000 Pa·m or less, and more preferably 20,000 Pa·m or less. The lower limit of ICT is not particularly limited, but it is often 8,000 Pa·m or more, and preferably 10,000 Pa·m or more. ICT is obtained by integrating the tensile stress in the depth region that exhibits tensile stress from the stress profile.

[0037] [plate thickness] The thickness of the chemically strengthened glass of the present invention can be adjusted as appropriate depending on the application, but is often 0.1 mm or more, preferably 0.2 mm or more, more preferably 0.3 mm or more, and even more preferably 0.4 mm or more. Furthermore, the thickness of the chemically strengthened glass of the present invention is often 2.0 mm or less, preferably 1.5 mm or less, more preferably 1.2 mm or less, even more preferably 1.0 mm or less, particularly preferably 0.8 mm or less, and may also be 0.7 mm or less.

[0038] [Physical properties] The Young's modulus of the chemically strengthened glass of the present invention is preferably 80 GPa or higher, more preferably 85 GPa or higher, even more preferably 90 GPa or higher, particularly preferably 95 GPa or higher, and most preferably 100 GPa or higher. There is no particular upper limit to the Young's modulus, but it is typically 120 GPa or lower. The Young's modulus of chemically strengthened glass usually coincides with the Young's modulus of glass used for chemical strengthening.

[0039] The fracture toughness value K of the chemically strengthened glass of the present invention IC This is 0.80 MPa·m 1 / 2 The above is preferable, and 0.85 MPa·m 1 / 2 The above is more preferable, 0.90 MPa·m 1 / 2 The above is even more preferable, and particularly preferable, is 1.00 MPa·m 1 / 2 In summary, the most preferred value is 1.10 MPa·m. 1 / 2 That concludes the explanation. Fracture toughness value K IC There is no particular upper limit, but it is typically 2.00 MPa·m 1 / 2 The following applies: Fracture toughness value K of chemically strengthened glass IC This is the fracture toughness value K of chemically strengthened glass. IC This usually matches.

[0040] [Element distribution] The chemically strengthened glass of the present invention preferably contains potassium near the surface. Whether or not the chemically strengthened glass of the present invention contains potassium near the surface can be confirmed by glow discharge optical emission spectrometry (GD-OES). According to GD-OES, a glow discharge generated within a hollow electrode ionizes a gas (typically Ar gas), and a high-frequency voltage is applied to the sample to cause the ionized gas to collide with the sample surface, resulting in sputtering. The atoms constituting the sputtered sample are supplied into the plasma generated by the glow discharge, where they are excited and de-excited, emitting light at wavelengths specific to each element. By analyzing this light, the elemental content ratios in the sample can be determined. Furthermore, since the analysis is performed while sputtering the surface of the sample, depth analysis is possible. The detailed analysis method is described in the section on examples that follows.

[0041] According to the method described above, the depth distribution of K can be measured. When the chemically strengthened glass of the present invention contains K near the surface, it is preferable that the K is introduced by a chemical strengthening treatment. That is, it is preferable that the K detected by the above method is introduced by ion exchange through a chemical strengthening treatment. More specifically, the depth to which K introduced by ion exchange exists (hereinafter also referred to as "K ion exchange depth") is preferably 1.5 μm or more, more preferably 1.8 μm or more, even more preferably 2.0 μm or more, and may also be 2.5 μm or more. The K ion exchange depth is preferably 10.0 μm or less, more preferably 8.0 μm or less, even more preferably 4.0 μm or less, and most preferably 3.0 μm or less. The K ion exchange depth is the depth obtained by measuring the distribution of K in the depth direction using the method described above and analyzing it using the method shown in the later section of the examples.

[0042] [composition] The chemically strengthened glass of the present invention is obtained by chemically strengthening glass before chemical strengthening (glass for chemical strengthening). The composition of chemically strengthened glass typically coincides with the composition at the center of the glass thickness. In other words, the preferred composition at the center of the glass thickness typically coincides with the preferred composition of chemically strengthened glass. The composition of chemically strengthened glass is expressed as a mole percentage based on oxides. SiO2 at 60-75%, Al2O3 in a concentration of 1-5%, P2O5 at 0-5%, Li2O at 6-30%, Na2O at 0-5%, K2O 0-2%, MgO 0-10%, CaO at 0-5%, It is preferable that it contains 1-10% ZrO2. More preferable compositions for chemically strengthened glass, as well as methods for manufacturing chemically strengthened glass, will be described in detail later.

[0043] Furthermore, it is preferable that the chemically strengthened glass be crystallized glass. When chemically strengthened glass that is crystallized glass is chemically strengthened, chemically strengthened glass that is crystallized glass is obtained. In other words, it is preferable that the chemically strengthened glass of the present invention be crystallized glass. Furthermore, the crystals contained in chemically strengthened glass are also contained in chemically strengthened glass, and the preferred embodiments of the crystals contained in chemically strengthened glass are the same as the preferred embodiments of the crystals contained in chemically strengthened glass. The preferred embodiments when the chemically strengthened glass is crystallized glass are the same as those when the chemically strengthened glass is crystallized glass, so the explanation is omitted.

[0044] <Method for manufacturing chemically strengthened glass> The present invention provides a method for manufacturing chemically strengthened glass, which involves contacting chemically strengthened glass with a molten salt to perform a chemical strengthening treatment and thereby producing chemically strengthened glass. Here, the KNO3 content in the molten salt is 60% by mass or more relative to the total mass of the molten salt, and the NaNO3 content in the molten salt is 20% by mass or more relative to the total mass of the molten salt. Furthermore, the temperature of the chemical strengthening treatment is 450°C or higher, and the duration of the chemical strengthening treatment is 6 hours or longer. The method for producing the chemically strengthened glass of the present invention will be described below.

[0045] [Chemically strengthened glass] (composition) The composition of the chemically strengthened glass used in the method for manufacturing chemically strengthened glass of the present invention will be described below. Hereinafter, the preferred composition of the chemically strengthened glass will also be referred to as the "master glass composition".

[0046] The preferred composition of the chemically strengthened glass of the present invention (matrix glass composition) is expressed in mole percentage based on oxides, SiO2 at 60-75%, Al2O3 in a concentration of 1-5%, P2O5 at 0-5%, Li2O at 6-30%, Na2O at 0-5%, K2O 0-2%, MgO 0-10%, CaO at 0-5%, It contains 1-10% ZrO2. The following describes each component included in the composition of the mother glass.

[0047] SiO2 is a component that makes up the network of glass. It is also a component that increases chemical durability and reduces the occurrence of cracks when the glass surface is scratched.

[0048] The SiO2 content is more preferably 63.0% or higher, and even more preferably 65.0% or higher, in order to improve chemical durability. On the other hand, from the viewpoint of improving meltable properties, the SiO2 content is more preferably 74.0% or lower, and even more preferably 72.0% or lower.

[0049] Al2O3 is a component that improves ion exchange performance during chemical strengthening and increases the surface compressive stress after strengthening. It also contributes to the formation of crystals containing Al and Li. From the viewpoint of obtaining the above effects, an Al2O3 content of 3.5% or more is more preferable, and 4.0% or more is even more preferable. On the other hand, there are cases where it is desired that crystal growth is less likely to occur during melting, that devitrification defects are less likely to occur and that the yield tends to be higher, and that the high-temperature viscosity of the glass is reduced to make it easier to melt. From this viewpoint, an Al2O3 content of 4.8% or less is more preferable, and 4.6% or less is even more preferable.

[0050] SiO2 and Al2O3 are both components that stabilize the structure of glass. To reduce brittleness, the total content of SiO2 and Al2O3 is preferably 64.0% or more, more preferably 66.0% or more, and even more preferably 68.0% or more. Furthermore, both SiO2 and Al2O3 tend to increase the melting temperature of glass. Therefore, in order to make it easier to melt, the total content of SiO2 and Al2O3 is preferably 80.0% or less, more preferably 78.0% or less, even more preferably 76.0% or less, and particularly preferably 74.0% or less.

[0051] Li2O is an ion-exchangeable component that improves the meltability of glass. When glass contains Li2O, Li ions on the glass surface are exchanged with external Na ions and incorporated into the glass, and these incorporated Na ions are then exchanged with external K ions. This method makes it easier to obtain a stress profile with high surface compressive stress and a thick compressive stress layer. Furthermore, including Li2O within the above range makes it easier to obtain crystallized glass when subjected to specific heat treatments. From the above viewpoint, the Li2O content is more preferably 15% or more, even more preferably 18% or more, 20% or more, and may also be 25% or more.

[0052] On the other hand, from the viewpoint of reducing the crystal growth rate during glass molding and minimizing quality degradation due to devitrification, a Li2O content of 29% or less is more preferable.

[0053] Na2O and K2O are components that improve the meltability of glass and reduce the crystal growth rate during glass molding. It is also preferable to include small amounts of these components to improve ion exchange performance.

[0054] Na2O is a component that can undergo ion exchange in chemical strengthening treatment using potassium salts, and also a component that reduces the viscosity of glass. To obtain the above effects, the Na2O content is preferably 0.3% or more, and more preferably, in order, 0.5% or more, 0.8% or more, 1.0% or more, 1.2% or more, 1.5% or more, 1.8% or more, and 2.1% or more. On the other hand, from the viewpoint of maintaining the glass network and avoiding a decrease in surface compressive stress (Na_CS) in the strengthening treatment with sodium salts, the Na2O content is preferably 3.0% or less, and more preferably 2.5% or less.

[0055] K2O is a component that suppresses devitrification by inhibiting the rise in devitrification temperature, and also improves ion exchange performance. The K2O content is more preferably 0.03% or more, even more preferably 0.05% or more, and particularly preferably 0.1% or more. On the other hand, from the viewpoint of avoiding a decrease in surface compressive stress (K_CS) during the strengthening treatment with sodium salts, the K2O content is preferably 1.0% or less, more preferably 0.8% or less, and even more preferably 0.5% or less. Furthermore, K2O does not necessarily need to be included.

[0056] The sum of the Li2O, Na2O, and K2O content, R, is more preferably 10-36%, even more preferably 15-34%, and particularly preferably 20-32%, from the viewpoint of suppressing the rise in devitrification temperature and reducing the crystal growth rate.

[0057] The ratio of Li2O content to R ([Li2O] / ([Li2O]+[Na2O]+[K2O]), hereinafter also referred to as "Li2O / R2O") is more preferably 0.88 or higher, and even more preferably 0.89 or higher, from the viewpoint of further improving deep stress in chemical strengthening properties. From the viewpoint of further improving chemical resistance, Li2O / R2O is more preferably 0.99 or lower, even more preferably 0.98 or lower, and particularly preferably 0.95 or lower.

[0058] The ratio of Na2O content to R ([Na2O] / ([Li2O]+[Na2O]+[K2O]), hereinafter also referred to as "Na2O / R2O") is preferably greater than 0, more preferably 0.01 or greater, even more preferably 0.02 or greater, particularly preferably 0.05 or greater, and most preferably 0.06 or greater, from the viewpoint of further improving the deep stress in chemical strengthening properties. From the viewpoint of further improving the chemical resistance of Na2O / R2O, it is preferably 0.40 or less, more preferably 0.30 or less, even more preferably 0.20 or less, and particularly preferably 0.15 or less.

[0059] The ratio of K2O content to R ([K2O] / ([Li2O]+[Na2O]+[K2O]), hereinafter also referred to as "K2O / R2O") is preferably 0.001 or higher, more preferably 0.004 or higher, and even more preferably 0.01 or higher, from the viewpoint of further increasing the electrical resistance of the glass. From the viewpoint of increasing the compressive stress near the surface in the chemical strengthening properties, the K2O / R2O ratio is preferably 0.50 or lower, more preferably 0.40 or lower, even more preferably 0.30 or lower, and particularly preferably 0.20 or lower. Note that the K2O / R2O ratio may be 0.

[0060] Furthermore, the product of Li2O / R2O, Na2O / R2O, and K2O / R2O is more preferably 0.00005 or higher, even more preferably 0.0001 or higher, and particularly preferably 0.01 or higher, from the viewpoint of suppressing the rise in devitrification temperature and reducing the crystal growth rate. Moreover, the above product is more preferably 0.020 or lower. The above product may be zero.

[0061] The ratio of Na2O content to Li2O content ([Na2O] / [Li2O], hereinafter also referred to as "Na2O / Li2O") is preferably 0.020 or higher, more preferably 0.050 or higher, and even more preferably 0.10 or higher, as this makes it easier to achieve a maximum measurement voltage within a predetermined range after chemical strengthening. Furthermore, the Na2O / Li2O ratio is preferably 0.200 or lower, more preferably 0.180 or lower, and even more preferably 0.150 or lower.

[0062] The ratio of Al2O3 content to R ([Al2O3] / ([Li2O]+[Na2O]+[K2O]), hereinafter also referred to as "Al2O3 / R2O") is preferably 0.05 or higher, more preferably 0.10 or higher, even more preferably 0.15 or higher, and particularly preferably 0.17 or higher. Al2O3 / R2O is preferably 0.50 or lower, more preferably 0.40 or lower, even more preferably 0.30 or lower, and particularly preferably 0.20 or lower.

[0063] The value represented by [Al2O3]-[Na2O]-[K2O]+[Li2O] is preferably 15.0% or more, and more preferably 20.0% or more. Furthermore, the above value is preferably 35.0% or less, and more preferably 30.0% or less.

[0064] MgO may be included to reduce viscosity during dissolution, etc. The MgO content is more preferably 0.05% or more, and even more preferably 0.5% or more, 1.0% or more, 2.0% or more, 3.0% or more, and 4.0% or more, in that order. On the other hand, in terms of making it easier to increase the compressive stress layer during chemical strengthening treatment, the MgO content is more preferably 9.0% or less, and even more preferably 8.0% or less, 7.0% or less, and 6.0% or less, in that order.

[0065] Furthermore, the inclusion of MgO can suppress the phase transition of the crystalline phase from the β-quartz solid solution to β-spodumene, thereby suppressing the precipitation of β-spodumene crystals. Therefore, in Embodiment 2, it is preferable to include MgO. From the above viewpoint, it is preferable to contain more than 0.5% and 7.0% or less of MgO. The more preferable range is as described above. MgO can be practically omitted.

[0066] CaO is a component that improves the meltability of glass and may be included. The CaO content is more preferably 0.005% or more, and even more preferably 0.01% or more. On the other hand, in terms of easily increasing the compressive stress value during chemical strengthening treatment, the CaO content is more preferably 2.0% or less, even more preferably 1.0% or less, particularly preferably 0.8% or less, and most preferably 0.5% or less.

[0067] SrO is an ingredient that improves the meltability of the glass and may be included. The SrO content is more preferably 0.1% or more, even more preferably 0.15% or more, and particularly preferably 0.5% or more. In terms of facilitating an increase in compressive stress during chemical strengthening treatment, the SrO content is more preferably 3.0% or less, even more preferably 2.0% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. SrO can be practically omitted.

[0068] BaO is an ingredient that improves the meltability of glass and may be included. When BaO is included, the content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.5% or more. In order to facilitate increasing the compressive stress value during chemical strengthening treatment, the BaO content is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, and particularly preferably 0.5% or less. BaO can be effectively omitted.

[0069] ZnO is a component that improves the meltability of glass. The ZnO content is more preferably 0.1% or more, even more preferably 0.15% or more, and particularly preferably 0.5% or more. In order to facilitate increasing the compressive stress value during chemical strengthening treatment, the ZnO content is more preferably 3.0% or less, even more preferably 2.0% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less. ZnO can be practically omitted.

[0070] lnW is a parameter that represents the degree of oxide mixing, calculated from the content of alkali metal oxides, alkaline earth metal oxides, and zinc oxide in the glass. lnW is expressed by the following formula. lnW=ln(([Li2O]+[Na2O]+[K2O]+[MgO]+[CaO]+[SrO]+[BaO]+[ZnO])! / ([Li 2O]!×[Na2O]!×[K2O]!×[MgO]!×[CaO]!×[SrO]!×[BaO]!×[ZnO]!))...Formula (W1) In formula (W1), [Li2O], [Na2O], [K2O], [MgO], [CaO], [SrO], [BaO], and [ZnO] represent the content of each component, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, and ZnO, expressed as a mole percentage on an oxide basis. Furthermore, ! indicates raising a positive integer to a factorial. For example, [XO]! means taking the molar percentage content of component XO on an oxide basis, truncating the decimal part to an integer, and then raising that integer to a factorial. For example, if Na2O is 4.8 mol%, the calculation would be the factorial of "4", i.e., 4 × 3 × 2 × 1. A larger lnW value indicates a higher degree of mixing of the metal oxides, thereby suppressing glass devitrification. From this viewpoint, lnW is preferably 10 or higher, more preferably 12 or higher, even more preferably 13 or higher, and particularly preferably 14 or higher. lnW is preferably 20 or lower, more preferably 18 or lower, and even more preferably 17 or lower.

[0071] TiO2 is a component that is highly effective in suppressing the solarization of glass and is a material that forms crystal nuclei, so it may be included. When TiO2 is included, the content is preferably 0.05% or more, more preferably 0.1% or more, even more preferably 0.2% or more, particularly preferably 0.5% or more, and most preferably 0.8% or more. On the other hand, since TiO2 has light absorption properties, from the viewpoint of preventing discoloration of the glass, the TiO2 content is preferably 2.5% or less, more preferably 2.0% or less, even more preferably 1.5% or less, and particularly preferably 1.0% or less. TiO2 does not necessarily need to be included.

[0072] ZrO2 is a component that facilitates increasing the surface compressive stress of chemically strengthened crystallized glass. Furthermore, since it is a material that forms crystal nuclei, it may be included. The ZrO2 content is more preferably greater than 1.0%, and even more preferably 2% or more, 2.5% or more, 3% or more, 3.5% or more, and 4.0% or more, in that order. The ZrO2 content is more preferably 8.0% or less, even more preferably 7.0% or less, and particularly preferably 6.0% or less.

[0073] P2O5 tends to increase the compressive stress layer during chemical strengthening. The P2O5 content is more preferably 0.2% or more, and even more preferably 0.5% or more. On the other hand, from the viewpoint of increasing acid resistance, the P2O5 content is more preferably 3.0% or less, and even more preferably 2.0% or less. From the viewpoint of preventing striation formation during melting, it is also preferable for it to be substantially absent.

[0074] B2O3 reduces the brittleness of glass, improves its crack resistance, or improves its meltability. The B2O3 content is preferably 0.5% or more, more preferably 1.0% or more, and even more preferably 1.2% or more. On the other hand, in terms of maintaining good acid resistance, the B2O3 content is preferably 8.0% or less. More preferably, the B2O3 content is 6.0% or less, even more preferably 4.0% or less, and particularly preferably 2.0% or less. From the viewpoint of preventing striation formation during melting, it is also preferable that it be substantially free of B2O3.

[0075] Y2O3 is a component that facilitates increasing the surface compressive stress of chemically strengthened crystallized glass while reducing the crystal growth rate. The Y2O3 content is preferably more than 0%, and more preferably 0.1% or more, 0.2% or more, 0.5% or more, and 0.8% or more, in that order. On the other hand, in terms of facilitating the creation of a larger compressive stress layer during chemical strengthening, the Y2O3 content is more preferably 2.0% or less, and even more preferably 1.5% or less. Y2O3 does not necessarily need to be included.

[0076] From the viewpoint of improving initial solubility, the total content of ZrO2 and Y2O3 is more preferably 5.0% or less. There is no particular lower limit to the total content of ZrO2 and Y2O3, but from the viewpoint of increasing the strength of the glass, it is more preferably 0.5% or more, and even more preferably 1.0% or more, and 1.5% or more, in that order.

[0077] La2O3 is not essential, but can be included for the same reasons as Y2O3. The amount of La2O3 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 there is too much, it becomes difficult to enlarge the compressive stress layer during chemical strengthening treatment, so the amount of La2O3 is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 2.0% or less, and particularly preferably 1.5% or less. It is also preferable that La2O3 is substantially absent.

[0078] Nb2O 5、Ta2O5, Gd2O3, and CeO2 are components that have the effect of suppressing the solarization of glass and improving meltability, and may be included. When these components are included, the content of each is preferably 0.03% or more, more preferably 0.1% or more, even more preferably 0.5% or more, particularly preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, it is preferably 3.0% or less, more preferably 2.0% or less, and even more preferably 1.0% or less.

[0079] Fe2O3 absorbs heat rays, thus improving the solubility of glass, and its inclusion is preferable when mass-producing glass using large melting furnaces. In this case, the content is preferably 0.002% or more, more preferably 0.005% or more, even more preferably 0.007% or more, and particularly preferably 0.01% or more, expressed as mass percent based on oxide. On the other hand, excessive Fe2O3 content causes discoloration, so from the viewpoint of improving the transparency of the glass, its 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, expressed as mass percent based on oxide.

[0080] Furthermore, other coloring components may be added, to the extent that they do not hinder the achievement of the desired chemical strengthening properties. Suitable other coloring components include, for example, Co3O4, MnO2, NiO, CuO, Cr2O3, V2O5, Bi2O3, SeO2, Er2O3, and Nd2O3.

[0081] SO3, chlorides, fluorides, etc., may be appropriately included as clarifying agents during glass melting. It is preferable that As2O3 is not included. If Sb2O3 is included, it is preferable that it be 0.3% or less, more preferably 0.1% or less, and most preferably not included. From the viewpoint of clarifying bubbles in the glass, the SnO2 content is more preferably 0.05% or more, and even more preferably 0.07% or more. Furthermore, to suppress the occurrence of defects, the SnO2 content is preferably 1% or less, more preferably 0.8% or less, even more preferably 0.7% or less, and particularly preferably 0.5% or less.

[0082] The glass used for chemical strengthening is preferably crystallized glass. The crystals contained in the crystallized glass are preferably one or more crystals selected from the group consisting of lithium silicate crystals, lithium aluminosilicate crystals, and lithium phosphate crystals, and more preferably one or more crystals selected from the group consisting of lithium silicate crystals and lithium aluminosilicate crystals. Preferred lithium silicate crystals include lithium metasilicate (Li2SiO3) crystals and lithium disilicate crystals (Li2Si2O5). Preferred lithium phosphate crystals include lithium orthophosphate crystals (Li3PO4). Preferred lithium aluminosilicate crystals include β-spodumene crystals (LiAlSi2O6), β-quartz solid solution crystals (LiAlSiO4), and petalite crystals (LiAlSi4O6). 10 ) etc. are preferred. Furthermore, it is preferable that the resulting crystallized glass also contains one or more crystals selected from the group consisting of lithium disilicate crystals, β-spodumene crystals, β-quartz solid solution crystals, and petalite crystals.

[0083] When chemically strengthened glass is crystallized glass, its crystallinity is preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, and particularly preferably 25% or more, in terms of improving mechanical strength. Furthermore, to increase transparency, it is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less. A low crystallinity is also advantageous in that it is easier to heat and bend or shape. The crystallinity can be calculated from the X-ray diffraction intensity using the Rietveld method. The Rietveld method is described in "Crystal Analysis Handbook" (Kyōritsu Shuppan, 1999, pp. 492-499), edited by the editorial committee of the Crystallographic Society of Japan.

[0084] When the chemically strengthened glass is crystallized glass, the average particle size of the precipitated crystals is preferably 300 nm or less, more preferably 200 nm or less, even more preferably 150 nm or less, and particularly preferably 100 nm or less, in order to achieve high transparency. The average particle size of the precipitated crystals can be determined from transmission electron microscope (TEM) images. It can also be estimated from scanning electron microscope (SEM) images.

[0085] (Physical properties) The following describes the desirable physical properties of chemically strengthened glass.

[0086] Chemically strengthened glass is preferably devitrified at a temperature of 1300°C or lower. More preferably at 1280°C or lower, and even more preferably at 1250°C or lower. Particularly preferred are, in order, 1240°C or lower, 1230°C or lower, 1220°C or lower, and 1210°C or lower. The lower limit of the devitrification temperature is not particularly limited, but is usually 1100°C or higher.

[0087] For chemically strengthened glass (for example, glass with the above-mentioned mother glass composition), a crystallization onset temperature Tcs measured by DSC is preferably 500°C or higher. There is no particular upper limit to the crystallization onset temperature, but it is usually 800°C or lower.

[0088] If the crystallization onset temperature Tcs is within the above range, then, for example, by performing a heat treatment in which the glass is held at 500-600°C for 1-6 hours and then at 600-800°C for 0.5-6 hours, crystals can be precipitated in the glass, and a chemically strengthened glass, which is a crystallized glass, can be obtained. The above heat treatment may be carried out in three stages. For example, chemically strengthened glass may be obtained by holding at 500-600°C for 1-6 hours, 550-650°C for 0.5-6 hours, and 600-800°C for 0.5-6 hours.

[0089] The glass transition temperature (Tg) is preferably 500°C or higher, more preferably 520°C or higher, and even more preferably 540°C or higher, from the viewpoint of reducing warping after chemical strengthening. From the viewpoint of ease of float molding, 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.

[0090] The chemically strengthened glass having the above-described matrix glass composition preferably has a crystallization peak temperature Tc of 600°C or higher, more preferably 650°C or higher, and even more preferably 700°C or higher. A crystallization peak temperature Tc of 600°C or higher allows for stable molding. It is most preferable that no crystallization peak is observed. There is no particular upper limit to the crystallization peak temperature Tc, but it is usually 950°C or lower.

[0091] Chemically strengthened glass has a β-OH value of 0.1 mm -1 Preferably, it is 0.15 mm or more. -1 The above is more preferable, 0.2 mm -1 The above is even more preferable, 0.22 mm -1 The above is particularly preferred, 0.25 mm -1 The above is the most preferable option.

[0092] The β-OH value is an indicator of the water content in glass. Glass with a high β-OH value tends to have a lower softening point and is easier to bend. On the other hand, from the perspective of improving the strength of glass through chemical strengthening, a higher β-OH value in glass tends to result in a lower surface compressive stress (CS) after chemical strengthening treatment. From the above perspective, a β-OH value of 0.5 mm is considered to be a good indicator. -1 The following is preferred: 0.4 mm -1 The following is more preferable: 0.3 mm -1 The following are even more preferable.

[0093] Chemically strengthened glass has a fracture toughness value (K IC ) However, 0.80 MPa·m 1 / 2 Preferably, it is 0.85 MPa·m 1 / 2 It is more preferable that the value be greater than or equal to 0.90 MPa·m1 / 2 It is even more preferable that the pressure be greater than or equal to 1.00 MPa·m, and particularly preferable that it be 1.00 MPa·m. 1 / 2 In summary, the most preferred value is 1.10 MPa·m. 1 / 2 That concludes the explanation. There is no particular upper limit to the fracture toughness value, but it is typically 1.60 MPa·m. 1 / 2 The following applies:

[0094] Chemically strengthened glass preferably has a Young's modulus of 80 GPa or higher, more preferably 85 GPa or higher, even more preferably 90 GPa or higher, particularly preferably 95 GPa or higher, and most preferably 100 GPa or higher. There is no particular upper limit to the Young's modulus, but it is typically 120 GPa or lower. The method for measuring the Young's modulus of chemically strengthened glass follows the method described in the examples section below.

[0095] [Chemical strengthening treatment] In the method for producing chemically strengthened glass of the present invention, chemical strengthening treatment is performed by contacting the chemically strengthened glass with a molten salt. When chemically strengthened glass is brought into contact with a molten salt, metal ions with small ionic radii in the chemically strengthened glass (typically Na ions or Li ions) are replaced by metal ions with large ionic radii (typically K ions for Na ions, and Na ions or K ions for Li ions). The method for bringing the chemically strengthened glass into contact with the molten salt is not particularly limited; for example, the chemically strengthened glass can be immersed in the molten salt. The following explains chemical strengthening treatment.

[0096] (molten salt) The molten salt used in the method for producing chemically strengthened glass of the present invention will be described. The KNO3 content in the molten salt is 60% by mass or more, preferably 65% ​​by mass or more, relative to the total mass of the molten salt. Furthermore, the KNO3 content in the molten salt is 80% by mass or less, preferably 75% by mass or less, relative to the total mass of the molten salt. The NaNO3 content in the molten salt is 20% by mass or more, preferably 25% by mass or more, relative to the total mass of the molten salt. Furthermore, the NaNO3 content in the molten salt is 40% by mass or less, preferably 35% by mass or less, relative to the total mass of the molten salt. By performing a chemical strengthening treatment using a molten salt of the above composition, it is easy to obtain chemically strengthened glass that exhibits the maximum measurement voltage within the predetermined range.

[0097] The molten salt may contain components other than KNO3 and NaNO3. Other components besides KNO3 and NaNO3 include, for example, one or more metal salts selected from the group consisting of nitrates, sulfates, carbonates, and chlorides. Examples of nitrates include lithium nitrate (LiNO3), rubidium nitrate (RbNO3), cesium nitrate (CsNO3), and silver nitrate (AgNO3). Examples of sulfates include lithium sulfate (Li2SO4), sodium sulfate (Na2SO4), potassium sulfate (K2SO4), rubidium sulfate (Rb2SO4), cesium sulfate (Cs2SO4), and silver sulfate (Ag2SO4). Examples of carbonates include lithium carbonate (Li2CO3), sodium carbonate (Na2CO3), and potassium carbonate (K2CO3). Examples of chlorides include lithium chloride (LiCl), sodium chloride (NaCl), potassium chloride (KCl), rubidium chloride (RbCl), cesium chloride (CsCl), and silver chloride (AgCl).

[0098] The molten salt may also preferably contain components other than those listed above. Other components include one or more metal salts selected from the group consisting of phosphates and silicates. Examples of phosphates include lithium phosphate, sodium phosphate, potassium phosphate, and rubidium phosphate. Examples of silicates include lithium silicate, sodium silicate, potassium silicate, and rubidium silicate.

[0099] (Processing conditions) In the method for manufacturing chemically strengthened glass of the present invention, the temperature of the chemical strengthening treatment is 450°C or higher. A chemical strengthening treatment temperature of 450°C or higher means that the temperature of the molten salt brought into contact with the chemically strengthened glass is 450°C or higher. Furthermore, in the following, the chemical strengthening treatment temperature refers to the temperature of the molten salt brought into contact with the chemically strengthened glass. The temperature for the chemical strengthening treatment is preferably 480°C or lower. In other words, the temperature for the chemical strengthening treatment is preferably 450 to 480°C.

[0100] In the method for manufacturing chemically strengthened glass of the present invention, the chemical strengthening treatment time is 6 hours or more. The chemical strengthening treatment time refers to the time during which the chemically strengthened glass is in contact with the molten salt. The chemical strengthening treatment time is preferably 7 hours or more, may be 10 hours or more, or may be 12 hours or more. The chemical strengthening treatment time is preferably 48 hours or less, and more preferably 36 hours or less. By using a molten salt of the above composition and performing the chemical strengthening treatment at the above chemical strengthening temperature and for the above chemical strengthening time, it is easy to obtain chemically strengthened glass that exhibits the above-mentioned maximum measurement voltage within the predetermined range.

[0101] <Application> The chemically strengthened glass of the present invention is useful, for example, as a cover glass. The above-mentioned cover glass can also be suitably used for surface protection of displays and solar cell modules, etc. When the chemically strengthened glass of the present invention is applied as a cover glass, the surface of the cover glass is less prone to static electricity, less likely to accumulate dust, and has excellent aesthetic appeal. In particular, the chemically strengthened crystallized glass of the present invention is useful as cover glass for mobile devices such as mobile phones, smartphones, personal digital assistants (PDAs), and tablet devices. Furthermore, it is useful for cover glass for display devices such as televisions (TVs), personal computers (PCs), and touch panels that are not intended for portability, as well as cover glass provided on the surface of solar cell modules, building materials such as elevator walls, walls of buildings such as houses and office buildings (full-surface displays), and window glass, and also for interiors of tabletops, automobiles, and airplanes. It is also useful as cover glass for the above-mentioned articles. Furthermore, it can be applied to applications such as casings with curved shapes by bending and bending forming.

[0102] Furthermore, the chemically strengthened glass of the present invention can also be applied to display modules and touch panel modules. Because the surface of the chemically strengthened glass of the present invention is less prone to static charge, modules to which the chemically strengthened glass of the present invention is applied have excellent electrostatic discharge resistance. For example, applying the chemically strengthened glass of the present invention to the above-mentioned module can reduce module malfunctions. More specifically, in a display module, abnormal light emission due to static charge can be reduced. In a touch panel module, reading errors due to static charge can be reduced. [Examples]

[0103] The present invention will be described in more detail below based on examples. The materials, quantities, proportions, processing details, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples. Examples 1-6, described later, are comparative examples, while Examples 7 and 8 are examples of actual cases.

[0104] <Preparation of chemically strengthened glass> First, glass materials A and B were obtained by melting the glass raw materials in a platinum crucible to obtain the compositions of each glass expressed as molar percentages based on oxides, as shown in Table 1. More specifically, oxides, hydroxides, carbonates, or nitrates used as glass raw materials were appropriately selected from commonly used glass raw materials and weighed to obtain 1000g of glass. Next, the mixed raw materials were placed in a platinum crucible and melted in a resistance-heated electric furnace at 1500-1700°C for about 3 hours. After degassing and homogenization, molten glass was obtained. The obtained molten glass was poured into a mold, held at a temperature 50°C above the glass transition point 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 to form glass plates.

[0105] Furthermore, after forming glass plate A, it was heat-treated by raising the temperature to 550°C, holding it for 2 hours, and then raising the temperature to 750°C and holding it for 2 hours. Furthermore, after forming glass plate B, the following heat treatments were performed: the temperature was raised to 540°C and held for 4 hours, then raised to 600°C and held for 4 hours, and finally raised to 650°C and held for 4 hours. The above heat treatment yielded crystallized glass with precipitated crystals. The obtained crystallized glass was used as chemically strengthened glass. The precipitated crystals and their degree of crystallinity after the above heat treatment are shown in Table 1 below.

[0106] In addition, the same heat treatment as described above is performed on the glass block separately to obtain a fracture toughness value (K IC Sample pieces for measurement and sample pieces for measuring Young's modulus were obtained, and the fracture toughness value and Young's modulus were measured using the method described later.

[0107] [Table 1]

[0108] <Fabrication of chemically strengthened glass> The chemically strengthened glass (glass material A and glass material B) obtained by the above procedure was subjected to chemical strengthening treatment under the conditions described in Table 2 to obtain the glasses of Examples 2 to 4 and Examples 6 to 8. In Examples 1 and 5, chemically strengthened glass was used as is.

[0109] <Measurement of electrostatic properties> The charging characteristics were measured using the procedure described above. More specifically, using the procedure described above, the maximum measurement voltage (V MAX ) and the measured voltage (V) measured 2 seconds after stopping the corona discharge. 2S ) and were measured. V MAX and V 2S From the values ​​of the above V 2S / V MAX The value was calculated.

[0110] <Measurement of stress profile> The stress profile of the chemically strengthened glass was measured using the method described above, and the parameters listed in the table below were obtained.

[0111] <Element distribution> In each glass sample, the elemental distribution was analyzed using the method described above, and the depth distribution of K was measured. Specifically, measurements were performed using a GD-OES device (GD-Profier2 manufactured by Horiba, Ltd.) under the following conditions. • Measurement pressure: 200 Pa • Discharge conditions: 40W (measured in low power mode) • Discharge range: 4mmφ • Discharge mode: Measured in pulse sputter mode (duty cycle 0.25 DS) Next, the depth distribution of K was extracted from the depth distribution of the content of each element obtained. For example, in the glass of Example 7, the depth distribution of K showed that the amount of detected K increased from the center of the plate thickness toward the surface (depth 0 μm). In the depth distribution of K, the amount of K detected at the center of the plate thickness (K C ) is the difference in the amount detected at the surface (depth 0 μm), K MAX This was calculated. Here, when the depth changes from the center of the plate thickness toward the surface, K occurs for the first time. MAX Only the value obtained by multiplying by 0.1 KCThe depth at which the amount of detected K increases is defined as the K ion exchange depth.

[0112] <Measurement of Young's modulus> In the procedure for obtaining each of the above glass materials, the Young's modulus of the chemically strengthened glass was measured using the cut sample pieces. Specifically, the measurement was performed using the ultrasonic pulse method with the above sample pieces in accordance with JIS R 1602. Furthermore, when Young's modulus was measured using the same method after chemical strengthening, it was the same as the value before chemical strengthening.

[0113] <Measurement of fracture toughness value> In the procedure for obtaining each of the above glass materials, the fracture toughness value K of the chemically strengthened glass is determined using the cut sample pieces. IC The following measurements were performed. Fracture toughness values ​​were measured using the DCDC method described above. Furthermore, the fracture toughness value K was determined using the same method after chemical strengthening. IC When measured, the values ​​were similar to those before chemical strengthening.

[0114] <Evaluation of drop height> For each example of glass obtained, the drop strength was evaluated using the following procedure. For each example, a pseudo-smartphone was created by fitting the chemically strengthened glass into a structure whose mass and rigidity were adjusted to match the size of a typical smartphone currently in use. The pseudo-smartphone was then free-dropped onto #80 SiC sandpaper at varying heights, with the side containing the chemically strengthened glass facing the ground. The first drop was from a height of 20 cm. If the chemically strengthened glass did not break at 20 cm, it was dropped from a height of 25 cm. If it still did not break at 25 cm, it was dropped from a height of 30 cm. This process of dropping the device from a height 5 cm higher than the previous drop until the chemically strengthened glass broke was repeated. The height at which the chemically strengthened glass first broke using the above procedure was defined as the drop height. The above drop heights were measured for each of the 19 tempered glass panels, and the arithmetic mean of the drop heights is shown in the table below. Furthermore, a larger value for the drop height corresponds to the fact that the chemically strengthened glass did not break even when dropped from a higher position, meaning it has higher drop resistance.

[0115] <Evaluation of 4-point bending strength> The bending strength at four points was evaluated by conducting a bending test using the following procedure. Specifically, a four-point bending test (4PB bending test) was conducted in accordance with JIS-R1601:2008. A Shimadzu Autograph AGS-10kNX desktop precision universal testing machine was used for the four-point bending test. The bending span was 20 mm at the top and 40 mm at the bottom. The crosshead movement speed was set to 5 mm / min. The crack stress was determined from the measured loads leading to crack initiation. The crack stress described above was measured on five samples, and the arithmetic mean of the measured crack stresses was defined as the mean crack stress.

[0116] <Result> Table 2 shows the type of chemically strengthened glass, chemical strengthening conditions, the measurement results, and the evaluation results for each example. In Table 2, the entries in the stress profile column have the following meanings. The calculation methods for each value are as described above or as shown below. CS 50 and CS 100 Compressive stress at each depth (unit: μm) of the obtained chemically strengthened glass • DOC: Compressive stress layer depth of chemically strengthened glass Note that "DOC" above refers to the depth at which the compressive stress is 0 MPa in the stress distribution obtained using only a scattered light photoelastic stress meter. • DOC / t: The value obtained by dividing the above DOC by the plate thickness t. Note that the units for DOC and plate thickness are μm. ·CT Max : Maximum tensile stress ·CT ave : Average value of tensile stress • ICT: Average value of tensile stress • K ion exchange depth: The depth to which K is introduced by ion exchange. ·V MAX : Maximum Measurable Voltage ·V 2S After performing the charging test, the corona discharge was stopped, and the measured voltage was measured 2 seconds after the corona discharge was stopped.

[0117] [Table 2]

[0118] From the results shown in Table 1, the chemically strengthened glass of Example 7 and Example 8 of the present invention exhibits the above-mentioned maximum measurement voltage (V MAX It was confirmed that the glass was a new type with a voltage of 800V or less. Furthermore, it was confirmed that the chemically strengthened glass of Example 7 and Example 8 of the present invention exhibits superior drop strength compared to the glass of the other examples.

Claims

1. It is a chemically strengthened glass, Chemically strengthened glass in which, in a charging test in which a corona discharge is generated by applying a static honest meter device with a voltage of 10 kV and the chemically strengthened glass is charged for 30 seconds, the absolute value of the maximum measured voltage is 800 V or less.

2. The chemically strengthened glass according to claim 1, wherein the ratio of the measured voltage measured 2 seconds after stopping the corona discharge following the charging test to the maximum measured voltage is 0.200 or less.

3. A chemically strengthened glass according to claim 1 or 2, wherein the Young's modulus is 90 GPa or higher.

4. The chemically strengthened glass according to claim 1 or 2, wherein the value of the compressive stress layer depth DOC is 0.16 times or more the thickness of the chemically strengthened glass. However, the unit of the compressive stress layer depth and the unit of the thickness of the chemically strengthened glass are μm.

5. Average value of tensile stress CT ａｖｅ The chemically strengthened glass according to claim 1 or 2, wherein the pressure is 80 MPa or less.

6. The chemically strengthened glass according to claim 1 or 2, wherein the K ion exchange depth is 1.8 μm or more.

7. The chemically strengthened glass according to claim 1 or 2, wherein the plate thickness is 1.0 mm or less.

8. A chemically strengthened glass according to claim 1 or 2, which is a crystallized glass.

9. The chemically strengthened glass according to claim 8, wherein the crystallized glass comprises one or more crystals selected from the group consisting of lithium silicate crystals and lithium aluminosilicate crystals.

10. The chemically strengthened glass according to claim 8, wherein the crystallized glass comprises one or more crystals selected from the group consisting of lithium disilicate crystals, β-spodumene crystals, β-quartz solid solution crystals, and petalite crystals.

11. A method for manufacturing chemically strengthened glass, comprising bringing chemically strengthened glass into contact with a molten salt to perform a chemical strengthening treatment, KNO in the molten salt ３ The content of is 60% by mass or more relative to the total mass of the molten salt, and the NaNO in the molten salt ３ The content of is 20% by mass or more relative to the total mass of the molten salt. A method for manufacturing chemically strengthened glass, wherein the temperature of the chemical strengthening treatment is 450°C or higher, and the duration of the chemical strengthening treatment is 6 hours or more.

12. The method for manufacturing chemically strengthened glass according to claim 11, wherein the temperature of the chemical strengthening treatment is 450 to 480°C.

13. A method for producing chemically strengthened glass according to claim 11 or 12, wherein the time of the chemical strengthening treatment is 6 to 24 hours.

14. The method for producing chemically strengthened glass according to claim 11 or 12, wherein the chemically strengthened glass is crystallized glass.

15. The method for producing chemically strengthened glass according to claim 14, wherein the crystallized glass comprises one or more crystals selected from the group consisting of lithium silicate crystals and lithium aluminosilicate crystals.

16. The method for producing chemically strengthened glass according to claim 14, wherein the crystallized glass comprises one or more crystals selected from the group consisting of lithium disilicate crystals, β-spodumene crystals, β-quartz solid solution crystals, and petalite crystals.

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