Chemically strengthened glass, chemically strengthened glass, and method for producing chemically strengthened glass

Abstract

The present invention relates to chemically strengthened glass, chemically strengthened glass, and a method for manufacturing chemically strengthened glass. An object of the present invention is to provide a chemically strengthened glass that is not easily scratched and is not prone to cracking or poor precision during bending. One embodiment of the present invention is a chemically strengthened glass having a Young's modulus E of 70 GPa or greater, a total of the values ​​X1, X2, and X3 (X1+X2+X3) of 1760 or less, the value X1 being the same as the value obtained by multiplying the Young's modulus E by the average thermal expansion coefficient α in the range of 50°C to 350°C [unit: kPa / °C], the value X2 being the same as the temperature Tf [unit: °C] at which the viscosity reaches 100 MPa·s, and the value X3 being the viscosity at Tf (100 MPa·s) and the viscosity η at a temperature 10°C higher than Tf. +10 The difference [unit: 10 5 Pa·s] have the same value.

Description

[0001] This application is a divisional application of the Chinese patent application with application number 201780063920.X and application date on October 12, 2017. Technical Field

[0002] The present invention relates to chemically strengthened glass and chemically strengthened glass, and also to a method for producing chemically strengthened glass. Background Art

[0003] Thin, high-strength chemically strengthened glass is used as a cover glass for display devices of mobile devices such as mobile phones and smartphones, and as a cover glass for vehicle-mounted display components such as dashboards or head-up displays (HUDs). For these display devices, curved cover glass is sometimes required to improve operability and visibility. Curved cover glass can be manufactured by heating a flat glass plate and bending it into a curved shape using a forming mold (also known as three-dimensional forming) (see Patent Document 1).

[0004] Patent Document 2 discloses lithium aluminosilicate glass having a glass transition temperature of 550° C. or lower and capable of three-dimensional molding and chemical strengthening.

[0005] Prior art literature

[0006] Patent Document 1: International Publication No. 2014 / 167894

[0007] Patent Document 2: Japanese Patent Application No. 2013-520385 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] When a glass sheet is bent and formed, thermal stress is generated by heating the glass sheet, which may cause the glass sheet to break. In addition, the shape of the formed glass sheet may change.

[0010] For example, the glass described in Patent Document 2 can be three-dimensionally formed, but tends to break easily when bent. In recent years, the demand for higher-definition displays and features such as waterproofing has led to higher molding precision than ever before, but this is insufficient.

[0011] An object of the present invention is to provide chemically strengthened glass that solves the problems of the conventional technology.

[0012] Means used to solve problems

[0013] The present inventors have studied bending of glass sheets and have discovered characteristics of glass sheets that are less likely to be scratched and less likely to cause problems such as cracking and poor precision during bending.

[0014] The present invention is based on the above findings. A chemically strengthened glass according to the present invention is a chemically strengthened glass having a Young's modulus E of 70 GPa or greater, wherein the sum X1+X2+X3 of the numerical values ​​X1, X2, and X3 is 1760 or less, the numerical value X1 being the same as the value obtained by multiplying the Young's modulus E by the average thermal expansion coefficient α in the range of 50°C to 350°C [unit: kPa / °C], the numerical value X2 being the same as the temperature Tf [unit: °C] at which the viscosity reaches 100 MPa·s, and the numerical value X3 being the viscosity at Tf (100 MPa·s) and the viscosity η at a temperature 10°C higher than Tf. +10 The difference [unit: 10 5 Pa·s] have the same value.

[0015] In one embodiment of the chemically strengthened glass of the present invention, the chemically strengthened glass may be lithium aluminosilicate glass.

[0016] In one embodiment of the chemically strengthened glass of the present invention, the chemically strengthened glass may contain, expressed in percentage by mass based on oxides, 56% to 73% of SiO2, 10% to 24% of Al2O3, 0% to 6% of B2O3, 0% to 6% of P2O5, 2% to 7% of Li2O, 3% to 11% of Na2O, 0% to 5% of K2O, 0% to 8% of MgO, 0% to 2% of CaO, 0% to 5% of SrO, 0% to 5% of BaO, 0% to 5% of ZnO, 0% to 2% of TiO2, and 0% to 4% of ZrO2.

[0017] Another chemically strengthened glass of the present invention has a Young's modulus E of 80 GPa to 90 GPa, and an average thermal expansion coefficient α in the range of 50°C to 350°C of 60×10 -7 / ℃~85×10 -7 / °C, expressed as mass percentages based on oxides, the other chemically strengthened glass contains 56% to 73% of SiO2, 10% to 24% of Al2O3, 0% to 6% of B2O3, 0% to 6% of P2O5, 2% to 7% of Li2O, 3% to 11% of Na2O, 0% to 5% of K2O, 0% to 8% of MgO, 0% to 2% of CaO, 0% to 5% of SrO, 0% to 5% of BaO, 0% to 5% of ZnO, 0% to 2% of TiO2, and 0% to 4% of ZrO2.

[0018] In one embodiment of the chemically strengthened glass of the present invention, the Tf may be 780° C. or lower.

[0019] In one embodiment of the chemically strengthened glass of the present invention, when differential scanning calorimetry is performed from room temperature to 1000°C at a heating rate of 10°C / min, no crystallization peak may be observed, or the temperature of the crystallization peak may be higher than the softening point.

[0020] In one embodiment of the chemically strengthened glass of the present invention, the thermal conductivity of the chemically strengthened glass at 500° C. may be 1.3 W / mK or higher.

[0021] In one embodiment of the chemically strengthened glass of the present invention, the mirror constant of the chemically strengthened glass may be 2.0 MPa·m 1 / 2 above.

[0022] In one embodiment of the chemically strengthened glass of the present invention, the slow cooling mirror constant measured after holding at a temperature 30°C higher than the glass transition temperature Tg for 1 hour and then slowly cooling to room temperature at a cooling rate of 1°C / min can be 2.0 MPa·m 1 / 2 above.

[0023] In one embodiment of the chemically strengthened glass of the present invention, the softening point of the chemically strengthened glass may be 820° C. or lower.

[0024] In the method for producing a chemically strengthened glass of the present invention, any of the above-mentioned glasses for chemical strengthening is heated and bent in a bending mold, and then chemically strengthened.

[0025] In one embodiment of the method for producing the chemically strengthened glass of the present invention, the bending can be performed by a press molding method.

[0026] The chemically strengthened glass of the present invention is a chemically strengthened glass that has been bent into a curved shape. The basic composition of the chemically strengthened glass, expressed in mass percentages based on oxides, comprises 56% to 73% of SiO2, 10% to 24% of Al2O3, 0% to 6% of B2O3, 0% to 6% of P2O5, 2% to 7% of Li2O, 3% to 11% of Na2O, 0% to 5% of K2O, 0% to 8% of MgO, 0% to 2% of CaO, 0% to 5% of SrO, 0% to 5% of BaO, 0% to 5% of ZnO, 0% to 2% of TiO2, and 0% to 4% of ZrO2, and no devitrification is observed.

[0027] Effects of the Invention

[0028] According to the glass for chemical strengthening of the present invention, a high-strength chemically strengthened glass that can be bent can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1This is a schematic diagram showing an example of an apparatus for bending a glass sheet.

[0030] Figure 2 This figure schematically shows the cracking pattern around the fracture starting point when glass with no internal residual stress fractures due to uniform tensile stress. DETAILED DESCRIPTION

[0031] Hereinafter, the chemically strengthened glass and the chemically strengthened glass of the present invention will be described.

[0032] In this specification, "chemically strengthened glass" refers to glass that has been subjected to a chemical strengthening treatment. On the other hand, "chemically strengthened glass" refers to glass before being subjected to a chemical strengthening treatment. "Chemically strengthened glass" is glass that can be chemically strengthened.

[0033] In this specification, the "basic composition of chemically strengthened glass" refers to the glass composition of chemically strengthened glass. Chemically strengthened glass typically forms a compressive stress layer on the glass surface due to ion exchange. Therefore, the glass composition of the non-ion-exchanged portion of the glass is consistent with the basic composition of the chemically strengthened glass.

[0034] In this specification, "to" means more than the lower limit value and less than the upper limit value.

[0035] In this specification, "mass percentage" and "weight percentage" have the same meaning.

[0036] (First embodiment of chemically strengthened glass)

[0037] First, a first embodiment of the chemically strengthened glass will be described.

[0038] The first aspect is a chemically strengthened glass having a Young's modulus E of 70 GPa or more.

[0039] In the chemically strengthened glass of the present embodiment, the sum X1+X2+X3 of the numerical values ​​X1, X2, and X3 is 1760 or less, the numerical value X1 is the same as the value obtained by multiplying the Young's modulus E by the average thermal expansion coefficient α in the range of 50°C to 350°C [unit: kPa / °C], the numerical value X2 is the same as the temperature Tf [unit: °C] at which the viscosity reaches 100 MPa·s, and the numerical value X3 is the viscosity at Tf (100 MPa·s) and the viscosity η at a temperature 10°C higher than Tf. +10 The difference [unit: 10 5 Pa·s] have the same value.

[0040] (Young's modulus E)

[0041] In this embodiment, the Young's modulus E of the chemically strengthened glass is 70 GPa or greater. Glass with a Young's modulus E of 70 GPa or greater is less susceptible to scratching. The Young's modulus E is preferably 78 GPa or greater, more preferably 80 GPa or greater. Furthermore, if the Young's modulus E is too high, it is prone to breakage during bending, as described later. Therefore, the Young's modulus E is preferably 90 GPa or less, more preferably 85 GPa or less. The Young's modulus E can be measured, for example, using an ultrasonic pulse method.

[0042] (X1+X2+X3)

[0043] In the chemically strengthened glass of the present embodiment, the sum of the numerical values ​​X1, X2, and X3 (X1+X2+X3) is small, the numerical value X1 is the same as the value obtained by multiplying the Young's modulus E and the average thermal expansion coefficient α in the range of 50°C to 350°C [unit: kPa / °C], the numerical value X2 is the same as the temperature Tf [unit: °C] at which the viscosity reaches 100 MPa·s, and the numerical value X3 is the viscosity at Tf (100 MPa·s) and the viscosity η at a temperature 10°C higher than Tf. +10 The difference [unit: 10 5 Pa·s] have the same value.

[0044] Regarding the values ​​X1 to X3, the size of each value has technical significance. By comparing these values ​​with other glasses, it can be determined whether a certain glass is suitable for bending forming.

[0045] As described in detail below, there is a tendency for glasses with smaller values ​​of X1 to X3 to be more suitable for 3D forming. The present inventors have studied various glasses and empirically found that glasses with smaller total values ​​of X1+X2+X3 are more suitable for bending.

[0046] For example, glass with a very low thermal expansion coefficient has a small X1, which is preferable because it is less likely to break during bending. However, glass with a low thermal expansion coefficient generally has high viscosity and tends to have a high forming temperature Tf, which results in a large X2. Therefore, it is important to minimize these values ​​in a balanced manner.

[0047] In the glass of this embodiment, X1+X2+X3 is 1760 or less, preferably 1670 or less, more preferably 1650 or less, and still more preferably 1645 or less. A smaller X1+X2+X3 is preferred from the viewpoint of better formability. However, for chemically strengthened glass, X1+X2+X3 is usually 1000 or more.

[0048] The numerical value X1 is the same as the value obtained by multiplying the Young's modulus E by the average thermal expansion coefficient α in the range of 50°C to 350°C [unit: kPa / °C]. Therefore, glass with a large Young's modulus and a large thermal expansion coefficient has a large X1. Glass with a large X1 value is more likely to break due to contact between the forming mold and the glass sheet, and the efficiency of bending tends to decrease.

[0049] The X1 of ordinary glass is about 900 or less, but in order to suppress cracking during bending, it is preferably 620 or less, more preferably 600 or less. A smaller X1 is preferred because it is less likely to crack, but X1 is usually 350 or more.

[0050] It should be noted that in order to ensure that the glass plate is not easily broken during molding, the average thermal expansion coefficient α is preferably 85×10 -7 / ℃ or less, more preferably 82×10 -7 / ℃ or less, more preferably 80×10 -7 / ℃ or less, particularly preferably 75×10 -7 / ℃ or less. However, since the melting temperature of glass with a small thermal expansion coefficient is high, there is a tendency for glass manufacturing efficiency to be poor. From the perspective of melting efficiency, the thermal expansion coefficient is preferably 50×10 -7 / ℃ or above, more preferably 60×10 -7 / ℃ or more, more preferably 70×10 -7 / ℃ or above.

[0051] The numerical value X2 is the same as the temperature Tf [unit: °C] at which the viscosity reaches 100 MPa·s. Generally, glass bending is preferably performed at a temperature near Tf, which is the temperature at which the viscosity reaches 100 MPa·s. Therefore, the larger the X2, the higher the temperature suitable for bending. Consequently, glass with a large X2 requires more energy for bending, and bending dies and other tools used for bending are more susceptible to degradation, which tends to reduce bending efficiency.

[0052] The X2 of ordinary glass is about 900 or less, but in order to improve the efficiency of bending, it is preferably 780 or less, more preferably 750 or less. The smaller the X2, the more favorable it is because bending can be performed at lower temperatures, but X2 is usually 550 or more.

[0053] That is, Tf is preferably 780° C. or lower, more preferably 750° C. or lower, and further preferably 710° C. or lower. In general, Tf is 550° C. or higher for chemically strengthened glass.

[0054] The temperature Tf can be measured using a beam bending method (JIS R3103-2:2001).

[0055] The value X3 is the viscosity at Tf (100 MPa·s) and the viscosity at a temperature 10°C higher than Tf. +10 The difference [unit: 10 5 Since X3 is the same as [Pa·s], the larger the glass, the greater the viscosity change near the forming temperature. Therefore, glass with a larger X3 tends to be more susceptible to problems such as inadequate bending or excessive deformation due to slight temperature fluctuations during bending. To prevent these problems, X3 is preferably 380 or less, more preferably 360 or less, and even more preferably 350 or less. Lower X3 values ​​can more effectively prevent these problems, but for typical glass, X3 is typically 100 or greater.

[0056] Viscosity η at a temperature 10°C higher than Tf +10 The measurement can be performed using a beam bending method (JIS R3103-2:2001).

[0057] (Other features)

[0058] The chemically strengthened glass of this embodiment preferably has a softening point of 820°C or lower, more preferably 800°C or lower, and even more preferably 780°C or lower. This is because a higher softening point of the glass increases the heat treatment temperature during bending, which in turn increases energy consumption and the load on the equipment. To reduce bending temperatures, a lower softening point is preferred. However, glass with an excessively low softening point tends to relax stress introduced during chemical strengthening, resulting in reduced strength. Therefore, the softening point of the chemically strengthened glass of the present invention is preferably 700°C or higher, more preferably 720°C or higher, and even more preferably 740°C or higher.

[0059] In order to reduce the temperature distribution inside the glass sheet during forming, the thermal conductivity σ of the chemically strengthened glass of this embodiment at 500°C is 500 It is preferably 1.3 W / mK or higher, more preferably 1.34 W / mK or higher, further preferably 1.38 W / mK or higher, 1.42 W / mK or higher, 1.46 W / mK or higher, or 1.5 W / mK or higher.

[0060] Thermal conductivity σ at room temperature 20 It is preferably 0.9 W / mK or higher, more preferably 1.0 W / mK or higher, and even more preferably 1.1 W / mK or higher.

[0061] On the other hand, in order to locally heat and shape a portion of the glass sheet, σ 500 It is preferably 2.0 W / mK or less. 20 It is preferably 3.0 W / mK or less.

[0062] Thermal conductivity can be measured by a laser flash method or the like.

[0063] For chemically strengthened glass, controlling the mirror constant within an appropriate range can suppress the scattering of fragments when the glass breaks, thereby improving safety. The mirror constant is described below.

[0064] It is known that when glass breaks, the shape of the fracture surface varies depending on the magnitude of the stress. Figure 2 FIG. 2 schematically shows the fracture pattern around the fracture starting point when glass having no internal residual stress, that is, glass that has not been chemically strengthened, fractures due to uniform tensile stress (refer to ASTM C-1678-10).

[0065] Figure 2 In the figure, a smooth surface called a mirror surface is generated around the fracture starting point represented by the black circle. In addition, a slightly rough boundary surface called a mist surface is generated around it, and a rough surface called a hackle surface is generated at its end. Figure 2 In the equation ( ), if the distance from the fracture starting point indicated by the black circle to the boundary between the mirror surface and the mist surface is R, and the stress at the time of fracture is s, it is known that s is proportional to the inverse of the square root of R, and the proportionality constant is the mirror constant A. That is, the relationship is as shown in the following equation.

[0066] s=A / R 1 / 2

[0067] The mirror constant A is experimentally determined by measuring the stress s at the time of fracture and the distance R from the fracture starting point to the interface between the mirror surface and the matte surface.

[0068] The mirror constant depends on the glass composition and the fictive temperature. The fictive temperature is an indicator of the disorder of the glass structure. It is known that even for the same glass composition, the glass structure will be different when the fictive temperature is different, so the physical properties such as density and refractive index will change. The relationship between the mirror constant and the glass composition will be described in detail later. In addition, the lower the fictive temperature of the glass, the larger the mirror constant. In addition, the slower the cooling rate after heating the glass, the lower the fictive temperature. Therefore, when the glass is cooled slowly enough so that the fictive temperature reaches below the glass transition temperature Tg (hereinafter referred to as Tg), the mirror constant is the largest, and when it is cooled rapidly, the mirror constant decreases.

[0069] The mirror constant A of chemically strengthened glass is 2.0 MPa·m 1 / 2When the glass is shattered, the number of fragments is small. Therefore, even if the internal tensile stress CT increases due to strengthening, the fragments are less likely to scatter, which improves safety and is therefore preferred. In this case, the surface compressive stress CS (hereinafter referred to as CS) after chemical strengthening can be increased. For chemically strengthened glass with a high CS, even if scratches occur on the surface, the surface compressive stress has the effect of narrowing the scratch, making it less likely to break.

[0070] The mirror constant A of the chemically strengthened glass of this embodiment is more preferably 2.1 MPa·m 1 / 2 More preferably, 2.3 MPa·m 1 / 2 above.

[0071] In this specification, the mirror constant measured by holding glass at a temperature 30°C above its Tg for one hour and then slowly cooling it to room temperature at a rate of 1°C / minute is referred to as the "slow cooling mirror constant." The mirror constant of glass depends on its composition and fictive temperature, which in turn depends on its thermal history. Therefore, the slow cooling mirror constant can be considered a characteristic value of glass that has been freed from the effects of thermal history.

[0072] The chemically strengthened glass of this embodiment preferably has an annealed mirror constant of 2.0 MPa·m 1 / 2 More than 2.1 MPa·m 1 / 2 More preferably, 2.3 MPa·m 1 / 2 above.

[0073] (Glass composition)

[0074] In order to obtain high strength by chemical strengthening, the chemically strengthened glass of this embodiment preferably has a glass composition suitable for ion exchange.

[0075] Chemical strengthening is typically performed by exchanging alkali metal ions with larger ionic radii from the glass surface for smaller alkali metal ions in the glass. Ion exchange confines the larger alkali metal ions to locations where smaller alkali metal ions are present, generating compressive stress in the areas where the ion exchange occurs. This compressive stress on the glass surface makes it less susceptible to scratching, and even if it does, it resists cracking.

[0076] In this embodiment, the glass used for chemical strengthening is preferably lithium aluminosilicate glass. Because lithium aluminosilicate glass contains lithium ions with a small ionic radius, sodium or potassium salts can be used for chemical strengthening. Furthermore, since lithium ions are easily mobilized through ion exchange, the depth of the compressive stress layer (DOL) (hereinafter referred to as DOL) can be easily increased. Furthermore, by using sodium and potassium salts for chemical strengthening, the surface compressive stress CS and DOL can be appropriately adjusted.

[0077] More specifically, it is preferred that the glass composition contain 56% to 73% SiO2, 10% to 24% Al2O3, 0% to 6% B2O3, 0% to 6% P2O5, 2% to 7% Li2O, 3% to 11% Na2O, 0% to 5% K2O, 0% to 8% MgO, 0% to 2% CaO, 0% to 5% SrO, 0% to 5% BaO, 0% to 5% ZnO, 0% to 2% TiO2, and 0% to 4% ZrO2, expressed in terms of mass percentage based on oxides.

[0078] In addition, a more preferred glass composition is one that contains, in terms of mass percentage based on oxides, 63% to 72% SiO2, 11% to 16% Al2O3, 0% to 5% B2O3, 0% to 4% P2O5, 2% to 5% Li2O, 4% to 8% Na2O, 0% to 2% K2O, 1% to 6.5% MgO, 0% to 2% CaO, 0% to 4% SrO, 0% to 4% BaO, 0% to 2% ZnO, 0% to 2% TiO2, and 0% to 3% ZrO2.

[0079] Lithium aluminosilicate glass is known to readily precipitate crystals, sometimes resulting from heat treatments used for bending. Crystals precipitated from lithium aluminosilicate glass are, for example, spodumene. Depending on the glass composition, lithium silicate, quartz solid solutions, and the like may also precipitate. Such crystals are prone to becoming defects, so their precipitation is preferably suppressed as much as possible.

[0080] In order to suppress the precipitation of crystals during bending, the crystallization peak temperature of the chemically strengthened glass measured by the following measurement method is preferably higher than the softening point of the glass. Furthermore, it is more preferable that no crystallization peak is observed.

[0081] (Measurement method)

[0082] About 70 mg of glass was pulverized and ground in an agate mortar, and measured using a differential scanning calorimeter (DSC) from room temperature to 1000° C. at a heating rate of 10° C. / min.

[0083] Furthermore, if a crystallization peak is observed using the above-mentioned measurement method, and the crystals precipitated during holding at that temperature are spodumene, the crystals will grow significantly during heating for bending, which can easily cause defects. This is because spodumene crystals grow rapidly.

[0084] Therefore, in the case of a glass composition that easily precipitates spodumene, it is particularly preferred that crystals are not easily formed. In addition, the thermal history received by the glass is preferably a thermal history in which crystals are not easily grown. This is because, even for the same glass composition, the longer the exposure time to the crystal nucleation temperature range, the easier it is to form crystals. For example, for glass obtained by melting at high temperature and then cooling, it is sometimes heated again for bending and forming, thereby facilitating crystallization.

[0085] Hereinafter, each component in the above-mentioned preferred glass composition will be described.

[0086] SiO2 is a component that forms the skeleton of glass. Furthermore, SiO2 improves chemical durability and reduces the occurrence of cracks when scratches (indentations) are applied to the glass surface. To suppress cracking, the SiO2 content is preferably 56% or greater, more preferably 63% or greater, further preferably 65% ​​or greater, and particularly preferably 68% or greater. On the other hand, to improve meltability during the glassmaking process, the SiO2 content is preferably 73% or less, more preferably 72% or less, further preferably 70% or less, and particularly preferably 68% or less.

[0087] Al2O3 is an effective component for improving the ion exchange performance during chemical strengthening and increasing the surface compressive stress CS after chemical strengthening. In addition, Al2O3 has the effect of increasing the mirror constant A of the glass. In addition, Al2O3 is a component that increases the Tg of the glass and is also a component that increases the Young's modulus. In order to improve the chemical strengthening characteristics, the Al2O3 content is preferably 10% or more, more preferably 11% or more. In addition, in order to increase the mirror constant, the Al2O3 content is further preferably 13% or more. On the other hand, when the Al2O3 content is too high, the acid resistance of the glass decreases or the devitrification temperature is easily increased. Therefore, the Al2O3 content is preferably 24% or less, more preferably 20% or less, and even more preferably 18% or less.

[0088] Furthermore, Al2O3 is a constituent of lithium aluminosilicate crystals. To suppress crystal precipitation during bending, the Al2O3 content is preferably 16% or less, more preferably 14% or less, and even more preferably 13% or less.

[0089] B2O3 is a component that improves the meltability of glass. It also improves the crack resistance of glass. B2O3 is not an essential component, but to improve meltability, its content, when present, is preferably 0.5% or higher, more preferably 1% or higher, and even more preferably 2% or higher. On the other hand, excessive B2O3 content can cause striae during melting, which can degrade the quality of chemically strengthened glass. Therefore, the B2O3 content is preferably 6% or lower, more preferably 5% or lower, even more preferably 3% or lower, and particularly preferably 1% or lower. To improve acid resistance, it is preferably substantially free of B2O3.

[0090] In this specification, "substantially free of" means free of impurities other than inevitable impurities contained in raw materials, etc., that is, not intentionally contained. Specifically, it means that the content in the glass composition is less than 0.1%.

[0091] P2O5 is a component that improves ion exchange performance and chipping resistance during chemical strengthening treatment. P2O5 is not an essential component, but when present, its content is preferably 0.5% or more, more preferably 1% or more, and even more preferably 2% or more. On the other hand, excessive P2O5 content significantly reduces acid resistance. Therefore, the P2O5 content is preferably 6% or less, more preferably 4% or less, even more preferably 3% or less, even more preferably 2% or less, and particularly preferably 1% or less. To improve acid resistance, it is preferably substantially free of P2O5.

[0092] Li2O is a component that forms a surface compressive stress layer by chemical strengthening treatment using sodium salts such as sodium nitrate, and is an essential component of lithium aluminosilicate glass.

[0093] A Li2O content of 2% or more increases the compressive stress generated by chemical strengthening, so it is preferred. A Li2O content of 3% or more is more preferred, and 5% or more is even more preferred. On the other hand, excessive Li2O content reduces weather resistance, so it is preferably 7% or less. Furthermore, to suppress crystal precipitation during bending, a Li2O content of 6% or less is preferred, and 5% or less is even more preferred.

[0094] Na 2 O is a component that forms a surface compressive stress layer during chemical strengthening treatment using potassium salt, and is also a component that can improve the solubility of glass.

[0095] To achieve this effect, the Na2O content is preferably 2% or more, more preferably 3% or more, and even more preferably 4% or more. On the other hand, to avoid a decrease in the surface compressive stress CS due to the sodium salt, the Na2O content is preferably 11% or less, more preferably 9% or less, even more preferably 8% or less, and particularly preferably 6% or less.

[0096] To improve the glass's meltability, K₂O may be contained. If K₂O is contained, the content is preferably 0.5% or greater, more preferably 1% or greater. On the other hand, to prevent degradation of the crushability of chemically strengthened glass, the K₂O content is preferably 5% or less, more preferably 3% or less, and even more preferably 2% or less.

[0097] MgO is not an essential component, but its inclusion is preferred to increase the surface compressive stress CS of chemically strengthened glass. MgO also has the effect of increasing the mirror constant A. Therefore, the MgO content is preferably 1% or greater, more preferably 2% or greater, and even more preferably 3% or greater. On the other hand, to suppress devitrification during glass melting, the MgO content is preferably 8% or less, more preferably 6.5% or less, and even more preferably 5% or less.

[0098] CaO is not an essential component, but it improves the meltability of the glass and has the effect of increasing the mirror constant A, so it may be contained. If CaO is contained, the content is preferably 0.1% or more, more preferably 0.15% or more, even more preferably 0.3% or more, and particularly preferably 1% or more. On the other hand, excessive CaO content may reduce ion exchange performance during chemical strengthening treatment. Therefore, it is preferably 2% or less, more preferably 1% or less, and even more preferably substantially no CaO is contained.

[0099] SrO is not an essential component, but it improves the meltability of the glass and has the effect of increasing the mirror constant A, so it may be contained. If SrO is contained, the content is preferably 0.1% or more, more preferably 0.15% or more, even more preferably 0.3% or more, and particularly preferably 1% or more. On the other hand, to improve ion exchange performance during chemical strengthening, the SrO content is preferably 5% or less, more preferably 4% or less, even more preferably 2% or less, and it is particularly preferred that SrO be substantially absent.

[0100] BaO is not an essential component, but it improves the meltability of the glass and has the effect of increasing the mirror constant A, so it may be contained. If BaO is contained, the content is preferably 0.1% or more, more preferably 0.15% or more, even more preferably 0.3% or more, and particularly preferably 1% or more. On the other hand, to improve ion exchange performance during chemical strengthening, the BaO content is preferably 5% or less, more preferably 4% or less, even more preferably 2% or less, and it is particularly preferred that substantially no BaO is contained.

[0101] ZnO is a component that improves the meltability of glass and may be contained. If ZnO is contained, the content is preferably 0.25% or greater, more preferably 0.5% or greater. On the other hand, a ZnO content of 5% or less is preferred because it improves the weather resistance of the glass. The ZnO content is more preferably 2% or less, even more preferably 1% or less, and it is particularly preferred that substantially no ZnO be contained.

[0102] TiO₂ is a component that suppresses changes in the color tone of glass caused by solarization, and may be contained. If TiO₂ is contained, the content is preferably 0.03% or more, more preferably 0.1% or more, even more preferably 0.2% or more, and particularly preferably 0.3% or more. On the other hand, to suppress devitrification during melting, the content is preferably 2% or less, more preferably 0.5% or less, and even more preferably 0.2% or less.

[0103] ZrO₂ is a component that increases the surface compressive stress CS generated by ion exchange during chemical strengthening treatment, and ZrO₂ may be contained. If ZrO₂ is contained, the content is preferably 0.5% or more, more preferably 0.75% or more, and even more preferably 1% or more. On the other hand, to suppress devitrification during melting and improve the quality of chemically strengthened glass, the content is preferably 4% or less, more preferably 3% or less, and particularly preferably 2% or less.

[0104] Fe₂O₃ absorbs heat rays, thus improving the solubility of glass. Therefore, Fe₂O₃ is preferably contained when mass-producing glass using large melting furnaces. In this case, the content is preferably 0.002% or greater, more preferably 0.005% or greater, even more preferably 0.007% or greater, and particularly preferably 0.01% or greater. On the other hand, excessive Fe₂O₃ can cause coloration. Therefore, to improve 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.

[0105] It should be noted that while all iron oxides in glass are described here as Fe2O3, in reality, oxidized Fe(III) and reduced Fe(II) are typically present in a mixture. Fe(III) produces a yellow color, while Fe(II) produces a blue color. The balance between the two creates a green color in the glass.

[0106] Y2O3, La2O3, and Nb2O5 may be contained. If these components are contained, their combined content is preferably 0.5% or greater, more preferably 1% or greater, even more preferably 1.5% or greater, particularly preferably 2% or greater, and most preferably 2.5% or greater. On the other hand, excessive Y2O3, La2O3, and Nb2O5 contents can easily lead to devitrification of the glass during melting, degrading the quality of the chemically strengthened glass. Therefore, the combined content of these components is preferably set to 8% or less. The combined content of Y2O3, La2O3, and Nb2O5 is more preferably 6% or less, even more preferably 5% or less, particularly preferably 4% or less, and most preferably 3% or less.

[0107] In order to improve the breakability of chemically strengthened glass, a small amount of Ta2O5 and Gd2O3 may be contained. However, since the refractive index and reflectivity increase, the content is preferably 1% or less, more preferably 0.5% or less, and even more preferably not contained.

[0108] Furthermore, when coloring the glass, coloring components may be added within a range that does not hinder the achievement of the desired chemical strengthening properties. Suitable coloring components include, for example, Co3O4, MnO2, NiO, CuO, Cr2O3, V2O5, Bi2O3, SeO2, CeO2, Er2O3, and Nd2O3.

[0109] A total content of 7% or less of coloring components is preferred, as this reduces the risk of problems such as devitrification. This content is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less. When prioritizing visible light transmittance of the glass, it is preferred that these components be substantially absent.

[0110] SO₃, chlorides, fluorides, etc. may be appropriately contained as clarifiers during glass melting. As₂O₃ has a large environmental impact, so it is preferably not contained. When Sb₂O₃ is contained, it is preferably 0.3% or less, more preferably 0.1% or less, and most preferably not contained.

[0111] Glass with a large β-OH value, which is an indicator of the amount of water in the glass, tends to have a lower Tf and be easier to bend. Therefore, the β-OH value is preferably 0.1 mm -1 More than 0.15 mm -1 More than, more preferably 0.2mm -1 Above, particularly preferably 0.22 mm -1 Above, most preferably 0.25mm -1 above.

[0112] On the other hand, from the perspective of improving strength by chemical strengthening of glass, when the β-OH value of glass increases, the value of surface compressive stress CS after chemical strengthening treatment decreases, making it difficult to improve strength. Therefore, the β-OH value is preferably 0.5 mm -1 Below, more preferably 0.4 mm -1 Below, more preferably 0.3 mm -1 the following.

[0113] Here, the "β-OH value" is the absorption wavelength of hydroxyl group at 3570 cm-1 measured by FT-IR method. -1 Minimum transmittance T2 (%) near the reference wavelength 4000cm -1 The transmittance T1 (%) and the thickness t (unit: mm) of the glass plate under the above conditions are calculated according to formula (1).

[0114] β-OH value = (1 / t)log 10 (T1 / T2) (1)

[0115] In addition, the β-OH value can be adjusted by the amount of water contained in the glass raw material and the melting conditions.

[0116] <Method for Manufacturing Chemically Strengthened Glass>

[0117] The chemically strengthened glass of this embodiment can be produced using conventional methods. For example, glass raw materials are appropriately blended, heated to approximately 1500°C to 1700°C for melting, homogenized by degassing and stirring, and then formed into a sheet using a known float method, down-draw method (melt method, etc.), or press method. Alternatively, glass sheets can be produced by casting into a block, slowly cooling, and then cutting into the desired size.

[0118] The chemically strengthened glass of this embodiment is ground as needed. However, in addition to or in place of grinding, the main surface of the chemically strengthened glass may be treated with a fluorine-containing agent or the like. In order to stably produce the chemically strengthened glass of the present invention, the float process or down-draw process is preferred as a sheet-forming method. The float process is particularly preferred for producing large-scale chemically strengthened glass. The float process lowers the fictive temperature, which facilitates an increase in the mirror constant.

[0119] The chemically strengthened glass sheet of this method is cut into sizes appropriate to the intended use. For example, when used in displays of mobile phones or various window glass applications, it is typically cut into rectangular shapes. However, other shapes such as circular or polygonal shapes are also possible, and hole drilling can be performed.

[0120] The chemically strengthened glass plate of this embodiment has a thickness suitable for its application. For example, when used as a cover glass for a display portion of a mobile phone, the thickness is preferably 2.0 mm or less, more preferably 1.0 mm or less, and even more preferably 0.75 mm or less.

[0121] <Bending>

[0122] The chemically strengthened glass of this embodiment can be bent. By bending the chemically strengthened glass of this embodiment and then subjecting it to the chemical strengthening treatment described below, a high-strength chemically strengthened glass that has been bent can be obtained.

[0123] Hereinafter, an example of bending of a glass sheet will be described, but the bending performed on the chemically strengthened glass of this embodiment is not limited thereto.

[0124] When bending a glass plate, a flat glass plate is usually cut, processed such as chamfering, and then bent.

[0125] As the bending forming method, any method can be selected from existing bending forming methods such as self-weight forming, vacuum forming, and press forming. In addition, two or more bending forming methods can be used in combination.

[0126] The self-weight forming method is a method in which a glass sheet is placed on a forming mold, the glass sheet is heated, and gravity is used to conform the glass sheet to the forming mold, thereby bending the glass sheet into a predetermined shape.

[0127] Vacuum forming involves placing a glass sheet in a forming mold, sealing the periphery of the glass sheet, and then reducing the pressure in the space between the forming mold and the glass sheet. This creates a pressure differential between the front and back surfaces of the glass sheet, thereby bending the sheet. A supplementary pressure may be applied to the top surface of the glass sheet.

[0128] Press molding is a method in which a glass sheet is placed between forming dies (a lower die and an upper die), the glass sheet is heated, and a pressing load is applied between the upper and lower forming dies to bend the glass sheet into a predetermined shape.

[0129] Figure 1 An example of a bending device based on a press forming method is shown. In order to explain an example of a bending method for chemically strengthened glass of this embodiment, first, Figure 1 An example of a method for bending a glass sheet will be described.

[0130] Figure 1The bending apparatus 100 shown includes an atmosphere replacement chamber 10, a forming chamber 20, and an atmosphere replacement chamber 30. The forming chamber 20 includes a heating area 21, a forming area 22, and a cooling area 23, each of which is equipped with forming dies 2 and 3 and a press 4. The forming dies 2 and 3 are made of, for example, carbon. To prevent degradation of the forming dies 2 and 3, the forming chamber 20 is filled with an inert gas such as nitrogen. To maintain an inert atmosphere within the forming chamber 20, the atmosphere replacement chamber 10 and the atmosphere replacement chamber 30 are located at both ends of the forming chamber 20.

[0131] First, the glass sheet 1 is inserted into the atmosphere replacement chamber 10. Next, the glass sheet 1 is conveyed to the heating area 21 of the molding chamber 20 by a conveying mechanism (not shown).

[0132] In the heating zone 21, the glass sheet 1 is heated by contact with the forming dies 2 and 3. The glass sheet 1 is conveyed from the heating zone 21 to the forming zone 22 and the cooling zone 23, sequentially, by a conveying mechanism. The forming dies 2 and 3 and the press 4 in each zone gradually heat and press the glass sheet 1, bending it into shape and then cooling it. The bent glass sheet is then conveyed into the atmosphere replacement chamber 30 and removed.

[0133] Figure 1 The lower mold 2 of the forming molds 2 and 3 is convex, but a curved forming mold with a concave lower mold may also be used. In addition, in the forming apparatus 100, the forming molds 2 and 3 and the press 4 are installed in each area of ​​the forming chamber 20. However, an apparatus may also be used in which a press equipped with a heating mechanism is installed in the forming chamber to perform forming while conveying the forming mold with the glass sheet placed thereon.

[0134] In either case, if the heating balance is disrupted, the glass sheet may be elastically deformed. The glass sheet may be broken by contact with the forming mold in the elastically deformed state.

[0135] In addition, because the glass sheet is heated from the surface, the temperature difference between the surface and the inside of the glass sheet sometimes increases. In this case, because thermal stress is generated inside the glass sheet, the glass sheet sometimes breaks.

[0136] Temperature fluctuations during molding can also affect the viscosity of the molded glass. If the viscosity of the glass is too high, the glass sheet will not easily deform due to viscous deformation, making it difficult to fully mold. If the viscosity of the glass is too low, the glass sheet will undergo excessive viscous deformation, sometimes preventing the desired shape from being achieved and easily causing surface defects.

[0137] The higher the temperature required for bending a glass sheet, the greater the energy consumption and the more susceptible the forming mold is to wear. In addition, the temperature gradient inside the forming device becomes larger, which makes it easy for the glass sheet to be heated unevenly.

[0138] <Chemical Strengthening Treatment>

[0139] Chemically strengthened glass is obtained by subjecting the chemically strengthened glass of this embodiment to a chemical strengthening treatment. Before the chemical strengthening treatment, it is preferably subjected to shape processing, such as cutting, end surface processing, and drilling processing, depending on the intended use.

[0140] The chemical strengthening treatment can be performed, for example, by cutting the produced chemically strengthened glass into a desired size, then preheating the chemically strengthened glass to approximately 400° C., and ion-exchanging Li on the surface of the glass sheet with Na in the molten salt, or ion-exchanging Na on the surface of the glass sheet with K in the molten salt.

[0141] Alternatively, chemically strengthened glass having higher strength can be obtained by performing ion exchange in a molten salt containing a specific salt, followed by acid treatment and alkali treatment.

[0142] Examples of molten salts used for ion exchange treatment include alkali metal nitrates, alkali metal sulfates, and alkali metal chlorides, such as potassium nitrate, sodium nitrate, potassium sulfate, and sodium sulfate. These molten salts can be used alone or in combination. Other salts can also be mixed to adjust chemical strengthening properties.

[0143] The surface compressive stress CS of the chemically strengthened glass can be adjusted by, for example, adjusting the Na concentration in the molten potassium nitrate salt used for ion exchange, the strengthening time, and the molten salt temperature.

[0144] Alternatively, the DOL can be adjusted by adjusting the sodium concentration in the molten potassium nitrate salt used in the ion exchange process, the strengthening time, and the temperature of the molten salt. To achieve a higher DOL, the molten salt temperature can be increased. Furthermore, the internal tensile stress (CT) of chemically strengthened glass can be adjusted by adjusting the CS and DOL as described above.

[0145] When a glass sheet is immersed in sodium nitrate at 450°C for 3 hours, followed by immersion in potassium nitrate at 450°C for 1.5 hours, the surface compressive stress CS is preferably 600 MPa or greater, more preferably 650 MPa or greater, and even more preferably 700 MPa or greater. On the other hand, if CS and DOL are too large, strengthening cracking may frequently occur during the strengthening process, resulting in a decrease in yield. Therefore, when a glass sheet is immersed in sodium nitrate at 450°C for 3 hours, followed by immersion in potassium nitrate at 450°C for 1.5 hours, the surface compressive stress CS is preferably 1100 MPa or less, more preferably 1000 MPa or less, and even more preferably 950 MPa or less.

[0146] When the glass plate is immersed in sodium nitrate at 450°C for one hour, the surface compressive stress CS is preferably 250 MPa or greater, more preferably 280 MPa or greater, and even more preferably 310 MPa or greater. Furthermore, the resulting DOL is preferably 80 μm or greater, more preferably 90 μm or greater, and even more preferably 100 μm or greater.

[0147] On the other hand, if CS and DOL are too large, strengthening cracks often occur during the strengthening process, resulting in a decrease in yield. Therefore, the surface compressive stress CS of a glass sheet immersed in sodium nitrate at 450°C for one hour is preferably 400 MPa or less, more preferably 380 MPa or less, and even more preferably 360 MPa or less. Furthermore, DOL is preferably 130 μm or less, more preferably 120 μm or less, and even more preferably 100 μm or less.

[0148] Ion exchange treatment with sodium salts is an effective chemical strengthening method for increasing the DOL while suppressing cracking caused by overstrengthening. On the other hand, ion exchange treatment with potassium salts is effective for increasing the compressive stress on the glass surface. Combining treatment with sodium and potassium salts can increase surface compressive stress and DOL while suppressing cracking caused by overstrengthening.

[0149] Chemically strengthened glass can be cut after chemical strengthening. Cutting methods include scribing and breaking with a conventional wheel-type wafer saw, or laser cutting. To maintain glass strength, the cut edges can be chamfered after cutting. This can be achieved by mechanical grinding or treatment with a reagent such as hydrofluoric acid.

[0150] [Second embodiment of chemically strengthened glass]

[0151] Next, a second embodiment of the chemically strengthened glass will be described.

[0152] The second embodiment has a Young's modulus of 80 GPa to 90 GPa and an average thermal expansion coefficient α within the range of 50°C to 350°C of 60×10 -7 / ℃~85×10 -7 / ℃ chemically strengthened glass.

[0153] Expressed in percentage by mass based on oxides, the chemically strengthened glass of this embodiment contains 56% to 73% of SiO2, 10% to 24% of Al2O3, 0% to 6% of B2O3, 0% to 6% of P2O5, 2% to 7% of Li2O, 3% to 11% of Na2O, 0% to 5% of K2O, 0% to 8% of MgO, 0% to 2% of CaO, 0% to 5% of SrO, 0% to 5% of BaO, 0% to 5% of ZnO, 0% to 2% of TiO2, and 0% to 4% of ZrO2.

[0154] <Young's modulus E>

[0155] The chemically strengthened glass of this embodiment has a Young's modulus of 80 GPa to 90 GPa to ensure scratch resistance and crack resistance during bending. To improve scratch resistance, the Young's modulus is preferably 80 GPa or higher, more preferably 81 GPa or higher, and even more preferably 82 GPa or higher. To improve crack resistance during bending, the Young's modulus is preferably 90 GPa or lower, more preferably 88 GPa or lower, and even more preferably 86 GPa. The Young's modulus E can be measured, for example, using an ultrasonic pulse method.

[0156] <Coefficient of Thermal Expansion>

[0157] For the chemically strengthened glass according to this embodiment, the average thermal expansion coefficient α in the range of 50°C to 350°C is adjusted to 85×10 -7 / ℃ or less. It should be noted that it is preferably 80×10 -7 / ℃ or less, more preferably 76×10 -7 On the other hand, since glass with a low thermal expansion coefficient has a high melting temperature and tends to have poor glass production efficiency, the average thermal expansion coefficient α in the range of 50°C to 350°C is adjusted to 60×10 -7 / ℃ or more. It should be noted that it is preferably 64×10 -7 / ℃ or more, more preferably 68×10 -7 / ℃ or above.

[0158] <Glass Composition>

[0159] Expressed in terms of mass percentages based on oxides, the chemically strengthened glass according to this embodiment contains 56% to 73% SiO2, 10% to 24% Al2O3, 0% to 6% B2O3, 0% to 6% P2O5, 2% to 7% Li2O, 3% to 11% Na2O, 0% to 5% K2O, 0% to 8% MgO, 0% to 2% CaO, 0% to 5% SrO, 0% to 5% BaO, 0% to 5% ZnO, 0% to 2% TiO2, and 0% to 4% ZrO2. The reason for specifying the components as described above is the same as that described in the first embodiment.

[0160] <Other features>

[0161] The temperature Tf at which the viscosity of the chemically strengthened glass according to the present embodiment reaches 100 MPa·s, the softening point, the thermal conductivity σ at 500° C. 500 , thermal conductivity σ at room temperature 20 , mirror constant, slow cooling mirror constant, the preferred numerical range of β-OH value and its accompanying technical effects are the same as those of the first embodiment

[0162] In addition, the method for producing the chemically strengthened glass according to the present embodiment is not particularly limited, and for example, the glass can be produced by the same method as that of the first embodiment.

[0163] The chemically strengthened glass according to this embodiment can be bent by the same method as that of the first embodiment.

[0164] The chemically strengthened glass according to this embodiment can be subjected to a chemical strengthening treatment by the same method as that of the first embodiment.

[0165] [Chemically strengthened glass]

[0166] Next, embodiments of the chemically strengthened glass of the present invention will be described.

[0167] The chemically strengthened glass of this embodiment is a chemically strengthened glass that has been bent into a curved shape.

[0168] The chemically strengthened glass of this embodiment has a basic composition, expressed in percentage by mass based on oxides, of 56% to 73% SiO2, 10% to 24% Al2O3, 0% to 6% B2O3, 0% to 6% P2O5, 2% to 7% Li2O, 3% to 11% Na2O, 0% to 5% K2O, 0% to 8% MgO, 0% to 2% CaO, 0% to 5% SrO, 0% to 5% BaO, 0% to 5% ZnO, 0% to 2% TiO2, and 0% to 4% ZrO2, and no devitrification is observed.

[0169] The chemically strengthened glass of this embodiment can be produced, for example, by subjecting the first embodiment of the chemically strengthened glass or the second embodiment of the chemically strengthened glass to bending and chemical strengthening treatment using the above-mentioned method.

[0170] The reason why the basic composition of the chemically strengthened glass according to this embodiment is defined as described above is the same as that described in the first embodiment.

[0171] The chemically strengthened glass of this embodiment has excellent quality because no devitrification is observed. Here, no devitrification is observed means that no crystal precipitation is observed on the surface or inside of the glass under optical microscope observation.

[0172] The chemically strengthened glass and the applications of the chemically strengthened glass of the present invention are not particularly limited. Since chemically strengthened glass has high mechanical strength, it is suitable for use in areas where impact from dropping or contact with other substances is expected.

[0173] Specifically, it is used as cover glass for displays of mobile phones (including multifunctional information terminals such as smartphones), PHS, PDAs, and tablet terminals, as well as cover glass for displays used in touch panel operations of these devices.

[0174] Furthermore, the present invention can also be used for window glass for vehicles, ships, airplanes, etc., and lighting equipment for household or industrial use.

[0175] Example

[0176] Hereinafter, the present invention will be further described using examples, but the present invention is not limited to the following examples.

[0177] For Examples 1-38, glass raw materials were prepared to obtain the compositions expressed in moles in Tables 1-4, placed in a platinum crucible, and melted at 1500°C to 1700°C for 3 hours. Degassing and homogenization were performed to produce approximately 1000 g of glass. For Examples 2, 3, 8-19, and 24-38, nitrogen gas with a dew point adjusted to 50°C was introduced into the glass melting furnace to increase the moisture content (β-OH value) in the glass. The resulting molten glass was poured into a mold, held at a temperature approximately 50°C above the glass transition temperature for 1 hour, and then cooled to room temperature at a cooling rate of 0.5°C / minute to produce glass blocks. The resulting glass blocks were cut, ground, and mirror-polished to produce glass plates of the desired shape.

[0178] Example 3A is an example of producing glass with a composition substantially the same as that of Example 3 by the float process, but because it contains a trace amount of TiO2, it is easier to crystallize than Example 3.

[0179] The physical property values of the obtained glass plates were measured using the following methods. The measurement results, X1, X2, X3 calculated from the measurement results, their sum, and the glass composition expressed in mass percentages are shown in Tables 5 to 8. It should be noted that the values shown within <> in Tables 5 to 8 are calculated values. Additionally, the blank columns indicate that the measurement was not performed.

[0180] <Density [unit: g / cm 3 >

[0181] Measurement was performed using the Archimedes method.

[0182] <Average thermal expansion coefficient α [unit: 10 -7 / ℃] and glass transition temperature Tg [unit: ℃]>

[0183] Measurement was performed using the method described in JIS R 3102:1995 to obtain the average thermal expansion coefficient α and the glass transition temperature Tg within the range of 50℃ to 350℃.

[0184] <Young's modulus E [unit: GPA], rigidity modulus G [unit: GPA], Poisson's ratio>

[0185] Measurement was performed using the ultrasonic pulse method (refer to JIS R1602:1995).

[0186] <Softening point [unit: ℃]>

[0187] Measurement was performed using the fiber stretching method described in JIS R3103-1: The physical property values of the obtained glass plates were measured using the following methods. The measurement results, X1, X2, X3 calculated from the measurement results, their sum, and the glass composition expressed in mass percentages are shown in Tables 5 to 8. It should be noted that the values shown within <> in Tables 5 to 8 are calculated values. Additionally, the blank columns indicate that the measurement was not performed.

[0188] <Tf [unit: ℃] and η +10 [unit: 10 5 Pa·s]>

[0189] Measurement was performed using the beam bending method (JIS R 3103-2:2001).

[0190] <Thermal conductivity [unit: W / mK]>

[0191] The thermal diffusivity at 500℃ and 20℃ was measured using a laser flash method measuring device (manufactured by ULVAC-RIKO, Inc., TC-9000). Based on the obtained values, the specific heat measured using an adiabatic specific heat measuring device (manufactured by Vacuum Riko Co., Ltd., SH-3000), and the density measured using the Archimedes method, the thermal conductivity at each temperature was calculated. The σ in the table 500 is the thermal conductivity at 500℃, and σ 20 is the thermal conductivity at 20℃.

[0192] It should be noted that for Examples 2, 5, 7 to 30, and 32 to 38, the thermal conductivity σ at500 The value was calculated using the method described in "Estimation formulas for thermal diffusivity, specific heat, and thermal conductivity of oxide glasses" in The Journal of the Japan Institute of Metals, Vol. 65, No. 8 (2001), pp. 680-687.

[0193] <Slow cooling mirror constant (unit: MPa·m 1 / 2 )>

[0194] Glass processing, scratching, bending test, and fracture surface observation were performed according to the following procedures to measure the slow cooling mirror constant.

[0195] (Processing)

[0196] The sheet was processed into a size of 40 mm × 6 mm × 3 mm, and the front and back surfaces and the end surfaces in the longitudinal direction (a total of four surfaces) were mirror-polished.

[0197] (Increase damage)

[0198] Using a Vickers hardness tester, a 110° diamond indenter was used to indent the specimens at various loads. The indentation loads were 0.05 kgf, 0.1 kgf, 0.3 kgf, 0.5 kgf, 0.75 kgf, 1.0 kgf, 2.0 kgf, and 3.0 kgf.

[0199] (Heat Treatment)

[0200] In order to remove the influence of strain caused by the scratch, the plate was kept at a temperature 30°C higher than Tg for 1 hour and then slowly cooled to room temperature at a rate of 1°C / min.

[0201] (Bending test)

[0202] A four-point bending jig with a span of 10 mm on the load side (upper) and 30 mm on the support side (lower) was used. Tape was applied to the surface of the glass opposite the scratched surface after scratching and heat treatment, with the scratched surface facing downward (the taped surface facing upward). A load was applied and the load at breakage was measured. The stress at breakage was calculated from the measured load using the following formula.

[0203] s={3F(Ls-Ll)} / (2wh 2 )

[0204] Here, s is the stress at the time of crushing (MPa), F is the load at the time of crushing (N), Ls is the distance between the lower support points (mm), Ll is the distance between the upper load points (mm), w is the sample width (mm), and h is the sample thickness (mm).

[0205] (Fractural observation)

[0206] The fracture surface was observed using a KEYENCE VHX-5000 digital microscope, and the distance R from the fracture start point to the interface between the mirror surface and the matte surface was measured. During observation, the sample was parallel to the microscope lens and observed at a magnification of 20×150.

[0207] The slow cooling mirror constant A is calculated using the following formula based on the results obtained by the above steps.

[0208] s=A / R 1 / 2

[0209] <Crystallization temperature Tc [unit: °C]>

[0210] About 70 mg of glass was finely pulverized in an agate mortar, and the temperature was raised to 1000° C. at a heating rate of 10° C. / min, and measured using a differential scanning calorimeter (DSC).

[0211] <β-OH value>

[0212] The FT-IR spectra at 3570 cm -1 The minimum transmittance near the absorption peak of OH group and the reference wavelength are 4000cm -1 The transmittance is measured and the β-OH value is calculated.

[0213] <Chemical Strengthening Properties by Two-Step Strengthening>

[0214] For each of the glasses of Examples 1-3 and 7-38, glass plates mirror-polished to a thickness of 0.8 mm on both sides were immersed in a 450°C sodium nitrate molten salt for 3 hours, followed by immersion in a 450°C potassium nitrate molten salt for 1.5 hours, thereby producing chemically strengthened glass. This treatment first forms a deep compressive stress layer through ion exchange between lithium ions in the glass composition and sodium ions in the molten salt. Subsequently, ion exchange between sodium ions in the glass and potassium ions in the molten salt creates a high compressive stress near the glass surface. The surface compressive stress CS1 [unit: MPa] and the compressive stress layer depth DOL1 [unit: μm] of the resulting chemically strengthened glass, measured using a stress meter manufactured by Orihara Seisakusho, Ltd., and a stress meter utilizing scattered light photoelasticity (SLP1000, manufactured by Orihara Seisakusho, Ltd., ER1 mode), are shown in Tables 5-8. Furthermore, the compressive stress layer depth DOL2 [unit: μm] of the same chemically strengthened glass, measured using a surface stress gauge manufactured by Orihara Seisakusho, Ltd., and a stress meter utilizing scattered light photoelasticity (SLP1000, ER1 mode, manufactured by Orihara Seisakusho, Ltd.), are also shown in the table. The FSM-6000 stress meter is suitable for measuring surface compressive stress, but it has difficulty accurately measuring the depth of the compressive stress layer generated by the ion exchange of lithium and sodium ions. On the other hand, the ER1 mode of the SLP1000 manufactured by Orihara Seisakusho can accurately measure the depth of the compressive stress layer generated by the ion exchange of lithium and sodium ions. Therefore, both devices were used for evaluation.

[0215] <Chemical Strengthening Properties Using Sodium Salts>

[0216] For each of the glasses of Examples 1 to 3 and 7 to 38, a glass plate having both surfaces mirror-polished to a thickness of 0.8 mm was immersed in a sodium nitrate molten salt at 450°C for 1 hour to obtain chemically strengthened glass. The compressive stress CS3 [unit: MPa] and the compressive stress layer depth DOL3 [unit: μm] of the obtained chemically strengthened glass were measured using a stress measuring instrument utilizing scattered light photoelasticity (ER1 mode of SLP1000 manufactured by Orihara Seisakusho Co., Ltd.) are shown in Tables 5 to 8.

[0217] Table 1

[0218] molar ratio Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 <![CDATA[SiO2]]> 64.9 69 70 64.5 67.1 68.8 68 67 69 <![CDATA[Al2O3]]> 15.6 9 7.5 8 13.1 2.9 10 11 9 <![CDATA[B2O3]]> 0 0 0 0 3.6 0 0 0 0 <![CDATA[P2O5]]> 1.2 0 0 0 0 0 0 0 0 <![CDATA[Li2O]]> 6.2 9.5 8 0 0 0 9.5 9 9.5 <![CDATA[Na2O]]> 10.8 4.5 5.3 12.5 13.7 14.2 4.5 6 4.5 <![CDATA[K2O]]> 0 1 1 4 0.1 0.1 1 1 1 MgO 0 6 7 10.6 2.3 6.1 6 6 4 CaO 0 0 0.2 0.1 0 7.8 0 0 2 SrO 0 0 0 0.1 0 0 0 0 0 BaO 0 0 0 0.1 0 0 0 0 0 ZnO 1.1 0 0 0 0 0 0 0 0 <![CDATA[TiO2]]> 0 0.04 0.04 0 0 0 0.04 0.04 0.04 <![CDATA[ZrO2]]> 0 1 1 0.1 0 0 0.5 0 1

[0219] Table 2

[0220] molar ratio Example 10 Example 11 Example 12 Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 Example 19 <![CDATA[SiO2]]> 69 69 69 69 69 69 69 69 65 69 <![CDATA[Al2O3]]> 9 9 9 8 7 9 9 8 9 9 <![CDATA[B2O3]]> 0 0 0 0 0 0 0 0 4 0 <![CDATA[P2O5]]> 0 0 0 0 0 0 0 0 0 0 <![CDATA[Li2O]]> 9.5 9.5 9.5 9.5 9.5 8.5 7.5 8.5 9.5 9.5 <![CDATA[Na2O]]> 4.5 4.5 4.5 5.5 6.5 5.5 6.5 6.5 4.5 4.5 <![CDATA[K2O]]> 1 1 1 1 1 1 1 1 1 1 MgO 4 2 4 6 6 6 6 6 6 5.5 CaO 0 2 1 0 0 0 0 0 0 0.5 SrO 2 2 1 0 0 0 0 0 0 0 BaO 0 0 0 0 0 0 0 0 0 0 ZnO 0 0 0 0 0 0 0 0 0 0 <![CDATA[TiO2]]> 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 <![CDATA[ZrO2]]> 1 1 1 1 1 1 1 1 1 0

[0221] Table 3

[0222] molar ratio Example 20 Example 21 Example 22 Example 23 Example 24 Example 25 Example 26 Example 27 Example 28 Example 29 <![CDATA[SiO2]]> 69 69 69 70 71 69.2 69.7 69.7 70.2 69 <![CDATA[Al2O3]]> 9 8 8 8 7 8 7.5 8 7.5 7.5 <![CDATA[B2O3]]> 0 0 0 0 0 0 0 0 0 0 <![CDATA[P2O5]]> 0 0 0 0 0 0 0 0 0 0 <![CDATA[Li2O]]> 9.5 8.5 8.5 8.5 8.5 8.5 8.5 8.5 8.5 8.5 <![CDATA[Na2O]]> 4.5 7.5 7.5 7.5 7.5 5.3 5.3 5.3 5.3 5.3 <![CDATA[K2O]]> 1 0 0 0 0 1 1 1 1 1 MgO 5 6 7 6 6 7 7 7 7 8 CaO 0.5 0 0 0 0 0 0 0 0 0.2 SrO 0.5 0 0 0 0 0 0 0 0 0 BaO 0 0 0 0 0 0 0 0 0 0 ZnO 0 0 0 0 0 0 0 0 0 0 <![CDATA[TiO2]]> 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 <![CDATA[ZrO2]]> 1 1 0 0 0 1 1 1 1 1

[0223] Table 4

[0224] molar ratio Example 30 Example 31 Example 32 Example 33 Example 34 Example 35 Example 36 Example 37 Example 38 <![CDATA[SiO2]]> 68 70 69 69 70 70 70 71.5 72.5 <![CDATA[Al2O3]]> 7.5 7.5 7.5 7.5 8 8.5 8 7.5 7.5 <![CDATA[B2O3]]> 0 0 0 0 0 0 0 0 0 <![CDATA[P2O5]]> 0 0 0 0 0 0 0 0 0 <![CDATA[Li2O]]> 8 7 7 7 7 7 7 7 7 <![CDATA[Na2O]]> 5.3 5.3 5.3 5.3 5.3 5.3 5.3 5.3 5.3 <![CDATA[K2O]]> 1 1 1 1 1 1 1 1 1 MgO 9 8 9 8 7.5 7 7 7 6 CaO 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 SrO 0 0 0 0 0 0 0 0 0 BaO 0 0 0 0 0 0 0 0 0 ZnO 0 0 0 0 0 0 0 0 0 <![CDATA[TiO2]]> 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 <![CDATA[ZrO2]]> 1 1 1 1 1 1 1 1 1

[0225] Table 5

[0226]

[0227] Table 6

[0228]

[0229] Table 7

[0230]

[0231] Table 8

[0232]

[0233] For the glasses of Examples 2, 3, and 4, use Figure 1 The device was bent into shape.

[0234] The glass of Example 4, where the value of X1+X2+X3 exceeded 1760, frequently cracked during bending. On the other hand, the glasses of Examples 2 and 3, where the values ​​of X1+X2+X3 were 1760 or less, could be bent without cracking. Similarly, the glasses of Example 1 and Examples 7 to 38, where the values ​​of X1+X2+X3 were 1760 or less, were presumably capable of bending without cracking. However, the glass of Example 2 sometimes developed white turbidity in the glass sheet.

[0235] The glass of Example 5 has a value of X1+X2+X3 of 1760 or less, but has a Young's modulus of less than 70 GPa, and is easily scratched during handling.

[0236] The present invention has been described in detail with reference to a specific embodiment, but various changes and modifications may be implemented without departing from the spirit and scope of the present invention, which will be apparent to those skilled in the art. It should be noted that this application is based on Japanese patent application (Japanese patent application No. 2016-204745) filed on October 18, 2016 and Japanese patent application (Japanese patent application No. 2017-141283) filed on July 20, 2017, the entire contents of which are incorporated herein by reference. In addition, all references cited herein are incorporated into this application in an integrated manner.

[0237] Reference numerals

[0238] 1: Glass pane

[0239] 2: Bending mold (lower mold)

[0240] 3: Bending mold (upper mold)

[0241] 4: Press

[0242] 10: Atmosphere replacement chamber

[0243] 20: Molding room

[0244] 21: Heating area

[0245] 22: Molding area

[0246] 23: Cooling area

[0247] 30: Atmosphere Replacement Chamber

Claims

1. A chemically strengthened glass having a Young's modulus E of 70 GPa or more, The total value X1+X2+X3 of the value X1, the value X2, and the value X3 is 1670 or less. The numerical value X1 is the same value obtained by multiplying the Young's modulus E and the average thermal expansion coefficient α in the range of 50°C to 350°C in units of kPa / °C. The numerical value X2 is the same as the temperature Tf in °C when the viscosity reaches 100 MPa·s. The value X3 is the viscosity at Tf and the viscosity η at a temperature 10°C higher than Tf. +10 The viscosity at Tf is 100 MPa·s, and the viscosity at Tf is η higher than the viscosity at a temperature 10°C higher than Tf. +10 The unit of the difference is 10 5 Pa·s, and The chemically strengthened glass contains, expressed in percentage by mass based on oxides, 56% to 69.5% SiO2, 14.7% to 24% Al2O3, 0% to 3% B2O3, 0% to 3% P2O5, 2% to 5% Li2O, 4% to 11% Na2O, 0.5% to 3% K2O, 0% to 5% MgO, 0% to 2% CaO, 0% to 4% SrO, 0% to 4% BaO, 0% to 5% ZnO, 0% to 2% TiO2, and 0.5% to 4% ZrO2. 2 . The chemically strengthened glass according to claim 1 , which is lithium aluminosilicate glass.

3. The chemically strengthened glass according to claim 2, wherein The chemically strengthened glass contains, expressed in percentage by mass based on oxides, 56% to 68% SiO2, 14.7% to 24% Al2O3, 0% to 1% B2O3, 0% to 2% P2O5, 2% to 5% Li2O, 4% to 11% Na2O, 0.5% to 2% K2O, 0% to 5% MgO, 0% to 1% CaO, 0% to 2% SrO, 0% to 2% BaO, 0% to 2% ZnO, 0% to 0.5% TiO2, and 1% to 4% ZrO2.

4. A chemically strengthened glass having a Young's modulus E of 80 GPa to 90 GPa and an average thermal expansion coefficient α in the range of 50°C to 350°C of 60×10 -7 / ℃~85×10 -7 / ℃, The total value X1+X2+X3 of the value X1, the value X2, and the value X3 is 1670 or less. The numerical value X1 is the same value obtained by multiplying the Young's modulus E and the average thermal expansion coefficient α in the range of 50°C to 350°C in units of kPa / °C. The numerical value X2 is the same as the temperature Tf in °C when the viscosity reaches 100 MPa·s. The value X3 is the viscosity at Tf and the viscosity η at a temperature 10°C higher than Tf. +10 The viscosity at Tf is 100 MPa·s, and the viscosity at Tf is η higher than the viscosity at a temperature 10°C higher than Tf. +10 The unit of the difference is 10 5 Pa·s, and The chemically strengthened glass contains, expressed in percentage by mass based on oxides, 56% to 69.5% SiO2, 14.7% to 24% Al2O3, 0% to 3% B2O3, 0% to 3% P2O5, 2% to 5% Li2O, 4% to 11% Na2O, 0.5% to 3% K2O, 0% to 5% MgO, 0% to 2% CaO, 0% to 4% SrO, 0% to 4% BaO, 0% to 5% ZnO, 0% to 2% TiO2, and 0.5% to 4% ZrO2.

5. The chemically strengthened glass according to claim 4, wherein The chemically strengthened glass contains, expressed in percentage by mass based on oxides, 56% to 68% SiO2, 14.7% to 24% Al2O3, 0% to 1% B2O3, 0% to 2% P2O5, 2% to 5% Li2O, 4% to 11% Na2O, 0.5% to 2% K2O, 0% to 5% MgO, 0% to 1% CaO, 0% to 2% SrO, 0% to 2% BaO, 0% to 2% ZnO, 0% to 0.5% TiO2, and 1% to 4% ZrO2.

6. The chemically strengthened glass according to claim 1 or 4, wherein The temperature Tf at which the viscosity reaches 100 MPa·s is 780° C. or lower.

7. The chemically strengthened glass according to claim 1 or 4, wherein When differential scanning calorimetry was performed from room temperature to 1000° C. at a heating rate of 10° C. / min, no crystallization peak was observed, or the temperature of the crystallization peak was higher than the softening point.

8. The chemically strengthened glass according to claim 1 or 4, wherein The thermal conductivity of the chemically strengthened glass at 500° C. is 1.3 W / mK or higher.

9. The chemically strengthened glass according to claim 1 or 4, wherein The mirror constant of the chemically strengthened glass is 2.0 MPa·m 1 / 2 above.

10. The chemically strengthened glass according to claim 1 or 4, wherein After being held at a temperature 30°C higher than the glass transition temperature Tg for 1 hour, the slow cooling mirror constant measured at a cooling rate of 1°C / min to room temperature was 2.0 MPa·m 1 / 2 above.

11. The chemically strengthened glass according to claim 1 or 4, wherein The softening point of the chemically strengthened glass is 820° C. or lower.

12. The chemically strengthened glass according to claim 1 or 4, wherein β-OH value is 0.1mm -1 above.

13. A method for producing chemically strengthened glass, wherein: The chemically strengthened glass according to claim 1 or 4 is heated and bent in a bending mold, and then chemically strengthened.

14. The method for producing chemically strengthened glass according to claim 13, wherein: The bending forming is performed by a press forming method.

15. A chemically strengthened glass in which no devitrification is observed, the chemically strengthened glass being bent into a curved shape, wherein: The total value X1+X2+X3 of the value X1, the value X2, and the value X3 is 1670 or less. The numerical value X1 is the same as the value obtained by multiplying the Young's modulus E and the average thermal expansion coefficient α in the range of 50°C to 350°C in units of kPa / °C. The numerical value X2 is the same as the temperature Tf in °C when the viscosity reaches 100 MPa·s. The value X3 is the viscosity at Tf and the viscosity η at a temperature 10°C higher than Tf. +10 The viscosity at Tf is 100 MPa·s, and the viscosity at Tf is η higher than the viscosity at a temperature 10°C higher than Tf. +10 The unit of the difference is 10 5 Pa·s, and The basic composition of chemically strengthened glass, expressed in percentage by mass based on oxides, comprises 56% to 69.5% SiO2, 14.7% to 24% Al2O3, 0% to 3% B2O3, 0% to 3% P2O5, 2% to 5% Li2O, 4% to 11% Na2O, 0.5% to 3% K2O, 0% to 5% MgO, 0% to 2% CaO, 0% to 4% SrO, 0% to 4% BaO, 0% to 5% ZnO, 0% to 2% TiO2, and 0.5% to 4% ZrO2.

16. The chemically strengthened glass according to claim 15, wherein Expressed in percentage by mass based on oxides, the chemically strengthened glass contains 56% to 68% SiO2, 14.7% to 24% Al2O3, 0% to 1% B2O3, 0% to 2% P2O5, 2% to 5% Li2O, 4% to 11% Na2O, 0.5% to 2% K2O, 0% to 5% MgO, 0% to 1% CaO, 0% to 2% SrO, 0% to 2% BaO, 0% to 2% ZnO, 0% to 0.5% TiO2, and 1% to 4% ZrO2.

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