Glass, chemically strengthened glass, and method for producing glass including curved shape

Abstract

The invention relates to a glass, a chemically strengthened glass, and a method for producing a glass including a curved shape. The present invention relates to a glass or the like that is a glass ceramic in which the difference (log [eta]-log [eta] 0 [dPa.s]), which is the difference between the log [eta] [dPa.s] of the bulk viscosity [eta] [dPa.s] of the bulk viscosity [eta] [dPa.s] and the log [eta] 0 [dPa.s] of the local viscosity [eta] 0 [dPa.s], is greater than 0 and 1.8 or less in a temperature range in which the log [eta] [dPa.s] of the bulk viscosity [eta] [dPa.s] is from 11.4 to 12.7.

Description

[0001] This application is a divisional application of the Chinese patent application with application date of August 10, 2021 and application number 202180007717.7. Technical Field

[0002] The present invention relates to glass containing glass-ceramics, and in particular to glass having a curved surface suitable for protective glass. In addition, the present invention also relates to a method for manufacturing glass containing glass-ceramics having a curved surface. Background Art

[0003] In recent years, there has been an increasing number of cases where protective glass is used to protect the display surface of a display and improve its appearance in mobile devices such as tablet PCs (personal computers) and smartphones (hereinafter also referred to as "smartphones, etc.") or display devices such as LCD TVs (liquid crystal panels), organic electroluminescent panels, and touch panels (hereinafter collectively referred to as "display devices, etc." in this specification).

[0004] In order to achieve design requirements, such as improving design, imparting a sense of luxury, and adapting to interior design or body design, the portion where the protective glass of the display device is disposed may have a curved surface. In this case, the protective glass also preferably has a curved surface.

[0005] As a method for manufacturing glass having a curved surface shape, for example, the following method can be cited: a flat glass plate is placed on a forming mold having a curved shape, the glass plate is heated to a temperature above the softening point to soften the glass plate, and the glass plate is deformed along the shape of the forming mold using its own weight to manufacture the glass plate (Patent Document 1).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Publication No. 35-16443 Summary of the invention

[0009] Problems to be solved by the invention

[0010] In order to produce glass with excellent design, it is necessary to improve shape accuracy and surface quality in a balanced manner. In the forming of glass, in order to improve shape accuracy, it is necessary to form the glass in a low viscosity region, but when forming the glass in a low viscosity region, there is a problem of reduced surface quality. On the other hand, in the forming of glass, in order to improve surface quality, it is necessary to form the glass in a high viscosity region, but there is a problem of excessive bending stress being applied to the glass during forming, causing cracks.

[0011] Therefore, an object of the present invention is to provide a method for producing glass containing glass-ceramics having excellent shape accuracy and surface quality and glass containing glass-ceramics having a curved surface shape.

[0012] Means used to solve problems

[0013] The inventors of the present invention studied the above-mentioned problems and found that by mixing particles in the amorphous part of the glass, a difference can be generated between the viscosity of the main material (バルク material) and the local viscosity, and cracking caused by bending in the high viscosity area can be suppressed, thereby completing the present invention.

[0014] The present invention relates to a glass, which is a microcrystalline glass, wherein, within the temperature range where the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] defined below is greater than 11.4 and less than 12.7, the difference between the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] and the logarithm logη0[dPa·s] of the local viscosity η0[dPa·s] defined below, i.e., logη-logη0[dPa·s], is greater than 0 and less than or equal to 1.8.

[0015] Bulk viscosity η: The bulk viscosity η is the viscosity of the glass as a whole and is measured by a penetration method or a parallel plate method.

[0016] Local viscosity η0: The local viscosity η0 is the viscosity of the amorphous part of the glass. When the crystallinity of the glass is less than 0.4, the local viscosity η0 is calculated from the bulk viscosity and the volume fraction of the particles according to the following formula (1). When the crystallinity of the glass is greater than 0.4, the local viscosity η0 is calculated from the bulk viscosity and the volume fraction of the particles according to the following formula (2). In the following formula (1), d represents the average particle size, S r Represents the specific surface area of ​​particles per unit volume, φ v represents volume concentration, φ vc represents the critical maximum volume concentration. In the following formula (2), φ v Indicates volume concentration. It should be noted that in the case of glass-ceramics, φ v The volume concentration represented by is the crystallinity in either of the following formulae (1) and (2).

[0017]

[0018] The present invention relates to a glass, wherein the glass comprises microcrystalline glass, and the peak value of the loss tangent tanδ represented by the ratio G'' / G' of the storage shear modulus G' to the loss shear modulus G'' of the glass sample (length 35 mm×width 8 mm×thickness 2 mm) measured by the following method is greater than 0.7.

[0019] The loss tangent tan δ was measured using a dynamic viscoelasticity measuring apparatus (Rheometer MCR502 / temperature control system CTD-1000 manufactured by Anton Paar) at a frequency of 1.0 Hz, a strain of 0.01%, a heating rate of 10° C. / min, and a shear measurement mode.

[0020] The present invention relates to a method for manufacturing glass including a curved surface shape, the method for manufacturing glass including a curved surface shape comprising the following steps: keeping the glass within a temperature range in which the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] defined below is greater than 11.4 and less than 12.7 and forming the glass into a curved surface by applying an external force to the glass, wherein the glass comprises microcrystalline glass, and within the temperature range in which the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] defined below is greater than 11.4 and less than 12.7, the difference between the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] of the glass and the logarithm logη0[dPa·s] of the local viscosity η0 defined below, i.e., logη-logη0[dPa·s], is greater than 0 and less than or equal to 1.8.

[0021] Bulk viscosity η (Valk viscosity): The bulk viscosity η is the viscosity of the entire glass and is measured by a penetration method or a parallel plate method.

[0022] Local viscosity η0: The local viscosity η0 is the viscosity of the amorphous part of the glass. When the crystallinity of the glass is less than 0.4, the local viscosity η0 is calculated from the bulk viscosity and the volume fraction of the particles according to the following formula (1). When the crystallinity of the glass is greater than 0.4, the local viscosity η0 is calculated from the bulk viscosity and the volume fraction of the particles according to the following formula (2). In the following formula (1), d represents the average particle size, S r Represents the specific surface area of ​​particles per unit volume, φ v represents volume concentration, φ vc represents the critical maximum volume concentration. In the following formula (2), φ v Indicates volume concentration. It should be noted that in the case of glass-ceramics, φ v The volume concentration represented by is the crystallinity in either of the following formulae (1) and (2).

[0023]

[0024] The present invention relates to a method for manufacturing glass including a curved surface shape, the method for manufacturing glass including a curved surface shape comprising the following steps: keeping the glass within a temperature range in which the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] defined below is greater than 11.4 and less than 12.7 and forming the glass into a curved surface by applying an external force to the glass, wherein the glass comprises microcrystalline glass, and the peak value of the loss tangent tanδ represented by the ratio G'' / G' of the storage shear modulus G' to the loss shear modulus G'' of the glass sample (length 35 mm×width 8 mm×thickness 2 mm) measured by the following method is greater than 0.7.

[0025] Bulk viscosity η: The bulk viscosity η is the viscosity of the glass as a whole and is measured by a penetration method or a parallel plate method.

[0026] The loss tangent tan δ was measured using a dynamic viscoelasticity measuring apparatus (Rheometer MCR502 / temperature control system CTD-1000 manufactured by Anton Paar) at a frequency of 1.0 Hz, a strain of 0.01%, a heating rate of 10° C. / min, and a shear measurement mode.

[0027] Effects of the Invention

[0028] The present invention provides a method for manufacturing glass containing microcrystalline glass and having excellent shape accuracy and surface quality and glass containing microcrystalline glass and having a curved surface shape. The glass containing microcrystalline glass of the present invention can reduce the bending stress applied to the glass during forming by making the difference between the viscosity of the main material and the local viscosity within a specific range, thereby suppressing the breakage caused when bending in the high viscosity area. Therefore, it shows excellent shape accuracy and surface quality. According to the manufacturing method of the present invention, by applying external force to the glass containing microcrystalline glass with a viscosity in a specific range to form a curved surface, it is possible to manufacture glass containing a curved shape with excellent shape accuracy and surface quality. DETAILED DESCRIPTION

[0029] In the present specification, unless otherwise specified, "to" indicating a numerical range is used to mean that the numerical values ​​described before and after it are included as the lower limit and the upper limit.

[0030] In this specification, "bulk viscosity η" refers to the viscosity of the entire glass, and is measured by the following method.

[0031] (Method for measuring bulk viscosity η)

[0032] The determination is carried out by the penetration method or the parallel plate method.

[0033] The measurement conditions are set to the following conditions, for example.

[0034] Measuring device: WRVM-313 manufactured by Opt Enterprises

[0035] Sample: φ10mm×6mm

[0036] Measurement conditions: 10°C / min from room temperature to (Tg-50)°C, measurement temperature range 5°C / min

[0037] Here, Tg in this specification represents the glass transition temperature.

[0038] In this specification, "local viscosity η0" means the viscosity of the amorphous portion when glass includes an amorphous portion and particles, and is determined by the following method.

[0039] (Method for calculating local viscosity η0)

[0040] When the crystallinity of the glass is less than 0.4, that is, the volume concentration or volume fraction is less than 40%, the local viscosity η0 is calculated from the bulk viscosity and the volume fraction of the particles according to the [local viscosity estimation formula (Mori-Ototake formula)] represented by the following formula (1) (Mori Yoshiro and Ototake Nao, "On the Viscosity of Suspensions", Chemical Engineering, Vol. 20, No. 9, pp. 16-22, 1956). The following formula (1) is a formula obtained by assuming that the highest volume concentration is spherical particles of equal diameter and the sparsest packing. In the following formula (1), d represents the average particle size, S r Represents the specific surface area of ​​particles per unit volume, φ v represents volume concentration, φ vc Indicates the critical maximum volume concentration.

[0041] When the crystallinity of the glass is greater than 0.4, that is, the volume concentration or volume fraction is greater than 40%, the local viscosity η0 is calculated according to the [local viscosity estimation formula (Brinkman, HC: The viscosity of concentrated suspensions and solutions, Jour. of Chem. Phys., Vol. 20, No. 4, page 571, April 1952)] represented by the following formula (2). The following formula (2) is a theoretical formula obtained by expanding the Einstein formula to a wide range of volume fractions. In the following formula (2), φ v Indicates volume concentration.

[0042]

[0043] The viscosity is measured, for example, under the following conditions.

[0044] Device: Opt Enterprises, WRVM-313

[0045] Sample: φ10mm×6mm

[0046] Measurement conditions: 10°C / min from room temperature to (Tg-50)°C, measurement temperature range 5°C / min

[0047] In this specification, "amorphous glass" refers to glass in which no diffraction peak indicating crystals is observed by the powder X-ray diffraction method described later. "Microcrystalline glass" is glass in which crystals are precipitated by heating "amorphous glass", and it contains crystals. In this specification, "amorphous glass" and "microcrystalline glass" are sometimes collectively referred to as "glass". In addition, amorphous glass that becomes microcrystalline glass by heat treatment is sometimes referred to as "matrix glass of microcrystalline glass".

[0048] In this specification, "loss tangent tan δ" is a value measured by the following method.

[0049] (Determination method of loss tangent tanδ)

[0050] The measurement was performed using a dynamic viscoelasticity measuring apparatus (Rheometer MCR502 / temperature control system CTD-1000 manufactured by Anton Paar) at a frequency of 1.0 Hz, a strain of 0.01%, and a temperature increase rate of 10° C. / min in a shear measurement mode.

[0051] In this specification, in powder X-ray diffraction determination, using CuKα ray to determine 2θ is the scope of 10 °~80 °, when diffraction peak occurs, by Hanawalt method, precipitated crystal is identified.In addition, the crystal identified by the peak group comprising the highest peak of integrated intensity in the crystal identified by this method is as main crystal.

[0052] The measurement of powder X-ray diffraction is performed, for example, under the following conditions.

[0053] Measuring device: Made by Rigaku Corporation, Smart Lab

[0054] Scanning speed: 10° / min, step distance: 0.02°

[0055] In this specification, unless otherwise specified, the glass composition is expressed in mol % based on oxides, and mol % is simply expressed as “%”.

[0056] In this specification, “substantially free of” means that the content is lower than the level of impurities contained in raw materials, etc., that is, it is not intentionally added. Specifically, for example, it is less than 0.1%.

[0057] Hereinafter, "chemically strengthened glass" refers to glass subjected to a chemical strengthening treatment.

[0058] In this specification, "stress distribution" refers to a curve that expresses compressive stress values ​​with depth from the glass surface as a variable. In stress distribution, tensile stress is expressed as negative compressive stress.

[0059] The "compressive stress value (CS)" can be measured by thinning a cross section of the glass and analyzing the thinned sample using a birefringence imaging system. The birefringence imaging system birefringence stress gauge is a device that uses a polarizing microscope and a liquid crystal compensator to measure the magnitude of the delay caused by stress, such as the birefringence imaging system Abrio-IM manufactured by CRi.

[0060] In addition, scattered light photoelasticity can also be used for measurement. In this method, light is incident from the surface of the glass, and the polarized light of the scattered light is analyzed to measure CS. As a stress measuring instrument using scattered light photoelasticity, there is, for example, the scattered light photoelasticity stress meter SLP-2000 manufactured by Orihara Manufacturing Co., Ltd.

[0061] In this specification, the “compressive stress layer depth (DOL)” is the depth at which the compressive stress value is zero. Hereinafter, the surface compressive stress value is sometimes referred to as CS0, and the compressive stress value at a depth of 50 μm is sometimes referred to as CS 50 In addition, "internal tensile stress (CT)" refers to the tensile stress value at a depth of (1 / 2×t) relative to the plate thickness t of the glass.

[0062] In this specification, "light transmittance" refers to the average transmittance of light with a wavelength of 380 nm to 780 nm. In addition, "haze value" is measured using C light source in accordance with JIS K7136:2000.

[0063] In this specification, the "fracture toughness value" is a value obtained by the IF method specified in JIS R1607:2015.

[0064] <Glass First Method>

[0065] As one embodiment (first embodiment) of the present invention, the glass is glass-ceramics, characterized in that, within a temperature range where the logarithm of the bulk viscosity η [dPa·s] logη [dPa·s] defined below is 11.4 or more and 12.7 or less,

[0066] The difference between the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] and the logarithm logη0[dPa·s] of the local viscosity η0[dPa·s] defined below, i.e., logη-logη0[dPa·s], is greater than 0 and less than or equal to 1.8.

[0067] The temperature range in which the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] is 11.4 or more and 12.7 or less includes the temperature range in which conventional glass forming is performed and the temperature range in which the glass becomes highly viscous. By making logη-logη0[dPa·s] greater than 0 and less than or equal to 1.8 within this temperature range, it is possible to suppress cracking during bending in the high viscosity region by reducing the change in viscosity caused by temperature change, and to improve shape accuracy and surface quality. The above-mentioned logη-logη0[dPa·s] is preferably greater than 0.1, more preferably greater than 0.2, and preferably less than 1.2, more preferably less than 0.8, and further preferably less than 0.6. As a combination thereof, it is preferably greater than 0.1 and less than 1.2, more preferably greater than 0.1 and less than 0.8, and further preferably greater than 0.2 and less than 0.6.

[0068] As described later, the glass of this embodiment is a microcrystalline glass, and includes an amorphous portion and particles mixed in the amorphous portion. By mixing the above particles in the amorphous portion, a difference can be generated between the bulk viscosity η and the local viscosity η0, and cracking caused when bending in a high viscosity region can be further suppressed. The degree of particle mixing can be uniform or non-uniform in the entire region of the amorphous portion.

[0069] The diameter of at least one particle of the particles mixed in the amorphous part measured by the following method is preferably 10nm or more, more preferably 20nm or more, further preferably 30nm or more, and particularly preferably 40nm or more. By having the above-mentioned diameter of 10nm or more, a difference can be generated between the bulk viscosity η and the local viscosity η0, and the rupture generated when bending in the high viscosity region can be further suppressed. There is no particular restriction on the upper limit of the particle diameter, but from the viewpoint of light transmittance and haze value, it is preferably 60nm or less.

[0070] (Measurement method of particle size)

[0071] The average particle size of the precipitated crystals can be calculated from the powder X-ray diffraction intensity using the Riedbold method.

[0072] The shape of the above-mentioned particles is preferably spherical or elliptical, and spherical particles and elliptical particles can also be mixed. When the shape of the particle is spherical or elliptical, the length ratio represented by the major axis / minor axis measured by the following method is preferably more than 1 and less than 5.1, more preferably more than 1 and less than 4, and more preferably more than 2 and less than 4. By major axis / minor axis being more than 1 and less than 5.1, the strength to bending can be improved, and the rupture generated when bending can be further suppressed.

[0073] (Method for measuring major axis / minor axis)

[0074] The measurement was performed by the following method using a cryo-TEM (transmission electron microscope) image.

[0075] The outer shape of the particle where the lattice fringes were observed was extracted within a 350 nm square field of view, and the length ratio of the major axis to the minor axis was calculated.

[0076] From the viewpoint of light transmittance and haze value, the volume fraction of the above particles relative to the entire glass can be 80% or less, preferably 60% or less, preferably 40% or less, more preferably 30% or less, and particularly preferably 25% or less. From the viewpoint of being able to fully obtain the effect of being able to produce a difference between the bulk viscosity η and the local viscosity η0, and being able to further suppress the cracking generated when bending in the high viscosity region, the volume fraction is preferably 10% or more. The volume fraction is measured by the following method.

[0077] (Measurement method of volume fraction)

[0078] Calculated from powder X-ray diffraction results by the Riedbold method.

[0079] The particles are not limited to microcrystalline glass or crystal grains analyzed from the amorphous part, and examples thereof include glass particles and SiC particles. Among them, crystal grains analyzed from the amorphous part are preferred from the viewpoint of sufficiently and simply reducing the reduction in light transmittance caused by reflection and scattering at the interface between the particles and the amorphous part and improving the fracture toughness value of the interface.

[0080] In the case where the above-mentioned particles are crystal grains analyzed from the amorphous part, the glass is a microcrystalline glass as the first mode. Therefore, as a preferred mode of the first mode, the following glass can be cited, wherein the glass is a glass including a curved surface shape including microcrystalline glass, wherein, within the temperature range where the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] is greater than 11.4 and less than 12.7, the difference between the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] and the logarithm logη0[dPa·s] of the local viscosity η0[dPa·s], i.e., logη-logη0[dPa·s] is greater than 0 and less than or equal to 1.8. Among them, the first mode is microcrystalline glass, but the case where the above-mentioned particles are glass particles or SiC particles is not excluded.

[0081] <<Glass composition>>

[0082] In the first embodiment, the glass composition preferably contains 40% to 90% SiO2, 0 to 15% Al2O3, and 0 to 35% in total Li2O, Na2O, and K2O, expressed as mol% based on oxides. The preferred glass composition when the glass is microcrystalline glass will be described later.

[0083] <Glass Second Method>

[0084] As one embodiment (second embodiment) of the present invention, the following glass can be cited, characterized in that the glass comprises glass-ceramics, and the peak value of the loss tangent tanδ represented by the ratio G'' / G' of the storage shear modulus G' and the loss shear modulus G'' of the glass sample (length 35 mm×width 8 mm×thickness 2 mm) measured by the following method is 0.7 or more. When the peak value of the above-mentioned loss tangent tanδ is 0.7 or more, the elastic stress inside the glass during bending can be suppressed, thereby suppressing the occurrence of glass breakage. The peak value of the above-mentioned loss tangent tanδ is preferably 0.9 or more, more preferably 0.95 or more, and even more preferably 1.0 or more.

[0085] (Determination method of loss tangent tanδ)

[0086] The measurement was performed using a dynamic viscoelasticity measuring apparatus (Rheometer MCR502 / temperature control system CTD-1000 manufactured by Anton Paar) at a frequency of 1.0 Hz, a strain of 0.01%, and a temperature increase rate of 10° C. / min in a shear measurement mode.

[0087] It should be noted that there is no particular restriction on the upper limit of the peak value of the loss tangent tanδ, but by setting the peak value of the loss tangent tanδ to below 15.0, the contribution rate of viscosity is small, stress can be quickly relaxed even in a high viscosity region, and even if external force is applied to the glass for bending forming, stress related to glass breakage is not easily generated, so it is preferred.

[0088] <<Glass-ceramic>>

[0089] The glass-ceramics in this embodiment (hereinafter, also referred to as the present glass-ceramics) preferably contains at least one selected from the group consisting of Li3PO4 crystals, Li4SiO4 crystals, Li2SiO3 crystals, Li2Mg(SiO4) crystals and Li2Si2O4 crystals. By using these crystals as the main crystals, the light transmittance increases and the haze value decreases. The present glass-ceramics may contain two or more of Li3PO4 crystals, Li4SiO4 crystals, Li2SiO3 crystals, Li2Mg(SiO4) crystals and Li2Si2O4 crystals, or any one of them as the main crystal. In addition, two or more solid solution crystals selected from the group consisting of Li3PO4, Li4SiO4, Li2SiO3, Li2Mg(SiO4) and Li2Si2O4 may be used as the main crystals.

[0090] In order to improve the mechanical strength, the crystallization rate of the present glass-ceramics is preferably 5% or more, more preferably 10% or more, further preferably 15% or more, and particularly preferably 20% or more.

[0091] In order to improve the strength, the average particle size of the precipitated crystals of the present microcrystalline glass is preferably 5 nm or more, particularly preferably 10 nm or more. In addition, in order to improve the transparency, the average particle size is preferably 80 nm or less, more preferably 60 nm or less, further preferably 50 nm or less, particularly preferably 40 nm or less, and most preferably 30 nm or less. The average particle size of the precipitated crystals is obtained from a transmission electron microscope (TEM) image.

[0092] The present microcrystalline glass is obtained by crystallizing amorphous glass described later by heat treatment.

[0093] <<<Glass composition of glass-ceramics>>>

[0094] In terms of molar % based on oxides, the present microcrystalline glass preferably meets the following requirements: 40% to 70% SiO2, 10% to 35% Li2O, 4% to 15% Al2O3, 0.5% to 5% P2O5, 1.5% to 5% ZrO2, 0 to 10% B2O3, 0 to 3% Na2O, 0 to 2% K2O, 0 to 4% SnO2, and 0 to 10% MgO.

[0095] In addition, the total amount of SiO2, Al2O3, P2O5 and B2O3 of the present glass-ceramics is preferably 60% to 80% in terms of molar % based on oxides. SiO2, Al2O3, P2O5 and B2O3 are network-forming components of glass (hereinafter also referred to as NWF). Due to the large total amount of these NWFs, the strength of the glass increases. This increases the fracture toughness value of the glass-ceramics, so the total amount of NWF is preferably 60% or more, more preferably 63% or more, and particularly preferably 65% ​​or more. On the other hand, from the perspective of manufacturability such as preventing the melting temperature from becoming too high, the total amount of NWF is preferably 80% or less, more preferably 75%, and further preferably 70% or less.

[0096] The ratio of the total amount of Li2O, Na2O and K2O in the present glass-ceramics to the total amount of NWF, namely SiO2, Al2O3, P2O5 and B2O3, is preferably 0.20 to 0.60.

[0097] Li2O, Na2O and K2O are network modifying components. Reducing the ratio to NWF increases the gaps in the network, thereby improving impact resistance. Therefore, the ratio of the total amount of Li2O, Na2O and K2O to the total amount of NWF is preferably 0.60 or less, more preferably 0.55 or less, and particularly preferably 0.50 or less. On the other hand, since Li2O, Na2O and K2O are essential components for chemical strengthening, in order to improve the chemical strengthening characteristics, the ratio of the total amount of Li2O, Na2O and K2O to the total amount of NWF is preferably 0.20 or more, more preferably 0.25 or more, and particularly preferably 0.30 or more.

[0098] Hereinafter, the glass composition will be described.

[0099] SiO2 is a component that forms a glass network structure. In addition, SiO2 is a component that improves chemical durability, and the content of SiO2 is preferably 40% or more, more preferably 45% or more, further preferably 48% or more, further preferably 50% or more, particularly preferably 52% or more, and extremely preferably 54% or more. On the other hand, in order to improve melting properties, the content of SiO2 is preferably 70% or less, more preferably 68% or less, further preferably 66% or less, and particularly preferably 64% or less.

[0100] Al2O3 is a component that increases the surface compressive stress generated by chemical strengthening when chemical strengthening is performed. The content of Al2O3 is preferably 4% or more, more preferably 5% or more, further preferably 5.5% or more, further preferably 6% or more, particularly preferably 6.5% or more, and most preferably 7% or more. On the other hand, in order not to make the devitrification temperature of the glass too high, the content of Al2O3 is preferably 15% or less, more preferably 12% or less, further preferably 10% or less, particularly preferably 9% or less, and most preferably 8% or less.

[0101] Li2O is a component that forms surface compressive stress through ion exchange and is a constituent of the main crystal, and is essential. The content of Li2O is preferably 10% or more, more preferably 14% or more, further preferably 20% or more, and particularly preferably 22% or more. On the other hand, in order to stabilize the glass, the content of Li2O is preferably 35% or less, more preferably 32% or less, and further preferably 30% or less.

[0102] Na2O is a component that improves the meltability of glass. Na2O is not essential, but when Na2O is contained, the content of Na2O is preferably 0.5% or more, more preferably 1% or more, and particularly preferably 2% or more. When Na2O is too much, crystals such as Li3PO4 as the main crystal are difficult to precipitate or the chemical strengthening characteristics are reduced, so the content of Na2O is preferably 3% or less, more preferably 2% or less, and further preferably 1% or less.

[0103] K2O is a component that lowers the melting temperature of glass like Na2O, and K2O may be contained. When K2O is contained, the content of K2O is preferably 0.5% or more, more preferably 1% or more, and further preferably 1.5% or more. When K2O is too much, the chemical strengthening characteristics are reduced or the chemical durability is reduced, so the content of K2O is preferably 2% or less, and most preferably 1% or less.

[0104] In order to improve the solubility of glass raw materials, the total content of Na2O and K2O (Na2O+K2O) is preferably 1% or more, more preferably 2% or more.

[0105] In addition, when the ratio of K2O content to the total content of Li2O, Na2O and K2O (hereinafter referred to as R2O) K2O / R2O is 0.2 or less, the chemical strengthening characteristics can be improved and the chemical durability can be improved, which is preferred. K2O / R2O is more preferably 0.15 or less, and further preferably 0.10 or less.

[0106] It should be noted that R2O is preferably 10% or more, more preferably 15% or more, and further preferably 20% or more. In addition, R2O is preferably 35% or less, preferably 29% or less, and more preferably 26% or less.

[0107] P2O5 is a constituent of Li3PO4 crystals and is indispensable. In order to promote crystallization, the content of P2O5 is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, particularly preferably 2% or more, and extremely preferably 2.5% or more. On the other hand, when the content of P2O5 is too much, phase separation is easy during melting, and acid resistance is significantly reduced. Therefore, the content of P2O5 is preferably 5% or less, more preferably 4.8% or less, further preferably 4.5% or less, and particularly preferably 4.2% or less.

[0108] ZrO2 is a component that improves mechanical strength and chemical durability, and ZrO2 is preferably contained. The content of ZrO2 is preferably 1.5% or more, more preferably 2% or more, and further preferably 2.5% or more. On the other hand, in order to suppress devitrification during melting, ZrO2 is preferably 5% or less, more preferably 4.5% or less, further preferably 4% or less, and particularly preferably 3.5% or less.

[0109] In order to improve chemical durability, ZrO2 / R2O is preferably 0.10 or more, more preferably 0.15 or more. In order to improve transparency after crystallization, ZrO2 / R2O is preferably 0.6 or less, more preferably 0.4 or less.

[0110] TiO2 is a component that can promote crystallization, and TiO2 may be contained. TiO2 is not essential, but when TiO2 is contained, the content of TiO2 is preferably 0.2% or more, and more preferably 0.5% or more. On the other hand, in order to suppress devitrification during melting, the content of TiO2 is preferably 4% or less, more preferably 2% or less, and further preferably 1% or less.

[0111] SnO2 has the function of promoting the formation of crystal nuclei, and SnO2 may be contained. SnO2 is not indispensable, but when SnO2 is contained, the content of SnO2 is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. On the other hand, in order to suppress devitrification during melting, the content of SnO2 is preferably 4% or less, more preferably 3% or less.

[0112] Y2O3 is a component that has the effect of making it difficult for fragments to fly when chemically strengthened glass breaks when chemically strengthened, and may contain Y2O3. The content of Y2O3 is preferably 1% or more, more preferably 1.5% or more, further preferably 2% or more, particularly preferably 2.5% or more, and extremely preferably 3% or more. On the other hand, in order to suppress devitrification during melting, the content of Y2O3 is preferably 5% or less, more preferably 4% or less.

[0113] B2O3 is a component that improves the crack resistance and solubility of the glass, and B2O3 may be contained. In order to improve solubility, when B2O3 is contained, the content of B2O3 is preferably 0.5% or more, more preferably 1% or more, and further preferably 2% or more. On the other hand, when the content of B2O3 is too much, ribs are easily generated or phase separation is easy during melting, so that the quality of the glass is easily reduced. Therefore, the content of B2O3 is preferably 10% or less, more preferably 5% or less, further preferably 4% or less, further preferably 3% or less, and particularly preferably 2% or less.

[0114] BaO, SrO, MgO, CaO and ZnO are all components that improve the melting property of glass, and BaO, SrO, MgO, CaO and ZnO may be contained. When containing these components, the total content of BaO, SrO, MgO, CaO and ZnO (hereinafter referred to as BaO+SrO+MgO+CaO+ZnO) is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. On the other hand, when the total of these contents is too much, the ion exchange rate decreases, so BaO+SrO+MgO+CaO+ZnO is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, further preferably 5% or less, and particularly preferably 4% or less.

[0115] Among them, in order to increase the light transmittance of microcrystalline glass by increasing the refractive index of the residual glass and approaching the precipitated crystal phase, and reduce the haze value, BaO, SrO, and ZnO may be contained. In this case, the total content of BaO, SrO and ZnO (hereinafter referred to as BaO+SrO+ZnO) is preferably 0.3% or more, more preferably 0.5% or more, further preferably 0.7% or more, and particularly preferably 1% or more. On the other hand, these components sometimes reduce the ion exchange rate. In order to improve the chemical strengthening properties, BaO+SrO+ZnO is preferably less than 2.5%, more preferably less than 2%, further preferably less than 1.7%, and particularly preferably less than 1.5%.

[0116] In addition, when MgO is contained, MgO is essential for the precipitation of Li2Mg(SiO4) crystals, so the content of MgO is preferably 0.1% or more, more preferably 4.0% or more. In addition, in order to improve the chemical strengthening characteristics, the content of MgO is preferably 10% or less, more preferably 5.4% or less.

[0117] La2O3, Nb2O5 and Ta2O5 are all components that make it difficult for fragments to fly when chemically strengthened glass breaks. In order to increase the refractive index, La2O3, Nb2O5 and Ta2O5 can be contained. In the case of containing La2O3, Nb2O5 and Ta2O5, the total content of La2O3, Nb2O5 and Ta2O5 (hereinafter referred to as La2O3+Nb2O5+Ta2O5) is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, and particularly preferably 2% or more. In addition, in order to make the glass less likely to lose transparency when melted, La2O3+Nb2O5+Ta2O5 is preferably 4% or less, more preferably 3% or less, further preferably 2% or less, and particularly preferably 1% or less.

[0118] In addition, CeO2 may be contained. CeO2 sometimes suppresses coloring by oxidizing the glass. When CeO2 is contained, the content of CeO2 is preferably 0.03% or more, more preferably 0.05% or more, and further preferably 0.07% or more. In order to improve transparency, the content of CeO2 is preferably 1.5% or less, and more preferably 1.0% or less.

[0119] When the glass is colored for use, a coloring component can be added within a range that does not hinder the realization of the desired chemical strengthening characteristics. Examples of the coloring component include Co3O4, MnO2, Fe2O3, NiO, CuO, Cr2O3, V2O5, Bi2O3, SeO2, Er2O3, and Nd2O3.

[0120] The content of the coloring components is preferably within a range of 1% or less in total. In the case where it is desired to further increase the visible light transmittance of the glass, it is preferred that these components are substantially not contained.

[0121] In addition, SO3, chloride, fluoride may be appropriately contained as a clarifier during glass melting, etc. Preferably, As2O3 is not contained. In the case of containing Sb2O3, the content of Sb2O3 is preferably 0.3% or less, more preferably 0.1% or less, and most preferably, no Sb2O3 is contained.

[0122] <<<Characteristics of this glass-ceramic>>>

[0123] When the light transmittance of the present microcrystalline glass is preferably 85% or more at a thickness of 0.7 mm, the screen of the display can be easily seen in the case of a protective glass for a portable display. The light transmittance is more preferably 88% or more, and more preferably 90% or more. The higher the light transmittance, the more preferred, but it is usually 91% or less. At a thickness of 0.7 mm, a light transmittance of 90% is equivalent to that of ordinary amorphous glass.

[0124] It should be noted that, when the actual thickness is not 0.7 mm, the light transmittance when the thickness is 0.7 mm can be calculated based on the measured value according to the Lambert-Beer law. In addition, when the plate thickness t is greater than 0.7 mm, the plate thickness can be adjusted to 0.7 mm by grinding, etching, etc. before measurement.

[0125] In addition, when the thickness is 0.7 mm, the haze value is 0.5% or less, preferably 0.4% or less, more preferably 0.3% or less, further preferably 0.2% or less, and particularly preferably 0.15% or less. The smaller the haze value, the more preferred, but it is usually 0.01% or more. When the thickness is 0.7 mm, a haze value of 0.02% is equivalent to that of ordinary amorphous glass.

[0126] It should be noted that when the total visible light transmittance of a glass-ceramic with a plate thickness of t [mm] is 100 × T [%] and the haze value is 100 × H [%], by citing the Lambert-Beer law and using the constant α, it can be expressed as T = (1-R) 2 × exp(-αt). When the constant α is used, it becomes: dH / dt∝exp(-αt)×(1-H).

[0127] That is, it can be considered that the haze value increases in proportion to the internal linear transmittance as the plate thickness increases. Therefore, the haze value H for a thickness of 0.7 mm is 0.7 It can be calculated by the following formula.

[0128]

[0129] When the plate thickness t is larger than 0.7 mm, the plate thickness may be adjusted to 0.7 mm by grinding, etching, etc. before measurement.

[0130] The fracture toughness value of the present glass-ceramics is high, and even if a large compressive stress is formed by chemical strengthening, it is not easy to break violently. When the fracture toughness value of the present glass-ceramics is preferably 0.81 MPa·m 1 / 2 More preferably, 0.84 MPa·m 1 / 2 More preferably, 0.87 MPa·m 1 / 2 When the fracture toughness value is above 1.0 MPa·m, the glass with high impact resistance can be obtained. The upper limit of the fracture toughness value of the present glass-ceramics is not particularly limited, but is typically 1.0 MPa·m 1 / 2 the following.

[0131] In order to suppress warping during chemical strengthening treatment, the Young's modulus of the present glass-ceramics is preferably 80 GPa or more, more preferably 85 GPa or more, further preferably 90 GPa or more, and particularly preferably 95 GPa or more. The present glass-ceramics is sometimes used after grinding. In order to easily grind, the Young's modulus is preferably 130 GPa or less, more preferably 120 GPa or less, and further preferably 110 GPa or less.

[0132] <<Amorphous glass>>

[0133] The present glass-ceramics is obtained by heat-treating amorphous glass (amorphous glass in the present embodiment) described below.

[0134] In terms of molar % based on oxides, the amorphous glass in the present embodiment (hereinafter also referred to as the present amorphous glass) preferably contains: 40% to 70% SiO2, 10% to 35% Li2O, 3% to 15% Al2O3, 0 to 5% P2O5, 1.5% to 5% ZrO2, 0 to 3% Na2O and 0 to 1% K2O.

[0135] As the preferred composition of the present amorphous glass, for example, in terms of molar % based on oxides, there can be listed a composition containing 40% to 70% SiO2, 10% to 32% Li2O, 5% to 15% Al2O3, 0.5% to 5% P2O5, 2% to 5% ZrO2, 0 to 10% B2O3, 0 to 3% Na2O, 0 to 1% K2O and 0 to 4% SnO2.

[0136] The total amount of SiO2, Al2O3, P2O5 and B2O3 in the amorphous glass is preferably 60% to 80%. In addition, the ratio of the total amount of Li2O, Na2O and K2O to the total amount of SiO2, Al2O3, P2O5 and B2O3 is preferably 0.20 to 0.60.

[0137] In order to prevent structural relaxation during chemical strengthening, the glass transition temperature Tg of the present amorphous glass is preferably 400°C or higher, more preferably 450°C or higher, and further preferably 500°C or higher. In addition, the glass transition temperature Tg is preferably 650°C or lower, and more preferably 600°C or lower.

[0138] The present amorphous glass is crushed, and the difference (Tc-Tg) between the glass transition temperature (Tg) obtained from the DSC curve obtained using a differential scanning calorimeter and the crystallization peak temperature (Tc) appearing in the lowest temperature range in the DSC curve is preferably 80°C or more, more preferably 85°C or more, further preferably 90°C or more, and particularly preferably 95°C or more. When (Tc-Tg) is large, it is easy to reheat the microcrystalline glass and perform bending processing, etc. (Tc-Tg) is preferably below 150°C, more preferably below 140°C.

[0139] <<Characteristics of this glass>>

[0140] The glass in the first and second embodiments (hereinafter also referred to as the present glass) preferably has a slope Δlogη / ΔT[dPa·s / K] of the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] within a temperature range of 11.4 or more and 12.7 or less, preferably Δlogη / ΔT[dPa·s / K] or more of -0.035, more preferably Δlogη / ΔT[dPa·s / K] or more of -0.035, further preferably Δlogη / ΔT[dPa·s / K] or more of -0.02, and further preferably Δlogη / ΔT[dPa·s / K] or more of -0.035, because the rate of change of the viscosity with respect to the temperature change is stable, the formability can be improved. When the slope of the viscosity is too large, a slight temperature change will deviate from the assumed viscosity range, and the glass is likely to break in the high viscosity region and surface deterioration is likely to occur in the low viscosity region. The upper limit of the slope Δlogη / ΔT [dPa·s / K] of the viscosity is not particularly limited, but is typically -0.005 or less.

[0141] The logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] of the present glass at the temperature at which the crystal nucleus growth rate reaches a peak value is preferably 12.7 or less, more preferably 12.0 or less, further preferably 11.4 or less, and further preferably 11.0 or less. By setting the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] at the temperature at which the crystal nucleus growth rate reaches a peak value to 12.7 or less, it is difficult for the nucleus to grow during forming, and the change of the physical properties accompanying the temperature change is suppressed, so that the formability can be improved. There is no particular restriction on the lower limit of the logarithm logη[dPa·s] of the bulk viscosity η[dPa·s] at the temperature at which the crystal nucleus growth rate reaches a peak value, and it is typically 4.0 or more.

[0142] When the glass is in a plate shape, the thickness (t) is preferably 3 mm or less, more preferably 2 mm or less, 1.6 mm or less, 1.1 mm or less, 0.9 mm or less, 0.8 mm or less, and 0.7 mm or less. In addition, in order to obtain sufficient strength through chemical strengthening treatment, the thickness (t) is preferably 0.3 mm or more, more preferably 0.4 mm or more, and further preferably 0.5 mm or more.

[0143] As the shape of the present glass, for example, a flat plate shape with uniform thickness, a three-dimensional shape having a curved portion or a bent portion in at least a portion, such as a 2.5D protective glass represented by a smartphone, and a 3D protective glass. It should be noted that the preferred range of the thickness of the present glass described above can also be applied to the preferred range of the thickness of the chemically strengthened glass described later.

[0144] When the present glass is a three-dimensional glass, it is particularly easy to improve the shape accuracy and surface quality. As a three-dimensional glass, for example, a glass having an average curvature radius of 5.0×10 2 The minimum R shape and average curvature radius of 1.0×10 3 Three-dimensional glass having a plurality of R shapes with a maximum R shape of mm or more. Specifically, there can be cited a three-dimensional glass plate having two opposite sides that are curved in a rectangular glass plate when viewed from above, and a three-dimensional glass plate having four corners that are curved around the rectangular glass plate.

[0145] <<Chemically strengthened glass>>

[0146] The glass of the present invention can be made into chemically strengthened glass (hereinafter also referred to as the present strengthened glass) by chemical strengthening treatment. The haze value of the present strengthened glass converted to a thickness of 0.7 mm is preferably 0.5% or less. The haze value and light transmittance of the present glass are substantially the same as those of the glass before chemical strengthening.

[0147] When the surface compressive stress value (CS0) of the tempered glass is 400 MPa or more, it is not easy to break due to deformation such as bending, so it is preferred. CS0 is more preferably 500 MPa or more, and more preferably 600 MPa or more. The larger the CS0, the higher the strength, but when the CS0 is too large, it is possible to produce severe crushing in the case of rupture, so it is preferably 1200 MPa or less, and more preferably 1000 MPa.

[0148] When the DOL of the present tempered glass is 70 μm or more, it is not easy to break even if damage occurs on the surface, so it is preferred. The DOL is more preferably 100 μm or more. The larger the DOL, the less likely it is to break even if damage occurs, but in chemically tempered glass, since tensile stress corresponding to the compressive stress formed near the surface is generated inside, it cannot be extremely increased. The DOL is preferably less than t / 4 relative to the thickness t of the tempered glass, and more preferably less than t / 5. In order to shorten the time required for chemical strengthening, the DOL is preferably less than 200 μm, and more preferably less than 180 μm.

[0149] When the CT of the present tempered glass is 110 MPa or less, the scattering of fragments is suppressed when the chemically tempered glass breaks, so it is preferred. The CT is more preferably 100 MPa or less, and further preferably 90 MPa or less. On the other hand, when the CT is reduced, the surface compressive stress becomes smaller, and there is a tendency that it is difficult to obtain sufficient strength. Therefore, the CT is preferably 50 MPa or more, more preferably 55 MPa or more, and further preferably 60 MPa or more.

[0150] The basic composition of the tempered glass preferably contains, in terms of mol % based on oxides, 40% to 70% of SiO2, 10% to 35% of Li2O, and 4% to 15% of Al2O3.

[0151] Here, "basic composition of chemically strengthened glass" refers to the composition before chemical strengthening. The composition of the present strengthened glass is generally similar to that of the glass before strengthening, except when an extreme ion exchange treatment is performed. In particular, except when an extreme ion exchange treatment is performed, the composition of the deepest part from the glass surface is the same as that of the glass before strengthening.

[0152] The present glass and the present tempered glass are also useful as protective glass used in electronic devices such as mobile phones, smart phones and other mobile devices. In addition, it is also useful for protective glass of electronic devices such as televisions, personal computers, touch panels, etc. that are not intended to be carried, walls of elevators, walls of buildings such as houses and buildings (full-screen displays). In addition, it is also useful for building materials such as window glass, interiors of desktops, cars or airplanes, etc., their protective glass, and shells with curved shapes.

[0153] <Method for producing glass having a curved surface>

[0154] <<Method for producing amorphous glass>>

[0155] Amorphous glass can be manufactured by a common method. For example, the raw materials of each component of the glass are mixed and heated and melted in a glass melting furnace. Then, the glass is homogenized by a known method, formed into a desired shape such as a glass plate, and slowly cooled. In the case of a glass plate, the glass can be formed into a plate by a float method, a pressing method, a down-draw method, etc. Alternatively, the molten glass can be formed into a block, slowly cooled, and then cut into a plate.

[0156] As methods for mixing particles into the amorphous part of the glass, for example, there can be listed a method of obtaining microcrystalline glass by heat-treating the above-mentioned amorphous glass using the method described later, and a method of mixing the desired particles when heating and melting the raw materials of the glass in a glass melting furnace during the manufacture of the above-mentioned amorphous glass.

[0157] <<Method for producing glass-ceramics>>

[0158] The amorphous glass obtained according to the above operation steps is subjected to a heat treatment so that the crystal grains are separated from the amorphous part, thereby obtaining microcrystalline glass. The heat treatment can be performed in two steps: heating from room temperature to a first treatment temperature and maintaining for a certain time, and then maintaining for a certain time at a second treatment temperature higher than the first treatment temperature. Alternatively, a one-step heat treatment can be performed by maintaining at a specific treatment temperature and then cooling to room temperature.

[0159] In the case of a two-step heat treatment, the first treatment temperature is preferably a temperature range in which the growth rate of the crystal nuclei increases for the glass composition, and the second treatment temperature is preferably a temperature range in which the growth rate of the crystal nuclei increases for the glass composition. In addition, regarding the holding time at the first treatment temperature, it is preferably held for a long time so that a sufficient number of crystal nuclei are generated. By generating a large number of crystal nuclei, the size of each crystal becomes smaller, so that a microcrystalline glass with high transparency can be obtained.

[0160] In the case of a two-step treatment, for example, a first treatment temperature of 500° C. to 700° C. is maintained for 1 to 6 hours, and then, for example, a second treatment temperature of 600° C. to 800° C. is maintained for 1 to 6 hours. In the case of a first step treatment, for example, a temperature of 500 to 800° C. is maintained for 1 to 6 hours.

[0161] The microcrystalline glass obtained by the above operation steps is ground and polished as needed to form a microcrystalline glass plate. When the microcrystalline glass plate is cut into a specified shape and size or chamfered, it is preferred to cut and chamfer before chemical strengthening treatment, because a compressive stress layer is also formed on the end face by the subsequent chemical strengthening treatment.

[0162] <<Molding>>

[0163] When the glass has a curved surface, it is preferred that after manufacturing a plate-shaped glass (glass plate), an external force is applied to form a curved surface by bending, and then chemical strengthening is performed. There is no particular restriction on the magnitude of the external force, for example, it is preferably 8 kN or less, more preferably 6 kN or less, and further preferably 2 kN or less. Since the glass has a difference between the local viscosity and the bulk viscosity, and since the loss tangent is small, the stress is easily relaxed and the formability is excellent, so the generation of cracks accompanying the increase of the external force can be suppressed.

[0164] As the method of bending forming, for example, self-weight forming method, vacuum forming method, press forming method etc. can be listed. In addition, two or more bending forming methods can be used in combination. In any case, a carbon mold can be widely used as a forming mold.

[0165] The self-weight forming method is a method of placing a glass plate on a forming mold, then heating the glass plate to soften it, and using gravity to make it adapt to the forming mold to form it.

[0166] The vacuum forming method is a method of bending the glass sheet by placing a glass sheet on 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. In this case, the upper surface side of the glass sheet can be pressurized.

[0167] The press forming method is a method of placing a glass plate between an upper mold and a lower mold of a forming mold including an upper mold and a lower mold, heating the glass plate, and applying a pressure load between the upper and lower forming molds to bend the glass plate into a predetermined shape.

[0168] As a heating method during press molding, for example, there is a method of heating by bringing a hot plate maintained at a high temperature into contact with the surfaces of the upper and lower molding dies, a method of heating by arranging a heater around the metal mold, and the like.

[0169] From the viewpoint of suppressing changes in physical properties before and after forming, the rate of change in crystallinity of glass-ceramics before and after forming is preferably 10% or less, more preferably 5% or less, and even more preferably 1% or less.

[0170] The rate of change of crystallinity of glass-ceramics before and after forming can be adjusted by changing the forming temperature and forming time.

[0171] When the glass is maintained in a temperature range where the logarithm of the bulk viscosity η [dPa·s] logη [dPa·s] is 11.4 or more and 12.7 or less and is formed into a curved surface by applying an external force, the transfer mark area detected by the transmitted light image is preferably 0 to 5% of the entire formed area, and more preferably 0 to 3%. When the transfer mark area is 0 to 5% of the entire formed area, excellent surface quality is exhibited.

[0172] In the above forming process, the bending forming can be performed while performing the heating treatment. During the bending forming, the radiation type heating treatment can be performed, and the contact type heating treatment can also be performed. In the case where there is a temperature difference between the curved surface shape and the flat surface shape, local heating can be performed, or there can be no temperature difference between the curved surface shape and the flat surface shape.

[0173] <<Chemical strengthening treatment>>

[0174] Chemical strengthening treatment is typically performed by immersing the glass in a melt of a metal salt such as potassium nitrate containing a metal ion with a large ionic radius such as Na ions or K ions, so that the glass is in contact with the metal salt. Thus, the metal ions with a small ionic radius in the glass are replaced with metal ions with a large ionic radius, thereby performing ion exchange. For example, ion exchange replaces Li ions with Na ions or K ions, and replaces Na ions with K ions.

[0175] In order to speed up the chemical strengthening treatment, it is preferred to use "Li-Na exchange" in which Li ions in the glass are exchanged with Na ions. In addition, in order to form a large compressive stress by ion exchange, it is preferred to use "Na-K exchange" in which Na ions in the glass are exchanged with K ions.

[0176] As molten salts for chemical strengthening treatment, for example, nitrates, sulfates, carbonates, chlorides, etc. can be cited. Among them, as nitrates, for example, lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, silver nitrate, etc. can be cited. As sulfates, for example, lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, silver sulfate, etc. can be cited. As carbonates, for example, lithium carbonate, sodium carbonate, potassium carbonate, etc. can be cited. As chlorides, for example, lithium chloride, sodium chloride, potassium chloride, cesium chloride, silver chloride, etc. can be cited. These molten salts can be used alone or in combination.

[0177] The treatment conditions of the chemical strengthening treatment can be selected in terms of time and temperature in consideration of the glass composition, the type of molten salt, etc. For example, the present glass can be subjected to a chemical strengthening treatment preferably for less than 1 hour at a temperature of preferably 450° C. or less. Specifically, for example, the glass can be immersed in a molten salt (e.g., a mixed salt of lithium nitrate and sodium nitrate) containing 0.3% by mass of Li and 99.7% by mass of Na at 450° C. for preferably about 0.5 hours.

[0178] The chemical strengthening treatment can be performed by two-step ion exchange as described below. First, the glass-ceramics is preferably immersed in a metal salt containing Na ions (e.g., sodium nitrate) at a temperature of preferably about 350°C to about 500°C for about 0.1 hour to about 10 hours. As a result, ion exchange between the Li ions in the glass-ceramics and the Na ions in the metal salt occurs, thereby forming a relatively deep compressive stress layer.

[0179] Next, the substrate is immersed in a metal salt containing K ions, such as potassium nitrate, preferably at about 350°C to about 500°C for about 0.1 hour to about 10 hours. As a result, a large compressive stress is generated in the portion within a depth of about 10 μm, for example, of the compressive stress layer formed in the previous treatment. According to such a two-step treatment, a stress distribution with a large surface compressive stress value is easily obtained.

[0180] Example

[0181] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited thereto.

[0182] <Evaluation Method>

[0183] (Specific gravity ρ)

[0184] The specific gravity of glass was measured by the Archimedean method. The results are shown in "ρ (g / cm 3 )"middle.

[0185] (Glass transition temperature Tg)

[0186] The glass was crushed using an agate mortar, and about 80 mg of the powder was placed in a platinum pool. The temperature was raised from room temperature to 1100°C at a heating rate of 10 / min. A differential scanning calorimeter (manufactured by Bruker; DSC3300SA) was used to measure the DSC curve to determine the glass transition temperature Tg, which is shown in "Tg" in Table 1.

[0187] (Haze value)

[0188] The haze value [unit: %] of the glass under illuminant C was measured using a haze meter (manufactured by Suga Test Instruments; HZ-V3). The results are shown in "Haze (%)" in Table 1.

[0189] (Young's modulus E)

[0190] The Young's modulus of the glass was measured by an ultrasonic method. The results are shown in "E (GPa)" in Table 1.

[0191] (Fracture toughness value Kc)

[0192] The fracture toughness value of the glass was measured by the IF method according to JIS R1607:2015. The results are shown in "Kc (MPa·m 1 / 2 )"middle.

[0193] (X-ray diffraction: precipitated crystals)

[0194] Powder X-ray diffraction of the glass was measured under the following conditions, and the precipitated crystals were identified. The results are shown in "Crystals" in Table 2.

[0195] Measuring device: Made by Rigaku Corporation, Smart Lab

[0196] Use X-ray: CuKα ray

[0197] Measuring range: 2θ = 10°~80°

[0198] Speed: 10° / min

[0199] Step distance: 0.02°

[0200] (Method for measuring bulk viscosity η)

[0201] The viscosity of the entire glass was measured by a fiber extension method according to JIS R3103-2 (2001). The logarithm of the bulk viscosity η during molding is shown in "viscosity logη during molding" in Table 2.

[0202] (Method for calculating local viscosity η0)

[0203] The viscosity of the amorphous part as the local viscosity η0 of the glass is calculated from the crystallinity according to the above formula (1) (Mori-Otsutake formula) or the formula (2) Brinkman formula. The logarithm of the obtained value is taken, and the value of logη-logη0 in the temperature range where logη is greater than 11.4 and less than 12.7 is shown in Table 2.

[0204] (Determination method of loss tangent tanδ)

[0205] The loss tangent tanδ of the glass was measured using a dynamic viscoelasticity measuring device (Rheometer MCR502 / temperature control system CTD-1000 manufactured by Anton Paar) at a frequency of 1.0 Hz, a strain of 0.01%, and a heating rate of 10°C / min in a shear measurement mode. The glass sample used a sample with a size of 35 mm in length × 8 mm in width × 2 mm in thickness. The peak value of tanδ at 1 Hz is shown in Table 2.

[0206] (Δlogη / ΔT)

[0207] The results are shown in Table 2. Δlogη / ΔT[dPa·s / K] was determined in the temperature range where the logarithm of the bulk viscosity η, logη[dPa·s], was 11.4 or more and 12.7 or less.

[0208] (logη at the temperature where the crystal nucleus growth rate reaches the peak)

[0209] The temperature at which the crystal nucleus growth rate reaches the peak value was measured by DSC under the following conditions, the bulk viscosity η was measured by the above-mentioned method for measuring the bulk viscosity η, and logη at the temperature was calculated.

[0210] Device: DSC3300SA manufactured by Bruker

[0211] Sample: Powder

[0212] Measurement conditions: Heating from room temperature to measurement temperature (basically 1100°C in the case of glass ceramics) at 10°C / min

[0213] (Particle size)

[0214] Powder X-ray diffraction of the glass was measured under the following conditions, and the precipitated crystals (main crystals) were identified. The results are shown in "Crystals" in Table 2.

[0215] In addition, the volume fraction of particles [unit: %] and the crystal particle size (crystal size) [unit: nm] were calculated using the Rydberg method. The results are shown in Table 2. In addition, the crystal particle size refers to the diameter of at least one particle in Table 2.

[0216] Measuring device: Smart Lab, manufactured by Rigaku Co., Ltd.

[0217] Use X-ray: CuKα ray

[0218] Measuring range: 2θ = 10°~80°

[0219] Speed: 10° / min

[0220] Step distance: 0.02°

[0221] (Particle shape, major axis / minor axis)

[0222] The particle shape and major axis / minor axis of the particles contained in the glass were calculated by observing the periphery of the particles where lattice fringes were observed from the cryoTEM images under the following conditions. The results are shown in "Particle shape" and "Major axis / minor axis of particles" in Table 2, respectively.

[0223] Measurement apparatus: Titan (trademark) transmission electron microscope (TEM) manufactured by Thermo Fisher Scientific

[0224] Field of view: □300nm

[0225] (Surface roughness Ra)

[0226] The surface roughness of the glass was measured by the following method. The measurement index was the arithmetic mean roughness Ra. These measurements were carried out in accordance with JIS B0601: 2001. The results are shown in Table 2 in "Surface roughness Ra (μm)".

[0227] Measuring device: NH-3MAS manufactured by Mitaka Optical Instruments

[0228] Measurement interval: 0.4μm

[0229] Measuring length: 5000 μm

[0230] Cut-off value: 0.08mm

[0231] (Deviation from design shape)

[0232] The difference (deviation) between the glass shape and the designed shape was evaluated by the following method.

[0233] The difference between the shape of the molded product and the designed shape was measured using a three-dimensional measuring device Atos manufactured by GOM Co. The results are shown in "Deviation from Design Shape" in Table 2.

[0234] (Occurrence of rupture)

[0235] The occurrence of glass cracks was evaluated according to the following criteria. The results are shown in "Occurrence of Cracks" in Table 2.

[0236] Cracks: Cracks larger than 0.5 mm are found in the transmitted light image.

[0237] No cracks: There are no cracks in the transmitted light image.

[0238] (Transmission image)

[0239] The formed glass sample was projected with a point light source (white light) to obtain a transmission image, which was binarized to measure the area ratio (%) of the transfer mark. The results are shown in Table 2 in the "Transfer mark area ratio".

[0240] <Production and evaluation of amorphous glass>

[0241] Glass raw materials were prepared to obtain the glass composition in mass % based on oxides in Table 1, and weighed to obtain 800 g of glass. The mixed glass raw materials were then placed in a platinum crucible, put into an electric furnace at 1400° C. to 1700° C., and melted for about 5 hours, followed by degassing and homogenization.

[0242] The obtained molten glass was poured into a mold, kept at a temperature about 30°C higher than the glass transition temperature for 1 hour, and then cooled to room temperature at a rate of 0.5°C / min to obtain a glass block. The glass transition temperature, specific gravity, Young's modulus, and fracture toughness value of the amorphous glass were evaluated using a portion of the obtained block, and the results are shown in Table 1.

[0243] "-" in Table 1 means not evaluated. R2O in Table 1 represents the total content of Li2O, Na2O and K2O, and NWF represents the total content of SiO2, Al2O3, P2O5 and B2O3.

[0244]

[0245] <Crystallization treatment and evaluation of glass-ceramics>

[0246] The obtained glass block was processed into 70 mm×70 mm×1.5 mm, and then heat-treated under the conditions described in Table 2 to obtain microcrystalline glass. The upper row of the "Heat Treatment" column indicating the crystallization conditions in Table 2 indicates the nucleation treatment conditions, and the lower row indicates the crystal growth treatment conditions. For example, when the upper row indicates 550°C for 2 hours and the lower row indicates 730°C for 2 hours, it means that the temperature is kept at 550°C for 2 hours and then kept at 730°C for 2 hours.

[0247] The obtained microcrystalline glass was processed and mirror-polished to obtain a glass plate with a thickness t of 0.55 mm. Under the conditions shown in Table 2, the plate glass was bent to fit the mold and formed into a predetermined shape to obtain a curved glass including a curved surface shape. The evaluation results of the curved glass are shown in Table 2.

[0248] A carbon die and a punch designed to form a curved surface with a curvature radius of 6.0 mm and a bending depth of 4.0 mm were prepared, and a chamfered glass plate was placed near the center of the glass contact surface of the die.

[0249] The glass sheet was preheated, deformed, and cooled while the concave mold and the convex mold on which the glass sheet was placed were fixed to the lower shaft and the upper shaft of a forming device (Glass element forming device: GMP-315V, manufactured by Toshiba Machine Co., Ltd.).

[0250] The preheating process takes 15 minutes to raise the temperature from room temperature to 500°C. At 500°C, the equilibrium viscosity of the glass plate is about 10 16 dPa·s. Next, the temperature was raised from 500°C to 630°C over 5 minutes. The equilibrium viscosity of the glass plate at 630°C was about 10 12.7 dPa·s.

[0251] The equilibrium viscosity of the center of the glass plate is kept at 10 12.5 dPa·s~10 12.7 dPa·s method, that is, the male mold is moved downward while the temperature is maintained at 630°C to 640°C, and pressed against the female mold at a maximum force of 2000 N for 3 minutes. During this time, 20 L / min of nitrogen gas is blown in from the through hole provided in the male mold to uniformly shape the glass sheet.

[0252] Then, it was slowly cooled to 480° C. over 20 minutes. The equilibrium viscosity of the glass plate at 480° C. was about 10 17.5 Next, the punch was raised at 2 mm / sec and retracted, and the glass plate was naturally cooled to room temperature.

[0253] Part of the remaining microcrystalline glass was crushed for analysis of precipitated crystals. The detected main crystals are shown in the crystal column of Table 2. Li3PO4 and Li4SiO4 are difficult to identify by powder X-ray diffraction, so both are recorded together. The evaluation results of microcrystalline glass are shown in Table 2. "-" means not evaluated. Examples 1 to 2 and Examples 6 to 9 are embodiments, and Examples 3 to 5 are comparative examples.

[0254]

[0255] As shown in Table 2, compared with the comparative example, Examples 1 and 2 as embodiments suppress viscosity changes caused by temperature changes, are less likely to cause glass breakage caused by bending in the high viscosity region, and show excellent shape accuracy and surface quality.

[0256] For the glass obtained by heat treating the glass G5 to change the crystallinity to 60% under the conditions of the Examples and Table 2 (Example 8), the difference (logη-logη0[dPa·s]) between logη[dPa·s] and the logarithm of the local viscosity η0[dPa·s] logη0[dPa·s] in the temperature range where logη[dPa·s] is greater than 11.4 and less than 12.7 was measured, and the result was 1.0.

[0257] For the glass (Example 9) obtained by heat treating the glass G5 whose crystallinity was changed to 80% under the same conditions as in the examples and Table 2, the difference (logη-logη0[dPa·s]) between logη[dPa·s] and the logarithm logη0[dPa·s] of the local viscosity η0[dPa·s] in the temperature range where logη[dPa·s] was 11.4 or more and 12.7 or less was measured, and the result was 1.74. In the case of manufacturing glass having a curved surface shape, even if the value obtained by measuring the difference (logη-logη0[dPa·s]) between logη[dPa·s] and the logarithm logη0[dPa·s] of the local viscosity η0[dPa·s] in the temperature range where logη[dPa·s] was 11.4 or more and 12.7 or less was within the range of 1.0 to 1.74, the glass is not easily broken by bending in the high viscosity region, and glass showing excellent shape accuracy and surface quality can be manufactured.

[0258] Although the present invention is described in detail and with reference to specific embodiments, various changes and modifications can be applied without departing from the spirit and scope of the present invention, which is obvious to those skilled in the art. This application is based on Japanese patent application (Japanese patent application 2020-141160) filed on August 24, 2020, the contents of which are incorporated herein by reference.

Claims

1. A glass, which is glass-ceramics, wherein: The microcrystalline glass comprises, in terms of mole % based on oxides, 40% to 70% SiO2, 20% to 35% Li2O, 0% to 15% Al2O3, 0.5% to 5% P2O5, 2.5% to 5% ZrO2, 0% to 10% B2O3, 0.5% to 3% Na2O, 0% to 2% K2O, 0% to 4% SnO2, and 0% to 10% MgO, and the microcrystalline glass does not contain La2O3. The average particle size of the precipitated crystals of the microcrystalline glass is less than 60 nm. The peak value of the loss tangent tanδ represented by the ratio G'' / G' of the storage shear modulus G' to the loss shear modulus G'' of a glass sample having a size of 35 mm in length×8 mm in width×2 mm in thickness measured by the following method is 1.03 or more, The loss tangent tanδ was measured using a dynamic viscoelasticity measuring device Rheometer MCR502 manufactured by Anton Paar, which was equipped with a temperature control system CTD-1000, at a frequency of 1.0 Hz, a strain of 0.01%, and a heating rate of 10°C / min in a shear measurement mode.

2. The glass according to claim 1, wherein: The microcrystalline glass contains at least one crystal selected from the group consisting of Li3PO4 crystals, Li4SiO4 crystals, Li2SiO3 crystals, Li2Mg(SiO4) crystals and Li2Si2O5 crystals as crystal grains.

3. The glass according to claim 1, wherein: The microcrystalline glass comprises LiAlSi4O 10 crystals and Li2Si2O5 crystals as grains.

4. The glass according to any one of claims 1 to 3, wherein The slope Δlogη / ΔT [dPa·s / K] of the logarithm logη of the bulk viscosity η defined below is -0.035 or more, Bulk viscosity η: The bulk viscosity η is the viscosity of the entire glass and is measured by a penetration method or a parallel plate method. The unit of the bulk viscosity η is dPa·s.

5. The glass according to claim 4, wherein: The logarithm logη of the bulk viscosity η [dPa·s] at a temperature at which the crystal nucleus growth rate reaches a peak value is 11.4 or less.

6. The glass according to claim 4, wherein: In the temperature range where the logarithm of the bulk viscosity η, logη, is 11.4 or more and 12.7 or less, The difference between the logarithm logη of the bulk viscosity η and the logarithm logη0 of the local viscosity η0 defined below, i.e., logη-logη0, is greater than 0 and less than or equal to 1.74, Local viscosity η0: The local viscosity η0 is the viscosity of the amorphous part of the glass. When the crystallinity of the glass is less than 0.4, the local viscosity η0 is calculated from the bulk viscosity and the volume fraction of the particles according to the following formula (1). In addition, when the crystallinity of the glass is greater than 0.4, the local viscosity η0 is calculated from the bulk viscosity and the volume fraction of the particles according to the following formula (2). The unit of the local viscosity η0 is dPa·s. In the above formula (1), d represents the average particle size, S r Represents the specific surface area of ​​particles per unit volume, φ v represents volume concentration, φ vc represents the critical maximum volume concentration, In the above formula (2), φ v represents the volume concentration, It should be noted that in the case of glass-ceramics, φ v The volume concentration represented by is the crystallinity in either of the above formulae (1) and (2).

7. The glass according to any one of claims 1 to 3, wherein the glass is glass-ceramics, wherein: The volume fraction of the crystal is less than 80%.

8. The glass according to any one of claims 1 to 3, wherein the glass is glass-ceramics, wherein: The volume fraction of the crystal is less than 60%.

9. The glass according to any one of claims 1 to 3, wherein The glass is microcrystalline glass, and the volume fraction of the crystals is greater than 10%.

10. The glass according to any one of claims 1 to 3, wherein the glass is glass-ceramics, wherein: The ratio of the major axis to the minor axis of the crystal is greater than or equal to 1 and less than or equal to 5.1, (Method for measuring major axis / minor axis) Using cryo-TEM (transmission electron microscope) images, the measurement was performed by the following method: The outer shape of the particle where the lattice fringes were observed was extracted within a 350 nm square field of view, and the length ratio of the major axis to the minor axis was calculated.

11. The glass according to claim 10, wherein the glass is glass-ceramics, wherein: The length ratio of the major axis / minor axis of the crystal is 4 or less.

12. The glass according to claim 10, wherein the glass is glass-ceramics, wherein: The length ratio of the major axis / minor axis of the crystal is 2 or more.

13. The glass according to any one of claims 1 to 3, wherein When the thickness of the glass is 0.7 mm, the light transmittance of the glass is greater than or equal to 85%.

14. The glass according to any one of claims 1 to 3, wherein The specific gravity of the glass is greater than or equal to 2.

47.

15. The glass according to any one of claims 1 to 3, wherein The glass transition temperature of the glass is 494° C. or higher and 560° C. or lower.

16. The glass according to any one of claims 1 to 3, wherein The Young's modulus of the glass is 95 GPa or more.

17. The glass according to any one of claims 1 to 3, wherein The Kc of the glass measured by the IF method is 0.8 MPa·m 1 / 2 above.

18. The glass according to any one of claims 1 to 3, wherein The glass includes a curved shape.

19. The glass according to any one of claims 1 to 3, wherein The glass is used as protective glass.

20. A chemically strengthened glass, wherein: The chemically strengthened glass is obtained by chemically strengthening the glass according to any one of claims 1 to 3.

21. The chemically strengthened glass according to claim 20, wherein: The surface compressive stress value (CS0) of the chemically strengthened glass is greater than or equal to 400 MPa and less than or equal to 1200 MPa.

22. The chemically strengthened glass according to claim 20, wherein: The DOL of the chemically strengthened glass is 70 μm or more.

23. The chemically strengthened glass according to claim 20, wherein: The DOL is t / 4 or less relative to the thickness t of the tempered glass.

24. The chemically strengthened glass according to claim 20, wherein: The surface roughness Ra of the chemically strengthened glass is 0.01414 μm or less.

25. The chemically strengthened glass according to claim 20, wherein: The chemically strengthened glass has a CT of 110 MPa or less.

26. A method for manufacturing glass, which is a method for manufacturing microcrystalline glass, wherein: The obtained microcrystalline glass comprises, in terms of mole % based on oxides, 40% to 70% SiO2, 20% to 35% Li2O, 0% to 15% Al2O3, 0.5% to 5% P2O5, 2.5% to 5% ZrO2, 0% to 10% B2O3, 0.5% to 3% Na2O, 0% to 2% K2O, 0% to 4% SnO2, and 0% to 10% MgO, and does not contain microcrystalline glass of La2O3. The average particle size of the precipitated crystals of the microcrystalline glass is less than 60 nm. The peak value of the loss tangent tanδ represented by the ratio G'' / G' of the storage shear modulus G' to the loss shear modulus G'' of a glass sample having a size of 35 mm in length×8 mm in width×2 mm in thickness measured by the following method is 1.03 or more, The loss tangent tanδ was measured using a dynamic viscoelasticity measuring device Rheometer MCR502 manufactured by Anton Paar, which was equipped with a temperature control system CTD-1000, at a frequency of 1.0 Hz, a strain of 0.01%, and a heating rate of 10°C / min in a shear measurement mode.

27. The method for manufacturing microcrystalline glass according to claim 26, wherein the microcrystalline glass is obtained by heat-treating amorphous glass, wherein: The amorphous glass is pulverized, and the difference (Tc-Tg) between the glass transition temperature (Tg) obtained from a DSC curve obtained using a differential scanning calorimeter and the crystallization peak temperature (Tc) appearing in the lowest temperature range in the DSC curve is 80° C. or more.

28. The method for manufacturing microcrystalline glass according to claim 26, wherein the microcrystalline glass is obtained by heat-treating amorphous glass, wherein: The amorphous glass is pulverized, and the difference (Tc-Tg) between the glass transition temperature (Tg) obtained from a DSC curve obtained using a differential scanning calorimeter and the crystallization peak temperature (Tc) appearing in the lowest temperature range in the DSC curve is 150°C or less.

29. The method for manufacturing microcrystalline glass according to claim 26, wherein the microcrystalline glass is obtained by heat-treating amorphous glass, wherein: Glass-ceramics is obtained by subjecting amorphous glass to two or more heat treatment steps.

30. A method for manufacturing glass, which is a method for manufacturing chemically strengthened glass-ceramics by subjecting chemically strengthened glass to ion exchange treatment to obtain chemically strengthened glass, wherein: The chemically strengthened glass is a microcrystalline glass, and comprises, in terms of mole percentage based on oxides, 40% to 70% of SiO2, 20% to 35% of Li2O, 0% to 15% of Al2O3, 0.5% to 5% of P2O5, 2.5% to 5% of ZrO2, 0% to 10% of B2O3, 0.5% to 3% of Na2O, 0% to 2% of K2O, 0% to 4% of SnO2, and 0% to 10% of MgO, and does not contain La2O3 microcrystalline glass, The average particle size of the precipitated crystals of the microcrystalline glass is less than 60 nm. The peak value of the loss tangent tanδ represented by the ratio G'' / G' of the storage shear modulus G' to the loss shear modulus G'' of a glass sample having a size of 35 mm in length×8 mm in width×2 mm in thickness measured by the following method is 1.03 or more, The loss tangent tanδ was measured using a dynamic viscoelasticity measuring device Rheometer MCR502 manufactured by Anton Paar, which was equipped with a temperature control system CTD-1000, at a frequency of 1.0 Hz, a strain of 0.01%, and a heating rate of 10°C / min in a shear measurement mode.

31. The method for producing chemically strengthened glass according to claim 30, wherein: Chemically strengthened glass is obtained by performing a two-step ion exchange treatment.

32. A method for manufacturing glass, which is a method for manufacturing microcrystalline glass having a curved surface shape, wherein: The obtained microcrystalline glass comprises, in terms of mole % based on oxides, 40% to 70% SiO2, 20% to 35% Li2O, 0% to 15% Al2O3, 0.5% to 5% P2O5, 2.5% to 5% ZrO2, 0% to 10% B2O3, 0.5% to 3% Na2O, 0% to 2% K2O, 0% to 4% SnO2, and 0% to 10% MgO, and does not contain microcrystalline glass of La2O3. The average particle size of the precipitated crystals of the microcrystalline glass is less than 60 nm. The peak value of the loss tangent tanδ represented by the ratio G'' / G' of the storage shear modulus G' to the loss shear modulus G'' of a glass sample having a size of 35 mm in length×8 mm in width×2 mm in thickness measured by the following method is 1.03 or more, The loss tangent tanδ was measured using a dynamic viscoelasticity measuring device Rheometer MCR502 manufactured by Anton Paar, which was equipped with a temperature control system CTD-1000, at a frequency of 1.0 Hz, a strain of 0.01%, and a heating rate of 10°C / min in a shear measurement mode.

33. The method for manufacturing glass-ceramics according to claim 32, which is a method for manufacturing glass-ceramics having a curved surface shape, wherein: Glass-ceramics is obtained by subjecting amorphous glass to two or more heat treatment steps.

34. The method for manufacturing glass-ceramics according to claim 32, which is a method for manufacturing glass-ceramics having a curved surface shape, wherein: After manufacturing a plate-shaped glass-ceramics, an external force of 8 kN or less is applied to form a curved surface by bending.

35. The method for manufacturing glass-ceramics according to claim 32, wherein: The bending is performed by at least one of self-weight forming, vacuum forming, and press forming.

36. The method for manufacturing glass-ceramics according to claim 32, wherein: The rate of change in crystallinity before and after the microcrystalline glass is formed is less than 10%.

37. A method for manufacturing glass-ceramics, which is a method for manufacturing glass-ceramics having a curved surface shape, wherein: The amorphous glass is heat-treated and crystallized and then bent.

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