Glass plate, method for producing same, and method for devitrifying glass plate

Abstract

Provided is a glass plate having a high average strength and a small degree of dispersion of the strength. A glass plate which contains a base glass phase and an intermediate phase, the base glass phase being an amorphous oxide that contains 50%-80% of SiO2, 0%-30% of Al2O3, and 0.1%-35% of Li2O in terms of oxide-based mol%, and the intermediate phase being an amorphous oxide that contains 50%-80% of SiO2, 5%-20% of Al2O3, and 5%-20% of Li2O in terms of oxide-based mol% and has a composition different from that of the base glass phase.

Description

Technical Field

[0001] This invention relates to glass plates, methods for manufacturing the same, and methods for removing devitrification from glass plates. Background Technology

[0002] In recent years, protective glass has been used to improve the protection and aesthetics of display devices such as mobile phones, smartphones, and tablets. For the glass sheets used in these protective applications, excellent strength is required to prevent breakage caused by impacts and other factors.

[0003] Previously, it was known to improve the surface strength of glass sheets by chemically strengthening them by immersing them in molten potassium nitrate salts, etc. (Patent Document 1).

[0004] Furthermore, the strength of the glass sheet can be further improved by chemically strengthening the glass sheet whose composition has been adjusted to a specific range. Examples of components that can increase strength by increasing their content in the glass composition include Al2O3 and Li2O (Patent Document 2).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Publication No. 2013-516387

[0008] Patent Document 2: Japanese Patent Publication No. 2013-520385 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] As mentioned above, the strength of the glass plate can be improved by increasing the content of Al2O3 and Li2O in the glass composition.

[0011] However, the devitrification temperature and devitrification growth rate of glass plates containing a large amount of Al2O3 and Li2O increase, which makes it easy for devitrification (crystalline phase) to occur in the matrix glass phase, which is an amorphous phase, during the forming process.

[0012] In most cases, the thermal expansion coefficients of the devitrifying (crystalline phase) and amorphous (matrix glass phase) phases are different. When heated or cooled, devitrification is the starting point for cracking, which can cause the glass plate to break.

[0013] Even if there is no breakage during forming, there are fine cracks that start with devitrification. Therefore, in the glass sheet used as a product, the degree of strength dispersion sometimes increases, or the average strength decreases.

[0014] The present invention was made in view of the above circumstances, and its object is to provide a glass plate with high average strength and low strength dispersion.

[0015] Furthermore, the present invention aims to provide a method for manufacturing a glass plate to obtain the above-mentioned glass plate and a method for removing devitrification from the glass plate.

[0016] means for solving problems

[0017] To achieve the above objectives, the inventors conducted in-depth research. The results showed that by locally heating the devitrifying (crystalline phase) formed in the matrix glass phase of the glass plate, at least a portion of the devitrification is removed, generating an intermediate phase with a composition different from the matrix glass phase. This reduces the intensity dispersion and increases the average strength, thus completing the present invention.

[0018] That is, the present invention is as follows.

[0019] [1] A glass plate comprising a matrix glass phase and an intermediate phase, wherein the matrix glass phase comprises 50% to 80% SiO2, 0% to 30% Al2O3, and 0.1% to 35% Li2O in molar percentage based on oxides, and the intermediate phase comprises 50% to 80% SiO2, 5% to 20% Al2O3, and 5% to 20% Li2O in molar percentage based on oxides, and is an amorphous oxide having a composition different from that of the matrix glass phase.

[0020] [2] According to the glass plate of [1], at least a portion of the intermediate phase is present at a position from the surface of the glass plate to a depth of 2000 μm.

[0021] [3] The glass plate according to [1] or [2], wherein the major axis of the intermediate phase is less than 2000 μm.

[0022] [4] A glass plate according to any one of [1] to [3], wherein the glass plate further comprises a crystalline phase, the intermediate phase being in contact with the crystalline phase and the matrix glass phase, the crystalline phase comprising 60% to 90% SiO2, 0% to 40% Al2O3, and 0% to 15% Na2O in molar percentage based on oxides, and at least a portion of the crystalline phase being present from the surface of the glass plate to a depth of 2000 μm.

[0023] [5] A glass plate according to any one of [1] to [4], wherein the thickness of the glass plate is 0.1 mm to 6.0 mm.

[0024] [6] The glass plate according to any one of [1] to [5], wherein the average strength obtained by performing the following ROR test 20 times is 30 MPa or more, and the Weibull coefficient m, which represents the dispersion of the strength, is 7 or more.

[0025] ROR test: The glass plate is placed on a lower ring containing stainless steel; the contact portion of the lower ring that contacts the glass plate has a diameter of 30 mm and a roundness with a radius of curvature of 2.5 mm; with the upper ring containing stainless steel in contact with the glass plate, a load is applied to the center of the upper ring under static load conditions; the contact portion of the upper ring that contacts the glass plate has a diameter of 10 mm and a roundness with a radius of curvature of 2.5 mm; the indentation speed of the upper ring is 1.0 mm / min; the fracture load at which the glass plate breaks is converted into fracture stress using the thickness of the glass plate and the location of the fracture initiation point, and this stress is calculated as the strength.

[0026] [7] The glass plate according to [4], wherein the crystalline phase comprises at least one of lithium phosphate crystal, lithium disilicate crystal, lithium aluminum silicate crystal, zirconium-containing crystal and magnesium-containing crystal.

[0027] [8] The glass plate according to any one of [1] to [7], wherein, based on the mole % of oxides, the matrix glass phase contains: 50% to 80% SiO2, 0% to 30% Al2O3, 0.1% to 35% Li2O, 0% to 8% B2O3, 0% to 6% P2O5, 0% to 20% Na2O, 0% to 10% K2O, 0% to 20% MgO, 0% to 20% CaO, 0% to 20% SrO, 0% to 15% BaO, 0% to 10% ZnO, 0% to 5% Ti2O, 0% to 8% ZrO2, and 0% to 8% Y2O3.

[0028] [9] A glass plate according to any one of [1] to [8], wherein the difference in thermal expansion coefficient Δα obtained by subtracting the thermal expansion coefficient of the intermediate phase from the thermal expansion coefficient of the matrix glass phase is less than 0 ppm / ℃.

[0029]

[10] The glass plate according to any one of [1] to [9], wherein the glass plate is a chemically strengthened glass with a compressive stress value of 400 MPa or more for the compressive stress layer.

[0030]

[11] A method for manufacturing a glass plate, wherein a crystalline phase-containing glass plate is prepared, wherein a crystalline phase exists at a position from the surface to a depth of 2000 μm, and a local heating treatment is performed on a heating region that is part of the crystalline phase-containing glass plate to obtain a glass plate, wherein the crystalline phase-containing glass plate contains the crystalline phase in the heating region, and the local heating treatment is a process of heating the heating region to a temperature T1 of 1500°C or higher and 2400°C or lower, and then cooling it to a temperature T2 of 800°C or higher and 1000°C or lower.

[0031]

[12] According to the glass plate manufacturing method of

[11] , a preheating treatment is performed before the local heating treatment is performed, wherein the glass plate containing the crystalline phase is heated to a preheating temperature of 800°C or higher and 1150°C or lower.

[0032]

[13] According to the glass plate manufacturing method described in

[11] , the local heating treatment is a process of raising the temperature of the heating area from the preheating temperature to the temperature T1 within 5s and cooling it from the temperature T1 to the temperature T2 within 300s.

[0033]

[14] The method for manufacturing a glass plate according to any one of

[11] to

[13] , wherein the local heating treatment is a process of heating the heating area by laser irradiation.

[0034]

[15] The method for manufacturing a glass plate as described in

[14] , wherein the wavelength of the laser is 2.5 μm to 12 μm.

[0035]

[16] In the method of manufacturing the glass plate according to

[14] , the laser is irradiated using a CO laser or a CO2 laser.

[0036]

[17] The method for manufacturing a glass plate according to any one of

[11] to

[13] , wherein the local heating treatment is a process of heating the heating area using a carbon heater.

[0037]

[18] A method for manufacturing a glass plate according to any one of

[11] to

[17] , wherein, in the implementation of the local heat treatment, the temperature of the region of the glass plate containing the crystalline phase other than the heating region is 1250°C or less.

[0038]

[19] A method for manufacturing a glass plate according to any one of

[11] to

[18] , wherein the localized heating treatment is performed in a floating polishing furnace for manufacturing the glass plate.

[0039]

[20] The method for manufacturing a glass plate according to any one of

[11] to

[19] , wherein, after the local heat treatment, the obtained glass plate is further subjected to a chemical strengthening treatment.

[0040]

[21] A method for removing devitrification from a glass plate, wherein a glass plate with devitrification is prepared at a depth of 2000 μm from the surface, the glass plate is preheated to a preheating temperature of 800°C or higher and 1150°C or lower, and then the heated area, which is part of the glass plate and includes the devitrified area, is heated from the preheating temperature to a temperature T1 of 1500°C or higher and 2400°C or lower within 5 seconds, and then cooled from the temperature T1 to a temperature T2 of 800°C or higher and 1000°C or lower within 300 seconds.

[0041] Invention Effects

[0042] According to the present invention, it is possible to provide a glass plate with high average strength and low strength dispersion.

[0043] Furthermore, according to the present invention, a method for manufacturing a glass plate to obtain the above-mentioned glass plate and a method for removing devitrification from the glass plate can also be provided. Attached Figure Description

[0044] Figure 1 This is a schematic diagram illustrating a laser heating device.

[0045] Figure 2 This is a cross-sectional image of the reflected electron beam from a glass plate before localized heating treatment.

[0046] Figure 3 This is a cross-sectional image of the reflected electron beam from a glass plate after localized heating. Detailed Implementation

[0047] The present invention is not limited to the following embodiments, and can be implemented in any modified way without departing from the spirit of the present invention.

[0048] In this specification, the glass composition is expressed as a mole percentage based on oxides, and mole % is sometimes simply stated as %. Additionally, the "~" indicating a numerical range is used to encompass the values ​​preceding and following it as lower and upper limits.

[0049] In this specification, the "compressive stress value (CS)" is determined by analyzing the thinned glass using a birefringence imaging system (CRi Abrio-IM).

[0050] In this specification, "depth of compressive stress layer (DOL)" refers to the depth at which the compressive stress value is zero. Additionally, "internal tensile stress (CT)" refers to the tensile stress value at a depth of 1 / 2 the plate thickness t.

[0051] [glass plate]

[0052] The glass plate of this embodiment (hereinafter also referred to as "this glass plate") is the glass plate containing a matrix glass phase and an intermediate phase, as described later.

[0053] This glass plate exhibits high average strength and minimal strength dispersion. This is presumably because the coexistence of the matrix glass phase and the intermediate phase applies compressive stress to the surrounding matrix glass phase, thus inhibiting crack propagation.

[0054] <Matrix glass phase>

[0055] The matrix glass phase is an amorphous oxide comprising 50%–80% SiO2, 0%–30% Al2O3, and 0.1%–35% Li2O in molar percentages based on oxides.

[0056] The matrix glass phase is the non-devitrifying amorphous (amorphous oxide) portion of the glass plate. Devitrification typically occurs during the cooling process of molten glass, therefore the composition of the matrix glass phase is consistent with that of the molten glass.

[0057] It should be noted that devitrification sometimes has a composition different from that of the matrix glass phase.

[0058] The amorphous portion near devitrification sometimes has a composition that differs from both the matrix glass phase and the devitrification.

[0059] The matrix glass phase, in molar percentage based on oxides, preferably comprises: 50%–80% SiO2, 0%~30% Al2O3, 0.1%–35% Li₂O, 0%~8% B2O3, 0%–6% P2O5, 0%~20% Na2O, 0%~10% K2O, 0%~20% MgO, 0%~20% CaO, 0%~20% SrO, 0%~15% BaO, 0%~10% ZnO, 0%~5% Ti2O, 0%–8% ZrO2, and 0% to 8% Y2O3.

[0060] The glass composition of the matrix glass phase is described below.

[0061] < <sio2>>

[0062] SiO2 is a component that makes up the glass network. In addition, SiO2 is a component that improves chemical durability and reduces the formation of cracks when the glass surface is damaged.

[0063] To improve chemical durability, the SiO2 content is 50% or more, preferably 54% or more, more preferably 58% or more, even more preferably 62% or more, and particularly preferably 64% or more.

[0064] On the other hand, from the viewpoint of making the meltability good, the SiO2 content is 80% or less, preferably 78% or less, more preferably 76% or less, even more preferably 74% or less, and particularly preferably 72% or less.

[0065] < <al2o3>>

[0066] Al2O3 is a component that improves ion exchange performance during chemical fortification and increases the CS (chemical ion exchange capacity) after fortification.

[0067] When Al2O3 is present, the content is preferably 1% or more. More preferably, the content of Al2O3 is 3% or more, 5% or more, 7% or more, 8% or more, 9% or more, 10% or more, 11% or more, and 12% or more.

[0068] On the other hand, when the Al2O3 content is greater than 30%, the acid resistance of the glass decreases. The Al2O3 content is 30% or less, preferably 25% or less, more preferably 20% or less, even more preferably 18% or less, and particularly preferably 15% or less.

[0069] Both SiO2 and Al2O3 are components that stabilize the structure of glass. To reduce brittleness, the combined content of SiO2 and Al2O3 is preferably 65% ​​or more, more preferably 70% or more, and even more preferably 74% or more.

[0070] Both SiO2 and Al2O3 tend to increase the melting temperature of glass. Therefore, for easy melting, their combined content is preferably 83% or less, more preferably 82% or less, and even more preferably 81% or less.

[0071] < <li2o>>

[0072] Li2O is a component that forms the compressive stress layer through ion exchange.

[0073] When the Li ions on the glass surface are exchanged for Na ions and chemically strengthened, from the viewpoint of easily obtaining a preferred stress distribution, the Li2O content is 0.1% or more, preferably 0.3% or more, more preferably 0.5% or more, further preferably 0.6% or more, and particularly preferably 0.7% or more.

[0074] On the other hand, when the Li2O content is greater than 35%, the acid resistance of the glass decreases significantly. The Li2O content is 35% or less, preferably 28% or less, more preferably 26% or less, even more preferably 23% or less, and particularly preferably 21% or less.

[0075] < <b2o3>>

[0076] B2O3 is a component that improves resistance to edge defects and enhances the melting properties of glass.

[0077] It may not contain B2O3, but when it does contain B2O3, the content is preferably 0.5% or more, more preferably 1% or more, and even more preferably 2% or more.

[0078] On the other hand, when the B2O3 content is greater than 8%, ripples may form due to volatilization during melting, leading to defects. The B2O3 content is preferably 8% or less, more preferably 6% or less, even more preferably 5% or less, and particularly preferably 4% or less.

[0079] < <p2o5>>

[0080] P2O5 is a component that improves ion exchange performance and resistance to edge defects.

[0081] It may not contain P2O5, but when it does contain P2O5, the content is preferably 0.5% or more, more preferably 1% or more, and even more preferably 2% or more.

[0082] On the other hand, when the P2O5 content is greater than 6%, the glass's brittleness and acid resistance decrease significantly. Therefore, the P2O5 content is preferably 6% or less, more preferably 5% or less, even more preferably 4% or less, and particularly preferably 3% or less.

[0083] < <na2o>>

[0084] Na₂O forms a compressive stress layer through ion exchange and also improves the meltability of the glass. It may not contain Na₂O, but it can be included if meltability is a key consideration. When Na₂O is present, its content is preferably 1% or more, more preferably 2% or more, and even more preferably 3% or more.

[0085] On the other hand, if the Na2O content is greater than 20%, the acid resistance of the glass will be significantly reduced. Therefore, the Na2O content is preferably 20% or less, more preferably 18% or less, even more preferably 16% or less, particularly preferably 15% or less, and most preferably 14% or less.

[0086] < <k2o>>

[0087] K2O is a component that improves ion exchange performance and may be present in the sample. When K2O is present, its content is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, and particularly preferably 3% or more.

[0088] On the other hand, when the K2O content is greater than 10%, the breakage of the glass is significantly reduced. Therefore, the K2O content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, particularly preferably 4% or less, and most preferably 2% or less.

[0089] < <mgo>>

[0090] MgO may be included to reduce viscosity during melting. When MgO is present, the content is preferably 2% or more, and more preferably 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, and 8% or more.

[0091] On the other hand, when the MgO content is greater than 20%, it may easily devitrify and lead to defects. Therefore, the MgO content is preferably 20% or less, and more preferably 18% or less, 15% or less, 14% or less, 13% or less, 12% or less, and 11% or less.

[0092] <<CaO and SrO>>

[0093] CaO and SrO are components that improve the meltability of glass, and may be present in glass. When CaO and SrO are present, their respective contents are preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, particularly preferably 3% or more, and most preferably 5% or more.

[0094] On the other hand, when the contents of CaO and SrO are each greater than 20%, the ion exchange performance decreases significantly. Therefore, the contents of CaO and SrO are preferably 20% or less, more preferably 18% or less, even more preferably 16% or less, particularly preferably 14% or less, and most preferably 12% or less.

[0095] < <bao>>

[0096] BaO is a component that improves the meltability of glass and may be present. When BaO is present, its content is preferably 0.5% or more, more preferably 1% or more, further preferably 2% or more, particularly preferably 3% or more, and most preferably 5% or more.

[0097] On the other hand, when the BaO content is greater than 15%, the ion exchange performance decreases significantly. Therefore, the BaO content is preferably 15% or less, more preferably 13% or less, even more preferably 11% or less, particularly preferably 9% or less, and most preferably 7% or less.

[0098] < <zno>>

[0099] ZnO is a component that improves the meltability of glass and may be present in glass. When ZnO is present, its content is preferably 0.25% or more, more preferably 0.5% or more.

[0100] On the other hand, when the ZnO content is greater than 10%, the weather resistance of the glass is significantly reduced. The ZnO content is preferably 10% or less, more preferably 7% or less, further preferably 5% or less, particularly preferably 2% or less, and most preferably 1% or less.

[0101] < <tio2>>

[0102] TiO2 is a component with a high effect on suppressing sunlight exposure on glass, and may contain TiO2. When TiO2 is present, its content is preferably 0.1% or more, more preferably 0.15% or more, and even more preferably 0.2% or more.

[0103] On the other hand, when the TiO2 content is greater than 5%, it may easily devitrify and lead to defects. Therefore, the TiO2 content is preferably 5% or less, more preferably 3% or less, further preferably 1% or less, particularly preferably 0.5% or less, and most preferably 0.25% or less.

[0104] < <zro2>>

[0105] ZrO2 is a component that increases the CS (chromatic crystalline solids) of chemically strengthened glass and may be present in the glass. When ZrO2 is present, its content is preferably 0.5% or more, more preferably 1% or more.

[0106] On the other hand, when the ZrO2 content is greater than 8%, it may easily devitrify and lead to defects. Therefore, the ZrO2 content is preferably 8% or less, more preferably 6% or less, further preferably 4% or less, particularly preferably 2% or less, and most preferably 1.5% or less.

[0107] < <y2o3>>

[0108] Y2O3 is a component that increases the CS (chromatic osmotic pressure) of chemically strengthened glass while reducing the devitrification growth rate, and may contain Y2O3. When Y2O3 is present, its content is preferably 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, particularly preferably 2% or more, and most preferably 2.5% or more.

[0109] On the other hand, when the Y2O3 content is greater than 8%, it may easily devitrify, leading to defects. Therefore, the Y2O3 content is preferably 8% or less, more preferably 6% or less, further preferably 5% or less, particularly preferably 4% or less, and most preferably 3% or less.

[0110] <<Coloring Components>>

[0111] Furthermore, when using colored glass, coloring components can be added within a range that does not hinder the achievement of the desired chemical strengthening properties.

[0112] As coloring components, suitable examples include metal oxides of Co, Mn, Fe, Ni, Cu, Cr, V, Bi, Se, Ti, Ce, Er, and Nd that have absorption in the visible light region, such as Co3O4, MnO, MnO2, Fe2O3, NiO, CuO, Cu2O, Cr2O3, V2O5, Bi2O3, SeO2, TiO2, CeO2, Er2O3, and Nd2O3.

[0113] When this glass plate is used as a colored glass, the matrix glass phase may contain coloring components (selected from at least one group consisting of metal oxides of Co, Mn, Fe, Ni, Cu, Cr, V, Bi, Se, Ti, Ce, Er, and Nd) in the range of less than 7% based on oxides. A content greater than 7% will cause the glass plate to devitrify, which is undesirable.

[0114] The content of the coloring component is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less.

[0115] When prioritizing the light transmittance of the glass plate, it is preferable to have substantially no (unintentionally) these coloring components. Specifically, for example, it is preferable to have less than 0.1%.

[0116] <<Other Ingredients>>

[0117] Other components may include, for example, SO3, chlorides, fluorides, etc., which serve as clarifying agents during glass melting.

[0118] <Intermediate Phase>

[0119] The intermediate phase is an amorphous oxide containing 50%–80% SiO2, 5%–20% Al2O3, and 5%–20% Li2O in molar percentage based on oxides, and having a composition different from the matrix glass phase.

[0120] The intermediate phase is an amorphous phase with an intermediate composition between the devitrification and the matrix glass phase, produced by localized heating treatment described later to amorphize at least a portion of the devitrification (crystalline phase) in the matrix glass phase. The intermediate composition refers to the composition of each component being between that of the devitrification and the matrix glass phase.

[0121] The intermediate phase is generated by local heating of the crystalline phase in the matrix glass phase. Therefore, even after local heating, the crystalline phase remains, and the intermediate phase comes into contact with both the crystalline phase and the matrix glass phase.

[0122] As will be described later, at least a portion of the crystalline phase is present, for example, at a location extending from the surface of the glass plate to a depth of 2000 μm.

[0123] Therefore, at least a portion of the intermediate phase produced by local heating of the crystalline phase also exists at a depth of 2000 μm from the surface of the glass plate.

[0124] At least a portion of the intermediate phase is preferably present at a depth of 1000 μm from the surface of the glass plate.

[0125] The intermediate and crystalline phases have compositions different from the matrix glass phase, and therefore are observed with different brightness in reflected electron beam images obtained using scanning electron microscopy (SEM).

[0126] The positions (depth (distance) from the surface of the glass plate) and major axis of the intermediate and crystalline phases are obtained by the following method.

[0127] A cross-section parallel to the thickness direction of a glass plate is prepared. This cross-section is mirror-polished and used as the observation surface. The observation surface is observed using SEM to obtain a reflected electron beam image. Using the obtained reflected electron beam image, the position (depth (distance) of the mesophase measured from the surface of the glass plate) and major axis are determined. The major axis of the mesophase is the linear distance of the portion of the mesophase with the largest linear distance in the reflected electron beam image of the observation surface.

[0128] The position and major axis of the crystalline phase were also determined in the same way.

[0129] The major axis of the mesophase is 2000 μm or less, preferably 1500 μm or less, more preferably 800 μm or less, even more preferably 400 μm or less, and particularly preferably 200 μm or less.

[0130] On the other hand, for the sake of superior strength, the major diameter of the mesophase is preferably 20 μm or more, more preferably 40 μm or more, even more preferably 60 μm or more, and particularly preferably 80 μm or more.

[0131] < <sio2>>

[0132] In the mesophase, the SiO2 content is 50% or more, preferably 54% or more, more preferably 58% or more, even more preferably 62% or more, and particularly preferably 64% or more.

[0133] On the other hand, the SiO2 content is 80% or less, preferably 78% or less, more preferably 76% or less, even more preferably 74% or less, and particularly preferably 72% or less.

[0134] < <al2o3>>

[0135] In the mesophase, the content of Al2O3 is 5% or more, preferably 7% or more, more preferably 9% or more, and even more preferably 11% or more.

[0136] On the other hand, the content of Al2O3 is 20% or less, preferably 18% or less, and more preferably 15% or less.

[0137] < <li2o>>

[0138] In the mesophase, the content of Li2O is 5% or more, preferably 7% or more, more preferably 9% or more, and even more preferably 11% or more.

[0139] On the other hand, the Li2O content is 20% or less, preferably 18% or less, and more preferably 16% or less.

[0140] <<Other Ingredients>>

[0141] The content of other components (such as Na2O) in the intermediate phase follows the content of the matrix glass phase.

[0142] <Crystallized Phase (Devitrification)>

[0143] The crystalline phase (devitrified) exists within the matrix glass phase.

[0144] At least a portion of the crystalline phase is present, for example, at a depth of 2000 μm from the surface of the glass plate.

[0145] The crystalline phase is composed of the components contained in the matrix glass, for example, in molar percentage based on oxides, it contains: 60% to 90% SiO2, 0% to 40% Al2O3, and 0% to 15% Na2O.

[0146] Glass plates can contain multiple crystalline phases (devitrification).

[0147] Examples of crystalline phases include: lithium phosphate crystals (Li3PO4), lithium disilicate crystals (Li2Si2O5), and lithium aluminum silicate crystals (LiAlSi4O). 10 (LiAlSi2O6), zirconium-containing crystals, magnesium-containing crystals, etc.

[0148] Lithium aluminum silicate crystals include β-quartz solid solution and β-spodumene.

[0149] β-quartz solid solution is sometimes simply referred to as β-quartz, and is also known as cordierite or β-quartz. Mg, Na, K, Ca, Sr, Ba, and other elements are dissolved in β-quartz solid solution.

[0150] Zirconium-containing crystals include zirconium oxide and zirconium oxide solid solutions. Zirconium oxide solid solutions can contain dissolved elements such as Y and Sn.

[0151] Magnesium-containing crystals include magnesium silicate.

[0152] When the glass plate has a crystalline phase, for the sake of superior strength, the major axis of the crystalline phase (the major axis after local heat treatment, as described later) is preferably 2000 μm or less, more preferably 1800 μm or less, even more preferably 1600 μm or less, particularly preferably 1400 μm or less, and most preferably 1200 μm or less.

[0153] <Methods for determining the content of each component>

[0154] The composition (content of each component) of the matrix glassy phase, intermediate phase and crystalline phase was determined by analysis using an electron probe microanalyzer (EPMA).

[0155] More specifically, the glass plates were ground to expose the phases, and the EPMA was analyzed using a JXA-8500F (manufactured by JEOL) under the following conditions.

[0156] • Spectroscopic crystals: For Na, Si, Al, P, Sr, and Zn, it is a TAP crystal; for Ca, it is a PETJ crystal; for Mg, it is a TAPH crystal; and for K, Zr, Y, Ti, and Ba, it is a PETH crystal.

[0157] Electron beam accelerating voltage: 15kV

[0158] • Electron beam current: 10 nA

[0159] • Irradiation acquisition time: 10s for peak position, 5s for background position

[0160] • Analysis software used: Software manufactured by JEOL Corporation included with the device.

[0161] <Average strength and Weibull coefficient m>

[0162] In this glass plate, the average strength (also referred to as "average strength") measured in the ROR test described later is preferably 30 MPa or more, more preferably 60 MPa or more, and even more preferably 90 MPa or more.

[0163] Furthermore, in this glass plate, the value of the Weibull coefficient m, which represents the degree of dispersion of the strength measured in the ROR test described later, is preferably greater than 6, and more preferably 7 or above.

[0164] <<ROR Test>>

[0165] First, a glass plate is arranged on a lower ring, which is made of stainless steel, with one of its main surfaces facing downwards. The contact portion of the lower ring (the part that contacts the glass plate) has a diameter of 30 mm and a roundness with a radius of curvature of 2.5 mm.

[0166] Next, the upper ring, which contains stainless steel, is brought into contact with the other main surface (the upper main surface) of the glass plate disposed on the lower ring. The contact portion of the upper ring has a diameter of 10 mm and a roundness with a radius of curvature of 2.5 mm.

[0167] In this state, using an Autograph AGS-10kNX (manufactured by Shimadzu Corporation), a load was applied to the center of the upper ring under static load conditions, causing the glass plate to break. The indentation speed of the upper ring was set to 1.0 mm / min.

[0168] The fracture load at which the glass plate breaks is converted into fracture stress (unit: MPa) using the thickness of the glass plate and the location of the fracture initiation point, and this stress is then calculated as the strength. An approximate conversion formula based on finite element method simulation is used in the conversion from fracture load to fracture stress.

[0169] Perform 20 such ROR tests and calculate the average strength (average strength).

[0170] The measured fracture load when the glass plate's fracture initiation point is located further outward than the indentation point of the upper ring is not used for the calculation of the average strength.

[0171] In addition, the Weibull coefficient m was calculated using 20 intensity values ​​according to JIS R 1625 (2010).

[0172] <Difference in thermal expansion coefficient Δα>

[0173] When the coefficient of thermal expansion of the intermediate phase is greater than that of the matrix glass phase, compressive stress is generated during cooling, thus increasing the strength of the glass plate.

[0174] The difference in thermal expansion coefficients, Δα (thermal expansion coefficient of the matrix glass phase - thermal expansion coefficient of the intermediate phase), obtained by subtracting the thermal expansion coefficient of the intermediate phase from the thermal expansion coefficient of the matrix glass phase, is preferably less than 0 ppm / ℃, more preferably less than -0.1 ppm / ℃, even more preferably less than -0.2 ppm / ℃, and particularly preferably less than -0.25 ppm / ℃.

[0175] The coefficient of thermal expansion (thermal expansion rate) of the matrix glass phase is the average coefficient of thermal expansion in the range of 50 to 350 °C. It is measured on the plate-shaped sample using a differential thermal dilatometer (DIL 402 SE manufactured by NETZSCH) according to the method described in JIS R 3102-1995.

[0176] Glass samples with the same composition as the mesophase were prepared, and the thermal expansion coefficient of the mesophase was measured in the same manner.

[0177] <shape>

[0178] The shape of this glass plate can be other than plate shape according to the products to be applied, uses, etc. For example, it can be a beveled shape where the thickness of the outer peripheral part is different from that of other parts.

[0179] The two main surfaces of this glass plate may not be parallel to each other, and all or part of one or both of the two main surfaces may be curved surfaces.

[0180] This glass plate can be, for example, a flat glass plate without warping, or alternatively, a curved glass plate with a curved surface.

[0181] <Plate thickness>

[0182] When this glass plate is in a flat shape, from the viewpoint of weight reduction of the protective glass, its plate thickness is, for example, 6.0 mm or less, preferably 5.0 mm or less, more preferably 4.5 mm or less, and further preferably 4.0 mm or less.

[0183] In addition, from the viewpoint of obtaining a sufficient effect of strength improvement based on chemical strengthening treatment, the plate thickness of this flat glass plate is preferably 0.1 mm or more, more preferably 0.2 mm or more, further preferably 0.3 mm or more, and particularly preferably 0.5 mm or more.

[0184] <CS and DOL (chemically strengthened glass)>

[0185] This glass plate can be a chemically strengthened glass having a compressive stress layer on the surface layer.

[0186] The compressive stress value (CS) of the compressive stress layer of the chemically strengthened glass is preferably 400 MPa or more, more preferably 500 MPa or more, and further preferably 600 MPa or more.

[0187] When the DOL (depth of the compressive stress layer) of the chemically strengthened glass is 70 μm or more, it is not easily broken even if damage occurs on the surface, and thus it is preferred. The DOL is more preferably 100 μm or more.

[0188] It should be noted that the larger the DOL, the more difficult it is to break even if damage occurs. However, in a chemically strengthened glass, a tensile stress is generated inside corresponding to the compressive stress formed near the surface, so the DOL cannot be extremely large. When the plate thickness is t, the DOL is preferably t / 4 or less, more preferably t / 5 or less. In order to shorten the time required for chemical strengthening, the DOL is preferably 200 μm or less, more preferably 180 μm or less.

[0189] [Manufacturing method of glass plate (devitrification removal method of glass plate)]

[0190] Next, the method for manufacturing the glass plate described above (hereinafter also referred to as "this manufacturing method") will be explained. The following explanation also serves as an explanation of the method for removing devitrification from the glass plate.

[0191] In this manufacturing method, generally speaking, firstly, a crystalline phase-containing glass plate is prepared, which has a crystalline phase (devitrification) at a depth of 2000 μm from the surface. Next, a localized heat treatment is performed on the heating area, which is part of the crystalline phase-containing glass plate.

[0192] Preparation of glass plates containing crystalline phases

[0193] First, the glass raw materials are weighed and mixed in a manner that constitutes the aforementioned matrix glass phase. Next, the resulting mixture is heated and melted to obtain molten glass. Then, the molten glass is shaped into a plate.

[0194] Methods for forming molten glass into a sheet include, for example, the float glass process, the pressing process, the fusion process, and the down-drawing process. The float glass process is particularly preferred when manufacturing large glass sheets. Additionally, continuous forming methods other than the float glass process, such as the fusion process and the down-drawing process, are also preferred.

[0195] The formed glass strip is ground and polished as needed to form a glass sheet.

[0196] It should be noted that if the glass plate is cut into a specified shape and size or beveled before the chemical strengthening treatment described later, a compressive stress layer will also be formed on the end face through the chemical strengthening treatment, which is therefore preferred.

[0197] During the glass forming process, crystallization occurs within the glass plate.

[0198] For example, in the case of float glass forming, the glass sheet is cooled from a high temperature within a float polishing furnace. Crystallization then occurs when the temperature range for nucleation overlaps with the temperature range for crystal growth.

[0199] Typically, the temperature range for nucleation does not overlap with the temperature range for crystal growth.

[0200] However, glasses containing large amounts of Al2O3 and Li2O tend to have a nucleation temperature range that overlaps with the crystal growth temperature range around 1000°C. Therefore, during the glass forming process, for example, crystalline phases (devitrification) sometimes form at a depth of 2000 μm from the surface of the glass plate.

[0201] This results in a glass plate containing a crystalline phase (devitrification).

[0202] <<Devitrification Temperature>>

[0203] The temperature at which devitrification occurs in the glass plate (devitrification temperature) is, for example, below 1250°C, preferably below 1240°C, more preferably below 1230°C, even more preferably below 1220°C, and particularly preferably below 1210°C. There is no particular limitation on the lower limit of the devitrification temperature, which is typically 900°C.

[0204] By setting the devitrification temperature below 1250°C, stable forming is possible, improving manufacturing characteristics. For example, in the case of float glass forming, when crystals form before the molten glass flows into the float polishing furnace, these crystals can erode the bricks constituting the furnace. In this case, by setting the devitrification temperature below 1250°C, the erosion of the bricks can be suppressed.

[0205] The devitrification temperature of the glass is determined by the following procedure.

[0206] First, crushed glass particles with a diameter of 2mm to 3mm are placed in a platinum dish and heated in an electric furnace at a controlled temperature for 17 hours. After heating, the glass is observed using an optical microscope to confirm the presence or absence of crystal precipitation. The minimum temperature at which crystals do not precipitate on the surface and inside the glass is determined as the devitrification temperature of the glass.

[0207] <<Nucleation Temperature>>

[0208] The nucleation temperature of the glass plate is, for example, 790°C or higher, preferably 800°C or higher, more preferably 810°C or higher, even more preferably 815°C or higher, particularly preferably 820°C or higher, and most preferably 825°C or higher. There is no particular upper limit to the nucleation temperature, but it is typically 900°C.

[0209] By using a nucleation temperature above 790℃, manufacturing characteristics can be improved.

[0210] For example, when a glass plate that has already been formed into a sheet is further heated to perform stereolithography, crystallization is likely to occur if the temperature used for stereolithography is higher than the nucleation temperature. In this case, by setting the nucleation temperature to 790°C or higher, the temperature used for stereolithography should not exceed the nucleation temperature, thus suppressing the formation of the crystalline phase.

[0211] Nucleation temperature was determined using a differential scanning calorimeter (DSC).

[0212] Specifically, the glass was ground in an agate mortar, and the temperature of about 70 mg of powder with a uniform particle size of 106 μm to 180 μm was set at a rate of 10 °C / min, and the temperature was increased from room temperature to 1200 °C.

[0213] <<Devitrification Growth Rate>>

[0214] When only β-quartz solid solution precipitates as the crystalline phase (devitrification), the devitrification growth rate is preferably 4000 μm / hour or less, more preferably 3800 μm / hour or less, even more preferably 3500 μm / hour or less, and particularly preferably 3200 μm / hour or less.

[0215] When β-quartz solid solution and β-spodumene coexist and precipitate as crystalline phases (devitrification), the devitrification growth rate of β-quartz solid solution is preferably 500 μm / hour or less, more preferably 450 μm / hour or less, even more preferably 400 μm / hour or less, and particularly preferably 350 μm / hour or less.

[0216] Localized heating treatment

[0217] Next, the obtained glass plate containing the crystalline phase is subjected to localized heat treatment.

[0218] More specifically, in the localized heating process, the heating region (the region containing the crystalline phase) that is part of the glass plate containing the crystalline phase is locally heated. As a result, at least a portion of the crystalline phase (devitrification) is amorphized and removed, and replaced by the aforementioned intermediate phase.

[0219] Figure 2 This is a cross-sectional image of the reflected electron beam from a glass plate before localized heating treatment. Figure 3 This is a cross-sectional image of the reflected electron beam from a glass plate after localized heating.

[0220] observe Figure 2 At that time, the presence of crystalline phase 12 could be confirmed separately from the matrix glass phase 11.

[0221] On the other hand, observation Figure 3 At that time, it was confirmed that through local heating treatment, a portion of the crystalline phase 12 became amorphous, generating the intermediate phase 13.

[0222] It should be noted that, in Figure 2 In this process, a region of high brightness can be identified between the crystalline phase 12 and the matrix glass phase 11. This region arises when the crystalline phase 12 is generated within the matrix glass phase 11, and the composition of the matrix glass phase 11 is inconsistent with that of the crystalline phase 12; this region is sometimes a residual glass phase. The composition of the residual glass phase compensates for the deviation between the composition of the matrix glass phase 11 and the crystalline phase 12.

[0223] Localized heating treatment is, for example, raising the temperature of the heated area to a temperature T1 of 1500℃ to 2400℃ and then cooling it down to a temperature T2 of 800℃ to 1000℃.

[0224] In the implementation of localized heating treatment, the temperature of the area outside the heating zone is preferably below 1250°C.

[0225] The temperature of the glass plate (temperature T1, temperature T2, etc.) was measured using an infrared camera.

[0226] In localized heating treatment, the faster the heating rate to temperature T1, the more effectively only the desired heating area can be heated. Therefore, the heating time from the starting temperature to temperature T1 is preferably within 5 seconds, more preferably within 4.5 seconds, and even more preferably within 4 seconds.

[0227] It should be noted that the starting temperature is the preheating temperature if the preheating treatment described later is performed, and room temperature (23℃±5℃) if no preheating treatment is performed.

[0228] Furthermore, by keeping the cooling time from temperature T1 to temperature T2 within 300 seconds, re-devitrification during the cooling process can be suppressed, which is therefore preferred. The cooling time is more preferably within 250 seconds, further preferably within 200 seconds, particularly preferably within 150 seconds, and most preferably within 100 seconds.

[0229] The smaller the heating area, the faster the heat diffuses from the heating area after heating, and the faster the cooling rate. Therefore, it is less likely to cause re-devitrification during the cooling process. In addition, because the glass plate is heated locally, it is possible to suppress the formation of unevenness or deformation on the glass plate surface.

[0230] Therefore, the major diameter of the heating zone is preferably 200 mm or less, and more preferably 100 mm or less.

[0231] On the other hand, when the heating zone is too small, devitrification cannot be fully removed.

[0232] Therefore, the major diameter of the heating zone is preferably 1 mm or more, more preferably 1.5 mm or more, and even more preferably 2 mm or more.

[0233] The heating zone is preferably the area extending from the surface of the glass plate to a depth of 2000 μm.

[0234] There are no particular restrictions on the heating method used in localized heating treatment.

[0235] Examples of heating devices used in localized heating processes include laser heating devices and carbon heaters. The following is based on... Figure 1 The local heating treatment using a laser heating device is explained.

[0236] <<Laser Heating Device>>

[0237] Figure 1 This is a schematic diagram illustrating a laser heating device 1. The laser heating device 1 irradiates a laser 4 generated by a laser source 8 into the heating region 3 of a glass plate 2, which is a glass plate containing a crystalline phase. It should be noted that, as described above, the heating region 3 is the region in the glass plate 2 containing the crystalline phase (… Figure 1 (Area not shown in the diagram).

[0238] More specifically, the laser 4 generated by the laser source 8 first changes its path by passing through a reflector 9 positioned above the laser guide window 6. Next, the laser 4 forms the desired cross-section through a lens 7 positioned between the reflector 9 and the laser guide window 6. Then, it irradiates the heating region 3 of the glass plate 2 through the laser guide window 6.

[0239] Regarding lens 7, its shape and material are not particularly limited as long as it enables laser 4 to form the desired cross-section and achieves the desired laser output power on the surface of glass plate 2. Furthermore, the number of lenses 7 can be one or more, depending on the focal length.

[0240] The laser 4 is preferably applied at an angle A of 45° or more relative to the surface of the glass plate 2. When the angle A is less than 45°, the cross-section of the laser 4 on the surface of the glass plate 2 becomes too large, and may not achieve the desired width. Angle A is more preferably 55° or more.

[0241] If the wavelength of laser 4 is too short, it may not be able to heat the laser sufficiently. For this reason, the wavelength of laser 4 is preferably 2.5 μm or more, more preferably 5 μm or more, and even more preferably 7.5 μm or more.

[0242] On the other hand, if the wavelength of the laser 4 is too long, it is difficult to obtain the laser heating device 1, which is impractical. Therefore, the wavelength of the laser 4 is preferably 12 μm or less, and more preferably 11 μm or less.

[0243] From the viewpoint of achieving sufficient heating, the output power of laser 4 is preferably 250W or more, more preferably 300W or more, and even more preferably 350W or more.

[0244] On the other hand, considering the availability of equipment and ease of power supply, the output power of the laser 4 is preferably 650W or less, more preferably 600W or less, and even more preferably 550W or less.

[0245] In order to ensure that heat is fully transferred to the entire heating area 3 of the glass plate 2, the scanning speed of the laser 4 is preferably 3500 mm / s or less, more preferably 3000 mm / s or less, and even more preferably 2500 mm / s or less.

[0246] On the other hand, in order to improve the efficiency of local heating treatment, the scanning speed of the laser 4 is preferably 800 mm / s or more, more preferably 1000 mm / s or more, and even more preferably 1200 mm / s or more.

[0247] The irradiation area of ​​laser 4 in the heating region 3 of glass plate 2 is set to be 1 / e, which maximizes the energy density distribution of the cross-section of laser 4 on the surface of glass plate 2. 2 The surface enclosed by partially connected curves.

[0248] At this point, considering the ease of fully removing devitrification, the energy density defined by the output power / irradiation area of ​​laser 4 is preferably 4 W / mm². 2 The above is preferred, with 5W / mm being even better. 2 The above is further optimized to 6W / mm. 2 above.

[0249] On the other hand, when the energy density of laser 4 is too high, sometimes laser 4 is excessively absorbed by glass plate 2, leading to uneven glass composition. Therefore, the energy density of laser 4 is preferably 20 W / mm². 2 The following is preferred: 15W / mm 2 The following is a further preferred value: 10W / mm 2 the following.

[0250] There are no particular restrictions on the oscillation mode of laser 4. It can be any of the following: continuous oscillation light (CW light), pulsed oscillation light, or modulated light of continuous oscillation light (which periodically imparts intensity changes by ON / OFF modulation of continuous oscillation light).

[0251] Preferably, the laser 4 with a frequency of 0.1 Hz or higher is used to irradiate for 0.001 seconds or more, and more preferably for 0.005 seconds or more.

[0252] During laser irradiation, for example, a CO laser or a CO2 laser is used.

[0253] The laser 4 with an oscillation wavelength of 10.6 μm is particularly preferred as a common CO2 laser. When the laser 4 is irradiated in this wavelength range, the laser 4 is almost entirely absorbed by the glass plate, which can locally raise the temperature of the heating region 3.

[0254] When the laser 4 is a pulsed oscillating light, the pulse width is preferably less than 600 ms, and more preferably less than 400 ms.

[0255] Such localized heating treatment can also be used to remove devitrification from glass ribbons manufactured continuously in a production line.

[0256] In the float glass and fusion glass processes, glass ribbons are continuously manufactured. However, if devitrification occurs during the manufacturing process, cracks may develop from this devitrification during cooling, eventually leading to the breakage of the final glass sheet and a decrease in manufacturing efficiency.

[0257] Therefore, localized heat treatment is applied to the continuously manufactured glass ribbon. This removes the devitrification generated in the glass ribbon, thus enabling the efficient production of glass sheets.

[0258] When only a portion of the crystalline phase (devitrification) is amorphized by localized heating, an intermediate phase is generated at the location between the matrix glass phase and the remaining devitrification.

[0259] On the other hand, when all the crystalline phases (devitrification) are made amorphous, an intermediate phase is generated at the location of the over-devitrification in the matrix glass phase.

[0260] To completely eliminate all crystalline phases through localized heating, longer heating times or higher temperatures are required. On the other hand, by amorphizing only a portion of the crystalline phase, the strength of the glass plate can be increased efficiently in a shorter time or at a lower temperature.

[0261] <Preheating Treatment>

[0262] Before localized heating treatment, the heating area and other areas can be preheated.

[0263] In the preheating process, the heating zone and other areas of the glass plate are heated to a preheating temperature. The preheating temperature is preferably 800°C or higher, more preferably 820°C or higher, even more preferably 830°C or higher, and particularly preferably 850°C or higher.

[0264] Furthermore, the preheating temperature is preferably below the glass transition temperature. The preheating temperature is preferably below 1150°C, more preferably below 980°C, even more preferably below 960°C, and particularly preferably below 950°C.

[0265] When local heating treatment is performed after preheating, the temperature of the area other than the heating area is, for example, below 1250°C.

[0266] <Chemical Enhancement Treatment>

[0267] Chemical strengthening treatment can be applied to glass plates that have undergone localized heat treatment. This results in chemically strengthened glass with a compressive stress layer on the surface, which can then be used as a glass plate.

[0268] Chemically strengthened glass can be manufactured by chemically strengthening glass sheets, followed by cleaning and drying.

[0269] Chemically strengthened glass has dimensions that can be formed using existing forming methods and is ultimately cut to the size suitable for its intended use.

[0270] When glass plates are cut into specified shapes and sizes or beveled, it is preferable to cut or bevel them before chemical strengthening treatment, as a compressive stress layer will also be formed on the end face through subsequent chemical strengthening treatment.

[0271] Chemical strengthening treatment can be carried out using well-known methods. In chemical strengthening treatment, a glass plate is brought into contact with a molten metal salt (e.g., potassium nitrate) containing metal ions with large ionic radii (typically K ions) by means of impregnation or the like. As a result, the metal ions with small ionic radii in the glass plate (typically Na or Li ions) are replaced by metal ions with large ionic radii (typically K ions for Na ions, and either Na or K ions for Li ions).

[0272] Chemical strengthening treatment, i.e., ion exchange treatment, can be performed, for example, by immersing the glass plate in a molten salt such as potassium nitrate heated to 360°C to 600°C for 0.1 hours to 500 hours. It should be noted that the heating temperature of the molten salt is preferably 375°C or higher, and more preferably 500°C or lower. The immersion time of the glass plate in the molten salt is preferably 0.3 hours or higher, and more preferably 200 hours or lower.

[0273] Examples of molten salts used for chemical fortification include nitrates, sulfates, carbonates, and chlorides.

[0274] Examples of nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate, and silver nitrate.

[0275] Examples of sulfates include lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, and silver sulfate.

[0276] Examples of carbonates include lithium carbonate, sodium carbonate, and potassium carbonate.

[0277] Examples of chlorides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, and silver chloride.

[0278] These molten salts can be used alone or in combination.

[0279] The appropriate conditions for chemical strengthening can be selected by considering the characteristics and composition of the glass plate, the type of molten salt, and the desired CS and DOL of the final chemically strengthened glass.

[0280] Chemical enhancement treatment can be performed once, or it can be performed multiple times under two or more different conditions (multi-step enhancement).

[0281] In the case of performing multiple chemical strengthening treatments, for example, as the first step of chemical strengthening treatment, chemical strengthening treatment is performed under conditions of large DOL and relatively small CS. Then, as the second step of chemical strengthening treatment, chemical strengthening treatment is performed under conditions of small DOL and relatively large CS. This can increase the CS of the outermost surface of the chemically strengthened glass and suppress the internal tensile stress area (St), thus suppressing the internal tensile stress (CT) to a low level.

[0282] In order to suppress warping during chemical strengthening treatment, the Young's modulus of the glass plate subjected to chemical strengthening treatment is preferably 70 GPa or more, more preferably 75 GPa or more, even more preferably 80 GPa or more, and particularly preferably 85 GPa or more.

[0283] On the other hand, the glass plate is sometimes ground before chemical strengthening treatment. For ease of grinding, the Young's modulus is preferably 130 GPa or less, more preferably 120 GPa or less, and even more preferably 110 GPa or less.

[0284] It should be noted that, as long as the effects of the present invention are not compromised, the manufacturing method may also include steps other than those described above. For example, after the chemical strengthening treatment step, a step of treatment with acid or alkali and a cleaning step may be included.

[0285] Example

[0286] The present invention will be described in detail below through examples, but the present invention is not limited to these examples.

[0287] Examples 1 to 4 are examples, Example 5 is a reference example, and Examples 6 to 7 are comparative examples.

[0288] <Example 1>

[0289] Glass raw materials were prepared in a manner that yielded the matrix glass phase composition shown in Table 1 below, and weighed to obtain 800g of glass. Next, the mixed glass raw materials were placed in a platinum crucible and melted in an electric furnace at 1400℃~1700℃ for approximately 5 hours to remove bubbles and homogenize, thereby obtaining molten glass.

[0290] Table 1

[0291] The resulting molten glass was poured into a mold and held at a temperature approximately 30°C higher than the glass transition temperature for 1 hour. It was then cooled to room temperature at a rate of 0.5°C / min, thus obtaining glass block A as an amorphous glass.

[0292] Using a portion of the obtained glass block A, the glass transition temperature, specific gravity, Young's modulus, and coefficient of thermal expansion of glass block A were determined. The results are shown in Table 2. Young's modulus was determined by ultrasonic method (the same applies below).

[0293] Table 2

[0294] A 15g glass slide B was cut from the obtained glass block A. Glass slide B was placed in a platinum container with a diameter of 40mm and heated to 1350℃ to melt it. The melt was removed, cooled to 900℃, and then heated to 1000℃ for 8 minutes, followed by air cooling, thus obtaining a glass plate C with a diameter of 40mm and a thickness of 4mm.

[0295] Glass plate C is a crystalline phase glass plate containing a crystalline phase (devitrification) with a major diameter of about 400 μm at a position from its surface to a depth of 2000 μm.

[0296] Powder X-ray diffraction was performed and identified under the following conditions, and the results showed that the crystalline phase was β-spodumene crystal (hereinafter referred to as "spodumene").

[0297] • Measuring device: Rigaku Manufacturing Co., Ltd. Smart Lab

[0298] • X-rays used: CuKα rays

[0299] • Measurement range: 2θ = 10°~80°

[0300] • Speed: 10° / minute

[0301] • Step size: 0.02°

[0302] Furthermore, the composition (content of each component) of the crystalline phase was determined using the above method, and the results are as follows. It should be noted that the value obtained by subtracting the total content of each component from 100% is taken as the content of Li (Li₂O).

[0303] SiO2: 70.4%

[0304] Al2O3: 27.6%

[0305] Na2O: 1.2%

[0306] Li2O: 0.1%

[0307] K2O: 0.5%

[0308] MgO: 0.2%

[0309] The glass plate C was subjected to the following treatments in sequence (preheating treatment and local heating treatment) to obtain the glass plate D.

[0310] <<Preheating Treatment>>

[0311] The ultra-high temperature heating plate (FT-HP-100) was set to 1000°C, and glass plate C was placed and heated. The surface temperature (preheating temperature) of glass plate C, measured using an infrared camera (FLIR Systems A 6500), was 800°C.

[0312] <<Local Heating Treatment>>

[0313] For the heated region containing the crystalline phase in glass plate C, which is mounted on an ultra-high temperature heating plate, a CO2 laser (E-400 manufactured by COHERENT) with a wavelength of 10.6 μm was used for irradiation. The irradiation conditions at this time are as follows.

[0314] Output power: 475W

[0315] Scanning speed: 2000 mm / s

[0316] Energy density: 9.45 W / mm 2

[0317] Working distance: 25000 (320mm)

[0318] Scanning interval: 0.01mm for the first scan, 0.05mm for subsequent scans.

[0319] Beam diameter: 6mm

[0320] Scanning area: 40mm

[0321] Scanning direction: bidirectional

[0322] In glass plate D, part of the crystalline phase present in glass plate C disappears, and an intermediate phase is generated at a depth of 2000 μm from its surface.

[0323] The Young's modulus and coefficient of thermal expansion of glass plates with the same composition as the mesophase are shown in Table 3 below.

[0324] Table 3

[0325] In addition, for glass plate D, the deepest point of the mesophase, the major axis of the mesophase, and the major axis of the remaining crystalline phase were measured. The results, along with the conditions of the local heat treatment, are shown in Table 4 below.

[0326] It should be noted that the "deepest depth (of the mesophase)" refers to the linear distance (distance in the thickness direction) measured from the surface of the glass plate, that is, the distance from the surface of the glass plate to the part farthest from the surface. The measurement is carried out in the same way as for the major axis.

[0327] <Example 2>

[0328] Except for changing the scanning speed of the laser to 1750 mm / s, a glass plate D was obtained in the same manner as in Example 1.

[0329] <Example 3>

[0330] Except for changing the plate thickness of the glass plate C to 6 mm, a glass plate D was obtained in the same manner as in Example 1.

[0331] <Example 4>

[0332] The scanning speed of the laser was changed to 1000 mm / s to completely disappear the crystalline phase of the glass plate C (crystalline-phase-containing glass plate), and a mesophase was formed. Except for this, a glass plate D was obtained in the same manner as in Example 1.

[0333] Since the crystalline phase has completely disappeared, "-" is recorded in the column of "major axis of the crystalline phase (after local heat treatment)" in Table 4 below.

[0334] <Example 5>

[0335] A glass plate having the same shape as the glass plate C was cut out from the glass block A and used as the glass plate D.

[0336] <Example 6>

[0337] Except for not performing local heat treatment on the glass plate C, a glass plate D was obtained in the same manner as in Example 1.

[0338] <Example 7>

[0339] The glass plate C was placed in a platinum container with a diameter of 40 mm, heated to 1500 °C using a muffle furnace to melt it, and then air-cooled while being formed into the same shape as the glass plate C, thereby obtaining a glass plate. During air-cooling, a crystalline phase was generated in the glass plate. The obtained glass plate was used as the glass plate D.

[0340] <ROR test>

[0341] For the glass plates D of Examples 1 to 7, the ROR test was carried out by the above method, and the average strength and Weibull coefficient m were obtained. The results are shown in Table 4 below.

[0342] The larger the value of the Weibull coefficient m, the smaller the degree of dispersion. <00​​​

[0344] <Summary of Evaluation Results>

[0345] As shown in Table 4 above, it can be seen that the glass plates D of Examples 1 to 4, which formed the mesophase through local heating treatment, have higher average strength and less dispersion in strength (larger value of Weibull coefficient m) compared with the glass plate D of Example 6, which did not undergo local heating treatment (no mesophase formed).

[0346] In addition, it can be seen that the glass plates D in Examples 1 to 4 have higher average strength and less dispersion in strength compared to the glass plate D in Example 7 (the value of the Weibull coefficient m is larger).

[0347] Furthermore, when comparing Example 4 and Example 5, it was confirmed that the average strength of the glass plate D in Example 4, which had its crystalline phase eliminated by localized heat treatment and formed an intermediate phase, was higher than that of the glass plate D in Example 5, which originally did not have a crystalline phase.

[0348] Furthermore, when comparing Examples 1 to 2 with Example 4, it can be seen that compared with Example 4, which caused all the crystalline phase to disappear, Examples 1 to 2, which had residual crystalline phase, showed a certain increase in intensity at a faster scanning speed. Therefore, from the viewpoint of energy efficiency and operating efficiency, they are superior.

[0349] It should be noted that the entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2023-113047, filed on July 10, 2023, are incorporated herein as a disclosure of the specification of this invention.

[0350] Label Explanation

[0351] 1: Laser heating device

[0352] 2: Glass plates (including crystalline phase glass plates)

[0353] 3: Heating area

[0354] 4: Laser

[0355] 6: Laser Injection Window

[0356] 7: Lens

[0357] 8: Laser source

[0358] 9: Reflector

[0359] 11: Matrix glass phase

[0360] 12: Crystalline phase (devitrified)

[0361] 13: Intermediate phase < / zno> < / bao> < / mgo>

Claims

1. A glass plate comprising a matrix glass phase and an intermediate phase, wherein, The matrix glass phase is an amorphous oxide comprising 50%–80% SiO2, 0%–30% Al2O3, and 0.1%–35% Li2O in molar percentages based on oxides. The intermediate phase is an amorphous oxide comprising 50%–80% SiO2, 5%–20% Al2O3, and 5%–20% Li2O in molar percentages based on oxides, and having a composition different from that of the matrix glass phase.

2. The glass plate according to claim 1, wherein, At least a portion of the intermediate phase exists at a depth of 2000 μm from the surface of the glass plate.

3. The glass plate according to claim 1 or 2, wherein, The major axis of the intermediate phase is less than 2000 μm.

4. The glass plate according to claim 1 or 2, wherein, The glass plate also contains a crystalline phase. The intermediate phase is in contact with the crystalline phase and the matrix glass phase. The crystalline phase, based on oxide molar percentages, comprises 60%–90% SiO2, 0%–40% Al2O3, and 0%–15% Na2O, and At least a portion of the crystalline phase exists at a depth of 2000 μm from the surface of the glass plate.

5. The glass plate according to claim 1 or 2, wherein, The thickness of the glass plate is 0.1mm to 6.0mm.

6. The glass plate according to claim 1 or 2, wherein, The average strength obtained by performing the following ROR test 20 times is 30 MPa or more, and the Weibull coefficient m, which represents the dispersion of the strength, is 7 or more. ROR test: The glass plate is placed on a lower ring containing stainless steel; the contact portion of the lower ring that contacts the glass plate has a diameter of 30 mm and a roundness with a radius of curvature of 2.5 mm; with the upper ring containing stainless steel in contact with the glass plate, a load is applied to the center of the upper ring under static load conditions; the contact portion of the upper ring that contacts the glass plate has a diameter of 10 mm and a roundness with a radius of curvature of 2.5 mm; the indentation speed of the upper ring is 1.0 mm / min; the fracture load at which the glass plate breaks is converted into fracture stress using the thickness of the glass plate and the location of the fracture initiation point, and this stress is calculated as the strength.

7. The glass plate according to claim 4, wherein, The crystalline phase comprises at least one of lithium phosphate crystals, lithium disilicate crystals, lithium aluminum silicate crystals, zirconium-containing crystals, and magnesium-containing crystals.

8. The glass plate according to claim 1 or 2, wherein, The matrix glass phase, in molar percentage based on oxides, contains: 50%–80% SiO2, 0%~30% Al2O3, 0.1%–35% Li₂O, 0%~8% B2O3, 0%~6% P2O5, 0%~20% Na2O, 0%~10% K2O, 0%~20% MgO, 0%~20% CaO, 0%~20% SrO, 0%~15% BaO, 0%~10% ZnO, 0%~5% Ti2O, 0%–8% ZrO2, and 0% to 8% Y2O3.

9. The glass plate according to claim 1 or 2, wherein, The difference in thermal expansion coefficients Δα, obtained by subtracting the thermal expansion coefficient of the intermediate phase from the thermal expansion coefficient of the matrix glass phase, is less than 0 ppm / ℃.

10. The glass plate according to claim 1 or 2, wherein, The glass plate is a chemically strengthened glass with a compressive stress value of 400 MPa or higher for the compressive stress layer.

11. A method for manufacturing a glass plate, wherein, A glass plate containing a crystalline phase, with the crystalline phase present at a depth of 2000 μm from the surface, is prepared. A localized heat treatment is performed on a heating region that is part of the crystalline phase-containing glass plate, thereby obtaining a glass plate. The crystalline phase-containing glass plate contains the crystalline phase in the heating zone. The local heating treatment involves raising the temperature of the heating area to a temperature T1 above 1500°C and below 2400°C, and then cooling it down to a temperature T2 above 800°C and below 1000°C.

12. The method for manufacturing a glass plate according to claim 11, wherein, Before performing the local heating treatment, a preheating treatment is performed to heat the glass plate containing the crystalline phase to a preheating temperature of 800°C or higher and 1150°C or lower.

13. The method for manufacturing a glass plate according to claim 11, wherein, The local heating treatment is a process in which the heating area is heated from the preheating temperature to the temperature T1 within 5 seconds and cooled from the temperature T1 to the temperature T2 within 300 seconds.

14. The method for manufacturing a glass plate according to any one of claims 11 to 13, wherein, The localized heating treatment is a process of heating the heating area by laser irradiation.

15. The method for manufacturing a glass plate according to claim 14, wherein, The wavelength of the laser is 2.5μm to 12μm.

16. The method for manufacturing a glass plate according to claim 14, wherein, The laser is irradiated using a CO laser or a CO2 laser.

17. The method for manufacturing a glass plate according to any one of claims 11 to 13, wherein, The localized heating treatment is a process of heating the heating area using a carbon heater.

18. The method for manufacturing a glass plate according to any one of claims 11 to 13, wherein, In the implementation of the localized heating treatment, the temperature of the region in the crystalline phase glass plate other than the heating region is below 1250°C.

19. The method for manufacturing a glass plate according to any one of claims 11 to 13, wherein, The localized heating treatment is performed in a floating blast furnace for manufacturing glass plates.

20. The method for manufacturing a glass plate according to any one of claims 11 to 13, wherein, Following the localized heat treatment, the resulting glass plate is further subjected to chemical strengthening treatment.

21. A method for removing devitrification from a glass plate, wherein, Prepare a glass plate with devitrification at a depth of 2000 μm from the surface. The glass plate is preheated to a preheating temperature of 800°C or higher and 1150°C or lower. Then, the heating area, which is part of the glass plate and includes the devitrifying heating area, is heated from the preheating temperature to a temperature T1 of 1500°C or higher and 2400°C or lower within 5 seconds, and then cooled from the temperature T1 to a temperature T2 of 800°C or higher and 1000°C or lower within 300 seconds.

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