GLASS SHEET AND MANUFACTURING METHOD FOR IT AND METHOD FOR REMOVING DEGLAZING FROM A GLASS SHEET

Abstract

A glass plate of high average strength with low strength variation is provided. The glass plate comprises a matrix glass phase and an intermediate phase. The matrix glass phase is an amorphous oxide containing, expressed in mol% on an oxide basis, 50-80% SiO2, 0-30% Al2O3, and 0.1-35% Li2O. The intermediate phase is an amorphous oxide containing, expressed in mol% on an oxide basis, 50-80% SiO2, 5-20% Al2O3, and 5-20% Li2O, and has a different composition than the matrix glass phase.

Description

Technical field

[0001] The present invention relates to a glass plate and a manufacturing method therefor, as well as a method for removing devitrification from a glass plate. General state of the art

[0002] For several years now, a cover glass has been used to protect and enhance the aesthetic appearance of the display devices of mobile phones, smartphones, tablets, and similar devices. A glass plate used for this purpose as a cover glass must be particularly strong to prevent damage from impacts or similar causes.

[0003] It is known from the prior art to increase the surface strength of a glass plate by means of a chemical strengthening process by immersing the glass in a potassium nitrate salt melt or the like (Patent document 1).

[0004] The strength of a glass plate can also be increased by chemically reinforcing a glass plate whose composition has been regulated within a specific range. Al₂O₃ and Li₂O can be cited as components with which an increase in strength can be achieved by increasing their content in the glass composition (Patent Document 2). State-of-the-art documents, patent documents Patent Document 1: JP 2013-516387 A Patent Document 2: JP 2013-520385 A Brief description of the invention Task of the invention

[0005] As described above, the strength of a glass plate can be increased by increasing the content of Al2O3 and Li2O in the glass composition.

[0006] In a glass plate with a high content of Al2O3 and Li2O, the devitrification temperature rises and the devitrification growth rate increases, so that devitrification (crystal phase) easily occurs in the amorphous matrix glass phase during the formation process.

[0007] The rate of thermal expansion of the devitrification (crystal phase) and the amorphous phase (matrix glass phase) is often different, which is why cracks easily form starting from the devitrification when heating or cooling, leading to a breakage of the glass plate.

[0008] Even if no breakage occurs during the forming process, fine cracks originating from the devitrification are present, resulting in increased fluctuations in strength of the glass plate product and a decrease in the average strength.

[0009] The present invention was made in view of the aforementioned circumstances, and one of its objectives is to provide a glass plate of high average strength with low variation in strength.

[0010] Furthermore, the present invention has as its objective a method for producing a glass plate in order to obtain the glass plate shown above, and a method for removing devitrification from the glass plate. Means of solving the task

[0011] To achieve the aforementioned goal, the inventors conducted intensive research. As a result, they discovered that by locally heating devitrification (crystal phase) generated in the matrix glass phase of a glass plate, the devitrification is at least partially eliminated, and an intermediate phase is produced whose composition differs from that of the matrix glass phase. This reduces fluctuations in strength and increases the average strength, leading to the present invention.

[0012] The present invention is as follows. (1) A glass plate comprising a matrix glass phase and an intermediate phase, wherein the matrix glass phase is an amorphous oxide comprising, expressed in mol% on an oxide basis, 50-80% SiO2, 0-30% Al2O3 and 0.1-35% Li2O, and the intermediate phase is an amorphous oxide comprising, expressed in mol% on an oxide basis, 50-80% SiO2, 5-20% Al2O3 and 5-20% Li2O and having a different composition than the matrix glass phase. (2) The glass plate of (1) wherein at least a part of the intermediate phase is located at a position at a depth of up to 2000 µm from the surface of the glass plate. (3) The glass plate of (2) wherein a principal axis diameter of the intermediate phase is 2000 µm or less. (4) Glass plate of one of (1) to (3) which further includes a crystalline phase, wherein the intermediate phase is in contact with the crystalline phase and the matrix glass phase, wherein the crystalline phase, expressed in mol% on an oxide basis, comprises 60-90% SiO2, 0-40% Al2O3 and 0-15% Na2O, wherein at least a part of the crystalline phase is located at a position at a depth of up to 2000 µm from the surface of the glass plate. (5) Glass plate of one of (1) to (4), wherein a plate thickness is 0.1-6.0 mm. (6) The glass plate of one of (1) to (5), wherein an average strength obtained by performing an ROR test 20 times is 30 MPa or more, and a value m of a Weibull coefficient indicating fluctuations in strength is 7 or more.

[0013] ROR test: A glass plate is mounted on a lower stainless steel ring. A contact section where the lower ring is in contact with the glass plate has a diameter of 30 mm and a radius of curvature of 2.5 mm. The glass plate, in contact with an upper stainless steel ring, is subjected to a static load at the center point of the upper ring. A contact section where the upper ring is in contact with the glass plate has a diameter of 10 mm and a radius of curvature of 2.5 mm. The contact speed of the upper ring is 1.0 mm / min. The stress at the moment of breakage is converted into a fracture stress based on the plate thickness and the fracture point location of the glass plate, and this is determined as the tensile strength.

[0014] (7) The glass plate of (4) wherein the crystal phase includes at least one of phosphoric acid lithium crystal, nickel acid lithium crystal, lithium aluminosilicate crystal, zirconium-containing crystal and magnesium-containing crystal.

[0015] (8) The glass plate of one of (1) to (7), wherein the matrix glass phase, expressed in mol% on an oxide basis, 50-80% SiO2, to 0-30% Al2O3, to 0.1-35% Li2O, to 0-8% B2O3, to 0-6% P2O5, to 0-20% Na2O, to 0-10% K2O, to 0-20% MgO, to 0-20% CaO, to 0-20% SrO, to 0-15% BaO, to 0-10% ZnO, to 0-5% Ti2O, to 0-8% ZrO2 and Contains 0-8% Y2O3.

[0016] (9) The glass plate from one of (1) to (8) wherein a thermal expansion rate difference Δα, where the thermal expansion rate of the intermediate phase has been subtracted from the thermal expansion rate of the matrix glass phase, is below 0 ppm / °C.

[0017] (10) The glass plate of one of (1) to (9), wherein it is chemically strengthened glass having a compressive stress value of a compressive stress layer of 400 MPa or more.

[0018] (11) A method for producing a glass plate, wherein a glass plate containing a crystalline phase is prepared in which the crystalline phase is located at a position at a depth of up to 2000 µm from the surface, wherein a local heating process is carried out in which a heating area which is part of the glass plate containing the crystalline phase is heated, wherein the glass plate containing the crystalline phase includes the crystalline phase within the heating area, wherein the local heating process is a process in which the heating area is heated to a temperature T1 of at least 1500 °C and at most 2400 °C and is subsequently cooled to a temperature T2 of at least 800 °C and at most 1000 °C.

[0019] (12) The method for producing a glass plate of (11) wherein a preheating process is carried out prior to the local heating process, in which the glass plate containing the crystal phases is heated to a preheating temperature of at least 800 °C and at most 1150 °C.

[0020] (13) The method for producing a glass plate of (11) wherein the local heating process is a process in which the heating area is heated from the preheating temperature to temperature T1 within 5 s and cooled from temperature T1 to temperature T2 within 300 s.

[0021] (14) The method for producing a glass plate from (11) to (13), wherein the local heating process is a process in which the heating area is heated by irradiation with laser light.

[0022] (15) The method for producing a glass plate of (14) wherein a wavelength of the laser light is 2.5-12 µm.

[0023] (16) The method for producing a glass plate of (14) wherein the laser light is emitted using a CO laser or a CO2 laser.

[0024] (17) The method for producing a glass plate from (11) to (13) wherein the local heating process is a process in which the heating area is heated with a carbon heating device.

[0025] (18) The method for producing a glass plate from (11) to (17) wherein, during the execution of the local heating process, the temperature of the remaining area of ​​the crystalline glass plate outside the heating area shall not exceed 1250 °C.

[0026] (19) The method for producing a glass plate from (11) to (18) wherein the local heating process is carried out in a float bath in which the glass plate is produced.

[0027] (20) The method for producing a glass plate from (11) to (19), wherein, after local heating processing, a chemical strengthening process is further carried out on the glass plate obtained.

[0028] (21) A method for removing devitrification from a glass plate, wherein a glass plate is prepared in which devitrification is present at a position at a depth of up to 2000 µm from the surface, wherein the glass plate is preheated to a preheating temperature of at least 800 °C and at most 1150 °C, and subsequently a heating area which is part of the glass plate and contains the devitrification is heated within 5 s from the preheating temperature to a temperature T1 of at least 1500 °C and at most 2400 °C, and then cooled within 300 s from the temperature T1 to a temperature T2 of at least 800 °C and at most 1000 °C. Effect of the invention

[0029] According to the present invention, a glass plate of high average strength with low fluctuation in strength can be provided.

[0030] Furthermore, according to the present invention, a method for producing a glass plate to obtain the glass plate described above and a method for removing devitrification from the glass plate can be provided. Brief description of the characters

[0031] They show: Fig. 1 a schematic view of a laser heating device; Fig. 2. A cross-sectional reflection electron image of a glass plate before local heating processing; and Fig. 3 A cross-sectional reflection electron image of a glass plate after local heating processing. embodiment of the invention

[0032] The present invention is not limited to the embodiment described below, but can be modified in any way within a scope that does not deviate from the essence of the present invention.

[0033] In this document, the glass composition is expressed in mole percent based on oxides and indicated as mol% or simply %. The hyphen “-” in numerical ranges indicates that the first and last values ​​represent the lower and upper limits, respectively.

[0034] In this document, a “compressive stress value (CS)” is measured by analyzing a thin piece of glass with a multiple refractive index (Abrio-IM from CRi).

[0035] In this document, a "depth of compressive stress layer (DOL)" is a depth at which the compressive stress value is zero. An "internal tensile stress (CT)" refers to a tensile stress value at half the depth of a plate thickness t. [Glass plate]

[0036] A glass plate of the present embodiment (hereinafter also referred to as "present glass plate") is a glass plate with a matrix glass phase and an intermediate phase.

[0037] The glass plate in question exhibits high average strength and low strength variation. This is thought to be due to the co-existence of the matrix glass phase and the intermediate phase, which exerts compressive stress on the matrix glass phase in the vicinity of the intermediate phase, thereby inhibiting the propagation of cracks. <matrixglasphase>

[0038] The matrix glass phase is an amorphous oxide which, expressed in mol% on an oxide basis, contains 50-80% SiO2, 0-30% Al2O3 and 0.1-35% Li2O.

[0039] The matrix glass phase is the amorphous part of the glass sheet without devitrification (amorphous oxide). Since devitrification usually occurs when molten glass is cooled, the composition of the matrix glass phase is identical to the composition of the molten glass.

[0040] Devitrification can also take on a composition that differs from that of the matrix glass phase.

[0041] The amorphous part near the devitrification stage can assume a composition that differs from both the matrix glass phase and the devitrification stage.

[0042] Preferably, the matrix glass phase contains, expressed in mol% on an oxide basis, 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 0-8% Y2O3.

[0043] The following describes the glass composition of the matrix glass phase. < <sio2>>

[0044] SiO2 is a component that forms the network of the glass. It also increases chemical resistance and reduces the formation of cracks when the glass surface is damaged.

[0045] To increase chemical resistance, the SiO2 content is at least 50%, preferably at least 54%, more preferably at least 58%, even more preferably at least 62%, and particularly preferably at least 64%.

[0046] On the other hand, the SiO2 content to improve the melting properties is at most 80%, preferably at most 78%, more preferably at most 76%, even more preferably at most 74% and particularly preferably at most 72%. < <a12o3>>

[0047] Al2O3 is a component that increases the ion exchange capacity during chemical enhancement and raises the CS after enhancement.

[0048] If Al₂O₃ is present, it is preferably present at a minimum of 1%. More preferably, the Al₂O₃ content is in the following steps: at least 3%, at least 5%, at least 7%, at least 8%, at least 9%, at least 10%, at least 11%, and at least 12%.

[0049] However, if the Al2O3 content is higher than 30%, the acid resistance of the glass decreases.

[0050] The Al2O3 content is at most 30%, and preferably at most 25%, more preferably at most 20%, even more preferably at most 18%, and most preferably at most 15%.

[0051] SiO2 and Al2O3 are both components that stabilize the structure of the glass. To reduce brittleness, their combined content is preferably at least 65%, more preferably at least 70%, and even more preferably at least 74%.

[0052] SiO2 and Al2O3 both tend to increase the melting point of the glass. Therefore, to facilitate melting, their combined content is preferably at most 83%, more preferably at most 82%, and even more preferably at most 81%. < <li2o>>

[0053] Li2O is a component that forms a pressure stress layer via ion exchange.

[0054] In the case of a chemical reinforcement process in which Li ions exchange with Na ions on the surface of the glass, the Li2O content is at least 0.1%, preferably at least 0.3%, more preferably at least 0.5%, even more preferably at least 0.6% and particularly preferably at least 0.7%, from the point of view of easier obtaining a preferred stress profile.

[0055] However, if the Li₂O content exceeds 35%, the acid resistance of the glass decreases. The Li₂O content is at most 35%, and preferably at most 28%, more preferably at most 26%, even more preferably at most 23%, and most preferably at most 21%. < <b2o3>>

[0056] B2O3 is a component that increases the chip resistance and improves the melting properties of the glass.

[0057] If B2O3 is included, the B2O3 content is preferably at least 0.5%, more preferably at least 1%, and even more preferably at least 2%.

[0058] However, if the B₂O₃ content exceeds 8%, there is a risk that it will cause the adverse formation of striae due to volatilization during melting. The B₂O₃ content is preferably at most 8%, more preferably at most 6%, even more preferably at most 5%, and most preferably at most 4%. < <p2o5>>

[0059] P2O5 is a component that increases ion exchange capacity and chip resistance.

[0060] If P2O5 is present, the P2O5 content is preferably at least 0.5%, more preferably at least 1%, and even more preferably at least 2%.

[0061] However, if the P₂O₅ content exceeds 6%, the fracture properties and acid resistance of the glass deteriorate significantly. Therefore, the P₂O₅ content is preferably at most 6%, more preferably at most 5%, even more preferably at most 4%, and most preferably at most 3%. < <na2o>>

[0062] Na₂O is a component that forms the compressive stress layer through ion exchange and improves the melting properties of the glass. Na₂O is not required, but may be included if the melting properties of the glass are considered important. If Na₂O is included, its content is preferably at least 1%, more preferably at least 2%, and even more preferably at least 3%.

[0063] However, if the Na2O content is higher than 20%, the acid resistance of the glass decreases.

[0064] The Na2O content is therefore preferably at most 20%, more preferably at most 18%, even more preferably at most 16%, most preferably at most 15% and most preferably at most 14%. < <k2o>>

[0065] K₂O is an optional component that improves the ion exchange capacity. If K₂O is included, its content is preferably at least 0.5%, more preferably at least 1%, even more preferably at least 2%, and particularly preferably at least 3%.

[0066] However, if the K₂O content exceeds 10%, the glass's fracture properties deteriorate significantly. Therefore, the K₂O content is preferably at most 10%, more preferably at most 8%, even more preferably at most 6%, particularly preferably at most 4%, and most preferably at most 2%. < <mgo>>

[0067] MgO may be included, among other things, to reduce viscosity during melting. If MgO is included, its content is preferably at least 2% and more preferably in the following steps: at least 3%, at least 4%, at least 5%, at least 6%, at least 7%, and at least 8%.

[0068] However, if the MgO content exceeds 20%, there is a risk that it will cause adverse devitrification. Therefore, the MgO content is preferably at most 20%, and more preferably in the following steps: at most 18%, at most 15%, at most 14%, at most 13%, at most 12%, and at most 11%. <<CaO und SrO> >

[0069] CaO and SrO are optional components that improve the melting properties of the glass. If they are included, their content is preferably at least 0.5%, more preferably at least 1%, even more preferably at least 2%, particularly preferably at least 3%, and most preferably at least 5%.

[0070] However, if their content exceeds 20%, the ion exchange capacity deteriorates significantly. Therefore, the content of CaO and SrO is preferably at most 20%, more preferably at most 18%, even more preferably at most 16%, particularly preferably at most 14%, and most preferably at most 12%. < <bao>>

[0071] BaO is an optional ingredient that improves the melting properties of the glass. If BaO is included, its content is preferably at least 0.5%, more preferably at least 1%, even more preferably at least 2%, particularly preferably at least 3%, and most preferably at least 5%.

[0072] However, if the BaO content exceeds 15%, the ion exchange capacity deteriorates significantly. Therefore, the BaO content is preferably at most 15%, more preferably at most 13%, even more preferably at most 11%, particularly preferably at most 9%, and most preferably at most 7%. < <zno>>

[0073] ZnO is an optional component that improves the melting properties of the glass. If ZnO is included, its content is preferably at least 0.25% and more preferably at least 0.5%.

[0074] However, if the ZnO content exceeds 10%, the weather resistance of the glass deteriorates significantly. The ZnO content is preferably at most 10%, more preferably at most 7%, even more preferably at most 5%, particularly preferably at most 2%, and most preferably at most 1%. < <tio2>>

[0075] TiO2 is an optional component with high efficacy in preventing solarization of the glass. If TiO2 is included, its content is preferably at least 0.1%, more preferably at least 0.15%, and even more preferably at least 0.2%.

[0076] However, if the TiO2 content exceeds 5%, there is a risk that it will cause adverse devitrification. Therefore, the TiO2 content is preferably at most 5%, more preferably at most 3%, even more preferably at most 1%, particularly preferably at most 0.5%, and most preferably at most 0.25%. < <zro2>>

[0077] ZrO2 is an optional component that increases the CS of the chemically strengthened glass. If ZrO2 is included, its content is preferably at least 0.5% and more preferably at least 1%.

[0078] However, if the ZrO2 content exceeds 8%, there is a risk that it will cause adverse devitrification. Therefore, the ZrO2 content is preferably at most 8%, more preferably at most 6%, even more preferably at most 4%, particularly preferably at most 2%, and most preferably at most 1.5%. < <y2o3>>

[0079] Y₂O₃ is an optional component that increases the CS of the chemically strengthened glass and reduces the devitrification rate. If Y₂O₃ is included, its content is preferably at least 0.5%, more preferably at least 1%, even more preferably at least 1.5%, particularly preferably at least 2%, and most preferably at least 2.5%. However, if the Y₂O₃ content exceeds 8%, there is a risk that it will become a cause of adverse devitrification. Therefore, the Y₂O₃ content is preferably at most 8%, more preferably at most 6%, even more preferably at most 5%, particularly preferably at most 4%, and most preferably at most 3%. <<Färbungsbestandteile> >

[0080] If the glass is used in a colored form, coloring components may be added as long as they do not impede the desired properties of the chemical reinforcement.

[0081] Suitable coloring components include metal oxides of Co, Mn, Fe, N, Cu, Cr, V, Bi, Se, Ti, Ce, Er and Nd, namely Co3O4, MnO, MnO2, Fe2O3, NiO, CuO, Cu2O, Cr2O3, V2O5, Bi2O3, SeO2, TiO2, CeO2, Er2O3 and Nd2O3.

[0082] If the glass plate in question is used as colored glass, the matrix glass phase, expressed in mol% on an oxide basis, may contain coloring components in a range of up to 7% (at least one selected from the group consisting of the metal oxides of Co, Mn, Fe, Ni, Cu, Cr, V, Bi, Se, Ti, Ce, Er, and Nd). A percentage above 7% is undesirable, as devitrification of the glass plate is more likely to occur at higher concentrations.

[0083] The content of coloring components is preferably at most 5%, more preferably at most 3% and even more preferably at most 1%.

[0084] If the light transmission of the glass plate is a priority, these coloring components are preferably substantially absent (not intentionally included). A concentration of less than 0.1% is preferred. <<Sonstige Bestandteile> >

[0085] Other ingredients may include, for example, SO3, which is a refining agent for glass melting, chloride, fluoride and the like, in a suitable manner. <Intermediäre Phase>

[0086] The intermediate phase is an amorphous oxide which, expressed in mol% on an oxide basis, contains 50-80% SiO2, 5-20% Al2O3 and 5-20% Li2O and whose composition differs from that of the matrix glass phase.

[0087] The intermediate phase is an amorphous phase with an intermediate composition between that of the devitrification and the matrix glass phase. It is formed by a local heating process, as described below, which renders at least a portion of the devitrification (crystal phase) amorphous within the matrix glass phase. An intermediate composition means that the individual components lie between those in the devitrification and the matrix glass phases.

[0088] Since the intermediate phase is created by the local heating processing of the crystal phase in the matrix glass phase, the crystal phase and the matrix glass phase are in contact with each other if crystal phase remains even after the local heating processing.

[0089] As described below, for example, at least part of the crystal phase is located at a position at a depth of up to 2000 µm from the surface of the glass plate.

[0090] Therefore, at least part of the intermediate phase resulting from the local heating processing of the crystal phase is located at a position at a depth of up to 2000 µm from the surface of the glass plate.

[0091] Preferably, at least part of the intermediate phase is located at a position at a depth of up to 1000 µm from the surface of the glass plate.

[0092] Since the intermediate phase and the crystal phase have a different composition than the matrix glass phase, they can be identified in a reflection electron image obtained using a scanning electron microscope (SEM) by their brightness, which differs from that of the matrix glass phase.

[0093] The position (depth (distance) from the surface of the glass plate) and the principal axis diameter of the intermediate phase and the crystal phase are determined in the following procedure.

[0094] A cross-sectional area parallel to the thickness direction of the glass plate is created. This cross-sectional area is mirror-polished and used as the viewing surface. The viewing surface is observed with the SEM (Search Electron Microscope) and a reflected electron image is obtained. Using this image, the position (depth (distance) from the surface of the glass plate) and the principal axis diameter of the intermediate phase are measured. The principal axis diameter of the intermediate phase in the reflected electron image of the viewing surface is the linear distance at the point where the linear distance of the intermediate phase is greatest.

[0095] The position and principal axis diameter of the crystal phase are also measured.

[0096] The main axis diameter of the intermediate phase is at most 2000 µm, preferably at most 1500 µm, more preferably at most 800 µm, even more preferably at most 400 µm and particularly preferably at most 200 µm.

[0097] Furthermore, for reasons of better strength, the main axis diameter of the intermediate phase is preferably at least 20 µm, more preferably at least 40 µm, even more preferably at least 60 µm and particularly preferably at least 80 µm. < <sio2>>

[0098] The SiO2 content in the intermediate phase is at least 50%, and preferably at least 54%, more preferably at least 58%, even more preferably at least 62%, and most preferably at least 64%.

[0099] The SiO2 content is also at most 80%, and preferably at most 78%, more preferably at most 76%, even more preferably at most 74%, and most preferably at most 72%. < <al2o3>>

[0100] In the intermediate phase, the Al2O3 content is at least 5%, preferably at least 7%, more preferably at least 9% and even more preferably at least 11%.

[0101] Furthermore, the Al2O3 content is at most 20%, preferably at most 18% and more preferably at most 15%. < <li2o>>

[0102] In the intermediate phase, the Li2O content is at least 5%, preferably at least 7%, more preferably at least 9% and even more preferably at least 11%.

[0103] Furthermore, the Li2O content is at most 20%, preferably at most 18% and more preferably at most 16%. <<Sonstige Bestandteile> >

[0104] The content of other components (Na2O and the like) in the intermediate phase corresponds to the content in the matrix glass phase. <Kristallphase (Entglasung)>

[0105] The crystalline phase (devitrification) is located within the matrix glass phase.

[0106] For example, at least part of the crystal phase is located at a position at a depth of up to 2000 µm from the surface of the glass plate.

[0107] The crystalline phase is formed by the compositional components contained in the matrix glass phase and contains, expressed in mol% on an oxide basis, 60-90% SiO2, 0-40% Al2O3 and 0-15% Na2O.

[0108] The glass plate can contain several types of crystal phases (devitrification).

[0109] Among others, the crystalline phases include lithium phosphoric acid crystal (Li3PO), lithium nickel acid crystal (Li2Si2O5), and lithium aluminosilicate crystal (LiAlSi4O). 10 , LiAlSi2O6), zirconium-containing crystal and magnesium-containing crystal.

[0110] Lithium aluminosilicate crystal contains β-quartz solid solution and β-spodumene.

[0111] Beta-quartz solid solution is also known simply as beta-quartz, purgelite, or high-grade quartz. Among other elements, magnesium, sodium, potassium, calcium, strontium, and barium are dissolved in beta-quartz solid solution.

[0112] Zirconium-containing crystals contain zirconium oxide and zirconium oxide solid solution. Y, Sn, and similar elements may also be dissolved in zirconium oxide solid solution.

[0113] Magnesium silicate is contained in the magnesium-containing crystal.

[0114] If the present glass plate has a crystalline phase, the principal axis diameter of the crystalline phase (principal axis diameter after the local heating processing described below) is preferably at most 2000 µm, more preferably at most 1800 µm, even more preferably at most 1600 µm, particularly preferably at most 1400 µm and most preferably at most 1200 µm for reasons of better strength. <Verfahren zum Messen des Gehalts der einzelnen Bestandteile>

[0115] The composition of the matrix glass phase, the intermediate phase and the crystal phase (the content of the individual components) was determined by analysis using an electron probe micro analyzer (EPMA).

[0116] More precisely, the glass plate was polished, the individual phases were exposed, and an analysis was carried out using a JXA-8500F (manufactured by JEOL) as an EPMA under the following conditions. - Analysis crystal: TAP crystal for the components Na, Si, Al, P, Sr and Zn, PETJ crystal for Ca, TAPH crystal for Mg, PETH crystal for K, Zr, Y, Ti and Ba - Electron beam acceleration voltage: 15 kV - Current of the emitted electron beam: 10 nA - Radiation exposure time: peak position 10 s, background position 5 s - Analysis software used: Software from the company JEOL <Mittlere Festigkeit und Weibull-Koeffizient m>

[0117] For the present glass plate, the average strength (also referred to as "mean strength"), which is determined in an ROR test described below, is preferably at least 30 MPa, more preferably at least 60 MPa and even more preferably at least 90 MPa.

[0118] For the present glass plate, the value of a Weibull coefficient m, which indicates the variation in the strength measured in the ROR test described below, is preferably more than 6 and more preferably more than 7. < <ror-versuch>>

[0119] First, a glass plate, with one main surface facing downwards, is placed on a lower stainless steel ring. A contact section of the lower ring (the part in contact with the glass plate) has a diameter of 30 mm and a roundness with a radius of curvature of 2.5 mm.

[0120] Then, an upper stainless steel ring is brought into contact with the top surface of the other main surface of the glass plate (the upper main surface) located on the lower ring. A contact section of the upper ring has a diameter of 10 mm and a roundness with a radius of curvature of 2.5 mm.

[0121] In this state, the glass plate is destroyed by applying a static load to the center of the upper ring using an Autographen AGS-10kNX (manufacturer: Shimadzu Corporation). The pressure applied to the upper ring is 1.0 mm / min.

[0122] The stress at the moment of breakage of the glass plate is converted into fracture stress (unit: MPa) based on the plate thickness and the initial fracture point position, and this is then determined as the strength. The conversion of the fracture stress to fracture stress is approximated using a finite element method simulation.

[0123] This ROR (Reference Operation) is performed 20 times to calculate the mean strength. However, measured fracture loads are not used for the calculation if the fracture point of the mean strength of the glass plate lies outside the contact point of the upper ring.

[0124] Furthermore, the Weibull coefficient m is calculated based on 20 strength values ​​according to JISR 1625(2010). <Wärmeausdehnungsratendifferenz Δα>

[0125] If the rate of thermal expansion of the intermediate phase is greater than the rate of thermal expansion of the matrix glass phase, compressive stress is created during heating, which increases the strength of the glass plate.

[0126] A thermal expansion rate difference Δα, where the thermal expansion rate of the intermediate phase has been subtracted from the thermal expansion rate of the matrix glass phase (thermal expansion rate of the matrix glass phase minus thermal expansion rate of the intermediate phase), is preferably less than 0 ppm / °C, more preferably less than -0.1 ppm / °C, even more preferably less than -0.2 ppm / °C and particularly preferably less than -0.25 ppm / °C.

[0127] The rate of thermal expansion (coefficient of thermal expansion) of the matrix glass phase is the mean rate of thermal expansion at 50-350 °C, where a plate-shaped sample is measured with a dilatometer (DIL402SE from NETZSCH) according to the procedure specified in JISR3102-1995.

[0128] The rate of thermal expansion of the intermediate phase is also measured, using a glass sample that has the same composition as the intermediate phase. <form>

[0129] The shape of the glass plate in question can vary depending on the product it is applied to, its purpose, etc. For example, it can be a rimmed shape where the thickness of the outer edge differs from the thickness of the rest of the plate.

[0130] The two main surfaces of the glass plate in question do not have to be parallel to each other, and one or both main surfaces may also be curved surfaces, either wholly or partially.

[0131] The glass plate in question can be, for example, a flat glass plate without curvature or a curved glass plate with a curved surface. <plattendicke>

[0132] If the glass plate in question has the form of a flat plate, its thickness, from the perspective of reducing the weight of the cover glass, is at most 6.0 mm, preferably at most 5.0 mm, more preferably at most 4.5 mm, and even more preferably at most 4.0 mm. Furthermore, from the perspective of sufficiently increasing the strength through chemical reinforcement, the thickness of the glass plate in question, in the form of a flat plate, is at least 0.1 mm, more preferably at least 0.2 mm, even more preferably at least 0.3 mm, and particularly preferably at least 0.5 mm. <CS und DOL (chemisch verstärktes Glas)>

[0133] The glass plate in question can be a chemically strengthened glass with a compressive stress layer on the top surface.

[0134] The compressive stress value (CS) of the compressive stress layer of the chemically strengthened glass is preferably at least 400 MPa, more preferably at least 500 MPa and even more preferably at least 600 MPa.

[0135] If the DOL (depth of compressive stress layer) of the chemically strengthened glass is at least 70 µm, breakage will not occur even if the surface is damaged, which is why this is preferred. More preferably, the DOL is at least 100 µm.

[0136] The higher the DOL, the less likely it is to break upon damage. However, since chemically strengthened glass exhibits internal tensile stress corresponding to the compressive stress formed near the surface, the DOL cannot be increased excessively. For a plate thickness of t, the DOL is preferably at most t / 4, and more preferably at most t / 5. To shorten the time required for chemical strengthening, the DOL is preferably at most 200 µm, and more preferably at most 180 µm. [Method for producing a glass plate (Method for removing devitrification from a glass plate)]

[0137] The following describes a process for manufacturing the glass plate discussed above (hereinafter also referred to as the "present manufacturing process"). The following description also serves as a description of a devitrification removal process for the glass plate. In the present manufacturing process, a glass plate containing crystalline phases is first prepared. This plate has a crystalline phase (devitrification) at a depth of up to 2000 µm from the surface. Then, a local heating process is carried out, in which a heating area is heated that is part of the crystalline glass plate. <Vorbereiten der kristallphasenhaltigen Glasplatte>

[0138] First, raw glass materials are weighed and mixed to create the composition of the matrix glass phase discussed above. The resulting mixture is then heated and melted to produce molten glass. Finally, the molten glass is formed into sheets.

[0139] Methods for shaping molten glass into sheets include, for example, the float process, the pressing process, the fusion process, and the stretching process. The float process is particularly preferred for the production of large glass sheets. Other continuous forming processes besides the float process include, for example, the fusion process and the stretching process.

[0140] A glass ribbon obtained through molding is subjected to grinding and polishing processes as needed to form the glass plate.

[0141] If the glass plate is cut to a specified shape and size or chamfered, a layer of compressive stress can also be formed on the end face by carrying out the cutting or chamfering of the glass plate before carrying out the chemical reinforcement process described below, which is why this is preferred.

[0142] Crystallization occurs within the glass plate during the forming process.

[0143] For example, when a glass plate is formed using the float process, it is cooled in the float bath from a high-temperature point. Crystallization occurs where the temperature range for nucleation and the temperature range for crystal growth overlap. Typically, there is no overlap between the temperature range for nucleation and the temperature range for crystal growth.

[0144] However, in glass with a high AL2O3 and Li2O content, there is a tendency around 1000 °C for an overlap between the temperature range in which nucleation occurs and the temperature range in which crystal growth occurs. Therefore, during the forming process of the glass plate, for example, a crystalline phase (devitrification) can form at a position up to a depth of 2000 µm from the surface of the glass plate.

[0145] In this way, the glass plate containing the crystal phase (devitrification) is obtained. < <entglasungstemperatur>>

[0146] The temperature at which devitrification occurs in the glass plate (devitrification temperature) is, for example, at most 1250 °C, preferably at most 1240 °C, more preferably at most 1230 °C, even more preferably at most 1220 °C, and particularly preferably at most 1210 °C. There is no specific limitation for the lower limit of the devitrification temperature, but it is generally around 900 °C.

[0147] If the devitrification temperature is no more than 1250 °C, stable forming can be achieved and the manufacturing properties can be improved. For example, if the glass sheet is formed using the float process and crystals form before the molten glass is poured into the float bath, these crystals erode the brick that forms the float bath. However, if the devitrification temperature is no more than 1250 °C, this erosion of the brick can be prevented.

[0148] The devitrification temperature of glass is determined as follows. First, glass crushed into 2-3 mm grains is placed in a platinum dish and heated for 17 hours in an electric furnace controlled to a specific temperature. After heating, the glass is examined under an optical microscope to check for crystal formation. The minimum temperature at which no crystal precipitation occurs on the surface or within the glass is determined as the devitrification temperature. <<Temperatur der Kristallisationskeimbildung> >

[0149] The temperature of crystallization nucleation in the glass plate is, for example, at least 790 °C, preferably at least 800 °C, more preferably at least 810 °C, even more preferably at least 815 °C, particularly preferably at least 820 °C, and most preferably at least 825 °C. There is no specific upper limit for the temperature of crystallization nucleation, but it is generally around 900 °C.

[0150] If the nucleation temperature is at least 790 °C, the manufacturing properties can be improved. If a glass plate in sheet form is further heated and, for example, shaped three-dimensionally, and the temperature used for three-dimensional shaping is higher than the nucleation temperature, crystallization can easily occur. By ensuring the nucleation temperature is at least 790 °C, the temperature used for three-dimensional shaping does not readily exceed this temperature, thus preventing the formation of the crystal phase.

[0151] The nucleation temperature is measured using differential scanning calorimetry (DSC).

[0152] Specifically, the glass is crushed with an agate mortar, and approximately 70 mg of a powder with a grain size of 106-180 µm is heated from room temperature to 1200 °C at a temperature increase rate of 10 °C / minute. < <entglasungswachstumsgeschwindigkeit>>

[0153] If the crystal phase (devitrification) consists exclusively of β-quartz solid solution, the devitrification growth rate is preferably at most 4000 µm / h, more preferably at most 3800 µm / h, even more preferably at most 3500 µm / h and particularly preferably at most 3200 µm / h.

[0154] When the crystal phase (devitrification) of β-quartz solid solution and β-spodumene precipitates together, the devitrification growth rate of the β-quartz solid solution is preferably at most 500 µm / h, more preferably at most 450 µm / h, even more preferably at most 400 µm / h and particularly preferably at most 350 µm / h. <Lokale Erwärmungsverarbeitung>

[0155] Next, the resulting glass plate containing the crystalline phase undergoes local heating. More precisely, in local heating, a heating area (the portion containing the crystalline phase) that is part of the glass plate containing the crystalline phase is heated locally. This causes at least part of the crystalline phase to become amorphous and be removed (devitrification), and the intermediate phase discussed above is formed in its place.

[0156] Fig. Figure 2 is a cross-sectional reflection electron image of a glass plate before local heating processing. Fig. Figure 3 is a cross-sectional reflection electron image of a glass plate after local heating processing.

[0157] When considering Fig. 2 can be seen that a crystal phase 12 is present separately from a matrix glass phase 11.

[0158] When considering Fig. In contrast, 3 shows that through local heating processing a part of the crystal phase 12 has become amorphous and an intermediate phase 13 has been created.

[0159] In Fig. Furthermore, a region of high brightness can be observed between crystal phase 12 and matrix glass phase 11. This region arises when, during the formation of crystal phase 12 in matrix glass phase 11, the composition of matrix glass phase 11 and the composition of crystal phase 12 do not match, and it is sometimes referred to as the residual glass phase. The composition of the residual glass phase compensates for the discrepancy between the composition of matrix glass phase 11 and the composition of crystal phase 12.

[0160] Local heating processing is a process in which the heating area is heated to a temperature T1 of 1500 °C to 2400 °C and then cooled to a temperature T2 of 800 °C to 1000 °C.

[0161] During the execution of the local heating process, the temperature of the remaining area outside the heating area is preferably no more than 1250 °C.

[0162] The temperature of the glass plate (temperature T1, temperature T2, etc.) is measured using an infrared camera.

[0163] The higher the heating rate up to temperature T1 during local heating processing, the more efficiently the heating area alone can be heated. Therefore, the time required to rise from the initial temperature to temperature T1 is preferably at most 5 s, more preferably at most 4.5 s, and even more preferably at most 4 s.

[0164] If a preheating process as described below is carried out, the initial temperature is the preheating temperature, and if no preheating process is carried out, it is, for example, room temperature (23 ±5 °C).

[0165] If the cooling time from temperature T1 to temperature T2 is at most 300 s, renewed devitrification during cooling can be prevented, which is why this is preferred. The cooling time is more preferably at most 250 s, even more preferably at most 200 s, particularly preferably at most 150 s, and most preferably at most 100 s.

[0166] The smaller the heating area, the faster the heat spreads from the heated area after heating, and the cooling rate increases, thus preventing re-devitrification during cooling. Since the glass plate is heated locally, the formation of irregularities or distortions on the glass plate surface is also prevented.

[0167] The main axis diameter of the heating area is therefore preferably at most 200 mm and more preferably at most 100 mm.

[0168] However, if the heating area is too small, the deglazing cannot be adequately eliminated.

[0169] Therefore, the main axis diameter of the heating area is preferably at least 1 mm, more preferably at least 1.5 mm and even more preferably at least 2 mm.

[0170] The heating area is preferably an area extending to a depth of 2000 µm from the surface of the glass plate.

[0171] There are no particular restrictions regarding the heating method used in local heating processing. Heating devices used in local heating processing include, among others, laser heating devices and carbon heating devices. Local heating processing is described below with reference to... Fig. 1 described when using a laser heating device. <<Lasererwärmungsvorrichtung> >

[0172] Fig. Figure 1 is a schematic view of a laser heating device 1. The laser heating device 1 irradiates a heating area 3 of a glass plate 2, which is a glass plate containing crystal phases, with laser light 4 generated by a laser light source 8. As described above, the heating area 3 is an area of ​​the glass plate 2 containing the crystal phase (in Fig. 1 not shown).

[0173] More precisely, the path of the laser light 4 generated at the laser light source 8 is first modified by means of a mirror 9, which is arranged above a laser light incidence window 6. Then, a desired profile of the laser light 4 is formed by means of a lens 7 arranged between the mirror 9 and the laser light incidence window 6. It is then directed through the laser light incidence window 6 onto the heating area 3 of the glass plate 2.

[0174] As long as the lens 7 forms the desired cross-sectional area of ​​the laser light 4 and the desired laser output power can be achieved at the surface of the glass plate 2, there are no particular restrictions regarding its shape and material. The lens 7 can be present singly or in multiples, depending on the focal length.

[0175] Preferably, the laser light 4 is emitted such that its angle A with respect to the surface of the glass plate 2 is at least 45°. If the angle A is less than 45°, the cross-sectional area of ​​the laser light 4 on the surface of the glass plate 2 is too large, so there is a risk that the desired width cannot be achieved. More preferably, the angle A is at least 55°.

[0176] If the wavelength of the laser light 4 is too short, there is a risk of insufficient heating, which is why it is preferably at least 2.5 µm, more preferably at least 5 µm and even more preferably at least 7.5 µm.

[0177] If, on the other hand, the wavelength of the laser light 4 is too long, this makes it difficult to procure the laser heating device 1 and is not feasible, which is why it is preferably at most 12 µm and more preferably at most 11 µm.

[0178] The output power of the laser light 4 is preferably at least 250 W, more preferably at least 300 W and even more preferably at least 350 W, from the point of view of sufficient heating.

[0179] For reasons of equipment availability and ensuring power supply, the output power of the laser light 4 is preferably at most 650 W, more preferably at most 600 W and even more preferably at most 550 W.

[0180] To ensure sufficient heat input into the entire heating area 3 of the glass plate 2, the scanning speed of the laser light 4 is preferably at most 3500 mm / s, more preferably at most 3000 mm / s and even more preferably at most 2500 mm / s.

[0181] To increase the efficiency of the local heating processing, the scanning speed of the laser light 4 is preferably at least 800 mm / s, more preferably at least 1000 mm / s and even more preferably at least 1200 mm / s.

[0182] An irradiation surface of the laser light 4 in the heating area 3 of the glass plate 2 is a plane surrounded by a curve that connects parts where the energy density distribution of the profile of the laser light 4 on the surface of the glass plate 2 has a maximum of 1 / e 2 exhibits.

[0183] For sufficient removal of devitrification, the energy density, which is defined as the output power of the laser light 4 / irradiation surface, is preferably at least 4 W / mm². 2 , preferably at least 5 W / mm 2 and even more preferably at least 6 W / mm2.

[0184] However, if the energy density of the laser light 4 is too high, it will be excessively absorbed by the glass plate 2, which can lead to inconsistencies in the glass composition. Therefore, the energy density of the laser light 4 is preferably no more than 20 W / mm². 2 , preferably no more than 15 W / mm 2 and even more preferably no more than 10 W / mm 2 .

[0185] There are no particular restrictions regarding the oscillation mode of the laser light 4, and it can be any continuous-wave laser light (CW light), light with pulsed oscillation, or modulated continuous-wave laser light (causing a modulated periodic change in intensity by switching continuous-wave laser light on and off). The laser light 4 at a frequency of at least 0.1 Hz is preferably emitted for at least 0.001 seconds, and more preferably for at least 0.005 seconds.

[0186] For example, when irradiating with laser light 4, a CO laser or a CO2 laser is used.

[0187] A CO2 laser is particularly preferred, in which the oscillation wavelength of the laser light 4 is typically 10.6 µm. When irradiated with laser light 4 in this wavelength range, the laser light 4 is essentially completely absorbed by the glass plate, so that the temperature of the heating area 3 can be locally increased.

[0188] If the laser light is oscillating light, its pulse width is preferably at most 600 ms (milliseconds) and more preferably at most 400 ms.

[0189] Such local heating processing can also be used to remove devitrification from glass ribbons that are continuously produced in a production line.

[0190] In the float or fusion glass production process, a glass ribbon is manufactured continuously. If devitrification occurs in the glass ribbon during production, cracks can develop during cooling, originating from the devitrification points, ultimately leading to breakage of the glass sheet and reducing production efficiency.

[0191] Therefore, local heating processing is applied to the continuously produced glass ribbon. Since this eliminates any devitrification that occurs in the glass ribbon, the glass sheet can be manufactured efficiently.

[0192] If only part of the crystal phase (devitrification) becomes amorphous through local heating processing, the intermediate phase is formed between the matrix glass phase and the remaining devitrification.

[0193] If, on the other hand, the entire crystal phase (devitrification) becomes amorphous, the intermediate phase is formed at the locations in the matrix glass phase where devitrification previously occurred.

[0194] To completely remove the crystalline phase through local heating, the heating process must be longer or at a higher temperature. Conversely, if only a portion of the crystalline phase is rendered amorphous, the strength of the glass plate can be increased more efficiently in a shorter time or at a lower temperature. <Vorwärmverarbeitung>

[0195] Prior to local heating processing, the heating area and the areas outside the heating area can be preheated.

[0196] During preheating, the heating area and the areas outside the heating area are heated to a preheating temperature. The preheating temperature is preferably at least 800 °C, more preferably at least 820 °C, even more preferably at least 830 °C, and particularly preferably at least 850 °C.

[0197] The preheating temperature is preferably at or below the glass transition temperature. The preheating temperature is preferably at most 1150 °C, more preferably at most 980 °C, even more preferably at most 960 °C, and most preferably at most 950 °C.

[0198] After preheating, the temperature of the remaining area outside the heating zone is, for example, 1250 °C or less. <Chemische Verstärkungsverarbeitung>

[0199] Following local heating, the glass plate can undergo chemical reinforcement. This results in a chemically reinforced glass plate with a stress-resistant layer on its top surface.

[0200] Chemically strengthened glass is produced by subjecting the glass sheet to a chemical strengthening process and then washing and drying it.

[0201] The chemically strengthened glass has dimensions that allow it to be shaped using an existing forming process, and is finally cut to a size suitable for its intended use.

[0202] If the glass plate is cut to a specific shape and size or chamfered, a compressive stress layer can also be formed on the end face by performing the cutting or chamfering process before the chemical reinforcement process, which is why this is preferred.

[0203] Chemical reinforcement can be carried out using a known process. In this process, the glass plate is brought into contact with a molten metal salt (for example, potassium nitrate) containing metal ions with a large ionic radius (usually K ions), either by immersion or similar means. Metal ions with a small ionic radius in the glass plate (usually Na ions or Li ions) are thereby replaced by metal ions with a large ionic radius (usually K ions in the case of Na ions and Na or K ions in the case of Li ions).

[0204] The chemical strengthening process, i.e., the ion exchange process, can be carried out, for example, by immersing the glass plate for 0.1–500 hours in a molten salt solution of potassium nitrate or the like, heated to 360–600 °C. The heating temperature of the molten salt is preferably at least 375 °C and more preferably at most 500 °C. The immersion time of the glass plate in the molten salt is preferably at least 0.3 hours and more preferably at most 200 hours.

[0205] Examples of molten salts used for chemical reinforcement processing include nitrate, sulfate, carbonate and chloride.

[0206] Examples of nitrates include lithium nitrate, sodium nitrate, potassium nitrate, cesium nitrate and silver nitrate.

[0207] Examples of sulfates include lithium sulfate, sodium sulfate, potassium sulfate, cesium sulfate, and silver sulfate.

[0208] Examples of carbonates include lithium carbonate, sodium carbonate, and potassium carbonate. Examples of chlorides include lithium chloride, sodium chloride, potassium chloride, cesium chloride, and silver chloride.

[0209] These molten salts can be used alone or in combination.

[0210] Suitable processing conditions can be selected for chemical reinforcement processing, taking into account, among other things, the properties of the glass plate, the composition of the glass plate, the type of molten salt, and the CS and DOL values ​​that are desired for the chemically reinforced glass ultimately obtained.

[0211] Chemical enhancement can be performed only once, or it can be performed two or more times under different conditions (multi-stage enhancement).

[0212] When multiple chemical strengthening processes are performed, for example, the first stage can involve a chemical strengthening process under conditions that result in a high DOL value and a relatively low CS value. Then, the second stage can involve a chemical strengthening process under conditions that result in a low DOL value and a relatively high CS value. In this way, by increasing the CS value at the outermost surface of the chemically strengthened glass, the surface area (St) of internal tensile stress can be limited, and the internal tensile stress (CT) can be kept low.

[0213] In order to prevent bulging during chemical strengthening processing, the Young's modulus of the glass plate subjected to chemical strengthening processing is preferably at least 70 GPa, more preferably at least 75 GPa, even more preferably at least 80 GPa and particularly preferably at least 85 GPa.

[0214] Sometimes the glass plate is ground before the chemical reinforcement process is carried out. To achieve good grindability, the Young's modulus is preferably at most 130 GPa, more preferably at most 120 GPa, and even more preferably at most 110 GPa.

[0215] The present manufacturing process may also include further steps, as long as the effect of the present invention is not thereby impaired. For example, after the step of carrying out the chemical strengthening process, a step involving acid or alkali processing or a washing step may be included. Examples of implementation

[0216] The present invention is described in detail below, including by means of exemplary embodiments, but the present invention is not limited to these examples.

[0217] Examples 1 to 4 are embodiments, example 5 is a reference example, and examples 6 and 7 are comparative examples. <Beispiel 1>

[0218] The raw glass material was mixed to achieve the composition of the matrix glass phase and weighed to obtain 800 g of glass. The mixed raw glass material was placed in a platinum pot, put into an electric furnace at 1400-1700 °C, and melted, degassed, and homogenized for approximately 5 hours, resulting in a glass melt. [Table 1] Table 1 Composition [mol-%] SiO2 Al2O3 Li2O Na2O K2O MgO CaO TiO2 ZrO2 Y2O3 Matrix glass phase 68, 1 12 10,4 2,4 1,3 3,5 0,2 0, 1 0, 6 1,4

[0219] The resulting molten glass was poured into a mold, held at a temperature approximately 30 °C higher than the glass transition point for 1 hour, and then cooled to room temperature at a rate of 0.5 °C / minute, resulting in a glass block A of amorphous glass.

[0220] Using a portion of the obtained glass block A, the glass transition temperature, specific gravity, Young's modulus, and rate of thermal expansion of glass block A were measured. The results are given in Table 2. The Young's modulus was measured using ultrasound (and is described below). [Table 2] Table 2 Young's modulus [GPa] Rate of thermal expansion [ppm / °C] Glass block A 86,36 6,47

[0221] From the obtained glass block A, a 15 g piece of glass B was cut off. This piece was placed in a platinum container with a diameter of 40 mm, heated to 1350 °C, and melted. The molten glass was removed, cooled to 900 °C, and then heated to 1000 °C for 8 minutes. Cooling in air then yielded a glass plate C with a diameter of 40 mm and a thickness of 4 mm.

[0222] Glass plate C was a glass plate containing crystalline phases, in which a crystalline phase (devitrification) with a principal axis diameter of about 400 µm was present down to a depth of 2000 µm from the surface.

[0223] When performing a measurement using powder X-ray diffraction under the conditions below, it was found that the crystal phase was a β-spodumene crystal (hereinafter also referred to as "spodumene"). - Measuring device: SmartLab, Manufacturer: Rigaku Corporation - X-rays used: CuKα rays - Measuring range: 2θ=10°-80° - Speed: 10° / minute - Step size: 0.02°

[0224] The composition of the crystal phase (the content of the individual components) was determined as discussed above and was as indicated below. The Li (Li2O) content was calculated by subtracting the sum of the proportions of the individual components from 100%. SiO2: 70.4% Al2O3: 27.6% Na2O: 1.2% Li2O: 0.1% K2O: 0.5% MgO: 0.2%

[0225] The following processes (preheating and local heating) were carried out successively on glass plate C, resulting in glass plate D. <<Vorwärmverarbeitung> >

[0226] An ultra-hot plate (FT-HP-100) was set to 1000 °C, and glass plate C was positioned and heated on it. The surface temperature of glass plate C (preheating temperature), measured with an infrared camera (A6500, manufacturer: FLIR Systems), was 800 °C. <<Lokale Erwärmungsverarbeitung> >

[0227] The heated area of ​​the glass plate C, which contained the crystal phase and was positioned on the ultra-hot plate, was irradiated with a CO2 laser (E-400, manufacturer: COHERENT) with laser light of a wavelength of 10.6 µm. The irradiation conditions were as described below. Output power: 475 W Scanning speed: 2000 mm / s Energy density: 9.45 W / mm² 2 Working distance: 25000 (320 mm) Sampling distance: 0.01 mm for the first scan, 0.05 mm for subsequent scans. Beam diameter: 6 mm Scanning range: 40 mm Sampling direction: both directions

[0228] Part of the crystalline phase present in glass plate C had been removed from glass plate D, and the intermediate phase had formed at a position extending to a depth of 2000 µm from its surface. The Young's modulus and the rate of thermal expansion of a glass plate with the same composition as the intermediate phase are given in Table 3 below. [Table 3] Table 3 Composition [mol-%] SiO2 Al2O3 Li2O Na2O K2O MgO CaO TiO2 ZrO2 Y2O3 Young's modulus [GPa] Rate of thermal expansion Intermediate phase 67,07 11,54 14,17 1,316 0,333 3,347 0,224 0,079 0,56 1,361 89,53 6,849

[0229] Furthermore, the principal axial diameter of the intermediate phase and the principal axial diameter of the remaining crystal phase were measured at the deepest part of the intermediate phase on glass plate D. The results, along with the conditions of the local heating process, etc., are given in Table 4.

[0230] The "deepest part of the intermediate phase" refers to the linear distance from the surface of the glass plate (distance in the thickness direction) and the distance from the surface of the glass plate to the furthest point. The measurement was performed in the same way as for the principal axis diameter. <Beispiel 2>

[0231] Apart from changing the scanning speed of the laser light to 1750 mm / s, a glass plate D was obtained, just as in Example 1. <Beispiel 3>

[0232] Apart from the fact that the thickness of glass plate C was changed to 6 mm, a glass plate D was obtained, just as in Example 1. <Beispiel 4>

[0233] The scanning speed of the laser light was changed to 1000 mm / s, the crystalline phase of glass plate C (glass plate containing the crystalline phase) was completely removed, and the intermediate phase was formed. Otherwise, glass plate D was obtained in the same way as in Example 1.

[0234] Since the crystal phase has been completely removed, the symbol “-” is shown in the column for the principal axis diameter of the crystal phase (after local heating processing). <Beispiel 5>

[0235] A glass plate of the same shape as glass plate C was cut from glass block A and used as glass plate D. <Beispiel 6>

[0236] Apart from the fact that no local heating process was carried out on the glass plate C, a glass plate D was obtained, just as in Example 1. <Beispiel 7>

[0237] A glass plate was obtained by placing glass plate C in a 40 mm platinum container, heating it to 1500 °C using a muffle furnace, melting it, and then shaping it into the same form as glass plate C while air-cooling it. During air cooling, a crystalline phase formed within the glass plate. The resulting glass plate was used as glass plate D. <ror-versuch>

[0238] A ROR test was performed on the glass plates D of Examples 1 to 7 using the method discussed above to determine the mean strength and the Weibull coefficient m. The results are shown in Table 4 below.

[0239] A larger value of the Weibull coefficient m indicates less fluctuation. [Table 4] Table 4 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Panel thickness [mm] 4 4 6 4 4 4 4 Type of crystal phase Spodumen Spodumen Spodumen Spodumen - Spodumen Spodumen Local heating processing Conditions of laser irradiation Output power [W] 475 475 475 475 - - Remelting Sampling speed [mm / s] 2000 1750 2000 1000 - - Energy density [W / mm²] 2 ] 9,45 9,45 9,45 9,45 - - Temperature T1 [°C] 1500 1600 1500 1800 - - 1500 Temperature rise time [s] 0,2 0,2 0,2 0,2 - - 3600 Temperature T2 [°C] 800 800 800 800 - - 800 Temperature reduction time [s] 10 12 10 16 - - 3600 Depth of the deepest part of the intermediate phase [µm] 100 125 100 400 - - - Principal axis diameter of the intermediate phase [µm] 200 250 200 800 - - - Principal axis diameter of the crystal phase [µm] (after local heating processing) 387 380 387 - - 500 1000 ROR trial Medium strength 70 70 70 124 110 20 20 m 7 7 7 7 7 5 6 <Zusammenfassung der Beurteilungsergebnisse>

[0240] As shown in Table 4, the mean strength of the glass plates D of Examples 1 to 4, in which the intermediate phase had been formed by means of local heating processing, was higher than that of the glass plate D of Example 6, on which no local heating processing had been carried out (no intermediate phase had been formed), and the fluctuation in strength was lower (the value of the Weibull coefficient m was higher).

[0241] Furthermore, the average strength of the glass plates D in examples 1 to 4 was higher and the fluctuation in strength was lower (the value of the Weibull coefficient m was higher) than that of the glass plate D in example 7.

[0242] A comparison of examples 4 and 5 shows that the average strength of the glass plate D of example 4, in which the crystalline phase had been removed by local heating processing and the intermediate phase had formed, was higher than that of the glass plate D of example 5, in which no crystalline phase was present from the beginning.

[0243] A comparison of examples 1 and 2 and example 4 also showed that, in examples 1 and 2, where a residue of the crystal phase had been left behind, compared to example 4, where the crystal phase had been completely removed, a certain increase in strength was observed at high scanning speeds, and they were therefore superior in terms of energy efficiency and work efficiency.

[0244] The complete content of the description, claims, figures and abstract of Japanese patent application No. 2023-113047, filed on 10.07.2023, is hereby incorporated by reference into the disclosure of the description of the present invention. Explanation of reference symbols 1 laser heating device 2 Glass plate (glass plate containing crystal phases) 3 Heating area 4 laser light 6 laser incidence windows 7 lens 8 Laser light source 9 mirrors 11 Matrix glass phase 12 Crystal phase (devitrification) 13 Intermediate phase QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2013-516387 A

[0004] JP 2013-520385 A

[0004] JP 2023-113047

[0244] Cited non-patent literature

[0000] JISR 1625(2010

[0124] < / entglasungswachstumsgeschwindigkeit> < / entglasungstemperatur> < / plattendicke> < / form> < / zno> < / bao> < / mgo> < / matrixglasphase>

Claims

[1] Glass plate containing a matrix glass phase and an intermediate phase, wherein the matrix glass phase is an amorphous oxide which, expressed in mol% on an oxide basis, contains 50-80% SiO2, 0-30% Al2O3 and 0.1-35% Li2O, and The intermediate phase is an amorphous oxide which, expressed in mol% on an oxide basis, contains 50-80% SiO2, 5-20% Al2O3 and 5-20% Li2O and whose composition differs from that of the matrix glass phase. [2] Glass plate according to claim 1, wherein at least a part of the intermediate phase is located at a position at a depth of up to 2000 µm from the surface of the glass plate. [3] Glass plate according to claim 1 or 2, wherein a principal axis diameter of the intermediate phase is 2000 µm or less. [4] Glass plate according to claim 1 or 2, further comprising a crystalline phase, wherein the intermediate phase is in contact with the crystalline phase and the matrix glass phase, wherein the crystalline phase, expressed in mol% on an oxide basis, comprises 60-90% SiO2, 0-40% Al2O3 and 0-15% Na2O, and at least a part of the crystalline phase is located at a position at a depth of up to 2000 µm from the surface of the glass plate. [5] Glass plate according to claim 1 or 2, wherein the plate thickness is 0.1-6.0 mm. [6] Glass plate according to claim 1 or 2, wherein an average strength obtained by performing a ROR test 20 times is 30 MPa or more, and a Weibull coefficient value m, indicating fluctuations in strength, is 7 or more. ROR test: The glass plate is mounted on a lower stainless steel ring. A contact section where the lower ring is in contact with the glass plate has a diameter of 30 mm and a roundness with a radius of curvature of 2.5 mm. The glass plate, in contact with an upper stainless steel ring, is subjected to static loading at the center point of the upper ring. A contact section where the upper ring is in contact with the glass plate has a diameter of 10 mm and a roundness with a radius of curvature of 2.5 mm. The contact speed of the upper ring is 1.0 mm / min.The stress at the moment the glass plate breaks is converted into fracture stress based on the plate thickness and the fracture point position of the glass plate, and this is determined as the strength. [7] Glass plate according to claim 4, wherein the crystal phase comprises at least one of phosphoric acid lithium crystal, nickel acid lithium crystal, lithium aluminosilicate crystal, zirconium-containing crystal and magnesium-containing crystal. [8] Glass plate according to claim 1 or 2, wherein the matrix glass phase, expressed in mol% on an oxide basis, 50-80% SiO2, to 0-30% Al2O3, to 0.1-35% Li2O to 0-8% B2O3, to 0-6% P2O5, to 0-20% Na2O, to 0-10% K2O, to 0-20% MgO, to 0-20% CaO, to 0-20% SrO, to 0-15% BaO, to 0-10% ZnO, to 0-5% Ti2O, to 0-8% ZrO2 and Contains 0-8% Y2O3. [9] Glass plate according to claim 1 or 2, wherein a thermal expansion rate difference Δα, where the thermal expansion rate of the intermediate phase has been subtracted from the thermal expansion rate of the matrix glass phase, is less than 0 ppm / °C. [10] Glass plate according to claim 1 or 2, wherein the glass is chemically strengthened and the compressive stress value of a compressive stress layer is 400 MPa or more. [11] Method for producing a glass plate, wherein a glass plate containing a crystal phase is prepared in which the crystal phase is located at a position at a depth of up to 2000 µm from the surface, wherein a local heating process is carried out in which a heating area which is part of the glass plate containing the crystal phase is heated, wherein the glass plate containing the crystal phase includes the crystal phase within the heating area, where the local heating process is a process in which the heating area is heated to a temperature T1 of at least 1500 °C and at most 2400 °C and then cooled to a temperature T2 of at least 800 °C and at most 1000 °C. [12] Method for producing a glass plate according to claim 11, wherein a preheating process is carried out prior to the local heating process, in which the glass plate containing the crystal phases is heated to a preheating temperature of at least 800 °C and at most 1150 °C. [13] Method for producing a glass plate according to claim 11, wherein the local heating process is a process in which the heating area is heated from the preheating temperature to the temperature T1 within 5 s and cooled from the temperature T1 to the temperature T2 within 300 s. [14] Method for producing a glass plate according to one of claims 11 to 13, wherein the local heating process is a process in which the heating area is heated by irradiation with laser light. [15] Method for producing a glass plate according to claim 14, wherein the wavelength of the laser light is 2.5-12 µm. [16] Method for producing a glass plate according to claim 14, wherein the laser light is emitted using a CO laser or a CO2 laser. [17] Method for producing a glass plate according to one of claims 11 to 13, wherein the local heating process is a process in which the heating area is heated with a carbon heating device. [18] Method for producing a glass plate according to one of claims 11 to 13, wherein during the execution of the local heating process the temperature of the remaining area of ​​the crystal phase-containing glass plate outside the heating area is at most 1250 °C. [19] Method for producing a glass plate according to any one of claims 11 to 13, wherein the local heating process is carried out in a float bath in which the glass plate is produced. [20] Method for producing a glass plate according to one of claims 11 to 13, wherein, after local heating processing, a chemical strengthening process is further carried out on the glass plate obtained. [21] Method for removing devitrification from a glass plate, wherein a glass plate is prepared in which devitrification is present at a position at a depth of up to 2000 µm from the surface, wherein the glass plate is preheated to a preheating temperature of at least 800 °C and at most 1150 °C and subsequently a heating area which is part of the glass plate and contains the devitrification is heated from the preheating temperature to a temperature T1 of at least 1500 °C and at most 2400 °C within 5 s and then cooled from the temperature T1 to a temperature T2 of at least 800 °C and at most 1000 °C within 300 s.

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