Alkali-free glass plate

Abstract

Provided is an alkali-free glass plate having a sufficiently high strain point and Young's modulus, together with excellent productivity.　The alkali-free glass plate is characterized by containing as the glass composition, in mol%, SiO2 63-70%, Al2O3 10-15%, B2O3 3-8%, Li2O+Na2O+K2O 0-0.5%, MgO 1-11%, CaO 2-11%, SrO 0-6%, BaO 0-8%, and MgO+CaO+SrO+BaO 13-20%, by the mol% ratio SiO2 / Al2O3 being 4.2-7, and by the mol% ratio (MgO+CaO+SrO+BaO) / Al2O3 being 0.9-2.

Description

Alkali-free glass plate

[0001] The present invention relates to an alkali-free glass plate, and more particularly to an alkali-free glass plate suitable as a substrate for an organic EL display or a magnetic recording medium.

[0002] 2. Description of the Related Art Electronic devices such as organic EL displays are thin, have excellent moving image display capabilities, and consume low power, and are therefore used in applications such as flexible devices and displays for mobile phones.

[0003] Glass plates are widely used as substrates for organic electroluminescence displays (see, for example, Patent Document 1). Glass plates for this application are primarily required to have the following properties: (1) They must contain almost no alkali metal oxides, i.e., be alkali-free glass (specifically, glass with an alkali oxide content of 0.5 mol % or less in the glass composition), in order to prevent alkali ions from diffusing into the semiconductor material formed in the heat treatment process; (2) They must be formed by the overflow downdraw method, which is likely to improve surface quality, and have excellent productivity, particularly excellent melting properties and devitrification resistance, in order to reduce the cost of the glass plate; and (3) They must have a high strain point in order to reduce thermal shrinkage of the glass plate in the LTPS (Low Temperature Poly Silicon) process and oxide TFT (Thin Film Transistor) process.

[0004] Furthermore, magnetic recording media such as magnetic disks and optical disks are used in various information devices. Glass plates have been widely used as substrates for magnetic recording media, replacing conventional aluminum alloy substrates (see, for example, Patent Document 2). In recent years, to meet the need for even higher recording densities, magnetic recording media using an energy-assisted magnetic recording method, i.e., energy-assisted magnetic recording media, have been studied. In energy-assisted magnetic recording media, glass plates are also used, and a magnetic layer or the like is formed on the surface of the glass plate. In energy-assisted magnetic recording media, ordered alloys with a large magnetic anisotropy coefficient Ku (hereinafter referred to as "high Ku") are used as the magnetic material for the magnetic layer.

[0005] JP 2012-106919 A ​​JP 2021-086643 A

[0006] Meanwhile, organic EL televisions, which are a type of organic EL device, are strongly required to be larger and thinner, and there is also growing demand for high-resolution displays such as 8K. Therefore, glass sheets for these applications are required to be large and thin, yet have thermal dimensional stability that can withstand the high-resolution requirements. Furthermore, organic EL televisions are required to be low-cost in order to reduce the price difference with liquid crystal displays, and glass sheets are also required to be low-cost. However, as glass sheets become larger and thinner, they tend to bend more easily, which can cause breakage and increase manufacturing costs, as described below.

[0007] Glass sheets formed by glass manufacturers undergo processes such as cutting, annealing, inspection, and cleaning. During these processes, the glass sheets are loaded into a cassette with multiple shelves and transported out. This cassette is usually designed so that opposing edges of the glass sheet can be placed on shelves formed on the left and right inner surfaces to hold the glass sheet horizontally. However, large, thin glass sheets tend to bend significantly, so that when the glass sheet is loaded into the cassette, part of the glass sheet may come into contact with the cassette and break, or the glass sheet may swing significantly when it is transported out. To solve this problem, an effective method is to increase the Young's modulus (rigidity) of the glass sheet to reduce the amount of deflection.

[0008] Furthermore, as described above, in the LTPS or oxide TFT process for obtaining a high-resolution display, it is necessary to increase the strain point of a large glass plate in order to reduce the thermal shrinkage of the glass plate.

[0009] However, attempts to increase the Young's modulus and strain point of a glass sheet disrupt the balance of the glass composition, reducing productivity, and particularly significantly reducing devitrification resistance and increasing the liquidus viscosity, making it impossible to form the glass by the overflow downdraw method. Furthermore, the melting property is reduced and the forming temperature of the glass increases, which tends to shorten the life of the formed glass. As a result, the cost of the glass sheet raw material increases.

[0010] In addition, glass plates for magnetic recording media are required to have a high Young's modulus so as not to undergo large deformation during high-speed rotation. Specifically, in disk-shaped magnetic recording media, the medium is rotated at high speed around the central axis, and information is written and read along the direction of rotation while the magnetic head is moved in the radial direction. In recent years, in order to increase the writing and reading speeds, the rotation speed has been increasing from 5,400 rpm to 7,200 rpm, and even 10,000 rpm. In disk-shaped magnetic recording media, the position for recording information is assigned in advance according to the distance from the central axis, so if the glass plate deforms during rotation, the magnetic head will be displaced, making accurate reading difficult.

[0011] In recent years, magnetic heads have been equipped with a dynamic flying height (DFH) mechanism, which significantly reduces the gap between the read / write element of the magnetic head and the surface of the magnetic recording medium (reducing the flying height), thereby achieving even higher recording densities. The DFH mechanism involves providing a heating element, such as a tiny heater, near the read / write element of the magnetic head, causing thermal expansion only around the element toward the surface of the medium. By incorporating such a mechanism, the distance between the magnetic head and the magnetic layer of the medium is reduced, making it possible to pick up signals from smaller magnetic particles and achieve higher recording densities. On the other hand, because the gap between the read / write element of the magnetic head and the surface of the magnetic recording medium is extremely small, for example, 2 nm or less, even a slight impact can cause the magnetic head to collide with the surface of the magnetic recording medium. This tendency becomes more pronounced as the rotation speed increases. Therefore, during high-speed rotation, it is important to prevent the glass plate from bending or fluttering, which can cause such collisions.

[0012] Furthermore, in order to increase the degree of ordering (ordering degree) of the magnetic layer and achieve a high Ku, the substrate including the glass plate may be heat-treated at a high temperature of about 800 ° C. during, before, or after the formation of the magnetic layer. The higher the recording density, the higher the heat treatment temperature needs to be. Furthermore, after the magnetic layer is formed, the substrate including the glass plate may be irradiated with a laser. Such heat treatment or laser irradiation also aims to increase the annealing temperature and coercivity of the magnetic layer containing an FePt-based alloy, etc. Therefore, a higher heat resistance, i.e., a higher strain point, is required than in conventional glass plates for magnetic recording media.

[0013] However, as described above, if an attempt is made to increase the Young's modulus and strain point of a glass sheet, the balance of the glass composition is lost, productivity decreases, and in particular, devitrification resistance is significantly reduced and the liquidus viscosity increases, making it impossible to form the glass by the overflow downdraw method. Furthermore, the melting property decreases and the forming temperature of the glass increases, which tends to shorten the life of the formed body. As a result, the cost of the glass sheet raw material increases.

[0014] The present invention has been made in view of the above circumstances, and its technical object is to provide an alkali-free glass sheet which is excellent in productivity and has a sufficiently high strain point and Young's modulus.

[0015] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using an alkali-free glass plate that satisfies a predetermined composition.

[0016] (1) The alkali-free glass plate of the present invention has a glass composition containing, in mol %, SiO ２ 63-70%, Al ２ O ３ 10-15%, B ２ O ３ 3-8% Li ２ O + Na ２ O+K ２ O 0-0.5%, MgO 1-11%, CaO 2-11%, SrO 0-6%, BaO 0-8%, MgO + CaO + SrO + BaO 13-20%, mol % ratio SiO ２ / Al ２ O ３is 4.2 to 7, mol% ratio (MgO+CaO+SrO+BaO) / Al ２ O ３ is 0.9 to 2. ２ O + Na ２ O+K ２ "O" is Li ２ O, Na ２ O and K ２ "MgO + CaO + SrO + BaO" refers to the total amount of MgO, CaO, SrO and BaO. "SiO ２ / Al ２ O ３ " is SiO ２ The content of Al ２ O ３ The value is calculated by dividing the content of (MgO + CaO + SrO + BaO) / Al ２ O ３ " is a composite of MgO, CaO, SrO and BaO. ２ O ３ The "alkali-free glass" in the present invention is a value obtained by dividing by the content of Li. ２ O + Na ２ O+K ２ This refers to glass with an O content of 0.5% or less.

[0017] (2) The alkali-free glass plate of the present invention has the above-mentioned constitution (1), and the glass composition contains, in mol %, SiO ２ 64-68%, Al ２ O ３ 11-14%, B ２ O ３ 4.1-6%, Li ２ O + Na ２ O+K ２ O 0-0.5%, MgO 2-9%, CaO 2-10%, SrO 1-4%, BaO 1-6%, MgO + CaO + SrO + BaO 14-18%, mol % ratio SiO ２ / Al ２ O ３ is more than 5 to 5.4, mol% ratio (MgO + CaO + SrO + BaO) / Al ２ O ３ is preferably 1.2 to 1.6.

[0018] (3) The alkali-free glass plate of the present invention has the above-mentioned constitution (1) or (2), and contains, in mol %, MgO+CaO+SrO+BaO-Al ２ O ３ It is preferable that the content of "MgO + CaO + SrO + BaO - Al" is 1 to 5%. ２ O ３ " is the total amount of MgO + CaO + SrO + BaO, ２ O ３ This is the value obtained by subtracting the content of

[0019] (4) In the alkali-free glass plate of the present invention having any one of the above structures (1) to (3), it is preferable that the glass plate contains, in mol %, 2.4% or more of BaO.

[0020] (5) The alkali-free glass plate of the present invention has the above-mentioned constitution (1) to (4), and further contains As in the glass composition. ２ O ３ and Sb ２ O ３ It is preferable that the glass composition does not substantially contain As. ２ O ３ and Sb ２ O ３ "Substantially does not contain As ２ O ３ and Sb ２ O ３ and the content thereof is 0.05 mol % or less.

[0021] (6) The alkali-free glass plate of the present invention has the constitution of any one of (1) to (5) above, and further contains, in mol %, SnO ２ It is preferable that the content be 0.001 to 1%.

[0022] (7) In the alkali-free glass plate of the present invention having any of the configurations (1) to (6) above, the strain point is preferably 680° C. or higher.

[0023] (8) In the alkali-free glass plate of the present invention having any of the configurations (1) to (7) above, the Young's modulus is preferably 75 GPa or more.

[0024] (9) The alkali-free glass plate of the present invention, in any one of the configurations (1) to (8), has a specific Young's modulus of 28 GPa / g cm －３ It is preferable that this is equal to or greater than this.

[0025] (10) In the alkali-free glass plate of the present invention having any of the configurations (1) to (9) above, the liquidus temperature is preferably 1,400° C. or lower.

[0026] (11) The alkali-free glass plate of the present invention, in any one of the configurations (1) to (10), has an average thermal expansion coefficient of 20×10 in a temperature range of 30 to 380° C. －７ ~50 x 10 －７ / °C.

[0027] (12) In the alkali-free glass plate of the present invention having any of the configurations (1) to (11) above, the annealing point is preferably 730° C. or higher.

[0028] (13) The alkali-free glass plate of the present invention has the configuration of any one of the above (1) to (12), and has a liquidus viscosity of 10 ４．２ It is preferably dPa·s or more.

[0029] (14) The alkali-free glass plate of the present invention, having the above configurations (1) to (13), is preferably used in an organic EL device.

[0030] (15) The alkali-free glass plate of the present invention, having the above configurations (1) to (13), is preferably used for a magnetic recording medium.

[0031] According to the present invention, an alkali-free glass sheet can be provided which is excellent in productivity and has a sufficiently high strain point and Young's modulus.

[0032] The alkali-free glass plate of the present invention has a glass composition comprising, in mol %, SiO ２ 63-70%, Al ２ O ３ 10-15%, B ２ O ３ 3-8% Li ２ O + Na ２ O+K ２O 0-0.5%, MgO 1-11%, CaO 2-11%, SrO 0-6%, BaO 0-8%, MgO + CaO + SrO + BaO 13-20%, mol % ratio SiO ２ / Al ２ O ３ is 4.2 to 7, mol% ratio (MgO+CaO+SrO+BaO) / Al ２ O ３ is 0.9 to 2. The reasons for limiting the content of each component as described above are as follows. In the explanation of the content of each component, % indicates mol% unless otherwise specified. Furthermore, unless otherwise specified, the upper limit indicates a value equal to or greater than the specified value, and the lower limit indicates a value equal to or less than the specified value.

[0033] SiO ２ is a component that forms the skeleton of glass. ２ If the content of SiO is too low, the thermal expansion coefficient becomes high and the density increases. ２ The lower limit of the amount of SiO is preferably 63%, more preferably 63.2%, even more preferably 63.4%, even more preferably 63.6%, even more preferably 63.8%, even more preferably 64%, even more preferably 64.1%, even more preferably 64.2%, even more preferably 64.5%, even more preferably 64.7%, even more preferably 65%, and most preferably 65.5%. ２ If the content is too high, the Young's modulus decreases, the viscosity at high temperatures increases, the amount of heat required for melting increases, the melting cost increases, and the SiO ２ The raw materials introduced may remain undissolved, which may cause a decrease in yield. In addition, devitrified crystals such as cristobalite may be easily precipitated, which may cause a decrease in liquidus viscosity. ２ The upper limit of the amount is preferably 70%, more preferably 69.7%, even more preferably 69.5%, even more preferably 69.2%, even more preferably 69%, even more preferably 68.7%, even more preferably 68.5%, even more preferably 68.3%, and most preferably 68%.

[0034] Al ２ O ３is a component that forms the skeleton of the glass, increases the Young's modulus, and also increases the strain point. ２ O ３ If the content of Al is too small, the Young's modulus is likely to decrease and the strain point is likely to decrease. ２ O ３ The lower limit of Al is preferably 10%, more preferably 10.2%, even more preferably 10.4%, even more preferably 10.6%, even more preferably 10.8%, even more preferably 11%, even more preferably 11.2%, even more preferably 11.4%, and most preferably 11.6%. ２ O ３ If the content of Al is too high, devitrified crystals such as mullite tend to precipitate, and the liquidus viscosity tends to decrease. ２ O ３ The upper limit of the amount is preferably 15%, more preferably 14.8%, even more preferably 14.6%, even more preferably 14.4%, even more preferably 14.2%, even more preferably 14%, even more preferably 13.9%, even more preferably 13.8%, even more preferably 13.7%, and most preferably 13.6%.

[0035] Mol% ratio SiO ２ / Al ２ O ３ is an important component ratio for increasing the strain point and decreasing the high-temperature viscosity. ２ / Al ２ O ３ If the mol% ratio of SiO is too small, the density tends to increase. ２ / Al ２ O ３ The lower limit of SiO is preferably 4.2, more preferably 4.4, more preferably 4.6, more preferably 4.8, more preferably 5, more preferably more than 5, more preferably 5.1, and most preferably 5.2. ２ / Al ２ O ３ If the mol % ratio of SiO is too large, the viscosity at high temperatures increases, which tends to increase the manufacturing cost of the glass sheet. ２ / Al ２ O ３The upper limit is preferably 7, more preferably 6.5, even more preferably 6, even more preferably 5.9, even more preferably 5.8, even more preferably 5.7, even more preferably 5.6, even more preferably 5.5, even more preferably 5.4, and most preferably 5.35.

[0036] B ２ O ３ has the effect of improving the melting property and the resistance to devitrification. ２ O ３ The lower limit of B is preferably 3%, more preferably 3.1%, more preferably 3.2%, more preferably 3.3%, more preferably 3.4%, more preferably 3.5%, more preferably 3.6%, more preferably 3.8%, more preferably 4%, more preferably 4.1%, and most preferably 4.3%. ２ O ３ If the content of B is too high, the Young's modulus and strain point tend to decrease. ２ O ３ The upper limit of the amount is preferably 8%, more preferably 7.5%, even more preferably 7%, even more preferably 6.8%, even more preferably 6.5%, even more preferably 6.3%, even more preferably 6%, even more preferably 5.9%, even more preferably 5.8%, and most preferably 5.5%.

[0037] Li ２ O, Na ２ O and K ２ O is a component that is inevitably mixed in from the glass raw materials, and its total content is 0 to 0.5%, preferably 0 to 0.1%, more preferably 0 to 0.09%, even more preferably 0.005 to 0.08%, still more preferably 0.008 to 0.06%, and most preferably 0.01 to 0.05%. ２ O, Na ２ O and K ２ If the total amount of O is too large, there is a risk that alkali ions will diffuse into the semiconductor material formed in the heat treatment process. ２ O, Na ２ O and K ２The individual content of O is preferably 0 to 0.3%, more preferably 0 to 0.1%, even more preferably 0 to 0.08%, still more preferably 0 to 0.07%, still more preferably 0 to 0.05%, and most preferably 0.001 to 0.04%.

[0038] Among alkaline earth metal oxides, MgO is a component that significantly increases Young's modulus. If the MgO content is too low, the melting property and Young's modulus tend to decrease. Therefore, the lower limit of MgO content is preferably 1%, more preferably 1.1%, more preferably 1.3%, even more preferably 1.5%, even more preferably 1.8%, even more preferably 2%, even more preferably 2.3%, and most preferably 2.5%. On the other hand, if the MgO content is too high, devitrified crystals such as mullite tend to precipitate, and the liquidus viscosity tends to decrease. Therefore, the upper limit of MgO content is preferably 11%, more preferably 10.5%, even more preferably 10.2%, even more preferably 10%, even more preferably 9.5%, even more preferably 9.2%, even more preferably 9%, even more preferably 8.8%, even more preferably 8.5%, even more preferably 8.3%, and most preferably 8%.

[0039] CaO is a component that reduces high-temperature viscosity and significantly improves meltability without lowering the strain point. It also increases Young's modulus. If the CaO content is too low, meltability tends to decrease. Therefore, the lower limit of CaO is preferably 2%, more preferably 2.2%, more preferably 2.5%, even more preferably 2.8%, even more preferably 3%, even more preferably 3.2%, even more preferably 3.5%, even more preferably 3.8%, and most preferably 4%. On the other hand, if the CaO content is too high, the liquidus temperature will increase. Therefore, the upper limit of CaO is preferably 11%, more preferably 10.5%, more preferably 10.2%, more preferably 10%, more preferably 9.8%, even more preferably 9.5%, even more preferably 9.3%, and most preferably 9%.

[0040] SrO is a component that improves devitrification resistance, reduces high-temperature viscosity without lowering the strain point, and improves meltability. It also suppresses a decrease in liquidus viscosity. Therefore, the lower limit of SrO is preferably 0%, more preferably greater than 0%, more preferably 0.1%, even more preferably greater than 0.1%, even more preferably 0.2%, even more preferably 0.3%, even more preferably greater than 0.3%, even more preferably 0.4%, even more preferably greater than 0.4%, even more preferably 0.5%, even more preferably 0.7%, and most preferably 1%. On the other hand, if the SrO content is too high, the thermal expansion coefficient and density tend to increase. Therefore, the upper limit of SrO is preferably 6%, more preferably less than 6%, even more preferably 5.8%, even more preferably 5.5%, even more preferably 5.3%, even more preferably 5%, even more preferably 4.8%, even more preferably 4.5%, even more preferably 4.3%, and most preferably 4%.

[0041] BaO is a component that enhances devitrification resistance. Therefore, the lower limit of BaO is preferably 0%, more preferably more than 0%, more preferably 0.1%, even more preferably more than 0.1%, even more preferably 0.2%, even more preferably 0.3%, even more preferably 0.4%, even more preferably 0.5%, even more preferably 0.7%, even more preferably 0.9%, even more preferably 1%, even more preferably 1.2%, even more preferably 1.4%, even more preferably 1.6%, even more preferably 1.8%, even more preferably 2%, even more preferably 2.2%, and most preferably 2.4%. On the other hand, if the BaO content is too high, the Young's modulus tends to decrease and the density tends to increase. As a result, the specific Young's modulus decreases, making the glass plate more prone to bending. Therefore, the upper limit of BaO is preferably 8%, more preferably 7.8%, more preferably 7.5%, even more preferably 7.3%, even more preferably 7%, even more preferably 6.8%, even more preferably 6.5%, even more preferably 6.3%, and most preferably 6%.

[0042] MgO, CaO, SrO, and BaO are components that increase density and thermal expansion coefficient. If the content of MgO + CaO + SrO + BaO is too low, the thermal expansion coefficient tends to decrease. Therefore, the lower limit of MgO + CaO + SrO + BaO is preferably 13%, more preferably 13.3%, more preferably 13.5%, even more preferably 13.8%, even more preferably 14%, even more preferably 14.2%, even more preferably 14.4%, even more preferably 14.6%, and most preferably 14.8%. On the other hand, if the content of MgO + CaO + SrO + BaO is too high, the density tends to increase. Therefore, the upper limit of MgO + CaO + SrO + BaO is preferably 20%, more preferably 19%, more preferably 18.8%, even more preferably 18.5%, even more preferably 18%, even more preferably 17.8%, and most preferably 17.6%.

[0043] (MgO+CaO+SrO+BaO) / Al ２ O ３ is an important parameter for lowering the thermal expansion coefficient and increasing the melting property. (MgO + CaO + SrO + BaO) / Al ２ O ３ If the ratio is too small, the high-temperature viscosity increases and the melting property decreases, which tends to increase the manufacturing cost of the glass sheet. ２ O ３ The lower limit of (MgO+CaO+SrO+BaO) / Al is preferably 0.9, more preferably 1, even more preferably 1.1%, still more preferably 1.2%, and most preferably 1.3. ２ O ３ If is too large, the thermal expansion coefficient tends to increase. ２ O ３ The upper limit is preferably 2, more preferably 1.9, even more preferably 1.8, even more preferably 1.7, even more preferably 1.6, even more preferably 1.5, and most preferably 1.4.

[0044] MgO+CaO+SrO+BaO-Al ２ O ３is an important parameter for lowering the thermal expansion coefficient and increasing the melting property. MgO + CaO + SrO + BaO - Al ２ O ３ If the ratio is too small, the high-temperature viscosity increases and the melting property decreases, which tends to increase the manufacturing cost of the glass sheet. ２ O ３ The lower limit of MgO+CaO+SrO+BaO-Al is preferably 1%, more preferably 1.2%, even more preferably 1.5%, even more preferably 1.7%, even more preferably 1.8%, even more preferably 1.9%, even more preferably 2%, even more preferably 2.1%, even more preferably 2.4%, even more preferably 2.6%, even more preferably 2.8%, even more preferably 3%, even more preferably 3.2%, and most preferably 3.5%. ２ O ３ If is too large, the thermal expansion coefficient tends to increase. ２ O ３ The upper limit is preferably 7%, more preferably 6.8%, even more preferably 6.5%, even more preferably 6.3%, even more preferably 6%, even more preferably 5.8%, even more preferably 5.5%, even more preferably 5.3%, and most preferably 5%.

[0045] A suitable glass composition range can be achieved by appropriately combining the suitable content ranges of each component. Among these, in order to optimize the effects of the present invention, the glass composition should contain, in mol %, SiO ２ 64-68%, Al ２ O ３ 11-14%, B ２ O ３ 4.1-6%, Li ２ O + Na ２ O+K ２ O 0-0.5%, MgO 2-9%, CaO 2-10%, SrO 1-4%, BaO 1-6%, MgO + CaO + SrO + BaO 14-18%, mol % ratio SiO ２ / Al ２ O ３ is more than 5 to 5.4, mol% ratio (MgO + CaO + SrO + BaO) / Al ２ O３ It is particularly preferable that the ratio is 1.2 to 1.6.

[0046] In addition to the above components, the following components may be added as optional components. Note that, from the viewpoint of accurately enjoying the effects of the present invention, the content of components other than the above components is preferably 10% or less in total, and particularly preferably 5% or less.

[0047] P ２ O ５ is a component that increases the strain point and is also a component that can significantly suppress the precipitation of devitrified crystals of alkaline earth aluminosilicates such as anorthite. ２ O ５ When a large amount of P is contained, the glass is more likely to undergo phase separation. ２ O ５ The content is preferably 0 to 2.5%, more preferably 0 to 1.5%, even more preferably 0 to 0.5%, even more preferably 0 to 0.3%, still more preferably 0 to less than 0.1%, and particularly preferably 0 to less than 0.01%.

[0048] TiO ２ is a component that reduces high-temperature viscosity and increases melting property, and also suppresses solarization. ２ If a large amount of TiO is contained, the glass becomes colored and the transmittance tends to decrease. ２ The content is preferably 0 to 2.5%, more preferably 0.0005 to 1%, even more preferably 0.001 to 0.5%, and particularly preferably 0.005 to 0.1%.

[0049] ZnO is a component that increases Young's modulus. However, if a large amount of ZnO is contained, the glass becomes more susceptible to devitrification and the strain point becomes lower. The ZnO content is preferably 0 to 3%, more preferably 0 to 2%, even more preferably 0 to 1%, even more preferably 0 to 0.8%, even more preferably 0 to 0.5%, and particularly preferably 0 to less than 0.5%.

[0050] Fe ２ O ３ is a component that is inevitably mixed in from glass raw materials and is a component that reduces electrical resistivity. ２ O ３The content of Fe is preferably 0 to 0.025%, 0.002 to 0.02%, particularly preferably 0.004 to 0.01%. ２ O ３ If the content is too low, the raw material cost tends to rise. ２ O ３ If the content is too large, the electrical resistivity of the molten glass increases, making it difficult to carry out electric melting.

[0051] ZrO ２ is a component that increases Young's modulus. ２ If a large amount of ZrO is contained, the glass is prone to devitrification. ２ The content is preferably 0 to 2.5%, more preferably 0.0005 to 1%, even more preferably 0.001 to 0.5%, and particularly preferably 0.005 to 0.1%.

[0052] M.O. ３ is a component that absorbs ultraviolet light (specifically, light with a wavelength of 200 to 300 nm). ３ is a component that reduces the water content in the glass. In particular, the raw material batch is melted by electric melting and heating, and MoO ３ By including MoO, the water content in the glass can be further reduced. When the water content in the glass is reduced, the liquidus viscosity and strain point increase, and the devitrification resistance and heat resistance of the glass can be improved. ３ The lower limit of MoO is preferably 0.00001%, more preferably 0.00005%, even more preferably 0.0001%, even more preferably 0.0002%, even more preferably 0.0003%, even more preferably 0.0004%, and particularly preferably 0.001%. ３ If the content of MoO is too high, the transmittance of ultraviolet light is reduced, and the yield of the display manufacturing process, particularly the laser peeling process, is likely to decrease. ３ The upper limit of the amount of is preferably 0.01%, more preferably 0.008%, even more preferably 0.006%, still more preferably 0.005%, still more preferably 0.004%, and particularly preferably 0.003%.

[0053] Y ２ O ３ , Nb２ O ５ , La ２ O ３ Y has the effect of increasing the strain point, Young's modulus, etc. The total amount and individual contents of these components are preferably 0 to 5%, more preferably 0 to 1%, even more preferably 0 to 0.5%, and particularly preferably 0 to less than 0.5%. ２ O ３ , Nb ２ O ５ , La ２ O ３ If the total amount or the individual contents of are too high, the density and raw material costs tend to increase.

[0054] SnO ２ is a component that has a good fining effect in the high temperature range, and also a component that increases the strain point and reduces the high-temperature viscosity. ２ The content of SnO is preferably 0 to 1%, 0.001 to 1%, 0.01 to 0.5%, and particularly preferably 0.05 to 0.3%. ２ If the content is too high, SnO ２ Devitrified crystals are more likely to precipitate.

[0055] As mentioned above, SnO ２ is suitable as a fining agent, but SnO is not suitable as a fining agent as long as the glass properties are not impaired. ２ Alternatively, SnO ２ Along with F, SO ３ , C, or metal powders such as Al and Si can be added in amounts up to 5% (preferably up to 1%, particularly up to 0.5%). ２ , F, etc. may also be added in an amount of up to 5% each (preferably up to 1%, particularly preferably up to 0.5%).

[0056] As a fining agent, As ２ O ３ , Sb ２ O ３ is also valid. However, As ２ O ３ , Sb ２ O ３ is a component that increases the environmental load. ２ O ３are components that reduce solarization resistance. Therefore, it is preferable that the alkali-free glass plate of the present invention is substantially free of these components.

[0057] Cl is a component that promotes the initial melting of the glass batch. Furthermore, adding Cl can promote the action of a fining agent. As a result, melting costs can be reduced while the life of a glass manufacturing furnace can be extended. However, if the Cl content is too high, the strain point tends to decrease. Therefore, the Cl content is preferably 0 to 3%, more preferably 0.0005 to 1%, and particularly preferably 0.001 to 0.5%. As a Cl introduction source, alkaline earth metal chlorides such as strontium chloride, aluminum chloride, etc. can be used.

[0058] The alkali-free glass plate of the present invention preferably has the following properties.

[0059] The average thermal expansion coefficient in the temperature range of 30 to 380°C is preferably 20 x 10 －７ ~50 x 10 －７ / ℃, 25 × 10 －７ ~48 x 10 －７ / ℃, 30 × 10 －７ ~45 x 10 －７ / ℃, 33 × 10 －７ ~44 x 10 －７ / °C, especially 35 x 10 －７ ~43 x 10 －７ / ° C. This facilitates matching with the thermal expansion coefficient of Si used in TFTs.

[0060] The Young's modulus is preferably 75 GPa or more, 76 GPa or more, 76.5 GPa or more, 77 GPa or more, 77.5 GPa or more, 78 GPa or more, 78.5 GPa or more, 78.7 GPa or more, 79 GPa or more, 79.5 GPa or more, particularly 80 to 120 GPa. If the Young's modulus is too low, problems due to bending of the glass plate are likely to occur.

[0061] The specific Young's modulus is preferably 28 GPa / g cm －３ Above, 28.5GPa / g・cm －３ Above, 29GPa / g・cm －３Above, 29.5GPa / g・cm －３ Above, 30GPa / g・cm －３ Above, 30.3GPa / g・cm －３ Above, 30.5GPa / g・cm －３ or more, particularly 31 to 37 GPa / g cm －３ If the specific Young's modulus is too low, problems due to bending of the glass sheet are likely to occur.

[0062] The strain point is preferably 680° C. or higher, 685° C. or higher, 687° C. or higher, 690° C. or higher, 692° C. or higher, or 695° C. or higher, particularly 700 to 820° C. In this way, thermal shrinkage of the glass sheet can be suppressed in the LTPS process.

[0063] The annealing point is preferably 730° C. or higher, 732° C. or higher, 735° C. or higher, 738° C. or higher, or 740° C. or higher, particularly 745° C. to 900° C. In this way, thermal shrinkage of the glass sheet can be suppressed in the LTPS process.

[0064] The liquidus temperature is preferably 1400°C or less, 1380°C or less, 1350°C or less, 1300°C or less, 1290°C or less, 1285°C or less, 1280°C or less, 1275°C or less, or 1270°C or less, and particularly 1060 to 1200°C. This makes it easier to prevent devitrification crystals from occurring during glass production, which reduces productivity. Furthermore, since the glass is easier to form using the overflow downdraw method, it is easier to improve the surface quality of the glass sheet and reduce the manufacturing costs of the glass sheet. The liquidus temperature is an indicator of devitrification resistance, and the lower the liquidus temperature, the better the devitrification resistance.

[0065] The liquidus viscosity is preferably 10 ４．２ dPa·s or more, 10 ４．５ dPa·s or more, 10 ４．８ dPa·s or more, 10 ５．１ dPa·s or more, preferably 10 ７．４ dPa・s or less, 10 ７．２ dPa·s or less, particularly 10 ５．２ ~10 ７．０In this way, devitrification is less likely to occur during forming, making it easier to form the glass by the overflow downdraw method, and as a result, it is possible to improve the surface quality of the glass sheet and reduce the manufacturing cost of the glass sheet. The liquidus viscosity is an index of devitrification resistance and formability, and the higher the liquidus viscosity, the more improved the devitrification resistance and formability.

[0066] High temperature viscosity 10 ２．５ The temperature at viscosity dPa·s is preferably 1700°C or less, 1680°C or less, 1650°C or less, particularly 1450 to 1600°C. ２．５ If the temperature at high viscosity 10 dPa·s is too high, it becomes difficult to melt the glass batch, and the manufacturing cost of the glass plate increases. ２．５ The temperature at dPa·s corresponds to the melting temperature, and the lower this temperature is, the more improved the melting property is.

[0067] The β-OH value is an index indicating the amount of water in glass, and reducing the β-OH value can increase the strain point. Furthermore, even when the glass composition is the same, a smaller β-OH value results in a smaller thermal shrinkage at temperatures below the strain point. The β-OH value is preferably 0.35 / mm or less, 0.30 / mm or less, 0.28 / mm or less, 0.25 / mm or less, 0.20 / mm or less, 0.17 / mm or less, and particularly 0.16 / mm or less. If the β-OH value is too small, the meltability tends to decrease. Therefore, the β-OH value is preferably 0.01 / mm or more, particularly 0.03 / mm or more.

[0068] The following methods can be used to lower the β-OH value: (1) Select raw materials with low water content. (2) Add components (Cl, SO) that lower the β-OH value to the glass. ３ (3) To reduce the amount of moisture in the furnace atmosphere. (4) To reduce the amount of N in the molten glass. ２ (5) Use a small melting furnace. (6) Increase the flow rate of molten glass. (7) Use an electric melting method.

[0069] Here, the "β-OH value" refers to a value obtained by measuring the transmittance of glass using an FT-IR (Fourier transform infrared spectrophotometer) and using the following formula:

[0070] β-OH value = (1 / X) log １０ (T １ / T ２ ) X: Plate thickness (mm) T １ :Reference wavelength 3846cm －１ Transmittance (%) at T ２ : Hydroxyl group absorption wavelength 3600 cm －１ Minimum transmittance (%) in the vicinity

[0071] The alkali-free glass sheet of the present invention is preferably formed by the overflow downdraw method. The overflow downdraw method is a method for producing a glass sheet by overflowing molten glass from both sides of a heat-resistant trough-shaped structure, and drawing the overflowing molten glass downward while joining at the lower end of the trough-shaped structure. In the overflow downdraw method, the surface that will become the surface of the glass sheet does not contact the trough-shaped refractory and is formed in a free surface state. Therefore, a glass sheet having an unpolished, fire-polished surface with good surface quality can be produced inexpensively, and thinning is also easy.

[0072] The alkali-free glass plate of the present invention may be formed by a float process, in which case a large glass plate can be produced inexpensively.

[0073] When the alkali-free glass plate of the present invention is used for a magnetic recording medium, the surface is preferably a polished surface. Polishing the glass surface can reduce the total thickness deviation (TTV). As a result, a magnetic film can be properly formed, making the glass suitable as a substrate for a magnetic recording medium. On the other hand, when the glass plate is used for an organic EL device, the surface is preferably a fire-polished surface (unpolished surface) formed by the overflow downdraw method.

[0074] The thickness of the alkali-free glass plate of the present invention is not particularly limited, but when used in an organic EL device, it is preferably less than 0.7 mm, 0.6 mm or less, or less than 0.6 mm, and particularly 0.05 to 0.5 mm. The thinner the plate thickness, the more lightweight the organic EL device can be. The plate thickness can be adjusted by the flow rate and plate drawing speed during glass production. On the other hand, when used in a magnetic recording medium, the plate thickness is preferably 1.5 mm or less, 1.2 mm or less, 0.2 to 1.0 mm, and particularly 0.3 to 0.9 mm. If the plate thickness is too thick, polishing (etching) is required to reach the desired plate thickness, which may increase processing costs.

[0075] When the alkali-free glass plate of the present invention is used in an organic EL device, the average surface roughness Ra of the surface is preferably 1.0 nm or less, 0.5 nm or less, and particularly 0.2 nm or less. If the average surface roughness Ra of the surface is large, it becomes difficult to accurately pattern electrodes, etc. in the display manufacturing process, resulting in an increased probability of circuit electrodes being disconnected or shorted, making it difficult to ensure the reliability of the display, etc. Here, the "average surface roughness Ra of the surface" refers to the average surface roughness Ra of the main surfaces (both surfaces) excluding the end faces, and can be measured, for example, using an atomic force microscope (AFM).

[0076] When the alkali-free glass plate of the present invention is used as a substrate for an organic EL television display panel or a carrier for manufacturing an organic EL display panel, the shape is preferably rectangular. When the alkali-free glass plate of the present invention is used as a substrate for a magnetic recording medium, particularly an energy-assisted magnetic recording medium, it is preferably processed, for example, by cutting, into a disk-shaped substrate. In this case, it is more preferable that the disk substrate have a circular opening formed in the center.

[0077] The present invention will be described below based on examples. Note that the following examples are merely illustrative and the present invention is not limited to the following examples.

[0078] Tables 1 and 2 show examples of the present invention (samples No. 1 to 17).

[0079]

[0080]

[0081] First, glass batches prepared by blending glass raw materials to obtain the glass compositions shown in the table were placed in platinum crucibles and melted at 1600 to 1680°C for 24 hours. The glass batches were homogenized by stirring using a platinum stirrer. The molten glass was then poured onto a carbon plate, formed into a plate, and slowly cooled at a temperature near the annealing point for 30 minutes. Glass samples were thus obtained.

[0082] For each sample obtained, the average coefficient of thermal expansion CTE in the temperature range of 30 to 380°C, density ρ, Young's modulus E, specific Young's modulus E / ρ, strain point Ps, annealing point Ta, softening point Ts, high-temperature viscosity 10 ４ Temperature at dPa·s, high temperature viscosity 10 ３ Temperature at dPa·s, high temperature viscosity 10 ２．５ Temperature in dPa s, liquidus temperature TL, viscosity at liquidus temperature TL, that is, liquidus viscosity log １０ ηTL was evaluated.

[0083] The average coefficient of thermal expansion CTE in the temperature range of 30 to 380° C. is a value measured with a dilatometer.

[0084] The density ρ is a value measured by the well-known Archimedes method.

[0085] The Young's modulus E refers to a value measured by the well-known resonance method.

[0086] The specific Young's modulus E / ρ is the value obtained by dividing the Young's modulus by the density.

[0087] The strain point Ps, annealing point Ta, and softening point Ts are values ​​measured based on the methods of ASTM C336 and C338.

[0088] High temperature viscosity 10 ４ dPa·s, 10 ３ dPa·s, 10 ２．５ The temperature at dPa·s is a value measured by the platinum sphere pull-up method.

[0089] The liquidus temperature TL is the temperature at which crystals precipitate when a glass powder that passes through a standard 30 mesh (500 μm) sieve and remains on a 50 mesh (300 μm) sieve is placed in a platinum boat and held in a temperature gradient furnace for 24 hours.

[0090] liquidus viscosity log １０ ηTL is the viscosity of the glass at the liquidus temperature TL measured by the platinum ball pull-up method.

[0091] As is clear from the table, Samples No. 1 to 17 have glass compositions regulated within a predetermined range, and therefore have Young's modulus of 76.8 GPa or more, strain point of 691°C or more, liquidus temperature of 1206°C or less, liquidus viscosity of 10 ４．７ Therefore, Samples Nos. 1 to 17 are excellent in productivity and have sufficiently high strain points and Young's moduli, making them suitable for use as substrates for organic EL devices and magnetic recording media.

[0092] The alkali-free glass plate of the present invention is suitable as a substrate for an organic EL device, particularly a display panel for an organic EL television, or a carrier for producing an organic EL display panel. The alkali-free glass plate of the present invention is also suitable as a substrate for a display such as a liquid crystal display, a cover glass for an image sensor such as a charge-coupled device (CCD) or a 1:1 proximity solid-state image sensor (CIS), a substrate or cover glass for a solar cell, a substrate for an organic EL lighting device, etc.

[0093] Furthermore, the alkali-free glass plate of the present invention has a sufficiently high strain point and Young's modulus, making it suitable as a glass substrate for magnetic recording media. A high strain point makes it difficult for the glass plate to deform, even when subjected to high-temperature heat treatment such as thermal assistance or laser irradiation. As a result, higher heat treatment temperatures can be used to increase Ku, making it easier to fabricate magnetic recording devices with high recording densities. Furthermore, a high Young's modulus makes it difficult for the glass substrate to bend or flutter during high-speed rotation, thereby preventing collisions between the magnetic recording medium and the magnetic head.

Claims

1. The glass composition is, in mol%, SiO ２ 63-70%, Al ２ O ３ 10-15%, B ２ O ３ 3-8%, Li ２ O+Na ２ O+K ２ O 0-0.5%, MgO 1-11%, CaO 2-11%, SrO 0-6%, BaO 0-8%, MgO+CaO+SrO+BaO 13-20%, mol% ratio SiO ２ / Al ２ O ３ is 4.2 to 7, mol% ratio (MgO+CaO+SrO+BaO) / Al ２ O ３ The alkali-free glass plate is characterized in that 2. The glass composition is, in mol%, SiO ２ 64-68%, Al ２ O ３ 11-14%, B ２ O ３ 4.1-6%, Li ２ O+Na ２ O+K ２ O 0-0.5%, MgO 2-9%, CaO 2-10%, SrO 1-4%, BaO 1-6%, MgO+CaO+SrO+BaO 14-18%, mol% ratio SiO ２ / Al ２ O ３ is more than 5 to 5.4, mol% ratio (MgO + CaO + SrO + BaO) / Al ２ O ３ The alkali-free glass sheet according to claim 1, wherein the viscosity is 1.2 to 1.

6.

3. In mol%, MgO+CaO+SrO+BaO-Al ２ O ３ The alkali-free glass sheet according to claim 1 or 2, characterized in that 4. The alkali-free glass sheet according to claim 1 or 2, characterized in that it contains, by mol %, 2.4% or more of BaO.

5. As in the glass composition ２ O ３ and Sb ２ O ３ The alkali-free glass sheet according to claim 1 or 2, which is substantially free of:

6. SnO in mol% ２ The alkali-free glass sheet according to claim 1 or 2, characterized in that it contains 0.001 to 1% of 7. The alkali-free glass sheet according to claim 1 or 2, characterized in that the strain point is 680° C. or higher.

8. The alkali-free glass sheet according to claim 1 or 2, characterized in that the Young's modulus is 75 GPa or more.

9. Specific Young's modulus is 28 GPa / g cm －３ 3. The alkali-free glass sheet according to claim 1, wherein the alkali-free glass sheet is an alkali-free glass sheet having the above structure.

10. The alkali-free glass sheet according to claim 1 or 2, characterized in that the liquidus temperature is 1,400° C. or lower.

11. The average thermal expansion coefficient in the temperature range of 30 to 380°C is 20 x 10 －７ ~50 x 10 －７ The alkali-free glass plate according to claim 1 or 2, wherein the temperature is 100° C. / ° C.

12. The alkali-free glass sheet according to claim 1 or 2, characterized in that the annealing point is 730° C. or higher.

13. Liquidus viscosity is 10 ４．２ The alkali-free glass plate according to claim 1 or 2, having a viscosity of dPa·s or more.

14. The alkali-free glass sheet according to claim 1 or 2, which is used in an organic EL device.

15. The alkali-free glass plate according to claim 1 or 2, which is used for a magnetic recording medium.

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