Alkali-free glass plate

Abstract

To provide an alkali-free glass panel that has excellent productivity and also has sufficiently high strain points and Young's moduli.SOLUTION: An alkali-free glass panel has a glass composition containing, in mol%, SiO2 64-72%, Al2O3 11-15%, B2O3 0-4%, Li2O+Na2O+K2O 0-0.5%, MgO 5-12%, CaO 7-12%, SrO 0-1%, BaO 0-1%, and MgO+CaO+SrO+BaO 15-19% with the mol% ratio B2O3 / Al2O3 of 0.1-0.4 and the mol% ratio MgO / CaO of 0.1-1.5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to alkali-free glass plates, and more particularly to alkali-free glass plates suitable for organic EL displays. [Background technology]

[0002] Electronic devices such as organic EL displays are thin, offer excellent video display capabilities, and consume low power, making them suitable for applications such as flexible devices and mobile phone displays.

[0003] Glass plates are widely used as substrates for organic EL displays. Glass plates for this application primarily require the following characteristics: (1) In order to prevent the diffusion of alkali ions into the semiconductor material formed during the heat treatment process, the material must contain almost no alkali metal oxides, that is, alkali-free glass (glass in which the alkali oxide content in the glass composition is 0.5 mol% or less). (2) In order to reduce the cost of glass plates, they are formed using the overflow downdraw method, which makes it easier to improve surface quality, and have excellent productivity, in particular excellent meltability and resistance to devitrification, (3) In the LTPS (low temperature polysilicon) process and oxide TFT process, the strain point is high in order to reduce thermal shrinkage of the glass plate.

[0004] Furthermore, various information devices utilize information recording media such as magnetic disks and optical disks.

[0005] Glass plates are widely used as substrates for information recording media, replacing conventional aluminum alloy substrates. In recent years, to meet the need for even higher recording density, magnetic recording media using energy-assisted magnetic recording methods, i.e., energy-assisted magnetic recording media, have been investigated. Energy-assisted magnetic recording media also use glass plates, and magnetic layers are deposited on the surface of the glass plates. 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. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2012-106919 [Patent Document 2] Japanese Patent Publication No. 2021-086643 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0007] Incidentally, OLED devices are also widely used in OLED televisions. There is a strong demand for larger and thinner OLED televisions, and the demand for high-resolution displays such as 8K is also increasing. Therefore, glass plates for these applications need to have thermal dimensional stability that can withstand the demands of high resolution while being large and thin. Furthermore, OLED televisions require low cost in order to reduce the price difference with LCD displays, and glass plates also need to be low cost. However, when glass plates are made larger and thinner, they become more prone to bending, which drives up manufacturing costs.

[0008] Glass plates formed by a glass manufacturer go through processes such as cutting, annealing, inspection, and cleaning. During these processes, the glass plates are loaded into and unloaded from a cassette with multiple shelves. This cassette is usually designed to hold the opposite sides of the glass plate on the shelves formed on the left and right inner surfaces and keep it horizontal. However, for large and thin glass plates, the amount of deflection is large. When loading the glass plate into the cassette, a part of the glass plate may contact the cassette and be damaged, or when unloading, it may swing greatly and become unstable. Since cassettes of this type are also used by electronic device manufacturers, similar problems will occur. To solve this problem, a method of increasing the Young's modulus of the glass plate to reduce the amount of deflection is effective.

[0009] Also, as described above, in the LTPS and oxide TFT processes for obtaining a high-resolution display, it is necessary to increase the strain point of the glass plate in order to reduce the thermal shrinkage of the large glass plate.

[0010] However, when trying to increase the Young's modulus and strain point of the glass plate, the balance of the glass composition is disrupted, productivity decreases, especially the devitrification resistance decreases significantly, and the liquid-phase viscosity increases, so it becomes impossible to form by the overflow down-draw method. Also, the melting property decreases, the forming temperature of the glass increases, and the life of the formed body tends to be short. As a result, the cost of the raw glass plate soars.

[0011] Furthermore, the glass plate for magnetic recording media is required to have high rigidity (Young's modulus) to prevent significant deformation during high-speed rotation. In detail, in a disk-shaped magnetic recording medium, information is written and read along the direction of rotation while the magnetic head moves radially and the medium rotates at high speed around a central axis. In recent years, the rotation speed to increase this writing and reading speed has been increasing from 5400 rpm to 7200 rpm, and even to 10000 rpm. However, in disk-shaped magnetic recording media, positions for recording information are assigned in advance according to the distance from the central axis. Therefore, if the glass plate deforms during rotation, the magnetic head will shift position, making accurate reading difficult.

[0012] In recent years, the Dynamic Flying Height (DFH) mechanism has been incorporated into magnetic heads to significantly reduce the gap between the recording / playback element of the magnetic head and the surface of the magnetic recording medium (reducing the amount of levitation), thereby achieving even higher recording densities. The DFH mechanism is a mechanism that provides a heating element, such as a tiny heater, near the recording / playback element of the magnetic head, causing thermal expansion only around the element towards 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 recording / playback element of the magnetic head and the surface of the magnetic recording medium becomes extremely small, for example, less than 2 nm, there is a risk that the magnetic head may collide with the surface of the magnetic recording medium even with a slight impact. This tendency becomes more pronounced at higher rotation speeds. Therefore, at high rotation speeds, it is important to prevent the bending and fluttering of the glass plate that can cause these collisions.

[0013] Furthermore, in order to increase the degree of orderliness (regularity) of the magnetic layer and achieve a high Ku content, the substrate containing the glass plate may be heat-treated at a high temperature of around 800°C during or before / after deposition of the magnetic layer. As the recording density increases, higher temperatures are required for this heat treatment, thus requiring even higher heat resistance, i.e., a higher strain point, than conventional glass plates for magnetic recording media. In addition, laser irradiation may be performed on the substrate containing the glass plate after deposition of the magnetic layer. Such heat treatment and laser irradiation also serve the purpose of increasing the annealing temperature and coercivity of the magnetic layer containing FePt-based alloys, etc.

[0014] However, as mentioned above, attempting to increase the Young's modulus and strain point of a glass plate disrupts the balance of the glass composition, leading to decreased productivity, a significant decline in devitrification resistance, and an increase in liquid-phase viscosity, making it impossible to mold using the overflow down-draw method. Furthermore, meltability decreases, and the glass molding temperature rises, tending to shorten the lifespan of the molded product. As a result, the cost of raw glass plates skyrockets.

[0015] Therefore, the present invention was devised in view of the above circumstances, and its technical objective is to provide an alkali-free glass plate that is highly productive and has sufficiently high strain point and Young's modulus. [Means for solving the problem]

[0016] The inventors, after conducting various experiments, have found that the above technical problems can be solved by strictly controlling the glass composition of alkali-free glass plates, and propose this as the present invention. Specifically, the alkali-free glass plate of the present invention contains, in mol% terms, SiO2 64-72%, Al2O3 11-15%, B2O3 0-4%, Li2O+Na2O+K2O 0-0.5%, MgO 5-12%, CaO 7-12%, SrO 0-1%, BaO 0-1%, and MgO+CaO+SrO+BaO 15-19%, characterized in that the mol% ratio of B2O3 / Al2O3 is 0.1-0.4 and the mol% ratio of MgO / CaO is 0.1-1.5. Here, "Li2O+Na2O+K2O" refers to the total amount of Li2O, Na2O, and K2O. "MgO+CaO+SrO+BaO" refers to the total amount of MgO, CaO, SrO, and BaO. "MgO / CaO" is the value obtained by dividing the mol% content of MgO by the mol% content of CaO. "B2O3 / Al2O3" is the value obtained by dividing the mol% content of B2O3 by the mol% content of Al2O3.

[0017] Furthermore, the alkali-free glass plate of the present invention preferably contains, in mol% terms, SiO2 64-72%, Al2O3 11-15%, B2O3 0-4%, Li2O+Na2O+K2O 0-0.1%, MgO 6-12%, CaO 7-11%, SrO 0-1%, BaO less than 0-1%, and MgO+CaO+SrO+BaO greater than 15-19%, with a mol% ratio of B2O3 / Al2O3 of 0.12-0.3 and a mol% ratio of MgO / CaO less than 0.5-1.4.

[0018] Furthermore, the alkali-free glass plate of the present invention preferably has a B2O3 content of 2 to 3 mol%. In the manufacturing process of glass plates, there is a step of polishing the edges, but chipping may occur when polishing the edges. This chipping can cause breakage. Therefore, by restricting the B2O3 content to 2 to 3 mol%, chipping is less likely to occur when polishing the edges.

[0019] Furthermore, the alkali-free glass plate of the present invention preferably contains substantially no As2O3 or Sb2O3 in its glass composition, and more preferably contains 0.001 to 1 mol% of SnO2. Here, "substantially free of As2O3" refers to a case where the As2O3 content is 0.05 mol% or less. "Substantially free of Sb2O3" refers to a case where the Sb2O3 content is 0.05 mol% or less.

[0020] Furthermore, the alkali-free glass plate of the present invention preferably has a Young's modulus of 83 GPa or higher, a strain point of 700°C or higher, and a liquidus temperature of 1350°C or lower. Here, "Young's modulus" refers to the value measured by the bending resonance method. Note that 1 GPa is approximately 101.9 kgf / mm². 2 This corresponds to: "Strain point" refers to the value measured according to the ASTM C336 method. "Liquid phase temperature" refers to the temperature at which crystals precipitate after glass powder that has passed through a standard 30-mesh (500 μm) sieve and remained in a 50-mesh (300 μm) sieve is placed in a platinum boat and held in a temperature gradient furnace for 24 hours.

[0021] Furthermore, the alkali-free glass plate of the present invention preferably has a strain point of 715°C or higher.

[0022] Furthermore, it is preferable that the alkali-free glass plate of the present invention has a Young's modulus higher than 84 GPa.

[0023] Furthermore, the alkali-free glass plate of the present invention has a specific Young's modulus of 34 GPa / g·cm². ―3 The above is preferable. Here, "specific Young's modulus" is the value obtained by dividing Young's modulus by density.

[0024] Furthermore, the alkali-free glass plate of the present invention has an average thermal expansion coefficient of 30 × 10 in the temperature range of 30 to 380°C. -7 ~50×10 -7 It is preferable that the temperature is / °C. Here, the "average thermal expansion coefficient in the temperature range of 30 to 380°C" can be measured with a dilatometer.

[0025] Furthermore, the alkali-free glass plate of the present invention has a liquid phase viscosity of 104.0 It is preferable that the viscosity is dPa·s or higher. Here, "liquid-phase viscosity" refers to the viscosity of the glass at the liquid-phase temperature and can be measured by the platinum ball pulling method.

[0026] Furthermore, the alkali-free glass plate of the present invention is preferably rectangular in shape, with its shorter side being 1500 mm or longer.

[0027] Furthermore, the alkali-free glass plate of the present invention is preferably used in organic EL devices.

[0028] Furthermore, the alkali-free glass plate of the present invention is preferably used in a magnetic recording medium. [Brief explanation of the drawing]

[0029] [Figure 1] This is an overhead perspective view showing an example of the shape of a glass substrate for magnetic recording media. [Modes for carrying out the invention]

[0030] The alkali-free glass plate of the present invention is characterized by having the following glass composition: SiO2 64-72%, Al2O3 11-15%, B2O3 0-4%, Li2O+Na2O+K2O 0-0.5%, MgO 5-12%, CaO 7-12%, SrO 0-1%, BaO 0-1%, and MgO+CaO+SrO+BaO 15-19%, with a mol% ratio of MgO / CaO of 0.1-1.5 and a mol% ratio of B2O3 / Al2O3 of 0.1-0.4. The reasons for limiting the content of each component as described above are explained below. In the explanation of the content of each component, the % indicates mol% unless otherwise specified.

[0031] SiO2 is a component that forms the skeleton of glass. If the SiO2 content is too low, the coefficient of thermal expansion increases, and the density increases. Therefore, the lower limit of SiO2 is preferably 64%, more preferably 64.2%, more preferably 64.5%, more preferably 64.8%, more preferably 65%, more preferably 65.5%, more preferably 65.8%, more preferably 66%, more preferably 66.3%, more preferably 66.5%, and most preferably 66.7%. On the other hand, if the SiO2 content is too high, the Young's modulus decreases, the high-temperature viscosity increases, the amount of heat required during melting increases, the melting cost rises, and undissolved SiO2 raw materials may occur, potentially leading to a decrease in yield. In addition, devitrified crystals such as cristobalite tend to precipitate, and the liquid phase viscosity tends to decrease. Therefore, the upper limit of SiO2 is preferably 72%, more preferably 71.8%, more preferably 71.6%, more preferably 71.4%, more preferably 71.2%, more preferably 71%, more preferably 70.8%, more preferably 70.6%, and most preferably 70.4%.

[0032] Al2O3 is a component that forms the skeleton of glass, increases Young's modulus, and raises the strain point. If the Al2O3 content is too low, Young's modulus tends to decrease, and the strain point also tends to decrease. Therefore, the lower limit of Al2O3 is preferably 11%, more preferably 11.2%, more preferably 11.4%, even more preferably more than 11.4%, even more preferably 11.5%, even more preferably 11.6%, even more preferably 11.8%, even more preferably 12%, even more preferably 12.2%, and most preferably 12.5%. On the other hand, if the Al2O3 content is too high, devitrified crystals such as mullite tend to precipitate, and the liquid phase viscosity tends to decrease. Therefore, the upper limit of Al2O3 is preferably 15%, more preferably 14.8%, 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%.

[0033] B2O3 is a component that enhances chipping resistance and can also enhance meltability and devitrification resistance. Therefore, the lower limit of B2O3 is preferably 0%, more preferably greater than 0%, more preferably 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 0.6%, even more preferably 0.8%, even more preferably 0.9%, even more preferably 1%, even more preferably 1.2%, even more preferably 1.5%, even more preferably 1.8%, even more preferably 2%, and most preferably greater than 2%. On the other hand, if the B2O3 content is too high, the Young's modulus and strain point tend to decrease. Therefore, the upper limit of B2O3 is preferably 4%, more preferably 3.9%, even more preferably 3.8%, even more preferably 3.7%, even more preferably 3.6%, even more preferably 3.5%, even more preferably 3.4%, even more preferably 3.3%, even more preferably 3.2%, and most preferably 3%.

[0034] The mol% ratio of B2O3 / Al2O3 is an important component ratio for increasing Young's modulus and lowering high-temperature viscosity. If the mol% ratio of B2O3 / Al2O3 is too low, the high-temperature viscosity increases, which tends to increase the manufacturing cost of glass plates. Therefore, the lower limit of the mol% ratio of B2O3 / Al2O3 is preferably 0.1, more preferably 0.11, even more preferably 0.12, even more preferably 0.13, even more preferably 0.14, even more preferably 0.15, even more preferably 0.16, even more preferably 0.17, even more preferably 0.18, and most preferably 0.2. On the other hand, if the mol% ratio of B2O3 / Al2O3 is too high, Young's modulus tends to decrease. Therefore, the upper limit of the mol% ratio of B2O3 / Al2O3 is preferably 0.4, more preferably less than 0.4, even more preferably 0.38, even more preferably 0.36, even more preferably 0.34, even more preferably 0.32, and most preferably 0.3.

[0035] Li2O, Na2O, and K2O are components that are inevitably mixed in from the glass raw materials, and their combined amount is 0 to 0.5%, preferably 0 to 0.1%, more preferably 0 to 0.09%, even more preferably 0.005 to 0.08%, even more preferably 0.008 to 0.06%, and most preferably 0.01 to 0.05%. If the combined amount of Li2O, Na2O, and K2O is too high, there is a risk that alkali ions will diffuse into the semiconductor material formed during the heat treatment process. The individual contents of Li2O, Na2O, and K2O are preferably 0 to 0.3%, more preferably 0 to 0.1%, even more preferably 0 to 0.08%, even more preferably 0 to 0.07%, even more preferably 0 to 0.05%, and most preferably 0.001 to 0.04%, respectively.

[0036] MgO is a component that significantly increases Young's modulus among alkaline earth metal oxides. If the MgO content is too low, mellowness and Young's modulus tend to decrease. Therefore, the lower limit of MgO is preferably 5%, more preferably 5.1%, more preferably 5.3%, even more preferably 5.5%, even more preferably 5.6%, even more preferably 5.7%, even more preferably 5.8%, and most preferably 6%. On the other hand, if the MgO content is too high, devitrified crystals such as mullite tend to precipitate, and the liquid phase viscosity tends to decrease. Therefore, the upper limit of MgO is preferably 12%, more preferably 11.8%, more preferably 11.5%, more preferably 11.3%, more preferably 11%, more preferably less than 11%, more preferably 10.8%, more preferably 10.6%, even more preferably 10.4%, even more preferably 10.2%, even more preferably 10%, and most preferably 9.8%.

[0037] The mol% ratio of B2O3 / MgO is an important component ratio for increasing Young's modulus and lowering high-temperature viscosity. If the mol% ratio of B2O3 / MgO is too low, the high-temperature viscosity increases, which tends to increase the manufacturing cost of glass plates. Therefore, the lower limit of the mol% ratio of B2O3 / MgO is preferably 0.10, more preferably 0.13, even more preferably 0.14, even more preferably 0.15, even more preferably 0.16, even more preferably 0.17, even more preferably 0.18, even more preferably 0.19, even more preferably 0.20, and most preferably 0.21. On the other hand, if the mol% ratio of B2O3 / MgO is too high, Young's modulus tends to decrease. Therefore, the upper limit of the mol% ratio of B2O3 / MgO is preferably 0.50, more preferably 0.48, even more preferably 0.46, even more preferably 0.45, even more preferably 0.44, even more preferably 0.43, and most preferably 0.42. Note that "B2O3 / MgO" is the value obtained by dividing the mol% content of B2O3 by the mol% content of MgO.

[0038] CaO is a component that significantly increases meltability by lowering high-temperature viscosity without reducing the strain point. It is also a component that increases Young's modulus. If the CaO content is too low, meltability tends to decrease. Therefore, the lower limit of CaO is preferably 7%, more preferably more than 7%, more preferably 7.1%, even more preferably 7.2%, even more preferably 7.3%, even more preferably 7.4%, even more preferably 7.5%, even more preferably 7.6%, and most preferably 8%. On the other hand, if the CaO content is too high, the liquidus temperature will rise. Therefore, the upper limit of CaO is preferably 12%, more preferably 11.9%, more preferably 11.8%, more preferably 11.6%, more preferably 11.5%, even more preferably 11.4%, even more preferably 11.3%, and most preferably 11%.

[0039] The mol% ratio of MgO / CaO is an important component ratio for increasing Young's modulus. If the mol% ratio of MgO / CaO is too low, Young's modulus tends to be low. Therefore, the lower limit of the mol% ratio of MgO / CaO is preferably 0.1, more preferably 0.15, even more preferably 0.2, even more preferably 0.25, even more preferably 0.3, even more preferably 0.34, even more preferably 0.36, even more preferably 0.4, even more preferably 0.42, even more preferably 0.44, even more preferably 0.46, even more preferably 0.48, and most preferably 0.5. On the other hand, if the mol% ratio of MgO / CaO is too high, the liquid phase viscosity decreases, and the manufacturing cost of the glass plate tends to increase. Therefore, the upper limit of the mol% ratio of MgO / CaO is preferably 1.5, more preferably less than 1.5, even more preferably 1.45, even more preferably 1.4, and most preferably less than 1.4.

[0040] SrO is not an essential component, but it enhances devitrification resistance, lowers high-temperature viscosity without reducing the strain point, and improves meltability. It also suppresses the decrease in liquid-phase 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%, and most preferably 0.5%. On the other hand, if the SrO content is too high, the coefficient of thermal expansion and density tend to increase. Therefore, the upper limit of SrO is preferably 1%, more preferably less than 1%, even more preferably 0.9%, even more preferably 0.8%, even more preferably 0.7%, and most preferably 0.6%.

[0041] BaO is not an essential component, but it is a component that enhances resistance to devitrification. 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 more than 0.4%, and most preferably 0.5%. 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 increases, and the glass plate becomes more prone to bending. Therefore, the upper limit of BaO is preferably 1%, more preferably less than 1%, more preferably 0.9%, even more preferably less than 0.9%, even more preferably 0.8%, even more preferably less than 0.8%, and most preferably 0.7%.

[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 15%, more preferably more than 15%, more preferably 15.1%, even more preferably more than 15.1%, even more preferably 15.2%, even more preferably 15.3%, even more preferably 15.4%, even more preferably more than 15.4%, and most preferably 15.5%. 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 19%, more preferably less than 19%, more preferably 18.9%, even more preferably less than 18.9%, even more preferably 18.8%, even more preferably less than 18.8%, and most preferably 18.7%.

[0043] The mol% ratio (B2O3+SrO+BaO) / Al2O3 is an important component ratio for increasing Young's modulus and lowering high-temperature viscosity. If the mol% ratio (B2O3+SrO+BaO) / Al2O3 is too low, the high-temperature viscosity increases, which tends to drive up the manufacturing cost of glass plates. Therefore, the lower limit of the mol% ratio (B2O3+SrO+BaO) / Al2O3 is preferably 0.1, more preferably 0.11, even more preferably 0.12, even more preferably 0.13, even more preferably 0.14, even more preferably 0.15, even more preferably 0.16, even more preferably 0.17, even more preferably 0.18, and most preferably 0.2. On the other hand, if the mol% ratio (B2O3+SrO+BaO) / Al2O3 is too high, Young's modulus tends to decrease. Therefore, the upper limit of the mol% ratio (B2O3+SrO+BaO) / Al2O3 is preferably 0.4, more preferably less than 0.4, even more preferably 0.38, even more preferably 0.36, even more preferably 0.34, even more preferably 0.32, and most preferably 0.3.

[0044] The mol% ratio (B2O3+SrO+BaO) / MgO is an important component ratio for increasing Young's modulus and lowering high-temperature viscosity. If the mol% ratio (B2O3+SrO+BaO) / MgO is too low, the high-temperature viscosity increases, which tends to drive up the manufacturing cost of glass plates. Therefore, the lower limit of the mol% ratio (B2O3+SrO+BaO) / MgO is preferably 0.10, more preferably 0.13, even more preferably 0.14, even more preferably 0.15, even more preferably 0.16, even more preferably 0.17, even more preferably 0.18, even more preferably 0.19, even more preferably 0.20, and most preferably 0.21. On the other hand, if the mol% ratio (B2O3+SrO+BaO) / MgO is too high, Young's modulus tends to decrease. Therefore, the upper limit of the mol% ratio (B2O3+SrO+BaO) / MgO is preferably 0.50, more preferably 0.48, even more preferably 0.46, even more preferably 0.45, even more preferably 0.44, even more preferably 0.43, and most preferably 0.42. Note that "(B2O3+SrO+BaO) / MgO" is the value obtained by dividing the total mol% content of B2O3, SrO, and BaO by the mol% content of MgO.

[0045] A suitable glass composition range can be achieved by appropriately combining the preferred content ranges of each component. However, in order to optimize the effects of the present invention, it is particularly preferable that the glass composition contains, in mol% terms, SiO2 64-72%, Al2O3 11-15%, B2O3 0-4%, Li2O+Na2O+K2O 0-0.1%, MgO 6-12%, CaO 7-11%, SrO 0-1%, BaO less than 0-1%, and MgO+CaO+SrO+BaO greater than 15-19%, with a mol% ratio of MgO / CaO of 0.5-1.4 and a mol% ratio of B2O3 / Al2O3 of 0.12-0.3.

[0046] In addition to the above components, the following components may be added as optional components. However, from the viewpoint of effectively enjoying the effects of the present invention, the total amount of other components is preferably 10% or less, and particularly preferably 5% or less.

[0047] P2O5 is a component that increases the strain point and can significantly suppress the precipitation of devitrified crystals of alkaline earth aluminosilicates such as anorthite. However, if a large amount of P2O5 is included, the glass will be more prone to phase separation. The P2O5 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%, and particularly preferably less than 0 to 0.1%.

[0048] TiO2 is a component that lowers high-temperature viscosity and increases meltability, as well as suppressing solarization. However, if a large amount of TiO2 is included, the glass tends to become discolored and its transmittance decreases. The TiO2 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 included, the glass becomes more prone to devitrification and the strain point tends to decrease. The ZnO content is preferably 0-6%, more preferably 0-5%, even more preferably 0-4%, and particularly preferably less than 0-3%.

[0050] Fe2O3 is an unavoidable component of glass raw materials and also reduces electrical resistivity. The Fe2O3 content is preferably 0 to 300 ppm by mass, 50 to 250 ppm by mass, and particularly 80 to 200 ppm by mass. If the Fe2O3 content is too low, raw material costs tend to increase. On the other hand, if the Fe2O3 content is too high, the electrical resistivity of the molten glass increases, making electromelting difficult.

[0051] ZrO2 is a component that increases Young's modulus. However, if a large amount of ZrO2 is included, the glass becomes more prone to devitrification. The ZrO2 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] Y2O3, Nb2O5, and La2O3 have the effect of increasing the strain point, Young's modulus, etc. The combined amount and individual content of these components are preferably 0-5%, more preferably 0-1%, even more preferably 0-0.5%, and particularly preferably less than 0-0.5%. If the combined amount and individual content of Y2O3, Nb2O5, and La2O3 are too high, the density and raw material costs tend to increase.

[0053] SnO2 is a component that exhibits good clarification properties in the high-temperature range, as well as a component that increases the strain point and reduces high-temperature viscosity. The preferred SnO2 content is 0-1%, 0.001-1%, 0.01-0.5%, and particularly 0.05-0.3%. If the SnO2 content is too high, devitrified crystals of SnO2 tend to precipitate. If the SnO2 content is less than 0.001%, it becomes difficult to enjoy the above effects.

[0054] As described above, SnO₂ is suitable as a fining agent. As long as the glass properties are not impaired, as a fining agent, instead of SnO₂ or together with SnO₂, F, SO₃, C, or metal powders such as Al and Si can be added up to 5% each (preferably up to 1%, particularly up to 0.5%). Further, as fining agents, CeO₂, F, etc. can also be added up to 5% each (preferably up to 1%, particularly up to 0.5%).

[0055] As₂O₃ and Sb₂O₃ are also effective as fining agents. However, As₂O₃ and Sb₂O₃ are components that increase the environmental load. Also, As₂O₃ is a component that reduces the solarization resistance. Therefore, it is preferable that the alkali-free glass sheet of the present invention does not substantially contain these components.

[0056] Cl is a component that promotes the initial melting of the glass batch. Also, by adding Cl, the action of the fining agent can be promoted. As a result of these, while reducing the melting cost, the long life of the glass manufacturing furnace can be achieved. 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%, particularly preferably 0.001 to 0.5%. In addition, as a raw material for introducing Cl, chlorides of alkaline earth metal oxides such as strontium chloride, or raw materials such as aluminum chloride can be used.

[0057] The alkali-free glass sheet of the present invention preferably has the following characteristics.

[0058] The average thermal expansion coefficient in the temperature range of 30 to 380 °C is preferably 30×10 -7 ~50×10 -7 / °C, 32×10 -7 ~48×10 -7 / °C, 33×10 -7 ~45×10 -7 / °C, 34×10 -7 ~44×10 -7 / °C, particularly 35×10 -7 ~43×10 -7The value is / °C. This makes it easier to match the thermal expansion coefficient of Si used in TFTs.

[0059] The Young's modulus is preferably 83 GPa or higher, greater than 83 GPa, 83.3 GPa or higher, 83.5 GPa or higher, 83.8 GPa or higher, 84 GPa or higher, 84.3 GPa or higher, 84.5 GPa or higher, 84.8 GPa or higher, 85 GPa or higher, 85.3 GPa or higher, 85.5 GPa or higher, and especially greater than 85.5 to 120 GPa. If the Young's modulus is too low, defects caused by the bending of the glass plate are more likely to occur.

[0060] The specific Young's modulus is preferably 32 GPa / g·cm. ―3 Above, 32.5 GPa / g cm ―3 Above, 33GPa / g cm ―3 Above, 33.3 GPa / g cm ―3 Above, 33.5 GPa / g cm ―3 Above, 33.8 GPa / g cm ―3 Above, 34GPa / g cm ―3 Above, 34GPa / g cm ―3 Ultra, 34.2GPa / g cm ―3 Above, 34.4 GPa / g cm ―3 In particular, the range of 34.5-37 GPa / g·cm² ―3 Therefore, if the Young's modulus is too low, problems caused by the bending of the glass plate are more likely to occur.

[0061] The strain point is preferably 715°C or higher, 717°C or higher, 720°C or higher, 723°C or higher, 725°C or higher, 727°C or higher, and particularly 730-820°C. In this way, thermal shrinkage of the glass plate can be suppressed in the LTPS process.

[0062] The liquidus temperature is preferably 1350°C or lower, less than 1350°C, 1300°C or lower, 1290°C or lower, 1285°C or lower, 1280°C or lower, 1275°C or lower, 1270°C or lower, 1160°C or higher, 1170°C or higher, and particularly 1180 to 1260°C. This makes it easier to prevent the formation of devitrified crystals during glass manufacturing, which would reduce productivity. Furthermore, it makes it easier to form using the overflow down-draw method, thus improving the surface quality of the glass plate and reducing the manufacturing cost of the glass plate. Note that the liquidus temperature is an indicator of devitrification resistance; the lower the liquidus temperature, the better the devitrification resistance.

[0063] The liquid phase viscosity is preferably 10 4.0 dPa·s or higher, 10 4.2 dPa·s or higher, 10 4.4 dPa·s or higher, 10 7.4 dPa·s or less, 10 7.2 dPa·s or less, especially 10 4.5 ~10 7.0 The viscosity is dPa·s. This method makes devitrification less likely to occur during molding, making it easier to mold using the overflow down-draw method. As a result, it is possible to improve the surface quality of the glass plate and reduce the manufacturing cost of the glass plate. Note that liquid-phase viscosity is an indicator of devitrification resistance and moldability; the higher the liquid-phase viscosity, the better the devitrification resistance and moldability.

[0064] High temperature viscosity 10 2.5 The temperature at dPa·s is preferably 1650°C or lower, 1630°C or lower, 1610°C or lower, 1450°C or higher, 1470°C or higher, 1490°C or higher, and particularly 1500-1600°C. High-temperature viscosity 10 2.5 If the temperature at dPa·s is too high, it becomes difficult to melt the glass batch, and the manufacturing cost of the glass plates increases. 2.5 The temperature in dPa·s corresponds to the melting temperature, and the lower this temperature, the better the meltability.

[0065] The β-OH value is an indicator of the water content in the glass, and lowering the β-OH value can raise the strain point. Furthermore, even with the same glass composition, a smaller β-OH value results in a smaller thermal shrinkage rate 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, and particularly 0.20 / mm or less. However, if the β-OH value is too low, the meltability tends to decrease. Therefore, the β-OH value is preferably 0.01 / mm or more, and particularly 0.03 / mm or more.

[0066] The following methods can be used to reduce the β-OH value: (1) Select raw materials with low water content. (2) Add components that reduce the β-OH value (Cl, SO3, etc.) to the glass. (3) Reduce the amount of moisture in the furnace atmosphere. (4) Perform N2 bubbling in the molten glass. (5) Use a small melting furnace. (6) Increase the flow rate of molten glass. (7) Use an electromelting method.

[0067] Here, the "β-OH value" refers to the value obtained by measuring the transmittance of the glass using FT-IR and using the following formula 1.

[0068] [Mathematics 1] β-OH value = (1 / X)log(T1 / T2) X: Plate thickness (mm) T1: Reference wavelength 3846cm -1 Transmittance (%) T2: Hydroxyl group absorption wavelength 3600 cm -1 Minimum transmittance in the vicinity (%)

[0069] The alkali-free glass plate of the present invention is preferably formed by the overflow downdraw method. The overflow downdraw method is a method of manufacturing a glass plate by allowing molten glass to overflow from both sides of a heat-resistant trough-shaped structure, and then stretching and forming the overflowed molten glass downwards while it converges at the lower end of the trough-shaped structure. In the overflow downdraw method, the surface that will become the surface of the glass plate does not come into contact with the trough-shaped refractory material and is formed in a free surface state. Therefore, it is possible to manufacture glass plates with good surface quality without polishing at low cost, and it is also easy to make them thinner.

[0070] The alkali-free glass plate of the present invention may also be formed by the float process. This allows for the inexpensive manufacture of large glass plates.

[0071] The alkali-free glass plate of the present invention preferably has a polished surface. Polishing the glass surface can reduce the overall plate thickness deviation TTV. As a result, a magnetic film can be properly formed, making it suitable as a substrate for magnetic recording media.

[0072] In the alkali-free glass plate of the present invention, the plate thickness is not particularly limited, but when used in organic EL devices, a thickness of less than 0.7 mm, 0.6 mm or less, less than 0.6 mm, and particularly 0.05 to 0.5 mm is preferred. The thinner the plate thickness, the lighter the organic EL device can be made. The plate thickness can be adjusted by the flow rate and plate drawing speed during glass manufacturing. On the other hand, when used in magnetic recording media, 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, etching to the desired plate thickness is required, which may increase processing costs.

[0073] The alkali-free glass plate of the present invention is rectangular, and preferably has a shorter side of 1500 mm or more. In display applications, multiple devices are fabricated on the glass plate, and then each device is cut separately to reduce costs (so-called chamfering). The larger the shorter side dimension of the glass plate, the more advantageous it is for chamfering.

[0074] In the alkali-free glass plate of the present invention, 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 and the like in the display manufacturing process, which increases the probability of circuit electrodes breaking or short-circuiting, making it difficult to ensure the reliability of the display and the like. Here, "average surface roughness Ra of the surface" refers to the average surface roughness Ra of the main surface (both surfaces) excluding the edge face, and can be measured, for example, with an atomic force microscope (AFM). [Examples]

[0075] The present invention will be described below based on examples. Note that the following examples are merely illustrative. The present invention is not limited in any way to the following examples.

[0076] Tables 1 and 2 show examples of the present invention (samples No. 1 to 21).

[0077] [Table 1]

[0078] [Table 2]

[0079] First, glass batches prepared with glass raw materials to achieve the glass composition shown in the table were placed in a platinum crucible and melted at 1600-1650°C for 24 hours. During the melting of the glass batches, a platinum stirrer was used to stir and homogenize them. Next, the molten glass was poured onto a carbon plate, formed into a plate shape, and then slowly cooled at a temperature near the annealing point for 30 minutes. For each obtained sample, the average thermal expansion coefficient CTE, density ρ, Young's modulus E, specific Young's modulus E / ρ, strain point Ps, annealing point Ta, softening point Ts, and high-temperature viscosity 10 were recorded in the temperature range of 30-380°C. 4 Temperature and high-temperature viscosity at dPa·s 10 3 Temperature and high-temperature viscosity at dPa·s 10 2.5Temperature in dPa·s, liquidus temperature TL, and viscosity log at liquidus temperature TL. 10 We evaluated ηTL.

[0080] The average thermal expansion coefficient CTE in the temperature range of 30 to 380°C is the value measured using a dilatometer.

[0081] The density ρ is a value measured by the well-known Archimedes method.

[0082] Young's modulus E refers to the value measured using a well-known resonance method.

[0083] The relative Young's modulus E / ρ is the value obtained by dividing Young's modulus by density.

[0084] The strain point Ps, slow cooling point Ta, and softening point Ts were measured according to the ASTM C336 and C338 methods.

[0085] High temperature viscosity 10 4 dPa·s, 10 3 dPa·s, 10 2.5 The temperature in dPa·s was measured using the platinum ball pulling method.

[0086] The liquidus temperature TL is the temperature at which crystals precipitate after the glass powder that passes through a standard 30-mesh (500 μm) sieve and remains in a 50-mesh (300 μm) sieve is placed in a platinum boat and held in a temperature gradient furnace for 24 hours.

[0087] liquidus viscosity log 10 ηTL is the viscosity of the glass at the liquidus temperature TL, measured using the platinum ball pulling method.

[0088] As is clear from the table, since the glass composition of samples No. 1 to 21 is restricted to a predetermined range, the Young's modulus is 85 GPa or higher, the strain point is 722°C or higher, the liquidus temperature is 1260°C or lower, and the liquidus viscosity is 10 4.3 The strain point is dPa·s or higher. Therefore, samples No. 1 to 21 are suitable as substrates for organic EL devices because they have excellent productivity and sufficiently high strain points and Young's moduli. [Industrial applicability]

[0089] The alkali-free glass plate of the present invention is suitable as a substrate for organic EL devices, particularly for display panels for organic EL televisions, and as a carrier for manufacturing organic EL display panels. In addition, it is also suitable as a cover glass for flat panel display substrates such as liquid crystal displays, charge-coupled elements (CCDs), image sensors such as 1:1 proximity solid-state image sensors (CIS), substrates and cover glass for solar cells, and substrates for organic EL lighting.

[0090] Furthermore, the alkali-free glass plate of the present invention is suitable as a substrate for magnetic recording media because it has a sufficiently high strain point and Young's modulus. A high strain point makes it difficult for the glass plate to deform even when subjected to high-temperature heat treatment such as heat assist or laser irradiation. As a result, higher heat treatment temperatures can be used when increasing Ku content, making it easier to manufacture magnetic recording devices with high recording density. In addition, a high Young's modulus makes it difficult for the glass plate to bend or flutter during high-speed rotation, thus preventing collisions between the information recording medium and the magnetic head. [Explanation of symbols]

[0091] 1 disk board

Claims

1. As a glass composition, in mol%, SiO ２ 64 to 72%, Al ２ O ３ 11 to 15%, B ２ O ３ 1.70 to 4%, Li ２ O + Na ２ O + K ２ O 0 to 0.5%, MgO 7.00 to 12%, CaO 7 to 12%, SrO 0 to 1%, BaO 0 to 1%, MgO + CaO + SrO + BaO 15 to 19%, and the mol% ratio of B ２ O ３ / Al ２ O ３ is 0.1 to 0.4, the mol% ratio of MgO / CaO is 0.1 to 1.5, the β-OH value is 0.35 / mm or less, and the strain point is 727 °C or higher. The alkali-free glass sheet is characterized by these features.

2. The glass composition is SiO2 in mol%. ２ 64-72%, Al ２ O ３ 11-15%, B ２ O ３ 1.70-4%, Li ２ O + Na ２ O+K ２ It contains O 0-0.1%, MgO 7.00-12%, CaO 7-11%, SrO 0-1%, BaO 0-1%, and MgO + CaO + SrO + BaO 15-19%, with a mol% ratio of B ２ O ３ / Al ２ O ３ An alkali-free glass plate characterized by having a methylnyl chloride ratio of 0.12 to 0.3, a mol% ratio of MgO / CaO of 0.5 to less than 1.4, a β-OH value of 0.35 / mm or less, and a strain point of 727°C or higher.

3. B ２ O ３ The alkali-free glass plate according to claim 1 or 2, characterized in that the content of is 2 to 3 mol%.

4. The glass composition contains substantially as ２ O ３ Sb ２ O ３ It does not contain SnO ２ An alkali-free glass plate according to any one of claims 1 to 3, characterized by containing 0.001 to 1 mol% of [the specified substance].

5. An alkali-free glass plate according to any one of claims 1 to 4, characterized in that it has a Young's modulus of 83 GPa or more and a liquidus temperature of 1350°C or less.

6. The alkali-free glass plate according to any one of claims 1 to 5, characterized in that its Young's modulus is higher than 84 GPa.

7. The relative Young's modulus is 34 GPa / g·cm －３ The alkali-free glass plate according to any one of claims 1 to 6, characterized in that it is as described above.

8. The average coefficient of thermal expansion in the temperature range of 30 to 380°C is 30 × 10⁻⁶. －７ ~50 x 10 －７ The alkali-free glass plate according to any one of claims 1 to 7, characterized in that it is / ℃.

9. Liquid phase viscosity is 10 ４．０ An alkali-free glass plate according to any one of claims 1 to 8, characterized in that it has a pH of dPa·s or higher.

10. An alkali-free glass plate according to any one of claims 1 to 9, characterized in that it is rectangular in shape and its shorter side is 1500 mm or longer.

11. An alkali-free glass plate according to any one of claims 1 to 10, characterized in that it is used in an organic EL device.

12. An alkali-free glass plate according to any one of claims 1 to 10, characterized in that it is used in a magnetic recording medium.

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