Alkali-free glass plate

Abstract

The alkali-free glass plate according to the present invention is characterized by containing, in mol%, 65 to 72% of SiO2, 11 to 15% of Al2O3, 2 to 5% of B2O3, 0 to 0.5% of Li2O + Na2O + K2O, 2 to 8% of MgO, 4 to 10% of CaO, 0 to 4% of SrO, 0 to 4% of BaO, and 11 to 17% of MgO + CaO + SrO + BaO, and satisfying the following conditions: mol% ratio (MgO + CaO + SrO + BaO-Al2O3) / B2O3 is 0.2 to 1, mol% ratio of SrO / CaO is 0 to 0.6, mol% ratio of BaO / CaO is 0 to 0.6, and 0.116 * [Al2O3]-0.079 * [B2O3] + 0.155 * [CaO] + 0.336 *

Description

Technical Field

[0001] The present invention relates to an alkali-free glass plate, and more particularly to an alkali-free glass plate suitable for an organic EL display and an information recording medium. Background Art

[0002] Electronic devices such as organic EL displays are used in applications such as flexible devices and mobile phone displays because they are thin, have excellent dynamic display capabilities, and consume little power.

[0003] Glass plates are widely used as substrates for organic EL displays. Glass plates for this purpose are mainly required to have the following properties.

[0004] (1) In order to prevent alkaline ions from diffusing into the semiconductor material being formed during the heat treatment process, alkali-free glass (glass containing 0.5 mol% or less of alkaline metal oxides) is used.

[0005] (2) To make glass sheets cheaper, the overflow down-draw method is used to form glass sheets, which can easily improve the surface quality and has excellent productivity, especially excellent melting properties and resistance to devitrification.

[0006] (3) In the LTPS (low temperature poly silicon) process and the oxide TFT process, the strain point is high in order to reduce the thermal shrinkage of the glass plate.

[0007] In addition, information recording media such as magnetic disks and optical disks are used in various information devices.

[0008] As a substrate for information recording media, glass plates are widely used instead of existing aluminum alloy substrates. In recent years, in order to meet the demand for higher recording density, magnetic recording media using energy-assisted magnetic recording, i.e., energy-assisted magnetic recording media, have been studied. Regarding energy-assisted magnetic recording media, glass plates are also used, and a magnetic layer is formed on the surface of the glass plate. In energy-assisted magnetic recording media, an ordered alloy with a large magnetic anisotropy coefficient Ku (hereinafter referred to as "high Ku") is used as the magnetic material of the magnetic layer.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Publication No. 2012-106919

[0012] Patent Document 2: Japanese Patent Application Publication No. 2021-086643

[0013] Patent Document 3: Japanese Patent No. 3804111 Summary of the invention

[0014] Problems to be solved by the invention

[0015] However, organic EL devices are also widely used in organic EL TVs. Organic EL TVs are strongly required to be larger and thinner, and there is a growing demand for high-resolution displays such as 8K. Therefore, the glass plates for these uses need to be larger and thinner, while also requiring thermal dimensional stability that can withstand the high-resolution requirements. In addition, in organic EL TVs, low costs are required to reduce the price difference with liquid crystal displays, and low costs are also required for glass plates. However, if the glass plate is larger and thinner, it is easy to bend, and the manufacturing cost rises sharply.

[0016] The glass plates formed by the glass manufacturing plant go through the processes of cutting, annealing, inspection, and cleaning. During these processes, the glass plates are loaded and unloaded in a cassette formed with multi-layer shelves. The cassette usually places the two opposite sides of the glass plate on the shelves formed by the inner surfaces of the left and right sides of the cassette, so that it can be held in the horizontal direction. Large and thin glass plates have a large amount of deflection, so when the glass plates are loaded into the cassette, part of the glass plates come into contact with the cassette and are easily damaged, or when they are unloaded, they are prone to swinging greatly and becoming unstable. This type of cassette is also used in electronic device manufacturers, so the same problem occurs. In order to solve this problem, an effective method is to increase the Young's modulus of the glass plate and reduce the deflection.

[0017] In addition, as described above, in LTPS and oxide TFT processes for obtaining high-resolution displays, in order to reduce the thermal shrinkage of a large glass plate, it is necessary to increase the strain point of the glass plate.

[0018] However, if the Young's modulus and strain point of the glass sheet are increased, the glass composition becomes unbalanced, productivity decreases, and in particular, the devitrification resistance decreases significantly, and the liquid phase viscosity increases, so that the overflow down-draw method cannot be used for forming. In addition, the melting property decreases, or the forming temperature of the glass increases, and the life of the formed body tends to be shortened. As a result, the original plate cost of the glass sheet increases.

[0019] In addition, if the Young's modulus and strain point of the glass plate are increased, its durability against buffered hydrofluoric acid (BHF) mainly composed of hydrofluoric acid, ammonium fluoride, etc., which is used for etching SiOx or SiNx, will decrease. As a result, the glass is easily etched in the LTPS and oxide TFT processes, and there is a possibility of white turbidity.

[0020] In addition, the glass plate for magnetic recording media needs to have high rigidity (Young's modulus) to avoid huge deformation during high-speed rotation. If described in detail, in a disc-shaped magnetic recording medium, the medium is rotated at high speed around the central axis, and at the same time, the magnetic head is moved in the radial direction while writing and reading information in the direction of rotation. In recent years, in order to increase its writing speed and reading speed, the rotation speed has developed in the direction of high speed, from 5400rpm to 7200rpm, and further to 10000rpm. Moreover, in a disc-shaped magnetic recording medium, the position of the recorded information is allocated in advance according to the distance from the central axis. Therefore, if the glass plate is deformed during rotation, the position of the magnetic head will be offset, and it will be difficult to read accurately.

[0021] In addition, in recent years, a DFH (Dynamic Flying Height) mechanism is being installed on the magnetic head to significantly reduce the gap between the recording and reproducing element of the magnetic head and the surface of the magnetic recording medium (reduce the amount of suspension), thereby achieving a higher recording density. The so-called DFH mechanism is a mechanism in which a very small heating unit such as a heater is set near the recording and reproducing element of the magnetic head, and only the periphery of the element unit is thermally expanded toward the surface of the medium. By having such a mechanism, the distance between the magnetic head and the magnetic layer of the medium is close, so it is possible to pick up signals of smaller magnetic particles, and high-density recording can be achieved. On the other hand, because the gap between the recording and reproducing element of the magnetic head and the surface of the magnetic recording medium becomes extremely small, for example, less than 2nm, even a slight impact may cause the magnetic head to collide with the surface of the magnetic recording medium. This tendency is more significant at higher speeds. Therefore, when rotating at high speeds, it is important to prevent the occurrence of bending and shaking (trembling) of the glass plate as the cause of this collision.

[0022] In addition, in order to increase the degree of order (order) of the magnetic layer and achieve high Ku, the substrate including the glass plate is heat treated at a high temperature of about 800°C during the formation of the magnetic layer or before and after the formation of the film. The higher the recording density, the higher the heat treatment temperature needs to be, so it is required to have higher heat resistance than the existing glass plate for magnetic recording media, that is, a high strain point. In addition, after the magnetic layer is formed, the substrate including the glass plate is also irradiated with a laser. Such heat treatment and laser irradiation are aimed at increasing the annealing temperature and coercive force of the magnetic layer containing FePt alloys, etc.

[0023] However, as mentioned above, if the Young's modulus and strain point of the glass sheet are increased, the glass composition becomes unbalanced, the productivity decreases, and in particular, the devitrification resistance decreases significantly, and the liquidus temperature increases, so that the overflow down-draw method cannot be used for forming. In addition, the melting property decreases, or the forming temperature of the glass increases, and the life of the formed body is easily shortened. As a result, the original plate cost of the glass sheet increases.

[0024] Therefore, the present invention has been made in view of the above circumstances, and a technical object of the present invention is to provide an alkali-free glass plate having excellent productivity, high durability against BHF, and sufficiently high strain point and Young's modulus.

[0025] Means of solving the problem

[0026] (1) The alkali-free glass plate of the present invention is characterized in that, as a glass composition, it contains, in mol%, 65 to 72% of SiO2, 11 to 15% of Al2O3, 2 to 5% of B2O3, 0 to 0.5% of Li2O+Na2O+K2O, 2 to 8% of MgO, 4 to 10% of CaO, 0 to 4% of SrO, 0 to 4% of BaO, and MgO+CaO+SrO+BaO 11~17%, mol% ratio (MgO+CaO+SrO+BaO-Al2O3) / B2O3 is 0.2~1, mol% ratio SrO / CaO is 0~0.6, mol% ratio BaO / CaO is 0~0.6, 0.116×[Al2O3]-0.079×[B2O3]+0.155×[MgO]+0.299×[CaO]+0.336×[SrO]+0.385×[BaO]is 2~8%. Here, “Li2O+Na2O+K2O” refers to the total amount of Li2O, Na2O and K2O. “MgO+CaO+SrO+BaO” refers to the total amount of mol% content of MgO, CaO, SrO and BaO. “(MgO + CaO + SrO + BaO - Al2O3) / B2O3” refers to the value obtained by subtracting the mol% content of Al2O3 from the total mol% content of MgO, CaO, SrO and BaO, and dividing the result by the mol% content of B2O3. “SrO / CaO” is the value obtained by dividing the mol% content of SrO by the mol% content of CaO. “BaO / CaO” is the value obtained by dividing the mol% content of BaO by the mol% content of CaO. In addition, the “alkali-free glass” referred to in the present invention refers to glass having a Li2O + Na2O + K2O content of less than 0.5%.

[0027] (2) In the configuration of (1) above, the glass composition preferably contains, in mol%, 66 to 71% SiO2, 12 to 14% Al2O3, 2.5 to 4% B2O3, 0 to 0.1% Li2O + Na2O + K2O, 3 to 7% MgO, 5 to 9% CaO, 0.1 to 3% SrO, 0.1 to 3% BaO, and MgO + CaO + SrO + BaO. The mol% ratio of (MgO + CaO + SrO + BaO - Al2O3) / B2O3 is 0.2 to 0.65, the mol% ratio of SrO / CaO is 0 to 0.32, the mol% ratio of BaO / CaO is 0 to 0.25, and 0.116×[Al2O3]-0.079×[B2O3]+0.155×[MgO]+0.299×[CaO]+0.336×[SrO]+0.385×[BaO] is 4.6 to 7%.

[0028] (3) In the above-mentioned structures (1) and (2), the glass composition preferably contains substantially no As2O3 and Sb2O3, and further contains 0.001 to 1 mol% of SnO2. Here, "substantially no As2O3" means that the content of As2O3 is 0.05 mol% or less. "Substantially no Sb2O3" means that the content of Sb2O3 is 0.05 mol% or less.

[0029] (4) In the above-mentioned configurations (1) to (3), preferably, the Young's modulus is 81 GPa or more, the strain point is 720°C or more, and the liquidus temperature is 1400°C or less. Here, "Young's modulus" refers to the value measured by the bending resonance method. In addition, 1 GPa is equivalent to about 101.9 Kgf / mm 2 "Strain point" refers to the value measured based on the method of ASTM C336. "Liquidus temperature" refers to the highest temperature at which crystals precipitate after glass powder passing through a standard sieve of 30 mesh (500 μm) and remaining at 50 mesh (300 μm) is placed in a platinum dish and kept in a temperature gradient furnace for 24 hours.

[0030] (5) In the above-mentioned configurations (1) to (4), the strain point is preferably 725° C. or higher.

[0031] (6) In the above-mentioned configurations (1) to (5), the Young's modulus is preferably higher than 82 GPa.

[0032] (7) In the configurations of (1) to (6) above, preferably, the specific Young's modulus is 31 GPa / g·cm －3 Here, the "specific Young's modulus" is a value obtained by dividing the Young's modulus by the density.

[0033] (8) In the above-mentioned configurations (1) to (7), it is preferred that the average thermal expansion coefficient in the temperature range of 30 to 380°C is 30×10 －7 ~50×10 －7 Here, the "average thermal expansion coefficient in the temperature range of 30 to 380° C." can be measured using a dilatometer.

[0034] (9) In the configurations of (1) to (8) above, it is preferred that the annealing point is 780° C. or higher. Here, the “annealing point” refers to a value measured by a method based on ASTM C336.

[0035] (10) In the above-mentioned configurations (1) to (9), preferably, the liquid phase viscosity is 10 3.9 Here, the "liquidus viscosity" refers to the viscosity of glass at the liquidus temperature, and can be measured by the platinum ball pulling method.

[0036] (11) In the above-mentioned configurations (1) to (10), the present invention is preferably used in an organic EL device.

[0037] (12) In the above-mentioned configurations (1) to (10), the present invention is preferably used in a magnetic recording medium.

[0038] Effects of the Invention

[0039] The alkali-free glass plate of the present invention is excellent in productivity, has high durability against BHF, and has sufficiently high strain point and Young's modulus. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is an upper perspective view for showing an example of the shape of a glass substrate for a magnetic recording medium. DETAILED DESCRIPTION

[0041] The alkali-free glass plate of the present invention is characterized in that, as a glass composition, it contains SiO2 65-72%, Al2O3 11-15%, B2O3 2-5%, Li2O+Na2O+K2O 0-0.5%, MgO 2-8%, CaO 4-10%, SrO 0-4%, BaO 0-4%, MgO+CaO+SrO+BaO 11 to 17%, mol% ratio (MgO + CaO + SrO + BaO - Al2O3) / B2O3 is 0.2 to 1, mol% ratio SrO / CaO is 0 to 0.6, mol% ratio BaO / CaO is 0 to 0.6, 0.116 × [Al2O3] - 0.079 × [B2O3] + 0.155 × [MgO] + 0.299 × [CaO] + 0.336 × [SrO] + 0.385 × [BaO] is 2 to 8%. The following is the reason for limiting the content of each component as described above. In addition, in the description of the content of each component, % indicates mol% unless otherwise specified. In addition, unless otherwise specified, the upper limit indicates the value below, and the lower limit indicates the value above.

[0042] SiO2 is the component of the skeleton of glass. If SiO2 content is too little, the thermal expansion coefficient becomes high, and density increases. Therefore, SiO2 lower limit is preferably 65%, more preferably 65.1%, more preferably 65.2%, more preferably 65.4%, more preferably 65.6%, more preferably 65.8%, more preferably 65.9%, more preferably 66%, more preferably 66.1%, more preferably 66.2%, more preferably 66.3%, more preferably 66.4%, more preferably 66.5%, more preferably 66.6%, more preferably 66.8%, more preferably 67%, more preferably 67.2%, more preferably 67.4%, more preferably 67.6%, more preferably 67.8%, particularly preferably 68%. On the other hand, if SiO2 content is too much, Young's modulus decreases, and in addition high temperature viscosity becomes high, and the heat required during melting increases, and melting cost rises, and the melting residue of the introduction raw material of SiO2 occurs, it is possible to become the reason for the reduction of production yield. In addition, devitrified crystals of cristobalite etc. are easily precipitated, and liquidus viscosity is easily reduced. Therefore, the upper limit of SiO2 is preferably 72%, more preferably 71.8%, further preferably 71.6%, further preferably 71.4%, further preferably 71.2%, further preferably 71%, further preferably 70,8%, further preferably 70.6%, further preferably 70.4%, further preferably 70.2%, further preferably 70%, and particularly preferably 69.8%.

[0043] Al2O3 is the component of the skeleton of glass, in addition is the component that improves Young's modulus, in addition or makes strain point rise the component.Al2O3 content is too little, Young's modulus is easily reduced, in addition, strain point is easily reduced.Therefore, Al2O3 lower limit is preferably 11%, more preferably 11.2%, more preferably 11.4%, more preferably 11.5%, more preferably 11.6%, more preferably 11.8%, more preferably 12%, more preferably 12.1%, more preferably 12.2%, more preferably 12.3%, more preferably 12.4%, particularly preferably 12.5%.On the other hand, if Al2O3 content is too much, then the devitrified crystals of mullite etc. are easily separated out, and liquidus viscosity is easily reduced. Therefore, the upper limit of Al2O3 is preferably 15%, more preferably 14.8%, further preferably 14.6%, further preferably 14.4%, further preferably 14.2%, further preferably 14%, further preferably 13.9%, further preferably 13.8%, further preferably 13.7%, and particularly preferably 13.6%.

[0044] The mol% ratio of SiO2 / Al2O3 is an important component ratio for increasing the strain point and reducing the high temperature viscosity. If the mol% ratio of SiO2 / Al2O3 is too small, the strain point tends to drop. For this reason, the lower limit of the mol% ratio of SiO2 / Al2O3 is preferably 4.5, more preferably 4.7, further preferably 4.9, further preferably 5, further preferably 5.1, further preferably higher than 5.1, and particularly preferably 5.2. On the other hand, if the mol% ratio of SiO2 / Al2O3 is too large, the high temperature viscosity increases, and the manufacturing cost of the glass sheet tends to rise. Therefore, the upper limit of the mol% ratio of SiO2 / Al2O3 is preferably 6.5, more preferably 6.3, further preferably 6.1, further preferably 6, further preferably 5.9, further preferably 5.8, further preferably 5.7, further preferably 5.6, further preferably 5.5, and particularly preferably 5.4.

[0045] B2O3 is a component that improves durability to BHF, and can also improve solubility and resistance to devitrification. Therefore, the lower limit of B2O3 is preferably 2%, more preferably 2.1%, more preferably 2.2%, more preferably 2.3%, more preferably 2.4%, and particularly preferably 2.5%. On the other hand, if the content of B2O3 is too much, Young's modulus and strain point are easily reduced. Therefore, the upper limit of B2O3 is preferably 5%, more preferably 4.9%, more preferably 4.8%, more preferably 4.7%, more preferably 4.6%, more preferably 4.5%, more preferably 4.4%, more preferably 4.3%, more preferably 4.2%, more preferably 4.1%, more preferably 4%, more preferably less than 4%, more preferably 3.9%, more preferably 3.8%, and particularly preferably 3.7%.

[0046] The mol% ratio B2O3 / Al2O3 is an important component ratio for increasing Young's modulus, increasing strain point, and improving durability to BHF. If the mol% ratio B2O3 / Al2O3 is too small, the Young's modulus is easily reduced. For this reason, the lower limit of the mol% ratio B2O3 / Al2O3 is preferably 0, more preferably 0.13, further preferably 0.135, further preferably 0.15, further preferably 0.18, further preferably 0.2, and particularly preferably 0.22. On the other hand, if the mol% ratio B2O3 / Al2O3 is too large, the strain point is easily reduced. Therefore, the upper limit of the mol% ratio B2O3 / Al2O3 is preferably 0.3, more preferably less than 0.3, further preferably 0.29, further preferably less than 0.29, further preferably 0.28, further preferably less than 0.28, and particularly preferably 0.27.

[0047] Li2O, Na2O and K2O are components that are inevitably mixed into the glass raw materials, and the total amount ranges from 0 to 0.5%, preferably 0 to 0.1%, more preferably 0 to 0.09%, further preferably 0.005 to 0.08%, further preferably 0.008 to 0.06%, and particularly preferably 0.01 to 0.05%. If the total amount of Li2O, Na2O and K2O is too much, it may cause alkaline ions to diffuse into the film-forming semiconductor material during the heat treatment process. In addition, the range of the individual content of Li2O, Na2O and K2O is preferably 0 to 0.3%, more preferably 0 to 0.1%, further preferably 0 to 0.08%, further preferably 0 to 0.07%, further preferably 0 to 0.05%, and particularly preferably 0.001 to 0.04%.

[0048] MgO is a component that significantly improves Young's modulus among alkaline earth metal oxides. If the content of MgO is too little, the solubility and Young's modulus are easily reduced. Therefore, the lower limit of MgO is preferably 2%, more preferably 2.1%, more preferably 2.3%, more preferably 2.5%, more preferably 2.8%, more preferably 3%, more preferably 3.3%, and particularly preferably 3.5%. On the other hand, if the content of MgO is too much, the devitrified crystals of mullite etc. are easily precipitated, and the liquidus viscosity is easily reduced. Therefore, the upper limit of MgO is preferably 8%, more preferably 7.8%, more preferably 7.6%, more preferably 7.5%, more preferably 7.4%, more preferably 7.3% is less than, more preferably 7.2%, more preferably 7.1%, more preferably 7.0%, more preferably 6.9%, and particularly preferably 6.8%.

[0049] CaO is a component that reduces high temperature viscosity without reducing the strain point and significantly improves solubility. It is also a component that improves Young's modulus. If the content of CaO is too little, the solubility is easily reduced. Therefore, the lower limit of CaO is preferably 4%, more preferably 4.2%, more preferably 4.3%, more preferably 4.5%, more preferably 4.6%, more preferably 4.7%, more preferably 5%, more preferably 5.2%, and particularly preferably 5.5%. On the other hand, if the content of CaO is too much, the liquidus temperature increases. Therefore, the upper limit of CaO is preferably 10%, more preferably 9.8%, more preferably 9.5%, more preferably 9.2%, more preferably 9%, more preferably 8.9%, more preferably 8.7%, and particularly preferably 8.5%.

[0050] The mol% ratio of MgO / CaO is an important component ratio for improving Young's modulus. If the mol% ratio of MgO / CaO is too small, the Young's modulus is easily reduced. For this reason, the lower limit of the mol% ratio of MgO / CaO is preferably 0.2, more preferably 0.21, further preferably 0.22, further preferably 0.23, further preferably 0.24, and particularly preferably 0.25. On the other hand, if the mol% ratio of MgO / CaO is too large, the resistance to devitrification is easily reduced. Therefore, the upper limit of the mol% ratio of MgO / CaO is preferably 1.5, more preferably 1.4, further preferably 1.3, further preferably 1.3, further preferably 1.2, further preferably 1.1, further preferably 1, further preferably 0.95, further preferably 0.94, and particularly preferably 0.935.

[0051] SrO is a component that improves the resistance to devitrification, and further reduces the high temperature viscosity and improves the solubility without reducing the strain point. It is also a component that inhibits the decrease in liquid phase viscosity. Therefore, the lower limit of SrO is preferably 0%, more preferably higher than 0%, more preferably 0.1%, further preferably higher than 0.1%, further preferably 0.2%, further preferably 0.3%, further preferably higher than 0.3%, further preferably 0.4%, further preferably higher than 0.4%, and particularly preferably 0.5%. On the other hand, if the content of SrO is too much, the thermal expansion coefficient and density are likely to increase. Therefore, the upper limit of SrO is preferably 4%, more preferably less than 4%, further preferably 3.8%, further preferably 3.5%, further preferably 3.3%, further preferably 3%, further preferably 2.8%, further preferably 2.5%, further preferably 2.3%, and particularly preferably 2%.

[0052] The mol% ratio SrO / CaO is an important component ratio for improving the durability to BHF. If the mol% ratio SrO / CaO is too small, the meltability is reduced and the manufacturing cost of the glass plate is likely to rise. For this reason, the lower limit of the mol% ratio SrO / CaO is preferably 0, more preferably 0.01, more preferably 0.02, more preferably 0.03, more preferably 0.04, more preferably 0.05, more preferably 0.06, more preferably 0.07, more preferably 0.08, more preferably 0.09, and particularly preferably 0.1. On the other hand, if the mol% ratio SrO / CaO is too large, the durability to BHF is likely to be reduced. Therefore, the upper limit of the mol% ratio SrO / CaO is preferably 0.6, more preferably 0.55, further preferably 0.53, further preferably 0.5, further preferably 0.48, further preferably 0.45, further preferably 0.43, further preferably 0.4, further preferably 0.38, further preferably 0.35, further preferably 0.33, further preferably 0.32, further preferably 0.31, further preferably 0.3, further preferably 0.29, further preferably 0.28, and particularly preferably 0.25.

[0053] BaO is a component that improves resistance to devitrification. Therefore, the lower limit of BaO is preferably 0%, more preferably 0% over, more preferably 0.1%, further preferably higher than 0.1%, further preferably 0.2%, further preferably 0.3%, further preferably 0.4%, further preferably higher than 0.4%, and particularly preferably 0.5%. On the other hand, if the content of BaO is too much, the Young's modulus is easily reduced, and the density is easily increased. As a result, the glass plate is easily flexed than the Young's modulus. Therefore, the upper limit of BaO is preferably 4%, more preferably lower than 4%, further preferably 3.8%, further preferably 3.5%, further preferably 3.3%, further preferably 3%, further preferably 2.8%, further preferably 2.5%, further preferably 2.3%, and particularly preferably 2%.

[0054] The mol% ratio of BaO / CaO is an important component ratio for improving the specific Young's modulus. If the mol% ratio of BaO / CaO is too small, the resistance to devitrification decreases, and the manufacturing cost of the glass plate tends to rise. For this reason, the lower limit of the mol% ratio of BaO / CaO is preferably 0, more preferably higher than 0, further preferably 0.001, further preferably 0.002, further preferably 0.004, further preferably 0.006, further preferably 0.008, further preferably 0.01, further preferably 0.012, further preferably 0.014, further preferably 0.016, further preferably 0.018, further preferably 0.02, further preferably 0.022, further preferably 0.024, further preferably 0.026, further preferably 0.028, further preferably 0.03, and particularly preferably 0.032. On the other hand, if the mol% ratio of BaO / CaO is too large, the specific Young's modulus tends to decrease. Therefore, the upper limit of the mol% ratio of BaO / CaO is preferably 0.6, more preferably 0.55, further preferably 0.53, further preferably 0.5, further preferably 0.48, further preferably 0.45, further preferably 0.43, further preferably 0.4, further preferably 0.38, further preferably 0.35, further preferably 0.33, further preferably 0.3, further preferably 0.29, further preferably 0.28, and particularly preferably 0.25.

[0055] MgO, CaO, SrO and BaO are components that increase density and thermal expansion coefficient. If the content of MgO + CaO + SrO + BaO is too little, the thermal expansion coefficient is likely to decrease. Therefore, the lower limit of MgO + CaO + SrO + BaO is preferably 11%, more preferably 11.2%, more preferably 11.5%, further preferably 11.8%, further preferably 12%, further preferably 12.3%, further preferably 12.5%, further preferably 12.8%, and particularly preferably 13%. On the other hand, if the content of MgO + CaO + SrO + BaO is too much, the density is likely to increase. Therefore, the upper limit of MgO + CaO + SrO + BaO is preferably 17%, more preferably 16.8%, more preferably 16.5%, further preferably less than 16.5%, further preferably 16.3%, further preferably 16.1%, and particularly preferably 16%.

[0056] The mol% ratio (MgO + CaO + SrO + BaO-Al2O3) / B2O3 is an important component ratio related to durability and solubility to BHF. Alkaline earth metal oxides are components that cut the network structure in glass. In contrast, B2O3 is a component that forms the network structure in glass. Alkaline earth metal oxides have the effect of cutting the network structure in glass, but since Al2O3 forms the network structure in glass, alkaline earth metal oxides with the same content as Al2O3 do not have the effect of cutting the network. In other words, the smaller the mol% ratio (MgO + CaO + SrO + BaO-Al2O3) / B2O3, the less the components that cut the network structure are relative to the components that form the network structure, so that chemical durability, especially durability to BHF, can be improved. If the mol% ratio (MgO + CaO + SrO + BaO-Al2O3) / B2O3 is too small, the solubility is likely to decrease, and the manufacturing cost of the glass plate is likely to increase. For this reason, the lower limit of the mol% ratio (MgO + CaO + SrO + BaO-Al2O3) / B2O3 is preferably 0.2, more preferably 0.21, further preferably 0.22, further preferably 0.23, further preferably 0.24, further preferably 0.24, further preferably 0.25, further preferably 0.26, further preferably 0.27, and particularly preferably 0.28. On the other hand, if the mol% ratio (MgO + CaO + SrO + BaO-Al2O3) / B2O3 is too large, the durability to BHF is likely to decrease. Therefore, the upper limit of the mol% ratio (MgO + CaO + SrO + BaO-Al2O3) / B2O3 is preferably 1, more preferably 0.9, further preferably 0.85, further preferably 0.8, further preferably 0.75, further preferably 0.7, and particularly preferably 0.65.

[0057] 0.116×[Al2O3]-0.079×[B2O3]+0.155×[MgO]+0.299×[CaO]+0.336×[SrO]+0.385×[BaO]is an important composition formula value related to durability and solubility to BHF. If 0.116×[Al2O3]-0.079×[B2O3]+0.155×[MgO]+0.299×[CaO]+0.336×[SrO]+0.385×[BaO]is too small, solubility is likely to decrease and the manufacturing cost of the glass plate is likely to increase. Therefore, the lower limit of 0.116×[Al2O3]-0.079×[B2O3]+0.155×[MgO]+0.299×[CaO]+0.336×[SrO]+0.385×[BaO] is preferably 2%, more preferably 2.5%, further preferably 3%, further preferably 3.5%, further preferably 3.8%, further preferably 4%, further preferably 4.2%, further preferably 4.4%, further preferably 4.6%, and particularly preferably 4.7%. On the other hand, if 0.116×[Al2O3]-0.079×[B2O3]+0.155×[MgO]+0.299×[CaO]+0.336×[SrO]+0.385×[BaO] is too large, the durability to BHF is likely to decrease. Therefore, the upper limit value of 0.116×[Al2O3]-0.079×[B2O3]+0.155×[MgO]+0.299×[CaO]+0.336×[SrO]+0.385×[BaO] is preferably 8%, more preferably 7.8%, further preferably 7.5%, further preferably 7.3%, further preferably 7%, further preferably 6.8%, further preferably 6.5%, further preferably 6.3%, further preferably 6%, further preferably 5.8%, further preferably 5.7%, further preferably 5.6%, further preferably 5.5%, further preferably 5.4%, further preferably 5.3%, further preferably 5.2%, and particularly preferably 5%.

[0058] The appropriate content range of each component can be appropriately combined as the preferred glass composition range, but in order to optimize the effect of the present invention, the glass composition is particularly preferably, in mol%, SiO2 66-71%, Al2O3 12-14%, B2O3 2.5-4%, Li2O+Na2O+K2O 0-0.1%, MgO 3-7%, CaO 5-9%, SrO 0.1-3%, BaO0.1-3%, MgO+CaO+SrO+BaO The mol% ratio of (MgO + CaO + SrO + BaO - Al2O3) / B2O3 is 0.2 to 0.65, the mol% ratio of SrO / CaO is 0 to 0.32, the mol% ratio of BaO / CaO is 0 to 0.25, and 0.116×[Al2O3]-0.079×[B2O3]+0.155×[MgO]+0.299×[CaO]+0.336×[SrO]+0.385×[BaO] is 4.6 to 7%.

[0059] In addition to the above-mentioned components, for example, the following components may be added as optional components. In addition, from the viewpoint of ensuring the effects of the present invention, the content of other components other than the above-mentioned components is 10% or less in total, and particularly preferably 5% or less.

[0060] P2O5 is a component that increases the strain point and is a component that can significantly inhibit the precipitation of devitrified crystals of alkaline earth aluminosilicates such as calcium feldspar. However, if a large amount of P2O5 is contained, the glass is prone to phase separation. The content of P2O5 is preferably in the range of 0 to 2.5%, more preferably 0 to 1.5%, further preferably 0 to 0.5%, further preferably 0 to 0.3%, further preferably 0 to less than 0.1%, and particularly preferably 0 to less than 0.01%.

[0061] TiO2 reduces high temperature viscosity, is a component that improves solubility, and is a component that suppresses discoloration (solarization) when exposed to light, but if TiO2 is contained in large quantities, the glass will be colored and the transmittance will be easily reduced. The range of the TiO2 content is preferably 0 to 2.5%, more preferably 0.0005 to 1%, further preferably 0.001 to 0.5%, and particularly preferably 0.005 to 0.1%.

[0062] ZnO is a component that increases the Young's modulus. However, if a large amount of ZnO is contained, the glass is prone to devitrification and the strain point is prone to decrease. The content of ZnO is preferably in the range of 0 to 3%, more preferably 0 to 2%, further preferably 0 to 1%, further preferably 0 to 0.8%, further preferably 0 to 0.5%, and particularly preferably 0 to less than 0.5%.

[0063] Fe2O3 is a component that is inevitably mixed from glass raw materials, and is also a component that reduces resistivity. The content of Fe2O3 is preferably in the range of 0 to 250 molppm, 20 to 200 molppm, and particularly 40 to 100 molppm. If the content of Fe2O3 is too low, the cost of raw materials tends to rise. On the other hand, if the content of Fe2O3 is too high, the resistivity of the molten glass increases, making it difficult to perform electric melting.

[0064] ZrO2 is a component that increases the Young's modulus. However, if ZrO2 is contained in large amounts, the glass is prone to devitrification. The content of ZrO2 is preferably in the range of 0 to 2.5%, more preferably 0.0005 to 1%, further preferably 0.001 to 0.5%, and particularly preferably 0.005 to 0.1%.

[0065] MoO3 is a component that absorbs ultraviolet rays (light with a wavelength of 200 to 300 nm). In addition, MoO3 is a component that reduces the amount of water in the glass. In particular, by melting the raw material batch by electric melting heating and containing MoO3, the amount of water in the glass can be further reduced. If the amount of water in the glass is reduced, the liquidus viscosity and strain point rise, which can improve the anti-devitrification and heat resistance of the glass. The lower limit of MoO3 is preferably 0.00001%, more preferably 0.00005%, further preferably 0.0001%, further preferably 0.0002%, further preferably 0.0003%, further preferably 0.0004%, and particularly preferably 0.001%. On the other hand, if the content of MoO3 is too much, the transmittance of ultraviolet rays is reduced, and the production yield of the laser stripping process, especially in the display manufacturing process, is easily reduced. Therefore, it is preferably 0.01%, more preferably 0.008%, further preferably 0.006%, further preferably 0.005%, further preferably 0.005%, and particularly preferably 0.003%.

[0066] Y2O3, Nb2O5, and La2O3 have the effect of increasing the strain point and Young's modulus. The total amount and individual content of these components are preferably in the range of 0 to 5%, more preferably 0 to 1%, further preferably 0 to 0.5%, and particularly preferably 0 to less than 0.5%. If the total amount and individual content of Y2O3, Nb2O5, and La2O3 are too much, the density and raw material cost are likely to increase.

[0067] SnO2 is a component that has a good clarification effect in a high temperature range, is a component that increases the strain point, and is also a component that reduces high temperature viscosity. The content of SnO2 is preferably in the range of 0-1%, 0.001-1%, 0.01-0.5%, and particularly preferably 0.05-0.3%. If the content of SnO2 is too much, devitrified crystals of SnO2 are easily precipitated. In addition, if the content of SnO2 is less than 0.001%, it is difficult to enjoy the above effects.

[0068] As mentioned above, SnO2 is suitable as a clarifier, but as long as the glass properties are not damaged, F, SO3, C, or metal powders such as Al and Si can be added as a clarifier to 5% (preferably to 1%, particularly preferably to 0.5%) instead of SnO2 or in combination with SnO2. In addition, CeO2, F, etc. can also be added as a clarifier to 5% (preferably to 1%, particularly preferably to 0.5%).

[0069] As clarifiers, As2O3 and Sb2O3 are also effective. However, As2O3 and Sb2O3 are components that increase environmental burden. In addition, As2O3 is a component that reduces the resistance to light discoloration. Therefore, the alkali-free glass plate of the present invention preferably does not substantially contain these components.

[0070] Cl is a component that promotes the initial melting of the glass batch. In addition, if Cl is added, the effect of the clarifier can be promoted. As a result, the melting cost can be reduced and the life of the glass manufacturing kiln can be extended. However, if the Cl content is too much, the strain point is easily reduced. Therefore, the range of the Cl content is preferably 0 to 3%, more preferably 0.0005 to 1%, and particularly preferably 0.001 to 0.5%. In addition, as the introduction raw material of Cl, chlorides of alkaline earth metal oxides such as strontium chloride, or raw materials such as aluminum chloride can be used.

[0071] The alkali-free glass plate of the present invention preferably has the following properties.

[0072] The average thermal expansion coefficient in the temperature range of 30 to 380°C is preferably 30×10 －7 ~50×10 －7 / ℃, more preferably 32×10 －7 ~48×10 －7 / ℃, more preferably 33×10 －7 ~45×10 －7 / ℃, more preferably 34×10 －7 ~44×10 －7 / ℃, particularly preferably 35×10 －7 ~43×10 －7 If so, it is easy to match the thermal expansion coefficient of Si used in TFT.

[0073] The Young's modulus is preferably 81 GPa or more, more preferably higher than 81 GPa, more preferably 81.3 GPa or more, more preferably 81.5 GPa or more, more preferably 81.8 GPa or more, more preferably 82 GPa or more, more preferably 82.3 GPa or more, more preferably 82.5 GPa or more, more preferably 82.8 GPa or more, and particularly preferably 83 GPa or more. If the Young's modulus is too low, problems caused by the deflection of the glass plate are likely to occur. In addition, the Young's modulus is preferably 120 GPa or less, more preferably 110 GPa or less, more preferably 100 GPa or less, and particularly preferably 95 GPa or less.

[0074] The specific Young's modulus is preferably 31 GPa / g·cm －3 More preferably, 31.1 GPa / g·cm －3 More preferably, 31.3 GPa / g·cm －3 More preferably, 31.5 GPa / g·cm －3 More preferably, 31.8 GPa / g·cm －3 More preferably, 32 GPa / g·cm －3 More preferably, 32.2 GPa / g·cm －3 More preferably, 32.4 GPa / g·cm －3 More preferably, 32.4 GPa / g·cm －3 More preferably, 32.8 GPa / g·cm －3 Above, particularly preferably 33 GPa / g·cm －3 If the specific Young's modulus is too low, problems caused by the bending of the glass plate are likely to occur. In addition, the specific Young's modulus is preferably 37 GPa / g·cm －3 Below, more preferably 36.5 GPa / g·cm －3 Below, more preferably 36 GPa / g·cm －3 Below, more preferably 35.7 GPa / g·cm －3 Below, particularly preferably 35.0 GPa / g·cm －3 the following.

[0075] The strain point is preferably 710°C or higher, more preferably 715°C or higher, further preferably 718°C or higher, further preferably 720°C or higher, further preferably 725°C or higher, further preferably 728°C or higher, further preferably 730°C or higher, further preferably 735°C or higher, further preferably 740°C or higher, and particularly preferably 745°C or higher. In this way, the thermal shrinkage of the glass sheet can be suppressed in the LTPS process. In addition, the strain point is preferably 820°C or lower, more preferably 815°C or lower, further preferably 810°C or lower, and particularly preferably 800°C or lower.

[0076] The annealing point is preferably 770°C or higher, more preferably 775°C or higher, further preferably 780°C or higher, further preferably 782°C or higher, further preferably 785°C or higher, and particularly preferably 790°C or higher. In this way, the thermal shrinkage of the glass sheet can be suppressed in the LTPS process. The annealing point is preferably 900°C or lower, more preferably 890°C or lower, further preferably 880°C or lower, and particularly preferably 870°C or lower.

[0077] The liquidus temperature is preferably below 1400°C, more preferably below 1380°C, further preferably below 1350°C, further preferably below 1300°C, further preferably below 1290°C, further preferably below 1285°C, further preferably below 1280°C, further preferably below 1275°C, and particularly preferably below 1270°C. The liquidus temperature is preferably above 1160°C, more preferably above 1170°C, and particularly preferably above 1180°C. In this way, it is easy to prevent the occurrence of devitrified crystals during glass manufacturing, which leads to a decrease in productivity. In addition, it is easy to form by overflow down-drawing method, so it is easy to improve the surface quality of the glass sheet, and the manufacturing cost of the glass sheet can be reduced. In addition, the liquidus temperature is an index of anti-devitrification, and the lower the liquidus temperature, the better the anti-devitrification.

[0078] The liquid phase viscosity is preferably 10 3.6 dPa·s or more, more preferably 10 3.8 dPa·s or more, more preferably 10 4.0 dPa·s or more, more preferably 10 4.2 dPa·s or more, more preferably 10 4.4 dPa·s or more, more preferably 10 4.6 dPa·s or more, more preferably 10 4.8 dPa·s or more, more preferably 10 5.0 dPa·s or more, particularly preferably 10 5.1 dPa·s or more. The liquid phase viscosity is preferably 10 7.4dPa·s or less, more preferably 10 7.2 dPa·s or less, particularly preferably 10 7.0 dPa·s or less. In this case, devitrification is unlikely to occur during forming, so it is easy to form by overflow down-drawing, resulting in an improvement in the surface quality of the glass sheet and a reduction in the manufacturing cost of the glass sheet. In addition, liquidus viscosity is an index of devitrification resistance and formability. The higher the liquidus viscosity, the higher the devitrification resistance and formability.

[0079] High temperature viscosity 10 2.5 The temperature at dPa·s is preferably 1700°C or lower, more preferably 1680°C or lower, further preferably 1660°C or lower, and particularly preferably 1650°C or lower. High temperature viscosity 10 2.5 The temperature at dPa·s is preferably 1560°C or higher, more preferably 1570°C, further preferably 1580°C, and particularly preferably 1590°C. 2.5 If the temperature at dPa·s is too high, the glass batch material will be difficult to melt, and the manufacturing cost of the glass plate will increase. 2.5 The temperature at dPa·s corresponds to the melting temperature, and the lower the temperature is, the higher the meltability is.

[0080] The β-OH value is an indicator of the amount of water in the glass. If the β-OH value is reduced, the strain point can be increased. In addition, even if the glass composition is the same, the thermal shrinkage rate at a temperature below the strain point is smaller when the β-OH value is small. The β-OH value is preferably less than 0.35 / mm, more preferably less than 0.30 / mm, further preferably less than 0.28 / mm, further preferably less than 0.25 / mm, further preferably less than 0.20 / mm, further preferably less than 0.17 / mm, and particularly preferably less than 0.15 / mm. In addition, if the β-OH value is too small, the solubility is easily reduced. Therefore, the β-OH value is preferably greater than 0.01 / mm, and particularly preferably greater than 0.03 / mm.

[0081] The following methods can be cited as methods for reducing the β-OH value. (1) Selecting raw materials with low water content. (2) Adding components that reduce the β-OH value (such as Cl and SO3) to the glass. (3) Reducing the amount of water in the furnace atmosphere. (4) Bubbling N2 in the molten glass. (5) Using a small melting furnace. (6) Increasing the flow rate of the molten glass. (7) Using the electric melting method.

[0082] Here, the “β-OH value” refers to a value obtained by measuring the transmittance of glass using FT-IR and using the following Formula 1.

[0083] [Formula 1]

[0084] β-OH value = (1 / X) log (T1 / T2)

[0085] X: Plate thickness (mm)

[0086] T1: Reference wavelength 3846cm －1 Transmittance (%)

[0087] T2: Hydroxyl absorption wavelength 3600cm －1 Minimum transmittance near

[0088] The alkali-free glass sheet of the present invention is preferably formed by an overflow down-draw method. The overflow down-draw method is a method for manufacturing a glass sheet by allowing molten glass to overflow from both sides of a heat-resistant trough-shaped structure, and while the overflowing molten glass is joined at the lower end of the trough-shaped structure, the glass sheet is stretched downward to form a shape. In the overflow down-draw method, the surface of the glass sheet does not contact the trough-shaped refractory, but is formed in a free surface state. Therefore, the glass sheet can be manufactured inexpensively, has a flame-polished surface with good surface quality without grinding, and can be easily thinned.

[0089] The alkali-free glass plate of the present invention is also preferably formed by a float process. According to this method, a large glass plate can be manufactured at low cost.

[0090] When the alkali-free glass plate of the present invention is used for information recording media, the surface is preferably a polished surface. If the glass surface is ground, the overall thickness deviation TTV can be reduced. As a result, since a magnetic film can be properly formed, it is suitable for a substrate of a magnetic recording medium. On the other hand, when used for an organic EL device, the surface is preferably a flame polished surface (unground surface) formed by an overflow down-draw method.

[0091] In the alkali-free glass plate of the invention, the plate thickness is not particularly limited, but when used for an organic EL device, it is preferably less than 0.7 mm, more preferably less than 0.7 mm, further preferably less than 0.6 mm, further preferably less than 0.6 mm, and particularly preferably less than 0.0.5 mm. The thinner the plate thickness, the lighter the organic EL device can be. However, if the plate thickness is too thin, the strength becomes weaker and it has excessive flexibility, so it is preferably more than 0.05 mm. The plate thickness can be adjusted by the flow rate and pulling speed during glass manufacturing. On the other hand, when used for magnetic recording media, the plate thickness is preferably less than 1.5 mm, more preferably less than 1.2 mm, further preferably less than 1.0 mm, and particularly preferably less than 0.9 mm. If the plate thickness is too thick, it must be etched to the desired plate thickness, and the processing cost may rise. In addition, if the plate thickness is too thin, flutter may occur, so it is preferably more than 0.2 mm, and particularly preferably more than 0.3 mm.

[0092] In the alkali-free glass plate of the present invention, when used for an organic EL device, the average surface roughness Ra of the surface is preferably 1.0 nm or less, more preferably 0.5 nm or less, and particularly preferably 0.2 nm or less. If the average surface roughness Ra of the surface is large, it is difficult to accurately pattern the electrodes, etc. in the manufacturing process of the display, resulting in an increase in the probability of disconnection and short circuit of the circuit electrodes, 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 surface (two surfaces) excluding the end surface, and can be measured, for example, by an atomic force microscope (AFM).

[0093] In addition, when the alkali-free glass plate of the present invention is used as a substrate for a display panel for an organic EL television or a carrier for manufacturing an organic EL display panel, the shape is preferably rectangular. In addition, the alkali-free glass plate of the present invention is preferably used for information recording media, especially for a substrate for energy-assisted magnetic recording media. In order to increase the degree of order (order) of the magnetic layer and achieve high Ku, when forming a magnetic layer on the substrate, or before and after the film formation, the base material including the glass substrate is heat-treated at a high temperature of about 800°C. In addition, it can also withstand the impact of the high rotation of the magnetic recording medium on the substrate. The alkali-free glass plate of the present invention is processed into Figure 1 Such a disk substrate 1 is shown. When used as a glass substrate for a magnetic recording medium, the disk substrate 1 preferably has a disk shape, and more preferably has a circular opening C formed in the center.

[0094] Example

[0095] Hereinafter, the present invention will be described based on examples. The following examples are merely illustrative and the present invention is not limited to the following examples in any way.

[0096] Tables 1 to 4 show examples (samples No. 1 to 35) of the present invention and a comparative example (sample No. 36).

[0097]

Table 1

[0098]

[0099]

Table 2

[0100]

[0101]

Table 3

[0102]

[0103]

Table 4

[0104]

[0105] First, mix the glass raw materials according to the glass composition in the table, put the prepared glass batch into a platinum crucible, and melt it at 1600-1680°C for 24 hours. When the glass batch is melted, stir it with a platinum stirrer to homogenize it. Next, pour the molten glass onto a carbon plate, shape it into a plate, and anneal it at a temperature near the annealing point for 30 minutes. For each sample obtained, evaluate the average thermal expansion coefficient CTE in the temperature range of 30-380°C, density ρ, Young's modulus E, 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 at dPa·s, liquidus temperature TL, and viscosity log at liquidus temperature TL 10 ηTL is used as an indicator of durability against BHF to evaluate the BHF etching amount.

[0106] The average thermal expansion coefficient CTE in the temperature range of 30 to 380° C. is a value measured with a dilatometer.

[0107] The density ρ is a value measured by the well-known Archimedean method.

[0108] Young's modulus E refers to a value measured by a well-known resonance method.

[0109] The specific Young's modulus E / ρ is a value obtained by dividing the Young's modulus by the density.

[0110] The strain point Ps, annealing point Ta, and softening point Ts are values ​​measured based on the methods of ASTM C336 and C338.

[0111] High temperature viscosity 10 4 dPa·s, 10 3 dPa·s, 10 2.5 The temperature in dPa·s is a value measured by the platinum ball pulling method.

[0112] The liquidus temperature TL is the temperature at which crystals precipitate after glass powder that passes through a standard sieve of 30 mesh (500 μm) and remains at 50 mesh (300 μm) is placed in a platinum dish and kept in a temperature gradient furnace for 24 hours.

[0113] Liquid viscosity log 10 ηTL is a value of the glass viscosity at the liquidus temperature TL measured by a platinum ball pulling method.

[0114] The BHF etching amount is obtained by optically polishing both sides of the sample, masking a portion of the sample surface, immersing the sample in a 63BHF (HF: 6% by mass, NH4F: 30% by mass) solution at room temperature for 30 minutes, and then measuring the height difference between the masked portion and the etched portion of the sample surface using a Surfcorder (surface roughness profiler) ET4000 (manufactured by Kosaka Laboratories Co., Ltd.).

[0115] As can be seen from the table, for samples No. 1 to 35, since the glass composition is limited to the specified range, the Young's modulus is above 81 GPa, the strain point is above 723°C, the liquidus temperature is below 1232°C, and the liquidus viscosity is 10 3.6 dPa·s or more, and the BHF etching amount is 4.0 μm or less. Therefore, Samples No. 1 to 35 have excellent productivity, high durability against BHF, and sufficiently high strain point and Young's modulus, and are therefore suitable for substrates of organic EL devices.

[0116] On the other hand, the BHF etching amount of sample No. 36 was as large as 6.8 μm, and the durability to BHF was low.

[0117] Industrial Applicability

[0118] The alkali-free glass plate of the present invention is suitable as a substrate for an organic EL device, in particular, a display panel for an organic EL television, and a carrier for manufacturing an organic EL display panel. In addition, the alkali-free glass plate of the present invention is also suitable for 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) and a nearly 1:1 type solid-state imaging device (CIS), a substrate and cover glass for a solar cell, a substrate for organic EL lighting, and the like.

[0119] In addition, the alkali-free glass plate of the present invention is also suitable as a glass substrate for magnetic recording media because the strain point and Young's modulus are sufficiently high. If the strain point is high, the glass plate is difficult to deform even if heat treatment and laser irradiation at high temperatures such as thermal assistance are performed. As a result, when pursuing high Ku, a higher heat treatment temperature can be used, so it is easy to make a magnetic recording device with high recording density. In addition, if the Young's modulus is high, it is difficult for the glass substrate to bend and shake (flutter) during high-speed rotation, so it can prevent the collision between the information recording medium and the magnetic head.

[0120] Description of Reference Numerals

[0121] 1 Disk substrate (glass substrate for magnetic recording media)

Claims

1. An alkali-free glass plate, characterized in that: The glass composition, in mol%, includes SiO2 65% to 72%, Al2O3 11% to 15%, B2O3 2% to 5%, Li2O + Na2O + K2O 0% to 0.5%, MgO 2% to 8%, CaO 4% to 10%, SrO 0% to 4%, BaO 0% to 4%, MgO + CaO + SrO + BaO The content of organic matter in the raw materials is 11% to 17%, the mol% ratio of (MgO + CaO + SrO + BaO - Al2O3) / B2O3 is 0.2 to 1, the mol% ratio of SrO / CaO is 0 to 0.6, the mol% ratio of BaO / CaO is 0 to 0.6, 0.116 × [Al2O3] - 0.079 × [B2O3] + 0.155 × [MgO] + 0.299 × [CaO] + 0.336 × [SrO] + 0.385 × [BaO] is 2% to 8%.

2. The alkali-free glass plate according to claim 1, characterized in that As for the glass composition, in mol%, it contains SiO2 66% to 71%, Al2O3 12% to 14%, B2O3 2.5% to 4%, Li2O + Na2O + K2O 0% to 0.1%, MgO 3% to 7%, CaO 5% to 9%, SrO 0.1% to 3%, BaO 0.1% to 3%, MgO + CaO + SrO + BaO The total weight of the raw materials is 12% to 16%, the mol% ratio of (MgO + CaO + SrO + BaO - Al2O3) / B2O3 is 0.2 to 0.65, the mol% ratio of SrO / CaO is 0 to 0.32, the mol% ratio of BaO / CaO is 0 to 0.25, 0.116×[Al2O3]-0.079×[B2O3]+0.155×[MgO]+0.299×[CaO]+0.336×[SrO]+0.385×[BaO] is 4.6% to 7%.

3. The alkali-free glass plate according to claim 1 or 2, characterized in that: The glass composition contains substantially no As2O3 and Sb2O3, and also contains 0.001 mol% to 1 mol% of SnO2.

4. The alkali-free glass plate according to claim 1 or 2, characterized in that: The Young's modulus is 81 GPa or more, the strain point is 720° C. or more, and the liquidus temperature is 1400° C. or less.

5. The alkali-free glass plate according to claim 1 or 2, characterized in that: The strain point is 725°C or higher.

6. The alkali-free glass plate according to claim 1 or 2, characterized in that: Young's modulus is higher than 82 GPa.

7. The alkali-free glass plate according to claim 1 or 2, characterized in that: Specific Young's modulus is 31GPa / g・cm －3 above.

8. The alkali-free glass plate according to claim 1 or 2, characterized in that: The average thermal expansion coefficient in the temperature range of 30℃ to 380℃ is 30×10 －7 / ℃~50×10 －7 / ℃.

9. The alkali-free glass plate according to claim 1 or 2, characterized in that: The annealing point is 780°C or above.

10. The alkali-free glass plate according to claim 1 or 2, characterized in that: Liquid viscosity is 10 3.9 dPa·s or more.

11. The alkali-free glass plate according to claim 1 or 2, characterized in that: Used in organic EL devices.

12. The alkali-free glass plate according to claim 1 or 2, characterized in that: For information recording media.

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