Alkali-free glass

Abstract

This invention relates to an alkali-free glass having a strain point of 700°C to 740°C, a density of 2.6 g / cm³ to 30 g, a Young's modulus of 90 GPa to 100 GPa, an average coefficient of thermal expansion of 30 × 10⁻⁷ / K to 39 × 10⁻⁷ / K between 50 and 350°C, a temperature T₂ at which the glass viscosity becomes 10⁻² dPa·s of 1590°C to 1690°C, a temperature T₄ at which the glass viscosity becomes 10⁻⁴ dPa·s of 1350°C to 30⁻⁴, a devitrification temperature (T₁c) at the glass surface not reaching T₄ + 80°C, and a specific modulus of elasticity of 36 MN·m / kg or higher. The aforementioned alkali-free glass has a specified glass composition.

Description

[Technical Field]

[0001] This invention relates to an alkali-free glass, which is suitable for use as a glass plate for various displays, photomasks, electronic device supports, information recording media, etc. [Previous Technology]

[0002] For a long time, glass used in various displays, photomasks, electronic device support, information recording media, especially glass with thin films of metal or oxides formed on the surface, has been required to have the following characteristics (1) to (4).

[0003] (1) When the glass contains alkali metal oxides, alkali metal ions diffuse into the thin film and degrade the film properties of the film. Therefore, it is required that the glass is substantially free of alkali metal ions. (2) When the glass plate is exposed to high temperature during the thin film forming step, a higher strain point is required in order to minimize the deformation of the glass plate and the shrinkage (thermal shrinkage) that occurs with the stabilization of the glass structure.

[0004] (3) Sufficient chemical durability is required for various chemicals used to form semiconductors. In particular, durability is required for the following substances: buffer hydrofluoric acid (BHF: a mixture of hydrofluoric acid and ammonium fluoride) used for etching SiO x or SiN x, hydrochloric acid-containing solutions used in etching ITO (Indium Tin Oxides), various acids (nitric acid, sulfuric acid, etc.) used in etching metal electrodes, and alkalis in resist stripping solutions, etc. (4) No defects (bubbles, streaks, inclusions, pits, scratches, etc.) are required on the interior and surface.

[0005] In addition to the above requirements, in recent years, the following (5) to (9) have also been required. (5) The display is required to be lightweight, and a glass with a lower specific gravity is expected. (6) The display is required to be lightweight, and the glass plate is expected to be thinner. (7) In addition to manufacturing amorphous silicon (a-Si) type liquid crystal displays, which have been manufactured for a long time, polycrystalline silicon (p-Si) type liquid crystal displays with higher heat treatment temperature have also begun to be manufactured (heat resistance of a-Si: about 350°C, heat resistance of p-Si: 350~550°C), so heat resistance is expected.

[0006] (8) In order to accelerate the heating and cooling rate of heat treatment during the manufacture of liquid crystal displays to improve productivity or to improve thermal shock resistance, the average coefficient of thermal expansion of the glass is required to be small. On the other hand, when the average coefficient of thermal expansion of the glass is too small, the following problems exist: if the various film-forming steps such as gate metal film or gate insulating film during the manufacture of liquid crystal displays increase, the warping of the glass will increase, and abnormalities such as cracks or scratches will occur when transporting the liquid crystal displays, and the deviation of the exposure pattern will increase. (9) In addition, in recent years, with the continuous development of larger and thinner glass plates, the specific elastic modulus (Young's modulus / density) of the glass is required to be higher.

[0007] Furthermore, displays are developing towards higher resolutions. In large-screen televisions, with the increasing emphasis on high definition, issues arise such as increased film thickness in Cu wiring and increased substrate warping due to various film formation processes. Therefore, the demand for glass plates with lower warping is rising. To address this, it is necessary to increase the Young's modulus of the glass. However, glass with a higher Young's modulus has a higher strain point and tends to have a devitrification temperature higher than T4, the temperature at which the glass viscosity reaches 10⁴ dPa·s. As a result, it is more difficult to form glass plates.

[0008] To address the problems in the prior art mentioned above, the applicant has proposed various glass compositions, for example, for glass used in liquid crystal display panels (see Patent Documents 1 and 2). Prior Art Documents Patent Documents

[0009] Patent Document 1: International Publication No. 2019 / 177069; Patent Document 2: Japanese Patent No. 6578774 [Summary of the Invention]

[0010] [The problem the invention aims to solve]

[0011] In recent years, due to the increasing expectation for higher resolution displays, there is a growing demand for further reduction in self-weight deflection. Furthermore, with the increasing size and thinner profile of glass substrates, there is a demand for glass with a higher Young's modulus and a higher specific modulus (Young's modulus / density). Furthermore, to improve the thermal shock resistance of glass, a lower coefficient of thermal expansion is required. In addition, according to requirements in the glass manufacturing process, there is a demand to reduce the viscosity of the glass, especially the temperature T2 when the glass viscosity becomes 10⁻² dPa·s and the temperature T4 when the glass viscosity becomes 10⁻⁴ dPa·s; to reduce the devitrification temperature of the glass surface; and to avoid excessively increasing the strain point. The glass described in Patent Documents 1 and 2 has a low Young's modulus and a low specific modulus, making it impossible to achieve sufficiently small self-weight deflection. Even if the Young's modulus is high, and therefore the specific modulus is also high, the high average coefficient of thermal expansion results in lower thermal shock resistance, making it difficult to meet the above requirements.

[0012] To overcome the above-mentioned shortcomings, the object of the present invention is to provide a glass that reduces its own weight deflection, has excellent thermal shock resistance, excellent formability, and places less burden on glass manufacturing equipment. [Technical Means for Solving the Problem]

[0013] [1] An alkali-free glass, having a strain point of 700℃ to 740℃, a density of 2.6 g / cm3 or less, a Young's modulus of 90 GPa to 100 GPa or less, an average coefficient of thermal expansion of 30×10⁻⁷ / K to 39×10⁻⁷ / K at 50 to 350℃, a temperature T₂ at which the glass viscosity becomes 10⁻² dPa·s of 1590℃ to 1690℃, a temperature T₄ at which the glass viscosity becomes 10⁻⁴ dPa·s of 1350℃ or less, a glass surface devitrification temperature (T₁c) not reaching T₄+80℃, and a specific elastic modulus of 36 MN·m / kg or more, wherein the alkali-free glass, expressed in moles % based on oxides, contains: 55% to 80% SiO₂, 12% to 20% Al₂O₃, 0.3% to 5% B₂O₃. When MgO is 5% to 18%, CaO is 0.1% to 12%, SrO is 0.1% to 8%, and BaO is 0% to 6%; and MgO + CaO + SrO + BaO is 20% or less, MgO / CaO is 1 or more, MgO / (MgO + CaO + SrO + BaO) is 0.5 or more, and MgO + Al₂O₃ is 24% to 38%, and when formula (I) is set as (-3.125×[SiO₂]-2.394×[Al₂O₃]-3.511×[B₂O₃]-2.167×[MgO]-2.608×[CaO]-3.161×[SrO]-3.583×[BaO]+3.795×10⁻²), the value of formula (I) is 90 to 100. [2] As described in [1], when formula (II) is set as (0.213×[SiO 2]+1.006×[Al 2O 3]-0.493×[B 2O 3]+1.158×[MgO]+1.386×[CaO]+3.092×[SrO]+4.198×[BaO]+2.004×10 2), the value of formula (I) / formula (II)×100 is 36 or more. [3] As described in [1] or [2], the value of (MgO+CaO) / (SrO+BaO) is 8 or more. [4] The alkali-free glass described in any of [1] to [3] has an average linear expansion coefficient of 50 to 350°C of α, a Young's modulus of E, and a photoelastic constant of C, the product of these equalities α・E・C is 9.2 × 10⁻⁷ / K or less. [5] The alkali-free glass described in any of [1] to [4] has a photoelastic constant of 31 nm / MPa / cm or less. [6] The alkali-free glass described in any of [1] to [5] has a glass transition point of 730°C or higher and 850°C or lower.[7] The alkali-free glass described in any one of [1] to [6] has a surface devitrification viscosity of 10 3.4 dPa·s or higher. [8] The alkali-free glass described in any one of [1] to [7] contains 0 to 1% ZrO 2, expressed in moles % based on oxides. [9] The alkali-free glass described in any one of [1] to [8] contains 0.2% or less of the total content of Li 2O, Na 2O and K 2O, expressed in moles % based on oxides.

[10] The alkali-free glass described in any one of [1] to [9] contains 0% to 0.5% SnO 2, expressed in moles % based on oxides.

[11] The alkali-free glass described in any one of [1] to

[10] contains 0% to 1% F, expressed in moles %.

[12] An alkali-free glass as described in any one of [1] to

[11] , wherein the β-OH value of the glass is 0.05 mm -1 or more and 0.6 mm -1 or less.

[13] A glass plate comprising an alkali-free glass as described in any one of [1] to

[12] , wherein at least one side is 2400 mm or more and the thickness is 1 mm or less.

[14] A method for manufacturing alkali-free glass, which is a method for manufacturing alkali-free glass as described in any one of [1] to

[12] , and is formed by a float glass method or a melting method. [Effects of the Invention].

[0014] According to the present invention, a glass can be provided that can reduce the self-weight deflection of the glass, has excellent thermal shock resistance, and also has excellent formability, and puts less burden on glass manufacturing equipment.

Implementation Method

[0015] Hereinafter, an alkali-free glass according to one embodiment of the present invention will be described. Hereinafter, the composition range of each component of the glass is expressed in moles (%) based on oxides.

[0016] The alkali-free glass of this embodiment contains 55% to 80% SiO2. If the SiO2 content is less than 55 moles (or less, simply referred to as %), the strain point cannot be sufficiently increased, the average coefficient of thermal expansion increases, and the density tends to increase. Therefore, the SiO2 content is 55% or more, preferably 58% or more, more preferably 60% or more, even more preferably 61% or more, particularly preferably 62% or more, and most preferably 63% or more. If the SiO2 content exceeds 80%, the solubility of the glass decreases, the Young's modulus decreases, and the devitrification temperature (Tc) of the glass surface tends to increase. Therefore, the SiO2 content is 80% or less, preferably 75% or less, even more preferably 73% or less, even more preferably 70% or less, particularly preferably 69% or less, and most preferably 68% or less.

[0017] The alkali-free glass of this embodiment contains 12% to 20% Al₂O₃. Al₂O₃ increases the Young's modulus, thus suppressing deflection, and also suppresses phase separation of the glass, increasing the fracture toughness value and thus improving the strength of the glass. If the content of Al₂O₃ is less than 12%, it is difficult to achieve these effects, and it will lead to a relative increase in other components that increase the average coefficient of thermal expansion. Therefore, the average coefficient of thermal expansion tends to increase. Therefore, the content of Al₂O₃ is 12% or more, preferably 12.3% or more, more preferably 12.6% or more, further preferably 13% or more, even more preferably 13.3% or more, particularly preferably 13.6% or more, and most preferably 14% or more. If the content of Al₂O₃ exceeds 20%, there are concerns that the solubility of the glass deteriorates, the strain point increases, and the devitrification temperature (Tc) of the glass surface increases. Therefore, the content of Al2O3 is 20% or less, preferably 18% or less, more preferably 17.5% or less, even more preferably 17% or less, further preferably 16.5% or less, especially preferably 16% or less, and most preferably 15.5% or less.

[0018] The alkali-free glass of this embodiment contains 0.3% to 5% B₂O. B₂O₃ can improve the resistance to buffered hydrofluoric acid (a mixture of hydrofluoric acid and ammonium fluoride, also known as BHF) and improve the melting reactivity of the glass, thereby lowering the devitrification temperature (Tc) of the glass surface. Therefore, it can contain 5% or less. The content of B₂O₃ is preferably 4% or less, more preferably 3.5% or less, further preferably 3% or less, particularly preferably 2.5% or less, and most preferably 2% or less. If the content of B₂O₃ is less than 0.3%, it is difficult to achieve these effects. Therefore, the content of B₂O₃ is 0.3% or more, preferably 0.5% or more, more preferably 0.6% or more, further preferably 0.7% or more, particularly preferably 0.8% or more, and most preferably 0.9% or more.

[0019] The alkali-free glass of this embodiment contains 5% to 18% MgO. MgO can increase the Young's modulus without increasing the density, thus reducing the self-weight deflection problem by increasing the specific modulus of elasticity and improving the fracture toughness value, thereby increasing the strength of the glass. Furthermore, MgO also improves solubility. If the MgO content is less than 5%, these effects are difficult to achieve, and there is a risk that the coefficient of thermal expansion will become too low. Therefore, the MgO content is 5% or more. Preferably, the MgO content is 7% or more, more preferably 9% or more, further preferably 10% or more, particularly preferably 10.5% or more, and most preferably 11% or more. However, if the MgO content is too high, the devitrification temperature (Tc) of the glass surface is prone to rise. Therefore, the MgO content is 18% or less, preferably 17.5% or less, more preferably 17% or less, further preferably 16.5% or less, particularly preferably 16.3% or less, and most preferably 16% or less.

[0020] The alkali-free glass of this embodiment contains 0.1% to 12% CaO. Among alkaline earth metals, CaO is second only to MgO, and has the characteristic of increasing the specific modulus of elasticity without excessively lowering the strain point. It also improves solubility, similar to MgO. Furthermore, compared to MgO, CaO is less likely to increase the devitrification temperature (Tc) of the glass surface. If the CaO content is less than 0.1%, these effects are difficult to achieve. Therefore, the CaO content is 0.1% or more. Preferably, the CaO content is 0.5% or more, more preferably 1% or more, further preferably 1.5% or more, particularly preferably 2% or more, and most preferably 2.5% or more. If the CaO content exceeds 12%, the average coefficient of thermal expansion becomes too large, and the devitrification temperature (Tc) of the glass surface increases, making devitrification problems more likely during glass manufacturing. Therefore, the CaO content is 12% or less, preferably 10% or less, even more preferably 9% or less, further preferably 8.5% or less, especially preferably 8% or less, and most preferably 7.5% or less.

[0021] The alkali-free glass of this embodiment contains 0.1% to 8% SrO. Although SrO improves solubility without increasing the devitrification temperature (Tc) of the glass surface, this effect is difficult to achieve if the SrO content is less than 0.1%. Therefore, the SrO content is 0.1% or more, preferably 0.15% or more, more preferably 0.2% or more, and even more preferably 0.3% or more, and particularly preferably 0.4% or more. The aforementioned effect of SrO is lower than that of BaO. If the SrO content exceeds 8%, there is too much SrO, which actually increases the density, and the average coefficient of thermal expansion also becomes too large. Therefore, the SrO content is 8% or less, preferably 6% or less, more preferably 5% or less, even more preferably 4% or less, particularly preferably 3% or less, and most preferably 2% or less.

[0022] The alkali-free glass of this embodiment contains 0% to 6% BaO. BaO improves solubility without raising the devitrification temperature (Tc) of the glass surface, and therefore can be contained therein. When BaO is contained, the BaO content is preferably 0.1% or more, more preferably 0.3% or more, further preferably 0.5% or more, particularly preferably 0.8% or more, and most preferably 1% or more. If more BaO is contained, the density increases, the Young's modulus decreases, and the average coefficient of thermal expansion tends to become too large. Therefore, the BaO content is 6% or less, preferably 5.5% or less, more preferably 5% or less, particularly preferably 4.5% or less, and most preferably 4% or less. Furthermore, given the toxicity of Ba, it is preferable that BaO is substantially absent. "Substantially absent" means that it is not contained except for unavoidable impurities. In this embodiment, the BaO content is, for example, less than 0.1%, preferably 0.05% or less, and more preferably 0.01% or less.

[0023] If the total amount of alkaline earth metal oxides, i.e., MgO + CaO + SrO + BaO, is too high, there is a risk that the average coefficient of thermal expansion may not be reduced. Furthermore, there is a risk that acid resistance may decrease. Therefore, the content of MgO + CaO + SrO + BaO is 20% or less, preferably 19.8% or less, more preferably 19.6% or less, further preferably 19.4% or less, particularly preferably 19.2% or less, and most preferably 19.1% or less. If the devitrification temperature (Tc) of the glass surface is low, the devitrification viscosity of the glass surface increases, and the formability improves. To lower the devitrification temperature (Tc) of the glass surface, the content of MgO + CaO + SrO + BaO is preferably 10% or more, more preferably 12% or more, further preferably 13% or more, even more preferably 14% or more, particularly preferably 15% or more, and most preferably 16% or more. Here, the content of MgO + CaO + SrO + BaO is, for example, more than 10% and less than 20%.

[0024] Furthermore, if the ratio of MgO to CaO, i.e., MgO / CaO, is low, the CaO-Al₂O₃-SiO₂ system is prone to devitrification, resulting in poor formability. Specifically, the devitrification temperature increases, and the devitrification viscosity at the glass surface decreases. Therefore, the MgO / CaO ratio is set to 1 or higher. Preferably, the MgO / CaO ratio is 1.1 or higher, more preferably 1.2 or higher, even more preferably 1.3 or higher, particularly preferably 1.5 or higher, and most preferably 1.8 or higher. On the other hand, if the MgO / CaO ratio is too high, the MgO-Al₂O₃-SiO₂ system is prone to devitrification, the devitrification temperature at the glass surface increases, and the devitrification viscosity at the glass surface decreases. Therefore, the MgO / CaO ratio is preferably 100 or lower, more preferably 30 or lower, even more preferably 15 or lower, particularly preferably 10 or lower, and most preferably 5 or lower. Here, the MgO / CaO ratio is, for example, 1 or higher and 100 or lower.

[0025] Furthermore, if the proportion of MgO in the total stoichiometry of alkaline earth metal oxides (MgO + CaO + SrO + BaO), i.e., MgO / (MgO + CaO + SrO + BaO), is low, the density increases and the specific elastic modulus decreases. Furthermore, the phase separation characteristics and acid resistance of the glass deteriorate. Therefore, MgO / (MgO + CaO + SrO + BaO) is set to 0.5 or more. MgO / (MgO + CaO + SrO + BaO) is preferably 0.52 or more, more preferably 0.54 or more, further preferably 0.56 or more, particularly preferably 0.58 or more, and most preferably 0.6 or more. On the other hand, in order to suppress devitrification in the MgO-Al₂O₃-SiO₂ system and suppress the rise in devitrification temperature, the ratio of MgO / (MgO+CaO+SrO+BaO) is preferably 0.95 or less, more preferably 0.9 or less, further preferably 0.85 or less, and especially preferably 0.8 or less. Here, the ratio of MgO / (MgO+CaO+SrO+BaO) is, for example, 0.5 or more and 0.95 or less.

[0026] Furthermore, the total content of MgO and Al₂O₃, i.e., MgO + Al₂O₃, is 24% to 38%. If the content of MgO + Al₂O₃ is less than 24%, the Young's modulus decreases, and the substrate deformation relative to external stress increases. Therefore, the content of MgO + Al₂O₃ is set to 24% or more. Preferably, it is 24.2% or more, more preferably 24.5% or more, even more preferably 25% or more, particularly preferably 25.5% or more, and most preferably 26% or more. On the other hand, if the content of MgO + Al₂O₃ exceeds 38%, the devitrification temperature increases, and the formability deteriorates. Therefore, the content of MgO + Al₂O₃ is set to 38% or less. Preferably, it is 35% or less, more preferably 33% or less, even more preferably 32% or less, particularly preferably 31% or less, and most preferably 30% or less.

[0027] In the alkali-free glass of this embodiment, if the mixing ratio of the total content of MgO and CaO to the total content of SrO and BaO, i.e., (MgO + CaO) / (SrO + BaO) is 8 or more, the increase in density can be suppressed, and the Young's modulus can be increased, thus increasing the specific modulus of elasticity, which is preferable. (MgO + CaO) / (SrO + BaO) is more preferably 10 or more, further preferably 12 or more, even more preferably 14 or more, particularly preferably 16 or more, and most preferably 18 or more. On the other hand, if (MgO + CaO) / (SrO + BaO) is 200 or less, the increase in devitrification temperature can be suppressed, which is preferable. (MgO + CaO) / (SrO + BaO) is preferably 100 or less, more preferably 75 or less, further preferably 60 or less, and particularly preferably 50 or less. Here, (MgO+CaO) / (SrO+BaO) is, for example, above 8 and below 200.

[0028] In the alkali-free glass of this embodiment, when formula (I) is set as (-3.125×[SiO 2]-2.394×[Al 2O 3]-3.511×[B 2O 3]-2.167×[MgO]-2.608×[CaO]-3.161×[SrO]-3.583×[BaO]+3.795×10 2), the value of formula (I) is 90 or more and 100 or less. The value represented by formula (I) is an index of Young's modulus. If the value is less than 90, Young's modulus tends to be lower, elastic modulus tends to be smaller, and self-weight deflection tends to be larger. If it exceeds 100, Young's modulus becomes too large, and cutting margin is impaired. The value represented by formula (I) is preferably 90.5 to 97, more preferably 90.8 to 95, further preferably 91 to 94, particularly preferably 91.2 to 93.5, and most preferably 91.5 to 93. Furthermore, the designation of "[metal oxide]" in the formula (e.g., "[SiO₂]") indicates the value when the metal oxide composition is expressed in moles (%) (as is the case in other parts of this specification). For example, when SiO₂ is 60 moles (expressed in moles based on oxides), "[SiO₂]" represents 60.

[0029] In the alkali-free glass of this embodiment, when formula (II) is set as (0.213×[SiO 2]+1.006×[Al 2O 3]-0.493×[B 2O 3]+1.158×[MgO]+1.386×[CaO]+3.092×[SrO]+4.198×[BaO]+2.004×10 2), the value of formula (I) / formula (II)×100 is preferably 36 or more. The value represented by formula (I) / formula (II)×100 is an index of the specific modulus of elasticity. If the value represented by formula (I) / formula (II)×100 is 36 or more, the specific modulus of elasticity becomes higher, which is preferable. The value of Equation (I) / Equation (II) × 100 is preferably 36.1 or higher, more preferably 36.2 or higher, even more preferably 36.3 or higher, particularly preferably 36.4 or higher, and most preferably 36.5 or higher. If the value of Equation (I) / Equation (II) × 100 is 50 or lower, the cutting margin can be maintained, which is preferred. Here, the value of Equation (I) / Equation (II) × 100 is, for example, 36 or higher and 50 or lower.

[0030] The value represented by formula (II) is an indicator of density. If it is below 260, the density is low, which is preferable. If the value represented by formula (II) is less than 240, the density may be too low. Therefore, the value represented by formula (II) is preferably above 240. The value represented by formula (II) is more preferably above 242 and below 259, further preferably above 244 and below 258, even more preferably above 246 and below 257, particularly preferably above 248 and below 256, and most preferably above 250 and below 255.

[0031] The alkali-free glass of this embodiment is preferably substantially free of alkali metal oxides such as Li₂O, Na₂O, and K₂O. In this embodiment, "substantially free of alkali metal oxides" means that it does not contain any alkali metal oxides except for unavoidable impurities mixed in from raw materials, etc., that is, it is not intentionally contained. For example, the content is 0.1% or less, preferably 0.08% or less, more preferably 0.05% or less, and even more preferably 0.03% or less.

[0032] However, a specified amount of alkali metal oxide may be included to obtain specific effects (lower strain point, lower Tg, lower cooling point, etc.). Specifically, the total content of Li₂O, Na₂O, and K₂O may be 0.2% or less. More preferably, 0.15% or less, more preferably 0.1% or less, more preferably 0.08% or less, and even more preferably 0.05% or less, most preferably 0.03% or less. The total content of Li₂O, Na₂O, and K₂O may also be 0.001% or more. Here, the total content of Li₂O, Na₂O, and K₂O is, for example, 0.001% or more and 0.2% or less.

[0033] When the alkali-free glass of this embodiment is used in a glass plate for a display, in order to prevent the thin film of metal or oxides disposed on the surface of the glass plate from deteriorating in properties, the alkali-free glass of this embodiment is preferably substantially free of P₂O₅. In this embodiment, "substantially free of P₂O₅" means, for example, that the content is 0.1% or less. Furthermore, in order to make the glass easy to reuse, and from the viewpoint of environmental impact, the alkali-free glass of this embodiment is preferably substantially free of PbO, As₂O₃, and Sb₂O₃. In this embodiment, "substantially free of PbO, As₂O₃, and Sb₂O₃" means that the content of PbO, As₂O₃, and Sb₂O₃ is, for example, 0.01% or less, preferably 0.005% or less.

[0034] On the other hand, in order to improve the solubility, clarity and formability of the glass, it may contain 1% or less of one or more of As 2O 3 and Sb 2O 3, preferably 0.5% or less, more preferably 0.3% or less, further preferably 0.2% or less, especially preferably 0.15% or less, and most preferably 0.1% or less.

[0035] In order to improve the solubility, clarity, and formability of the glass, the alkali-free glass of this embodiment may also contain one or more of ZrO2, ZnO, Fe2O3, SO3, F, Cl, and SnO2 in total content of 2% or less. Preferably, it is 1% or less, and more preferably 0.5% or less.

[0036] The alkali-free glass of this embodiment may also contain ZrO2 to lower the glass melting temperature, increase Young's modulus, and improve chemical resistance. For example, it may contain 0.001% or more. However, if the content of ZrO2 is too high, there is a risk that the devitrification temperature of the glass surface will increase, the dielectric constant ε will increase, and the glass will become inhomogeneous. Furthermore, when applied to semiconductor devices, there is a risk of malfunction due to alpha rays. Therefore, the content of ZrO2 is preferably 1% or less, more preferably 0.5% or less, further preferably 0.2% or less, even more preferably 0.1% or less, particularly preferably 0.05% or less, even more preferably 0.04% or less, especially preferably 0.03% or less, and most preferably substantially free of ZrO2. "Substantially free of ZrO2" means that it is not contained except for unavoidable impurities mixed in from raw materials, etc., that is, it is not intentionally contained. In this embodiment, "substantially free of ZrO2" means that the ZrO2 content is, for example, less than 0.01%, preferably less than 0.005%.

[0037] The alkali-free glass of this embodiment may also contain 0% to 0.5% SnO2 to improve the solubility and clarity of the glass. The SnO2 content is preferably 0.4% or less, and more preferably 0.3% or less.

[0038] The alkali-free glass of this embodiment may also contain F to improve the glass's solubility and clarity. When F is present, the F content is expressed in moles (%), preferably 1% or less, more preferably 0.5% or less, further preferably 0.4% or less, even more preferably 0.3% or less, particularly preferably 0.2% or less, and especially preferably 0.1% or less. Furthermore, the F content refers to the amount remaining in the molten glass, not the amount added to the glass raw material. The same applies to the Cl content, which will be discussed later.

[0039] In the alkali-free glass of this embodiment, the content of Fe can be between 0.001% and 0.05% (calculated as Fe₂O₃) to improve the solubility of the glass. If the Fe content of the glass is reduced, the amount of infrared absorption obtained by Fe²⁺ in the melting process decreases, resulting in an increase in the thermal conductivity of the glass. Therefore, for example, when the glass is heated and melted in a glass melting furnace using heat rays such as burner flames, the temperature distribution of the molten glass becomes smaller, the convection rate of the molten glass decreases, and the bubble quality or homogeneity of the glass product may deteriorate. If the Fe content is 0.001% or more (calculated as Fe₂O₃), there are fewer concerns about the above-mentioned problems. Furthermore, clarity or homogeneity depends on sufficient convection of the molten glass. When it is desired to improve the solubility of glass, the Fe content, converted from Fe2O3, is preferably 0.002% or more, more preferably 0.005% or more, even more preferably 0.008% or more, particularly preferably 0.01% or more, even more preferably 0.02% or more, especially preferably 0.03% or more, and most preferably 0.04% or more.

[0040] If the Fe content in the glass increases, the Fe will exist in the glass in the form of Fe2+ or Fe3+, which may reduce the transmittance of the glass. In particular, since Fe3+ has absorption properties in the wavelength range below 300 nm, the ultraviolet transmittance of the glass may decrease. For example, in the case of glass panels used in various displays, if the panel thickness is 0.5 mm and the transmittance at a wavelength of 300 nm is 20% or more, it is preferable to use a photocurable resin to bond the two substrate glass panels constituting the flat panel display. To produce glass with a thickness of 0.5 mm and a transmittance of 20% or more at a wavelength of 300 nm, the Fe content, converted from Fe₂O₃, is preferably 0.05% or less, more preferably 0.04% or less, further preferably 0.03% or less, even more preferably 0.02% or less, particularly preferably 0.01% or less, even more preferably 0.008% or less, even more preferably 0.006% or less, especially preferably 0.004% or less, and most preferably 0.002% or less.

[0041] To improve the clarity of the glass, the content of Cl can be expressed in moles (%) as 0.1% to 1.0%. If the Cl content is 0.1% or more, the clarifying effect during the melting of the glass raw materials becomes good. The Cl content is preferably 0.15% or more, more preferably 0.2% or more, further preferably 0.25% or more, and particularly preferably 0.3% or more. If the Cl content is 1.0% or less, the effect of suppressing the enlargement of the bubble layer during glass manufacturing becomes good. It is preferably 0.8% or less, more preferably 0.6% or less.

[0042] The alkali-free glass of this embodiment may also contain, based on the following purposes, such as improving the solubility, clarity, and formability of the glass, obtaining absorption at a specific wavelength, and improving density, hardness, flexural stiffness, and durability, one or more of Se₂O₃, TeO₂, Ga₂O₃, In₂O₃, GeO₂, CdO, BeO, and Bi₂O₃, preferably 1% or less, more preferably 0.5% or less, further preferably 0.3% or less, further preferably 0.1% or less, particularly preferably 0.05% or less, and most preferably 0.01% or less. The GeO₂ content is preferably less than 0.1%, more preferably 0.08% or less, further preferably 0.05% or less, even more preferably 0.03% or less, particularly preferably 0.01% or less, and most preferably substantially none. The term "substantially free of GeO 2" means that it does not contain any GeO 2 except for unavoidable impurities mixed in from raw materials, etc., i.e., it is not intentionally contained. In this embodiment, "substantially free of GeO 2" means that the content of GeO 2 is, for example, 0.05% or less, preferably 0.01% or less, and more preferably 0.005% or less.

[0043] In order to improve the solubility, clarity, and formability of the glass, and to improve the hardness of the glass, such as Young's modulus, the alkali-free glass of this embodiment may also contain rare earth oxides and transition metal oxides.

[0044] The alkali-free glass of this embodiment may also contain 2% or less of one or more of Sc 2O 3, Y 2O 3, La 2O 3, Ce 2O 3, CeO 2, Pr 2O 3, Nd 2O 3, Pm 2O 3, Sm 2O 3, Eu 2O 3, Gd 2O 3, Tb 2O 3, Dy 2O 3, Ho 2O 3, Er 2O 3, Tm 2O 3, Yb 2O 3 and Lu 2O 3 as rare earth oxides, preferably 1% or less, more preferably 0.5% or less, further preferably 0.3% or less, even more preferably 0.1% or less, particularly preferably 0.05% or less, and most preferably 0.01% or less. The La₂O₃ content is preferably less than 1%, more preferably less than 0.5%, further preferably less than 0.3%, even more preferably less than 0.1%, particularly preferably less than 0.05%, and most preferably substantially free of La₂O₃. "Substantially free of La₂O₃" means that it is not present except for unavoidable impurities introduced from raw materials, etc., i.e., it is not intentionally present. In this embodiment, "substantially free of La₂O₃" means that the La₂O₃ content is, for example, less than 0.05%, preferably less than 0.01%, and more preferably less than 0.005%.

[0045] The alkali-free glass of this embodiment may also contain 2% or less of one or more of V₂O₅, Ta₂O₃, Nb₂O₅, WO₃, MoO₃ and HfO₂ as transition metal oxides, preferably 1% or less, more preferably 0.5% or less, further preferably 0.3% or less, even more preferably 0.1% or less, particularly preferably 0.05% or less, and most preferably 0.01% or less.

[0046] In order to improve the solubility of the glass, the alkali-free glass of this embodiment may also contain 2% or less of ThO2 as an actinide oxide, preferably 1% or less, more preferably 0.5% or less, further preferably 0.3% or less, even more preferably 0.1% or less, especially preferably 0.05% or less, particularly preferably 0.01% or less, and most preferably 0.005% or less.

[0047] Regarding the alkali-free glass of this embodiment, a β-OH value of 0.05 mm⁻¹ or more and 0.6 mm⁻¹ or less is preferred, as it can suppress the thermal shrinkage of the glass. The β-OH value is an indicator of the moisture content in the glass and is determined by measuring the absorbance of the glass sample for light with a wavelength of 2.75 to 2.95 μm, dividing the maximum absorbance βmax by the thickness (mm) of the sample, thereby obtaining the β-OH value. The β-OH value of the glass is more preferably 0.45 mm⁻¹ or less, more preferably 0.4 mm⁻¹ or less, further preferably 0.35 mm⁻¹ or less, particularly preferably 0.3 mm⁻¹ or less, even more preferably 0.28 mm⁻¹ or less, especially preferably 0.25 mm⁻¹ or less, and most preferably 0.23 mm⁻¹ or less. On the other hand, if the β-OH value is 0.05 mm⁻¹ or more, the strain point of the glass described later can be easily achieved. Therefore, the β-OH value is preferably 0.08 mm -1 or higher, more preferably 0.1 mm -1 or higher, even more preferably 0.13 mm -1 or higher, particularly preferably 0.15 mm -1 or higher, especially preferably 0.18 mm -1 or higher, and most preferably 0.2 mm -1 or higher.

[0048] The strain point of the alkali-free glass in this embodiment is 700°C or higher and 740°C or lower. If the strain point is below 700°C, deformation of the glass plate and shrinkage (thermal shrinkage) accompanying the structural stabilization of the glass are easily caused when the glass plate is exposed to high temperatures during the thin film formation step of the display. The strain point is preferably 705°C or higher, more preferably 710°C or higher, even more preferably 715°C or higher, particularly preferably 720°C or higher, and most preferably 725°C or higher. On the other hand, if the strain point is too high, the temperature of the cooling device needs to be increased accordingly, which tends to reduce the lifespan of the cooling device. Therefore, the strain point is 740°C or lower. The strain point is preferably 738°C or lower, more preferably 736°C or lower, and even more preferably 735°C or lower.

[0049] The density of the alkali-free glass in this embodiment is 2.6 g / cm³ or less. If the density is 2.6 g / cm³ or less, the self-weight deflection is reduced, making the handling of large substrates easier. Furthermore, the weight of the device using the glass can be reduced. The density is preferably 2.59 g / cm³ or less, more preferably 2.58 g / cm³ or less, further preferably 2.57 g / cm³ or less, particularly preferably 2.56 g / cm³ or less, and most preferably 2.55 g / cm³ or less. Furthermore, a large substrate, for example, refers to a substrate with at least one side being 1800 mm or more. On the other hand, if the density is 2.4 g / cm³ or more, the stability during handling becomes better, which is also preferable. The density is preferably 2.42 g / cm³ or higher, more preferably 2.44 g / cm³ or higher, even more preferably 2.46 g / cm³ or higher, particularly preferably 2.48 g / cm³ or higher, and most preferably 2.5 g / cm³ or higher. Here, the density is, for example, 2.4 g / cm³ or higher and 2.6 g / cm³ or lower.

[0050] Furthermore, the Young's modulus of the alkali-free glass in this embodiment is 90 GPa or higher and 100 GPa or lower. If the Young's modulus is 90 GPa or higher, substrate deformation relative to external stress is suppressed. For example, when a film is formed on the surface of the glass substrate, substrate warping can be suppressed. As a specific example, in the manufacture of the TFT (Thin-film transistor) side substrate of a flat panel display, substrate warping can be suppressed when a gate metal film such as copper or a gate insulating film such as silicon nitride is formed on the surface of the substrate. Furthermore, deflection can also be suppressed, for example, when the size of the substrate becomes larger. The Young's modulus is preferably 90.5 GPa or higher, more preferably 91 GPa or higher, further preferably 91.2a or higher, particularly preferably 91.5 GPa or higher, and most preferably 92 GPa or higher. If the Young's modulus is 100 GPa or lower, the cutting margin becomes larger. The Young's modulus is preferably below 98 GPa, more preferably below 97 GPa, further preferably below 96 GPa, and most preferably below 95 GPa. The Young's modulus can be determined using ultrasound.

[0051] The average coefficient of thermal expansion of the alkali-free glass in this embodiment at 50–350°C is 30 × 10⁻⁷ / K or higher. When the coefficient is less than 30 × 10⁻⁷ / K, for example, in the manufacture of a TFT-side substrate for a flat panel display, sometimes a gate metal film such as copper and a gate insulating film such as silicon nitride are sequentially deposited on the alkali-free glass. However, the difference in thermal expansion between the alkali-free glass and the gate metal film such as copper formed on the substrate surface is large, which may lead to problems such as substrate warping and film peeling. The average coefficient of thermal expansion at 50–350°C is preferably 30.5 × 10⁻⁷ / K or higher, more preferably 31 × 10⁻⁷ / K or higher, even more preferably 31.5 × 10⁻⁷ / K or higher, particularly preferably 32 × 10⁻⁷ / K or higher, and most preferably 32.5 × 10⁻⁷ / K or higher. On the other hand, if the average coefficient of thermal expansion at 50–350°C exceeds 39 × 10⁻⁷ / K, there is a risk of glass breakage during the manufacturing process of products such as displays, and the thermal shock resistance of the glass decreases. Therefore, the average coefficient of thermal expansion at 50–350°C is 39 × 10⁻⁷ / K or less. Preferably, the average coefficient of thermal expansion at 50–350°C is 38.5 × 10⁻⁷ / K or less, more preferably 38 × 10⁻⁷ / K or less, further preferably 37.5 × 10⁻⁷ / K or less, particularly preferably 37.3 × 10⁻⁷ / K or less, and most preferably 37 × 10⁻⁷ / K or less. Here, the average coefficient of thermal expansion at 50–350°C is, for example, 30 × 10⁻⁷ / K or more and 39 × 10⁻⁷ / K or less.

[0052] In the alkali-free glass of this embodiment, the temperature T2 (the temperature at which logη = 2) at which the glass viscosity η becomes 10 2 dPa·s is 1590°C or higher and 1690°C or lower. If T2 is 1590°C or higher, SO3 can be used as a clarifying agent in the glass manufacturing process. T2 is preferably 1592°C or higher, more preferably 1594°C or higher, even more preferably 1596°C or higher, particularly preferably 1598°C or higher, and most preferably 1600°C or higher. On the other hand, if T2 is 1690°C or lower, the glass has excellent solubility. Therefore, the burden on manufacturing equipment can be reduced. For example, the lifespan of equipment such as furnaces that melt the glass can be extended, and productivity can be improved. Furthermore, defects originating from the furnace (such as foreign matter defects, Zr defects, etc.) can be reduced. The temperature of T2 is preferably below 1670°C, more preferably below 1660°C, further preferably below 1650°C, even more preferably below 1640°C, and most preferably below 1635°C.

[0053] In the alkali-free glass of this embodiment, the temperature T4 (the temperature at which logη = 4) at which the glass viscosity η becomes 10⁴ dPa·s is 1350°C or lower. If T4 is 1350°C or lower, the glass has excellent formability. Furthermore, for example, by lowering the temperature during glass forming, volatiles in the atmosphere surrounding the glass can be reduced, thereby reducing defects in the glass. Since the glass can be formed at a lower temperature, the burden on manufacturing equipment can be reduced. For example, the lifespan of equipment such as the float polishing furnace used for glass forming can be extended, and productivity can be improved. T4 is preferably 1340°C or lower, more preferably 1330°C or lower, further preferably 1320°C or lower, even more preferably 1310°C or lower, particularly preferably 1300°C or lower, and most preferably 1295°C or lower. The lower limit of T4 is not particularly limited, and is generally 1100°C or higher. T4 is, for example, between 1100°C and 1350°C. T2 and T4 can be determined as follows: Viscosity is measured using a rotational viscometer according to the method specified in ASTM C 965-96. The temperature at which the viscosity becomes 10⁻² d·Pa·s is taken as T2, and the temperature at which the viscosity becomes 10⁻⁴ d·Pa·s is taken as T4. Furthermore, in the embodiments described later, NBS710 and NIST717a are used as reference samples for device calibration.

[0054] The surface devitrification temperature (Tc) of the alkali-free glass in this embodiment does not reach T4 + 80°C. If Tc does not reach T4 + 80°C, the glass has excellent formability. It can suppress the formation of crystals inside the glass during the forming process, thus reducing the transmittance. Furthermore, it can reduce the burden on manufacturing equipment. For example, it can extend the life of equipment such as floating polishing furnaces used for glass forming, thereby improving productivity. Tc is preferably below T4 + 75°C, more preferably below T4 + 70°C, further preferably below T4 + 60°C, even more preferably below T4 + 50°C, particularly preferably below T4 + 40°C, and most preferably below T4 + 30°C. The lower limit of Tc is not particularly limited, and is usually above 1000°C. For example, Tc is above 1000°C and does not reach T4 + 80°C. The surface devitrification temperature (Tc) of the glass in this embodiment can be determined by the following method. That is, the crushed glass particles are placed in a platinum dish and heat-treated in an electric furnace at a fixed temperature for 17 hours. After heat treatment, an optical microscope is used to observe the highest temperature at which crystals precipitate on the glass surface and the lowest temperature at which no crystals precipitate. The average value of these values ​​is taken as the devitrification temperature (Tc) of the glass surface.

[0055] The viscosity (glass surface devitrification viscosity (ηc)) of the alkali-free glass at the glass surface devitrification temperature (Tc) of this embodiment is preferably 10 3.4 dPa·s or higher. If the glass surface devitrification viscosity (ηc) is 10 3.4 dPa·s or higher, the formability of the glass sheet is excellent. Furthermore, it can suppress the formation of crystals inside the glass during the forming process, thus reducing the transmittance. It can also reduce the burden on manufacturing equipment. For example, it can extend the lifespan of equipment such as float polishing furnaces used to form glass sheets, thereby improving productivity. ηc is more preferably 10 3.5 dPa·s or higher, more preferably 10 3.6 dPa·s or higher, particularly preferably 10 3.7 dPa·s or higher, and most preferably 10 3.8 dPa·s or higher. There is no particular limitation on the upper limit of ηc, and it is generally 10 6 dPa·s or lower. For example, ηc is above 10 3.4 dPa·s or below 10 6 dPa·s.

[0056] The specific modulus of elasticity (Young's modulus (GPa) / density (g / cm³)) of the alkali-free glass in this embodiment is 36 MN・m / kg or higher. If the specific modulus of elasticity is 36 MN・m / kg or higher, the self-weight deflection is smaller, making the processing of large substrates easier. The specific modulus of elasticity is preferably 36.1 MN・m / kg or higher, more preferably 36.2 MN・m / kg or higher, further preferably 36.3 MN・m / kg or higher, particularly preferably 36.4 MN・m / kg or higher, and most preferably 36.5 MN・m / kg or higher. There is no particular limitation on the upper limit of the specific modulus of elasticity; it is generally 50 MN・m / kg or lower. For example, the specific modulus of elasticity is 36 MN・m / kg or higher and 50 MN・m / kg or lower. Furthermore, a large substrate, for example, refers to a substrate with at least one side being 1800 mm or higher. At least one side of the large substrate may be 2000 mm or more, or 2500 mm or more, or 3000 mm or more, or 3500 mm or more.

[0057] The glass transfer point (hereinafter, also referred to as Tg) of the alkali-free glass in this embodiment is preferably 850°C or lower. If Tg is 850°C or lower, the burden on manufacturing equipment can be reduced. For example, the surface temperature of the rollers used in glass forming can be reduced, extending the equipment's lifespan and improving productivity. Tg is more preferably 830°C or lower, more preferably 820°C or lower, further preferably 810°C or lower, and particularly preferably 800°C or lower. From the viewpoint of heat resistance, Tg is preferably 730°C or higher. Tg is more preferably 740°C or higher, further preferably 750°C or higher, particularly preferably 760°C or higher, and most preferably 770°C or higher. Here, Tg is preferably 730°C or higher and 850°C or lower.

[0058] The photoelastic constant of the alkali-free glass in this embodiment is preferably 31 nm / MPa / cm or less. Due to stress generated during the manufacturing process of the liquid crystal display panel or during the use of the liquid crystal display device, the glass substrate may exhibit birefringence, causing black displays to appear grayish and reducing the contrast of the liquid crystal display. Setting the photoelastic constant to 31 nm / MPa / cm or less can suppress this phenomenon. More preferably, the photoelastic constant is 30 nm / MPa / cm or less, further preferably 29 nm / MPa / cm or less, even more preferably 28 nm / MPa / cm or less, particularly preferably 27.5 nm / MPa / cm or less, and most preferably 27 nm / MPa / cm or less. Considering the ease of ensuring other physical properties, the photoelastic constant is preferably 23 nm / MPa / cm or more, and more preferably 25 nm / MPa / cm or more. Furthermore, the photoelastic constant can be measured using the circular plate compression method at a measurement wavelength of 546 nm. Here, the photoelastic constant is preferably above 23 nm / MPa / cm and below 31 nm / MPa / cm.

[0059] When using the alkali-free glass of this embodiment as the glass plate for a liquid crystal display, when the average linear expansion coefficient at 50–350°C is set as α, the Young's modulus is set as E, and the photoelastic constant is set as C, the product of α, E, and C, α・E・C, is preferably 9.2 × 10⁻⁷ / K or less. In a liquid crystal display, heat from the backlight causes the temperature distribution of the glass plate (in TFT-LCD (Thin-film transistor-Liquid crystal display device), referring to the array glass plate) near the backlight to become uneven. If the difference between the highest and lowest temperatures within the glass plate is set as ΔT, the maximum value F of the stress generated within the glass plate is expressed by the following formula: F = α・E・ΔT. The optical path difference, i.e., the retardation R, generated on the thickness of the glass plate due to this stress F is expressed by the following formula. R = C·F·L = (α·E·C)·ΔT·L. Therefore, the smaller α·E·C is, the smaller R is, and the better the contrast of the liquid crystal display. If α·E·C is 9.2×10⁻⁷ / K or less, when the alkali-free glass of this embodiment is used as the glass plate for the liquid crystal display, the contrast of the liquid crystal display becomes good, and it is not easy to cause poor contrast.

[0060] α・E・C is preferably 9×10⁻⁷ / K or less, further preferably 8.8×10⁻⁷ / K or less, even more preferably 8.7×10⁻⁷ / K or less, particularly preferably 8.6×10⁻⁷ / K or less, and most preferably 8.5×10⁻⁷ / K or less. The lower limit of α・E・C is not particularly limited, and is generally 5×10⁻⁷ / K or more. α・E・C is preferably 5×10⁻⁷ / K or more and 9.2×10⁻⁷ / K or less.

[0061] The alkali-free glass of this embodiment has a Young's modulus of 90 GPa or higher and a specific modulus of elasticity of 36 MN・m / kg or higher, thus reducing its self-weight deflection. Therefore, it is suitable for use as a glass plate for large substrates. A large substrate, for example, refers to a glass plate with at least one side being 1800 mm or more; specifically, it is suitable for glass plates with a long side of 1800 mm or more and a short side of 1500 mm or more.

[0062] The alkali-free glass of this embodiment is more preferably a glass plate with at least one side being 2400 mm or more, for example, a glass plate with a long side of 2400 mm or more and a short side of 2100 mm or more; it is even more preferably a glass plate with at least one side being 3000 mm or more, for example, a glass plate with a long side of 3000 mm or more and a short side of 2800 mm or more; it is particularly preferably a glass plate with at least one side being 3200 mm or more, for example, a glass plate with a long side of 3200 mm or more and a short side of 2900 mm or more; and it is best for a glass plate with at least one side being 3300 mm or more, for example, a glass plate with a long side of 3300 mm or more and a short side of 2950 mm or more.

[0063] Regarding the glass plate of this embodiment, lightweighting can be achieved with a thickness of 1 mm or less, which is preferable. The thickness of the glass plate in this embodiment is more preferably 0.7 mm or less, further preferably 0.65 mm or less, even more preferably 0.55 mm or less, particularly preferably 0.45 mm or less, and most preferably 0.4 mm or less. The thickness of the glass plate in this embodiment can also be set to 0.1 mm or less, or 0.05 mm or less. However, from the viewpoint of preventing deflection due to its own weight, the thickness is preferably 0.1 mm or more, more preferably 0.2 mm or more. The thickness of the glass plate is preferably 0.1 mm or more and 1 mm or less.

[0064] The manufacture of alkali-free glass according to this embodiment can be carried out, for example, according to the following steps: The raw materials of the above-mentioned components are prepared in such a way that they are in the target content in the glass composition, and then put into a melting furnace and heated to 1500-1800°C to melt them, thereby obtaining molten glass. In a forming apparatus, the obtained molten glass is formed into a glass strip of a specified thickness, and after the glass strip is slowly cooled, it is cut to obtain alkali-free glass.

[0065] In this embodiment, it is preferable to use a float glass method or a melting method to form molten glass into a glass sheet. From the viewpoint of stably producing large glass sheets with a high Young's modulus (e.g., one side being 1800 mm or more), the float glass method is preferred. Example

[0066] Hereinafter, examples will be described, but the present invention is not limited to these examples. Hereinafter, Examples 1 to 14 and 24 to 55 are examples, and Examples 15 to 23 are comparative examples. Taking the glass composition as shown in Examples 1 to 55 (unit: moles%), the raw materials of each component were prepared and melted at 1600°C for 1 hour using a platinum crucible. After melting, the molten liquid was poured onto a carbon plate and held at a temperature of (glass transition point + 30°C) for 60 minutes, and then cooled to room temperature (25°C) at a rate of 1°C per minute to obtain a plate-shaped glass. The plate-shaped glass was mirror-polished to obtain a glass plate, and various evaluations were performed on it. Furthermore, the β-OH value of the glass was determined according to the following steps. (β-OH value) The absorbance of the glass sample to light with a wavelength of 2.75 to 2.95 μm was measured, and the maximum absorbance βmax was divided by the thickness (mm) of the sample to obtain the β-OH value. The results are shown in Tables 1 through 8. Furthermore, the values ​​shown in parentheses in Tables 1 through 8 are calculated values.

[0067] The following shows the methods for measuring each physical property. (Average coefficient of thermal expansion α) Measured using a dilatometer according to the method specified in JIS R3102 (1995). The measurement temperature range is set from room temperature to 400°C or higher, and the average coefficient of thermal expansion at 50 to 350°C is expressed in units of 10⁻⁷ / K. (Density) Measured using Archimedes' method on a glass block of approximately 20 g without air bubbles, according to the method specified in JIS Z 8807. (Strain point) Measured using the fiber elongation method, according to the method specified in JIS R3103-2 (2001). (Tg) Measured using the thermal expansion method, according to the method specified in JIS R3103-3 (2001). (Young's Modulus) The method specified in JIS Z 2280 is used to measure the thickness of glass from 0.5 to 10 mm using the ultrasonic pulse method.

[0068] (T 2) The viscosity is determined using a rotational viscometer according to the method specified in ASTM C 965-96, and the temperature T 2 (°C) at which the viscosity becomes 10 2 d·Pa·s is measured. (T 4) The viscosity is determined using a rotational viscometer according to the method specified in ASTM C 965-96, and the temperature T 4 (°C) at which the viscosity becomes 10 4 d·Pa·s is measured. (Devitrification temperature T c of glass surface) The glass is crushed and classified using a test sieve in a particle size range of 2 to 4 mm. The obtained glass shards are ultrasonically cleaned in isopropanol for 5 minutes, cleaned with deionized water, dried, placed in a platinum pan, and heat-treated in an electric furnace at a controlled temperature for 17 hours. The heat treatment temperature is set in 10°C intervals. After heat treatment, the glass is removed from the platinum tray, and an optical microscope is used to observe the highest temperature at which crystals precipitate on the glass surface and the lowest temperature at which no crystals precipitate. Each of these measurements is performed once (or twice if crystal precipitation is difficult to determine). The average value of these measurements is taken as the glass surface devitrification temperature Tc. Furthermore, in the table below, to easily distinguish the relationship between Tc and T4 as specified in claim 1, Tc is expressed as T4 - T4. (Glass surface devitrification viscosity ηc) Using the above method, the glass surface devitrification temperature (Tc) is determined, and the viscosity of the glass at the glass surface devitrification temperature (Tc) is measured to obtain the glass surface devitrification viscosity (ηc). Furthermore, the logarithmic value of the glass surface devitrification viscosity (ηc) is shown in the table below. (Specific elastic modulus) The specific elastic modulus is obtained by dividing the Young's modulus obtained by the above steps by the density.

[0069] (Photoelastic constant) The photoelastic constant was measured using the circular plate compression method at a measurement wavelength of 546 nm. (BHF haze) The glass plate was immersed in 19BHF solution at 25°C for 20 minutes. If the change in haze before and after immersion was less than 1%, it was evaluated as 0; if it exceeded 1%, it was evaluated as ×.

[0070] [Table 1] Table 1 (mol%) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 SiO2 66.0 64.2 66.2 66.0 66.2 66.3 Al2O3 14.0 15.4 14.1 13.4 13.5 13.5 B2O3 0.9 1.9 1.1 1.2 1.2 1.2 MgO 12.1 12.5 14.6 11.5 11.5 11.5 High 6.6 5.5 3.1 7.4 6.4 5.7 SrO 0.4 0.5 0.9 0.5 1.2 1.8 Bag 0 0 0 0 0 0 Li2O 0 0 0 0 0 0 Na2O 0.01 0.01 0.01 0.01 0.01 0.01 K2O 0 0 0 0 0 0 F 0 0 0 0 0 0 β-OH(mm , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ) (0.25) (0.25) (0.25) (0.25) (0.25) (0.25) MgO+CaO+SrO+BaO 19.1 18.5 18.6 19.4 19.1 19.0 MgO / (MgO+CaO+SrO+BaO) 0.63 0.68 0.78 0.59 0.60 0.61 (MgO+CaO) / (SrO+BaO) 46.8 36.0 19.7 37.5 14.9 9.5 MgO / CaO 1.8 2.3​​​​​​​​​​​​​​​​​​​​​​​​​91.9 92.3 92.4 91.2 90.7 90.3 The value of equation (II) 252 252 252 252 253 254 Formula (I) / Formula (II) × 100 36.4 36.6 36.7 36.1 35.8 35.5 Average thermal expansion coefficient α (×10 -7 / K) 36 36 36 37 36 37 Density (g / cm³) 3 ) 2.52 2.53 2.52 2.53 2.53 2.54 Strain point (°C) 734 729 731 (721) (722) (722) Tg (°C) 789 786 787 779 789 787 Young's modulus E (GPa) 92 92 93 91 93 92 T2[logη=2](℃) 1634 1599 1630 1624 1628 1634 T4[logη=4](℃) 1290 1270 1289 1286 1288 1293 Surface devitrification temperature T c (°C) 1295 1340 1360 1295 1305 1305 T c -T4 (°C) 5 70 71 9 17 12 log(surface devitrification viscosity η) c (dPa・s)) 4.0 3.4 3.5 3.9 3.9 3.9 Specific modulus of elasticity (MN・m / kg) 36.5 36.4 36.7 36.1 36.7 36.1 Photoelastic constant C (nm / MPa / cm) (25.3) (24.9) (25.3) (25.8) (25.9) (26.0) α・E・C(×10 -7 / K) (8.5) (8.2) (8.3) (8.8) (8.8) (8.7) BHF Haze 〇 〇 〇 〇 〇 〇

[0071] [Table 2] Table 2 (mol%) Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 SiO2 66.0 64.3 68.0 69.0 68.5 66.0 Al2O3 14.3 15.2 13.0 13.0 14.0 14.7 B2O3 2.0 0.7 1.0 1.0 1.0 1.0 MgO 13.5 10.5 12.5 13.0 14.5 13.0 CaO 3.2 8.3 4.5 3.0 1.0 4.3 SrO 1.0 1.0 1.0 1.0 1.0 1.0 Bag 0 0 0 0 0 0 Li2O 0 0 0 0 0 0 Na2O 0.01 0.01 0.01 0.01 0.01 0.01 K2O 0 0 0 0 0 0 F 0 0 0 0 0 0 β-OH(mm -1 ) (0.25) (0.25) (0.25) (0.25) (0.25) (0.25) MgO + CaO + SrO + BaO 17.7 19.8 18.0 17.0 16.5 18.3 MgO / (MgO + CaO + SrO + BaO) 0.76 0.53 0.69 0.76 0.88 0.71 (MgO + CaO) / (SrO + BaO) 16.7 18.8 17.0 16.0 15.5 17.3 MgO / CaO 4.2 1.3 2.8 4.3 14.5 3.0 MgO + Al2O3 27.8 25.7 25.5 26.0 28.5 27.7 The value of equation (I) 91.2 92.2 90.4 90.1 91.2 92.0 The value of equation (II) 251 256 251 250 250 253 Formula (I) / Formula (II) × 100 36.3 36.0 36.0 36.0 36.5 36.4 Average thermal expansion coefficient α (×10) -7 / K) 34(34) 39 35 35 30 35(35) Density (g / cm³) 3 ) 2.51(2.51) 2.56 2.51 2.49 2.49 2.52(2.53) Strain point (°C) 726(725) 738 731 733 740 733(735) Tg (°C) 786(779) 791 786 787 791 796(795) Young's modulus E (GPa) 91(90) 92 91 91 92 92(93) T2[logη=2](℃) 1625(1633) 1604 1664 1684 1666 1630(1632) T4[logη=4](℃) 1280(1289) 1273 1307 1322 1312 1290(1283) Surface devitrification temperature T c (°C) 1335(1336) 1285 1325(1318) 1355 (1362) (1330) T c -T4 (°C) 55(47) 12 18(11) 33 (50) (47) log(surface devitrification viscosity η) c (dPa・s)) 3.6(3.6) 3.9 3.9(3.9) 3.7 (3.6) (3.7) Specific modulus of elasticity (MN・m / kg) 36.4 (36.0) 36.1 36.1 36.4 36.9 36.5 (36.6) Photoelastic constant C (nm / MPa / cm) (25.9) (24.4) (26.5) (26.8) (26.1) (25.2) α・E・C(×10 -7 / K) (8.0) (8.7) (8.3) (8.5) (7.1) (8.2) BHF Haze 〇 〇 〇 〇 〇 〇

[0072] [Table 3] Table 3 (mol%) Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 SiO2 65.5 67.2 68.6 63.5 64.3 67.1 Al2O3 15.5 14.3 12.7 15.5 15.5 11.6 B2O3 1.0 2.0 0.3 3.3 0 0 MgO 13.0 14.0 11.4 7.5 15.7 13.1 High 3.0 1.5 4.1 5.9 4.5 8.3 SrO 2.0 1.0 2.7 4.3 0 0 Bag 0 0 0.3 0 0 0 Li2O 0 0 0 0 0 0 Na2O 0.01 0.01 0.01 0 0.03 0 K2O 0 0 0 0 0 0 F 0 0 0 0 0.08 0 β-OH(mm -1 ) (0.25) (0.25) (0.2) - 0.25 - MgO + CaO + SrO + BaO 18.0 16.5 18.5 17.7 20.2 21.4 MgO / (MgO+CaO+SrO+BaO) 0.72 0.85 0.62 0.42 0.78 0.61 (MgO+CaO) / (SrO+BaO) 8.0 15.5 5.2 3.1 - - MgO / CaO 4.3 9.3 2.8 1.3 3.5 1.6 MgO + Al2O3 28.5 28.3 24.1 23.0 31.2 24.6 The value of equation (I) 91.9 90.8 88.7 87.1 95.7 92.3 The value of equation (II) 255 249 256 258 254 253 Formula (I) / Formula (II) × 100 36.1 36.4 34.6 33.8 37.7 36.5 Average thermal expansion coefficient α (×10 -7 / K) 35(35) 32(32) (36.6) (39.6) (35.0) (39.0) Density (g / cm³) 3 ) 2.55 2.49 (2.56) (2.57) 2.55 2.53 Strain point (°C) 736 731 (737) (705) (744) (726) Tg (°C) 797(790) 787(785) (791) (766) (797) 783 Young's modulus E (GPa) 93 91 (89) (85) 95 91 T2[logη=2](℃) 1643 1622 (1671) (1623) (1589) (1612) T4[logη=4](℃) 1297 1286 (1316) (1280) (1268) (1265) Surface devitrification temperature T c (°C) 1355(1336) 1365(1357) - (≦1315) (>1288) (1345) T c -T4 (°C) 58(39) 79(71) - ≤35 (>20) (80) log(surface devitrification viscosity η) c (dPa・s)) 3.6(3.7) 3.4(3.5) - - (<3.8) (<3.4) Specific modulus of elasticity (MN・m / kg) 36.5 36.6 (34.8) (33.1) 37.4 36.1 Photoelastic constant C (nm / MPa / cm) (24.8) (26.3) (26.0) (27.0) (25.3) (25.7) α・E・C(×10 -7 / K) (8.0) (7.6) (8.5) (9.1) (8.4) (9.2) BHF Haze 〇 〇 - - (×) (×)

[0073] [Table 4] Table 4 (mol%) Example 19 Example 20 Example 21 Example 22 Example 23 SiO2 65.0 68.5 62.4 64.4 65.2 Al2O3 12.8 13.8 16.0 13.8 13.5 B2O3 0.5 0.2 0.7 1.6 1.2 MgO 11.0 12.8 11.0 13.0 9.2 CaO 9.7 4.1 8.8 1.6 9.7 SrO 1.0 0.7 1.0 5.6 1.2 BaO 0 0 0 0 0 Li2O 0 0 0 0 0 Na2O 0 0 0.08 0 0 K2O 0 0 0 0 0 F 0 0 0.13 0 0 β-OH (mm) -1 ) - - 0.32 - - MgO + CaO + SrO + BaO 21.7 17.6 20.8 20.2 20.1 MgO / (MgO+CaO+SrO+BaO) 0.51 0.73 0.53 0.64 0.46 (MgO+CaO) / (SrO+BaO) 20.7 24.1 19.8 2.6 15.8 MgO / CaO 1.1 3.1 1.3 8.1 0.9 MgO + Al2O3 23.8 26.6 27.0 26.8 22.7 The value of equation (I) 91.7 91.1 93.8 89.5 90.2 The value of equation (II) 256 251 257 262 255 Formula (I) / Formula (II) × 100 35.8 36.2 36.4 34.2 35.4 Average thermal expansion coefficient α (×10 -7 / k) (40.9) (35.4) 39.7 (38.5) 39.6 Density (g / cm³) 3 ) (2.56) (2.51) (2.57) (2.61) 2.55 Strain point (°C) (714) (722) (715) (725) 712 Tg (°C) (770) (807) (773) (788) 768 Young's modulus E (GPa) (92) (88) (93) (88) 92 T2[logη=2](℃) (1603) (1663) (1577) (1615) 1616 T4[logη=4](℃) (1266) (1317) (1255) (1270) 1279 Surface devitrification temperature T c (°C) (≦1286) - (≦1275) - 1275 T c -T4 (°C) (≦20) - (≦20) - -4 log(surface devitrification viscosity η) c (dPa・s)) (≧3.8) - (≧3.8) - 4.0 Specific modulus of elasticity (MN・m / kg) (35.8) (35.1) (36.2) (33.7) 36.0 Photoelastic constant C (nm / MPa / cm) (25.1) (25.0) (24.5) (25.9) (25.7) α・E・C(×10 -7 / K) (9.4) (7.8) (9.0) (8.8) (9.4) BHF Haze - (×) - - -

[0074] [Table 5] Table 5 (mol%) Example 24 Example 25 Example 26 Example 27 Example 28 Example 29 Example 30 Example 31 SiO2 66.0 66.0 66.0 66.0 65.9 63.3 65.9 66.0 Al2O3 14.0 14.0 14.0 13.4 14.0 14.7 14.0 14.0 B2O3 0.9 0.9 0.9 1.2 0.9 2.0 0.9 0.9 MgO 12.1 11.5 12.1 11.5 12.1 13.5 12.1 12.1 CaO 6.0 6.6 6.6 7.4 6.6 5.2 6.6 6.6 SrO 1.0 1.0 0.4 0.5 0.4 0.8 0.4 0.4 BaO 0 0 0 0 0 0.5 0 0 Li2O 0 0 0 0 0 0 0.05 0 Na2O 0.01 0.01 0.01 0.01 0.01 0.05 0.05 0.05 K2O 0 0 0 0 0 0 0.05 0 SnO2 0 0 0 0 0 0 0 0 ZrO2 0 0 0 0 0 0 0 0 Fe2O3 0.010 0.012 0.008 0.011 0.007 0.015 0.008 0.008 Cl 0 0 0 0 0 0 0 0 F 0 0 0.05 0.05 0.1 0 0 0 β-OH(mm -1 ) (0.25) (0.25) (0.25) (0.25) (0.25) (0.25) (0.30) (0.05) MgO + CaO + SrO + BaO 19.1 19.1 19.1 19.3 19.1 20.0 19.1 19.1 MgO / (MgO + CaO + SrO + BaO) 0.63 0.60 0.63 0.59 0.63 0.67 0.63 0.63 (MgO + CaO) / (SrO + BaO) 18.1 18.1 46.8 37.5 46.8 14.4 46.8 46.8 MgO / CaO 2.0 1.7 1.8 1.6 1.8 2.6 1.8 1.8 MgO + Al2O3 26.1 25.5 26.1 24.9 26.1 28.2 26.1 26.1 The value of equation (I) 91.5 91.3 92.0 91.3 92.2 92.5 92.3 92.0 The value of equation (II) 254 254 252 252 252 255 252 252 Formula (I) / Formula (II) × 100 36.1 36.0 36.5 36.2 36.5 36.3 36.6 36.4 Average thermal expansion coefficient α (×10) -7 / K) (37) (37) 36 37 36 (38) (37) (37) Density (g / cm³) 3 ) 2.53 2.53 2.51 2.52 2.52 (2.55) (2.52) (2.52) Strain point (°C) (727) (727) 732 722 728 (713) (721) (730) Tg (°C) (785) (785) 790 782 787 (767) (778) (787) Young's modulus E (GPa) 92 91 92 91 92 (92) (92) (92) T2[logη=2](℃) (1630) (1630) 1623 1624 1622 (1590) (1625) (1625) T4[logη=4](℃) (1290) (1290) 1282 1282 1281 (1260) (1285) (1285) Surface devitrification temperature T c (°C) (<1370) (<1370) 1300 1280 1320 (<1340) (<1330) (<1330) T c -T4 (°C) (<80) (<80) 18 -2 39 (<80) (<45) (<45) log(surface devitrification viscosity η) c (dPa・s)) (≧3.4) (≧3.4) 3.9 4.0 3.7 (≧3.4) (≧3.9) (≧3.9) Specific modulus of elasticity (MN・m / kg) (36.2) (36.0) 36.6 36.1 36.5 (36.0) (36.5) (36.5) Photoelastic constant C (nm / MPa / cm) (24.4) (23.9) (25.1) (25.9) (25.1) (25.2) (25.1) (25.1) α・E・C(×10 -7 / K) (8.2) (8.1) (8.4) (8.8) (8.3) (8.7) (8.4) (8.4) BHF Haze (〇) (〇) (〇) (〇) (〇) (〇) (〇) (〇)

[0075] [Table 6] Table 6 (mol%) Example 32 Example 33 Example 34 Example 35 Example 36 Example 37 Example 38 Example 39 SiO2 66.0 65.7 65.2 62.1 63.4 62.8 63.7 64.8 Al2O3 14.0 13.9 13.7 16.6 14.9 18.6 15.2 13.6 B2O3 0.9 0.9 1.3 1.3 1.9 0.6 1.1 1.3 MgO 12.1 12.1 12.6 15.8 15.3 8.9 10.1 13.0 CaO 6.6 6.6 6.1 1.8 1.4 8.5 9.3 6.0 SrO 0.4 0.4 0.7 0.8 3.1 0.4 0.6 1.0 BaO 0 0 0 1.5 0 0 0 0 Li2O 0.05 0 0 0.03 0 0 0 0 Na2O 0 0.08 0.13 0.04 0.06 0.09 0.006 0.03 K2O 0 0 0 0.02 0.01 0.01 0.003 0 SnO2 0 0 0.3 0 0 0 0 0.3 ZrO2 0 0 0 0 0 0 0 0 Fe2O3 0.015 0.012 0.014 0.007 0.002 0.016 0.005 0.012 Cl 0 0 0 0.31 0 0 0.27 0 F 0 0.3 0.02 0.03 0.01 0.08 0 0 β-OH(mm -1 ) (0.45) (0.20) (0.33) (0.21) (0.26) (0.45) (0.05) (0.12) MgO + CaO + SrO + BaO 19.1 19.0 19.4 19.9 19.8 17.8 20.0 20.0 MgO / (MgO + CaO + SrO + BaO) 0.63 0.63 0.65 0.79 0.77 0.50 0.51 0.65 (MgO + CaO) / (SrO + BaO) 46.8 46.8 26.7 7.7 5.4 43.5 32.3 18.9 MgO / CaO 1.8 1.8 2.1 8.8 10.9 1.0 1.1 2.2 MgO + Al2O3 26.1 26.0 26.3 32.4 30.2 27.5 25.3 26.6 The value of equation (I) 92.0 93.0 93.1 94.4 92.7 93.8 92.3 92.9 The value of equation (II) 252 252 253 259 257 256 255 254 Formula (I) / Formula (II) × 100 36.4 36.8 36.9 36.4 36.0 36.7 36.2 36.6 Average thermal expansion coefficient α (×10) -7 / K) (37) (37) (37) (37) (37) (36) (39) (38) Density (g / cm³) 3 ) (2.52) (2.52) (2.53) (2.58) (2.56) (2.56) (2.55) (2.54) Strain point (°C) (723) (719) (714) (726) (712) (739) (725) (718) Tg (°C) (780) (777) (771) (777) (770) (803) (784) (775) Young's modulus E (GPa) (92) (92) (92) (93) (92) (94) (92) (92) T2[logη=2](℃) (1625) (1625) (1615) (1595) (1590) (1595) (1590) (1605) T4[logη=4](℃) (1285) (1285) (1275) (1265) (1260) (1285) (1265) (1270) Surface devitrification temperature T c (°C) (<1330) (<1330) (<1355) (<1345) (<1340) (<1365) (<1345) (<1350) T c -T4 (°C) (<45) (<45) (<80) (<80) (<80) (<80) (<80) (<80) log(surface devitrification viscosity η) c (dPa・s)) (≧3.9) (≧3.9) (≧3.4) (≧3.4) (≧3.4) (≧3.4) (≧3.4) (≧3.4) Specific modulus of elasticity (MN・m / kg) (36.5) (36.5) (36.3) (36.1) (36.0) (36.7) (36.1) (36.2) Photoelastic constant C (nm / MPa / cm) (25.1) (25.1) (25.4) (23.6) (24.1) (21.2) (24.3) (25.4) α・E・C(×10 -7 / K) (8.4) (8.4) (8.6) (8.2) (8.2) (7.2) (8.7) (8.8) BHF fog level (〇) (〇) (〇) (〇) (〇) (〇) (〇) (〇)

[0076] [Table 7] Table 7 (mol%) Example 40 Example 41 Example 42 Example 43 Example 44 Example 45 Example 46 Example 47 SiO2 67.8 62.5 65.0 65.5 66.6 64.4 65.9 65.7 Al2O3 13.0 19.0 13.4 14.0 14.4 16.7 14.0 13.1 B2O3 1.0 4.5 1.2 0.8 0.9 1.6 1.0 0.9 MgO 12.5 11.5 12.6 12.2 11.3 10.9 12.0 12.1 High 4.5 1.3 6.6 6.5 5.4 5.1 6.0 6.6 SrO 1.0 1.0 0.6 0.5 1.3 1.3 1.0 0.4 Bag 0 0 0 0 0 0 0 0 Li2O 0 0 0 0.01 0 0 0.08 0 Na2O 0.01 0.02 0.05 0.04 0.08 0.02 0.06 0.07 K2O 0 0 0 0.01 0 0 0 0 SnO2 0.2 0.2 0 0 0 0 0 0 ZrO2 0 0 0 0.4 0 0 0 1.1 Fe2O3 0.009 0.017 0.009 0.013 0.011 0.041 0.034 0.006 Cl 0.11 0 0.18 0 0 0.22 0 0 F 0 0 0.6 0.03 0.02 0 0 0.05 β-OH(mm -1 ) (0.25) (0.30) (0.12) (0.39) (0.20) (0.18) (0.14) (0.31) MgO+CaO+SrO+BaO 18.0 13.8 19.8 19.2 18.0 17.3 19.0 19.1 MgO / (MgO+CaO+SrO+BaO) 0.69 0.83 0.64 0.64 0.63 0.63 0.63 0.63 (MgO+CaO) / (SrO+BaO) 17.0 12.8 32.0 37.4 12.8 12.3 18.0 46.8 MgO / CaO 2.8 8.8 1.9 1.9 2.1 2.1 2.0 1.8 MgO + Al2O3 25.5 30.5 26.0 26.2 25.7 27.6 26.0 25.2 The value of equation (I) 91.0 91.5 93.8 93.5 91.1 91.7 91.8 95.1 The value of equation (II) 251 249 253 253 253 254 253 252 Formula (I) / Formula (II) × 100 36.2 36.8 37.1 37.0 36.0 36.1 36.3 37.8 Average thermal expansion coefficient α (×10 -7 / K) (35) (30) (38) (37) (36) (35) (37) (37) Density (g / cm³) 3 ) (2.51) (2.50) (2.53) (2.53) (2.53) (2.54) (2.53) (2.52) Strain point (°C) (729) (739) (707) (722) (731) (738) (724) (719) Tg (°C) (786) (800) (764) (780) (789) (799) (782) (776) Young's modulus E (GPa) (91) (90) (92) (92) (91) (92) (92) (92) T2[logη=2](℃) (1660) (1595) (1610) (1620) (1645) (1615) (1625) (1630) T4[logη=4](℃) (1305) (1285) (1275) (1285) (1300) (1290) (1285) (1285) Surface devitrification temperature T c (°C) (<1385) (<1365) (<1355) (<1365) (<1380) (<1370) (<1365) (<1365) T c -T4 (°C) (<80) (<80) (<80) (<80) (<80) (<80) (<80) (<80) log(surface devitrification viscosity η) c (dPa・s)) (≧3.4) (≧3.4) (≧3.4) (≧3.4) (≧3.4) (≧3.4) (≧3.4) (≧3.4) Specific modulus of elasticity (MN・m / kg) (36.1) (36.1) (36.3) (36.5) (36.0) (36.2) (36.2) (36.4) Photoelastic constant C (nm / MPa / cm) (26.1) (22.6) (25.6) (24.9) (25.0) (23.2) (25.2) (25.7) α・E・C(×10 -7 / K) (8.3) (6.1) (8.8) (8.4) (8.1) (7.5) (8.5) (8.7) BHF Haze (〇) (〇) (〇) (〇) (〇) (〇) (〇) (〇)

[0077] [Table 8] Table 8 (mol%) Example 48 Example 49 Example 50 Example 51 Example 52 Example 53 Example 54 Example 55 SiO2 70.0 64.0 63.4 64.2 64.0 61.3 63.8 65.0 Al2O3 12.0 17.0 15.4 14.8 15.5 17.6 15.1 14.9 B2O3 1.2 3.1 2.8 2.4 1.1 1.3 1.1 1.3 MgO 14.0 11.4 13.4 14.1 15.7 16.7 15.7 14.8 High 2.3 3.5 3.1 3.6 2.4 0.4 1.9 2.0 SrO 0.5 1.0 1.8 0.9 1.0 0.3 0.9 1.0 Bag 0 0 0 0 0.2 2.2 1.3 0.9 Li2O 0 0 0 0 0 0 0 0 Na2O 0.06 0.04 0.06 0.03 0.03 0.08 0.06 0.03 K2O 0 0 0 0 0 0 0 0 SnO2 0 0 0 0 0.1 0.2 0.1 0.2 ZrO2 0 0 0 0 0 0 0 0 Fe2O3 0.031 0.024 0.026 0.015 0.009 0.014 0.026 0.004 Cl 0 0 0 0 0.34 0 0 0 F 0 0 0 0 0 0 0 0 β-OH(mm -1 ) (0.21) (0.33) (0.35) (0.21) (0.15) (0.35) (0.21) (0.24) MgO + CaO + SrO + BaO 16.8 15.9 18.3 18.6 19.3 19.6 19.8 18.7 MgO / (MgO + CaO + SrO + BaO) 0.83 0.72 0.73 0.76 0.81 0.85 0.79 0.79<00024​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​ 94.8 93.2 92.2 The value of equation (II) 248 251 253 252 255 261 258 255 Formula (I) / Formula (II) × 100 36.4 36.3 36.2 36.7 37.0 36.4 36.2 36.1 Average thermal expansion coefficient α (×10 -7 / K) (32) (33) (36) (35) (35) (37) (37) (36) Density (g / cm³) 3 ) (2.48) (2.51) (2.53) (2.52) (2.54) (2.60) (2.57) (2.55) Strain point (°C) (733) (731) (714) (720) (732) (730) (726) (729) Tg (°C) (788) (791) (771) (778) (791) (778) (776) (782) Young's modulus E (GPa) (90) (91) (91) (92) (94) (93) (92) (92) T2[logη=2](℃) (1690) (1609) (1591) (1598) (1601) (1595) (1615) (1630) T4[logη=4](℃) (1325) (1285) (1263) (1267) (1272) (1266) (1275) (1288) Surface devitrification temperature T c (°C) (<1405) (<1365) (<1343) (<1347) (<1352) (<1346) (<1355) (<1368) T c -T4 (°C) (<80) (<80) (<80) (<80) (<80) (<80) (<80) (<80) log(surface devitrification viscosity η) c (dPa・s)) (≧3.4) (≧3.4) (≧3.4) (≧3.4) (≧3.4) (≧3.4) (≧3.4) (≧3.4) Specific modulus of elasticity (MN・m / kg) (36.5) (36.1) (36.0) (36.5) (37.1) (36.0) (36.0) (36.0) Photoelastic constant C (nm / MPa / cm) (27.0) (23.7) (24.5) (24.7) (23.3) (23.2) (24.7) (24.9) α・E・C(×10 -7 / K) (7.9) (7.0) (7.9) (8.0) (7.7) (8.0) (8.5) (8.2) BHF Haze (〇) (〇) (〇) (〇) (〇) (〇) (〇) (〇)

[0078] For examples 1 to 14 and 24 to 55, where MgO + CaO + SrO + BaO is 20% or less, MgO / CaO is 1 or more, MgO / (MgO + CaO + SrO + BaO) is 0.5 or more, MgO + Al₂O₃ is 24% or more and 38% or less, and the value of formula (I) is 90 or more and 100 or less, the strain point is 700℃ or more and 740℃ or less, the density is 2.6 g / cm³ or less, the Young's modulus E is 90 GPa or more and 100 GPa or less, the average coefficient of thermal expansion α at 50 to 350℃ is 30×10⁻⁷ / K or more and 39×10⁻⁷ / K or less, the temperature T₂ at which the glass viscosity becomes 10⁻² dPa·s is 1590℃ or more and 1690℃ or less, and the temperature T₂ at which the glass viscosity becomes 10⁻⁴ dPa·s is 10⁻² dPa·s or less. 4. The temperature is below 1350℃, the difference between the devitrification temperature (Tc) and T4 on the glass surface (Tc-T4) does not reach 80℃, and the specific modulus of elasticity is 36 MN・m / kg or higher. As mentioned above, if the specific modulus of elasticity is 36 MN・m / kg or higher, the self-weight deflection becomes smaller.

[0079] Regarding Example 15, where the value of Equation (I) is less than 90, its Young's modulus E is low, less than 90 GPa, and its specific elastic modulus is low, less than 36 MN・m / kg. Regarding Example 16, where MgO / (MgO+CaO+SrO+BaO) is less than 0.5, MgO+Al 2O 3 is less than 24%, and the value of Equation (I) is less than 90, its average coefficient of thermal expansion α at 50~350℃ is high, exceeding 39×10 -7 / K, its Young's modulus E is low, less than 90 GPa, and its specific elastic modulus is low, less than 36 MN・m / kg. Regarding Example 17, which does not contain B 2O 3 and SrO, and MgO+CaO+SrO+BaO exceeds 20%, its strain point is high, exceeding 740℃, and the temperature T2 at which the glass viscosity becomes 10 2 dPa・s is low, less than 1590℃. Regarding example 18, which contains no B₂O₃ and SrO, has an Al₂O₃ content of less than 12%, and has MgO+CaO+SrO+BaO exceeding 20%, its surface devitrification temperature (Tc) is above T₄+80℃. Regarding example 19, which contains MgO+CaO+SrO+BaO exceeding 20% ​​and MgO+Al₂O₃ less than 24%, its average coefficient of thermal expansion α is relatively high at 0–350℃, exceeding 39 × 10⁻⁷ / K, and its specific modulus of elasticity is relatively low, less than 36 MN・m / kg. Regarding example 20, which contains less than 0.3% B₂O₃, its Young's modulus E is relatively low, less than 90 GPa, and its specific modulus of elasticity is relatively low, less than 36 MN・m / kg. Regarding Example 21, which contains more than 20% MgO + CaO + SrO + BaO, its average coefficient of thermal expansion α is relatively high, exceeding 39 × 10⁻⁷ / K, and the temperature T₂ at which the glass viscosity becomes 10² dPa·s is relatively low, not reaching 1590℃. Regarding Example 22, which contains more than 20% MgO + CaO + SrO + BaO, its density is relatively high, exceeding 2.6 g / cm³, and its Young's modulus E is relatively low, not reaching 90 GPa. Regarding Example 23, which contains more than 20% MgO + CaO + SrO + BaO, but the MgO / CaO ratio is less than 1, the MgO / (MgO + CaO + SrO + BaO) ratio is less than 0.5, and the MgO + Al₂O₃ ratio is less than 24%, its average coefficient of thermal expansion α is relatively high, exceeding 39 × 10⁻⁷ / K, within the range of 0–350℃.

[0080] The invention has been described in detail with reference to specific embodiments, but those skilled in the art will understand that various changes and modifications can be made without departing from the spirit and scope of the invention. Furthermore, this application is based on Japanese Patent Application No. 2021-145677, filed on September 7, 2021, the entire contents of which are incorporated herein by reference. All references incorporated herein by reference are incorporated in their entirety. [Industrial Applicability]

[0081] The alkali-free glass of this embodiment is preferably used for display panels, semiconductor devices, carrier substrates for manufacturing flexible devices, carrier substrates for manufacturing semiconductor devices, information recording media, planar antennas, dimming laminates, vehicle window glass, and audio diaphragms.

Claims

1. An alkali-free glass having a strain point of 700℃ to 740℃, a density of 2.6 g / cm³ to 0.6 g / cm³, a Young's modulus of 90 GPa to 100 GPa, an average coefficient of thermal expansion of 30×10⁻⁷ / K to 39×10⁻⁷ / K between 50 and 350℃, a temperature T2 at which the glass viscosity becomes 10² dPa·s of 1590℃ to 1690℃, a temperature T4 at which the glass viscosity becomes 10⁴ dPa·s of 1350℃ to 0.4 dPa·s of 1350℃, a surface devitrification temperature (Tc) not reaching T4 + 80℃, and a specific modulus of elasticity of 36 MN·m / kg or higher. The alkali-free glass, expressed in moles (%) based on oxides, contains: SiO₂ 55% to 80%, Al₂O₃ 12% to 20%, B₂O₃ 0.3% to 5%, MgO 5% to 18%, and CaO. The content of MgO is 0.1% to 12%, SrO is 0.1% to 8%, and BaO is 0% to 6%; and MgO + CaO + SrO + BaO is 20% or less, MgO / CaO is 1 or more, MgO / (MgO + CaO + SrO + BaO) is 0.5 or more, and MgO + Al2O3 is 24% to 38%. When formula (I) is set as (-3.125×[SiO2]-2.394×[Al2O3]-3.511×[B2O3]-2.167×[MgO]-2.608×[CaO]-3.161×[SrO]-3.583×[BaO]+3.795×102), the value of formula (I) is 90 to 100.

2. For the alkali-free glass of claim 1, wherein when formula (II) is set as (0.213×[SiO2]+1.006×[Al2O3]-0.493×[B2O3]+1.158×[MgO]+1.386×[CaO]+3.092×[SrO]+4.198×[BaO]+2.004×102), the value of formula (I) / formula (II)×100 is 36 or more.

3. For alkali-free glass as requested in item 1 or 2, wherein (MgO + CaO) / (SrO + BaO) is 8 or higher.

4. For the alkali-free glass of claim 1 or 2, wherein when the average linear expansion coefficient at 50 to 350°C is set as α, the Young's modulus is set as E, and the photoelastic constant is set as C, the product of these equalities, α・E・C, is less than 9.2×10-7 / K.

5. The alkali-free glass of request item 1 or 2 has a photoelastic constant of less than 31 nm / MPa / cm.

6. For alkali-free glass as requested in item 1 or 2, the glass transition point is above 730°C and below 850°C.

7. For the alkali-free glass of request item 1 or 2, the devitrification viscosity of the glass surface is 103.4 dPa・s or higher.

8. The alkali-free glass of claim 1 or 2, wherein it contains 0 to 1% ZrO2, expressed in moles based on oxides.

9. The alkali-free glass of claim 1 or 2, wherein the total content of Li2O, Na2O and K2O, expressed in moles % based on oxides, is less than 0.2%.

10. The alkali-free glass of claim 1 or 2, wherein the glass contains more than 0% and less than 0.5% SnO2, expressed in moles based on oxides.

11. The alkali-free glass as requested in item 1 or 2, wherein, expressed in moles, it contains 0% to 1% F.

12. The alkali-free glass as requested in item 1 or 2, wherein the β-OH value of the glass is 0.05 mm-1 or more and 0.6 mm-1 or less.

13. A glass plate comprising alkali-free glass as claimed in any one of claims 1 to 12, wherein at least one side is 2400 mm or more and the thickness is less than 1 mm.

14. A method for manufacturing alkali-free glass, which is the method for manufacturing alkali-free glass as described in any one of claims 1 to 12, and is formed by a float glass method or a melting method.