Alkali-free glass

Abstract

The present invention relates to alkali-free glass having a prescribed glass composition and having: a strain point of 700°C-740°C; a density of 2.6 g / cm３ or less; a Young's modulus of 90 GPa-100 GPa; an average coefficient of thermal expansion at 50-350°C of 30×10-7 / K-39×10-７ / K; a temperature T２ at which glass viscosity is 102 dPa・s of 1590°C- 1690°C; a temperature T4 at which glass viscosity is 104 dPa・s of 1350°C or less; a glass surface devitrification temperature (Tc) of less than T4＋80℃; and a specific modulus of 36 MN・m / kg or more.

Description

[Technical Field]

[0001] This invention relates to alkali-free glass suitable for use as glass plates for various displays, photomasks, electronic device supports, information recording media, and the like. [Background technology]

[0002] Conventionally, glass plates used for various displays, photomasks, electronic device supports, and information recording media, particularly glass plates on which thin films of metal or oxide are formed on the surface, have been required to have the following characteristics (1) to (4).

[0003] (1) If the glass contains alkali metal oxides, alkali metal ions will diffuse into the thin film and degrade the film properties of the thin film; therefore, the glass must be substantially free of alkali metal ions. (2) The strain point is high so as to minimize deformation of the glass plate and shrinkage (thermal shrinkage) associated with the stabilization of the glass structure when the glass plate is exposed to high temperatures during the thin film formation process.

[0004] (3) It must have sufficient chemical resistance to various chemicals used in semiconductor formation. In particular, SiO x ya SiN x It must be resistant to buffered hydrofluoric acid (BHF: a mixture of hydrofluoric acid and ammonium fluoride) used for etching, hydrochloric acid-containing chemicals used for etching ITO, various acids (nitric acid, sulfuric acid, etc.) used for etching metal electrodes, and alkalis in resist stripping solutions. (4) The interior and surface must be free from defects (bubbles, striations, inclusions, pits, scratches, etc.).

[0005] In addition to the above requirements, the following requirements (5) to (9) have also been made in recent years. (5) There is a demand for lighter displays, and glass with a low specific gravity is desired. (6) There is a demand for lighter displays, and thinner glass plates are desired. (7) In addition to the amorphous silicon (a-Si) type liquid crystal displays that have been used until now, polycrystalline silicon (p-Si) type liquid crystal displays with higher heat treatment temperatures are now being manufactured (heat resistance of a-Si: approximately 350°C, heat resistance of p-Si: 350~550°C), so heat resistance is desired.

[0006] (8) In order to increase productivity by speeding up the heating and cooling rate during the heat treatment process in the manufacture of liquid crystal displays, and to improve thermal shock resistance, glass with a small average coefficient of thermal expansion is required. On the other hand, if the average coefficient of thermal expansion of the glass is too small, when there are many film deposition processes such as gate metal films and gate insulating films in the manufacture of liquid crystal displays, the glass warps significantly, which can lead to problems such as cracks and scratches during the transport of the liquid crystal displays, and large misalignments of the exposure pattern. (9) Furthermore, in recent years, with the increasing size and thinning of glass sheets, there has been a demand for glass with a high specific modulus of elasticity (Young's modulus / density).

[0007] Furthermore, as displays move towards even higher resolution, large-screen televisions face the problem of increased substrate warping due to various film deposition processes, such as increased thickness of copper wiring. Therefore, there is a growing need for glass plates with less warping, and to meet this need, it is necessary to increase the Young's modulus of the glass. However, glass with a high Young's modulus has a high strain point, and glass viscosity 10 4 The devitrification temperature tends to be higher than the devitrification temperature T4, which is the temperature at which dPa·s occurs. As a result, forming the glass plate becomes difficult.

[0008] To solve the problems in the prior art described 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] [Problems to be Solved by the Invention]

[0010] In recent years, due to the increasing demand for higher definition displays, there is a need to further reduce self-weight deflection. Furthermore, with the increase in the size and decrease in the thickness of glass substrates, glass with a high Young's modulus and a high specific elastic modulus (Young's modulus / density) is required. Furthermore, in order to increase the thermal shock resistance of glass, it is required that the thermal expansion coefficient of the glass be small. In addition, due to requirements in the glass manufacturing process, it is required to lower the temperature T2 at which the glass viscosity is 10 2 dPa·s and the temperature T4 at which the glass viscosity is 10 4 dPa·s, lower the devitrification temperature of the glass surface, and furthermore, not raise the strain point excessively. The glass described in Patent Documents 1 and 2 has a low Young's modulus and a low specific elastic modulus, so that the self-weight deflection cannot be sufficiently reduced, or even if the Young's modulus is high and the specific elastic modulus is also high, the average thermal expansion coefficient is high, so that the thermal shock resistance is low, and it has been difficult to meet these requirements.

[0011] An object of the present invention is to solve the above-mentioned drawbacks, provide a glass that can reduce the self-weight deflection of the glass, has excellent thermal shock resistance, excellent formability, and a low burden on glass manufacturing equipment. [Means for Solving the Problems]

[0012] [1] The strain point is 700 °C or higher and 740 °C or lower, the density is 2.6 g / cm 3 or less, the Young's modulus is 90 GPa or higher and 100 GPa or lower, the average thermal expansion coefficient at 50 to 350 °C is 30 × 10 -7 / K or higher and 39 × 10 -7 / K or lower, the glass viscosity is 10 2The temperature T2 at which dPa·s occurs is between 1590°C and 1690°C, and the glass viscosity is 10. 4 The temperature T4 at which dPa·s occurs is 1350℃ or less, and the glass surface devitrification temperature (T c ) has a temperature of less than T4 + 80℃ and a specific modulus of elasticity of 36 MN·m / kg or more. In mole percent based on oxides SiO255% or more and 80% or less, Al2O3 12% or more and 20% or less, B2O3 0.3% or more and 5% or less, MgO 5% or more and 18% or less, CaO 0.1% or more and 12% or less, SrO 0.1% or more and 8% or less, BaO 0% or more and 6% or less It contains, MgO + CaO + SrO + BaO is less than 20%. MgO / CaO is 1 or more, MgO / (MgO+CaO+SrO+BaO) is 0.5 or higher. MgO + Al2O3 is between 24% and 38%. Equation (I) is (-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 Alkali-free glass, where the value of equation (I) is between 90 and 100 when given the condition (I). [2] Equation (II) is (0.213×[SiO2]+1.006×[Al2O3]-0.493×[B2O3]+1.158×[MgO]+1.386×[CaO]+3.092×[SrO]+4.198×[BaO]+2.004×10 2 The alkali-free glass described in [1], wherein the value of equation (I) / equation (II) × 100 is 36 or greater. [3] Alkali-free glass as described in [1] or [2], wherein (MgO+CaO) / (SrO+BaO) is 8 or greater. [4] When the mean coefficient of linear expansion at 50 to 350°C is α, Young's modulus is E, and the photoelastic constant is C, the product of these values ​​α·E·C is 9.2 × 10 -7Alkali-free glass as described in any of [1] to [3], with a temperature of 0.1K or less. [5] Alkali-free glass as described in any of [1] to [4], wherein the photoelastic constant is 31 nm / MPa / cm or less. [6] Alkali-free glass according to any of [1] to [5], wherein the glass transition temperature is 730°C or higher and 850°C or lower. [7] glass surface devitrification viscosity is 10 3.4 Alkali-free glass as described in any of [1] to [6], having a pressure of dPa·s or higher. [8] Alkali-free glass as described in any of [1] to [7], containing 0 to 1% ZrO2 in mol% based on oxides. [9] Alkali-free glass as described in any of [1] to [8], wherein the combined amount of Li2O, Na2O, and K2O is 0.2% or less in mole percent on an oxide basis.

[10] Alkali-free glass as described in any of [1] to [9], containing 0% or more and 0.5% or less of SnO2, expressed in mole percent on an oxide basis.

[11] Alkali-free glass as described in any of [1] to

[10] , containing 0% to 1% of F in mol%.

[12] The β-OH value of the glass is 0.05 mm -1 0.6mm or more -1 Alkali-free glass as described in any of the following [1] to

[11] .

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

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

[14] A method for producing alkali-free glass according to any of [1] to

[12] , wherein the glass is formed by the float method or the fusion method. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide glass that has reduced self-weight deflection, excellent thermal shock resistance, excellent moldability, and places a low burden on glass manufacturing equipment. [Modes for carrying out the invention]

[0014] The alkali-free glass according to one embodiment of the present invention will be described below. In the following, the compositional range of each component of glass is expressed in mole percent based on the oxide.

[0015] The alkali-free glass of this embodiment contains 55% to 80% SiO2. If the SiO2 content is less than 55 mol% (hereinafter simply referred to as %), the strain point does not rise sufficiently, and the average coefficient of thermal expansion tends to increase, leading to an increase in density. 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. When the SiO2 content exceeds 80%, the solubility of the glass decreases, the Young's modulus decreases, and the glass surface devitrification temperature (T) decreases. c ) tends to increase. Therefore, the SiO2 content is 80% or less, preferably 75% or less, more preferably 73% or less, even more preferably 70% or less, particularly preferably 69% or less, and most preferably 68% or less.

[0016] The alkali-free glass of this embodiment contains 12% to 20% Al2O3. Al2O3 increases Young's modulus, suppresses deflection, suppresses phase separation of the glass, and improves fracture toughness, thereby increasing glass strength. If the Al2O3 content is less than 12%, these effects are less likely to appear, and other components that increase the average thermal expansion coefficient will relatively increase, resulting in a tendency for the average thermal expansion coefficient to become larger. For this reason, the Al2O3 content is 12% or more, preferably 12.3% or more, more preferably 12.6% or more, even more preferably 13% or more, still even more preferably 13.3% or more, particularly preferably 13.6% or more, and most preferably 14% or more. When the Al2O3 content exceeds 20%, the solubility of the glass deteriorates, the strain point increases, and the glass surface devitrification temperature (T) rises. cThis may increase the amount of ) and therefore the Al2O3 content is 20% or less, preferably 18% or less, more preferably 17.5% or less, even more preferably 17% or less, still more preferably 16.5% or less, particularly preferably 16% or less, and most preferably 15.5% or less.

[0017] The alkali-free glass of this embodiment contains 0.3% to 5% B2O. B2O3 improves the buffered hydrofluoric acid (a mixture of hydrofluoric acid and ammonium fluoride, also known as BHF) resistance and improves the dissolution reactivity of the glass, thereby lowering the glass surface devitrification temperature (T c To reduce the amount of ), it can be contained at a concentration of 5% or less. The B2O3 content is preferably 4% or less, more preferably 3.5% or less, even more preferably 3% or less, particularly preferably 2.5% or less, and most preferably 2% or less. These effects are less likely to appear when the B2O3 content is less than 0.3%. Therefore, the B2O3 content is 0.3% or more, preferably 0.5% or more, more preferably 0.6% or more, even more preferably 0.7% or more, particularly preferably 0.8% or more, and most preferably 0.9% or more.

[0018] The alkali-free glass of this embodiment contains 5% to 18% MgO. MgO increases Young's modulus without increasing density, thereby increasing the specific modulus, reducing the problem of self-weight deflection, improving fracture toughness, and increasing glass strength. Furthermore, MgO also improves solubility. If the MgO content is less than 5%, these effects are less likely to appear, and the coefficient of thermal expansion may become too low. Therefore, the MgO content is 5% or more. Preferably, the MgO content is 7% or more, more preferably 9% or more, even more 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 glass surface devitrification temperature (T c) tends to increase. Therefore, the MgO content is 18% or less, preferably 17.5% or less, more preferably 17% or less, even more preferably 16.5% or less, particularly preferably 16.3% or less, and most preferably 16% or less.

[0019] The alkali-free glass of this embodiment contains 0.1% to 12% CaO. CaO has the characteristics of having the second highest specific modulus among alkaline earth metals after MgO, without excessively lowering the strain point, and also improves solubility similar to MgO. Furthermore, compared to MgO, it has a glass surface devitrification temperature (T c It also has the characteristic of being difficult to raise. When the CaO content is less than 0.1%, these effects are less likely to appear. For this reason, the CaO content is 0.1% or more. The CaO content is preferably 0.5% or more, more preferably 1% or more, even more 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 thermal expansion coefficient becomes too high, and the glass surface devitrification temperature (T c The ) becomes high, making devitrification a problem during glass manufacturing. Therefore, the CaO content is 12% or less, preferably 10% or less, more preferably 9% or less, even more preferably 8.5% or less, particularly preferably 8% or less, and most preferably 7.5% or less.

[0020] The alkali-free glass of this embodiment contains 0.1% to 8% SrO. SrO is the glass surface devitrification temperature (T c This improves solubility without increasing the SrO content, but these effects become less apparent when 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, even more preferably 0.3% or more, and particularly preferably 0.4% or more. SrO exhibits the above effects less than BaO, and if the SrO content exceeds 8%, the effect of increasing density outweighs the effect of SrO, resulting in an excessively high average thermal expansion coefficient. 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.

[0021] In this embodiment, the alkali-free glass contains 0% to 6% BaO. BaO is the glass surface devitrification temperature (T c It can be included to improve solubility without increasing the ) content. If BaO is included, the BaO content is preferably 0.1% or more, more preferably 0.3% or more, even more preferably 0.5% or more, particularly preferably 0.8% or more, and most preferably 1% or more. When BaO is present in large quantities, the density increases, the Young's modulus decreases, and the average coefficient of thermal expansion tends to become too large. Therefore, the BaO content should be 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, considering the toxicity of Ba, it is preferable that the product is substantially free of BaO. "Substantially free" means that it is free of 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.

[0022] If the total amount of alkaline earth metal oxides, i.e., MgO + CaO + SrO + BaO, is too high, it may not be possible to reduce the average coefficient of thermal expansion. It may also worsen the acid resistance. Therefore, the amount of MgO + CaO + SrO + BaO is 20% or less, preferably 19.8% or less, more preferably 19.6% or less, even more preferably 19.4% or less, particularly preferably 19.2% or less, and most preferably 19.1% or less. Glass surface devitrification temperature (T c When the glass surface devitrification temperature (T) is low, the devitrification viscosity of the glass surface increases, improving moldability. cTo lower the ) ratio, the amount of MgO+CaO+SrO+BaO is preferably 10% or more, more preferably 12% or more, even more preferably 13% or more, still more preferably 14% or more, particularly preferably 15% or more, and most preferably 16% or more. Here, the amount of MgO+CaO+SrO+BaO is, for example, 10% to 20%.

[0023] Furthermore, if the MgO / CaO ratio is low, devitrification of the CaO-Al2O3-SiO2 system is more likely to occur, resulting in poor moldability. Specifically, the devitrification temperature increases, and the devitrification viscosity of the glass surface decreases. Therefore, the MgO / CaO ratio should be 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, devitrification of the MgO-Al2O3-SiO2 system is more likely to occur, leading to a higher glass surface devitrification temperature and a lower glass surface devitrification viscosity. Therefore, the MgO / CaO ratio is preferably 100 or less, more preferably 30 or less, even more preferably 15 or less, particularly preferably 10 or less, and most preferably 5 or less. Here, the MgO / CaO ratio is, for example, between 1 and 100.

[0024] Furthermore, if the proportion of MgO in the total amount of alkaline earth metal oxides (MgO + CaO + SrO + BaO), i.e., MgO / (MgO + CaO + SrO + BaO), is low, the density increases and the specific modulus decreases. In addition, the phase separation properties and acid resistance of the glass deteriorate. For this reason, MgO / (MgO + CaO + SrO + BaO) should be 0.5 or higher. MgO / (MgO + CaO + SrO + BaO) is preferably 0.52 or higher, more preferably 0.54 or higher, even more preferably 0.56 or higher, particularly preferably 0.58 or higher, and most preferably 0.6 or higher. On the other hand, in order to suppress devitrification of the MgO-Al2O3-SiO2 system and to suppress the rise in devitrification temperature, MgO / (MgO+CaO+SrO+BaO) is preferably 0.95 or less, more preferably 0.9 or less, even more preferably 0.85 or less, and particularly preferably 0.8 or less. Here, MgO / (MgO+CaO+SrO+BaO) is, for example, 0.5 or more and 0.95 or less.

[0025] Furthermore, the combined amount of MgO and Al2O3, i.e., MgO + Al2O3, is between 24% and 38%. If the MgO+Al2O3 content is less than 24%, the Young's modulus becomes low, and the deformation of the substrate in response to external stress increases. Therefore, the MgO+Al2O3 content should be 24% or more. Preferably, the MgO+Al2O3 content 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 MgO + Al2O3 content exceeds 38%, the devitrification temperature rises, and the moldability deteriorates. Therefore, the MgO + Al2O3 content should be 38% or less. Preferably, the MgO + Al2O3 content 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.

[0026] In this embodiment, the alkali-free glass is preferable because, when the ratio of the total amount of MgO and CaO to the total amount of SrO and BaO, i.e., (MgO+CaO) / (SrO+BaO), is 8 or more, it is possible to improve the Young's modulus while suppressing an increase in density, thereby increasing the specific modulus of elasticity. (MgO+CaO) / (SrO+BaO) is more preferably 10 or more, even more preferably 12 or more, still still preferably 14 or more, particularly preferably 16 or more, and most preferably 18 or more. On the other hand, a (MgO+CaO) / (SrO+BaO) ratio of 200 or less is preferable because it suppresses the rise in devitrification temperature. (MgO+CaO) / (SrO+BaO) is preferably 100 or less, more preferably 75 or less, even more preferably 60 or less, and particularly preferably 50 or less. Here, (MgO+CaO) / (SrO+BaO) is, for example, 8 to 200.

[0027] The alkali-free glass of this embodiment is expressed 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 When this is the case, the value of equation (I) is between 90 and 100. The value represented by formula (I) is an index of Young's modulus. If this value is less than 90, Young's modulus tends to be low, specific modulus tends to be small, and self-weight deflection tends to be large. If it is greater than 100, Young's modulus becomes too large, and the cutting margin is impaired. The value represented by formula (I) is preferably 90.5 to 97, more preferably 90.8 to 95, even more preferably 91 to 94, particularly preferably 91.2 to 93.5, and most preferably 91.5 to 93. In the formula, the notation [metal oxide] (e.g., [SiO2]) represents the value of the metal oxide component when expressed in mole percent (the same applies to other parts of this specification). For example, if SiO2 is 60 mol% when expressed in mole percent based on the oxide, then [SiO2] represents 60.

[0028] The alkali-free glass of this embodiment is expressed as (0.213×[SiO2]+1.006×[Al2O3]-0.493×[B2O3]+1.158×[MgO]+1.386×[CaO]+3.092×[SrO]+4.198×[BaO]+2.004×10 2 When this is the case, it is preferable that the value of equation (I) / equation (II) × 100 is 36 or more. The value expressed by formula (I) / formula (II) × 100 is an indicator of the specific modulus of elasticity. A value of 36 or higher is preferable because it indicates a high specific modulus of elasticity. The value of formula (I) / formula (II) × 100 is more preferably 36.1 or higher, even more preferably 36.2 or higher, still more preferably 36.3 or higher, particularly preferably 36.4 or higher, and most preferably 36.5 or higher. It is preferable that the value of equation (I) / equation (II) × 100 is 50 or less, as this allows the cutting margin to be maintained. Here, the value of equation (I) / equation (II) × 100 is, for example, between 36 and 50.

[0029] The value expressed by equation (II) is an indicator of density, and a value of 260 or less is preferable because it indicates a low density. If the value expressed by equation (II) is less than 240, the density may become too low. Therefore, a value of 240 or more is preferable. The value represented by formula (II) is more preferably 242 to 259, even more preferably 244 to 258, still more preferably 246 to 257, particularly preferably 248 to 256, and most preferably 250 to 255.

[0030] The alkali-free glass of this embodiment preferably contains substantially no alkali metal oxides such as Li2O, Na2O, and K2O. In this embodiment, substantially no alkali metal oxides means that they are not present except for unavoidable impurities introduced from the raw materials, that is, they are intentionally omitted. 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.

[0031] However, alkali metal oxides may be included in predetermined amounts for the purpose of obtaining specific effects (such as lowering the strain point, lowering the Tg, or lowering the slow cooling point). Specifically, the combined amount 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, even more preferably 0.05% or less, and most preferably 0.03% or less. The combined amount of Li2O, Na2O, and K2O may be 0.001% or more. Here, the combined amount of Li2O, Na2O, and K2O is, for example, 0.001% or more and 0.2% or less.

[0032] When the alkali-free glass of this embodiment is used as a glass plate for a display, it is preferable that the alkali-free glass of this embodiment substantially does not contain P2O5 in order to prevent deterioration of the properties of thin films such as metals or oxides that are provided on the surface of the glass plate. In this embodiment, substantially free of P2O5 means, for example, that the content is 0.1% or less. Furthermore, in order to facilitate the recycling of glass and from the viewpoint of environmental impact, it is preferable that the alkali-free glass of this embodiment substantially does not contain 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, and preferably 0.005% or less, respectively.

[0033] On the other hand, in order to improve the solubility, clarity, and moldability of the glass, one or more of As2O3 and Sb2O3 may be included in a total amount of 1% or less, preferably 0.5% or less, more preferably 0.3% or less, even more preferably 0.2% or less, particularly preferably 0.15% or less, and most preferably 0.1% or less.

[0034] To improve the solubility, clarity, and moldability of the glass, the alkali-free glass of this embodiment may contain 2% or less in total amount of one or more of ZrO2, ZnO, Fe2O3, SO3, F, Cl, and SnO2. Preferably, it is 1% or less, and more preferably 0.5% or less.

[0035] The alkali-free glass of this embodiment may contain ZrO2 to lower the glass melting temperature, increase the Young's modulus, and improve chemical resistance, for example, it may contain 0.001% or more. However, if the ZrO2 content is too high, the devitrification temperature of the glass surface may increase, the dielectric constant ε may increase, and the glass may become non-uniform. Furthermore, when applied to semiconductor devices, it may cause failure due to alpha radiation. For this reason, the ZrO2 content is preferably 1% or less, more preferably 0.5% or less, even more preferably 0.2% or less, still more preferably 0.1% or less, especially preferably 0.05% or less, even more preferably 0.04% or less, particularly preferably 0.03% or less, and most preferably substantially absent. Substantially absent ZrO2 means that it is not contained except as an unavoidable impurity introduced from the raw materials, that is, it is intentionally omitted. In this embodiment, substantially absent ZrO2 means that the ZrO2 content is, for example, 0.01% or less, preferably 0.005% or less.

[0036] The alkali-free glass of this embodiment may contain 0% to 0.5% of SnO2 to improve the solubility and clarity of the glass. The SnO2 content is preferably 0.4% or less, more preferably 0.3% or less.

[0037] The alkali-free glass of this embodiment may contain fluorine (F) to improve the solubility and clarity of the glass. If F is included, the F content is preferably 1% or less in mole percent, more preferably 0.5% or less, even more preferably 0.4% or less, still more preferably 0.3% or less, especially preferably 0.2% or less, and particularly preferably 0.1% or less. Note that the F content refers to the amount remaining in the molten glass, not the amount added to the glass raw materials. The same applies to the Cl content, which will be discussed later.

[0038] The alkali-free glass of this embodiment may contain Fe in an amount of 0.001% or more and 0.05% or less in terms of Fe2O3 to improve the solubility of the glass. Lowering the Fe content of the glass will reduce the amount of Fe in the melting process. 2+ The amount of infrared absorption decreases, resulting in an increase in the thermal conductivity of the glass. This can lead to a smaller temperature distribution in the molten glass when it is heated and melted using a heat source such as a burner flame in a glass melting furnace, reducing the convection velocity of the molten glass and potentially degrading the foam quality and homogeneity of the glass product. The above problems are less likely to occur if the Fe content is 0.001% or higher in terms of Fe2O3. Furthermore, clarity and homogeneity depend on sufficient convection of the molten glass. If you want to improve the solubility of the glass, an Fe content of 0.002% or more in terms of Fe2O3 is more preferable, 0.005% or more is even preferable, 0.008% or more is even preferable, 0.01% or more is particularly preferable, 0.02% or more is even preferable, 0.03% or more is particularly preferable, and 0.04% or more is most preferable.

[0039] When the Fe content of glass increases, Fe is absorbed into the glass. 2+ Or Fe 3+ It exists as such, and there is a risk that the transmittance of the glass will decrease. Especially Fe 3+ Because it has absorption in the wavelength range of 300 nm or less, the ultraviolet transmittance of the glass may be low. For example, in the case of glass plates for various displays, it is preferable that the transmittance at a wavelength of 300 nm is 20% or more for a plate thickness of 0.5 mm, because this allows two substrate glass plates constituting a flat panel display to be bonded together using a photocurable resin. In order to make glass with a plate thickness of 0.5 mm and a transmittance at a wavelength of 300 nm of 20% or more, the Fe content is preferably 0.05% or less in terms of Fe2O3, more preferably 0.04% or less, even more preferably 0.03% or less, still even more preferably 0.02% or less, especially preferably 0.01% or less, even more preferably 0.008% or less, still even more preferably 0.006% or less, particularly preferably 0.004% or less, and most preferably 0.002% or less.

[0040] To improve the clarity of the glass, the glass may contain 0.1% to 1.0% of Cl in molar percentage. A Cl content of 0.1% or more results in good clarification during the melting of the glass raw materials. The Cl content is preferably 0.15% or more, more preferably 0.2% or more, even more preferably 0.25% or more, and particularly preferably 0.3% or more. When the Cl content is 1.0% or less, it effectively suppresses the enlargement of the bubble layer during glass manufacturing. Preferably, it is 0.8% or less, and more preferably 0.6% or less.

[0041] For purposes such as improving the solubility, clarity, and moldability of the glass, obtaining absorption at specific wavelengths, and improving density, hardness, bending rigidity, and durability, the alkali-free glass of this embodiment may contain 2% or less in total amount of one or more of Se2O3, TeO2, Ga2O3, In2O3, GeO2, CdO, BeO, and Bi2O3, preferably 1% or less, more preferably 0.5% or less, even more 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 GeO2 content is preferably less than 0.1%, more preferably 0.08% or less, even more preferably 0.05% or less, still more preferably 0.03% or less, particularly preferably 0.01% or less, and most preferably substantially absent. Substantially absent GeO2 means that it is not contained except as an unavoidable impurity introduced from the raw materials, i.e., intentionally omitted. In this embodiment, "substantially GeO2-free" means that the GeO2 content is, for example, 0.05% or less, preferably 0.01% or less, and more preferably 0.005% or less.

[0042] To improve the solubility, clarity, and moldability of the glass, and to improve the hardness of the glass, such as Young's modulus, the alkali-free glass of this embodiment may contain rare earth oxides and transition metal oxides.

[0043] The alkali-free glass of this embodiment may contain 2% or less in total amount of one or more of the rare earth oxides Sc2O3, Y2O3, La2O3, Ce2O3, CeO2, Pr2O3, Nd2O3, Pm2O3, Sm2O3, Eu2O3, Gd2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, and Lu2O3, preferably 1% or less, more preferably 0.5% or less, even more preferably 0.3% or less, still 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 0.5% or less, even more preferably 0.3% or less, still more preferably 0.1% or less, particularly preferably 0.05% or less, and most preferably substantially absent. "Substantially La2O3-free" means that it is not present except as an unavoidable impurity introduced from the raw materials, etc., that is, it is intentionally omitted. In this embodiment, "substantially La2O3-free" means that the La2O3 content is, for example, less than 0.05%, preferably 0.01% or less, and more preferably 0.005% or less.

[0044] The alkali-free glass of this embodiment may contain one or more transition metal oxides from V2O5, Ta2O3, Nb2O5, WO3, MoO3, and HfO2 in a total amount of 2% or less, preferably 1% or less, more preferably 0.5% or less, even more preferably 0.3% or less, still more preferably 0.1% or less, particularly preferably 0.05% or less, and most preferably 0.01% or less.

[0045] To improve the solubility of the glass, the alkali-free glass of this embodiment may contain 2% or less of actinide oxide, ThO2, preferably 1% or less, more preferably 0.5% or less, even more preferably 0.3% or less, still 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.

[0046] The alkali-free glass of this embodiment has a β-OH value of 0.05 mm -10.6mm or more -1 The following is preferable because it suppresses thermal shrinkage of the glass. The β-OH value is an indicator of the water content in glass. The absorbance of glass samples to light with wavelengths of 2.75 to 2.95 μm is measured, and the maximum absorbance value β is used. max This is determined by dividing it by the thickness (mm) of the sample. The β-OH value of glass is 0.45 mm -1 The following is more preferable, and even more preferably, 0.4 mm -1 Further preferably, 0.35 mm -1 The following is particularly preferable: 0.3 mm -1 More preferably, 0.28 mm -1 The following is particularly preferred: 0.25 mm -1 Below, the most preferred is 0.23 mm -1 The following applies. On the other hand, the β-OH value is 0.05 mm -1 This makes it easier to achieve the glass strain point described later. Therefore, the β-OH value is 0.08 mm. -1 The above is more preferable, and even more preferably 0.1 mm -1 More preferably, 0.13 mm -1 The above is the case, and more preferably 0.15 mm -1 In particular, 0.18 mm is preferred. -1 The most preferred size is 0.2 mm. -1 That's all.

[0047] The alkali-free glass of this embodiment has a strain point of 700°C to 740°C. If the strain point is below 700°C, deformation of the glass plate and shrinkage (thermal shrinkage) due to structural stabilization of the glass are more likely to occur when the glass plate is exposed to high temperatures during the thin-film formation process 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 slow cooling device needs to be increased accordingly, which tends to reduce the lifespan of the slow cooling device. Therefore, the strain point should be 740°C or lower. Preferably, the strain point is 738°C or lower, more preferably 736°C or lower, and even more preferably 735°C or lower.

[0048] The alkali-free glass of this embodiment has a density of 2.6 g / cm³. 3 The following is the density: 2.6 g / cm³ 3 The following conditions reduce self-weight deflection, making it easier to handle large substrates. Furthermore, it allows for weight reduction of devices using glass. The density is preferably 2.59 g / cm³. 3 More preferably, 2.58 g / cm³ 3 More preferably, 2.57 g / cm³ 3 The following is particularly preferred: 2.56 g / cm³ 3 The most preferred value is 2.55 g / cm³. 3 The following applies. Note that a large circuit board is, for example, a circuit board with at least one side measuring 1800mm or more. On the other hand, the density is 2.4 g / cm³. 3 A density of 2.42 g / cm³ is preferable because it ensures good stability during transport. 3 More preferably 2.44 g / cm³ 3 More preferably, 2.46 g / cm³ 3 In particular, 2.48 g / cm³ is preferred. 3 In summary, the most preferred amount is 2.5 g / cm³. 3 That's all. Here, the density is, for example, 2.4 g / cm³. 3 More than 2.6g / cm 3 The following applies:

[0049] Furthermore, the Young's modulus of the alkali-free glass in this embodiment is 90 GPa or more and 100 GPa or less. When the Young's modulus is 90 GPa or more, deformation of the substrate in response to external stress is suppressed. For example, when a film is formed on the surface of a glass substrate, warping of the substrate can be suppressed. Specifically, in the manufacturing of the TFT side substrate of a flat panel display, warping of the substrate is 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. Also, deflection when the size of the substrate is increased can be suppressed. The Young's modulus is preferably 90.5 GPa or more, more preferably 91 GPa or more, even more preferably 91.2 GPa or more, particularly preferably 91.5 GPa or more, and most preferably 92 GPa or more. A Young's modulus of 100 GPa or less results in a larger cutting margin. The Young's modulus is preferably 98 GPa or less, more preferably 97 GPa or less, even more preferably 96 GPa or less, and most preferably 95 GPa or less. The Young's modulus can be measured by ultrasonic testing.

[0050] The alkali-free glass of this embodiment has an average thermal expansion coefficient of 30 × 10 at 50 to 350°C. -7 It is greater than / K. 30 × 10 -7 If the temperature is less than / K, for example, in the manufacturing of the TFT side substrate for flat panel displays, a gate metal film such as copper and a gate insulating film such as silicon nitride may be sequentially laminated on alkali-free glass. However, the difference in thermal expansion between the gate metal film such as copper formed on the substrate surface and the surrounding material becomes large, which may cause problems such as the substrate warping or film delamination. The average coefficient of thermal expansion at 50-350°C is preferably 30.5 × 10⁻⁶. -7 / K or higher, more comfortably 31×10 -7 / K or higher, more preferably 31.5 × 10 -7 / K or higher, particularly preferably 32 × 10 -7 / K or higher, most preferably 32.5 × 10 -7 It is greater than or equal to / K. On the other hand, the average coefficient of thermal expansion at 50-350°C is 39 × 10⁻⁶. -7If the temperature exceeds 1 / K, there is a risk of the glass cracking during the manufacturing process of products such as displays, and the thermal shock resistance of the glass will also decrease. Therefore, 39×10 -7 It is less than or equal to / K. The average coefficient of thermal expansion at 50-350°C is preferably 38.5 × 10⁻⁶. -7 / K or less, more preferably 38 × 10 -7 / K or less, more preferably 37.5 × 10 -7 / K or less, particularly preferably 37.3 × 10 -7 / K or less, most preferably 37 × 10 -7 It is less than or equal to / K. Here, the average coefficient of thermal expansion at 50-350°C is, for example, 30 × 10 -7 / K or more 39×10 -7 It is less than or equal to / K.

[0051] The alkali-free glass of this embodiment has a glass viscosity η of 10 2 The temperature T2 (the temperature at which logη=2) at which dPa·s occurs is between 1590°C and 1690°C. When 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, when T2 is 1690°C or lower, the glass melting properties are excellent. Therefore, the burden on manufacturing equipment can be reduced. For example, the lifespan of equipment such as glass melting furnaces can be extended, and productivity can be improved. In addition, defects originating from the furnace (e.g., pitting defects, Zr defects, etc.) can be reduced. T2 is preferably 1670°C or lower, more preferably 1660°C or lower, even more preferably 1650°C or lower, still still more preferably 1640°C or lower, and most preferably 1635°C or lower.

[0052] The alkali-free glass of this embodiment has a glass viscosity η of 10 4The temperature T4 (the temperature at which logη = 4) is 1350 °C or lower, which results in dPa·s. When T4 is 1350 °C or lower, the glass has excellent formability. Also, for example, by lowering the temperature during glass forming, the volatiles in the atmosphere around the glass can be reduced, thereby reducing the defects of the glass. Since the glass can be formed at a low temperature, the burden on the manufacturing equipment can be reduced. For example, the lifespan of equipment such as a float bath for forming glass can be extended, and productivity can be improved. T4 is preferably 1340 °C or lower, more preferably 1330 °C or lower, still more preferably 1320 °C or lower, yet 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, but it is usually 1100 °C or higher. For example, T4 is 1100 °C or higher and 1350 °C or lower. T 2、 T4 is determined by measuring the viscosity using a rotational viscometer according to the method specified in ASTM C 965 - 96, and the temperature when it reaches 10 2 d·Pa·s is defined as T2, and the temperature when it reaches 10 4 d·Pa·s can be determined as T4. In the examples described later, NBS710 and NIST717a were used as reference samples for device calibration.

[0053] The alkali - free glass of this embodiment has a glass surface devitrification temperature (T c ) less than T4 + 80 °C. When T c is less than T4 + 80 °C, the glass has excellent formability. During forming, the occurrence of crystals inside the glass and the resulting decrease in transmittance can be suppressed. Also, the burden on the manufacturing equipment can be reduced. For example, the lifespan of equipment such as a float bath for forming glass can be extended, and productivity can be improved. T c is preferably T4 + 75 °C or lower, more preferably T4 + 70 °C or lower, still more preferably T4 + 60 °C or lower, yet more preferably T4 + 50 °C or lower, particularly preferably T4 + 40 °C or lower, and most preferably T4 + 30 °C or lower. T c The lower limit of is not particularly limited, but it is usually 1000 °C or higher. T cis, for example, 1000 °C or higher and lower than T4 + 80 °C. The devitrification temperature (T c ) of the glass surface in this embodiment can be determined as follows. That is, glass particles crushed are placed in a platinum dish and heat-treated in an electric furnace controlled at a constant temperature for 17 hours. After the heat treatment, using an optical microscope, the highest temperature at which crystals precipitate on the glass surface and the lowest temperature at which crystals do not precipitate are observed, and the average value is taken as the devitrification temperature (T c ) of the glass surface.

[0054] The alkali-free glass of this embodiment has a viscosity (glass surface devitrification viscosity (η c )) at the glass surface devitrification temperature (T c ) of preferably 10 3.4 dPa·s or more. When the glass surface devitrification viscosity (η c ) is 10 3.4 dPa·s or more, the formability of the glass plate is excellent. Also, during forming, the generation of crystals inside the glass and the reduction of transmittance can be suppressed. Further, the burden on the manufacturing equipment can be reduced. For example, the service life of equipment such as a float bath for forming a glass plate can be extended, and productivity can be improved. η c is more preferably 10 3.5 dPa·s or more, still more preferably 10 3.6 dPa·s or more, particularly preferably 10 3.7 dPa·s or more, and most preferably 10 3.8 dPa·s or more. The upper limit of η c is not particularly limited, but is usually 10 6 dPa·s or less. η c is, for example, 10 3.4 dPa·s or more and 10 6 dPa·s or less.

[0055] The alkali-free glass of this embodiment has a specific elastic modulus (Young's modulus (GPa) / density (g / cm 3The specific modulus is 36 MN·m / kg or more. When the specific modulus is 36 MN·m / kg or more, the self-weight deflection becomes smaller, making it easier to handle large substrates. The specific modulus is preferably 36.1 MN·m / kg or more, more preferably 36.2 MN·m / kg or more, even more preferably 36.3 MN·m / kg or more, particularly preferably 36.4 MN·m / kg or more, and most preferably 36.5 MN·m / kg or more. There is no particular upper limit to the specific modulus of elasticity, but it is usually 50 MN·m / kg or less. For example, the specific modulus of elasticity is between 36 MN·m / kg and 50 MN·m / kg. A large substrate is, for example, a substrate with at least one side measuring 1800 mm or more. At least one side of a large substrate may be, for example, 2000 mm or more, 2500 mm or more, 3000 mm or more, or 3500 mm or more.

[0056] The alkali-free glass of this embodiment preferably has a glass transition temperature (hereinafter also referred to as Tg) of 850°C or lower. If Tg is 850°C or lower, the burden on the manufacturing equipment can be reduced. For example, the surface temperature of the rolls used in glass molding can be lowered, the lifespan of the equipment can be extended, and productivity can be improved. A Tg of 830°C or lower is more preferable, 820°C or lower is even more preferable, 810°C or lower is even more preferable, and 800°C or lower is particularly preferable. From the viewpoint of heat resistance, a Tg of 730°C or higher is preferable. A Tg of 740°C or higher is more preferable, 750°C or higher is even more preferable, 760°C or higher is particularly preferable, and 770°C or higher is most preferable. Here, a Tg of 730°C or higher and 850°C or lower is preferable.

[0057] In this embodiment, the alkali-free glass preferably has a photoelastic constant of 31 nm / MPa / cm or less. Stress generated during the liquid crystal display panel manufacturing process or during the use of liquid crystal display equipment can cause the glass substrate to exhibit birefringence, resulting in black appearing gray and a decrease in the contrast of the liquid crystal display. This phenomenon can be suppressed if the photoelastic constant is 31 nm / MPa / cm or less. More preferably, the photoelastic constant is 30 nm / MPa / cm or less, even more preferably 29 nm / MPa / cm or less, still 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 higher, and more preferably 25 nm / MPa / cm or higher. The photoelastic constant can be measured at a measurement wavelength of 546 nm by the disk compression method. Here, the photoelastic constant is preferably between 23 nm / MPa / cm and 31 nm / MPa / cm.

[0058] When the alkali-free glass of this embodiment is used as a glass plate for a liquid crystal display, if the average coefficient of linear expansion at 50 to 350°C is α, Young's modulus is E, and the photoelastic constant is C, then the product of α, E, and C, α·E·C, is 9.2 × 10⁻⁶. -7 It is preferable that the value is less than or equal to / K. In liquid crystal displays, the heat from the backlight causes an uneven temperature distribution on the glass plate closest to the backlight (the array glass plate in TFT-LCDs). If ΔT is the difference between the highest and lowest temperatures within the glass plate, the maximum stress F generated within this glass plate is expressed by the following equation. F = α·E·ΔT The optical path difference, or retardation R, generated in a glass plate of a certain thickness due to this stress F is expressed by the following equation. R = C·F·L = (α·E·C)·ΔT·L Therefore, the smaller α·E·C is, the smaller R becomes, resulting in better contrast in the liquid crystal display. α·E·C is 9.2 × 10 -7When the alkali-free glass of this embodiment is used as a glass plate for a liquid crystal display, the contrast of the liquid crystal display is good and contrast defects are less likely to occur.

[0059] α·E·C is more comfortable 9×10 -7 / K or less, more preferably 8.8 × 10 -7 / K or less, more preferably 8.7 × 10 -7 / K or less, particularly preferably 8.6 × 10 -7 / K or less, most preferably 8.5 × 10 -7 It is less than or equal to / K. The lower limit of α·E·C is not particularly limited, but is usually 5 × 10 -7 It is greater than or equal to / K. α·E·C is 5 × 10 -7 / K or more 9.2×10 -7 It is preferable that the value is less than or equal to / K.

[0060] The alkali-free glass of this embodiment has a high Young's modulus of 90 GPa or higher and a high specific modulus of elasticity of 36 MN·m / kg or higher, which allows for small self-weight deflection. Therefore, it is suitable for use as a glass plate for large substrates. A large substrate refers to, for example, a glass plate with at least one side of 1800 mm or more, and specifically, a glass plate with a long side of 1800 mm or more and a short side of 1500 mm or more is suitable.

[0061] The alkali-free glass of this embodiment is preferably a glass plate with at least one side measuring 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; more preferably a glass plate with at least one side measuring 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; particularly preferably a glass plate with at least one side measuring 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 most preferably a glass plate with at least one side measuring 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.

[0062] In this embodiment, the glass plate is preferably 1 mm or less in thickness to achieve weight reduction. More preferably, the glass plate in this embodiment is 0.7 mm or less, even more preferably 0.65 mm or less, still more preferably 0.55 mm or less, particularly preferably 0.45 mm or less, and most preferably 0.4 mm or less. The glass plate in this embodiment can also be 0.1 mm or less, or 0.05 mm or less in thickness. However, from the viewpoint of preventing deflection due to its own weight, a thickness of 0.1 mm or more is preferred, and 0.2 mm or more is more preferred. The thickness of the glass plate is preferably 0.1 mm or more and 1 mm or less.

[0063] The alkali-free glass of this embodiment can be manufactured, for example, by following the procedure below. The raw materials for each of the above components are blended to achieve the target content in the glass composition, and this mixture is placed in a melting furnace and heated to 1500-1800°C to melt and obtain molten glass. The obtained molten glass is then formed into a glass ribbon of a predetermined thickness using a molding device, and after slow cooling, this glass ribbon is cut to obtain alkali-free glass.

[0064] In this embodiment, it is preferable to form the molten glass into a glass plate using the float method or the fusion method. From the viewpoint of stably producing large glass plates with a high Young's modulus (for example, with sides of 1800 mm or more), it is preferable to use the float method. [Examples]

[0065] Examples will be described below, but the present invention is not limited to these examples. In the following, Examples 1 to 14 and 24 to 55 are examples, and Examples 15 to 23 are comparative examples. The raw materials for each component were prepared so that the glass composition would match the target composition (in mol%) shown in Examples 1-55, and melted at 1600°C for 1 hour using a platinum crucible. After melting, the molten liquid was poured onto a carbon plate, 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-like glass. This was then mirror-polished to obtain a glass plate, which was then evaluated in various ways. The β-OH value of the glass was determined using the following procedure. (β-OH value) The absorbance of the glass sample was measured for light with wavelengths of 2.75 to 2.95 μm, and the maximum absorbance value β was determined. max The β-OH value was determined by dividing the value by the thickness (mm) of the sample. The results are shown in Tables 1 to 8. Note that the values ​​in parentheses in Tables 1 to 8 are calculated values.

[0066] The measurement methods for each physical property are shown below. (Average thermal expansion coefficient α) The measurement was performed using a differential thermal expander (dilatometer) in accordance with the method specified in JIS R3102 (1995). The measurement temperature range was from room temperature to 400°C or higher, and the average thermal expansion coefficient between 50 and 350°C was measured in units of 10. -7 This was represented as / K. (density) A 20g glass mass free of bubbles was measured using the Archimedes method, in accordance with the method specified in JIS Z 8807. (distortion point) The measurement was performed using the fiber stretching method in accordance with the method specified in JIS R3103-2 (2001). (Tg) The measurement was performed using the thermal expansion method in accordance with the method specified in JIS R3103-3 (2001). (Young's modulus) Measurements were taken using the ultrasonic pulse method on glass with a thickness of 0.5 to 10 mm, in accordance with the method specified in JIS Z 2280.

[0067] (T2) The viscosity was measured using a rotational viscometer according to the method specified in ASTM C 965-96, and 10 2 The temperature T2 (°C) at which the temperature was d·Pa·s was measured. (T4) The viscosity was measured using a rotational viscometer according to the method specified in ASTM C 965-96, and 10 4 The temperature T4 (°C) at which the temperature was d·Pa·s was measured. (glass surface devitrification temperature T) c ) The glass was crushed and classified using a test sieve to obtain particles in the range of 2-4 mm. The resulting glass cullet was ultrasonically cleaned in isopropyl alcohol for 5 minutes, washed with deionized water, dried, placed in a platinum dish, and heat-treated in an electric furnace controlled to a constant temperature for 17 hours. The heat treatment temperature was set in 10°C increments. After heat treatment, the glass was removed from the platinum dish, and the highest temperature at which crystals precipitated on the glass surface and the lowest temperature at which crystals did not precipitate were observed using an optical microscope. The highest temperature at which crystals precipitated on the glass surface and the lowest temperature at which crystals did not precipitate were each measured once. (If it was difficult to determine crystal precipitation, measurements were taken twice.) The average value is calculated using the highest temperature at which crystals precipitate on the glass surface and the lowest temperature at which crystals do not precipitate, and the glass surface devitrification temperature T is determined. c That's what I decided. Note that in the table below, T as defined in claim 1 c To make it easier to distinguish between T4 and temperatures below 80℃, c -T4 was used to indicate this. (Glass surface devitrification viscosity η) c ) By the method described above, the glass surface devitrification temperature (T c ) is determined, and the glass surface devitrification temperature (T c The viscosity of the glass at ) was measured, and the glass surface devitrification viscosity (η) was determined. c The following table shows the glass surface devitrification viscosity (η). c The logarithm (log value) of ) is shown. (Specific modulus of elasticity) The specific modulus was determined by dividing the Young's modulus, obtained using the procedure described above, by the density.

[0068] (Photoelastic constant) The photoelastic constant was measured at a wavelength of 546 nm using the disk compression method. (BHF Haze) A glass plate was immersed in a 19BHF solution at 25°C for 20 minutes. If the haze change before and after immersion was 1% or less, it was marked as ○; if it was greater than 1%, it was marked as ×.

[0069] [Table 1]

[0070] [Table 2]

[0071] [Table 3]

[0072] [Table 4]

[0073] [Table 5]

[0074] [Table 6]

[0075] [Table 7]

[0076] [Table 8]

[0077] Examples 1-14 and 24-55, in which 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% to 38%, and the value of formula (I) is 90 to 100, have a strain point of 700°C to 740°C and a density of 2.6 g / cm³. 3 Below, the Young's modulus E is between 90 GPa and 100 GPa, and the average thermal expansion coefficient α at 50-350°C is 30 × 10⁻¹⁰. -7 / K or more 39×10 -7 / K or less, glass viscosity 102 The temperature T2 at which dPa·s occurs is between 1590°C and 1690°C, and the glass viscosity is 10. 4 The temperature T4 at which dPa·s occurs is 1350℃ or less, and the glass surface devitrification temperature (T c ) and the difference between T4 (T c -T4) was less than 80℃, and the specific modulus was 36 MN·m / kg or higher. As mentioned above, when the specific modulus is 36 MN·m / kg or higher, the self-weight deflection becomes small.

[0078] In Example 15, where the value of equation (I) was less than 90, the Young's modulus E was low (less than 90 GPa) and the specific modulus was low (less than 36 MN·m / kg). Example 16, in which MgO / (MgO+CaO+SrO+BaO) is less than 0.5, MgO+Al2O3 is less than 24%, and the value of equation (I) is less than 90, has a high average thermal expansion coefficient α between 50 and 350°C, which is 39 × 10⁻⁶. -7 The coefficient of elasticity was greater than / K, the Young's modulus E was low (less than 90 GPa), and the specific modulus was low (less than 36 MN·m / kg). Example 17, which does not contain B2O3 and SrO and has more than 20% MgO+CaO+SrO+BaO, has a high strain point above 740°C and a glass viscosity of 10 2 The temperature T2 at which dPa·s occurred was low, below 1590°C. Example 18, which does not contain B2O3 and SrO, has an Al2O3 content of less than 12%, and contains more than 20% MgO+CaO+SrO+BaO, has a glass surface devitrification temperature (T c The temperature was T4 + 80°C or higher. In example 19, where MgO+CaO+SrO+BaO makes up more than 20% and MgO+Al2O3 makes up less than 24%, the average thermal expansion coefficient α at 0-350°C is high at 39×10⁻⁶. -7 The value was greater than / K, and the specific modulus was low, less than 36 MN·m / kg. Example 20, which had a B2O3 content of less than 0.3%, had a low Young's modulus E of less than 90 GPa and a low specific modulus of elasticity of less than 36 MN·m / kg. Example 21, in which MgO+CaO+SrO+BaO exceeds 20%, has a high average thermal expansion coefficient α from 0 to 350°C, at 39 × 10⁻⁶. -7 / K or higher, glass viscosity 10 2The temperature T2 at which dPa·s occurred was low, below 1590°C. Example 22, where MgO+CaO+SrO+BaO exceeds 20%, has a high density of 2.6 g / cm³. 3 It was extremely low, with a Young's modulus E of less than 90 GPa. In example 23, where MgO+CaO+SrO+BaO is greater than 20%, MgO / CaO is less than 1, MgO / (MgO+CaO+SrO+BaO) is less than 0.5, and MgO+Al2O3 is less than 24%, the average thermal expansion coefficient α at 0-350°C is high at 39×10⁻⁶. -7 It was over / K.

[0079] Although the invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications are possible without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2021-145677, filed on 7 September 2021, which is incorporated by reference in its entirety. All references herein are incorporated as a whole. [Industrial applicability]

[0080] The alkali-free glass of this embodiment is preferably used in display panels, semiconductor devices, carrier substrates for manufacturing flexible devices, information recording media, planar antennas, dimmable laminates, vehicle window glass, and acoustic diaphragms.

Claims

1. The deviation point is 700 °C or higher and 740 °C or lower, the density is 2.6 g / cm ３ or lower, the Young's modulus is 90 GPa or higher and 100 GPa or lower, and the average coefficient of thermal expansion at 50 to 350 °C is 30×10 －７ / K or higher and 39×10 －７ / K or lower. The temperature T ２ at which the glass viscosity is 10 ２ dPa·s is 1590 °C or higher and 1690 °C or lower. The temperature T ４ at which the glass viscosity is 10 ４ dPa·s is 1350 °C or lower. The devitrification temperature of the glass surface (T ｃ ) is less than T ４ +80 °C, and the specific modulus of elasticity is 36 MN·m / kg or higher. In mole percent based on oxides SiO ２ 55% to 80% Al ２ O ３ 12% to 20% B ２ O ３ 0.3% to 5% MgO 5% or more and 18% or less, CaO 0.1% or more and 12% or less, SrO 0.1% or more and 8% or less, BaO 0% or more and 6% or less It contains, MgO + CaO + SrO + BaO is less than 20%. MgO / CaO is 1 or more, If MgO / (MgO+CaO+SrO+BaO) is 0.5 or higher, MgO + Al ２ O ３ between 24% and 38%, Equation (I) is (-3.125 × [SiO ２ ]-2.394×[Al ２ O ３ ] -3.511 × [B ２ O ３ ]-2.167×[MgO]-2.608×[CaO]-3.161×[SrO]-3.583×[BaO]+3.795×10 ２ Alkali-free glass, where the value of equation (I) is between 90 and 100 when given the condition.

2. Equation (II) is (0.213 × [SiO ２ ]+1.006×[Al ２ O ３ ] -0.493 × [B ２ O ３ ]+1.158×[MgO]+1.386×[CaO]+3.092×[SrO]+4.198×[BaO]+2.004×10 ２ The alkali-free glass according to claim 1, wherein when this is the case, the value of formula (I) / formula (II) × 100 is 36 or more.

3. The alkali-free glass according to claim 1, wherein the ratio of (MgO + CaO) / (SrO + BaO) is 8 or greater.

4. When the average coefficient of linear expansion at 50 to 350°C is α, Young's modulus is E, and the photoelastic constant is C, their product α・E・C is 9.2 × 10⁻⁶. －７ The alkali-free glass according to claim 1, wherein the temperature is less than or equal to / K.

5. The alkali-free glass according to claim 1, wherein the photoelastic constant is 31 nm / MPa / cm or less.

6. The alkali-free glass according to claim 1, wherein the glass transition temperature is 730°C or higher and 850°C or lower.

7. The devitrification viscosity of the glass surface is 10 ３．４ The alkali-free glass according to claim 1, wherein the pH is dPa·s or higher.

8. In mole percent based on oxides, ZrO ２ The alkali-free glass according to claim 1, containing 0 to 1% of [the specified substance].

9. Li ２ O, Na ２ O and K ２ The alkali-free glass according to claim 1, wherein the total amount of O is 0.2% or less in mole percent based on oxides.

10. SnO ２ The alkali-free glass according to claim 1, containing 0% or more and 0.5% or less of [the substance].

11. The alkali-free glass according to claim 1, containing 0% or more and 1% or less of F in mole percentage.

12. The β-OH value of the glass is 0.05 mm －１ 0.6 mm or more －１ The alkali-free glass according to claim 1, which is as follows:

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

14. A method for producing alkali-free glass according to any one of claims 1 to 12, wherein the glass is formed by a float method or a fusion method.

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