Alkali-free glass plate

Abstract

The alkali-free glass plate according to the present invention is characterized in that the glass composition contains, in mass%, 58 to 65% of SiO2, 18 to 21% of Al2O3, 2 to 5% of B2O3, 0.005 to 0.2% of Li2O + Na2O + K2O, 2 to 6% of MgO, 3 to 7.5% of CaO, 0.5 to 5.5% of SrO, 0.3 to 10% of BaO, 0.005 to 0.15% of ZrO2, 0.005 to 0.1% of TiO2, 0.1 to 0.35% of SnO2, and 0.01 to 0.15% of ZrO2 + TiO2, the strain point being 700 DEG C or higher, and the ss-OH being 0.3 / mm or less.

Description

Technical Field

[0001] The present invention relates to an alkali-free glass sheet, and more specifically, to an alkali-free glass sheet applicable to a display or the like having a thin film transistor (TFT: Thin Film Transistor) equipped with an oxide TFT film such as IGZO, or an LTPS (low temperature polycrystalline silicon) TFT. Background Art

[0002] As a support substrate for a display, a glass sheet is generally used. On the surface of the glass sheet, a circuit pattern such as a TFT is formed. As such a glass sheet, an alkali-free glass sheet containing no alkali metal component is widely used so as not to have an adverse effect on the TFT or the like.

[0003] In addition, the glass sheet is exposed to a high-temperature atmosphere in a circuit pattern forming process such as a thin film forming process or a thin film patterning process. If the glass sheet is exposed to a high-temperature atmosphere, the structural relaxation of the glass proceeds, and thus the volume of the glass sheet shrinks (hereinafter referred to as "thermal shrinkage"). In the circuit pattern forming process, if the glass sheet undergoes thermal shrinkage, the shape and size of the circuit pattern formed on the glass sheet deviate from the design values, and it is difficult to obtain a display having desired electrical properties. Therefore, a glass sheet having a thin film pattern such as a circuit pattern formed on its surface is desired to have a small thermal shrinkage rate.

[0004] Especially in the case of a high-definition display having a TFT with an oxide film such as IGZO, when forming the oxide film, it is exposed to a high-temperature atmosphere of 400°C to 500°C. In addition, if it is a TFT having an LTPS film, it is exposed to an even higher temperature atmosphere of 500°C to 600°C. In addition, for a display driven by a TFT such as IGZO or LTPS, since its circuit pattern is finer, if thermal shrinkage occurs, it is difficult to obtain desired electrical properties. Therefore, for a glass sheet used for such a purpose, it is strongly desired that its thermal shrinkage rate is very small.

[0005] However, as a forming method of a glass sheet for a display or the like, a down-draw method typified by an overflow down-draw method is known.

[0006] The down-draw method is a method of stretching molten glass downward to form a plate shape. As an overflow down-draw method, which is a kind of down-draw method, since the surface of the glass ribbon does not come into contact with anything other than air, after forming, a glass sheet with a flat surface can be obtained without grinding the surface, and it has the advantage of being easy to form a thin glass sheet.

[0007] On the other hand, in terms of the structure of the equipment, it is difficult to arrange a long annealing furnace under the formed body. If the annealing furnace is short, the cooling rate of the glass ribbon is accelerated, and thus it is difficult to form a glass sheet with a small thermal shrinkage rate.

[0008] Therefore, it is proposed to increase the strain point of the glass and reduce the thermal shrinkage rate of the glass. For example, Patent Document 1 discloses a low-alkali glass with a high strain point. In addition, it is described in the same document that the lower the β-OH value indicating the water content in the glass, the higher the strain point.

[0009] Prior art documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2013-151407 Summary of the invention

[0012] Problems to be solved by the invention

[0013] Examples of devices equipped with high-definition displays include mobile devices such as smartphones. For such devices, being thin and lightweight is very important. Therefore, a thinner display panel is manufactured by treating a plurality of completed display panels with a hydrofluoric acid-based chemical solution. However, such a process is costly and requires waste liquid treatment of a large amount of chemical solution, etc., and has a great adverse impact on the environment. Therefore, it is required to be easily thinned without using a large amount of hydrofluoric acid-based chemical solution.

[0014] In addition, such a thin-walled glass plate is likely to be deformed during the manufacturing process, so it may be damaged due to contact with manufacturing equipment, etc.

[0015] The present invention provides an alkali-free glass plate that is thin-walled, not easily damaged, and also difficult to thermally shrink.

[0016] Means for solving the problems

[0017] (1) The alkali-free glass plate of the present invention is characterized in that, as a glass composition, in terms of mass%, it contains SiO 2 58 to 65%, Al 2 O 3 18 to 21%, B 2 O 3 2 to 5%, Li 2 O + Na 2 O + K 2 O 0.005 to 0.2%, MgO 2 to 6%, CaO 3 to 7.5%, SrO 0.5 to 5.5%, BaO 0.3 to 10%, ZrO 2 0.005 to 0.15%, TiO 2 0.005 to 0.1%, SnO 2 0.1 to 0.35%, ZrO 2 + TiO 20.01 to 0.15%, the strain point is above 700 °C, and β-OH is 0.3 / mm or less. Here, "ZrO 2 +TiO 2 " means the total amount of ZrO 2 and TiO 2 ."Li 2 O + Na 2 O + K 2 O" means the total amount of Li 2 O, Na 2 O, and K 2 O. "Strain point" means the value measured by the method based on ASTM C336. "β-OH" means the value obtained by measuring the transmittance of the glass using FT-IR and using the following formula 1. Also, the "alkali-free glass" mentioned in the present invention means a glass in which the content of Li 2 O + Na 2 O + K 2 O is 0.2 mass% or less.

[0018] (Formula 1)

[0019] β-OH = (1 / X) log (T 1 / T 2 )

[0020] X: Plate thickness (mm)

[0021] T 1 : Transmittance (%) at a reference wavelength of 3846 cm －1

[0022] T 2 : Minimum transmittance (%) near the hydroxyl absorption wavelength of 3600 cm －1

[0023] (2) Preferably, the alkali-free glass plate of the present invention, in the composition of (1), as the glass composition, contains, by mass%, SiO 2 58 to 65%, Al 2 O 3 18 to 21%, B 2 O 3 2 to 5%, Li 2 O + Na 2 O + K 2 O 0.005 to 0.2%, MgO 2 to 6%, CaO 3 to 7.5%, SrO 0.5 to 5.5%, BaO 1 to 10%, ZrO 2 0.005 to 0.15%, TiO 2 0.005 to 0.1%, SnO 2 0.1 to 0.35%, ZrO2 +TiO 2 0.01 to 0.15%, the strain point is 700 °C or higher, and β-OH is 0.3 / mm or less.

[0024] (3) Preferably, in the structure of the above (1) or (2), the crack occurrence rate when an indentation is applied to at least one surface with a load of 500 g using a Vickers indenter is 50% or less. Here, the "crack occurrence rate" is a value measured in the following manner. First, in a constant temperature and humidity chamber where the humidity is maintained at 30% and the temperature is maintained at 25 °C, a Vickers indenter set at a load of 500 g is pressed into the surface of the glass plate for 15 seconds. After 15 seconds, the number of cracks occurring from the four corners of the indentation (up to 4 for each indentation) is counted. The indenter is pressed in 50 times in this way. After obtaining the total number of cracks, it is obtained by the formula (total number of cracks / 200) × 100. However, since the crack occurrence rate changes depending on the moisture state of the glass surface, before measurement, annealing is first performed at (strain point - 180 °C) for 60 minutes, and then measurement is carried out. The "strain point" is a value measured based on the method of ASTM C336. The "liquidus temperature" means the temperature at which crystal precipitation occurs after putting glass powder that has passed through a 30-mesh (500 μm) standard sieve and remains on a 50-mesh (300 μm) sieve into a platinum dish and keeping it in a temperature gradient furnace for 24 hours.

[0025] (4) Preferably, for the alkali-free glass plate of the present invention, in any one of the structures of (1) to (3), the average linear thermal expansion coefficient in the temperature range of 30 to 380 °C is 30×10 －7 ~40×10 －7 / °C, and the Young's modulus is 80 GPa or more. Here, the "Young's modulus" is a value measured by the bending resonance method. Also, 1 GPa is equivalent to about 101.9 Kgf / mm 2 . Here, the "average thermal expansion coefficient in the temperature range of 30 to 380 °C" is measured with an extensometer.

[0026] (5) Preferably, for the alkali-free glass plate of the present invention, in any one of the structures of (1) to (4), the thermal shrinkage rate after heat treatment at 500 °C for 60 minutes is 20 ppm or less.

[0027] (6) Preferably, for the alkali-free glass plate of the present invention, in any one of the structures of (1) to (5), it has a rectangular shape, the longitudinal and transverse dimensions are each 1800 mm or more, and the thickness is 0.5 mm or less.

[0028] (7) Preferably, for the alkali-free glass plate of the present invention, in any one of the structures of (1) to (6), the average surface roughness Sa of at least one main surface is 0.5 nm or less. Here, the "average surface roughness Sa" is a value measured using an atomic force microscope (AFM) based on the method of ISO25178.

[0029] (8) Preferably, in the non-alkali glass sheet of the present invention, in any one of the constitutions of (1) to (7), at least one main surface is a flame-polished surface or a surface equivalent to the flame-polished surface.

[0030] (9) The non-alkali glass sheet of the present invention is characterized in that the content of Li 2 O + Na 2 O + K 2 O is 0.005 to 0.2% by mass, the content of BaO is 1 to 10% by mass, the average linear thermal expansion coefficient in the temperature range of 30 to 380 °C is 30×10 －7 to 40×10 －7 / °C, the Young's modulus is 80 GPa or more, the density is 2.55 g / cm 3 or less, the strain point is 700 °C or more, the thermal shrinkage rate after heat treatment at 500 °C for 60 minutes is 20 ppm or less, the average surface roughness Ra of at least one surface is 0.5 nm or less, the longitudinal and transverse dimensions are 1800 mm or more, the thickness is 0.5 mm or less, and the crack occurrence rate when an indentation is applied to at least one surface with a load of 500 g using a Vickers indenter is 50% or less.

[0031] (10) The non-alkali glass sheet of the present invention is characterized in that, as the glass composition, in terms of mass%, it contains SiO 2 58 to 65%, Al 2 O 3 18 to 21%, B 2 O 3 2 to 5%, Li 2 O + Na 2 O + K 2 O 0.005 to 0.2%, MgO 2 to 6%, CaO 3 to 7.5%, SrO 0.5 to 5.5%, BaO 1 to 10%, B 2 O 3 + MgO 4 to 9%, and the average linear thermal expansion coefficient in the temperature range of 30 to 380 °C is 30×10 －7 to 40×10 －7 / °C, the Young's modulus is 80 GPa or more, the density is 2.59 g / cm 3 or less, the strain point is 700 °C or more, β-OH is 0.3 / mm or less, and the crack occurrence rate when an indentation is applied to at least one surface with a load of 500 g using a Vickers indenter is 50% or less. Here, "B 2 O 3 + MgO" means the total amount of B 2 O 3 and MgO.

[0032] (11) The alkali-free glass sheet of the present invention is characterized in that, as the glass composition, in terms of mass%, it contains SiO 2 58-65%, Al 2 O 3 18-21%, B 2 O 3 2-5%, Li 2 O + Na 2 O + K 2 O 0.005-0.2%, MgO 2-6%, CaO 3-7.5%, SrO 0.5-5.5%, BaO 0.3-10%, B 2 O 3 + MgO 4-9%, and the average linear thermal expansion coefficient in the temperature range of 30-380 °C is 30×10 －7 - 40×10 －7 / °C, the Young's modulus is 80 GPa or more, the density is 2.59 g / cm 3 or less, the strain point is 700 °C or more, β-OH is 0.3 / mm or less, and the crack occurrence rate when an indentation is applied to at least one surface with a load of 500 g using a Vickers indenter is 50% or less.

[0033] (12) Preferably, the alkali-free glass sheet of the present invention is used as a substrate for an electronic display in any one of the configurations of (1)-(11).

[0034] Effects of the Invention

[0035] According to the present invention, an alkali-free glass sheet with a thin wall, which is not easily damaged and is also difficult to thermally shrink, can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1A It is a diagram for explaining the thermal shrinkage rate.

[0037] Figure 1B It is a diagram for explaining the thermal shrinkage rate.

[0038] Figure 1C It is a diagram for explaining the thermal shrinkage rate. DETAILED DESCRIPTION OF THE INVENTION

[0039] The alkali-free glass sheet of one embodiment of the present invention, as the glass composition, in terms of mass%, contains SiO 2 58-65%, Al 2 O 3 18-21%, B 2 O 3 2-5%, Li 2 O + Na2 O + K 2 O 0.005 to 0.2%, MgO 2 to 6%, CaO 3 to 7.5%, SrO 0.5 to 5.5%, BaO 0.3 to 10%, ZrO 2 0.005 to 0.15%, TiO 2 0.005 to 0.1%, SnO 2 0.1 to 0.35%, ZrO 2 + TiO 2 0.01 to 0.15%. The reasons for limiting the content of each component as described above are shown below. Also, in the description of the content of each component, unless otherwise specified, the display of % means mass%. In addition, unless otherwise specified, X to Y means X or more and Y or less. Also, regarding the lower limit and the lower limit value, the expression "preferably X" means preferably X or more, unless otherwise specified. On the other hand, regarding the upper limit and the upper limit value, the expression "preferably Y" means preferably Y or less, unless otherwise specified.

[0040] SiO 2 is a component that forms the skeleton of the glass. If the content of SiO 2 is too small, the thermal expansion coefficient becomes high and the density increases. In addition, the acid resistance and hydrofluoric acid resistance decrease. Therefore, the lower limit of SiO 2 is preferably 58%, more preferably 58.2%, further preferably 58.5%, further preferably 58.8%, further preferably 59%, further preferably 59.2%, further preferably 59.5%, further preferably 59.8%, and most preferably 60%. On the other hand, if the content of SiO 2 is too large, the Young's modulus decreases, and in addition, the high-temperature viscosity becomes high, the heat required for melting increases, and the melting cost rises. In addition, the melting residue of the raw material for introducing SiO 2 occurs, which may cause a decrease in the production yield. In addition, devitrified crystals such as cristobalite are likely to precipitate, and the liquid-phase viscosity is likely to decrease. Therefore, the upper limit of SiO 2 is preferably 65%, more preferably 64.5%, further preferably 64.3%, further preferably 64%, further preferably 63.8%, further preferably 63.5%, further preferably 63.0%, further preferably 62.8%, and most preferably 62.5%.

[0041] Al 2 O 3 is a component that forms the glass skeleton, and is also a component that increases the Young's modulus and further a component that raises the strain point. If Al 2 O 3If the content is too small, the Young's modulus is likely to decrease, and the strain point is also likely to decrease. Therefore, for Al 2 O 3 , the lower limit is preferably 18%, more preferably 18.2%, further preferably 18.4%, further preferably higher than 18.4%, further preferably 18.5%, further preferably 18.6%, further preferably 18.8%, further preferably higher than 18.8%, and most preferably 19%. On the other hand, if the content of Al 2 O 3 is too large, devitrified crystals such as mullite are likely to precipitate, and the liquid-phase viscosity is likely to decrease. Therefore, the upper limit of Al 2 O 3 is preferably 21%, more preferably 20.8%, further preferably 20.6%, further preferably 20.4%, further preferably 20.2%, and most preferably 20%.

[0042] B 2 O 3 is a component that improves the edge chipping resistance and crack resistance characteristics, and can also enjoy the effects of improving the fusibility and devitrification resistance. Therefore, the lower limit of B 2 O 3 is preferably 2%, more preferably 2.2%, further preferably 2.5%, further preferably 2.8%, further preferably 3%, and most preferably 3+%. On the other hand, if the content of B 2 O 3 is too large, the Young's modulus and strain point are likely to decrease. Therefore, the upper limit of B 2 O 3 is preferably 5%, more preferably 4.9%, further preferably 4.8%, further preferably 4.7%, further preferably 4.6%, further preferably 4.5%, further preferably 4.4%, and most preferably 4.2%.

[0043] Li 2 O, Na 2 O, and K 2 O are components inevitably mixed in from the glass raw materials, and their total content is 0 to 0.2%, preferably 0 to 0.1%, more preferably 0 to 0.09%, further preferably 0.005 to 0.08%, further preferably 0.008 to 0.06%, and most preferably 0.01 to 0.05%. If the total content of Li 2 O, Na 2 O, and K 2 O is too large, it may cause the diffusion of alkaline ions into the semiconductor material of the film during the heat treatment process. In addition, the individual content of Li 2 O and Na 2 O, regarding Na 2O is preferably 0.001 to 0.05%, more preferably 0.001 to 0.03%, still more preferably 0.001 to 0.02%, and most preferably 0.001 to 0.015%. Additionally, regarding Li 2 O, it is preferably 0.001% or less, more preferably 0.0005% or less, and most preferably 0.0003% or less.

[0044] Among alkaline earth metal oxides, MgO is a component that significantly increases the Young's modulus. If the content of MgO is too small, the fusibility and Young's modulus tend to decrease. Therefore, the lower limit of the content of MgO is preferably 2%, more preferably 2.1%, still more preferably 2.3%, and most preferably 2.5%. On the other hand, if the content of MgO is too large, devitrified crystals such as enstatite or Si - Al - Mg - O systems tend to precipitate, and the liquid phase viscosity tends to decrease. Additionally, the strain point decreases and the heat resistance is impaired. Therefore, the upper limit of the content of MgO is 6%, more preferably 5.8%, still more preferably 5.6%, still more preferably 5.5%, still more preferably 5.4%, still more preferably less than 5.3%, still more preferably 5.2%, still more preferably 5.1%, still more preferably 5%, still more preferably 4.9%, and most preferably 4.8%.

[0045] B 2 O 3 The total amount with MgO affects the crack resistance. If the total amount of B 2 O 3 and MgO is too small, the crack resistance decreases. Therefore, the lower limit value of the total amount of B 2 O 3 and MgO is preferably 4%, more preferably 4.2%, still more preferably 4.4%, still more preferably 4.8%, still more preferably 5.0%, and most preferably 5.2%. On the other hand, if the total amount of B 2 O 3 and MgO is too large, the strain point decreases and the thermal shrinkage increases. Therefore, the upper limit value of the total amount of B 2 O 3 and MgO is preferably 9%, more preferably 8.7%, still more preferably 8.4%, still more preferably 8%, and most preferably 7.5%.

[0046] The mass ratio of B 2 O 3 / MgO affects the rigidity. If the mass ratio of B 2 O 3 / MgO is too large, the Young's modulus decreases and it is difficult to maintain the rigidity. Therefore, the mass ratio of B 2 O 3The upper limit value of / MgO is preferably 2.5, more preferably 2.0, further preferably 1.8, more preferably 1.7, further preferably 1.6, further preferably 1.5, and most preferably 1.4. On the other hand, if the mass percentage ratio B 2 O 3 / MgO is too small, the devitrification resistance decreases, and crystalline foreign substances are likely to occur in the glass. Therefore, the lower limit value of the mass percentage ratio B 2 O 3 / MgO is preferably 0.4, more preferably 0.5, further preferably 0.6, further preferably 0.7, and most preferably 0.8.

[0047] CaO is a component that reduces the high-temperature viscosity without lowering the strain point and significantly improves the meltability. It is also a component that increases the Young's modulus. If the content of CaO is too small, the meltability is likely to decrease. Therefore, the lower limit amount of CaO is preferably 3%, more preferably 3.2%, further preferably 3.5%, further preferably 3.8%, further preferably 4%, further preferably 4.2%, and most preferably 4.5%. On the other hand, if the content of CaO is too much, the liquidus temperature rises. Therefore, the upper limit amount of CaO is preferably 7.5%, more preferably 7.3%, further preferably 7.2%, further preferably 7%, further preferably 6.8%, further preferably 6.5%, further preferably 6.3%, and most preferably 6%.

[0048] SrO is a component that improves the devitrification resistance. In addition, it reduces the high-temperature viscosity without lowering the strain point and improves the meltability. It is also a component that suppresses the decrease in the liquid-phase viscosity. Therefore, the lower limit amount of SrO is preferably 0.5%, more preferably 1%, further preferably 1.5%, further preferably 1.7%, and most preferably 2%. On the other hand, if the content of SrO is too much, the thermal expansion coefficient and density are likely to increase, and the chemical durability decreases. Therefore, the upper limit amount of SrO is preferably 5.5%, more preferably less than 5%, further preferably 4.8%, further preferably 4.5%, further preferably 4.3%, and most preferably 4%.

[0049] BaO is a component that improves the devitrification resistance. Therefore, the lower limit amount of BaO is preferably 0.3%, more preferably 0.7%, more preferably 1%, more preferably 1.5%, further preferably 2%, further preferably 2.5%, and most preferably 3%. On the other hand, if the content of BaO is too much, the Young's modulus is likely to decrease, and the density is likely to increase. As a result, the specific Young's modulus increases, and the glass plate is likely to warp. Therefore, the upper limit amount of BaO is preferably 10%, more preferably 9.5%, further preferably 9%, further preferably 8.5%, further preferably 8.2%, further preferably 8%, further preferably 7.5%, further preferably 7%, and most preferably 6%.

[0050] MgO, CaO, SrO, and BaO are components that increase density and the coefficient of thermal expansion. If the content of MgO + CaO + SrO + BaO (the total amount of MgO, CaO, SrO, and BaO) is too small, the coefficient of thermal expansion is likely to decrease. Therefore, the lower limit of MgO + CaO + SrO + BaO is preferably 10%, more preferably 10.2%, further preferably 10.5%, further preferably 10.8%, further preferably 11%, further preferably 11.3%, further preferably 11.5%, further preferably 11.8%, and most preferably 12%. On the other hand, if the content of MgO + CaO + SrO + BaO is too large, the density is likely to increase. Therefore, the upper limit of MgO + CaO + SrO + BaO is preferably 19%, more preferably 18%, further preferably 17%, and most preferably 16%.

[0051] ZrO 2 is a component that increases Young's modulus and crack resistance. Therefore, ZrO 2 The lower limit is preferably 0.005%, more preferably 0.007%, and further preferably 0.01%. On the other hand, if a large amount of ZrO 2 is contained, the glass is likely to devitrify. Therefore, the upper limit of ZrO 2 is preferably 0.15%, more preferably 0.12%, further preferably 0.10%, further preferably 0.08%, and most preferably 0.06%.

[0052] TiO 2 is a component that reduces high-temperature viscosity and improves meltability, and is also a component that increases Young's modulus, crack resistance, and chemical durability. Therefore, TiO 2 The lower limit is preferably 0.005%, more preferably 0.007%, and further preferably 0.01%. On the other hand, if a large amount of TiO 2 is contained, the glass is colored and the transmittance is likely to decrease. Therefore, the upper limit of TiO 2 is preferably 0.1%, more preferably 0.08%, further preferably 0.07%, 0.05%, and most preferably 0.04%.

[0053] ZrO 2 and TiO 2 The total amount affects Young's modulus and crack resistance. ZrO 2 and TiO 2 The lower limit of the total amount is preferably 0.01%, more preferably 0.03%, and most preferably 0.05%. ZrO 2 and TiO 2The upper limit value of the total amount is preferably 0.15%, more preferably 0.13%, and most preferably 0.11%.

[0054] SnO 2 is a component that has a good clarification effect in the high temperature range, is a component that increases the strain point, and is also a component that reduces the high temperature viscosity. Therefore, SnO 2 The lower limit amount is preferably 0.1%, more preferably 0.12%, further preferably 0.15%, and most preferably 0.16%. On the other hand, if the content of SnO 2 is too much, the devitrified crystals of SnO 2 are likely to precipitate. Therefore, the upper limit amount of SnO 2 is preferably 0.35%, more preferably 0.3%, further preferably 0.27%, and most preferably 0.25%.

[0055] In addition to the above components, for example, the following components can also be added as optional components. Also, from the viewpoint of ensuring the effects of the present invention, the content of other components other than the above components is preferably 5% or less, particularly preferably 3% or less, in terms of the total amount.

[0056] P 2 O 5 is a component that increases the strain point and is a component that can significantly inhibit the precipitation of devitrified crystals of alkaline earth aluminosilicates such as anorthite. However, if P 2 O 5 is contained in a large amount, the glass is likely to phase-separate. The content of P 2 O 5 is preferably 0 to 2.5%, more preferably 0 to 1.5%, further preferably 0 to 0.5%, further preferably 0 to 0.3%, further preferably 0 to less than 0.1%, and particularly preferably 0.0001 to less than 0.01%.

[0057] ZnO is a component that increases the Young's modulus. However, if ZnO is contained in a large amount, the glass is likely to devitrify and the strain point is likely to decrease. The content of ZnO is preferably 0 to 3%, more preferably 0 to 2%, further preferably 0 to 1%, further preferably 0 to 0.8%, further preferably 0 to 0.5%, and most preferably 0.0001 to less than 0.5%.

[0058] Fe 2 O 3 is a component that is inevitably mixed in from the glass raw materials and is also a component that reduces the resistivity. Fe 2 O 3 The content is preferably 0 to 250 mass ppm, more preferably 20 to 200 mass ppm, 40 to 150 mass ppm, and most preferably 60 to 120 mass ppm. If Fe2 O 3 has too little content, the raw material cost is likely to increase. On the other hand, if the content of Fe 2 O 3 is too high, the ultraviolet transmittance of the glass decreases, and malfunctions may occur when using UV light or UV laser in the manufacturing process of electronic displays such as liquid crystal displays. For example, the TFT substrate of the LCD panel is sealed with the counter substrate or the CF substrate by a UV curable resin, but if the ultraviolet transmittance is low, poor sealing is likely to occur. In addition, UV alignment treatment for aligning liquid crystal molecules is performed using UV light, but if the ultraviolet transmittance is low, the specified alignment treatment may not be possible. Or, in an OLED display (POLED) having a TFT element and an electronic circuit formed on a polyimide film coated and fired on a glass carrier, there is a so-called laser lift-off process of lifting off the polyimide film using UV laser, but if the ultraviolet transmittance of the glass plate is low, it is difficult to irradiate the UV laser through the glass plate.

[0059] Y 2 O 3 、Nb 2 O 5 、La 2 O 3 has the effect of increasing the strain point, Young's modulus, etc. The total amount and individual content of these components are preferably 0 to 5%, more preferably 0 to 1%, further preferably 0 to 0.5%, and most preferably 0.0001 to less than 0.5%. If the total amount and individual content of Y 2 O 3 、Nb 2 O 5 、La 2 O 3 are too much, the density and raw material cost are likely to increase.

[0060] As a fining agent, As 2 O 3 、Sb 2 O 3 are also effective. However, As 2 O 3 、Sb 2 O 3 are components that increase the environmental burden. In addition, As 2 O 3 is a component that reduces the resistance to exposure discoloration. Therefore, the alkali-free glass plate of the present invention preferably substantially does not contain these components.

[0061] Cl is a component that promotes the initial melting of the glass batch. Additionally, if Cl is added, the effect of the fining agent can be promoted. As a result, the melting cost can be reduced, and at the same time, the long life of the glass manufacturing furnace can be achieved. However, if the content of Cl is too high, the strain point is likely to decrease. Therefore, the content of Cl is preferably 0 to 0.1%, more preferably 0 to 0.08%, and most preferably 0 to 0.05%. Also, as a raw material for introducing Cl, chlorides of alkaline earth metal oxides such as strontium chloride, or raw materials such as aluminum chloride can be used.

[0062] The alkali-free glass plate according to one embodiment of the present invention preferably has the following characteristics.

[0063] The crack occurrence rate when an indentation is applied with a load of 500 g using a Vickers indenter is preferably 50% or less. If the crack occurrence rate obtained based on the indentation caused by the Vickers indenter is 50% or less, breakage during the TFT manufacturing process can be reduced in thin and large glass plates. Additionally, a decrease in the strength of the thin display panel itself can be suppressed. The crack occurrence rate is preferably 45% or less, more preferably 40% or less, further preferably 30% or less, and most preferably 20% or less.

[0064] The average coefficient of thermal expansion in the temperature range of 30 to 380 °C is preferably 30×10 －7 ~40×10 －7 / °C, more preferably 32×10 －7 ~39×10 －7 / °C, further preferably 33×10 －7 ~38×10 －7 / °C, further preferably 33×10 －7 ~37×10 －7 / °C, most preferably 34×10 －7 ~36×10 －7 / °C. If so, it is easy to match the coefficient of thermal expansion of Si used in the TFT.

[0065] The Young's modulus is preferably 80 GPa or more, more preferably 81 GPa or more, further preferably 81.3 GPa or more, further preferably 81.5 GPa or more, further preferably 81.8 GPa or more, further preferably 82 GPa or more, further preferably 82.3 GPa or more, further preferably 82.5 GPa or more, further preferably 82.8 GPa or more, and most preferably especially 83 GPa or more. Additionally, the Young's modulus is preferably 120 GPa or less. If the Young's modulus is too low, problems are likely to occur due to the flexure of the glass plate.

[0066] The specific Young's modulus (the value obtained by dividing the Young's modulus by the density) is preferably 31 GPa / g·cm－3 Above, more preferably 31.1 GPa / g·cm －3 Above, further preferably 31.3 GPa / g·cm －3 Above, further preferably 31.5 GPa / g·cm －3 Above, further preferably 31.8 GPa / g·cm －3 Above, further preferably 32 GPa / g·cm －3 Above, further preferably 32.2 GPa / g·cm －3 Above, further preferably 32.4 GPa / g·cm －3 Above, further preferably 32.8 GPa / g·cm －3 Above, most preferably 33 GPa / g·cm －3 Above. In addition, the specific Young's modulus is preferably 37 GPa / g·cm －3 Below. If the specific Young's modulus is too low, problems are likely to occur due to the flexure of the glass plate. Also, the density is preferably 2.59 g / cm 3 Below, more preferably 2.57 g / cm 3 Below, particularly preferably 2.55 g / cm 3 Below.

[0067] The strain point is preferably 700 °C or higher, more preferably 705 °C or higher, further preferably 710 °C or higher, further preferably 715 °C or higher, further preferably 718 °C or higher, and most preferably 720 °C or higher. The strain point is preferably 750 °C or lower. If so, thermal shrinkage of the glass plate can be suppressed in the LTPS process.

[0068] Regarding the amount of thermal shrinkage, the thermal shrinkage rate after heat treatment at 500 °C for 60 minutes is preferably 20 ppm or less, more preferably 18 ppm or less, more preferably 16 ppm or less, further preferably 15 ppm or less, further preferably 14 ppm or less, further preferably 13 ppm or less, and most preferably 12 ppm or less.

[0069] The "thermal shrinkage rate after heat treatment at 500 °C for 60 minutes" is measured by the following method. First, as Figure 1A shown, as a measurement sample, a narrow strip sample G of 160 mm × 30 mm is prepared. Using #1000 waterproof sandpaper, marks M are formed at positions 20 - 40 mm from the edge at both ends in the long side direction of the narrow strip sample G. Thereafter, as Figure 1BAs shown, a narrow strip-shaped sample G with a mark M is folded in half along the direction orthogonal to the mark M to produce sample pieces Ga and Gb. Then, only one sample piece Gb is heat-treated by heating it from room temperature to 500°C at a rate of 5°C / minute, holding it at 500°C for 1 hour, and then cooling it at a rate of 5°C / minute. After the above heat treatment, as Figure 1C shown, in a state where the sample piece Ga that has not been heat-treated and the sample piece Gb that has been heat-treated are arranged in parallel, the misalignment amounts (ΔL1, ΔL2) of the marks M on the two sample pieces Ga and Gb are read by a laser microscope, and the thermal shrinkage rate is calculated by the following formula 2. Also, l0 mm in the following formula is the initial distance between the marks M.

[0070] (Formula 2)

[0071] Thermal shrinkage rate (ppm) = [{ΔL 1 (μm) + ΔL 2 (μm)} × 10 3 / l 0 (mm)

[0072] The annealing point is preferably 800°C or higher, more preferably 801°C or higher, further preferably 803°C or higher, further preferably 805°C or higher, further preferably 808°C or higher, and most preferably 809°C or higher. In addition, the annealing point is preferably 900°C or lower. If so, it is possible to suppress the thermal shrinkage of the glass plate in the LTPS process without impairing the meltability and formability.

[0073] The liquidus temperature is preferably 1400°C or lower, more preferably 1380°C or lower, further preferably 1350°C or lower, further preferably 1300°C or lower, further preferably 1290°C or lower, further preferably 1285°C or lower, further preferably 1280°C or lower, further preferably 1275°C or lower, further preferably 1270°C or lower, and most preferably 1260°C or lower. If so, it is easy to prevent the occurrence of devitrified crystals during glass manufacturing, which may lead to a reduction in productivity. In addition, since it is easy to form by the overflow down-draw method, it is easy to improve the surface quality of the glass plate and reduce the manufacturing cost of the glass plate. Also, the liquidus temperature is preferably 1160°C or higher, more preferably 1170°C or higher, and most preferably 1180°C or higher. Further, the liquidus temperature is an index of devitrification resistance, and the lower the liquidus temperature, the more excellent the devitrification resistance.

[0074] The liquid-phase viscosity is preferably 10 4.6 dPa·s or higher, more preferably 10 4.7 dPa·s or higher, further preferably 10 4.8 dPa·s or higher, further preferably 10 4.9 dPa·s or higher, further preferably 105.0 dPa·s or more, more preferably 10 5.1 dPa·s or more, most preferably 10 5.2 dPa·s or more. If so, devitrification hardly occurs during forming, so it is easy to form by the overflow down-draw method. As a result, the surface quality of the glass plate can be improved, and in addition, the manufacturing cost of the glass plate can be reduced. Also, the liquid-phase viscosity is an index of devitrification resistance and formability. The higher the liquid-phase viscosity, the higher the devitrification resistance and formability. Also, the liquid-phase viscosity is preferably 10 7.4 dPa·s or less, more preferably 10 7.2 dPa·s or less, most preferably 10 7.0 dPa·s or less. Also, for the glass of this composition system, if the liquid-phase viscosity is very high, the melting temperature and forming temperature increase. Therefore, it is sometimes not preferable for the manufacture of the glass plate.

[0075] The temperature of the high-temperature viscosity of 10 2.5 dPa·s is preferably 1630 °C or lower, more preferably 1620 °C or lower, further preferably 1610 °C or lower, and most preferably 1605 °C or lower. If the temperature of the high-temperature viscosity of 10 2.5 dPa·s is too high, it is difficult to melt the glass batch, and the manufacturing cost of the glass plate increases. Also, the temperature of the high-temperature viscosity of 10 2.5 dPa·s corresponds to the melting temperature, and the lower this temperature, the higher the meltability. The temperature of the high-temperature viscosity of 10 2.5 dPa·s is preferably 1500 °C or higher, more preferably 1510 °C or higher, further preferably 1520 °C or higher, and most preferably 1530 °C or higher. If the high-temperature viscosity is too low, the strain point of the glass decreases, so the thermal shrinkage of the glass becomes larger and the heat resistance decreases. In addition, the liquid-phase viscosity of the glass decreases, and crystalline foreign substances may easily be generated in the glass plate.

[0076] β-OH is an index indicating the moisture content in the glass. If β-OH is reduced, the strain point can be increased. In addition, even when the glass composition is the same, when the β-OH value is small, the thermal shrinkage rate at temperatures below the strain point becomes smaller. β-OH is preferably 0.3 / mm or less, more preferably 0.25 / mm or less, further preferably 0.22 / mm or less, further preferably 0.2 / mm or less, further preferably 0.17 / mm or less, further preferably 0.15 / mm or less, further preferably 0.12 / mm or less, and most preferably 0.10 / mm or less. Also, if β-OH is too small, the meltability tends to decrease. Therefore, β-OH is preferably 0.01 / mm or more, and most preferably 0.03 / mm or more.

[0077] As a method for reducing the β-OH value, the following methods can be cited. (1) Select raw materials with low water content. (2) Add components (Cl, SO 3 etc.) that reduce the β-OH value to the glass. (3) Reduce the moisture content in the furnace atmosphere. (4) Conduct N 2 bubbling in the molten glass. (5) Use a small melting furnace. (6) Increase the flow rate of the molten glass. (7) Adopt the electric melting method.

[0078] The average surface roughness Sa of the main surface is preferably 0.5 nm or less, more preferably 0.4 nm or less, and most preferably 0.3 nm or less. If so, it is possible to prevent disconnection of the fine TFT elements or electrode film wirings formed on the glass surface. Here, the "average surface roughness Sa of the main surface" means the average surface roughness Sa of the main surface excluding the positions within 10 mm from the peripheral part of the main surface of the non-alkali glass plate for displays, and the average surface roughness Sa of at least one main surface is preferably 0.5 nm or less.

[0079] The average linear transmittance in the wavelength range of 380 nm to 1500 nm is preferably 90% or more. Here, the "average linear transmittance in the wavelength range of 380 nm to 1500 nm" can be measured by a so-called double-beam spectrophotometer. For example, use UH-4150 manufactured by Hitachi, etc.

[0080] The plate thickness is not particularly limited, but when used for an organic EL device, it is preferably less than 0.7 mm, more preferably 0.6 mm or less, further preferably less than 0.6 mm, further preferably 0.5 mm or less, and most preferably 0.41 mm or less. If the plate is thin, it is possible to easily obtain a thin display panel even without using a large amount of hydrofluoric acid-based chemical solution to thin the glass plate. In addition, the organic EL device can be made lighter. The plate thickness can be adjusted by the flow rate and pulling speed during glass manufacturing. In addition, considering the strength of the glass plate, the plate thickness is preferably 0.2 mm or more.

[0081] The surface area is preferably 2.5 m 2 or more, a rectangle with a side dimension of 1500 mm or more, more preferably an area of 4 m 2 or more, a rectangle with a side dimension of 1800 mm or more, and most preferably an area of 4.5 m 2 or more, a rectangle with a side dimension of 2000 mm or more.

[0082] The alkali-free glass plate of one embodiment of the present invention is preferably formed by the overflow down-draw method. The overflow down-draw method is a method of manufacturing a glass plate by melting and overflowing molten glass from both sides of a heat-resistant trough-shaped structure, and while causing the overflowing molten glass to converge at the lower end of the trough-shaped structure, stretching it downward to form a glass plate. In the overflow down-draw method, the surface to be the surface of the glass plate does not contact the trough-shaped refractory, but is formed in a free surface state. Therefore, it is possible to inexpensively manufacture a glass plate having a flame-polished surface with good surface quality without grinding, and it is also easy to make it thinner.

[0083] Such a glass with a flame-polished surface has excellent characteristics such as the surface roughness Sa being 0.5 nm or less and excellent scratch resistance. In addition, even if the surface is cleaned with a cleaning agent such as alkaline or acidic, or rinsed with warm pure water, or the surface is cleaned with various chemical solutions and detergents used in the substrate manufacturing process for display applications described in the present invention, it still maintains characteristics as good as those of the flame-polished surface. If a treatment such as a grinding process is applied to the surface, the excellent characteristics of the flame-polished surface may be impaired.

[0084] Examples

[0085] Hereinafter, the present invention will be described based on examples. In addition, the following examples are only illustrative. The present invention is not limited by any of the following examples.

[0086] Table 1 shows the examples (Sample Nos. 1 to 7) and comparative examples (Sample Nos. 8 to 10) of the present invention.

[0087]

Table 1

[0088]

[0089] First, glass raw materials and cullet are blended according to the glass composition in the table (glass raw material mass: cullet mass = 65:35), and the blended glass batch is put into an electric melting furnace without using a burner to melt the glass batch. Then, in the clarification tank and the adjustment tank, the molten glass is clarified and homogenized, and adjusted to a viscosity suitable for forming.

[0090] Next, the molten glass is supplied to an overflow down-draw forming device, formed into a plate shape, and then cut to obtain a 0.5-mm-thick glass sample. Here, the molten glass discharged from the melting furnace is supplied to the forming device while only contacting platinum or a platinum alloy. In addition, for Sample No. 8, its surface is further polished using cerium oxide.

[0091] For each obtained sample, β-OH, the average coefficient of thermal expansion in the temperature range of 30 to 380 °C, density, strain point, annealing point, softening point, the temperature of high-temperature viscosity 10 4.5 dPa·s, the temperature of high-temperature viscosity 10 4.0The temperature and high-temperature viscosity of dPa·s, 10 3.0 The temperature and high-temperature viscosity of dPa·s, 10 2.5 The temperature of dPa·s, the liquidus temperature, and the viscosity logη, Young's modulus, specific Young's modulus, crack occurrence rate under a 500 g load, thermal shrinkage rate after heat treatment at 500 °C for 60 minutes, and surface roughness Sa at the liquidus temperature TL.

[0092] β-OH is a value calculated based on the transmittance of the glass measured by FT-IR.

[0093] The average thermal expansion coefficient in the temperature range of 30 to 380 °C is a value measured with a dilatometer.

[0094] The density ρ is a value measured by the well-known Archimedes method.

[0095] The strain point, annealing point, and softening point are values measured based on the methods of ASTM C336 and C338.

[0096] High-temperature viscosity 10 4.5 dPa·s, 10 4 dPa·s, 10 3 dPa·s, 10 2.5 The temperature of dPa·s is a value measured by the platinum ball pulling method.

[0097] The liquidus temperature is the temperature at which crystals precipitate after putting glass powder that passes through a standard sieve of 30 mesh (500 μm) and remains on a 50 mesh (300 μm) into a platinum dish and keeping it in a temperature gradient furnace for 24 hours.

[0098] The liquid-phase viscosity logη is a value measured by the platinum ball pulling method for the viscosity of the glass at the liquidus temperature.

[0099] Young's modulus refers to a value measured by a well-known resonance method.

[0100] The specific Young's modulus is the value obtained by dividing Young's modulus by the density.

[0101] The crack occurrence rate is obtained as follows. First, after measuring the strain point Ps, annealing is performed for 60 minutes in the temperature range of (Ps - 180) °C. Then, in a constant temperature and humidity chamber with a humidity of 30% and a temperature of 25 °C, a Vickers indenter set at a 500 g load is pressed into the surface of the glass plate for 15 seconds (a total of 50 times). After 15 seconds, the number of cracks occurring at the four corners of the indenter is counted.

[0102] The thermal shrinkage rate after heat treatment at 500°C for 60 minutes was obtained as follows. (1) Marks M were formed at positions 20 to 40 mm from the edges at both ends in the long side direction of a 60 mm × 30 mm sample. (2) Thereafter, the sample with the marks M formed was folded in half along the direction orthogonal to the marks M to produce sample pieces Ga and Gb. (3) Then, only one sample piece Ga was subjected to heat treatment in which it was heated from room temperature to 500°C at 5°C / min, held at 500°C for 1 hour, and then cooled at 5°C / min. (4) After the heat treatment, the sample piece Gb that had not been heat-treated was arranged in parallel with the sample piece Ga that had been heat-treated. In this state, the displacement amounts (ΔL1, ΔL2) of the marks M on the two sample pieces Ga and Gb were read by a laser microscope, and the thermal shrinkage rate was calculated.

[0103] The surface roughness Sa is a value measured by an atomic force microscope (AFM).

[0104] As can be seen from Table 1, for Samples No. 1 to 7, since the glass composition, strain point, and β-OH are within the specified ranges, the crack occurrence rate is 40% or less. On the other hand, for Sample No. 8, its glass composition is outside the specified range, and the crack occurrence rate is as high as 80%. In addition, for Samples No. 9 and 10, their glass compositions are outside the specified range and the liquid-phase viscosity is low, so it is speculated that it is difficult to form large-area glass plates.

[0105] Description of reference numerals

[0106] G narrow strip sample, M mark

Claims

1. An alkali-free glass sheet, characterized in that, As a glass composition, in mass %, it contains SiO 2 58% to 65%, Al 2 O 3 18% to 21%, B 2 O 3 2% to 5%, Li 2 O + Na 2 O + K 2 O 0.005% to 0.2%, MgO 2% to 6%, CaO 3% to 7.5%, SrO 0.5% to 5.5%, BaO 0.3% to 10%, ZrO 2 0.005% to 0.15%, TiO 2 0.005% to 0.1%, SnO 2 0.1% to 0.35%, ZrO 2 + TiO 2 0.01% to 0.15%, the strain point is 700 °C or higher, and β-OH is 0.3 mm －1 or less.

2. The alkali-free glass sheet according to claim 1, characterized in that, As a glass composition, by mass%, it contains SiO 2 58% to 65%, Al 2 O 3 18% to 21%, B 2 O 3 2% to 5%, Li 2 O + Na 2 O + K 2 O 0.005% to 0.2%, MgO 2% to 6%, CaO 3% to 7.5%, SrO 0.5% to 5.5%, BaO 1% to 10%, ZrO 2 0.005% to 0.15%, TiO 2 0.005% to 0.1%, SnO 2 0.1% to 0.35%, ZrO 2 + TiO 2 0.01% to 0.15%, the strain point is 700 °C or higher, and β-OH is 0.3 mm －1 or less.

3. The alkali-free glass sheet according to claim 1 or 2, wherein, when an indentation is applied to at least one surface with a Vickers indenter under a load of 500 g, the crack incidence rate is 50% or less.

4. The alkali-free glass sheet according to claim 1 or 2, wherein, The average linear thermal expansion coefficient in the temperature range of 30°C to 380°C is 30×10 －7 / °C to 40×10 －7 / °C, and the Young's modulus is 80 GPa or more.

5. The alkali-free glass sheet according to claim 1 or 2, wherein, the thermal shrinkage rate after heat treatment at 500 °C for 60 minutes is 20 ppm or less.

6. The alkali-free glass sheet according to claim 1 or 2, wherein, it has a rectangular shape, the longitudinal and transverse dimensions are each 1800 mm or more, and the thickness is 0.5 mm or less.

7. The alkali-free glass sheet according to claim 1 or 2, wherein, the average surface roughness Sa of at least one main surface is 0.5 nm or less.

8. The alkali-free glass sheet according to claim 1 or 2, wherein, at least one main surface is a flame-polished surface or a surface equivalent to a flame-polished surface.

9. An alkali-free glass sheet, characterized in that, Li in the glass composition 2 O + Na 2 O + K 2 The content of O is 0.005 mass% to 0.2 mass%, the content of BaO is 1 mass% to 10 mass%, the average linear thermal expansion coefficient in the temperature range of 30°C to 380°C is 30×10 －7 / °C to 40×10 －7 / °C, the Young's modulus is 80 GPa or more, the density is 2.55 g / cm 3 or less, the strain point is 700°C or more, the thermal shrinkage rate after heat treatment at 500°C for 60 minutes is 20 ppm or less, the average surface roughness Ra of at least one surface is 0.5 nm or less, the longitudinal and transverse dimensions are 1800 mm or more, the thickness is 0.5 mm or less, and the crack occurrence rate when an indentation is applied to at least one surface with a load of 500 g using a Vickers indenter is 50% or less.

10. An alkali-free glass sheet, characterized in that, As a glass composition, by mass %, it contains SiO 2 58% to 65%, Al 2 O 3 18% to 21%, B 2 O 3 2% to 5%, Li 2 O + Na 2 O + K 2 O 0.005% to 0.2%, MgO 2% to 6%, CaO 3% to 7.5%, SrO 0.5% to 5.5%, BaO 1% to 10%, B 2 O 3 + MgO 4% to 9%, and the average linear thermal expansion coefficient in the temperature range of 30°C to 380°C is 30×10 －7 / °C to 40×10 －7 / °C, the Young's modulus is 80 GPa or more, the density is 2.59 g / cm 3 or less, the strain point is 700°C or more, β-OH is 0.3 / mm or less, and the crack incidence rate when an indentation is applied to at least one surface with a load of 500 g using a Vickers indenter is 50% or less.

11. An alkali-free glass sheet, characterized in that, As a glass composition, in terms of mass%, it contains SiO 2 58% to 65%, Al 2 O 3 18% to 21%, B 2 O 3 2% to 5%, Li 2 O + Na 2 O + K 2 O 0.005% to 0.2%, MgO 2% to 6%, CaO 3% to 7.5%, SrO 0.5% to 5.5%, BaO 0.3% to 10%, B 2 O 3 + MgO 4% to 9%, and the average linear thermal expansion coefficient in the temperature range of 30°C to 380°C is 30×10 －7 / °C to 40×10 －7 / °C, the Young's modulus is 80 GPa or more, the density is 2.59 g / cm 3 or less, the strain point is 700°C or more, β-OH is 0.3 / mm or less, and the crack incidence rate when an indentation is applied to at least one surface with a load of 500 g using a Vickers indenter is 50% or less.

12. The alkali-free glass sheet according to any one of claims 1, 2, 9 to 11, characterized in that, it is used as a substrate for an electronic display.

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