glass substrate

Abstract

The glass substrate of the present invention is characterized by having a deformation point of 695 to 740°C, a temperature of 104.5 dPa·s of 1300°C or less, a liquid phase viscosity of 104.5 dPa·s or more, a Young's modulus of 78 GPa or more, and a thermal shrinkage rate of 20 ppm or less when heat treatment is performed at 500°C for 1 hour.

Description

Technology Field

[0001] The present invention relates to a glass substrate, specifically to a glass substrate suitable for organic EL (OLED) displays and liquid crystal displays, and to a glass substrate preferred for oxide TFTs and low-temperature p-Si·TFT (LTPS) driven displays. Background Technology

[0002] Traditionally, glass substrates have been widely used as substrates for flat panel displays such as liquid crystal displays, hard disks, filters, sensors, and the like. Recently, in addition to conventional liquid crystal displays, OLED displays have been actively developed due to their self-emissive properties, high color reproduction, wide viewing angle, high response speed, and high clarity, and some have already been commercialized.

[0003] Furthermore, since liquid crystal and OLED displays in mobile devices such as smartphones are required to display a large amount of information on a small surface area, ultra-high definition screens are necessary. In addition, high-speed response is required to display video.

[0004] For such applications, OLED displays or liquid crystal displays driven by LTPS are preferred. OLED displays emit light when current flows through the OLED elements that constitute the pixels. For this reason, materials with low resistance and high electron mobility are used as driving TFT elements. As for these materials, in addition to the aforementioned LTPS, oxide TFTs, such as IGZO (indium, gallium, zinc oxide), are attracting attention. Oxide TFTs have low resistance and high mobility, and can also be formed at relatively low temperatures. Conventional p-Si TFTs, particularly LTPS, are prone to variations in TFT characteristics when forming elements on large-area glass substrates due to the instability of the excimer laser used to polycrystalline amorphous Si (a-Si) films, and non-uniformity in screen display is likely to occur in applications such as TVs. On the other hand, oxide TFTs are attracting attention as promising TFT forming materials because they exhibit excellent homogeneity of TFT characteristics when forming elements on large-area glass substrates, and some have already been commercialized.

[0005] Many characteristics are required for glass substrates used in high-definition displays. In particular, the following characteristics (1) and (2) are required.

[0006] (1) If there is a large amount of alkali components in the glass, alkali ions diffuse into the semiconductor material formed during heat treatment, causing deterioration of the film's properties. Therefore, the alkali components (especially Li and Na components) are present in small amounts or are substantially absent.

[0007] (2) In processes such as film deposition, dehydrogenation, crystallization of the semiconductor layer, and annealing, the glass substrate is heat-treated at several hundred degrees. As a problem that occurs during heat treatment, pattern misalignment caused by thermal shrinkage of the glass substrate is listed. As the display becomes higher in clarity, the heat treatment temperature becomes higher, but conversely, the allowable range of pattern misalignment becomes smaller. Therefore, it is required that the glass substrate has small dimensional changes during heat treatment. The main factors causing dimensional changes during heat treatment are thermal shrinkage and film stress after film deposition. Therefore, in order to minimize dimensional changes during heat treatment, it is required that the deformation point be high and the Young's modulus (or non-Young's modulus) be high, for example, 78 GPa or higher.

[0008] In addition, from the perspective of manufacturing a glass substrate, the glass substrate requires the following characteristics (3) to (5).

[0009] (3) To extend the lifespan of the molding equipment, the molding temperature is low.

[0010] (4) To prevent melting defects such as bubbles, foreign matter, and slag, it has excellent meltability.

[0011] (5) To avoid incorporation of devitrified crystals into the glass substrate, excellent devitrification properties. The problem to be solved

[0012] As mentioned above, one approach to reducing thermal shrinkage is to design a high deformation point. However, if the deformation point is excessively high, the melting temperature or molding temperature becomes high, which has the disadvantage of shortening the lifespan of the melting or molding equipment.

[0013] In addition, as mentioned above, one approach to reducing thermal shrinkage is to slow down the cooling rate during molding. However, slowing down the cooling rate has the disadvantage of lowering the production efficiency of the glass substrate.

[0014] The present invention has been made in consideration of the above circumstances, and its technical objective is to provide a glass substrate capable of reducing dimensional changes during heat treatment without lowering production efficiency. means of solving the problem

[0015] As a result of careful consideration, the inventors have discovered that the above technical problem can be solved by regulating the glass properties of the glass substrate within a predetermined range, and propose this as the present invention. That is, the glass substrate of the present invention has a deformation point of 695 to 740°C, 10 4.5 The temperature at dPa·s is 1300℃ or lower, and the liquid phase viscosity is 10 4.5 It is characterized by having a Young's modulus of 78 GPa or higher, a thermal shrinkage rate of 20 ppm or less when heat-treated at 500°C for 1 hour. Here, "deformation point" refers to a value measured based on the ASTM C336 method. "10 4.5"Temperature at dPa·s" represents the value measured by the platinum ball pull method. "Liquid phase viscosity" represents the value of the viscosity of the glass at the liquid phase temperature measured by the platinum ball pull method. "Liquid phase temperature" represents the temperature at which glass powder that passes through a standard 30-mesh (500 μm) sieve and remains on a 50-mesh (300 μm) sieve is placed in a platinum boat, maintained in a furnace with a temperature gradient set from 1100°C to 1350°C for 24 hours, and then the platinum boat is withdrawn and devitrified crystals (crystalline impurities) are confirmed in the glass. "Young's modulus" represents the value measured by the dynamic elastic modulus measurement method (resonance method) based on JIS R1602. "Thermal shrinkage rate when heat treatment is performed at 500°C for 1 hour" was measured by the following method. First, as shown in Fig. 1(a), a rectangular sample G with a shape of 160 mm × 30 mm was prepared as a measurement sample. Marking M was formed on each of the two ends along the long side direction of the rectangular sample G using #1000 water-resistant abrasive paper at a position 20 to 40 mm away from the end edge. Then, as shown in FIG. 1(b), the rectangular sample G with the formed marking M was folded into two pieces along the direction perpendicular to the marking M to produce sample pieces Ga and Gb.

[0016] Then, heat treatment was performed on only one sample, Gb, by increasing the temperature from room temperature to 500°C at a rate of 5°C / min, maintaining it at 500°C for 1 hour, and then decreasing the temperature at a rate of 5°C / min. After the heat treatment, as shown in Fig. 1(c), with the sample Ga that was not heat-treated and the sample Gb that was heat-treated arranged in parallel, the positional misalignment (ΔL1, ΔL2) of the marking M on the two sample Ga and Gb was read using a laser microscope, and the thermal shrinkage rate was calculated using the following formula. In addition, 10mm in the following formula is the distance between the initial marking M.

[0017] Thermal shrinkage rate (ppm) = [{ΔL1(㎛)+ΔL2(㎛)}×10 3 ] / lO(mm)

[0018] In the glass substrate of the present invention, the deformation point is 695–740°C, 10 4.5 The temperature at dPa·s is 1300℃ or lower, and the liquid phase viscosity is 10 4.5 The thermal shrinkage rate is regulated to be 20 ppm or less when heat treatment is performed at 500°C for 1 hour, with a Young's modulus of 78 GPa or more. By doing so, it is possible to obtain a glass substrate that can reduce dimensional changes during heat treatment without lowering production efficiency.

[0019] In the glass substrate of the present invention, the deformation point is 740°C or lower, and the thermal shrinkage rate is 20 ppm or lower when heat treatment is performed at 500°C for 1 hour. Although it is difficult to achieve both characteristics in conventional manufacturing equipment and manufacturing methods, it becomes possible to achieve both characteristics by adopting a method that, for example, makes the slow cooling path longer than conventional and slows down the slow cooling speed. However, although there is a concern that the productivity of the glass substrate may decrease in this method, if two G6 size glass substrates are taken from a glass substrate after forming an extra-large size glass plate of G10.5, the production efficiency of the glass substrate can be maintained.

[0020] In addition, the glass substrate of the present invention preferably contains, in mol%, SiO2 60-70%, Al2O3 10-15%, B2O 30-5%, Li2O 0-0.1%, Na2O 0-0.1%, K2O 0-1%, MgO 0-8%, CaO 0-10%, SrO 0-10%, BaO 0-10%, ZnO 0-10%, P2O 50-10%, and SnO2 0-1% as the glass composition. Brief explanation of the drawing

[0021] Figure 1 is an explanatory diagram for explaining the method of measuring thermal shrinkage rate. Specific details for implementing the invention

[0022] In the glass substrate of the present invention, the thermal shrinkage rate when heat treatment is performed at 500°C for 1 hour is 20 ppm or less, preferably 19 ppm or less, 18 ppm or less, 17 ppm or less, 16 ppm or less, 15 ppm or less, 14 ppm or less, 13 ppm or less, and particularly 12 ppm or less. By doing so, even if heat treatment is performed during the manufacturing process of LTPS, it becomes difficult for defects such as pattern misalignment to occur. Furthermore, if the thermal shrinkage rate is too low, the production efficiency of the glass substrate is prone to decrease. Accordingly, the thermal shrinkage rate is preferably 1 ppm or more, 2 ppm or more, 3 ppm or more, 4 ppm or more, and particularly 5 ppm or more.

[0023] The higher the deformation point, the lower the thermal shrinkage rate can be. The deformation point is 695°C or higher, preferably 697°C or higher, 700°C or higher, 702°C or higher, 705°C or higher, 710°C or higher, 711°C or higher, 712°C or higher, 713°C or higher, 714°C or higher, and particularly 715°C or higher. On the other hand, if the deformation point is excessively high, the melting temperature or molding temperature becomes high, which makes it easy for the production efficiency of the glass substrate to decrease. Therefore, the deformation point is 740°C or lower, preferably 735°C or lower, 730°C or lower, 725°C or lower, 720°C or lower, and particularly 715°C or lower. The most preferred range for the deformation point is 715 to 735°C.

[0024] 10 4.5 The lower the temperature in dPa·s, the lower the load on the molding equipment can be reduced. 10 4.5 The temperature in dPa·s is 1300°C or lower, preferably 1290°C or lower, 1280°C or lower, 1275°C or lower, 1270°C or lower, 1265°C or lower, 1260°C or lower, 1255°C or lower, and particularly 1250°C or lower. Meanwhile, 10 4.5 If the temperature in dPa·s is too low, it becomes impossible to design a high strain point. Therefore, 10 4.5The temperature in dPa·s is preferably 1150°C or higher, 1170°C or higher, 1180°C or higher, 1185°C or higher, 1190°C or higher, 1195°C or higher, and particularly 1200°C or higher.

[0025] When forming into a plate shape using methods such as the overflow downdraw method, internal permeability becomes important. Considering the forming temperature of glass containing SiO2, Al2O3, B2O3, and alkaline earth metal oxides (RO) in the glass composition, the liquid phase temperature is preferably 1300°C or lower, 1280°C or lower, 1270°C or lower, 1250°C or lower, 1240°C or lower, 1230°C or lower, 1220°C or lower, 1210°C or lower, and particularly 1200°C or lower. In addition, the liquid phase viscosity is 10 4.5 dPa·s or higher, preferably 10 4.6 dPa·s or higher, 10 4.7 dPa·s or higher, 10 4.8 dPa·s or higher, 10 4.9 dPa·s or higher, 10 5.0 dPa·s or higher, 10 5.2 dPa·s or higher, especially 10 5.3 It is dPa·s or more.

[0026] The higher the Young's modulus, the harder it is for the glass substrate to deform. The Young's modulus is 78 GPa or higher, preferably 78.5 GPa or higher, 79 GPa or higher, 79.5 GPa or higher, and particularly 80 to 120 GPa.

[0027] In addition to the above characteristics, the glass substrate of the present invention preferably has the following characteristics.

[0028] The desirable upper limit range for the coefficient of thermal expansion is 45×10⁻⁶ -7 / ℃ or less, 42×10 -7 / ℃ or less, 41×10 -7 / ℃ or lower, especially 40×10 -7 It is / ℃ or lower, and the desirable lower limit range is 35×10 -7 / ℃ or higher, 36×10 -7 / ℃ or higher, especially 37×10 -7It is greater than / ℃. If the coefficient of thermal expansion falls outside the above range, it becomes mismatched with the coefficient of thermal expansion of various films (e.g., a-Si, p-Si), and problems such as film peeling and dimensional changes during heat treatment are likely to occur. In addition, the “coefficient of thermal expansion” represents the average coefficient of thermal expansion measured in a temperature range of 30 to 380℃, and can be measured, for example, with a dilatometer.

[0029] When immersed in a 10 mass% aqueous HF solution at room temperature for 30 minutes, the etching depth is preferably 20 μm or more, 23 μm or more, 25 μm or more, 27 μm or more, 28 μm or more, 29 to 50 μm, and particularly 30 to 40 μm. If the etching depth is excessively small, it becomes difficult to thin the glass substrate during the slimming process. In addition, the etching depth serves as an indicator of the etching rate. That is, if the etching depth is large, the etching rate increases, and if the etching depth is small, the etching rate decreases.

[0030] The β-OH value is preferably 0.50 / mm or less, 0.45 / mm or less, 0.40 / mm or less, 0.35 / mm or less, 0.30 / mm or less, 0.25 / mm or less, 0.20 / mm or less, 0.15 / mm or less, and particularly 0.10 / mm or less. Lowering the β-OH value can raise the deformation point. The following methods are listed as methods to lower the β-OH value: (1) Select raw materials with low moisture content. (2) Add components (Cl, SO3, etc.) that reduce the moisture content in the glass. (3) Reduce the moisture content in the furnace atmosphere. (4) Perform N2 bubbling in the molten glass. (5) Adopt a small melting furnace. (6) Increase the flow rate of the molten glass. (7) Adopt an electric melting method. Here, the "β-OH value" represents the value obtained by measuring the transmittance of the glass using FT-IR and using the following formula.

[0031] β-OH value = (1 / X)log(T1 / T2)

[0032] X: Glass thickness (mm)

[0033] T1: Reference wavelength 3846 cm -1 Transmittance (%) in

[0034] T2: Hydroxyl absorption wavelength 3600 cm -1 Minimum transmittance (%) in the vicinity

[0035] The glass substrate of the present invention preferably contains, as a glass composition in mol%, SiO2 60-70%, Al2O3 10-15%, B2O 30-5%, Li2O 0-0.1%, Na2O 0-0.1%, K2O 0-1%, MgO 0-8%, CaO 0-10%, SrO 0-10%, BaO 0-10%, ZnO 0-10%, P2O 50-10%, and SnO2 0-1%. The reasons for limiting the content range of each component as described above are shown below. Furthermore, in the description of the content range of each component, % indicates mol%.

[0036] If the SiO2 content is excessively low, chemical resistance, particularly acid resistance, is prone to deterioration, and the deformation point is prone to deterioration. On the other hand, if the SiO2 content is excessively high, the etching rate by hydrofluoric acid or a mixed solution of hydrofluoric acid is prone to slowing down, and the high-temperature viscosity is high, which is prone to deterioration in meltability, and SiO2-based crystals, particularly cristobalite, are precipitated, which is prone to deterioration in liquid phase viscosity. Accordingly, the preferred upper limit content of SiO2 is 70%, 69.5%, 69%, 68.5%, 68%, particularly 67.5%, and the preferred lower limit content is 60%, 61%, 62%, 62.5%, 63%, 63.5%, 64%, 64.5%, particularly 65%. The most preferred content range is 65 to 67.5%.

[0037] If the Al2O3 content is excessively low, the deformation point decreases, the amount of thermal shrinkage increases, the Young's modulus decreases, and the glass substrate becomes prone to bending. On the other hand, if the Al2O3 content is excessively high, resistance to BHF (buffered hydrofluoric acid) decreases, cloudiness is prone to occur on the glass surface, and crack resistance is prone to decrease. In addition, SiO2-Al2O3 crystals, particularly mullite, precipitate in the glass, making it prone to a decrease in liquid phase viscosity. The preferred upper limit content of Al2O3 is 15%, 14.5%, particularly 14%, and the preferred lower limit content is 10%, 10.5%, 11%, 11.5%, particularly 12%. The most preferred content range is 12 to 14%.

[0038] B2O3 is a component that functions as a flux and improves meltability by reducing viscosity. If the content of B2O3 is excessively low, it does not function sufficiently as a flux, and resistance to BHF or cracking is prone to deterioration. Additionally, the liquid phase temperature is prone to rising. On the other hand, if the content of B2O3 is excessively high, the deformation point, heat resistance, and acid resistance are prone to deterioration, and the deformation point is particularly prone to deterioration. Additionally, the glass is prone to pulverization. The preferred upper limit content of B2O3 is 5%, particularly 4.5%, and the preferred lower limit content is 0%, 1%, 1.5%, 2%, particularly 2.5%. The most preferred content range is 2.5 to 4.5%.

[0039] Since alkali metal oxides (Li2O, Na2O, K2O) degrade the characteristics of various films or semiconductor devices formed on a glass substrate, it is desirable to reduce their content to 0.1% (preferably 0.06%, 0.05%, 0.02%, and particularly 0.01%).

[0040] MgO is a component that improves meltability by reducing high-temperature viscosity without lowering the deformation point. Additionally, while MgO has the greatest density-reducing effect among RO components, excessive introduction can lead to the precipitation of SiO2-based crystals, particularly cristobalite, which tends to lower liquid-phase viscosity. Furthermore, MgO is a component that readily reacts with BHF to form byproducts. These reaction products may adhere to the device surface or the glass substrate, potentially causing cloudiness to the device or the glass substrate. Moreover, there is a risk that impurities such as Fe2O3 from MgO introduction raw materials, such as dolomite, may be incorporated into the glass, thereby reducing the transmittance of the glass substrate. Accordingly, the preferred upper limit content of MgO is 8%, 7.5%, 7%, 6.5%, particularly 6%, and the preferred lower limit content is 0%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, particularly 4.5%. The most preferred content range is 4.5 to 6%.

[0041] CaO is a component that significantly improves meltability by lowering high-temperature viscosity without lowering the deformation point, just like MgO. However, if the CaO content is excessively high, SiO2-Al2O3-RO crystals, particularly anotite, precipitate, which tends to lower liquid phase viscosity and reduce BHF resistance. Additionally, there is a risk that reaction products may adhere to the device on the glass surface or to the glass substrate, causing the device or glass substrate to become cloudy. Therefore, the preferred upper limit content of CaO is 10%, 9.5%, 9%, particularly 8.5%, and the preferred lower limit content is 0%, 1%, 2%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 5.6%, 6%, particularly 6.5%. The most preferred content range is 6.5 to 8.5%.

[0042] SrO is a component that increases chemical resistance and impermeability, but if its proportion is excessively high in the total RO, meltability is prone to decrease, and density and coefficient of thermal expansion are prone to increase. Therefore, the content of SrO is preferably 0 to 10%, 0 to 9%, 0 to 8%, 0 to 7%, 0 to 6%, and particularly 0 to 5%.

[0043] BaO is a component that improves chemical resistance and permeability, but if its content is excessive, the density tends to increase. In addition, since SiO2-Al2O3-B2O3-RO glass is generally difficult to melt, it is very important to improve meltability and reduce the defect rate caused by bubbles, foreign substances, etc. from the perspective of supplying high-quality glass substrates at a low cost and in large quantities. However, BaO is insufficient to improve meltability in RO. Therefore, the preferred upper limit content of BaO is 10%, 9%, 8%, 7%, 6%, particularly 5%, and the preferred lower limit content is 0%, 0.1%, 0.3%, particularly 0.2%.

[0044] ZnO is a component that improves meltability and resistance to BHF, but if its content is excessively high, the glass becomes prone to devitrification or the deformation point is lowered, making it difficult to secure heat resistance. Therefore, the content of ZnO is preferably 0 to 10%, 0 to 5%, 0 to 3%, 0 to 2%, and particularly 0 to 1%.

[0045] P2O5 is a component that lowers the liquidus temperature of SiO2-Al2O3-CaO-based crystals (especially anotite) and SiO2-Al2O3-based crystals (especially mullite). However, if a large amount of P2O5 is introduced, the glass becomes prone to pulverization. Therefore, the content of P2O5 is preferably 0 to 10%, 0 to 5%, 0 to 3%, 0 to 2%, 0 to 1%, and particularly 0 to 0.1%.

[0046] SnO2 functions as a clarifying agent to reduce bubbles in the glass. On the other hand, if the SnO2 content is excessively high, devitrification crystals of SnO2 are likely to occur in the glass. The preferred upper limit content of SnO2 is 1%, 0.5%, 0.4%, particularly 0.3%, and the preferred lower limit content is 0%, 0.01%, 0.03%, particularly 0.05%. The most preferred content range is 0.05 to 0.3%.

[0047] In addition to the above components, other components may be introduced. The amount introduced is preferably 5% or less, 3% or less, and particularly 1% or less.

[0048] ZrO2 is a component that enhances chemical durability, but if the amount introduced increases, ZrSiO4 crystals are prone to forming. The preferred upper limit content of ZrO2 is 1%, 0.5%, 0.3%, 0.2%, and particularly 0.1%, and it is desirable to introduce at least 0.001% from the perspective of chemical durability. The most preferred content range is 0.001% to 0.1%. In addition, ZrO2 may be introduced from raw materials or by leaching from refractory materials.

[0049] TiO2 is a component that lowers high-temperature viscosity to increase meltability and also increases chemical durability, but if introduced in excess, ultraviolet transmittance is prone to decreasing. The content of TiO2 is preferably 3% or less, 1% or less, 0.5% or less, 0.1% or less, 0.05% or less, 0.03%, and particularly 0.01% or less. In addition, if a very small amount of TiO2 is introduced (e.g., 0.0001% or more), an effect of suppressing discoloration caused by ultraviolet rays is obtained. The most preferred content range is 0.0001 to 0.01%.

[0050] As2O3 and Sb2O3 are components that act as clarifying agents, but since they are environmentally burdensome chemicals, it is desirable to avoid using them as much as possible. The content of As2O3 and Sb2O3 is preferably less than 0.3%, less than 0.1%, less than 0.09%, less than 0.05%, less than 0.03%, less than 0.01%, less than 0.005%, and particularly less than 0.003%.

[0051] Iron is an impurity and is a component incorporated from raw materials, but if the iron content is excessively high, there is a risk that the ultraviolet transmittance will decrease. If the ultraviolet transmittance decreases, there is a risk that problems may occur in the photolithography process for fabricating TFTs, the liquid crystal alignment process using ultraviolet light, or the laser lift-off process in the plastic OLED manufacturing process. Accordingly, the preferred lower limit iron content is 0.0001%, 0.0005%, 0.001%, and particularly 0.0015% when converted to Fe2O3, and the preferred upper limit iron content is 0.01%, 0.009%, 0.008%, 0.007%, and particularly 0.006% when converted to Fe2O3. The most preferred content range is 0.0015% to 0.006%.

[0052] Cr2O3 is an impurity and is a component incorporated from raw materials; however, if the content of Cr2O3 is excessively high, when light is incident from the end surface of the glass substrate and foreign matter is inspected inside the glass substrate by scattered light, light transmission becomes difficult, and there is a risk of defects in the foreign matter inspection. In particular, this problem is more likely to occur when the substrate size is 730 mm × 920 mm or larger. In addition, if the thickness of the glass substrate is small (e.g., 0.5 mm or less, 0.4 mm or less, particularly 0.3 mm or less), the light incident from the end surface of the glass substrate decreases, so the significance of regulating the content of Cr2O3 increases. The preferred upper limit content of Cr2O3 is 0.001%, 0.0008%, 0.0006%, 0.0005%, and particularly 0.0003%, and the preferred lower limit content is 0.00001%. The most desirable content range is 0.00001 to 0.0003%.

[0053] SO3 is an impurity and is a component incorporated from raw materials; however, if the SO3 content is excessively high, it may cause bubbles called reboiling during melting or molding, which may lead to defects in the glass. The preferred upper limit for SO3 content is 0.005%, 0.003%, 0.002%, and particularly 0.001%, and the preferred lower limit is 0.0001%. The most preferred content range is 0.0001% to 0.001%.

[0054] Preferably, the glass substrate of the present invention is formed by the overflow downdraw method. The overflow downdraw method is a method of forming a glass substrate by allowing molten glass to overflow from both sides of a wedge-shaped trough-shaped refractory material, and then stretching and forming the overflowing molten glass downward while joining it at the bottom of the wedge. In the overflow downdraw method, the surface of the glass substrate is not in contact with the refractory material and is formed in a free surface state. For this reason, it is easy to produce a glass substrate with good surface quality without polishing, and it is also easy to increase the surface area or thin the form factor.

[0055] In addition to the overflow downdraw method, it is also possible to form glass substrates using other downdraw methods (slot down method, lead draw method, etc.), float method, etc.

[0056] In the glass substrate of the present invention, the plate thickness is not particularly limited, but preferably 0.5 mm or less, 0.4 mm or less, 0.35 mm or less, and particularly 0.3 mm or less. The smaller the plate thickness, the easier it is to lighten the device. On the other hand, although the glass substrate becomes more prone to bending as the plate thickness decreases, the glass substrate of the present invention has a high Young's modulus or non-Young's modulus, so defects caused by bending are unlikely to occur. In addition, the plate thickness can be adjusted by the flow rate or plate lifting speed during glass manufacturing.

[0057] Example 1

[0058] The present invention will be described in detail below based on examples. Furthermore, the following examples are merely illustrative. The present invention is not limited in any way to the following examples.

[0059] Tables 1 to 5 show embodiments of the present invention (samples No. 1 to 51).

[0060]

[0061]

[0062]

[0063]

[0064]

[0065] Each sample was prepared as follows. First, a glass batch of glass raw materials was combined to have the glass composition shown in the table, placed in a platinum crucible, and melted at 1600°C for 24 hours. During the melting of the glass batch, stirring was performed using a platinum stirrer, and homogenization was carried out. Subsequently, the molten glass was poured onto a carbon plate and formed into a flat plate shape. For each obtained sample, the β-OH value, density, coefficient of thermal expansion, Young's modulus, strain point, temperature at 104.5 dPa·s, liquid phase temperature, liquid phase viscosity, and thermal shrinkage rate were evaluated.

[0066] The β-OH value is the value calculated by the above formula.

[0067] Density is a value measured by the well-known Archimedes' method.

[0068] The coefficient of thermal expansion is the average coefficient of thermal expansion measured by a dilatometer in the temperature range of 30 to 380°C.

[0069] Young's modulus is a value measured by the dynamic elastic modulus measurement method (resonance method) based on JIS R1602.

[0070] The deformation point is a value measured based on the ASTM C336 method.

[0071] High temperature viscosity 10 4.5 The temperature in dPa·s is a value measured by the platinum-ball pull method.

[0072] The liquid phase temperature is the temperature at which glass powder is ground, passed through a standard 30-mesh (500 μm) sieve, and remains on a 50-mesh (300 μm) sieve, placed in a platinum boat, maintained in a furnace with a temperature gradient set from 1100°C to 1350°C for 24 hours, and then the platinum boat is withdrawn and devitrification crystals (crystalline impurities) are confirmed in the glass. The liquid phase viscosity is the value of the viscosity of the glass at the liquid phase temperature measured by the platinum ball pull method.

[0073] A sample for measuring thermal shrinkage was prepared by the following method. First, a glass substrate measuring 160 mm × 30 mm was prepared. This was heated to 900°C, then cooled down to 500°C over approximately 180 seconds, and subsequently cooled by leaving it to stand naturally. This slow cooling condition corresponds to a slow cooling condition in which the slow cooling path is made longer and the slow cooling speed is slower than in the overflow downdraw method. For this sample, the thermal shrinkage was measured according to the above measurement method.

[0074] Samples No. 1 to 51 have a coefficient of thermal expansion of 37×10 -7 ~40×10 -7 / ℃, Young's modulus of 80 GPa or higher, deformation point of 715℃ or higher, and thermal shrinkage rate of 14.0 ppm or lower, so it is believed that dimensional changes during heat treatment can be reduced. In addition, samples No. 1 to 51 are 10 4.5 The temperature in dPa·s is 1270℃ or lower, the liquid phase temperature is 1260℃ or lower, and the liquid phase viscosity is 10 4.5 Since it is dPa·s or higher, the production efficiency of the glass substrate can be increased.

[0075] Example 2

[0076] Glass batches having the glass compositions of samples No. 1 to 51 listed in Tables 1 to 5 were melted in a test melting furnace, and after obtaining molten glass, a glass plate of size G 10.5 with a plate thickness of 0.5 mm was formed using the overflow downdraw method. Subsequently, this glass plate was cut, and two glass substrates of size G6 were obtained. In addition, during the forming process, by making the slow cooling path longer than conventional and the slow cooling speed slower than conventional, glass substrates having thermal shrinkage rates corresponding to samples No. 1 to 51 listed in Tables 1 to 5 were obtained.

Claims

Claim 1 As a glass composition, it contains SiO2 60–68%, Al2O3 12.59–15%, MgO 0–6.5%, and BaO 0–3.51% in mol%, and has a deformation point of 710–740℃, 10 4.5 The temperature at dPa·s is 1300℃ or lower, and the liquid phase viscosity is 10 4.5 A glass substrate characterized by having a dPa·s or higher, a Young's modulus of 78 GPa or higher, a thermal shrinkage rate of 14 ppm or less when heat-treated at 500°C for 1 hour, and a β-OH value of 0.30 / mm or less. Claim 2 A glass substrate according to claim 1, characterized in that, as a glass composition, it contains B2O 30-5%, Li2O 0-0.1%, Na2O 0-0.1%, K2O 0-1%, CaO 0-10%, SrO 0-10%, ZnO 0-10%, P2O 50-10%, and SnO 20-1% in mol%.

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