glass

Abstract

To provide a glass that has high heat resistance, low thermal expansion coefficient, and excellent producibility.SOLUTION: The glass of the present invention is characterized by containing, as the glass composition in mole%, 55 to 80% of SiO2, 12 to 30% of Al2O3, 0 to 3% of B2O3, 0 to 1% of Li2O+Na2O+K2O, 5 to 35% of MgO+CaO+SrO+BaO, and having a thermal expansion coefficient in the temperature range of 30 to 380°C of less than 40×10-7 / °C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to glass, and more particularly to alkali-free glass suitable for use as a substrate for organic displays and liquid crystal displays. [Background technology]

[0002] Electronic devices such as OLED displays are thin, excel at displaying video, and have low power consumption. Because of its low power consumption, it is used in applications such as mobile phone displays.

[0003] Glass substrates are widely used as substrates for organic EL displays. For this application, alkali-free glass (glass with an alkali content of 0.5 mol% or less) is used. This prevents alkali ions from diffusing into the semiconductor material formed during the heat treatment process.

[0004] For this application, alkali-free glass is required to have, for example, the following characteristics (1) to (3). (1) To reduce the cost of glass substrates, they must have excellent productivity, particularly in terms of devitrification resistance and meltability. (2) In the manufacturing process of p-Si·TFTs, especially high-temperature p-Si, the strain point is high in order to reduce thermal shrinkage of the glass substrate. (3) Having a low coefficient of thermal expansion so as to match the coefficient of thermal expansion of the component (e.g., p-Si) to be deposited on the glass substrate. [Overview of the project] [Problems that the invention aims to solve]

[0005] However, achieving both the above required characteristics (1) and (2) is not easy. In other words, when attempting to increase the strain point of alkali-free glass, the devitrification resistance and meltability tend to decrease, and conversely, when attempting to increase the devitrification resistance and meltability of alkali-free glass, the strain point tends to decrease.

[0006] Furthermore, achieving both the required characteristics (1) and (3) above is not easy. In other words, attempting to lower the coefficient of thermal expansion of alkali-free glass tends to decrease its resistance to devitrification and meltability, while attempting to improve the resistance to devitrification and meltability of alkali-free glass tends to increase its coefficient of thermal expansion.

[0007] Furthermore, chemical etching of glass substrates is commonly used to thin displays. This method involves immersing a display panel, which is made by bonding two glass substrates together, in an HF (hydrofluoric acid)-based chemical solution to thin the glass substrates. Therefore, when performing chemical etching of glass substrates, in addition to the required characteristics (1) to (3), a high etching rate by HF is required to increase the production efficiency of display panels.

[0008] Furthermore, a high Young's modulus (or relative Young's modulus) is sometimes required to suppress defects caused by the bending of the glass substrate.

[0009] This invention was made in view of the above circumstances, and its technical objective is to create a glass that has high heat resistance, a low coefficient of thermal expansion, and excellent productivity. [Means for solving the problem]

[0010] The inventors, after conducting various experiments, have found that the above technical problems can be solved by restricting the glass composition to a predetermined range, and propose this as the present invention. Specifically, the glass of the present invention contains, in molar percent, SiO2 55-80%, Al2O3 12-30%, B2O 30-3%, Li2O+Na2O+K2O 0-1%, and MgO+CaO+SrO+BaO 5-35%, and has a thermal expansion coefficient of 40 × 10 in the temperature range of 30-380°C. -7It is characterized by being less than / ℃. Here, "Li2O + Na2O + K2O" refers to the total content of Li2O, Na2O, and K2O. "MgO + CaO + SrO + BaO" refers to the total content of MgO, CaO, SrO, and BaO. The "thermal expansion coefficient in the temperature range of 30 to 380℃" refers to the average value measured by a dilatometer.

[0011] The glass of the present invention regulates the content of Al2O3 in the glass composition to be 12 mol% or more, the content of B2O3 in the glass composition to be 3 mol% or less, and the content of Li2O + Na2O + K2O to be 1 mol% or less. By doing so, the strain point can be significantly increased, and the heat resistance of the glass substrate can be greatly enhanced. Furthermore, it becomes easier to lower the thermal expansion coefficient.

[0012] Also, the glass of the present invention contains 5 to 25 mol% of MgO + CaO + SrO + BaO in the glass composition. By doing so, the devitrification resistance can be enhanced.

[0013] Second, it is preferable that the content of B2O3 in the glass of the present invention is less than 1 mol%.

[0014] Third, it is preferable that the content of Li2O + Na2O + K2O in the glass of the present invention is 0.5 mol% or less.

[0015] Fourth, it is preferable that the molar ratio (MgO + CaO + SrO + BaO) / Al2O3 of the glass of the present invention is 0.3 to 3. Here, "(MgO + CaO + SrO + BaO) / Al2O3" is the value obtained by dividing the total content of MgO, CaO, SrO, and BaO by the content of Al2O3.

[0016] Fifth, it is preferable that the molar ratio MgO / (MgO + CaO + SrO + BaO) of the glass of the present invention is 0.5 or more. Here, "MgO / (MgO + CaO + SrO + BaO)" is the value obtained by dividing the content of MgO by the total content of MgO, CaO, SrO, and BaO.

[0017] Sixth, the glass of the present invention preferably has a strain point of 750°C or higher. Here, "strain point" refers to the value measured according to the method of ASTMC336.

[0018] Seventh, it is preferable that the glass of the present invention has a strain point of 800°C or higher.

[0019] Eighth, the glass of the present invention is (10 2.5 It is preferable that the temperature-strain point (dPa·s) is 1000°C or less. Here, "high temperature viscosity 10 2.5 "Temperature in dPa·s" refers to the value measured by the platinum ball pulling method.

[0020] Ninthly, the glass of the present invention is 10 2.5 It is preferable that the temperature at which the viscosity is dPa·s is 1800°C or lower.

[0021] Tenth, the glass of the present invention is preferably in a flat plate shape.

[0022] Eleventh, the glass of the present invention is preferably used as a substrate for an organic EL display. [Modes for carrying out the invention]

[0023] The glass of the present invention contains, in molar percentages, SiO2 55-80%, Al2O3 12-30%, B2O 30-3%, Li2O+Na2O+K2O 0-3%, and MgO+CaO+SrO+BaO 5-35%. The reasons for regulating the content of each component as described above are explained below. In the descriptions of each component, the percentages below refer to molar percentages.

[0024] The preferred lower limit range for SiO2 is 55% or more, 58% or more, 60% or more, 65% or more, and especially 68% or more. The preferred upper limit range is preferably 80% or less, 75% or less, 73% or less, 72% or less, 71% or less, and especially 70% or less. If the SiO2 content is too low, defects due to devitrified crystals containing Al2O3 are more likely to occur, and the strain point tends to decrease. In addition, the high-temperature viscosity decreases, and the liquid-phase viscosity tends to decrease. On the other hand, if the SiO2 content is too high, the coefficient of thermal expansion decreases unduly, the high-temperature viscosity increases, the meltableness decreases, and devitrified crystals containing SiO2 are more likely to occur.

[0025] The preferred lower limit range for Al2O3 is 11% or more, 12% or more, 13% or more, 14% or more, and especially 15% or more, while the preferred upper limit range is 30% or less, 25% or less, 20% or less, 17% or less, and especially 16% or less. If the Al2O3 content is too low, the Young's modulus will decrease, the strain point will tend to decrease, and the high-temperature viscosity will increase, leading to a decrease in meltability. On the other hand, if the Al2O3 content is too high, devitrified crystals containing Al2O3 are likely to form.

[0026] The molar ratio of SiO2 / Al2O3 is preferably 2-6, 3-5.5, 3.5-5.5, 4-5.5, 4.5-5.5, and particularly 4.5-5, from the viewpoint of achieving both a high strain point and high resistance to devitrification. Note that "SiO2 / Al2O3" is the value obtained by dividing the SiO2 content by the Al2O3 content.

[0027] The preferred upper limit for B2O3 is 3% or less, 1% or less, less than 1%, and especially 0.1% or less. If the B2O3 content is too high, there is a risk that the strain point or Young's modulus will decrease significantly.

[0028] The preferred upper limits for Li2O+Na2O+K2O are 1% or less, less than 1%, 0.5% or less, and especially 0.2% or less. If the content of Li2O+Na2O+K2O is too high, alkali ions will diffuse into the semiconductor material during high-temperature p-Si processes, etc., which can easily degrade the semiconductor properties. The preferred upper limits for Li2O, Na2O, and K2O are 1% or less, less than 1%, 0.5% or less, 0.3% or less, and especially 0.2% or less, respectively.

[0029] The preferred lower limit range for MgO+CaO+SrO+BaO is 5% or more, 7% or more, 9% or more, 11% or more, 13% or more, and especially 14% or more. The preferred upper limit range is 35% or less, 30% or less, 25% or less, 20% or less, 18% or less, 17% or less, and especially 16% or less. If the content of MgO+CaO+SrO+BaO is too low, the liquidus temperature rises significantly, making it easier for devitrified crystals to form in the glass, and the high-temperature viscosity increases, making it easier for meltability to decrease. On the other hand, if the content of MgO+CaO+SrO+BaO is too high, the strain point tends to decrease, and devitrified crystals containing alkaline earth elements tend to form.

[0030] The preferred lower limit range for MgO is 0% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, and especially 6% or more, while the preferred upper limit range is 15% or less, 10% or less, 8% or less, and especially 7% or less. If the MgO content is too low, the mellowness tends to decrease, and the devitrification of crystals containing alkaline earth elements tends to increase. On the other hand, if the MgO content is too high, it promotes the precipitation of devitrified crystals containing Al2O3, which can reduce the liquid phase viscosity and significantly lower the strain point. MgO has the effect of increasing Young's modulus, and this effect is most pronounced among alkaline earth oxides.

[0031] The preferred lower limit range for CaO is 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, and especially 7% or more, while the preferred upper limit range is 20% or less, 15% or less, 12% or less, 11% or less, 10% or less, and especially 9% or less. If the CaO content is too low, the meltability tends to decrease. On the other hand, if the CaO content is too high, the liquid phase temperature rises, and devitrified crystals tend to form in the glass. Compared to other alkaline earth oxides, CaO has a greater effect in improving liquid phase viscosity without lowering the strain point and in increasing meltability. Also, although slightly inferior to MgO, CaO is an effective component for increasing Young's modulus.

[0032] The preferred lower limit for SrO is 0% or more, 1% or more, and especially 2% or more, while the preferred upper limit is 10% or less, 8% or less, 7% or less, 6% or less, 5% or less, and especially 4% or less. If the SrO content is too low, the strain point tends to decrease. On the other hand, if the SrO content is too high, the liquidus temperature rises, and devitrification crystals tend to form in the glass. Also, the meltability tends to decrease. Furthermore, if the SrO content is high in the presence of CaO, the resistance to devitrification tends to decrease.

[0033] The preferred lower limit range for BaO is 0% or more, 1% or more, 2% or more, 3% or more, and especially 4% or more, while the preferred upper limit range is 15% or less, 12% or less, 11% or less, and especially 10% or less. If the BaO content is too low, the strain point and thermal expansion coefficient tend to decrease. On the other hand, if the BaO content is too high, the liquidus temperature rises, and devitrified crystals tend to form in the glass. Also, the meltability tends to decrease. Since BaO is the element that has the greatest effect in lowering Young's modulus among alkaline earth metal oxides, from the viewpoint of achieving a high Young's modulus, it is necessary to keep the content as low as possible, or if the content is high, to design it to coexist with MgO.

[0034] From the viewpoint of improving resistance to devitrification, the lower limit range of the molar ratio MgO / CaO is preferably 0.1 or higher, 0.2 or higher, 0.3 or higher, and particularly 0.4 or higher, and the upper limit range is preferably 2 or lower, 1 or lower, 0.8 or lower, 0.7 or lower, and particularly 0.6 or lower. Note that "MgO / CaO" refers to the value obtained by dividing the MgO content by the CaO content.

[0035] From the viewpoint of improving resistance to devitrification, the lower limit range of the molar ratio BaO / CaO is preferably 0.2 or higher, 0.5 or higher, 0.6 or higher, 0.7 or higher, and particularly 0.8 or higher, and the upper limit range is preferably 5 or lower, 4.5 or lower, 3 or lower, 2.5 or lower, and particularly 2 or lower. Note that "BaO / CaO" refers to the value obtained by dividing the BaO content by the CaO content. Considering the balance between strain point and meltableness, the lower limit of the molar ratio (MgO+CaO+SrO+BaO) / Al2O3 is preferably 0.3 or higher, 0.5 or higher, 0.7 or higher, and particularly 0.8 or higher, and the upper limit is preferably 3.0 or lower, 2.5 or lower, 2.0 or lower, 1.5 or lower, 1.2 or lower, and particularly 1.1 or lower.

[0036] The molar ratio MgO / (MgO+CaO+SrO+BaO) is preferably 0.1 or higher, 0.2 or higher, 0.3 or higher, 0.4 or higher, 0.5 or higher, and particularly 0.6 or higher. This makes it easier to improve melting properties. On the other hand, MgO is a component that significantly reduces the strain point, and the effect of reducing the strain point is particularly pronounced in regions where the MgO content is low. Therefore, it is preferable for the MgO content in alkaline earth metal oxides to be low, and the molar ratio MgO / (MgO+CaO+SrO+BaO) is preferably 0.8 or lower, and particularly 0.7 or lower.

[0037] The ratio of 7×[MgO]+5×[CaO]+4×[SrO]+4×[BaO] is preferably 100% or less, 90% or less, 80% or less, 70% or less, 65% or less, and especially 60% or less. All alkaline earth metal elements have the effect of lowering the strain point, but this effect is greater for elements with smaller ionic radii. Therefore, by regulating the upper limit of 7×[MgO]+5×[CaO]+4×[SrO]+4×[BaO] so that the proportion of alkaline earth elements with larger ionic radii is larger, the strain point can be preferentially increased. Note that [MgO] refers to the content of MgO, [CaO] refers to the content of CaO, [SrO] refers to the content of SrO, and [BaO] refers to the content of BaO. Furthermore, "7×[MgO]+5×[CaO]+4×[SrO]+4×[BaO]" refers to the combined amounts of 7 times [MgO], 5 times [CaO], 4 times [SrO], and 4 times [BaO].

[0038] The ratio of 21×[MgO]+20×[CaO]+15×[SrO]+12×[BaO] is preferably 200% or more, 210% or more, 220% or more, 230% or more, 240% or more, 250% or more, and especially 300-1000%. All alkaline earth metal elements have the effect of increasing melting, but this effect is greater for elements with smaller ionic radii. Therefore, by regulating the lower limit of 21×[MgO]+20×[CaO]+15×[SrO]+12×[BaO] so that the proportion of alkaline earth elements with small ionic radii is small, melting can be preferentially increased. However, if 21×[MgO]+20×[CaO]+15×[SrO]+12×[BaO] is too large, there is a risk that the strain point will decrease. Note that "21×[MgO]+20×[CaO]+15×[SrO]+12×[BaO]" refers to the combined amounts of 21 times [MgO], 20 times [CaO], 15 times [SrO], and 12 times [BaO].

[0039] According to the inventors' research, increasing the Al2O3 content and the proportion of alkaline earth elements with small ionic radii (especially increasing the MgO content and decreasing the BaO content) can effectively increase the Young's modulus. Therefore, 9×[Al2O3]+7×[MgO]-4×[BaO] is preferably 95% or more, 105% or more, 115% or more, 125% or more, and especially 135% or more. Note that "9×[Al2O3]+7×[MgO]-4×[BaO]" refers to the amount obtained by subtracting 4 times the amount of [BaO] from the combined amount of 9 times [Al2O3] and 7 times [MgO].

[0040] The ratio of [MgO]+[CaO]+3×[SrO]+4×[BaO] is preferably 27% or less, 26% or less, 25% or less, 24% or less, and especially 23% or less. If the ratio of [MgO]+[CaO]+3×[SrO]+4×[BaO] is too high, the density tends to increase, which lowers the specific Young's modulus and increases the amount of deflection due to its own weight. Note that "[MgO]+[CaO]+3×[SrO]+4×[BaO]" refers to the combined amounts of [MgO], [CaO], 3 times [SrO], and 4 times [BaO].

[0041] In addition to the components listed above, the following components may also be introduced into the glass composition.

[0042] ZnO is a component that enhances meltability, but if it is included in large quantities in the glass composition, the glass becomes more prone to devitrification and its strain point tends to decrease. Therefore, the ZnO content is preferably 0-5%, 0-3%, 0-0.5%, 0-0.3%, and particularly 0-0.1%. ZrO2 is a component that increases Young's modulus. The ZrO2 content is preferably 0-5%, 0-3%, 0-0.5%, 0-0.2%, and especially 0-0.02%. If the ZrO2 content is too high, the liquid phase temperature will rise, making it easier for devitrified zircon crystals to precipitate. TiO2 is a component that lowers high-temperature viscosity and improves meltability, as well as suppressing solarization. However, if it is included in large quantities in the glass composition, the glass becomes more prone to discoloration. Therefore, the TiO2 content is preferably 0-5%, 0-3%, 0-1%, 0-0.1%, and particularly 0-0.02%.

[0043] P2O5 is a component that enhances resistance to devitrification, but if it is included in large quantities in the glass composition, the glass may easily undergo phase separation and become opaque, and its water resistance may be significantly reduced. Therefore, the P2O5 content is preferably 0-5%, 0-4%, 0-3%, less than 0-2%, 0-1%, 0-0.5%, and especially 0-0.1%. SnO2 is a component that has a good clarifying effect in the high-temperature range and also reduces high-temperature viscosity. The SnO2 content is preferably 0-1%, 0.01-0.5%, 0.01-0.3%, and particularly 0.04-0.1%. If the SnO2 content is too high, devitrified crystals of SnO2 tend to precipitate. As described above, the glass of the present invention is preferably enriched with SnO2 as a clarifying agent, but CeO2, SO3, C, and metal powders (e.g., Al, Si, etc.) may be added as clarifying agents up to 1%, as long as they do not impair the glass properties.

[0044] As2O3, Sb2O3, F, and Cl also act effectively as clarifying agents, and the glass of the present invention does not exclude the inclusion of these components. However, from an environmental standpoint, the content of each of these components is preferably less than 0.1%, and particularly less than 0.05%. If the glass contains 0.01-0.5% SnO2, excessive Rh2O3 content can easily cause discoloration. Note that Rh2O3 may be introduced from the platinum manufacturing container. The Rh2O3 content is preferably 0-0.0005%, more preferably 0.00001-0.0001%.

[0045] SO3 is an impurity that is introduced from the raw materials. However, if the SO3 content is too high, it can cause bubbles called reboil during melting and molding, potentially leading to defects in the glass. The preferred lower limit for SO3 is 0.0001% or more, and the preferred upper limits are 0.005% or less, 0.003% or less, 0.002% or less, and especially 0.001% or less. The content of rare earth oxides (oxides such as Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc.) is preferably less than 2%, 1% or less, particularly less than 1%. In particular, the content of La2O3 + Y2O3 is preferably less than 2%, less than 1%, less than 0.5%, particularly less than 0.1%. The content of La2O3 is preferably less than 2%, less than 1%, less than 0.5%, particularly less than 0.1%. If the content of rare earth oxides is too high, the batch cost is likely to increase. Note that "Y2O3 + La2O3" is the total amount of Y2O3 and La2O3.

[0046] The glass of the present invention preferably has the following characteristics. The density is preferably 2.80 g / cm 3 Hereinafter, 2.70 g / cm 3 Hereinafter, 2.60 g / cm 3 Hereinafter, particularly 2.50 g / cm 3 Hereinafter. If the density is too high, it is difficult to achieve weight reduction of the display.

[0047] The thermal expansion coefficient in the temperature range of 30 to 380 °C is preferably less than 40×10 -7 / °C, 38×10 -7 / °C or less, 36×10 -7 / °C or less, 34×10 -7 / °C or less, particularly 28×10 -7 ~33×10 -7 / °C is preferred. If the thermal expansion coefficient in the temperature range of 30 to 380 °C is too high, it becomes difficult to match the thermal expansion coefficient of the member (for example, p-Si) formed on the glass substrate, and the glass substrate is likely to warp. The strain point is preferably 750 °C or higher, 780 °C or higher, 800 °C or higher, 810 °C or higher, 820 °C or higher, particularly 830 to 1000 °C is preferred. If the strain point is too low, the glass substrate is likely to thermally contract in the heat treatment process.

[0048] The Young's modulus is preferably greater than 75 GPa, 77 GPa or higher, 78 GPa or higher, 79 GPa or higher, and especially 80 GPa or higher. If the Young's modulus is too low, problems caused by the bending of the glass substrate, such as distorted image surfaces on electronic devices, are more likely to occur. The specific Young's modulus is preferably 30 GPa / (g / cm²). 3 ) super, 30.2GPa / (g / cm 3 ) or more, 30.4GPa / (g / cm 3 ) or more, 30.6GPa / (g / cm 3 ) Above 30.8 GPa / (g / cm³) 3 ) That's all. If the relative Young's modulus is too low, problems such as breakage during transport of the glass substrate are more likely to occur due to the bending of the glass substrate.

[0049] When immersed in a 10% by mass HF aqueous solution at room temperature for 30 minutes, the etching depth is preferably 25 μm or more, 27 μm or more, 28 μm or more, 29-50 μm, and particularly preferably 30-45 μm. This etching depth serves as an indicator of the etching rate. That is, a larger etching depth results in a faster etching rate, while a smaller etching depth results in a slower etching rate. In addition, reducing the SiO2 content makes it easier to increase the etching rate, but it is also easier to increase the etching rate by preferentially introducing elements with large ionic radii among alkaline earth metals.

[0050] The SiO2-Al2O3-RO (RO refers to alkaline earth metal oxide) glass according to the present invention is generally difficult to melt. Therefore, improving meltability is a challenge. Improving meltability reduces the defect rate due to bubbles, foreign matter, etc., so that high-quality glass substrates can be supplied in large quantities and at low cost. On the other hand, if the high-temperature viscosity is too high, degassing in the melting process becomes difficult. Therefore, the high-temperature viscosity should be 10 2.5 The temperature at dPa·s is preferably 1800°C or lower, 1750°C or lower, 1700°C or lower, 1680°C or lower, 1670°C or lower, 1650°C or lower, and especially 1630°C or lower. 2.5The temperature in dPa·s corresponds to the melting temperature; the lower this temperature, the better the melting properties.

[0051] (10 2.5 The temperature-strain point ratio in dPa·s is preferably 1000°C or lower, 900°C or lower, 850°C or lower, and particularly 800°C or lower, from the viewpoint of achieving both a high strain point and a low melting temperature.

[0052] When forming into a flat plate shape, devitrification resistance is important. Considering the molding temperature of the SiO2-Al2O3-RO glass according to the present invention, the liquidus temperature is preferably 1450°C or lower, 1400°C or lower, and particularly 1300°C or lower. The liquidus viscosity is preferably 10 3.0 dPa·s or higher, 10 3.5 dPa·s or higher, especially 10 4.0 The pressure is dPa·s or higher. Note that "liquid phase temperature" refers to the temperature at which crystals precipitate after the glass powder, which has passed through a standard 30-mesh (500 μm) sieve and remained in a 50-mesh (300 μm) sieve, is placed in a platinum boat and held in a temperature gradient furnace for 24 hours. "Liquid phase viscosity" refers to the viscosity of the glass at the liquid phase temperature, measured using the platinum ball pulling method.

[0053] The glass of the present invention can be molded using various molding methods. For example, glass substrates can be molded using the overflow downdraw method, slot downdraw method, redraw method, float method, rollout method, etc. Furthermore, molding the glass substrate using the overflow downdraw method makes it easier to produce glass substrates with high surface smoothness.

[0054] When the glass of the present invention is in a flat plate shape, its thickness is preferably 1.0 mm or less, 0.7 mm or less, 0.5 mm or less, and particularly 0.4 mm or less. The smaller the plate thickness, the easier it is to lighten electronic devices. On the other hand, the smaller the plate thickness, the more easily the glass substrate flexes, but because the glass of the present invention has a high Young's modulus and specific Young's modulus, problems caused by flexing are less likely to occur. The plate thickness can be adjusted by the flow rate and plate drawing speed during molding.

[0055] In the glass of the present invention, the strain point can be increased by lowering the β-OH value. The β-OH value is preferably 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, and particularly 0.15 / mm or less. If the β-OH value is too high, the strain point tends to decrease. If the β-OH value is too low, the meltability tends to decrease. Therefore, the β-OH value is preferably 0.01 / mm or more, and particularly 0.05 / mm or more.

[0056] The following methods can be used to reduce the β-OH value: (1) Select raw materials with low water content. (2) Add components that reduce the amount of water in the glass (Cl, SO3, etc.). (3) Reduce the amount of water in the furnace atmosphere. (4) Perform N2 bubbling in the molten glass. (5) Use a small melting furnace. (6) Increase the flow rate of the molten glass. (7) Use an electromelting method.

[0057] Here, the "β-OH value" refers to the value obtained by measuring the transmittance of the glass using FT-IR and using the following formula. β-OH value = (1 / X)log(T1 / T2) X: Glass thickness (mm) T1: Reference wavelength 3846cm -1 Transmittance (%) T2: Hydroxyl group absorption wavelength 3600 cm -1 Minimum transmittance in the vicinity (%)

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

[0059] Tables 1-4 show examples of the present invention (samples No. 1-58).

[0060] [Table 1]

[0061] [Table 2]

[0062] [Table 3]

[0063] [Table 4]

[0064] Each sample was prepared as follows. First, a glass batch containing glass raw materials, formulated to match the glass composition shown in the table, was placed in a platinum crucible and melted at 1600-1750°C for 24 hours. During the melting of the glass batch, a platinum stirrer was used to ensure homogenization. Next, the molten glass was poured onto a carbon plate and formed into a flat plate shape. For each obtained sample, the density ρ, thermal expansion coefficient α, strain point Ps, annealing point Ta, softening point Ts, and high-temperature viscosity 10 were determined. 4.0 Temperature and high-temperature viscosity at dPa·s 10 3.0 Temperature and high-temperature viscosity at dPa·s 10 2.5 Temperature, liquidus temperature TL, and liquidus viscosity logηTL at dPa·s were evaluated.

[0065] The density ρ is a value measured by the well-known Archimedes method. The thermal expansion coefficient α is the average value measured with a dilatometer in the temperature range of 30 to 380°C.

[0066] The strain point Ps, slow cooling point Ta, and softening point Ts are values ​​measured in accordance with ASTM C336 or ASTM C338.

[0067] High temperature viscosity 10 4.0 Temperature and high-temperature viscosity at dPa·s 10 3.0 Temperature and high-temperature viscosity at dPa·s 10 2.5 The temperature in dPa·s was measured using the platinum ball pulling method.

[0068] The liquidus temperature TL is the temperature at which devitrification (devitrified crystals) was observed in the glass after each sample was pulverized, passed through a standard 30-mesh (500 μm) sieve, and the glass powder remaining in a 50-mesh (300 μm) sieve was placed in a platinum boat and held in a temperature gradient furnace for 24 hours. The platinum boat was then removed. The liquidus viscosity logηTL is the value obtained by measuring the viscosity of the glass at the liquidus temperature TL using the platinum ball pulling method.

[0069] The β-OH value is the value calculated using the above formula.

[0070] As is clear from Tables 1-4, samples No. 1-58 have high strain points, low thermal expansion coefficients, and possess mass-producible meltability and devitrification resistance. Therefore, samples No. 1-58 are considered suitable as substrates for organic EL displays. [Industrial applicability]

[0071] The glass of the present invention has a high strain point, a low coefficient of thermal expansion, and possesses mass-producible meltability and devitrification resistance. Therefore, the glass of the present invention is suitable not only as a substrate for organic EL displays but also as a substrate for displays such as liquid crystal displays, and is particularly suitable as a substrate for displays driven by LTPS and oxide TFTs. Furthermore, the glass of the present invention is also suitable as a substrate for LEDs for manufacturing semiconductor materials at high temperatures.

Claims

1. As a glass composition, in mol%, SiO ２ 55 to 73%, Al ２ O ３ 13 to 17%, B ２ O ３ 0 to 1%, Li ２ O + Na ２ O + K ２ O 0 to 0.2%, MgO 4 to 6%, CaO 2 to 7.5%, SrO 0 to 8.5%, BaO 0 to 2.5%, ZnO 0 to 0.5%, MgO + CaO + SrO + BaO 5 to 35%, SnO ２ containing 0.01 to 1% and having a thermal expansion coefficient in the temperature range of 30 to 380°C less than 40×10 －７ / °C, characterized by a glass.

2. B ２ O ３ The glass according to claim 1, characterized in that the content of is less than 1 mol%.

3. B ２ O ３ The glass according to claim 1 or 2, characterized in that the content of is 0.1 mol% or less.

4. Molar ratio (MgO + CaO + SrO + BaO) / Al ２ O ３ The glass according to claim 1 or 2, characterized in that the ratio is 0.3 to 3.

5. The glass according to claim 1 or 2, characterized in that its strain point is 750°C or higher.

6. (10 ２．５ The glass according to claim 1 or 2, characterized in that the temperature-strain point (dPa·s) is 1000°C or less.

7. 10 ２．５ The glass according to claim 1 or 2, characterized in that the temperature at which the viscosity of dPa·s is 1800°C or lower.

8. The glass according to claim 1 or 2, characterized in that it is in a flat plate shape.

9. The glass according to claim 1 or 2, characterized in that it is used as a substrate for an organic EL display.

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