glass

Abstract

To create a glass that has small amounts of heat shrinkage in the production process of p-Si TFT and also has high devitrification resistance and melting properties.SOLUTION: A glass according to the present invention is characterized by having a glass composition that contains, in mol%, SiO2 of 67 to 73%, Al2O3 of 10 to 15%, B2O3 of less than 0 to 3%, Li2O+Na2O+K2O of 0 to 0.5%, MgO of 0 to 8.5%, CaO of 3.5 to 12%, SrO of 0 to 2.5%, BaO of 1 to 6%, where a value obtained by dividing a strain point (°C) by the content (mol%) of Al2O3 is 51 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to glass, and in particular to glass suitable for use as a substrate for an organic EL display, a carrier glass used when fabricating an organic EL element on a polyimide substrate, and the like. [Background technology]

[0002] Electronic devices such as organic light-emitting diode (OLED) displays are thin, have excellent video display capabilities, and consume little power, making them suitable for use in mobile phone displays, etc. Furthermore, organic EL displays using polyimide substrates are lightweight and flexible, making them increasingly applicable to a variety of displays.

[0003] Glass plates are widely used as substrates for organic EL displays. Glass plates are also used as carrier glass when fabricating organic EL elements on polyimide substrates. Glass plates for these applications are required to have the following main properties: (1) The content of alkali metal oxides is low to prevent alkali ions from diffusing into the semiconductor material formed during the heat treatment process. (2) To reduce the cost of glass sheets, the glass must be highly productive, and in particular, it must have excellent resistance to devitrification and melting properties. (3) The strain point must be high to reduce the amount of thermal shrinkage during the manufacturing process of p-Si TFTs. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2009-525942 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] To elaborate on the above-mentioned required characteristic (3), the film formation process for p-Si TFTs involves a heat treatment step at 400-600°C, which causes minute dimensional changes in the glass plate known as thermal shrinkage. If the amount of thermal shrinkage is large, it can cause deviations in the pixel pitch of the TFT, resulting in display defects. In the case of organic EL displays, even dimensional shrinkage of a few ppm can cause display defects. The higher the heat treatment temperature the glass plate is subjected to, the greater the thermal shrinkage.

[0006] Furthermore, the carrier glass used when fabricating organic EL elements on a polyimide substrate also undergoes a heat treatment process at the same temperature as when fabricating organic EL elements on a glass plate. If the amount of thermal shrinkage of the glass plate is large, that thermal shrinkage is transmitted to the polyimide substrate, causing deviation in pixel pitch.

[0007] As can be seen from the above, glass sheets that are less susceptible to thermal shrinkage are advantageous for these applications. One method for reducing the amount of thermal shrinkage is to anneal the glass sheet at a temperature close to the annealing point after forming it. However, the annealing process requires a long time, which increases the manufacturing cost of the glass sheet.

[0008] Another method is to increase the strain point of the glass plate. The higher the strain point, the less likely thermal shrinkage occurs during the manufacturing process of p-Si TFTs. For example, Patent Document 1 discloses a glass plate with a high strain point.

[0009] However, high strain point glasses generally contain large amounts of refractory SiO2 and Al2O3, which result in poor devitrification resistance and meltability (especially batch meltability), making it difficult to stably produce inexpensive, high-quality glass. Therefore, high strain point glasses have difficulty satisfying the required characteristic (2).

[0010] The present invention has been made in view of the above circumstances, and its technical objective is to invent a glass that has a small amount of thermal shrinkage during the manufacturing process of p-Si TFTs and also has high resistance to devitrification and melting properties. [Means for solving the problem]

[0011] After repeated experiments, the inventors discovered that the above technical problems can be solved by strictly controlling the glass composition of low-alkali glass and the relationship between Al2O3 and the strain point, and have proposed this finding as the present invention. Specifically, the glass of the present invention contains, in mole percent, 67-73% SiO2, 10-15% Al2O3, 0-3% or less B2O3, 0-0.5% Li2O + Na2O + K2O, 0-8.5% MgO, 3.5-12% CaO, 0-2.5% SrO, and 1-6% BaO, and is characterized by a strain point (°C) divided by the Al2O3 content (mol %) of 51 or greater. Here, "Li2O + Na2O + K2O" refers to the combined amount of Li2O, Na2O, and K2O. The "strain point" refers to a value measured according to the method of ASTM C336.

[0012] The glass of the present invention has a glass composition containing, in mole percent, 67-73% SiO2, 10-15% Al2O3, 0-1.3% B2O3, 0-0.5% Li2O + Na2O + K2O, 0-3.2% MgO, 3.5-12% CaO, 0-2% SrO, and 3.5-6% BaO, characterized in that CaO-(SrO + BaO) is 3.1% or more, the molar ratio CaO / Al2O3 is 1.05 or less, and the molar ratio SrO / BaO is 0.03-0.50. Here, "CaO-(SrO + BaO)" refers to the value obtained by subtracting the combined amount of SrO and BaO from the CaO content. "CaO / Al2O3" refers to the value obtained by dividing the CaO content by the Al2O3 content. "SrO / BaO" refers to the value obtained by dividing the SrO content by the BaO content.

[0013] The glass of the present invention has a glass composition containing, in mole percent, 67 to 73% of SiO2, 12 to 15% of Al2O3, 0 to less than 1.8% of B2O3, 0 to less than 0.5% of Li2O + Na2O + K2O, 0 to 6% of MgO, 5% or more of CaO, 0 to 2% of SrO, and 3.5% or more of BaO, wherein CaO-(SrO + BaO) is 0.7% or more, the molar ratio SrO / BaO is 0.38 or less, the molar ratio (MgO + CaO + SrO + BaO) / Al2O3 is 1.09 to 1.70, and the value obtained by dividing the strain point (°C) by the Al2O3 content (mol%) is 55 or more. Here, "(MgO+CaO+SrO+BaO) / Al2O3" refers to the value obtained by dividing the total amount of MgO, CaO, SrO, and BaO by the content of Al2O3. DETAILED DESCRIPTION OF THE INVENTION

[0014] The glass of the present invention preferably contains, in mole percent, 67-73% SiO2, 10-15% Al2O3, 0-less than 3% B2O3, 0-0.5% Li2O + Na2O + K2O, 0-8.5% MgO, 3.5-12% CaO, 0-2.5% SrO, and 1-6% BaO as a glass composition. The reasons for specifying the content range of each component as above are as follows. In the explanation of the content range of each component, % means mol% unless otherwise specified.

[0015] SiO2 is a component that forms the glass skeleton and raises the strain point. It also increases resistance to chemicals such as hydrochloric acid. On the other hand, if the SiO2 content is too high, the melting property decreases significantly and the HF etching rate decreases. Therefore, the preferred lower limit of SiO2 is 67% or more, 68% or more, 69% or more, and particularly 70% or more, and the preferred upper limit is 73% or less, particularly 72% or less.

[0016] Al2O3 is a component that increases the strain point and Young's modulus. On the other hand, if the Al2O3 content is too high, the batch solubility during initial melting decreases and the molding temperature increases. The preferred lower limit of Al2O3 is 10% or more, 11% or more, and particularly 12% or more, and the preferred upper limit is 15% or less, 14% or less, 13% or less, and particularly 12.5% ​​or less. When a small amount of B2O3 is introduced to reduce meltability and molding viscosity, a relatively large amount of Al2O3 can be introduced into the glass composition. On the other hand, when almost no B2O3 is contained, it is not possible to introduce too much Al2O3 into the glass composition. In this case, it is preferable that the Al2O3 content be as low as possible.

[0017] B2O3 is a component that improves meltability and devitrification resistance, and also lowers the molding temperature. On the other hand, if a large amount of B2O3 is introduced, the strain point and Young's modulus also decrease. The B2O3 content is preferably less than 3%, 2.5% or less, 2% or less, less than 1.8%, 1.3% or less, and particularly preferably 0.8% or less.

[0018] As will be described in detail later, the raw material for introducing B2O3 is the source of much of the moisture in the glass. Therefore, from the viewpoint of reducing the moisture content, it is preferable that the B2O3 content be as low as possible. Furthermore, when producing glass sheets using full electric melting without combustion, the lower the B2O3 content, the easier it is for the glass batch to spread uniformly in the melting furnace, thereby improving the homogeneity of the molten glass.

[0019] Li2O, Na2O, and K2O are components that improve meltability and reduce the electrical resistivity of molten glass. However, excessive amounts of Li2O, Na2O, and K2O may cause contamination of semiconductor materials due to the diffusion of alkali ions. Therefore, the total amount of Li2O, Na2O, and K2O is preferably 0 to 0.5%, less than 0 to 0.5%, 0.01 to 0.3%, 0.02 to 0.2%, and particularly less than 0.03 to 0.1%. The Na2O content is preferably 0 to 0.3%, 0.01 to 0.3%, 0.02 to 0.2%, and particularly less than 0.03 to 0.1%. The K2O content is preferably 0 to 0.3%, 0 to 0.2%, and particularly less than 0 to 0.1%.

[0020] MgO is a component that enhances meltability and Young's modulus. On the other hand, MgO lowers the strain point. When reducing the amount of Al2O3 to lower the melting temperature or molding temperature, it is necessary to incorporate a large amount of SiO2 to maintain a high strain point. Incorporating a large amount of MgO into such a SiO2-rich composition facilitates cristobalite precipitation during molding, further lowering the strain point. Therefore, in this case, the MgO content is preferably as low as possible, and the MgO content is preferably 0-8.5%, 0-6%, 0-5%, 0-3.2%, 0-3%, and particularly 0-1%. Furthermore, when incorporating a small amount of B2O3 to lower the melting temperature or molding temperature, the SiO2 content can be relatively low and the Al2O3 content can be relatively high. In this case, it is preferable to actively incorporate MgO, and the MgO content is preferably 1-8.5%, 2-6%, and particularly 2.5-5%.

[0021] CaO is a component that improves meltability and batch solubility. Furthermore, since CaO is a relatively inexpensive raw material among alkaline earth metal oxides, it is a component that reduces raw material costs. It is also a component that suppresses the precipitation of devitrified crystals containing Mg. On the other hand, if the CaO content is too high, feldspar-based devitrified crystals containing Ca (e.g., anorthite) tend to precipitate during molding. Therefore, the CaO content is preferably 3.5 to 12%, 4 to 11%, 5 to 11%, and particularly 5.5 to 11%.

[0022] SrO is a component that makes it difficult for cristobalite to precipitate during molding, and also lowers the melting temperature without significantly lowering the strain point. On the other hand, if the SrO content is too high, the density increases and the Young's modulus tends to decrease. Furthermore, in a composition range where anorthite is likely to precipitate as the primary phase, if the SrO content is too high, the liquidus temperature decreases, and the productivity of the glass sheet tends to decrease. Therefore, the SrO content is preferably 0 to 2.5%, 0 to 2%, and particularly 0.1 to 1.3%.

[0023] Among alkaline earth metal oxides, BaO is a component that suppresses the precipitation of devitrified crystals such as mullite and anorthite, which contain Al, during molding. On the other hand, if the BaO content is too high, the density increases and the Young's modulus tends to decrease. The preferred lower limit of BaO is 1% or more, 2% or more, 3% or more, and particularly 3.5% or more, and the preferred upper limit is 12% or less, 11% or less, 10% or less, 8% or less, and particularly 6% or less.

[0024] Alkaline earth metal oxides are very important components for increasing the strain point, devitrification resistance, and meltability. A low alkaline earth metal oxide content increases the strain point, but Al2O3-based devitrification crystals are more likely to precipitate during molding, and the high-temperature viscosity increases, resulting in decreased meltability. Therefore, the ratio of the total amount of alkaline earth metal oxides (MgO + CaO + SrO + BaO) to the Al2O3 content is very important. Specifically, as the molar ratio (MgO + CaO + SrO + BaO) / Al2O3 increases, meltability and moldability improve, but the strain point tends to decrease. Conversely, as this value decreases, the strain point increases, but meltability and moldability tend to decrease. Therefore, the preferred lower limit of the molar ratio (MgO + CaO + SrO + BaO) / Al2O3 is 0.95 or more, 1.00 or more, 1.05 or more, and particularly 1.09 or more, and the preferred upper limit is 1.70 or less.

[0025] The molar ratio CaO / Al2O3 is one of the important indicators for maintaining a high strain point while ensuring meltability. In a composition region containing a large amount of CaO, it is important to design the composition so that the strain point does not decrease. In alkaline earth aluminosilicate glass, Al2O3 is the main component other than SiO2 that raises the strain point. From these perspectives, the molar ratio CaO / Al2O2 is preferably 1.09 or less, 1.07 or less, or 1.05 or less, and particularly 0.25 to 1.05.

[0026] In order to produce glass with a high strain point while reducing the manufacturing load, the blending ratio of the four alkaline earth metal oxide components is extremely important. From this viewpoint, CaO-(SrO+BaO) is preferably -3% or more, -1% or more, 0% or more, 0.7% or more, 2% or more, particularly 3.1 to 15%. When CaO-(SrO+BaO) is increased, the melting temperature and forming temperature decrease, thereby increasing the productivity of glass sheets.

[0027] In a composition region containing a large amount of CaO, controlling the molar ratio of SrO / BaO is important from the perspective of devitrification resistance. Specifically, as mentioned above, in a composition region containing a large amount of CaO, anorthite is more likely to precipitate as the primary phase. Among alkaline earth metal oxides, SrO is a component that increases the liquidus temperature of anorthite, while BaO is a component that decreases the liquidus temperature of anorthite. Therefore, the smaller the molar ratio of SrO / BaO, the lower the liquidus temperature of anorthite. However, if no SrO is added, devitrification crystals such as cristobalite are more likely to precipitate during molding. Taking these points into consideration, the preferred lower limit of the molar ratio of SrO / BaO is 0 or more, particularly 0.03 or more, and the preferred upper limit is 0.70 or less, 0.63 or less, 0.50 or less, particularly 0.38 or less.

[0028] In addition to the above components, the following components may be incorporated:

[0029] ZnO is a component that improves meltability, but if the amount of ZnO is too high, the glass becomes more susceptible to devitrification and the strain point tends to decrease. Therefore, the ZnO content is preferably 0 to 5%, 0 to 3%, 0 to 0.5%, particularly preferably 0 to 0.2%.

[0030] P2O5 is a component that lowers the liquidus temperature of Al-based devitrified crystals, but if the P2O5 content is too high, the strain point will decrease and cristobalite will be more likely to precipitate during molding. Therefore, the P2O5 content is preferably 0 to 1.5%, 0 to 1.2%, and particularly preferably 0 to less than 0.1%.

[0031] TiO2 is a component that reduces high-temperature viscosity, improves meltability, and also suppresses solarization. However, if the TiO2 content is too high, the glass becomes colored and transmittance tends to decrease. Therefore, the TiO2 content is preferably 0 to 5%, 0 to 3%, 0 to 1%, 0 to 0.1%, and particularly preferably 0 to 0.02%.

[0032] ZrO2, Y2O3, Nb2O5, and La2O3 function to increase the strain point, Young's modulus, etc. However, increasing the content of these components tends to increase the density. Therefore, the contents of ZrO2, Y2O3, Nb2O5, and La2O3 are preferably 0 to 5%, 0 to 3%, 0 to 1%, and 0 to less than 0.1%, and especially 0 to less than 0.05%, respectively. Furthermore, the combined content of Y2O3 and La2O3 is preferably less than 0.1%.

[0033] SnO2 is a component that has a good clarifying effect in the high temperature range, as well as a component that increases the strain point and reduces high-temperature viscosity. The SnO2 content is preferably 0 to 1%, 0.001 to 1%, 0.01 to 0.5%, and particularly preferably 0.05 to 0.3%. If the SnO2 content is too high, devitrified crystals of SnO2 are more likely to precipitate during molding.

[0034] As long as the glass properties are not impaired, up to 2% of fining agents such as F2, Cl2, SO3, C, or metal powders such as Al and Si can be added. CeO2 and other fining agents can also be added up to 1%.

[0035] As2O3 and Sb2O3 are effective fining agents, and although the glass of the present invention does not completely exclude the incorporation of these components, from an environmental perspective, it is preferable to minimize the use of these components. Furthermore, since a high content of As2O3 tends to reduce solarization resistance, its content is preferably 0.1% or less, and it is desirable that it be substantially absent. Here, "substantially free of As2O3" refers to a glass composition in which the As2O3 content is less than 0.05%. Furthermore, the Sb2O3 content is preferably 0.2% or less, particularly 0.1% or less, and it is desirable that it be substantially absent. Here, "substantially free of Sb2O3" refers to a glass composition in which the Sb2O3 content is less than 0.05%.

[0036] Fe2O3 is a component that reduces the electrical resistivity of molten glass. The Fe2O3 content is preferably 0 to 0.2%, 0.001 to 0.1%, 0.005 to 0.05%, and particularly 0.008 to 0.015%. If the Fe2O3 content is low, it becomes difficult to achieve the above-mentioned effects. On the other hand, if the Fe2O3 content is high, the transmittance in the ultraviolet range tends to decrease, and the irradiation efficiency when using an ultraviolet laser in the display manufacturing process tends to decrease. Note that when electric melting is performed, it is preferable to actively incorporate Fe2O3, and in that case, the Fe2O3 content is preferably 0.005 to 0.03%, 0.008 to 0.025%, and particularly 0.01 to 0.02%. Furthermore, when it is desired to increase the transmittance in the ultraviolet region, the content of Fe2O3 is preferably 0.020% or less, 0.015% or less, 0.011% or less, and particularly preferably 0.010% or less.

[0037] In addition, in relation to Fe2O3, the raw material for introducing MgO is the main source of contamination with Fe2O3. Therefore, from the viewpoint of increasing transmittance in the ultraviolet region, it is preferable to keep the content of MgO as low as possible.

[0038] Cl has the effect of promoting the melting of low-alkali glass, and adding Cl can lower the melting temperature and promote the action of a fining agent. Cl also has the effect of lowering the β-OH value of molten glass. However, if the Cl content is too high, the strain point will decrease and the environmental load will increase. Therefore, the Cl content is preferably 0.5% or less, particularly 0.001 to 0.2%. Note that, as a source of Cl, a chloride of an alkaline earth metal oxide such as strontium chloride, or a source such as aluminum chloride can be used.

[0039] The glass of the present invention preferably has the following properties:

[0040] The strain point is preferably 730° C. or higher, 735° C. or higher, 740° C. or higher, particularly 745° C. If the strain point is low, the glass plate is prone to thermal shrinkage during the manufacturing process of p-Si·TFT.

[0041] In order to obtain glass with low thermal shrinkage and high melting property in the manufacturing process of p-Si TFTs, it is important to simultaneously increase the strain point and batch solubility. On the other hand, Al2O3 is a component that significantly reduces batch solubility. Therefore, from the above perspective, it is important to increase the value obtained by dividing the strain point (°C) by the Al2O3 content (mol%). The value obtained by dividing the strain point (°C) by the Al2O3 content (mol%) is preferably 51 or higher, 53 or higher, and particularly 55 to 80.

[0042] The density is preferably 2.71 g / cm 3 Below, 2.69g / cm 3 Below, 2.67g / cm 3 Below, especially 2.64 g / cm 3 When the density is high, the specific Young's modulus increases, making the glass plate more likely to bend under its own weight, and when used as a substrate, the mass of the organic EL display increases.

[0043] Reducing the β-OH value can increase the strain point. The β-OH value is preferably 0.30 / mm or less, 0.25 / mm or less, 0.20 / mm or less, 0.15 / mm or less, particularly 0.10 / mm or less. As the β-OH value increases, the strain point tends to decrease. Note that if the β-OH value is made too small, there is a risk of excessive Cl in the glass. Therefore, the β-OH value is preferably 0.01 / mm or more, particularly 0.02 / mm or more.

[0044] The following methods can be used to reduce the β-OH value: (1) Select glass raw materials with a low water content. (2) Add components (Cl, SO3, etc.) that reduce the water content in the glass. (3) Reduce the water content in the furnace atmosphere. (4) Bubble N2 in the molten glass. (5) Use a small melting furnace. (6) Increase the flow rate of the molten glass. (7) Use an electric melting method.

[0045] Here, the "β-OH value" refers to a value obtained by measuring the transmittance of 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 3600cm -1 Minimum transmittance (%) in the vicinity

[0046] The liquidus temperature is preferably less than 1320°C, 1300°C or less, 1280°C or less, 1260°C or less, or 1240°C or less, particularly 1220°C or less. If the liquidus temperature is high, devitrified crystals precipitate during forming by an overflow downdraw method or the like, reducing the productivity of the glass sheet. The "liquidus temperature" refers to the temperature at which crystals (primary phase) precipitate when a glass powder that passes through a standard 30 mesh sieve (sieve opening 500 μm) and remains on a 50 mesh sieve (sieve opening 300 μm) is placed in a platinum boat and held in a temperature gradient furnace for 24 hours.

[0047] The liquidus viscosity is preferably 10 4.5dPa·s or more, 10 4.8 dPa·s or more, 10 5.0 dPa·s or more, 10 5.2 dPa·s or more, especially 10 5.3 It is dPa·s or higher. If the liquidus viscosity is low, devitrification crystals will precipitate during forming using the overflow downdraw method, etc., reducing the productivity of glass sheets. Note that "liquidus viscosity" refers to the viscosity of glass at the liquidus temperature measured using the platinum sphere pull-up method.

[0048] High temperature viscosity 10 4.5 The temperature in dPa·s is preferably less than 1320°C, 1310°C or less, 1305°C or less, and particularly 1300°C or less. 4.5 The temperature at dPa·s corresponds to the forming temperature when forming using the overflow downdraw method. If the forming temperature becomes too high, creep deformation of the formed body will progress more easily, making it impossible to stably produce high-quality glass sheets. It is possible to produce glass sheets by replacing the formed body that has progressed in creep deformation, but this will increase the manufacturing cost of glass sheets as the formed body is very expensive. 4.5 The "temperature at dPa·s" can be measured using the platinum sphere pull-up method.

[0049] High temperature viscosity 10 2.5 Let η be the temperature in dPa·s. 2.5 , high temperature viscosity 10 4.0 Let η be the temperature in dPa·s. 4.0 When this is done, (η 2.5 -η 4.0 ) / η 2.5 is preferably 0.158 or more, 0.163 or more, particularly 0.170 or more. 2.5 The temperature at which the viscosity drops to 10 dPa·s is generally an index of melting property, and the lower this temperature, the higher the melting property. However, when the composition is designed to achieve a high strain point as in the present invention, the high-temperature viscosity of 10 2.5The temperature at 1000 dPa·s becomes high. When using a heat-resistant metal such as platinum in the fining vessel (fining pipe), it becomes difficult to raise the temperature of the fining vessel (fining pipe) to a temperature sufficient for fining due to the heat limit of platinum. However, even in such a case, the high-temperature viscosity of 10 2.5 If the temperature change relative to the viscosity change around the temperature in dPa·s is large, the process window will be wider, which is advantageous for improving the foam quality. 2.5 -η 4.0 ) / η 2.5 " is a high temperature viscosity 10 2.5 Viscosity in dPa·s from 10 to 100°C 4.0 The temperature at which the viscosity at dPa·s is reduced is the high temperature viscosity 10 2.5 It is the value divided by the temperature in dPa·s. 2.5 "Temperature in dPa·s" and "High temperature viscosity 10 4.0 The "temperature at dPa·s" can be measured using the platinum sphere pull-up method.

[0050] Specific Young's modulus is preferably 29.5 GPa / g cm -3 Above, 29.7 GPa / g cm -3 More than 30GPa / g cm -3 Above, 31GPa / g cm -3 Above, 31.5 GPa / g cm -3 Above, especially 32 GPa / g cm -3 That's all. If the specific Young's modulus is low, the glass plate will bend easily under its own weight, making it more likely to break during the film formation process for p-Si TFTs. Note that "specific Young's modulus" is the value obtained by dividing Young's modulus by density. "Young's modulus" can also be measured using the well-known resonance method.

[0051] The etching rate using HF is preferably 0.8 μm / min or more, 0.9 μm / min or more, particularly 1.0 μm / min or more. When a glass plate is used as a substrate for a mobile device or the like, it is thinned (slimmed) by hydrofluoric acid (HF) etching. If the HF etching rate is low, slimming takes a long time, which increases costs. Here, the "HF etching rate" refers to the etching depth when a mirror-polished glass surface is etched with a 10 mass % HF aqueous solution at 20°C for 30 minutes.

[0052] The glass of the present invention preferably has a flat plate shape and has an overflow confluence surface at the center in the plate thickness direction. That is, it is preferably formed by the overflow downdraw method. The overflow downdraw method is a method in which molten glass is allowed to overflow from both sides of a wedge-shaped refractory, and the overflowed molten glass is drawn downward while being joined at the lower end of the wedge to form a flat plate. In the overflow downdraw method, the surface that will become the surface of the glass plate does not come into contact with the refractory and is formed in a free surface state. Therefore, unpolished glass plates with good surface quality can be produced inexpensively. Furthermore, it is easy to increase the area and reduce the thickness.

[0053] In addition to the overflow downdraw method, it is also possible to form a glass sheet by, for example, a slot-down method, a redraw method, a float method, or a roll-out method.

[0054] The thickness of the glass of the present invention (plate thickness in the case of a glass plate) is not particularly limited, but is preferably 1.0 mm or less, 0.7 mm or less, 0.5 mm or less, and particularly 0.05 to 0.4 mm. The smaller the thickness, the easier it is to reduce the weight of the organic EL display. The thickness can be adjusted by the flow rate and forming speed (plate drawing speed) during glass production.

[0055] A method for industrially producing the glass of the present invention preferably comprises a melting step of charging a glass batch prepared so as to contain, in mole percent, 67 to 73% of SiO2, 10 to 15% of Al2O3, but less than 0 to 3% of B2O3, 0 to 0.5% of Li2O + Na2O + KO, 0 to 8.5% of MgO, 3.5 to 12% of CaO, 0 to 2.5% of SrO, and 1 to 6% of BaO into a melting furnace and subjecting the batch to electrical heating using heating electrodes to obtain molten glass, and a forming step of forming the obtained molten glass into a flat glass plate having a thickness of 0.1 to 0.7 mm by an overflow downdraw method.

[0056] The manufacturing process of a glass sheet generally includes a melting step, a fining step, a supplying step, a stirring step, and a forming step. The melting step is a step of melting a glass batch prepared by blending glass raw materials to obtain molten glass. The fining step is a step of fining the molten glass obtained in the melting step using a fining agent or the like. The supplying step is a step of transferring the molten glass between each step. The stirring step is a step of stirring and homogenizing the molten glass. The forming step is a step of forming the molten glass into a plate-shaped glass. Note that, if necessary, a step other than the above, for example, a conditioning step of adjusting the molten glass to a state suitable for forming, may be incorporated after the stirring step.

[0057] Conventional low-alkali glasses are generally melted by heating with a burner combustion flame. The burner is usually located above a melting furnace and uses a fossil fuel, specifically a liquid fuel such as heavy oil or a gaseous fuel such as LPG, as fuel. The combustion flame can be obtained by mixing a fossil fuel with oxygen gas. However, this method tends to increase the β-OH value because a large amount of water is mixed into the molten glass during melting. Therefore, when producing the glass of the present invention, it is preferable to perform electrical heating using a heating electrode. It is also preferable to perform melting by electrical heating using a heating electrode without heating with a burner combustion flame, i.e., complete electrical melting. This reduces the likelihood of water being mixed into the molten glass during melting, making it easier to regulate the β-OH value to 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. Furthermore, when electrical heating is performed using a heating electrode, the amount of energy per mass required to obtain molten glass is reduced, and the amount of molten volatiles is also reduced, thereby reducing the environmental load.

[0058] Furthermore, with regard to this electrical heating, the lower the moisture content in the glass batch, the easier it is to reduce the moisture content in the glass sheet. Furthermore, the raw material for B2O3 tends to be the largest source of moisture contamination. Therefore, from the viewpoint of producing a glass sheet with low moisture content, it is preferable to keep the B2O3 content as low as possible. Furthermore, the lower the moisture content in the glass batch, the easier it is for the glass batch to spread uniformly in the melting furnace, making it easier to produce a homogeneous, high-quality glass sheet.

[0059] The electrical heating using the heating electrode is preferably carried out by applying an AC voltage to the heating electrode provided at the bottom or side of the melting furnace so as to be in contact with the molten glass in the melting furnace. The material used for the heating electrode is preferably heat-resistant and corrosion-resistant to the molten glass, and examples of usable materials include tin oxide, molybdenum, platinum, and rhodium. In particular, molybdenum is preferred from the viewpoint of flexibility in installation in the furnace.

[0060] The glass of the present invention has a high electrical resistivity due to its low alkali metal oxide content. Therefore, when applying electrical heating to low-alkali glass using heating electrodes, current flows not only through the molten glass but also through the refractories constituting the furnace, potentially causing premature damage to the refractories. To prevent this, it is preferable to use a zirconia-based refractory with high electrical resistivity, particularly electroformed zirconia bricks, as the furnace refractory. It is also preferable to incorporate small amounts of components (e.g., Li2O, Na2O, K2O, Fe2O3) that reduce electrical resistivity into the molten glass (glass composition), particularly in amounts of Li2O, Na2O, K2O, etc. (e.g., 0.01 mass% or more, particularly 0.02 mass% or more). The Fe2O3 content is preferably 0.005 to 0.03 mass%, 0.008 to 0.025 mass%, and particularly 0.01 to 0.02 mass%. Furthermore, the content of ZrO2 in the zirconia-based refractory is preferably 85% by mass or more, particularly preferably 90% by mass or more. [Example]

[0061] The present invention will be described below based on examples. However, the following examples are merely illustrative and the present invention is not limited to the following examples.

[0062] Tables 1 to 6 show examples of the present invention (samples No. 1 to 91). In the tables, "NA" means not measured.

[0063] [Table 1]

[0064] [Table 2]

[0065] [Table 3]

[0066] [Table 4]

[0067] [Table 5]

[0068] [Table 6] First, a glass batch prepared by blending glass raw materials to obtain the glass composition shown in the table was placed in a platinum crucible and melted at 1600-1650°C for 24 hours. The glass batch was homogenized by stirring using a platinum stirrer. The molten glass was then poured onto a carbon plate, formed into a plate, and annealed for 1 hour at a temperature close to the annealing point. The density ρ, average thermal expansion coefficient α in the temperature range of 30-380°C, β-OH value, strain point Ps, annealing point Ta, softening point Ts, and high-temperature viscosity 10 4.5 Temperature in dPa·s, high temperature viscosity 10 4.0 Temperature in dPa·s, high temperature viscosity 10 3.0 Temperature in dPa·s, high temperature viscosity 10 2.5 The temperature in dPa·s, liquidus viscosity logηatTL, ​​Young's modulus E, shear modulus G, Poisson's ratio γ, specific Young's modulus E / ρ, and HF etching rate were evaluated.

[0069] The density ρ is a value measured by the well-known Archimedes method.

[0070] The average thermal expansion coefficient α in the temperature range of 30 to 380° C. is a value measured with a dilatometer.

[0071] The β-OH value is a value measured by the above method.

[0072] The strain point Ps, annealing point Ta, and softening point Ts are values ​​measured based on the methods of ASTM C336 and C338.

[0073] High temperature viscosity 10 4.5dPa·s, 10 4.0 dPa·s, 10 3.0 dPa·s and 10 2.5 The temperature at dPa·s was measured by the platinum sphere pulling method.

[0074] The liquidus viscosity logηatTL is the viscosity of glass at the liquidus temperature TL, measured by the platinum ball pull-up method. The liquidus temperature TL is the temperature at which crystals (primary phase) precipitate when glass powder that passes through a standard 30-mesh sieve (sieve opening 500 μm) and remains on a 50-mesh sieve (sieve opening 300 μm) is placed in a platinum boat and held in a temperature gradient furnace for 24 hours.

[0075] Young's modulus E and rigidity modulus G are values ​​measured using the well-known resonance method. Poisson's ratio is a value calculated from Young's modulus E and rigidity modulus G. Specific Young's modulus E / ρ is the value obtained by dividing Young's modulus by density.

[0076] The HF etching rate is the etching depth when a mirror-polished glass surface is etched with a 10 mass % HF aqueous solution at 20° C. for 30 minutes.

[0077] As is clear from Tables 1 to 9, Samples Nos. 1 to 91 have a low content of alkali metal oxides, a strain point Ps of 734°C or higher, and a high-temperature viscosity of 10 2.5 The temperature at dPa·s is 1693°C or less, and the liquidus viscosity is 10 4.32 Therefore, samples Nos. 1 to 91 are considered suitable as substrates for organic EL displays and carrier glasses used when fabricating organic EL elements on polyimide substrates.

Claims

【Request Item 1】 The glass composition is, in mol%, SiO ２ 67-73%, Al ２ O ３ 10-15%, B ２ O ３ 0 to less than 3%, Li ２ O + Na ２ O+K ２ O 0-0.5%, MgO 0-8.5%, CaO 3.5-12%, SrO 0-2.5%, BaO 1-6%, and the strain point (°C) is ２ O ３ The glass characterized in that the value obtained by dividing by the content (mol %) of 【Request Item 2】 The glass composition is, in mol%, SiO ２ 67-73%, Al ２ O ３ 10-15%, B ２ O ３ 0-1.3%, Li ２ O + Na ２ O+K ２ O 0-0.5%, MgO 0-3.2%, CaO 3.5-12%, SrO 0-2%, BaO 3.5-6%, CaO-(SrO+BaO) is 3.1% or more, and the molar ratio CaO / Al ２ O ３ 2. The glass according to claim 1, wherein the molar ratio of SrO / BaO is 0.03 to 0.

50. 【Request Item 3】 The glass composition is, in mol%, SiO ２ 67-73%, Al ２ O ３ 12-15%, B ２ O ３ 0 to less than 1.8%, Li ２ O + Na ２ O+K ２ Contains O 0 to less than 0.5%, MgO 0 to 6%, CaO 5% or more, SrO 0 to 2%, BaO 3.5% or more, CaO-(SrO+BaO) is 0.7% or more, the molar ratio SrO / BaO is 0.38 or less, and the molar ratio (MgO+CaO+SrO+BaO) / Al ２ O ３ is 1.09 to 1.70, strain point (°C) is Al ２ O ３ 2. The glass according to claim 1, wherein the value obtained by dividing by the content (mol %) of

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