glass

Abstract

We invent glass that has high heat resistance and a high coefficient of thermal expansion, and can be formed into a flat plate shape. [Solution] The glass of the present invention is characterized by having a glass composition containing, in mole percent, 55 to 80% of SiO2, 11 to 30% of Al2O3, 0 to 3% of B2O3, 0 to 3% of Li2O+Na2O+K2O, and 5 to 35% of MgO+CaO+SrO+BaO, and having a strain point higher than 700°C.

Description

[Technical Field]

[0001] The present invention relates to high heat-resistant glass, and more particularly to a glass substrate for producing semiconductor crystals for LEDs at high temperatures. [Background technology]

[0002] It is known that the semiconductor properties of semiconductor crystals used in LEDs and other applications improve as the film is deposited at higher temperatures.

[0003] For this application, high-heat-resistant sapphire substrates are commonly used. Sapphire substrates are also used in other applications where semiconductor crystals are deposited at high temperatures (e.g., above 700°C). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-243229 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Incidentally, in recent years, techniques for depositing large-area semiconductor crystals have been actively investigated. This technology is considered promising as a surface-emitting light source for large displays.

[0006] However, sapphire substrates are difficult to scale up to large areas and are therefore unsuitable for the above applications.

[0007] While using a glass substrate instead of a sapphire substrate would allow for a larger substrate area, conventional glass substrates have insufficient heat resistance, making them prone to thermal deformation during high-temperature heat treatment.

[0008] Furthermore, attempting to improve the heat resistance of conventional glass substrates can lead to an unreasonable decrease in the thermal expansion coefficient of the glass substrate, making it difficult to match the thermal expansion coefficient of the semiconductor crystal. This can result in the glass substrate becoming prone to warping or the semiconductor film becoming more susceptible to cracking after the semiconductor crystal has been fabricated. Moreover, attempting to improve the heat resistance of the glass substrate can reduce its devitrification resistance, making it difficult to form it into a flat 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 and thermal expansion coefficient, and can also be molded into a flat plate shape. [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 is characterized by containing, in molar percent, SiO2 55-80%, Al2O3 11-30%, B2O 30-3%, Li2O+Na2O+K2O 0-3%, and MgO+CaO+SrO+BaO 5-35%, and having a strain point higher than 700°C. Here, "Li2O+Na2O+K2O" refers to the combined amount of Li2O, Na2O, and K2O. "MgO+CaO+SrO+BaO" refers to the combined amount of MgO, CaO, SrO, and BaO. Here, "strain point" refers to the value measured according to the ASTMC336 method.

[0011] The glass of the present invention restricts the content of Al2O3 to 11 mol% or more, the content of B2O3 to 3 mol% or less, and the content of Li2O+Na2O+K2O to 3 mol% or less in its glass composition. By doing so, the strain point is significantly increased, and the heat resistance of the glass substrate can be greatly improved.

[0012] Furthermore, the glass of the present invention contains 5 to 25 mol% of MgO + CaO + SrO + BaO in its glass composition. This allows for an increase in the coefficient of thermal expansion while simultaneously improving resistance to devitrification.

[0013] Second, the glass of the present invention preferably has a B2O3 content of less than 1 mol%.

[0014] Third, the glass of the present invention preferably has a content of Li2O + Na2O + K2O of 0.2 mol% or less.

[0015] Fourth, the glass of the present invention preferably has a molar ratio (MgO + CaO + SrO + BaO) / Al2O3 of 0.5 to 5. Here, "(MgO + CaO + SrO + BaO) / Al2O3" is the value obtained by dividing the total amount of MgO, CaO, SrO, and BaO by the Al2O3 content.

[0016] Fifth, the glass of the present invention preferably has a molar ratio of MgO / (MgO + CaO + SrO + BaO) of less than 0.5. Here, "MgO / (MgO + CaO + SrO + BaO)" is the value obtained by dividing the MgO content by the total amount of MgO, CaO, SrO, and BaO.

[0017] Sixth, the glass of the present invention preferably has a thermal expansion coefficient in the temperature range of 30 to 380 °C of 40×10 -7 / °C or more. Here, the "thermal expansion coefficient in the temperature range of 30 to 380 °C" refers to the average value measured by a dilatometer.

[0018] Seventh, the glass of the present invention preferably has a strain point of 800 °C or more.

[0019] Eighth, the glass of the present invention preferably has a (temperature - strain point at 10 2.5 dPa·s) of 900 °C or less. Here, the "temperature at a high-temperature viscosity of 10 2.5 dPa·s" refers to the value measured by the platinum ball pulling-up method.

[0020] Ninth, the glass of the present invention preferably has a temperature at a viscosity of 10 2.5 dPa·s of 1750 °C or less.

[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 growing semiconductor crystals. [Modes for carrying out the invention]

[0023] The glass of the present invention contains, in molar percentages, SiO2 55-80%, Al2O3 11-30%, B2O 30-3%, Li2O+Na2O+K2O 0-3%, and MgO+CaO+SrO+BaO 5-35%. The reasons for the restrictions on the content of each component as described above are explained below. In the descriptions of each component, the percentages below refer to molar percentages. It refers to.

[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. The preferred upper limit range is 30% or less, 25% or less, 20% or less, 18% or less, 17% or less, and especially 16% or less. If the Al2O3 content is too low, the strain point tends to decrease, and the high-temperature viscosity tends to increase, leading to a decrease in meltability. On the other hand, if the Al2O3 content is too high, devitrified crystals containing Al2O3 tend to form.

[0026] From the viewpoint of achieving both a high strain point and high resistance to devitrification, 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. 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 will decrease significantly.

[0028] The preferred upper limits for Li2O+Na2O+K2O are 3% or less, 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, the properties of the semiconductor crystal formed on the glass may deteriorate. The preferred upper limits for Li2O, Na2O, and K2O are 3% or less, 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, and especially 5% 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 decrease the liquid phase viscosity and significantly lower the strain point. MgO has the effect of increasing the coefficient of thermal expansion, but among alkaline earth oxides, this effect is the smallest.

[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 mellowness tends to decrease. On the other hand, if the CaO content is too high, the liquidus temperature rises, and devitrified crystals tend to form in the glass. Compared to other alkaline earth oxides, CaO has a greater effect in improving liquidus viscosity and mellowness without lowering the strain point, and it also has a greater effect in increasing the coefficient of thermal expansion than MgO.

[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, making it easier for devitrification crystals to form in the glass, and also tends to decrease mellowness. Furthermore, when the SrO content is high in the presence of CaO, the resistance to devitrification tends to decrease. Note that SrO has a greater effect on increasing the coefficient of thermal expansion than MgO or CaO.

[0033] The preferred lower limit range for BaO is 0%, 3%, 4%, 5%, 6%, 7%, and especially 8% 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, making it easier for devitrified crystals to form in the glass. It also tends to decrease mellowness. Among alkaline earth metal oxides, BaO has the greatest effect in increasing the thermal expansion coefficient and strain point.

[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.

[0036] Considering the balance between strain point and meltableness, the lower limit of the molar ratio (MgO+CaO+SrO+BaO) / Al2O3 is preferably 0.5 or higher, 0.6 or higher, 0.7 or higher, and particularly 0.8 or higher, and the upper limit is preferably 5.0 or lower, 4.0 or lower, 3.0 or lower, 2.0 or lower, 1.5 or lower, 1.2 or lower, and particularly 1.1 or lower.

[0037] The molar ratio MgO / (MgO+CaO+SrO+BaO) is preferably 0.6 or less, less than 0.5, 0.4 or less, 0.3 or less, 0.2 or less, and particularly 0.1 or less. 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 to have a low MgO content among alkaline earth metal oxides.

[0038] 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 small ionic radii does not become large, 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].

[0039] 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 large, 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].

[0040] In addition to the components listed above, the following components may also be introduced into the glass composition.

[0041] 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%.

[0042] 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.

[0043] 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%.

[0044] 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%.

[0045] 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.

[0046] 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.

[0047] 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%.

[0048] 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%.

[0049] 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.

[0050] The content of rare earth oxides (oxides of 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, less than 0.5%, and particularly less than 0.1%. In particular, the content of La2O3 + Y2O3 is preferably less than 2%, less than 1%, less than 0.5%, and particularly less than 0.1%. The content of La2O3 is preferably less than 2%, less than 1%, less than 0.5%, and particularly less than 0.1%. If the content of rare earth oxides is too high, batch costs tend to increase. Note that "Y2O3 + La2O3" refers to the combined amount of Y2O3 and La2O3.

[0051] The glass of the present invention preferably has the following properties.

[0052] The density is preferably 3.20 g / cm³. 3 Below 3.00g / cm 3 Below, 2.90g / cm 3 The following, in particular, is 2.80 g / cm³. 3The following is true. If the density is too high, it becomes difficult to achieve weight reduction of electronic devices.

[0053] The coefficient of thermal expansion in the temperature range of 30 to 380 °C is preferably 40×10 -7 / °C or more, 42×10 -7 / °C or more, 44×10 -7 / °C or more, 46×10 -7 / °C or more, particularly 48×10 -7 ~80×10 -7 / °C is preferable. If the coefficient of thermal expansion in the temperature range of 30 to 380 °C is too low, the coefficients of thermal expansion of the semiconductor crystal (e.g., nitride semiconductor crystal) and the glass substrate do not match, and the glass substrate is likely to warp or cracks are likely to occur in the semiconductor crystal.

[0054] The strain point is preferably above 700 °C, 750 °C or more, 780 °C or more, 800 °C or more, 810 °C or more, 820 °C or more, particularly preferably 830 to 1000 °C. If the strain point is too low, the heat treatment temperature cannot be increased, and it becomes difficult to enhance the semiconductor characteristics of the semiconductor crystal.

[0055] The SiO2 - Al2O3 - RO (RO refers to alkaline earth metal oxide) - based glass according to the present invention is generally difficult to melt. Therefore, improving the meltability becomes an issue. Enhancing the meltability reduces the defect rate due to bubbles, foreign substances, etc., and thus 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, it becomes difficult to promote defoaming in the melting process. Therefore, the temperature at 10 2.5 dPa·s is preferably 1750 °C or less, 1700 °C or less, 1680 °C or less, 1670 °C or less, 1650 °C or less, particularly 1630 °C or less. Note that the temperature at 10 2.5 dPa·s corresponds to the melting temperature, and the lower this temperature is, the better the meltability.

[0056] (The temperature - strain point at 10 2.5 dPa·s) is preferably 900 °C or less, 850 °C or less, particularly 800 °C or less from the viewpoint of achieving both a high strain point and a low melting temperature.

[0057] 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 when glass powder that 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 a platinum sphere. This refers to the value measured using the pull-up method.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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 (%) [Examples]

[0063] The present invention will be described in detail below based on the following examples. Note that the following examples are merely illustrative. The present invention is not limited in any way to the following examples.

[0064] Tables 1-4 show examples of the present invention (samples No. 1-63).

[0065] [Table 1]

[0066] [Table 2]

[0067] [Table 3]

[0068] [Table 4]

[0069] 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.

[0070] The density ρ is a value measured by the well-known Archimedes method.

[0071] The thermal expansion coefficient α is the average value measured with a dilatometer in the temperature range of 30 to 380°C.

[0072] The strain point Ps, slow cooling point Ta, and softening point Ts are values ​​measured in accordance with ASTM C336 or ASTM C338.

[0073] 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.

[0074] 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.

[0075] The β-OH value is the value calculated using the above formula.

[0076] As is clear from Tables 1-4, samples No. 1-63 have high strain points and coefficients of thermal expansion, and possess devitrification resistance that allows them to be molded into a flat plate shape. Therefore, samples No. 1-63 are considered suitable as substrates for growing semiconductor crystals (e.g., nitride semiconductor crystals, particularly gallium nitride-based semiconductor crystals) at high temperatures. [Industrial applicability]

[0077] The glass of the present invention has a high strain point and thermal expansion coefficient, and possesses good resistance to devitrification. Therefore, the glass of the present invention is suitable not only as a substrate for fabricating semiconductor crystals at high temperatures, but also as a substrate for displays such as OLED displays and liquid crystal displays, and is particularly suitable as a substrate for displays driven by LTPS and oxide TFTs.

Claims

1. The glass composition is SiO in mol%. ２ 55-73%, Al ２ O ３ 13-17%, B ２ O ３ 0-1%, Li ２ O + Na ２ O+K ２ A glass characterized by containing 0-3% O, 4-7.5% CaO, 2.5-8.5% BaO, and 14-30% MgO + CaO + SrO + BaO, having a liquidus temperature of 1450°C or lower and a strain point higher than 700°C.

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

3. Li ２ O + Na ２ O+K ２ The glass according to claim 1 or 2, characterized in that the O content is 0.2 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 0.5 to 5.

5. The glass according to claim 1 or 2, characterized in that the molar ratio MgO / (MgO+CaO+SrO+BaO) is less than 0.

5.

6. The coefficient of thermal expansion in the temperature range of 30 to 380°C is 40 × 10⁻⁶. －７ The glass according to claim 1 or 2, characterized in that it is above / ℃.

7. The glass according to claim 1 or 2, characterized in that its strain point is 800°C or higher.

8. (10 ２．５ The glass according to claim 1 or 2, characterized in that the temperature-strain point (dPa·s) is 900°C or less.

9. 10 ２．５ The glass according to claim 1 or 2, characterized in that the temperature at which the viscosity of dPa·s is 1750°C or lower.

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

11. The glass according to claim 1 or 2, characterized in that it is used as a substrate for producing semiconductor crystals.

Images