TW201936533A - Glass substrate and method for manufacturing same - Google Patents

Abstract

The present invention addresses the technical problem of providing: a glass substrate which, because of having a small heat shrinkage rate, is suitable for a high-definition display substrate and which is unlikely to induce charge detachment; and a method for manufacturing such a glass substrate. The glass substrate according to the present invention is characterized by comprising, by mass percentage, 50-70% of SiO2, 10-25% of Al2O3, at least 0% but less than 3% of B2O3, 0-10% of MgO, 0-15% of CaO, 0-10% of SrO, 0-15% of BaO, and 0.005-0.3% of Na2O, and having a [beta]-OH value of less than 0.18/mm and a strain point of at least 735 DEG C.

Description

Glass substrate and method of manufacturing same

The present invention relates to a glass substrate which is suitable for a high-definition display and a method of manufacturing the same, which is less likely to cause electrostatic charging even after peeling after contact with other members.

Glass has been widely used as a substrate for a flat panel display such as a liquid crystal display, a hard disk, a filter, a sensor, or the like. In recent years, in addition to the conventional liquid crystal displays, high-definition displays such as low-temperature polysilicon TFTs or organic ELs have been actively developed in the industry, and some have been put into practical use.

For the glass substrate used for the high-definition display, the following characteristics (1) to (5) are particularly required.

(1) is an alkali-free glass. That is, when the content of the alkali metal oxide in the glass substrate is large, alkali ions are diffused into the semiconductor material which has been formed during the heat treatment, and the characteristics of the film are deteriorated.
(2) The heat shrinkage rate is low and the thermal stability is excellent. That is, the glass substrate is heat-treated to several hundred degrees in the steps of film formation, annealing, and the like. At the time of heat treatment, if the glass substrate is thermally shrunk, pattern shift or the like is likely to occur. For example, in the manufacturing step of the low-temperature polysilicon TFT, there is a heat treatment step of 400 to 600 ° C, in which the glass substrate is thermally shrunk and dimensional changes occur. If the size change is large, the pixel pitch of the TFT is shifted, which causes display failure. Further, in the case of the organic EL, even if there is a slight dimensional change, there is a problem of display failure, and therefore a glass substrate having an extremely low heat shrinkage rate is required.
(3) In order to suppress the abnormality due to the deflection of the glass substrate, the Young's modulus or the Young's modulus is higher.
(4) From the viewpoint of the production of glass, it is excellent in meltability or resistance to devitrification.
(5) The chemical resistance or etching performance required in the manufacturing steps of the display.

Patent Document 1 discloses an alkali-free glass substrate suitable for a high-definition display.
[Previous Technical Literature]
[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2016-183091

[The problem that the invention wants to solve]

As described above, the glass substrate used for the display uses an alkali-free glass substrate containing no alkali metal oxide, but there is a problem that charging with static electricity causes a problem. The glass which is originally an insulator is very easy to be charged, and the alkali-free glass is particularly easy to be charged, and there is a tendency that the static electricity that is temporarily charged does not escape and is maintained. In the manufacturing steps of a liquid crystal display or the like, charging of the glass substrate is caused in various steps, and charging due to peeling of the glass substrate and the metal or insulator flat plate in the film forming step or the like is referred to as peeling electrification. The stripping of the glass substrate occurs not only in the step of atmospheric pressure, but also in the step of etching the film on the surface of the substrate or a vacuum such as a film forming step. A discharge occurs when a conductive substance approaches a charged glass substrate. Further, since the voltage of the charged static electricity is as large as several 10 kV, the element or the electrode wire on the surface of the glass substrate or the glass substrate itself is destroyed (insulation breakdown or electrostatic breakdown) due to discharge, which causes display failure. Among the liquid crystal displays, in particular, a low-temperature polycrystalline germanium TFT display has fine semiconductor elements or electronic circuits such as thin film transistors formed on the surface of the glass substrate, but this element or circuit is extremely weak against static electricity, which causes a problem in particular. Moreover, it also attracts dust present in the charged environment and causes the surface contamination of the substrate.

As a countermeasure against static electricity of a glass substrate, a method of neutralizing electric charges by using an ionizer, or raising the temperature in the environment, and discharging the accumulated electric charge into the air is known. However, these countermeasures are not only the cause of the increase in cost, but also because there are many places where there is a charge in the step, so there is a problem that it is difficult to give an effective countermeasure. Further, these methods cannot be used in a vacuum process such as a plasma process. Therefore, for a flat panel display represented by a liquid crystal display, a glass substrate which is not easily charged is strongly required.

A technical object of the present invention is to provide a glass substrate which is suitable as a high-definition display substrate because of its low heat shrinkage rate and which is less likely to cause peeling electrification.
[Technical means to solve the problem]

The glass substrate of the present invention to solve the above problems is characterized by containing 50 to 70% of SiO ₂ , 10 to 25% of Al ₂ O ₃ , 0% or more and less than 3% of B ₂ by mass percentage. O ₃ , 0 to 10% of MgO, 0 to 15% of CaO, 0 to 10% of SrO, 0 to 15% of BaO, and 0.005 to 0.3% of Na ₂ O, and the β-OH value is less than 0.18/ Mm, the strain point is above 735 °C.

Moreover, the method for producing a glass substrate of the present invention is characterized by comprising a raw material preparation step of preparing a glass batch which is 50% to 70% by mass of SiO ₂ and 10 to 25% by mass. Al ₂ O ₃ , 0% or more and less than 3% of B ₂ O ₃ , 0 to 10% of MgO, 0 to 15% of CaO, 0 to 10% of SrO, 0 to 15% of BaO, and 0.005~ a glass of 0.3% Na ₂ O; a melting step of melting the glass batch in an electric melting furnace; a forming step of forming the molten glass into a plate shape; and a slow cooling step of slab-shaped glass Slow cooling in a slow cooling furnace; and a processing step of cutting the slow-cooled sheet glass into a specific size; and the manufacturing method obtains a β-OH value of less than 0.18/mm and a strain point of 735 ° C or more. glass substrate.

According to the findings of the present inventors, the lower the β-OH value of the alkali-free glass substrate, the lower the heat shrinkage rate, but if the β-OH value is less than 0.18/mm, it is significantly charged. According to the present invention, although the β-OH value is less than 0.18/mm, since it contains 0.005 mass% or more of Na ₂ O having a function of lowering the specific resistance of the glass, charging of the glass substrate can be suppressed. On the other hand, when a glass containing a large amount of B ₂ O ₃ contains Na ₂ O, B ₂ O _{3 is} easily volatilized as a sodium compound when the glass is melted. Therefore, in the present invention, B ₂ O _{3 is} limited to less than 3% by mass, and volatilization of B ₂ O ₃ at the time of glass melting can be suppressed, and the amount of Na ₂ O in the glass can be stabilized. Thereby, a glass substrate having a low heat shrinkage rate and being difficult to charge can be stably obtained.
In addition, the "β-OH value" is a value obtained by measuring the transmittance of glass using FT-IR (Fourier Transform Infrared Radiation) and using the following formula.
β-OH value = (1/X) log (T1/T2)
X: glass thickness (mm)
T1: transmittance at a reference wavelength of 3846 cm ^-1 (%)
T2: Minimum transmittance (%) near the hydroxyl absorption wavelength of 3600 cm ^-1

As a method of lowering the β-OH value of the glass substrate in the present invention, the following methods can be mentioned. (1) Select a glass batch with a lower water content (a glass material having a smaller water content, or a cullet which is pulverized by crushing a glass body having a small water content). (2) A component (Cl, SO ₃ or the like) having an effect of reducing the amount of water in the glass is added. (3) The amount of water in the atmosphere in the furnace is lowered. (4) N _{2 is introduced} into the molten glass. (5) A small melting furnace is used. (6) Increase the flow rate of the molten glass. (7) An electric melting furnace is used.

When the glass substrate of the present invention is produced as described above, from the viewpoint of lowering the β-OH value, it is preferred to use a glass batch having a lower water content as much as possible, and to use an electric melting furnace. When the glass batch is melted by using an electric melting furnace, since the moisture content of the atmosphere due to combustion of the gas in the melting furnace or the like is suppressed, the moisture in the molten glass is easily made compared to the gas burning furnace. The amount is reduced. Therefore, the β-OH value of the glass produced by the electric melting furnace is lowered. Further, as the β-OH value decreases, the strain point of the glass increases, and the glass substrate having a lower heat shrinkage rate is more easily obtained. The electric melting furnace is preferably a pure electric melting furnace that does not use a burner, but may be an electric melting furnace equipped with a burner or a heater for assisting radiant heating in the initial stage of melting.

In the present invention, the heat shrinkage rate of the glass substrate is preferably 20 ppm or less, 15 ppm or less, 12 ppm or less, 10 ppm or less, 9 ppm or less, 8 ppm or less, 7 ppm or less, 6 ppm or less, or particularly 5 ppm or less. . However, when the heat shrinkage ratio of the glass substrate is 0 ppm, the productivity is remarkably lowered, so it is preferably 1 ppm or more, 2 ppm or more, and particularly 3 ppm or more. Further, the deviation of the heat shrinkage ratio of the glass substrate from the target value is preferably ±1.0 ppm or less, particularly ±0.5 ppm or less. When the heat shrinkage rate of the glass substrate is high, the display failure of the display of the low-temperature polycrystalline TFT or the organic EL is liable to occur, and if the variation in the heat shrinkage ratio of the glass substrate is large, the display substrate cannot be stably produced. In order to reduce the variation in the heat shrinkage rate of the glass substrate, the water content of the glass raw material may be adjusted, or the cooling rate of the slow cooling step may be adjusted.

The method for forming the glass substrate of the present invention is not particularly limited, and from the viewpoint of extending the slow cooling step, the floating method is preferable, and the surface quality of the glass substrate is improved or the thickness thereof is reduced. Preferably, the down-draw method, especially the overflow down-draw method. In the overflow down-draw method, the surface of the glass substrate which is to be the front side and the back surface is not in contact with the molded body, but is formed in a state of a free surface. Therefore, it is possible to obtain a glass substrate in which the central portion in the thickness direction is an overflow confluent surface and both surfaces are flame-polished surfaces. Thereby, a glass substrate which is not polished and which is excellent in surface quality (small surface roughness or undulation) can be produced at low cost.

In the present invention, when the down-draw method is employed, the length (height difference) of the slow cooling furnace is preferably 3 m or more. The slow cooling step is a step of removing the strain of the glass substrate. The longer the slow cooling furnace, the easier it is to adjust the cooling rate of the sheet glass, and the more easily the heat shrinkage rate of the glass substrate is reduced. Therefore, the length of the slow cooling furnace is preferably 5 m or more, 6 m or more, 7 m or more, 8 m or more, 9 m or more, and particularly 10 m or more.

In the present invention, the cooling rate of the plate glass in the slow cooling step is preferably from 50 to 1000 ° C / min, from 100 to 1000 ° C / min, 100 in the temperature range from the slow cooling point to (slow cooling point - 100 ° C). Average cooling rate of ~800 ° C / min, 300 ° C / min ~ 1000 ° C / min. The heat shrinkage rate of the glass substrate also varies depending on the cooling rate when the sheet glass is slowly cooled. That is, the heat shrinkage rate of the glass substrate which is rapidly cooled becomes high, and the heat shrinkage rate of the glass substrate which is slowly cooled by the contrary becomes low.

In the present invention, the slow-cut sheet glass is subjected to a cutting process. That is, the formed plate-shaped glass (glass ribbon) is cut into a specific size. Thereafter, the end face grinding process or the end face grinding process may be performed in order to prevent breakage of the self-end face. Preferably, the glass substrate thus obtained has a short side of 1500 mm or more and a long side of 1850 mm or more. That is, the larger the size of the glass substrate, the higher the production efficiency of the glass substrate, so the short side is preferably 1950 mm or more, 2200 mm or more, 2800 mm or more, especially 2950 mm or more, and the long side is preferably 2250 mm or more. , 2500 mm or more, 3000 mm or more, especially 3400 mm or more.

In the present invention, the thickness of the glass substrate is preferably 0.7 mm or less, 0.6 mm or less, 0.5 mm or less, or particularly 0.4 mm or less. The smaller the thickness, the more lightweight the glass substrate can be, and the more suitable it is for a mobile display substrate. However, if the thickness of the glass substrate is too small, it is liable to be damaged by peeling and charging, and therefore it is preferably 0.1 mm or more and further 0.2 mm or more.

In order to further suppress the peeling electrification of the glass substrate of the present invention, it is preferable that at least one surface is a fine uneven surface. The surface shape of the fine uneven surface may be such that the surface roughness Ra is 0.1 to 10 nm. As a method for making the surface of the glass substrate into a fine uneven surface, a method of chemically polishing using a polishing apparatus, or applying an etching liquid to a glass substrate, or a method of chemical etching by spraying an etching gas may be employed. When the latter chemical etching is used, it is not easy to adhere the glass frit or the like to the glass substrate, and it is preferable to be able to clean the surface. Since the glass substrate of the present invention is less likely to cause peeling electrification, even when fine irregularities are formed on the surface thereof, the processing time can be shortened and productivity can be improved.
[Effects of the Invention]

According to the present invention, it is possible to stably obtain a glass substrate which is suitable as a high-definition display substrate because of a low heat shrinkage rate and which is less likely to cause peeling electrification.

In the present specification, the numerical range represented by "~" means a range in which the numerical values described before and after "~" are respectively included as the minimum value and the maximum value.
The glass substrate of the present invention contains 50 to 70% of SiO ₂ , 10 to 25% of Al ₂ O ₃ , 0% or more and less than 3% of B ₂ O ₃ , 0 to 10% of MgO, and 0% by mass. ~15% CaO, 0~10% SrO, 0~15% BaO, and 0.005~0.3% Na ₂ O. The reason for limiting the content of each glass constituent component as described above will be described below. In addition, the % of each component below shows the mass % unless otherwise indicated.

When the content of SiO ₂ is small, the chemical resistance, particularly the acid resistance, is liable to lower, and the strain point is liable to lower. Further, the density is increased, and it is difficult to reduce the weight of the glass substrate. The density of the glass is preferably less than 2.70 g/cm ³ and further less than 2.65 g/cm ³ . On the other hand, when the content of SiO ₂ is increased, the high-temperature viscosity is increased, the meltability is liable to be lowered, and it takes time in the case of etching. Further, precipitation of SiO ₂ -based crystals, in particular, vermiculite, tends to lower the liquidus viscosity, that is, the devitrification resistance is liable to lower. Therefore, SiO _{2 is} preferably 50% or more, 55% or more, 58% or more, 60.5% or more, and further 61% or more, and preferably 70% or less, 65% or less, 64% or less, 63.5% or less, and 63%. Hereinafter, it is 62.5% or less, and further 62% or less.

When the content of Al ₂ O ₃ is small, the strain point is lowered, the heat shrinkage rate is increased, and the Young's modulus is lowered, and the glass substrate is easily bent. On the other hand, when the content of Al ₂ O ₃ is increased, the resistance to BHF (Buffered Hydrogen Fluoride) is lowered, white turbidity is likely to occur on the surface of the glass, and crack resistance is lowered, and breakage is likely to occur. Further, SiO ₂ -Al ₂ O ₃ -based crystals, particularly mullite, are precipitated in the glass, and the liquidus viscosity is liable to lower. Therefore, Al ₂ O _{3 is} preferably 10% or more, 13% or more, 15% or more, 16% or more, 17% or more, 17.5% or more, and further 18% or more, and preferably 25% or less and 23% or less. 21% or less, 20% or less, 19% or less, 19.7% or less, and further 19.5% or less.

B ₂ O ₃ functions as a flux to lower the viscosity and improve the meltability. When the content of B ₂ O ₃ is increased, the molten glass is volatilized, and the glass component is easily changed. Further, the more the content of B ₂ O ₃ is, the lower the strain point is, and the more the heat resistance or the acid resistance is lowered. Further, the Young's modulus is lowered, and the amount of deflection of the glass substrate is likely to be large. Therefore, B ₂ O _{3 is} preferably less than 3%, 2% or less, 1.7% or less, 1.5% or less, 1.4% or less, 1% or less, and more preferably substantially not contained. However, from the viewpoint of improving the meltability and preventing the decrease in BHF resistance or crack resistance, it may contain 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and further 0.5% or more of B ₂ O. ₃ .

As described above, the β-OH value of the glass is susceptible to the moisture contained in the glass batch fed to the glass melting furnace, and in particular, the glass material which becomes the boron source is hygroscopic and contains crystal water. Therefore, it is easy to bring moisture into the glass. Therefore, the more the content of B ₂ O _{3 in} the glass is decreased, the more the β-OH value of the glass is easily lowered. Further, as the β-OH value decreases, the strain point of the glass increases, and the heat shrinkage rate of the glass substrate is more easily lowered. For the above reasons, in the present invention, it is preferred to reduce B ₂ O ₃ as much as possible, and it is preferable that substantially no B ₂ O ₃ is contained. Here, the term "substantially does not contain B ₂ O _{3 "} refers to the raw material, and does not intentionally contain B ₂ O ₃ , and does not negate the incorporation of impurities. Specifically, it means that the content of B ₂ O ₃ is 0.1% or less.

MgO is a component that lowers the high-temperature viscosity and improves the meltability, and significantly increases the Young's modulus component among the alkaline earth metal oxides. However, if it is introduced excessively, SiO ₂ -based crystals, especially vermiculite, are precipitated. The liquidus viscosity is easy to decrease. Further, MgO is easily reacted with BHF to form a component of the product. When the content of MgO is small, the above effects are not easily obtained, and when MgO is increased, the devitrification resistance or the strain point is liable to lower. Therefore, the content of MgO is preferably 10% or less, 9% or less, 8% or less, 6% or less, 5% or less, 4% or less, 3.5% or less, or particularly 3% or less. Further, it is preferably 1% or more, 1.5% or more, and particularly preferably 2% or more.

The CaO system does not lower the strain point and lowers the high temperature viscosity, and the composition of the melt is remarkably improved. Further, among the alkaline earth metal oxides, since the raw materials are introduced relatively inexpensively, the raw materials are reduced in cost. If the content of CaO is small, the above effects are not easily obtained. On the other hand, if the content of CaO is too large, the glass is easily devitrified and the coefficient of thermal expansion is liable to become high. Therefore, the content of CaO is preferably 15% or less, 12% or less, 11% or less, 8% or less, or particularly 6% or less. Further, it is preferably 1% or more, 2% or more, 3% or more, 4% or more, and particularly preferably 5% or more.

SrO suppresses the phase separation of the glass and improves the resistance to devitrification. Further, it is a component which does not lower the strain point, lowers the high-temperature viscosity, improves the meltability, and suppresses an increase in the liquidus temperature. When the content of SrO is small, the above effects are not easily obtained. On the other hand, when the content of SrO is increased, the devitrified crystal of bismuth ruthenate is easily precipitated, and the devitrification resistance is liable to lower. Therefore, the content of SrO is preferably 10% or less, 7% or less, 5% or less, 4% or less, or particularly 3% or less. Further, it is preferably 0.1% or more, 0.2% or more, 0.3% or more, 0.5% or more, 1.0% or more, and particularly preferably 1.5% or more.

The BaO system significantly improves the resistance to devitrification. If the content of BaO is small, the above effects are not easily obtained. On the other hand, if the content of BaO is increased, the density becomes too high, and the meltability is liable to lower. Further, it is easy to precipitate devitrified crystals containing BaO, and the liquidus temperature tends to rise. Therefore, the content of BaO is preferably 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, 10.5% or less, 10% or less, 9.5% or less, or particularly 9% or less. Further, it is preferably 1% or more, 3% or more, 4% or more, 5% or more, 6% or more, and particularly preferably 7% or more.

Na ₂ O is a component that lowers the specific resistance of glass. When the content of Na ₂ O is small, it is difficult to enjoy the above effects. On the other hand, when the content of Na ₂ O is increased, alkali ions are diffused into the semiconductor material which has been formed during the heat treatment, and the characteristics of the film are deteriorated. Therefore, Na ₂ O is preferably 0.005% or more, 0.008% or more, 0.01% or more, 0.02% or more, 0.025% or more, 0.03% or more, further 0.05% or more, and preferably 0.3% or less and further 0.2% or less.

K ₂ O may also be added as an alkali metal oxide other than Na ₂ O. K ₂ O is also a component that lowers the specific resistance of the glass. If the content of K ₂ O is small, the above effects are not easily obtained. On the other hand, when the content of K ₂ O is increased, alkali ions are diffused into the semiconductor material which has been formed during the heat treatment, and the characteristics of the film are deteriorated. Therefore, K ₂ O is preferably 0.001% or more, 0.002% or more, 0.005% or more, 0.01% or more, 0.02% or more, 0.025% or more, 0.03% or more, further 0.05% or more, and preferably 0.3% or less, and further 0.2% or less. K ₂ O can be contained more than Na ₂ O.

Further, Li ₂ O which is an alkali metal oxide other than Na ₂ O or K ₂ O can be appropriately added. However, if the content of the alkali metal oxide is increased, the alkali ions may diffuse into the film-formed semiconductor material during the heat treatment, resulting in deterioration of the characteristics of the film, so the total amount of the alkali metal oxide (Na ₂ O, The total amount of Li ₂ O and K ₂ O is preferably set to 0.4% or less.

In the present invention, the glass substrate can contain the following components in addition to the above components.

The glass substrate of the present invention preferably contains 0.005 to 0.1% of Fe ₂ O ₃ . Similarly to Na ₂ O, Fe ₂ O ₃ has a function of lowering the specific resistance of the glass, and further contains a certain amount or more of Fe ₂ O ₃ to further enhance the effect of suppressing charging of the glass substrate. Fe ₂ O _{3 is} preferably contained in an amount of 0.005% or more, 0.008% or more, and particularly preferably 0.01% or more. However, when more than 0.1% of Fe ₂ O ₃ is contained, the transmittance of the glass is lowered, so that the display substrate is not preferable, so Fe ₂ O _{3 is} preferably 0.1% or less.

The glass substrate of the present invention preferably contains 0.001 to 0.5% of SnO ₂ . SnO ₂ has a good clarifying effect in the high temperature region, which increases the strain point and lowers the composition of the high temperature viscosity. Further, in the case of an electric melting furnace using a molybdenum electrode, there is an advantage that the electrode is not etched. On the other hand, when the content of SnO ₂ is increased, the devitrified crystal of SnO ₂ is easily precipitated, and the precipitation of devitrified crystal of ZrO ₂ is easily promoted. Therefore, the content of SnO ₂ is preferably 0.001 to 0.5%, 0.001 to 0.45%, 0.001 to 0.4%, 0.01 to 0.35%, 0.1 to 0.3%, especially 0.15 to 0.3%.

Further, other components which can be contained in the glass substrate of the present invention will be described.
ZnO is a component that improves the meltability. However, if the content of ZnO is increased, the glass is easily devitrified and the strain point is liable to lower. The content of ZnO is preferably 0 to 5%, 0 to 4%, 0 to 3%, especially 0 to 2%.

ZrO ₂ is a component that enhances chemical durability. However, if the content of ZrO ₂ is increased, devitrification and agglomeration of ZrSiO ₄ is liable to occur. The content of ZrO ₂ is preferably 0 to 5%, 0 to 4%, 0 to 3%, especially 0.01 to 2%.

TiO ₂ reduces the high-temperature viscosity and improves the meltability, and suppresses the coloring component due to the exposure effect. However, when the content of TiO ₂ is increased, the glass is colored, and the transmittance is liable to lower. The content of TiO ₂ is preferably 0 to 5%, 0 to 4%, 0 to 3%, 0 to 2%, especially 0 to 0.1%.

The P ₂ O ₅ system increases the strain point and suppresses the precipitation of the devitrified crystal of the alkaline earth aluminosilicate such as anorthite. However, if P ₂ O ₅ is contained in a large amount, the glass is easily phase-separated. The content of P ₂ O ₅ is preferably from 0 to less than 0.15%, from 0 to 1%, and from 0 to 0.1%, and particularly preferably from the viewpoint of facilitating reuse of the glass, it is preferably substantially not contained, specifically In terms of less than 0.01%.

Metal powders such as Cl, F, SO ₃ , C, CeO ₂ , or Al, Si, etc. may contain up to 3% by total. Although As ₂ O ₃ or Sb ₂ O ₃ is useful as a clarifying agent, it is preferably substantially not contained in view of the environment or the prevention of etching of the electrode. Here, the substantially non-containing system means that the total amount of As ₂ O ₃ and Sb ₂ O ₃ is 0.1% or less.

The glass substrate of the present invention has a β-OH value of less than 0.18/mm. As the β-OH value of the glass decreases, the strain point of the glass increases, and the heat shrinkage rate decreases. Therefore, the β-OH value is preferably less than 0.15/mm, 0.12/mm or less, 0.1/mm or less, 0.07/ Below mm, especially below 0.05/mm. However, from the viewpoint of suppressing charging of the glass substrate, the β-OH value is preferably 0.01/mm or more, 0.02/mm or more, and particularly 0.03/mm or more.

The glass substrate of the present invention has a strain point of 735 ° C or higher. In order to lower the heat shrinkage rate of the glass substrate, it is preferable to increase the strain point as much as possible, and it is preferably 740 ° C or higher, 745 ° C or higher, and further 750 ° C or higher. However, as the strain point is increased, the temperature at the time of glass melting or molding becomes higher, and the manufacturing cost of the glass substrate increases. Therefore, the strain point is preferably 800 ° C or lower.

The glass substrate of the present invention preferably has a slow cooling point of 780 ° C or more, 790 ° C or more, 800 ° C or more, 810 ° C or more, and particularly 820 ° C or more, for the same reason as the strain point. However, as the slow cooling point is increased, the temperature at the time of glass melting or molding becomes higher, and the production cost of the glass substrate increases. Therefore, the slow cooling point is preferably 850 ° C or lower and further 840 ° C or lower.

The glass substrate of the present invention preferably has a Young's modulus of 80 GPa or more. The higher the Young's modulus, the smaller the deflection of the glass substrate, and the easier the operation at the time of transportation or packaging. The Young's modulus is preferably 81 GPa or more, 82 GPa or more, 83 GPa or more, 84 GPa or more, and further 85 GPa or more.

The glass substrate of the present invention preferably has a temperature of 1330 ° C or less, 1320 ° C or less, and particularly 1310 ° C or less, corresponding to 10 ^4.5 dPa·s. When the temperature corresponding to 10 ^4.5 dPa·s becomes high, the temperature at the time of molding becomes too high, and the manufacturing yield is liable to lower.

The glass substrate of the present invention preferably has a temperature of 1670 ° C or less, 1660 ° C or less, and especially 1650 ° C or less, corresponding to 10 ^2.5 dPa·s. When the temperature corresponding to 10 ^2.5 dPa·s becomes high, the glass is not easily melted, defects such as bubbles are increased, or the manufacturing yield is liable to be lowered.

The glass substrate of the present invention preferably has a liquidus temperature of less than 1,250 ° C, less than 1,240 ° C, less than 1,230 ° C, especially less than 1,220 ° C. In this case, since the devitrified crystal is less likely to be generated during the production of the glass, it is easily formed into a plate shape by the overflow down-draw method. Thereby, the surface quality of the glass substrate can be improved, and the reduction in the manufacturing yield can be suppressed. From the viewpoint of the enlargement of the glass substrate or the high definition of the display, it is very important to increase the resistance to devitrification of the glass and to suppress the devitrification which may become a surface defect as much as possible.

The glass substrate of the present invention preferably has a viscosity at a liquidus temperature of 10 ^4.9 dPa·s or more, 10 ^5.0 dPa·s or more, 10 ^5.1 dPa·s or more, 10 ^5.2 dPa·s or more, and particularly 10 ^5.3 dPa·s. the above. In this case, since devitrification is less likely to occur during the molding of the glass, it is easy to form into a plate shape by the overflow down-draw method, and the surface quality of the glass substrate can be improved. Further, the viscosity at the liquidus temperature is an index of formability, and the higher the viscosity at the liquidus temperature, the more the formability is improved.

[Examples]
(Example 1)
Tables 1 and 2 show the glass (sample Nos. 1 to 9) and the previous glass (sample No. 10) of the examples of the present invention. In addition, the content of the components other than Na ₂ O, K ₂ O, Fe ₂ O ₃ , and ZrO ₂ in the table is obtained by rounding off the second decimal place.

[Table 1]

[Table 2]

The glass samples of Tables 1 and 2 were produced in the following manner. First, the glass batch obtained by modulating the glass raw material in the form of a composition in the table was placed in a platinum crucible, and then melted at 1600 to 1650 ° C for 24 hours. When the glass batch was melted, it was stirred using a platinum stirrer for homogenization. Then, the molten glass was discharged to a carbon plate and formed into a plate shape, and then slowly cooled at a temperature near the slow cooling point for 30 minutes. The strain point, the slow cooling point, the density, the Young's modulus, the temperature corresponding to 10 ^4.5 dPa·s, the temperature corresponding to 10 ^2.5 dPa·s, the liquidus temperature TL, and the liquid phase were measured for each sample thus obtained. The viscosity ηTL (dPa·s) at the phase temperature was measured for Log ₁₀ ηTL.

Further, the strain points and slow cooling points in Tables 1 and 2 were measured by the method of ASTM (American Society for Testing Materials) C336.

Density is determined using the Archimedes method according to ASTM C693.

The Young's modulus is measured by a bending resonance method according to JIS R1602.

Temperatures corresponding to 10 ^4.5 dPa·s and 10 ^2.5 dPa·s were measured by a platinum ball pulling method.

The liquidus temperature TL is measured at a temperature, that is, a glass powder which has passed through a standard sieve of 30 mesh (500 μm) and remains at 50 mesh (300 μm) is put into a platinum boat at a temperature gradient furnace set at 1100 ° C to 1350 ° C. After holding for 24 hours, the platinum boat was taken out, and the temperature of devitrification (crystal foreign matter) was confirmed in the glass.

Viscosity at liquidus temperature Log ₁₀ ηTL The viscosity ηTL of the glass at the liquidus temperature was measured by a platinum ball pulling method to calculate Log ₁₀ ηTL.

The β-OH value was measured by FT-IR and measured by the following formula.
β-OH value = (1/X) log (T1/T2)
X: glass thickness (mm)
T1: transmittance at a reference wavelength of 3846 cm ^-1 (%)
T2: Minimum transmittance (%) near the hydroxyl absorption wavelength of 3600 cm ^-1

According to Tables 1 and 2, each of the samples Nos. 1 to 9 has a strain point of 735 ° C or higher and a slow cooling point of 785 ° C or higher, so that the glass having a heat shrinkage ratio of 20 ppm or less is easily used. Further, since the Young's modulus is 80.4 GPa or more, it is less likely to be deflected, and since the liquidus temperature TL is 1246 ° C or lower and the viscosity η TL at the liquidus temperature is 10 ^4.9 dPa·s or more, it is less likely to be lost during molding. through. In particular, each sample No. 1, 2, and 7 to 9 has a viscosity ηTL of 10 ^5.2 dPa·s or more at a liquidus temperature, and is therefore suitable for an overflow down-draw method.

(Example 2)
A glass batch was prepared in the same manner as the glass of Sample Nos. 8 and 10 of Table 2. Then, the glass batch is put into an electric melting furnace, melted at 1600 to 1650 ° C, and then the molten glass is clarified and homogenized in a clarification tank and a homogenization tank, and then adjusted to be suitable for forming in a pot. Viscosity. Then, after the molten glass is formed into a plate shape by an overflow pull-down device, the average cooling rate in the temperature range from the slow cooling point to the (slow cooling point -100 ° C) is set to 385 ° C in a slow cooling furnace of 5 m in length. /min to slow down. Thereafter, the sheet glass was cut and subjected to end surface processing to prepare a glass substrate having a size of 1500 × 1850 × 0.7 mm.

The β-OH value and the heat shrinkage ratio of each of the glass substrates thus obtained were measured. As a result, the glass substrate of sample No. 8 had a β-OH value of 0.1/mm and a heat shrinkage ratio of 10 ppm. On the other hand, the glass substrate of sample No. 10 had a β-OH value of 0.3/mm and a heat shrinkage rate of 25 ppm.

The heat shrinkage rate of the glass substrate was measured by the following method. First, as shown in Fig. 1 (a), a short strip sample G of 160 mm × 30 mm was prepared as a sample of a glass substrate. The water-resistant abrasive paper of #1000 was used for each of the both end portions in the longitudinal direction of the short strip sample G, and the mark M was formed at a position of 20 to 40 mm from the end edge. Thereafter, as shown in FIG. 1(b), the short strip-shaped sample G on which the mark M is formed is folded in two in a direction orthogonal to the mark M to form test pieces Ga and Gb. Further, only one test piece Gb was heated from room temperature (25 ° C) to 500 ° C at 5 ° C / min, held at 500 ° C for 1 hour, and then heat-treated at 5 ° C / min to room temperature. After the heat treatment, as shown in FIG. 1(c), two test pieces Ga and Gb are read by a laser microscope in a state in which the test piece Ga not subjected to heat treatment and the test piece Gb subjected to heat treatment are arranged side by side. The positional deviation amount (ΔL1, ΔL2) of the mark M is calculated, and the heat shrinkage rate is calculated according to the following formula. Furthermore, l ₀ in the formula is the distance between the initial marks M.
Heat shrinkage rate = [{ΔL1(μm) + ΔL2(μm)} × 10 ³ ] / l ₀ (mm) (ppm)

Next, the glass substrates of the sample Nos. 8 and 10 were evaluated for peeling electrification using the apparatus shown in Fig. 2 .

As shown in Fig. 2 (a), the support table 1 of the glass substrate G is provided with a pad 2 made of Teflon (registered trademark) which supports the four corners of the glass substrate G. The support table 1 is provided with a metal aluminum platform 3 capable of lifting and lowering, and the glass substrate G is peeled off by bringing the glass substrate G into contact with the stage 3 as shown in FIG. 2(b), thereby allowing the glass substrate G to be peeled off. The glass substrate G is charged. Furthermore, the platform 3 is grounded. Further, a singular or plural number of holes (not shown) are formed in the stage 3, and the holes are connected to a diaphragm type vacuum pump (not shown). When the vacuum pump is driven, air is sucked from the hole of the stage 3, whereby the glass substrate G is vacuum-adsorbed to the stage 3. Further, a surface potentiometer 4 was provided at a position 10 mm above the glass substrate G, whereby the amount of charge generated in the central portion of the glass substrate G was continuously measured. Further, an air gun 5 with an ionizer attached to the glass substrate G is provided, whereby the charging of the glass substrate G can be eliminated.

The stripping electrification of the glass substrate was measured using the apparatus in the following procedure. Furthermore, the experiment was carried out in a clean room at a temperature of 25 ° C and a humidity of 40%. Since the amount of electricity is subject to large changes due to the influence of the atmosphere, especially the humidity in the atmosphere, it is especially necessary to consider the adjustment of the humidity.

(1) The glass substrate G is placed on the support pad 2 of the support table 1.
(2) The static electricity of the glass substrate G is removed by the air gun 5 with the ionizer.
(3) The stage 3 was raised, brought into contact with the glass substrate G, and vacuum-adsorbed, and the stage 3 and the glass substrate G were adhered to each other for 20 seconds.
(4) The glass substrate G is peeled off from the stage 3 by lowering the stage 3, and the amount of charge generated in the central portion of the glass substrate G is continuously measured by the surface potentiometer 4.
(5) A total of five peeling evaluations were continuously performed by repeating the above steps (3) and (4).
The maximum charge amount in each measurement was obtained, and the like was used as the peeling charge amount.

As a result, the peeling charge amount of the glass substrate of sample No. 8 was 1000 V, whereas the peeling charge amount of sample No. 10 was 2000 V large. Further, an etching gas was sprayed on one surface of the glass substrate of sample No. 8, and the surface roughness Ra was made 1 nm, and then the peeling charge amount was measured and found to be 800 V.

1‧‧‧Support Desk

2‧‧‧ pads

3‧‧‧ platform

4‧‧‧ Surface Potentiometer

5‧‧‧Air gun with ionizer

G‧‧‧glass sample (glass substrate)

Ga, Gb‧‧‧ test strip l _{0 the} initial mark distance

M‧‧‧ mark

Offset of ΔL1, ΔL2‧‧‧ mark

1(a) to 1(c) are explanatory views showing a method of measuring the heat shrinkage rate of a glass substrate.

2 is an explanatory view showing an apparatus for measuring the amount of peeling charge of a glass substrate, wherein (a) is an explanatory view showing a state in which the glass substrate is separated from the stage, and (b) is a state in which the glass substrate is placed on the stage. Description of the figure.

Claims (14)

A glass substrate characterized by containing 50 to 70% of SiO ₂ , 10 to 25% of Al ₂ O ₃ , 0% or more and less than 3% of B ₂ O ₃ , and 0 to 10% by mass percentage. MgO, 0~15% CaO, 0~10% SrO, 0~15% BaO, and 0.005~0.3% Na ₂ O, and β-OH value is less than 0.18/mm, strain point is above 735 °C . The glass substrate of claim 1, which contains 0.005 to 0.1% of Fe ₂ O ₃ by mass percentage. The glass substrate of claim 1 or 2, which contains 0.001 to 0.5% of SnO ₂ by mass percentage. The glass substrate according to any one of claims 1 to 3, which has a Young's modulus of 80 GPa or more. The glass substrate according to any one of claims 1 to 4, which has a heat shrinkage ratio of 20 ppm or less. The glass substrate according to any one of claims 1 to 5, which has a short side of 1500 mm or more and a long side of 1850 mm or more. The glass substrate according to any one of claims 1 to 6, which has a thickness of 0.7 mm or less. The glass substrate according to any one of claims 1 to 7, wherein at least one surface thereof is a fine uneven surface. The glass substrate of claim 8 has a surface roughness Ra of a fine uneven surface of 0.1 to 10 nm. A method for producing a glass substrate, comprising: a raw material preparation step of preparing a glass batch, wherein the glass batch is made to contain 50 to 70% of SiO ₂ and 10 to 25% of Al ₂ O by mass percentage. ₃ , 0% or more and less than 3% of B ₂ O ₃ , 0 to 10% of MgO, 0 to 15% of CaO, 0 to 10% of SrO, 0 to 15% of BaO, and 0.005 to 0.3% a method of preparing a glass of Na ₂ O; a melting step of melting the glass batch in an electric melting furnace; a forming step of forming the molten glass into a plate shape; and a slow cooling step of slowly drying the plate-shaped glass a slow cooling in the furnace; and a processing step of cutting the slowly cooled sheet glass into a specific size; and the manufacturing method obtains a glass substrate having a β-OH value of less than 0.18/mm and a strain point of 735 ° C or higher. . The method for producing a glass substrate according to claim 10, wherein the cooling rate of the plate glass in the slow cooling step is from 50 ° C / min to 1000 ° C / min in a temperature range from a slow cooling point to (slow cooling point - 100 ° C) The average cooling rate. A method of producing a glass substrate according to claim 10 or 11, wherein at least one surface is chemically etched. A method of producing a glass substrate according to claim 10 or 11, wherein at least one surface is physically ground. A method of producing a glass substrate according to claim 12 or 13, wherein the surface roughness Ra is set to 0.1 to 10 nm.