KR20200110299A - Glass substrate and its manufacturing method - Google Patents

Abstract

The present invention makes it a technical subject to provide a glass substrate that has a low thermal contraction rate, is suitable as a high-precision display substrate, and is unlikely to cause peeling charge, and a method for producing the same.
The glass substrate of the present invention, by mass percentage, SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 25%, B ₂ O ₃ 0% to less than 3%, MgO 0 to 10%, CaO 0 to 15%, It contains 0 to 10% of SrO, 0 to 15% of BaO, and 0.005 to 0.3% of Na ₂ O, has a β-OH value of less than 0.18/mm, and a distortion point of 735°C or more.

Description

Glass substrate and its manufacturing method

[0001] The present invention relates to a glass substrate that is suitable for high-precision displays, and is difficult to generate static electricity even if it is peeled off after contacting with other members, and a method of manufacturing the same.

[0002] Conventionally, glass has been widely used as a substrate for a flat panel display such as a liquid crystal display, a hard disk, a filter, and a sensor. In recent years, in addition to conventional liquid crystal displays, high-precision displays such as low-temperature polysilicon TFTs and organic ELs have been actively developed, and some have already been put into practical use.

[0003] In particular, the following characteristics (1) to (5) are required for glass substrates used for high-precision displays.

(1) It should be an alkali-free glass. That is, if the content of the alkali metal oxide in the glass substrate is large, alkali ions diffuse into the film-formed semiconductor material during heat treatment, resulting in deterioration of film properties.

(2) Low heat shrinkage and excellent heat stability. That is, the glass substrate is heat-treated at several hundreds of degrees in processes such as film formation and annealing. In the case of heat treatment, when the glass substrate is heat-shrunk, it becomes easy to cause a pattern shift or the like. For example, in the manufacturing process of a low-temperature polysilicon TFT, a heat treatment process of 400 to 600° C. exists, and in this heat treatment process, the glass substrate is thermally contracted, resulting in a size change. If this size change is large, a shift occurs in the pixel pitch of the TFT, which causes display defects. In addition, in the case of organic EL, there is a concern that even a small size change may cause display defects, and a glass substrate having a very low thermal contraction rate is required.

(3) In order to suppress the problem caused by the warping of the glass substrate, the Young's modulus or specific Young's modulus should be high.

(4) From the viewpoint of glass manufacturing, it should be excellent in melting properties and devitrification resistance (耐失透性).

(5) It must have chemical resistance or etching performance required in the manufacturing process of the display.

[0005] Patent Document 1 proposes an alkali-free glass substrate suitable for a high-precision display.

Japanese Patent Laid-Open Publication No. 2016-183091

[0007] As described above, an alkali-free glass substrate that does not contain an alkali metal oxide is used as a glass substrate used for a display, but static electricity may be a problem. Glass, which is originally an insulator, is very easy to be charged, but alkali-free glass is particularly easy to be charged, and once charged static electricity tends to be maintained without escaping. In a manufacturing process of a liquid crystal display or the like, charging of a glass substrate occurs in various processes, and charging that occurs by peeling the glass substrate in contact with a metal or insulator plate in a film forming process or the like is called peeling charging. The peeling charging of the glass substrate occurs not only during a process in the atmosphere under normal pressure, but also during a vacuum process such as a process of etching a thin film on the surface of the substrate or a film formation process. Discharge occurs when a conductive material approaches the charged glass substrate. In addition, since the voltage of the charged static electricity reaches several tens of kV, a breakdown (insulation breakdown or electrostatic breakdown) of an element or electrode wire on the surface of the glass substrate or the glass substrate itself occurs due to discharge, causing display failure. Among liquid crystal displays, in particular, low-temperature polysilicon TFT displays are particularly problematic because fine semiconductor elements such as thin film transistors or electronic circuits are formed on the surface of a glass substrate, and these elements and circuits are very susceptible to electrostatic breakdown. In addition, it attracts dust existing in the charged environment and causes contamination of the substrate surface.

[0008] As an antistatic measure of a glass substrate, a method of neutralizing charges using an ionizer or raising a temperature in an environment to discharge accumulated charges into the air is well known. However, this countermeasure not only increases the cost, but also remains a problem that it is difficult to implement effective countermeasures because there are many places where charging occurs during the process. Also, such means cannot be used during vacuum processes such as plasma processes. Therefore, for applications such as liquid crystal displays and other flat panel displays, there is a strong demand for a glass substrate that is difficult to be charged.

An object of the present invention is to provide a glass substrate having a low thermal contraction rate, suitable as a high-precision display substrate, and less likely to cause peeling and charging.

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

[0011] In addition, the manufacturing method of the glass substrate of the present invention, by mass percentage, SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 25%, B ₂ O ₃ 0% to less than 3%, MgO 0 to 10 %, CaO 0-15%, SrO 0-10%, BaO 0-15%, Na ₂ O A raw material preparation process to prepare a glass batch prepared to be a glass containing 0.005 to 0.3% , Melting process of melting a batch of glass in an electric melting furnace, molding process of molding molten glass into a plate shape, slow cooling process of slow cooling plate-shaped glass in a slow cooling furnace, and slow cooling plate-shaped glass It includes a processing step of cutting to size, characterized by obtaining a glass substrate having a β-OH value of less than 0.18/mm and a distortion point of 735°C or higher.

According to the knowledge of the present inventors, the alkali-free glass substrate, the lower the β-OH value, the lower the thermal contraction rate, but when the β-OH value is less than 0.18/mm, it becomes remarkably easy to be charged. According to the present invention, even though the β-OH value is less than 0.18/mm, since it contains 0.005% by mass or more of Na ₂ O, which has an action of lowering the specific resistance of the glass, it is possible to suppress the charging of the glass substrate. It is possible. On the other hand, if containing Na ₂ O in a glass containing B ₂ O ₃ in a large amount, the B ₂ O ₃ at the time of the molten glass is apt to volatilize as the sodium compound. For this reason, in this invention, B ₂ O ₃ is regulated to less than 3 mass %, and volatilization of B ₂ O _{3 at} the time of melting|melting of glass can be suppressed, and the amount of Na ₂ O in glass can be stabilized. This makes it possible to stably obtain a glass substrate having a low thermal contraction rate and difficult to be charged.

In addition, "β-OH value" refers to a value obtained by measuring the transmittance of the glass using FT-IR, and using the following equation.

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 in the vicinity of 3600 cm ^-1 of the absorption wavelength of hydroxyl groups (%)

[0014] In the present invention, as a method of reducing the β-OH value of a glass substrate, the following method may be mentioned. (1) Select a glass batch with a low water content (a glass raw material with a low water content or a glass cullet in which a glass body with a low water content is finely crushed). (2) Add components (Cl, SO _3, etc.) that have an action of reducing the water content in the glass. (3) The amount of moisture in the atmosphere in the furnace is reduced. (4) N ₂ bubbling is performed in molten glass. (5) Adopt a small melting furnace. (6) Increase the flow rate of the molten glass. (7) Adopt an electric melting furnace.

When manufacturing the glass substrate of the present invention as described above, from the viewpoint of lowering the β-OH value, it is preferable to use a glass batch having a low water content as possible and to use an electric melting furnace. When the glass batch is melted using an electric melting furnace, since the increase in the amount of moisture in the atmosphere due to gas combustion in the melting furnace or the like is suppressed, it is easier to reduce the amount of moisture in the molten glass compared to the gas combustion furnace. For this reason, the β-OH value of the glass manufactured by the electric melting furnace is lowered. Further, as the β-OH value decreases, the distortion point of the glass increases, so that a glass substrate having a low thermal contraction rate can be easily obtained. The electric melting furnace is preferably a complete electric melting furnace without using a burner, but may be an electric melting furnace equipped with a burner or heater for auxiliary radiant heating at the initial stage of melting.

In the present invention, it is preferable that the heat shrinkage of the glass substrate is 20ppm or less, 15ppm or less, 12ppm or less, 10ppm or less, 9ppm or less, 8ppm or less, 7ppm or less, 6ppm or less, particularly 5ppm or less. However, in order to set the thermal contraction rate of the glass substrate to 0 ppm, a significant decrease in productivity is accompanied, so it is preferably 1 ppm or more, 2 ppm or more, and particularly 3 ppm or more. Further, it is preferable that the deviation of the thermal contraction rate of the glass substrate from the target value is ±1.0 ppm or less, particularly ±0.5 ppm or less. When the thermal contraction rate of the glass substrate is high, display defects tend to occur in the display of the low-temperature polysilicon TFT or the organic EL display, and when the variation in the thermal contraction rate of the glass substrate is large, the display substrate cannot be stably produced. In order to reduce the variation in the thermal contraction rate of the glass substrate, the moisture content of the glass raw material may be adjusted or the cooling rate in the slow cooling step may be adjusted.

[0017] The method for forming a glass substrate of the present invention is not particularly limited, but a float method is preferable from the viewpoint of lengthening the slow cooling process, and further improves the surface quality of the glass substrate, or reduces its thickness. From the viewpoint of, the downdraw method, particularly the overflow downdraw method is preferable. In the overflow downdraw method, the surface to be the front and back surfaces of the glass substrate does not contact the molded body, but is molded in a state of being a free surface. For this reason, it is possible to obtain a glass substrate in which the central portion in the thickness direction is an overflow confluence surface, and both (兩) surfaces are fire polished surfaces. Thereby, a glass substrate excellent in surface quality (small surface roughness and waveform) in an unpolished state can be manufactured inexpensively.

In the present invention, when employing the downdraw method, the length of the slow cooling furnace (high and low difference (高低差)) is preferably 3m or more. The slow cooling process is a process for removing distortion of a glass substrate, and the longer the slow cooling furnace is, the easier it is to adjust the cooling rate of the plate-shaped glass, and it becomes easier to reduce the heat shrinkage rate of the glass substrate. Therefore, the length of the slow cooling furnace is preferably 5m or more, 6m or more, 7m or more, 8m or more, 9m or more, particularly 10m or more.

[0019] In the present invention, the cooling rate of the plate-shaped glass in the slow cooling step is 50 to 1000°C/min, 100 to 1000°C/min, 100 to 100°C in the temperature range from the slow cooling point to (slow cooling point-100°C) It is preferably an average cooling rate of 800°C/min and 300°C/min to 800°C/min. The thermal contraction rate of a glass substrate also fluctuates with the cooling rate at the time of slow cooling a plate-shaped glass. That is, the rapidly cooled glass substrate has a higher heat shrinkage rate, whereas the slowly cooled glass substrate has a lower heat shrinkage rate.

In the present invention, cutting processing is performed on the slowly cooled plate-shaped glass. That is, the molded plate-shaped glass (glass ribbon) is cut into a predetermined size. Thereafter, in order to prevent damage from the end surface, an end surface grinding processing or an end surface polishing processing may be performed. It is preferable that the short side of the glass substrate obtained in this way is 1500 mm or more, and the long side is 1850 mm or more. That is, as the size of the glass substrate increases, the production efficiency of the glass substrate improves. Therefore, the short side is preferably 1950 mm or more, 2200 mm or more, 2800 mm or more, particularly 2950 mm or more, and the long side is 2250 mm or more, 2500 mm It is more preferably 3000 mm or more, particularly 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, particularly 0.4 mm or less. As the thickness decreases, the weight of the glass substrate can be reduced, and thus it is suitable for a mobile type display substrate. However, when the thickness of the glass substrate is too small, it becomes liable to be damaged by peeling and charging, and therefore, 0.1 mm or more, and further 0.2 mm or more is preferable.

In order to further suppress the peeling and charging of the glass substrate of the present invention, it is preferable that the surface of at least one side is a fine uneven surface. As the surface shape of the fine uneven surface, the surface roughness Ra may be 0.1 to 10 nm. As a method for making the surface of a glass substrate into a finely uneven surface, a method by physical polishing using a polishing device or a method by chemical etching in which an etching solution is applied to the glass substrate or an etching gas is sprayed may be employed. When the latter chemical etching is employed, glass powder or the like is less likely to adhere to the glass substrate, and since the surface is cleaned, it is preferable. Since the glass substrate of the present invention is inherently unlikely to cause peeling and charging, even when fine irregularities are formed on the surface, the processing time can be shortened and productivity can be improved.

[0023] According to the present invention, it is possible to stably obtain a glass substrate that is suitable as a high-precision display substrate due to a low heat shrinkage rate, and is difficult to cause peeling charging.

1 is an explanatory view showing a method of measuring the thermal contraction rate of a glass substrate.
Fig. 2 is an explanatory diagram showing an apparatus used for measuring the peeling charge amount of a glass substrate, (a) is an explanatory diagram showing a state in which the glass substrate is separated from the table, and (b) is the glass substrate It is an explanatory diagram showing the state placed on the table.

[0025] In the present specification, the numerical range indicated by using "-" means a range including the numerical values before and after "-" as a minimum value and a maximum value, respectively.

The glass substrate of the present invention, by mass percentage, SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 25%, B ₂ O ₃ 0% or more and less than 3%, MgO 0 to 10%, CaO 0 to It contains 15%, SrO 0-10%, BaO 0-15%, and Na ₂ O 0.005-0.3%. The reason for regulating the content of each glass component as described above will be described below. In addition, the% indication of each of the following components indicates mass% unless otherwise specified.

When the content of SiO ₂ decreases, chemical resistance, particularly acid resistance, tends to decrease, and distortion points tend to decrease. Moreover, the density becomes high, and it becomes difficult to achieve weight reduction of a glass substrate. It is preferable that the density of the glass is 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 increases, the high-temperature viscosity increases and the meltability tends to decrease, and it takes time in the case of etching. In addition, SiO ₂ -based crystals, particularly cristobalite, are precipitated to lower the liquidus viscosity, that is, the devitrification resistance tends to decrease. Therefore, SiO ₂ is preferably 50% or more, 55% or more, 58% or more, 60.5% or more, and further 61% or more, and 70% or less, 65% or less, 64% or less, 63.5% or less, 63% or less, 62.5 % Or less, more preferably 62% or less.

[0028] When the content of Al ₂ O ₃ decreases, the distortion point decreases, the thermal contraction rate increases, and the Young's modulus decreases, so that the glass substrate is liable to bend. On the other hand, when the content of Al ₂ O ₃ increases, BHF (buffered hydrofluoric acid) resistance decreases, white turbidity tends to occur on the glass surface, and crack resistance decreases, leading to breakage. Furthermore, SiO ₂ -Al ₂ O ₃ -based crystals, especially mullite, are precipitated in the glass, and the liquidus viscosity tends to decrease. Therefore, Al ₂ O ₃ is preferably 10% or more, 13% or more, 15% or more, 16% or more, 17% or more, and further 18% or more, and 25% or less, 23% or less, 21% or less, 20% or less. , 19% or less, 19.7% or less, and further preferably 19.5% or less.

B ₂ O ₃ is a component that acts as a flux and improves the meltability by lowering the viscosity. When the content of B ₂ O ₃ increases, the molten glass volatilizes and the glass component is liable to fluctuate. Further, as the content of B ₂ O ₃ increases, the distortion point decreases, and heat resistance and acid resistance also tend to decrease. In addition, the Young's modulus decreases, and the amount of warpage of the glass substrate tends to be large. Therefore, it is preferable that B ₂ O ₃ is substantially free of less than 3%, 2% or less, 1.7% or less, 1.5% or less, 1.4% or less, 1% or less, and furthermore. However, from the viewpoint of improving meltability and preventing a decrease in BHF resistance and crack resistance, B ₂ O ₃ may be contained 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, and further 0.5% or more. .

[0030] As described above, the β-OH value of the glass is susceptible to moisture contained in the glass batch that is introduced into the glass melting furnace, and in particular, the glass raw material serving as a boron source has hygroscopicity (吸濕性). In addition, some contain crystal water, so it is easy to bring moisture into the glass. For this reason, as the content of B ₂ O _{3 in} the glass is decreased, the β-OH value of the glass is more likely to decrease. Further, as the β-OH value decreases, the distortion point of the glass becomes higher, and it becomes easier to attain a decrease in the thermal contraction rate of the glass substrate. For the above reasons, in the present invention, it is preferable to reduce B ₂ O ₃ as much as possible, and it is preferable not to contain B ₂ O ₃ substantially. Where it substantially does not contain B ₂ O _3, as a raw material is by a means that not containing B ₂ O _3, it is not to deny the incorporation of impurities from. Specifically, it means that the content of B ₂ O ₃ is 0.1% or less.

[0031] MgO is a component that increases meltability by lowering high temperature viscosity, and among alkaline earth metal oxides, it is a component that significantly increases the Young's modulus, but when introduced in excess, SiO ₂ based crystals, especially cristobalite, are precipitated, resulting in liquidus viscosity It becomes easy to deteriorate. Furthermore, MgO is a component that is easy to react with BHF to form a product. When the content of MgO is small, it becomes difficult to enjoy the above effect, and when the content of MgO is large, devitrification resistance and distortion point tend to decrease. 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, particularly 3% or less. Further, it is preferably 1% or more, 1.5% or more, particularly 2% or more.

CaO is a component that does not lower the distortion point, lowers the high temperature viscosity, and significantly increases the meltability. In addition, among alkaline earth metal oxides, since the raw material to be introduced is relatively inexpensive, it is a component that reduces raw material cost. When the CaO content is reduced, it becomes difficult to enjoy the above effects. On the other hand, when the CaO content is too large, the glass tends to deviate and the coefficient of thermal expansion tends to increase. Therefore, it is preferable that the content of CaO is 15% or less, 12% or less, 11% or less, 8% or less, particularly 6% or less. Further, it is preferably 1% or more, 2% or more, 3% or more, 4% or more, particularly 5% or more.

SrO is a component that increases devitrification resistance by suppressing the powder phase of the glass. In addition, it is a component that lowers the high-temperature viscosity without lowering the distortion point to increase meltability and suppresses an increase in liquidus temperature. When the content of SrO decreases, it becomes difficult to enjoy the above effects. On the other hand, when the content of SrO increases, strontium silicate-based devitrification crystals tend to precipitate, and devitrification resistance tends to decrease. Therefore, it is preferable that the content of SrO is 10% or less, 7% or less, 5% or less, 4% or less, 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, particularly 1.5% or more.

BaO is a component that significantly increases devitrification resistance. When the content of BaO decreases, it becomes difficult to enjoy the above effect. On the other hand, when the content of BaO increases, the density becomes too high and the meltability tends to decrease. Moreover, the devitrification crystal containing BaO is liable to precipitate, and the liquidus temperature is liable 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, particularly 9% or less. Further, it is preferably 1% or more, 3% or more, 4% or more, 5% or more, 6% or more, particularly 7% or more.

Na ₂ O is a component that reduces the specific resistance of the glass. When the content of Na ₂ O decreases, it becomes difficult to enjoy the above effect. On the other hand, when the content of Na ₂ O increases, alkali ions diffuse into the film-formed semiconductor material during heat treatment, causing deterioration of film properties. 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 preferably 0.05% or more, 0.3% or less, and further 0.2% or less. .

As an alkali metal oxide other than Na ₂ O, K ₂ O may be added. K ₂ O is also a component that lowers the specific resistance of glass. When the content of K ₂ O decreases, it becomes difficult to enjoy the above effect. On the other hand, when the content of K ₂ O increases, alkali ions diffuse into the film-formed semiconductor material during heat treatment, resulting in deterioration of film properties. 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, and further 0.05% or more, 0.3% or less, further 0.2% or more. The following are preferable. K ₂ O can be contained more than Na ₂ O.

In addition, it is possible to appropriately add Li ₂ O, which is an alkali metal oxide other than Na ₂ O and K ₂ O. However, if the content of the alkali metal oxide increases, alkali ions diffuse into the film-formed semiconductor material during heat treatment, resulting in deterioration of the film properties, so the total amount of alkali metal oxides (Na ₂ O, Li ₂ O and K ₂ It is preferable that the sum of 0 is 0.4% or less.

[0038] In the present invention, it is possible to contain the following components in addition to the above components in a glass substrate.

The glass substrate of the present invention preferably contains 0.005 to 0.1% Fe ₂ O ₃ . Like Na ₂ O, Fe ₂ O ₃ is a component having an effect of lowering the specific resistance of glass, and by containing Fe ₂ O ₃ in a certain amount or more, the effect of suppressing the charging of the glass substrate is further enhanced. It is preferable to contain Fe ₂ O ₃ at least 0.005%, at least 0.008%, and particularly at least 0.01%. However, if Fe ₂ O ₃ is contained in an amount exceeding 0.1%, the transmittance of the glass is lowered, and thus there is a possibility that it may become unfavorable as a display substrate. Therefore, Fe ₂ O ₃ is preferably 0.1% or less.

The glass substrate of the present invention preferably contains 0.001 to 0.5% SnO ₂ . SnO ₂ is a component that has a good clarification action in a high-temperature region and increases the distortion point and lowers the high-temperature viscosity. In addition, in the case of an electric melting furnace using a molybdenum electrode, there is an advantage that the electrode is not eroded. On the other hand, when the content of SnO ₂ increases, the devitrification crystals of SnO ₂ are liable to precipitate, and the precipitation of the devitrification crystals 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%, particularly 0.15 to 0.3%.

In addition, other components that may be contained in the glass substrate of the present invention will be described.

ZnO is a component that improves the meltability. However, when the content of ZnO increases, the glass is liable to devitrify and the distortion point is liable to decrease. The content of ZnO is preferably 0 to 5%, 0 to 4%, 0 to 3%, particularly 0 to 2%.

ZrO ₂ is a component that enhances chemical durability, but when the content of ZrO ₂ increases, the devitrification of ZrSiO ₄ is likely to occur. The content of ZrO ₂ is preferably 0 to 5%, 0 to 4%, 0 to 3%, particularly preferably 0.01 to 2%.

TiO ₂ is a component that lowers high-temperature viscosity to increase meltability and suppresses coloring due to solarization. When the content of TiO ₂ increases, the glass is colored and the transmittance is liable to decrease. The content of TiO ₂ is preferably 0 to 5%, 0 to 4%, 0 to 3%, 0 to 2%, and particularly 0 to 0.1%.

P ₂ O ₅ is a component that increases the distortion point and suppresses the precipitation of alkaline earth aluminosilicate-based devitrified crystals such as anorthite. However, when P ₂ O ₅ is contained in a large amount, the glass is liable to be powdered. The content of P ₂ O ₅ is preferably 0 to less than 0.15%, 0 to 1%, and 0 to 0.1%, and in particular, from the viewpoint of facilitating the recycling of glass, it is preferably not substantially contained, specifically Is preferably less than 0.01%.

[0046] Metal powders such as Cl, F, SO ₃ , C, CeO ₂ or Al, Si may be contained up to 3% in total amount. Although As ₂ O ₃ and Sb ₂ O ₃ are useful as a clarifying agent, they are preferably substantially free from the viewpoint of preventing erosion of the environment or the electrode. Substantially not contained herein 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 distortion point of the glass increases and the heat shrinkage decreases, so the β-OH value is less than 0.15/mm, 0.12/mm or less, 0.1/mm or less, 0.07/mm or less, especially 0.05/mm or less. It is desirable. However, from the viewpoint of suppressing the 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 distortion point of 735°C or higher. In order to reduce the thermal contraction rate of the glass substrate, it is preferable to raise the distortion point as much as possible, and it is preferable that it is 740 degreeC or more, 745 degreeC or more, and further 750 degreeC or more. However, the higher the distortion point is attempted, the higher the temperature at the time of melting or molding the glass, and the higher the manufacturing cost of the glass substrate, so the distortion point is preferably 800°C or less.

[0049] The glass substrate of the present invention preferably has a slow cooling point of 780°C or higher, 790°C or higher, 800°C or higher, 810°C or higher, particularly 820°C or higher for the same reason as the distortion point. However, the higher the slow cooling point is attempted, the higher the temperature at the time of melting or molding the glass, and the higher the manufacturing cost of the glass substrate, so the slower cooling point is preferably set to 850°C or less, and further to 840°C or less.

[0050] It is preferable that the glass substrate of the present invention has a Young's modulus of 80 GPa or more. The higher the Young's modulus, the smaller the warp of the glass substrate, and the easier the handling at the time of conveyance 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 more preferably 85 GPa or more.

[0051] The glass substrate of the present invention preferably has a temperature corresponding to 10 ^4.5 dPa·s of 1330°C or less, 1320°C or less, and particularly 1310°C or less. When the temperature corresponding to 10 ^4.5 dPa·s increases, the temperature during molding becomes too high and the production yield is liable to decrease.

[0052] The glass substrate of the present invention preferably has a temperature corresponding to 10 ^2.5 dPa·s of 1670°C or less, 1660°C or less, and particularly 1650°C or less. When the temperature corresponding to 10 ^2.5 dPa·s increases, the glass becomes difficult to melt, defects such as bubbles increase, and the manufacturing yield tends to decrease.

The glass substrate of the present invention preferably has a liquidus temperature of less than 1250°C, less than 1240°C, less than 1230°C, and particularly less than 1220°C. In this way, since devitrification crystals are less likely to occur during glass production, it becomes easy to mold into a plate shape by an overflow downdraw method. Thereby, it is possible to improve the surface quality of the glass substrate and to suppress a decrease in the manufacturing yield. From the viewpoint of increasing the size of the glass substrate and the high precision of the display, the significance of improving the devitrification resistance of the glass and suppressing devitrification objects that may become surface defects as much as possible is very significant.

[0054] The glass substrate of the present invention has a viscosity of 10 ^4.9 dPa·s or more, 10 ^5.0 dPa·s 10 ^5.1 dPa·s or more, 10 ^5.2 dPa·s or more, particularly 10 ^5.3 dPa·s or more at a liquidus temperature. It is desirable. In this way, since devitrification is less likely to occur at the time of glass molding, it becomes easy to mold into a plate shape by the overflow downdraw method, and the surface quality of the glass substrate can be improved. Further, the viscosity at the liquidus temperature is an index of moldability, and the higher the viscosity at the liquidus temperature, the better the moldability.

Example

[0055] (Example 1)

Tables 1 and 2 show the glass (Sample No. 1 to 9) and the conventional glass (Sample No. 10) of the examples of the present invention. For reference, the content of components other than Na ₂ O, K ₂ O, Fe ₂ O ₃ and ZrO _{2 in the} table is rounded to the second decimal place.

Glass samples in Tables 1 and 2 were prepared as follows. First, a glass batch in which the glass raw materials were combined so as to be the composition in the table was put in a platinum crucible, and then melted at 1600 to 1650°C for 24 hours. In melting of a glass batch, it was homogenized by stirring using a platinum stirrer. Then, the molten glass was poured onto a carbon plate to form a plate shape, and then slowly cooled at a temperature near the slow cooling point for 30 minutes. For each sample thus obtained, the distortion point, slow cooling point, density, Young's modulus, temperature equivalent to 10 ^4.5 dPa·s, temperature equivalent to 10 ^2.5 dPa·s, liquidus temperature (TL), and viscosity at liquidus temperature Log ₁₀ ηTL was measured for (ηTL(dPa·s)).

In addition, the distortion point and slow cooling point in Tables 1 and 2 were measured by the method of ASTM C336.

Density was measured by the Archimedes method according to ASTM C693.

The Young's modulus was measured by a bending resonance method according to JISR1602 (共振法).

Temperatures corresponding to 10 ^4.5 dPa·s and 10 ^2.5 dPa·s were measured by a platinum ball pulling method (白金球引上法).

Liquidus temperature (TL) is passed through a standard sieve (篩, sieve) 30 mesh (500㎛), 50 mesh (300㎛) and put the remaining glass powder into a platinum boat (boat), from 1100 ℃ After holding for 24 hours in a temperature gradient furnace set at 1350° C., a platinum boat was taken out, and the temperature at which devitrification (crystal foreign matter) was observed in the glass was measured.

The viscosity at the liquidus temperature (Log ₁₀ ηTL) was measured by measuring the viscosity (ηTL) of the glass at the liquidus temperature by the platinum ball pulling method, and calculated Log ₁₀ ηTL.

Β-OH value, the transmittance of the glass was measured using FT-IR, and was calculated using the following equation.

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 in the vicinity of 3600 cm ^-1 of hydroxyl absorption wavelength (%)

As can be seen from Tables 1 and 2, each sample of No. 1 to 9 has a distortion point of 735° C. or higher, and a slow cooling point of 785° C. or higher, so that it is easy to reduce the heat shrinkage to 20 ppm or less. In addition, because the Young's modulus is 80.4GPa at least, does not easily bend, so the liquid temperature (TL) is less than 1246 ℃, the viscosity (ηTL) of the liquid temperature 10 ^4.9 dPa · s or more, it is difficult to devitrification occurs during forming. In particular, No.1, 2, each sample of 7-9 is, since the viscosity (ηTL) of the liquid temperature 10 ^5.2 dPa · s or more, and was suitable for the overflow down draw method.

[0067] (Example 2)

A glass batch was prepared so as to be the glass of Sample Nos. 8 and 10 in Table 2. Then, this 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 a viscosity suitable for molding in the pot. Adjusted to. Then, after molding the molten glass into a plate shape by an overflow downdraw device, in a slow cooling furnace with a length of 5 m, the average cooling rate in the temperature range from the slow cooling point to (slow cooling point -100°C) was 385°C/min. It was set to and slowly cooled. Thereafter, the plate-shaped glass was cut and processed in cross section to produce a glass substrate having a size of 1500×1850×0.7 mm.

As a result of measuring the β-OH value and thermal contraction rate of each glass substrate thus obtained, the β-OH value of the glass substrate of Sample No. 8 was 0.1/mm, and the thermal contraction rate was 10 ppm. On the other hand, the β-OH value of the glass substrate of Sample No. 10 was 0.3/mm, and the thermal contraction rate was 25 ppm.

The thermal contraction rate of the glass substrate was measured by the following method. First, as shown in Fig. 1A, a 160 mm×30 mm strip-shaped sample G was prepared as a sample of a glass substrate. Markings M were formed on each of the both ends of the strip-shaped sample G in the long side direction at a position 20 to 40 mm away from the end edge using #1000 water resistant abrasive paper. Thereafter, as shown in (b) of FIG. 1, the strip-shaped sample (G) having the marking (M) formed thereon was divided into two along the direction perpendicular to the marking (M), and the sample piece (Ga, Gb) was produced. Then, only the sample piece (Gb) of one side was raised from room temperature (25℃) to 500℃ at 5℃/min. After holding at 500℃ for 1 hour, the temperature was raised to room temperature at 5℃/min. Lowering heat treatment was performed. After the heat treatment, as shown in Fig. 1(c), in a state in which the sample piece (Ga) not subjected to heat treatment and the sample piece (Gb) subjected to heat treatment are arranged in parallel, two sample pieces (Ga, The positional shift amounts (ΔL1, ΔL2) of the marking M of Gb) were read with a laser microscope, and the thermal contraction rate was calculated by the following equation. In addition, I ₀ in the formula is the distance between initial markings (M).

Heat shrinkage rate=[｛ΔL1(㎛)+ΔL2(㎛)｝×10 ³ ]/I ₀ (㎜)(ppm)

Next, for each of the glass substrates of Samples No. 8 and 10 described above, peeling charging evaluation was performed using the apparatus shown in FIG. 2.

As shown in Figure 2 (a), the support 1 of the glass substrate G is provided with a pad 2 made of Teflon (registered trademark) for supporting the four corners of the glass substrate G Are doing. On the support 1, a table 3 made of metal aluminum that can be lifted is installed, and by moving the table 3 up and down as shown in Fig. 2(b), the glass substrate G and the table ( After bringing 3) into contact, the glass substrate G can be charged by peeling the glass substrate G. In addition, the table 3 is grounded. Further, the table 3 has a single or a plurality of holes (not shown), which are connected to a diaphragm-type vacuum pump (not shown). When the vacuum pump is driven, air is sucked in from the hole of the table 3, whereby the glass substrate G can be vacuum-adsorbed on the table 3. Further, a surface potentiometer 4 is 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 is continuously measured. In addition, an air gun 5 equipped with an ionizer is installed above the glass substrate G, and through this, it is possible to eliminate the charge of the glass substrate G.

[0072] In the next step using this apparatus, the peeling charge of the glass substrate was measured. In addition, the experiment was carried out in a clean booth having a temperature of 25°C and a humidity of 40%. Since the amount of charge varies greatly depending on the atmosphere, particularly the humidity in the atmosphere, consideration is particularly required for humidity control.

(1) Put the glass substrate (G) on the support pad (2) of the support (1).

(2) The glass substrate G is discharged by the air gun 5 equipped with the ionizer.

(3) The table 3 is raised and brought into contact with the glass substrate G, and at the same time, the table 3 and the glass substrate G are brought into close contact with each other for 20 seconds by vacuum adsorption.

(4) By lowering the table 3, the glass substrate G is peeled off from the table 3, and the amount of charge generated in the central portion of the glass substrate G is continuously measured with the surface potentiometer 4.

(5) By repeating the above steps (3) and (4), a total of five peel evaluations are continuously performed.

The maximum charge amount of each measurement is obtained, and this is accumulated to obtain the peeling charge amount.

As a result, the peeling charge amount of the glass substrate of Sample No. 8 was 1000V, while the peeling charge of Sample No. 10 was as large as 2000V. Further, the etching gas was sprayed onto the surface of one side of the glass substrate as Sample No. 8, the surface roughness (Ra) was set to 1 nm, and then the peeling charge amount was measured and found to be 800 V.

G glass sample (glass substrate)
M marking
1 support
2 pad
3 tables
4 surface potentiometer
5 Air gun with ionizer

Claims (14)

By mass percentage, SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 25%, B ₂ O ₃ 0% or more and less than 3%, MgO 0 to 10%, CaO 0 to 15%, SrO 0 to 10%, BaO A glass substrate containing 0 to 15% and 0.005 to 0.3% of Na ₂ O, having a β-OH value of less than 0.18/mm, and a distortion point of 735°C or higher. The method of claim 1,
A glass substrate containing 0.005 to 0.1% of Fe ₂ O ₃ by mass percentage. The method according to claim 1 or 2,
A glass substrate comprising 0.001 to 0.5% of SnO ₂ by mass percentage. The method according to any one of claims 1 to 3,
A glass substrate having a Young's modulus of 80 GPa or more. The method according to any one of claims 1 to 4,
A glass substrate having a thermal contraction rate of 20 ppm or less. The method according to any one of claims 1 to 5,
A glass substrate having a size having a short side of 1500 mm or more and a long side of 1850 mm or more. The method according to any one of claims 1 to 6,
A glass substrate having a thickness of 0.7 mm or less. The method according to any one of claims 1 to 7,
Glass substrate, characterized in that the surface of at least one side is a fine uneven surface. The method of claim 8,
A glass substrate characterized in that the surface roughness (Ra) of the fine uneven surface is 0.1 to 10 nm. By mass percentage, SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 25%, B ₂ O ₃ 0% or more and less than 3%, MgO 0 to 10%, CaO 0 to 15%, SrO 0 to 10%, BaO A raw material preparation step of preparing a glass batch prepared to form a glass containing 0 to 15%, Na ₂ O 0.005 to 0.3%, a melting step of melting the glass batch in an electric melting furnace, and melting the glass into a plate shape It includes a molding process for molding, a slow cooling process for slow cooling a plate-shaped glass in a slow cooling furnace, and a processing process for cutting a slow-cooled plate-shaped glass into a predetermined size, with a β-OH value of less than 0.18/mm, and a distortion point of 735. A method for producing a glass substrate, characterized by obtaining a glass substrate having a temperature equal to or higher than C. The method of claim 10,
A method for producing a glass substrate, wherein the cooling rate of the plate-shaped glass in the slow cooling step is an average cooling rate of 50°C/min to 1000°C/min in a temperature range from the slow cooling point (slow cooling point -100°C) . The method of claim 10 or 11,
A method for producing a glass substrate, comprising chemically etching at least one surface. The method of claim 10 or 11,
A method of manufacturing a glass substrate, characterized in that the surface of at least one side is physically polished. The method of claim 12 or 13,
A method for producing a glass substrate, wherein the surface roughness (Ra) is 0.1 to 10 nm.

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