JP5428137B2 - Alkali-free glass and alkali-free glass substrate - Google Patents

Description

  The present invention relates to a flat panel display substrate such as a liquid crystal display (hereinafter referred to as LCD) or an EL display, a cover glass for an image sensor such as a charge coupled device (CCD) or an equal magnification proximity solid-state imaging device (CIS), and a solar cell. The present invention relates to a non-alkali glass and a non-alkali glass substrate that are suitable for a substrate for use.

  Electronic devices such as thin film transistor type active matrix liquid crystal displays (hereinafter referred to as TFT-LCDs) are thin and have low power consumption. Therefore, they are used in various applications such as car navigation, digital camera viewfinders, and recently PC monitors and televisions Is used.

  Conventionally, glass has been widely used as a flat panel display substrate such as an LCD or EL display. As is well known, TFT-LCD panel manufacturers produce a plurality of devices on a glass substrate (base plate) formed by a glass manufacturer, and then divide and cut each device into a product. To improve productivity and reduce costs.

In recent years, displays such as personal computer monitors and televisions have become larger in screen size, and a large glass substrate of 2200 × 2400 mm is required in order to obtain a large number of these devices. In particular, there is a great demand for an increase in screen size for a display for TV use, and a technique for stably manufacturing a large glass substrate is important. In television applications, amorphous silicon TFT-LCD (hereinafter referred to as a-Si.TFT-LCD) is generally employed.
JP-A-7-277762

The following characteristics are required for a glass substrate used for a-Si • TFT-LCD or the like.
(1) If an alkali metal oxide is contained in the glass, alkali ions diffuse into the semiconductor material on which the film is formed during the heat treatment, resulting in deterioration of the film characteristics. Do not contain.
(2) To have chemical resistance that does not deteriorate due to various acids, alkalis, and other chemicals used in the photoetching process.
(3) No thermal contraction in heat treatment processes such as film formation and annealing. Therefore, it must have a high strain point.

In consideration of meltability and moldability, this type of glass substrate is also required to have the following characteristics.
(4) The glass is excellent in meltability so as not to cause undesirable melting defects as glass substrates in the glass. There should be no bubble defects.
(5) Excellent devitrification resistance so that there is no foreign matter generated during melting and molding in the glass.

For the following reason, (6) glass having a thermal expansion coefficient of 40 to 50 × 10 ⁻⁷ / ° C. is required. The TFT-LCD manufacturing process has many heat treatment processes, and the glass substrate is repeatedly subjected to rapid heating and rapid cooling, so that the thermal shock applied to the glass substrate increases. In addition, if the glass substrate is enlarged, not only the temperature distribution is likely to occur in the glass substrate, but also the probability that minute scratches and cracks will occur on the end face increases, and the probability that the glass substrate will break during the heat treatment process also increases. . In order to solve this problem, it is most effective to reduce the thermal stress caused by the difference in thermal expansion coefficient. The smaller the thermal expansion coefficient of the glass substrate, the smaller the thermal stress generated during the heat treatment process. . On the other hand, if the coefficient of thermal expansion is reduced, the meltability and formability of the glass material tend to be impaired. Therefore, it is not a good idea to reduce the expansion rate unnecessarily. Therefore, it can be said that the thermal expansion coefficient of the glass substrate needs to be regulated within an appropriate range. Furthermore, matching the thermal expansion coefficient of the glass substrate used for the TFT-LCD with various film materials formed on the glass substrate is also important. If these films do not match the thermal expansion coefficient, the glass substrate may be warped and the glass substrate may be damaged. A variety of films are formed on the glass substrate, from low expansion oxide films such as SiNx to high expansion metal films such as Al and Mo. It is necessary to set the expansion coefficient. Considering the above points, the thermal expansion coefficient of glass is preferably 40 to 50 × 10 ⁻⁷ / ° C.

  Furthermore, for the following reasons, (7) glass having a viscosity characteristic suitable for stably producing a thin plate and a large glass substrate is required. In portable devices such as mobile phones and laptop computers, the weight reduction of the device is required for convenience in carrying, and the glass substrate is also required to be lightened accordingly. In order to reduce the weight of the glass substrate, it is effective to reduce the thickness of the glass substrate. At present, the standard thickness of the glass substrate for TFT-LCD is as thin as about 0.7 mm. On the other hand, the thinner the glass substrate is, the more difficult it is to produce. However, if the glass has a viscosity that rises quickly upon cooling, it is advantageous to easily form a thin glass substrate flat. In particular, in the case of downdraw molding, the furnace distance used for slow cooling is limited in equipment design, and the slow cooling time of the glass substrate is also limited accordingly, for example, cooling from the molding temperature to room temperature in a few minutes. Must. Therefore, in the case of downdraw molding, a glass whose viscosity rises quickly upon cooling is further advantageous.

  As described above, in the LCD, a large glass substrate is required in order to perform multiple chamfering of the display. The larger the glass substrate is, the more difficult it is to produce. However, if the glass has a viscosity that rises quickly upon cooling, it is easy to form a large glass substrate flat, which is advantageous. In particular, in the case of downdraw molding, the furnace distance used for slow cooling is limited in equipment design, and the slow cooling time of the glass substrate is also limited accordingly, for example, cooling from the molding temperature to room temperature in a few minutes. Must. Therefore, a glass whose viscosity rises quickly during cooling is further advantageous. In addition, if there is temperature unevenness in the plate width direction of the glass substrate, undulation or warpage occurs in the plate width direction, making it difficult to form the glass substrate flat. In order to solve the temperature unevenness, it is important to strictly control the temperature when forming the glass substrate. However, when the glass whose viscosity rises slowly during cooling is a long time until the glass is cooled and solidified when a flat glass substrate is produced, strict temperature control becomes difficult. In particular, a glass having a plate width of 2000 mm or more requires strict temperature control in the drawing direction, so that it is more difficult to produce a flat glass. Accordingly, there is a demand for a glass whose viscosity rises quickly during cooling and can be quickly formed into a glass substrate shape.

  However, since conventional alkali-free glass has a viscosity curve in which the viscosity slowly increases during cooling, it is difficult to determine the shape of warp and undulation in the thickness and width direction of the glass, and large and thin glass substrates It was difficult to form the flat.

Accordingly, the present invention satisfies the above required characteristics (1) to (5), (6) has a thermal expansion coefficient of 40 to 50 × 10 ⁻⁷ / ° C., and (7) a thin plate and a large glass substrate. It is a technical problem to obtain a glass suitable for TFT-LCD, particularly a-Si TFT-LCD having a viscosity characteristic suitable for the stable production of glass.

As a result of diligent efforts, the present inventors have made SiO ₂ 45 to 65%, Al ₂ O ₃ 12 to 17%, B ₂ O ₃ 7.5 to 15%, MgO 0 to 1 %, CaO 5% by mass. 5~15%, SrO 0~5%, BaO 5~15%, ZnO 0~ 0.5%, MgO + CaO + SrO + BaO + ZnO 15~23%, ZrO 2 0~5%, TiO 2 0~5%, P 2 O 5 0 Regulating the glass composition in the range of ˜5%, substantially containing no alkali metal oxide, regulating the value of (CaO + BaO—MgO) / SiO ₂ to 0.25 to 0.4 by mass fraction, In addition, the inventors have found that the above problem can be solved by regulating the average thermal expansion coefficient in the temperature range of 30 to 380 ° C. to 40 to 50 × 10 ⁻⁷ / ° C., and propose the present invention. In the present invention, “substantially no alkali metal oxide” refers to a case where the content of alkali metal oxide in the glass composition is 1000 ppm or less. In the present invention, “average thermal expansion coefficient in a temperature range of 30 to 380 ° C.” refers to a value measured using a dilatometer.

  If the glass composition is regulated within the above range, viscosity characteristics suitable for downdraw molding, particularly overflow downdraw molding can be obtained. Moreover, if the glass composition is regulated within the above range, a glass having good devitrification resistance can be obtained, and overflow downdraw molding can be stably performed. Therefore, the alkali-free glass of the present invention can be said to be a glass suitable for overflow downdraw molding. Furthermore, if the glass composition is regulated within the above range, a glass satisfying the required characteristics (1) to (7) can be easily obtained. The present invention does not exclude molding methods other than overflow downdraw molding. Even in a molding method other than overflow downdraw molding, the glass substrate has a better devitrification resistance in the glass production process, so the glass substrate production efficiency is improved. Needless to say, the method is also suitable.

  If the glass composition is regulated within the above range, the viscosity increases rapidly during cooling, and a glass that can be quickly formed into a glass substrate shape can be obtained. Therefore, since the alkali-free glass of the present invention is a glass whose viscosity rises quickly when cooled, it is easy to form a thin glass substrate flat, which is advantageous. Moreover, since the alkali-free glass of the present invention is a glass whose viscosity rises quickly upon cooling, it is easy to form a large glass substrate flatly, which is advantageous. Furthermore, in the case of downdraw molding, the furnace distance used for slow cooling is limited due to equipment design, and as a result, the slow cooling time of the glass substrate is also limited. For example, in a few minutes from the molding temperature to room temperature. Must be cooled. Therefore, in the case of downdraw molding, a glass whose viscosity rises quickly upon cooling is further advantageous.

The alkali-free glass of the present invention contains substantially no alkali metal oxide (Na ₂ O, K ₂ O, Li ₂ O) in the glass composition. Accordingly, the alkali-free glass of the present invention diffuses into the semiconductor material on which the alkali ions are formed during the heat treatment in the TFT manufacturing process, and the film characteristics are not deteriorated, and the reliability of the TFT-LCD is impaired. There is no.

The alkali-free glass of the present invention regulates the value of (CaO + BaO—MgO) / SiO ₂ to 0.25 to 0.4 in terms of mass fraction. If the value of (CaO + BaO—MgO) / SiO ₂ is regulated within the above range in terms of mass fraction, specifically, the liquidus viscosity of 10 ^5.4 dPa · s or more is achieved without reducing devitrification resistance. However, the high-temperature viscosity can be reduced, and viscosity characteristics suitable for downdraw molding can be obtained. Further, in order to reduce the high temperature viscosity increases the alkaline earth metal oxide, but to reduce the content of SiO ₂ is effective to increase the alkaline earth metal oxide, SiO ₂ content If the value is decreased, the strain point is lowered. If the value of (CaO + BaO-MgO) / SiO ₂ is regulated to the above range in terms of mass fraction, the alkaline earth metal oxide is increased, and even if the SiO ₂ content is decreased, the strain point is lowered. The high temperature viscosity can be reduced. In addition, the devitrification resistance is not deteriorated. Therefore, if the value of (CaO + BaO—MgO) / SiO ₂ is regulated to the above range by mass fraction, the disadvantage caused by increasing the alkaline earth metal oxide and decreasing the SiO ₂ content is solved. Can do. As will be described later, when a large amount of MgO is contained, devitrification resistance is impaired.

In the alkali-free glass of the present invention, the average coefficient of thermal expansion in the temperature range of 30 to 380 ° C. is regulated to 40 to 50 × 10 ⁻⁷ / ° C. If the coefficient of thermal expansion of glass is regulated as described above, it is possible to match the coefficient of thermal expansion with peripheral materials (especially organic materials and metals), and the glass substrate can be used in the manufacturing process of a-Si TFT-LCD. The probability of breakage can be reduced. Furthermore, regulating the thermal expansion coefficient of glass as described above can reduce the thermal stress resulting from the thermal expansion difference, reduce the probability that the glass substrate will break during the heat treatment process, and consequently break the glass substrate. By doing so, it is possible to effectively avoid a situation in which the operating rate of the production line is reduced or fine glass powder generated at the time of breakage adheres to the glass substrate, resulting in disconnection failure or patterning failure.

Alkali-free glass of the present invention, as a mass fraction (MgO + CaO + SrO + BaO + ZnO) / SiO 2 values is preferably 0.3 to 0.4.

The alkali-free glass of the present invention does not substantially contain As ₂ O ₃ and preferably contains 0 to 3% of Sb ₂ O ₃ + SnO ₂ + Cl in mass% in terms of the following oxide. In the present invention, “substantially does not contain As ₂ O ₃ ” refers to a case where the content of As ₂ O ₃ is 1000 ppm or less.

The alkali-free glass of the present invention does not substantially contain As ₂ O ₃ or Sb ₂ O _3, and preferably contains 0 to 1% of SnO ₂ in mass% in terms of the following oxides. In the present invention, “substantially does not contain Sb ₂ O ₃ ” refers to a case where the content of Sb ₂ O ₃ is 0.05% by mass or less.

Alkali-free glass of the present invention preferably has a liquidus temperature of 1150 ° C. or less and / or liquidus viscosity of ¹⁰ 5.4 dPa · s or more. “Liquid phase temperature” as used in the present invention refers to pulverizing glass, passing through a standard sieve 30 mesh (500 μm), and putting the glass powder remaining on 50 mesh (300 μm) into a platinum boat, and keeping it in a temperature gradient furnace for 24 hours. Is the temperature at which crystals are precipitated in the glass. The “liquid phase viscosity” as used in the present invention refers to the viscosity of the glass at the liquid phase temperature, and the viscosity of the glass refers to a value measured by a known fiber elongation method or platinum ball pulling method.

Alkali-free glass of the present invention, in mass% terms of oxide, as a glass composition, a SnO ₂ containing 0-0.5 wt%, and up to SnO ₂ of 0.5 wt%, a SnO ₂ When added, the liquid phase temperature of the glass obtained is preferably 1150 ° C. or lower. Referred to in the present invention, "until SnO ₂ of 0.5 wt%, upon addition of SnO _2, the liquidus temperature of the glass to be obtained", as the batch as a raw material, SnO ₂ in the glass composition is 0.5 mass After adding SnO ₂ until the total content reaches 100% (total glass composition is 100% by mass), the glass is melted and molded, and then the obtained glass sample is pulverized and passed through a standard sieve 30 mesh (500 μm). Then, the glass powder remaining in 50 mesh (300 μm) is placed in a platinum boat and held in a temperature gradient furnace for 1 week, and then refers to the temperature at which crystals precipitate.

The alkali-free glass of the present invention preferably has a liquidus temperature of 1150 ° C. or lower when 1% by mass of ZrO ₂ is added to the glass composition. "Upon addition of ZrO ₂ 1 wt% in the glass composition, the liquidus temperature of the glass to be obtained" in the present invention, the batch of raw material, the amount equivalent to ZrO ₂ to 1 mass% in the glass composition added ( The glass composition is apparently a total of 101% by mass), and the glass is melted and molded. Thereafter, the obtained glass sample is pulverized, passed through the standard sieve 30 mesh, and the glass powder remaining on 50 mesh is obtained. It refers to the temperature at which crystals precipitate after being placed in a platinum boat and held in a temperature gradient furnace for 1 week.

The alkali-free glass of the present invention preferably has a strain point of 630 ° C. or higher. In the present invention, “strain point” refers to a value measured by a method based on ASTM C336.

The alkali-free glass of the present invention preferably has a temperature at 10 ^2.5 dPa · s of 1535 ° C. or lower. In the present invention, “temperature at 10 ^2.5 dPa · s” refers to a value measured by a well-known platinum ball pulling method.

The alkali-free glass of the present invention satisfies the relationship of T ₁ −T ₂ ≦ 880 ° C. when the temperature at 10 ^2.5 dPa · s is T ₁ (° C.) and the strain point is T ₂ (° C.). Is preferred .

The alkali-free glass of the present invention preferably satisfies the relationship of T ₃ −T ₄ ≦ 330 ° C. when the temperature at 10 ⁴ dPa · s is T ₃ (° C.) and the softening point is T ₄ (° C.). . In the present invention, “temperature at 10 ⁴ dPa · s” refers to a value measured by a well-known platinum ball pulling method, and “softening point” refers to a value measured by a method based on ASTM C338.

When the alkali-free glass of the present invention is immersed in a 10% aqueous HCl solution at 80 ° C. for 24 hours, the erosion amount is preferably 5 μm or less. According to the present invention, “the amount of erosion when immersed in a 10% HCl aqueous solution at 80 ° C. for 24 hours” refers to the concentration of the 10% HCl aqueous solution after optically polishing both surfaces of the glass sample and then masking a part thereof. After immersing in an 80 ° C. chemical solution prepared for 24 hours, the mask is removed, and the level difference between the mask portion and the erosion portion is measured with a surface roughness meter. Note that the measurement was performed by optically polishing both surfaces of each glass sample, treating with chemicals under the above conditions, and then removing the mask.

When the alkali-free glass of the present invention is immersed in a 130 buffered hydrofluoric acid solution (NH ₄ HF ₂ : 4.6 mass%, NH ₄ F: 36 mass%) at 20 ° C. for 30 minutes, the erosion amount is 2 μm or less. It is preferable that In the present invention, “the amount of erosion when immersed in a 130 buffered hydrofluoric acid solution at 20 ° C. for 30 minutes” is a value measured under a treatment condition of 30 minutes using a 130 buffered hydrofluoric acid solution at 20 ° C. First, after optically polishing both sides of each glass sample, after masking a part and then immersing in a chemical solution of 20 ° C. prepared to the above concentration for 30 minutes, the mask is removed, and the step between the mask portion and the erosion portion is removed. The value measured with a surface roughness meter. Note that the measurement was performed by optically polishing both surfaces of the glass sample, treating with chemicals under the above conditions, and then removing the mask.

When the alkali-free glass of the present invention is immersed in a 10% HCl aqueous solution at 80 ° C. for 3 hours, it is preferable that white turbidity and roughness are not observed by visual observation of the surface.

When the alkali-free glass of the present invention is immersed in a 63 buffered hydrofluoric acid solution (HF: 6 mass%, NH ₄ F: 30 mass%) at 20 ° C. for 30 minutes, white turbidity and roughness are observed by visual observation of the surface. Preferably not.

Alkali-free glass of the present invention preferably has a specific Young's modulus is 27GPa / (g · ^{cm -3)} or greater. The “specific Young's modulus” in the present invention refers to a value calculated by dividing Young's modulus by density, and “Young's modulus” refers to a value measured by a resonance method.

The alkali-free glass substrate of the present invention is preferably composed of any alkali-free glass described above.

The alkali-free glass substrate of the present invention is preferably formed by downdraw molding.

The alkali-free glass substrate of the present invention is preferably formed by overflow down draw molding.

The alkali-free glass substrate of the present invention is preferably used for a display.

The alkali-free glass substrate of the present invention is preferably used for an LCD.

The alkali-free glass substrate of the present invention is preferably used for an a-Si • TFT-LCD.

The alkali-free glass substrate of the present invention preferably has a substrate size of 32 inches or more.

  The reason for limiting the glass composition range as described above will be described in detail. In addition, the following% display points out the mass% display except the case where there is especially limitation.

SiO ₂ is a component forming a glass network, the content is 45 to 65%, preferably 48 to 62%, more preferably 50% to 60%, more preferably 52 to 58%. When the content of SiO ₂ is less than 45%, chemical resistance, particularly acid resistance deteriorates, and the density increases. On the other hand, when the content of SiO ₂ is more than 65%, the high-temperature viscosity is increased, the meltability is deteriorated, and devitrified foreign matter (cristobalite) is easily generated in the glass.

Al ₂ O ₃ is a component that has an effect of increasing the strain point of the glass and improves the Young's modulus, and its content is 12 to 17%, preferably 14 to 16.5%, more preferably 15 ~ 16%. When the content of Al ₂ O ₃ is less than 12%, the effect of increasing the strain point becomes poor. If the content of _Al 2 _{O 3} is less than 12%, the Young's modulus tends to decrease. On the other hand, when the content of _Al 2 _{O 3} is more than 17%, the liquidus temperature becomes high, it tends to be devitrified.

B ₂ O ₃ is a component that acts as a flux, lowers the viscosity of the glass, improves the meltability, and lowers the liquidus temperature, and its content is 7.5 to 15%. Preferably it is 7.7 to 13%, more preferably 8 to 12%. When the content of B ₂ O ₃ is less than 7.5%, the function as a flux becomes insufficient and the buffered hydrofluoric acid resistance (hereinafter referred to as BHF resistance) deteriorates. Furthermore, when the content of B ₂ O ₃ is less than 7.5%, the liquidus temperature tends to increase because devitrification easily occurs. Further, when the content of B ₂ O ₃ is more than 15%, the strain point of the glass is lowered, together with the heat resistance is lowered, there is a possibility that acid resistance is deteriorated. Furthermore, when the content of B ₂ O ₃ is more than 15%, the Young's modulus decreases and the specific Young's modulus tends to decrease.

MgO is a component that lowers the high-temperature viscosity and improves the meltability while increasing the Young's modulus of the glass, and is the component that has the effect of reducing the density most among the alkaline earth metal oxides. However, when the content of MgO is large, the strain point is lowered and the glass is easily devitrified. In addition, MgO reacts with BHF to form a product, and the product is formed on the device on the glass substrate surface. There is a possibility that the glass substrate may become clouded due to fixation or adhesion, so that the content is limited. Accordingly, the content of MgO is 0 to 1 %, preferably 0 to 0.5%, more preferably 0 to 0.3%, most preferably 0 to 0.2%, ideally substantially. It is desirable not to contain. Here, “substantially does not contain MgO” refers to a case where the content of MgO is 0.05% or less.

CaO is a component that lowers the high-temperature viscosity without lowering the strain point of the glass, and is a component that improves devitrification resistance, and its content is 5.5 to 15%, preferably 6 to It is 14%, more preferably 6.5 to 14%, still more preferably 7 to 12%. Since the glass composition system according to the present invention is not easily melted and bubbles are likely to remain in the glass, many bubble defects are generated in the glass substrate as a result. In order to reduce foam defects, it is important to increase the meltability. In the glass composition system according to the present invention, when the amount of SiO ₂ is decreased, the meltability is increased, but in addition to the extreme decrease in acid resistance, the density and the thermal expansion coefficient are increased. Therefore, the alkali-free glass of the present invention contains 5.5% or more of CaO in order to improve the meltability of the glass. On the other hand, if the content of CaO is more than 15%, the BHF resistance of the glass deteriorates and the glass substrate surface is easily eroded, and the reaction product adheres to the glass substrate surface, causing the glass substrate to become cloudy. There is a risk of causing. Furthermore, when the content of CaO is more than 15%, the density and the thermal expansion coefficient are too high.

  SrO is a component that improves the chemical resistance of the glass and lowers the high temperature viscosity without reducing the strain point and improves the meltability, and its content is 0 to 5%, preferably 0 to 0%. It is 4%, more preferably 0-3.5%, still more preferably 0-3%. When the content of SrO is more than 5%, the density and the coefficient of thermal expansion increase or the glass tends to devitrify.

  BaO is a component that improves the chemical resistance and devitrification resistance of glass and improves meltability, and its content is 5 to 15%, preferably 7 to 14%, more preferably 8 to 13%, More preferably, it is 10 to 13%. When there is more content of BaO than 15%, devitrification resistance will deteriorate and there exists a tendency for a density and a thermal expansion coefficient to rise. On the other hand, when the content of BaO is less than 5%, the liquidus viscosity is lowered and devitrification tends to occur. As described above, the introduction of CaO is effective for improving devitrification resistance. If a large amount of CaO is contained, the meltability can be improved and the life of the kiln can be extended. However, when the high temperature viscosity is remarkably lowered, the liquid phase viscosity is lowered, so that there is a disadvantage that it is difficult to form the glass substrate. Therefore, when an appropriate amount of BaO is contained instead of CaO, a decrease in high temperature viscosity can be suppressed, and the liquid phase viscosity can be improved.

ZnO is a component that improves the BHF resistance of the glass and improves the meltability. However, when it is contained in a large amount, it tends to be devitrified and the strain point tends to be lowered. Therefore, the content of ZnO is 0 to 0.5%.

In order to obtain a viscosity characteristic suitable for downdraw molding, it is effective to increase the content of alkaline earth metal oxide that lowers the high-temperature viscosity and decrease the content of SiO ₂ . However, if the alkaline earth metal oxide is increased and the content of SiO ₂ is decreased, the strain point is lowered. In order to reduce the high temperature viscosity while specifically achieving a liquid phase viscosity of 10 ^5.4 dPa · s or more without deteriorating devitrification resistance, the mass fraction is (CaO + BaO—MgO) / SiO 2. The value of ₂ may be 0.25 to 0.40, preferably 0.26 to 0.39, more preferably 0.27 to 0.38, and still more preferably 0.30 to 0.36. That is, by regulating the value of (CaO + BaO—MgO) / SiO ₂ to 0.25 to 0.40, the high temperature viscosity can be lowered without lowering the strain point, and the devitrification resistance is deteriorated. I don't have to. When the value of (CaO + BaO-MgO) / SiO ₂ is smaller than 0.25, the high-temperature viscosity becomes high or the glass tends to devitrify. On the other hand, when the value of (CaO + BaO—MgO) / SiO ₂ is larger than 0.40, the density tends to increase and the thermal expansion coefficient tends to increase.

  When each component of MgO, CaO, SrO, BaO, and ZnO is mixed and contained, the liquidus temperature of the glass is lowered, and it is difficult to form a crystalline foreign substance in the glass. The moldability can be improved. The total amount of these components (MgO + CaO + SrO + BaO + ZnO) is 15 to 23%, preferably 17 to 22%, more preferably 18 to 21%. When the total amount is less than 15%, the function as a flux is not sufficient, and the meltability is likely to deteriorate. On the other hand, when the total amount is more than 23%, the density and the thermal expansion coefficient are increased, the specific Young's modulus is further decreased, and devitrification is easily caused.

ZrO ₂ is a component that improves the chemical resistance of glass, particularly acid resistance, and improves the Young's modulus, and its content is 0 to 5%, preferably 0 to 3%, more preferably 0 to 1. %. If the content of ZrO ₂ is more than 5%, the liquidus temperature rises and zircon devitrified foreign matter is likely to appear.

TiO ₂ is a component that improves the chemical resistance of glass, particularly acid resistance, and lowers the high temperature viscosity to improve the meltability, and its content is 0 to 5%, preferably 0 to 3%, More preferably, it is 0 to 1%, more preferably 0 to less than 0.5%, and most preferably 0 to 0.3%. When the content of TiO ₂ is more than 5%, the glass is colored and its transmittance is lowered, so that it is difficult to use it for display applications.

P ₂ O ₅ is a component that improves the devitrification resistance of the glass, and its content is 0 to 5%, preferably 0 to 3%, more preferably 0 to 1%, and still more preferably 0 to 0%. Less than 0.5%, most preferably 0-0.3%. When the content of P ₂ O ₅ is more than 5%, in addition to the occurrence of phase separation and milk white in the glass, the acid resistance is remarkably deteriorated.

As described above, when both SnO ₂ and ZrO ₂ are contained in a large amount, devitrification tends to occur in the glass. However, if the value of (MgO + CaO + SrO + BaO + ZnO) / SiO ₂ is preferably regulated to 0.3 to 0.4, more preferably 0.32 to 0.39, and even more preferably 0.34 to 0.38 in terms of weight fraction. , SnO ₂ and ZrO ₂ -based devitrification can be suppressed.

The alkali-free glass of the present invention can contain various components in addition to the above components. For example, Y ₂ O ₃ , Nb ₂ O ₅ , and La ₂ O ₃ can be contained up to 5%. . These components have a function of increasing the strain point, Young's modulus, etc. of the glass, but if the content is more than 5%, the density tends to increase.

In the case of melting the glass composition system according to the present invention, As ₂ O ₃ that works as a fining agent at a high temperature has been conventionally used. However, it is preferable not to use an environmentally hazardous chemical substance such as As ₂ O ₃ as much as possible because of recent environmental considerations. SnO ₂ has a clarification power at a high temperature similar to As ₂ O _3, and is very effective as a clarifier for melting the alkali-free glass of the present invention. Therefore, in the alkali-free glass of the present invention, the content of SnO ₂ is preferably 0 to 5%, more preferably 0 to 2%, still more preferably 0 to 0.5%, and particularly preferably 0 to 0.35%. preferable. If the SnO ₂ content is more than 5%, devitrification is likely to occur. In addition, since the alkali-free glass of the present invention has excellent meltability, a glass substrate free from bubble defects can be efficiently obtained by adding a clarifier such as SnO ₂ without adding As ₂ O ₃ as a clarifier. Can be manufactured well.

  Cl has the effect of accelerating the melting of alkali-free glass, melts the glass at a low temperature, works to make the refining agent work more effectively, lowers the melting cost of the glass, and extends the life of the manufacturing equipment. The content is preferably 0 to 3%. If the Cl content is more than 3%, the strain point may be lowered. Note that, as a raw material of the Cl component, a raw material such as an alkaline earth metal oxide chloride such as barium chloride or aluminum chloride can be used.

Sb ₂ O ₃ is also effective as a fining agent for the alkali-free glass of the present invention. However, since the alkali-free glass generally has a high melting temperature, the effect as a fining agent is small compared to As ₂ O ₃ . Therefore, when using Sb ₂ O ₃ as a fining agent, it is desirable to increase the amount of addition or to lower the melting temperature by combining with a component that promotes melting properties such as Cl. However, when 5% or more of Sb ₂ O ₃ is contained, the density tends to increase, and the addition amount is preferably 0 to 2%, and more preferably 0 to 1.5%. Further, _Sb 2 _{O 3} can also be used a part of a glass material or the whole as _Sb 2 _{O 5.}

Furthermore, in the alkali-free glass of the present invention, when As ₂ O ₃ is not used as the fining agent, one or more selected from the group of Sb ₂ O ₃ , SnO ₂ and Cl are added in an amount of 0 to 3%. preferably contained, in _{particular, Sb 2 O 3 0~2%,} SnO 2 0.01~1%, more preferably be contained in a proportion of Cl 0 to 1%.

Sb ₂ O ₃ is less toxic than As ₂ O ₃ , but it is an environmentally hazardous substance, so it is preferable that it is not substantially contained from an environmental point of view. Further, since halogens such as Cl are toxic to volatiles generated during glass melting, it is preferable that they are not substantially contained from an environmental point of view. Here, “substantially free of halogen such as Cl” refers to the case where the halogen content in the glass composition is 0.05% or less. In view of the above environmental considerations, as a clarifying agent, it contains substantially no As ₂ O ₃ or Sb ₂ O ₃ (preferably does not contain As ₂ O ₃ , Sb ₂ O ₃ , or Cl), and the following oxides Most preferably, SnO ₂ is contained in an amount of 0 to 1% (desirably 0.01 to 1%) in terms of mass%.

The alkali-free glass of the present invention can contain up to 3% using F, SO ₃ , C, etc. as a clarifier, as long as the properties are not impaired. Moreover, metal powders, such as Al and Si, etc. can be contained to 3% as a clarifier. _Furthermore, it can be contained up to 5% CeO 2, _Fe 2 _{O 3} or the like as a fining agent.

In the above glass composition range, it is naturally possible to select a preferable glass composition range by arbitrarily combining the preferable content ranges of the respective components, but there is a more preferable glass composition range as an alkali-free glass. Is SiO ₂ 50-60% by mass%, Al ₂ O ₃ 14-16.5%, B ₂ O ₃ 7.7-13%, MgO 0-0.5%, CaO 6-14%, SrO 0 ~3.5%, BaO 7~14%, ZnO 0~ 0.5%, MgO + CaO + SrO + BaO + ZnO 17~22%, ZrO 2 0~1%, TiO 2 0~3%, containing _P 2 O 5 _0~3% and, substantially containing no alkali metal oxide, in a mass fraction (CaO + BaO-MgO) / SiO 2 values are 0.25 to 0.4, and an average in the temperature range of 30 to 380 ° C. Expansion coefficient include glass to 42~48 × ^{10 -7} / ℃. If the composition range of the glass is regulated as described above, the devitrification resistance can be greatly improved and the viscosity characteristics necessary for overflow downdraw molding can be ensured accurately.

As a further preferred embodiment of the alkali-free glass, _SiO 2 52 to _58% by _{mass%, Al 2 O 3 15~16%} , B 2 O 3 8~12%, 0~0.5% MgO, CaO 7~12% SrO 0-3%, BaO 10-13%, ZnO 0-0.5%, MgO + CaO + SrO + BaO + ZnO 18-21%, ZrO ₂ 0-1%, TiO ₂ 0-0.5%, P ₂ O ₅ 0-0 0.5%, substantially no alkali metal oxide, (CaO + BaO—MgO) / SiO ₂ value of 0.25 to 0.4 by mass fraction, and 30 to 380 ° C. Examples include glasses having an average coefficient of thermal expansion in the temperature range of 44 to 47 × 10 ⁻⁷ / ° C. If the glass composition range is regulated as described above, devitrification resistance can be remarkably improved, and viscosity characteristics suitable for overflow downdraw molding can be obtained with certainty.

The alkali-free glass of the present invention has an average coefficient of thermal expansion in the temperature range of 30 to 380 ° C. of 40 to 50 × 10 ⁻⁷ / ° C., preferably 42 to 49 × 10 ⁻⁷ / ° C., more preferably 43 to 48 × 10 ⁻⁷ / ° C., more preferably 44 to 47 × 10 ⁻⁷ / ° C. If the average coefficient of thermal expansion is smaller than 40 × 10 ⁻⁷ / ° C., there is a possibility that the thermal expansion coefficient cannot be matched with the surrounding materials (particularly, organic materials or metals). On the other hand, if the average thermal expansion coefficient is larger than 50 × 10 ⁻⁷ / ° C., the probability of breakage of the glass substrate increases in the TFT-LCD manufacturing process. In LCD applications, the thermal shock resistance of glass substrates is also an important requirement. Even if the end face of the glass substrate is chamfered, fine scratches and cracks are present, and if the tensile stress due to heat is concentrated on the scratches and cracks, the glass substrate sometimes breaks. If the glass substrate is damaged, not only the operating rate of the production line is lowered, but also fine glass powder generated at the time of the damage adheres to the glass substrate, which may cause disconnection failure or patterning failure. The manufacturing process of TFT-LCD, especially polycrystalline silicon TFT-LCD (p-Si TFT-LCD), has many heat treatment processes, and the glass substrate is repeatedly heated and cooled repeatedly. It gets bigger. Furthermore, as described above, the glass substrate tends to be large, and the large glass substrate not only tends to cause a temperature difference in the heat treatment process, but also has a high probability of generating minute scratches and cracks on the end face, The probability that the glass substrate breaks during the heat treatment process is increased. The most fundamental and effective method for solving this problem is to reduce the thermal stress resulting from the difference in thermal expansion. Therefore, a glass having a low thermal expansion coefficient is required. Specifically, the thermal expansion coefficient is 50 There is a demand for glass of × 10 ⁻⁷ / ° C. or lower.

  In the alkali-free glass of the present invention, the liquidus temperature is preferably 1150 ° C. or less, more preferably 1080 ° C. or less, further preferably 1050 ° C. or less, and most preferably 1030 ° C. or less. In general, down-draw molding, especially overflow down-draw molding, has a higher viscosity during glass molding than other molding methods, so if glass has poor devitrification resistance, devitrification will occur during molding. However, it becomes difficult to form the glass substrate. Specifically, if the liquidus temperature is higher than 1150 ° C., overflow downdraw molding becomes difficult, and a molding method such as float molding must be adopted, and a glass substrate with good surface quality is obtained separately. , Forced to add processing steps. Accordingly, when the liquidus temperature is higher than 1150 ° C., an unreasonable restriction is imposed on the alkali-free glass forming method, and a glass having a desired surface quality cannot be formed. The lower the liquidus temperature, the better the devitrification resistance of the glass.

In the alkali-free glass of the present invention, the liquid phase viscosity is preferably 10 ^5.4 dPa · s or more, more preferably 10 ^5.6 dPa · s or more, still more preferably 10 ^5.8 dPa · s or more, and 10 ^{6. 0} dPa · s or more is most preferable. Generally, down-draw molding, especially overflow down-draw molding, has a higher viscosity during glass molding than other molding methods. And it becomes difficult to form a glass substrate. Specifically, when the liquid phase viscosity is lower than 10 ^5.4 dPa · s, overflow downdraw molding becomes difficult, and a molding method such as float molding has to be adopted, and a glass substrate with good surface quality is obtained. In order to obtain, it is necessary to add a processing step separately. Therefore, if the liquidus viscosity is lower than 10 ^5.4 dPa · s, an undue restriction is imposed on the method for forming the alkali-free glass, and a glass substrate having a desired surface quality cannot be formed. In addition, devitrification resistance of glass is so favorable that liquid phase viscosity is large.

The non-alkali glass of the present invention contains SnO ₂ in an amount of the following oxide equivalent mass%, 0 to 0.5 mass%, and SnO ₂ as a glass composition until SnO ₂ becomes 0.5 mass%. When added, the liquidus temperature of the glass obtained is preferably 1150 ° C. or lower, more preferably 1100 ° C. or lower. If there are internal defects such as bubbles in the glass, light transmission is hindered, which is a fatal defect for a glass substrate for display. In general, as the glass substrate becomes larger, the probability that bubbles remain is increased, the probability that defects are caused by bubbles increases, and the productivity of the glass substrate decreases. Therefore, a technique for reducing bubbles in the glass is important. As a method for reducing bubbles contained in glass, there are a method of using a fining agent and a method of lowering the high temperature viscosity. In the former method, As ₂ O ₃ is the most effective as a clarifier for alkali-free glass, but As ₂ O ₃ is an environmentally hazardous chemical, its use needs to be reduced. Therefore, from the environmental point of view, the introduction of SnO ₂ as an alternative fining agent for As ₂ O ₃ has been studied. However, SnO ₂ is likely to cause crystalline foreign matter (devitrification), which is an internal defect of the glass substrate. There is a risk. Therefore, if the glass is not easily devitrified with respect to SnO ₂ , even if SnO ₂ is introduced as a clarifier, it is difficult to cause devitrification. It is possible to achieve both and is considered very effective. In addition, in the manufacturing process of the glass substrate, it is assumed that the Sn electrode is eluted to some extent in the glass. Therefore, glass that is less susceptible to devitrification with respect to SnO ₂ is further advantageous. In that respect, according to the alkali-free glass of the present invention, even if the SnO ₂ content in the glass composition is increased to 0.5%, the liquidus temperature of the obtained glass can be 1150 ° C. or less, The above effects can be fully enjoyed. On the other hand, when the content of SnO ₂ in the glass composition is 0.5%, the above effect is difficult to receive if the liquid phase temperature of the obtained glass is higher than 1150 ° C.

In the alkali-free glass of the present invention, when 1% of ZrO ₂ is added to the glass composition, the liquidus temperature of the obtained glass is preferably 1150 ° C. or less, and more preferably 1100 ° C. or less. As a measure for reducing the manufacturing cost of the glass substrate other than reducing internal defects such as bubbles and foreign matters, it is effective to lengthen the life of the melting kiln and reduce the frequency of repairing the kiln. As a means for that, it is preferable to use a Zr-based refractory that is not easily eroded by molten glass, but as the number of use points of the Zr-based refractory increases, Zr-based crystalline foreign matters (devitrification) are likely to occur. This may become an internal defect of the glass substrate. Therefore, if the glass is less susceptible to devitrification with respect to ZrO ₂ , even if a Zr-based refractory is used as the refractory for the melting furnace, devitrification due to this hardly occurs. Costs can be reduced and are considered very effective. In that respect, according to the alkali-free glass of the present invention, even if 1% of ZrO ₂ is added to the glass composition, the liquidus temperature of the obtained glass can be reduced to 1150 ° C. or less, so that the above effect is maximized. Can enjoy. On the other hand, when 1% of ZrO ₂ is added to the glass composition, if the liquid phase temperature of the obtained glass is higher than 1150 ° C., the above effect is hardly obtained.

In the alkali-free glass of the present invention, the temperature at 10 ^2.5 dPa · s is preferably 1535 ° C. or lower, more preferably 1530 ° C. or lower, further preferably 1520 ° C. or lower, particularly preferably 1510 ° C. or lower, most preferably 1500 ° C. or lower. preferable. As described above, if the glass is melted at a high temperature for a long time, internal defects such as bubbles and foreign matters in the glass can be reduced. However, melting at a high temperature region increases the burden on the glass melting furnace. For example, refractories such as alumina and zirconia used in kilns are eroded violently by molten glass as the temperature rises, and the life cycle of the kiln is shortened accordingly. In addition, melting in a high temperature region is disadvantageous in manufacturing a glass substrate, for example, the running cost for keeping the interior of the kiln always high is higher than that of glass that melts at a low temperature. Therefore, the alkali-free glass is required to be meltable at a low temperature. In that respect, according to the alkali-free glass of the present invention, the temperature at a high temperature viscosity of 10 ^2.5 dPa · s can be made 1535 ° C. or lower, so that the above effect can be enjoyed accurately. On the other hand, when the temperature at the high temperature viscosity of 10 ^2.5 dPa · s is higher than 1535 ° C., it is difficult to enjoy the above effect. The temperature of the molten glass at a high temperature viscosity of 10 ^2.5 dPa · s corresponds to the melting temperature.

  The alkali-free glass of the present invention preferably has a strain point of 630 ° C. or higher, more preferably 635 ° C. or higher, still more preferably 640 ° C. or higher, and most preferably 645 ° C. or higher. The glass substrate is subjected to high-temperature heat treatment in the manufacturing process of the TFT-LCD. If the heat resistance of the glass substrate is low, for example, when the glass substrate is exposed to a high temperature of 400 to 600 ° C., minute dimensional shrinkage called thermal shrinkage occurs, which causes a shift in the pixel pitch of the TFT and causes a display defect. This may cause Further, if the heat resistance of the glass substrate is further lowered, the glass substrate may be deformed or warped. Furthermore, in order to prevent the glass substrate from being thermally contracted in the TFT-LCD manufacturing process such as a film forming process, a glass having excellent heat resistance is required. In that respect, according to the alkali-free glass of the present invention, the strain point can be set to 630 ° C. or higher, and thus the above-described problem hardly occurs. On the other hand, if the strain point is less than 630 ° C., the above problem becomes serious. In addition, since the heat treatment temperature is higher in the manufacturing process of p-Si · TFT-LCD than a-Si · TFT-LCD, a glass substrate having a high strain point is suitable for p-Si · TFT-LCD. .

The alkali-free glass of the present invention satisfies the relationship of T ₁ −T ₂ ≦ 880 ° C. when the temperature at 10 ^2.5 dPa · s is T ₁ (° C.) and the strain point is T ₂ (° C.). Is preferred. T ₁ corresponds to the temperature at which corresponds to the melting temperature, melting the glass kiln. T ₂ is an index of heat resistance, and heat resistance is excellent when T ₂ is high. Generally, if you lower the T _1, T ₂ is also lowered, if trying to raise the T _2, but T ₁ is increased, a melt at relatively low temperatures, and the glass excellent in heat resistance Therefore, T ₁ -T ₂ is preferably 880 ° C. or less, more preferably 870 ° C. or less, further preferably 860 ° C. or less, and most preferably 850 ° C. or less. . When T ₁ -T ₂ is higher than 880 ° C., it is difficult to achieve both low temperature melting and heat resistance.

The alkali-free glass of the present invention preferably satisfies the relationship of T ₃ −T ₄ ≦ 330 ° C. when the temperature at 10 ⁴ dPa · s is T ₃ (° C.) and the softening point is T ₄ (° C.). . The thickness of the glass substrate and the shape of warpage and undulation in the plate width direction are substantially determined until the temperature of the molten glass reaches the softening point from the molding temperature. _Therefore, reducing the T 3 -T _4, specifically, preferably _T 3 -T ₄ of 330 ° C. or less, more preferably 325 ° C. or less, more preferably be below 320 ° C., a glass substrate thickness, the plate It becomes easier to control the shape of warpage and undulation in the width direction. Also, if regulated to T ₃ -T ₄ ≦ 330 ℃, the viscosity increases quickly upon cooling, can be quickly formed on the glass substrate shape. That is, when T ₃ -T _{4 is set} to 330 ° C. or less, a thin glass substrate can be easily formed flat. Further, when T ₃ -T _{4 is set} to 330 ° C. or less, a large glass substrate can be easily formed flat. Furthermore, in the case of downdraw molding, the furnace distance used for slow cooling is limited due to equipment design, and as a result, the slow cooling time of the glass substrate is also limited. For example, in a few minutes from the molding temperature to room temperature. Must be cooled. Thus, the above viscosity characteristics are very advantageous. On the other hand, if T ₃ -T ₄ is higher than 330 ° C., it becomes difficult to control the thickness of the glass substrate, the shape of the warp and the undulation in the plate width direction. Incidentally, T ₃ corresponds to the molding temperature.

Alkali-free glass of the present invention, the density is preferably at 2.80 g / cm ³ or less, more preferably 2.70 g / cm ³ or less, more preferably 2.68 g / cm ³ or less, and most preferably 2.65g / Cm ³ or less. As the glass density is lower, the weight of the glass can be reduced, and as a result, the weight of the TFT-LCD can be reduced. On the other hand, in an alkali-free glass system, generally, when the density of glass is lowered, the viscosity of the glass increases, the meltability deteriorates, the tendency to devitrification increases, and the moldability also deteriorates. For example, quartz glass has a density as low as 2.2 g / cm ³ , but it must be melted at a very high temperature and is inferior in devitrification resistance. Is difficult to melt without defects. Thus, density and melting property, if standing on the viewpoint of achieving both the density and formability, density is a measure that a 2.50 g / cm ³ or more (preferably 2.60 g / cm ³ or higher).

When the alkali-free glass of the present invention is immersed in a 10% HCl aqueous solution at 80 ° C. for 24 hours, the amount of erosion is 5 μm or less and / or is immersed in a 10% HCl aqueous solution at 80 ° C. for 3 hours. It is preferable that no cloudiness or roughness is observed. In addition, when the alkali-free glass of the present invention is immersed in a 130 BHF solution at 20 ° C. for 30 minutes, the erosion amount is 2 μm or less and / or when immersed in a 63 BHF solution at 20 ° C. for 30 minutes, It is preferred that no roughness is observed. A transparent conductive film, an insulating film, a semiconductor film, a metal film, and the like are formed on the surface of the glass substrate for TFT-LCD, and various circuits and patterns are formed by photolithography etching (photoetching). In these film formation and photoetching steps, the glass substrate is subjected to various heat treatments and chemical treatments. In general, in the TFT array process, a series of processes including a film formation process, a resist pattern formation, an etching process, and a resist stripping process is repeated. At that time, as an etchant, a phosphoric acid solution is used for etching Al and Mo films, an aqua regia (HCl + HNO ₃ ) solution is used for etching ITO films, a BHF solution is used for etching SiNx, SiO ₂ films, and the like. A wide variety of chemical solutions are used, and these are not disposable but a circulating liquid system flow in consideration of cost reduction. If the chemical resistance of the glass substrate is low, the reaction product of the chemical and the glass substrate may clog the filter of the circulating liquid system during etching, or the glass substrate surface may become cloudy due to inhomogeneous etching or etching. Changes in the components of the liquid may cause various problems such as an unstable etching rate. In particular, a hydrofluoric acid-based chemical solution typified by BHF erodes the glass substrate strongly, so that the above-mentioned problems are likely to occur, and the glass substrate is required to have excellent BHF resistance. In other words, the chemical resistance of the glass is very important from the viewpoint of preventing contamination of the chemical solution and clogging of the filter during the process due to reaction products. In addition, the chemical resistance of the glass substrate is not only small in the amount of erosion on the surface of the glass substrate, but also important in not causing a change in appearance. It is an indispensable characteristic for a glass substrate for a display such as a TFT-LCD in which light transmittance is important because the appearance of the glass does not change due to chemical treatment, such as white turbidity or roughness. The evaluation results of the erosion amount and the appearance change do not necessarily match in BHF resistance. For example, even if the glass shows the same erosion amount, the appearance change may or may not be caused after chemical treatment depending on the glass composition. is there. In that respect, according to the alkali-free glass of the present invention, when immersed in a 10% HCl aqueous solution at 80 ° C. for 24 hours, the erosion amount is 5 μm or less, and when immersed in a 10% HCl aqueous solution at 80 ° C. for 3 hours. In addition, since it is possible to prevent white turbidity and roughness from being observed by visual observation of the surface, the above-mentioned problems can be reliably solved. In particular, according to the alkali-free glass of the present invention, even if immersed in a 130 BHF solution at 20 ° C. for 30 minutes, or even if immersed in a 63 BHF solution at 20 ° C. for less than 2 μm, the surface observation by visual observation Therefore, the above-mentioned problems can be reliably solved.

The alkali-free glass of the present invention preferably has a specific Young's modulus (value obtained by dividing Young's modulus by density) of 27 GPa / g · cm ⁻³ or more, more preferably 28 GPa / g · cm ⁻³ or more, and 29 GPa / g · cm. ^-3 or more is more preferable. When the specific Young's modulus is set to 27 GPa / g · cm ⁻³ or more, even a large and thin glass substrate can be suppressed to a deflection amount that does not cause a problem.

  The alkali-free glass substrate of the present invention is a molten glass prepared by feeding a batch prepared with glass raw materials so as to have a desired glass composition into a continuous melting furnace, heating and melting, defoaming, and supplying to a molding apparatus. Can be manufactured by forming into a plate shape and slowly cooling.

  The alkali-free glass substrate of the present invention is preferably down-draw molding, particularly overflow down-draw molding, from the viewpoint of producing a glass substrate with good surface quality. The reason for this is that, in the case of overflow down draw molding, the glass substrate surface that should be the surface of the glass substrate does not come into contact with the bowl-shaped refractory, and is molded in a free surface state, so that the glass substrate has good surface quality without polishing. This is because it can be molded. Here, overflow down-draw molding is performed by causing molten glass to overflow from both sides of the heat-resistant bowl-shaped structure, and then stretching and molding the overflowed molten glass at the lower end of the bowl-shaped structure to form a glass substrate. It is a method of manufacturing. The structure and material of the bowl-shaped structure are not particularly limited as long as the dimensions and surface quality of the glass substrate can be set to a desired state and the quality usable for the glass substrate for TFT-LCD can be realized. Moreover, in order to perform the downward extending | stretching shaping | molding, you may apply force with what kind of method with respect to a glass substrate. For example, a method may be employed in which a heat-resistant roll having a sufficiently large width is rotated and stretched in contact with the glass substrate, or a plurality of pairs of heat-resistant rolls are only near the end face of the glass substrate. You may employ | adopt the method of making it contact and extending | stretching. The alkali-free glass of the present invention is excellent in devitrification resistance and has a viscosity characteristic suitable for molding, so that overflow downdraw molding can be performed with high accuracy.

  As a method for producing an alkali-free glass substrate of the present invention, various methods other than overflow down draw molding can be employed. For example, various molding methods such as float molding, slot down draw molding, redraw molding, and roll-out molding can be employed. From the viewpoint of manufacturing a glass substrate at a low cost, float molding is preferable.

  The alkali-free glass of the present invention is preferably used as a glass substrate. The alkali-free glass of the present invention can employ various molding methods, but in any case, since the alkali-free glass of the present invention is excellent in devitrification resistance and has an appropriate viscosity characteristic, it is excellent in glass. It can be formed into a substrate and can be applied to a display such as an LCD.

As described above, the glass substrate tends to increase in size, but as the substrate size increases, the probability of devitrification appearing in the substrate increases and the yield rate decreases rapidly. Therefore, according to the alkali-free glass substrate of the present invention having good devitrification resistance, there is a great merit in producing a large glass substrate. For example, the substrate size is 0.1 m ² or more (specifically, a size of 320 mm × 420 mm or more), particularly 0.5 m ² or more (specifically, a size of 630 mm × 830 mm or more), 1.0 m ² or more ( Specifically, a size of 950 mm × 1150 mm or more, further 2.3 m ² or more (specifically, a size of 1400 mm × 1700 mm or more), 3.5 m ² or more (specifically, 1750 mm × 2050 mm or more) The size becomes larger as the size increases to 4.8 m ² or more (specifically, the size of 2100 mm × 2300 mm or more). In terms of the screen size of the display, the substrate size is preferably 32 inches or more, more preferably 36 inches or more, and still more preferably 40 inches or more. Further, according to the alkali-free glass substrate of the present invention, a thin glass substrate can be formed with high accuracy in addition to the characteristics of low density and high specific Young's modulus. For example, if the wall thickness is 0.8 mm or less (preferably 0.7 mm or less, more preferably 0.5 mm or less, and further preferably 0.4 mm or less), the advantages of the present invention can be enjoyed effectively. . In addition, the alkali-free glass substrate of the present invention can reduce the amount of deflection of the glass substrate even when the thickness of the glass substrate is reduced compared to the conventional glass substrate. This makes it easier to prevent breakage during loading and unloading.

  The alkali-free glass substrate of the present invention is preferably used for a display such as an LCD, particularly an a-Si • TFT-LCD. Since the alkali-free glass substrate of the present invention can satisfy the above-described properties (1) to (7) required for a glass substrate for LCD, it is suitable for the above applications. In addition, the alkali-free glass of the present invention is excellent in devitrification resistance and has a viscosity characteristic suitable for overflow downdraw molding, so that a large and / or thin glass substrate can be efficiently produced. It is possible to accurately meet the demand for larger size (especially a glass substrate for TV use). The alkali-free glass substrate of the present invention is also suitable for a p-Si • TFT-LCD glass substrate.

  Hereinafter, the present invention will be described in detail based on examples.

  Tables 1 to 7 show Example Glass (Sample Nos. 1 to 38) and Comparative Example Glass (Sample Nos. A and B) of the present invention.

  Each glass sample in the table was prepared as follows.

  First, a batch in which glass raw materials were prepared so as to have the composition shown in the table was put into a platinum crucible, melted at 1550 ° C. for 24 hours, and then poured out onto a carbon plate to be formed into a plate shape. For the glass sample thus obtained, density, thermal expansion coefficient, strain point, annealing point, softening point, high temperature viscosity, Young's modulus, specific Young's modulus, devitrification resistance (liquidus temperature, liquidus viscosity) Various properties of chemical resistance (BHF resistance, HCl resistance) were measured and shown in the table.

  The density was measured by the well-known Archimedes method.

  The coefficient of thermal expansion was determined by measuring an average value in a temperature range of 30 to 380 ° C. using a dilatometer.

  The strain point and annealing point were measured by a method based on ASTM C336. The higher these values, the higher the heat resistance of the glass.

  The softening point was measured by a method based on ASTM C338.

Each temperature at high temperature viscosity ^{10 4.0 dPa · s, 10 3.0} dPa · s, 10 2.5 dPa · s were measured in a known platinum ball pulling method.

  Young's modulus was measured by a resonance method. Specific Young's modulus was calculated by dividing Young's modulus by density.

  The liquid phase temperature is obtained by pulverizing each glass sample, passing through a standard sieve 30 mesh (500 μm), putting the glass powder remaining on 50 mesh (300 μm) into a platinum boat, and holding it in a temperature gradient furnace for 24 hours. The temperature at which crystals are precipitated is measured.

The liquidus temperature when SnO ₂ was added (SnO ₂ devitrification resistance in the table) was added to the raw material batch until SnO ₂ was 0.5% in the glass composition, and the same conditions as above The glass is melted and molded with, then the glass sample is pulverized, passed through a standard sieve 30 mesh (500 μm), and the glass powder remaining on 50 mesh (300 μm) is placed in a platinum boat and kept in a temperature gradient furnace for 1 week. Then, the temperature at which crystals were deposited was measured. Next, “◯” indicates that no devitrification was observed at 1150 ° C., and “X” indicates that devitrification was observed at 1150 ° C. In parallel with this evaluation, when the clarity of the glass was evaluated, no bubble defects were observed in the glass when SnO ₂ was added to 0.5%.

The liquidus temperature when ZrO ₂ is added (ZrO ₂ devitrification resistance in the table) is the same conditions as above when ZrO ₂ is added in an amount corresponding to 1% in the glass composition to the raw material batch. The glass is melted and molded with, then the glass sample is pulverized, passed through a standard sieve 30 mesh (500 μm), and the glass powder remaining on 50 mesh (300 μm) is placed in a platinum boat and kept in a temperature gradient furnace for 1 week. Then, the temperature at which crystals were deposited was measured. Next, “X” indicates that devitrification was observed at 1150 ° C., and “◯” indicates that no devitrification was observed at 1150 ° C.

  The liquid phase viscosity indicates the viscosity of the glass at the liquid phase temperature. The viscosity of the glass was measured by a well-known platinum ball pulling method. The lower the liquidus temperature and the higher the liquidus viscosity, the better the devitrification resistance and the better the moldability.

BHF resistance and HCl resistance were evaluated by the following methods. First, after both surfaces of each glass sample were optically polished, they were immersed for a predetermined time at a predetermined temperature in a chemical solution prepared by masking a part and then preparing a predetermined concentration. After the chemical treatment, the mask was removed, the step between the mask portion and the erosion portion was measured with a surface roughness meter, and the value was taken as the erosion amount. Each measurement was performed by optically polishing both surfaces of each glass sample, then treating with chemicals under the following conditions, and then removing the mask. The chemical solution and the treatment conditions were such that the amount of erosion of BHF resistance was measured under a treatment condition of 20 ° C. for 30 minutes using a 130 BHF solution (NH ₄ HF ₂ : 4.6% by mass, NH ₄ F: 36% by mass). . In BHF resistance, “で あ れ ば” is indicated when the erosion amount is less than 1 μm, and “◯” is indicated when the amount is 1-2 μm. The HCl-resistant erosion amount was measured under a treatment condition of 80 ° C. for 24 hours using a 10 mass% hydrochloric acid aqueous solution. If the HCl-resistant erosion amount was less than 2.5 μm, “◎”, 2.5˜ When it was 5 μm, “◯” and those larger than 5 μm were set as “X”.

The chemical solution and the processing conditions in the appearance evaluation were performed using a BHF resistance of 63 BHF solution (HF: 6% by mass, NH ₄ F: 30% by mass) under a processing condition of 20 ° C. for 30 minutes, and an HCl resistance of 10 The treatment was performed at 80 ° C. for 3 hours using a mass% hydrochloric acid aqueous solution. The glass surface was visually observed, and “O” indicates that the glass surface is not clouded, rough, or cracked, and “X” indicates that the glass surface is clouded, rough, or cracked.

No. as an example. Each glass sample of 1 to 38 does not contain an alkali metal oxide, has a density of 2.67 g / cm ³ or less, a thermal expansion coefficient of 43 to 48 × 10 ⁻⁷ / ° C., and a strain point of 637 ° C. or more. Met. The specific Young's modulus was 29 GPa / g · cm ⁻³ or more. Furthermore, each of these samples is easy to melt because the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is 1532 ° C. or less, the liquidus temperature is 1070 ° C. or less, and the liquidus viscosity is 10 ^5.4 dPa · s or more. Therefore, it was excellent in devitrification resistance. Therefore, it can be judged that each sample of the example is excellent in productivity of the glass substrate. In addition, each sample of the examples was excellent in BHF resistance and HCl resistance, and the appearance evaluation was also good. Considering the above points, each sample of the example is considered suitable as a glass substrate for TFT-LCD.

On the other hand, in the glass sample A of the comparative example, the value of (CaO + BaO—MgO) / SiO ₂ was 0.05, and the temperature at a high temperature viscosity of 10 ^2.5 dPa · s was as high as 1542 ° C. Moreover, the glass sample B of the comparative example had a (CaO + BaO—MgO) / SiO ₂ value of 0.43 and a strain point as low as 626 ° C.

  Further, Example Sample No. 17 glass was melted in a test melting furnace, and a glass substrate for display having a substrate size of 900 mm × 1100 mm and a thickness of 0.5 mm was produced by overflow down draw molding. The warpage of the glass substrate was 0.05% or less, The waviness (WCA) was 0.1 μm or less, the surface roughness (Ry) was 50 μm or less (cut-off λc: 9 μm), the surface quality was excellent, and it was suitable as a glass substrate for LCD. In overflow downdraw molding, by appropriately adjusting the speed of the pulling roller, the speed of the cooling roller, the temperature distribution of the heating device, the temperature of the molten glass, the flow rate of the glass, the drawing speed, the rotation speed of the stirring stirrer, etc. The surface quality of the glass substrate was adjusted. “Warpage” is measured by placing a glass substrate on an optical surface plate and using a clearance gauge described in JIS B-7524. “Waviness” is a value obtained by measuring WCA (filtered center line waviness) described in JIS B-0610 using a stylus type surface shape measuring device. This measurement is performed by SEMI STD D15-1296 “FPD”. Measured by a method in accordance with “Measurement method of surface waviness of glass substrate”, cut-off at the time of measurement is 0.8 to 8 mm, measured at a length of 300 mm in a direction perpendicular to the drawing direction of the glass substrate. is there. “Average surface roughness (Ry)” is a value measured by a method based on SEMI D7-94 “Measurement method of surface roughness of FPD glass substrate”.

  Accordingly, the alkali-free glass of the present invention is applied to flat display substrates such as LCDs and EL displays, cover glasses for image sensors such as charge coupled devices (CCD) and equal-magnification proximity solid-state imaging devices (CIS), and substrates for solar cells. Is preferred.

Claims (23)

A glass composition, _SiO 2 45 to _65% by _{mass%, Al 2 O 3 12~17%} , B 2 O 3 7.5~15%, MgO 0~ 1%, CaO 5.5~15%, SrO 0 ~5%, BaO 5~15%, ZnO 0~ 0.5%, MgO + CaO + SrO + BaO + ZnO 15~23%, containing _{ZrO 2 0~5%, TiO 2 0~5} %, the _P 2 O 5 _0~5%, It contains substantially no alkali metal oxide, has a mass fraction (CaO + BaO—MgO) / SiO ₂ value of 0.25 to 0.4, and an average coefficient of thermal expansion in the temperature range of 30 to 380 ° C. Is an alkali-free glass, characterized in that it is 40 to 50 × 10 ⁻⁷ / ° C. _2. The alkali-free glass according to claim 1, wherein the value of (MgO + CaO + SrO + BaO + ZnO) / SiO ₂ is 0.3 to 0.4 in terms of mass fraction. _{3. The} alkali-free glass according to claim 1, which contains substantially no As ₂ O ₃ and contains 0 to 3% of Sb ₂ O ₃ + SnO ₂ + Cl in mass% in terms of the following oxides. . _{3. The} alkali-free glass according to claim 1, wherein the glass is substantially free of As ₂ O ₃ and Sb ₂ O _3, and contains 0 to 1% of SnO ₂ in mass% in terms of the following oxides. . The alkali-free glass according to claim 1, wherein the liquidus temperature is 1150 ° C. or less and / or the liquidus viscosity is 10 ^5.4 dPa · s or more. By mass% terms of oxide, as a glass composition, a SnO ₂ containing 0-0.5 wt%, and up to SnO ₂ of 0.5 wt%, upon addition of SnO _2, the glass obtained Liquid phase temperature is 1150 degrees C or less, The alkali free glass in any one of Claims 1-5 characterized by the above-mentioned. The alkali-free glass according to any one of claims 1 to 6, wherein when 1% by mass of ZrO ₂ is added to the glass composition, the resulting glass has a liquidus temperature of 1150 ° C or lower.   The alkali-free glass according to any one of claims 1 to 7, wherein the strain point is 630 ° C or higher. The alkali-free glass according to any one of claims 1 to 8, wherein the temperature at 10 ^2.5 dPa · s is 1535 ° C or lower. 10. The relationship of T ₁ −T ₂ ≦ 880 ° C. is satisfied when the temperature at 10 ^2.5 dPa · s is T ₁ (° C.) and the strain point is T ₂ (° C.). The alkali-free glass according to any one of 9. The temperature at 10 ⁴ dPa · s satisfies T ₃ -T ₄ ≦ 330 ° C. when the temperature is T ₃ (° C.) and the softening point is T ₄ (° C.). The alkali-free glass according to any one of the above.   The alkali-free glass according to any one of claims 1 to 11, wherein when immersed in a 10% HCl aqueous solution at 80 ° C for 24 hours, the erosion amount is 5 µm or less.   The alkali-free glass according to any one of claims 1 to 12, wherein when immersed in a 130 buffered hydrofluoric acid solution at 20 ° C for 30 minutes, the erosion amount is 2 µm or less.   The alkali-free glass according to any one of claims 1 to 13, wherein when immersed in a 10% aqueous HCl solution at 80 ° C for 3 hours, white turbidity and roughness are not observed by visual surface observation.   The alkali-free glass according to any one of claims 1 to 14, wherein when immersed in a 63 buffered hydrofluoric acid solution at 20 ° C for 30 minutes, white turbidity and roughness are not observed by visual surface observation. The non-alkali glass according to claim 1, wherein the specific Young's modulus is 27 GPa / (g · cm ⁻³ ) or more.   An alkali-free glass substrate comprising the alkali-free glass according to any one of claims 1 to 16.   The alkali-free glass substrate according to claim 17, which is down-draw molded.   19. The alkali-free glass substrate according to claim 18, wherein the downdraw molding is overflow downdraw molding.   The alkali-free glass substrate according to any one of claims 17 to 19, which is used for a display.   The alkali-free glass substrate according to claim 20, wherein the display is a liquid crystal display.   The alkali-free glass substrate according to claim 20 or 21, wherein the display is an amorphous silicon TFT liquid crystal display.   The alkali-free glass substrate according to any one of claims 17 to 22, wherein the substrate size is 32 inches or more.