TWI402237B - E-glass substrate - Google Patents

Description

Alkali-free glass substrate

The present invention relates to an alkali-free glass substrate, which is suitable for use as a substrate for a flat panel display such as a liquid crystal display, an EL (electroluminescence) display, and a charge coupled device (CCD), etc. Substrates such as various image sensors, hard disks, filters, etc., such as components (CIS, Contact Image Sensor).

Previously, glass substrates have been widely used as substrates for flat panel displays such as liquid crystal displays and EL displays.

In particular, electronic devices such as thin-film transistor-liquid crystal display (TFT-LCD) are used in car navigation and digital camera viewfinders because of their thin size and low power consumption. , personal computer monitors and TV (Television, TV) and other uses.

In order to drive the liquid crystal display, a driving element typified by a TFT (thin-film transistor) element must be formed on the glass substrate. In the manufacturing process of the TFT element, a transparent conductive film, an insulating film, a semiconductor film, a metal film, or the like is formed on the glass substrate. Further, in the photolithography etching step, the glass substrate is treated by various heat treatments and chemical treatments. For example, in a TFT type active matrix liquid crystal display, an insulating film and a transparent conductive film are formed on a glass substrate. Further, a plurality of amorphous germanium and polycrystalline TFTs (thin film transistors) are formed on the glass substrate by a photolithography etching step. In the above manufacturing steps, the glass substrate is subjected to heat treatment at 300 to 600 ° C, and is also treated with various chemicals such as sulfuric acid, hydrochloric acid, an alkaline solution, hydrofluoric acid, and buffered hydrofluoric acid. Therefore, the glass substrate for a TFT liquid crystal display is required to have the following characteristics: (1) if the glass contains an alkali metal oxide, the alkaline ions may diffuse into the film-formed semiconductor material during the heat treatment, resulting in deterioration of the characteristics of the film. Therefore, an alkali metal oxide is not actually contained.

(2) It is excellent in chemical resistance to a solution such as an acid or an alkali used in the photolithography etching step.

(3) In the steps of film formation, annealing, etc., the glass substrate is exposed to high temperatures. At this time, it is desirable that the glass substrate has a small heat shrinkage rate. The reason for this is that if the heat shrinkage rate is large, the circuit pattern formed on the substrate is shifted. From the viewpoint of reducing the heat shrinkage rate, the strain point of the glass is high.

Further, in addition to the above, the glass substrate for a TFT liquid crystal display is required to have the following characteristics: (4) Excellent resistance to devitrification so that foreign matter does not occur in the glass during the melting step and the forming step of the glass. In particular, when the glass is formed by a down-draw method such as an overflow down-draw method, the devitrification resistance of the glass is important, and when the glass forming temperature is considered, the liquidus temperature is required to be 1200 ° C or lower.

(5) The density is low to reduce the weight of the liquid crystal display. In particular, a glass substrate mounted on a notebook computer has a strong demand for weight reduction, and specifically, it is required to be 2.50 g/cm ³ or less.

(6) The flatness of the surface is high. For example, in a liquid crystal display, a liquid crystal layer sandwiched between two thin glass substrates functions as a shutter, and the layer is displayed by blocking light or transmitting light. The liquid crystal layer is maintained to have a very thin thickness of several μm to 10 μm. Therefore, the flatness of the surface of the glass substrate, in particular, the unevenness of the thickness of μm, which is called undulation, is likely to affect the thickness of the liquid crystal layer (referred to as cell gap), and if the surface is undulating, display unevenness may be caused.

Further, in recent years, in order to achieve high-speed response and high definition, the cell gap tends to be further thinned in the liquid crystal display. Therefore, it is increasingly important to reduce the surface fluctuation of the glass substrate used. In order to reduce the surface undulation of the glass substrate, the most effective method is to precisely polish the surface of the formed glass substrate, but in this method, the manufacturing cost of the glass substrate is very high. Therefore, at present, a glass substrate having a surface undulation as small as possible is formed by a forming method such as an overflow down-draw method or a floating method, and is marketed in an unpolished state or with extremely slight grinding (contact polishing).

In order to satisfy these characteristics, various glass substrates have been proposed. (For example, refer to Patent Document 1)

[Patent Document 1] Japanese Patent Laid-Open No. Hei 8-811920

As described above, it is generally considered that the smaller the heat shrinkage rate of the glass substrate, the better. However, in recent years, in consideration of the heat shrinkage rate of a glass substrate, a technique of correcting with a photomask at the time of circuit formation has been started. As a result, if it is a small-sized glass substrate, even if the heat shrinkage rate is not sufficiently small, the problem of pattern shift can be solved. However, if it is a large glass substrate such as the sixth generation (for example, a glass substrate having 1500 mm or more on each side), it is difficult to adopt this technique.

It is an object of the present invention to provide a large-sized alkali-free glass substrate which can be corrected by a photomask at the time of circuit formation, and a method of manufacturing the same.

The present inventors have conducted various studies, and as a result, the present invention has been finally proposed in view of the fact that the larger the size of the substrate and the greater the unevenness of the heat shrinkage rate in the substrate.

That is, the present invention relates to the following (1) to (11).

(1) An alkali-free glass substrate having a short side and a long side of 1500 mm or more, characterized in that it is heated at a rate of 10 ° C/min from normal temperature and maintained at a temperature of 450 ° C for 10 hours. Further, when the temperature is lowered at a rate of 10 ° C /min (heat treatment according to the temperature schedule shown in Fig. 1), the difference between the maximum value and the minimum value of the absolute value of the heat shrinkage ratio in the substrate is within 5 ppm.

(2) The alkali-free glass substrate of (1), wherein the temperature is raised at a rate of 10 ° C /min from normal temperature, and maintained at a holding temperature of 450 ° C for 10 hours, and then decreased at a rate of 10 ° C / minute. The absolute value of the heat shrinkage rate in the central portion of the substrate is 40 ppm or more.

(3) The alkali-free glass substrate according to (1) or (2), which is formed by an overflow down-draw method.

(4) The alkali-free glass substrate according to any one of (1) to (3) which contains, by weight%, 50 to 70% of SiO ₂ , 1 to 20% of Al ₂ O ₃ , 0 to 15% B ₂ O ₃ , 0 to 30% of MgO, 0 to 30% of CaO, 0 to 30% of SrO, and 0 to 30% of BaO.

(5) A method for producing an alkali-free glass substrate, which comprises producing an alkali-free glass substrate by melting and molding a glass raw material, wherein: during the cooling process during molding, the temperature is adjusted from the cold point to the cold point. The average cooling rate in the temperature range of -100 ° C) is such that the difference between the average cooling rate of the central portion and the end portion in the sheet width direction is within 100 ° C / min.

(6) The method for producing an alkali-free glass substrate according to (5), wherein the glass is formed to have an effective width of 1500 mm or more.

(7) The method for producing an alkali-free glass substrate according to (5) or (6), wherein an average cooling rate in a temperature range from a cold point to a (cold cold point - 100 ° C) during cooling during forming The central portion in the plate width direction is 200 ° C / min or more.

(8) The method for producing an alkali-free glass substrate according to any one of (5) to (7), wherein, in the cooling process during forming, from a cold point to a temperature range of (cold cold point - 100 ° C) The speed of the pull plate is 150 cm/min or more.

(9) The method for producing an alkali-free glass substrate according to any one of (5) to (8), wherein the molding is carried out by an overflow down-draw method.

(10) The method for producing an alkali-free glass substrate according to any one of (5) to (9), which comprises producing an alkali-free glass substrate having a composition of 50 to 70% by weight of SiO ₂ , 1 ~20% Al ₂ O ₃ , 0 to 15% B ₂ O ₃ , 0 to 30% MgO, 0 to 30% CaO, 0 to 30% SrO, 0 to 30% BaO.

(11) An alkali-free glass substrate produced by the method according to any one of (5) to (10).

In the glass substrate of the present invention, the unevenness of the heat shrinkage rate in the substrate is small. Therefore, when the TFT circuit is formed and corrected by the photomask, since the thermal contraction in the substrate is always within a fixed range, the pattern can be formed with high yield and stability.

Further, according to the production method of the present invention, the glass substrate can be produced relatively easily.

The heat shrinkage rate of the glass substrate is affected by the cooling rate at the time of forming the glass sheet. According to the investigation by the inventors of the present invention, as shown in Fig. 2, the heat shrinkage rate of the glass plate cooled at a relatively fast cooling rate is large, whereas the heat shrinkage rate of the glass plate cooled at a slower speed is small. . Further, since the glass substrate is continuously pulled by the glass forming apparatus, the temperature history (cooling rate) is less changed in the direction of the drawing. Therefore, the difference in heat shrinkage rate is less likely to occur in the direction of the pull plate. On the other hand, the temperature difference is apt to occur in the width direction of the board, especially the temperature history (cooling speed) of the central portion and the end portion may be different. Therefore, the difference in heat shrinkage ratio in the direction of the sheet width is large.

The greater the plate width, the more pronounced this tendency. That is, the unevenness of the heat shrinkage rate in one substrate increases as the size of the glass substrate increases.

According to investigations by the inventors of the present invention, it is known that the difference in cooling rate from the temperature of (cold cold point + 50 ° C) to the temperature range of (cold cold point - 100 ° C) causes a difference in heat shrinkage rate. Furthermore, it has been clarified that the cooling conditions from the cold point to the temperature range of (Xu cold point - 100 ° C) do not have a large influence on the thickness and strain, and the plate thickness and strain are important characteristics for the flat display substrate. . Therefore, the thickness and strain can be controlled in the temperature region above the cold point, and the unevenness of the heat shrinkage rate can be adjusted in the temperature range from the cold point to the (cold cold point - 100 ° C) temperature range (= cold zone).

As a method for adjusting the uneven heat shrinkage rate, the difference in the cooling rate in the width direction of the sheet can be reduced in the temperature range from the cold point to the (cold cold point -100 ° C), specifically, in the temperature range Inside, the difference in cooling rate between the central portion and the end portion in the plate width direction was adjusted to within 100 ° C / min. The cooling rate is mainly adjusted by the speed of the pulling plate and the heating of the heater in the quenching furnace. To adjust the difference in cooling speed in the direction of the plate width, the electric power of the heater in the width direction of the plate can be adjusted.

Moreover, by speeding up the cooling rate, the unevenness of the heat shrinkage rate can also be reduced. That is, as is clear from Fig. 2, the faster the cooling rate, the larger the heat shrinkage rate, but the heat shrinkage rate hardly changes even if the cooling rate slightly changes.

The manufacturing method of the present invention is described in further detail.

First, the glass material that has been formulated into the desired composition is melted. The glass raw material can be formulated by weighing and mixing a glass raw material such as an oxide, a nitrate or a carbonate, glass cullet or the like to form a composition having a glass suitable for the properties of the application. The type of the glass is not particularly limited, and quartz glass, borosilicate glass, aluminosilicate glass, or the like can be used, but among them, it is preferable to form a pull-down method, particularly an overflow down-draw method. And the formed glass. The glass which can be formed by the down-draw method refers to, for example, when the overflow down-draw method is used, the liquid viscosity is 10 ^{4 . 5} Pa. Above s, preferably 10 ^{5 . 0} Pa. Glass above s. Furthermore, the viscosity of the liquid phase is the viscosity at the time of crystal precipitation, and the stronger the liquid phase viscosity, the less likely the devitrification occurs when the glass is formed, which makes the manufacturing easier.

As a glass composition suitable for a liquid crystal display substrate, as described later, an aluminosilicate type alkali-free glass composition containing 50 to 70% of SiO ₂ and 1 to 20% of Al _{2 may} be cited. O ₃ , 0 to 15% of B ₂ O ₃ , 0 to 30% of MgO, 0 to 30% of CaO, 0 to 30% of SrO, and 0 to 30% of BaO, especially in % by weight, Containing 50 to 70% SiO ₂ , 10 to 20% Al ₂ O ₃ , 3 to 15% B ₂ O ₃ , 0 to 15% MgO, 0 to 15% CaO, 0 to 15% SrO, 0~15% of the composition of BaO.

The glass raw material formulated as described above is supplied to a glass melting device and melted. The melting temperature can be appropriately adjusted depending on the kind of the glass. For example, when the glass contains the above composition, it can be melted at a temperature of about 1,500 to 1,650 °C. Further, the so-called melting in the present invention includes various steps such as clarification and stirring.

Next, the molten glass is formed into a glass plate shape and cooled. In order to reduce the unevenness of the heat shrinkage rate in the glass substrate, it is necessary to manage the temperature history in the temperature region where the formed glass plate is cooled to room temperature as described above. It is important that, in particular, the cooling rate difference does not occur in the temperature range from the cold point to the (cold cold point - 100 ° C). Specifically, the difference between the average cooling rates in the temperature range from the cold point to the (cold cold point -100 ° C) can be adjusted so that the average cooling rate difference between the central portion and the end portion in the sheet width direction is 100 ° C / Within minutes, it is preferably within 50 ° C / min, more preferably within 20 ° C / min.

As a method of reducing the difference in cooling rate between the central portion and the end portion, a method of reducing the electric power of the heater in the central portion in the width direction of the plate and increasing the electric power of the heater at the end portion can be employed.

Further, in order to further reduce the unevenness of the heat shrinkage rate in the substrate, it is preferred to increase the cooling rate. Specifically, the average cooling rate in the temperature range from the cold point to the (cold cold point - 100 ° C) can be adjusted. When the temperature is in the temperature range, the average cooling rate in the central portion in the width direction of the sheet is 200 ° C / min or more, especially 300 ° C / min or more, further 350 ° C / min or more, and further 400 ° C / min or more, and more. Further, at 500 ° C / min or more, a glass substrate having a very small unevenness in the substrate can be obtained relatively easily. Further, the glass plate cooled at a relatively fast cooling rate is formed into a glass plate having a large absolute heat shrinkage rate at the central portion of the substrate, and specifically, the absolute value of the heat shrinkage rate is 40 ppm or more, especially It is 50 ppm or more, further 53 ppm or more, and further 55 ppm, and further more than 57 ppm. Further, in order to prevent an inappropriate strain in the glass or to apply an excessive load to the molded body, it is preferred that the upper limit of the average cooling rate in the central portion in the sheet width direction is 1000 ° C / min or less. In the present invention, the "absolute value of heat shrinkage rate" means that the temperature is raised at a rate of 10 ° C /min from normal temperature, and maintained at a holding temperature of 450 ° C for 10 hours, and then at a rate of 10 ° C / minute. The heat shrinkage rate of each part of the substrate when cooling (heat treatment according to the temperature schedule shown in Fig. 1). In addition, the "average cooling rate" refers to the time in which the glass passes through a region corresponding to the region of the cold zone (the temperature range from the cold zone to the cold zone - 100 ° C), and then the zone is cooled. The temperature difference is divided by the speed obtained by the passage time.

As one of the most effective methods for changing the average cooling rate, there is a method of changing the speed of the drawing of the glass sheet. The faster the pulling speed is, the larger the absolute value of the heat shrinkage rate of the glass is, so that the uneven heat shrinkage rate caused by the change of the pulling speed can be reduced. Furthermore, the speed of the pulling plate can be increased by speeding up the rotation speed of the stretching rolls for elongating the formed glass. Further, when the cooling zone (cold furnace) in the forming step is extremely shorter than the floating method of the lowering method, the average cooling rate in the temperature region can be easily changed. Further, when the molding is carried out by the overflow down-draw method, which is one of the down-draw methods, a glass substrate having an excellent surface level can be obtained, and therefore, the polishing step can be omitted. Specifically, it is preferable that the pulling speed in the temperature range from the cold point to the (cold cold point -100 ° C) is preferably 150 cm/min or more, more preferably 270 cm/min or more, and further More preferably, it is 320 cm/min or more, and particularly preferably 400 cm/min or more. Further, the upper limit of the pulling speed is not particularly limited, but it is preferably 800 cm/min or less in consideration of the load of the forming device. In addition, the "pull plate speed" as used herein refers to the average speed of the central portion of the glass substrate in the width direction of the plate passing through the cold region (the region from the cold point to the temperature range of (cold cold point - 100 ° C)). .

Further, when formed by the down-draw method, the temperature of the end portion in the cold furnace is more likely to fall than the central portion in the width direction of the plate. That is, the central portion is better in heat preservation, and the end portion is easier to dissipate heat. Therefore, it is difficult to fix the cooling rate in the width direction of the sheet, and the heat shrinkage ratio in the sheet width direction tends to be largely uneven. Therefore, it can be said that the benefits of using the method of the present invention are large when formed by the down-draw method.

Further, if the distance in the width direction of the glass sheet is increased, the heat shrinkage rate unevenness of the obtained glass substrate tends to increase. That is, when the effective width of the glass is 1500 mm or more, especially 1800 mm or more, the temperature difference in the sheet width direction tends to become large during the cooling step during molding, so that there is no heat shrinkage ratio. The tendency to become bigger. Therefore, it can be said that when a large glass substrate is to be formed, the benefits of using the method of the present invention are large.

Thereafter, the glass formed into a plate shape is cut into a specific size, and then subjected to necessary treatment such as end surface treatment and cleaning.

According to the above aspect, a glass substrate having a small unevenness in heat shrinkage rate can be obtained.

Next, the glass substrate of the present invention obtained as described above will be described.

The glass substrate of the present invention is characterized in that the unevenness of the heat shrinkage rate in one of the substrates is small. Specifically, when the temperature is raised from normal temperature at a rate of 10 ° C / minute, and maintained at a holding temperature of 450 ° C for 10 hours, and then cooled at a rate of 10 ° C / minute (heat treatment according to the temperature schedule shown in Figure 1) When the absolute value of the absolute value of the heat shrinkage ratio in the substrate is within 5 ppm, preferably within 3 ppm, more preferably within 1 ppm. When the difference between the maximum value and the minimum value of the absolute value of the heat shrinkage ratio in the substrate exceeds 5 ppm, the difference in pattern shift in the substrate increases, making correction by the mask difficult, resulting in remarkable display performance of the display device. reduce. Furthermore, in order to reduce the difference in thermal shrinkage rate in the substrate, the average cooling rate in the temperature range from the cold point to the (cold cold point -100 ° C) can be adjusted in the central portion of the glass sheet width direction and the end portion is not greatly different. .

The glass substrate to which the present invention is applied is an alkali-free glass substrate having a short side and a long side of 1500 mm or more, particularly 1800 mm or more, and further 2000 mm or more. In such a large glass substrate, the requirement for uneven heat shrinkage rate is more stringent. That is, when the unevenness of the absolute values of the heat shrinkage ratio is the same, the unevenness of the dimensional change due to the heat shrinkage of the large-sized glass substrate is larger than that of the small substrate. In the case of manufacturing a large substrate, in the cooling step during molding, the temperature difference in the sheet width direction tends to be large, and the unevenness in the heat shrinkage ratio tends to increase. Therefore, it is important to reduce the unevenness of the heat shrinkage rate in one substrate.

Further, the glass substrate to which the present invention is applied is a glass substrate produced at a faster cooling rate (that is, a glass substrate having a higher absolute heat shrinkage ratio), and the unevenness of heat shrinkage in one substrate can be reduced. . The reason is that the absolute value of the glass heat shrinkage rate of the glass substrate having a high cooling rate is increased, and on the other hand, even if the cooling rate is slightly changed, the heat shrinkage rate hardly changes, and the heat shrinkage rate in the substrate is small. The difference is narrowed. Further, the glass substrate produced at a relatively fast cooling rate means that the average cooling rate in the temperature range from the cold point to the (cold cold point - 100 ° C) is 200 ° C in the central portion in the sheet width direction. More than a minute, especially 300 ° C / min or more, further 350 ° C / min, further 400 ° C / min or more, and further more than 500 ° C / min or more, the glass substrate, or the center of the substrate (near the center of gravity) The absolute value of the heat shrinkage rate is 40 ppm or more, especially 50 ppm or more, further 53 ppm or more, more preferably 55 ppm or more, and further, 57 ppm or more of the glass substrate. Further, when the absolute value of the heat shrinkage rate of the glass is increased, there is a drawback in that even if the cooling rate is slightly changed, the heat shrinkage rate hardly changes, and thus the unevenness of the heat shrinkage ratio between the substrates is small.

Further, when the absolute values of the heat shrinkage ratio of the glass substrate are the same, the higher the strain point of the glass substrate, the smaller the amount of change in the heat shrinkage rate tends to be. Therefore, it can be said that the strain point of the glass is high. Specifically, the strain point of the glass is preferably 630 ° C or higher, particularly preferably 650 ° C or higher.

Further, in the case of the glass suitable for the above-mentioned use, various glasses such as quartz glass, borosilicate glass, and aluminosilicate glass can be used as the alkali-free glass constituting the glass substrate of the present invention. Among them, it is preferred to include a glass which can be formed by an overflow down-draw method. That is, the glass substrate formed by the overflow down-draw method also has an excellent surface grade and can be used without being ground. Further, in the glass substrate formed by the down-draw method, the cooling rate in the sheet width direction is generally difficult to be fixed, and thus the heat shrinkage rate tends to be uneven in the substrate. Therefore, it is very important to adjust the unevenness of the heat shrinkage rate in the substrate to a fixed range.

The glass which can be formed by the down-draw method means, for example, when the overflow down-draw method is used, the liquid viscosity is 10 ^{4 . 5} Pa. Above s, preferably 10 ^{5 . 0} Pa. Glass above s.

Further, examples of the glass to be applied to the liquid crystal display substrate include an aluminosilicate-based alkali-free glass containing 50 to 70% of SiO ₂ and 1 to 20% of Al ₂ O ₃ and 0 to 15 in terms of % by weight. % B ₂ O ₃ , 0 to 30% MgO, 0 to 30% CaO, 0 to 30% SrO, 0 to 30% BaO composition, and preferably in weight %, containing 50~ 70% SiO ₂ , 10 to 20% Al ₂ O ₃ , 3 to 15% B ₂ O ₃ , 0 to 15% MgO, 0 to 15% CaO, 0 to 15% SrO, 0 to 15 The composition of % BaO. Within this range, a glass substrate having the above-described required characteristics can be obtained.

SiO ₂ forms a component of a glass network forming agent. When the content of SiO ₂ is more than 70% by weight, the high-temperature viscosity is enhanced and the meltability is deteriorated, and the devitrification property is also deteriorated, which is not preferable. If it is less than 50% by weight, the chemical durability is deteriorated, which is not preferable.

The Al ₂ O ₃ system increases the composition of the strain point. When the content of Al ₂ O ₃ is more than 20% by weight, the devitrification property and the chemical durability to the hydrofluoric acid buffer solution are deteriorated, which is not preferable. On the other hand, if it is less than 1% by weight, the strain point will decrease, which is not preferable. It is preferably 10 to 20% by weight.

The B ₂ O ₃ system functions as a solvent to improve the meltability of the glass. When the content of B ₂ O ₃ is more than 15% by weight, the strain point is lowered, and the chemical resistance to hydrochloric acid is deteriorated, which is not preferable. On the other hand, if it is too small, the high temperature viscosity will increase and the meltability will deteriorate. It is preferably from 3 to 15% by weight.

Further, MgO is a component which lowers the high-temperature viscosity and improves the meltability of the glass, and is preferably 0 to 30% by weight, particularly preferably 0 to 15% by weight. If the content of MgO is too large, the devitrification property is deteriorated, and the chemical durability against the hydrofluoric acid buffer solution is also deteriorated.

CaO is the same as MgO, and is also a component which lowers the high-temperature viscosity to improve the meltability of the glass, and the content thereof is preferably from 0 to 30% by weight, particularly preferably from 0 to 15% by weight. If the content of CaO is too large, the devitrification property is deteriorated, and the chemical durability of the hydrofluoric acid buffer solution is also deteriorated, which is not preferable.

SrO is a component that improves devitrification and chemical durability. When the content of SrO is more than 30% by weight, the density becomes large, the high-temperature viscosity is enhanced, and the meltability is deteriorated, which is not preferable. A preferred range is from 0 to 15% by weight.

BaO is the same as SrO, and is also a component which improves devitrification and chemical durability, and is preferably 0 to 30% by weight, particularly preferably 0 to 15% by weight. If the content of BaO is too large, the density becomes large, the high-temperature viscosity is enhanced, and the meltability is deteriorated, which is not preferable.

Further, in addition to the above, various components such as a clarifying agent may be added as needed.

[Examples]

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

First, in terms of % by weight, containing 60% SiO ₂ , 15% Al ₂ O ₃ , 10% B ₂ O ₃ , 0% MgO, 5% CaO, 5% SrO, 2% The glass raw materials were blended and mixed in the form of BaO, and then continuously melted at a maximum temperature of 1,650 ° C by a melting furnace. Further, under various conditions shown in Table 1, the molten glass was formed into a plate shape by an overflow down-draw method, and was cold-cooled. Thereafter, the plate glass was cut, whereby an alkali-free glass substrate of 1500 × 1800 × 0.65 mm size was obtained. The glass substrate has a strain point of 650 ° C, a cold point of 705 ° C, and a liquid phase viscosity of 10 ^{5 . 0} Pa. The characteristics of s. Further, the strain point and the cold point were confirmed by the fiber elongation method. The glass is pulverized and passed through a standard sieve of 30 meshes (500 μm mesh), and the glass powder remaining in 50 mesh (300 μm mesh) standard sieve is placed in a platinum boat at a temperature. The temperature was maintained in a gradient furnace for 24 hours, and the precipitation temperature of the crystal, that is, the liquidus temperature was measured, and then determined based on the high temperature viscosity corresponding to the temperature. Further, the high temperature viscosity was measured by a platinum ball lifting method.

Table 1 shows the glass heat shrinkage ratio of the central portion and the end portion in the sheet width direction of the obtained glass substrate.

As is clear from Table 1, the smaller the difference in the cooling rate between the central portion and the end portion in the plate width direction, or the faster the cooling rate, the smaller the unevenness of the heat shrinkage ratio in the substrate.

In addition, the speed of the drawing plate refers to the speed at which the central portion in the plate width direction of the continuously formed glass substrate passes through the quenching region, and in the present embodiment, the measuring roller is abutted in the central portion of the plate width direction. The intermediate point of the area (corresponding to the position of the cold point -50 ° C) is measured. The term "cold zone" refers to the zone in the width direction of the plate, which corresponds to the temperature range from the cold point to the (cold point -100 ° C). In this embodiment, it means cooling from 705 ° C to 605 ° C. The area. In addition, the average cooling rate refers to a speed obtained by dividing the temperature difference in the cold portion of the center portion or the end portion by the passage time by calculating the time during which the glass passes through the region corresponding to the cold region.

The absolute value of the heat shrinkage rate was measured by the following method. First, the glass plate sample is cut out from the central portion of the obtained glass substrate and the portion (end portion) corresponding to the position of 900 mm from the central portion in the direction from the central portion to the end portion, respectively, and then as shown in FIG. (a), after the linear marking is added to a specific portion of the glass sheet 1, the glass sheet 1 is folded in a direction perpendicular to the marking to be divided into two glass sheets 1a and 1b. Then, only one of the glass sheets 1a is subjected to heat treatment according to the temperature schedule shown in FIG. 1 (heating at a temperature of 10 ° C/min from normal temperature, and maintaining at a holding temperature of 450 ° C for 10 hours, and then 10 °C / minute speed to cool down). Thereafter, as shown in FIG. 3(b), the heat-treated glass sheet piece 1a is placed side by side with the untreated glass sheet piece 1b, and both are fixed by an adhesive tape (not shown), and then the laser is used. The deviation of the reticle is measured by a microscope, and is obtained by using the following formula 1. Further, l ₀ in the formula 1 represents the distance between the reticle lines, and ΔL ₁ and ΔL ₂ represent the positional shift amount of the reticle.

The present invention has been described in detail above with reference to the specific aspects thereof. It is obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

Further, the present application is based on a Japanese patent application filed on Jan. 12, 2006, the entire disclosure of which is hereby incorporated by reference.

Moreover, all references cited herein are incorporated by reference in their entirety.

[Industrial availability]

The heat shrinkage rate in the substrate of the glass substrate of the present invention is small. Therefore, when the TFT circuit is formed and corrected by the photomask, the thermal contraction in the substrate is always within a fixed range, so that the pattern can be formed with high yield and stability.

Further, according to the production method of the present invention, the glass substrate can be produced relatively easily.

1. . . glass plate

1a, 1b. . . Glass plate

△L ₁ , △L ₂ . . . Position offset

l ₀ . . . Distance between marking lines

Fig. 1 is an explanatory view showing a temperature schedule for determining the absolute value of the heat shrinkage rate.

Fig. 2 is a graph showing the relationship between the average cooling rate and the absolute value of the heat shrinkage rate.

3(a) and 3(b) are explanatory views showing a method of measuring the absolute value of the heat shrinkage rate.

1. . . glass plate

1a, 1b. . . Glass plate

△L ₁ , △L ₂ . . . Position offset

1 ₀ . . . Distance between marking lines

Claims (11)

An alkali-free glass substrate having a short side and a long side of 1500 mm or more, characterized in that it is heated at a rate of 10 ° C/min from normal temperature, and maintained at a temperature of 450 ° C for 10 hours, and then 10 When the temperature is lowered at a rate of ° C/min (heat treatment according to the temperature schedule shown in Fig. 1), the difference between the maximum value and the minimum value of the absolute value of the heat shrinkage ratio in the substrate is within 5 ppm. The alkali-free glass substrate of claim 1, wherein the substrate is heated at a temperature of 10 ° C / min from normal temperature, and maintained at a temperature of 450 ° C for 10 hours, and then cooled at a rate of 10 ° C / minute, the central portion of the substrate The absolute heat shrinkage rate is 40 ppm or more. The alkali-free glass substrate of claim 1 or 2 is formed by an overflow down-draw method. The alkali-free glass substrate according to claim 1 or 2, which contains 50 to 70% of SiO ₂ , 1 to 20% of Al ₂ O ₃ , 0 to 15% of B ₂ O ₃ , and 0 to 30% by weight. % of MgO, 0 to 30% of CaO, 0 to 30% of SrO, and 0 to 30% of BaO. A method for producing an alkali-free glass substrate, which is characterized in that an alkali-free glass substrate is produced by melting and forming a glass raw material, and is adjusted from a cold point to a cold point during cooling during forming. The average cooling rate in the temperature range of 100 ° C) is such that the difference between the average cooling rate of the central portion and the end portion in the sheet width direction is within 100 ° C / min. The method for producing an alkali-free glass substrate according to claim 5, wherein the glass is formed to have an effective width of 1500 mm or more. The method for producing an alkali-free glass substrate according to claim 5 or 6, wherein in the cooling process during forming, the temperature range from the cold point to the (cold cold point -100 ° C) In the circumference, the average cooling rate in the central portion in the sheet width direction is 200 ° C / min or more. The method for producing an alkali-free glass substrate according to claim 5 or 6, wherein in the cooling process during forming, the drawing speed in the temperature range from the cold point to the (cold cold point - 100 ° C) is 150 cm/min. the above. The method for producing an alkali-free glass substrate according to claim 5 or 6, which is formed by an overflow down-draw method. The method for producing an alkali-free glass substrate according to claim 5 or 6, which comprises producing an alkali-free glass substrate having 50% to 70% of SiO ₂ and 1 to 20% of Al ₂ O ₃ by weight %; 0 to 15% of B ₂ O ₃ , 0 to 30% of MgO, 0 to 30% of CaO, 0 to 30% of SrO, and 0 to 30% of BaO. An alkali-free glass substrate produced by the method of any one of claims 5 to 10.