JP5083707B2 - Method for producing alkali-free glass substrate - Google Patents

Description

  The present invention is a non-alkali suitable as a substrate for flat display substrates such as liquid crystal displays and EL displays, various image sensors such as charge-coupled devices (CCD) and equal-magnification proximity solid-state imaging devices (CIS), hard disks and filters. It relates to a glass substrate.

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

  In particular, electronic devices such as thin-film transistor active matrix liquid crystal displays (TFT-LCDs) are thin and have low power consumption, so they are used in various applications such as car navigation, digital camera finder, PC monitor and TV. Yes.

In order to drive a liquid crystal display, it is necessary to form a driving element typified by a TFT element on a glass substrate. In the manufacturing process of a TFT element, a transparent conductive film, an insulating film, a semiconductor film, a metal film, etc. are formed on a glass substrate. Further, in the photolithography-etching process, the glass substrate is processed by various heat treatments and chemical treatments. For example, in a TFT type active matrix liquid crystal display, an insulating film or a transparent conductive film is formed on a glass substrate. Further, a large number of TFTs (thin film transistors) made of amorphous silicon or polycrystalline silicon are formed on a glass substrate by a photolithography-etching process. In such a manufacturing process, the glass substrate is subjected to heat treatment at 300 to 600 ° C., and is also subjected to treatment with various chemicals such as sulfuric acid, hydrochloric acid, alkaline solution, hydrofluoric acid, and buffered hydrofluoric acid. Therefore, the following characteristics are required for a glass substrate for a TFT liquid crystal display.
(1) If an alkali metal oxide is contained in the glass, alkali ions are diffused 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) Photolithography—Excellent resistance to acid, alkali, and other solutions used in the etching process, that is, chemical resistance.
(3) The glass substrate is exposed to a high temperature in processes such as film formation and annealing. At that time, it is desired that the thermal shrinkage of the glass substrate is small. That is, if the thermal contraction rate is large, the circuit pattern formed on the substrate is shifted. From the viewpoint of reducing the heat shrinkage rate, it is advantageous that the glass has a higher strain point.

In addition to the above, the following characteristics are required for a glass substrate for a TFT liquid crystal display.
(4) Excellent devitrification resistance so that no foreign matter is generated in the glass during the glass melting or forming step. In particular, when glass is formed by a downdraw method such as an overflow downdraw method, the devitrification resistance of the glass is important, and when the glass forming temperature is taken into account, the liquidus temperature may be 1200 ° C. or lower. Required.
(5) The density is low in order to reduce the weight of the liquid crystal display. In particular, a glass substrate mounted on a notebook personal computer has a strong demand for weight reduction, and specifically, it is required to be 2.50 g / cm ³ or less.
(6) The surface flatness is high. For example, in a liquid crystal display, a liquid crystal layer sandwiched between two thin glass substrates works as an optical shutter, and this layer displays light by shielding or transmitting light. This liquid crystal layer is maintained at a very thin thickness of several μm to several tens μm. Therefore, the flatness of the surface of the glass substrate, particularly the irregularities of the μm level called waviness, can easily affect the thickness of the liquid crystal layer (called cell gap). If the waviness of the surface is large, display defects such as display unevenness can occur. Cause.

  In recent years, liquid crystal displays have a tendency to make the cell gap thinner for the purpose of high-speed response and high definition. Therefore, it is increasingly important to reduce the waviness of the surface of the glass substrate used for this purpose. It is coming. The most effective method for reducing the waviness of the surface of the glass substrate is to precisely polish the surface of the glass substrate after molding, but this method increases the manufacturing cost of the glass substrate. For that reason, glass substrates with as little surface waviness as possible are formed by molding methods such as the overflow downdraw method and the float method, and they are shipped without being polished or subjected to extremely light polishing (touch polishing). Yes.

In order to satisfy these characteristics, various glass substrates have been proposed. (For example, Patent Document 1)
JP-A-8-811920

  As described above, the smaller the heat shrinkage rate of the glass substrate, the better. However, in recent years, taking into account the thermal shrinkage rate of the glass substrate, a technique for performing correction using a photomask during circuit formation has been adopted. As a result, the medium-to-small glass substrate can solve the problem of pattern deviation even when the thermal shrinkage rate is not sufficiently small. However, it is still difficult to adopt this technology for a large glass substrate (for example, a glass substrate having a side of 1500 mm or more) as called the sixth generation.

  An object of the present invention is to provide a large alkali-free glass substrate that can be corrected by a photomask during circuit formation and a method for manufacturing the same.

  As a result of various studies, the present inventor has come to propose the present invention by paying attention to the fact that the variation in the thermal shrinkage rate in the substrate increases as the substrate size increases.

The method for producing an alkali-free glass substrate of the present invention is a method for producing an alkali-free glass substrate by melting and molding a glass raw material, and in the cooling process at the time of molding, from a slow cooling point (slow cooling point-100). The average cooling rate in the temperature range of 200 ° C. is adjusted to be 200 ° C./min or more at the center portion in the plate width direction and within 100 ° C./min at the center portion and the end portion in the plate width direction. It is characterized by doing.

The glass substrate obtained by the production method of the present invention has a small variation in thermal shrinkage rate within the substrate. Therefore, when correction using a photomask is performed at the time of forming a TFT circuit, the thermal contraction in the substrate is always within a certain range, so that pattern formation can be performed stably with high yield.

  Moreover, according to the manufacturing method of this invention, an above-described glass substrate can be produced easily.

  The thermal shrinkage rate of the glass substrate depends on the cooling rate at the time of forming the glass sheet. According to the investigation by the present inventors, as shown in FIG. 2, the plate glass cooled at a high cooling rate has a large heat shrinkage rate, and conversely, the plate glass cooled at a low rate has a low heat shrinkage rate. Moreover, since the glass substrate is continuously drawn by the glass forming apparatus, the temperature history (cooling rate) varies little in the drawing direction. Accordingly, a difference in heat shrinkage rate is unlikely to occur in the plate drawing direction. On the other hand, a temperature difference is likely to occur in the plate width direction, and in particular, the temperature history (cooling rate) between the central portion and the end portion is different. Therefore, the difference in thermal shrinkage in the plate width direction is large.

  This tendency becomes more prominent as the plate width increases. That is, as the glass substrate becomes larger, the variation in the thermal shrinkage rate within one substrate becomes larger.

  According to the investigation by the present inventors, the difference in the cooling rate in the temperature range from (annealing point + 50 ° C.) to (annealing point−100 ° C.) causes the difference in heat shrinkage rate. I found out. Furthermore, it has been found that the cooling conditions in the temperature range from the annealing point (annealing point−100 ° C.) do not significantly affect the plate thickness and distortion, which are important characteristics for the flat panel display substrate. Therefore, the thickness and strain are controlled in the temperature range above the annealing point, and the variation of the thermal shrinkage rate in the temperature range (= annealing region) from the annealing point (annealing point-100 ° C) may be adjusted. .

  As a means for adjusting the variation of the thermal shrinkage rate, the difference in the cooling rate in the plate width direction should be made small in the temperature range from the annealing point to (annealing point−100 ° C.). In this case, the cooling rate difference between the central portion in the plate width direction and the end portion may be adjusted to be within 100 ° C./min. The cooling rate is adjusted mainly by the sheet drawing speed and the heating of the heater in the slow cooling furnace. To adjust the cooling temperature difference in the sheet width direction, the power of the heater in the sheet width direction may be adjusted.

  Also, the variation in the thermal shrinkage rate can be reduced by increasing the cooling rate. In other words, it can be seen from FIG. 2 that the higher the cooling rate, the greater the heat shrinkage rate, but the heat shrinkage rate hardly changes even if the cooling rate changes somewhat.

  The production method of the present invention will be further described in detail.

First, a glass material prepared so as to have a desired composition is melted. The glass raw material may be prepared by weighing and mixing glass raw materials such as oxides, nitrates and carbonates, cullet and the like so as to obtain a glass composition having characteristics suitable for the application. There are no particular restrictions on the type of glass, such as silica glass, borosilicate glass, aluminosilicate glass, etc. Among them, it is preferable to prepare a glass that can be molded by the downdraw method, particularly the overflow downdraw method. For example, in the overflow downdraw method, the glass that can be formed by the downdraw method is a glass having a liquid phase viscosity of 10 ^4.5 Pa · s or more, preferably 10 ^5.0 Pa · s or more. In addition, liquid phase viscosity is a viscosity at the time of a crystal | crystallization precipitating, and devitrification does not generate | occur | produce easily at the time of glass shaping, and it becomes easy to manufacture, so that a liquid phase viscosity is high.

As a glass composition suitable for the liquid crystal display substrate application, as will be described later, SiO ₂ 50 to 70%, Al ₂ O ₃ 1 to 20%, B ₂ O ₃ 0 to 15%, MgO 0 to 30% by mass%, as described later. CaO 0~30%, SrO 0~30%, BaO 0~30%, in particular SiO ₂ 50-70% by _{mass%, Al 2 O 3 10~20%} , B 2 O 3 3~15%, MgO 0~ Aluminosilicate-based alkali-free glass composition containing 15%, CaO 0-15%, SrO 0-15%, BaO 0-15%.

  The glass raw material thus prepared is supplied to a glass melting apparatus and melted. What is necessary is just to adjust a melting temperature suitably according to the kind of glass, for example, in the case of the glass which has the said composition, what is necessary is just to fuse | melt at the temperature of about 1500-1650 degreeC. The melting referred to in the present invention includes various steps such as clarification and stirring.

  Next, the molten glass is formed into a plate glass and cooled. In order to reduce the variation of the thermal shrinkage rate in the glass substrate, as described above, it is necessary to manage the temperature history in the temperature region where the molded plate glass is cooled to room temperature. In particular, it is important to prevent a difference in cooling rate from occurring in the temperature range from the annealing point (annealing point−100 ° C.). Specifically, the difference in average cooling rate in the temperature range from the annealing point to (annealing point−100 ° C.) is within 100 ° C./min, preferably 50 ° C., between the central portion and the end portion in the plate width direction. / Min., Or even 20 ° C./min.

  As a method for reducing the difference in cooling rate between the central portion and the end portion, methods such as lowering the power of the heater in the central portion in the plate width direction and increasing the power of the end heater can be employed.

  In order to reduce the variation in the thermal shrinkage rate in the substrate, it is preferable to increase the cooling rate. Specifically, the average cooling rate in the temperature range from the annealing point to (annealing point−100 ° C.) may be adjusted. In this temperature region, the average cooling rate of the central portion in the plate width direction is 200 ° C./min or more, particularly 300 ° C./min or more, further 350 ° C./min or more, more preferably 400 ° C./min or more, further 500 ° C./min. In this way, it is possible to easily obtain a glass substrate with very little variation in the substrate. The plate glass cooled at a high cooling rate is a plate glass having a large absolute value of the heat shrinkage rate at the center of the substrate, specifically 40 ppm or more, particularly 50 ppm or more, further 53 ppm or more, further 55 ppm, or even 57 ppm or more. It becomes the plate glass which has a shrinkage | contraction rate absolute value. The upper limit of the average cooling rate at the central portion in the plate width direction is preferably 1000 ° C./min or less in order to prevent inappropriate distortion in the glass or excessive load on the formed body. . In the present invention, the “absolute value of heat shrinkage rate” means that the temperature is increased from room temperature at a rate of 10 ° C./min, held at a holding temperature of 450 ° C. for 10 hours, and cooled at a rate of 10 ° C./min (shown in FIG. 1). It means the thermal contraction rate of each part of the substrate when it is heat-treated). The “average cooling rate” refers to the time during which the glass passes through the zone corresponding to the slow cooling region (the temperature range from the slow cooling point to (slow cooling point−100 ° C.)), and the temperature within the slow cooling region. It refers to the speed obtained by dividing the difference by the transit time.

  One of the most effective methods for changing the average cooling rate is a method for changing the drawing speed of the plate glass. As the sheet drawing speed is increased, the absolute value of the heat shrinkage rate of the glass increases, and the variation in the heat shrinkage ratio due to fluctuations in the sheet drawing speed can be reduced. In addition, what is necessary is just to raise the rotational speed of the tension | pulling roller which extends the shape | molded glass in order to raise a plate | board drawing speed | rate. In the case of the downdraw method in which the cooling region (slow cooling furnace) in the molding process is extremely short compared to the float method, the average cooling rate in this temperature region can be easily changed. Furthermore, if it is formed by an overflow downdraw method which is a kind of downdraw method, a glass substrate having excellent surface quality can be obtained, and there is an advantage that the polishing step can be omitted. Specifically, the sheet drawing speed in the temperature range from the annealing point (annealing point−100 ° C.) is preferably 150 cm / min or more, 270 cm / min or more, further 320 cm / min or more, particularly 400 cm. / Min or more is desirable. The upper limit of the drawing speed is not particularly limited, but is preferably 800 cm / min or less in consideration of the load on the molding apparatus. In addition, the "plate drawing speed" demonstrated here is the speed which the plate width direction center part of a glass substrate passes through a slow cooling area | region (area | region in the temperature range from a slow cooling point to (slow cooling point-100 degreeC)). Means the average.

  In the case of molding by the downdraw method, the temperature at the end tends to decrease in the slow cooling furnace as compared with the central portion in the plate width direction. That is, the central portion has good heat retention, but heat easily escapes from the end portion. Therefore, the cooling rate in the plate width direction is difficult to be constant, and there is a tendency that the heat shrinkage rate in the plate width direction varies greatly. Therefore, when molding by the downdraw method, it can be said that the merit of employing the method of the present invention is great.

  Moreover, when the distance of the glass width direction of glass becomes long, the dispersion | variation in the thermal contraction rate of the glass substrate obtained tends to become large. In other words, when the glass is formed so that the effective width is 1500 mm or more, particularly 1800 mm or more, the temperature difference in the sheet width direction tends to be large in the cooling process at the time of forming, and the variation in the thermal shrinkage rate tends to increase. It is in. Therefore, when a large glass substrate is to be molded, it can be said that the merit of employing the method of the present invention is great.

  Thereafter, the glass formed into a plate shape is cut into a predetermined size and then subjected to necessary processing such as end face processing and washing.

  In this way, a glass substrate having a small variation in thermal shrinkage rate can be obtained.

Next, a description will be given Ruga glass substrate obtained as described above.

The glass substrate obtained by the method of the present invention is characterized by small variation in thermal shrinkage rate within one substrate. Specifically, when the temperature is raised from room temperature at a rate of 10 ° C./min, held at a holding temperature of 450 ° C. for 10 hours, and cooled 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 rate in the substrate is within 5 ppm, preferably within 3 ppm, more preferably within 1 ppm. If the difference between the maximum value and the minimum value of the absolute value of the thermal contraction rate in the substrate exceeds 5 ppm, the difference in pattern deviation in the substrate becomes large, and correction with a photomask becomes difficult, and the productivity of the display device is reduced. It drops significantly. In order to reduce the thermal shrinkage difference in the substrate, the average cooling rate in the temperature range from the annealing point to (annealing point−100 ° C.) does not differ greatly between the central portion and the end portion of the glass in the plate width direction. Adjust as follows.

  The glass substrate which is an object of the present invention 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 demand for variation in the heat shrinkage rate becomes more severe. That is, when the absolute value of the thermal shrinkage rate is the same, the large glass substrate has a larger variation in dimensional change due to thermal contraction than the small substrate. Nevertheless, when manufacturing a large substrate, the temperature difference in the plate width direction tends to increase in the cooling process during molding, and the variation in thermal shrinkage tends to increase. Therefore, it is important to reduce the variation in the thermal shrinkage rate within one substrate.

  Moreover, the glass substrate which is the object of the present invention is a glass substrate produced at a high cooling rate (that is, a glass substrate having a high absolute value of the thermal shrinkage rate). Variation can be reduced. In other words, a glass substrate with a high cooling rate has a large absolute value of the heat shrinkage rate of the glass. On the other hand, even if the cooling rate varies slightly, the heat shrinkage rate hardly changes and the difference in heat shrinkage rate within the substrate becomes small. It is. The glass substrate produced at a high cooling rate means that the average cooling rate in the temperature range from the annealing point to (annealing point−100 ° C.) is 200 ° C./min or more, particularly 300 ° C. in the central part in the plate width direction. / Min or more, further 350 ° C./min, further 400 ° C./min or more, further 500 ° C./min or more, or the absolute value of the heat shrinkage rate at the center of the substrate (near the center of gravity) The glass substrate is 40 ppm or more, particularly 50 ppm or more, further 53 ppm or more, further 55 ppm or more, 57 ppm or more. Further, if the absolute value of the heat shrinkage rate of the glass is increased, the heat shrinkage rate hardly changes even if the cooling rate is slightly changed.

  If the absolute value of the heat shrinkage rate of the glass substrate is the same, the amount of change in the heat shrinkage rate tends to be smaller as the strain point of the glass substrate is higher. Therefore, it can be said that a higher strain point of glass is advantageous. Specifically, the strain point of the glass is preferably 630 ° C. or higher, particularly 650 ° C. or higher.

Alkali-free glass constituting the or glass substrate is silica glass, if the glass suitable for the application, borosilicate glass, aluminosilicate glass, various glass can be used. Among them, it is preferable to be made of glass that can be molded by the overflow downdraw method. That is, the glass substrate formed by the overflow downdraw method has excellent surface quality and has an advantage that it can be used without being polished. Note that a glass substrate formed by the downdraw method generally has a tendency that the cooling rate in the plate width direction is hardly constant, and thus the thermal shrinkage rate tends to vary within the substrate. Therefore, it is very important to adjust so that the variation of the thermal shrinkage rate in the substrate is within a certain range.

For example, in the overflow downdraw method, the glass that can be formed by the downdraw method is a glass having a liquid phase viscosity of 10 ^4.5 Pa · s or more, preferably 10 ^5.0 Pa · s or more.

Also suitable glass LCD substrate applications, SiO ₂ 50-70% by _{mass%, Al 2 O 3 1~20%} , B 2 O 3 0~15%, 0~30% MgO, CaO 0~30 %, SrO 0~30%, BaO 0~30 %, preferably SiO ₂ 50-70% by _{mass%, Al 2 O 3 10~20%} , B 2 O 3 3~15%, 0~15% MgO, Examples include aluminosilicate-based alkali-free glass containing CaO 0 to 15%, SrO 0 to 15%, BaO 0 to 15%. Within this range, it is possible to obtain a glass substrate that satisfies the above required characteristics.

SiO ₂ is a component that becomes a glass network former. When the content of SiO ₂ is more than 70%, the high temperature viscosity is increased, the meltability is deteriorated, and the devitrification property is also deteriorated. If it is less than 50%, the chemical durability is deteriorated.

Al ₂ O ₃ is a component that increases the strain point. If the content of Al ₂ O ₃ is more than 20%, devitrification and chemical durability against buffered hydrofluoric acid are deteriorated, which is not preferable. On the other hand, if it is less than 1%, the strain point is lowered, which is not preferable. Preferably it is 10 to 20%.

B ₂ O ₃ is a component that acts as a flux and improves the meltability of the glass. When the content of B ₂ O ₃ is more than 15%, the strain point is lowered and the chemical resistance against hydrochloric acid is deteriorated, which is not preferable. On the other hand, if the amount is too small, the high-temperature viscosity becomes high and the meltability deteriorates. Preferably it is 3 to 15%.

  MgO is a component that lowers the high-temperature viscosity and improves the meltability of the glass, and is preferably 0 to 30%, particularly preferably 0 to 15%. When there is too much content of MgO, devitrification will worsen and the chemical durability with respect to buffered hydrofluoric acid will also worsen.

  CaO, like MgO, is a component that lowers the high-temperature viscosity and improves the meltability of the glass, and its content is preferably 0 to 30%, particularly preferably 0 to 15%. If the content of CaO is too large, devitrification is deteriorated and chemical durability against buffered hydrofluoric acid is also deteriorated.

  SrO is a component that improves devitrification and chemical durability. When the content of SrO is more than 30%, the density increases, the high temperature viscosity increases, and the meltability deteriorates. The preferred range is 0-15%.

  BaO, like SrO, is a component that improves devitrification and chemical durability, and is preferably 0 to 30%, particularly preferably 0 to 15%. If the content of BaO is too large, the density increases, the high-temperature viscosity increases, and the meltability deteriorates.

  In addition to the above, various components such as a clarifying agent can be added as necessary.

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

First, a glass raw material is prepared so as to have a composition of SiO ₂ 60%, Al ₂ O ₃ 15%, B ₂ O ₃ 10%, MgO 0%, CaO 5%, SrO 5%, BaO 2% by mass%, After mixing, it was melted at a maximum temperature of 1650 ° C. in a continuous melting furnace. Further, the molten glass was formed into a plate shape by the overflow down draw method under various conditions shown in Table 1, and gradually cooled. Thereafter, the glass sheet was cut to obtain an alkali-free glass substrate having a size of 1500 × 1800 × 0.65 mm. This glass substrate had the characteristics of a strain point of 650 ° C., an annealing point of 705 ° C., and a liquidus viscosity of 10 ^5.0 Pa · s. The strain point and annealing point were confirmed by the fiber elongation method. The glass is pulverized, passed through a standard sieve 30 mesh (a sieve opening of 500 μm), and the glass powder remaining in a 50 mesh (a sieve opening of 300 μm) is put in a platinum boat and kept in a temperature gradient furnace for 24 hours. The temperature at which precipitation occurred, that is, the liquidus temperature, was measured and determined from the high temperature viscosity corresponding to that temperature. The high temperature viscosity was measured by a platinum ball pulling method.

  About the obtained glass substrate, Table 1 shows the thermal contraction rate of the glass in a plate width direction center part and an edge part.

  From Table 1, it can be seen that the smaller the difference in the cooling rate between the central portion and the end portion in the plate width direction and the faster the cooling rate, the smaller the variation in the thermal shrinkage rate within the substrate.

  The sheet drawing speed refers to the speed at which the central portion of the continuously formed glass substrate in the plate width direction passes through the slow cooling region, and in this embodiment, the middle point of the slow cooling region at the central portion in the plate width direction ( It is measured by bringing a measuring roller into contact with the annealing point (position corresponding to -50 ° C.). The slow cooling region means a region corresponding to a temperature range from the slow cooling point to (slow cooling point−100 ° C.) in each part in the plate width direction. In this embodiment, the temperature is lowered from 705 ° C. to 605 ° C. Refers to the area. The average cooling rate is a rate obtained by calculating the time required for the glass to pass through the zone corresponding to the slow cooling region and dividing the temperature difference in the slow cooling region at the center or end by the passing time. Point to.

The absolute value of heat shrinkage rate was measured by the following method. First, a glass plate sample was cut out from the center portion of the obtained glass substrate and a place (end portion) corresponding to a position 900 mm away from the center portion toward the end portion side, and the glass plate 1 as shown in FIG. After placing a linear marking at a predetermined position, the glass plate 1 is folded perpendicularly to the marking and divided into two glass plate pieces 1a and 1b. Then, only one glass plate piece 1a is heat-treated according to the temperature schedule shown in FIG. ). Thereafter, as shown in FIG. 3 (b), the glass plate piece 1a subjected to the heat treatment and the untreated glass plate piece 1b are arranged and fixed with an adhesive tape (not shown), and then the marking shift is performed. Measure with a laser microscope and use the following formula 1. In Equation 1, l ₀ indicates the distance between the markings, and ΔL ₁ and ΔL ₂ indicate the amount of marking displacement.

It is explanatory drawing which shows the temperature schedule for calculating | requiring an absolute value of thermal contraction rate. It is a graph which shows the relationship between an average cooling rate and a thermal contraction rate absolute value. It is explanatory drawing which shows the method of measuring a thermal contraction rate absolute value.

Claims (5)

  A method for producing a non-alkali glass substrate by melting and forming a glass raw material, wherein an average cooling rate in a temperature range from an annealing point to (an annealing point−100 ° C.) A method for producing an alkali-free glass substrate, characterized in that the difference is adjusted to be 200 ° C./min or more at the center portion in the plate width direction and within 100 ° C./min between the center portion and the end portion in the plate width direction. .   2. The method for producing an alkali-free glass substrate according to claim 1, wherein the glass is molded so that the effective width is 1500 mm or more.   A method for producing an alkali-free glass substrate by melting and forming a glass raw material, and in the cooling process at the time of forming, the drawing speed in the temperature range from the annealing point to (annealing point−100 ° C.) is 150 cm. The method for producing an alkali-free glass substrate according to claim 1 or 2, wherein the production rate is at least 1 minute.   It shape | molds with the overflow downdraw method, The manufacturing method of the alkali free glass substrate in any one of Claims 1-3 characterized by the above-mentioned. _SiO 2 _50-70% by _{mass%, Al 2 O 3 1~20%} , B 2 O 3 0~15%, 0~30% MgO, CaO 0~30%, SrO 0~30%, BaO 0~30 %. The method for producing an alkali-free glass substrate according to claim 1, wherein an alkali-free glass substrate containing 1% is produced.