WO2007080924A1

WO2007080924A1 - Alkali-free glass substrate

Info

Publication number: WO2007080924A1
Application number: PCT/JP2007/050243
Authority: WO
Inventors: Yoshinari Kato
Original assignee: Nippon Electric Glass Co., Ltd.
Priority date: 2006-01-12
Filing date: 2007-01-11
Publication date: 2007-07-19
Also published as: CN101370742A; TWI402237B; CN101370742B; KR101282952B1; KR20080081155A; TW200730462A

Abstract

Disclosed is an alkali-free glass substrate wherein both the long side and the short side are not less than 1500 mm. This alkali-free glass substrate is characterized in that the difference between the maximum value and the minimum value of the absolute values of the thermal shrinkage rate of the substrate is not more than 5 ppm when the substrate is heated from room temperature at a rate of 10˚C/min, kept at 450˚C for 10 hours, and then cooled at a rate of 10˚C/min (namely, when the substrate is heat-treated according to the temperature schedule shown in Fig. 1). Such a substrate can be produced by adjusting the average cooling rate within the range from the slow cooling point to the point lower than the slow cooling point by -100˚C in the cooling process during production to not more than 100˚C/min in the central portion and the end portion of the substrate in the width direction.

Description

Specification

Alkali-free glass substrate

Technical field

The present invention relates to 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), substrates for hard disks, filters and the like. It relates to a suitable alkali-free glass substrate.

Background art

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

[0003] In particular, electronic devices such as thin-film transistor active matrix liquid crystal displays (TFT-LCDs) are thin and have low power consumption. Therefore, they are used in various applications such as car navigation systems, digital camera viewfinders, PC monitors and TVs. It is used for various purposes.

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 TFT element manufacturing process, a transparent conductive film, insulating film, semiconductor film, metal film, etc. are formed on a glass substrate. Furthermore, in the photolithography-etching process, the glass substrate is treated with 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. In addition, amorphous silicon and polycrystalline silicon TFTs (thin film transistors) are formed on a glass substrate by a photolithography-etching process. In such a manufacturing process, the glass substrate is subjected to a heat treatment at 300 to 600 ° C., and is also treated with various chemicals such as sulfuric acid, hydrochloric acid, alkaline solution, hydrofluoric acid, and buffered hydrofluoric acid. Therefore, the following characteristics are required for glass substrates for TFT liquid crystal displays.

(1) If an alkali metal oxide is contained in the glass, alkali ions diffuse into the deposited semiconductor material during the heat treatment and cause deterioration of the film properties. Do not contain oxides.

(2) Photolithography-Resistance to acid and alkali solutions used in the etching process Excellent in chemical properties, 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 glass substrate has a low thermal shrinkage. That is, if the thermal contraction rate is large, the circuit pattern formed on the substrate will be 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 glass substrate for TFT liquid crystal display is required to have the following characteristics.

(4) Excellent devitrification resistance so that no foreign matter is generated in the glass during the glass melting or forming process. In particular, when glass is formed by a downdraw method such as the overflow downdraw method, the devitrification resistance of the glass is important. When the glass forming temperature is taken into consideration, the liquidus temperature is 1200 ° C or less. It is required to be.

(5) The density is low in order to reduce the weight of the liquid crystal display. In particular, glass substrates mounted on laptop computers are required to have a weight of 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 functions as an optical shutter, and this layer displays images by shielding or transmitting light. This liquid crystal layer is maintained at a very thin thickness of several μη to several tens μη. Therefore, the flatness of the surface of the glass substrate, especially the irregularities of the μm level called waviness, affects the thickness of the liquid crystal layer (called cell gap), and if the surface waviness is large immediately, display defects such as display unevenness Cause.

[0006] In recent years, the liquid crystal display has a tendency to make the cell gap thinner for the purpose of high-speed response and high definition. Therefore, it is possible to reduce the undulation of the surface of the glass substrate used for this. It is becoming increasingly important. 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 this reason, glass substrates with as little surface waviness as possible are formed by molding methods such as the overflow-down-draw method and float method, and they are shipped without being polished or subjected to extremely light polishing (touch polish). Has been. [0007] Various glass substrates have been proposed to satisfy these characteristics. (For example, see Patent Document 1.)

Patent Document 1: JP-A-8-811920

Disclosure of the invention

[0008] As described above, the smaller the thermal contraction rate of the glass substrate, the better. However, in recent years, taking into account the thermal contraction 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 called the 6th generation (for example, a glass substrate having a side of 1500 mm or more).

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 contraction rate in the substrate increases as the substrate size increases.

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

(1)

On a non-alkali glass substrate with a short side and long side of 1500 mm or more, the temperature is raised from room temperature at a rate of 10 ° CZ, held at a holding temperature of 450 ° C for 10 hours, and cooled at a rate of 10 ° CZ (Figure 1). A non-alkali glass substrate characterized in that the difference between the maximum value and the minimum value of the absolute value of thermal shrinkage in the substrate is within 5 ppm when heat treatment is performed according to the temperature schedule shown in Fig. 3.

(2)

When the temperature is raised from room temperature at a rate of 10 ° C / min, held for 10 hours at a holding temperature of 450 ° C, and the temperature is lowered at a rate of 10 ° C / min, the absolute value of the heat shrinkage at the center of the substrate is 40 ppm or more The alkali-free glass substrate according to (1), wherein

(3)

The alkali-free glass substrate according to (1) or (2), which is formed by an overflow down-draw method. SiO 50-70% by weight ^{_{0/0, Α1 Ο 1 ~}} 20%, BO 0~: 15%, 0~30% MgO,

CaO 0-30%, SrO 0-30%, BaO 0-30%, The alkali-free glass substrate according to any one of (1) to (3).

(Five)

This is a method for producing an alkali-free glass substrate by melting and forming glass raw material, and the average over the temperature range from the annealing point to (annealing point _100 ° C) during the cooling process during molding. A method for producing an alkali-free glass substrate, wherein the cooling rate is adjusted so as to have a difference of 100 ° C / min or less between the central portion and the end portion in the plate width direction.

(6)

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

(7)

In the cooling process at the time of molding, the average cooling rate in the temperature range from the annealing point to (annealing point-100 ° C) is 200 ° C / min or more at the center in the plate width direction. (5) or (6) a method for producing an alkali-free glass substrate.

(8)

In the cooling process at the time of molding, the sheet drawing speed in the temperature range from the annealing point to (annealing point-100 ° C) is 150 cm / min or more (5) to (7) A method for producing any alkali-free glass substrate.

(9)

The method for producing an alkali-free glass substrate according to any one of (5) to (8), which is formed by an overflow downdraw method.

(Ten)

SiO 50-70% by weight ^{_{0/0, Α1 Ο 1 ~}} 20% BO 0~:. 15%, MgO0~30%,

A non-alkali glass substrate having a composition of CaO 0 to 30%, SrO 0 to 30%, BaO 0 to 30% is manufactured. Production method. (1 1)

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

[0012] The glass substrate of the present invention has a small variation in thermal shrinkage within the substrate. Therefore, if correction using a photomask is performed when forming a TFT circuit, the thermal contraction in the substrate is always within a certain range, so that the pattern can be formed stably with a high yield.

[0013] Further, according to the production method of the present invention, the glass substrate described above can be easily produced.

Brief Description of Drawings

FIG. 1 is an explanatory diagram showing a temperature schedule for obtaining an absolute value of a heat shrinkage rate.

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

FIG. 3 is an explanatory diagram showing a method for measuring the absolute value of the heat shrinkage rate.

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] The thermal shrinkage 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, a plate glass cooled at a high cooling rate has a large heat shrinkage rate, whereas a plate glass cooled at a low rate has a low heat shrinkage rate. In addition, since the glass substrate is continuously drawn by a glass forming apparatus, the temperature history (cooling rate) varies little in the drawing direction. Therefore, the difference in heat shrinkage is unlikely to occur in the drawing direction. On the other hand, a temperature difference occurs in the plate width direction, and the temperature history (cooling speed) of the central portion and the edge portion is particularly different. Therefore, the difference in thermal shrinkage in the plate width direction is large.

[0016] This tendency becomes more prominent as the plate width increases. In other words, as the glass substrate increases in size, the variation in thermal shrinkage within a single substrate increases.

[0017] According to the study by the present inventors, the difference in cooling rate in the temperature range from (annealing point + 50 ° C) to (annealing point-100 ° C) is the difference in heat shrinkage rate. It was found that this was the cause of Furthermore, it was found that the cooling conditions in the temperature range from the annealing point (annealing point-100 ° C) have no significant effect on the plate thickness and distortion, which are important characteristics for flat panel display substrates. Therefore, the plate thickness and strain are controlled in the temperature range above the annealing point, and the variation in thermal shrinkage from the annealing point to the temperature range (= annealing point-100 ° C) is adjusted. do it.

[0018] As a means for adjusting the variation of the thermal shrinkage rate, it is only necessary to reduce the difference in cooling rate in the plate width direction in the temperature range from the annealing point to (annealing point _100 ° C). In this temperature range, the cooling rate difference between the central part and the edge part in the plate width direction should 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.

[0019] The variation in the thermal shrinkage rate can also be reduced by increasing the cooling rate. In other words, it can be seen from FIG. 2 that the heat shrinkage rate increases as the cooling rate increases. Even if the cooling rate changes slightly, the heat shrinkage rate hardly changes.

[0020] The production method of the present invention will be described in further detail.

[0021] First, a glass material prepared 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, etc. so as to obtain a glass composition having characteristics suitable for the application. Silica glass, porosilicate glass, aluminosilicate glass, etc. are not particularly limited in the type of glass, but among these, it is preferable to prepare a glass that can be molded by the downdraw method, particularly the overflow downdraw method. . The glass that can be formed by the downdraw method is, for example, a glass having a liquidus viscosity of 10 ⁴ ' ⁵ Pa's or more, preferably 10 ⁵ ' ° Pa's or more, in the case of overflow overflow method. The liquid phase viscosity is a viscosity at the time when crystals are precipitated, and the higher the liquid phase viscosity, the more difficult it is to produce devitrification during glass molding.

As a glass composition suitable for the liquid crystal display substrate application, as will be described later, by weight%, Si 0 50 to 70%, A1 0 1 to 20%. BO 0 to 15%, MgO 0 to 30%, Ca ○ 0 ~ 30

%, SrO 0 to 30%, Ba 0 0 to 30%, especially Si 0 50 to 70% at a weight of ⁰ / o, Al 10

~ 20%, B O 3 ~: 15%, MgO 0 ~ 15%, Ca 0 ~ 15%, Sr 0 0 ~ 15%, Ba

〇 0-: Aluminosilicate-based alkali-free glass composition having a composition of 15%

[0023] The glass raw material thus prepared is supplied to a glass melting apparatus and melted. The melting temperature may be appropriately adjusted according to the type of glass, for example, the glass having the above composition. In such a case, it may be melted at a temperature of about 1500 to 1650 ° C. In the present invention, melting 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, it is necessary to manage the temperature history in the temperature region where the molded plate glass is cooled to room temperature as described above. In particular, it is important not to cause a difference in cooling rate in the temperature range from the annealing point to (annealing point_100 ° C). Specifically, the difference in average cooling rate in the temperature range from the annealing point (annealing point-100 ° C) is preferably less than 100 ° C / min at the center and the edge in the plate width direction. Adjust the temperature within 50 ° C / min, and even within 20 ° C / min.

[0025] 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 at the central portion in the plate width direction and increasing the power of the end heater can be employed.

[0026] It is preferable to increase the cooling rate in order to reduce the variation in the thermal shrinkage rate in the substrate. Specifically, the average cooling rate in the temperature range from the annealing point to (annealing point-100 ° C) may be adjusted. In this temperature range, the average cooling rate in the central part in the plate width direction is 200 ° C / min or more, especially 300 ° C / min or more, further 350 ° C / min or more, further 400 ° C / min or more, If the temperature is 500 ° C / min or more, a glass substrate with very little variation in the substrate can be easily obtained. Sheet glass cooled at a high cooling rate is a sheet glass having a large absolute value of heat shrinkage at the center of the substrate, specifically 40 ppm or more, particularly 5 Oppm or more, further 53 ppm or more, further 55 ppm, or even 57 ppm or more. A plate glass having an absolute value of the heat shrinkage rate is obtained. Note that the upper limit of the average cooling rate in the central part in the plate width direction must be 1000 ° CZ or less in order to prevent inappropriate distortion in the glass and excessive load on the compact. preferable. The “heat shrinkage absolute value” in the present invention means that the temperature is raised from room temperature at a rate of 10 ° CZ, held at a holding temperature of 450 ° C for 10 hours, and cooled at a rate of 10 ° CZ (see Fig. 1). It means the thermal shrinkage of each part of the substrate when it is heat-treated with the temperature schedule shown. The “average cooling rate” is calculated by calculating the time required for the glass to pass through the zone corresponding to the annealing zone (temperature range from annealing point to (slow cooling point-100 ° C)). The speed obtained by dividing the temperature difference by the passage time. As one of the most effective ways to change the average cooling rate, There is a way to change. The higher the sheet drawing speed, the larger the absolute value of the heat shrinkage of the glass, and the variation in the heat shrinkage due to fluctuations in the sheet drawing speed can be reduced. In order to increase the drawing speed, it is only necessary to increase the rotation speed of the pulling roller that stretches the formed glass. In addition, when the cooling region (gradual cooling furnace) in the molding process is a down draw method that is extremely short compared to the float method, the average cooling rate in this temperature region can be easily changed. Further, if an overflow downdraw method, which is a kind of downdraw method, is used, a glass substrate with excellent surface quality can be obtained, and there is an advantage that the polishing step can be omitted. Specifically, the drawing speed in the temperature range from the annealing point to (annealing point-100 ° C) is preferably 150 cm / min or more, 270 cm / min or more, further 320 cm / min or more, In particular, it is desirable to set it to 400 cm / min or more. The upper limit of the sheet drawing speed is not particularly limited, but it is preferably 800 cm / min or less in consideration of the load on the molding apparatus. The “sheet drawing speed” described here means that the central portion of the glass substrate in the plate width direction passes through the annealing region (the region in the temperature range from the annealing point to (annealing point-100 ° C)). Means the average speed.

[0027] When molding by the downdraw method, the temperature at the end tends to decrease in the slow cooling furnace as compared to the central portion in the plate width direction. In other words, the central part has good heat retention, but heat easily escapes at the end. Therefore, the cooling rate in the plate width direction is constant, and there is a tendency for large variation in the heat shrinkage rate in the plate width direction. Therefore, when molding by the downdraw method, it can be said that the merit of adopting the method of the present invention is great.

[0028] Further, when the distance in the plate width direction of the glass is increased, the variation of the thermal shrinkage rate of the obtained glass substrate tends to increase. In other words, when the glass is molded so that the effective width is 1500 mm or more, especially 1800 mm or more, the temperature difference in the sheet width direction tends to increase in the cooling process during molding, and the variation in the easy heat shrinkage tends to increase. is there. Therefore, when trying to mold a large glass substrate, it can be said that the merit of employing the method of the present invention is great.

[0029] 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 cleaning.

[0030] In this way, a glass substrate having a small variation in thermal shrinkage can be obtained.

[0031] Next, the glass substrate of the present invention obtained as described above will be described. [0032] The glass substrate of the present invention is characterized by a small variation in thermal shrinkage rate within one substrate. Specifically, when the temperature is raised from normal temperature at a rate of 10 ° CZ, held for 10 hours at a holding temperature of 450 ° C, and cooled down at a rate of 10 ° CZ (heat treatment according to the temperature schedule shown in Fig. 1). In addition, 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, and more preferably within 1 ppm. If the difference between the maximum value and the minimum value of the absolute value of heat shrinkage in the substrate exceeds 5 ppm, the difference in pattern deviation in the substrate becomes large, making correction with a photomask difficult, and display device productivity. Is significantly reduced. 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) is greatly different between the central part and the end part in the glass sheet width direction. Adjust so that it does not.

[0033] The glass substrate which is the subject 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 shrinkage 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 the thermal contraction rate tends to increase. Therefore, it is important to reduce the variation in the thermal shrinkage rate within a single substrate.

[0034] In addition, the glass substrate that is the subject of the present invention is a glass substrate manufactured at a high cooling rate (that is, a glass substrate having a high absolute value of thermal contraction rate). Variations in heat shrinkage 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. A glass substrate produced at a high cooling rate has an average cooling rate in the temperature range from the annealing point to (annealing point _100 ° C) at 200 ° C / min or more at the center in the plate width direction. Glass substrate made at 300 ° C / min or higher, 350 ° CZ min, 400 ° CZ min or higher, or even 500 ° CZ min or higher, or thermal contraction at the center of the substrate (near the center of gravity) The absolute value of the rate is 40 ppm or more, especially 50 ppm or more, further 53 ppm or more, further 55 ppm or more, 57 ppm or more. It is a glass substrate. In addition, if the absolute value of the heat shrinkage rate of the glass is increased, the heat shrinkage rate will hardly change even if the cooling rate is slightly changed.

[0035] 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 the higher the strain point of glass, the more advantageous. Specifically, the strain point of the glass is preferably 630 ° C or higher, particularly 650 ° C or higher.

[0036] As the alkali-free glass constituting the glass substrate of the present invention, various glasses such as silica glass, polysilicate glass, and aluminosilicate glass can be used as long as they are suitable for the application. In particular, it is preferably made of glass that can be molded by the overflow downdraw method. In other words, the glass substrate formed by the overflow downdraw method has excellent surface quality and has the advantage that it can be used without being polished. A glass substrate formed by the downdraw method generally has a tendency that the cooling rate in the plate width direction is not uniform, and thus the thermal shrinkage rate tends to vary within the substrate. Therefore, it is very important to adjust the variation of the thermal shrinkage rate within the substrate to be within a certain range.

[0037] Glass that can be formed by the downdraw method is, for example, a glass having a liquidus viscosity of 10 ⁴ ' ⁵ Pa' s or more, preferably 10 ⁵ '° Pa' s or more in the overflow down draw method. .

[0038] Further, as a glass suitable for a liquid crystal display substrate, SiO 50 to 70% by weight is used.

2

, A1 0 1 ~ 20%, B O 0 ~: 15%, MgO 0 ~ 30%, CaO 0 ~ 30%, SrO 0

2 3 2 3

To 30%, BaO 0 to 30%, preferably SiO 50-70% by weight ^_0/0, A1_rei 10-20%

2 2 3

,: B 3 O ~: 15%, Mg 0 0 ~: 15%, Ca 0 0 ~: 15%, SrO 0 ~: 15%, BaO 0 ~

twenty three

Aluminosilicate non-alkali glass having a composition of 15%. Within this range, it is possible to obtain a glass substrate that satisfies the above required characteristics.

[0039] SiO is a component that becomes a glass network former. SiO content is 70 wt.

twenty two

If it is more than%, the high-temperature viscosity will be high, the meltability will be poor, and the devitrification will also be bad, which is preferable. If it is less than 50% by weight, the chemical durability is deteriorated.

[0040] Al 2 O is a component that increases the strain point. If the Al O content exceeds 20% by weight, devitrification And preferable because the chemical durability against buffered hydrofluoric acid deteriorates. On the other hand, less than 1% by weight is preferable because the strain point is lowered. Preferably 10-20% by weight

[0041] B 2 O is a component that acts as a flux and improves the meltability of the glass. B O content is 1

2 3 2 3

If it is more than 5% by weight, the strain point is unfavorable because the chemical resistance against hydrochloric acid and hydrochloric acid deteriorates. On the other hand, if the amount is too small, the high-temperature viscosity becomes high and the meltability deteriorates. Preferably 3 to 15% by weight.

[0042] MgO is a component that lowers the viscosity at high temperature and improves the meltability of the glass, and is preferably 0 to 30% by weight, particularly 0 to 15% by weight. If the MgO content is too high, the devitrification will be poor and the chemical durability against buffered hydrofluoric acid will also be poor.

[0043] CaO is also a component that lowers the high-temperature viscosity and improves the meltability of the glass as with MgO, and its content is preferably 0 to 30% by weight, particularly 0 to 15% by weight. If the content of CaO is too large, devitrification is deteriorated and chemical durability against buffered hydrofluoric acid is also deteriorated.

[0044] SrO is a component that improves devitrification and chemical durability. If the SrO content is more than 30% by weight, the density increases, the high-temperature viscosity increases, and the meltability deteriorates. The preferred range is 0 to: 15% by weight.

[0045] BaO is also a component for improving devitrification and chemical durability similar to SrO, 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 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.

Example

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

[0047] First SiO 60% by weight ^{_{0/0, Al O 15%}} , BO 10%, MgO 0%, Ca_〇 5%, Sr

2 2 3 2 3

〇 Glass raw materials were prepared so as to have a composition of 5% and BaO 2%, mixed, and then melted at a maximum temperature of 1650 ° C in a continuous melting furnace. Furthermore, the molten glass was formed into a plate shape by the overflow down draw method under various conditions shown in Table 1, and then gradually cooled. Then cut the glass sheet By cutting, an alkali-free glass substrate having a size of 1500 × 1800 × 0.665 mm was obtained. This glass substrate had characteristics of a strain point of 650 ° C, an annealing point of 705 ° C, and a liquid phase viscosity of 10 ⁵ '° Pa's. The strain point and the annealing point were confirmed by the fiber elongation method. The glass is crushed, passed through a standard sieve 30 mesh (500 μm sieve opening), and the glass powder remaining on the 50 mesh (300 μm sieve sieve) is placed in a platinum boat and kept in a temperature gradient furnace for 24 hours. Then, the temperature at which crystals precipitate, 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.

[0048] Table 1 shows the thermal contraction rate of the glass at the center and end portions in the plate width direction of the obtained glass substrate.

[0049] [Table 1]

[0050] From Table 1, it can be seen that the smaller the difference in cooling rate between the central part and the edge part in the plate width direction, and the faster the cooling rate, the smaller the variation in the thermal shrinkage rate in the substrate.

[0051] Note that the sheet drawing speed refers to the speed at which the central portion in the plate width direction of the glass substrate that is continuously formed passes through the slow cooling region, and in this embodiment, the slow cooling region in the central portion in the plate width direction. The measurement was made by bringing a measuring roller into contact with the intermediate point (position corresponding to an annealing point of 50 ° C). The slow cooling region means a region corresponding to the temperature range from the slow cooling point to (slow cooling point-100 ° C) in each part in the plate width direction. In this example, from 705 ° C to 605 ° C. This refers to the area where the temperature is lowered. The average cooling rate is the rate obtained by calculating the time 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. [0052] The absolute value of the 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 location (end portion) corresponding to a position 900 mm away from the center portion toward the end portion, and the glass plate 1 was cut as shown in FIG. 3 (a). After placing a linear marking at a predetermined position, fold the glass plate 1 perpendicular to the marking and divide it into two glass plate pieces la and lb. Then, heat treatment was performed on only one glass plate piece la at the temperature schedule shown in Fig. 1 (temperature was raised from normal temperature at a rate of 10 ° C / min, held at a holding temperature of 450 ° C for 10 hours, and 10 ° CZ min. (Temperature decrease) After that, as shown in FIG. 3 (b), the heat-treated glass plate piece la and the untreated glass plate piece lb are arranged and fixed with an adhesive tape (not shown). Measure with a laser microscope and use Equation 1 below. In Equation 1, 1 is the distance between markings, AL and are the marking positions.

0 1 2

The amount of displacement is shown.

[0053] Although the invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application filed on January 12, 2006 (Japanese Patent Application No. 2006-4984), which is incorporated by reference in its entirety.

Also, all references cited herein are incorporated as a whole.

Industrial applicability

[0054] The glass substrate of the present invention has a small variation in thermal shrinkage within the substrate. Therefore, if correction using a photomask is performed when forming a TFT circuit, the thermal shrinkage within the substrate is always within a certain range, so that pattern formation can be performed stably with high yield.

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

Claims

The scope of the claims

[1] On a non-alkali glass substrate with a short side and long side of 1500 mm or more, 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 at a rate of 10 ° C / min. The alkali-free glass substrate is characterized in that the difference between the maximum value and the minimum value of the absolute value of heat shrinkage within the substrate is within 5ppm when the temperature is lowered at (heat treatment according to the temperature schedule shown in Fig. 1).

[2] The absolute value of heat shrinkage at the center of the substrate 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 lowered at a rate of 10 ° C / min. The alkali-free glass substrate according to claim 1, wherein is 40 ppm or more.

[3] The alkali-free glass substrate according to claim 1 or 2, wherein the alkali-free glass substrate is formed by an overflow downdraw method.

[4] SiO 50~70% by weight ^{_{0/0, Α1 Ο:!}} ~ 20%, B_〇 0~: 15%, 0~30% MgO ,

The non-strength glass substrate according to any one of claims 1 to 3, characterized by containing CaO 0 to 30%, SrO 0 to 30%, BaO 0 to 30%.

[5] A method for producing a non-alkali glass substrate by melting and forming a glass raw material. The temperature range from the annealing point to (annealing point _100 ° C) during the cooling process at the time of molding. A method for producing an alkali-free glass substrate, characterized in that the average cooling rate in the step is adjusted so that the difference between the central portion and the end portion in the plate width direction is within 100 ° C / min.

6. The method for producing an alkali-free glass substrate according to claim 5, wherein the glass is formed so that the effective width is 1500 mm or more.

[7] In the cooling process at the time of molding, the average cooling rate in the temperature range from the annealing point to (annealing point-100 ° C) should be 200 ° C / min or more at the center in the plate width direction. The method for producing an alkali-free glass substrate according to claim 5 or 6.

[8] The sheet drawing speed in the temperature range from the annealing point to (annealing point-100 ° C) in the cooling process during molding is 150 cm / min or more. A method for producing an alkali-free glass substrate according to any of the above.

[9] The method for producing an alkali-free glass substrate according to any one of claims 5 to 8, wherein the alkali-free glass substrate is molded by an overflow downdraw method.

[10] SiO 50~70% by weight ^{_{0/0, Α1 Ο:!}} ~ 20%, B_〇 0~: 15%, MgO0~30%, 10. The method for producing an alkali-free glass substrate according to claim 5, wherein an alkali-free glass substrate having a composition of CaO 0-30%, SrO 0-30%, BaO 0-30% is produced. .

An alkali-free glass substrate produced by the method according to claim 5.