WO2008004480A1

WO2008004480A1 - Process for producing alkali-free glass substrate

Info

Publication number: WO2008004480A1
Application number: PCT/JP2007/062913
Authority: WO
Inventors: Satoshi Takeda; Shirou Tanii; Seiji Higashi
Original assignee: Asahi Glass Co., Ltd.
Priority date: 2006-07-07
Filing date: 2007-06-27
Publication date: 2008-01-10
Also published as: TW200811068A; CN101489946B; TW201300334A; KR101107369B1; JP5239859B2; CN101489946A; TWI379815B; KR20090029785A; JPWO2008004480A1

Abstract

A process for producing an alkali-free glass substrate in which a protective coating film capable of being easily removed in a cleaning step is efficiently formed and the back side of the glass substrate is inhibited from being marred while reducing the amount of sulfur dioxide to be used; and an alkali-free glass substrate obtained by the process. The process for alkali-free glass substrate production produces an alkali-free glass substrate by the float method. It comprises a forming step in which a molten glass is formed on molten tin into a glass substrate and an annealing step in which the glass substrate formed in the forming step is annealed. The process further comprises a first supply step in which an inorganic substance containing an alkali metal is blown against that surface of the glass substrate which was in contact with the molten tin and a second supply step in which after the first supply step, SO2 gas is blown against that surface of the glass substrate which was in contact with the molten tin.

Description

Specification

Method for producing alkali-free glass substrate

Technical field

[0001] The present invention relates to a method for producing an alkali-free glass substrate.

Background art

[0002] Many glass substrates including a glass substrate for display are manufactured by a float process or a fusion process. Unlike the fusion method, the float method is superior in that it can efficiently produce large-area glass substrates.

This float method generally includes a molding step for forming molten glass on a glass substrate on molten tin in a molten tin bath, and a slow cooling step for gradually cooling the glass substrate formed by the molding step. It is a life.

However, the glass substrate molded by this molding process is transported by the roller after leaving the molten tin bath, so the back surface (the surface that hits the roller) is damaged during transportation! Teshima! There was a problem that the quality of the glass substrate deteriorated.

[0003] Therefore, in order to prevent scratches on the back surface of the glass substrate that occur during the conveyance, sulfurous acid gas (SO gas) is sprayed on the back surface of the glass substrate, and alkali metals (for example,

2

There is known a method for preventing scratches by reacting with sodium, etc., forming sodium sulfate on the back surface of the glass substrate, and acting as a protective film (for example, Patent Document 1 and Non-Patent Document 1) See) o

[0004] Patent Document 1: International Publication No. 2002Z051767 Pamphlet

Non-Patent Document 1: U. Senturk etc, J. Non— Cryst. Solids, No. 222, p. 160 (199 7)

Disclosure of the invention

Problems to be solved by the invention

[0005] However, in order to realize the high scratch-preventing ability required for high-quality displays in recent years, it is necessary to increase the thickness of the protective film, and for that purpose, it is necessary to use a large amount of sulfurous acid gas. Therefore, there was a problem of environmental load and work environment deterioration. Also, sulfurous acid Since the gas is highly corrosive, there was a problem that the furnace material was corroded and the life of the furnace material was shortened.

[0006] In particular, when manufacturing a glass substrate composed of glass that does not substantially contain an alkali metal (hereinafter also referred to as “non-alkali glass”), depending on the method of blowing sulfurous acid gas, sodium sulfate may be used. It is not formed, and salts such as calcium sulfate and strontium sulfate, which are reaction products with alkaline earth metals, are formed on the glass substrate. Although these salts derived from alkaline earth metals act as protective films to prevent scratches on the glass substrate, their production efficiency is significantly lower than that of sodium sulfate, so their effects may not be sufficient. there were. Moreover, since it is a hardly water-soluble salt even if it is produced, there is a problem that it is extremely difficult to remove in a subsequent washing step.

In addition, although these salts can be removed by polishing, in order to obtain a glass substrate with high smoothness, it is necessary to polish a forceful thickness, which increases manufacturing time and manufacturing cost. There was a problem to do.

Furthermore, non-alkali glass is required to have a high-quality surface such as a flat panel display, and if there is a scratch on the glass substrate, it will cause defects such as poor disconnection, so that scratches smaller than those for window glass and automotive glass are also a problem. .

Therefore, the present invention is a method for producing a glass substrate made of alkali-free glass (hereinafter also referred to as “alkali-free glass substrate”) used in a liquid crystal display, and is easily removed in a cleaning process. A method for producing an alkali-free glass substrate capable of efficiently generating a protective coating that can be used and suppressing the occurrence of scratches on the back surface of the glass substrate while reducing the amount of sulfurous acid used, and the method for producing the same An object is to provide an alkali-free glass substrate obtained by the above.

Means for solving the problem

[0008] As a result of intensive investigations to achieve the above object, the present inventor has found that an inorganic substance containing an alkali metal is in contact with the molten tin of the glass substrate in the production process by the float process. Blow the surface to supply alkali metal, then blow SO gas to the surface.

2

As a result, a protective coating that can be easily removed in the cleaning process can be efficiently generated, and the amount of sulfurous acid gas used can be reduced while preventing scratches on the back side of the glass substrate. The present invention has been completed.

That is, the present invention provides the following (1) to (14).

(1) A method for producing an alkali-free glass substrate by producing an alkali-free glass substrate by a float process,

A forming step of forming molten glass on a molten tin on a glass substrate, and a slow cooling step of gradually cooling the glass substrate formed by the forming step,

A first supply step of spraying an inorganic substance containing an alkali metal on a surface of the glass substrate that contacts the molten tin; and after the first supply step, a side of the glass substrate that contacts the molten tin. A second supply step of blowing SO gas on the surface

2

A method for producing an alkali-free glass substrate.

[0010] (2) The method for producing an alkali-free glass substrate according to (1), wherein the first supply step is performed between the forming step and the slow cooling step.

(3) The method for producing an alkali-free glass substrate according to (1), wherein the first supply step is performed at a temperature in the range of the glass transition point of the glass substrate ± 100 ° C.

(4) The method for producing an alkali-free glass substrate according to (1), wherein the first supply step is performed at 600 to 800 ° C.

(5) The method for producing an alkali-free glass substrate according to any one of (1) to (4), wherein the second supply step is performed between the molding step and the slow cooling step.

(6) The production of the alkali-free glass substrate according to any one of (1) to (4), wherein the second supply step is performed at a temperature in the range of glass transition point ± 100 ° C of the glass substrate. Method.

(7) The method for producing an alkali-free glass substrate according to any one of (1) to (4), wherein the second supply step is performed at 600 to 800 ° C.

[0011] (8) A method for producing an alkali-free glass substrate for producing an alkali-free glass substrate by a float method,

Comprising a molding step of forming molten glass on a molten tin on a glass substrate;

After the first supply step of spraying an inorganic substance containing an alkali metal on the surface of the glass substrate in contact with the molten tin at 600 to 800 ° C., and after the first supply step, 600 to 800 ° C. Blow SO gas on the surface of the glass substrate that contacts the molten tin. A non-alkali glass substrate manufacturing method, comprising: a second supplying step.

[0012] (9) The method for producing an alkali-free glass substrate according to any one of (1) to (8), further comprising a cleaning step of removing the protective film.

(10) The method for producing an alkali-free glass substrate according to any one of (1) to (9), wherein the inorganic substance containing an alkali metal contains sodium and boron.

(11) The method for producing an alkali-free glass substrate according to the above (10), wherein the inorganic substance containing the alkali metal is sodium tetraborate.

[0013] (12) An alkali-free glass substrate produced by the production method described in (10) or (11) above.

(13) An alkali-free glass substrate produced by the production method according to (10) or (11) above,

The glass substrate is a mass percentage display based on oxide,

SiO: 30

2 to 85%,

AI O: 0

2 3 ~ 35%,

B O: 0

2 3 ~ 35%,

MgO :. ~ 35%,

CaO: ~ 35%,

SrO :. ~ 35%,

BaO :. ~ 35%,

Alkali metal component: 0.5% or less

Containing

An alkali-free glass substrate in which the average boron concentration on the surface of the glass substrate that has been in contact with the molten tin is 4 to 10 atomic% and the diffusion depth of boron into the glass substrate is 5 nm or more.

[14] (14) Oxide-based mass percentage display,

SiO: 30 to 85%

2

AI O: 0-35%

twenty three

BO: 0-35% MgO :. ~ 35%,

CaO: ~ 35%,

SrO :. ~ 35%,

BaO :. ~ 35%,

Alkali metal component: 0.5% or less

Containing

An alkali-free glass substrate in which the average boron concentration on at least one surface is 4 to 10 atomic% and the diffusion depth of boron into the surface force is 5 nm or more.

The invention's effect

[0016] As described below, according to the present invention, a protective coating that can be easily removed in a cleaning process is efficiently generated, and the amount of sulfurous acid gas used is reduced while reducing the amount of sulfur dioxide used. A method for producing an alkali-free glass substrate that suppresses the generation of scratches and an alkali-free glass substrate obtained by the production method can be provided.

Brief Description of Drawings

[0017] FIG. 1 is a conceptual diagram showing an example of a glass production line by a float process.

FIG. 2 is a cross-sectional view of the large tubular furnace used in the examples.

[FIG. 3] FIG. 3 is an explanatory view showing a portion (wear portion) hit by a wear ring and a site for measuring the number of scratches (measurement portion) of the Taber experimental machine used for evaluation of scratch resistance.

Explanation of symbols

[0018] 1 Molten tin

2 Molten tin bath

3 Melting kiln

4 Molten glass

5 Drawer roll

6 Slow cooling furnace

11 Large tubular furnace

12 Quartz tube

13 Alkali-free glass substrate 14 Alumina boat

15 Reagents

16, 17 arrows

18 Specimen

19 Wear part

20 Measuring unit

BEST MODE FOR CARRYING OUT THE INVENTION

[0019] The present invention is described in detail below.

The method for producing an alkali-free glass substrate according to the first aspect of the present invention (hereinafter also referred to as “the production method of the present invention”) is a method for producing an alkali-free glass substrate for producing an alkali-free glass substrate by a float process. Because

First, an inorganic substance containing an alkali metal (hereinafter also referred to as “alkali metal-containing inorganic substance”) is sprayed on the surface of the glass substrate that contacts the molten tin (hereinafter also referred to as “bottom surface”). After the supplying step and the first supplying step, the surface of the glass substrate on the side in contact with the molten tin, that is, the bottom surface on which the inorganic substance is sprayed is SO.

2 A method for producing an alkali-free glass substrate, comprising a second supply step of blowing gas.

Moreover, it is preferable that the manufacturing method of the present invention further includes a cleaning step for removing the protective film.

Next, the molding step, the slow cooling step, the first supply step and the second supply step, and the cleaning step provided as desired in the production method of the present invention will be described in detail.

[0020] [Molding process]

The forming step is a step of forming molten glass on a glass substrate on molten tin in a molten tin bath, and is a conventionally known step in a general float method.

FIG. 1 is a conceptual diagram showing an example of a glass production line by a float process.

As shown in Fig. 1, in the float process, first a molten tin bath 2 filled with molten tin 1 On the surface of the bath, molten glass 4 flows continuously from the melting furnace 3 to form a glass ribbon. Next, the glass ribbon is advanced along the bath surface of the molten tin bath 2 while being buoyant, so that the glass ribbon is formed into a plate shape as the temperature decreases. Thereafter, the glass substrate thus produced is drawn out by the drawing roll 5 and is conveyed to the slow cooling furnace 6 in a continuous state in the longitudinal direction.

Here, in FIG. 1, the forming step is a step until the molten glass 4 is formed into a plate shape through a glass ribbon.

In the present invention, similar to the general float process, the molten tin bath 2 is composed of a tin bath furnace and a ceiling wall lined with a special refractory on the inside of a metal case, and tin oxide is used. To prevent this, use a sealed structure. As the atmospheric gas in the molten tin bath, a mixed gas composed of hydrogen and nitrogen (hydrogen content: 2 to 10% by volume) can be used. Further, the temperature condition in the molten tin bath in the molding step is 600 to 1050 ° C., that is, the temperature of the molten glass flowing into the molten tin bath is 900 to 1050 ° C. Therefore, it is possible to achieve a force S of 600-800 ° C on the downstream side. Note that this temperature is normally maintained by the amount of heat of the molten glass. A heater or cooler may be used to adjust the temperature.

In the production method of the present invention, an alkali-free glass substrate is formed on molten tin by the above-described forming step.

Here, the non-crisp glass is glass that does not substantially contain an alkali metal as described above. Specifically, in the present invention, the alkali-free glass is represented by a mass percentage display based on an oxide,

SiO: 30 to 85%

2

AI O: 0-35%

twenty three

B O: 0-35%

twenty three

MgO :. ~ 35%,

CaO: ~ 35%,

SrO :. ~ 35%,

BaO: 0-35%, Alkali metal component: 0.5% or less

Containing. The “alkali metal component” refers to an alkali metal component inevitably contained regardless of the first supply step described later.

[0024] [Slow cooling step]

The slow cooling step is a step of slowly cooling the glass substrate formed by the forming step.

Here, in FIG. 1, in the slow cooling step, the glass substrate that has been made is pulled out by the pulling roll 5 and then transferred to the slow cooling furnace 6 in a continuous state in the longitudinal direction until it is gradually cooled. It is this process.

In the present invention, the slow cooling furnace may be the same as that used in a general float method, and a heater or the like may be provided for temperature control.

In addition, the annealing conditions in the annealing furnace in the annealing process can be set to temperatures of 550 to 750 ° C at the inlet of the annealing furnace and 200 to 300 ° C at the outlet, as in the general float method. Yes, the speed of temperature drop can be 90 ° C ± 10 ° C / m.

[0026] [First supply step]

The first supply step is a step of spraying an alkali metal-containing inorganic substance onto the bottom surface of the glass substrate to supply the alkali metal to the bottom surface.

Here, the alkali metal-containing inorganic substance means an inorganic substance containing an alkali metal as described above, and includes, for example, lithium (Li), sodium (Na), potassium (K), cesium (Cs) and the like. This applies to inorganic substances.

Using such an alkali metal-containing inorganic substance, an alkali metal is supplied to the bottom surface of the glass substrate, and then SO gas is blown to form an alkali sulfate salt.

2

A protective coating can be produced efficiently. In addition, this protective film can be easily removed by a cleaning process. Furthermore, the same protective effect can be obtained even if the amount of SO gas is reduced.

2

In addition, it is possible to suppress the occurrence of scratches on the back surface of the glass substrate while reducing the amount of sulfurous acid gas used.

This is because the SO gas sprayed in the second supply step described later is supplied to the bottom surface.

2

It reacts preferentially with the alkali metal generated, and it is a water-insoluble solution that exists even in alkali-free glass. This is thought to be because the reaction with alkaline earth metals (Ca, Sr, etc.) is suppressed. In addition, by blowing an external force from an alkali metal source called an alkali metal-containing inorganic substance,

2

The same protective effect can be achieved with a small amount of SO gas compared to the amount of SO gas used to obtain reactive organisms (calcium sulfate, strontium sulfate, etc.) as a protective coating.

twenty two

You can get it.

[0027] Specific examples of the inorganic substance containing Na include, for example, NaOH, Na S, NaCl, N

2

aF, NaBr, Nal, soda ash, NaNH, sodium benzyloxide, NaBH, NaCN

twenty four

, NaNO, Na B O— 10H O (sodium tetraborate decahydrate), Na B O, (C H) B

3 2 4 7 2 2 4 7 2 5 4

Na and the like can be mentioned, and these may be used alone or in combination of two or more.

[0028] Specific examples of inorganic substances containing K include, for example, KOH, KC1, KF, KBr, KI, KCN, KCO, potassium gnoleconate, KHF, KNO, KBO-4H O (tetraboric acid Cali

2 3 2 3 2 4 7 2

Um tetrahydrate), K B O, KBF, etc. These may be used alone or in combination of two

2 4 7 4

You may use the above together.

[0029] Specific examples of the inorganic substance containing Cs include CsOH, CsCl, CsF, CsBr, Csl, cesium acetylethylacetonate, HCO Cs, and CsNO.

twenty three

Species may be used alone or in combination of two or more.

[0030] Although the alkali metal-containing inorganic substance is an inorganic substance containing Na, the production efficiency of the protective film (sodium sulfate) formed in the second supply step, which will be described later, is further improved and easy to remove with water. Preferred because it becomes.

[0031] Among them, the alkali metal-containing inorganic material strength Na and boron-containing inorganic material are alkali-free glass substrate strength obtained by the production method of the present invention, and further have wear resistance even after the cleaning step described later. Therefore, it is more preferable. Specifically, Na B

2

O-10H 0, Na B O is preferred Na B O—10H O is more preferred

4 7 2 2 4 7 2 4 7 2

That's right.

As a result of supplying not only Na but also boron by spraying an inorganic substance containing Na and boron, boron diffuses from the bottom surface into the glass substrate, and the strength of the glass substrate itself is improved.

Therefore, in addition to alkali-free glass substrates, for example, glass substrates for DNA chips, A high level of scratch resistance can be satisfied by utilizing this diffusion of boron to a glass substrate for a black chip / biochip.

[0032] The first supply step is a force for supplying alkali metal to the bottom surface by spraying such an alkali metal-containing inorganic substance onto the bottom surface of the glass substrate. As for the spraying method, the following modes are suitably exemplified.

[0033] The timing of spraying the alkali metal-containing inorganic substance is not particularly limited as long as it is before the second supply step described later. Specifically, even at the same time as the molding step described above, the timing is gradually decreased. Although it may be simultaneous with the cooling step, it is preferable that it is between the molding step and the slow cooling step because the occurrence of scratches on the back surface of the glass substrate can be further suppressed.

Here, “simultaneously with the molding process” means a stage immediately after forming the glass substrate in the molding process and included in the molding process, for example, a forming furnace, a molten tin bath (float bath), and the entire furnace. In the case where an exit portion (shield rare) is provided, it means that the spray rare may be sprayed. Further, “simultaneously with the slow cooling step” means that the spraying may be performed near the inlet of the slow cooling furnace or upstream of the slow cooling furnace. Furthermore, “between the forming step and the slow cooling step” means that the glass substrate may be sprayed between the forming furnace and the slow cooling furnace.

[0034] On the other hand, the method of spraying the alkali metal-containing inorganic substance is, for example, a method of heating and vaporizing the alkali metal-containing inorganic substance and spraying the vaporized substance onto the bottom surface of the glass substrate using a nozzle; A method of heating and vaporizing an alkali metal-containing inorganic substance by heating, infrared lamp heating, laser heating, etc. is preferred. The vaporizing substance is sprayed at a temperature in the range of the glass transition temperature of the glass substrate ± 100 ° C. Preferably it is applied. In particular, the glass transition point of the glass substrate is preferably in the range of 30 ° C to glass transition point + 100 ° C. This is because if the spraying is performed within this temperature range, the glass becomes soft at the glass transition point, so that a film can be formed in that region, thereby preventing damage more effectively.

Specifically, the force applied at 600-800 ° C vaporizes the substance efficiently, and the glass This is preferable in that the substrate temperature does not drop abruptly when sprayed onto the substrate surface. Moreover, spraying of the vaporized material, 0. 2: The LOLZm that is ² to is preferred instrument 0. 2~3L / m ² is more preferred instrument 0. 2~lL / m ² Is particularly preferred. When the spraying amount is within this range, the bottom surface of the glass substrate is suppressed while suppressing the amount of SO gas spraying.

2

The supply amount of the alkali metal to be supplied becomes sufficient, and the production efficiency of the protective film formed by reacting with the SO gas sprayed in the second supply step described later is further improved.

2

[0035] When sodium tetraborate decahydrate is used as the alkali metal-containing inorganic substance, it is 850 ° in a furnace other than a glass substrate forming furnace and a slow cooling furnace (for example, a large tube furnace used in the examples). After vaporizing sodium tetraborate at a temperature of about C, the vaporized material is about 700 ° C. using a nozzle, and the glass substrate transported between these forming furnaces or slow cooling furnaces or between these furnaces is used. A method of spraying on the bottom surface is a preferred embodiment.

[0036] By spraying the alkali metal-containing inorganic substance by such a method, the alkali metal is supplied to the bottom surface of the glass substrate. The presence of alkali metal on the bottom surface of the glass substrate can be confirmed by X-ray photoelectron spectroscopy (XPS) or fluorescent X-ray analysis of the bottom surface of the glass substrate.

[0037] [Second supply step]

In the second supply step, after the first supply step, SO gas is sprayed on the bottom surface of the glass substrate to which the alkali metal has been supplied to form a protective film on the bottom surface.

2

It is a process.

This second supply step is different from a conventionally known step in a general float method in that a protective film is formed on the bottom surface of the glass substrate supplied with the alkali metal.

That is, in the second supply step, the alkali metal and the SO gas are sprayed by blowing SO gas onto the bottom surface of the glass substrate to which the alkali metal has been supplied in the first supply step.

This is a step of reacting 2 2 to form a protective film made of alkali sulfate (eg, sodium sulfate) on the bottom surface of the glass substrate.

[0038] Timing (timing) and spraying of SO gas in the second supply step About the method, the aspect shown below is illustrated suitably.

[0039] The timing of blowing the SO gas is not particularly limited as long as it is after the first supply step.

2

However, from the viewpoint of preventing scratches on the surface of the glass substrate being transported, it is more preferably between the molding step and the slow cooling step that is preferably immediately after the first supply step. Note that it is not preferable to spray each gas simultaneously because each gas reacts and it becomes difficult to form a film.

[0040] On the other hand, a method of blowing SO gas is a conventionally known method in a general float method.

2

Can be done in the same way. Specifically, for example, it can be carried out by a method of spraying a nozzle force installed below the glass substrate in the width direction of the glass substrate (for example, the method described in claim 12 of Patent Document 1).

However, in the present invention, the same protective effect is ensured as compared with the conventional example using a sulfate (eg, calcium sulfate) derived from an alkaline earth metal as a protective coating on the alkali-free glass substrate. Of SO gas

2 The amount of spray can be reduced. As described above, this is because the SO gas sprayed in the second supply process was supplied to the bottom surface.

2

This is presumably because the reaction with alkali metals (Ca, Sr, etc.), which reacts preferentially with alkali metals and is less reactive than alkali-free glasses, is suppressed. Specifically, in the present invention, SO, particularly 0.05 to 0.3.

LZm ² can be reduced.

Also, the SO gas is sprayed at a temperature in the range of ± 100 ° C of the glass transition point of the glass substrate.

2

Preferably it is applied. Since glass becomes soft at the glass transition point, forming a protective film in that region also has the ability to more effectively prevent scratches. Specifically, the so 2 gas spraying is more preferably performed at 600 to 800 ° C. When spraying is performed at this temperature, a protective coating made of sulfate that can be easily removed in the cleaning process is generated more efficiently, and the occurrence of scratches on the back surface of the glass substrate is further suppressed. It is the power that can be.

[0041] [Washing process]

The cleaning step performed as desired is a step of cleaning and removing the protective film formed in the second supply step, and is a conventionally known step in a general float method. [0042] As for the timing (timing) of the cleaning step and the cleaning method, the following modes are preferably exemplified.

[0043] The timing of the cleaning step is not particularly limited as long as it is after the second supply step, but the protective coating is made against a scratch on the surface (bottom surface) of the glass substrate that occurs during roller conveyance. Therefore, the final stage of the slow cooling step or immediately after the slow cooling step is preferable.

[0044] On the other hand, the cleaning method in the above-described cleaning step is an easy method because a protective film made of a sulfate derived from alkali metal (for example, a water-soluble salt such as sodium sulfate) is formed in the present invention. For example, it can be removed by washing with water. If the first supply process is not performed and SO gas is sprayed, the glass substrate

2

The protective coating formed on the tom surface becomes a sulfate derived from an alkaline earth metal (for example, a poorly water-soluble salt such as calcium sulfate), which makes it difficult to clean easily.

[0045] In the production method of the present invention, the smoothness of the obtained alkali-free glass substrate is improved, and the distortion, undulation, microcorrugation, scratches and foreign matter defects of the glass substrate are reduced, and the uniformity is high. In order to obtain the surface quality, a polishing step may be provided as necessary after the cleaning step.

This polishing process is a conventionally known process in a general float process. Specifically, the polishing process is a glass substrate placed on urethane foam using an acid-cerium-based abrasive. The method of polishing is mentioned.

[0046] A method for producing an alkali-free glass substrate according to the second aspect of the present invention is a method for producing an alkali-free glass substrate by a float method, wherein the molten glass is glass on molten tin. A molding process for molding on a substrate,

After the first supply step of spraying an inorganic substance containing an alkali metal on the surface of the glass substrate in contact with the molten tin at 600 to 800 ° C., and after the first supply step, 600 to 800 ° C. Blow SO gas on the surface of the glass substrate that contacts the molten tin.

2 is a method for producing an alkali-free glass substrate, comprising a second supplying step.

[0047] Here, the forming step in the second aspect of the present invention is the same as that described in the first aspect of the present invention, and the temperature is set to 600 for the first supply step and the second supply step. Except for the range of ˜800 ° C., the same as described in the first embodiment of the present invention. Also in the second aspect of the present invention, it is preferable to include the above-described cleaning step, and it is possible to further include the above-described polishing step.

[0048] The present invention can be obtained by the production method of the present invention when an inorganic substance containing Na and boron is used in the production method of the present invention (including the second aspect, the same shall apply hereinafter). The present invention also provides a non-alkali glass substrate.

Specifically, an alkali-free glass substrate is provided by spraying an inorganic substance containing Na and boron onto the bottom surface of the glass substrate in the first supply step, and then performing the cleaning step as necessary. be able to.

[0049] The alkali-free glass substrate of the present invention preferably has the following composition.

That is, in the alkali-free glass substrate of the present invention, the glass substrate is expressed in terms of mass percentage based on oxide,

SiO: 30 to 85%

2

AI O: 0-35%

twenty three

B O: 0-35%

twenty three

MgO :. ~ 35%,

CaO: ~ 35%,

SrO :. ~ 35%,

BaO :. ~ 35%,

Alkali metal component: 0.5% or less

Containing, and

The average boron concentration of the bottom surface of the glass substrate is 4 to: L0 atomic%, and the diffusion depth of boron into the glass substrate is 5 nm or more.

[0050] Here, the SiO content (expressed in terms of mass percentage based on oxide) is 50 to 80%.

2

It is particularly preferred that it is 58-60%, more preferably 56-66%, more preferably 50-70%.

In addition, the content of Al 2 O (expressed in terms of mass percentage based on oxide) is preferably 0 to 30%.

twenty three

3-22% is more preferred 3-20% is more preferred 15-20 % Is particularly preferred, with 15-19% being most preferred.

In addition, the content of B 2 O (expressed in terms of mass percentage based on oxide) is preferably 0 to 30%.

twenty three

It is more preferably 5 to 12%, more preferably 0 to 15%.

Further, the content of MgO (expressed in terms of mass percentage based on oxide) is preferably 0 to 20%, more preferably 0 to 8%, and even more preferably 0 to 6%. .

Further, the content of CaO (expressed in terms of mass percentage based on oxide) is preferably 0 to 20%, more preferably 0 to 9%, and even more preferably 0 to 8%. .

The SrO content (expressed as a percentage by mass on the oxide basis) is preferably 0 to 20%, more preferably 0 to 12.5%, and 3 to 12.5%. Is more preferable. Further, the BaO content (expressed in terms of mass percentage based on oxide) is preferably 0 to 20%, more preferably 0% or more and less than 2%.

In addition, the content of alkali metal component (expressed in terms of mass percentage based on oxide) is preferably 0.5% or less, more preferably 0.2% or less, and more preferably 0.1% or less. More preferably.

[0051] Here, SiO, Al 2 O, B 2 O, MgO, CaO, SrO, BaO and A

2 2 3 2 3

As described above, the content of the alkali metal component is in the range of the composition of the alkali-free glass used for the alkali-free glass substrate.

In the present invention, the average boron concentration on the bottom surface of the glass substrate can be obtained as an average value when arbitrarily measured at five points by X-ray photoelectron spectroscopy. In X-ray photoelectron spectroscopy, an XPS spectrometer (5500 type, manufactured by PHI) was used, and X-rays α rays monochromatized with a monochromator were used as the X-ray source. The X-ray photoelectron detection angle was 75 °, and measurement was performed by irradiating an electron shower to correct charging.

[0053] In the present invention, the diffusion depth of boron into the glass substrate is estimated from the depth at which the secondary ion intensity reaches the same level as the background by secondary ion mass spectrometry (SIMS). Is pretty.

Specifically, the diffusion depth was measured at five points on each of the five points on the glass substrate using a secondary ion mass spectrometer (ADEPT1010, ULVAC “Phine”), and the average value was obtained. Here, the conversion of the splatter time to the splatter depth is performed using SiO conversion (4 nm = lmin). I got it. The primary ion is an oxygen ion beam, the acceleration voltage is 5 keV, the beam current is 400 ηΑ, the incident angle of the primary ion is 45 degrees with respect to the normal of the sample surface, and the beam scanning range is 400 X 400 μm ² Measured with

[0054] In the alkali-free glass substrate of the present invention, the average boron concentration of the bottom surface of the glass substrate is 4 to: L0 atomic%, and the diffusion depth of boron into the glass substrate is 5 nm or more and 80 nm. In the following, since the thickness is preferably 50 nm or less, the strength of the glass substrate itself is improved, the wear resistance is excellent, and the transportation and processing steps after the protective coating is removed! Even if it is, it will be excellent in scratch resistance. The reason why boron has a bottom surface force also diffuses into the glass substrate and remains on the surface of the glass substrate, so that the wear resistance and the scratch resistance are improved is because the glass network structure is strengthened. Conceivable.

[0055] The alkali-free glass substrate of the present invention is not limited to the glass substrate because boron remains on the surface layer of the glass substrate not only before the cleaning step but also after the cleaning step if necessary. Since it is possible to continue to suppress the occurrence of scratches on the back surface, it is preferable.

Note that boron remains in the surface layer of the non-alkali glass substrate of the present invention and the surface layer of the glass substrate according to the first supply step as described above. I guess it's easy to survive! /, And! /

[0056] Therefore, the present invention represents the oxide-based mass percentage,

SiO: 30 to 85%

2

AI O: 0-35%

twenty three

B O: 0-35%

twenty three

MgO :. ~ 35%,

CaO: ~ 35%,

SrO :. ~ 35%,

BaO :. ~ 35%,

Alkali metal component: 0.5% or less

Containing

It is also possible to provide an alkali-free glass substrate having an average boron concentration of at least one surface of 4 to 10 atomic% and a surface force of boron diffusion depth of 5 nm or more inside. Togashi.

Example

[0057] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

[Example 1]

The experimental apparatus shown in Fig. 2 was used. FIG. 2 is a cross-sectional view of the large tubular furnace used in the examples.

Specifically, a quartz tube 12 is installed in a large-sized tubular furnace 11 whose temperature can be adjusted, and a non-alkali glass substrate 13 (10 cm square) having a thickness of 0.7 mm is placed in the quartz tube 12, and the large tubular furnace 11 is placed. Was heated to 700 ° C. Here, `` Non-alkali glass substrate '' is expressed in terms of mass percentage based on oxide, 68% ≤ SiO ≤ 80%, 0% ≤ A1 O <12%, 0% <B O <7

2 2 3 2 3

%, 0% ≤MgO≤12%, 0% ≤CaO≤15%, 0% ≤SrO≤4%, 0% ≤BaO≤l% An alkali-free glass was used. The glass transition point of the glass was 700 ° C.

Next, the sodium tetraborate decahydrate reagent 15 placed in the alumina boat 14 is locally heated to about 850 ° C to vaporize the vaporized material, and the end force of the quartz tube also moves in the direction indicated by the arrow 16. By spraying, sodium, which is an alkali metal, was supplied to the surface of the alkali-free glass substrate 13. The spray amount of sodium tetraborate decahydrate at this time was 0.4 L / m ² , and the temperature of the alkali-free glass substrate 13 was 700 ° C.

Next, SO gas was sprayed from the direction indicated by the arrow 17 to form a protective coating so that the amount of spraying on the surface of the alkali-free glass substrate 13 was 0.1 lZm ² .

2

An alkali-free glass substrate was produced. The temperature of the alkali-free glass substrate 13 at this time was 700 ° C.

In this example, the conditions are the same as those in which an alkali metal-containing inorganic substance was sprayed between the molding step and the slow cooling step and so gas was sprayed immediately thereafter.

2

[Example 2]

The protective coating was applied in the same manner as in Example 1 except that the amount of SO gas sprayed was 0.4 LZm ^2.

2

A non-alkali glass substrate with a film was produced. [0060] (Example 3)

The protective coating was applied in the same manner as in Example 1 except that the amount of SO gas sprayed was 1. OLZm ^2.

2

A non-alkali glass substrate with a film was produced.

[0061] (Comparative Example 1)

The same as Example 1 except that sodium tetraborate was not used and only SO gas was sprayed.

2

The alkali-free glass substrate with a protective film was manufactured by the method.

[0062] (Comparative Example 2)

Same as Example 2 except that sodium tetraborate was not used and only SO gas was sprayed.

2

[0063] (Comparative Example 3)

Same as Example 3 except that sodium tetraborate was not used and only SO gas was sprayed.

2

[0064] (Comparative Example 4)

Without using sodium tetraborate and without blowing SO gas, simply heat at 700 ° C for 15 minutes.

2

A non-alkali glass substrate was produced in the same manner as in Example 1 except that.

[0065] (Comparative Example 5)

Same as Example 1 except that sodium tetraborate was not used and SO gas was also applied.

2

An alkali-free glass substrate was produced by the method described above.

[0066] For each non-alkali glass substrate with a protective coating obtained in Examples 1 to 3 and Comparative Examples 1 to 3, the amount of protective coating deposited, scratch resistance, average boron concentration, diffusion depth, and wear resistance Were measured and evaluated by the methods shown below. The results are shown in Table 1 below.

In addition, since each of the glass substrates for flat panel glass obtained in Comparative Examples 4 and 5 was not sprayed with SO gas and a protective film was not formed, only the wear resistance was as follows.

2

It measured by the method shown in. The results are shown in Table 1 below.

[0067] <Amount of protective coating>

The obtained protective coating of each alkali-free glass substrate with protective coating was dissolved in pure water, sulfur was quantified using ICP emission analysis, and sodium was quantified using atomic absorption spectrometry.

From these quantitative values, the amount of sodium sulfate adhering was calculated as the amount of protective coating adhered. I put it out. The adhesion amount was determined as an average value calculated from 10 sheets of the obtained alkali-free glass substrate.

[0068] <Scratch resistance>

The scratch resistance was evaluated by a Taber test according to JIS R3221 (1990). The Taber test was conducted using a Taber tester (Tdedyne Taber Model 503), with the wear wheel fixed to CS-10F, the load fixed to 250 g, and the wear frequency fixed to 3 times. Thereafter, in order to remove the protective coating of each alkali-free glass substrate with a protective coating used as a test specimen, the substrate was washed with a shower for 30 seconds under flowing pure water (3 liters Z) at 20 ° C.

The surface of the glass substrate obtained by removing the protective film was observed with a microscope, and the number of scratches (number of scratches) with a length of 0.2 mm or more in the long axis direction existing within 1 cm × 1 cm square was measured. . The measurement part was the central part of the part subjected to the Taber test (see Fig. 3). In FIG. 3, a wear part 19 due to a wear ring is formed on a specimen (non-alkali glass substrate) 18, but the measurement part 20 is the central part of the wear part 19.

The number of scratches was measured for 10 arbitrary points on each glass substrate, and the average value was obtained. Furthermore, the number of scratches was determined as an average value obtained by calculating the 10-sheet force of the obtained glass substrate.

[0069] <Average boron concentration and diffusion depth>

(1) Each of the obtained alkali-free glass substrates with a protective coating was washed with water in a place where pure water (flow rate: 3 liters Z) at 20 ° C flows down to remove the protective coating. After that, the average boron concentration on the surface of the cleaned glass substrate was determined as the average value when five points were measured by X-ray photoelectron spectroscopy. In the X-ray photoelectron spectroscopy, an XPS spectrometer (5500, manufactured by PHI) was used, and X-rays α rays monochromatized with a monochromator were used as the X-ray source. The X-ray photoelectron detection angle was 75 °, and measurement was performed by irradiating an electron shower to correct the charge.

[0070] (2) The diffusion depth of boron into the glass substrate was estimated from the depth at which the secondary ion intensity reached the same level as the background by secondary ion mass spectrometry (SIMS).

Specifically, using a secondary ion mass spectrometer (ADEPT1010, ULVAC “Phine”), measured the diffusion depth at 5 points on the glass substrate after cleaning, and calculated the average value. Asked. Here, the conversion of the splatter time to the splatter depth is SiO conversion (4nm = lmin)

2

I went there.

The primary ions are measured under the conditions of an oxygen ion beam, acceleration voltage is 5 keV, beam current is 400 nA, the incident angle of primary ions is 45 degrees with respect to the normal of the sample surface, and the beam scanning range is 400 X 400 IX m ^2. did.

In Table 1 below, the diffusion depth column of Comparative Examples 1 to 3 is “-”, which indicates that the diffusion was not confirmed.

[0071] <Abrasion resistance>

Abrasion resistance was determined by examining the rate of change in the haze rate before and after the Taber test (rate of change in haze).

First, the haze ratio of each obtained alkali-free glass substrate was measured with a haze meter. Next, the obtained alkali-free glass substrate was subjected to a Taber test according to JIS R3221 (1990). The Taber test was conducted using a Taber tester (Tdedyne Taber Model 503), with the wear wheel fixed to CS-10F and the load fixed to 500 g.

Next, the haze rate after 1000 times Taber abrasion was measured with a haze meter, and the haze rate power before the Taber test was determined.

Here, the haze value is defined by the scattered light (Td) and the transmitted light (Tt) as follows.

Haze rate = (Td / Tt) X 100%

Further, the change rate (ΔH) of the haze ratio (H) is represented by the following formula.

Δ Η = Haze rate after 1000 wears H—Haze rate before Taber test H [0072] [Table 1] table 1

[0073] From the results shown in Table 1, the non-alloyed glass substrate of Examples 1 to 3 obtained using sodium tetraborate was sprayed with SO gas equal to or less than that of Comparative Example:! To 3 Amount

2

However, it was important to form a protective coating efficiently. In addition, the boron concentration increased and the scratch resistance was remarkably improved.

In Comparative Examples 1 to 3, even though the amount of sodium sulfate was the same, the reason why the scratch count decreased with the increase in the amount of SO gas sprayed was that the sulfate (sulfuric acid derived from alkaline earth metal) This is because calcium, strontium sulfate, etc.) are produced and function as a protective coating.

In addition, it was confirmed that the non-alkali glass substrates of Examples 1 to 3 had a clean surface after the protective coating formed on the surface of the glass substrate was removed after normal water washing. On the other hand, in the non-alkali glass substrates of Comparative Examples 1 to 3, the protective coating formed on the surface of the glass substrate could not be removed even after ordinary water washing, and remained. Further, when the components of the remaining film were measured, they were calcium sulfate and strontium sulfate.

Furthermore, the alkali-free glass substrates of Examples 1 to 3 have a reduced haze change rate and improved wear resistance compared to the alkali-free glass substrates of Comparative Examples 1 to 5 due to diffusion of boron. It was a component.

[0074] Although the invention has been described in detail and 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. is there. This application is based on a Japanese patent application filed on July 7, 2006 (Japanese Patent Application No. 2006-187727), the contents of which are incorporated herein by reference.

Industrial applicability

According to the present invention, a non-alkali which efficiently generates a protective film that can be easily removed in a cleaning process, and suppresses the occurrence of scratches on the back surface of the glass substrate while reducing the amount of sulfurous acid gas used. A method for producing a glass substrate and an alkali-free glass substrate obtained by the production method can be provided. The alkali-free glass substrate of the present invention can be suitably used for high-quality displays.

Claims

The scope of the claims

[1] A method for producing an alkali-free glass substrate by producing an alkali-free glass substrate by a float process,

A forming step of forming molten glass on a molten tin on a glass substrate; and a slow cooling step of gradually cooling the glass substrate formed by the forming step,

A first supply step of spraying an inorganic substance containing an alkali metal on a surface of the glass substrate in contact with the molten tin; and after the first supply step, on the side of the glass substrate in contact with the molten tin A second supply step of blowing SO gas on the surface

2

A method for producing an alkali-free glass substrate.

[2] The method for producing an alkali-free glass substrate according to [1], wherein the first supply step is performed between the forming step and the slow cooling step.

[3] The method for producing an alkali-free glass substrate according to [1], wherein the first supply step is performed at a temperature in a range of a glass transition point of the glass substrate ± 100 ° C.

[4] The method for producing an alkali-free glass substrate according to claim 1, wherein the first supply step is performed at 600 to 800 ° C.

[5] The first supply step is performed between the molding step and the slow cooling step.

5. A method for producing an alkali-free glass substrate according to any one of 4 above.

[6] The method for producing an alkali-free glass substrate according to any one of [1] to [4], wherein the second supply step is performed at a temperature in the range of 100 ° C. of the glass transition point of the glass substrate.

[7] The method for producing an alkali-free glass substrate according to any one of [1] to [4], wherein the second supply step is performed at 600 to 800 ° C.

[8] A method for producing an alkali-free glass substrate by producing an alkali-free glass substrate by a float process,

A first supply step of spraying an inorganic substance containing an alkali metal on the surface of the glass substrate in contact with the molten tin at 600 to 800 ° C, and after the first supply step, 600 to 800 ° C To blow SO gas on the surface of the glass substrate that contacts the molten tin.

2. A method for producing an alkali-free glass substrate, comprising a second supply step to be applied.

[9] The method for producing an alkali-free glass substrate according to any one of claims 1 to 8, further comprising a cleaning step of removing the protective film.

10. The method for producing an alkali-free glass substrate according to any one of claims 1 to 9, wherein the inorganic substance containing an alkali metal contains sodium and boron.

[11] The method for producing an alkali-free glass substrate according to [10], wherein the inorganic substance containing an alkali metal is sodium tetraborate.

[12] An alkali-free glass substrate produced by the production method according to claim 10 or 11.

[13] An alkali-free glass substrate produced by the production method according to claim 10 or 11,

The glass substrate is a mass percentage display based on oxide,

SiO: 30 to 85%

2

AI O: 0

2 3 ~ 35%,

B O: 0

2 3 ~ 35%,

MgO :. ~ 35%,

CaO: ~ 35%,

SrO :. ~ 35%,

BaO :. ~ 35%,

Alkali metal component: 0.5% or less

Containing

An alkali-free glass substrate having an average boron concentration of 4 to 10 atomic% on the surface of the glass substrate in contact with the molten tin and a boron diffusion depth of 5 nm or more into the glass substrate.

[14] Oxide-based mass percentage display,

SiO: 30 to 85%

2

AI O: 0-35%

twenty three

B O: 0-35%

twenty three

MgO :. ~ 35%,

CaO: 0-35%, SrO: 0-35%,

BaO: 0-35%,

Alkali metal component: 0.5% or less

Containing

An alkali-free glass substrate in which the average boron concentration on at least one surface is 4 to: LO atomic%, and the diffusion depth of boron from the surface to the inside is 5 nm or more.