KR20090029785A - Method for producing alkali free glass substrate - Google Patents

Abstract

The present invention provides a method for producing an alkali-free glass substrate and a method for producing an alkali-free glass substrate which efficiently produce a protective film that can be easily removed in a washing step, and suppress the occurrence of scratches on the back surface of the glass substrate while reducing the amount of sulfite gas used. It is a subject to provide the alkali free glass substrate obtained by this. This invention is a manufacturing method of the alkali free glass substrate which manufactures an alkali free glass substrate by the float method, The molding process of shape | molding a molten glass to a glass substrate on molten tin, and the slow cooling of the said glass substrate shape | molded by the said molding process are carried out. And a slow cooling step, wherein 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 and the molten tin of the glass substrate after the first supply step non relates to a process for producing alkali-free glass substrate having a second supply step of spraying the SO ₂ gas to the surface of the side in contact with.

Description

Production method of an alkali-free glass substrate {PROCESS FOR PRODUCING ALKALI-FREE GLASS SUBSTRATE}

The present invention relates to a method for producing an alkali free glass substrate.

Most of glass substrates, including a glass substrate for a display, are manufactured by the float method or the fusion method. Unlike the fusion method, the float method is an excellent manufacturing method in that a large-area glass substrate can be efficiently produced.

This float method is generally provided with the shaping | molding process which shape | molds a molten glass to a glass substrate on molten tin in a molten tin bath, and the slow cooling process which slow-cools the glass substrate shape | molded by the shaping | molding process.

However, since the glass substrate molded by this molding process is conveyed by the roller after taking out in a molten tin bath, the back surface (surface contacting the roller) of the glass substrate is scratched during conveyance, thereby degrading the quality of the glass substrate. There was.

Accordingly, in order to prevent scratches on the rear surface glass substrate that occur during the conveying, spraying a sulfur dioxide (SO ₂ gas) to the back glass substrate, (e.g., sodium, etc.), alkali metal present in the glass is reacted with a glass A method of preventing scratches is known by forming sodium sulfate on the back surface of a substrate and making it function as a protective film (see, for example, Patent Document 1, Non-Patent Document 1, and the like).

Patent Document 1: International Publication No. 2002/051767

Non-Patent Document 1: U. Senturk etc, J. Non-Cryst. Solids, Vol. 222, p. 160 (1997)

<Start of invention>

Problems to be Solved by the Invention

However, in order to realize the high scratch prevention capability currently required for high-quality displays, it is necessary to increase the thickness of the protective film more, and in order to do this, it is necessary to use a large amount of sulfurous acid gas, which is a problem of deterioration of environmental load and working environment. There was. Moreover, since sulfurous acid gas is highly corrosive gas, there also existed a problem that corrosion of surrounding furnace materials shortened and the lifetime of a furnace material was shortened.

In particular, in the case of producing a glass substrate composed of glass substantially free of alkali metal (hereinafter also referred to as "alkali free glass"), sodium sulfate is not produced by the method of spraying sulfurous acid gas, and alkali Salts, such as calcium sulfate and strontium sulfate, which are reaction products with an earth metal, are produced on the glass substrate. These salts derived from alkaline earth metals act as protective films for preventing scratches of the glass substrate, but their production efficiency is significantly lower than that of sodium sulfate, so the action may be insufficient. Moreover, even if it is produced, since it is a hardly water-soluble salt, there is a problem that it is very difficult to remove later in the washing step.

Moreover, although these salts can be removed by grinding | polishing, in order to obtain the glass substrate with high smoothness, they have to grind considerable thickness, and there existed a problem that manufacturing time and manufacturing cost increase.

In addition, since alkali-free glass requires a high quality surface such as a flat panel display, and the presence of scratches on the glass substrate causes problems such as disconnection defects, small scratches also become a problem due to abnormal use of window glass or automobile glass. .

Therefore, this invention is a manufacturing method of the glass substrate (henceforth "alkali glass substrate") comprised from the alkali free glass used for a liquid crystal display, and efficiently produces the protective film which can be easily removed in a washing process. And it aims at providing the manufacturing method of the alkali free glass substrate which can suppress the generation | occurrence | production of the scratch on the back surface of a glass substrate, and aims at reducing the usage-amount of sulfurous acid gas, and the alkali free glass substrate obtained by the said manufacturing method.

Means for solving the problem

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to achieve the said objective, in the manufacturing process by a float method, the inorganic material containing alkali metal was sprayed on the surface of the side which contacted molten tin of a glass substrate, and an alkali metal is supplied, Then, by spraying SO ₂ gas on the surface, it is possible to efficiently produce a protective film that can be easily removed in the cleaning process, and to prevent scratches on the back surface of the glass substrate while reducing the amount of sulfite gas used. Discovered to complete the present invention.

That is, this invention provides the following (1)-(14).

(1) It is a manufacturing method of the alkali free glass substrate which manufactures an alkali free glass substrate by a float method,

A molding step of molding the molten glass onto a glass substrate on molten tin, and a slow cooling step of slowly cooling the glass substrate molded by the molding 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 a surface of the glass substrate in contact with the molten tin after the first supply process. the method of alkali-free glass substrate having a second supply step of spraying the SO ₂ gas.

(2) The manufacturing method of the alkali free glass substrate of said (1) in which the said 1st supply process is performed between the said molding process and the said slow cooling process.

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

(4) The manufacturing method of the alkali free glass substrate of said (1) in which the said 1st supply process is performed at 600-800 degreeC.

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

(6) The method for producing an alkali-free glass substrate according to any one of the above (1) to (4), wherein the second supply process is performed at a temperature in a glass transition point ± 100 ° C of the glass substrate.

(7) The manufacturing method of the alkali free glass substrate in any one of said (1)-(4) in which the said 2nd supply process is performed at 600-800 degreeC.

(8) It is a manufacturing method of the alkali free glass substrate which manufactures an alkali free glass substrate by the float method,

A molding step of molding the molten glass onto the glass substrate on the molten tin;

A first supply step of spraying an inorganic material containing an alkali metal on the surface of the glass substrate at the side in contact with the molten tin at 600 to 800 ° C., and after the first supply step, the glass substrate at 600 to 800 ° C. the method of alkali-free glass substrate having a second supply step of spraying the SO ₂ gas to the surface of the side contacting the molten tin.

(9) The manufacturing method of the alkali free glass substrate in any one of said (1)-(8) provided with the washing | cleaning process which removes the said protective film further.

(10) The method for producing an alkali-free glass substrate according to any one of (1) to (9), wherein the inorganic material containing the 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.

The alkali free glass substrate manufactured by the manufacturing method as described in said (10) or (11).

(13) It is an alkali free glass substrate manufactured by the manufacturing method of said (10) or (11),

The glass substrate is expressed as a percentage of mass on an oxide basis,

SiO ₂ : 30 to 85%,

Al ₂ O ₃ : 0 to 35%,

B ₂ O ₃ : 0 to 35%,

MgO: 0 to 35%,

CaO: 0-35%,

SrO: 0 to 35%,

BaO: 0 to 35%,

Alkali metal component: 0.5% or less

Containing,

The alkali free glass substrate of which the average boron concentration of the surface of the side in contact with the said molten tin of the said glass substrate is 4-10 atomic%, and the diffusion depth of boron into the inside of the said glass substrate is 5 nm or more.

(14) In the indication of the mass percentage on the basis of oxide,

SiO ₂ : 30 to 85%,

Al ₂ O ₃ : 0 to 35%,

B ₂ O ₃ : 0 to 35%,

MgO: 0 to 35%,

CaO: 0-35%,

SrO: 0 to 35%,

BaO: 0 to 35%,

Alkali metal component: 0.5% or less

Containing,

The alkali free glass substrate whose average boron concentration of at least one surface is 4-10 atomic%, and the diffusion depth of boron from the said surface to the inside is 5 nm or more.

Effect of the Invention

As shown below, according to the present invention, an alkali-free glass substrate which efficiently generates a protective film that can be easily removed in a cleaning process and suppresses the occurrence of scratches on the back of the glass substrate while reducing the amount of sulfurous acid gas used. The alkali free glass substrate obtained by the manufacturing method and the said manufacturing method can be provided.

FIG. 1: is a conceptual diagram which shows an example of the glass manufacturing line by a float method. FIG.

2 is a sectional view of a large tubular furnace used in the embodiment.

FIG. 3: is explanatory drawing which shows the part (wear part) which the abrasion ring of the taper tester used for evaluation of scratch resistance abutted, and the number measurement site | part (measurement part) of a damage | wound.

<Brief description of symbols for the main parts of the drawings>

1: molten tin

2: molten tin bath

3: melting kiln

4: molten glass

5: withdraw roll

6: slow cooling furnace

11: large pipe furnace

12: quartz tube

13: alkali free glass substrate

14: Alumina Bow

15: Reagent

16, 17: arrow

18: test body

19: wear parts

20: measuring unit

Best Mode for Carrying Out the Invention

The present invention is described in detail below.

The manufacturing method of an alkali free glass substrate (henceforth "the manufacturing method of this invention") which concerns on the 1st aspect of this invention is a manufacturing method of the alkali free glass substrate which manufactures an alkali free glass substrate by a float method,

A molding step of molding the molten glass onto a glass substrate on molten tin, and a slow cooling step of slowly cooling the glass substrate molded by the molding step,

First supply which sprays the inorganic material containing alkali metal (henceforth an "alkali metal containing inorganic material") to the surface (henceforth a "lower surface") of the glass substrate at the side which contacts said molten tin. An alkali free glass substrate comprising a step and a second supply step of spraying SO ₂ gas on a surface of the side of the glass substrate in contact with the molten tin after the first supply step, that is, a lower surface onto which the inorganic material is sprayed. It is a manufacturing method.

Moreover, it is preferable that the manufacturing method of this invention further includes the washing | cleaning process which removes the said protective film.

Next, the shaping | molding process in the manufacturing method of this invention, a slow cooling process, a 1st supply process, a 2nd supply process, and the washing process provided according to a request are explained in full detail.

[Molding process]

The said molding process is a process of shape | molding a molten glass on a glass substrate on molten tin in a molten tin bath, and is a conventionally well-known process in the general float method.

1 is a conceptual diagram illustrating an example of a glass production line by the float method.

As shown in FIG. 1, in the float method, first, the molten glass 4 flows in continuously from the molten kiln 3 on the bath surface of the molten tin bath 2 which satisfy | filled the molten tin 1, and is glass. Ribbon is formed. Next, by advancing the glass ribbon while floating along the bath surface of the molten tin bath 2, the glass ribbon is molded into a plate shape at the same time as the temperature decreases. Then, the produced glass substrate is taken out by the take-out roll 5, and is conveyed to the slow cooling furnace 6 in the continuous state in the longitudinal direction.

Here, in FIG. 1, the said molding process is a process until the molten glass 4 is shape | molded in plate shape via a glass ribbon.

In the present invention, similarly to the general float method, the molten tin bath 2 is composed of a tin bath in which the inside of the metal case is lined with special refractory and a ceiling, and a sealed structure is used to prevent oxidation of tin. As an atmosphere gas in a molten tin bath, the mixed gas containing hydrogen and nitrogen (content of hydrogen is 2-10 volume%) can be used.

Moreover, the temperature conditions in the molten tin bath of the said shaping | molding process are 600-1050 degreeC similarly to the general float method, ie, the temperature of the molten glass which flows into a molten tin bath is 900-1050 degreeC in an upstream, and 600 in a downstream side. To 800 ° C. In addition, although this temperature is normally maintained by the amount of heat of a molten glass, you may use a heater and a cooler for temperature control.

In the manufacturing method of this invention, the glass substrate of an alkali free glass is shape | molded on molten tin by the said molding process.

An alkali free glass is glass which does not contain an alkali metal substantially as mentioned above here. Specifically, an alkali free glass is the mass percentage display of an oxide standard in this invention,

SiO ₂ : 30 to 85%,

Al ₂ O ₃ : 0 to 35%,

B ₂ O ₃ : 0 to 35%,

MgO: 0 to 35%,

CaO: 0-35%,

SrO: 0 to 35%,

BaO: 0 to 35%,

Alkali metal component: 0.5% or less

It contains. In addition, an "alkali metal component" means the thing of the alkali metal component inevitably contained regardless of the 1st supply process mentioned later.

[Slow cooling process]

The slow cooling step is a step of slowly cooling the glass substrate molded by the molding step.

Here, in FIG. 1, the said slow cooling process is a process to take out the manufactured glass substrate with the takeout roll 5, and to carry it to the slow cooling furnace 6 in the continuous state in the longitudinal direction, and to cool slowly.

In the present invention, as the slow cooling furnace, one used by a general float method can be used, and a heater or the like can be provided for temperature control.

In addition, the slow cooling conditions in the slow cooling furnace of the slow cooling process can be made into the temperature of 550-750 degreeC at the inlet of a slow cooling furnace and 200-300 degreeC at the outlet like the general float method, and the speed | rate of a temperature drop is 90 It can be set to ° C ± 10 ° C / m.

[First Supply Process]

The said 1st supply process is a process of spraying an alkali metal containing inorganic substance to the lower surface of the said glass substrate, and supplying an alkali metal to the said lower surface.

The alkali metal-containing inorganic substance herein refers to an inorganic substance containing an alkali metal as described above, and for example, an inorganic substance containing lithium (Li), sodium (Na), potassium (K), cesium (Cs), or the like. This corresponds.

By supplying an alkali metal to the lower surface of the glass substrate using such an alkali metal-containing inorganic substance, and then spraying SO ₂ gas, a protective film containing a salt of alkali sulfate can be efficiently produced. In addition, this protective film can be easily removed in a washing | cleaning process. In addition, since less and also the same protective effect is obtained the amount of SO ₂ gas, it is possible while achieving a reduction in the amount of the sulfur dioxide to suppress the occurrence of scratches when the glass substrate.

This is because the SO ₂ gas sprayed by the second supply process described later preferentially reacts with the alkali metal supplied to the lower surface, and the reaction with the poorly water-soluble alkaline earth metals (Ca, Sr, etc.) existing even in the alkali free glass is suppressed. I think it is because. In addition, by spraying an alkali metal source such as an alkali metal-containing inorganic substance from the outside, the amount of SO ₂ gas used to obtain a reactive film (calcium sulfate, strontium sulfate, etc.) between the SO ₂ gas and the alkaline earth metal as a protective film is less. The equivalent protective effect can be obtained with the amount of SO ₂ gas.

As the inorganic substance containing Na, specifically, for example, NaOH, Na ₂ S, NaCl, NaF, NaBr, NaI, soda ash, NaNH ₂ , sodium benzyloxide, NaBH ₄ , NaCN, NaNO ₃ , Na ₂ B ₄ O ₇ -10H ₂ O (sodium tetraborate decahydrate), Na ₂ B ₄ O ₇ , (C ₂ H ₅ ) ₄ BNa, and the like, and these may be used alone or in combination of two or more thereof. It can also be used in combination.

As the inorganic substance containing K, specifically, for example, KOH, KCl, KF, KBr, KI, KCN, K ₂ CO ₃ , potassium gluconate, KHF ₂ , KNO ₃ , K ₂ B ₄ O ₇ − 4H ₂ O may be made of (potassium tetraborate tetrahydrate), such as _{K 2 B 4 O 7, KBF} 4, and these may be used alone or may be used in combination of two or more.

Specific examples of the inorganic substance containing Cs include CsOH, CsCl, CsF, CsBr, CsI, cesium acetylacetonate, HCO ₂ Cs, CsNO ₃ , and the like, and these may be used alone. In addition, you may use 2 or more types together.

The alkali metal-containing inorganic substance is preferably an inorganic substance containing Na because the production efficiency of the protective film (sodium sulfate) formed in the second supply step described later is further improved, and water washing removal is facilitated.

Especially, since the alkali metal containing inorganic substance is an inorganic substance containing Na and boron, since the alkali free glass substrate obtained by the manufacturing method of this invention will further have abrasion resistance after the washing | cleaning process mentioned later, it is more preferable. _{Specifically, Na 2 B 4 O 7 -10H} 2 O, preferably in the Na ₂ B ₄ O _7, and more preferably _{Na 2 B 4 O 7 -10H 2} O.

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

For this reason, high levels of scratch resistance can be satisfied by using diffusion of this boron in addition to the alkali free glass substrate, for example, the DNA substrate glass substrate, the microchip biochip glass substrate, and the like.

Although the said 1st supply process supplies an alkali metal to the said lower surface by spraying such an alkali metal containing inorganic substance to the lower surface of the said glass substrate, the aspect shown below about the timing (timing) and the spraying method of this spraying Is preferably illustrated.

The timing for spraying the alkali metal-containing inorganic substance is not particularly limited as long as it is before the second supply step described later. Specifically, the molding step may be simultaneous with the molding process or may be concurrent with the slow cooling process described later. It is preferable that it is between the said slow cooling process and can suppress the flaw generation on the back surface of a glass substrate more.

The term "simultaneous to the molding process" herein means a step immediately after the glass substrate is formed in the molding process and included in the molding process, for example, a molten tin bath (float bath) in the forming furnace and an outlet portion of the entire furnace (shield rare). ) Is installed, it means that the spray can also be sprayed on the shield rare. In addition, "simultaneous with slow cooling process" means that it can also spray in the vicinity of the inlet of a slow cooling furnace, or upstream of a slow cooling furnace. In addition, "between the said molding process and the said slow cooling process" means that it can also spray between a formation furnace and a slow cooling furnace, conveying a glass substrate.

On the other hand, the method for spraying the alkali metal-containing inorganic material, for example, a method of heating and vaporizing the alkali metal-containing inorganic material, and spraying the vaporized material on the lower surface of the glass substrate using a nozzle; The method of heat-vaporizing an alkali metal containing inorganic substance by heater heating, infrared lamp heating, laser heating, etc. are mentioned preferably.

In addition, the spraying of the vaporized substance is preferably carried out at a temperature in the range of the glass transition point ± 100 ℃ of the glass substrate. In particular, it is preferable that it is the range of glass transition point -30 degreeC-glass transition point +100 degreeC of a glass substrate. This is because when the spraying is carried out in this temperature range, the glass becomes soft at the glass transition point, and thus, the formation of a film in that area can prevent the scratches from occurring more effectively.

It is preferable to carry out at 600-800 degreeC specifically, in that a vaporization material vaporizes efficiently and when a spray is sprayed on the glass substrate surface, a substrate temperature does not fall rapidly.

Moreover, it is preferable that the spray amount of a vaporizing substance is 0.2-10 L / m <2>, It is more preferable that it is 0.2-3 L / m <2>, It is especially preferable that it is 0.2-1 L / m <2>. Protection spray amount is while suppressing the spray amount of SO ₂ gas within this range, the amount of the alkali metal to be supplied to the lower surface of the glass substrate becomes sufficient, formed by reaction with SO ₂ gas is sprayed at a second supplying step which will be described later film The production efficiency of is further improved.

When sodium tetraborate decahydrate is used as the alkali metal-containing inorganic substance, it is used at a temperature of about 850 ° C. in a furnace for forming a glass substrate and a furnace other than a slow cooling furnace (for example, a large tubular furnace used in the examples). After evaporating the sodium borate, the vaporizing substance is sprayed onto a forming furnace or a slow cooling furnace or a lower surface of the glass substrate conveyed between these furnaces using a nozzle, and the like are preferred embodiments. have.

By spraying the said alkali metal containing inorganic substance by this method, an alkali metal is supplied to the lower surface of the said glass substrate. The presence of the alkali metal in the lower surface of the glass substrate can be confirmed by analyzing the lower surface of the glass substrate by X-ray photoelectron spectroscopy (XPS) or fluorescent X-ray analysis.

Second Supply Process

The second supply step is a step of forming a protective film on the lower surface by spraying SO ₂ gas on the lower surface of the glass substrate supplied with the alkali metal after the first supply process.

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

That is, the second supply step causes the alkali metal and the SO ₂ gas to react by spraying SO ₂ gas on the lower surface of the glass substrate supplied with the alkali metal by the first supply step, thereby lowering the glass substrate. It is a process of forming the protective film containing alkali sulfate (for example, sodium sulfate etc.) in the cotton.

For the time (timing) and the spray method of spraying of the SO ₂ gas in the second supply step, the embodiments described below are preferred exemplifying.

The time for spraying the SO ₂ gas is not particularly limited as long as it is later than the first supply step, but is preferably immediately after the first supply step from the viewpoint of preventing scratches on the surface of the glass substrate during transport. It is more preferable that it is between the said slow cooling processes. Moreover, spraying each gas simultaneously is not preferable because each gas reacts and formation of a film becomes difficult.

On the other hand, a method of spraying the SO ₂ gas can be carried out by conventional methods known to a method similar to in the general float method. Specifically, it can implement by the method (for example, the method of Claim 12 of the said patent document 1) of the nozzle provided in the width direction of a glass substrate below the glass substrate.

However, the In, spray amount of the alkali-free with a protective film of the glass substrate compared to the conventional example of using a sulfate of alkaline earth metal-derived (e. G., Calcium sulfate, etc.), such unequal securing a protective effect and SO ₂ gas in the present invention Can be reduced. As described above, the SO ₂ gas sprayed by the second supply process preferentially reacts with the alkali metal supplied to the lower surface, and reacts with the less reactive alkaline earth metals (Ca, Sr, etc.) that are also present in the alkali free glass. It is considered that the reaction is suppressed. Specifically, in the present invention, the spray amount of the SO ₂ gas can be reduced to 0.05 to 2.5 L / m 2, particularly 0.05 to 0.3 L / m 2.

In addition, the spraying of the SO ₂ gas is preferably carried out at a temperature in the glass transition point ± 100 ° C of the glass substrate. This is because the glass becomes soft at the glass transition point, and thus, by forming a protective film in the region, it is possible to more effectively prevent scratches from occurring. Specifically, the spraying of the SO ₂ gas is more preferably performed at 600 to 800 ° C. It is because when spraying is performed at this temperature, the protective film containing the sulfate which can be easily removed in a washing | cleaning process can be produced more efficiently, and the occurrence of a scratch on the back surface of a glass substrate can be suppressed more.

[Cleaning process]

The said washing process performed as desired is a process of washing and removing the protective film formed by the said 2nd supply process, and is a conventionally well-known process in the general float method.

About the timing (timing) and the washing | cleaning method of the said washing | cleaning process, the aspect shown below is illustrated preferably.

Although the timing of the said washing process is not specifically limited if it is after the said 2nd supply process, Since the protective film was made about the damage to the surface (lower surface) of the glass substrate which arises during roller conveyance, it is the last step of the slow cooling process, or It is preferable that it is immediately after the said slow cooling process.

On the other hand, the cleaning method in the cleaning step can be removed by an easy method since a protective film containing a sulfate (for example, a water-soluble salt such as sodium sulfate) derived from an alkali metal is formed in the present invention. For example, it can remove by water washing process. In addition, when SO ₂ gas is sprayed without performing the said 1st supply process, the protective film formed in the lower surface of a glass substrate is a sulfate (for example, hardly water-soluble salts, such as calcium sulfate) derived from alkaline earth metals. It becomes difficult to wash easily.

In the manufacturing method of this invention, in order to improve the smoothness of the obtained alkali free glass substrate, to reduce torsion, bending, micro-corrugation and a flaw or a foreign material defect of a glass substrate, and to obtain a uniform surface quality After the said washing process, you may provide a grinding | polishing process as needed.

This grinding | polishing process is a conventionally well-known process in the general float method, As a grinding | polishing method, the method of grinding | polishing the glass substrate put on foamed urethane using the cerium oxide type abrasive specifically, is mentioned.

The manufacturing method of the alkali free glass substrate which concerns on the 2nd aspect of this invention is a manufacturing method of the alkali free glass substrate which manufactures an alkali free glass substrate by a float method,

A molding step of molding the molten glass onto the glass substrate on the molten tin;

A first supply step of spraying an inorganic material containing an alkali metal on the surface of the glass substrate at the side in contact with the molten tin at 600 to 800 ° C., and after the first supply step, the glass substrate at 600 to 800 ° C. a method of producing an alkali-free glass substrate having a second supply step of spraying the SO ₂ gas to the surface of the side contacting the molten tin.

Here, the shaping | molding process in the 2nd aspect of this invention is the same as what was demonstrated in the 1st aspect of this invention, Except having prescribed | regulated temperature to 600-800 degreeC also about a 1st supply process and a 2nd supply process. Is the same as that described in the first aspect of the present invention. Moreover, also in the 2nd aspect of this invention, it is preferable to provide the said washing process, and you may also provide the said grinding | polishing process.

This invention provides the alkali free glass substrate obtained by the manufacturing method of this invention, when the inorganic substance containing Na and boron is used in the manufacturing method of this invention (it also includes a 2nd aspect. It is.

Specifically, an alkali-free glass substrate can be provided by spraying an inorganic substance containing Na and boron onto the lower surface of the glass substrate in the first supplying step, and then performing the cleaning step as necessary.

It is preferable that the alkali free glass substrate of this invention is the following compositions.

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

SiO ₂ : 30 to 85%,

Al ₂ O ₃ : 0 to 35%,

B ₂ O ₃ : 0 to 35%,

MgO: 0 to 35%,

CaO: 0-35%,

SrO: 0 to 35%,

BaO: 0 to 35%,

Alkali metal component: 0.5% or less

It contains

The average boron concentration of the lower surface of the glass substrate is 4 to 10 atomic%, and the diffusion depth of boron into the interior of the glass substrate is 5 nm or more.

Here, the content of SiO ₂ (weight percentage display of the oxide basis) that is from 50 to 80% preferred, 50 to 70% more preferably, 56 to 66 percent is more preferred, and 58 to 60% Particularly preferred.

Further, the content of Al ₂ O ₃ (weight percentage display of the oxide basis) is from 0 to 30% is preferred, more preferably from 3 to 22%, 3 to 20%, and more preferably, 15 to 20% It is especially preferable that it is and it is most preferable that it is 15 to 19%.

Further, the content of B ₂ O ₃ (weight percentage display of an oxide basis) and preferably from 0 to 30%, more preferably from 0 to 15%, more preferably from 5 to 12%.

Moreover, it is preferable that it is 0 to 20%, as for the content rate of MgO (mass percentage display based on an oxide), it is more preferable that it is 0 to 8%, and it is still more preferable that it is 0 to 6%.

Moreover, it is preferable that it is 0 to 20%, as for the content rate of CaO (mass percentage display based on an oxide), it is more preferable that it is 0 to 9%, and it is still more preferable that it is 0 to 8%.

Moreover, it is preferable that it is 0 to 20%, as for the content rate of SrO (mass percentage display based on an oxide), it is more preferable that it is 0 to 12.5%, and it is still more preferable that it is 3 to 12.5%.

Moreover, it is preferable that it is 0 to 20%, and, as for the content rate of BaO (mass percentage display based on an oxide), it is more preferable that it is 0% or more and less than 2%.

Moreover, it is preferable that it is 0.5% or less, as for the content rate (mass percentage display based on an oxide) of an alkali metal component, It is more preferable that it is 0.2% or less, It is further more preferable that it is 0.1% or less.

Here, SiO _2, Al ₂ O _3, B ₂ O _3, MgO, CaO, SrO, BaO, and the content of the alkali metal component of the glass substrate, the composition of the alkali-free glass used in the alkali-free glass substrate as described above Range.

In this invention, the average boron concentration of the said lower surface of the said glass substrate can be calculated | required as an average value at the time of measuring five points arbitrarily by X-ray photoelectron spectroscopy. In the X-ray photoelectron spectroscopy, an X-ray AlKα ray monochromated with a monochromator was used as an X-ray source using an XPS spectrometer (5500 type, manufactured by PHI). In addition, the detection angle of the X-ray photoelectron was 75 degrees, and the measurement was performed by irradiating an electronic shower for charge correction.

In the present invention, the diffusion depth of the boron to the inside of the glass substrate can be estimated from the depth reaching the secondary ionic strength at the same level as the background by secondary ion mass spectrometry (SIMS).

Specifically, 5 points of diffusion depths were measured at 5 points on the glass substrate by the secondary ion mass spectrometer (ADEPT1010, Albag Pai Co., Ltd.), respectively, and the average value was calculated | required.

Here, conversion of the sputtering time to the sputtering depth was performed in terms of SiO ₂ (4 nm = 1 min). In addition, the primary ion was measured under an oxygen ion beam, the acceleration voltage was 5 keV, the beam current was 400 nA, the incident angle of the primary ion was 45 degrees with respect to the normal of the sample surface, and the beam scanning range was 400 × 400 μm ² . .

In the alkali-free glass substrate of the present invention, the average boron concentration of the lower surface of the glass substrate is 4 to 10 atomic%, and the diffusion depth of boron into the interior of the glass substrate is 5 nm or more and 80 nm or less, preferably Since it becomes 50 nm or less, the intensity | strength of the glass substrate itself improves, it is excellent in abrasion resistance, and it becomes the thing excellent in abrasion resistance also in the transport and processing process after a protective film is removed. The reason that abrasion resistance and abrasion resistance improves by boron being diffused from the lower surface into the glass substrate and remaining in the surface layer of the glass substrate is considered to be because the network structure of the glass is firm.

In the alkali-free glass substrate of the present invention, since boron remains on the surface layer of the glass substrate before performing the cleaning step as well as after the cleaning step if necessary, the occurrence of scratches on the back surface of the glass substrate can be continuously suppressed. It is preferable because there is.

In addition, in the alkali free glass substrate of this invention, boron remains in the surface layer of a glass substrate because boron easily enters inside of a glass substrate by the said 1st supply process, and it is easy to remain in the surface layer of a glass substrate. I guess it is because.

Therefore, the present invention is expressed in terms of mass percentage based on oxide,

SiO ₂ : 30 to 85%,

Al ₂ O ₃ : 0 to 35%,

B ₂ O ₃ : 0 to 35%,

MgO: 0 to 35%,

CaO: 0-35%,

SrO: 0 to 35%,

BaO: 0 to 35%,

Alkali metal component: 0.5% or less

Containing,

An alkali free glass substrate having an average boron concentration of at least one surface of 4 to 10 atomic% and a diffusion depth of boron from the surface to the inside of 5 nm or more can also be provided.

Although an Example is given to the following and this invention is concretely demonstrated to it, this invention is not limited to this.

(Example 1)

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

Specifically, the quartz tube 12 is installed in the large tubular furnace 11 whose temperature can be adjusted, and the alkali-free glass substrate 13 (10 cm on each side) having a thickness of 0.7 mm is placed in the quartz tube 12. The large tubular furnace 11 was heated to 700 ° C. Here, "alkali-free glass substrate" includes, by mass percent representation of the oxide _{basis, 68% ≤SiO 2 ≤80%,} 0% ≤Al 2 O 3 <12%, 0% <B 2 O 3 <7%, 0 Alkali-free glass of the composition which uses% <MgO <= 12%, 0% <= CaO <15%, 0% <SrO <= 4%, 0% <= BaO <= 1%, and an alkali content of 0.05 mass% or less was used. . In addition, the glass transition point of the said glass was 700 degreeC.

Subsequently, the reagent 15 of sodium tetraborate decahydrate placed in the alumina boat 14 is locally heated to about 850 ° C. to vaporize, and the vaporized substance is sprayed from the end of the quartz tube in the direction indicated by the arrow 16. Thus, sodium which is an alkali metal was supplied to the surface of the alkali free glass substrate 13. The spraying quantity of the sodium tetraborate decahydrate at this time was 0.4 L / m <2>, and the temperature of the alkali free glass substrate 13 was 700 degreeC.

Subsequently, SO ₂ gas is sprayed in the direction indicated by the arrow 17 so that the spray amount on the surface of the alkali-free glass substrate 13 is 0.1 L / m ₂ , a protective film is formed to form a non-alkali glass substrate with a protective film. Was prepared. The temperature of the alkali free glass substrate 13 at this time was 700 degreeC.

In addition, the present embodiment is the same as the condition of spraying the alkali metal-containing inorganic material between the forming step and the slow cooling step, and spraying the SO ₂ gas immediately.

(Example 2)

An alkali free glass substrate with a protective film was produced in the same manner as in Example 1 except that the SO ₂ gas had a spray amount of 0.4 L / m 2.

(Example 3)

An alkali free glass substrate with a protective film was produced in the same manner as in Example 1 except that the spray amount of the SO ₂ gas was 1.0 L / m 2.

(Comparative Example 1)

An alkali free glass substrate with a protective coating was produced in the same manner as in Example 1 except that only SO ₂ gas was sprayed without using sodium tetraborate.

(Comparative Example 2)

An alkali free glass substrate with a protective coating was produced in the same manner as in Example 2 except that only SO ₂ gas was sprayed without using sodium tetraborate.

(Comparative Example 3)

An alkali free glass substrate with a protective coating was produced in the same manner as in Example 3 except that only SO ₂ gas was sprayed without using sodium tetraborate.

(Comparative Example 4)

An alkali free glass substrate was produced in the same manner as in Example 1, except that sodium tetraborate was not used and SO ₂ gas was not sprayed, but was simply heated at 700 ° C. for 15 minutes.

(Comparative Example 5)

An alkali-free glass substrate was produced in the same manner as in Example 1 except that no sodium tetraborate was used and no SO ₂ gas was sprayed.

About the alkali free glass substrate with a protective film obtained by Examples 1-3 and Comparative Examples 1-3, the adhesion amount of a protective film, abrasion resistance, average boron concentration, the diffusion depth, and abrasion resistance were measured by the method shown below. Evaluated. The results are shown in Table 1 below.

Further, since Comparative Example 4, and not for each of the flat panel glass substrate obtained from glass 5, not to form the protective film without spraying the SO ₂ gas was measured by the method shown below is representative of the wear resistance. The results are shown in Table 1.

<Protective film adhesion amount>

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

The amount of sodium sulfate affixed from these quantitative values was computed as the adhesion amount of a protective film. In addition, this adhesion amount was calculated | required as an average value computed from 10 sheets of the obtained alkali free glass substrate.

<Scratch resistance>

Evaluation of scratch resistance was performed by the taper test based on JISR3221 (1990). In addition, the taper test was carried out using a taper tester (Tdedyne Taber Model 503), the wear ring was fixed to CS-10F, the load was 250g, the number of wear was fixed three times.

Then, in order to remove the protective film of the alkali free glass substrate with a protective film used as a test body, the board | substrate was washed with a 30 second shower under the flowing water of 20 degreeC pure water (3 L / min) for 30 second.

The surface of the glass substrate obtained by removing the protective film was observed under a microscope, and the number of scratches (the number of scratches) whose length in the major axis direction existing within 1 cm x 1 cm of each side was 0.2 mm or more was measured. The measurement part was the center part of the site | part provided for the taper test (refer FIG. 3). In FIG. 3, although the abrasion part 19 by a wear wheel is formed in the test body (alkali-free glass substrate) 18, the measurement part 20 becomes a center part of the abrasion part 19. In FIG.

In addition, the measurement of the number of scratches was performed about arbitrary ten points with respect to each glass substrate, and the average value was calculated | required. In addition, the number of scratches was calculated | required as an average value computed from 10 sheets of the obtained glass substrate.

<Average boron concentration, diffusion depth>

(1) The obtained alkali free glass substrate with each protective film was washed with water at the place where 20 degreeC pure water (flow rate: 3 L / min) flows, and the protective film was removed. Then, the average boron concentration of the glass substrate surface after washing | cleaning was calculated | required as an average value when five points were measured by X-ray photoelectron spectroscopy. In the X-ray photoelectron spectroscopy, an XPS spectrometer (5500 type, manufactured by PHI Co., Ltd.) was used to make an X-ray AlKα ray monochromated with a monochromator as an X-ray source. In addition, the detection angle of the X-ray photoelectron was 75 degrees, and the measurement was performed by irradiating an electronic shower for charge correction.

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

Specifically, 5 points of diffusion depths were measured at 5 points on the glass substrate after washing with the secondary ion mass spectrometer (ADEPT1010, Albag phi Co., Ltd.), respectively, and the average value was calculated | required. Here, conversion of the sputtering time to the sputtering depth was performed in terms of SiO ₂ (4 nm = 1 min).

In addition, the primary ion was measured under an oxygen ion beam, the acceleration voltage was 5 keV, the beam current was 400 nA, the incident angle of the primary ion was 45 degrees with respect to the normal of the sample surface, and the beam scanning range was 400 × 400 μm ² . .

In the following Table 1, although the column of the diffusion depth of Comparative Examples 1-3 is "-", it shows that a diffusion cannot be confirmed.

<Wear resistance>

Wear resistance was performed by examining the change rate (haze change rate) of the haze rate before and behind a taper test.

First, the haze rate of each obtained alkali free glass substrate was measured with the haze meter.

Next, about each obtained alkali free glass substrate, the taper test based on JISR3221 (1990) was done. In addition, the taper test was performed using the taper tester (Tdedyne Taber Model503), the wear ring was fixed to CS-10F, and the load was fixed at 500g.

Next, the haze rate after 1000 times of taper wear was measured by a haze meter, and the rate of change thereof was determined from the haze rate before the taper test.

Here, the haze value is defined by the scattered light Td and the transmitted light Tt as in the following equation.

Haze rate = (Td / Tt) × 100%

In addition, the change rate (DELTA) H of the haze rate H is represented by the following formula.

Haze rate H before ΔH = 1000 times of abrasion test

From the results shown in Table 1, the alkali-free glass substrates of Examples 1 to 3 obtained by using sodium tetraborate have an SO ₂ gas spraying amount equal to or less than that of Comparative Examples 1 to 3, and effectively form a protective film. I could see that. Furthermore, it turned out that boron concentration becomes high and the scratch resistance also becomes especially favorable.

In Comparative Examples 1 to 3, although the amount of sodium sulfate was the same amount, the reason why the number of scratches was decreased at the same time as the amount of SO ₂ gas spraying was increased was that sulfates derived from alkaline earth metals (calcium sulfate, strontium sulfate, etc.) It is because these are produced and they function as a protective film.

In addition, the alkali free glass substrates of Examples 1 to 3 confirmed that the protective coating formed on the surface of the glass substrate was removed after normal water washing, and a clean surface appeared. On the other hand, with the alkali free glass substrates of Comparative Examples 1-3, even if normal water washing was performed, the protective film formed in the surface of the glass substrate was not able to be removed, and it remained. In addition, when the component of the film | membrane which remained was measured, it was calcium sulfate and strontium sulfate.

Moreover, as for the alkali free glass substrates of Examples 1-3, since a boron spread | diffused, it turned out that haze change rate decreases and wear resistance improves compared with the alkali free glass substrates of Comparative Examples 1-5.

Although this invention was demonstrated in detail with reference to the more specific embodiment, it is clear for those skilled in the art that various changes and correction can be added without deviating from the mind and range of this invention.

This application is based on the JP Patent application (Japanese Patent Application 2006-187727) of an application on July 7, 2006, The content is taken in here as a reference.

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

Claims (14)

It is a manufacturing method of the alkali free glass substrate which manufactures an alkali free glass substrate by the float method, A molding step of molding the molten glass onto a glass substrate on molten tin, and a slow cooling step of slowly cooling the glass substrate molded by the molding 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 a surface of the glass substrate in contact with the molten tin after the first supply process. the method of alkali-free glass substrate having a second supply step of spraying the SO ₂ gas. The manufacturing method of the alkali free glass substrate of Claim 1 in which the said 1st supply process is performed between the said molding process and the said slow cooling process. The method for producing an alkali free glass substrate according to claim 1, wherein the first supply process is performed at a temperature in a glass transition point ± 100 ° C. of the glass substrate. The manufacturing method of the alkali free glass substrate of Claim 1 in which the said 1st supply process is performed at 600-800 degreeC. The manufacturing method of the alkali free glass substrate of any one of Claims 1-4 in which the said 2nd supply process is performed between the said molding process and the said slow cooling process. The manufacturing method of the alkali free glass substrate of any one of Claims 1-4 in which the said 2nd supply process is performed at the temperature of the glass transition point ± 100 degreeC of the said glass substrate. The manufacturing method of the alkali free glass substrate of any one of Claims 1-4 with which the said 2nd supply process is performed at 600-800 degreeC. It is a manufacturing method of the alkali free glass substrate which manufactures an alkali free glass substrate by the float method, A molding step of molding the molten glass onto the glass substrate on the molten tin; A first supply step of spraying an inorganic material containing an alkali metal on the surface of the glass substrate at the side in contact with the molten tin at 600 to 800 ° C., and after the first supply step, the glass substrate at 600 to 800 ° C. the method of alkali-free glass substrate having a second supply step of spraying the SO ₂ gas to the surface of the side contacting the molten tin. The manufacturing method of the alkali free glass substrate of any one of Claims 1-8 further equipped with the washing process of removing the said protective film. The method for producing an alkali-free glass substrate according to any one of claims 1 to 9, wherein the inorganic material containing an alkali metal contains sodium and boron. The manufacturing method of the alkali free glass substrate of Claim 10 whose said inorganic substance containing alkali metal is sodium tetraborate. The alkali free glass substrate manufactured by the manufacturing method of Claim 10 or 11. It is an alkali free glass substrate manufactured by the manufacturing method of Claim 10 or 11, The glass substrate is expressed as a percentage of mass on an oxide basis, SiO ₂ : 30 to 85%, Al ₂ O ₃ : 0 to 35%, B ₂ O ₃ : 0 to 35%, MgO: 0 to 35%, CaO: 0-35%, SrO: 0 to 35%, BaO: 0 to 35%, Alkali metal component: 0.5% or less Containing, The alkali free glass substrate of which the average boron concentration of the surface of the side in contact with the said molten tin of the said glass substrate is 4-10 atomic%, and the diffusion depth of boron into the inside of the said glass substrate is 5 nm or more. In terms of mass percentages in terms of oxides, SiO ₂ : 30 to 85%, Al ₂ O ₃ : 0 to 35%, B ₂ O ₃ : 0 to 35%, MgO: 0 to 35%, CaO: 0-35%, SrO: 0 to 35%, BaO: 0 to 35%, Alkali metal component: 0.5% or less Containing, The alkali free glass substrate whose average boron concentration of at least one surface is 4-10 atomic%, and the diffusion depth of boron from the said surface to the inside is 5 nm or more.

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