TWI473770B - Glass substrate for flat panel displays - Google Patents

Description

Glass substrate for flat panel display

The present invention relates to a method of manufacturing a glass substrate for a flat panel display.

In recent years, a flat panel display, in particular, a plasma display panel (hereinafter also referred to as "PDP (plasma display panel)" which is a type of thin flat type gas discharge display panel, has been accepted as a thin and large flat type color display device. attention.

The PDP divides the cells by the front glass substrate, the back glass substrate, and the barrier ribs, and generates a plasma discharge in the cell, thereby causing the phosphor layer on the inner wall of the cell to emit light to form an image.

In general, the front glass substrate and the back glass substrate of the PDP are float glass which is easy to increase the size of the glass substrate and is excellent in flatness and homogeneity, that is, a glass substrate formed on the molten tin by a floating method.

Further, a surface of the glass substrate used in the PDP which is not in contact with the molten tin (hereinafter, also referred to as "top surface") is formed as a transparent electrode containing ITO (indium tin oxide). The silver paste was applied by screen printing, and then fired at 520 to 600 ° C to form a silver electrode.

However, there is a problem in that when the silver paste is fired to form a silver electrode, the color of the glass substrate is yellow, and the quality of the PDP color display is lowered. Specifically, the white screen is slightly yellowish around the silver electrode, or The brightness of the blue screen is reduced.

It is generally believed that the yellowing of the above color is caused by the color development of the colloid. When the gel system forms a silver electrode, silver ions (Ag ⁺ ) diffused from the top surface of the front glass substrate to the inner (surface layer) are present. The Ag ⁰ which is reduced to zero valence in the surface layer by Fe ²⁺ , Sn ²⁺ or the like is generated by aggregating the Ag ⁰ (for example, refer to Patent Documents 1 and 2).

On the other hand, the surface of the glass substrate produced by the floating method represented by the PDP and the side of the molten tin in the molten tin bath (hereinafter also referred to as "bottom surface") must be prevented from leaving the molten metal. Scars generated when transported by a roller after a tin bath. In order to achieve the object, a method is known in which a sulfur dioxide (SO ₂ gas) is sprayed to react with an alkali metal (for example, sodium or the like) or an alkaline earth metal (for example, calcium or the like) present in the glass. Sodium sulfate is formed on the surface of the glass substrate to act as a protective film to prevent the occurrence of scratches (for example, refer to Patent Document 3 and Non-Patent Document 1).

[Patent Document 1] Japanese Laid-Open Patent Publication No. Hei. No. Hei. No. Hei. No. Hei. No. 2005-55669 (Patent Document 3) International Publication No. 2002/051767

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

Further, the inventors of the present invention conducted further research on the cause of the color development of the Ag colloid, and as a result, found that the SO ₂ gas sprayed onto the bottom surface of the glass substrate to form the protective film also flows into the top surface of the glass substrate.

That is, it has been found that since the SO ₂ gas flows into the top surface, a protective film is formed on the top surface, and at the same time, H ⁺ penetrates from the top surface into the inside (surface layer) of the glass substrate, and as a result, When the silver electrode is formed, Ag ⁺ easily enters the surface layer. Specifically, it has been found that the SO ₂ gas reacts with water vapor in the ambient gas to form H ₂ SO ₃ (H ₂ O+SO ₂ →H ₂ SO ₃ ), and Na is present by the surface layer. ⁺ and H ⁺ substitution reaction (2Na ⁺ + H ₂ SO ₃ → 2H ⁺ + Na ₂ SO ₃ ), H ⁺ infiltrates into the surface layer of the glass substrate, and then exchanges the H ⁺ and Ag ⁺ When the silver electrode is formed, Ag ^{+ is} easily introduced into the surface layer.

On the other hand, as described above, from the viewpoint of forming a glass protective film to prevent the occurrence of scratches on the glass substrate, the operation of spraying the SO ₂ gas onto the bottom surface of the glass substrate is a necessary treatment to some extent.

Here, an object of the present invention is to provide a method for producing a glass substrate for a flat panel display which can maintain good scratch resistance and prevent color development of an Ag colloid, and a glass substrate for a flat panel display obtained by the method.

In order to achieve the above object, the inventors of the present invention have found that in the production process using the floating method, an alkali metal is supplied by spraying an inorganic substance containing an alkali metal onto the bottom surface and/or the top surface of the glass substrate. Then, the SO ₂ gas is sprayed onto the bottom surface to maintain good scratch resistance, and the Ag colloid is prevented from developing color, thereby completing the present invention.

That is, the present invention provides the following (1) to (17).

(1) A method for producing a glass substrate for a flat panel display, which is a glass substrate for a flat panel display by a floating method, comprising: a molding step of forming molten glass on a molten tin into a glass substrate; a cooling step of causing the glass substrate formed by the forming step to be cold-cooled, and a first supplying step of spraying an alkali metal-containing inorganic substance onto a surface of the glass substrate on the side in contact with the molten tin; In the second supply step, after the first supply step, the SO ₂ gas is sprayed onto the surface of the glass substrate on the side in contact with the molten tin.

(2) A method for producing a glass substrate for a flat panel display, which is a glass substrate for a flat panel display by a floating method; and a molding step of forming a molten glass on a molten tin into a glass substrate; a cooling step of causing the glass substrate formed by the forming step to be cold-cooled, and a first supplying step of spraying an alkali metal-containing inorganic substance onto a surface of the glass substrate that is not in contact with the molten tin; And a second supply step of spraying SO ₂ gas onto the surface of the glass substrate on the side in contact with the molten tin after the first supply step.

(3) The method for producing a glass substrate for a flat panel display according to (1) or (2), wherein the first supply step is performed between the molding step and the quenching step.

(4) The method for producing a glass substrate for a flat panel display according to (1) or (2), wherein the first supply step is performed at a temperature within a range of ±100 ° C of a glass transition point of the glass substrate.

(5) The method for producing a glass substrate for a flat panel display according to the above (1) or (2), wherein the first supply step is performed at 550 to 750 °C.

(6) The method for producing a glass substrate for a flat panel display according to any one of the above (1), wherein the second supply step is performed between the forming step and the quenching step.

(7) The method for producing a glass substrate for a flat panel display according to any one of the above (1), wherein the second supply step is performed at a temperature within a range of ±100 ° C of a glass transition point of the glass substrate. Implementation.

(8) The method for producing a glass substrate for a flat panel display according to any one of the above (1), wherein the second supply step is performed at 550 to 750 °C.

(9) A method for producing a glass substrate for a flat panel display, which is a glass substrate for a flat panel display by a floating method; and a molding step of forming a molten glass on a molten tin into a glass substrate; In the first supply step, an alkali metal-containing inorganic substance is sprayed onto the surface of the glass substrate on the side in contact with the molten tin at 550 to 750 ° C; and a second supply step is performed after the first supply step, at 550 The SO ₂ gas was sprayed onto the surface of the glass substrate on the side in contact with the molten tin at ~750 °C.

(10) A method for producing a glass substrate for a flat panel display, which is a glass substrate for a flat panel display by a floating method; and a molding step of forming a molten glass on a molten tin into a glass substrate; In the first supply step, an inorganic substance containing an alkali metal is sprayed onto a surface of the glass substrate not in contact with the molten tin at 550 to 750 ° C; and a second supply step is performed after the first supply step The SO ₂ gas is sprayed onto the surface of the glass substrate on the side in contact with the molten tin at 550 to 750 °C.

(11) The method for producing a glass substrate for a flat panel display according to any one of the above (1), wherein the inorganic substance containing an alkali metal contains sodium and boron.

(12) The method for producing a glass substrate for a flat panel display according to the above (11), wherein the inorganic substance containing an alkali metal is sodium tetraborate.

(13) A glass substrate for a flat panel display produced by the above (11) or (12) manufacturing method.

(14) A glass substrate for a flat panel display, which is produced by the production method of the above (11) or (12), wherein the glass substrate is expressed by mass percentage based on an oxide, and contains: SiO ₂ : 45~ 70%, Al ₂ O ₃ : 0 to 20%, CaO: 0 to 20%, ZrO ₂ : 0 to 13%, total amount of alkaline earth metal oxide components: 5 to 40%, total amount of alkali metal oxide components 5 to 30%, the surface of the glass substrate on the side in contact with the molten tin and/or the surface of the glass substrate not in contact with the molten tin has an average boron concentration of 2 to 6 atom%, and the boron direction The inside of the glass substrate has a diffusion depth of 20 to 80 nm.

(15) The glass substrate for a flat panel display according to the above (14), wherein the average H atom concentration from the surface of the glass substrate which is not in contact with the molten tin to a depth of 0.1 μm is 2.5 mol% or less .

(16) A glass substrate for a flat panel display, which is produced by the production method of the above (11) or (12), wherein the glass substrate is expressed by mass percentage based on an oxide, and contains: SiO ₂ : 45~ 70%, Al ₂ O ₃ : 0 to 20%, CaO: 0 to 20%, ZrO ₂ : 0 to 13%, total amount of alkaline earth metal oxide components: 5 to 40%, total amount of alkali metal oxide components 5 to 30%, the average H atom concentration from the surface of the glass substrate which is not in contact with the molten tin to a depth of 0.1 μm is 2.5 mol% or less.

(17) A glass substrate for a flat panel display, which is expressed by mass percentage based on an oxide, and contains: SiO ₂ : 45 to 70%, Al ₂ O ₃ : 0 to 20%, and CaO: 0 to 20%. ZrO ₂ : 0~13%, the total amount of alkaline earth metal oxide components: 5~40%, the total amount of alkali metal oxide components: 5~30%, and the average boron concentration of at least one surface is 2~6 atom% And the diffusion depth of boron from the surface to the inside is 20 to 80 nm.

As described below, according to the present invention, it is possible to provide a method for producing a glass substrate for a flat panel display which can maintain good scratch resistance and prevent color development of an Ag colloid, and a glass substrate for a flat panel display obtained by the method. .

Further, the present invention can be applied not only to a PDP but also to a surface field emission display (FED (Field Emission Display)], a surface conduction type electron emission display (SED), and the like. It is resistant to scratches and prevents the Ag colloid from developing color. Therefore, it is also suitable for surface field emission displays, surface conduction type electron emission displays, and the like.

Hereinafter, the present invention will be described in detail.

A method for producing a glass substrate for a flat panel display according to a first aspect of the present invention (hereinafter also referred to as "the first manufacturing method of the present invention") is a method for manufacturing a glass substrate for a flat panel display by a floating method; a molding step of forming molten glass on molten tin into a glass substrate; and a step of cooling to freeze the glass substrate formed by the molding step; and providing a first supply step to the glass substrate An inorganic substance containing an alkali metal (hereinafter also referred to as "alkali-containing metal inorganic substance") is sprayed on the surface on the side in contact with the molten tin; and a second supply step is performed on the glass substrate after the first supply step The surface on the side in contact with the above molten tin, that is, the surface on which the above inorganic substance is sprayed, is sprayed with SO ₂ gas.

Further, a method for producing a glass substrate for a flat panel display according to a second aspect of the present invention (hereinafter also referred to as "the second manufacturing method of the present invention") is a method for manufacturing a glass substrate for a flat panel display by a floating method; The method includes a molding step of forming a molten glass on a molten tin into a glass substrate, and a step of cooling to freeze the glass substrate formed by the molding step, and a first supply step to the glass substrate An inorganic substance containing an alkali metal is sprayed on a surface not in contact with the molten tin; and a second supply step is performed on the surface of the glass substrate on the side in contact with the molten tin after the first supply step SO ₂ gas.

Next, the first manufacturing method and the second manufacturing method of the present invention (hereinafter, collectively referred to as "the manufacturing method of the present invention" unless otherwise specified), the forming step, the cooling step, and the first supplying step will be described in detail. And a second supply step.

[Forming step]

The above-described forming step is a step of forming molten glass on a molten tin in a molten tin bath into a glass substrate, which is a previously known step of the usual floating method.

Fig. 1 is a conceptual view showing an example of a glass manufacturing line using a floating method.

As shown in Fig. 1, in the floating method, first, on the bath surface of the molten tin bath 2 filled with the molten tin 1, the molten glass 4 is continuously flowed from the melting kiln 3 to form a glass ribbon. Next, the glass ribbon is floated along the bath surface of the molten tin bath 2. The float side advances, thereby lowering the temperature and shaping the glass ribbon into a plate shape. Thereafter, the plate-shaped glass substrate is guided by the guide rolls 5, and is conveyed to the quenching furnace 6 in a state of being continuous in the longitudinal direction.

Here, in FIG. 1, the said shaping|molding process is the process of the molten glass 4 by the glass ribbon until shaping|molding into a plate shape.

In the present invention, as in the conventional floating method, as the molten tin bath 2, a sealed structure in which a tin bath furnace and a ceiling including a special refractory cover the inside of the metal case are used to prevent oxidation of tin are used. As the ambient gas in the molten tin bath, a mixed gas including hydrogen gas and nitrogen gas (hydrogen content of 2 to 10% by volume) can be used.

Further, the temperature conditions in the molten tin bath in the molding step are the same as those in the usual floating method, and are 600 to 1050 ° C, that is, the temperature of the molten glass flowing into the molten tin bath can be set to 900 to 1050 on the upstream side. °C, set to 600~800 °C on the downstream side. Further, the temperature is usually maintained by the heat of the molten glass, and a heater or a cooler may be used in order to adjust the temperature.

The production method of the present invention is a method for producing a glass substrate for a flat panel display. Therefore, it is preferred that the glass substrate formed on the molten tin has the following composition, and is expressed by mass percentage based on the oxide, and contains: SiO ₂ : 45~70%, Al ₂ O ₃ : 0~20%, CaO: 0~20%, ZrO ₂ : 0~13%, the total amount of alkaline earth metal oxide components: 5~40%, alkali metal oxide component Total measurement: 5~30%.

In the present invention, it is more preferable that the glass substrate formed on the molten tin has the following composition, and is expressed by mass percentage based on the oxide, and contains: SiO ₂ : 50 to 65%, Al ₂ O ₃ : 0~ 15%, MgO: 0~15%, CaO: 0~15%, SrO: 0~20%, BaO: 0~20%, ZrO ₂ : 0~13%, total content of alkaline earth metal oxide components: 5~ 40%, the total amount of alkali metal oxide components: 5 to 30%.

Further, in the present invention, it is more preferable that the glass substrate formed on the molten tin has the following composition, and is expressed by mass percentage based on the oxide, and contains: SiO ₂ : 50 to 65%, Al ₂ O ₃ : 2~15%, MgO: 0~15%, CaO: 0~15%, SrO: 0~20%, BaO: 0~20%, ZrO ₂ : 0~6%, the total amount of alkaline earth metal oxide components: 10~30%, the total amount of alkali metal oxide components: 6~15%.

Further, in the present invention, it is more preferable that the glass substrate formed on the molten tin has the following composition, and is expressed by mass percentage based on the oxide, and contains: SiO ₂ : 52 to 62%, Al ₂ O ₃ : 5~12%, MgO: 0~5%, CaO: 3~12%, SrO: 4~18%, BaO: 0~13%, ZrO ₂ : 0~6%, the total amount of alkaline earth metal oxide components: 15~30%, the total amount of alkali metal oxide components: 6~14%.

Further, in the present invention, it is particularly preferable that the glass substrate formed on the molten tin has the following composition, based on the oxide and expressed by mass percentage, and contains: SiO ₂ : 52 to 62%, Al ₂ O ₃ : 5~12%, MgO: 0~4%, CaO: 3~5.5%, SrO: 6~9%, BaO: 0~13%, ZrO ₂ : 0.2~6%, total amount of alkaline earth metal oxide components : 17~27%, the total amount of alkali metal oxide components: 7~14%.

In the present invention, it is formed into a solution from the viewpoint of strength and transmittance. The thickness of the glass substrate on the tin is preferably 1 to 3 mm.

[徐冷步骤]

The above-described cold cooling step is a step of quenching the glass substrate formed by the above-described forming step.

Here, in the above-described cold-cold step, the step of transporting the plate-shaped glass substrate from the guide roller 5 to the step of cooling to the quenching furnace 6 in the longitudinal direction is performed. .

In the present invention, as the quenching furnace, a quenching furnace similar to that of the user of the usual floating method can be used, and a heater or the like can be provided in order to control the temperature.

Moreover, the cold-cooling condition of the above-mentioned cold cooling furnace is the same as that of the normal floating method, and can be set at 550 to 750 ° C at the inlet of the cold furnace, and set at a temperature of 200 to 300 ° C at the outlet, and the temperature is lowered. It can be set to 90 °C ± 10 °C / m.

[First Supply Step]

In the first production method of the present invention, the first supply step is a step of spraying an alkali metal-containing inorganic substance onto the bottom surface of the glass substrate and supplying an alkali metal to the bottom surface (hereinafter, also referred to as "the first supply step ( The first manufacturing method))).

In the first supply step (the first production method), a method for producing a glass substrate for a flat panel display can be provided by supplying an alkali metal to the bottom surface of the glass substrate by using an alkali metal-containing inorganic substance, thereby maintaining good It is resistant to damage and prevents the Ag colloid from developing color.

The reason for this is considered to be that the SO ₂ gas sprayed by the second supply step described below preferentially reacts with the alkali metal supplied to the bottom surface, thereby preventing the SO ₂ gas from flowing into the top surface of the glass substrate.

Further, by using an alkali metal-containing inorganic substance to supply an alkali metal to the bottom surface of the glass substrate, generation of a sulfate (for example, calcium sulfate, barium sulfate, etc.) derived from an alkaline earth metal can be suppressed, and effective generation can be achieved. A protective film of a sulfate derived from an alkali metal (for example, sodium sulfate or the like) can also reduce the amount of SO ₂ gas used. Further, since the sulfate of an alkaline earth metal such as calcium sulfate or barium sulfate is hardly soluble in water, it is poorly reactive as a reactive organism.

On the other hand, in the second production method of the present invention, the first supply step is a step of spraying an alkali metal-containing inorganic substance onto the top surface of the glass substrate and supplying the alkali metal to the top surface (hereinafter also This is called "the first supply step (second manufacturing method)").

In the first supply step (second manufacturing method), a method for producing a glass substrate for a flat panel display can be provided, wherein an alkali metal is supplied to the top surface of the glass substrate by using an alkali metal-containing inorganic substance, thereby preventing Ag Colloid color.

Here, the alkali metal-containing inorganic substance means 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 belongs to this.

Specific examples of the inorganic substance containing Na include NaOH, Na ₂ S, NaCl, NaF, NaBr, NaI, soda ash, NaNH ₂ , sodium benzyl ether, 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, etc. These may be used alone or in combination of two or more.

Specific examples of the inorganic substance containing K include KOH, KCl, KF, KBr, KI, KCN, K ₂ CO ₃ , potassium gluconate, KHF ₂ , KNO ₃ , and K ₂ B ₄ O ₇ -4H. ₂ O (potassium tetraborate tetrahydrate), K ₂ B ₄ O ₇ , KBF _4, etc. These may be used alone or in combination of two or more.

Specific examples of the inorganic substance containing Cs include CsOH, CsCl, CsF, CsBr, CsI, guanidine acetonate, HCO ₂ Cs, and CSNO ₃ , and these may be used alone or in combination. 2 or more types.

For the reason shown below, the alkali metal-containing inorganic substance is preferably an inorganic substance containing Na.

In other words, in the first production method of the present invention, the production efficiency of the protective film (sodium sulfate) formed by the second supply step described below is further improved, and as a result, the color of the Ag colloid can be further prevented, so that it is preferable. .

Among them, the inorganic material containing an alkali metal inorganic substance containing Na and boron is particularly preferable because the glass substrate for a flat panel obtained by the production method of the present invention further has abrasion resistance. Specifically, the alkali metal-containing inorganic substance is preferably Na ₂ B ₄ O ₇ -10H ₂ O or Na ₂ B ₄ O ₇ , more preferably Na ₂ B ₄ O ₇ -10H ₂ O.

By spraying an inorganic substance containing Na and boron, not only Na but also boron is supplied, and as a result, boron diffuses from the bottom surface to the inside of the glass substrate, and the strength of the glass substrate itself is improved.

Therefore, in addition to the glass substrate for a flat panel, for example, a glass substrate for a DNA wafer, a microchip. Glass substrate for biochip, etc. The diffusion of boron is utilized to satisfy a high degree of scratch resistance.

In the first supply step, when the alkali metal-containing inorganic substance is sprayed onto the bottom surface or the top surface of the glass substrate, the alkali metal is supplied to the surfaces, and the time (timing) and the spraying method of the spraying are performed. The following can be suitably exemplified.

The time for spraying the alkali metal-containing inorganic substance is not particularly limited as long as the first supply step (first production method) and the first supply step (second production method) are earlier than the second supply step described below. Specifically, it may be simultaneously with the above-described forming step, and may be simultaneously performed with the following cold-cooling step. However, it is preferable to further suppress the occurrence of scratches on the bottom surface of the glass substrate between the forming step and the above-mentioned cold-cold step.

Here, the phrase "at the same time as the molding step" means that the glass substrate is formed in the molding step, and is then included in the molding step, for example, a molten bath (floating bath) is provided in the furnace. In the case of the entire outlet of the furnace (shield rare, unshielded), it can be sprayed at the unshielded place. In addition, the term "concurrent with the cold step" means that it can be sprayed near the inlet of the cold furnace or the upstream side of the cold furnace. In addition, the "between the above-described forming step and the above-described cold cooling step" means that the glass substrate may be sprayed while the glass substrate is being conveyed between the forming furnace and the quenching furnace.

On the other hand, in the first supply step (first production method) and the first supply step (second production method), the method of spraying the alkali metal-containing inorganic substance may be, for example, appropriately: heating the alkali metal-containing material a method of vaporizing an inorganic substance, spraying the vaporized substance onto the bottom surface of the glass substrate using a nozzle; and heating by a heater, heating by an infrared lamp, heating by a laser, or the like And a method of heating and vaporizing an alkali metal-containing inorganic substance.

Further, it is preferred that the vaporization material is sprayed at a temperature within a range of ±100 ° C of the glass transition point of the glass substrate. Particularly preferred is the glass transition point of the glass substrate of -30 ° C ~ glass transfer point + 100 ° C range. This is because if the film is sprayed in this temperature range, the glass is softened at the glass transition point, so that a film is formed in the region, whereby the occurrence of scratches can be more effectively prevented.

Specifically, it is preferably carried out at 550 to 750 ° C in terms of effectively vaporizing the vaporized material and spraying the surface of the glass substrate without drastically lowering the temperature of the substrate.

Further, the amount of the vaporized substance to be sprayed is preferably in the first supply step (first production method) and the first supply step (second production method), and is preferably 0.2 to 10 L/m ² , more preferably It is 0.2~3 L/m ² , especially 0.2~1 L/m ² . When the amount of the spray in the first production method of the present invention is within this range, the supply amount of the alkali metal supplied to the bottom surface of the glass substrate is sufficient, and the spray is further increased in the second supply step described below. The production efficiency of the protective film formed by the reaction of the SO ₂ gas. Further, in the second production method of the present invention, when the amount of the spray is within this range, the diffusion of boric acid into the glass substrate can be effectively performed, so that the wear resistance can be effectively improved.

When sodium tetraborate decahydrate is used as the above-mentioned alkali metal-containing inorganic substance, the following methods and the like are exemplified as the preferred embodiment: a furnace for forming a glass substrate and a furnace other than the quench furnace (for example, used in the examples) In a large-scale tube furnace, etc., after vaporizing sodium tetraborate at a temperature of about 850 ° C, the vaporized material is sprayed to a furnace of about 700 ° C by a nozzle or A cold furnace or a bottom surface or a top surface of a glass substrate conveyed between the furnaces.

The alkali metal is sprayed onto the bottom surface or the top surface of the glass substrate by spraying the alkali metal-containing inorganic substance by the above method. The presence of the alkali metal on the bottom or top surface of the glass substrate can be confirmed by X-ray photoelectron spectroscopy (XPS) or fluorescent X-ray analysis of the underside of the glass substrate.

[Second supply step]

In the first production method of the present invention, after the first supply step, the second supply step is performed by spraying SO ₂ gas onto the bottom surface of the glass substrate to which the alkali metal is supplied, and forming a protective film on the bottom surface. step. (hereinafter, also referred to as "second supply step (first manufacturing method)").

In the second supply step (first production method), a protective film is formed on the bottom surface of the glass substrate to which the alkali metal is supplied, which is different from the previously known steps of the usual floating method.

In other words, the second supply step (first manufacturing method) is a step of spraying an SO ₂ gas onto the bottom surface of the glass substrate to which an alkali metal is supplied by the first supply step, thereby causing an alkali metal and SO _{2 .} The gas reacts to form a protective film containing an alkali sulfate salt (for example, sodium sulfate or the like) on the bottom surface of the glass substrate.

On the other hand, in the second manufacturing method of the present invention, the second supply step is a step of spraying SO ₂ gas onto the bottom surface of the glass substrate and forming a protective film on the bottom surface after the first supply step (hereinafter Also referred to as "the second supply step (second manufacturing method)"), is the same step as the previously known steps of the usual floating method.

The spraying time (timing) and the spraying method of the SO ₂ gas in the second supply step can be appropriately exemplified in the second supply step (first manufacturing method) and the second supply step (second manufacturing method). The following is the case.

The time for spraying the SO ₂ gas is not particularly limited as long as it is later than the first supply step. From the viewpoint of preventing the surface of the glass substrate from being scratched during the transfer, it is preferable that the first supply step is followed by More preferably, between the above forming step and the above-described quenching step. Further, at the same time, the respective gas systems are sprayed to react with the respective gases, and it is difficult to form a film, which is not preferable.

On the other hand, the method of spraying the SO ₂ gas can be carried out by the same method as the conventionally known method of the usual floating method. Specifically, for example, it can be implemented by a method of spraying a nozzle provided under the glass substrate (for example, the method disclosed in claim 12 of Patent Document 3) in the width direction of the glass substrate.

However, in the first production method of the present invention, it is possible to ensure the same as the previous example in which a sulfate (for example, calcium sulfate) derived from an alkaline earth metal can be used as a protective film for a glass substrate for a flat panel. Protects the effect and reduces the amount of SO ₂ gas sprayed. The reason for this is that, as described above, the SO ₂ gas sprayed by the second supply step preferentially reacts with the alkali metal supplied to the bottom surface, thereby suppressing the reaction between the SO ₂ gas and the alkaline earth metal (Ca, Sr, etc.). . Specifically, in the first production method of the present invention, the amount of SO ₂ gas to be sprayed can be reduced to 0.05 to 2.5 L/m ² , particularly 0.05 to 0.3 L/m ² .

Further, the spraying of the SO ₂ gas is preferably carried out at a temperature within a range of ±100 ° C of the glass transition point of the glass substrate, more preferably at 550 to 750 ° C. When the spraying is carried out at this temperature, the production efficiency of the protective film can be further improved, and as a result, the Ag colloid can be further prevented from developing color.

The manufacturing method of the present invention is a method for producing a glass substrate for a flat panel display comprising the above-described molding step, cold cooling step, first supply step, and second supply step, and may further include a cleaning step described below.

(washing step)

In the manufacturing method of the present invention, in order to perform defect inspection such as air bubbles, foreign matter, and scratches to obtain high permeability, the protective film formed by the second supply step may be washed and removed as needed. Washing steps.

This washing step is a previously known step of the usual floating method, and the following examples can be appropriately exemplified with respect to the time (timing) and the washing method.

The time of the cleaning step is not particularly limited as long as it is later than the second supply step. However, since the protective film is provided for the flaw on the surface (bottom surface) of the glass substrate generated during the drum conveyance process, it is preferable. Yes, immediately after the final stage of the above-mentioned cold step or the above-mentioned cold step.

On the other hand, in the cleaning method of the above-described washing step, since a protective film comprising a sulfate derived from an alkali metal (for example, a water-soluble salt such as sodium sulfate) is formed in the present invention, an easy method can be utilized. To remove, for example, it can be removed by a water washing process. Further, when the first supply step is not performed and the SO ₂ gas is sprayed, the protective film formed on the bottom surface of the glass substrate becomes a sulfate derived from an alkaline earth metal (for example, water-soluble such as calcium sulfate) Salt), and it is difficult to wash easily.

A method for producing a glass substrate for a flat panel display according to a third aspect of the present invention (hereinafter also referred to as "the third manufacturing method of the present invention") is a method for manufacturing a glass substrate for a flat panel display by a floating method; In the forming step, the molten glass is formed into a molten glass on the molten tin, and the first supply step is performed, and the inorganic metal containing the alkali metal is sprayed onto the surface of the glass substrate on the side in contact with the molten tin at 550 to 750 ° C. In the second supply step, after the first supply step, the SO ₂ gas is sprayed onto the surface of the glass substrate on the side in contact with the molten tin at 550 to 750 °C.

Here, the molding step of the third manufacturing method of the present invention is the same as that described in the production method of the present invention, and the first supply step and the second supply step are also performed except that the temperature is set to 550 to 750 °C. Both are the same as those described in the first production method of the present invention. Moreover, in the third manufacturing method of the present invention, the washing step may be further provided.

Further, a method for producing a glass substrate for a flat panel display according to a fourth aspect of the present invention (hereinafter also referred to as "the fourth manufacturing method of the present invention") is a method for manufacturing a glass substrate for a flat panel display by a floating method; a molding step of forming molten glass on molten tin into a glass substrate, and a first supply step of spraying a base containing the alkali on the surface of the glass substrate that is not in contact with the molten tin at 550 to 750 °C. The inorganic material of the metal; and the second supplying step, after the first supplying step, the SO ₂ gas is sprayed onto the surface of the glass substrate on the side in contact with the molten tin at 550 to 750 °C.

Here, the molding step of the fourth production method of the present invention is the same as that described in the production method of the present invention, and the first supply step and the second supply step are also performed except that the temperature is set to 550 to 750 °C. Both are the same as those described in the second manufacturing method of the present invention. Moreover, in the fourth manufacturing method of the present invention, the washing step may be further provided.

In the case where an inorganic substance containing Na or boron is used in the first to fourth production methods of the present invention, a glass substrate for a flat panel display obtained by the above methods is also provided.

Specifically, the inorganic substance containing Na and boron is sprayed onto the bottom surface and/or the top surface of the glass substrate in the first supply step, and the cleaning step is performed as needed, thereby providing a flat panel display. Use a glass substrate.

Preferably, the glass substrate for a flat panel display of the present invention has the following composition.

In other words, in the glass substrate for a flat panel display of the present invention, the glass substrate is expressed by mass percentage based on oxides, and contains SiO ₂ : 45 to 70%, Al ₂ O ₃ : 0 to 20%, and CaO: 0. ~20%, ZrO ₂ : 0~13%, the total amount of alkaline earth metal oxide components: 5~40%, the total amount of alkali metal oxide components: 5~30%, the bottom surface and/or top surface of the above glass substrate Preferably, the average boron concentration of the top surface is 2 to 6 atom%, preferably 2 to 4 atom%, and the diffusion depth of boron to the inside of the glass substrate is 20 to 80 nm, preferably 30. ~50 nm.

Moreover, as another specific composition, the composition similar to the above-mentioned composition is mentioned as the composition of the glass substrate formed on the molten tin.

In the present invention, the average boron concentration of the bottom surface or the top surface of the glass substrate can be determined as an average value when five points are arbitrarily measured by X-ray photoelectron spectroscopy.

Further, in the X-ray photoelectron spectroscopy, an XPS spectrometer (Model 5500, manufactured by PHI Corporation) was used, and an X-ray AlKα line monochromated by a monochromator was used as an X-ray source. Further, the X-ray photoelectron detection angle was 75°, and the measurement was performed by irradiating a cascade shower for charging correction.

Further, in the present invention, the diffusion depth of boron into the inside of the glass substrate can be evaluated by secondary ion mass spectroscopy (SIMS) from the depth of reaching the secondary ion intensity equivalent to the substrate.

Specifically, the diffusion depth at five points was measured at five points on the glass substrate by a secondary ion mass spectrometer (ADEPT 1010, manufactured by Ulvac Phi Co., Ltd.), and the average value thereof was determined.

Here, the sputter time is converted into a spatter depth by SiO ₂ conversion (4 nm = 1 min). Furthermore, in the case where the primary ion is an oxygen ion beam, the accelerating voltage is 5 keV, the beam current is 400 nA, the incident angle of the primary ion is 45 degrees with respect to the normal to the sample surface, and the beam scanning range is 400×400 μm ² . The measurement was carried out.

In the glass substrate for a flat panel of the present invention, the bottom surface or the top surface of the glass substrate has an average boron concentration of 2 to 6 atom%, preferably 2 to 4 atom%, and boron is inside the glass substrate. The diffusion depth is 20 to 80 nm, preferably 30 to 50 nm. Therefore, the strength of the glass substrate itself is improved, and the abrasion resistance is excellent, and the scratch resistance is excellent in the transportation or processing step after removing the protective film. By allowing boron to diffuse from the bottom surface or the top surface to the inside of the glass substrate and remaining on the surface layer of the glass substrate, abrasion resistance and scratch resistance can be improved. The reason for this is that the mesh structure of the glass is firm.

The glass substrate for a flat panel display of the present invention is self-evident until the cleaning step is performed. After the cleaning step is performed as needed, boron remains on the surface layer of the glass substrate, so that the scratch on the back surface of the glass substrate can be continuously suppressed. Produced, so it is better.

In addition, in the glass substrate for a flat panel display of the present invention, it is presumed that boron remains on the surface layer of the glass substrate because boron is easily entered into the glass substrate by the first supply step, and is likely to remain on the glass substrate. surface layer.

Further, in the glass substrate for a flat panel display of the present invention, the average H atom concentration from the top surface of the glass substrate to a depth of 0.1 μm is preferably 2.5 mol% or less, more preferably 2.0 mol% or less. . If the average H atom concentration is within this range, the chance of causing the above-described exchange reaction of Ag ⁺ and H ⁺ will be reduced, and when the silver electrode is formed, Ag ⁺ will not enter the surface layer, thereby further preventing the Ag colloid from developing color.

Here, the average H atom concentration from the top surface of the glass substrate to a depth of 0.1 μm can be measured between the top surface and the depth of 0.1 μm using a secondary ion mass spectrometer (ADEPT 1010, manufactured by Ulvac Phi Co., Ltd.). Five points were obtained as the average value. Furthermore, the primary ion is Cs ⁺ , the accelerating voltage is 5 keV, the beam current is 400 nA, the incident angle of the primary ion is 60 degrees with respect to the normal to the sample surface, and the beam scanning range is 200×200 μm ² . The measurement was carried out.

Therefore, the present invention can also provide a glass substrate for a flat panel display, which is expressed by mass percentage based on oxides, and contains: SiO ₂ : 45 to 70%, Al ₂ O ₃ : 0 to 20%, CaO: 0 ~20%, ZrO ₂ : 0~13%, the total amount of alkaline earth metal oxide components: 5~40%, the total amount of alkali metal oxide components: 5~30%, the average boron concentration of at least one surface is 2 ~6 atom%, and the diffusion depth of boron from the surface to the inside is 20 to 80 nm.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the invention is not limited thereto.

(Example 1)

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

Specifically, a quartz tube 12 is placed in a large tubular furnace 11 having an adjustable temperature, and a glass substrate 13 (10 cm square) for a flat panel display having a thickness of 2.8 mm is placed in the quartz tube 12, and the large tubular furnace 11 is heated to 600 ° C. Here, as the "glass substrate for flat panel display", a glass having the following composition based on an oxide and expressed by mass percentage is used: SiO ₂ : 58.6, Al ₂ O ₃ : 6.9, MgO: 1.9, CaO: 4.8, SrO: 6.9, BaO: 7.9, Na ₂ O: 4.0, K ₂ O: 6.1, ZrO ₂ : 2.8, Fe ₂ O ₃ : 0.09. Further, the glass transition point of the above glass was 600 °C.

Next, the reagent 15 of sodium tetraborate decahydrate placed in the alumina boat 14 is locally heated to about 850 ° C to vaporize it, and the vaporized material is sprayed from the end of the quartz tube in the direction indicated by the arrow 16. Thereby, sodium tetraborate is supplied to the surface (bottom surface) of the glass substrate 13 for flat panel. At this time, the amount of sodium tetraborate decahydrate sprayed was 0.4 L/m ² , and the temperature of the glass substrate 13 for a flat panel was 600 °C.

Then, SO ₂ gas is sprayed from the direction indicated by the arrow 17 so as to form a protective film so that the amount of the surface (bottom surface) of the glass substrate 13 for the flat panel display supplied with sodium is 0.1 L/m ² . A glass substrate for a flat panel display with a protective film is produced. At this time, the temperature of the glass substrate 13 for a flat panel display was 600 °C.

Further, the conditions of the present embodiment are the same as the conditions for spraying the SO ₂ gas immediately after the alkali metal-containing inorganic substance is sprayed between the above-described forming step and the above-mentioned cold step.

(Example 2)

A glass substrate for a flat panel display with a protective film was produced in the same manner as in Example 1 except that the amount of the SO ₂ gas to be sprayed was changed to 0.4 L/m ² .

(Example 3)

A glass substrate for a flat panel display with a protective film was produced in the same manner as in Example 1 except that the amount of the SO ₂ gas to be sprayed was changed to 1.0 L/m ² .

(Comparative Example 1)

A glass substrate for a flat panel display with a protective film was produced in the same manner as in Example 1 except that only sodium diborate was not used and only SO ₂ gas was sprayed.

(Comparative Example 2)

A glass substrate for a flat panel display with a protective film was produced in the same manner as in Example 2, except that sodium tetraborate was not used and only SO ₂ gas was sprayed.

(Comparative Example 3)

A glass substrate for a flat panel display with a protective film was produced in the same manner as in Example 3, except that sodium tetraborate was not used and only SO ₂ gas was sprayed.

(Comparative Example 4)

A glass substrate for a flat panel display was produced in the same manner as in Example 1 except that sodium tetraborate was not used and SO ₂ gas was not sprayed, and the mixture was heated at 700 ° C for 15 minutes.

(Comparative Example 5)

A glass substrate for a flat panel display was produced in the same manner as in Example 1 except that sodium tetraborate was not used and SO ₂ gas was not sprayed.

The glass substrates for flat panel displays each having the protective film obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were protected by the methods described below. Adhesion of the film, damage resistance, average boron concentration. The diffusion depth, the average H atom concentration of the top surface, the yellowness index of the top surface, and the wear resistance were measured and evaluated. The results are disclosed in Table 1 below.

Further, in the glass substrates for flat panel displays obtained in Comparative Examples 4 and 5, since the SO ₂ gas was not sprayed and the protective film was not formed, only the abrasion resistance was performed by the method described below. Determination. The results are shown in Table 1 below.

<protection film adhesion amount>

The protective film of the obtained glass substrate for a flat panel with a protective film obtained was dissolved in pure water, sulfur was quantified by ICP emission spectrometry, and sodium, calcium, and barium were quantified by atomic absorption.

Based on these quantitative values, the amount of sulfate adhering to the bottom surface was calculated as the amount of adhesion of the protective film. In addition, the adhesion amount was obtained as an average value calculated from the obtained ten glass substrates for flat panel displays with a protective film obtained.

<resistance>

The evaluation of the scratch resistance was carried out using the Taber test in accordance with JIS R3221 (1990). Furthermore, the Taber test was carried out using a Taber tester (Tdedyne Taber Model 503) with a wear wheel fixed to CS-10F, a load of 250 g, and a fixed number of wear times of three.

Thereafter, in order to remove the protective film used as the glass substrate for the flat panel display with the protective film as the test body, the substrate was washed by showering under a pure water of 3 ° C (3 liter / minute) for 30 seconds. .

Using a microscope to observe the surface of the glass substrate obtained by removing the protective film For the surface, the number of scratches in the length of 0.2 mm or more in the longitudinal direction of 1 cm × 1 cm square (the number of scars) was measured. The measurement unit is a central portion of a portion to be tested by Taber (see FIG. 3). In FIG. 3, the wear portion 19 is formed by the wear wheel in the test body (glass substrate for flat panel display) 18, and the measurement unit 20 serves as a central portion of the wear portion 19.

Further, the number of occurrences of the flaws was measured for any 10 points on each of the glass substrates, and the average value thereof was determined. Further, the number of occurrences of the flaws was determined as an average value calculated from the obtained ten glass substrates.

<Average boron concentration. Diffusion depth>

(1) Where a pure water (flow rate: 3 liters/min) was poured at 20 ° C, the obtained glass substrate for a flat panel display having a protective film was washed with water to remove the protective film. Thereafter, the average value of the boron concentration on the bottom surface of the glass substrate after the cleaning was determined as an average value measured by X-ray photoelectron spectroscopy at five points. Further, in the X-ray photoelectron spectroscopy, an XPS spectrometer (Model 5500, manufactured by PHI Corporation) was used, and X-ray AlKα rays monochromated by a monochromator were used as an X-ray source. Further, the X-ray photoelectron detection angle was 75°, and in order to perform charging correction, the cascade was irradiated to perform measurement.

In the following Table 1, the average boron concentration column of Comparative Examples 1 to 3 was "-", which means that boron could not be detected.

(2) The depth of diffusion of boron into the interior of the glass substrate is evaluated by using secondary ion mass spectrometry (SIMS) to achieve a depth equal to the secondary ionic strength of the substrate.

Specifically, a diffusion depth of 5 points was measured at 5 points on the cleaned glass substrate by a secondary ion mass spectrometer (ADEPT 1010, manufactured by Ulvac Phi Co., Ltd.), and the average value thereof was determined. Here, the sputter time is converted into a spatter depth by SiO ₂ conversion (4 nm = 1 min).

Furthermore, in the case where the primary ion is an oxygen ion beam, the accelerating voltage is 5 keV, the beam current is 400 nA, the incident angle of the primary ion is 45 degrees with respect to the normal to the sample surface, and the beam scanning range is 400×400 μm ² . The measurement was carried out under the conditions.

In the following Table 1, the diffusion depth column of Comparative Examples 1 to 3 was "-", which indicates that diffusion cannot be confirmed.

<Average H atom concentration of the top surface>

Using a secondary ion mass spectrometer (ADEPT 1010, manufactured by Ulvac Phi Co., Ltd.), five points from the top surface to a depth of 0.1 μm were measured, and the obtained flat panel display with the protective film was obtained as an average value thereof. The average H atom concentration of the glass substrate from the top surface of the glass substrate to a depth of 0.1 μm. Furthermore, the primary ion is Cs ⁺ , the accelerating voltage is 5 keV, the beam current is 400 nA, the incident angle of the primary ion is 60 degrees with respect to the normal to the sample surface, and the beam scanning range is 200×200 μm ² . The measurement was carried out.

<Top yellowness index (b ^* )>

The yellowness index of the top surface of the glass substrate of each of the obtained glass substrates for a flat panel display with a protective film was measured by an automatic recording spectrophotometer (U-3500 type) manufactured by Hitachi, Ltd., and the sample was measured in accordance with JIS-Z8729. (Ag was coated on the top surface to a thickness of 20 μm, dried at 110 ° C for 20 minutes, and then fired at 560 ° C for 60 minutes, and then cooled to remove Ag by nitric acid). Further, the coefficient of thermal expansion at 50 to 350 ° C was measured at 83 × 10 ^-7 / ° C and the softening point was 570 ° C.

<Abrasion resistance>

The abrasion resistance was carried out by investigating the rate of change of the turbidity rate (turbidity change rate) before and after the Taber test.

First, the haze ratio of each of the obtained glass substrates for a flat panel was measured with a turbidimeter.

Then, the glass substrate for each flat panel was subjected to the Taber test in accordance with JIS R3221 (1990). Furthermore, the Taber test was carried out using a Taber tester (Tdedyne Taber Model 503) with a wear wheel fixed to CS-10F and a load fixed at 500 g.

Then, the turbidity rate after 1000 times of Taber abrasion was measured by a turbidimeter, and the rate of change was determined from the turbidity rate before the Taber test.

Here, the haze value can be defined as the following formula using scattered light (Td) and transmitted light (Tt).

Turbidity rate = (Td / Tt) × 100%

Further, the rate of change (ΔH) of the turbidity rate (H) can be expressed by the following formula.

△H=turbidity rate after 1000 times of abrasion turbidity rate H before H-Taber test

As is clear from the results shown in Table 1, the glass substrates for flat panel displays of Examples 1 to 3 obtained by using sodium tetraborate were comparable to Comparative Examples 1 to 3, even if the amount of SO ₂ gas sprayed was equal to or less than the same. The damage resistance is satisfactorily maintained at the same level or higher, so that the yellowness index of the top surface, that is, Ag colloid color development can be suppressed.

Further, even if an equivalent amount of sodium sulfate was adhered, that is, in Comparative Example 1 and Comparative Example 2, the number of occurrences of scratches in the glass substrate for a flat panel display of Example 1 obtained by using sodium tetraborate was small. The reason for this is that the anti-friction property of the glass substrate itself is improved by diffusion of boron to the glass substrate.

Further, it has been confirmed that the glass substrates for flat panels of Examples 1 to 3 are usually washed with water, and the protective film formed on the surface of the glass substrate is removed to exhibit a clean surface. On the other hand, in the glass substrate for a flat panel of Comparative Examples 1 to 3, even if the water is washed normally, the protective film formed on the surface of the glass substrate cannot be removed and remains. Further, when the remaining film component is measured, it is calcium sulfate and barium sulfate.

Further, it is known that the glass substrates for flat panels of Examples 1 to 3 are diffused by boron, so that the turbidity change rate is reduced and the wear resistance is improved as compared with the glass substrates for flat panels of Comparative Examples 1 to 5.

The present invention has been described with reference to the specific embodiments of the invention, and it is understood that various changes and modifications may be made without departing from the spirit and scope of the invention.

The present application is based on Japanese Patent Application No. 2006-188036, filed on Jan.

[Industrial availability]

According to the present invention, it is possible to provide a method for producing a glass substrate for a flat panel display which can maintain good scratch resistance and prevent color development of an Ag colloid, and a glass substrate for a flat panel display obtained by the method.

Further, the present invention is applicable not only to a PDP but also to FED, SED, etc., while maintaining good scratch resistance and preventing color development of the Ag colloid.

1‧‧‧ molten tin

2‧‧‧ molten tin bath

3‧‧‧ melting kiln

4‧‧‧ molten glass

5‧‧‧ Guide roller

6‧‧‧Xu cold furnace

11‧‧‧ Large tubular furnace

12‧‧‧Quartz tube

13‧‧‧Glass substrates for flat panel displays

14‧‧‧Alumina boat

15‧‧‧Reagents

16, 17‧‧‧ arrows

18‧‧‧Test body

19‧‧‧Wearing Department

20‧‧‧Determination Department

Fig. 1 is a conceptual view showing an example of a glass manufacturing line using a floating method.

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

3 is an explanatory view showing a portion (abrasion portion) and a flaw number measurement portion (measurement portion) which are touched by the abrasion wheel of the Taber test machine used for the evaluation of the scratch resistance.

1‧‧‧Fused tin

2‧‧‧Fused tin bath

3‧‧‧melting kiln

4‧‧‧Solder glass

5‧‧‧ Guide roller

6‧‧‧Xu cold furnace

Claims (2)

A glass substrate for a flat panel display, which is expressed by mass percentage based on an oxide, and contains: SiO ₂ : 45 to 70%, Al ₂ O ₃ : 0 to 20%, CaO: 0 to 20%, ZrO ₂ : 0~13%, the total amount of alkaline earth metal oxide components: 5~40%, the total amount of alkali metal oxide components: 5~30%, the average boron concentration of at least one surface is 2~6 atom%, and boron The depth of diffusion from the surface to the inside is 20 to 80 nm. The glass substrate for a flat panel display according to claim 1, wherein an average H atom concentration of the surface from a surface to a depth of 0.1 μm is 2.5 mol% or less.