JP2008108541A - Forming method of transparent conductive film, and transparent conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forming method of a transparent conductive film by which a transparent conductive film of low resistance and high quality can be formed without requiring a pressure-reduced atmosphere and which is superior in mass-producibility and manufacturing cost by using a coating method, and a transparent conductive film. <P>SOLUTION: In the manufacturing method of a transparent conductive film, a substrate with the film 11 in which a conductive coated film 13 is formed on the surface of a substrate 12 is mounted on a lower electrode 5, a reaction gas g of atmospheric pressure or near the atmospheric pressure is introduced on the substrate with the film 11, and the reaction gas g is made an unbalanced plasma state by impressing a voltage between the lower electrode 5 and an upper electrode 3. This unbalanced plasma p is irradiated on the conductive coated film 13 to reform it, and the transparent conductive film is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for forming a transparent conductive film and a transparent conductive film, and more particularly, a plasma display (PDP), a liquid crystal display (LCD), an electroluminescence display (EL), a cathode ray tube (CRT), a projection (PJTV), and the like. The present invention relates to a technique capable of forming a low-resistance and high-quality transparent conductive film on a display surface or the like of an image display device.

Conventionally, in an image display unit of an image display device such as a plasma display (PDP), a liquid crystal display (LCD), an electroluminescence display (EL), a cathode ray tube (CRT), a projection (PJTV), a glass substrate, an organic polymer film, etc. A flat panel in which a transparent conductive film is formed on a transparent substrate is used.
As a method for forming this transparent conductive film, conventionally, a dry method in which a transparent conductive film made of a metal or a metal oxide is formed on a transparent substrate by a vacuum deposition method, an ion plating method, a sputtering method, or the like, a coating method is used. Two methods of a wet method for forming a transparent conductive film by a construction method are known. However, in the conventional dry method, a manufacturing apparatus becomes quite expensive, so the obtained transparent conductive film is very expensive. In addition, in the conventional wet method, it is difficult to use an organic polymer film as a transparent substrate because heat treatment is required to obtain desired conductivity. Therefore, in order to improve the problems in the conventional dry method and wet method, it is necessary to irradiate the coating film with plasma in the air, thereby requiring a heat treatment or a reduced pressure atmosphere. A method of forming a transparent conductive film having low resistance have been proposed.

  In particular, deposition technology using arc plasma is a technology that effectively modifies the coating film by promoting the effects of electrons, ions, excited molecules, and radical species in the plasma, and changes the plasma state. By doing so, the film quality of the coating film can be improved to a high quality.

On the other hand, in recent years, a technique for generating non-equilibrium plasma (glow discharge plasma) under the release of atmospheric pressure has been developed and used in various applications. This technology introduces helium, argon, nitrogen gas, etc. under a pressure close to atmospheric pressure between a pair of electrodes facing each other at a certain interval, and applies a high-frequency AC voltage, a pulse voltage, etc. between these electrodes. By doing so, a stable glow discharge is generated between these electrodes.
This chemical vapor deposition method (CVD method) using non-equilibrium plasma (glow discharge plasma) is attracting attention as a technique capable of depositing an oxide film on a low-temperature substrate (for example, see Patent Documents 1 and 2). ).
JP 2003-89875 A JP 2005-259628 A

  However, in the conventional film forming technology using plasma, when a conductive coating film is brought close to the plasma, electrons in the plasma move in the surface of the coating film, and at the boundary between the coating film and the plasma, a spark (spark) Problems such as arcing, streamers, or formation of arc spots occur, resulting in peeling of the coating, partial chipping (shaving) of the coating, and holes in the coating In addition, various problems such as discoloration occur, and it is difficult to stably form a low-resistance and high-quality transparent conductive film.

In addition, when a long arc substrate is used in the conventional arc plasma, a plurality of plasma electrodes are arrayed in order to apply the technique of irradiating the arc plasma to the long substrate. There is a problem that adjustment of the power source and selection of the irradiation conditions for the coating film become extremely complicated.
On the other hand, in the conventional non-equilibrium plasma (glow discharge plasma), the film formation rate is slow or abnormally grown crystals such as whiskers are generated on the film. There was a problem that it was difficult to manufacture.

  The present invention was made in order to solve the above-mentioned problem, and by irradiating the conductive coating film with non-equilibrium plasma under atmospheric pressure or near atmospheric pressure, a reduced pressure atmosphere is not required, To provide a transparent conductive film forming method and a transparent conductive film that can form a low-resistance and high-quality transparent conductive film and that are excellent in mass productivity and manufacturing cost by using a coating method. With the goal.

  As a result of intensive studies to solve the above problems, the present inventors applied a conductive paint on a base material to form a conductive coating film, and the conductive coating film was subjected to atmospheric pressure or By irradiating non-equilibrium plasma generated near atmospheric pressure, a low-resistance and high-quality transparent conductive film can be formed with good productivity and at low cost without the need for a reduced-pressure atmosphere. The headline and the present invention were completed.

  That is, in the method for forming a transparent conductive film of the present invention, a base material having a conductive coating film formed on one main surface is disposed between a pair of opposing electrodes, and atmospheric pressure or atmospheric pressure is applied on the conductive coating film. A reactive gas in the vicinity of atmospheric pressure is introduced, a voltage is applied between the pair of electrodes to bring the reactive gas into a non-equilibrium plasma state, and the conductive coating film is irradiated with the non-equilibrium plasma on the conductive coating film. A transparent conductive film is formed by modification.

The reaction gas is preferably a rare gas or a mixed gas containing a rare gas and one or more selected from the group of hydrogen, ammonia, and nitrogen.
The voltage is preferably one or more selected from the group of a pulse voltage, an alternating voltage, a high frequency voltage, and a bipolar pulse voltage.
The substrate is preferably made of glass or an organic polymer compound.
The conductive coating film preferably contains one or more of organic metal compounds, metal inorganic acid salts, metal organic acid salts, metal oxide fine particles, and fine particles made of a metal or an alloy. .
The conductive coating film contains one or more of organic metal compounds, metal inorganic acid salts, metal organic acid salts, metal oxide fine particles, and fine particles made of metal or alloy. It is preferable that it is formed by coating.

  The transparent conductive film of the present invention is formed by the method for forming a transparent conductive film of the present invention.

According to the method for forming a transparent conductive film of the present invention, a reactive gas at atmospheric pressure or near atmospheric pressure is introduced onto a conductive coating film, and a voltage is applied between the electrodes to form a non-equilibrium plasma state. By irradiating the conductive coating film with this non-equilibrium plasma and modifying the conductive coating film, a transparent conductive film is formed. Therefore, a low-resistance and high-quality transparent film is not required without a reduced pressure atmosphere. A conductive film can be easily formed.
Moreover, since this conductive coating film can be easily formed by applying a conductive paint on a substrate, it is excellent in terms of mass productivity and cost.

According to the transparent conductive film of the present invention, since the transparent conductive film is formed by the method for forming a transparent conductive film of the present invention, the resistance and the quality of the transparent conductive film can be reduced.
In addition, since this transparent conductive film is obtained by modifying the conductive coating film by irradiating the conductive coating film with non-equilibrium plasma, the in-plane uniformity of the film despite the thin film thickness. Can be improved, and the surface resistance can be lowered.

A method for forming a transparent conductive film and a best mode for carrying out the transparent conductive film of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

"Method for forming transparent conductive film"
In the method for forming a transparent conductive film of the present invention, a substrate having a conductive coating film formed on one main surface is disposed between a pair of opposing electrodes, and the atmospheric pressure or near atmospheric pressure is formed on the conductive coating film. Then, a voltage is applied between the pair of electrodes to bring the reaction gas into a non-equilibrium plasma state, and the conductive coating film is irradiated with the non-equilibrium plasma to modify the conductive coating film. This is a method for forming a transparent conductive film.
This conductive coating film is a conductive paint containing any one or more of organic metal compounds, metal inorganic acid salts, metal organic acid salts, metal oxide fine particles, fine particles made of metals or alloys. Is formed, and then dried.

Next, a method for forming this transparent conductive film will be described in detail.
"Conductive paint"
This conductive paint is an organic metal compound, metal inorganic acid salt, metal organic acid salt, metal oxide fine particles, metal / alloy fine particles (fine particles made of metal or alloy), or one or more of them are organic. It is a paint dissolved or dispersed in a solvent and / or water (hereinafter also simply referred to as a solvent).
As an organometallic compound to be used, a material containing a metal element constituting the transparent conductive film may be appropriately selected, and is not particularly limited.

As the above-mentioned organometallic compound, for example, metal alkyl or metal aryl containing indium, tin, zinc, cadmium, gallium, antimony, aluminum or the like is preferably used, and in particular, metal acetylacetonate such as indium acetylacetonate. Is preferred.
As the metal inorganic acid salt, for example, nitrates, hydrochlorides, sulfates, and phosphates containing one or more of indium, tin, zinc, cadmium, gallium, antimony, and aluminum are preferably used. . In place of the metal inorganic acid salt, a hydrate of the metal inorganic acid salt may be used.

  As the metal organic acid salt, a salt of a metal and a carboxylic acid such as a saturated aliphatic monocarboxylic acid, a saturated aliphatic dicarboxylic acid, an unsaturated fatty acid, a carbocyclic carboxylic acid, or a heterocyclic carboxylic acid is preferably used. , Acetate, tartrate, formate, oxalate, 2-ethylhexanoate, and the like containing any one or more of indium, tin, zinc, cadmium, gallium, antimony, and aluminum.

Examples of the metal oxide fine particles include fine particles such as indium oxide, zinc oxide, cadmium oxide, gallium oxide, antimony oxide, and aluminum oxide, or tin-added indium oxide (ITO) obtained by adding other metal elements to these oxides. Fine particles such as antimony-added tin oxide (ATO), zinc-added indium oxide (IZO), aluminum-added zinc oxide (AZO), and gallium-added zinc oxide (GZO) are preferably used.
Among these metal oxides, those that constitute a transparent conductive film include tin-added indium oxide (ITO), antimony-added tin oxide (ATO), zinc-added indium oxide (IZO), and aluminum-added zinc oxide (AZO). In addition, gallium-doped zinc oxide (GZO), indium oxide (I 2 O 3), zinc oxide (ZnO), and the like are preferable.

The average primary particle diameter of the metal oxide fine particles is preferably 1 nm or more and 100 nm or less, more preferably 1 nm or more and 30 nm or less.
The reason is that if the average primary particle diameter of the metal oxide fine particles is less than 1 nm, the crystallinity of the transparent conductive film is lowered, and as a result, the electrical conductivity of the film is lowered (surface resistance is raised). In addition, if it exceeds 100 nm, the transparency and sinterability of the transparent conductive film deteriorate.
Here, when the average primary particle diameter is 1 nm or more and 30 nm or less, the sinterability between the metal oxide fine particles is improved, and the densification of the coating film is facilitated.

Examples of metal / alloy fine particles include fine particles such as indium, tin, zinc, cadmium, gallium, antimony, and aluminum, or indium-tin alloy, indium-zinc alloy, antimony-tin alloy, zinc-aluminum alloy, zinc-gallium. Fine particles such as alloys are preferably used.
The average primary particle diameter of the metal / alloy fine particles is preferably 1 nm or more and 100 nm or less, more preferably 1 nm or more and 30 nm or less.
The reason is that when the average primary particle diameter of the metal / alloy fine particles is less than 1 nm, the crystallinity of the transparent conductive film is lowered, and as a result, the electrical conductivity of the film is lowered (surface resistance is raised). In addition, if it exceeds 100 nm, the transparency and sinterability of the transparent conductive film deteriorate.

  The organic solvent may be appropriately selected depending on the organometallic compound, metal inorganic acid salt, metal organic acid salt, metal oxide fine particle, metal / alloy fine particle to be used, and is not particularly limited. Monohydric alcohols such as ethanol, 2-propanol and butanol, dihydric alcohols such as ethylene glycol, ketones such as acetone, methyl ethyl ketone and diethyl ketone, esters such as ethyl acetate, butyl acetate and benzyl acetate, methoxyethanol, Examples include ether alcohols such as ethoxyethanol, ethers such as dioxane and tetrahydrofuran, acid amides such as N, N-dimethylformamide, and aromatic hydrocarbons such as toluene and xylene.

  The amount of the solvent used can be easily applied and a desired film thickness can be obtained according to the organometallic compound, metal inorganic acid salt, metal organic acid salt, metal oxide fine particle, and metal / alloy fine particle to be used. In this way, it may be selected as appropriate. For example, when metal oxide fine particles or metal / alloy fine particles are dissolved or dispersed in a solvent, the amount of fine particles is preferably 1% by weight or more and 10% by weight or less based on the total amount of the solvent.

"Conductive coating"
This conductive coating film is obtained by applying the above-mentioned conductive paint on a substrate and then drying.
It does not specifically limit as a base material, A glass substrate and a plastic substrate (organic polymer compound board | substrate) can be mentioned, As a shape, any, such as a flat plate, a film, a sheet | seat, may be sufficient.
The plastic substrate is preferably a transparent plastic sheet or a transparent plastic film.

The material of the plastic substrate is not particularly limited. For example, cellulose acetate, polystyrene (PS), polyethylene terephthalate (PET), polyether, polyimide, epoxy, phenoxy, polycarbonate (PC), polyvinylidene fluoride, etc. Can be appropriately selected.
Also, the thickness of the plastic substrate is not particularly limited, and a film of about 50 to 250 μm can be used for a film, and a sheet of about 10 mm can be used for a sheet.
These substrates may be used alone, or may be used as a substrate having a laminated structure in which a plurality of substrates are bonded and integrated. This substrate is preferably cleaned using a cleaning liquid such as pure water or an organic solvent before applying the conductive paint. If an ultrasonic wave is applied to the cleaning liquid during the cleaning, the cleaning power is greatly increased. Therefore, it is preferable.

Examples of the coating method include spin coating, spray coating, ink jet, dip coating, roll coating, bar coating, meniscus coating, screen printing, and the like. The method of apply | coating to is taken.
The conductive paint applied on the substrate is dried at room temperature in the atmosphere, or dried at a predetermined temperature, for example, 50 ° C. to 80 ° C. It becomes a coating film.
In addition, if there is little content of a solvent and there is no possibility that a film quality will change even if it irradiates with a plasma or electromagnetic waves, a drying process can be skipped.

"Non-equilibrium plasma irradiation"
The atmospheric pressure or a reaction gas near the atmospheric pressure introduced onto the conductive coating film is brought into a non-equilibrium plasma state, and the conductive coating film is irradiated with the non-equilibrium plasma to modify the conductive coating film. Thus, a transparent conductive film is formed on the substrate.
A plasma irradiation apparatus is used for this non-equilibrium plasma irradiation.

  FIG. 1 is a cross-sectional view showing a plasma irradiation apparatus used for non-equilibrium plasma irradiation according to the present invention. In the figure, 1 is a gas introduction pipe for introducing a reactive gas g composed of the above rare gas or mixed gas, An insulating portion 3 provided with a vent hole 2a for introducing a reaction gas into the central portion of the casing made of an insulating material provided at the distal end portion of the gas introduction pipe 1 maintains electrical insulation at the lower end of the insulating portion 2. The upper electrode for plasma generation provided in the state, 4 is an insulating film coated on the lower surface of the upper electrode for plasma generation 3, 5 is the lower electrode for plasma generation disposed opposite to the lower electrode for plasma generation 3, 6 Is a plasma generating power source that applies a voltage for generating plasma between the upper electrode 3 and the lower electrode 5. Reference numeral 11 denotes a film-coated substrate in which a conductive coating film 13 is formed on the surface of the substrate 12.

The upper electrode 3 and the lower electrode 5 are made of conductive metal, and stainless steel, aluminum, titanium, or the like is preferably used as the conductive metal.
The shapes of the upper electrode 3 and the lower electrode 5 can be appropriately selected according to the shape of the film-coated substrate 11 such as a flat plate shape, a disk shape, and a cylindrical shape.

  As shown in FIG. 2, holes 15 for allowing the reaction gas g to pass through are formed in the upper electrode 3 at predetermined intervals in the vertical and horizontal directions. The shape of the opening end of the hole 15 is circular. The total area of the open ends of these holes 15 is preferably 1% or more and 70% or less, more preferably 3% or more and 60% or less of the surface (one principal surface) 3a of the upper electrode 3. is there.

  Here, the reason why the total area of the open ends of the holes 15 is limited as described above is that when the total area of the open ends of the holes 15 is less than 1%, the reaction gas g is sufficient on the surface of the substrate 11 with film. This is because the film is not supplied, the film reforming rate is delayed, and it takes a long time to obtain a low-resistance transparent conductive film, and the quality of the film is deteriorated. This is because if it exceeds 70%, the plasma concentrates on a part of the upper electrode 3 and unevenness of the film is generated.

  Instead of the upper electrode 3, as shown in FIG. 3, the plasma generating upper electrode 18 in which square (or polygonal) holes 17 are formed in a mesh shape, or as shown in FIG. 4, An upper electrode 21 for plasma generation in which equilateral triangular (or other triangular) holes 20 are formed in a mesh shape may be used.

  The plasma generating power source 6 may be any power source as long as it can apply a high voltage between the upper electrode 3 and the lower electrode 5, and may be any one of an AC voltage, a high frequency voltage, a high frequency pulse voltage, a bipolar pulse voltage, or The voltage which combined these effectively can be applied. Among these voltages, a high frequency pulse voltage is particularly preferably used.

In this plasma irradiation apparatus, a plasma generating voltage is applied between the upper electrode 3 and the lower electrode 5 by the plasma generating power source 6, so that a non-equilibrium plasma state is generated between the upper electrode 3 and the lower electrode 5. Plasma p is generated.
In particular, when a high frequency pulse voltage is applied between the upper electrode 3 and the lower electrode 5, generation of heat due to non-equilibrium plasma can be suppressed, which is effective when a plastic substrate (organic polymer compound substrate) is used. It is.
The plasma p in the non-equilibrium plasma state can be arbitrarily controlled by adjusting the plasma output, frequency, and pulse width of the plasma generating power source 6.

Next, a method for modifying the conductive coating film 13 by non-equilibrium plasma irradiation using this plasma irradiation apparatus will be described.
First, the film-coated substrate 11 is placed on the plasma generating lower electrode 5 and the distance between the film-coated substrate 11 and the upper electrode 3 is adjusted. This interval is preferably 0.1 mm to 20 mm.
This is because it is actually difficult to control the distance between the film-coated substrate 11 and the upper electrode 3 if the distance is less than 0.1 mm, and on the other hand, if the distance exceeds 20 mm, the conductivity due to non-equilibrium plasma irradiation. This is because the modification of the conductive coating film 13 becomes insufficient and a low-resistance and high-quality transparent conductive film cannot be obtained.

Next, the reaction gas g is introduced between the upper electrode 3 and the lower electrode 4 through the gas introduction pipe 1.
The reaction gas was selected from a group of rare gases such as He, Ne, Ar, Kr, and Xe, or these rare gases and hydrogen (H ₂ ), ammonia (NH ₃ ), and nitrogen (N ₂ ). A mixed gas containing one kind or two or more kinds is preferably used.

Next, a plasma generation voltage is applied between the upper electrode 3 and the lower electrode 5 by the plasma generation power source 6.
As a range of a plasma output, 0.5-50 W / cm < ² > is preferable, More preferably, it is 1-10 W / cm < ² >. This is because if the plasma output is less than 0.5 W / cm ² , the reactive gas g is not in a predetermined stable non-equilibrium plasma state, and the conductive coating film 13 may not be sufficiently modified. On the other hand, if it exceeds 50 W / cm ² , the active energy of the plasma p becomes too large, and the conductive coating film 13 may be damaged.

The range of the pulse width is preferably 0.01 to 20 μs, more preferably 0.1 to 10 μs. This is because if the pulse width is less than 0.01 μs or exceeds 20 μs, the stability of the non-equilibrium plasma becomes poor, the modification of the conductive coating film 13 becomes insufficient, and the film quality deteriorates.
The range of the intermittent frequency is preferably 10 Hz to 3 kHz, more preferably 100 Hz to 1 kHz. This is because if the intermittent frequency is less than 10 Hz or exceeds 3 kHz, the stability of the plasma p is lowered, the conductive coating film 13 is not sufficiently modified, and the film quality is lowered.

  By this voltage application, the reaction gas g introduced between the upper electrode 3 and the lower electrode 5 becomes a non-equilibrium plasma state, and this non-equilibrium plasma p irradiates the conductive coating film 13, thereby The film 13 is modified into a high-quality film having low resistance and excellent transparency and flatness. Thereby, a low-resistance and high-quality transparent conductive film can be easily obtained.

Thus, since the conductive coating film 13 is modified by non-equilibrium plasma irradiation using the above plasma irradiation apparatus, a low-resistance and high-quality transparent conductive film can be easily formed without requiring a reduced-pressure atmosphere. can do.
Moreover, since this conductive coating film 13 can be easily formed by applying a conductive paint on the substrate 12, it is excellent in terms of mass productivity and cost.

For the non-equilibrium plasma irradiation of the present invention, the plasma irradiation apparatus shown in FIG. 5 can be used in addition to the above plasma irradiation apparatus.
The plasma irradiation apparatus is different from the plasma irradiation apparatus shown in FIG. 1 in that the plasma generating upper electrode 31 is made of a conductive metal plate, and the lower surface of the plasma generating upper electrode 31 is coated with an insulating film 32. A gas introduction pipe 33 and an insulating part 34 for introducing the reaction gas g are arranged on the side portions of the pair of the upper electrode 31 and the lower electrode 5 facing each other, and the reaction gas g sent out from the gas introduction pipe 33 is supplied to the insulating part 34. It is a point introduced between the upper electrode 31 and the lower electrode 5 via

As shown in FIGS. 5 and 6, the insulating portion 34 includes a plurality of holes 36 for allowing the reaction gas g to pass therethrough at predetermined intervals on the laterally long side surface 35 a of the box-shaped housing 35 (see FIG. 5 and FIG. 6). 6 is 7), and these holes 36 have a nozzle shape. The shape of the opening end of the hole 36 is circular.
The shape of the insulating portion 34 and the shape and number of the holes 36 can be appropriately selected according to the shape of the substrate 11 with film. Moreover, the hole 36 should just be what can make the flow of the reactive gas g uniform, for example, a flat nozzle etc. can be used conveniently.

  In this plasma irradiation apparatus, since the gas introduction pipe 33 and the insulating part 34 are provided between the upper electrode 31 and the lower electrode 5, the flow of the reaction gas g becomes uniform, and plasma can be stably generated. Therefore, the film-coated substrate 11 can be optimally modified under suitable conditions, and the in-plane uniformity of this modification process can be further improved.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely by Examples 1-5 and Comparative Examples 1-3, this invention is not limited by these Examples.

[Example 1]
Tin-doped indium oxide (ITO) fine particles (primary particle size: 20 nm) containing 5% Sn were dispersed in a methanol-diethylene glycol solution so as to have a concentration of 5% by weight to prepare a conductive paint.
This conductive paint was applied on a glass substrate by a spin coat method to form a conductive coating film having a film thickness of about 300 nm. Next, this conductive coating film is irradiated with non-equilibrium plasma with an output of 5 W / cm ² under atmospheric pressure using the plasma irradiation apparatus shown in FIGS. 1 and 2 to modify the conductive coating film, The transparent conductive film of Example 1 was produced. Here, a mixed gas of 99.5% He-0.5% H ₂ was used as the reaction gas. In addition, the plasma irradiation time was set to three types of 5 minutes, 10 minutes, and 30 minutes, and three types of transparent conductive films were produced.

The surface resistance (Ω / □) and visible light transmittance (%) of these three types of transparent conductive films were measured.
The measuring method is as follows.
(1) Surface resistance (Ω / □): Measured with Loresta (manufactured by Mitsubishi Chemical Corporation).
(2) Visible light transmittance: Measured with a haze meter (manufactured by Nippon Denshoku Co., Ltd.) according to Japanese Industrial Standard JIS K 7105 “Testing method for optical properties of plastics”.
The measurement results are shown in Table 1.
These three types of transparent conductive films were sufficiently densified and had low surface resistance. It was also found that the visible light transmittance was good.

[Example 2]
A conductive paint was prepared in the same manner as in Example 1.
Next, this conductive paint was applied on a glass substrate by a spin coating method to form a conductive coating film having a thickness of about 300 nm. Next, the conductive coating film was irradiated with non-equilibrium plasma with an output of 5 W / cm ² under atmospheric pressure using the plasma irradiation apparatus shown in FIGS. 5 and 6 to modify the conductive coating film. The transparent conductive film of Example 2 was produced. Here, a mixed gas of 98% He-2% H ₂ was used as the reaction gas. The plasma irradiation time was set to 3 minutes, 5 minutes, and 10 minutes, and three types of transparent conductive films were produced.

Subsequently, according to Example 1, the surface resistance (Ω / □) and visible light transmittance (%) of these three types of transparent conductive films were measured.
The measurement results are shown in Table 1.
These three types of transparent conductive films were sufficiently densified and had low surface resistance. It was also found that the visible light transmittance was good.

[Example 3]
8.00 g of indium (III) chloride tetrahydrate, 0.74 g of tin (II) chloride dihydrate and 30 g of trisodium citrate were dissolved in 700 mL of deoxygenated water with sufficient stirring, and the resulting solution was dissolved. Further, granular sodium hydroxide was added to adjust the pH to 7.0.
The solution was then warmed to 65 ° C. using a water bath. Thereafter, a reducing solution in which 6.00 g of sodium tetrahydroborate is dissolved in 80 g of deoxygenated water is added to the heated solution, and a reduction reaction is performed at 65 ° C. for 10 minutes. The temperature was lowered to room temperature. During this reduction process, the solution changed from colorless and transparent to brown, and became an In—Sn alloy fine particle dispersion.

Next, the In—Sn alloy fine particle dispersion was subjected to ultracleaning with deoxygenated water. Here, washing was repeated until the electrical conductivity of the filtrate reached 100 μS / cm. The In—Sn alloy fine particle dispersion after washing was stable, and the average particle size of the obtained In—Sn alloy fine particles was 10 nm.
Subsequently, the In—Sn alloy fine particles were dispersed in an ethanol-water mixed solution so as to have a concentration of 5% by weight to prepare a conductive paint.

Next, this conductive paint was applied onto a glass substrate by a spin coat method, and then baked at 250 ° C. under atmospheric pressure to form a conductive coating film having a film thickness of about 200 nm. Next, this conductive coating film is irradiated with non-equilibrium plasma with an output of 5 W / cm ² under atmospheric pressure using the plasma irradiation apparatus shown in FIGS. 1 and 2 to modify the conductive coating film, A transparent conductive film of Example 3 was produced. Here, a mixed gas of 98% He-2% H ₂ was used as the reaction gas. In addition, the plasma irradiation time was set to three types of 5 minutes, 10 minutes, and 30 minutes, and three types of transparent conductive films were produced.

Subsequently, according to Example 1, the surface resistance (Ω / □) and visible light transmittance (%) of these three types of transparent conductive films were measured.
The measurement results are shown in Table 1.
These three types of transparent conductive films were sufficiently densified and had low surface resistance. It was also found that the visible light transmittance was good.

[Example 4]
After 0.93 g of indium (III) isopropoxide and 0.13 g of tin (IV) isopropoxide were sufficiently dissolved in 40 g of toluene, 0.2 g of acetylacetone was added to prepare a conductive paint.
Next, this conductive paint was applied onto a glass substrate by a spin coating method to form a conductive coating film having a thickness of about 150 nm.

Next, the conductive coating film was irradiated with non-equilibrium plasma with an output of 5 W / cm ² under atmospheric pressure using the plasma irradiation apparatus shown in FIGS. 5 and 6 to modify the conductive coating film. A transparent conductive film of Example 4 was produced. Here, a mixed gas of 98% He-2% H ₂ was used as the reaction gas. The plasma irradiation time was set to 3 minutes, 5 minutes, and 10 minutes, and three types of transparent conductive films were produced.

Subsequently, according to Example 1, the surface resistance (Ω / □) and visible light transmittance (%) of these three types of transparent conductive films were measured.
The measurement results are shown in Table 1.
These three types of transparent conductive films were sufficiently densified and had low surface resistance. It was also found that the visible light transmittance was good.

[Example 5]
A conductive paint was prepared in the same manner as in Example 1.
Next, this conductive paint was applied on a glass substrate by a spin coating method to form a conductive coating film having a thickness of about 300 nm. Next, this conductive coating film is irradiated with non-equilibrium plasma with an output of 5 W / cm ² under atmospheric pressure using the plasma irradiation apparatus shown in FIGS. 1 and 2 to modify the conductive coating film, A transparent conductive film of Example 5 was produced. Here, a mixed gas of 97% He-3% H ₂ was used as the reaction gas. In addition, the plasma irradiation time was set to three types of 5 minutes, 10 minutes, and 30 minutes, and three types of transparent conductive films were produced.

Subsequently, according to Example 1, the surface resistance (Ω / □) and visible light transmittance (%) of these three types of transparent conductive films were measured.
The measurement results are shown in Table 1.
These three types of transparent conductive films were sufficiently densified and had low surface resistance. It was also found that the visible light transmittance was good.

[Comparative Example 1]
A conductive paint was prepared in the same manner as in Example 1.
Next, this conductive paint was applied on a glass substrate by a spin coating method to form a conductive coating film having a thickness of about 300 nm. Next, this conductive coating film was baked at 550 ° C. for 30 minutes under atmospheric pressure using a heating apparatus, and the transparent conductive film of Comparative Example 1 was produced.
Subsequently, according to Example 1, the surface resistance (Ω / □) and the visible light transmittance (%) of the transparent conductive film were measured.
The measurement results are shown in Table 1.

[Comparative Example 2]
A conductive paint was prepared in the same manner as in Example 1.
Next, this conductive paint was applied on a glass substrate by a spin coating method to form a conductive coating film having a thickness of about 300 nm. Next, this conductive coating film was irradiated with plasma with an output of 5 W / cm ² under atmospheric pressure using the plasma irradiation apparatus shown in FIGS. 1 and 2 to modify the conductive coating film. 2 transparent conductive films were produced. Here, He gas was used as the reaction gas. In addition, the plasma irradiation time was set to 2 minutes and 5 minutes, and two types of transparent conductive films were produced.
Subsequently, according to Example 1, the surface resistance (Ω / □) and visible light transmittance (%) of these two types of transparent conductive films were measured.
The measurement results are shown in Table 1.

[Comparative Example 3]
A conductive paint was prepared in the same manner as in Example 1.
Next, this conductive paint was applied on a glass substrate by a spin coating method to form a conductive coating film having a thickness of about 300 nm. Next, the conductive coating film was irradiated with arc plasma with an output of 100 W / cm ² under atmospheric pressure using an arc plasma generator to modify the conductive coating film, and the transparent conductive film of Comparative Example 3 was used. Was made. Here, a mixed gas of 80% N ₂ -20% O ₂ was used as the reaction gas. The plasma irradiation time was set to 5 minutes. According to Example 1, the surface resistance (Ω / □) and the visible light transmittance (%) were measured for the obtained transparent conductive film.
The measurement results are shown in Table 1.
In the obtained transparent conductive film, many arc spots due to arc plasma were generated. Moreover, since the coating film was peeled off, the surface resistance was high, and a defect due to an arc spot was generated, so that the film had a low visible light transmittance.

According to Table 1, it turned out that the transparent conductive film of Examples 1-5 has low surface resistance compared with the transparent conductive film of Comparative Examples 1-3.
Moreover, even when any one of an organometallic compound, a metal inorganic salt, and a metal organic salt was added to each of the conductive paints of Examples 1 to 5, the resulting conductive coating film was subjected to atmospheric pressure and a reducing atmosphere. It was confirmed that a low-resistance transparent conductive film can be obtained by irradiating plasma, or electromagnetic waves such as laser and ultraviolet rays.

  The method for forming a transparent conductive film of the present invention is a low-resistance and high-quality transparent film that does not require a reduced pressure atmosphere by irradiating a conductive coating film with non-equilibrium plasma to modify the conductive coating film. Since the conductive film can be easily formed, various display devices such as plasma display (PDP), liquid crystal display (LCD), electroluminescence display (EL), cathode ray tube (CRT), projection (PJTV), etc. Of course, the present invention can be applied to various industrial fields such as windows for automobiles, buildings, etc., and the effect is great.

It is sectional drawing which shows an example of the plasma irradiation apparatus used for the nonequilibrium plasma irradiation of this invention. It is a partial top view which shows the upper electrode for plasma generation of this plasma irradiation apparatus. It is a fragmentary top view which shows the modification of the upper electrode for plasma generation of this plasma irradiation apparatus. It is a fragmentary top view which shows the other modification of the upper electrode for plasma generation of this plasma irradiation apparatus. It is sectional drawing which shows another example of the plasma irradiation apparatus used for the nonequilibrium plasma irradiation of this invention. It is a front view which shows the insulation part of this plasma irradiation apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas introduction pipe 2 Insulating part 2a Vent 3 Upper electrode for plasma generation 4 Insulating coating 5 Lower electrode for plasma generation 6 Power source for plasma generation 11 Base material with film 12 Base material 13 Conductive coating film 15 Hole 17 Hole 18 Plasma generation Upper electrode 20 hole 21 Upper electrode for plasma generation 31 Upper electrode for plasma generation 32 Insulating coating 33 Gas introduction pipe 34 Insulating portion 35 Housing 35a Side surface 36 Hole g Reaction gas p Non-equilibrium plasma

Claims (7)

  A substrate having a conductive coating film formed on one main surface is disposed between a pair of opposing electrodes, and a reaction gas at or near atmospheric pressure is introduced onto the conductive coating film, and the pair of electrodes A transparent conductive film is formed by applying a voltage in between to bring the reactive gas into a non-equilibrium plasma state and irradiating the conductive film with the non-equilibrium plasma to modify the conductive film. A method for forming a transparent conductive film.   2. The transparent conductive film according to claim 1, wherein the reaction gas is a rare gas or a mixed gas containing one or more selected from a group of a rare gas and hydrogen, ammonia, and nitrogen. Forming method.   3. The method for forming a transparent conductive film according to claim 1, wherein the voltage is one or more selected from the group consisting of a pulse voltage, an AC voltage, a high frequency voltage, and a bipolar pulse voltage.   4. The method for forming a transparent conductive film according to claim 1, wherein the substrate is made of glass or an organic polymer compound.   The conductive coating film contains one or more of organic metal compounds, metal inorganic acid salts, metal organic acid salts, metal oxide fine particles, and fine particles composed of metals or alloys. The method for forming a transparent conductive film according to any one of claims 1 to 4.   The conductive coating film contains one or more of organic metal compounds, metal inorganic acid salts, metal organic acid salts, metal oxide fine particles, and fine particles made of metal or alloy. The method for forming a transparent conductive film according to claim 1, wherein the transparent conductive film is formed by coating the film.   A transparent conductive film formed by the method for forming a transparent conductive film according to claim 1.

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