JP4730768B2 - Method for forming transparent conductive film and transparent conductive film - Google Patents

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. In electronic devices and devices having electrodes such as display panels such as image display devices and touch panels, solar cells such as silicon-based solar cells, wet solar cells, or Gretzel cells, have both translucency and conductivity. High-quality transparent conductive film can be stably used for functional parts that require light transmission or low resistance at the same time as functional parts that require optical properties, or for optical components such as glass and lenses. It relates to a technology that can be formed.

Conventionally, image display devices such as plasma display (PDP), liquid crystal display (LCD), electroluminescence display (EL), cathode ray tube (CRT), projection (PJTV), display panels such as touch panels, silicon solar cells, wet solar cells In an electronic device or device having an electrode such as a solar battery such as a Gretzel cell or the like, a functional component that needs to have both translucency and conductivity, or an optical member such as glass and a lens. In a functional component or the like that needs to have both translucency and low resistance as an antifogging function, a flat panel in which a transparent conductive film is formed on a transparent substrate is used. As a base material, a metal substrate, an organic polymer film, paper, etc. other than transparent substrates, such as a glass substrate and a translucent ceramic substrate, are used.
Conventionally, methods for forming a transparent conductive film on a transparent substrate can be broadly divided into two methods, a dry method and a wet method, and many studies have been energetically performed so far.

The dry method is a method of forming a transparent conductive film made of a metal or a metal oxide on a transparent substrate by a vacuum deposition method, an ion plating method, a sputtering method or the like.
Further, the wet method is a method of forming a transparent conductive film by a coating method, a method of forming a metal oxide thin film on a transparent substrate by a sol-gel method using hydrolysis and condensation polymerization reaction of metal alkoxide, metal particles Or the method of apply | coating the coating liquid which disperse | distributed the metal oxide particle to the organic solvent on a transparent base material etc. are known (for example, refer patent document 1).
In order to stabilize the dispersion state of the particles and improve the in-plane uniformity of the obtained film, a coating solution using metal fine particles or metal oxide fine particles having a smaller particle diameter has been proposed. (For example, refer to Patent Document 2).

However, with the conventional dry method, high-quality film formation is possible, but since a relatively high degree of vacuum is required, the manufacturing apparatus becomes quite expensive, resulting in an increase in film formation cost. There was a problem that the obtained transparent conductive film would be very expensive. In addition, since it is a batch type, the number of production per lot is limited, and it is difficult to increase productivity.
On the other hand, in the conventional wet method, since the coating film apparatus is inexpensive, an inexpensive transparent conductive film can be provided, and continuous production is possible, so that it is easy to increase productivity. However, there is a problem that 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 of the conventional dry method and wet method, a transparent conductive film having a low resistance can be obtained by irradiating plasma on the coating film in the air without requiring heat treatment or a reduced pressure atmosphere. There has been proposed a method for forming the.
A film forming technique using plasma is a technique for effectively modifying a coating film by promoting the effects of electrons, ions, excited molecules, and radical species in the plasma.
JP-A-60-220507 Japanese Patent Laid-Open No. 11-31417

However, in the conventional technology using plasma, when a conductive coating film is brought close to the plasma, electrons in the plasma move within the coating surface, and sparks and arcing occur at the boundary between the coating film and the plasma. There is a problem that defects such as generation, streamers, arc spots are formed, and the coating film peels off, is partially scraped, has holes, or discolors. I understood.
In particular, when a conductive coating is brought close to a plasma region (for example, an arc column) in which electrons are actively flowing, the generation of arc spots becomes remarkable, and a uniform and high-quality transparent conductive film can be stably formed. There was a problem that it was difficult.
Further, when the coating film is irradiated with plasma, there is a problem that the plasma does not reach the surface of the coating film due to the influence of the interface between the substrate and the reactive gas.

  The present invention has been made in order to solve the above-mentioned problems, and by irradiating the coating film with plasma in the air, high-quality transparent conductive material is not required without requiring heat treatment or a reduced-pressure atmosphere. Another object of the present invention is to provide a transparent conductive film forming method and a transparent conductive film which can form a film stably and are excellent in mass productivity and cost by using a coating method.

  As a result of intensive studies, the present inventors applied a conductive paint on a base material to form a coating film, and this coating film was irradiated with plasma generated under atmospheric pressure, whereby heat treatment was performed. It has been found that a high-quality transparent conductive film can be formed stably and at low cost without requiring a reduced pressure atmosphere, and the present invention has been completed.

  That is, in the method for forming a transparent conductive film of the present invention, a conductive paint is applied on a substrate to form a coating film, a reaction gas is introduced onto the coating film at atmospheric pressure, and the reaction gas is converted into plasma. Forming a weakly ionized plasma state plasma and irradiating the weakly ionized plasma state plasma to the coating film to modify the coating film, thereby forming a transparent conductive film on the substrate It is characterized by.

The reaction gas preferably contains one or more selected from the group of nitrogen, rare gas, oxygen, ozone, hydrogen, and ammonia.
The reactive gas preferably contains one or more organometallic compounds.

It is preferable to provide a rectifying plate between the plasma generating part for generating the plasma and the coating film to control the flow of the plasma.
More preferably, the plasma generation unit includes a plasma generation electrode, and the rectifying plate is provided between the plasma generation electrode and the coating film.
The substrate is preferably made of glass or an organic polymer compound.
The conductive paint preferably contains any one of an organic metal compound, a metal inorganic acid salt, a metal organic acid salt, a metal oxide fine particle, and a fine particle composed of a metal or an alloy.

  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 is introduced onto the coating film under atmospheric pressure, and the reactive gas is turned into plasma to generate a weakly ionized plasma state plasma. Since the coating film is modified by irradiating the coating film with a high temperature, a high-quality and low-resistance transparent conductive film can be easily formed without requiring a heat treatment or a reduced-pressure atmosphere.
Moreover, since a coating film is formed by applying a conductive paint on a substrate, a transparent conductive film excellent in mass productivity and cost can be obtained.

In addition, since the coating film is irradiated with plasma in a weakly ionized plasma state, a high-quality transparent conductive film that does not cause defects such as arc spots on the film surface can be obtained.
Further, if a rectifying plate is provided between the plasma generating electrode for generating the plasma and the coating film, the plasma can be made to reach the surface of the coating film by controlling the flow of the plasma. The coating film can be reliably irradiated with plasma, and a high-quality transparent conductive film can be stably obtained.

According to the transparent conductive film of the present invention, since it was formed by the method for forming a transparent conductive film of the present invention, it is possible to reduce the resistance and improve the quality of the transparent conductive film without requiring heat treatment or a reduced pressure atmosphere. it can.
Moreover, since this transparent conductive film is obtained by modifying the coating film by plasma irradiation, the in-plane uniformity of the film can be improved and the surface resistance can be lowered despite the thin film thickness.

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.

  In the method for forming a transparent conductive film of the present invention, a conductive paint is applied onto a substrate to form a coating film, and a reaction gas is introduced onto the coating film at atmospheric pressure to convert the reaction gas into plasma. A method of forming a transparent conductive film on the substrate by generating a plasma in a weakly ionized plasma state and irradiating the coating film with the plasma in a weakly ionized plasma state to modify the coated film .

"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.
What is necessary is just to select suitably the thing containing the metal element to be used for the organometallic compound etc. to be used, and it is not specifically limited.

  As the organometallic compound, for example, metal alkyl and metal aryl such as indium, tin, zinc, cadmium, gallium, antimony, and aluminum are preferably used, and metal acetylacetonate such as indium acetylacetonate is particularly suitable. It is. Moreover, metal alkoxides, such as indium isopropoxide, can also be used conveniently.

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 above-mentioned 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, tin oxide, zinc oxide, cadmium oxide, gallium oxide, antimony oxide, and aluminum oxide, or tin-added indium oxide obtained by adding other metal elements to these oxides. Fine particles such as (ITO), antimony-added tin oxide (ATO), zinc-added indium oxide (IZO) and aluminum-added zinc oxide (AZO) are preferably used.
In particular, as the metal oxide constituting the transparent conductive film, tin-added indium oxide (ITO), antimony-added tin oxide (ATO), zinc-added indium oxide (IZO), aluminum-added zinc oxide (AZO), indium oxide (In) ₂ O ₃ ), tin oxide (SnO ₂ ) and the like are preferably used.

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 of the metal oxide fine particles is 1 nm or more and 30 nm or less, the sinterability between the metal oxide fine particles is improved and the coating film is easily densified, which is particularly preferable.

Examples of the metal / alloy fine particles include metal fine particles such as indium, tin, zinc, cadmium, gallium, antimony, and aluminum, or alloys such as indium-tin alloy, indium-zinc alloy, antimony-tin alloy, and zinc-aluminum alloy. Fine particles 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 organic solvent and / or water used can be easily applied according to the organometallic compound, metal inorganic acid salt, metal organic acid salt, metal oxide fine particle, metal / alloy fine particle used, and has a desired film thickness. May be selected as appropriate so that can be obtained. For example, when metal oxide fine particles or metal / alloy fine particles are dissolved or dispersed in an organic solvent and / or water, the amount of fine particles is preferably 1 to 10% by weight based on the total amount of the solvent.

"Coating"
The conductive paint is applied onto a substrate to form a coating film.
It does not specifically limit as a base material, A glass substrate and a plastic substrate (organic polymer compound substrate) can be mentioned, As a shape, a flat plate, a film, a sheet | seat, etc. may be sufficient. As the plastic substrate, a transparent plastic sheet or a transparent plastic film is preferable.

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, It can be appropriately selected from acrylic, polyethylene (PE), nylon, polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), polyfluoroacetylene (PFA) and the like.
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 ultrasonic waves are applied to the cleaning liquid during this cleaning, the cleaning power is greatly improved. This is preferable.

As a coating method, for example, a usual method such as a spin coating method, a spray coating method, an ink jet method, a dip method, a roll coating method, a screen printing method, or the like is used. The conductive paint is applied onto the substrate by these application methods.
Since the conductive coating applied on the substrate contains a solvent, the substrate coated with the conductive coating is dried at room temperature in the atmosphere, or at a predetermined temperature, for example, 50 ° C. to 80 ° C. By drying at a temperature of ° C., the solvent contained in the conductive paint is dissipated to form 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.

"Plasma irradiation"
A reactive gas is introduced onto the coating film at atmospheric pressure, and the reactive gas is converted into plasma to generate a plasma in a weakly ionized plasma state. A transparent conductive film is formed on the substrate by modifying the coating film.
In this case, the reactive gas is selected from the group consisting of nitrogen (N ₂ ), He, Ne, Ar, Kr, Xe and other rare gases, oxygen (O ₂ ), ozone (O ₃ ), and hydrogen (H ₂ ). In addition, a mixed gas containing one kind or two or more kinds is used.

This reaction gas may contain one or more organic metal compounds.
In addition, water, hydrogen peroxide, alcohols and the like may be added to the reaction gas.
When water is added to the reaction gas, the plasma activation power can be improved and the electrode can be effectively cooled, so that there is an effect of suppressing the consumption of the electrode and further suppressing the generation of ozone. Further, when hydrogen peroxide or alcohols are added, the plasma activity is further improved, which is suitable for film modification.

Next, a plasma irradiation apparatus used for this plasma irradiation will be described.
FIG. 1 is a cross-sectional view showing the plasma irradiation apparatus, and FIG. 2 is a cross-sectional view showing a rectifying plate of the plasma irradiation apparatus. In the figure, 1 is a gas introduction pipe for introducing a reactive gas, 2 is a gas introduction pipe 1 The plasma generation unit 2 includes a pair of plasma generation electrodes 3 and 3 provided below the front end of the gas introduction tube 1 and sandwiching the center line Ax. The plasma generating power source 4 is configured to generate a plasma between the plasma generating electrodes 3 and 3 by applying a high voltage between the plasma generating electrodes 3 and 3.

A substrate 6 with a film is disposed below the plasma generating unit 2. This film-coated base material 6 is obtained by forming a coating film 8 formed by applying and drying the above conductive paint on a transparent base material 7 such as a glass substrate or a plastic substrate.
Between this plasma generation part 2 and the coating film 8, plate-shaped rectifying plates 10 and 10 made of a semiconductor or an insulator for controlling the flow of plasma are provided.
In FIG. 1, rectifying plates 10 and 10 are provided between a pair of plasma generating electrodes 3 and 3 and a coating film 8.

  The plasma generating power source 4 may be any power source as long as it can apply a high voltage between the plasma generating electrodes 3 and 3. For example, a high frequency pulse power source is preferably used. When this high-frequency pulse power supply is used, the generation of heat due to plasma can be suppressed, which is particularly effective when a plastic substrate (organic polymer compound substrate) is used. This plasma can be arbitrarily controlled by adjusting the plasma output, frequency, pulse width, and intermittent frequency of the plasma generating power source 4.

The rectifying plates 10 and 10 are arranged on one plane (here, on a horizontal plane) so that the end faces 10a and 10a face each other with the center line Ax as the axis of symmetry, and a gap b is provided between the rectifying plates 10 and 10. By providing this, the interval b becomes the slit 11 for controlling the flow of the arc column P and the plume P ′.
By providing these rectifying plates 10 and 10 between the plasma generating electrodes 3 and 3 and the coating film 8, an arc column P and plume P generated when a high voltage is applied between the plasma generating electrodes 3 and 3. 'Can control the flow.

The size and shape of the slit 11 may be any shape that can control the flow of plasma, and is appropriately selected depending on the plasma irradiation mode. The slit 11 may be appropriately changed to another shape such as a mesh shape or a lattice shape.
The range of the interval b is 0.5 to 30 mm, preferably 1 to 10 mm. If the distance b is less than 0.5 mm or exceeds 30 mm, the activation energy of the plume P ′ cannot be sufficiently applied to the coating film 8.

Plasma is irradiated to a coating film using this plasma irradiation apparatus.
First, a base material 6 with a film in which a coating film 8 is formed on a base material 7 such as a glass substrate is prepared. The rectifying plates 10 and 10 are disposed below and between the coating film 8 and the plasma generating electrodes 3 and 3.

  Next, the reaction gas g is introduced between the plasma generating electrodes 3 and 3 through the gas introduction tube 1, and a high voltage such as a high frequency pulse voltage is applied between the plasma generating electrodes 3 and 3 through the plasma generating power source 4. By applying and generating arc discharge under atmospheric pressure, plasma is generated between the plasma generating electrodes 3 and 3.

Examples of the reactive gas g include nitrogen (N ₂ ), rare gases such as He, Ne, Ar, Kr, and Xe, oxygen (O ₂ ), ozone (O ₃ ), hydrogen (H ₂ ), and ammonia (NH ₃ ). A gas containing at least one of them is used. For example, a mixed gas such as 80 v / v% N ₂ -20 v / v% O ₂ or the like.

Further, if an organometallic component is added to the reaction gas g, the sinterability of the film can be improved, which is effective in obtaining a high-quality film.
When water is added to the reaction gas g, the plasma activation power is improved, and the electrode is effectively cooled, so that consumption of the electrode is suppressed, and generation of ozone is further suppressed. Moreover, if hydrogen peroxide or alcohols are added to the reaction gas g, the plasma activation power is further improved, which is suitable for film modification.

This plasma is composed of an arc column P and a plume P ′, and emits active particles such as electrons, ions, radicals, excited atoms / molecules and the like.
Here, the arc column P is weak electric field plasma and is a state in which electrons actively flow. On the other hand, the plume P ′ generated at the tip of the arc column P is a strong electric field plasma, which is a plasma state with a low ionization degree.
When the conductive coating film 8 is irradiated with the arc column P in the strong electric field state, defects such as arc spots are likely to occur in the coating film 8. Therefore, the coating film 8 is irradiated with a plume P ′ having a weak electric field generated at the tip of the arc column P so as not to cause the above problem.

The range of the plasma output is 10 to 1000 W / cm ² , preferably 50 to 300 W / cm ² . If the plasma output is less than 10 W / cm ² , the activation energy of the plume P ′ cannot be sufficiently applied to the coating film 8. On the other hand, if it exceeds 1000 W / cm ² , the active energy of the plume P ′ is too large, and there is a risk that thermal damage may occur in the coating film 8 and the substrate 7.
The frequency range is 1 to 30 kHz, preferably 10 to 25 kHz. When the frequency is less than 1 kHz or more than 30 kHz, the stability of the plasma becomes poor, and the active energy of the plume P ′ cannot be sufficiently applied to the coating film 8.

The range of the pulse width is 1 to 20 μs, preferably 2 to 10 μs. If the pulse width is less than 1 μs or exceeds 20 μs, the stability of the plasma becomes poor, and the activation energy of the plume P ′ cannot be sufficiently applied to the coating film 8.
The range of the intermittent frequency is 10 to 3 kHz, preferably 100 to 1 kHz. When the intermittent frequency is less than 10 Hz or exceeds 3 kHz, the stability of the plasma becomes poor, and the activation energy of the plume P ′ cannot be sufficiently applied to the coating film 8.

Here, the distance d between the plasma generating electrodes 3, 3 and the coating film 8, the plasma output, and the plasma irradiation are controlled depending on the shape of the film-coated substrate 6 so that the plume P ′ is efficiently irradiated onto the coating film 8. The angle b and the interval b between the rectifying plates 10 and 10 that control the plasma flow are adjusted as appropriate.
Here, the distance d between the plasma generating electrodes 3 and 3 and the coating film 8 was adjusted, and the optimum distance d was set to 1 to 50 mm. If the distance d is less than 1 mm, the plume P ′ becomes unstable and the substrate 7 itself is heated, which is not preferable. On the other hand, if the distance d exceeds 50 mm, the active energy of the plume P ′ is sufficient for the coating film 8. It is because it cannot be granted to.

  The plasma irradiation angle θ is the center line Ax between the plasma generating electrodes 3 and 3, that is, the central axis in the flow direction of the arc column P and plume P ′, and the surface of the coating film 8, that is, the arc column P and plume. It is an angle made with the irradiation surface of P ′, and is set in accordance with the shape of the substrate 6. The range of the plasma irradiation angle θ is 0.1 to 179.9 degrees, preferably 10 to 170 degrees. When the plasma irradiation angle θ is less than 0.1 degrees or exceeds 179.9 degrees, the activation energy of the plume P ′ cannot be sufficiently applied to the coating film 8.

  When the coating film 8 is irradiated with the plume P ′ at the interval b between the current plates 10 and 10 and the plasma irradiation angle θ, the coating film 8 contains an organic metal compound, a metal inorganic acid salt, a metal organic acid salt, or the like. Can react with each other to obtain a uniform transparent conductive film 9 with low resistance. When metal oxide fine particles, metal / alloy fine particles, etc. are contained, these fine particles are fused together. Thus, the low resistance transparent conductive film 9 can be obtained.

According to the present invention, since the plume P ′ is irradiated to the coating film 8, the activation energy of the plume P ′ can be sufficiently imparted to the coating film 8, and thus the transparent conductive film 9 with high quality and low resistance can be obtained. It can be formed easily.
Moreover, since a coating film is formed by applying a conductive paint on the substrate 7, a transparent conductive film excellent in mass productivity and cost can be obtained.
Further, since the plume P ′ is irradiated onto the coating film 8, a high-quality transparent conductive film that does not cause a defect such as an arc spot on the film surface can be obtained.

In the present embodiment, the case where arc discharge, particularly gliding arc is used as the plasma source has been described. However, as the plasma source, in addition to the above arc discharge, AC / DC / pulse glow discharge, dielectric barrier discharge, An RF discharge, a microwave discharge, a PEN jet (see the following document), and the like can also be used.
Literature: Jungo Toshifuji, Takashi Katsumata, Hirofumi Takikawa, Tateki Sakakibara, Ichiro Shimizu: "Cold arc-plasma jet under atomospheric pressure for surface modification", Surface and Coatings Technology vol.171, (2003) pp302-306

  In particular, in the case of glow discharge, dielectric barrier discharge, RF discharge, and microwave discharge, the electrode and the plasma may not be in direct contact with each other. When using this type of discharge, the plasma flow is controlled between the plasma generator and the coating so that the strongly ionized plasma does not touch the coating and damage the coating. It is preferable to provide a rectifying plate.

EXAMPLES Hereinafter, although this invention is demonstrated concretely by Examples 1-6 and a comparative example, this invention is not limited by these Examples.
[Example 1]
In-Sn alloy powder obtained by reducing tin-added indium oxide (ITO) fine particles (primary particle size: 100 nm or less) containing 5 wt% of Sn with a mixed gas of 50% Ar-50% H ₂ at 400 ° C. Got. The obtained In—Sn alloy powder had an average primary particle size of 20 nm. Next, this In—Sn alloy powder was dispersed in cyclohexane 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 spin coating to form a coating film having a film thickness of about 300 nm. The resulting coating film was modified by irradiating the plume P 'in a weakly ionized plasma state at atmospheric pressure using a plasma irradiation apparatus shown in FIG. 1 without using a heating device.

Here, the irradiation conditions are an output of 80 W / cm ² , a frequency of 20 kHz, a pulse width of 2 μs, an intermittent frequency of 300 Hz, a distance d between the plasma generating electrodes 3 and 3 and the coating film 8 of 25 mm, and a plasma irradiation angle θ of 70 degrees. As a reaction gas, an 80 v / v% N ₂ -20 v / v% O ₂ mixed gas was used, and the flow rate of this mixed gas was set to 20 L / min. The interval b between the current plates 10 and 10 was 3 mm.

Here, the plasma irradiation time was set to 3 minutes and 2/5, and the surface resistance (sheet resistance: Ω / □) and visible light transmittance (%) of each transparent conductive film obtained were measured.
The measuring method is as follows.
Surface resistance (sheet resistance Ω / □): measured with Loresta (Mitsubishi Chemical Corporation) Visible light transmittance: measured with Nippon Denshoku Co., Ltd. haze meter according to Japanese Industrial Standard “JIS K 7105” Measurement results are shown in Table 1. Shown in
The obtained transparent conductive film was sufficiently dense and the surface resistance was small. Further, no arc spot or the like was observed on the coating surface during the treatment, and no trace of the occurrence of the arc spot or the like was observed in the observation after the treatment.

[Example 2]
A conductive coating material was prepared by dispersing tin-added indium oxide (ITO) fine particles (primary particle size: 100 nm or less) containing 5 wt% of Sn in isopropyl alcohol so as to have a concentration of 5 wt%.
This conductive paint was applied on a glass substrate by spin coating to form a coating film having a film thickness of about 300 nm. The obtained coating film is modified by irradiating the plume P ′ in a weakly ionized plasma state under atmospheric pressure using the plasma irradiation apparatus shown in FIGS. 1 and 2 without using a heating device. It was.

Here, the irradiation conditions are an output of 96 W / cm ² , a frequency of 23 kHz, a pulse width of 2 μs, an intermittent frequency of 300 Hz, a distance d between the plasma generating electrodes 3 and 3 and the coating film 8 of 25 mm, and a plasma irradiation angle θ of 60 degrees. The reaction gas was a 97 v / v% N ₂ -3 v / v% H ₂ mixed gas, and the flow rate of this mixed gas was 20 L / min. The interval b between the current plates 10 and 10 was 3 mm.

Here, the plasma irradiation time is 5 minutes, 10 minutes, and 3 times 15 minutes, and the surface resistance (sheet resistance: Ω / □) and visible light transmittance (%) of each transparent conductive film obtained are: The measurement was performed according to Example 1.
The measurement results are shown in Table 2.
The obtained transparent conductive film was sufficiently dense and the surface resistance was small. Further, no arc spot or the like was observed on the coating surface during the treatment, and no trace of the occurrence of the arc spot or the like was observed in the observation after the treatment.

[Example 3]
2 g of indium nitrate trihydrate (In (NO ₃ ) ₃ .3H ₂ O) and 0.16 g of tin (IV) chloride pentahydrate (SnCl ₄ .5H ₂ O) were dissolved in 2 g of acetylacetone, Further, 5 g of acetone was added, and then the mixture was stirred for 24 hours at room temperature (25 ° C.) using a magnetic stirrer to prepare a conductive paint.
This conductive paint was applied on a glass substrate by a spin coating method to form a coating film. The obtained coating film is modified by irradiating the plume P ′ in a weakly ionized plasma state under atmospheric pressure using the plasma irradiation apparatus shown in FIGS. 1 and 2 without using a heating device. It was.

Here, the irradiation conditions are an output of 120 W / cm ² , a frequency of 20 kHz, a pulse width of 3 μs, an intermittent frequency of 300 Hz, a distance d between the plasma generating electrodes 3 and 3 and the coating film 8 of 25 mm, and a plasma irradiation angle θ of 80 degrees. As a reaction gas, a 50 v / v% N ₂ -50 v / v% O ₂ mixed gas was used, and the flow rate of this mixed gas was set to 20 L / min. The interval b between the current plates 10 and 10 was 3 mm.

The formation of the coating film and the plasma irradiation were repeated three times in total to produce a transparent conductive film having a film thickness of about 300 nm.
For each of the obtained transparent conductive films, the surface resistance (sheet resistance: Ω / □) and the visible light transmittance (%) were measured according to Example 1.
Table 3 shows the measurement results.
The obtained transparent conductive film was sufficiently dense and the surface resistance was small. Further, no arc spot or the like was observed on the coating surface during the treatment, and no trace of the occurrence of the arc spot or the like was observed in the observation after the treatment.

[Example 4]
Indium isopropoxide _{(In (O-i-C} 3 H 7)) 0.4g, tin isopropoxide _{(Sn (O-i-C} 3 H 7)) and 0.03g was dissolved in cyclohexane 10 g, then The mixture was stirred for 24 hours at room temperature (25 ° C.) in an argon (Ar) atmosphere using a magnetic stirrer to prepare a conductive paint.
This conductive paint was applied on a glass substrate by a spin coating method to form a coating film. The obtained coating film is modified by irradiating the plume P ′ in a weakly ionized plasma state under atmospheric pressure using the plasma irradiation apparatus shown in FIGS. 1 and 2 without using a heating device. It was.

Here, the irradiation conditions are an output of 80 W / cm ² , a frequency of 20 kHz, a pulse width of 2 μs, an intermittent frequency of 300 Hz, a distance d between the plasma generating electrodes 3 and 3 and the coating film 8 of 25 mm, and a plasma irradiation angle θ of 80 degrees. As a reaction gas, a 70 v / v% N ₂ -30 v / v% O ₂ mixed gas was used, and the flow rate of this mixed gas was set to 20 L / min. The interval b between the current plates 10 and 10 was 3 mm.

The formation of the coating film and the plasma irradiation were repeated 5 times in total to produce a transparent conductive film having a film thickness of about 300 nm.
For each of the obtained transparent conductive films, the surface resistance (sheet resistance: Ω / □) and the visible light transmittance (%) were measured according to Example 1.
Table 4 shows the measurement results.
The obtained transparent conductive film was sufficiently dense and the surface resistance was small. Further, no arc spot or the like was observed on the coating surface during the treatment, and no trace of the occurrence of the arc spot or the like was observed in the observation after the treatment.

[Example 5]
Into a separable flask, tin-added indium oxide (ITO) fine particles (primary particle size: 100 nm or less) containing 5 wt% of Sn and acetic acid were added, and then a reflux apparatus was assembled using the separable flask to determine the boiling point of acetic acid. Under reflux for 24 hours, a basic indium acetate-tin salt was synthesized.
2.5 g of the obtained basic indium acetate-tin salt was dissolved in ₂ g of diethanolamine (DEA) and 19 g of absolute ethanol (C ₂ H ₅ OH), and then 24 hours at room temperature (25 ° C.) using a magnetic stirrer. The mixture was stirred for a time to prepare a conductive paint.

  This conductive paint was applied on a glass substrate by a spin coating method to form a coating film. The obtained coating film is modified by irradiating the plume P ′ in a weakly ionized plasma state under atmospheric pressure using the plasma irradiation apparatus shown in FIGS. 1 and 2 without using a heating device. It was.

Here, the irradiation conditions are an output of 96 W / cm ² , a frequency of 23 kHz, a pulse width of 2 μs, an intermittent frequency of 300 Hz, a distance d between the plasma generating electrodes 3 and 3 and the coating film 8 of 25 mm, and a plasma irradiation angle θ of 80 degrees. As a reaction gas, 75 v / v% N ₂ -25 v / v% O ₂ mixed gas was used, and the flow rate of this mixed gas was set to 20 L / min. The interval b between the current plates 10 and 10 was 3 mm.

Here, the plasma irradiation time is 5 minutes, 10 minutes, and 3 times 15 minutes, and the surface resistance (sheet resistance: Ω / □) and visible light transmittance (%) of each transparent conductive film obtained are: The measurement was performed according to Example 1.
Table 5 shows the measurement results.
The obtained transparent conductive film was sufficiently dense and the surface resistance was small. Further, no arc spot or the like was observed on the coating surface during the treatment, and no trace of the occurrence of the arc spot or the like was observed in the observation after the treatment.

[Example 6]
A conductive coating material was prepared by dispersing tin-added indium oxide (ITO) fine particles (primary particle size: 100 nm or less) containing 5 wt% of Sn in isopropyl alcohol so as to have a concentration of 5 wt%.
This conductive paint was applied on a glass substrate by a spin coat method to form a coating film having a thickness of about 250 nm. The obtained coating film is modified by irradiating the plume P ′ in a weakly ionized plasma state under atmospheric pressure using the plasma irradiation apparatus shown in FIGS. 1 and 2 without using a heating device. It was.

Here, the irradiation conditions are an output of 72 W / cm ² , a frequency of 20 kHz, a pulse width of 3 μs, an intermittent frequency of 300 Hz, a distance d between the plasma generating electrodes 3 and 3 and the coating film 8 of 25 mm, and a plasma irradiation angle θ of 60 degrees. The plasma irradiation time was 15 minutes. In addition, as a reaction gas, a mixed solution of trimethylindium (In (CH ₃ ) ₃ ) and tetraethyltin (Sn (C ₂ H ₅ ) ₄ ) is heated to 80 ° C., and 80 v / v% N is contained in the mixed solution. _A gas bubbled with a mixed gas of 2-20 v / v% O ₂ was used, and the flow rate of the reaction gas was 15 L / min. The interval b between the current plates 10 and 10 was 3 mm.

The film thickness of the obtained transparent conductive film was about 300 nm. Thereafter, the surface resistance (sheet resistance: Ω / □) and visible light transmittance (%) of the transparent conductive film were measured according to Example 1.
Table 6 shows the measurement results.
The obtained transparent conductive film was sufficiently dense and the surface resistance was small. Moreover, generation | occurrence | production of the arc spot etc. was not seen by the coating-film surface.

[Comparative Example 1]
A conductive coating material was prepared by dispersing tin-added indium oxide (ITO) fine particles (primary particle size: 100 nm or less) containing 5 wt% of Sn in isopropyl alcohol so as to have a concentration of 5 wt%.
This conductive paint was applied on a glass substrate by spin coating to form a coating film having a film thickness of about 300 nm.

Subsequently, this coating film was baked for 30 minutes at the maximum holding temperature under atmospheric pressure using a heating apparatus to obtain a transparent conductive film.
Here, the maximum holding temperature was set to three types of 300 ° C, 400 ° C, and 500 ° C. The surface resistance (sheet resistance: Ω / □) and visible light transmittance (%) of each transparent conductive film obtained were measured according to Example 1.
Table 7 shows the measurement results.
In the obtained transparent conductive film, the occurrence of arc spots was remarkable and the surface resistance was large.

[Comparative Example 2]
A conductive coating material was prepared by dispersing tin-added indium oxide (ITO) fine particles (primary particle size: 100 nm or less) containing 5 wt% of Sn in isopropyl alcohol so as to have a concentration of 5 wt%.
This conductive paint was applied on a glass substrate by spin coating to form a coating film having a film thickness of about 300 nm.

Irradiation of the arc column P, which is a strong electric field plasma, under atmospheric pressure using the plasma irradiation apparatus shown in FIG. 1 and FIG. It was.
Here, the irradiation conditions are an output of 80 W / cm ² , a frequency of 20 kHz, a pulse width of 3 μs, an intermittent frequency of 300 Hz, a distance d between the plasma generating electrodes 3 and 3 and the coating film 8 of 25 mm, and a plasma irradiation angle θ of 80 degrees. As a reaction gas, an 80 v / v% N ₂ -20 v / v% O ₂ mixed gas was used, and the flow rate of this mixed gas was set to 20 L / min. The interval b between the current plates 10 and 10 was 3 mm.

Here, the plasma irradiation time is 1 minute, 3 minutes, and 5 minutes, and the surface resistance (sheet resistance: Ω / □) and visible light transmittance (%) of each transparent conductive film obtained are The measurement was performed according to Example 1.
Table 8 shows the measurement results.
In the obtained transparent conductive film, generation of an arc spot was remarkable, the coating surface was damaged with the irradiation time, and the surface resistance was increased.

According to the above measurement results, the transparent conductive films of Examples 1 to 6 have a smaller surface resistance (sheet resistance) than the transparent conductive films of Comparative Examples 1 and 2, and defects such as arc spots on the coating film surface. There was no outbreak.
In addition, even when any one of an organometallic compound, a metal inorganic salt, and a metal organic salt was added to each of the coating solutions of Examples 1 to 6, the obtained coating film was plasma at atmospheric pressure and in an oxidizing atmosphere. It was confirmed that a low-resistance and high-quality transparent conductive film can be stably formed by generating a violet ray and irradiating the plume.

  The method for forming a transparent conductive film of the present invention is a method of irradiating a coating film formed on a substrate with a plume P ′ in a weakly ionized plasma state under atmospheric pressure to modify the coating film, thereby improving the quality. Since a transparent conductive film can be stably formed, various kinds of plasma display (PDP), liquid crystal display (LCD), electroluminescence display (EL), cathode ray tube (CRT), projection (PJTV), etc. In addition to being applicable to a display device, the effect is also great in various industrial fields such as windows for automobiles and buildings.

It is sectional drawing which shows the plasma irradiation apparatus used for the plasma irradiation of this invention. It is sectional drawing which shows the baffle plate of the plasma irradiation apparatus used for the plasma irradiation of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas introduction pipe 2 Plasma generating part 3 Plasma generating electrode 4 Plasma generating power source 6 Base material with film 7 Base material 8 Coating film 9 Transparent conductive film 10 Current plate 10a End face 11 Slit g Reaction gas P Arc column P 'plume

Claims (8)

  A conductive paint is applied on a substrate to form a coating film, and a reactive gas is introduced onto the coating film under atmospheric pressure to convert the reactive gas into a plasma to generate plasma in a weakly ionized plasma state, A method for forming a transparent conductive film, comprising forming the transparent conductive film on the substrate by irradiating the plasma in the weakly ionized plasma state to modify the coating film.   2. The method for forming a transparent conductive film according to claim 1, wherein the reactive gas includes one or more selected from the group consisting of nitrogen, rare gas, oxygen, ozone, hydrogen, and ammonia.   The method for forming a transparent conductive film according to claim 1, wherein the reaction gas contains one or more organic metal compounds.   4. The method for forming a transparent conductive film according to claim 1, wherein a rectifying plate is provided between the plasma generating part for generating the plasma and the coating film, and the flow of the plasma is controlled.   5. The method for forming a transparent conductive film according to claim 4, wherein the plasma generating portion includes a plasma generating electrode, and the rectifying plate is provided between the plasma generating electrode and the coating film.   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 paint includes any one of an organic metal compound, a metal inorganic acid salt, a metal organic acid salt, metal oxide fine particles, and fine particles made of a metal or an alloy. The formation method of the transparent conductive film of claim | item.   A transparent conductive film formed by the method for forming a transparent conductive film according to claim 1.

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