JP4007082B2 - Transparent conductive film and method for forming the same - Google Patents

Description

【００７７】
作製した透明導電膜を以下の方法で評価した。
〈比抵抗〉
ＪＩＳ−Ｒ−１６３７に従い、四端子法により求めた。なお、測定には三菱化学社製ロレスタ−ＧＰ、ＭＣＰ−Ｔ６００を用いた。
【００７８】
〈透過率〉
ＪＩＳ−Ｒ−１６３５に従い、日立製作所製分光高度計１Ｕ−４０００型を用いて測定した。試験光の波長は５５０ｎｍとした。
【００７９】
〈耐湿・耐熱性〉
試料を恒温器を用いて６０℃、９０％ＲＨの条件で２４０時間保存した後、比抵抗を測定した。加湿・加熱前後の比抵抗をそれぞれＲ₀、Ｒとし、変化率Ｒ／Ｒ₀を耐湿・耐熱性の指標とした。
【００８０】
評価の結果を表２に示す。
【００８１】
【表２】

【００８２】
【発明の効果】
本発明により、低抵抗かつ耐湿、耐熱性に優れた透明導電膜及びその形成方法を提供することができた。
【図面の簡単な説明】
【図１】本発明に用いられる大気圧プラズマ放電処理装置の一例を示す断面図である。
【符号の説明】
１ 基材
２、３ 電極
４、４′ 高周波電源
５ 加熱ヒーター[0001]
BACKGROUND OF THE INVENTION
The present invention is suitably used for various electronic devices such as liquid crystal display devices, organic electroluminescence devices (hereinafter also referred to as organic EL devices), plasma display panels (hereinafter abbreviated as PDP), electronic paper, touch panels, solar cells and the like. The present invention relates to a transparent conductive film and a method for forming the same.
[0002]
[Prior art]
Conventionally, transparent conductive films have been widely used for liquid crystal display elements, organic EL elements, solar cells, touch panels, electromagnetic wave shielding materials, infrared reflective films, and the like. As the transparent conductive film, metal thin films such as Pt, Au, Ag, and Cu, SnO₂, In₂O_Three, CdO, ZnO₂, SnO₂: Sb, SnO₂: F, ZnO: AL, In₂O_Three: Composite oxide film made of oxide such as Sn and dopant, chalcogenide, LaB₆, Non-oxides such as TiN and TiC. Among them, an indium oxide film doped with tin (hereinafter referred to as ITO) is most widely used because of its excellent electrical characteristics and ease of processing by etching. These are formed by vacuum deposition, sputtering, ion plating, vacuum plasma CVD, spray pyrolysis, thermal CVD, sol-gel, or the like.
[0003]
In recent years, flat panel displays such as liquid crystal display elements and organic EL elements have been increased in area and definition, and a higher performance transparent conductive film has been demanded. In a liquid crystal display element, in order to obtain an element or device having a high electric field response, use of a transparent conductive film having a high electron mobility is required. In addition, in an organic EL element, a transparent conductive film having a lower resistance is required in order to adopt a current driving method.
[0004]
Among the methods for forming a transparent conductive film, a low resistance transparent conductive film can be obtained by vacuum deposition or sputtering. Industrially, a specific resistance value of 10 can be obtained by using a DC magnetron sputtering apparatus.^-FourAn ITO film having excellent conductivity on the order of Ω · cm can be obtained.
[0005]
However, in these physical fabrication methods (PVD method), a target substance is deposited on a substrate in a gas phase to grow a film, and a vacuum vessel is used. Therefore, the apparatus is large and expensive, and the use efficiency of raw materials is poor, so that the film forming speed is low and the productivity is low. Also, it was difficult to form a large area.
[0006]
The sol-gel method (coating method) can form a film with a large area, but it does not only require many processes such as dispersion preparation, coating, and drying, but also has low adhesiveness to the substrate to be treated, so it is a binder resin. Becomes necessary and transparency becomes worse. Moreover, the electrical characteristics of the obtained transparent conductive film are also inferior compared to the PVD method.
[0007]
The thermal CVD method forms a film by applying a precursor of the target substance to a substrate by spin coating, dip coating, printing, etc., and firing (pyrolysis) to form a film. However, there is an advantage that it is excellent in productivity and easy to form a film with a large area, but there is a problem that a high temperature treatment of 400 to 600 ° C. is required at the time of normal firing.
[0008]
As a method for overcoming the above disadvantages of obtaining a high-performance thin film by the sol-gel method (coating method) and the disadvantage of low productivity by using a vacuum apparatus, the gas is discharged under atmospheric pressure or a pressure close to atmospheric pressure. Has been proposed to form a thin film on a substrate (hereinafter referred to as atmospheric pressure plasma CVD method).
[0009]
Japanese Patent Application Laid-Open No. 2000-303175 discloses a technique for forming a transparent conductive film by an atmospheric pressure plasma CVD method. However, the resistance of the transparent conductive film obtained is about 10 in terms of specific resistance.^-2Ω · cm, high specific resistance 10^-3It is insufficient as a transparent conductive film for flat panel displays such as liquid crystal elements, organic EL elements, PDPs, and electronic papers that require excellent electrical characteristics of Ω · cm or less. Moreover, moisture resistance and heat resistance were bad. Further, triethylindium is used as a CVD raw material, and this compound has a safety problem such as being ignited and explosive in normal temperature and air.
[0010]
Japanese Patent Application Laid-Open No. 2001-74906 has a function of preventing infrared rays and electromagnetic waves, has a high adhesion between a hard coat layer / transparent conductive layer / antireflection layer, and has excellent scratch resistance and surface hardness for PDP or FED. Although the example of a transparent conductive layer is disclosed as an antireflection film and a method for producing the same, the transparent conductive layer described in the patent cannot meet the demand for a transparent conductive film having a lower resistance.
[0011]
In general, it is known that the specific resistance value decreases as the substrate temperature increases in the formation of a transparent conductive film, but the method of forming a transparent conductive film with low resistance, good moisture resistance and good heat resistance by the atmospheric pressure plasma method is Not disclosed.
[0012]
[Problems to be solved by the invention]
An object of the present invention is to provide a transparent conductive film excellent in low resistance, moisture resistance and heat resistance, and a method for forming the transparent conductive film.
[0013]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following configurations.
[0014]
1. An electric field applied to the discharge space in the method for forming a transparent conductive film, wherein the transparent conductive film is formed by exposing the substrate to a gas that is introduced into the discharge space and brought into a plasma state under atmospheric pressure or a pressure near atmospheric pressure. However, at a high frequency voltage exceeding 100 kHz, the discharge output density is 1 W / cm.²The method for forming a transparent conductive film, wherein the gas contains a thin film forming gas and a reactive gas, the reactive gas contains a reducing gas, and the substrate temperature is 200 to 400 ° C.
[0015]
2. 2. The method for forming a transparent conductive film as described in 1 above, wherein the reducing gas is hydrogen.
[0016]
  3. The transparent conductive film is formed by the method for forming a transparent conductive film according to 1 or 2, and the composition of the transparent conductive film is ITO (In₂O_Three: Sn), ZnO, IZO (In₂O_Three: ZnO) or FTO (SnO ₂ : FThe transparent conductive film characterized by these.
[0017]
4). The transparent conductive film is formed by the method for forming a transparent conductive film according to 1 or 2 above, the composition of the transparent conductive film is ITO, and the specific resistance value is 3.0 × 10.^-FourA transparent conductive film characterized by having a resistance of Ωcm or less.
[0018]
5. A transparent conductive film formed by the method for forming a transparent conductive film according to 1 or 2 above, wherein the rate of increase in resistance after 240 hours at 60 ° C. and 90% RH is 1.2 or less.
[0019]
Hereinafter, the present invention will be described in detail.
As a result of diligent research, the present inventors have found that, in the atmospheric pressure plasma CVD method, the electric field applied to the discharge space is a high frequency voltage exceeding 100 kHz, and the discharge output density is 1 W / cm.²A transparent conductive film having low resistance, excellent moisture resistance and heat resistance is obtained by forming a film with the above high power and a substrate temperature of 200 to 400 ° C. and introducing a reaction gas containing a reducing gas. I found out that The reducing gas is preferably hydrogen.
[0020]
In the present invention, the transparent conductive film is generally well known as an industrial material and is a transparent film that absorbs almost no visible light (400 to 700 nm) and is transparent. It is used as a transparent electrode or an antistatic film because the transmission characteristics of a free charged substance carrying electricity is high in the visible light range, is transparent, and has high electrical conductivity.
[0021]
  Note that although it is referred to as a “film”, it may be formed on the object to be processed to such an extent that it has a function depending on the application, and is not necessarily a continuous curtain covering all or part of the object to be processed. As the transparent conductive film, metal thin films such as Pt, Au, Ag, and Cu, SnO₂, In₂O_Three, CdO, ZnO₂, SnO₂: Sb, SnO₂: F, ZnO: AL, In₂O_Three: Composite oxide film made of oxide such as Sn and dopant, chalcogenide, LaB₆, Non-oxides such as TiN and TiC. In the present invention, the composition of the transparent conductive film is ITO (In₂O_Three: Sn), ZnO, IZO (In₂O_Three: ZnO) or FTO (SnO ₂ : F) Is preferable.
[0022]
The atmospheric pressure plasma CVD method, which is a method for forming the transparent conductive film of the present invention, will be described.
[0023]
In the present invention, a transparent conductive film is formed on the substrate by introducing a gas into the discharge space into a plasma state under atmospheric pressure or a pressure near atmospheric pressure, and exposing the substrate to the plasma state gas. In the method for forming a transparent conductive film, at least one of the gases is a reducing gas such as hydrogen.
[0024]
In the atmospheric pressure plasma CVD of the present invention, a high-frequency voltage exceeding 100 kHz and a discharge output density of 1 W / cm are provided between opposing electrodes.²The above power (power density) is supplied to excite the gas to generate plasma.
[0025]
In the present invention, the lower limit value of the frequency of the high-frequency voltage applied between the electrodes is preferably more than 100 kHz, and more preferably 200 kHz. More preferably, it is 800 kHz. The upper limit is preferably 150 MHz.
[0026]
The lower limit value of the power supplied between the electrodes is 1 W / cm.²Preferably 1.2 W / cm²It is. The upper limit is preferably 100 W / cm², More preferably 50 W / cm²It is. More preferably 20 W / cm²It is. The discharge area (/ cm²) Refers to the area of the electrode where discharge occurs.
[0027]
The high-frequency voltage applied between the electrodes may be an intermittent pulse wave or a continuous sine wave. However, in order to obtain the effect of the present invention, it is a continuous sine wave. It is preferable.
[0028]
In the present invention, it is necessary to employ an electrode capable of maintaining a uniform glow discharge state by applying such a voltage in a plasma discharge processing apparatus.
[0029]
A plasma discharge processing apparatus using such an electrode discharges between a ground electrode and a fixed electrode, which is an application electrode disposed at an opposite position, and introduces a gas between the electrodes to form a plasma state. A thin film is formed by exposing the material to the gas in the plasma state, but the apparatus for carrying out the thin film forming method of the present invention is not limited to this, stably maintaining the glow discharge, What is necessary is just to excite gas and form a plasma state in order to form a thin film. As another method, there is a jet method in which a base material is placed or transported in the vicinity of an electrode that is not between electrodes and a generated plasma is sprayed onto the base material to form a thin film.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view showing an example of an atmospheric pressure plasma discharge treatment apparatus used in the present invention. In FIG. 1, 2 is a flat electrode, 3 is a prismatic electrode, and a plurality of electrodes 3 are arranged. Since the prismatic electrode 3 has an effect of expanding the discharge range as compared with the cylindrical electrode, it is preferably used in the thin film forming method of the present invention. The electrode 2 and the electrode 3 are disposed so as to face each other.
[0031]
For the electrodes 2 and 3, it is necessary to apply an electrode capable of maintaining a uniform glow discharge state by applying a high-frequency voltage to the atmospheric pressure plasma processing apparatus.
[0032]
The electrode 2 has a structure capable of holding the substrate 1 and incorporates a heater 5. Furthermore, the electrode 2 can reciprocate in the horizontal direction. The heater 5 can be preheated by applying a voltage with the high frequency power source 4 and exposing the surface temperature of the substrate 1 to the discharge plasma between the electrodes 2 and 3.
[0033]
Examples of the material for the electrode include metals such as silver, platinum, stainless steel aluminum, and iron. Stainless steel is preferable from the viewpoint of processing.
[0034]
Further, the electrodes 2 and 3 are preferably coated with a dielectric. It is preferable to coat a dielectric on at least one side of the opposed application electrode and the ground electrode, and more preferably coat both the opposed application electrode and the ground electrode with a dielectric.
[0035]
The dielectric is preferably an inorganic dielectric. Examples of such a dielectric include ceramics such as alumina and silicon nitride, or glass lining materials such as silicate glass and borate glass. is there.
[0036]
In addition, when the substrate is placed between the electrodes or transported between the electrodes and exposed to plasma, not only the roll electrode specification that allows the substrate to be transported in contact with one electrode, but also the surface of the dielectric is polished. Finishing and setting the electrode surface roughness Rmax (JIS B 0601) to 10 μm or less allows the dielectric thickness and the gap between the electrodes to be kept constant, the discharge state to be stabilized, and the heat shrinkage difference In addition, it is possible to greatly improve durability by eliminating strain and cracking due to residual stress and coating with a highly accurate inorganic dielectric that is not porous. More preferably, the maximum value of the surface roughness is 8 μm or less, and particularly preferably 7 μm or less. The centerline average surface roughness (Ra) specified by JIS B 0601 is preferably 0.5 μm or less, more preferably 0.1 μm or less.
[0037]
In addition, when manufacturing electrodes with a dielectric coating on electrodes at high temperatures, it is necessary to polish at least the dielectric on the side in contact with the substrate, and to minimize the difference in thermal expansion between the electrode and the dielectric. Therefore, as a layer that can absorb stress on the electrode surface, the amount of bubbles mixed is controlled to line an inorganic material, and in particular, the material is preferably a glass obtained by a melting method known as flaws. By making the amount of bubbles mixed in the lowermost layer in contact with 20 to 30% by volume and the subsequent layer and subsequent layers to be 5% by volume or less, a fine electrode that is dense and does not generate cracks or the like can be obtained.
[0038]
Another method of coating the electrode with a dielectric is to perform ceramic thermal spraying to a porosity of 10% by volume or less, and to perform a sealing treatment with an inorganic material that is cured by a sol-gel reaction. In order to accelerate the sol-gel reaction, heat curing or UV curing is good. Further, diluting the sealing liquid and repeating coating and curing several times in succession further improves the mineralization, resulting in a dense electrode without deterioration. it can.
[0039]
The distance between the electrodes is determined in consideration of the thickness of the solid dielectric placed on the electrodes, the magnitude of the applied voltage, the purpose of using plasma, and the like. The shortest distance between the solid dielectric and the electrode when a solid dielectric is placed on one of the electrodes, and the distance between the solid dielectrics when a solid dielectric is placed on both of the electrodes is uniform in any case From the viewpoint of discharging, 0.5 to 20 mm is preferable, and 1 mm ± 0.5 mm is particularly preferable.
[0040]
Reference numeral 4 denotes a high-frequency power source for applying a high-frequency voltage between the electrodes 2 and 3. The high-frequency power source that can be used in the present invention is not particularly limited, but the high-frequency power source (200 kHz) manufactured by Pearl Industry, the high-frequency power source (800 kHz) manufactured by Pearl Industry, the high-frequency power source (13.56 MHz) manufactured by JEOL Ltd., A high frequency power source (150 MHz) manufactured by Pearl Industrial Co., Ltd. can be used.
[0041]
The frequency and power of the voltage applied between the electrodes 2 and 3 from the high-frequency power source 4 are appropriately determined. For example, the voltage is adjusted to about 0.5 to 10 kV. As for the method of applying power, either a continuous sine wave continuous oscillation mode called a continuous mode or an intermittent oscillation mode called ON / OFF intermittently called a pulse mode may be adopted, but the continuous mode is better. A denser and better quality film can be obtained.
[0042]
Moreover, in order to suppress the influence on the base material at the time of discharge plasma processing to the minimum, it is necessary to adjust the temperature of the base material surface at the time of discharge plasma processing to 200-400 degreeC. In order to adjust to the above temperature range, the electrode and the substrate are subjected to a discharge plasma treatment while being cooled by a cooling means as necessary.
[0043]
In the present invention, it is important that the substrate temperature during film formation is 200 to 400 ° C. Here, the substrate temperature refers to the temperature of the substrate surface formed by plasma discharge. The temperature of the substrate surface can be known, for example, by a method of measuring by installing a liquid crystal type temperature display sheet on the substrate surface when performing offline, or by measuring with a radiation thermometer outside the discharge space. When the film is formed at a substrate temperature of less than 200 ° C., a low resistivity film that is the object of the present invention cannot be obtained. In addition, it is known that the characteristics of a transparent conductive film greatly change above and below the crystallization temperature. When the temperature is lower than 200 ° C., the substrate temperature and the gas flow rate slightly change, and the resistivity and film surface are changed. The flatness has changed greatly and it has been difficult to maintain stable characteristics. Moreover, when the temperature exceeds 400 ° C., the dielectric breakdown covering the discharge electrode is liable to occur, and it becomes difficult to maintain a stable glow discharge state. The substrate temperature is preferably 250 to 350 ° C, more preferably 300 to 350 ° C. In order to keep the substrate temperature at 200 ° C. or higher, a heating means can be provided on the electrode holding the substrate. It can be achieved by a method of adjusting water or oil by circulating water or oil inside as a heating means, a method of installing a heater, or the like. Moreover, in order to control substrate temperature as needed, an electrode and discharge gas can be heated.
[0044]
In the present invention, the above-described discharge plasma treatment is performed at or near atmospheric pressure. Here, “near atmospheric pressure” represents a pressure of 20 to 110 kPa. In order to preferably obtain the effects described in the present invention. Is preferably 93 to 104 kPa.
[0045]
Next, the gas introduced into the discharge space according to the method for forming a transparent conductive film of the present invention will be described. In carrying out the method for forming a transparent conductive film of the present invention, the gas to be used varies depending on the type of transparent conductive film to be provided on the substrate, but basically consists of a thin film forming gas, a reactive gas, and a discharge gas. The reaction gas includes a reducing gas. A preferable example of the reducing gas is hydrogen. The amount of hydrogen can be used in the range of 0.0001 to 5.0% by volume with respect to the gas introduced into the discharge space. A preferred range is 0.001 to 3.0% by volume.
[0046]
In the present invention, in addition to the above-mentioned thin film forming gas, an organometallic compound containing at least one oxygen atom in the molecule can be used. This organometallic compound is in a plasma state in the discharge space and contains components that form a transparent conductive film, and organometallic compounds such as β-diketone metal complexes, metal alkoxides, and alkyl metals are used.
[0047]
Preferred compounds include indium hexafluoropentanedionate, indiummethyl (trimethyl) acetylacetate, indium acetylacetonate, indium isoporopoxide, indium trifluoropentanedionate, tris (2,2,6,6-tetramethyl 3,5-heptanedionate) indium, di-n-butylbis (2,4-pentanedionate) tin, di-n-butyldiacetoxytin, di-t-butyldiacetoxytin, tetraisopropoxytin, tetra Examples include butoxytin and zinc acetylacetonate.
[0048]
Of these, indium acetylacetonate, tris (2,2,6,6-tetramethyl 3,5-heptanedionate) indium, zinc acetylacetonate and di-n-butyldiacetoxytin are particularly preferable. . These organometallic compounds are generally commercially available. For example, indium acetylacetonate can be easily obtained from Tokyo Chemical Industry Co., Ltd.
[0049]
In the present invention, in addition to the organometallic compound containing at least one oxygen atom in the molecule, a doping gas used for improving conductivity can be used. As a thin film forming gas used for doping, for example, aluminum isopropoxide, nickel acetylacetonate, manganese acetylacetonate, boron isopropoxide, n-butoxyantimony, tri-n-butylantimony, di-n-butylbis ( 2,4-pentanedionate) tin, di-n-butyldiacetoxytin, di-t-butyldiacetoxytin, tetraisopropoxytin, tetrabutoxytin, tetrabutyltin, zinc acetylacetonate, propylene hexafluoride, A cyclobutane octafluoride, methane tetrafluoride, etc. can be mentioned.
[0050]
Examples of the thin film forming gas used for adjusting the specific resistance value of the transparent conductive film include titanium triisopropoxide, tetramethoxysilane, tetraethoxysilane, and hexamethyldisiloxane.
[0051]
The amount ratio between the thin film forming gas used as the main component of the transparent conductive film and the thin film forming gas used in small amounts for the purpose of doping varies depending on the type of the transparent conductive film to be formed. For example, in an ITO film obtained by doping tin with indium oxide, the amount of thin film forming gas is adjusted so that the In / Sn atomic ratio of the obtained ITO film is in the range of 100 / 0.1 to 100/15. adjust. Preferably, it adjusts so that it may become the range of 100 / 0.5-100 / 10. The atomic ratio of In / Sn can be determined by XPS measurement.
[0052]
In a transparent conductive film (referred to as an FTO film) obtained by doping fluorine into tin oxide, a thin film is formed so that the Sn / F atomic ratio of the obtained FTO film is in the range of 100 / 0.01 to 100/50. Adjust the amount ratio of forming gas. The atomic ratio of Sn / F can be determined by XPS measurement.
[0053]
In₂O_ThreeIn the -ZnO-based amorphous transparent conductive film, the amount ratio of the thin film forming gas is adjusted so that the In / Zn atomic ratio is in the range of 100/50 to 100/5. The atomic ratio of In / Zn can be determined by XPS measurement.
[0054]
Further, the thin film forming gas includes a thin film forming gas which is a main component of the transparent conductive film and a thin film forming gas which is used in a small amount for the purpose of doping. Furthermore, a thin film forming gas can be added to adjust the specific resistance value of the transparent conductive film.
[0055]
It is preferable to contain 0.01-10 volume% of said thin film formation gas with respect to the gas introduce | transduced into discharge space. As the film thickness of the transparent conductive film, a transparent conductive film in the range of 0.1 to 1000 nm is obtained.
[0056]
In the present invention, the thin film forming gas, the reactive gas, and the discharge gas are introduced into the plasma space. Here, the discharge gas includes the 18th group element of the periodic table, specifically helium, neon, argon, krypton, xenon, radon, and nitrogen gas. In order to obtain the effects described in the present invention. In particular, argon or helium is preferably used.
[0057]
The transparent conductive film obtained by the transparent conductive film forming method of the present invention is characterized by having high carrier mobility. As is well known, the electrical conductivity of the transparent conductive film is represented by the following formula (1).
[0058]
σ = neμ (1)
Here, σ is the electric conductivity, n is the carrier density, e is the quantity of electrons, and μ is the carrier mobility. In order to increase the electric conductivity, it is necessary to improve the carrier density or the carrier mobility, but if the carrier density is increased, 2 × 10^{twenty one}cm^-3Transparency is lost because the reflectance increases from the vicinity. Therefore, it is necessary to improve carrier mobility in order to improve electric conductivity. The carrier mobility of a transparent conductive film produced by a commercially available DC magnetron sputtering method is 30 cm.²/ Sec · V, but according to the method for forming a transparent conductive film of the present invention, a transparent conductive film having a carrier mobility exceeding the transparent conductive film formed by the DC magnetron sputtering method is optimized by optimizing the conditions. It is possible to form.
[0059]
Since the method for forming a transparent conductive film of the present invention has a high carrier mobility, the specific resistance value is 3 × 10 3 even without doping.^-3A transparent conductive film having a low resistance of Ω · cm or less can be obtained. It is possible to further reduce the specific resistance by doping and increasing the carrier density.
[0060]
The transparent conductive film obtained by the method for forming a transparent conductive film of the present invention has a carrier mobility of 10 cm.²/ V · sec or more.
[0061]
The transparent conductive film obtained by the method for forming a transparent conductive film of the present invention has a carrier density of 1 × 10.¹⁹cm^-3As described above, under more preferable conditions, 1 × 10²⁰cm^-3That's it.
[0062]
Moreover, the transparent conductive film obtained by the formation method of the transparent conductive film of this invention may contain a trace amount carbon. In this case, the carbon content is preferably 0 to 5.0 atom concentration. Particularly preferably, it is within the range of 0.01 to 3 atomic number concentration.
[0063]
The substrate that can be used in the present invention is not particularly limited as long as it is a substrate that can withstand the film-forming temperature, such as a film-like material, a sheet-like material, and a three-dimensional material such as a lens shape. Usually, it forms into a film on a glass substrate. As the glass substrate, soda glass and inorganic alkali glass can be used, but inorganic alkali glass is preferable. If the substrate can be placed between the electrodes, it can be placed between the electrodes, and if the substrate cannot be placed between the electrodes, the generated plasma can be sprayed onto the substrate to conduct transparent conduction. A film may be formed.
[0064]
In the present invention, the transparent conductive film is formed on a substrate such as glass or a plastic film, but an adhesive layer may be provided between the substrate and the transparent conductive film as necessary to improve the adhesiveness. Good. In addition, in order to improve the optical characteristics, it is possible to provide an antireflection film on the surface opposite to the surface provided with the transparent conductive film. Further, an antifouling layer can be provided on the outermost layer of the film. In addition, a layer for imparting gas barrier properties and solvent resistance may be provided as necessary.
[0065]
The method for forming these layers is not particularly limited, and a coating method, a vacuum deposition method, a sputtering method, an atmospheric pressure plasma CVD method, or the like can be used. Particularly preferred is the atmospheric pressure plasma CVD method.
[0066]
As a method for forming these layers by atmospheric pressure plasma CVD, for example, a method disclosed in Japanese Patent Application No. 2000-021573 can be used as a method for forming an antireflection film.
[0067]
In the present invention, when the transparent conductive film according to the present invention is provided on the substrate surface as described above, it is preferable to provide a film thickness deviation of ± 10% with respect to the average film thickness, more preferably It is preferably within ± 5%, particularly preferably within ± 1%.
[0068]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these.
[0069]
Example 1
(Preparation of transparent conductive film 1)
As the base material, a glass substrate (50 mm × 50 mm × 1 mm) on which a silica film having a film thickness of about 50 nm was formed as an alkali barrier coat was used.
[0070]
Using the atmospheric pressure plasma processing apparatus shown in FIG. 1, the glass substrate was placed between the electrodes, and the following mixed gas was introduced to form a thin film.
[0071]
The electrode 2 was coated with 1 mm of alumina by ceramic spraying on a stainless steel jacket base material incorporating a heating wire as the heater 5, and after coating and drying a solution obtained by diluting tetramethoxysilane with ethyl acetate, irradiation with ultraviolet rays was performed. After curing and sealing, the surface was smoothed to have a dielectric having a Rmax of 5 μm (relative dielectric constant 10). On the other hand, as the electrode 3, a hollow square stainless steel pipe was covered with the same dielectric as described above under the same conditions.
[0072]
The power source used for plasma generation was a high-frequency power source manufactured by Pearl Industrial Co., Ltd. The output is 5W / cm²Power was supplied.
[0073]
The substrate 1 is heated by the heater 5 until the surface temperature reaches 250 ° C., the frequency between the electrodes 2 and 3 is 13.56 MHz, and the discharge output density is 5 W / cm.²Is applied to generate discharge plasma, the substrate 1 is exposed to the discharge plasma, and the electrode 2 is moved several tens of times while taking a pause of 1 sec in the horizontal direction until the film thickness reaches 100 nm. A transparent conductive film 1 was produced by film formation.
[0074]
The surface temperature of the substrate during the discharge plasma treatment is a temperature after the plasma treatment by applying a temperature patch (manufactured by IP Giken) in advance to the surface of the substrate and changing the heating temperature of the following electrodes at several points. The lower electrode temperature was set so as to obtain a desired temperature, obtained from the color change of the patch.
[0075]
<Gas introduced into the discharge space>
Discharge gas: Helium 98.5% by volume
Reaction gas: Hydrogen 0.25% by volume
Thin film forming gas 1: Indium acetylacetonate 1.2% by volume
Thin film forming gas 2: 0.05% by volume of dibutyltin diacetate
(Preparation of transparent conductive films 2 to 17)
Transparent conductive films 2 to 17 were produced in the same manner as the transparent conductive film 1 except that the frequency, power density, substrate temperature, discharge gas, reaction gas, thin film forming gas 1 and 2 and power source were changed as shown in Table 1. .
[0076]
[Table 1]

[0077]
The produced transparent conductive film was evaluated by the following method.
<Resistivity>
According to JIS-R-1637, it calculated | required by the four terminal method. For measurement, Loresta-GP and MCP-T600 manufactured by Mitsubishi Chemical Corporation were used.
[0078]
<Transmissivity>
According to JIS-R-1635, it was measured using a spectrophotometer 1U-4000 manufactured by Hitachi, Ltd. The wavelength of the test light was 550 nm.
[0079]
<Moisture and heat resistance>
The sample was stored for 240 hours under conditions of 60 ° C. and 90% RH using a thermostat, and then the specific resistance was measured. Specific resistance before and after humidification and heating is R₀, R and rate of change R / R₀Was used as an indicator of moisture resistance and heat resistance.
[0080]
The evaluation results are shown in Table 2.
[0081]
[Table 2]

[0082]
【The invention's effect】
According to the present invention, it was possible to provide a transparent conductive film excellent in low resistance, moisture resistance and heat resistance, and a method for forming the same.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an atmospheric pressure plasma discharge treatment apparatus used in the present invention.
[Explanation of symbols]
1 Base material
2, 3 electrodes
4, 4 'high frequency power supply
5 Heating heater

Claims (5)

An electric field applied to the discharge space in the method for forming a transparent conductive film, wherein the transparent conductive film is formed by exposing the substrate to a gas that is introduced into the discharge space and brought into a plasma state under atmospheric pressure or a pressure near atmospheric pressure. However, at a high frequency voltage exceeding 100 kHz, the discharge output density is 1 W / cm ² or more, the gas contains a thin film forming gas and a reactive gas, the reactive gas contains a reducing gas, and the substrate temperature is 200. A method for forming a transparent conductive film, characterized in that the temperature is ˜400 ° C.   The method for forming a transparent conductive film according to claim 1, wherein the reducing gas is hydrogen. Claim 1 or 2 formed by the method for forming a transparent conductive film according, ITO is the composition of the transparent conductive film _{(In 2 O 3: Sn)} , ZnO, IZO (In 2 O 3: ZnO) or FTO (SnO _2: F )). The transparent conductive film characterized by the above-mentioned. A transparent conductive film formed by the method for forming a transparent conductive film according to claim 1, wherein the composition of the transparent conductive film is ITO, and the specific resistance value is 3.0 × 10 ⁻⁴ Ωcm or less. .   A transparent conductive film formed by the method for forming a transparent conductive film according to claim 1 or 2, wherein a resistance increase rate after 240 hours at 60 ° C. and 90% RH is 1.2 or less.

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