JP4616688B2 - Conductive film - Google Patents

Description

  The present invention relates to a conductive film excellent in transparency and conductivity. More specifically, the present invention relates to a transparent conductive film having improved contact resistance and suitable as a transparent electrode such as a liquid crystal display (LCD), a transparent touch panel, an organic electroluminescence element, and an inorganic electroluminescence lamp.

Conventionally, a transparent conductive film is suitably used as a transparent electrode such as a liquid crystal display or a transparent touch panel or an electromagnetic shielding material. Examples of such transparent conductive films include indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), In ₂ O _{3 on} at least one surface of a transparent film surface such as polyethylene terephthalate (PET) or triacetyl cellulose (TAC). It is well known that a mixed sintered body (ITO) of SnO ₂ and SnO ₂ is provided by a dry process such as vacuum deposition, sputtering, or ion plating.

  However, the transparent conductive film usually has continuous processing and punching processing in a web shape, and is used in a bent state during surface processing and is also stored. In the conductive film, cracks may occur during the processing step or storage, and the surface resistance may increase.

  On the other hand, the transparent conductive coating layer formed by applying a conductive polymer on a transparent substrate film (wet process) has flexibility in the film itself, and problems such as cracks hardly occur. In addition, the method of obtaining a transparent conductive film by applying a conductive polymer has the advantage that the manufacturing cost is relatively low unlike the dry process, and the coating speed is generally high, so that the productivity is excellent. . Transparent conductive films obtained by applying such conductive polymers are charged with polythiophene, polyaniline, polypyrrole, etc., which have been generally used so far, because high conductivity cannot be obtained at the initial stage of development. The use was limited to the prevention use etc., or the hue of the conductive coating layer itself was problematic. However, these problems have recently been improved by improving the production method. For example, a conductive polymer (Patent Document 1) comprising a poly (3,4-dialkoxythiophene) obtained by oxidative polymerization of 3,4-dialkoxythiophene in the presence of a polyanion and a polyanion is a recent production method. (Patent Document 2 and Patent Document 3) improve the surface resistance while maintaining a high light transmittance.

  However, a transparent conductive film having such a conductive polymer as a transparent conductive coating layer, for example, when used as a base material for a touch panel, has high contact resistance. When used as a transparent electrode such as a luminescence element or an inorganic electroluminescence lamp, there is a problem that predetermined conductivity cannot be obtained.

Japanese Patent Laid-Open No. 1-313521 JP 2002-193972 A JP 2003-286336 A

  The present invention has been made in view of the above-mentioned background art, and the object is to have excellent transparency and conductivity while using a conductive polymer, and is excellent as well as a laminate of ITO. It is to provide a conductive film.

  As a result of diligent studies to achieve the above-mentioned problems, the present inventors have found that when a conductive polymer composed of a polycationic polythiophene and a polyanion is used, the polyanion component is unevenly distributed on the surface layer of the transparent conductive coating layer. For example, if used as a base material for a touch panel, erroneous operation can be suppressed, and even when used as a transparent electrode such as an organic electroluminescence element or an inorganic electroluminescence lamp, desired electrical conductivity can be expressed. The present invention has been found.

（式中、Ｒ^１およびＲ^２は相互に独立して水素または炭素数１〜４のアルキル基を表すか、あるいは一緒になって任意に置換されてもよい炭素数１〜１２のアルキレン基を表す）で表される繰り返し単位からなるポリカチオン状のポリチオフェンとポリアニオンとからなる導電性高分子を含有する透明導電性塗膜が設けられた導電性フィルムであって、該透明導電性塗膜の表面側における該ポリチオフェンが含まれていない層厚さが５ｎｍ以下であり、透明導電性塗膜の全厚みが５０ｎｍ以上３００ｎｍ以下であり、かつ、該導電性フィルムの全光線透過率が８２％以上、表面抵抗率が１０〜１×１０^４Ω／□であることを特徴とする導電性フィルム。」が提供される。 Thus, according to the present invention, “at least one side of the base film has the following general formula:

(Wherein R ¹ and R ² each independently represent hydrogen or an alkyl group having 1 to 4 carbon atoms, or an alkylene group having 1 to 12 carbon atoms which may be optionally substituted together) A conductive film comprising a conductive polymer composed of a polycationic polythiophene and a polyanion composed of a repeating unit represented by the following formula: The layer thickness not containing the polythiophene on the surface side is 5 nm or less, the total thickness of the transparent conductive coating film is 50 nm or more and 300 nm or less, and the total light transmittance of the conductive film is 82 % or more. And a surface resistivity of 10 to 1 × 10 ⁴ Ω / □. Is provided.

  The conductive film of the present invention is formed by forming a transparent conductive coating film containing a specific polythiophene-based conductive polymer, and the surface layer thickness of the transparent conductive coating film that does not include the polythiophene-based conductive polymer. Is 5 nm or less, it has transparency and electrical conductivity superior to or equal to those of ITO, and at the same time has good surface resistance. Therefore, it can be suitably used as a transparent electrode such as a liquid crystal display (LCD) touch panel, an organic electroluminescence element, and an inorganic electroluminescence lamp.

で表される繰り返し単位からなるポリカチオン状のポリチオフェン（以下、“ポリ（３，４−ジ置換チオフェン）”と称することがある）と、ポリアニオンとからなる導電性高分子を構成成分として含有する透明導電性塗膜が形成されている。ここで、上記式中Ｒ^１およびＲ^２は、相互に独立して水素または炭素数が１〜４のアルキル基を表すか、あるいは一緒になって任意に置換されてもよい炭素数が１〜１２のアルキレン基を表す。Ｒ^１およびＲ^２が一緒になって形成される、置換基を有してもよい炭素数が１〜１２のアルキレン基の代表例としては、１，２−アルキレン基（例えば、１，２−シクロヘキシレン、２，３−ブチレンなど）があげられる。この１，２−アルキレン基は、α−オレフィン類（例えば、エテン、プロペン、ヘキセン、オクテン、デセン、ドデセンおよびスチレン）を臭素化して得られる１，２−ジブロモアルカン類から誘導される。Ｒ^１およびＲ^２が一緒になって形成される炭素数が１〜１２のアルキレン基の好適な置換基は、メチレン、１，２−エチレンおよび１，３−プロピレン基であり、１，２−エチレン基が特に好適である。 The conductive film of the present invention has the following general formula on at least one side of the base film.

A conductive polymer composed of a polycationic polythiophene composed of repeating units represented by the formula (hereinafter sometimes referred to as “poly (3,4-disubstituted thiophene)”) and a polyanion is contained as a constituent component. A transparent conductive coating film is formed. Here, R ¹ and R ² in the above formula independently represent hydrogen or an alkyl group having 1 to 4 carbon atoms, or have 1 to 1 carbon atoms that may be optionally substituted together. 12 alkylene groups are represented. As a typical example of the alkylene group having 1 to 12 carbon atoms which may be substituted and formed by R ¹ and R ² together, a 1,2-alkylene group (for example, 1,2- Cyclohexylene, 2,3-butylene, etc.). This 1,2-alkylene group is derived from 1,2-dibromoalkanes obtained by brominating α-olefins (for example, ethene, propene, hexene, octene, decene, dodecene and styrene). Suitable substituents of the alkylene group having 1 to 12 carbon atoms formed by combining R ¹ and R ² are methylene, 1,2-ethylene and 1,3-propylene groups, An ethylene group is particularly preferred.

  On the other hand, the polyanion constituting the conductive polymer includes polymeric carboxylic acids (for example, polyacrylic acid, polymethacrylic acid, polymaleic acid, etc.), and polymeric sulfonic acids (for example, polystyrene sulfonic acid, polyvinyl sulfonic acid, etc.). Etc. These polymeric carboxylic acids and sulfonic acids may also be copolymers of vinyl carboxylic acids and vinyl sulfonic acids with other polymerizable monomers such as acrylates and styrene. Among these polyanions, those in which polystyrene sulfonic acid and all or a part thereof are metal salts are particularly suitable. The number average molecular weight of the polyanion is suitably in the range of 1,000 to 2,000,000, particularly preferably in the range of 2,000 to 500,000.

  The transparent conductive coating film containing the conductive polymer may contain diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, or the like from the viewpoint of improving the conductive performance. Further, a water-soluble compound that is liquid at room temperature having an amide bond in the molecule may be contained.

  These compounds are preferably contained in the range of 10 to 1000 parts by weight, preferably in the range of 30 to 600 parts by weight, with respect to 100 parts by weight of the conductive polymer. When the content is less than 10 parts by weight, the effect of improving the conductive performance is reduced. Conversely, when the content is more than 1000 parts by weight, the haze value of the coating is increased and the transparency is lowered. Since the strength of the film itself is reduced, the film easily peels off, and when the film is wound into a roll, a problem such as easy transfer to the back surface with which the coating film comes into contact easily occurs. Here, “with respect to 100 parts by weight of the conductive polymer” means “with respect to 100 parts by weight of the solid content of the conductive polymer”.

  Next, you may add an alkoxysilane compound to the transparent conductive coating film concerning this invention in order to improve the intensity | strength of the coating film obtained. These silane compounds are present in the coating film in the form of a reaction product obtained by hydrolysis and subsequent condensation reaction. Examples of these silane compounds include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetraisobutoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, trimethylethoxysilane, phenyltriethoxysilane, and γ-glycidoxy. Examples include trialkoxysilanes having reactive functional groups other than alkoxy groups such as propyltrimethoxysilane and vinyltriethoxysilane, especially 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropylmethyl having an epoxy group. Dimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and the like are preferable.

  The amount of the alkoxysilane compound added is preferably in the range of 20 to 500 parts by weight with respect to 100 parts by weight of the conductive polymer. When the added amount is less than 20 parts by weight, the effect of improving the coating film strength is reduced, while when it exceeds 500 parts by weight, the surface resistivity tends to increase.

  In order to efficiently proceed such hydrolysis / condensation of the silane compound, it is preferable to use a catalyst in combination. As the catalyst, either an acidic catalyst or a basic catalyst can be used. As the acidic catalyst, inorganic acids such as acetic acid, hydrochloric acid and nitric acid, and organic acids such as acetic acid, citric acid, propionic acid, oxalic acid and p-toluenesulfonic acid are suitable. On the other hand, as the basic catalyst, organic amine compounds such as ammonia, triethylamine and tripropylamine, and alkali metal compounds such as sodium methoxide, potassium methoxide, potassium ethoxide, sodium hydroxide and potassium hydroxide are suitable.

  In the present invention, as the coating composition for forming the transparent conductive coating film layer, a dispersion liquid in which the conductive polymer as a main component is dispersed in water is used. If necessary, polyester, polyacryl, polyurethane A suitable organic polymer material such as polyvinyl acetate or polyvinyl butyral can be added as a binder.

  Furthermore, if necessary, an appropriate solvent compatible with water can be added for the purpose of dissolving the binder, improving the wettability to the base film, or adjusting the solid content concentration. . For example, alcohols (methanol, ethanol, propanol, isopropanol, etc.), amides (formamide, N, N-dimethylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpropionamide) and the like are preferable. Used.

  Furthermore, you may add a small amount of surfactant to the said coating composition in order to improve the wettability with respect to a base film. Preferred surfactants include nonionic surfactants (eg, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, sorbitan fatty acid ester, etc.), and fluorosurfactants (eg, fluoroalkylcarboxylates, Fluoroalkylbenzene sulfonate, perfluoroalkyl quaternary ammonium salt, perfluoroalkyl polyoxyethylene ethanol, etc.).

  The surface layer of the transparent conductive coating film containing the conductive polymer of the present invention has a thickness of the layer not containing the polythiophene of 5 nm or less, preferably 3 nm or less, particularly preferably 2 nm or less. is required. When this film thickness exceeds 5 nm, the contact resistance increases and the electrical conductivity decreases. For example, when used as a base material for a touch panel, problems such as erroneous operation occur, and organic When used as a transparent electrode such as an electroluminescence element or an inorganic electroluminescence lamp, there arises a problem that predetermined conductivity cannot be obtained.

  The thickness of the fully transparent conductive coating layer is preferably 50 nm or more, particularly 70 nm or more, and preferably 500 nm or less, particularly 300 nm or less. If the thickness of the coating film is too thin, sufficient conductivity may not be obtained. Conversely, if it is too thick, transparency may be insufficient or blocking may occur.

  Next, the base film used in the present invention is not particularly limited, but polyester, polystyrene, polyimide, polyamide, polysulfone, polycarbonate, polyvinyl chloride, polyethylene, polypropylene, blends and copolymers thereof, and phenol A film made of resin, epoxy resin, ABS resin or the like is preferable.

  Among them, a polyester film, particularly a biaxially oriented polyester film is preferable because it has excellent dimensional stability, mechanical properties, heat resistance, electrical properties, and the like, and more preferably polyethylene terephthalate or polyethylene-2,6-naphthalate. However, it is more preferable because it has excellent mechanical properties such as a high Young's modulus and thermal properties such as good heat-resistant dimensional stability. The thickness of the base film is not particularly limited, but is preferably 500 μm or less. When it is thicker than 500 μm, the rigidity is too strong, and the handleability when the obtained conductive film is attached to a display or the like tends to be lowered.

The conductive film of the present invention described above further has a total light transmittance of 70% or more, preferably 80% or more, more preferably 83% or more, and at the same time a surface resistivity on the transparent conductive coating film side. It is necessary to be 10 to 1 × 10 ⁴ Ω / □, preferably 10 to 5 × 10 ³ Ω / □. When the total light transmittance is less than 70%, the transparency becomes insufficient. For example, even if a touch panel is prepared, it is dark and the display screen is difficult to see. In addition, when the surface resistivity exceeds 1 × 10 ⁴ Ω / □, the resistance is too high and the predetermined conductivity is not exhibited. On the other hand, when the surface resistivity is less than 10Ω / □, the conductive polymer is not preferable. It is not economical because the amount of use increases significantly and the manufacturing cost increases.

  The method for producing the conductive film of the present invention described above is not particularly limited, but when the coating composition for forming the transparent conductive coating layer is applied and dried, the polyanion component is on the surface layer. Since it easily migrates, for example, it is applied in two or more times, the polyanion component layer is removed by corona discharge treatment or plasma discharge treatment after the coating film is formed, or before the coating composition is applied, A preferred example is a method in which a component having a high affinity is previously applied to a substrate film. Among them, the method of applying the coating composition two or more times is that the thickness of the polyanion component layer is proportional to about 2 to 10% of the applied transparent conductive coating layer thickness, and Since the polyanion component layer is present on the upper part of the previously applied transparent conductive coating layer, a component having a high affinity with the polyanion component is applied in advance, which is preferable because the anion component layer on the surface layer can be thinned. .

  In addition, removal of the polyanion component layer by plasma discharge treatment is one of the preferred methods as in the case of two-time overcoating, as reproducibility and fine control become possible due to recent development of plasma treatment technology.

  As a method for applying the transparent conductive coating layer, a method known per se can be adopted. For example, a lip direct method, a comma coater method, a slit reverse method, a die coater method, a gravure roll coater method, a blade coater method, a spray coater method, an air knife coat method, a dip coat method, a bar coater method and the like are preferable. The heating and drying conditions are preferably 80 to 160 ° C. for 10 to 300 seconds, particularly preferably 100 to 150 ° C. for 20 to 120 seconds.

  When the base film is a polyester film, it is preferable to adopt an in-line coating method during the film forming process, in particular, applying the coating liquid after vertically stretching the unstretched film, and then heat-treating after drying and horizontal stretching. .

  According to such an in-line coating method, for example, the adhesion to the base film is improved compared to the off-line processing, and the film obtained by gripping both ends of the film with a clip at the time of heat treatment does not have wrinkles and is flat. Is effective. In addition, it is preferable to perform the heat processing by an in-line coating method at 200 degreeC or more. In addition, when applying the coating liquid, if necessary, physical surface treatment such as corona discharge treatment or plasma discharge treatment is applied to the substrate film surface as a preliminary treatment for further improving the adhesion and coating properties. May be applied.

  As described above, the conductive film of the present invention requires a polythiophene-based transparent conductive coating layer to be laminated on at least one side of the base film, but the side on which the transparent conductive coating layer is formed. A coating film such as an anchor coat layer or a hard coat layer can be provided on the opposite surface to the surface as needed.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In addition, each evaluation in an Example followed the following method.

(1) Thickness of transparent conductive coating layer An ultra-thin film slice was cut out of a conductive film perpendicularly to the film surface with a microtome ULTRACUT-S, and this ultra-thin film slice was measured with a transmission electron microscope LEM-2000 at an acceleration voltage of 100 kV The layer thickness was measured by observation and photographing.

(2) Thickness of the layer not containing polythiophene The thickness was calculated from the peak due to polythiophene using ESCALAB-200 (ESCA: Electron Spectroscopy for Chemical Analysis) manufactured by VG.

(3) Total light transmittance and haze Measured with a haze meter HCM-2B manufactured by Suga Test Instruments Co., Ltd. according to JIS K7150.

(4) Surface resistivity It measured based on JISK7194 using Mitsubishi Chemical Corporation Lorester MCP-T600. The measurement was performed five times at an arbitrary location, and the average value thereof was taken.

(5) Suitability test for touch panel As a measure of suitability of the conductive film to the touch panel, a model touch panel was prepared, and a linearity test by pen input was performed. In this test, the conductive film of the present invention was cut out to 100 mm × 100 mm, and electrodes having a width of 5 mm were applied to both ends of the transparent conductive coating layer forming surface by applying silver paste. A voltage of 5V is applied between the electrodes by a constant voltage power source, and the voltage Vi, j (i, j = at 2500 points (x1, y1) to (x50, y50) in the center of the sample 50 mm × 50 mm at 1 mm vertical and horizontal intervals. 1-50) was measured. The deviation from the theoretical voltage Ui, j = V1,1 + (V50,50-V1,1) / 50 × (j-1) at each voltage measurement point is Δi, j = (Vi, j-Ui, j) / Ui, j and the maximum absolute value of Δi, j is defined as linearity.
The test was performed by applying a load of 250 gf with a touch pen made of polyacetal resin and having a pen tip radius of 0.8 mm from the side of the panel plate made of a conductive film.
○: Linearity is less than 3%.
X: Linearity is 3% or more.

[Example 1]
Conductive paint comprising poly (3,4-ethylenedioxythiophene) and polystyrene sulfonic acid as main components, and containing a silane coupling agent and diethylene glycol (Nippon Agfa Gevaert Co., Ltd., trade name: Orgacon S) -300) is applied onto a substrate film (PET film, manufactured by Teijin DuPont Films, trade name: O3PF8W-100) using a Mayer bar, and dried at 140 ° C. for 1 minute to obtain a film thickness. A 100 nm transparent conductive coating layer was formed. Next, the same conductive paint (product name: Orgacon S-300, manufactured by Nippon Agfa / Gebart Co., Ltd.) was applied again on the transparent conductive coating layer using a Meyer bar, and 1 at 140 ° C. A transparent conductive coating layer having a total film thickness of 150 nm was formed by drying for a minute. Table 1 shows the properties of the obtained conductive film.

[Example 2]
Conductive paint comprising poly (3,4-ethylenedioxythiophene) and polystyrene sulfonic acid as main components and containing a silane coupling agent and diethylene glycol (manufactured by Nippon Agfa Gevaert Co., Ltd., trade name: Orgacon S) -300) is applied onto a substrate film (PET film, manufactured by Teijin DuPont Films, trade name: O3PF8W-100) using a Mayer bar, and dried at 140 ° C. for 1 minute to obtain a film thickness. A 150 nm transparent conductive coating layer was formed. The resulting conductive film was used in a table corona discharge treatment machine CG-102 manufactured by Kasuga Denki, using an alumina electrode, with an applied current of 4 A, a distance between the film and the electrode of 1 mm, and a film processing speed of 0.1 m / s. The treatment was performed 6 times. Table 1 shows the properties of the obtained conductive film.

[Example 3]
The same operation as in Example 2 was performed except that the corona discharge treatment was changed to the plasma discharge treatment. At this time, the plasma discharge treatment was performed using a normal pressure plasma surface treatment apparatus (AP-T03-L manufactured by Sekisui Chemical Co., Ltd.) under a nitrogen stream (60 L / min) at a treatment speed of 0.2 m / min. Plasma treatment was performed 4 times on the surface. Table 1 shows the properties of the obtained conductive film.

[Comparative Example 1]
Conductive paint comprising poly (3,4-ethylenedioxythiophene) and polystyrene sulfonic acid as main components, and containing a silane coupling agent and diethylene glycol (Nippon Agfa Gevaert Co., Ltd., trade name: Orgacon S) -300) is coated on a substrate film (PET film, manufactured by Teijin DuPont Films, trade name O3PF8W-100) using a Mayer bar, and dried at 140 ° C. for 1 minute to obtain a film thickness. Formed a transparent conductive coating layer having a thickness of 150 nm. Table 1 shows the properties of the obtained conductive film.

[Example 4]
In Example 1, an electroconductive paint Orgacon S-300, 100 weight of an aqueous dispersion (BaytronP: manufactured by Bayer AG) containing 1.3% by weight of poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid The coating composition was changed to 3 parts by weight of diethylene glycol, 0.65 parts by weight of 3-glycidoxypropyltrimethoxysilane and 1 part by weight of PLUSCOAT RY-2 (manufactured by Kyoyo Chemical) as a surfactant. Except that, the same operation as in Example 1 was performed. Table 1 shows the properties of the obtained conductive film.

[Comparative Example 2]
In Comparative Example 1, the conductive paint Orgacon S-300 is made of 100% by weight of an aqueous dispersion (BaytronP: manufactured by Bayer AG) containing 1.3% by weight of poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid. The coating composition was changed to 3 parts by weight of diethylene glycol, 0.65 parts by weight of 3-glycidoxypropyltrimethoxysilane and 1 part by weight of PLUSCOAT RY-2 (manufactured by Kyoyo Chemical) as a surfactant. The same operation as in Comparative Example 1 was performed except that. Table 1 shows the properties of the obtained conductive film.

[Example 5]
Conductive paint (Nippon Agfa Gebalt Co., Ltd., trade name: Orgacon S-300) on a base film (PET film, Teijin DuPont Films, trade name: O3PF8W-100) using a Mayer bar And dried at 140 ° C. for 1 minute to obtain a transparent conductive coating layer having a thickness of 50 nm. The resulting conductive film was used in a table corona discharge treatment machine CG-102 manufactured by Kasuga Denki, using an alumina electrode, with an applied current of 4 A, a distance between the film and the electrode of 1 mm, and a film processing speed of 0.1 m / s. The treatment was performed 3 times. Table 1 shows the properties of the obtained conductive film.

  As is clear from Table 1, it can be seen that the conductive film of the present invention is excellent in transparency and conductivity, and at the same time, when used as a transparent electrode of a touch panel.

  The conductive film of the present invention described above has transparency and conductivity equivalent to those obtained by laminating ITO while using a conductive polymer. For example, a transparent touch panel, a liquid crystal display ( LCD), organic electroluminescence elements, inorganic electroluminescence elements and the like can be suitably used as transparent electrodes.

Claims (4)

On at least one side of the base film, the following general formula

(Wherein R ¹ and R ² each independently represent hydrogen or an alkyl group having 1 to 4 carbon atoms, or an alkylene group having 1 to 12 carbon atoms which may be optionally substituted together) A conductive film comprising a conductive polymer composed of a polycationic polythiophene and a polyanion composed of a repeating unit represented by the following formula: The layer thickness not containing the polythiophene on the surface side is 5 nm or less, the total thickness of the transparent conductive coating film is 50 nm or more and 300 nm or less, and the total light transmittance of the conductive film is 82 % or more. And a surface resistivity of 10 to 1 × 10 ⁴ Ω / □. Conductive film according to claim 1 front surface resistivity of ^{3 Ω} / □ ^10~5 × 10. Base film, conductive film according to claim 1 or 2 which is a polyester film. In producing the conductive film according to any one of claims 1 to 3, when applying a coating composition for forming a transparent conductive coating film, it is applied in two or more times, or A method for producing a conductive film, wherein a corona discharge treatment or a plasma discharge treatment is performed on the transparent conductive coating after the formation of the transparent conductive coating.