JP2009211978A - Transparent conductive film, and optical device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent conductive film having a high conductivity and a high light transmittance, and an optical device using this. <P>SOLUTION: The transparent conductive film includes a conductive polymer layer (PEDOT) laminated on a transparent substrate (PET) and a CNT layer laminated on the conductive polymer layer. The CNT layer and the conductive polymer layer is formed by either a coating method, a dip method, or a spin coating method. The transparent conductive film includes a layer consisting of a sandwich structure in which the CNT layer is pinched by two layers of the conductive polymer. The layer consisting of the sandwich structure may have a plurality of layers, and the CNT is laminated on the uppermost layer. The transparent conductive film includes excellent conductive characteristics and optical characteristics, and the transparent substrate on which this transparent electrode is formed can be used suitably as a substrate in a touch panel, an electroluminescent device, an electrochromic device, and an optical device such as a solar cell. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transparent conductive film and an optical device using the same.

  Conventionally, indium tin oxide (ITO) has been mainly used as a transparent conductive film material, but its mechanical properties are poor, it is weak against bending, etc., and it is flexible such as a display using a flexible plastic substrate, a solar cell, etc. There is a problem that it is not suitable for use, and there are few resources and indium is expensive.

  Carbon nanotubes (hereinafter abbreviated as CNT) have excellent electrical and mechanical properties, and are expected to be applied in a wide range of fields as potential materials for nanotechnology. It is actively done. As one of them, preparation of a transparent conductive film by a method such as applying a solution containing CNT or the like on a substrate has been studied.

  Patent Document 1 entitled “Method for Producing Carbon Nanotube-Containing Film and Carbon Nanotube-Containing Coating” includes the following description.

  In the method for producing a CNT-containing coating film, the method for producing a CNT-containing coating film comprises applying a first dispersion containing at least CNT and a solvent to the surface of a substrate, and removing the solvent of the first dispersion. Then, the CNT is made into a three-dimensional network structure, and further, a second dispersion containing at least a resin and a solvent is applied thereon, and the second dispersion penetrates into the three-dimensional network structure of the CNT. A method for producing a CNT-containing coating film, characterized by being made.

  The film of the invention of Patent Document 1 provides excellent conductivity and transparency with a low CNT content. In a preferred embodiment, the CNT is present in the film from about 0.001 to about 1% by weight. Preferably, about 0.01 to about 0.1% of CNT is present in the film, which provides excellent transparency and low haze.

  Patent Document 2 entitled “Carbon Nanotube Dispersion Solution and Carbon Nanotube Dispersion” has the following description.

  In the prior art, in order to improve the dispersibility of the CNT in the solution, there has been a problem that the properties of the original CNT, for example, high conductivity and semiconductor characteristics are impaired when the surface of the CNT is modified. Therefore, in order to solve the above problems, the present invention maintains CNTs with high conductivity and semiconductor characteristics, and has excellent dispersibility in a solvent, a CNT dispersion solution containing the CNTs, and a CNT obtained by the solution. Provide a dispersion.

In order to achieve the above object, the invention of Patent Document 2 has the following configuration.
(1) A carbon nanotube dispersion solution having carbon nanotubes and a solvent, wherein the conjugated polymer is attached to at least a part of the carbon nanotubes, and the carbon nanotubes are dispersed in the solvent.
(2) A step of attaching a conjugated polymer to at least a part of the carbon nanotubes, a step of washing the carbon nanotubes attached with the conjugated polymer with a solvent in which the conjugated polymer is soluble, and the above steps. And a step of dissolving the obtained carbon nanotubes in a solvent.
(3) A CNT dispersion formed by applying the carbon nanotube dispersion solution of (1) above.

  According to the invention of Patent Document 2, CNT can be uniformly dispersed in a solution, and by using the obtained CNT dispersion solution, a dispersion having high conductivity inherent in CNT itself and excellent semiconductor characteristics. Can be formed at room temperature without the need for high temperatures. Moreover, according to the invention of Patent Document 2, since the film thickness of the CNT dispersion can be formed uniformly, an electron-emitting device using the CNT dispersion film as an electron emission source can be obtained, and the film thickness of the CNT dispersion can be obtained. By thinning, a transparent conductor can be obtained.

  In the invention of Patent Document 2, a uniform CNT dispersion solution can be formed by dispersing CNT with a conjugated polymer adhering to at least a part thereof in a solvent, and further, a uniform CNT dispersion can be achieved by coating the solution on a substrate. The body is obtained. In the invention of Patent Document 2, the term “dispersion” is used, which includes a phenomenon in which CNT is dissolved in a solvent.

Hereinafter, the invention of Patent Document 2 will be described in detail. In the invention of Patent Document 2, the polymer attached to the CNT needs to be a conjugated polymer, and more preferably a linear conjugated polymer. Here, the straight chain means that the skeleton structure of the polymer does not take a spiral structure in a stable state (a state in which no external force is applied) and extends straight, and the conjugated polymer is a polymer. The polymer in which the carbon-carbon bonds of the skeleton are alternately linked with single bonds and double bonds. Since the conjugated polymer has a structure in which the conjugated structure is extended, the charge transfer between the CNT and the polymer is smooth, and a polymer other than the polymer attached to the CNT does not intervene. Characteristics and efficient use of semiconductor characteristics. By changing the CNT concentration in the CNT dispersion solution of the invention of Patent Document 2, the conductivity and semiconductor characteristics of the substrate coated with the solution can be controlled.

  Examples of the conjugated polymer include a polythiophene polymer, a polypyrrole polymer, a polyaniline polymer, a polyacetylene polymer, a poly-p-phenylene polymer, and a poly-p-phenylene vinylene polymer.

  Patent Document 3 entitled “Carbon Nanotube-Containing Composition, Composite Containing the Coated Film, and Manufacturing Method Thereof” includes the following description.

  The first invention of Patent Document 3 contains a conductive polymer (a) having an ammonium salt of a sulfonic acid group and / or an ammonium salt of a carboxylic acid group, a solvent (b), and CNT (c). It is a CNT containing composition. The CNT-containing composition of Patent Document 3 further contains a polymer compound (d), a basic compound (e), a surfactant (f), a silane coupling agent (g) and / or colloidal silica (h). As a result, the performance can be improved.

  In the second invention of Patent Document 3, a conductive polymer (a) having an ammonium salt of a sulfonic acid group and / or an ammonium salt of a carboxylic acid group, a solvent (b), and CNT (c) are mixed, and ultrasonic waves are mixed. It is the manufacturing method of the CNT containing composition characterized by irradiating.

  A third aspect of the invention of Patent Document 3 is a composite comprising a coating film comprising the CNT-containing composition of the invention of Patent Document 3 on at least one surface of a substrate. A fourth aspect of the invention of Patent Document 3 is characterized in that the CNT-containing composition of Patent Document 3 is applied on at least one surface of a substrate, and a coating film is formed by standing or heating at room temperature. This is a method for producing a composite.

  In Patent Document 3, No. 5, a CNT-containing composition of Patent Document 3 is applied on at least one surface of a substrate, and a coating film is formed by standing or heating at room temperature. It is a CNT physical property evaluation method characterized by evaluating physical properties of a film. The sixth of Patent Document 3 is a CNT-containing polymer material obtained by desolvating the CNT-containing composition of the invention. The seventh of Patent Document 3 is a CNT-containing carbon material obtained by firing the CNT-containing polymer material of Patent Document 3.

  Patent Document 4 entitled “Molded Body Having Protruding Conductive Layer” has the following description.

  One embodiment of the invention of Patent Document 4 is a conductive molded body composed of a base material and a conductive layer formed on the surface of the base material, and the conductive layer contains fine conductive fibers dispersed therein. Then, at least a part with fibers is fixed to the substrate, at least a part with the fibers protrudes from the outermost surface of the conductive layer, and the fibers are arranged in electrical contact with each other. Preferably, the fibers are in electrical contact with each other at a portion protruding from the outermost surface or a portion fixed to the substrate.

The substrate comprises a substrate body and a surface layer, and the portion of the fiber fixed to the substrate is fixed to the surface layer, or the portion of the fiber fixed to the substrate is the end of the fiber or The middle part of the fiber. Preferably, the fibers are separated from other fibers, and if a large number of fibers form a bundle, the bundle of fibers is separated from the other. A preferred fiber is carbon fiber, but is not limited thereto. The carbon fiber is preferably CNT. The thickness of the conductive layer is preferably 5 to 500 nm. The surface layer is preferably formed from a curable resin, and such a surface layer is also preferably formed from a thermoplastic resin. The conductive layer preferably has a surface resistivity of about 10 ⁰ to about 10 ¹¹ Ω / □, and has a light transmittance of 550 nm of 50% or more and a surface resistivity of 10 ⁰ to 10 ¹¹ Ω / □. Is preferred.

Patent Document 5 entitled “Touch Panel” has the following description.
The transparent conductive film on the upper surface of the glass substrate is prepared by preparing a CNT mixed acrylic resin in which less than 10% of CNT is kneaded with a matte material (silicon oxide) in a transparent liquid UV curable acrylic resin, and using a roll. The CNT mixed acrylic resin is applied to the upper surface of the glass substrate to form a coating film, and finally the ultraviolet resin is irradiated to cure the acrylic resin. Within the transparent conductive film, the CNTs are irregularly arranged.

  Non-Patent Document 1 describes a resistance between SWNTs.

  Non-Patent Document 2 describes the formation of a SWNT transparent film by a filtration method.

  Non-Patent Document 2 describes that the SWNT film is coated with PEDOT: PSS to reduce the surface roughness.

Japanese Patent No. 3665969 (Claims (Claim 1), Paragraph 0013) JP 2005-89738 A (paragraphs 0005 to 0010) Japanese Patent Laying-Open No. 2005-281672 (paragraphs 0009 to 0013) JP-T-2006-519712 (paragraphs 0008 to 0009) JP 2007-11997 (paragraph 0012, FIG. 3) M. S. Fuhrer et al, “Crossed Nanotube Junctions”, Science, Vol.288 (2000) 494-497 (page 494) Z. Wu et al, “Transparent, conductive Carbon Nanotube Films”, Science, Vol. 305 (2004) 1273-1276 (page 1273) M. W. Rowell et al, “Organic solar cells with carbon nanotube network electrodes”, Appl. Phys. Lett., 88, 233506 (2006) (233506-2)

  Conventionally, film formation of a transparent conductive film has been studied by a method such as applying a solution containing CNT or the like on a substrate, but CNT can be stably dispersed in a solution when mixed in a solvent. Since it is very difficult and easily aggregates, there is a problem that it is difficult to form a uniform conductive film by coating or the like. For this reason, a method of preparing a stable dispersion solution using a dispersant or the like, a method of uniformly forming a film after being dispersed, and the like have been studied.

  As a method for uniformly forming a film, for example, there is a filter method in which CNTs in a solution are uniformly deposited on a filter, and the CNTs are transferred onto a transparent substrate, and the film forming process is very complicated. There is a problem that it contains a lot of impurities.

  In addition, there is a method of voluntarily adhering CNT to the substrate using the affinity between the CNT and the substrate. In this method, the conductive film is formed on a silicon substrate having a relatively large surface energy. There is a problem of being limited. In addition, as other methods, there are an electrodeposition method, a method using CVD, and the like, but there is a problem that scale-up is very difficult.

  In order to put a transparent conductive film using CNT into practical use instead of the ITO transparent conductive film used for a transparent electrode or the like, it is necessary to improve transparency and conductivity.

  FIG. 3 is a conceptual diagram illustrating problems in putting a CNT transparent conductive film into practical use. FIG. 3A is a composite in which CNTs are dispersed in a polymer, and FIG. 3B is an ideal view. FIG. 3C is a diagram for explaining the resistance between the CNTs in FIGS. 3A and 3B.

  Conventionally, in many cases, composites containing CNTs are contained in a thermoplastic or thermosetting polymer (resin) 20a such as an acrylic resin in order to maintain mechanical strength, as shown in FIG. The CNT 10a is mixed and compounded, and the CNT 10a is randomly present in the sea of the polymer 20a via the polymer 20a, and the CNT network structure is disturbed, as shown in FIG. As shown in the left side view, since the gap between the CNTs 10a is a space filled with the polymer 20a, the direct contact between the CNTs 10a is poor, resulting in high resistance and high It becomes difficult to obtain conductivity. In order to achieve high conductivity, the composite needs to contain CNT 10a at a sufficient concentration, but in this case, the composite exhibits a fairly strong black color and has a reduced light transmittance. There is a problem that it ends up.

  In order to solve this problem, as shown in FIG. 3B, an ideal three-dimensional network structure in which the CNTs 10b are in contact with each other is maintained, and as shown in the right side of FIG. It is desirable that the gap is filled with the conductive material 20b. However, in reality, an ideal three-dimensional network structure is not formed, the CNTs 10b are close to each other and in contact with each other, and the CNTs 10b are close to each other. Even in the case of having a three-dimensional network structure as a whole, including a portion that is not in contact with the CNT, at least a part of the gap (which may exist in a plurality of locations) of the CNT 10b is formed by the conductive material 20b. If it is satisfied, the conductivity of the composite is expected to be high.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a transparent conductive film having high conductivity and high light transmittance, and an optical device using the same. is there.

  That is, the present invention relates to a conductive polymer layer (for example, a PEDOT film in a later-described embodiment) laminated in contact with a substrate (for example, a PET substrate in a later-described embodiment), and the conductive polymer. The present invention relates to a transparent conductive film having a carbon nanotube layer (for example, a CNT film in an embodiment described later) laminated in contact with the layer.

  The present invention also includes a layer having a sandwich structure in which a carbon nanotube layer and a conductive polymer layer stacked on a substrate are provided, and the conductive polymer layer is stacked in contact with the two carbon nanotube layers. And having one of the carbon nanotube layers in contact with the substrate to be laminated.

  In addition, the present invention provides an optical device having a first substrate on which the transparent conductive film is formed, and a second substrate provided with an electrode with a gap and facing the first substrate ( For example, the present invention relates to a touch panel in an embodiment described later.

  According to the transparent conductive film of the present invention, since the conductive polymer layer stacked in contact with the substrate and the carbon nanotube layer stacked in contact with the conductive polymer layer are provided, A transparent conductive film having a smaller surface resistance (sheet resistance) than the transparent conductive film formed by directly contacting the carbon nanotube layers can be realized.

  The transparent conductive film of the present invention includes a carbon nanotube layer and a conductive polymer layer stacked on a substrate, and the conductive polymer layer is stacked in contact with the two carbon nanotube layers. Since the carbon nanotube layer has a structure in which one of the carbon nanotube layers is stacked in contact with the substrate, the transparent layer is formed by directly contacting the carbon nanotube layer on the substrate. A transparent conductive film having a surface resistance smaller than that of the conductive film can be realized.

  In addition, according to the optical device of the present invention, the first substrate on which the transparent conductive film is formed, and the second substrate provided with an electrode provided to face the first substrate with a gap therebetween, Therefore, it is possible to provide an optical device such as a touch panel, an electroluminescence device, an electrochromic device, and a solar cell, which has a small surface resistance, a high light transmittance, and an excellent electrical property and optical property.

  In the transparent conductive film of the present invention, it is preferable that the carbon nanotube layer has a layer having a sandwich structure in which the carbon nanotube layer is laminated in contact with the two conductive polymer layers. According to this configuration, a transparent conductive film having a smaller surface resistance can be realized.

  The carbon nanotube layer is preferably laminated on the uppermost layer. According to this configuration, a transparent conductive film having a smaller surface resistance can be realized.

  Further, the conductive polymer layer is preferably laminated on the uppermost layer. According to this configuration, a transparent conductive film having a smaller surface resistance can be realized.

  The sheet resistance is preferably 1 Ω / □ or more and 10,000 Ω / □ or less. According to this configuration, an optical device having a small surface resistance and excellent electrical characteristics can be provided.

  In addition, the visible light transmittance is preferably 70% or more. According to this configuration, an optical device having a large light transmittance and excellent optical characteristics can be provided. Note that the visible light transmittance of 70% or more indicates the light transmittance in the entire visible light region, and the light transmittance relating only to the transparent conductive film not including the substrate in the transparent conductive film formed on the substrate. Is 70% or more.

  The conductive polymer layer and the carbon nanotube layer may have a thickness of several nm or more and 100 nm or less. According to this configuration, it is possible to realize a transparent conductive film having a low surface resistance, a high light transmittance, and excellent electrical characteristics and optical characteristics.

  The carbon nanotube layer may be formed by applying a solution in which carbon nanotubes are dispersed in a solvent. According to this configuration, the transparent conductive film can be provided without requiring a complicated device.

  The conductive polymer layer may be formed by applying a solution obtained by diluting a conductive polymer in a solvent. According to this configuration, the transparent conductive film can be provided without requiring a complicated device.

  In the carbon nanotube layer, one carbon nanotube molecule is preferably in contact with a plurality of carbon nanotube molecules. According to this configuration, since the carbon nanotube layer forms a three-dimensional network of carbon nanotube molecules in contact with each other, a transparent conductive film having high conductivity can be realized.

  The substrate may be a transparent substrate, preferably a polymer substrate. According to this configuration, a transparent conductive film that can be deformed flexibly and has a desired shape can be realized.

  In the optical device of the present invention, the transparent conductive film is preferably used. According to this configuration, an optical device having excellent electrical characteristics and optical characteristics can be provided.

  Moreover, what was comprised as a touchscreen is good. According to this configuration, a touch panel excellent in electrical characteristics and optical characteristics can be realized.

  Further, it is preferable that a light emitting layer that emits light by applying a voltage between the first substrate and the second substrate is provided and configured as an electroluminescence device. According to this configuration, it is possible to realize an electroluminescence device that is excellent in electrical characteristics and optical characteristics.

  Further, it is preferable that an electrochromic compound is supported on the first substrate and configured as an electrochromic device. According to this configuration, an electrochromic device having excellent electrical characteristics and optical characteristics can be realized.

  Further, a solar cell having a structure in which an electrolyte is sandwiched between a titanium dioxide layer having an organic dye adsorbed between the first substrate and the second substrate is preferable. According to this configuration, a solar cell having excellent electrical characteristics and optical characteristics can be realized.

  The present invention includes (1) a first step of bringing a conductive polymer layer into contact with a substrate and a second step of forming a carbon nanotube layer in contact with the conductive polymer layer. The present invention relates to a method for producing a transparent conductive film.

  The present invention also includes (2) a step of contacting a substrate to form a carbon nanotube layer, a contact with the carbon nanotube layer to form a conductive polymer layer, and then contacting the conductive polymer layer to And a step of forming a carbon nanotube layer and forming a layer having a sandwich structure.

  (3) In (1), it is preferable to have a third step of laminating the conductive polymer layer in contact with the carbon nanotube layer.

  (4) In (3), it is preferable to have a fourth step of laminating the carbon nanotube layer in contact with the conductive polymer layer.

  (5) In (1), the method includes a third step of laminating the conductive polymer layer in contact with the carbon nanotube layer, and repeating the second step and the third step. It is good to do.

  In addition, in (6) and (5), it is preferable to have a fourth step of laminating the carbon nanotube layer in contact with the conductive polymer layer.

  (7) In (2), it is preferable to have a third step of laminating the conductive polymer layer in contact with the carbon nanotube layer.

  In (8) (1) or (2), the sheet resistance is preferably 1 Ω / □ or more and 10,000 Ω / □ or less.

  In (9), (1), or (2), the visible light transmittance is preferably 70% or more.

  In (10), (1) or (2), it is preferable that the conductive polymer layer and the carbon nanotube layer have a thickness of several nm or more and 100 nm or less.

  In (11), (1) or (2), the carbon nanotube layer may be formed by applying a solution in which carbon nanotubes are dispersed in a solvent.

  In (12) (1) or (2), the conductive polymer layer may be formed by applying a solution obtained by diluting a conductive polymer in a solvent.

  (13) In (1) or (2), it is preferable that one carbon nanotube molecule is in contact with a plurality of carbon nanotube molecules in the carbon nanotube layer.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.

  The transparent conductive film comprises a conductive polymer layer having a thickness of several nm or more and 100 nm or less laminated on a transparent substrate, and a thickness of several nm or more and 100 nm or less laminated on the conductive polymer layer. It has a carbon nanotube (CNT) layer. The CNT layer is formed by a coating method such as a dipping method or a spin coating method using a solution in which CNTs are dispersed in a solvent, and has a three-dimensional network structure in which CNT molecules are in contact with each other. The conductive polymer layer is formed by a coating method such as a dipping method or a spin coating method using a solution obtained by diluting a conductive polymer in a solvent. The CNT layer and the conductive polymer layer can also be formed by a printing method.

  The transparent conductive film has a layer having a sandwich structure in which a CNT layer is sandwiched between two conductive polymer layers, and a plurality of layers having a sandwich structure may be provided. It is laminated on the upper layer.

  The transparent conductive film includes a CNT layer and a conductive polymer layer stacked on a transparent substrate, and has a layer having a sandwich structure in which the conductive polymer layer is stacked between two CNT layers. One CNT layer is laminated on a transparent substrate, and a plurality of layers having a sandwich structure may be provided, and the conductive polymer layer is laminated on the uppermost layer.

  As the substrate on which the transparent conductive film is formed, a glass substrate and various polymer substrates (polymer substrates) can be used. Examples of the polymer substrate include polyethylene terephthalate (PET), polyethylene naphthalate (PAN), and polyethylene naphthalate. Polyester films such as phthalate (PEN), polybutylene terephthalate (PBT), polypropylene (PP), polyethylene (PE), polyethersulfone (PES), polyimide (PI), polycarbonate (PC), polyarylate ( A transparent substrate such as PAR) or polysulfone (PS) can be used.

  The conductive polymer layer may be formed using an organic conductive material (conductive polymer) mainly composed of a polymer such as polyaniline, polythiophene, polypyrrole, polyacetylene, polyparaphenylene, or polyparaphenylene vinylene. it can.

For example, as a conductive polymer, a polythiophene-based conductive polymer, Baytron (registered trademark) PEDOT (3,4-ethylenedioxythiophene) manufactured by Starck Vitec Co., Ltd. (purchased by: Pure Chemical), is polymerized in high molecular weight styrene sulfonic acid. A conductive polymer) can be used. Baytron is a bluish polymer, highly transparent, and capable of surface resistance of several hundred to 10 ⁸ Ω / □.

  PEDOT (poly (3,4-ethylenedioxythiophene)) is inherently insoluble but is obtained as a colloidal dispersion in an aqueous solution in the presence of polystyrene sulfonic acid (PSS). This PEDOT / PSS aqueous dispersion It can be applied by spin, spray coating or the like.

  In the present invention, a CNT layer having a three-dimensional network structure is obtained by evaporating the solvent on a substrate (glass or polymer plate or filter) using a dispersion liquid in which CNT is dispersed in a solvent, leaving only the CNT. By forming and stacking the CNT layer and the conductive polymer layer, the conductive polymer penetrates the gap between the CNTs in the CNT layer at the joint portion where the CNT layer and the conductive polymer layer are stacked. CNT layer and conductive polymer layer with excellent electrical and optical properties with high electrical conductivity and high light transmittance, with good electrical contact and good bonding strength between the two layers A transparent conductive film can be formed as a composite in which is laminated.

  The transparent conductive film according to the present invention has high transparency, electrical conductivity and mechanical strength, has a sheet resistance of 1Ω / □ or more and 10,000Ω / □ or less, and has a light transmittance of 70% or more for visible light. It has conductive and optical properties. For optical devices such as electroluminescence (EL) devices, electrochromic (EC) devices, liquid crystal devices (LCD), light-emitting diode elements (LEDs), plasma display panels (PDP), etc., a sheet of 10Ω / □ to 100Ω / □ Resistance, characteristics of transmittance of 70% or more (excluding the substrate on which the transparent electrode is formed), solar cell, sheet resistance of 1Ω / □ to 20Ω / □, transmittance of 70% or more (transparent electrode is formed) For the touch panel, it is desirable to use a transparent electrode having a sheet resistance of 100Ω / □ to 10 kΩ / □ and a transmittance of 92% or more (excluding the substrate on which the transparent electrode is formed). The transparent conductive electrode is required to have high transparency and low resistance. The transparent conductive film according to the present invention can be suitably used as a transparent electrode in optical devices such as touch panels, EL devices, EC devices, LCDs, LEDs, PDPs, ordinary silicon solar cells, and dye-sensitized solar cells. it can.

Embodiment FIG. 1 illustrates the structure of a transparent conductive film in which (A) a PEDOT film and a CNT film, (B) a CNT film and a PEDOT film are sequentially laminated on a PET film in an embodiment of the present invention. FIG.

  As shown in FIG. 1, the transparent conductive film is formed on a transparent substrate using PET as a transparent substrate, and has a CNT layer having a three-dimensional network structure formed in a network shape (in FIG. 1, simply referred to as CNT). And a conductive polymer layer (simply referred to as PEDOT in FIG. 1) formed by using the above-described PEDOT / PSS aqueous dispersion (product name: Baytron P HCV4). Have.

In FIG. 1 (A),
(A1) shows a perspective view and a sectional view showing a CNT / PEDOT transparent conductive film in which a PEDOT film and a CNT film are laminated on a PET film,
(A2) is a perspective view showing a PEDOT / CNT / PEDOT transparent conductive film having a PEDOT / CNT / PEDOT sandwich structure, in which a PEDOT film, a CNT film, and a PEDOT film are sequentially laminated on a PET film;
(A3) is a perspective view showing a CNT / PEDOT / CNT / PEDOT transparent conductive film having a PEDOT / CNT / PEDOT sandwich structure in which a PEDOT film, a CNT film, a PEDOT film, and a CNT film are sequentially laminated on a PET film. And
(A4) has a PEDOT / CNT / PEDOT sandwich structure, and a PEDOT / CNT / PEDOT / CNT / PEDOT transparent conductor in which a PEDOT film, a CNT film, a PEDOT film, a CNT film, and a PEDOT film are sequentially laminated on a PET film. It is a perspective view which shows a film | membrane.

In FIG. 1 (B)
(B1) shows a perspective view and a sectional view showing a PEDOT / CNT transparent conductive film in which a CNT film and a PEDOT film are sequentially laminated on a PET film,
(B2) is a perspective view showing a CNT / PEDOT / CNT transparent conductive film having a CNT / PEDOT / CNT sandwich structure, in which a CNT film, a PEDOT film, and a CNT film are sequentially laminated on a PET film;
(B3) has a CNT / PEDOT / CNT sandwich structure, and a PEDOT / CNT / PEDOT / CNT transparent conductor in which a CNT film, a PEDOT film, a CNT film, and a PEDOT film are sequentially laminated on a PET film. It is a perspective view showing a membrane,
(B4) has a CNT / PEDOT / CNT sandwich structure, and a CNT / PEDOT / CNT / PEDOT / CNT transparent conductor in which a CNT film, a PEDOT film, a CNT film, a PEDOT film, and a CNT film are sequentially laminated on a PET film. It is a perspective view which shows a film | membrane.

In the transparent conductive film shown in FIG. 1A, since the PEDOT film is first formed on the PET film, the compatible polymers are bonded to each other, and the bonding (adhesion) strength between the PET substrate and the PEDOT layer is increased. In the transparent conductive films shown in FIGS. 1 (A) and 1 (B), the surface of the three-dimensional network structure of the CNT layer formed for each lamination and the surface of the PEDOT layer formed for each lamination are respectively provided. Since there is unevenness, the PEDOT layer is formed on the CNT layer, and the bonding area when forming the CNT layer on the PEDOT layer is large, the bonding (adhesion) strength between the two layers is increased, and the mechanical strength is increased. A transparent conductive film having high strength is formed on the PET substrate.

  In the process of forming the transparent conductive film shown in FIG. 1, since the PEDOT layer is formed on the CNT layer while maintaining the three-dimensional network structure of the CNT layer, the three-dimensional network structure of the CNT layer is not disturbed. The conductivity of the transparent conductive film can be increased by supporting the electric conduction between the CNT layers by the PEDOT layer. In addition, by reducing the thickness of the stacked CNT layer and PEDOT layer, the contact frequency between the conductive polymer (PEDOT) and the CNT molecules is increased in the stacked surface direction and the entire stacked direction of the stacked CNT layers. In addition, the conductivity of the transparent conductive film can be made higher.

  The CNT layer is formed with a film thickness of 2 nm to 10 nm, for example, by impregnating a transparent substrate with a solution in which CNT is dispersed in a solvent and holding the CNT on the substrate. The PEDOT layer is formed with a film thickness of 2 nm to 10 nm by, for example, a spin coating method.

  As will be described later, the light transmittance of the CNT layer is slightly small on the short wavelength side and large on the long wavelength side, while the light transmittance of the PEDOT layer is large on the short wavelength side and small on the long wavelength side. By alternately laminating CNT layers and PEDOT layers having different light transmission characteristics, the light transmittance does not change greatly depending on the wavelength, and a transparent conductive film with little discoloration can be formed.

  The CNT used for forming the CNT layer is manufactured by any one of an arc discharge method, a laser ablation method, a CVD method, a vapor phase growth method, and the like. For example, HiPco (manufactured by Carbon Nanotechnologies Inc.) (Registered trademark) single-walled CNTs can be used. It is preferable to use CNTs that have been highly purified by purification such as oxidation, washing, filtration, and centrifugal separation. In order to form a transparent conductive film with higher conductivity, metallic CNTs and semiconducting materials are used. It is preferable to separate the CNTs and use metallic CNTs. Further, as the CNTs, single-walled CNTs, multilayered CNTs, and encapsulated tubes in which fullerenes, metals, etc. are encapsulated in their hollow portions can also be used.

  In the present invention, as shown in the right side view of FIG. 3 (C), in order to improve the characteristics of the composite by combining the CNT and the conductive polymer material, a base material is used by using a dispersion in which CNT is dispersed in a solvent. The solvent is evaporated on glass (polymer substrate or filter), leaving only CNTs to form a three-dimensional network structure, and a PEDOT layer is laminated as a conductive polymer layer on the CNT layer maintaining the network structure. However, when the PEDOT layer is formed, the conductive polymer 20b (PEDOT) penetrates into the gap between the CNTs 10b in the CNT layer, and the CNs 10b are in contact with each other via the conductive polymer 20b. The electrical contact between the CNT layer and the PEDOT layer is maintained, and the bonding (adhesion) strength between the CNT layer and the PEDOT layer is maintained. High conductivity and high light transmission It is possible to form a transparent conductive layer as a complex with.

  The transparent conductive film according to the present invention can be used in various optical devices that have electrodes and have opposing substrates. At least one of the transparent conductive films shown in FIG. Yes. Hereinafter, an example of the optical device will be briefly described.

  2A and 2B are diagrams illustrating a touch panel using a transparent conductive film according to an embodiment of the present invention. FIG. 2A is a cross-sectional view, and FIG. 2B is a plan view of the transparent conductive film. It is.

  Normally, the touch panel is placed on top of LCD (Liquid Crystal Display) or CRT (Cathode Ray Tube), and therefore requires a transmittance of 80% (550 nm) or more. The uniformity of the resistance of the constituent film is required.

  As shown in FIG. 2A (A1), the transparent touch panel includes a deformable PET substrate (upper substrate) 2a having a transparent conductive film 1a formed as an upper electrode, and an electrically insulating dot spacer 3 on the surface. A transparent conductive film 1b formed with a glass substrate (lower substrate) 2b on which a lower electrode is formed. The upper substrate 2a and the lower substrate 2b maintain a slight gap (space) 5 so that both electrodes face each other. They are joined via the electrical insulating layer 4.

  The distance 5 between the upper substrate 2a and the lower substrate 2b is, for example, 100 μm to 300 μm. With respect to this distance 5, the height of the dot spacer 3 is such that the upper electrode and the lower electrode are always in contact with each other to be in the ON state. Is, for example, about 5 μm to 50 μm so as not to affect the image displayed on the panel. In a state where both electrodes are not touched, no current flows because both electrodes are not in contact by the minute dot spacer 3. The lower electrode may be formed of an ITO film.

  As shown in (A2) of FIG. 2A, when the PET substrate 2a side is touched and pressed with a finger or a dedicated pen, the touched portion of the PET substrate 2a is deformed, and the transparent conductive films 1a and 1b come into contact with each other. Electricity flows and a switch action occurs and the input is detected.

  As shown in (B1) to (B4) of FIG. 2B, the transparent conductive films 1a and 1b constituting the upper electrode and the lower electrode are arranged on a continuous planar transparent conductive film and a two-dimensional matrix. It can be set as the transparent conductive film which consists of the made discontinuous microelectrode.

  In the example shown in (B1), (B3), and (B4) of FIG. 2 (B), the contact points of the upper electrode and the lower electrode generated by the deformation of the PET substrate 2a by pressing (the upper electrode and the lower electrode are closed circuit). The position of the above-mentioned microelectrodes forming the above, that is, the pressed position (coordinates) is detected by a reading circuit to which the microelectrodes are connected.

  The example shown in (B2) of FIG. 2 (B) is an analog type resistive film type touch panel, which is pressed by measuring the voltage dividing ratio by the resistance of the transparent conductive films 1a and 1b constituting the upper electrode and the lower electrode, respectively. The detected position (coordinates) is detected.

  Although not shown in FIG. 2, in the example shown in (B4) of FIG. 2 (B), the microelectrodes 1a arranged in one row in the horizontal direction are formed as strip-like electrodes connected to each row, and are arranged in one row in the horizontal direction. The microelectrode 1b is a strip-shaped electrode connected to each column, the strip electrodes constituting the upper electrode and the lower electrode are arranged so as to be orthogonal to each other, and the strip electrodes of the upper electrode and the lower electrode are connected to the reading circuit. The contact point of the upper and lower electrodes generated by pressing (position where the upper electrode and the lower electrode strip electrode come into contact to form a closed circuit) is detected by the reading circuit. You can also.

  The transparent conductive film of the present invention can be used as a transparent electrode in an electrochromic device (not shown). An electrochromic device is an electrochemical redox reaction of an electrochromic compound, which occurs when a voltage is applied between a transparent electrode carrying an electrochromic compound made of an organic or inorganic compound and an electrode facing the transparent electrode. It utilizes the accompanying change in absorption spectrum (electrochromic phenomenon) and is applied to a display device or the like.

  The transparent conductive film of the present invention can be used as a transparent electrode in an electroluminescence device (not shown). An electroluminescent device uses a light emission generated by applying a voltage between two electrodes, in which a light emitter made of an inorganic material such as zinc sulfide or an organic material such as diamine is disposed between two electrodes. And is applied to display devices, lighting devices, and the like.

  Furthermore, the transparent conductive film of the present invention can be used as a transparent electrode in a solar cell (not shown), and has a simple structure in which a titanium dioxide layer adsorbing a trace amount of pigment and an electrolyte are sandwiched between two transparent electrodes. In the dye-sensitized solar cell having the above, it can be used as a transparent conductive film for forming an electrode (anode electrode) on the light incident side.

Example First, a method for forming a PEDOT film was examined, and film characteristics such as transmittance, conductivity, thickness, and surface shape were evaluated, and the characteristics were compared with those of a CNT film. In the following, a PEDOT / PSS aqueous dispersion (product name Baytron P HCV4) was used.

  As a method for forming the PEDOT film, an immersion method (pull-up method) and a spin coating method were examined, but a spin coating method was selected from the viewpoint of uniformity.

Although it was adjustment of the solution for spin coats used for a spin coat method, it was not able to dilute with acetone or IPA (isopropyl alcohol) in the state as a commercial PEDOT / PSS aqueous dispersion. Thus, first, a commercially available PEDOT / PSS aqueous dispersion was mixed with H ₂ O, and then diluted by adding IPA. As a result, a uniform solution for spin coating could be prepared. As a result of examining the mixing ratio of PEDOT (commercially available PEDOT / PSS aqueous dispersion), H ₂ O, and IPA, as a solution for spin coating, a mixing ratio of PEDOT: H ₂ O: IPA = 1: 1: 5 to 10 Was found to be appropriate. Using this spin coating solution, a PEDOT film having a transmittance of 99% or more could be formed by spin coating.

  A uniform PEDOT film was obtained under spin coating conditions in which the rotational speed was about 2000 rpm to about 8000 rpm and the spin coating time was about 1 minute. After spin coating, post-baking was performed on a hot plate at 100 degrees (Celsius) for about 1 minute. A PEDOT film having good conductivity was obtained by natural drying.

  Since a thick PEDOT film cannot be formed simply by spin coating, IPA and PEDOT (commercially available PEDOT / PSS aqueous dispersion) in a spin coating solution, as in the film forming method shown in FIG. The concentration ratio (IPA / PEDOT) and spin coating conditions were changed in various ways, a PEDOT film was formed on a glass substrate by a spin coating method, and the film thickness and characteristics (sheet resistance, transmission by the PEDOT film forming method) Rate).

In addition, the transmittance | permeability demonstrated below was measured in the wavelength range of 400 nm-800 nm using U4000 type Hitachi spectrophotometer.

  FIG. 4 shows the relationship between the PEDOT film forming method, sheet resistance, transmittance at 550 nm (transmittance not including the glass substrate on which the PEDOT film is formed), and film thickness in the examples of the present invention. It is a figure explaining.

  In the spin coating conditions of the film forming method (1) shown in FIG. 4, the concentration ratio (IPA / PEDOT) = 5 of the IPA and PEDOT (commercially available PEDOT / PSS aqueous dispersion) in the spin coating solution is 6000 rpm. The spin coating time was 1 minute. The thickness of the PEDOT film formed under these conditions was 2.4 nm, and the sheet resistance was> 2 MΩ / □.

  In the spin coating conditions of the film forming method (2), the concentration ratio (IPA / PEDOT) = 2, the rotation speed was 3000 rpm, and the spin coating time = 1 minute. The thickness of the PEDOT film formed under these conditions was 14 nm, the sheet resistance was 108 kΩ / □, and the transmittance was 98.7%.

  In the spin coating conditions of the film forming method (3), the concentration ratio (IPA / PEDOT) = 2 and the spin coating time = instantaneous. The thickness of the PEDOT film formed under these conditions was 19 nm, the sheet resistance was 22.5 kΩ / □, and the transmittance was 97.0%.

The spin coating conditions of the film forming method (4) were set so that the spin coating conditions of the film forming method (3) were repeated twice. The thickness of the PEDOT film deposited by the condition 69 nm, sheet resistance 11.7 k Ω / □, and the transmittance was 96.2%.

In the spin coating conditions of the film forming method (5), the concentration ratio (IPA / PEDOT) = 1 and the spin coating time = instantaneous. The thickness of the PEDOT film deposited by the condition 109 nm, sheet resistance 2.69 k Ω / □, and the transmittance was 90.1%.

The spin coating conditions of the film forming method (6) were the conditions for repeating the spin coating conditions of the film forming method (5) three times. The thickness of the PEDOT film formed under these conditions was 153 nm, the sheet resistance was 1.38 Ω k / □, and the transmittance was 81.5%.

  Even if the concentration ratio (IPA / PEDOT) in the spin coating solution and the spin coating time are changed as in the film forming methods (1) to (4), the amount of PEDOT adhesion (that is, the film thickness) can be controlled. Although the sheet resistance decreased as the film thickness increased, almost no change was observed in the transmittance characteristics of the PEDOT film.

  FIG. 5 is a diagram for explaining the transmittance of the PEDOT film and the CNT film in the example of the present invention. FIG. 5A is a diagram showing the transmittance of the PEDOT film formed by the above-described spin coating method. 5 (B) is a diagram showing the transmittance of a CNT film formed on a glass substrate by a filter method using CNT synthesized by a laser ablation method.

  Although the PEDOT film itself has been studied as an alternative material for ITO, it has a disadvantage that it has a dark blue color. Curves (2) to (6) in FIG. Shows the transmittance of PEDOT films having a film thickness of 14 nm, 19 nm, 69 nm, 109 nm, and 153 nm by the film forming methods (2) to (6) shown in FIG. Yes.

  Curves (1) to (5) in FIG. 5B indicate the transmittance of a CNT film having a thickness of 3 nm, 8 nm, 13 nm, 51 nm, and 65 nm in this order (transmission not including a glass substrate on which the CNT film is formed). The absorption increases as the film thickness increases. Compared to the PEDOT film shown in FIG. 5A, the CNT film has less discoloration, but slightly absorbs light on the short wavelength side. Considering this result, in terms of the color of the conductive film, the CNT film and the PEDOT film are complementary, and by combining these films together, a conductive film with less discoloration is obtained. be able to.

  FIG. 6 is a diagram for explaining an example of the relationship between the sheet conductivity and the absorbance when the film thicknesses of both the PEDOT film and the CNT film are changed in the embodiment of the present invention. Indicates sheet conductivity (S / sq), and FIG. 6B is an enlarged view of a region having a small absorbance in FIG. Note that the data indicated by arrows and frames in FIG. 6B indicate the characteristics of the PEDOT film according to the spin coating conditions of the film forming method (2) shown in FIG.

  In FIG. 6, the transmittance of a CNT film formed on a glass substrate by a filter method using CNT synthesized by a laser ablation method (in FIG. 6A, (1) Laser CNT) is used (FIG. 5). (B).) A plot showing the relationship between the absorbance converted from (1) and the sheet conductivity, and the transmittance of the PEDOT film shown in FIG. 5 (A) is converted into absorbance, and the sheet resistance is converted into sheet conductivity. It is a plot which shows the converted relationship. 6A shows the relationship between the absorbance of the CNT film at 550 nm and the sheet conductivity, and FIGS. 6B and 6B show the relationship between the absorbance of the PEDOT film at 800 nm and 550 nm and the sheet conductivity, respectively. It is a plot.

  Comparing the characteristics of the CNT film and the PEDOT film shown in FIG. 6, it can be seen that the characteristics of the CNT film are excellent. The PEDOT film reflects the result shown in FIG. 5, and it can be seen that the absorption at 800 nm is nearly twice that at 550 nm. Further, FIG. 6B shows data of the low absorption region of the PEDOT film. In order to obtain a sheet resistance of 2 MΩ / □ or less (depending on the upper limit of the measuring device), the transmittance is about 99%. It is necessary to apply PEDOT. Among these results, the knowledge that the sheet resistance of a PEDOT film having a transmittance of about 99% is 100 kΩ / □ or more is very important.

  FIG. 7 is a view for explaining an AFM image of a PEDOT film under the spin coating conditions of the film forming method (4) shown in FIG. 4 and its three-dimensional display in the embodiment of the present invention, and FIG. FIG. 7B is a diagram showing a three-dimensional display of an AFM image (the unit of numerical values shown in three directions is nm).

  FIG. 7A shows that the PEDOT film is formed of particles of several nm to several tens of nm. As mentioned above, PEDOT (poly (3,4-ethylenedioxythiophene)) is inherently insoluble, and in exchange for obtaining water dispersibility in the presence of PSS as a dopant, PEDOT is divided into short segments, It is a colloidal dispersion in an aqueous solution, and the AFM image is considered to have such a segment size.

  FIG. 7B shows that the surface of the PEDOT film has a roughness (roughness, unevenness) of several nm. Further, the roughness (roughness, unevenness) of the surface of the PEDOT film prepared by another film forming method shown in FIG. 4 was the same as 7 (B). The film formation methods (1) and (2) shown in FIG. 4 are standard conditions for producing a PEDOT film in the present invention, and the film thicknesses are 2.4 nm and 14 nm, respectively. The PEDOT film formed on the film has a thickness of several nm, and its roughness (roughness, unevenness) is also considered to be several nm.

  On the other hand, since the CNT film created by the dipping method (Dip method, dipping method) in which the substrate is immersed in a dispersion liquid in which CNT is dispersed in a solvent and the CNT is attached to the substrate, the CNTs are stacked in several layers. Even in the thick part where CNTs overlap, it is about several nm. Further, since the entire surface cannot be completely filled with CNTs with the technology up to now, naturally the roughness (roughness, unevenness) can be considered to be several nm.

  As described above, the structural units of the CNT film and the PEDOT film are the primary fine wires of the CNT particles and the short segments, respectively, and differ in both films, but the outer surfaces of both films formed are about several nm. It is considered that the surface shape is similar with roughness (roughness, unevenness), and bonding at the interface between the CNT film and the PEDOT film is considered to be good.

  Next, in order to investigate the effect of the coating of PEDOT on the CNT film (a CNT film formed by the Dip method or the filter method), a two-layer film is formed by coating PEDOT on the CNT conductive film. Then, as a result of evaluating the sheet resistance, a result of examining a change in the surface state of the substrate such as a contact angle due to PEDOT application will be described.

  FIG. 8 is a diagram for explaining changes in transmittance and sheet resistance due to formation of the PEDOT film on the CNT film in the example of the present invention.

  FIG. 8 shows the transmittance at 550 nm before and after the formation of the PEDOT film on the CNT film (formed on the glass substrate) formed by the Dip method and the filter method using HiPco single-walled CNT ( The transmittance does not include a glass substrate on which a CNT film and a PEDOT film are formed.), Sheet resistance. The PEDOT film was formed by the spin coating method under the above-mentioned conditions of the concentration ratio (IPA / PEDOT) = 5 in the spin coating solution, the rotational speed of 6000 rpm, and the spin coating time of 1 minute.

  As shown in FIG. 8, the transmittance of the CNT film (film thickness 5 nm) formed by the Dip method is 95.48%, and the PEDOT / CNT transparent film in which the PEDOT film (estimated film thickness 3 nm) is formed on this CNT film. The transmittance of the conductive film is 95.32%, and the transmittance is reduced by only 0.16% before and after the formation of the PEDOT film. Since the sheet resistance of the PEDOT film (film thickness 2.4 nm) formed by the film forming method (1) shown in FIG. 4 was 2 MΩ / □, the PEDOT / CNT transparent conductive film has a value that hardly changes with this sheet resistance. Although the sheet resistance of the CNT film was actually 14 kΩ / □ as shown in FIG. 8, the sheet resistance of the PEDOT / CNT transparent conductive film was 8 kΩ / □. The sheet resistance decreased by 43% before and after film formation.

  Further, as shown in FIG. 8, the transmittance of the CNT film (film thickness 67 nm) formed by the filter method is 65.79%, and the PEDOT / film having an PEDOT film (estimated film thickness 3 nm) formed on the CNT film. The transmittance of the CNT transparent conductive film is 65.37%, and the transmittance decreases only by 0.42% before and after the formation of the PEDOT film. Since the sheet resistance of the PEDOT film (film thickness 2.4 nm) formed by the film forming method (1) shown in FIG. 4 was 2 MΩ / □, the PEDOT / CNT transparent conductive film has a value that hardly changes with this sheet resistance. As shown in FIG. 8, the sheet resistance of the CNT film was 885Ω / □, but the sheet resistance of the PEDOT / CNT transparent conductive film was 537Ω / □. The sheet resistance decreased by 39% before and after the film formation.

  As described above, the sheet resistance is reduced by about 40% before and after the formation of the PEDOT film on the CNT film formed by either the Dip method or the filter method, although there is almost no change in transmittance. It was found that the sheet resistance can be reduced by about 40% without changing the transmittance of the transparent conductive film by forming the PEDOT film on the CNT film. The reduction in sheet resistance before and after the formation of the PEDOT film is due to the penetration of the conductive polymer (PEDOT) into the interior of the CNT three-dimensional network structure near the surface of the CNT film when the PEDOT film is formed on the CNT film. It is considered that the resistance between the CNT molecules is reduced by the presence of the conductive polymer (PEDOT) in the vicinity of the CNT molecules.

  Next, in order to investigate the effect due to the difference in film thickness of the CNT film, three CNT films having different sheet resistances created by the filter method are applied on the CNT film by the same method as described in FIG. A PEDOT film was formed, and changes in transmittance and sheet resistance before and after the formation of the PEDOT film were examined.

  FIG. 9 is formed on the CNT film in the embodiment of the present invention. ) Is a diagram for explaining changes in transmittance and sheet resistance due to the formation of the PEDOT film on the top, in which the horizontal axis represents the transmittance (%) and the vertical axis represents the sheet resistance (Ω / sq).

  FIG. 9 shows the transmittance at 550 nm before and after the formation of the PEDOT film on the CNT film (formed on the glass substrate) formed by the filter method using HiPco single-walled CNT (CNT film, The transmittance does not include the glass substrate on which the PEDOT film is formed.), The sheet resistance.

  As shown in FIG. 9, as the film thickness of the CNT film increases to 8 nm, 67 nm, and 150 nm, the transmittance and sheet resistance of the CNT film decrease. In addition, in the PEDOT / CNT transparent conductive film in which the PEDOT film having an estimated thickness of 3 nm, 3 nm, and 4 nm is formed on each of these CNT films, the transmittance slightly decreases before and after the formation of the PEDOT film, but the sheet resistance Are greatly reduced to 80%, 39%, and 27%. This reduction in sheet resistance becomes more significant as the film thickness of the CNT film becomes thinner and the sheet resistance increases. The sheet resistance is at most close to 1/10 of the value before the formation of the PEDOT film.

  As shown in FIG. 9, as the film thickness of the CNT film increases, the decrease in sheet resistance before and after the formation of the PEDOT film decreases. When the PEDOT film is formed, the conductive polymer (PEDOT) does not penetrate deeply into the CNT three-dimensional network structure of the CNT film, and the conductive polymer (PEDOT) penetrates into the three-dimensional network structure. This is considered to be because the sheet resistance is not greatly reduced by the formation of the PEDOT film because it reaches only near the surface.

  Therefore, in order for the PEDOT / CNT transparent conductive film in which the PEDOT film is formed on the CNT film to have a smaller sheet resistance, the thinner the CNT film, the more desirable.

  FIG. 10 is a diagram for explaining an SEM image (magnification 10,000) after the formation of the PEDOT film on the CNT film in the example of the present invention.

  FIG. 10 shows the concentration ratio (IPA) in the spin coating solution described above on a 50 nm-thick CNT film (formed on a glass substrate) formed by the filter method using HiPco single-walled CNTs. / PEDOT) = 5, the rotational speed is 5000 rpm, and the spin coating time is 1 minute. A PEDOT film is formed by spin coating, and the resulting PEDOT / CNT transparent conductive film is an SEM image. A three-dimensional network structure of the CNT layer exposed to the outside as a result of the excessive irradiation of the line and the disappearance of the PEDOT film can be seen in the central right part of the SEM image. Thus, the observation of the three-dimensional network structure of the CNT layer indicates that the three-dimensional network structure of the CNT layer is kept undisturbed when the PEDOT layer is formed on the CNT layer.

  As described above, it has been found that the PEDOT / CNT transparent conductive film in which the PEDOT film is formed on the CNT layer has improved conductivity as compared with the transparent conductive film using only the CNT layer.

Next, a PEDOT film and a CNT film are formed on a PET film that has been subjected to a hydrophilic treatment so that the CNT easily adheres, and the contact angles of the CNT film and the PEDOT film with respect to H ₂ O are measured. The CNT film and the PEDOT film The surface state of each surface of was examined.

  FIG. 11 is a diagram for explaining the contact angle with respect to water of a laminated film obtained by laminating a PET film, a hydrophilic treated PET film, a CNT film, and a PEDOT film in an example of the present invention. Degree).

  As shown in FIG. 11, the contact angle of the PET substrate surface that has not been subjected to hydrophilic treatment shows a large value of about 85 degrees, but the contact angle is greatly reduced by subjecting the PET substrate to hydrophilic treatment with a silane coupling material. In addition, the adhesion of CNT is improved.

  The contact angle of the PEDOT film surface formed by spin coating on this hydrophilic treated PET substrate is about 30 degrees, which is lower than the 85 degrees of the PET substrate, and is formed on the PET substrate by the Dip method. The contact angle of the formed CNT film surface was about 60 degrees larger than that of the PEDOT film surface. This is considered because CNT itself has high hydrophobicity.

  Although we tried to attach a large amount of CNTs to the substrate by the Dip method, even if we tried to attach more CNTs by repeating the Dip method multiple times on the CNT film formed on the substrate, a certain amount or more CNT could not be deposited on the CNT film once formed. This supports the experimental fact shown in FIG. 11 that the contact angle of the CNT film surface is large.

  The contact angle of the PEDOT film surface formed by the spin coating method on the above-mentioned CNT film formed on the above-mentioned hydrophilic-treated PET substrate was further formed on the hydrophilic-treated PET substrate. It decreased to the same value as the contact angle of the above-mentioned PEDOT film surface.

  From the experimental facts described above, the hydrophilicity of the PEDOT film is considered to be relatively high and the affinity with the CNT is considered to be relatively good. By forming the PEDOT film on the CNT film, the conductive property can be obtained as described above. In addition to improving the properties, the PEDOT film can be expected to be a layer that acts as an adhesive layer between the CNT films.

  Next, based on the above results, a transparent conductive film having a multilayered CNT film composed of a CNT film and a PEDOT film was prepared, and its optical and electrical characteristics were examined.

  Making a transparent conductive film with a CNT film multilayered by using a PEDOT film leads to an improvement in the conductivity of the transparent conductive film.

  Conventionally, increasing the adhesion amount of CNTs by repeating the Dip method to increase the adhesion amount of CNTs to the substrate and improving the conductivity of the transparent conductive film without causing a large decrease in light transmittance. It was difficult to attach only about 1% of light absorption. For applications such as a touch panel where the sheet resistance is several kΩ / □ and the transmittance excluding the substrate is almost 100%, for example, a CNT deposition amount of about 1% of light absorption is sufficient. However, in order to use a transparent conductive film as a transparent electrode for a solar cell or the like that requires higher transparency and low sheet resistance such as several Ω to several tens of Ω / □, a large amount of CNT is attached to the substrate. There is a need.

  Hereinafter, a transparent conductive film composed of a multilayered CNT film in which a thin CNT layer and a PEDOT film are brought into close contact with each other and having a low sheet resistance without causing a large decrease in light transmittance will be described.

  FIG. 12 is a diagram for explaining the relationship between the structure and characteristics of a transparent conductive film in which a PEDOT film and a CNT film are sequentially laminated on a PET film in an example of the present invention, and FIG. 12 (A) shows absorbance and sheet conductivity. The horizontal axis indicates the absorbance, the vertical axis indicates the sheet conductivity (S / sq), FIG. 12B shows the relationship between the transmittance and the sheet resistance, and the horizontal axis indicates the sheet resistance (kΩ / sq). The vertical axis represents the transmittance (%). In FIG. 12, the absorbance and transmittance show values at 550 nm and do not include the contribution of the PET substrate.

  First, a PEDOT film is formed by spin coating on a PET substrate that has been subjected to the above-described hydrophilic treatment, and (1) a CNT film is formed by Dip on the previously formed PEDOT film. (2) A PEDOT film is formed on the previously formed CNT film, and (3) a transparent conductive film having a PEDOT / CNT / PEDOT sandwich structure is formed by repeating (1) and (2) a plurality of times. . The transmittance and sheet resistance of the transparent conductive films formed in this manner, such as CNT / PEDOT, PEDOT / CNT / PEDOT, CNT / PEDOT / CNT / PEDOT, PEDOT / CNT / PEDOT / CNT / PEDOT, were measured. .

  In FIG. 12A, the measured transmittance is converted into absorbance and the sheet resistance is converted into sheet conductivity and plotted. In FIG. 12B, the measured transmittance and sheet resistance are plotted. ing. For reference, data on the PEDOT film is also plotted.

The transmittance (%) at 550 nm for each of the CNT / PEDOT, PEDOT / CNT / PEDOT, CNT / PEDOT / CNT / PEDOT, and PEDOT / CNT / PEDOT / CNT / PEDOT shown in FIG. When kΩ / sq) = R _s is expressed by (T, R _s ), (98.5, 9.1), (97.8, 5.0), (97.0, 3.2), ( 96.2, 2.3).

  Note that a CNT film (film thickness: 2 nm to 10 nm) is formed on the previously formed PEDOT film by the Dip method using HiPco single-layer CNT, and the PEDOT film ( A film thickness of 2 nm to 10 nm) was formed by spin coating. As for Dip conditions, a 1,2-dichloroethane solution was used as a solvent for dispersing CNT, the concentration of CNT was 0.1 g / L, and the immersion time was 60 sec. The spin coating conditions were the concentration ratio (IPA / PEDOT) = 5 in the above-described spin coating solution, the rotation speed was 5000 rpm, and the spin coating time was 1 minute.

  In FIG. 12A, it can be seen that the absorbances of the CNT film and the PEDOT film are approximately the same because the absorption plots are arranged at almost equal intervals. Even if the amount of PEDOT adhering to the CNT film is further reduced, it is considered that the result is almost the same as in FIG.

  From the results shown in FIG. 12, every time the PEDOT film is formed on the CNT film except for the PEDOT film formed in close contact with the PET film, the transmittance decreases by about 1%. Here, in the single layer of each of the CNT film and the PEDOT film, the sheet conductivity at a film thickness exhibiting 1% light absorption was examined. 30 μS / □ (@ 1% absorption) for the CNT film and 5 μS for the PEDOT film / □ (@ 1% absorption).

  From this result, it can be seen that the conductivity of CNT is nearly 6 times higher. Further, in FIG. 12, the sheet conductivity of only the CNT film and only the PEDOT film is indicated by a broken line, but the conductivity of the composite film in which the CNT film and the PEDOT film are laminated is only the CNT film indicated by the broken line, and the PEDOT film. It can be seen that it is much higher than the sheet conductivity of only.

  As shown in FIG. 12, the sheet conductivity of the PEDOT / CNT transparent conductive film having the PEDOT film in the lower layer is assumed to be sufficiently improved by the PEDOT film formed in the lower layer, and the PEDOT / CNT transparent conductive film is assumed. It is assumed that the sheet conductivity of the PEDOT / CNT / PEDOT transparent conductive film in which the PEDOT film is formed on the CNT film is only slightly higher than the sheet conductivity of the PEDOT / CNT transparent conductive film.

  However, in actuality, the sheet conductivity of the PEDOT / CNT / PEDOT transparent conductive film has been improved by up to twice the sheet conductivity of the PEDOT / CNT transparent conductive film. The contribution of the PEDOT film deposited on the sheet conductivity of the transparent conductive film is very significant.

  In FIG. 12, a graph obtained by simply doubling the sheet conductivity of the PEDOT / CNT transparent conductive film is indicated by a broken line, but the actually measured value of the sheet conductivity is approximately twice the value indicated by the broken line. It is getting bigger.

  From the above, even if the CNT film has a thickness of about several nanometers, it is insufficient to sufficiently improve the sheet conductivity by the PEDOT film formed only on one side (one surface) of the CNT film. It is clear that the sheet conductivity is further improved by sandwiching the CNT film from both sides (both surfaces) with the PEDOT film.

  Thus, a transparent conductive film having a large sheet conductivity can be produced by providing a PEDOT / CNT / PEDOT sandwich structure sandwiched by PEDOT films from both sides of the CNT film.

  As shown in FIG. 12, the sheet conductivity of the CNT / PEDOT / CNT / PEDOT transparent conductive film in which the CNT film is formed on the PEDOT / CNT / PEDOT transparent conductive film is further improved. The sheet conductivity of the PEDOT / CNT / PEDOT / CNT / PEDOT transparent conductive film in which a PEDOT film is formed on the CNT film is further improved.

  The sheet resistance of the PEDOT / CNT / PEDOT / CNT / PEDOT transparent conductive film is 2.3 kΩ / □, the transmittance (excluding the PET substrate) is 96.2%, and it has excellent conductivity and high transparency. A conductive film could be created. By repeatedly forming the PEDOT / CNT / PEDOT sandwich structure, as shown in FIG. 12B, when estimated by extrapolation, the transmittance at 550 nm is about 95%, and the sheet resistance is about 500Ω / □. It is thought that a transparent conductive film can be created.

  Conventionally, only the conductive film of about 10 kΩ / □ was obtained by the Dip method, but the conductivity could be improved as compared with the conventional case by multilayering the CNT film by repeatedly forming the PEDOT / CNT / PEDOT sandwich structure. .

  As described above, the PEDOT film is formed in close contact with the PET substrate and the transparent conductive film having the PEDOT / CNT / PEDOT sandwich structure has been described. Next, the CNT film is formed in close contact with the PET substrate, and the CNT / PEDOT / A transparent conductive film having a CNT sandwich structure will be described.

  FIG. 13 shows the relationship between the structure of a transparent conductive film in which (a) a PEDOT film and a CNT film are laminated on a PET film, and (b) a CNT film and a PEDO film in that order, the absorbance and the sheet conductivity. The horizontal axis indicates the absorbance, and the vertical axis indicates the sheet conductivity (S / sq).

  (A) shown in FIG. 13 is a solid line graph shown in FIG. 12 (A), showing the relationship between the absorbance of the transparent conductive film including the PEDOT / CNT / PEDOT sandwich structure and the sheet conductivity, and is shown in FIG. b) shows the relationship between the absorbance of the transparent conductive film including the CNT / PEDOT / CNT sandwich structure and the sheet conductivity.

  In the same manner as the transparent conductive film shown in FIG. 12, a CNT film is first formed on the PET substrate by the Dip method on the PET substrate subjected to the above-described hydrophilic treatment, and (1) the CNT formed first. A PEDOT film is formed on the film, and then (2) a CNT film is formed on the previously formed PEDOT film, and (3) (1) and (2) are repeated a plurality of times. A transparent conductive film having a PEDOT / CNT sandwich structure is formed.

  The transmittance and sheet resistance of the transparent conductive films formed as described above, such as PEDOT / CNT, CNT / PEDOT / CNT, PEDOT / CNT / PEDOT / CNT, and CNT / PEDOT / CNT / PEDOT / CNT, were measured. .

  In FIG. 13B, the measured transmittance is converted into absorbance, and the sheet resistance is converted into sheet conductivity and plotted. For reference, data on the CNT film is also plotted.

  A PEDOT film (film thickness 2 nm to 10 nm) is formed on the previously formed CNT film by spin coating, and a CNT film (film thickness 2 nm to 10 nm) is formed on the previously formed PEDOT film. , And formed by the Dip method using HiPco monolayer CNTs.

  As for Dip conditions, a 1,2-dichloroethane solution was used as a solvent for dispersing CNT, the concentration of CNT was 0.1 g / L, and the immersion time was 60 sec. The spin coating conditions were the concentration ratio (IPA / PEDOT) = 5 in the above-described spin coating solution, the rotation speed was 5000 rpm, and the spin coating time was 1 minute.

  As apparent from the comparison between FIG. 12 and FIG. 13, the sheet conductivity of the PEDOT / CNT transparent conductive film in which the PEDOT film is formed on the CNT film with respect to the CNT film formed in close contact with the PET substrate (FIG. 13). And the sheet conductivity of the PEDOT / CNT / PEDOT / CNT transparent conductive film in which the PEDOT film is formed on the CNT film of the transparent conductive film with respect to the CNT / PEDOT / CNT transparent conductive film. The improvement in the ratio (shown in FIG. 13B) is remarkable, and the PEDOT / CNT / PEDOT transparent film in which the PEDOT film is formed on the CNT film of the transparent conductive film with respect to the PEDOT / CNT transparent conductive film. This is comparable to the improvement in sheet conductivity of the conductive film (shown in FIG. 13A and FIG. 12).

  From the above, the sheet conductivity of the transparent conductive film having the PEDOT film as the outermost layer is about twice the sheet conductivity of the transparent conductive film having the CNT film as the outermost layer, and the CNT / PEDOT / CNT sandwich structure is obtained. As in the transparent conductive film having the PEDOT / CNT / PEDOT sandwich structure, the PEDOT film is provided as the outermost layer in the point of creating a transparent conductive film having a large sheet conductivity. preferable.

  As shown in FIG. 13B, by forming a CNT film on the outermost PEDOT film of the transparent conductive film having the PEDOT film as the outermost layer, the sheet conductivity can be improved about twice. it can.

  From comparison of (a) and (b) in FIG. 13, (1) CNT / PEDOT transparent conductive film and PEDOT / CNT transparent conductive film, (2) PEDOT / CNT / PEDOT transparent conductive film and CNT / PEDOT / CNT transparent Conductive film, (3) CNT / PEDOT / CNT / PEDOT transparent conductive film and PEDOT / CNT / PEDOT / CNT transparent conductive film, (4) PEDOT / CNT / PEDOT / CNT / PEDOT transparent conductive film and CNT / PEDOT / CNT / Each of the PEDOT / CNT transparent conductive films has the same transmittance and sheet conductivity, and depending on the conductivity and transparency required for the optical device in which the transparent conductive film is used as a transparent electrode, By selecting the stacking order of the film and the PEDOT film on the substrate, the transmission with the most suitable optical and electrical characteristics is achieved. It is possible to create a conductive film.

  Conventionally, only the conductive film of about 10 kΩ / □ has been obtained by the Dip method, but the conductivity can be improved as compared with the conventional case by multilayering the CNT film by repeatedly forming the CNT / PEDOT / CNT sandwich structure. It was.

  As described above, in the present invention, in order to improve the characteristics of the CNT transparent conductive film, as a result of studying the composite of CNT and the conductive polymer PEDOT, it is not possible to simply mix and composite the two. In addition, while maintaining the three-dimensional network structure of the CNT film, by forming a layered structure of the CNT film and the PEDOT film, the two are integrated to maintain the conductive path existing in the three-dimensional network structure of the CNT film. By compounding, the PEDOT film formed in contact with the CNT film not only improves the conductivity, but effectively acts as an adhesive layer between the CNT films due to the surface state and hydrophilicity of the PEDOT film. Due to the action of the PEDOT film as an adhesive layer, a multilayer film can be formed by laminating the CNT film and the PEDOT film. By forming the EDOT film, the sheet conductivity can be improved by about 2 times. Even if the CNT film thickness is several nm, a sandwich structure in which the CNT film is sandwiched from above and below by the PEDOT film, or CNT By forming a sandwich structure in which the PEDOT film was sandwiched from above and below by the film, the conductivity could be further improved.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, Various deformation | transformation based on the technical idea of this invention is possible. For example, in the transparent conductive film, the thickness of the CNT film and the PEDOT film constituting this, the number of CNT films and the PEDOT film to be stacked, the stacking order, the material of the substrate on which the transparent conductive film is formed, etc. It can be set arbitrarily and appropriately as necessary so as to satisfy the performance required by an optical device using a transparent conductive film. In addition to the transparent electrode, the transparent conductive film according to the present invention can be used as a transparent antistatic film.

As described above, according to the present invention, it is possible to provide a transparent conductive film having high conductivity and high light transmittance and an optical device using the same.

It is a figure explaining the structure of the transparent conductive film which laminated | stacked (A) PEDOT film | membrane, CNT film | membrane, (B) CNT film | membrane, and PEDOT film | membrane in order in PET film in embodiment of this invention. It is a figure explaining the touch panel which uses a transparent conductive film same as the above. It is a conceptual diagram explaining the problem of a CNT transparent conductive film same as the above. In the Example of this invention, it is a figure explaining the relationship between the film-forming method of a PEDOT film | membrane, and sheet resistance, the transmittance | permeability, and film thickness. It is a figure explaining the transmittance | permeability of a PEDOT film | membrane and a CNT film | membrane same as the above. It is a figure explaining the example of the relationship between the sheet electrical conductivity of a PEDOT film | membrane and a CNT film | membrane, and an absorbance same as the above. It is a figure explaining the AFM image and its three-dimensional display of a PEDOT film | membrane same as the above. It is a figure explaining the change of the transmittance | permeability and sheet resistance by formation of a PEDOT film | membrane on a CNT film | membrane same as the above. It is a figure explaining the change of the transmittance | permeability and sheet resistance by formation of a PEDOT film | membrane on a CNT film | membrane same as the above. It is a figure explaining the SEM image after formation of the PEDOT film | membrane on a CNT film | membrane same as the above. It is a figure explaining the contact angle with respect to the water of the laminated film which laminated | stacked PET film, the PET film which performed the hydrophilic treatment, CNT film | membrane, and PEDOT film | membrane same as the above. It is a figure explaining the relationship between the structure of a transparent conductive film which laminated | stacked the PEDO film and the CNT film | membrane in order on the PET film | membrane, and a characteristic same as the above. It is a figure explaining the relationship between the structure of the transparent conductive film which laminated | stacked (a) PEDO film | membrane, CNT film | membrane, (b) CNT film | membrane, and PEDO film | membrane in order on the PET film | membrane, and an absorbance and sheet conductivity.

Explanation of symbols

1a, 1b ... transparent conductive film, 2a ... PET substrate, 2b ... glass substrate, 3 dot spacer,
4 ... Insulating layer, 5 ... Space, 10a, 10b ... CNT, 20a ... Polymer, 20b ... Conductive material

Claims (18)

A conductive polymer layer laminated in contact with the substrate;
A transparent conductive film having a carbon nanotube layer laminated in contact with the conductive polymer layer.     A carbon nanotube layer and a conductive polymer layer laminated on a substrate, wherein the conductive polymer layer has a layer having a sandwich structure laminated in contact with the two carbon nanotube layers; A transparent conductive film in which a carbon nanotube layer is laminated in contact with the substrate.   The transparent conductive film according to claim 1, wherein the carbon nanotube layer has a layer having a sandwich structure in which the carbon nanotube layer is laminated in contact with the two conductive polymer layers.   The transparent conductive film according to claim 1, wherein the carbon nanotube layer is laminated on the uppermost layer.   The transparent conductive film according to claim 2, wherein the conductive polymer layer is laminated on the uppermost layer.   The transparent conductive film according to claim 1 or 2, wherein the sheet resistance is 1Ω / □ or more and 10,000Ω / □ or less.   The transparent conductive film according to claim 1, wherein the visible light transmittance is 70% or more.   The transparent conductive film according to claim 1 or 2, wherein a thickness of the conductive polymer layer and the carbon nanotube layer is several nm or more and 100 nm or less.   The transparent conductive film according to claim 1 or 2, wherein the carbon nanotube layer is formed by applying a solution in which carbon nanotubes are dispersed in a solvent.   The transparent conductive film according to claim 1 or 2, wherein the conductive polymer layer is formed by applying a solution obtained by diluting a conductive polymer in a solvent.   The transparent conductive film according to claim 1, wherein one carbon nanotube molecule is in contact with a plurality of carbon nanotube molecules in the carbon nanotube layer.   The transparent conductive film according to claim 1, wherein the substrate is a transparent polymer substrate. A first substrate on which the transparent conductive film according to claim 1 or 2 is formed;
An optical device having a second substrate provided with an electrode and facing the first substrate with a gap.   The optical device according to claim 13, wherein the transparent conductive film is the transparent conductive film according to any one of claims 3 to 11.   The optical device according to claim 13 configured as a touch panel.   The optical device according to claim 13, wherein a light emitting layer that emits light by applying a voltage between the first substrate and the second substrate is provided and configured as an electroluminescence device.   The optical device according to claim 13, wherein an electrochromic compound is supported on the first substrate and configured as an electrochromic device.   The optical device according to claim 13, wherein the optical device is configured as a solar cell having a structure in which an electrolyte is sandwiched between a titanium dioxide layer having an organic dye adsorbed between the first substrate and the second substrate.