JP6716366B2 - Transparent conductive sheet and method for manufacturing the same - Google Patents

Description

The present invention relates to a transparent conductive sheet and a method for manufacturing the same.

In recent years, thiophene-based and aniline-based polymers have excellent stability and conductivity, so that their use as organic conductive materials is expected. As one of its applications, a coating composition in which a conductive polymer is dispersed in a solvent is used for forming transparent electrodes used in various devices such as liquid crystal displays and transparent touch panels.

In Patent Document 1, "a transparent conductive coating composition comprising a conductive polymer, a resin, and a solvent, wherein the resin contains polyvinylidene fluoride, the solvent is a protic polar solvent, a non-polar A dispersion particle size of the polyvinylidene fluoride in the coating composition containing a protic polar solvent is 0.3 μm or less, and the content of the conductive polymer is a total solid content in the coating composition. 3% by mass or more and 45% by mass or less with respect to the mass of the component, and the content of the aprotic polar solvent is 25% by mass or more and 50% by mass or less with respect to the total mass of the solvent". Coating compositions have been proposed.

JP, 2016-3312, A

However, when a transparent conductive sheet is manufactured using the coating composition described in Patent Document 1, the hardness of the transparent conductive sheet is not sufficient, and the transparent conductive sheet may be damaged or damaged during the manufacturing process. , It turned out that there is a problem with the physical properties.

The present invention has been made to solve the above problems, and particularly provides a transparent conductive sheet having a transparent conductive film having excellent physical properties, and a method for producing the same.

According to an example of the present invention, the transparent conductive sheet is a transparent conductive sheet including a transparent base material and a transparent conductive film formed on the main surface of the transparent base material, wherein the transparent conductive film is a transparent conductive film. Includes a conductive polymer and a hydrophobic resin, the hydrophobic resin forms a plurality of lumps, the conductive polymer is disposed between the lumps, three-dimensionally The conductive polymer is connected and a part of the conductive polymer reaches the surface of the transparent conductive film.

According to the present invention, it is possible to provide a transparent conductive sheet having a transparent conductive film having excellent physical properties.

FIG. 1 is a schematic sectional view of a transparent conductive sheet according to an embodiment of the present invention. FIG. 2 is a schematic sectional view of a conventional transparent conductive sheet. FIG. 3 is a view showing a field emission scanning electron microscope photograph of a cross section of the transparent conductive sheet of Example 1. FIG. 4 is a diagram showing an AFM current image obtained by simultaneous AFM/current measurement on the surface of the transparent conductive sheet of Example 1. 5: is a figure which shows the AFM current image by the AFM/current simultaneous measurement of the cross section of the transparent conductive sheet of Example 1. FIG.

(Transparent conductive sheet)
The transparent conductive sheet according to an embodiment of the present invention comprises a transparent substrate and a transparent conductive film formed on the main surface of the transparent substrate, the transparent conductive film is a conductive polymer, A hydrophobic resin, wherein the hydrophobic resin forms a plurality of lumps, the conductive polymer is disposed between the lumps, three-dimensionally connected, the conductive polymer Partially reaches the surface of the transparent conductive film.

More specifically, the transparent conductive sheet according to one embodiment of the present invention includes a transparent base material and a transparent conductive film formed on the main surface of the transparent base material, and the transparent conductive film is A conductive polymer and a hydrophobic resin are contained, the pencil hardness of the transparent conductive film is B or more, and the surface electric resistance value of the transparent conductive film is 50 Ω/square or more and 200 Ω/square or less. The total light transmittance of the transparent conductive sheet is 85% or more.

In the transparent conductive film of the transparent conductive sheet according to one embodiment of the present invention, the hydrophobic resin forms a plurality of lumps, and the conductive polymer is arranged between the lumps to form a three-dimensional structure. To form a three-dimensional conductive path, a part of the conductive polymer forming the three-dimensional conductive path reaches the surface of the transparent conductive film, electrical characteristics, optical characteristics , Excellent in physical properties and heat and humidity resistance.

The agglomerate is composed of a single particle of the hydrophobic resin, or is composed of an aggregate of a single particle of the hydrophobic resin, and an aggregate of a single particle and an aggregate of a single particle. May be mixed.

Further, since the hydrophobic resin functions as a binder for the transparent conductive film, the adhesion between the transparent conductive film and the transparent substrate can be improved. In particular, when a flexible substrate such as a resin film is used as the transparent substrate, the fact that the transparent conductive film contains a hydrophobic resin means that the transparent conductive film and the transparent substrate have good adhesion and followability. From the viewpoint of.

The conductive polymer is a polymer called Conductive Polymers (CPs), which itself exhibits conductivity in the state where a polyradical cationic salt or a polyradical anionic salt is formed by doping with a dopant. Refers to a possible polymer. Specific examples thereof include π-conjugated conductive polymers such as polythiophene, polyaniline, polypyrrole and their derivatives.

In one embodiment of the present invention, as the conductive polymer, a polymer containing a polythiophene compound and a dopant can be used. As the conductive polymer, a mixture (also referred to as PEDOT/PSS) containing poly(3,4-ethylenedioxythiophene) as a polythiophene-based compound and polystyrene sulfonic acid as a dopant can be used. Not limited to.

As the PEDOT/PSS, for example, the composition ratio of PEDOT and PSS is preferably 300 parts by mass or less with respect to 100 parts by mass of PEDOT. Examples of such a combination include "PH1000", "PH750", "PH500", "PHCV4" and the like in the Clevios series manufactured by Heraeus.

Next, the form of the PEDOT/PSS will be described. First, PEDOT is an oligomer having a molecular weight of about 1000 to 2500, and PSS is a polymer having a molecular weight of about 10,000 to 500,000, from which a primary structure of PEDOT/PSS is formed. Next, a large number of Cationic PEDOT molecules are adsorbed to the anionic PSS chain to form a secondary structure that forms a salt. Furthermore, the PSS chains are entangled with each other to form a gel-like tertiary structure, and when dispersed in water, a colloidal state is formed. In addition, the morphology of PEDOT/PSS, which is a conductive polymer, deforms from the colloidal state while maintaining a constant volume due to the presence of the hydrophobic resin when the transparent conductive film is formed.

The average particle size of the conductive polymer in the aqueous dispersion is preferably about 10 nm to 500 nm, and more preferably 10 nm to 100 nm from the viewpoint of improving electrical characteristics, optical characteristics, physical characteristics and wet heat resistance.

The average particle size of the conductive polymer is measured as follows. First, an aqueous dispersion of a conductive polymer is collected and frozen, and a fracture surface is prepared. Then, using a field emission scanning electron microscope (FE-SEM) manufactured by FEI, observation is performed at an acceleration voltage of 1.0 kV and a magnification of 50,000 times to obtain a secondary electron image. Image processing is performed on the obtained secondary electron image, and the maximum major axis diameter of each particle is calculated. After that, the arithmetic mean value of the calculated maximum major axis diameters is calculated and used as the average particle diameter of the conductive polymer.

It is necessary that a part of the conductive polymer reaches the surface of the transparent conductive film, whereby the surface electricity of the transparent conductive film of the transparent conductive sheet according to the embodiment of the present invention is reduced. The resistance value can be reliably reduced.

Here, the reason why the electrical and physical properties of the transparent conductive film are improved will be described based on the drawings as compared with a conventional transparent conductive film.

FIG. 1 is a schematic sectional view of a transparent conductive sheet according to an embodiment of the present invention. In FIG. 1, a transparent conductive sheet 10 according to an embodiment of the present invention includes a transparent base material 11 and a transparent conductive film 12 formed on the transparent base material 11. The transparent conductive film 12 is formed of a hydrophobic resin 12a that functions as a binder and a conductive polymer 12b. The hydrophobic resin 12a forms a lump, and the conductive polymer 12b is arranged between the hydrophobic resins 12a forming the lump. Further, it is considered that the agglomerates consist of single particles of the hydrophobic resin or an aggregate of single particles of the hydrophobic resin. Further, the agglomerates may include agglomerates composed of single particles and agglomerates composed of aggregates of single particles.

The conductive polymer 12b is three-dimensionally connected in the transparent conductive film 12 to form a three-dimensional conductive path, and a part of the conductive polymer forming the three-dimensional conductive path. However, it reaches the surface of the transparent conductive film 12. Here, forming a three-dimensional conductive path means a state in which the conductive polymer is conducted in the three-dimensional direction. The conductive polymer having a three-dimensional conductive path may be completely integrated in the transparent conductive film 12, or a plurality of conductive polymers having a three-dimensional conductive path may be formed. It is also possible to form a set and connect them to be electrically connected to each other. That is, in the transparent conductive film 12, it is sufficient that the conductive polymer 12b forms a conductive path, that is, a conductive network. It is considered that this can improve the conductivity of the transparent conductive sheet 10.

The conductive polymer 12b is three-dimensionally connected in the transparent conductive film 12, and a part of the conductive polymer has reached the surface of the transparent conductive film 12 means that the transparent conductive film 12 is transparent. The surface and cross section of the film 12 can be confirmed by performing simultaneous AFM/current measurement using an atomic force microscope (AFM) and visualizing the conductive part.

On the surface of the transparent conductive film 12, the conductive polymer and the hydrophobic resin are present at a constant ratio. It is considered that the hydrophobic resin 12a also exists near the surface of the transparent conductive film 12 and the surface hardness of the transparent conductive film 12 can be improved by supplementing the conductive polymer 12b which is weak in strength. On the other hand, it is known that the conductive polymer 12b on the surface is divided into a conductive polymer that forms a three-dimensional conductive path and a conductive polymer that does not form a three-dimensional conductive path. Since the conductive polymer forming the three-dimensional conductive path is protected by the hydrophobic resin 12a, it functions as a transparent conductive film even if surface friction is applied. Further, the transparent conductive film 12 is filled with the lumps of the hydrophobic resin 12a, and the conductive polymer 12b is scattered between the lumps of the hydrophobic resin 12a. Therefore, it is considered that the lumps of the hydrophobic resin 12a as a three-dimensional structure are arranged in order while giving chemical interaction and physical interaction to each other, and the internal hardness of the transparent conductive film 12 is also improved. ..

On the other hand, FIG. 2 is a schematic cross-sectional view of a conventional transparent conductive sheet using a hydrophilic resin instead of the hydrophobic resin. In FIG. 2, the conventional transparent conductive sheet 20 includes a transparent base material 21 and a transparent conductive film 22 formed on the transparent base material 21. The transparent conductive film 22 is formed of a hydrophilic resin 22a and a conductive polymer 22b. In a coating liquid for forming a transparent conductive film containing a conductive polymer, a hydrophobic resin, and a solvent, when the solvent is water, the hydrophobic resin becomes an emulsion type in the solvent, but the hydrophilic resin 22a Does not take the form of emulsion and dissolves in the solvent. Further, it is considered that the hydrophilic resin 22a is almost randomly dispersed in the transparent conductive film 22 and the conductive polymer 22b is arranged between the hydrophilic resins 22a.

In addition, the conductive polymer 22b is almost isolated in the transparent conductive film 22, and the conductive polymer 22b does not form a three-dimensional conductive path in the transparent conductive film 22. Or, it is considered that its formation is insufficient. Therefore, it is considered that the conductive polymer 22b does not sufficiently function as a conductive path and the conductivity of the transparent conductive sheet 20 cannot be improved. That is, in the conventional transparent conductive sheet using a hydrophilic resin, in order to form a conductive path, it is necessary to increase the content of the conductive polymer or increase the film thickness of the transparent conductive film, As a drawback in that case, deterioration of optical characteristics is considered.

Furthermore, since it is considered that the hydrophilic resin 22a and the conductive polymer 22b are randomly entangled inside the transparent conductive film 22, the resistance of the transparent conductive film 22 to external stress is reduced, and the transparent conductive film 22 is transparent. It is considered that the hardness of the conductive film 22 decreases.

Examples of the hydrophobic resin include polyvinylidene fluoride resin (PVDF), vinylidene fluoride-acrylic copolymer, vinylidene fluoride-hexafluoropropylene copolymer, acrylic resin, polyester resin, polyamide resin, polycarbonate resin, polyurethane resin, Resins such as polystyrene resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, polyolefin resin, polyethylene glycol (PEG), polyethylene oxide and polypropylene oxide can be used. In the present invention, the hydrophobic resin means a resin having a lower solubility in water as compared with the conductive polymer, and particularly preferably a resin having a hydrophobic group in the resin skeleton.

An emulsion type can be used as the usage form of the hydrophobic resin. Particularly, PVDF emulsion, vinylidene fluoride-acrylic copolymer emulsion, vinylidene fluoride-hexafluoropropylene copolymer emulsion, acrylic resin emulsion, polyester emulsion, polyolefin emulsion and the like are preferable. The average particle diameter of the resin particles in the emulsion is preferably 10 to 300 nm, and the average particle diameter can be measured by a known particle size distribution meter.

The volume ratio of the conductive polymer to the hydrophobic resin can be 1:99 to 70:30. If the volume ratio of the conductive polymer and the hydrophobic resin is within the above range, in forming the three-dimensional structure of the transparent conductive film, the conductive polymer and the hydrophobic resin are arranged in an orderly manner. The electrical property, optical property, physical property and wet heat resistance of the transparent conductive film can be improved. Particularly, in forming the transparent electrode, a more preferable volume ratio is 10:90 to 35:65.

The pencil hardness of the transparent conductive film of the transparent conductive sheet is preferably B or higher, and more preferably HB or higher. The higher the pencil hardness, the better the physical properties.

The surface electric resistance value of the transparent conductive film of the transparent conductive sheet is preferably 50 Ω/square or more and 10000 Ω/square or less. Furthermore, when the transparent conductive film is used as an electrode for a touch panel, the surface resistance value of the transparent conductive film is preferably 50Ω/square or more and 200Ω/square or less. The smaller the surface electric resistance value, the better the electric characteristics.

The total light transmittance of the transparent conductive sheet is preferably 85% or more, more preferably 90% or more. The higher the total light transmittance, the better the optical properties. The total light transmittance can be measured by a spectrophotometer, for example, "V-570" manufactured by JASCO Corporation.

The thickness of the transparent conductive film is appropriately set depending on the application, but is usually about 0.01 to 10 μm. If the film thickness is too thin or too thick, it becomes difficult to form a uniform transparent conductive film. Although it depends on the ratio of the conductive polymer, when the film thickness is thin, the surface electric resistance value tends to increase, and when the film thickness is too thick, the total light transmittance tends to decrease. In the present embodiment, 150 to 300 nm is preferable.

Various materials such as plastic, rubber, glass, and ceramics can be used as the transparent substrate.

(Method for producing transparent conductive sheet)
A method for producing a transparent conductive sheet according to an embodiment of the present invention comprises a step of producing a transparent conductive film-forming coating liquid containing a conductive polymer, a hydrophobic resin, and a solvent, and the transparent conductive film. Forming the transparent conductive film on the transparent base material by applying the coating liquid for formation onto the transparent base material and heating.

According to the method for manufacturing a transparent conductive sheet according to an embodiment of the present invention, it is possible to manufacture a transparent conductive sheet including a transparent conductive film having excellent electric characteristics, optical characteristics, physical characteristics, and heat and humidity resistance.

<Coating liquid for forming transparent conductive film>
As the conductive polymer, a mixture (PEDOT/PSS) containing poly(3,4-ethylenedioxythiophene) as the above polythiophene-based compound and polystyrene sulfonic acid as the dopant can be used. Not limited. Usually, the conductive polymer is supplied in the form of an aqueous dispersion of the conductive polymer.

The content of the conductive polymer in the coating liquid for forming the transparent conductive film is 0.7% by mass or more and 70.0% by mass with respect to the mass of all solid components contained in the coating liquid for forming the transparent conductive film. % Or less is preferable. When the content of the conductive polymer is less than 0.7 mass% with respect to the mass of all solid components contained in the transparent conductive film-forming coating liquid, the conductivity of the transparent conductive film is lowered, and 70 If it exceeds 0.0% by mass, the physical properties and wet heat resistance of the transparent conductive film tend to deteriorate.

As the hydrophobic resin, the same resin as the hydrophobic resin described in the above-mentioned transparent conductive sheet can be used, but it is preferably used as a hydrophobic resin aqueous emulsion. Since the conductive polymer is usually used as a conductive polymer aqueous dispersion, the use of the hydrophobic resin aqueous emulsion improves the miscibility with the conductive polymer aqueous dispersion.

Since the hydrophobic resin is originally a water-insoluble resin, the hydrophobic resin and the conductive polymer are used when the transparent conductive film-forming coating liquid is prepared by using the hydrophobic resin as an aqueous emulsion. Are separated, the hydrophobic resin forms a plurality of lumps, and the conductive polymer can be arranged between the lumps of the hydrophobic resin.

The content of the hydrophobic resin is preferably 30.0% by mass or more and 99.3% by mass or less, and more preferably 65.0% by mass based on the mass of all solid components contained in the coating liquid for forming the transparent conductive film. It is from 9% to 95.0% by mass. If the content of the hydrophobic resin is too small, it tends to be difficult to obtain a transparent conductive film having sufficient hardness, if the content of the hydrophobic resin is too large, the transparent conductive film becomes cloudy, optical The characteristics tend to deteriorate.

The solvent preferably contains a protic polar solvent and an aprotic polar solvent. The protic solvent has an effect of uniformly dispersing the conductive polymer in the state of the coating liquid and an effect of uniformly dispersing or dissolving the hydrophobic resin. Further, the aprotic solvent, after applying the coating liquid to the substrate, in the drying step of removing the solvent by drying to form a conductive film, the conductive polymer is oriented and crystallized to form a conductive network. Has the effect of forming. Further, by using the protic polar solvent and the aprotic polar solvent in combination, each solvent is effective for the conductive polymer and the hydrophobic resin from the preparation of the coating liquid to the formation of the conductive film. Therefore, a transparent conductive film having excellent transparency can be obtained at a relatively low drying temperature.

Examples of the protic polar solvent include water, ethyl alcohol, methyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, ethylene glycol, propylene glycol, acetic acid, etc. Examples of the polar solvent include dimethyl sulfoxide, N-methylpyrrolidone, N-ethylpyrrolidone, N,N-dimethylformamide, acetonitrile, acetone and tetrahydrofuran.

The content of the aprotic polar solvent is preferably 1.0% by mass or more and 50.0% by mass or less based on the total mass of the solvent. When the content of the aprotic polar solvent is less than 1.0% by mass with respect to the total mass of the solvent, the orientation and crystallization of the conductive polymer are less likely to occur, so that the electrical characteristics of the transparent conductive film are If it exceeds 50.0 mass %, aggregation of the conductive polymer or the hydrophobic resin is likely to occur, so that the optical characteristics of the transparent conductive film tend to be deteriorated.

The content of the solvent is not particularly limited, but may be 50.0% by mass or more and 99.5% by mass or less with respect to the total mass of the transparent conductive film-forming coating liquid. Moreover, the solvent may include a nonpolar solvent.

The transparent conductive film forming coating solution can be produced by mixing the conductive polymer, the hydrophobic resin, and the solvent. Further, it is preferable that the coating liquid for forming the transparent conductive film is further subjected to a dispersion treatment using a disperser. By performing dispersion treatment using the above dispersing machine, the hydrophobic resin surely forms a plurality of lumps, and the conductive polymer is disposed between the lumps and three-dimensionally connected to form a three-dimensional body. A part of the conductive polymer that forms a conductive path and forms a three-dimensional conductive path can reach the surface of the transparent conductive film.

As the disperser, a media disperser having a media such as a ball mill, a sand mill, a pico mill, and a paint conditioner interposed, and a medialess disperser such as an ultrasonic disperser, a high pressure homogenizer, a homomixer, a disper, a jet mill can be used .. Particularly preferred is a high pressure homogenizer.

Further, it is preferable that the transparent conductive film forming coating liquid contains a leveling agent. This ensures that the hydrophobic resin forms a plurality of lumps, and the conductive polymer is placed between the lumps and connected three-dimensionally to form a three-dimensional conductive path, thereby forming a three-dimensional conductive path. A part of the conductive polymer forming the conductive path can reach the surface of the transparent conductive film.

Examples of the leveling agent include silicone compounds having a polydimethylsiloxane structure. Specifically, BYK-300, BYK-302, BYK-306, BYK-307, BYK-310, BYK-315, BYK-320, BYK-322, BYK-323, BYK-325, BYK manufactured by Big Chemie. -330, BYK-331, BYK-333, BYK-337, BYK-344, BYK-370, BYK-375, BYK-377, BYK-UV3500, BYK-UV3510, BYK-UV3570; TEGO-RAD2100 manufactured by Degussa. , TEGO-RAD2200N, TEGO-RAD2250, TEGO-RAD2300, TEGO-RAD2500, TEGO-RAD2600, TEGO-RAD2700; Granol 100, Granol 115, Granol 400, Granol 410, Granol 435, Granol 440, Granol 450 manufactured by Kyoeisha Chemical Co., Ltd. , B-1484, Polyflow ATF-2, KL-600, UCR-L72, UCR-L93 and the like. You may use these individually or in mixture of 2 or more. Among these, BYK-337 and BYK-377 manufactured by Big Chemie are more preferable. The content of the leveling agent may be about 0.01 to 5.0 mass% with respect to the total mass of the transparent conductive film-forming coating liquid.

<Formation of transparent conductive film>
Examples of the method for applying the transparent conductive film-forming coating liquid on a transparent substrate include, for example, bar coating method, reverse method, gravure coating method, micro gravure coating method, die coating method, dipping method, spin coating method, A coating method such as a slit coating method or a spray coating method can be used.

The heating after the coating may be performed under the condition that the solvent component of the coating liquid for forming the transparent conductive film is evaporated, and is preferably performed at 100 to 150° C. for 1 to 60 minutes. If the solvent remains in the transparent conductive film, the strength tends to be poor. As a heating method, for example, a hot air drying method, a heating drying method, a vacuum drying method, a natural drying method or the like can be used. In addition, the transparent conductive film may be formed by irradiating the coating film with UV light or EB light to cure the coating film, if necessary.

<Conductive pattern forming step>
A method for manufacturing a transparent conductive sheet according to an embodiment of the present invention uses a step of forming a resist film at a position where a conductive pattern is formed on the transparent conductive film, and a deactivator for deactivating conductivity. And a step of deactivating the conductivity of the exposed portion of the transparent conductive film using the resist film as a mask. This makes it possible to easily and inexpensively form a highly accurate conductive pattern on a transparent substrate.

The resist film can be formed, for example, by screen-printing a resist agent on the transparent conductive film. The resist agent is not particularly limited and can be appropriately selected.

The deactivator may be any one that can deactivate the conductive polymer, and examples thereof include an oxidizing compound and a basic compound.

Examples of the oxidizable compound include hydrogen peroxide compounds, perchloric acid compounds, hypochlorous acid compounds, peracetic acid compounds, metachlorobenzoic acid compounds, and sulfite compounds.

Examples of the basic compound include ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, pyridine, 4-methylpyridine, tetramethylammonium hydroxide and the like.

Examples of the present invention will be described below. However, the present invention is not limited to the following examples. In the following, "part" means "part by mass" unless otherwise specified.

(Example 1)
<Preparation of coating liquid for forming transparent conductive film>
First, the following components were added and mixed to prepare a mixed liquid for forming a transparent conductive film.
(1) Conductive polymer aqueous dispersion (trade name "Clevios PH1000" manufactured by Heraeus, conductive polymer: PEDOT-PSS, solid content concentration: 1.2% by mass, average particle diameter of PEDOT-PSS: 70 nm ): 40.00 parts (2) Hydrophobic resin emulsion (PVDF emulsion manufactured by Arkema, solid content concentration: 24% by mass, solvent: water): 6.00 parts (3) aprotic polar solvent (dimethyl sulfoxide) : 12.70 parts (4) Protic polar solvent (ethyl alcohol): 33.20 parts (5) Protic polar solvent (ion-exchanged water): 8.10 parts

Next, the transparent conductive film forming mixed liquid was subjected to a dispersion treatment using a high pressure homogenizer at a pressure of 80 MPa to prepare a transparent conductive film forming coating liquid.

<Formation of transparent conductive sheet>
Next, a 100 μm-thick polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., trade name “COSMOSHINE A4300”, total light transmittance: 92.3%) was used as a substrate, and the entire one main surface of the substrate was used. The above coating solution for forming a transparent conductive film was applied to the above by a bar coating method, and then heated at 120° C. for 2 minutes. As a result, the transparent conductive sheet of Example 1 having the transparent conductive film formed on one main surface was produced. The film thickness of the transparent conductive film was 290 nm.

<Observation of surface and cross section of transparent conductive film>
The cross-sectional structure of the transparent conductive film of the produced transparent conductive sheet was observed as follows. First, an epoxy resin was applied and embedded on the transparent conductive film of the produced transparent conductive sheet, and the surface of the epoxy resin was subjected to mechanical polishing. After that, a cross section was prepared by ion polishing using a cross-section sample preparation device "SM-09010" (trade name) manufactured by JEOL Ltd., and flat milling was performed to obtain a cross-section observation sample. Using a field emission scanning electron microscope (FE-SEM) manufactured by Hitachi, Ltd., the cross-section observation sample is observed at an accelerating voltage of 2.0 kV and a magnification of 100,000 times to obtain a secondary/reflection electron hybrid image. It was The observed image is shown in FIG.

From FIG. 3, in the transparent conductive sheet 30, the transparent conductive film 32 is formed on the PET film 31, the epoxy resin layer 33 is formed on the transparent conductive film 32, and the hydrophobic resin 32a is formed. Forms a plurality of layered continuous films, the conductive polymer 32b forms a plurality of layered films, and the film of the conductive polymer 32b is disposed between the continuous films of the hydrophobic resin 32a. You can confirm that. Further, from FIG. 3, the thickness of the continuous film of the hydrophobic resin 32a was about 20 to 100 nm.

<Visualization of the conductive polymer that forms a three-dimensional conductive path on the surface and cross section of the transparent conductive film>
After applying a silver paste as a conductive material around the processed surface of the transparent conductive film of the transparent conductive sheet, AFM/current simultaneous measurement is performed on the surface and the cross section of the transparent conductive sheet to obtain three-dimensional conductivity. The conductive polymer (conductive network) forming the path was visualized.

Specifically, an atomic force microscope "Nano NaviII/E-Sweep" manufactured by Hitachi High-Tech Science Co., Ltd. was used to perform current simultaneous measurement in SIS (Sample Intelligence Scan) mode. In the surface analysis, the tip used was made of Au-coated Si ₃ N ₄ (spring constant 0.1 N/m), the scanning area was 1 μm ² , the applied voltage was 0.3 V, and the amplifier was a nano-amplifier. did. Further, in the cross-sectional analysis, a probe made of Pt-coated Si (spring constant 3 N/m) was used, a scan area was 2 μm ² , an applied voltage was 0.7 V, and a pico-amplifier was used as an amplifier.

FIG. 4 shows an AFM current image obtained by simultaneous AFM/current measurement on the surface of the transparent conductive film. From FIG. 4, the non-conductive part 41 and the dot-shaped conductive part 42 can be confirmed on the surface of the transparent conductive film. The non-conductive part 41 is formed of PVDF, and the conductive part 42 shows a state in which a part of the conductive polymer forming the three-dimensional conductive path reaches the surface of the transparent conductive film. However, it is considered that not all conductive polymers existing on the surface form a three-dimensional conductive path.

Further, FIG. 5 shows an AFM current image of the cross section of the transparent conductive film by simultaneous AFM/current measurement. From FIG. 5, the transparent conductive film 40 is formed of the non-conductive portion 41 and the conductive portion 42, and the conductive portion 42 is formed of the conductive polymer that forms a three-dimensional conductive path inside the transparent conductive film 40. It can be confirmed that a conductive network is formed in the.

From FIGS. 3 to 5, in the transparent conductive film, the hydrophobic resin forms a plurality of lumps, and the conductive polymer is arranged between the lumps and three-dimensionally connected to form a three-dimensional structure. It can be seen that a part of the conductive polymer that forms a three-dimensional conductive path forming a specific conductive path reaches the surface of the transparent conductive film.

(Example 2)
The following components were added and mixed to prepare a transparent conductive film-forming mixed solution, and the transparent conductive film-forming mixed solution was subjected to a dispersion treatment using a high-pressure homogenizer in the same manner as in Example 1 to obtain a transparent conductive film. A transparent conductive sheet of Example 2 was prepared in the same manner as in Example 1 except that a coating liquid for forming a film was prepared and the coating liquid for forming a transparent conductive film was used to form a film having a thickness of 180 nm. Was produced.
(1) Conductive polymer aqueous dispersion (manufactured by Heraeus, trade name "Clevios PH1000", conductive polymer: PEDOT-PSS, solid content concentration: 1.2 mass%, PEDOT-PSS average particle size: 70 nm ): 60.00 parts (2) Hydrophobic resin emulsion (acrylic resin emulsion manufactured by Daicel Finechem, trade name “AST499” solid content concentration: 41.7% by mass, solvent: water): 3.00 parts (3) Leveling agent (manufactured by BYK Japan KK, trade name "BYK-337", mixed solution of 15% by mass of polyether-modified polydimethylsiloxane and 85% by mass of dipropylene glycol monomethyl ether): 0.20 parts (4) aprotic Polar solvent (ethylene glycol): 10.00 parts (5) protic polar solvent (n-propyl alcohol): 20.00 parts (6) protic polar solvent (ion-exchanged water): 6.80 parts

When the cross section of the transparent conductive film of the produced transparent conductive sheet was observed in the same manner as in Example 1, an observation image similar to that in FIG. 3 was obtained, and the thickness of the continuous film of the hydrophobic resin was obtained from the observation image. The length was about 30 to 150 nm. Further, when a conductive polymer forming a three-dimensional conductive path on the surface and cross section of the transparent conductive film was visualized in the same manner as in Example 1, AFM current images similar to those in FIGS. 4 and 5 were obtained. Obtained.

(Example 3)
The transparent conductive sheet of Example 3 was carried out in the same manner as in Example 1 except that the mixed liquid for forming a transparent conductive film was used as it was as a coating liquid for forming a transparent conductive film without performing a dispersion treatment using a high pressure homogenizer. Was produced.

When the cross section of the transparent conductive film of the produced transparent conductive sheet was observed in the same manner as in Example 1, an observation image similar to that in FIG. 3 was obtained, and the thickness of the continuous film of the hydrophobic resin was obtained from the observation image. The length was about 40 to 200 nm. Further, when a conductive polymer forming a three-dimensional conductive path on the surface and cross section of the transparent conductive film was visualized in the same manner as in Example 1, AFM current images similar to those in FIGS. 4 and 5 were obtained. Obtained.

(Example 4)
0.20 part of a leveling agent (manufactured by BYK Japan KK, trade name "BYK-337") was added, the amount of the protic polar solvent (ion-exchanged water) was changed to 7.90 parts, and a high-pressure homogenizer was used. A transparent conductive film-forming coating liquid was prepared in the same manner as in Example 1 except that the dispersion treatment was not performed, and the same procedure as in Example 1 was performed except that this transparent conductive film-forming coating liquid was used. A transparent conductive sheet of Example 4 was produced.

When the cross section of the transparent conductive film of the produced transparent conductive sheet was observed in the same manner as in Example 1, an observation image similar to that in FIG. 3 was obtained, and the thickness of the continuous film of the hydrophobic resin was obtained from the observation image. The length was about 30 to 175 nm. Further, when a conductive polymer forming a three-dimensional conductive path on the surface and cross section of the transparent conductive film was visualized in the same manner as in Example 1, AFM current images similar to those in FIGS. 4 and 5 were obtained. Obtained.

(Comparative Example 1)
The following components were added and mixed to prepare a mixed liquid for transparent conductive film formation, and the mixed liquid for transparent conductive film formation was subjected to a dispersion treatment using a high pressure homogenizer in the same manner as in Example 1 to obtain a transparent conductive film. A transparent conductive sheet of Comparative Example 1 was prepared in the same manner as in Example 1 except that a coating solution for forming a film was prepared and the coating solution for forming a transparent conductive film was used to change the thickness of the transparent conductive film to 389 nm. Was produced.
(1) Conductive polymer aqueous dispersion (trade name "Clevios PH1000" manufactured by Heraeus, conductive polymer: PEDOT-PSS, solid content concentration: 1.2% by mass, average particle diameter of PEDOT-PSS: 70 nm ): 39.20 parts (2) Hydrophilic resin (polyvinyl alcohol manufactured by Kuraray Co., Ltd., trade name "PVA-217"): 1.41 parts (3) Aprotic polar solvent (dimethyl sulfoxide): 12.70 parts (4) Protic polar solvent (ethyl alcohol): 33.20 parts (5) Protic polar solvent (ion-exchanged water): 13.49 parts

When the cross section of the transparent conductive film of the produced transparent conductive sheet was observed in the same manner as in Example 1, it was confirmed that, unlike FIG. 3, the cross sectional structure of the transparent conductive film was a uniform single-layer structure. confirmed. Further, when a conductive polymer that forms a three-dimensional conductive path on the surface and cross section of the transparent conductive film was visualized in the same manner as in Example 1, unlike in FIGS. 4 and 5, high conductivity was obtained. It was found that the formation of the conductive network by the molecules was insufficient.

(Comparative example 2)
<Preparation of coating liquid for forming transparent conductive film>
First, the following components were added and mixed to prepare a coating liquid for forming a transparent conductive film. In Comparative Example 2, the dispersion treatment using the high pressure homogenizer was not performed.
(1) Conductive polymer aqueous dispersion (manufactured by Heraeus, trade name "PH-500", conductive polymer: PEDOT-PSS, solid content concentration: 1.0% by mass, average particle diameter of PEDOT-PSS: 120 nm): 2.5 parts (2) Hydrophobic resin emulsion (PVDF emulsion manufactured by Arkema, solid content concentration: 20% by mass, solvent: water): 2.4 parts (3) aprotic polar solvent (dimethyl sulfoxide) ): 3.9 parts (4) Protic polar solvent (ethyl alcohol): 1.2 parts

<Formation of transparent conductive sheet>
Next, a 0.7-cm thick 10 cm square alkali-free glass (total light transmittance: 91.2%) was used as a substrate, and one of the main surfaces of the substrate was spin-coated with the above coating liquid for forming a transparent conductive film. Method was applied at a rotation speed of 800 rpm for 30 seconds, and then heated at 100° C. for 5 minutes. As a result, a transparent conductive sheet of Comparative Example 2 having a transparent conductive film formed on one main surface was produced. The film thickness of the transparent conductive film was 500 nm.

Next, the following evaluations were performed on the transparent conductive sheets of Examples 1 to 4 and Comparative Examples 1 and 2 obtained above.

<Electrical characteristics>
The electrical characteristics of the transparent conductive sheet were evaluated by measuring the surface electrical resistance value of the transparent conductive film of the transparent conductive sheet as described below.

The surface electric resistance value of the transparent conductive film of the transparent conductive sheet was measured using a resistivity measuring device “Loresta-GP” (MCP-T610 type) manufactured by Mitsubishi Chemical Analytech Co., Ltd. and an LSP probe.

<Optical properties>
The optical characteristics of the transparent conductive sheet were evaluated by measuring the total light transmittance of the transparent conductive sheet as described below.

The total light transmittance of the transparent conductive sheet was measured using a haze meter "NDH2000" manufactured by Nippon Denshoku Industries Co., Ltd.

<Physical properties>
The physical properties of the transparent conductive sheet were evaluated by measuring the pencil hardness of the transparent conductive film of the transparent conductive sheet as described below.

The pencil hardness of the transparent conductive film of the transparent conductive sheet is based on the pencil hardness measuring method specified in Japanese Industrial Standard (JIS) K5400 using a surface property tester “HEIDON-14DR” manufactured by Shinto Scientific Co., Ltd. Was measured.

<Moisture and heat resistance>
The moist heat resistance of the transparent conductive sheet was evaluated by conducting a storage test on the transparent conductive sheet as described below.

First, the initial surface electric resistance value of the transparent conductive film of the transparent conductive sheet was measured in the same manner as the above-mentioned evaluation of electric characteristics. Next, the transparent conductive sheet was placed in a thermo-hygrostat and stored at 65° C. and 90% relative humidity for 500 hours. Subsequently, the surface electric resistance value of the transparent conductive film of the transparent conductive sheet after storage was measured in the same manner as above. Finally, the degree of change in surface electric resistance value was calculated by the following formula (1).
Degree of change in surface electric resistance value=surface electric resistance value after storage/initial surface electric resistance value (1)

As a result of the above measurement, when the degree of change in the surface electrical resistance value was 1.2 or less, it was determined that the moist heat resistance was good, and when the degree of change in the surface resistance value was more than 1.2, the moisture heat resistance was judged to be poor. ..

The results of the above evaluations are shown in Table 1.

From Table 1, in the transparent conductive sheets of Examples 1 to 4 of the present invention, the surface electric resistance values of the transparent conductive films are all below 180 Ω/square, the electric characteristics are good, and the total light transmittances are all 85. It can be seen that the optical characteristics were good, and the wet heat resistance was all good, and the pencil hardness, which is a physical property, was all B or higher. In particular, Examples 1 and 2 using the coating liquid for forming a transparent conductive film which was subjected to dispersion treatment using a high-pressure homogenizer were the same as Examples 3 and 4 using a coating liquid for forming a transparent conductive film which was not subjected to dispersion treatment. It can be seen that the electrical characteristics are further improved in comparison. In addition, in Examples 3 and 4 in which neither dispersion treatment was performed using a high-pressure homogenizer, Example 4 in which a leveling agent was added to the transparent conductive film-forming coating liquid was an example in which no leveling agent was added. The electrical characteristics were improved as compared with 3.

On the other hand, it can be seen that in Comparative Example 1 using the hydrophilic resin, the optical characteristics and the wet heat resistance are inferior, the pencil hardness is 5 B or less, and the physical characteristics are inferior. Further, it can be seen that in Comparative Example 2 corresponding to Example 3 of Patent Document 1, the electrical characteristics and the pencil hardness are poor.

Subsequently, the patterning suitability of the transparent conductive sheet obtained above was evaluated as follows.

<Formation of resist film>
First, a resist agent (made by Heraeus, trade name "Clvious SET S") is printed by a screen printing method on a 5 cm square area of the central portion of the main surface of the transparent conductive sheet on the transparent conductive film side, and then 100°C. Heated for 5 minutes. As a result, a resist film was formed on the transparent conductive film.

<Reduction in conductivity>
Next, the transparent conductive sheet having a resist film formed on the transparent conductive film is dipped in a solution prepared by preparing a 10% aqueous solution of a chlorine-based deactivator (product name "Clvious Etch" manufactured by Heraeus) for 20 minutes. After that, it was washed with distilled water and heated at 100° C. for 5 minutes. This reduced the conductivity of the exposed portion of the transparent conductive film.

<Removal of resist film>
Next, the transparent conductive sheet was immersed in toluene for 3 minutes, the resist film was peeled off, washed with distilled water, and dried at 100° C. for 5 minutes.

Next, the electrical characteristics of the obtained transparent conductive sheet were evaluated. The evaluation method will be described below.

<Electrical characteristics>
First, on the conductive pattern forming surface of the transparent conductive sheet, the surface electrical resistance value of the conductive portion on which the conductive pattern is formed is measured by a resistivity measuring instrument “Loresta-GP” (MCP-T610 type manufactured by Mitsubishi Chemical Analytech Co., Ltd.). ) And an LSP probe. Further, on the conductive pattern forming surface of the transparent conductive sheet, the surface electric resistance value of the non-conductive portion where the conductive pattern is not formed is measured by a resistivity measuring instrument “Hiresta-UP” (MCP-HT450 manufactured by Mitsubishi Chemical Analytech Co., Ltd.). Type) and a URS probe. Here, when the difference between the surface electrical resistance values of the conductive portion and the non-conductive portion is 1×10 ⁶ Ω/square or more, it is evaluated that good electrical contrast is obtained.

As a result, it was found that good electrical contrast was obtained with the transparent conductive sheets of Examples 1 to 4, and good electrical contrast was not obtained with the transparent conductive sheets of Comparative Examples 1 and 2. I found out.

10, 20, 30 Transparent conductive sheet 11, 21 Transparent base material 31 PET film 12, 22, 32, 40 Transparent conductive film 12a, 22a, 32a Hydrophobic resin 12b, 22b, 32b Conductive polymer 33 Epoxy resin layer 41 Non-conductive part 42 Conductive part

Claims (9)

A transparent substrate, a transparent conductive sheet comprising a transparent conductive film formed on the main surface of the transparent substrate,
The transparent conductive film contains a conductive polymer and a hydrophobic resin,
The hydrophobic resin forms a plurality of lumps,
The conductive polymer is disposed between the lumps, three-dimensionally connected,
A transparent conductive sheet, wherein a part of the conductive polymer reaches the surface of the transparent conductive film. Pencil hardness before Symbol transparent conductive film is not less than B, before Symbol total light transmittance of the transparent conductive sheet, the transparent conductive sheet according to claim 1 is 85% or more. The transparent conductive sheet according to claim 1, wherein a surface electric resistance value of the transparent conductive film is 50 Ω/square or more and 200 Ω/square or less. The transparent conductive sheet according to claim 1, wherein the conductive polymer contains a polythiophene compound and polystyrene sulfonic acid. The transparent conductive sheet according to claim 1, wherein a volume ratio of the conductive polymer to the hydrophobic resin in the transparent conductive film is 1:99 to 70:30. The transparent substrate is a transparent conductive sheet according to any one of claims 1-5 made of plastic, rubber, glass or ceramics. It is a manufacturing method of the transparent conductive sheet in any one of Claims 1-6, Comprising :
A step of producing a transparent conductive film-forming coating liquid containing a conductive polymer, a hydrophobic resin, and a solvent,
A step of forming a transparent conductive film on the transparent base material by applying the coating liquid for forming the transparent conductive film on a transparent base material and heating the same. Sheet manufacturing method. After preparing a transparent conductive film forming coating liquid containing the conductive polymer, the hydrophobic resin, and the solvent, the transparent conductive film forming coating liquid is subjected to dispersion treatment using a disperser. The method for producing a transparent conductive sheet according to claim 7 , further comprising a step. The method for producing a transparent conductive sheet according to claim 7, wherein the coating liquid for forming the transparent conductive film further contains a leveling agent.