JP2009146576A - Transparent conductive coating, transparent conductive film, and flexible transparent plane electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent conductive coating which has a high conductivity and an excellent transparency as well and can be manufactured easily by a liquid phase deposition, to provide a transparent film employing the coating, and to provide a flexible transparent plane electrode in which a voltage drop in the electrode in a large area is controlled. <P>SOLUTION: In the transparent conductive coating containing at least metal nano-wires, at least some parts of the metal nano-wires are bonded each other by an electric conduction process. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a transparent conductive film having both high conductivity and good transparency, which can be suitably used in various fields such as liquid crystal display elements, organic light emitting elements, inorganic electroluminescent elements, solar cells, electromagnetic wave shields, touch panels and the like. The present invention relates to a transparent conductive film that can be easily manufactured by liquid phase film formation, and further relates to a transparent conductive film and a flexible transparent surface electrode using the transparent conductive film.

  Transparent conductive films are used in liquid crystal displays, electroluminescence displays, plasma displays, electrochromic displays, transparent electrodes such as solar cells, touch panels, electronic paper, and electromagnetic shielding materials.

  In general, for example, a metal oxide is used as the transparent conductive film. Specifically, indium oxide doped with tin or zinc (ITO, IZO), zinc oxide doped with aluminum or gallium (AZO, GZO), Examples thereof include tin oxide (FTO, ATO) doped with fluorine or antimony. In general, the metal oxide transparent conductive film is produced by a vapor deposition method such as a vacuum deposition method, a sputtering method, or an ion plating method. However, since these film forming methods require a vacuum environment, the apparatus is large and complicated, and since a large amount of energy is consumed for film forming, it is necessary to develop a technology that can reduce the manufacturing cost and environmental load. It was done. On the other hand, as represented by a liquid crystal display and a touch display, an increase in the area of the transparent conductive film has been aimed at, and accordingly, demands for weight reduction and flexibility of the transparent conductive film have increased. Furthermore, in a large-area transparent electrode, the effect of the voltage drop of the transparent electrode becomes large, and further reduction in resistance has been demanded.

  In response to such a demand, a method of forming a transparent conductive film by a liquid phase film forming method such as coating or printing using a liquid material containing conductive fine particles has been proposed.

  However, in the conventional method, after forming a coating film by applying a coating liquid and drying, it is necessary to perform a heat treatment at 200 ° C. or higher in order to produce a conductive film having a high conductivity. When polymer materials such as resins are exposed to such high temperatures, they are damaged by deformation, melting, deterioration, etc., so it is applicable when forming a transparent conductive film on a resin substrate such as a plastic film. Can not.

  Compared to metal oxides, the conductivity of metal materials such as Ag, Cu, and Au is two orders of magnitude higher, which is preferable from the viewpoint of conductivity, but has a problem that transparency cannot be secured. On the other hand, it has been reported that both conductivity and transparency can be achieved by forming a uniform ultra-thin gold film. However, in order to form a uniform ultra-thin gold film, a special vacuum film forming method called a dual ion beam sputtering method is required, and reduction of manufacturing cost and environmental load cannot be realized.

  Further, as a transparent conductive film technology capable of liquid phase film formation, a method using CNT (carbon nanotube) or metal nanowire as a conductor (for example, see Patent Documents 1 and 2) has been proposed. In a transparent conductive film using conductive fibers such as CNTs or metal nanowires as a conductor, conductivity is exhibited by forming an electrical network between the conductive fibers. Therefore, ideally, all the conductive fibers have at least two or more contacts with other conductive fibers, and are in a state where they are widely distributed spatially to form a network. And transparency are preferable. However, it is difficult to obtain satisfactory conductivity because the network formation of the conductive fibers cannot be controlled.

On the other hand, it is known to improve electrical conductivity by energizing a circuit or coating film formed of metal fine particles (see, for example, Patent Documents 3 and 4). However, since the loss at the particle bonding interface is not completely eliminated, the inherent conductivity of the metal cannot be expressed in the coating film made of metal fine particles. Further, when a conductive film is formed on the entire surface as a surface electrode, there is a problem that transparency cannot be obtained.
Japanese translation of PCT publication No. 2004-526838 Japanese translation of PCT publication No. 2004-526838 JP 11-97849 A JP 2004-79243 A

  An object of the present invention is to provide a transparent conductive film that has both high conductivity and good transparency and can be easily produced by liquid phase film formation. Further, a transparent conductive film using the transparent conductive film, Furthermore, it is providing the flexible transparent surface electrode by which the voltage drop in an electrode was suppressed also in a large area.

  The above object of the present invention is achieved by the following configurations.

  1. A transparent conductive film containing at least metal nanowires, wherein at least some of the metal nanowires are bonded to each other by energization treatment.

  2. 2. The transparent conductive film according to 1 above, further comprising metal fine particles, wherein at least some of the metal nanowires are bonded via the metal fine particles by an energization treatment.

  3. 3. The transparent conductive film according to 1 or 2, wherein the energization process is a pulse current energization process.

  4). The transparent conductive film which has a transparent conductive film of any one of said 1-3 on a transparent resin film.

  5). 5. The transparent conductive film as described in 4 above, wherein a conductive polymer or a conductive fine particle-containing layer is further laminated on the transparent conductive film.

  6). 6. The transparent transparent electrode according to claim 4, wherein the transparent conductive film is used.

  According to the present invention, a transparent conductive film that has both high conductivity and good transparency and can be easily manufactured by liquid phase film formation, a transparent conductive film using this transparent conductive film, and even a large area A flexible transparent electrode in which a voltage drop at the electrode is suppressed can be provided.

  As a result of intensive studies in view of the above problems, the present inventor has found that a transparent conductive film containing at least metal nanowires has a high conductivity by virtue of a transparent conductive film in which at least some of the metal nanowires are joined by an energization process. Thus, the inventors have found that a transparent conductive film having both properties and good transparency and can be easily produced by liquid phase film formation is obtained, and the present invention has been achieved.

  The transparent conductive film of the present invention is a transparent conductive film characterized in that at least some of the metal nanowires are joined directly or via metal fine particles by energization treatment. According to the present invention, since a conductive path having conductivity close to that of a bulk metal can be formed, a transparent conductive film having high transparency and conductivity can be formed.

  In the present application, “bonded” means a state in which metal nanowires or metal fine particles are fused and can be regarded as one continuous body electrically. In the case of simple contact, a loss of conductivity due to contact resistance occurs, but in the case of a joined body, there is no influence, so that the conductivity can be improved.

  Hereinafter, the present invention, its components, and the best mode for carrying out the present invention will be described in detail.

[Metal nanowires]
In the transparent conductive film of the present invention, the metal nanowire functions as a main conductor. In the present invention, an element having a conductivity in a bulk state of 1 × 10 ⁶ S / m or more can be used as the metal element of the metal nanowire. Specific examples of metal elements of the metal nanowire that can be preferably used in the present invention include Ag, Cu, Au, Al, Rh, Ir, Co, Zn, Ni, In, Fe, Pd, Pt, Sn, Ti, and the like. Can be mentioned. In the present invention, two or more kinds of metal nanowires can be used in combination, but from the viewpoint of conductivity, it is preferable to use at least an element selected from Ag, Cu, Au, Al, and Co.

  In the present invention, the means for producing the metal nanowire is not particularly limited, and for example, known means such as a liquid phase method and a gas phase method can be used. Moreover, there is no restriction | limiting in particular in a specific manufacturing method, A well-known manufacturing method can be used. For example, as a method for producing Ag nanowires, Adv. Mater. , 2002, 14, 833-837; Chem. Mater. , 2002, 14, 4736-4745, etc. As a method for producing Co nanowires, a method for producing Au nanowires is disclosed in JP 2006-233252A, and a method for producing Cu nanowires is disclosed in JP 2002-266007 A, etc. Reference can be made to Japanese Unexamined Patent Publication No. 2004-149871. In particular, Adv. Mater. And Chem. Mater. The method for producing Ag nanowires reported in 1 can produce silver nanowires easily and in large quantities in an aqueous system, and the conductivity of silver is the largest among metals, so that the production of metal nanowires according to the present invention is possible. It can be preferably applied as a method.

  In the present invention, the average diameter of the metal nanowires is preferably 200 nm or less from the viewpoint of transparency, and preferably 10 nm or more from the viewpoint of conductivity. If the average diameter is 200 nm or less, the influence of light scattering can be reduced, and a smaller average diameter is preferable because light transmittance reduction and haze deterioration can be suppressed. On the other hand, if the average diameter is 10 nm or more, the function as a conductor can be expressed significantly, and a larger average diameter is preferable because conductivity is improved. Therefore, it is more preferably 20 to 150 nm, and further preferably 40 to 150 nm.

  In the present invention, the average length of the metal nanowires is preferably 1 μm or more from the viewpoint of conductivity, and preferably 100 μm or less from the viewpoint of the effect on the transparency due to aggregation. More preferably, it is 1-50 micrometers, and it is still more preferable that it is 3-50 micrometers.

  In the present invention, the average diameter and average length of the metal nanowires can be obtained from the arithmetic average of the measured values of individual nanowire images by taking electron micrographs of a sufficient number of nanowires using SEM or TEM. The length of the nanowire should be calculated in a straight line, but in reality, it is often bent, so the projection diameter and projected area of the nanowire can be determined from an electron micrograph using an image analyzer. The calculation is performed assuming a cylindrical body (length = projected area / projected diameter). The number of nanowires to be measured is preferably at least 100 or more, and more preferably 300 or more nanowires.

[Metal fine particles]
In a transparent conductive film containing at least metal nanowires and metal fine particles, the metal fine particles have entered the gaps between the metal nanowires or adhered to the surface. Many paths can be formed.

In the present invention, an element having a bulk conductivity of 1 × 10 ⁶ S / m or more can be used as the metal element of the metal fine particles. Specific examples of metal elements of the fine metal particles that can be preferably used in the present invention include Ag, Cu, Au, Al, Rh, Ir, Co, Zn, Ni, In, Fe, Pd, Pt, Sn, Ti, and the like. Can be mentioned. Moreover, these alloys may be sufficient. In the present invention, two or more kinds of metal fine particles can be used in combination, but from the viewpoint of conductivity and bonding operation, it is preferable to use particles containing at least an element selected from Ag, Cu, and Au.

  In the present invention, the means for producing metal fine particles is not particularly limited, and can be produced by using a known method such as a liquid phase method or a gas phase method. Examples of the liquid phase method include a liquid phase reduction method, an alkoxide method, a reverse micelle method, a hot soap method, a chemical liquid phase method such as a hydrothermal reaction method, and a physical liquid phase method such as a spray drying method. Can be used. As the vapor phase method, for example, a general chemical vapor deposition method (CVD method), a physical vapor deposition method (PVD), or the like can be used. Moreover, there is no restriction | limiting in particular in a specific manufacturing method, A well-known manufacturing method can be used. For example, as a method for producing Ag, Rh, Pd, and Pt fine particles, J.A. Phys. Chem. , B205, 109, 16326-16331, and methods for producing Au fine particles include Nature (London) Phys. Sci. , 241, 20 (1973); Chem. Soc. , Chem. Commun. 1994, 801, as a method for producing Cu fine particles, reference can be made to JP-A-2005-281781.

  In the present invention, the average particle diameter of the metal fine particles is preferably 2 to 500 nm, more preferably 5 to 100 nm, and particularly preferably 10 to 80 nm. Although it is effective to use a large number of particles to effectively form a conductive path, if a large number of particles exceeding 500 nm are used, the permeability is remarkably deteriorated. A particle size of 100 nm or less is preferable because the influence of light scattering can be reduced, and a decrease in light transmittance and haze deterioration can be suppressed. On the other hand, it is preferably larger than 2 nm from the viewpoint of stability, more preferably larger than 5 nm from the viewpoint of conductivity, and more preferably 10 nm or more.

  In the present invention, the average particle diameter of the metal fine particles can be obtained from an arithmetic average of measured values of individual fine particle images obtained by taking an electron micrograph of a sufficient number of fine particles using SEM or TEM. Note that the average particle diameter is obtained as the diameter of a circle having an area equivalent to the calculated area of the fine particles calculated from an electron micrograph using an image analyzer. The number of metal fine particles to be measured is preferably at least 100 or more, and more preferably 300 or more metal fine particles are measured.

  The ratio of the metal fine particles to the metal nanowires is not particularly limited, but if the amount of metal fine particles is larger than that of the metal nanowires by mass%, the transparency is remarkably inferior, and may be less than the mass% of the metal nanowires. Preferably, in this region, the ratio can be determined as appropriate depending on which of transparency and conductivity is prioritized. When priority is given to transparency, the ratio of the metal fine particles is preferably 1/10 or less of the mass% of the metal nanowires, and more preferably 1/100 or less.

[Energizing treatment]
In the present invention, the conductive film containing at least metal nanowires or the transparent conductive film containing at least metal nanowires and fine metal particles is energized to bond between the metal nanowires or between the metal nanowires and the metal fine particles. However, the energization method is not particularly limited. Any known method can be used as long as an electrical stimulus is applied. For example, a coating film containing at least metal nanowires, or a coating film containing at least metal nanowires and metal fine particles, and a method in which a power supply terminal is connected to both ends of the coating film and energized can be exemplified. In addition, the current to be energized is not particularly limited, and examples thereof include direct current, alternating current, induction current, pulse current energization, and the like. In addition to fusing due to heat generation due to contact resistance between nanowires, plasma discharge repeatedly occurs between metal nanowires or between metal fine particles and metal nanowires, removing the oxide film and deposits on the surface, and active state Since it can be in a so-called welded state, it can be most preferably used. The temperature rise by energization is also suppressed to 100 ° C. or less, and it can be applied to a transparent conductive film on a resin substrate such as a plastic film.

In the case of applying the pulse current energization process, as the optimum conditions for the pulse current to be applied, a condition with a current density of 1 to 2000 A / cm ² and a pulse width of 0.01 to 1000 ms is preferably used. The current density is less than 1A / cm ^2, the removal of the oxide film and resin present in the interface between the metal powder without being welded is difficult, also exceeds 2000A / cm ^2, the resin substrate takes place partially heating It may be hurt. Desirably, the energization time of one pulse is 3 seconds or less. Desirably, the pulse current is applied for 5 seconds to 5 minutes, particularly 10 seconds to 1 minute.

  The pulse current is preferably a rectangular wave. A sine wave or the like is also used, but a rectangular wave is most effective. The pulse current is preferably a direct current pulse. The rectangular wave is more likely to cause discharge between particles than the sine wave, and the surface cleaning effect is higher, and the direct current of the pulse current is less likely to adhere to the cleaned particle surface than the alternating current. Because.

By applying heat treatment to the conductive film by applying current after the pulse current is applied, the resistance of the transparent conductive film can be further increased by lowering the resistance and improving the bonding force. The energization process may be a direct current or an alternating current having a current density of 1 to 4000 A / cm ² .

  Further, this energization heating can be performed simultaneously with the application of the pulse current described above. Specifically, when a waveform in which a DC pulse current and a DC current are combined, that is, a current in which the upper portion of the DC current waveform is a rectangular wave, is applied, the action of current heating and the discharge welding action by the application of the pulse current are simultaneously performed. Can be added.

In the present invention, the shape of the metal fine particles may change before and after the energization treatment, and various bonding states can be formed depending on the particle size and material of the metal nanowires and metal fine particles, various conditions during the bonding operation, and the like. it can. For example, in the present invention, “at least a part of the metal nanowires are bonded via metal fine particles”
a) a state in which at least one metal fine particle is bonded to two or more metal nanowires while maintaining almost the shape of the metal fine particle before treatment;
b) A state in which at least one metal fine particle is joined to two or more metal nanowires in a greatly different shape from the metal fine particle before treatment,
c) A state in which a plurality of metal fine particles are joined in a string shape and bonded to two or more metal nanowires,
d) A state in which a plurality of metal fine particles are bonded to two or more metal nanowires in an aggregated state.

  In the present invention, the equivalent film thickness of the metal nanowires and the metal fine particles in the transparent conductive film is preferably 5 to 100 nm, more preferably 10 to 80 nm, from the relationship between conductivity and transparency. Here, the equivalent film thickness means the thickness of a uniform metal film having a mass equal to the average mass of the metal nanowires and metal fine particles per unit area of the transparent conductive element.

[Transparent resin]
The transparent conductive film of the present invention may contain a transparent resin in addition to the metal nanowires and the metal fine particles. As the transparent resin, a polyester resin, a polystyrene resin, an acrylic resin, a polyurethane resin, an acrylic urethane resin, a polycarbonate resin, a cellulose resin, a butyral resin, or the like can be used alone or in combination. These can be included in a coating solution containing at least metal nanowires, or a coating solution containing at least metal nanowires and metal fine particles, etc., but can be prepared as another coating solution and overcoated. Also good. The coating amount is preferably an amount that does not completely bury the metal nanowires.

[Conductive polymer compound]
The transparent conductive film of the present invention is formed by laminating a conductive polymer compound or a conductive fine particle-containing layer in addition to a transparent conductive film containing at least metal nanowires or a transparent conductive film containing at least metal nanowires and metal fine particles. Also good. This may be provided on either side of the transparent conductive film containing at least metal nanowires or the transparent conductive film containing at least metal nanowires and metal fine particles, but at least the transparent conductive film containing metal nanowires or at least metal More preferably, at least part of the transparent conductive film containing nanowires and metal fine particles overlaps with the conductive polymer compound or the conductive fine particle-containing layer. For example, it can be formed by overcoating a conductive polymer compound or a coating solution containing conductive fine particles on a transparent conductive film containing at least metal nanowires or a transparent conductive film containing at least metal nanowires and metal fine particles. As described above, the conductive polymer compound or the conductive fine particle-containing coating solution is applied to the metal nanowire on the transparent conductive film including the metal nanowire and the metal fine particles containing the transparent resin in an amount that the metal nanowire is not completely buried. Overcoating in an amount that can be completely buried provides a more preferable form because the surface can be flattened while minimizing the decrease in transparency due to the conductive polymer compound or the conductive fine particle-containing layer.

  Examples of the conductive polymer used in the present invention include polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polyphenylacetylene, polydiacetylene and Mention may be made of compounds selected from the group consisting of polynaphthalene. One type of these conductive polymers may be used alone, or two or more types may be used in combination.

In the present invention, a doping treatment can be performed in order to further increase the conductivity of the conductive polymer. As a dopant for the conductive polymer, for example, a sulfonic acid having a hydrocarbon group having 6 to 30 carbon atoms (hereinafter also referred to as “long-chain sulfonic acid”) or a polymer thereof (for example, polystyrene sulfonic acid), halogen Lewis acid, proton acid, transition metal halide, transition metal compound, alkali metal, alkaline earth metal, MClO ₄ (M = Li ⁺ , Na ⁺ ), R ₄ N ⁺ (R = CH ₃ , C ₄ H ₉ , C ₆ H ₅ ), or R ₄ P ⁺ (R═CH ₃ , C ₄ H ₉ , C ₆ H ₅ ). Of these, the long-chain sulfonic acid is preferable.

  Moreover, the transparent conductive film of the present invention may contain a water-soluble organic compound. Among water-soluble organic compounds, compounds having an effect of improving conductivity by adding to a conductive polymer material are known, and 2nd. Sometimes referred to as a dopant (or sensitizer). 2nd. Which can be used in the present invention. There is no restriction | limiting in particular in a dopant, It can select suitably from well-known things, For example, an oxygen containing compound is mentioned suitably. Among these, it is particularly preferable to use at least one selected from dimethyl sulfoxide, ethylene glycol, and diethylene glycol.

  The conductive fine particles are preferably inorganic semiconductor fine particles because of transparency. For example, indium oxide doped with tin or zinc (ITO, IZO), zinc oxide doped with aluminum or gallium (AZO, GZO), fluorine, Examples thereof include fine particles such as tin oxide (FTO, ATO) doped with antimony.

〔Additive〕
In the transparent conductive film containing at least metal nanowires and the transparent conductive film containing at least metal nanowires and metal fine particles of the present invention, depending on the purpose, stabilizers such as plasticizers, antioxidants, migration inhibitors, Additives such as surfactants, dispersants, colorants such as dyes and pigments may be included.

[Hydrophobic treatment]
In the present invention, metal nanowires and metal nanoparticles produced in an aqueous system can be hydrophobized as necessary. For example, as a method for hydrophobizing metal nanowires, JP 2007-500606 A can be referred to. JP, 2006-299329, A, etc. can be referred as a method of hydrophobizing metal nanoparticles.

[Liquid phase deposition]
As a method of forming a transparent conductive film containing at least metal nanowires or a transparent conductive film containing at least metal nanowires and metal fine particles according to the present invention, both high productivity and reduction in production cost and environmental load reduction are considered. A method of forming on a substrate using a liquid phase film forming method such as a coating method or a printing method is preferable. As coating methods, roll coating method, bar coating method, dip coating method, spin coating method, casting method, die coating method, blade coating method, bar coating method, gravure coating method, curtain coating method, spray coating method, doctor coating method Etc. can be used. As a printing method, a letterpress (letter) printing method, a stencil (screen) printing method, a lithographic (offset) printing method, an intaglio (gravure) printing method, a spray printing method, an ink jet printing method, or the like can be used.

  After forming the transparent conductive film according to the present invention by a liquid phase film forming method, a drying process can be appropriately performed. Although there is no restriction | limiting in particular as conditions of a drying process, It is preferable to process at the temperature of the range which does not damage a transparent resin film or a transparent conductive layer. Moreover, after forming a transparent conductive film, a pressurization or pressurization heat processing can also be performed as needed at any timing. Thereby, higher conductivity can be obtained and the surface can be smoothed. In pressurizing, the surface is pressed on the plate with the plate, the nip roll pressurizing while the base film is passed between the rolls, and the combined pressurizing with the rolls on the plate Can be adopted. Moreover, since it becomes effective when it heats at the time of pressurization, it is preferable to heat in the range of 40-300 degreeC. In particular, when a transparent resin is used in combination, it is preferable to heat to a Tg or higher of the transparent resin. The heating time is adjusted in relation to the temperature, and can be short at a high temperature and long at a low temperature. In the case of a nip roll, the heating method includes a method of heating the roll to a predetermined temperature in advance and a method of heating in a heating chamber such as an autoclave chamber.

[Transparent conductive film]
A transparent conductive film containing at least metal nanowires or a transparent conductive film containing at least metal nanowires and fine metal particles according to the present invention is provided on a transparent resin film (transparent resin support). Can do. As a substrate of a transparent conductive film containing at least metal nanowires or a transparent conductive film containing at least metal nanowires and metal fine particles, a transparent resin film may be used directly on the transparent resin film, or on another substrate Then, it may be transferred to a transparent resin film.

  There is no restriction | limiting in particular in the transparent resin film used for this invention, About the material, a shape, a structure, thickness, etc., it can select suitably from well-known things. For example, polyester resin films such as polyethylene terephthalate (PET), polyethylene naphthalate, modified polyester, polyethylene (PE) resin films, polypropylene (PP) resin films, polystyrene resin films, polyolefin resin films such as cyclic olefin resins, Vinyl resin films such as polyvinyl chloride and polyvinylidene chloride, polyether ether ketone (PEEK) resin film, polysulfone (PSF) resin film, polyether sulfone (PES) resin film, polycarbonate (PC) resin film, polyamide resin A film, a polyimide resin film, an acrylic resin film, a triacetyl cellulose (TAC) resin film, and the like can be given. If the resin film transmittance of 80% or more in nm), can be preferably applied to a transparent resin film according to the present invention. Among these, from the viewpoint of transparency, heat resistance, ease of handling, strength and cost, it is preferably a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene naphthalate film, a polyethersulfone film, or a polycarbonate film, and biaxially stretched. More preferred are polyethylene terephthalate films and biaxially stretched polyethylene naphthalate films.

  In order to ensure the wettability and adhesiveness of the coating solution, the transparent resin film can be subjected to a surface treatment or an easy adhesion layer. A conventionally well-known technique can be used about a surface treatment or an easily bonding layer. For example, the surface treatment includes surface activation treatment such as corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow discharge treatment, active plasma treatment, and laser treatment. Examples of the easy adhesion layer include polyester, polyamide, polyurethane, vinyl copolymer, butadiene copolymer, acrylic copolymer, vinylidene copolymer, and epoxy copolymer. When the transparent resin film is a biaxially stretched polyethylene terephthalate film, the refractive index of the easy-adhesion layer adjacent to the film is 1.57 to 1.63, so that the interface reflection between the film substrate and the easy-adhesion layer can be reduced. Since it can reduce and can improve the transmittance | permeability, it is more preferable. As a method for adjusting the refractive index, the refractive index can be prepared by appropriately adjusting the ratio of the oxide sol having a relatively high refractive index such as tin oxide sol or cerium oxide sol and the binder resin. The easy adhesion layer may be a single layer, but may be composed of two or more layers in order to improve adhesion.

  The total light transmittance of the transparent conductive film of the present invention is 60% or more, preferably 70% or more, and particularly preferably 80% or more. The total light transmittance can be measured according to a known method using a spectrophotometer, a haze meter or the like.

The electrical resistance value in the transparent conductive film of the present invention is preferably 10 ⁴ Ω / □ or less, more preferably 10 ³ Ω / □ or less, and more preferably 10 ² Ω / □ or less as the surface resistivity. It is particularly preferred. The surface resistivity can be measured based on, for example, JIS K6911, ASTM D257, etc., and can be easily measured using a commercially available surface resistivity meter.

  The transparent conductive film of the present invention can be preferably used as the following various transparent electrodes and electromagnetic shielding films.

[Flexible transparent electrode]
The transparent conductive film of this invention can be preferably used as a flexible transparent surface electrode, for example, can be preferably used as transparent electrodes, such as organic EL, an inorganic EL display, illumination, various electronic paper, a solar cell. In particular, when used as an electrode having a large area of about 10 cm, A4 size or more, with a conventional ITO film, a slight voltage drop at the electrode is not negligible at a portion far from the power supply, resulting in an adverse effect. . On the other hand, in the flexible transparent electrode of the present invention, the present invention is particularly effective because a low resistance metal nanowire portion can supply a current with little voltage drop to a portion far from the power supply.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "%" is used in an Example, unless otherwise indicated, "mass%" is represented.

Example 1
[Production of transparent conductive film]
(Underdrawn PET film)
Applying a corona discharge treatment of 12 W · min / m ^{2 on} both sides of a 100 μm biaxially stretched PET film, applying an undercoating solution B-1 to each surface to a dry film thickness of 0.1 μm; The B-1 dry film on each surface was subjected to a corona discharge treatment of 12 W · min / m ² , and the undercoat coating liquid B-2 was applied to a dry film thickness of 0.2 μm. Thereafter, a heat treatment was performed at 120 ° C. for 1.5 minutes to obtain an underdrawn PET film.

<Undercoat coating liquid B-1>
Copolymer latex liquid of 20 parts by mass of styrene, 40 parts by mass of glycidyl methacrylate and 40 parts by mass of butyl acrylate (solid content: 30%) 50 g
SnO ₂ sol (A) 440g
Compound (UL-1) 0.2g
Finish with water 1000ml
<Undercoat coating liquid B-2>
Modified polyester A (solid content 18%) 215 g
Compound (UL-3) 0.4g
True spherical silica matting agent Seahoster KE-P50 (Nippon Shokubai Co., Ltd.) 0.3g
Finish up to 1000 ml with water.

(Synthesis of SnO ₂ sol (A))
65 g of SnCl ₄ .5H ₂ O was dissolved in 2000 ml of distilled water to obtain a homogeneous solution, which was then boiled to obtain a precipitate. The formed precipitate was taken out by decantation and washed with distilled water many times. Silver nitrate was added dropwise to distilled water in which the precipitate was washed, and after confirming that there was no reaction of chlorine ions, distilled water was added to the washed precipitate to make a total volume of 2000 ml. To this, 40 ml of 30% aqueous ammonia was added and heated to obtain a uniform sol. Further, while adding ammonia water, the solution was concentrated by heating until the solid content concentration of SnO ₂ became 8.3% by mass to obtain SnO ₂ sol (A).

<Synthesis of modified aqueous polyester A>
In a reaction vessel for polycondensation, 35.4 parts by mass of dimethyl terephthalate, 33.63 parts by mass of dimethyl isophthalate, 17.92 parts by mass of 5-sulfo-isophthalic acid dimethyl sodium salt, 62 parts by mass of ethylene glycol, calcium acetate monohydrate 0.065 parts by mass of salt and 0.022 parts by mass of manganese acetate tetrahydrate were added, and the ester exchange reaction was performed while distilling off methanol at 170 to 220 ° C. in a nitrogen stream. 04 parts by mass, 0.04 parts by mass of antimony trioxide as a polycondensation catalyst and 6.8 parts by mass of 1,4-cyclohexanedicarboxylic acid were added, and the theoretical amount of water was distilled off at 220 to 235 ° C. for esterification. went. Thereafter, the reaction system was further depressurized and heated for about 1 hour, and finally subjected to polycondensation at 280 ° C. and 133 Pa or less for about 1 hour to obtain a precursor of modified aqueous polyester A. The intrinsic viscosity of the precursor was 0.33.

  850 ml of pure water was put into a 2 L three-necked flask equipped with a stirring blade, a reflux condenser, and a thermometer, and 150 g of the precursor was gradually added while rotating the stirring blade. After stirring for 30 minutes at room temperature, the mixture was heated to an internal temperature of 98 ° C. over 1.5 hours, and heated and dissolved at this temperature for 3 hours. After completion of the heating, the mixture was cooled to room temperature over 1 hour and left overnight to prepare a solution having a solid content concentration of 15% by mass.

  1900 ml of the precursor solution was placed in a 3 L four-necked flask equipped with a stirring blade, a reflux condenser, a thermometer, and a dropping funnel, and the internal temperature was heated to 80 ° C. while rotating the stirring blade. To this, 6.52 ml of a 24% aqueous solution of ammonium persulfate was added, and a monomer mixture (28.5 g of glycidyl methacrylate, 21.4 g of ethyl acrylate, 21.4 g of methyl methacrylate) was dropped over 30 minutes. The reaction was continued for another 3 hours. Then, it cooled to 30 degrees C or less, and filtered, and prepared the solution of the modified aqueous polyester A whose solid content concentration is 18 mass% (polyester component / acrylic component = 80/20).

(Preparation of transparent conductive film 101)
Chem. Mater. , 2002, 14, 4736-4745, silver nanowires having an average diameter of 60 nm and an average length of 5.5 μm were prepared, and the silver nanowires were filtered using a filter, and washed with water. Silver nanowire dispersion liquid W-10 (silver nanowire content: 0.5%) was prepared by redispersion in ethanol.

  In addition, J.H. Chem. Soc. , Chem. Commun. , 1994, 801, the gold fine particles having an average particle diameter of 25 nm are prepared, and the gold fine particles are filtered and washed with an ultrafiltration membrane, and then redispersed in ethanol. A gold fine particle dispersion G-10 (gold nanoparticle content: 0.5%) was prepared. The obtained W-10 and G-10 were mixed so that the mass ratio of silver nanowires and gold fine particles was 300: 1 to prepare a mixed dispersion M-10 of silver nanowires and gold fine particles.

  The coating liquid M-10 was applied on the above-described underdrawn PET film so that the equivalent film thickness was 30 nm, and then dried at 80 ° C. Subsequently, a solution of butyral resin BM-S (manufactured by Sekisui Chemical Co., Ltd.) (a mixed solvent having a mass ratio of methyl ethyl ketone / toluene = 2/1) was applied so that the converted thickness after drying was equivalent to 40 nm.

This film was cut into 10 cm × 12 cm, and a silver paste was sufficiently applied to the end portions on both sides of the 10 cm side with a width of 5 mm. The end portions on both sides were connected to a power source, 1000 A / cm ² , pulse width 0. The transparent conductive film 101 of the present invention was produced by applying a pulse current treatment at 02 seconds for 30 seconds.

(Preparation of transparent conductive film 102)
In producing the transparent conductive film 101, the transparent conductive film 102 of the present invention was produced in the same manner except that only the silver nanowire dispersion W-10 was used without using the gold fine particle dispersion G-10.

(Preparation of transparent conductive film 103)
In the production of the transparent conductive film 101, the transparent conductive film 103 of the present invention was similarly prepared except that W-10 and P-10 were mixed so that the mass ratio of the silver nanowires to the gold fine particles was 100: 1. Was made.

(Preparation of transparent conductive film 201)
In the production of the transparent conductive film 101, a comparative transparent conductive film 201 was produced in the same manner except that the pulse current treatment was not performed.

[Evaluation of transparent conductive film]
The surface resistivity and total light transmittance (hereinafter simply referred to as “transmittance”) of each of the produced transparent conductive films were measured by methods according to JIS K 7194: 1994 and JIS K 7361-1: 1997, respectively. . The obtained results are shown in Table 1.

  From the table, it can be seen that the transparent conductive film of the present invention has higher conductivity and better transparency than the comparative transparent conductive film. Further, when each transparent conductive film was observed with an electron microscope, the transparent conductive film 102 of the present invention was bonded to metal nanowires, and the transparent conductive films 101 and 103 were bonded to each other through metal (gold) fine particles. However, in the comparative transparent conductive film 201, metal (gold) fine particles in contact with the metal nanowire were present but were not joined.

Example 2
[Production of display element]
(Preparation of transparent conductive film 104)
On the transparent conductive film 101 produced in Example 1, a conductive polyaniline dispersion ORMECON D1033 (manufactured by Olmecon, Germany) containing a sulfonic acid dopant as a conductive polymer layer is used. The transparent conductive film 104 of the present invention was produced by applying and drying to 130 nm.

(Preparation of transparent conductive film 105)
In the production of the transparent conductive film 104, the conductive polymer is replaced with the following ITO fine particles, and a solution of butyral resin BM-S (manufactured by Sekisui Chemical Co., Ltd.) (a mixed solvent having a mass ratio of methyl ethyl ketone / toluene = 2/1) is used. A transparent conductive film 105 of the present invention was produced in the same manner except that the ITO particles and butyral resin were mixed at a volume ratio of 2: 1.

(ITO fine particles)
An aqueous solution containing 35% by mass of InCl ₃ and an aqueous solution containing 80% by mass of SnCl ₄ are mixed, and 6.3% ammonia water is gradually added while maintaining the solution temperature at 27 ° C., so that the pH of the aqueous solution becomes 9. Adjusted as follows. This solution was stirred at 27 ° C. for 50 minutes to obtain a coprecipitated hydroxide of In and Sn. The coprecipitate was separated by filtration, washed with ion exchange water, and then fired at 500 ° C. for 2.5 hours to obtain an aggregate of acicular ITO particles. The particles were mechanically pulverized to obtain ITO fine particles.

(Preparation of transparent conductive film 202)
A comparative transparent conductive film 202 was produced by producing an ITO film on the biaxially stretched PET film having a thickness of 100 μm by a known sputtering method. The surface resistance was 100Ω / □.

(Preparation of display element S-101)
A transparent conductive film 101 was prepared and used as a transparent surface electrode 101.

(Preparation of electrolyte solution 1)
In 2.5 g of dimethyl sulfoxide, 90 mg of sodium iodide and 75 mg of silver iodide were added and completely dissolved, then 0.5 g of titanium oxide was added, and the titanium oxide was dispersed with an ultrasonic disperser. 150 mg of polyvinyl alcohol (degree of saponification: about 87-89%, degree of polymerization: 4500) was added to this solution and stirred for 1 hour while heating at 120 ° C. to obtain an electrolyte solution 1.

(Production of metal electrodes)
A Cu film was formed on the entire surface of a glass substrate having a thickness of 1.5 mm and 10 cm × 12 cm by a known sputtering method, and then 10 μm of silver was deposited on the Cu electrode by electrolytic plating to obtain a silver electrode (electrode 2). It was.

(Production of display element)
A solution prepared by adding polyacrylic spherical beads having an average particle diameter of 20 μm to the prepared electrolyte solution 1 so that the volume fraction is 4% by volume is applied onto the electrode 2, and Thus, the display element S-101 was manufactured by combining the transparent surface electrodes 101 in the perpendicular direction. The overlapped 10 cm × 10 cm portion is a display portion (black / white solid), and the remaining portion is used as a lead portion. A sufficient amount of silver paste was applied to the lead portion.

  The transparent conductive film 101 was changed to the transparent conductive films 104, 105, 201, and 202, and display elements S-104, S-105, S-201, and S-202 were produced in the same manner.

[Evaluation of display element]
About each produced display element, using a power source in which two single dry batteries are connected in series,-is connected to the transparent electrode side and + is connected to the electrode 2 side, and the entire display state is visually observed to display a minute region. The state was loupe observation.

  As a result, S-101 using the transparent electrode of the present invention displayed a substantially uniform black display on the entire surface. Although it was at a level that would not cause a problem when observed with a magnifying glass, subtle density unevenness was observed. S-104 and S-105 using the transparent surface electrode of the present invention showed a uniform black display for both visual observation and loupe observation. On the other hand, S-201 using the comparative transparent surface electrode has a slightly lower density at a portion far from the lead, which is a level that can be visually observed, and is an NG level. When observed with a magnifying glass, subtle density unevenness was also observed. In the case of S-202 using a comparative transparent electrode, the density is clearly reduced in the portion far from the lead, and it is NG.

Claims (6)

A transparent conductive film containing at least metal nanowires, wherein at least some of the metal nanowires are bonded to each other by energization treatment. 2. The transparent conductive film according to claim 1, further comprising metal fine particles, wherein at least some of the metal nanowires are bonded via the metal fine particles by an energization treatment. The transparent conductive film according to claim 1, wherein the energization process is a pulse current energization process. A transparent conductive film comprising the transparent conductive film according to any one of claims 1 to 3 on a transparent resin film. The transparent conductive film according to claim 4, wherein a conductive polymer or a conductive fine particle-containing layer is further laminated on the transparent conductive film. A flexible transparent electrode using the transparent conductive film according to claim 4.