JP2013151752A - Method for manufacturing metal nano-wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal nano-wire excellent in conductivity and improved in stability and durability, and to provide a transparent conductor that has high light transmittance and low surface resistance and is improved in stability and durability.SOLUTION: A metal nano-wire contains at least a metal other than gold and silver. In the nano-wire, at least a metal other than silver is plated over a surface of silver.

Description

  The present invention relates to a metal nanowire excellent in stability and durability, and a transparent conductor having high conductivity and good transparency and having both excellent stability and durability.

  In recent years, various types of display technologies such as liquid crystal, plasma, organic electroluminescence, and field emission have been developed in response to increasing demand for thin TVs. In any of these displays having different display methods, a transparent electrode using a transparent conductive film is an essential constituent technology. In addition to the TV, the transparent conductive film is an indispensable technical element in touch panels, mobile phones, electronic paper, various solar cells, and various electroluminescence light control elements.

Conventionally, as a transparent conductive film, various metal thin films such as Au, Ag, Pt, Cu, indium oxide doped with tin or zinc (ITO, IZO), zinc oxide doped with aluminum or gallium (AZO, GZO), fluorine And metal oxide thin films such as tin oxide (FTO, ATO) doped with antimony, conductive nitride thin films such as TiN, ZrN, and HfN, and conductive boride thin films such as LaB ₆ are also known. Various electrodes such as combined Bi ₂ O ₃ / Au / Bi ₂ O ₃ and TiO ₂ / Ag / TiO ₂ are also known. In addition to inorganic substances, a transparent conductive film using a conductive polymer has also been proposed (see, for example, Non-Patent Document 1).

  However, since the metal thin film, nitride thin film, boron thin film and conductive polymer thin film described above cannot have both light transmission properties and conductive properties, special technical fields such as electromagnetic shielding and the like are relatively high. It was used only in the touch panel field where resistance values are allowed.

  On the other hand, metal oxide thin films are becoming mainstream of transparent conductive films because they can achieve both light transmission and conductivity and are excellent in durability. Among the metal oxide materials specifically exemplified, ITO has a good balance between light transmittance and conductivity, and it is easy to form an electrode fine pattern by wet etching using an acid solution. Therefore, transparent electrodes for various optoelectronics are used. It is often used as.

  In general, vapor-phase film formation methods such as vacuum deposition, sputtering, and ion plating are used for producing metal oxide thin films including ITO. However, since these film forming methods require a vacuum environment, the apparatus is large and complicated, and a large amount of energy is consumed for the film forming. It was sought after.

  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 is directed, and accordingly, demands for light weight and flexibility of the transparent conductive material have increased.

  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.

For example, a method of forming a transparent conductive film by applying a dispersion containing conductive metal oxide particles made of indium oxide or tin oxide on a support and performing a heat treatment is disclosed (for example, Patent Documents). 1). Further, a film forming method is disclosed in which the surface of inorganic oxide fine particles applied on a substrate is dissolved and then stabilized by heat treatment (see, for example, Patent Document 2). Furthermore, a method of forming a transparent conductive film by applying a dispersion containing CNT (carbon nanotube) or metal nanowire on a support is disclosed (for example, see Patent Documents 3 to 5).

  In a transparent conductive film using conductive fibers such as CNTs and metal nanowires as a conductor, conductivity is manifested by forming an electrical network between the conductive fibers, but several μm to several tens μm depending on one conductive fiber. Therefore, the percolation threshold for the material containing the conductive fiber to exhibit conductivity is very small, and therefore both conductivity and transparency can be achieved. In addition, unlike the case of using the conductive metal oxide as described above, since there is no need for heat treatment, it is possible to form a transparent conductive film on a resin support such as a plastic film. It has excellent properties as a transparent conductive material that can be formed into a film.

  CNT has a structure in which a six-membered ring network (graphene sheet) made of carbon has a single-layer or multi-layer coaxial tubular structure, and is excellent in stability and durability. In addition, the conductivity varies depending on the number of layers and the structure, and single-walled CNT exhibits the most excellent conductivity. Single-walled CNTs have three types of structures depending on the orientation of the six-membered ring network. Two types are semiconducting and the other type is metallic.

  This metallic CNT (armchair-type single-walled CNT) is said to have the same degree of conductivity as copper and is preferred as a conductive material, but no industrially selectable method has been developed. Moreover, it is practically difficult to select and use metallic CNT, such as the yield obtained by isolation technique of metallic CNT (for example, see Non-Patent Document 2) is only 1%. At present, the transparent conductive film has not achieved a sufficiently low resistance.

On the other hand, although metal varies depending on the element, the metal generally has high conductivity, and nanowires of metal elements having a bulk state conductivity of 1 × 10 ⁷ S / m or more can be obtained by various methods such as a liquid phase method and a gas phase method. It has been reported that it can be produced.

  For example, a method for producing Ag nanowires (for example, see Non-Patent Documents 3 and 4), a method for producing Au nanowires (for example, see Patent Literature 6), a method for producing Cu nanowires (for example, see Patent Literature 7), a Co nanowire Manufacturing methods (see, for example, Patent Document 8) are known and can be referred to.

  In particular, silver has the highest conductivity among metals, and according to Non-Patent Document 3 and Non-Patent Document 4, since a silver nanowire can be easily produced in an aqueous system, a transparent conductive film using conductive fibers is used. In this case, silver nanowires can be positioned as the most excellent conductive material.

  However, an element using silver as an electrode is prone to failure due to a phenomenon in which silver precipitates and grows from the electrode (hereinafter also referred to as migration), and the surface is sulfided due to a reaction with a sulfide compound in the environment. There are known problems with stability and durability, such as the formation of a silver film and the resulting deterioration in resistance over time, which is a major obstacle to the use of transparent conductive materials using silver nanowires. ing.

In addition, regarding the formation of an electrical network between conductive fibers, ideally, all the conductive fibers have at least two or more contacts with other conductive fibers and are widely distributed in the network. In order to achieve both conductivity and transparency, it is preferable that the film is in a state of forming a film. However, it is difficult to obtain satisfactory conductivity because the network formation of the conductive fibers cannot be controlled.
Japanese Patent No. 3251066 JP 2006-245516 A JP 2005-255985 A JP 2006-519712 A US Patent Application Publication No. 2007 / 0074316A1 JP 2006-233252 A JP 2002-266007 A Japanese Patent Application Laid-Open No. 2004-149871 "Technology of transparent conductive film", page 80 (Ohm Publishing Co.) URL: http: // www. aist. go. jp / aist_j / press release / pr2006 / pr2006060215 / pr20066021. html Chem. Mater. 2002, 14, 4736-4745 Adv. Mater. 2002, 14, 833-837

  As described above, none of the conventional methods can solve the problem of obtaining a transparent electrode satisfying various characteristics. Accordingly, an object of the present invention is to provide a transparent conductive material having high light transmittance and low surface resistance, and improved stability and durability. Specifically, the object is to provide a metal nanowire having excellent conductivity and improved stability and durability, and further using the metal nanowire, having high light transmittance and low surface resistance, It is an object of the present invention to provide a transparent conductor having improved durability.

  A metal nanowire containing silver and at least one metal other than silver, wherein the at least one metal other than silver is plated on the surface of silver. It was found that the problem can be solved, and the present invention has been achieved. In addition, by using a transparent resin film for the transparent support, a transparent conductor satisfying both lightness and flexibility can be obtained.

  That is, the above object according to the present invention is achieved by the following configuration.

  1. A metal nanowire containing silver and at least one metal other than silver, wherein at least one metal other than silver is plated on the surface of silver.

  2. 2. The metal nanowire according to 1 above, wherein the at least one metal other than silver is at least one metal selected from precious metals, iron, cobalt, nickel, copper and tin.

  3. A transparent conductor having a conductive layer on a support, wherein the conductive layer contains the metal nanowire described in 1 or 2 above.

  4). 4. The transparent conductor according to 3 above, wherein the metal nanowire is plated after a conductive layer is formed on a support.

According to the above-mentioned means of the present invention, it is possible to obtain a metal nanowire with excellent conductivity and improved stability and durability as an effect, and furthermore, using the metal nanowire, high light transmittance and low surface resistance can be obtained. It is possible to obtain a transparent conductor having improved stability and durability and reduced production cost and environmental load by liquid phase film formation. The transparent conductor of the present invention is used for various optoelectronic devices such as transparent electrodes such as flat panel displays and solar cells that require high transparency and high conductivity, and electronic paper and touch panels that require lightweight and flexibility. It can be preferably used for transparent electrodes, transparent circuits, and transparent wiring.

  The metal nanowire of the present invention is a metal nanowire containing silver and at least one metal other than silver, wherein at least one metal other than silver is plated on the surface of silver. This feature is a technical feature common to claims 1 to 4 according to the present invention.

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

[Metal nanowires]
In general, a metal nanowire refers to a linear structure having a metal element as a main component and having a diameter from the atomic scale to the nm size.

  When metal nanowires are used as a transparent conductive material, the average diameter is preferably smaller than 200 nm in order to reduce the influence of light scattering and increase transparency, while the average diameter is preferably larger in order to increase conductivity. . In this invention, 10-200 nm is preferable as an average diameter of metal nanowire, and it is more preferable that it is 30-180 nm.

  In the transparent conductor of the present invention, the conductive layer has a three-dimensional conductive network structure formed by contacting metal nanowires with each other, and exhibits conductivity. Therefore, a longer metal nanowire is preferable because it is advantageous for forming a conductive network. On the other hand, if the metal nanowire is too long, the metal nanowires are entangled with each other to form an aggregate, and as a result, light scattering may occur.

  Since the rigidity and diameter of the metal nanowire influences the formation of the conductive network and the formation of aggregates, it is preferable to use a metal wire having an optimum wire length according to the material of the metal nanowire to be used. When the metal nanowire of the present invention is used for the transparent conductor of the present invention, the average length of the metal nanowire is preferably about 3 to 500 μm, more preferably 5 to 300 μm.

  In the present invention, the average diameter and average length and average aspect ratio (average length / average diameter) of the metal nanowires of the present invention are obtained by taking an electron micrograph of a sufficient number of metal nanowires, From the measured length, it can be obtained by arithmetic average. Strictly speaking, the length of the metal nanowire should be measured in a linearly stretched state, but in reality it may be curved, so the projected diameter of the nanowire can be measured using an image analyzer from an electron micrograph. Further, the projected area may be calculated and calculated assuming a cylindrical body (length = projected area / projected diameter). The number of measured metal nanowires is preferably at least 100 or more, more preferably 300 or more.

  The metal nanowire of the present invention is characterized in that at least one metal other than silver is plated on the surface of silver. Silver has the highest conductivity among metals, but silver is considered to be the metal most prone to migration among metals, and the effect of preventing sulfidation, oxidation, and migration by the metal nanowire of the present invention Can be increased. Furthermore, the formation of an electrical network between metal nanowires is strengthened by plating, and the conductivity can be dramatically increased.

A metal other than silver contained in the metal nanowire of the present invention is not particularly limited, and may contain at least one kind of noble metal or base metal, but noble metals other than silver (for example, gold, platinum, palladium, rhodium, iridium) , Ruthenium, osmium), iron, cobalt, nickel, copper, tin, and preferably at least one metal belonging to the group consisting of tin, and more preferably noble metals other than silver.

  As for the metal composition of the inside and the surface of the metal nanowire, a cross-section sample of the metal nanowire is prepared using a microtome or the like, and the metal composition of the internal region including the center of the cross-sectional sample and the surface region along the outer peripheral portion is determined by the EPMA. It can investigate by analyzing using etc. In the present invention, the thickness of the plating layer formed of at least one metal other than silver on the surface of silver is preferably 100 nm or less, and preferably 1 to 50 nm.

[Method for producing metal nanowires]
In general, metal nanowires can be produced by reducing metal ions to form metal nanoparticles and forming metal nanowires by Ostwald ripening between metal nanoparticles, or by first reducing metal ions in the nucleation step. In the present invention, there is a method of forming metal nanoparticles by forming metal nanoparticles on the core particles by reducing and depositing metal ions on the core particles in the particle growth step after forming the core nanoparticles. From the viewpoint of improving the controllability of the form (diameter and length) of the metal nanowire and the metal composition, a method of forming the metal nanowire by separating the nucleation step and the particle growth step is preferably used.

[Compound having reducibility]
In the method for producing a metal nanowire of the present invention, the reducing compound used for the production of the metal nanowire or the metal nanoparticle is not particularly limited as long as it is a compound capable of reducing the target metal. At least one selected from reducing agents can be used. Examples of compounds having reducibility that can be preferably used in the present invention include primary or secondary alcohols, glycols, ethers in which a hydrogen atom is bonded to a carbon atom adjacent to an oxygen atom, ethanolamines, Examples thereof include at least one selected from the group consisting of borohydrides and hydrazines.

[Protective colloid agent]
In the present invention, the protective colloid agent used in the production of metal nanowires or metal nanoparticles is not particularly limited as long as it is a compound having a protective colloid action on a microstructure such as a target metal nanowire or nanoparticle. For example, hydrophilic polymer, metal coordination molecule, amphiphilic molecule, anionic compound and the like can be mentioned.

  Examples of the hydrophilic polymer applicable to the present invention include amide groups, hydroxyl groups such as polyvinyl pyrrolidone (for example, poly (N-vinyl-2-pyrrolidone)), polyvinyl alcohol, and poly (meth) acrylate. In addition to polymers containing carboxyl groups and / or amino groups, or copolymers of these monomers for forming a hydrophilic homopolymer, natural products such as cyclodextrin, aminopectin, methylcellulose, gelatin and the like can be mentioned.

  Examples of metal coordinating molecules applicable to the present invention include functional groups capable of coordinating to metals such as amino groups, thiol groups, disulfide groups, amide groups, carboxylic acid groups, phosphine groups, and sulfonic acid groups. Mention may be made of organic molecules having one or more, carbon monoxide, and nitric oxide.

  Examples of amphiphilic molecules applicable to the present invention include various monofunctional or polyfunctional surfactants (any of anionic, cationic, nonionic, and amphoteric), such as sodium dodecyl sulfate, polyethylene glycol monolaur. Rate.

  Examples of anionic compounds applicable to the present invention include halides such as chlorides, perchlorates, various alkoxides, and salts of carboxylic acids such as oxalic acid, tartaric acid, and citric acid. Examples thereof include alkali metal salts, ammonium salts, and amine salts.

  In this invention, the usage-amount of a protective colloid agent should just exist 0.1 mol or more with respect to 1 mol of metals, Preferably it is 1-50 mol. In addition, when the colloid protective agent is a polymer, the one converted to the number of moles per monomer unit is applied.

[Form control agent]
In the present invention, it is preferable to use a shape control agent in order to form metal nanowires. The shape control agent is a compound having a function of defining the growth direction of metal particles in a one-dimensional manner. In many cases, the shape control agent preferentially or selectively adsorbs on a specific crystal plane of a target particle to control the growth orientation by suppressing the growth of the adsorption plane.

  In the present invention, polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol and the like listed as exemplary compounds of the protective colloid agent can be preferably used as a form control agent for nanowire particle formation.

[Plating method]
The metal nanowire formed in the above process is plated by a plating process. In the metal nanowire of the present invention, the improvement of migration resistance, sulfidation resistance, oxidation resistance and conductivity is obtained by the feature that the surface of the metal nanowire is plated with at least one metal other than silver.

  The plating may be either electroless plating (chemical reduction plating or displacement plating), electrolytic plating, or both. For electroless plating and electrolytic plating in the present invention, a known plating technique can be used. As the electroless plating, for example, gold plating includes a cyanide bath using potassium tetrahydroborate or dimethylamine borane as a reducing agent and potassium gold cyanide as a gold salt.

  Electroless copper plating solutions include copper sources such as copper sulfate and copper chloride, reducing agents such as formalin, glyoxylic acid, potassium tetrahydroborate, dimethylamine borane, EDTA, diethylenetriaminepentaacetic acid, Rochelle salt, glycerol, mesoerythritol Adenyl, D-mannitol, D-sorbitol, dulcitol, iminodiacetic acid, 1,2-cyclohexanediaminetetraacetic acid, 1,3-diaminopropan-2-ol, glycol ether diamine, triisopropanolamine, triethanolamine, etc. It contains a copper complexing agent, a pH adjusting agent such as sodium hydroxide, potassium hydroxide, and lithium hydroxide.

  Furthermore, polyethylene glycol, yellow blood salt, bipyridyl, o-phenanthroline, neocuproine, thiourea, cyanide, and the like can also be included as additives for improving bath stabilization and plating film smoothness.

  The plating solution is preferably aerated to increase stability. In the present invention, for the purpose of promoting electroless plating, treatment with a solution containing palladium can also be performed. Palladium may be in the form of a divalent palladium salt or a complex salt thereof, or may be metallic palladium.

However, it is preferable to use a palladium salt or a complex salt thereof because of the stability of the liquid and the stability of the treatment. Examples of the electrolytic plating include a gold bromide bath and an acidic gold bath for gold plating, and a copper bromide bath, a copper sulfate bath, a copper pyrophosphate bath, and the like for copper plating. For the platinum plating, an acidic or neutral plating bath using cis- [Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ] (cis-dinitrodiaminoplatinum) is widely used. The electroless plating and the electrolytic plating method are described in detail in, for example, “Plating Technology Guidebook” (edited by the Technical Committee of Tokyo Sheet Metal Cooperative Association, 1987).

  The plating in the present invention is performed before and / or after forming the conductive layer by providing the metal nanowire on the support. When plating is performed before forming the conductive layer, it is preferable to perform plating by electroless plating. When plating is performed after the conductive layer is formed, either electroless plating or electrolytic plating may be performed. In order to further strengthen the formation of an electrical network between the metal nanowires, it is preferable to perform plating after forming the conductive layer.

[Transparent conductor]
The transparent conductor of the present invention is a transparent conductor having a conductive layer on a support, and contains the metal nanowire of the present invention in the conductive layer. In the transparent conductor of the present invention, the conductive layer may contain a transparent binder material or additive in addition to the metal nanowire of the present invention.

  The transparent binder material can be selected from a wide range of natural polymer resins or synthetic polymer resins. For example, transparent thermoplastic resin (eg, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polymethyl methacrylate, nitrocellulose, chlorinated polyethylene, chlorinated polypropylene, vinylidene fluoride), heat, light, electron beam Transparent curable resins that are cured by radiation (for example, melamine acrylate, urethane acrylate, epoxy resin, polyimide resin, silicone resin such as acrylic-modified silicate) can be used.

  Examples of additives include stabilizers such as plasticizers and antioxidants, surfactants, dissolution accelerators, polymerization inhibitors, and colorants such as dyes and pigments. Furthermore, from the viewpoint of improving workability such as coating properties, it contains a solvent (for example, water, organic solvents such as alcohols, glycols, cellosolves, ketones, esters, ethers, amides, hydrocarbons). You may go out.

  The thickness of the conductive layer containing the metal nanowires varies depending on the average diameter and content of the metal nanowires to be used, but as a rough guide, it is preferably not less than the average diameter of the metal nanowires and not more than 500 nm. It is preferable to reduce the thickness of the conductive layer including the metal nanowire of the present invention because the network formation of conductive fibers in the thickness direction can be made dense.

  The transparent conductor of the present invention may contain a conductive polymer in the conductive layer according to the present invention or other conductive layers. Examples of the conductive polymer that can be used in the transparent conductor of the present invention include polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, poly Examples thereof include compounds selected from the group consisting of phenylacetylene, polydiacetylene and polynaphthalene derivatives.

The transparent conductor of the present invention may contain one kind of conductive polymer alone or may contain two or more kinds of conductive polymers in combination, but from the viewpoint of conductivity and transparency. To polyaniline having a repeating unit represented by the following general formula (I) or general formula (II) or a derivative thereof, a polypyrrole derivative having a repeating unit represented by the following general formula (III), or the following general formula (IV) More preferably, it contains at least one compound selected from the group consisting of polythiophene derivatives having a repeating unit represented by the formula:

In the above general formulas (III) and (IV), R is mainly a linear organic substituent, preferably an alkyl group, an alkoxy group, an allyl group, or a combination of these groups. As long as it does not lose its properties, a sulfonate group, an ester group, an amide group, or the like may be bonded to or combined with these. Note that n is an integer.

The conductive polymer used in the transparent conductor of the present invention can be subjected to a doping treatment in order to further increase the conductivity. Examples of the dopant for the conductive polymer include a sulfonic acid having a hydrocarbon group having 6 to 30 carbon atoms (hereinafter also referred to as a long-chain sulfonic acid) or a polymer thereof (for example, polystyrene sulfonic acid), a halogen atom. 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.

Examples of the long chain sulfonic acid include dinonyl naphthalene disulfonic acid, dinonyl naphthalene sulfonic acid, and dodecylbenzene sulfonic acid. As halogen, Cl ₂ , B
r ₂ , I ₂ , ICl ₃ , IBr, IF _{5 and the} like can be mentioned. Lewis acids include PF ₅ , As
Examples thereof include F ₅ , SbF ₅ , BF ₃ , BCl ₃ , BBr ₃ , SO ₃ , and GaCl ₃ . Examples of the protonic acid include HF, HCl, HNO ₃ , H ₂ SO ₄ , HBF ₄ , HClO ₄ , FSO ₃ H, ClSO ₃ H, CF ₃ SO ₃ H, and the like.

Transition metal halides include NbF ₅ , TaF ₅ , MoF ₅ , WF ₅ , RuF ₅ , Bi.
_{F 5, TiCl 4, ZrCl 4} , MoCl 5, MoCl 3, WCl 5, FeCl 3, TeCl 4, SnCl 4, SeCl 4, FeBr 3, etc. SnI ₅ and the like. The transition metal _{compound, AgClO 4, AgBF 4, La} (NO 3) 3, Sm (NO 3) 3 and the like. Examples of the alkali metal include Li, Na, K, Rb, and Cs. Examples of the alkaline earth metal include Be, Mg, Ca, Sc, and Ba.

  The dopant for the conductive polymer may be introduced into fullerenes such as hydrogenated fullerene, hydroxylated fullerene, and sulfonated fullerene. In the transparent conductor, the dopant is preferably contained in an amount of 0.001 part by mass or more with respect to 100 parts by mass of the conductive polymer. Furthermore, it is more preferable that 0.5 mass part or more is contained.

The transparent conductor of the present invention includes a long-chain sulfonic acid, a polymer of long-chain sulfonic acid (for example, polystyrene sulfonic acid), halogen, Lewis acid, proton acid, transition metal halide, transition metal compound, alkali metal, Both at least one dopant selected from the group consisting of alkaline earth metals, MClO ₄ , R ₄ N ⁺ , and R ₄ P ⁺ and fullerenes may be included.

  As the conductive polymer used for the transparent conductor of the present invention, a conductive polymer modified by a metal disclosed in JP-T-2001-511581, JP-A-2004-99640, JP-A-2007-165199, or the like. Can also be used.

  The conductive layer containing the conductive polymer according to the transparent conductor 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 called a dopant (or sensitizer).

  2nd. Which can be used in the transparent conductor of 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. The oxygen-containing compound is not particularly limited as long as it contains oxygen, and examples thereof include a hydroxyl group-containing compound, a carbonyl group-containing compound, an ether group-containing compound, and a sulfoxide group-containing compound.

  Examples of the hydroxyl group-containing compound include ethylene glycol, diethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, and glycerin. Among these, ethylene glycol and diethylene glycol are preferable. Examples of the carbonyl group-containing compound include isophorone, propylene carbonate, cyclohexanone, and γ-butyrolactone. Examples of the ether group-containing compound include diethylene glycol monoethyl ether. Examples of the sulfoxide group-containing compound include dimethyl sulfoxide. These may be used alone or in combination of two or more, but it is particularly preferable to use at least one selected from dimethyl sulfoxide, ethylene glycol, and diethylene glycol.

  In the conductive layer containing the conductive polymer according to the transparent conductor of the present invention, the 2nd. 0.001 mass part or more is preferable, as for content of a dopant, 0.01-50 mass parts is more preferable, and 0.01-10 mass parts is especially preferable.

  The conductive layer containing the conductive polymer according to the transparent conductor of the present invention may contain a transparent resin component or additive in addition to the conductive polymer in order to ensure film formability and film strength. . The transparent resin component is not particularly limited as long as it is compatible with or mixed with the conductive polymer, and may be a thermosetting resin or a thermoplastic resin.

  For example, polyester resins such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate, polyimide resins such as polyimide and polyamideimide, polyamide resins such as polyamide 6, polyamide 6,6, polyamide 12 and polyamide 11, polyvinylidene fluoride, Fluorine resin such as polyvinyl fluoride, polytetrafluoroethylene, ethylene tetrafluoroethylene copolymer, polychlorotrifluoroethylene, etc., vinyl resin such as polyvinyl alcohol, polyvinyl ether, polyvinyl butyral, polyvinyl acetate, polyvinyl chloride, epoxy resin, xylene Resin, aramid resin, polyurethane resin, polyurea resin, melamine resin, phenol resin, polyether, acrylic resin and this And La copolymers thereof.

  Various functional layers such as a hard coat layer, a non-glare coat layer, a barrier coat layer, an anchor coat layer, a carrier transport layer, and a carrier accumulation layer can be added to the transparent conductor of the present invention as necessary. When providing a hard coat layer or a non-glare coat layer, it is preferable to place the transparent support on the side opposite to the conductive layer according to the present invention, and when providing a barrier coat layer, It is preferable to dispose between the conductive layers according to the present invention. When an anchor coat layer, a carrier transport layer, or a carrier accumulation layer is provided, the transparent support is disposed on the same side as the conductive layer according to the present invention. It is preferable to make it.

  There is no restriction | limiting in particular in the thickness of the transparent conductor of this invention, Although it can select suitably according to the objective, Generally it is preferable that it is 10 micrometers or less, and since transparency improves as thickness becomes thin, it is more preferable. .

  The total light transmittance in the transparent conductor of the present invention is preferably 60% or more, 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 or the like.

The electrical resistance value of the transparent conductor of the present invention is 10 ⁴ Ω /
□ or less is preferable, 10 ³ Ω / □ or less is more preferable, and 10 ² Ω / □ or less is particularly preferable. If it exceeds 10 ⁴ Ω / □, when used as a transparent electrode such as a liquid crystal display or a transparent touch panel, or as an electromagnetic shielding material, it may not function sufficiently as an electrode, or sufficient electromagnetic shielding characteristics may not be obtained. The surface resistivity can be measured based on, for example, JIS K7194, ASTM D257, etc., or can be easily measured using a commercially available surface resistivity meter.

(Transparent support)
The transparent support constituting the transparent conductor of the present invention is not particularly limited as long as it has high light transmittance, and its material, shape, structure, thickness, etc. are appropriately selected from known ones. Can do. For example, a glass substrate, a resin substrate, a resin film, etc. are preferably mentioned in terms of excellent hardness as a base material and easy formation of a conductive layer on the surface, but from the viewpoint of lightness and flexibility It is preferable to use a resin film.

The resin is not particularly limited and can be appropriately selected from known ones. For example, polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polyvinyl chloride resin, polyethersulfone resin, polycarbonate resin,
Polystyrene resin, polyimide resin, polyetherimide resin, polyvinyl acetate resin, polyvinylidene chloride resin, polyvinylidene fluoride resin, polyvinyl alcohol resin, polyvinyl acetal resin, polyvinyl butyral resin, polymethyl methacrylate resin, polyacrylonitrile resin, polyolefin polystyrene Examples thereof include resins, polyamide resins, polybutadiene resins, cellulose acetate, cellulose nitrate, and acrylonitrile-butadiene-styrene copolymer resins. These may be used individually by 1 type and may be used in combination of 2 or more type. Among these, polyethylene terephthalate resin is preferable in terms of excellent transparency and flexibility.

[Method for producing transparent conductor]
The method for producing the transparent conductor of the present invention is not particularly limited, but from the viewpoints of productivity and production cost, electrode quality such as smoothness and uniformity, and reduction of environmental burden, a coating method is used for forming the conductive layer. It is preferable to use a liquid phase film forming method such as a printing method.

  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 the 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, and the like can be used.

  Moreover, the transparent conductive material containing the metal nanowire of this invention can also be pattern-formed on a transparent support body, and a transparent wiring and a transparent circuit can also be formed. In addition, as needed, physical surface treatments, such as a corona discharge treatment and a plasma discharge treatment, can also be performed on the transparent support surface as a preliminary treatment for improving adhesion and coating properties.

  The transparent conductor of the present invention includes various types of optoelectronic devices such as liquid crystal, plasma, organic electroluminescence, field emission display, touch panel, mobile phone, electronic paper, various solar cells, various electroluminescence dimming elements, etc. Can be preferably used for transparent electrodes, transparent circuits, and transparent wiring.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
[Production of metal nanowires]
<< Production of Metal Nanowire SW-1 >>
Using ethylene glycol (EG) as a reducing agent and polyvinylpyrrolidone (PVP) as a protective colloid agent and form control agent with reference to the method described in Non-Patent Document 4 (Adv. Mater. 2002, 14, 833-383) And the silver nanowire was produced with the following methods.

(Nucleation process)
While stirring 1000 ml of EG solution kept at 170 ° C. in the reaction vessel, 100 ml of EG solution of silver nitrate (silver nitrate concentration: 1.5 × 10 ⁻⁴ mol / L) was added at a constant flow rate for 10 seconds. Thereafter, aging was carried out at 170 ° C. for 10 minutes to form silver core particles. The reaction solution after completion of ripening exhibited a yellow color derived from surface plasmon absorption of silver nanoparticles, and it was confirmed that silver ions were reduced and silver nanoparticles were formed.

(Particle growth process)
The reaction solution containing the core particles after completion of the ripening is kept at 170 ° C. with stirring, and 1000 ml of a silver nitrate EG solution (silver nitrate concentration: 1.0 × 10 ⁻¹ mol / L) and a PVP EG solution (VP Concentration conversion: 5.0 × 10 ⁻¹ mol / L) 1000 ml was added at a constant flow rate for 100 minutes using the double jet method. When the reaction solution was sampled every 20 minutes in the particle growth process and confirmed with an electron microscope, the silver nanoparticles formed in the nucleation process grew mainly in the long axis direction of the nanowires over time. No new core particles were observed in the grain growth process.

(Washing process)
After completion of the particle growth step, the reaction solution was cooled to room temperature, filtered using a filter, and the silver nanowires separated by filtration were redispersed in ethanol. Filtration of silver nanowires with a filter and redispersion in ethanol were repeated five times, and finally an ethanol dispersion of silver nanowires was prepared to produce metal nanowire SW-1.

  When a small amount of the obtained dispersion was collected and confirmed with an electron microscope, it was confirmed that silver nanowires having an average diameter of 85 nm and an average length of 7.4 μm were formed.

<< Production of Metal Nanowire SW-2: Present Invention >>
Before the silver nanowires were finally dispersed in ethanol, the same procedure as in SW-1 was performed except that electroless nickel plating was applied to the silver nanowires separated by filtration so as to have a plating thickness of 2 nm. Metal nanowire SW-2 was produced.

[Production of transparent conductor]
<< Production of Transparent Conductor TC-11: Comparison >>
Using the produced dispersion liquid of metal nanowire SW-1, a transparent conductor TC-11 was produced according to the following method.

A dispersion of metal nanowire SW-1 is applied onto a polyethylene terephthalate (PET) support having a total light transmittance of 90% using a spin coater so that the basis weight of the metal nanowire is 0.3 g / m ² and dried. did. Subsequently, after applying a calender treatment to the coating layer of the metal nanowire SW-1, a methyl isobutyl ketone solution of urethane acrylate was applied using a spin coater and dried to prepare a transparent conductor TC-11. The thickness of the urethane acrylate layer was set such that the metal nanowire layer was not completely buried, a part of the urethane acrylate layer was exposed from the urethane acrylate layer, and the metal nanowire layer could be fixed to the support.

Total light transmittance and surface resistivity of the produced transparent conductor TC-11 (based on JIS K7194)
Was measured. As a result, the transparent conductor TC-11 had a total light transmittance of 86% and a surface resistivity of 38Ω / □.

<< Preparation of Transparent Conductor TC-12: Present Invention >>
In producing the transparent conductor TC-11, a transparent conductor TC-12 was produced in the same manner as the transparent conductor TC-11 except that the metal nanowire SW-2 was used.

<< Preparation of Transparent Conductor TC-13: Present Invention >>
In the production of the transparent conductor TC-11, the transparent conductor TC except that the metal nanowire applied to the transparent conductor TC-11 was subjected to electroless nickel plating by a known method so that the plating thickness was 2 nm. Transparent conductor TC-13 was produced in the same manner as -11.

<< Preparation of Transparent Conductor TC-14: Present Invention >>
In the production of the transparent conductor TC-11, the transparent conductor TC- was used except that the metal nanowire applied to the transparent conductor TC-11 was subjected to electrolytic copper plating by a known method so that the plating thickness was 3 nm. In the same manner as in Example 11, a transparent conductor TC-14 was produced.

<< Preparation of Transparent Conductor TC-15: Present Invention >>
In the production of the transparent conductor TC-11, the transparent conductor TC- was used except that the metal nanowire applied to the transparent conductor TC-11 was subjected to electrolytic platinum plating so as to have a plating thickness of 3 nm. In the same manner as in Example 11, a transparent conductor TC-15 was produced.

<< Preparation of Transparent Conductor TC-16: Present Invention >>
In the production of the transparent conductor TC-12, the transparent conductor TC- was used except that the metal nanowire applied to the transparent conductor TC-12 was subjected to electrolytic gold plating by a known method so that the plating thickness was 2 nm. In the same manner as in Example 12, a transparent conductor TC-16 was produced.

  Subsequently, the total light transmittance and surface resistivity of each transparent conductor were measured by the same method as the transparent conductor TC-11. The results are shown in Table 1.

  As a result, each of the transparent conductors TC-12 to TC-16 has a surface that is lower than the transparent conductor TC-11 while having the same total light transmittance as the transparent conductor TC-11 within the measurement error range. It was confirmed to have resistivity. In particular, the transparent conductors TC-13 to TC-16 are considered to be because the electrical network formation between metal nanowires was strengthened by plating and the conductivity was increased.

[Evaluation of transparent conductor]
(Migration resistance)
Using the produced transparent conductors TC-11 to TC-16, migration resistance was evaluated by a forced deterioration test as follows.

  Each transparent conductor was cut into a 5 cm × 5 cm square shape, and a gold electrode having a width of 0.5 cm was formed by vapor deposition on both short sides thereof. After forming the gold electrode, a 500 μm thick agar gel is applied on the metal nanowire layer immobilized on the support, and a 0.2 μm thick silver electrode is further bonded thereon to prepare a migration resistance evaluation sample. Produced.

  Under the conditions of 23 ° C. and 93% RH, the positive electrode side of the DC power source was connected to the gold electrode of the transparent conductor and the negative electrode side was connected to the silver electrode, and a DC voltage of 50 V was applied between the two electrodes, Changes were observed and evaluated with an electron microscope. The sensory evaluation of the results obtained by observation with the electron microscope was performed, and migration resistance was evaluated according to the following criteria.

A: No change in the metal nanowires is observed. O: Almost no change in the metal nanowires is observed. Δ: Dissolution and precipitation of the metal nanowires due to the migration are slightly observed, but within a practically acceptable range. Dissolution of metal nanowires and dendritic precipitation is observed due to XX: Dissolution of metal nanowires and dendritic precipitation due to migration is clearly observed, and the metal nanowire and silver electrode are short-circuited. The evaluation located in the middle is indicated by, for example, Δ to ○ and × to Δ.

  The results obtained as described above are shown in Table 1.

As is clear from the results shown in Table 1, it can be seen that the migration resistance of the transparent conductors TC-12 to TC-16 of the present invention is improved with respect to the comparative transparent conductor TC-11. Among these, the migration resistance of the transparent conductor TC-15 and the transparent conductor TC-16 is better. This is due to the migration resistance of platinum and gold itself plated on the silver surface.

Example 2
Using the transparent conductors TC-11 to TC-16 produced in Example 1, the resistance to sulfidation was evaluated from the change in surface resistivity under a dilute hydrogen sulfide gas atmosphere. As a result, the transparent conductor TC-12 of the present invention was evaluated. Good results were obtained at ~ TC-16.

Claims (4)

  A metal nanowire containing silver and at least one metal other than silver, wherein at least one metal other than silver is plated on the surface of silver.   2. The metal nanowire according to claim 1, wherein the at least one metal other than silver is at least one metal selected from precious metal, iron, cobalt, nickel, copper, and tin.   A transparent conductor having a conductive layer on a support, the metal nanowire according to claim 1 or 2 being contained in the conductive layer.   The transparent conductor according to claim 3, wherein the metal nanowire is plated after a conductive layer is formed on the support.