JP2012222055A - Conductive emulsion ink, and method for forming conductive thin film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to form a conductive thin film including metal nanoparticles into various base materials by a simple operation for a short time at a room temperature without performing a thermal treatment.SOLUTION: The conductive emulsion ink comprises a continuous phase, and first and second discontinuous phases dispersed in the continuous phase. In the conductive emulsion ink, the first discontinuous phase includes metal nanoparticles, and the second discontinuous phase includes a reducer for the metal nanoparticles and/or a photocatalyst. In the case of the second discontinuous phase including the reducer, a conductive thin film can be formed by applying the ink to an appropriate base material surface, or patterning the ink on the base material surface. In the case of the second discontinuous phase including the photocatalyst, the conductive thin film can be formed by executing the step of applying the ink to an appropriate base material surface, or patterning the ink on the base material surface, and the step of irradiating the applied or patterned ink with ultraviolet light. The continuous phase may include the metal nanoparticles. It is preferred that the continuous phase is an oil phase, and the first and second discontinuous phases are a water phase.

Description

  The present invention relates to an ink containing metal nanoparticles that can easily form a conductive thin film such as a wiring pattern on a substrate surface in a short time.

  Currently, vacuum processes and photolithography techniques are mainly used in the process of creating wiring patterns of electronic devices such as semiconductor elements, circuit boards, liquid crystal displays, and thin film solar cells. The photolithographic technique is a patterning technique for producing a necessary wiring pattern by applying a photosensitive material to a substrate surface and exposing it to ultraviolet rays to expose it.

  Under these circumstances, in recent years, a great deal of attention has been paid to a technique (printable electronics) for producing an electronic device by a solution process such as printing or coating, and research and development have been actively conducted. By using this solution process, a “de-vacuum process”, “de-high temperature process”, and “de-photolithography” can be realized, and the merit that productivity is remarkably improved can be obtained. As a method for producing a wiring pattern by printing, a method using screen printing or ink jet printing has been proposed and partially commercialized.

  However, when producing a wiring pattern by printing, it is necessary to fuse the conductive fillers contained in the ink in order to develop conductivity. For this reason, conventionally, a conductive ink is printed to form a wiring pattern. This was fired at a high temperature. However, since such high-temperature baking consumes a large amount of energy, there is a demand for reduction of environmental burden and cost reduction. In addition, a polymer substrate having no heat resistance such as PET and PP, and TFT (thin film transistor). There is also a demand for the formation of a wiring pattern on a glass substrate on which is mounted, and a reduction in the firing temperature is desired.

  In Patent Document 1, after surface treatment of a substrate with a surface treatment liquid containing an alkali metal compound, a conductive ink containing metal nanoparticles is applied to the substrate, and then the conductive ink is reduced. Although a method of firing in an atmosphere is disclosed, since acetic acid, formic acid, hydrochloric acid, or the like is used in the reducing atmosphere, the substrate needs to have acid resistance, and the range of selection of the substrate is narrowed.

  Patent Document 2 discloses a method of developing the conductivity of a metal fine particle layer by printing the metal fine particle layer on a substrate and then treating the metal fine particle layer with an acid solution for a short time. However, since it is necessary to immerse the substrate in an acid solution, the substrate is required to have acid resistance, and the range of selection of the substrate is narrowed.

  Patent Document 3 includes a step of forming a pattern to be a wiring precursor on a base material using a metal nanoparticle paste, and a polar solvent solution containing a polar solvent or a dissolution aid in the pattern on the base material. A method for producing a wiring board is disclosed, which includes a step of acting, and a step of drying the base material to sinter the metal nanoparticles to form a wiring. There is a problem that it takes a long time of about 2 hours to make it. Moreover, since it is necessary to immerse the base material in a polar solvent or a polar solvent solution containing a solubilizing agent, the base material is required to have solvent resistance, and the selection range of the base material is narrowed.

  Patent Document 4 discloses a method for printing and forming a wiring with a conductive ink containing a metal source that is a substantial metal salt, an antioxidant, and a reducing agent. However, a baking treatment at 150 ° C. is required. Further, reduction of the reduction temperature is desired, and the metal salt and the reducing agent are mixed in the conductive ink, so there is a concern about storage stability.

  Patent Document 5 discloses a method of developing conductivity by applying metal nanoparticles dispersed in water or an organic solvent on a substrate and causing a reducing substance to act on the substrate. Immersion treatment is disclosed as a method for causing a reducing substance to act, but there is a problem in that the number of treatment steps increases, the operation becomes complicated, and the productivity is lowered. In addition, a method of surface-treating a base material with a reducing substance in advance and applying metal nanoparticles on the base material is also disclosed, but there is a problem similar to the above, and the range of selection of the base material Becomes narrower.

JP 2006-287217 A JP 2006-313891 A JP 2008-72052 A JP 2008-166590 A JP 2008-235224 A

  An object of the present invention is to allow a conductive thin film made of metal nanoparticles to be formed on various substrates at room temperature in a short time and with a simple operation without heat treatment.

  According to the present invention, the object is to provide a first discontinuous phase containing metal nanoparticles in a continuous phase, and a second discontinuous phase containing a reducing agent and / or a photocatalyst of the metal nanoparticles. Is emulsified and dispersed to form a one-pack type conductive emulsion ink.

  That is, according to one aspect of the present invention, in the continuous phase, a first discontinuous phase containing metal nanoparticles and a second discontinuous phase containing a reducing agent and / or a photocatalyst of the metal nanoparticles. A conductive emulsion ink is provided.

Moreover, according to the other situation of this invention, the formation method of the electroconductive thin film which consists of the process of apply | coating or patterning the said electroconductive emulsion ink containing a reducing agent is provided.
Furthermore, according to another aspect of the present invention, a conductive thin film comprising a step of applying or patterning the conductive emulsion ink containing a photocatalyst, and a step of subjecting the applied or patterned conductive emulsion ink to UV irradiation. A forming method is provided.

  The conductive emulsion ink of the present invention contains metal nanoparticles in a first discontinuous phase dispersed in a continuous phase and is dispersed in the continuous phase separately from the first discontinuous phase. In addition, since the metal nanoparticle reducing agent and / or photocatalyst is contained in the second discontinuous phase, the metal nanoparticle and the reducing agent and / or photocatalyst are separated before use so as not to cause a reaction. In the dispersed phase, and the storage stability is maintained well.

  When the conductive emulsion ink of the present invention contains the reducing agent, after the transfer to the substrate, the emulsion collapses and the metal nanoparticles and the reducing agent come into contact with each other. The particles are fused together to develop conductivity.

  In addition, when the conductive emulsion ink of the present invention contains the photocatalyst, the emulsion is disintegrated after being transferred to the base material, the metal nanoparticles and the photocatalyst come into contact with each other, and is subjected to UV irradiation. Due to the action, the metal nanoparticles are fused with each other to develop conductivity.

  Hereinafter, the conductive emulsion ink of the present invention will be described in detail with reference to embodiments.

1. Conductive emulsion ink In the conductive emulsion ink of the present invention, the metal nanoparticles, the reducing agent of the metal nanoparticles and the photocatalyst are all contained in the discontinuous phase, but the metal nanoparticles are used as the reducing agent and / or The discontinuous phase containing the photocatalyst (ie, the second discontinuous phase) is contained in the discontinuous phase (ie, the first discontinuous phase) dispersed in the continuous phase. The emulsion form of the conductive emulsion ink of the present invention may be W / O type in which the outer phase is an oil phase or O / W type in which the outer phase is an aqueous phase. When the conductive emulsion ink of the present invention is W / O type, the continuous phase is an oil phase and the discontinuous phase is an aqueous phase. When the conductive emulsion ink of the present invention is O / W type, the continuous phase is an aqueous phase and the discontinuous phase is an oil phase. From the viewpoint of reactivity when forming the conductive thin film, it is preferable to contain a reducing agent in the aqueous phase. Therefore, the conductive emulsion ink of the present invention is preferably a W / O type emulsion having a water phase as a discontinuous phase when a metal nanoparticle reducing agent is used.
Further, in order to improve the expression of conductivity, it is preferable to contain metal nanoparticles in the continuous phase as well as the discontinuous phase of the conductive emulsion ink of the present invention.

2. Metal nanoparticles The metal nanoparticles used in the present invention are obtained by coating the surface of nano-sized metal fine particles with a protective agent and stably dispersing them in a dispersion medium. Examples of the metal used for the metal nanoparticles include known materials such as silver, copper, gold, palladium, nickel, and rhodium. Also, an alloy composed of at least two of these, or an alloy of at least one of these and iron can be used. Examples of the former alloy include platinum-gold alloy, platinum-palladium alloy, gold-silver alloy, silver-palladium alloy, palladium-gold alloy, platinum-gold alloy, rhodium-palladium alloy, silver-rhodium alloy, copper-palladium. Examples include alloys and nickel-palladium alloys. Examples of the latter alloy with iron include iron-platinum alloy, iron-platinum-copper alloy, iron-platinum-tin alloy, iron-platinum-bismuth alloy, and iron-platinum-lead alloy. These metals or alloys can be used alone or in combination of two or more.

  The average particle diameter of the metal nanoparticles is usually in the range of 1 to 100 nm, preferably 1 to 50 nm, and more preferably 1 to 10 nm. When the average particle size of the metal nanoparticles is 100 nm or more, fusion between particles due to a melting point drop is less likely to occur, and the conductivity of the resulting thin film is also lowered.

  The amount of metal nanoparticles added is preferably 30 to 50% by mass of the total amount of the oil phase when contained in the oil phase, and preferably 10 to 40% by mass of the total amount of the aqueous phase when contained in the aqueous phase. Further, the addition amount of the metal nanoparticles is preferably 5 to 20% by mass of the total amount of the ink.

As the protective agent of metal nanoparticles, heterocycle is heterocycle and alkyl-substituted _{and, -COOH, -SH, -SOH, -SO} 2 H, -SO 3 H, -NH 2, -NOH, -NO 2 H _{, -OH, -SiOH, -Si (OH} ) 2, -Si (OH) 3, -PO 2 H 2, -PO 3 H 2, -PO 4 H, -COO -, - CON -, - CONH-, _{-CONH 2, -S -, - SO} -, - SO 2 -, - NH -, - NO -, - O -, - SiO -, - PH -, - PH 2 -, - PO -, - POH-, _{-POH 2 -, - PO 2 -} , - PO 2 H -, - PO 3 -, - PO 3 H -, - PO 4 -, - N (-) -, - Si (O-) 2 and -Si ( alkanes containing one or more selected from the group consisting of O-) _3, alkenes, alkynes, aromatic hydrocarbons, a Kill substituted aromatic hydrocarbons include those formed from one or more selected from the group consisting of heterocycle and substituted heterocycle.

  Among these protective agents, it is preferable to use a protective agent having a linear or branched alkyl chain having 10 to 20 carbon atoms, particularly fatty acids or aliphatic amines, thiols or alcohols. . The reason for limiting the carbon number in this way is that if the carbon number is less than 10, the storage stability of the metal nanoparticles cannot be maintained, and if the carbon number is larger than 20, it is difficult to obtain good conductivity. is there.

  The fatty acids may be any of saturated fatty acids and unsaturated fatty acids, such as decanoic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, eicosanoic acid, docosanoic acid, 2-ethylhexanoic acid, Examples include oleic acid, linoleic acid, linolenic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid, heptadecenoic acid, oleic acid, and elaidic acid. These can be used alone or in combination of two or more.

  Examples of the aliphatic amines include decylamine, undecylamine, dodecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, nonadecylamine, decenylamine, undecenylamine, dodecenylamine, tridecenylamine. Ruamine, tetradecenylamine, pentadecenylamine, hexadecenylamine, heptadecenylamine, octadecenylamine, nonadecenylamine, oleylamine, icocenylamine, nonacosenylamine, dipentylamine, dihexylamine, dodecyldimethylamine, N, N-dimethyloctylamine, naphthalenediamine, octamethylenediamine, nonanediamine and the like can be mentioned. These can be used alone or in combination of two or more.

  Examples of the aliphatic thiols include decanethiol, undecanethiol, dodecanethiol, tridecanethiol, tetradecanthiol, pentadecanethiol, hexadecanethiol, heptadecanethiol, octadecanethiol, nonadecanethiol, icosanethiol, decenethiol. , Undecene thiol, dodecene thiol, tridecene thiol, tetradecene thiol, pentadecene thiol, hexadecene thiol, heptacene thiol, octadecene thiol, nonadecene thiol, icosene thiol, nonacene thiol, etc. Is mentioned. These can be used alone or in combination of two or more.

  Examples of the aliphatic alcohols include decanol, undecanol, dodecanol, tridecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol, icosanol and the like. These can be used alone or in combination of two or more.

  Metal nanoparticle production methods include gas evaporation, sputtering, metal vapor synthesis, colloid, alkoxide, coprecipitation, homogeneous precipitation, thermal decomposition, chemical reduction, amine reduction, solvent evaporation Conventionally known methods such as the method can be used. Each of these has specific characteristics, but it is preferable to use a chemical reduction method or an amine reduction method particularly for mass production. In carrying out these production methods, a known reducing agent or the like can be appropriately used in addition to selecting and using the protective agent as necessary.

3. Reducing agent As reducing agent, sodium borohydride, sodium hypochlorite, sodium sulfite, ascorbic acid, ascorbate, ascorbic acid derivative, citric acid, citrate, tartaric acid, tartrate, malic acid, hydrazine compound, Conventionally used drugs such as thiourea dioxide, sulfoxide, formic acid, formaldehyde, and tocopherol can be used. In consideration of safety when using the reducing agent, it is preferable to use a reducing agent contained in food such as ascorbic acid, ascorbate, citric acid, citrate, malic acid, tocopherol and the like.

  The concentration of the reducing agent in the ink varies depending on the type of the reducing agent and cannot be generally stated, but is usually 0.1 to 1.0% by mass of the total amount of the ink. When the reducing agent is contained in the aqueous phase, the concentration of the reducing agent in the aqueous phase is usually 0.001 to 1 mol / l, preferably 0.005 to 0.5 mol / l. When the concentration is less than 0.001 mol / l, the time required for the reduction treatment becomes longer and the conductivity of the obtained thin film becomes lower. On the other hand, if the concentration exceeds 1 mol / l, the coating film is easily peeled off during the reduction treatment.

4). Photocatalyst As the photocatalyst, a known photocatalyst such as titanium oxide, zinc oxide, tantalum oxide, fullerene can be used.
The concentration of the photocatalyst in the ink varies depending on the type of the photocatalyst, so it cannot be generally stated. When the photocatalyst is contained in the aqueous phase, the concentration of the photocatalyst in the aqueous phase is usually 1 to 30% by mass, preferably 5 to 20% by mass. When the concentration is less than 1% by mass, the resulting thin film has low conductivity. On the other hand, when the concentration exceeds 20% by mass, the photocatalyst tends to aggregate in the aqueous phase.

5. Oil phase 5-1. Oil-based medium As the oil-based medium that can constitute the oil phase of the conductive emulsion ink of the present invention, a water-insoluble solvent that is generally used for ink or the like can be used. Specific examples of water-insoluble solvents include naphthenic, paraffinic and isoparaffinic mineral oils, soybean oil, corn oil, sunflower oil, rapeseed oil, safflower oil, grape seed oil, sesame oil, castor oil, camellia oil, olive oil. , Vegetable oils such as palm oil, palm oil, fatty acids such as isopalmitic acid, oleic acid, isostearic acid, methyl laurate, isopropyl laurate, isopropyl myristate, isopropyl palmitate, isostearyl palmitate, methyl oleate, Ethyl oleate, isopropyl oleate, butyl oleate, methyl linoleate, isobutyl linoleate, ethyl linoleate, isopropyl isostearate, methyl soybean oil, soybean oil isobutyl, tall oil methyl, tall oil isobutyl, diisopropyl adipate, seba Esters such as diisopropyl acid, diethyl sebacate, propylene glycol monocaprate, trimethylolpropane tri-2-ethylhexanoate, glyceryl tri-2-ethylhexanoate, alcohols such as isopalmityl alcohol, isostearyl alcohol, oleyl alcohol, Examples include hydrocarbons such as hexane, octane, cyclohexane, toluene, and xylene. These solvents can be used alone or in admixture of two or more.

5-2. Other oil phase components In addition to the binder component for improving the adhesion between the base material and the metal nanoparticles, the oil phase includes, for example, an antioxidant and a viscosity modifier, as long as the effect of the present invention is not hindered. Further, other known components such as a rust inhibitor can be contained. As the binder component, the type varies depending on the base material (described later) to be used, and it cannot be generally stated. For example, known resins such as acrylic resin, urethane resin, epoxy resin, phenol resin, and butyral resin can be used.

5-3. Preparation Method of Oil Phase The oil phase can be prepared by dispersing or dissolving necessary components in the oily medium. Dispersion or dissolution can be performed using a known ultrasonic disperser, kneader, homogenizer, or the like. This ultrasonic disperser can be used in combination with other kneaders. In addition, a commercially available metal nanoparticle, reducing agent, or photocatalyst solvent solution or dispersion can be used as it is or after being concentrated or diluted.

6). Aqueous phase 6-1. Aqueous medium As the aqueous medium that can constitute the aqueous phase of the conductive emulsion ink of the present invention, water and, if desired, a water-soluble organic solvent can be used. Examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and other alkylene glycols, glycerin, acetins, and triethylene glycol. Glycol ethers such as monomethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, triethanolamine, 1-methyl-2-pyrrolidone, β-thioglycol, sulfolane, etc. Can be used. These water-soluble organic solvents can be used alone or in combination of two or more.
The content of the water-soluble organic solvent in the aqueous medium is preferably 80% by mass or less.

6-2. Other aqueous phase components In addition to the above components, the aqueous phase includes a wetting agent (humectant), a surface tension adjuster (surfactant), an antifoaming agent, a binder component, as long as the effects of the present invention are not impaired. A pH adjuster, antioxidant, preservative and the like can be appropriately contained. Examples of the binder component include those described for the oil phase component. When the photocatalyst is contained in the aqueous phase, it is preferable to add a surfactant to the aqueous phase in order to favorably disperse the photocatalyst in the aqueous phase.

6-3. Method for Preparing Aqueous Phase The aqueous phase can be prepared by dispersing or dissolving necessary components in the aqueous medium. Dispersion or dissolution can be performed using a known ultrasonic disperser, kneader, homogenizer, or the like. This ultrasonic disperser can be used in combination with other kneaders. In addition, an aqueous solution or dispersion of a commercially available metal nanoparticle, reducing agent, or photocatalyst can be used as it is or after being concentrated or diluted.

7). Preparation of Conductive Emulsion Ink When the conductive emulsion ink of the present invention is a W / O type emulsion ink, for example, a first W obtained by emulsifying and dispersing an aqueous phase containing metal nanoparticles in an oil phase. After preparing the / O type emulsion and the second W / O type emulsion in which the aqueous phase containing the reducing agent and / or photocatalyst is emulsified and dispersed in the oil phase, the first and second W / O type emulsion can be prepared by mixing. In addition, after preparing a first aqueous phase containing metal nanoparticles and a second aqueous phase containing a reducing agent and / or a photocatalyst, either one of the first and second aqueous phases is added to the oil phase. It can also be prepared by emulsifying and dispersing, and then emulsifying and dispersing the other aqueous phase.

  In the case of the O / W type emulsion ink, the conductive emulsion ink of the present invention is, for example, a first O / W type emulsion in which an oil phase containing metal nanoparticles is emulsified and dispersed in an aqueous phase. And a second O / W type emulsion in which an oil phase containing a reducing agent and / or a photocatalyst is emulsified and dispersed in an aqueous phase, and then the first and second O / W type emulsions are prepared. Can be prepared by mixing. Moreover, after preparing the 1st oil phase containing a metal nanoparticle, and the 2nd oil phase containing a reducing agent and / or a photocatalyst, either one of a 1st and 2nd oil phase is carried out in an aqueous phase. It can also be prepared by emulsifying and dispersing, and then emulsifying and dispersing the other oil phase.

The emulsification can be prepared by mixing an oil phase, an aqueous phase and an emulsifier and emulsifying using a known emulsifier.
As the emulsifier, a disper mixer, a homomixer, a high-pressure homogenizer, an ultrasonic disperser, or the like can be used.
During emulsification, the emulsifier may be added in advance to at least one of the oil phase and the water phase, or may be added simultaneously with the mixing of the oil phase and the water phase.

  As an emulsifier, anionic surfactants such as metal soaps, higher alcohol sulfates, sulfate esters of polyoxyethylene adducts; cationic surfactants such as primary to tertiary amine salts and quaternary ammonium salts ; Ether type nonionic surfactants such as polyoxyethylene ethers of higher alcohols, alkylphenol polyoxyethylene ethers, polyoxyethylene ethers of polyoxypropylene; consisting of polyhydric alcohols such as sorbitan fatty acid esters and polyglycerin fatty acid esters and fatty acids Ester type nonionic surfactants; Ether ester type nonionic surfactants such as polyoxyethylene ethers of fatty acids, polyoxyethylene ethers of polyglycerol fatty acid esters, polyoxyethylene ethers of castor oil; fatty acid alkylo Nitrogen-containing type nonionic surfactants such as amide. These emulsifiers can be used alone or in combination of two or more. Generally, when forming a W / O type emulsion, a surfactant of HLB 3-6 is used, and when forming an O / W type emulsion, a surfactant of HLB 8-16 is used.

The addition amount of the emulsifier can be appropriately determined in consideration of the molar concentration of the emulsifier to be used, the area of the interface between the water phase and the oil phase, and the area of the interface between the oil phase and a solid such as a pigment. It is 0.1-10 mass% normally with respect to the whole quantity, Preferably it is 1-5 mass%.
The mass ratio of the oil phase to the water phase (oil phase / water phase) can be in the range of 1 to 99/99 to 1, preferably 10 to 90/90 to 10, and 30 to 70/70 to 30. More preferred.

In order to improve the electrical conductivity, it is preferable to contain at least one selected from the group consisting of a polymer compound and a water-soluble organic solvent in the oil phase and / or aqueous phase of the conductive emulsion ink of the present invention. .
Examples of such polymer compounds include rosin-modified phenol resins (for example, Hariphenol KZ-115 (trade name; manufactured by Harima Chemical Co., Ltd.), etc.) Other polymers include maleic acid resins, petroleum resins, xylene resins. It is preferable to use rosin ester, polymerized rosin ester, hydrogenated rosin ester, ketone resin, cured resin, acrylic resin, rubber derivative, terpene resin and the like.
Examples of the water-soluble organic solvent include those described above with respect to the aqueous medium in the aqueous phase, but include many esters such as carbonate esters such as propylene carbonate, ethylene glycol, 1,2-pentanediol, 1,5-pentanediol, and glycerin. Preferred are monohydric alcohol solvents, glycol ether solvents such as ethylene glycol monoethyl ether and diethylene glycol, and lactone solvents such as γ-butyrolactone.

8). Method for Forming Conductive Thin Film When the conductive emulsion ink of the present invention contains a reducing agent, the conductive thin film can be formed by applying or patterning the ink on a suitable substrate surface.
Further, when the conductive emulsion ink of the present invention contains a photocatalyst, a step of coating or patterning the ink on an appropriate substrate surface and a step of subjecting the coated or patterned ink to UV irradiation are performed. A conductive thin film can be formed. UV irradiation can be performed using a commercially available UV lamp, for example, Handheld UV Lamp, UVGL-58 type (wavelength: 254/365 nm) manufactured by Funakoshi Co., Ltd.
The method for forming a conductive thin film of the present invention can be applied to the formation of any thin film element that can be formed by printable electronics in addition to a wiring pattern.

8-1. Base Material Examples of the base material to which the conductive emulsion ink of the present invention can be applied include conventionally known insulating substrates used for wiring pattern formation. The material of this insulating substrate may be either inorganic or organic. As the inorganic substrate, a glass substrate, a semiconductor substrate such as silicon or germanium, a compound semiconductor substrate such as gallium-arsenic, indium-antimony, or the like can be used. These may be used alone or in combination of two or more. The inorganic substrate can also be used after at least one thin film of another material is laminated on the surface thereof. Other materials in this case include, for example, silicon dioxide, fluorinated glass, phosphorous glass, boron-phosphorous glass, borosilicate glass, polycrystalline silicon, alumina, titania, zirconia, silicon nitride, titanium nitride, tantalum nitride, boron nitride. And inorganic compounds such as ITO (indium tin oxide), amorphous carbon, and fluorinated amorphous carbon.

  In addition, as an organic substrate, for example, a polymer film made of polyethylene, polypropylene, polystyrene, vinyl chloride resin, polyamide, polyimide, polycarbonate, polyethylene terephthalate (PET), vinylidene chloride resin, fluorine resin, unsaturated polyester resin, In addition to sheets and other resin molded products, paper, woven fabric, non-woven fabric, and the like can be given. These can also be used alone or in combination, for example, by suitably laminating two or more kinds.

  In addition, if necessary, the surface of the substrate can be subjected to the following treatment in advance in order to improve the adhesion with the conductive emulsion ink. As this treatment, for example, physical means such as plasma treatment or electron beam treatment or chemical means such as application of an adhesion improver can be applied to the surface of the substrate. In this case, as the adhesion improver, known agents such as those used as so-called silane coupling agents and aluminum chelate compounds can be used. A liquid-absorbing layer for suppressing the permeation of metal nanoparticles can be provided on a substrate such as paper.

8-2. Application or patterning process The process of applying or patterning the conductive emulsion ink on the surface of the substrate includes conventionally known coating methods such as bar coater, spray coating, spin coating, screen printing, intaglio printing, letterpress printing, stencil printing, inkjet printing, etc. The conventionally known printing method can be used.
When the conductive emulsion ink is transferred to the surface of the substrate, the emulsion collapses and the metal nanoparticles come into contact with the reducing agent and / or the photocatalyst, and the metal nanoparticles are brought into action by the action of the reducing agent or the action of the photocatalyst under UV irradiation. They are fused together to develop conductivity.

The mechanism by which a reducing agent acts on metal nanoparticles has not been fully elucidated at present, but the reducing agent removes the protective agent that coats the metal nanoparticles. In addition, it is presumed that the oxide film formed on the surface of the metal nanoparticles can be reduced and removed.
The mechanism by which photocatalyst is allowed to act on metal nanoparticles has not been fully elucidated at present, but it is presumed that the protective agent for metal nanoparticles is decomposed by photocatalyst. The

8-3. UV irradiation process When the conductive emulsion ink of the present invention contains a photocatalyst, the conductive emulsion ink coated or patterned in the above process can be subjected to UV irradiation to form a thin film with more excellent conductivity. .
UV irradiation can be performed using, for example, Handheld UV Lamp, UVGL-58 type (wavelength: 254/365 nm) manufactured by Funakoshi Corporation.

  Next, the conductive emulsion ink of the present invention and a method for forming a thin film using the same will be described in detail with reference to examples.

Preparation Example (1) Preparation of First Aqueous Phase Silver nanoparticle ink for ink jet (concentration 15% by mass) manufactured by Mitsubishi Paper Industries was used as it was as the first aqueous phase. It was about 10 nm when the average particle diameter of the silver nanoparticle was measured visually by observation with a transmission electron microscope (TEM). This aqueous phase was used as the aqueous phase of emulsions A and D in Table 1 below.

(2) Preparation of second aqueous phase 1 part by weight of ascorbic acid was dissolved in 99 parts by weight of water to prepare a 1 (w / w)% aqueous solution of ascorbic acid. This aqueous phase was used as the aqueous phase of emulsion B in Table 1 below.

(3) Preparation of second aqueous phase 1 part by weight of sodium sulfite was dissolved in 99 parts by weight of water to prepare a 1 (w / w)% aqueous solution of sodium sulfite. This aqueous phase was used as the aqueous phase of emulsion C in Table 1 below.

(4) Preparation of Second Aqueous Phase 2 parts by weight of Demol EP, 20 parts by weight of titanium oxide, and 78 parts by weight of water were mixed, and an aqueous phase was prepared using a rocking mill (manufactured by Seiwa Giken). This aqueous phase was used as the aqueous phase of Emulsion E in Table 1 below.

(5) Preparation of second aqueous phase Mixing 2 parts by weight of Demol EP, 20 parts by weight of titanium oxide, 1 part by weight of ascorbic acid and 77 parts by weight of water, and using a rocking mill (Seiwa Giken Co., Ltd.), Was prepared. This aqueous phase was used as the aqueous phase of emulsion F in Table 1 below.

(6) Preparation of aqueous phase (control) An aqueous phase was prepared by dissolving 1 part by weight of ascorbic acid in 99 parts by weight of silver nanoparticle ink manufactured by Mitsubishi Paper Industries Co., Ltd. (1). This aqueous phase was used as the aqueous phase of emulsion H in Table 1 below.

(7) Preparation of oil phase 30 parts by weight of naphthenic non-aqueous solvent (AF Solvent No. 4, manufactured by Shin Nippon Oil Co., Ltd.) and 2 parts by weight of emulsifier (Hexagrin 5-O, manufactured by Nikko Chemicals Co., Ltd.) And an oil phase was prepared.
This oil phase was used as the oil phase of emulsions A to C and E to H described below.

(8) Preparation of oil phase 10 g of silver acetate was added to 250 ml of oleylamine, heated and dissolved at 60 ° C, and then heated and stirred at 200 ° C for 30 minutes. After standing at room temperature, methanol was added to the obtained silver nanoparticle dispersion, and silver nanoparticles precipitated were collected by sedimentation with a centrifuge. The obtained silver nanoparticles were purified by repeated dissolution in hexane and precipitation with ethanol. It was about 10 nm when the average particle diameter of the obtained silver nanoparticle was visually measured by transmission electron microscope (TEM) observation.
15 parts by weight of the obtained silver nanoparticles, 15 parts by weight of a naphthenic non-aqueous solvent (AF Solvent No. 4, manufactured by Shin Nippon Oil Co., Ltd.), and 2 parts by weight of an emulsifier (Hexagrin 5-O, manufactured by Nikko Chemicals Co., Ltd.) Parts were mixed and processed with an ultrasonic disperser to prepare an oil phase.
This oil phase was used as the oil phase of emulsion D in Table 1 below.

(9) Preparation of emulsions A to H While ultrasonically dispersing 32 parts by weight of the oil phase shown in Table 1 below, 68 parts by weight of the water phase shown in Table 1 below was added to prepare emulsions A to H.

The details of the raw materials listed in Table 1 are as follows.
AF Solvent No. 4 (trade name): A naphthenic non-aqueous solvent manufactured by JX Nippon Oil & Energy.
Hexagrin 5-O (trade name): surfactant manufactured by Nikko Chemicals, Inc. Hexaglyceryl pentaoleate.

Example 1
Emulsion A and Emulsion B shown in Table 1 were mixed at a weight ratio of 1: 1 to prepare a W / O type emulsion ink. The prepared emulsion ink was applied to glossy paper (Askul inkjet paper glossy paper Photo Cast Coated Gloss) with a bar coater. The volume resistance value of the obtained coating film was measured by Mitsubishi Chemical Analytech Co., Ltd. 4 terminal 4 probe method resistivity meter Loresta EP, MCP-T360 type. In addition, one day after the preparation of the emulsion ink, the presence or absence of aggregation of the emulsion ink was visually observed. The results are shown in Table 2.

Example 2
Emulsion A and Emulsion C shown in Table 1 were mixed at a weight ratio of 1: 1 to prepare a W / O type emulsion ink, and evaluated in the same manner as in Example 1. The results are shown in Table 2.

Example 3
Emulsion B and Emulsion D shown in Table 1 were mixed at a weight ratio of 1: 1 to prepare a W / O type emulsion ink, and evaluated in the same manner as in Example 1. The results are shown in Table 2.

Example 4
Emulsion A and Emulsion E shown in Table 1 were mixed at a weight ratio of 1: 1 to prepare a W / O emulsion ink, and after forming a coating film by the same method as in Example 1, Handheld UV manufactured by Funakoshi Co., Ltd. UV irradiation was performed for 10 minutes using Lamp, UVGL-58 type (wavelength: 254/365 nm) (integrated light amount: 1200 μW / cm 2). The results are shown in Table 2.

Example 5
Emulsion D and Emulsion E shown in Table 1 were mixed at a weight ratio of 1: 1 to prepare a W / O type emulsion ink, which was evaluated in the same manner as in Example 4. The results are shown in Table 2.

Example 6
Emulsion A and Emulsion F shown in Table 1 were mixed at a weight ratio of 1: 1 to produce a W / O type emulsion ink, and evaluated in the same manner as in Example 4. The results are shown in Table 2.

Comparative Example 1
Emulsion A and Emulsion G shown in Table 1 were mixed at a weight ratio of 1: 1 to produce a W / O type emulsion ink and evaluated in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 2
Emulsion G and Emulsion H shown in Table 1 were mixed at a weight ratio of 1: 1 to produce a W / O type emulsion ink and evaluated in the same manner as in Example 1. The results are shown in Table 2.

  The details of the raw materials described in Table 2 are the same as in Table 1.

  From the evaluation results of Table 2, according to the conductive emulsion ink of the present invention, a conductive thin film can be formed in a short time and with a simple operation by simply applying a one-component conductive emulsion ink to the substrate surface. You can see that On the other hand, the emulsion ink of Comparative Example 1 containing only metal nanoparticles in the discontinuous phase does not exhibit conductivity, and the emulsion ink of Comparative Example 2 in which the metal nanoparticles and the reducing agent coexist in the discontinuous phase is Both conductivity and discontinuous phase stability were inferior.

  The conductive emulsion ink of the present invention can be effectively applied to printable electronics technology for forming a wiring pattern by a printing process.

Claims (4)

  A conductive emulsion ink in which a first discontinuous phase containing metal nanoparticles and a second discontinuous phase containing a reducing agent and / or a photocatalyst of the metal nanoparticles are dispersed in a continuous phase.   The conductive emulsion ink according to claim 1, wherein the continuous phase contains metal nanoparticles. The conductive emulsion ink according to claim 1, wherein the continuous phase is an oil phase, and the first and second discontinuous phases are aqueous phases.
  The electroconductivity which consists of the process of apply | coating or patterning the electroconductive emulsion ink of any one of Claims 1-3 containing a photocatalyst, and the process of attaching | subjecting this electroconductive emulsion ink coated or patterned to UV irradiation. Method for forming a thin film.