Metallic microparticle dispersions

Abstract

The present invention relates to a metal fine particle dispersion, an ink containing the metal fine particle dispersion, and a method for producing a printed matter using the ink. The metal fine particle dispersion contains metal fine particles A, a polyalkylene glycol dialkyl ether B, and a polyol C, the content mass ratio (polyalkylene glycol dialkyl ether B / metal fine particles A) of the polyalkylene glycol dialkyl ether B with respect to the metal fine particles A is 0.5 or greater and 1.5 or less, and the metal fine particles A are dispersed with a dispersant D.

Description

Technical Field

[0001] This invention relates to a metal microparticle dispersion, an ink containing the metal microparticle dispersion, and a method for manufacturing printed matter using the ink. Background Technology

[0002] Due to the diversity of functions and properties exhibited by using metals miniaturized to the nanoscale, the development of various industrial applications for metal microparticles is anticipated.

[0003] As part of its industrial development, research is underway on the use of inks containing metal particles in printed electronics, which utilize printing technology to form electronic circuits or devices.

[0004] From the perspective of improving the convenience and promoting energy conservation of information and communication terminal equipment such as displays and sensors, it is expected that printed electronics will conduct research on improving the performance of inks containing metal particles and the metal particle dispersions used in these inks.

[0005] For example, in Japanese Patent Application Publication No. 2007-194174 (Patent Document 1), an ink for conductor patterns is described with the aim of providing an ink for conductor patterns that can produce fewer cracks. The ink is composed of a colloidal solution, wherein the colloidal solution contains at least colloidal particles containing silver, and the colloidal solution contains one or more nonionic compounds selected from tetraethylene glycol, polyethylene glycol, and propylene oxide-ethylene oxide block copolymer, and the content of the nonionic compound is more than 5% by mass relative to the silver.

[0006] In Japanese Patent Application Publication No. 2007-327034 (Patent Document 2), with the aim of providing a metallic ink composition for inkjet printing using nanoparticles synthesized in an aqueous system, a metallic ink composition is described that contains a specified amount of metallic nanoparticles and an organic solvent, wherein the organic solvent is an ether of the ethylene glycol series or a mixed solvent containing the organic solvent.

[0007] In Japanese Patent Application Publication No. 2013-231103 (Patent Document 3), a composition containing metal ultrafine particles is described with the aim of providing a conductive pattern with excellent conductivity and good printing stability. The composition contains water, metal ultrafine particles, sugars, polyols and / or their derivatives, polyethylene glycol and / or their derivatives, and the proportions of water, polyols and / or their derivatives, and polyethylene glycol and / or their derivatives in the total composition containing metal ultrafine particles satisfy a specified relationship. Summary of the Invention

[0008] This invention relates to a metal microparticle dispersion, comprising metal microparticles A, polyalkylene glycol dialkyl ether B, and polyol C, wherein the mass ratio of polyalkylene glycol dialkyl ether B to metal microparticles A (polyalkylene glycol dialkyl ether B / metal microparticles A) is 0.5 or more and 1.5 or less, and the metal microparticles A are dispersed using a dispersant D. Detailed Implementation

[0009] In the application of inks containing metal particles in printed electronics, the resistivity of the metal film formed by sintering the metal particles has not been sufficiently reduced, and further improvements are required.

[0010] In addition, inks containing metal particles must be refrigerated to ensure the dispersion stability of the metal particles. This can sometimes impair the operability of the ink. In addition, it is necessary to preserve metal particle dispersions and inks containing metal particles in environments above room temperature.

[0011] However, the technologies in Patent Documents 1-3 cannot meet the requirements for resistivity and storage stability of the sintered metal film, and further improvements are needed in the performance of metal particle dispersions and inks containing metal particles.

[0012] This invention relates to a metal microparticle dispersion with excellent storage stability and capable of forming a metal film with low resistivity, an ink containing the metal microparticle dispersion, and a printing method for printed matter using the ink.

[0013] The inventors have discovered that by containing polyalkylene glycol dialkyl ether and polyol in a dispersion of metal particles, wherein the mass ratio of the polyalkylene glycol dialkyl ether to the metal particles is within a specific range, the dispersion stability of the metal particles can be improved, and a good metal film can be formed. This has led to the discovery of a metal particle dispersion with excellent storage stability and capable of forming a metal film with low resistivity, an ink containing the metal particle dispersion, and a printing method for printed materials using the ink.

[0014] That is, the present invention relates to the following [1] to [3].

[0015] [1] A metal particle dispersion, comprising: metal particles A, polyalkylene glycol dialkyl ether B and polyol C, wherein the mass ratio of polyalkylene glycol dialkyl ether B to metal particles A (polyalkylene glycol dialkyl ether B / metal particles A) is 0.5 or more and 1.5 or less, and the metal particles A are dispersed by dispersant D.

[0016] [2] An ink comprising the metal microparticle dispersion described in [1] above.

[0017] [3] A method for manufacturing a printed matter, wherein the ink described in [2] above is applied to a printing substrate to obtain a printed matter having a metal film formed thereon.

[0018] According to the present invention, a metal particle dispersion with excellent storage stability and capable of forming a metal film with low resistivity, an ink containing the metal particle dispersion, and a printing method for a printed matter using the ink can be provided.

[0019] [Metal microparticle dispersion]

[0020] The metal particle dispersion of the present invention contains metal particles A, polyalkylene glycol dialkyl ether B, and polyol C. The mass ratio of polyalkylene glycol dialkyl ether B to metal particles A (polyalkylene glycol dialkyl ether B / metal particles A) is 0.5 or more and 1.5 or less. Metal particles A are dispersed by dispersant D.

[0021] In this invention, the metal particle dispersion is formed by dispersing metal particles A with dispersant D in a medium containing polyalkylene glycol dialkyl ether B and polyol C.

[0022] According to the present invention, it is possible to provide a metal microparticle dispersion with excellent preservation stability and capable of forming a metal film with low resistivity, an ink containing the metal microparticle dispersion, and a printing method for a printed matter using the ink. The reasons for this are not yet clear, but are believed to be as follows.

[0023] The metal particle dispersion of the present invention comprises metal particles dispersed with a dispersant, polyalkylene glycol dialkyl ether, and a polyol. It is presumed that during sintering, the metal particles are concentrated through the volatilization of the polyol, thus promoting sintering. Furthermore, the polyalkylene glycol dialkyl ether has a specific mass ratio to the metal particles within a certain range; therefore, during the sintering of the metal particles, these solvents gradually detach, thereby forming a well-formed metal film with reduced porosity and lower resistivity.

[0024] Furthermore, in the metal particle dispersion of the present invention, it is believed that the metal particles are dispersed with a dispersant, and then the polyalkylene glycol dialkyl ether slowly covers the surface of the metal particles, thereby improving the dispersion stability of the metal particles. Furthermore, it is believed that by using the polyalkylene glycol dialkyl ether in combination with a polyol, the storage stability is improved.

[0025] <Metal Particle A>

[0026] Examples of metals (metal atoms) constituting the metal particle A of this invention include group 4 transition metals such as titanium and zirconium; group 5 transition metals such as vanadium and niobium; group 6 transition metals such as chromium, molybdenum, and tungsten; group 7 transition metals such as manganese, technetium, and rhenium; group 8 transition metals such as iron and ruthenium; group 9 transition metals such as cobalt, rhodium, and iridium; group 10 transition metals such as nickel, palladium, and platinum; group 11 transition metals such as copper, silver, and gold; group 12 transition metals such as zinc and cadmium; group 13 metals such as aluminum, gallium, and indium; and group 14 metals such as germanium, tin, and lead. The metal constituting the metal particle A can be a single metal or can be used in combination of two or more metals as an alloy. From the viewpoint of improving the preservation stability of the dispersion and reducing the resistivity of the metal film, the metal constituting the metal particle A preferably contains a transition metal from Group 4 to Group 11 and from Period 4 to Period 6, more preferably contains a noble metal such as copper, gold, silver, platinum, or palladium, further preferably contains at least one selected from gold, silver, copper, and palladium, even more preferably contains at least one selected from gold, silver, and copper, even more preferably contains at least one selected from silver and copper, and even more preferably contains silver. The type of metal can be confirmed by high-frequency inductively coupled plasma optical emission analysis.

[0027] From the viewpoint of improving the dispersion stability of metal particles and the preservation stability of the dispersion, the cumulative average particle size of metal particles A in the metal particle dispersion of the present invention is preferably 10 nm or more, more preferably 15 nm or more, further preferably 17 nm or more, and even more preferably 20 nm or more. Furthermore, from the viewpoint of miniaturizing metal particles and reducing the resistivity of the metal film, it is preferably 100 nm or less, more preferably 80 nm or less, further preferably 60 nm or less, even more preferably 50 nm or less, even more preferably 40 nm or less, and even more preferably 35 nm or less.

[0028] The cumulative average particle size, as described in the examples, can be determined by cumulative analysis using the "ELS-8000" laser particle analysis system (manufactured by Otsuka Electronics Co., Ltd.). The measurement conditions were: temperature 25°C, incident light angle with detector 90°, 100 cumulative measurements, using the refractive index of water (1.333) as the dispersion solvent, and a sample concentration of 5 × 10⁻⁶. -3 Mass % (conversion of solid component concentration).

[0029] From the viewpoint of facilitating the preparation of inks using this dispersion and reducing the resistivity of the metal film, the content of metal particles A in the metal particle dispersion of the present invention is preferably 2% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 20% by mass or more, and even more preferably 25% by mass or more. Furthermore, from the viewpoint of improving the dispersion stability of the metal particles and improving the storage stability of the dispersion, it is preferably 85% by mass or less, more preferably 70% by mass or less, even more preferably 50% by mass or less, even more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0030] When the metal constituting the metal particle A contains silver and copper, from the viewpoint of improving the storage stability of the dispersion and reducing the resistivity of the metal film, the total content of silver and copper in the metal particle A is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably substantially 100% by mass.

[0031] Furthermore, when the metal constituting the metal particles A contains silver, from the viewpoint of improving the storage stability of the dispersion and reducing the resistivity of the metal film, the silver content in the metal particles A is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably substantially 100% by mass.

[0032] Furthermore, when the metal constituting the metal particles A contains copper, from the viewpoint of improving the storage stability of the dispersion and reducing the resistivity of the metal film, the copper content in the metal particles A is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably substantially 100% by mass.

[0033] Here, "substantially 100% by mass" means that it may include unintentionally included components. Examples of unintentionally included components include, for instance, unavoidable impurities.

[0034] <Polyalkylene glycol dialkyl ether B>

[0035] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the metal particle dispersion of the present invention contains polyalkylene glycol dialkyl ether B.

[0036] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of dispersions, and reducing the resistivity of metal films, the polyoxyalkylene group constituting polyalkylene glycol dialkyl ether B is preferably selected from at least one of polyoxyethylene and polyoxypropylene groups, more preferably polyoxyethylene.

[0037] Examples of alkyl groups constituting polyalkylene glycol dialkyl ether B include methyl, ethyl, propyl, butyl, and pentyl. From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the number of carbon atoms in the alkyl group is preferably 1 or more and 5 or less, more preferably 1 or more and 4 or less, further preferably 1 or more and 3 or less, even more preferably 1 or more and 2 or less, and even more preferably 1. Polyalkylene glycol dialkyl ether B can be used alone or in combination with two or more types.

[0038] Specifically, examples of polyalkylene glycol dialkyl ethers (B) include polyoxyethylene dimethyl ether, polyoxyethylene diethyl ether, polyoxyethylene dipropyl ether, polyoxyethylene dibutyl ether, polyoxyethylene dipentyl ether, triethylene glycol dimethyl ether, etc.; and polyoxypropylene dimethyl ether, polyoxypropylene diethyl ether, polyoxypropylene dipropyl ether, polyoxypropylene dibutyl ether, polyoxypropylene dipentyl ether, tripropylene glycol dipentyl ether, etc.

[0039] From the perspectives of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, polyalkylene glycol dialkyl ether B is preferably selected from at least one of polyoxyethylene dialkyl ether and polyoxypropylene dialkyl ether, more preferably polyoxyethylene dialkyl ether, and even more preferably polyoxyethylene dimethyl ether.

[0040] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the number average molecular weight of polyalkylene glycol dialkyl ether B is preferably 100 or more, more preferably 160 or more, and even more preferably 200 or more. Furthermore, it is preferably 5,000 or less, more preferably 3,000 or less, even more preferably 2,000 or less, even more preferably 1,500 or less, even more preferably 1,000 or less, even more preferably 800 or less, even more preferably 500 or less, and even more preferably 300 or less.

[0041] The number-average molecular weight of polyalkylene glycol dialkyl ether B can be determined by gel permeation chromatography (GPC).

[0042] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the polyalkylene glycol dialkyl ether B preferably includes at least one of polyoxyethylene dialkyl ethers selected from those with 1 or more and 5 or less carbon atoms in the alkyl group and polyoxypropylene dialkyl ethers selected from those with 1 or more and 5 or less carbon atoms in the alkyl group, more preferably includes at least one of polyoxyethylene dimethyl ether and polyoxypropylene dimethyl ether, further preferably includes polyoxyethylene dimethyl ether, even more preferably includes polyoxyethylene dimethyl ether with a number average molecular weight of 160 or more and 1500 or less, and even more preferably includes polyoxyethylene dimethyl ether with a number average molecular weight of 160 or more and 800 or less.

[0043] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, it is preferable to select at least one of polyoxyethylene dialkyl ethers with 1 or more and 5 or less carbon atoms in the alkyl group and polyoxypropylene dialkyl ethers with 1 or more and 5 or less carbon atoms in the alkyl group; more preferably, it is preferable to select at least one of polyoxyethylene dimethyl ethers and polyoxypropylene dimethyl ethers; even more preferably, it is preferable to select polyoxyethylene dimethyl ethers; even more preferably, it is preferable to select polyoxyethylene dimethyl ethers with a number average molecular weight of 160 or more and 1500 or less; even more preferably, it is preferable to select polyoxyethylene dimethyl ethers with a number average molecular weight of 160 or more and 800 or less; the total content of polyoxyethylene dimethyl ethers in polyalkylene glycol dialkyl ether B is 80% by mass or more; more preferably, it is preferable to select polyoxyethylene dimethyl ethers with a number average molecular weight of 160 or more and 800 or less; even ... As an unintentionally included component, for example, the polyalkylene glycol dialkyl ether B component other than the aforementioned preferred polyalkylene glycol dialkyl ether contained in the aforementioned preferred polyalkylene glycol dialkyl ether as a raw material can be cited.

[0044] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the content of polyalkylene glycol dialkyl ether B in the metal particle dispersion of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, even more preferably 20% by mass or more, and even more preferably 25% by mass or more. Furthermore, from the viewpoint of reducing the resistivity of the metal film, it is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0045] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the mass ratio of polyalkylene glycol dialkyl ether B to metal particles A in the metal particle dispersion of the present invention (polyalkylene glycol dialkyl ether B / metal particles A) is 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more, further preferably 0.8 or more, even more preferably 0.9 or more, and is 1.5 or less, preferably 1.4 or less, more preferably 1.3 or less, even more preferably 1.2 or less, and even more preferably 1.1 or less.

[0046] <Polyol C>

[0047] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the metal particle dispersion of the present invention contains polyol C.

[0048] There are no particular restrictions on polyol C as long as it is a compound having two or more alcoholic hydroxyl groups in one molecule. Examples of polyol C include ethylene glycol (boiling point 197℃), 1,2-propanediol (boiling point 188℃), 1,2-butanediol (boiling point 193℃), 1,2-pentanediol (boiling point 206℃), 1,2-hexanediol (boiling point 223℃), and other 1,2-alkyldiols; diethylene glycol (boiling point 245℃), triethylene glycol (boiling point 287℃), tetraethylene glycol (314℃), polyethylene glycol, and dipropylene glycol (boiling point 245℃), triethylene glycol (boiling point 287℃), tetraethylene glycol (boiling point 314℃), polyethylene glycol, and dipropylene glycol (boiling point 245℃). Polyalkylene glycols such as tripropylene glycol (boiling point 232℃) and tripropylene glycol (boiling point 271℃); α,ω-alkyl glycols such as 1,3-propanediol (boiling point 210℃), 1,4-butanediol (boiling point 230℃), and 1,5-pentanediol (boiling point 242℃); diols such as 1,3-butanediol (boiling point 208℃), 3-methyl-1,3-butanediol (boiling point 203℃), and 2-methyl-2,4-pentanediol (boiling point 196℃); triols such as glycerol, etc. Polyol C can be used alone or in combination of two or more types.

[0049] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the boiling point of polyol C is preferably 70°C or higher, more preferably 90°C or higher, even more preferably 110°C or higher, even more preferably 130°C or higher, even more preferably 150°C or higher, and preferably 300°C or lower, more preferably 250°C or lower, even more preferably 230°C or lower, and even more preferably 200°C or lower.

[0050] It should be noted that when two or more polyols C are used together, the boiling point of polyol C is a weighted average of the content (mass%) of each polyol.

[0051] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of dispersions, and reducing the resistivity of metal films, polyol C preferably contains at least one selected from diols and triols, more preferably contains at least one selected from 1,2-alkyldiol, polyalkylene glycol, α,ω-alkyldiol, and glycerol, further preferably contains at least one selected from 1,2-alkyldiol, α,ω-alkyldiol, and glycerol, and even more preferably contains at least one selected from 1,2-alkyldiol and α,ω-alkyldiol (hereinafter, they are collectively referred to as (C-1) components). Furthermore, from the same perspective as above, polyol C preferably includes at least one selected from ethylene glycol, 1,2-propanediol, 1,4-butanediol, and glycerol; more preferably includes at least one selected from ethylene glycol, 1,2-propanediol, and 1,4-butanediol; even more preferably includes at least one selected from 1,2-propanediol and 1,4-butanediol; and even more preferably includes 1,2-propanediol (hereinafter collectively referred to as (C-2) component).

[0052] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the total content of the (C-1) component or (C-2) component in polyol C is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably substantially 100% by mass. Here, "substantially 100% by mass" means that it may include components that are unintentionally included. Examples of unintentionally included components include, for example, polyol C components other than the (C-1) and (C-2) components contained in the polyol used as a raw material.

[0053] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the content of polyol C in the metal particle dispersion of the present invention is preferably 3% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 20% by mass or more, and preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and even more preferably 25% by mass or less.

[0054] From the viewpoint of improving the dispersion stability of metal particles and the storage stability of the dispersion, the mass ratio of polyol C to metal particle A in the metal particle dispersion of the present invention (polyol C / metal particle A) is preferably 0.1 or more, more preferably 0.3 or more, further preferably 0.5 or more, and even more preferably 0.7 or more. Furthermore, from the viewpoint of reducing the resistivity of the metal film, it is preferably 1.3 or less, more preferably 1.2 or less, further preferably 1.0 or less, even more preferably 0.9 or less, and even more preferably 0.8 or less.

[0055] From the viewpoint of improving the dispersion stability of metal particles and the storage stability of the dispersion, the total content of polyalkylene glycol dialkyl ether B and polyol C in the metal particle dispersion of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more, even more preferably 40% by mass or more, even more preferably 42% by mass or more, even more preferably 45% by mass or more, and even more preferably 50% by mass or more. Moreover, from the viewpoint of reducing the resistivity of the metal film, it is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, and even more preferably 55% by mass or less.

[0056] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the mass ratio of polyalkylene glycol dialkyl ether B to polyol C in the metal particle dispersion (polyalkylene glycol dialkyl ether B / polyol C) is preferably 0.3 or more, more preferably 0.5 or more, further preferably 0.7 or more, even more preferably 1 or more, even more preferably 1.1 or more, and preferably 2.5 or less, more preferably 2 or less, even more preferably 1.7 or less, and even more preferably 1.5 or less.

[0057] <Dispersant D>

[0058] In this invention, metal particles A are dispersed by dispersant D. There are no particular limitations on the dispersant B, as long as it has the function of dispersing metal particles such as surfactants and polymers.

[0059] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the dispersant D is preferably a polymer containing hydrophilic groups. More preferably, the side chains of the polymer have the hydrophilic groups.

[0060] Examples of hydrophilic groups include nonionic groups such as polyoxyalkylene groups, hydroxyl groups, and amide groups; groups that dissociate to release hydrogen ions, such as carboxyl groups (-COOM), sulfonic acid groups (-SO3M), and phosphate groups (-OPO3M2), or their ionic derivatives (-COO). - -SO3 - -OPO3 2- -OPO3 - Anionic groups such as M; protonated salts of primary, secondary, or tertiary amino groups, and cationic groups such as quaternary ammonium groups. In the above chemical formulas, M represents a hydrogen atom, an alkali metal, ammonium, or an organic ammonium.

[0061] From the perspectives of improving the dispersion stability of metal particles, improving the storage stability of dispersions, and reducing the resistivity of metal films, dispersant D is preferably a polymer having at least one of nonionic and anionic groups.

[0062] Examples of polymers with nonionic groups include polymers containing polyoxyalkylene groups, polymers with structures derived from vinylpyrrolidone such as polyvinylpyrrolidone, polymers with structures derived from acrylamide such as polyacrylamide, and polyvinyl alcohol.

[0063] Polymers with anionic groups are preferably polymers with carboxyl groups. Examples of basic structures for polymers with carboxyl groups include vinyl polymers such as acrylic resins, styrene resins, styrene-acrylic resins, and silicone acrylic resins; and condensation polymers such as polyesters and polyurethanes.

[0064] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of dispersions, and reducing the resistivity of metal films, dispersant D preferably contains at least one selected from polymers containing carboxyl groups and polymers containing polyoxyalkylene groups, more preferably contains a polymer containing carboxyl groups, even more preferably contains a vinyl polymer containing a structural unit derived from a monomer (d-2) having a carboxyl group, and even more preferably contains a vinyl polymer containing a structural unit derived from a monomer (d-2) having a carboxyl group.

[0065] [Monomers with carboxyl groups (d-2)]

[0066] The carboxyl groups contained in monomer (d-2) are as described above.

[0067] As monomers (d-2), specifically, examples include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, and 2-methacryloyloxymethylsuccinic acid; and unsaturated dicarboxylic acids such as maleic acid, itaconic acid, fumaric acid, and citraconic acid. It should be noted that the above-mentioned unsaturated dicarboxylic acids can also be anhydrides.

[0068] The monomer (d-2) can be used alone or in combination with two or more monomers.

[0069] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the monomer (d-2) is preferably selected from at least one of (meth)acrylic acid and maleic acid.

[0070] In this specification, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid. The term "(meth)acrylic acid" will have the same meaning hereinafter.

[0071] The vinyl polymer used as dispersant D, which contains structural units derived from monomers (d-2) having carboxyl groups, is preferably selected from one or more homopolymers of monomers (d-2) having carboxyl groups and copolymers containing structural units derived from monomers (d-2) having carboxyl groups.

[0072] As homopolymers of monomers (d-2) containing carboxyl groups, polycarboxylic acids such as poly(meth)acrylic acid and polymaleic anhydride are preferred from the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film. Among these, poly(meth)acrylic acid is preferred from the same viewpoints as described above.

[0073] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, vinyl polymers comprising structural units derived from both a carboxyl-based monomer (d-2) and a monomer (d-1) with a polyoxyalkylene group are preferred examples of copolymers containing structural units derived from a carboxyl-based monomer (d-2). In this case, the vinyl polymer can be obtained by copolymerizing a raw material monomer comprising monomer (d-1) and monomer (d-2). The aforementioned vinyl polymer can be any of block copolymers, random copolymers, or alternating copolymers.

[0074] [Monomers with polyoxyalkylene groups (d-1)]

[0075] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the monomer (d-1) is preferably a monomer capable of incorporating polyoxyalkylene groups as side chains of the vinyl polymer. Examples of this monomer (d-1) include polyalkylene glycol (meth)acrylate, alkoxy polyalkylene glycol (meth)acrylate, and phenoxy polyalkylene glycol (meth)acrylate. One monomer (d-1) may be used alone or in combination with two or more. In this specification, "(meth)acrylate" refers to at least one selected from acrylates and methacrylates. The term "(meth)acrylate" will have the same meaning hereinafter.

[0076] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the monomer (d-1) is preferably selected from at least one of polyalkylene glycol (meth)acrylate and alkoxy polyalkylene glycol (meth)acrylate, more preferably alkoxy polyalkylene glycol (meth)acrylate. From the same viewpoint, the alkoxy polyalkylene glycol (meth)acrylate preferably has 1 or more and 8 or less carbon atoms in its alkoxy group, more preferably 1 or more and 4 or less.

[0077] Examples of alkoxy polyalkylene glycol (meth)acrylates include methoxy polyalkylene glycol (meth)acrylate, ethoxy polyalkylene glycol (meth)acrylate, propoxy polyalkylene glycol (meth)acrylate, butoxy polyalkylene glycol (meth)acrylate, and octoxy polyalkylene glycol (meth)acrylate.

[0078] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the polyoxyalkylene group of the monomer (d-1) preferably includes units derived from alkylene oxides having 2 or more but less than 4 carbon atoms. Examples of such alkylene oxides include ethylene oxide, propylene oxide, and butane oxide, with ethylene oxide being preferred.

[0079] From the viewpoints of improving the dispersion stability of metal particles, improving the preservation stability of the dispersion, and reducing the resistivity of the metal film, the number of units derived from alkylene oxides in the above-mentioned polyoxyalkylene group is preferably 2 or more, more preferably 5 or more, and preferably 100 or less, more preferably 70 or less, further preferably 50 or less, further preferably 30 or less, and even more preferably 15 or less.

[0080] The aforementioned polyoxyolefin can be a copolymer containing units derived from ethylene oxide and units derived from propylene oxide. From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the molar ratio of units derived from ethylene oxide (EO) to units derived from propylene oxide (PO) [EO / PO] is preferably 60 / 40 or more, more preferably 65 / 35 or more, even more preferably 70 / 30 or more, and preferably 90 / 10 or less, more preferably 85 / 15 or less, and even more preferably 80 / 20 or less.

[0081] A copolymer containing units derived from ethylene oxide and units derived from propylene oxide can be any of the following: block copolymer, random copolymer, or alternating copolymer.

[0082] Specific examples of commercially available monomers (d-1) include NK Ester AM-90G, NK Ester AM-130G, NK Ester AMP-20GY, NK Ester M-20G, NK Ester M-40G, NK Ester M-90G, and NK Ester M-230G from Shin-Nakamura Chemical Industry Co., Ltd.; and Blemmer PE-90, Blemmer PE-200, Blemmer PE-350, Blemmer PME-100, Blemmer PME-200, Blemmer PME-400, Blemmer PME-1000, Blemmer PME-4000, Blemmer PP-500, Blemmer PP-800, Blemmer PP-1000, Blemmer AP-150, Blemmer AP-400, and Blemmer PME-400 from Nichiyu Corporation. AP-550, etc., Blemmer 50PEP-300, Blemmer 50POEP-800B, Blemmer 43PAPE-600B, etc.

[0083] Without impairing the effects of the invention, the vinyl polymer may also contain structural units derived from other monomers besides monomers having polyoxyalkylene groups (d-1) and monomers having carboxyl groups (d-2).

[0084] Other examples of monomers include monomers containing aromatic groups; hydrophobic monomers such as (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols.

[0085] In this specification, "hydrophobic monomer" refers to a monomer whose dissolved amount is less than 10g when dissolved in 100g of ion-exchanged water at 25°C until saturation.

[0086] The monomer containing an aromatic group is preferably a vinyl monomer having an aromatic group having 6 or more and 22 or fewer carbon atoms, and may also have a substituent containing a heteroatom. More preferably, it is at least one selected from styrene monomers and (meth)acrylates containing aromatic groups. The molecular weight of the monomer containing the aromatic group is preferably less than 500.

[0087] Examples of styrene monomers include styrene, α-methylstyrene, 2-methylstyrene, 4-vinyltoluene (4-methylstyrene), and divinylbenzene. From the perspectives of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, styrene and α-methylstyrene are preferred.

[0088] As (meth)acrylates containing aromatic groups, phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, etc. are preferred, and benzyl (meth)acrylate is more preferred.

[0089] From the perspectives of improving the dispersion stability of metal particles, improving the preservation stability of dispersions, and reducing the resistivity of metal films, (meth)acrylates having hydrocarbon groups derived from aliphatic alcohols are preferably those having hydrocarbon groups derived from aliphatic alcohols with 1 or more and 22 or fewer carbon atoms. Examples include: methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, stearyl methacrylate, etc., which are (meth)acrylates with straight-chain alkyl groups; isopropyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isoamyl methacrylate, isooctyl methacrylate, isodecyl methacrylate, isododecyl methacrylate, isostearyl methacrylate, 2-ethylhexyl methacrylate, etc., which are (meth)acrylates with branched-chain alkyl groups; and cyclohexyl methacrylate, etc., which are (meth)acrylates with alicyclic alkyl groups.

[0090] When dispersant D is a vinyl polymer containing structural units derived from monomers having polyoxyalkylene groups (d-1) and structural units derived from monomers having carboxyl groups (d-2), from the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the content of each monomer in the raw material monomers (as the content of unneutralized amount; the same applies below) or the content of structural units derived from each monomer in the vinyl polymer is as follows.

[0091] The content of the monomer (d-1) having a polyoxyalkylene group is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, and preferably 99% by mass or less, more preferably 98.5% by mass or less, even more preferably 98% by mass or less, and even more preferably 97.5% by mass or less.

[0092] The content of the monomer (d-2) having a carboxyl group is preferably 1% by mass or more, more preferably 1.5% by mass or more, even more preferably 2% by mass or more, and even more preferably 2.5% by mass or more. It is also preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0093] The mass ratio of the content of the monomer having a carboxyl group (d-2) to the monomer having a polyoxyolefin group (d-1) [monomer (d-2) / monomer (d-1)] is preferably 0.01 or more, more preferably 0.02 or more, even more preferably 0.03 or more, and preferably 1 or less, more preferably 0.5 or less, even more preferably 0.1 or less, even more preferably 0.07 or less, and even more preferably 0.05 or less.

[0094] When the dispersant D is a vinyl polymer containing structural units derived from monomers (d-1) having polyoxyalkylene groups and structural units derived from monomers (d-2) having carboxyl groups, from the same viewpoint as described above, the total content of structural units derived from monomers (d-1) and structural units derived from monomers (d-2) is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and preferably 100% by mass or less.

[0095] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the dispersant D is preferably a vinyl polymer comprising a structural unit derived from alkoxy polyalkylene glycol (meth)acrylate as monomer (d-1) and a structural unit derived from at least one monomer selected from (meth)acrylic acid and maleic acid as monomer (d-2).

[0096] The aforementioned vinyl polymers can be polymers synthesized using known methods, or commercially available products. Examples of commercially available vinyl polymers include DISPERBYK-190 and DISPERBYK-2015 manufactured by BYK Corporation.

[0097] When the dispersant D is the aforementioned polycarboxylic acid, or a vinyl polymer comprising structural units derived from alkoxy polyalkylene glycol (meth)acrylate as monomer (d-1) and structural units derived from at least one monomer selected from (meth)acrylic acid and maleic acid as monomer (d-2), the number average molecular weight of the vinyl polymer is preferably 1,000 or more, more preferably 2,000 or more, further preferably 3,000 or more, and preferably 100,000 or less, more preferably 50,000 or less, further preferably 30,000 or less, even more preferably 10,000 or less, and even more preferably 7,000 or less. If the number average molecular weight of the vinyl polymer is within the above range, the adsorption force on metal particles is sufficient, and dispersion stability can be exhibited. The above-mentioned number average molecular weight is determined by the method described in the examples.

[0098] When the dispersant D is a vinyl polymer comprising a structural unit derived from alkoxy polyalkylene glycol (meth)acrylate as monomer (d-1) and a structural unit derived from at least one monomer selected from (meth)acrylic acid and maleic acid as monomer (d-2), from the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the acid value of the vinyl polymer is preferably 5 mg KOH / g or more, more preferably 10 mg KOH / g or more, further preferably 15 mg KOH / g or more, and preferably 200 mg KOH / g or less, more preferably 100 mg KOH / g or less, further preferably 50 mg KOH / g or less, and even more preferably 30 mg KOH / g or less.

[0099] The acid value of the aforementioned vinyl polymers can also be calculated based on the mass ratio of the constituent monomers. Alternatively, it can be determined by dissolving or swelling the polymer in a suitable solvent and then titrating it.

[0100] When the dispersant D is a polymer, the polymer exists in the metal particle dispersion in three forms: the polymer is adsorbed onto the metal particles, the polymer contains metal particles encapsulated within the metal particles (capsules), and the polymer is not adsorbed onto the metal particles. From the viewpoint of the dispersion stability of the metal particles, the form in which the polymer contains metal particles is preferred, and the form in which the polymer contains metal particles encapsulated within the metal particles is even more preferred.

[0101] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the mass ratio of the content of dispersant D in the metal particle dispersion of the present invention relative to the total amount of dispersant D and metal particles A [dispersant D / (dispersant D + metal particles A)] is preferably 0.01 or more, more preferably 0.03 or more, further preferably 0.05 or more, and preferably 0.3 or less, more preferably 0.2 or less, and further preferably 0.15 or less.

[0102] The above-mentioned content-to-mass ratio [dispersant D / (dispersant D + metal particles A)] is calculated based on the mass of dispersant D and metal particles A measured using a differential thermogravimetric analyzer (TG / DTA) by the method described in the examples.

[0103] From the viewpoint of improving the dispersion stability of metal particles and the storage stability of the dispersion, the content of dispersant D in the metal particle dispersion of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. Furthermore, from the viewpoint of reducing the resistivity of the metal film, it is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less.

[0104] When dispersant D contains a vinyl polymer comprising structural units derived from monomers (d-2) having carboxyl groups, from the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the content of this vinyl polymer comprising structural units derived from monomers (d-2) having carboxyl groups in dispersant D is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably substantially 100% by mass. Here, "substantially 100% by mass" means that it may include components that are unintentionally included. For example, unintentionally included components may include dispersant D components other than those contained in the aforementioned vinyl polymer used as a raw material.

[0105] The metal microparticle dispersion of the present invention preferably contains water as a dispersion medium in addition to polyalkylene glycol dialkyl ether B and polyol C.

[0106] From the viewpoints of improving the dispersion stability of metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, the water content in the metal particle dispersion of the present invention is preferably 0.5% by mass or more, more preferably 1% by mass or more, further preferably 3% by mass or more, even more preferably 5% by mass or more, even more preferably 10% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0107] (Preparation of metal microparticle dispersions)

[0108] The metal particle dispersion of the present invention can be obtained by methods such as adding and mixing a dispersion medium and dispersant D into pre-prepared metal particles using known methods, or by mixing a metal raw material compound, a reducing agent, and dispersant D and reducing the metal raw material compound. From the viewpoints of improving the dispersion stability of the metal particles, improving the storage stability of the dispersion, and reducing the resistivity of the metal film, it is preferable to first obtain a dried metal particle powder containing dispersant D, and then add and mix a dispersion medium containing polyalkylene glycol dialkyl ether B and polyol C.

[0109] Metal microparticle dry powder can be obtained by mixing a metal raw material compound, a reducing agent and a dispersant D, reducing the metal raw material compound with the reducing agent to obtain a dispersion of metal microparticles dispersed with dispersant D, and then drying the dispersion of metal microparticles by freeze drying or the like.

[0110] From the viewpoint of reducing the particle size of metal particles and making them uniform, the temperature of the reduction reaction is preferably 10°C or higher, more preferably 20°C or higher, and even more preferably 30°C or higher. Furthermore, from the viewpoint of stably producing metal particles, it is preferably carried out in the range of 70°C or lower, more preferably 60°C or lower, and even more preferably 50°C or lower. The reduction reaction can be carried out in an air atmosphere or in an inert gas atmosphere such as nitrogen.

[0111] There are no particular restrictions on compounds that are metal raw material compounds, as long as they contain the metal that constitutes the aforementioned metal particles A.

[0112] As a reducing agent, there are no particular limitations; any type of reducing agent, whether inorganic or organic, can be used, with organic reducing agents being preferred.

[0113] Examples of organic reducing agents include alcohols such as ethylene glycol and propylene glycol; aldehydes such as formaldehyde, acetaldehyde, and propionaldehyde; acids such as ascorbic acid and citric acid and their salts; alkyl amines such as ethanolamine, N-methylethanolamine, N,N-dimethylethanolamine (2-(dimethylamino)ethanol), N,N-diethylethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, propanolamine, N,N-dimethylpropanolamine, butanolamine, and hexanolamine; and propylamine, butanolamine, etc. Alkylamines such as hexylamine, diethylamine, dipropylamine, dimethylethylamine, diethylmethylamine, and triethylamine; aliphatic amines such as ethylenediamine, triethylenediamine, tetramethylethylenediamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine, and tetraethylenepentamine; alicyclic amines such as piperidine, pyrrolidine, N-methylpyrrolidine, and morpholine; aromatic amines such as aniline, N-methylaniline, toluidine, anisidine, and ethoxyaniline; and aralkylamines such as benzylamine and N-methylbenzylamine.

[0114] The reducing agent can be used alone or in combination of two or more.

[0115] In the manufacture of the metal particle dispersion of the present invention, from the viewpoint of removing impurities such as unreacted reducing agent and residual dispersant D that does not contribute to the dispersion of metal particles A, the dispersion of metal particles may be purified before freeze drying.

[0116] There are no particular limitations on the methods for purifying dispersions of metal particles; examples include membrane treatments such as dialysis and ultrafiltration, and centrifugal separation. From the viewpoint of effectively removing impurities, membrane treatment is preferred, and dialysis is even more preferred. As the material for the dialysis membrane used in dialysis, regenerated cellulose is preferred.

[0117] From the viewpoint of effectively removing impurities, the molecular weight cutoff of the dialysis membrane is preferably 1,000 or more, more preferably 5,000 or more, even more preferably 10,000 or more, and preferably 100,000 or less, more preferably 70,000 or less.

[0118] The metal particle dispersion of the present invention can form a metal film with excellent dispersion stability of metal particles, excellent storage stability at temperatures above room temperature, and low resistivity, and therefore can be used in a wide range of applications. Examples of such applications include various inks; wiring materials, electrode materials, conductive materials such as MLCCs (multilayer ceramic capacitors, hereinafter also referred to as "MLCCs"); bonding materials such as solders; various sensors; antennas such as tags using near-field wireless communication (RFID (radio frequency identifier); hereinafter also referred to as "RFID") technology; catalysts; optical materials; medical materials, etc.

[0119] [Ink]

[0120] The ink of the present invention contains the aforementioned metal particle dispersion. It is speculated that because this metal particle dispersion contains polyalkylene glycol dialkyl ether B and polyol C, the ink's coatability on printing substrates is improved, and these solvents gradually detach during the sintering of the metal particles, thus enabling the formation of a metal film with reduced porosity and lower resistivity.

[0121] The ink of the present invention can directly use the above-mentioned metal particle dispersion. In addition, besides the above-mentioned metal particle dispersion, various additives such as fixing aids, humectants, wetting agents, penetrants, surfactants, viscosity modifiers, defoamers, preservatives, mildew inhibitors, and rust inhibitors, which are commonly used in inks, can be added as needed, and then filtered using filters or the like.

[0122] The cumulative average particle size of the metal particles A in the above-mentioned ink is preferably the same as the cumulative average particle size of the metal particle dispersion, and the preferred embodiment of this average particle size is also the same as the preferred embodiment of the cumulative average particle size of the metal particle dispersion. The cumulative average particle size of the metal particles A in the above-mentioned ink can be measured by the same method as the cumulative average particle size in the above-mentioned metal particle dispersion.

[0123] From the viewpoint of preservation stability, the viscosity of the above-mentioned ink at 25°C is preferably 2 mPa·s or more, more preferably 3 mPa·s or more, further preferably 4 mPa·s or more, even more preferably 5 mPa·s or more, and preferably 12 mPa·s or less, more preferably 9 mPa·s or less, even more preferably 7 mPa·s or less, and even more preferably 6.5 mPa·s or less. The viscosity of the above-mentioned ink can be measured using an E-type viscometer.

[0124] From the viewpoint of preservation stability, the pH of the above-mentioned ink at 20°C is preferably 7.0 or higher, more preferably 7.2 or higher, and even more preferably 7.5 or higher. Furthermore, from the viewpoint of component resistance and skin irritation, the pH is preferably 11 or lower, more preferably 10 or lower, and even more preferably 9.5 or lower. The pH of the above-mentioned ink can be determined by conventional methods.

[0125] [Methods for manufacturing printed materials]

[0126] The method for manufacturing printed matter according to the present invention is to apply the ink to a printing substrate to obtain printed matter with a metal film formed thereon.

[0127] The aforementioned ink exhibits excellent storage stability at temperatures above room temperature and can form a low-resistivity metal film. Therefore, it is particularly suitable for various printing applications, including inkjet printing, flexographic printing, gravure printing, and screen printing. The ink is preferably used for inkjet printing. It is speculated that because the ink contains polyalkylene glycol dialkyl ether B and polyol C, the wetting and spreading properties of the ink dots on the printing substrate are improved. Furthermore, these solvents gradually detach during the sintering of the metal particles, thus enabling the formation of a metal film with reduced porosity and lower resistivity.

[0128] When the above-mentioned ink is used for inkjet printing, the ink can be filled into a known inkjet printing device and ejected as ink droplets onto a printing substrate to form a printed image, etc.

[0129] As inkjet printing devices, there are thermal and piezoelectric types, and the inks mentioned above are more preferably used for thermal inkjet printing.

[0130] Examples of printing substrates include metal parts, resin films, glass, ceramics, coated paper, art paper, synthetic paper, and processed paper.

[0131] Examples of metal components include gold substrates, gold-plated substrates, silver substrates, silver-plated metal substrates, copper substrates, palladium substrates, palladium-plated metal substrates, platinum substrates, or platinum-plated metal substrates, aluminum substrates, nickel substrates, nickel-plated substrates, tin substrates, tin-plated metal substrates, and other metal substrates or metal-made substrates; and metal parts such as electrodes of electrically insulating substrates.

[0132] Examples of resin films include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyamide (PA), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA), polypropylene (PP), polystyrene (PS), acrylonitrile-butadiene-styrene copolymer (ABS), acrylonitrile-styrene copolymer (AS), and polycarbonate (PC).

[0133] (Inkjet printing conditions)

[0134] From the viewpoint of reducing the resistivity of the metal film, the printhead temperature is preferably 15°C or higher, more preferably 20°C or higher, even more preferably 25°C or higher, and preferably 45°C or lower, more preferably 40°C or lower, and even more preferably 35°C or lower.

[0135] From the viewpoint of printing efficiency, the head voltage of the inkjet head is preferably 5V or higher, more preferably 10V or higher, even more preferably 15V or higher, and preferably 40V or lower, more preferably 35V or lower, even more preferably 30V or lower.

[0136] From the viewpoint of printing efficiency, the driving frequency of the printing head is preferably 1 kHz or higher, more preferably 5 kHz or higher, even more preferably 10 kHz or higher, and preferably 50 kHz or lower, more preferably 40 kHz or lower, and even more preferably 35 kHz or lower.

[0137] The amount of ink ejected as droplets is preferably 5 pL or more, more preferably 10 pL or more, and preferably 30 pL or less, more preferably 20 pL or less.

[0138] The amount of ink applied to the printing substrate, based on solid content, is preferably 0.5 g / m². 2 The above, more preferably 1g / m 2 The above is further preferred to be 2g / m 2 The above, and preferably 20g / m 2 The following is more preferably 15g / m 2 The following is a further preferred value: 10 g / m 2 the following.

[0139] The resolution is preferably 200 dpi or higher, more preferably 300 dpi or higher, and preferably 1,000 dpi or lower, more preferably 800 dpi or lower, and even more preferably 600 dpi or lower. Here, "resolution" in this specification refers to the number of dots per inch (2.54 cm) formed on the printing substrate. For example, "resolution of 600 dpi" means that when ink droplets are ejected onto the printing substrate using a line head configured with 600 dpi (dots / inch) of nozzle holes per unit length of nozzle array, a column of 600 dpi dots per inch is formed in a direction perpendicular to the transport direction of the printing substrate, and when ink droplets are ejected while the printing substrate is moved in the transport direction, a column of 600 dpi dots per inch is also formed on the printing substrate in the transport direction. In this specification, the resolution in the direction perpendicular to the transport direction of the printing substrate and the resolution in the transport direction are expressed as the same value.

[0140] (Heat treatment)

[0141] In this invention, from the viewpoint of reducing the resistivity of the metal film, it is preferable to heat-treat the ink coating on the printing substrate after the ink is applied to the printing substrate.

[0142] Through heat treatment, the medium in the ink coating can be evaporated and dried, thereby causing the metal particles to sinter and form a metal film with low resistivity.

[0143] There are no particular limitations on the heat treatment method. Examples include heating the ink-coated surface of the printing substrate by applying hot air, heating the ink-coated surface of the printing substrate by bringing the heater close to it, heating the printing substrate by bringing the heater into contact with the opposite side of the ink-coated surface, and heating the substrate by steam curing with high-temperature steam under normal or high pressure.

[0144] The heat treatment temperature is preferably lower than the temperature at which the printing substrate deforms.

[0145] From the viewpoint of reducing the resistivity of the metal film, the heat treatment temperature is preferably 50°C or higher, more preferably 70°C or higher, even more preferably 100°C or higher, and even more preferably 130°C or higher. It is also preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 180°C or lower. From the viewpoint of reducing the resistivity of the metal film, the heat treatment time in this case is preferably 1 minute or higher, and from the viewpoint of productivity, it is preferably 30 minutes or lower, more preferably 20 minutes or lower, and even more preferably 15 minutes or lower.

[0146] The surface resistivity ρs of the metal film of the present invention is preferably 10 Ω / □ or less, more preferably 7 Ω / □ or less, further preferably 5 Ω / □ or less, even more preferably 3 Ω / □ or less, even more preferably 1 Ω / □ or less, even more preferably 0.7 Ω / □ or less, even more preferably 0.5 Ω / □ or less, even more preferably 0.3 Ω / □ or less, and from the viewpoint of ease of printing production, it is preferably 0.01 Ω / □ or more, more preferably 0.05 Ω / □ or more, and even more preferably 0.07 Ω / □ or more. The above-mentioned surface resistivity ρs is measured by the method described in the examples.

[0147] The metal film of this invention exhibits high conductivity, and therefore can be used as a conductive component in various electronic and electrical devices. This conductive component is preferably used in RFID tags; capacitors such as MLCCs; electronic paper; image display devices such as liquid crystal displays and organic EL displays; organic EL elements; organic transistors; wiring boards such as printed wiring boards and flexible wiring boards; organic solar cells; sensors such as flexible sensors; and bonding agents such as solder. From the viewpoint of ease of manufacture using inkjet printing, it is particularly preferred for use in RFID tags and MLCCs.

[0148] In addition to the above-described embodiments, the present invention also discloses the following embodiments.

[0149] <1> A metal microparticle dispersion, comprising: metal microparticles A, polyalkylene glycol dialkyl ether B, and polyol C.

[0150] The mass ratio of polyalkylene glycol dialkyl ether B to metal microparticle A (polyalkylene glycol dialkyl ether B / metal microparticle A) is 0.5 or more and 1.5 or less.

[0151] Metal particles A are dispersed using dispersant D.

[0152] <2> The metal microparticle dispersion as described in <1>, wherein it contains: metal microparticles A, polyalkylene glycol dialkyl ether B, and polyol C.

[0153] The mass ratio of polyalkylene glycol dialkyl ether B to metal microparticle A (polyalkylene glycol dialkyl ether B / metal microparticle A) is 0.5 or more and 1.5 or less.

[0154] Metal particles A are dispersed using dispersant D.

[0155] The metal particles A consist of one or more metals selected from silver and copper.

[0156] Polyalkylene glycol dialkyl ether B comprises at least one of the following: polyoxyethylene dialkyl ethers having 1 or more and 5 or fewer carbon atoms in the alkyl group, and polyoxypropylene dialkyl ethers having 1 or more and 5 or fewer carbon atoms in the alkyl group.

[0157] Polyol C contains at least one selected from 1,2-alkyldiol, polyalkylene glycol, α,ω-alkyldiol, and glycerol.

[0158] Dispersant D contains a vinyl polymer comprising structural units derived from monomers (d-2) having carboxyl groups.

[0159] <3> The metal microparticle dispersion as described in <1> or <2>, wherein it contains: metal microparticles A, polyalkylene glycol dialkyl ether B, and polyol C.

[0160] The mass ratio of polyalkylene glycol dialkyl ether B to metal microparticle A (polyalkylene glycol dialkyl ether B / metal microparticle A) is 0.5 or more and 1.5 or less.

[0161] Metal particles A are dispersed using dispersant D.

[0162] The metal particles A consist of one or more metals selected from silver and copper.

[0163] Polyalkylene glycol dialkyl ether B comprises at least one selected from polyoxyethylene dimethyl ether and polyoxypropylene dimethyl ether.

[0164] Polyol C includes at least one selected from ethylene glycol, 1,2-propanediol, 1,4-butanediol, and glycerol.

[0165] Dispersant D contains a vinyl polymer comprising structural units derived from monomers (d-2) having carboxyl groups.

[0166] <4> The metal particle dispersion as described in any one of <1> to <3>, wherein the content of metal particles A in the metal particle dispersion is 10% by mass or more and 50% by mass or less.

[0167] <5> The metal particle dispersion as described in any one of <1> to <4>, wherein the combined content of silver and copper in metal particles A is 80% by mass or more.

[0168] <6> The metal microparticle dispersion as described in any one of <1> to <5>, wherein the mass ratio of the content of dispersant D in the metal microparticle dispersion relative to the total amount of dispersant D and metal microparticle A [dispersant D / (dispersant D + metal microparticle A)] is 0.01 or more and 0.3 or less.

[0169] <7> The metal microparticle dispersion as described in any one of <1> to <6>, wherein the mass ratio of polyol C to metal microparticle A in the metal microparticle dispersion (polyol C / metal microparticle A) is 0.5 or more and 1.3 or less.

[0170] <8> The metal microparticle dispersion as described in any one of <1> to <7>, wherein the mass ratio of polyol C to metal microparticle A in the metal microparticle dispersion (polyol C / metal microparticle A) is 0.5 or more and 1.0 or less.

[0171] <9> The metal microparticle dispersion as described in any one of <1> to <8>, wherein the content of polyalkylene glycol dialkyl ether B in the metal microparticle dispersion is 5% by mass or more and 50% by mass or less.

[0172] <10> The metal microparticle dispersion as described in any one of <2> to <9>, wherein the total content of one or more of the polyalkylene glycol dialkyl ether B selected from polyoxyethylene dialkyl ethers with 1 or more and 5 or less carbon atoms of alkyl groups and polyoxypropylene dialkyl ethers with 1 or more and 5 or less carbon atoms of alkyl groups is 80% by mass or more.

[0173] <11> The metal microparticle dispersion as described in any one of <3> to <9>, wherein the total content of one or more of the polyalkylene glycol dialkyl ether B selected from polyoxyethylene dimethyl ether and polyoxypropylene dimethyl ether is 80% by mass or more.

[0174] <12> The metal microparticle dispersion as described in any one of <1> to <11>, wherein the content of polyol C in the metal microparticle dispersion is 3% by mass or more and 40% by mass or less.

[0175] <13> The metal microparticle dispersion as described in any one of <2> to <12>, wherein the total content of one or more of the polyol C selected from 1,2-alkyldiol, polyalkylene diol, α,ω-alkyldiol and glycerol is 80% by mass or more.

[0176] <14> The metal microparticle dispersion as described in any one of <3> to <12>, wherein the total content of one or more of the polyol C selected from ethylene glycol, 1,2-propanediol, 1,4-butanediol and glycerol is 80% by mass or more.

[0177] <15> The metal particulate dispersion as described in any one of <1> to <14>, wherein the polyalkylene glycol dialkyl ether B comprises polyoxyethylene dimethyl ether.

[0178] <16> The metal microparticle dispersion as described in <15>, wherein the content of polyoxyethylene dimethyl ether in the polyalkylene glycol dialkyl ether is 80% by mass or more.

[0179] <17> The metal particulate dispersion as described in any one of <1> to <16>, wherein the number average molecular weight of the polyalkylene glycol dialkyl ether B is 100 or more and 1,500 or less.

[0180] <18> The metal particulate dispersion as described in any one of <1> to <17>, wherein the number average molecular weight of polyalkylene glycol dialkyl ether B is 160 or more and 800 or less.

[0181] <19> The metal particulate dispersion as described in any one of <1> to <18>, wherein the dispersant D is a vinyl polymer comprising structural units derived from a monomer (d-2) having a carboxyl group and structural units derived from a monomer (d-1) having a polyoxyalkylene group.

[0182] <20> An ink containing any one of the metal microparticle dispersions described in <1> to <19>.

[0183] <21> The ink as described in <20>, wherein the ink is for inkjet printing.

[0184] <22> A method for manufacturing a printed matter, wherein the ink described in <20> or <21> is applied to a printing substrate to obtain a printed matter having a metal film formed thereon.

[0185] Example

[0186] In the following synthesis examples, manufacturing examples, embodiment examples and comparative examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified.

[0187] (1) Determination of the number-average molecular weight of vinyl polymers

[0188] Phosphoric acid and lithium bromide were dissolved in N,N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively. The resulting liquid was used as the eluent. Gel permeation chromatography was performed using a GPC apparatus (HLC-8320GPC) manufactured by Tosoh Corporation, and columns manufactured by Tosoh Corporation (TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgelguardcolumn Super AW-H), with a flow rate of 0.5 mL / min. Monodisperse polystyrene kits with known molecular weights (PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500), manufactured by Tosoh Corporation) were used as standards.

[0189] The sample was tested by mixing 0.1 g of polymer with 10 mL of the above eluent in a glass bottle, stirring with a magnetic stirrer at 25 °C for 10 hours, and filtering the sample through a syringe filter (DISMIC-13HP PTFE 0.2 μm, manufactured by ADVANTEC Co., Ltd.).

[0190] (2) Determination of the concentration of solid components in metal particulate dispersions or inks

[0191] In 30 ml of glass solvent ( 10.0 g of sodium sulfate, which has been constant in a desiccator (height = 30 mm), was measured into a container. Approximately 1.0 g of sample was added, and the mixture was accurately weighed. The mixture was then kept at 150°C and 60 Torr for 10 hours to remove volatile components. After further placing the mixture in a desiccator at room temperature (25°C) for 15 minutes, the mass was measured. The mass of the sample after removing volatile components was taken as the solid content, and divided by the mass of the added sample to determine the solid content concentration.

[0192] (3) Calculation of content-to-mass ratio [dispersant D / (dispersant D + metal particles A)]

[0193] The obtained metal particle dispersion or ink was freeze-dried using a freeze dryer (Tokyo Rikka Kyokai Co., Ltd., model: DRC-1000) equipped with a drying chamber (Tokyo Rikka Kyokai Co., Ltd., model: FDU-2110) under drying conditions (freezing at -25°C for 1 hour, depressurization at -10°C for 9 hours, depressurization at 25°C for 5 hours, depressurization degree of 5 Pa), thereby obtaining a dried metal particle powder containing dispersant D.

[0194] For this dried metal particle powder, a differential thermogravimetric analysis (TG / DTA) apparatus (manufactured by Hitachi High-Tech Science Inc., trade name: STA7200RV) was used. 10 mg of sample was placed in an aluminum crucible, and the temperature was increased from 35 °C to 550 °C at a rate of 10 °C / min. The mass loss was measured under an air flow of 50 mL / min. The mass loss from 35 °C to 550 °C was taken as the mass of dispersant D, and the remaining mass at 550 °C was taken as the mass of metal particles A. The content-mass ratio [dispersant D / (dispersant D + metal particles A)] was calculated.

[0195] (4) Calculation of the content (metal concentration) of metal particles A in metal particulate dispersions or inks.

[0196] Based on the mass ratio [dispersant D / (dispersant D + metal particle A)] obtained in (3) above and the solid component concentration of the metal particle dispersion or ink obtained in (2) above, the content (metal concentration) of metal particle A in the metal particle dispersion or ink can be calculated.

[0197] (5) Cumulative average particle size of metal particles A in the metal particle dispersion

[0198] The cumulative average particle size of metal particles A in the metal particle dispersion was determined by cumulative analysis using a laser particle analysis system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.). The measurement conditions were: temperature 25°C, incident light angle with detector 90°, 100 cumulative analyses, and the refractive index of water (1.333) was used as the dispersion solvent. The sample concentration was 5 × 10⁻⁶. -3 Mass % (conversion of solid component concentration).

[0199] Synthesis Example 1 (Synthesis of Dispersant D1)

[0200] In a 1000mL four-necked round-bottom flask equipped with a thermometer, a 200mL dropping funnel (1) with nitrogen bypass, a 50mL dropping funnel (2) with nitrogen bypass, and a reflux device, 100g of ion-exchanged water was added. The mixture was stirred vigorously with a magnetic stirrer, and the internal temperature of the flask was heated to 80°C using an oil bath. Nitrogen bubbling was then performed for 10 minutes. Then, 97g of methoxy polyethylene glycol (EO9 mol) acrylate (NK Ester AM-90G manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), 3g of 98% acrylic acid (manufactured by Fujifilm and Kohden Chemical Co., Ltd., premium reagent), and 1.5g of 3-mercaptopropionic acid (manufactured by Fujifilm and Kohden Chemical Co., Ltd., premium reagent) were dissolved in a plastic beaker and placed in the dropping funnel (1). Next, 20g of ion-exchanged water and 2g of ammonium persulfate (manufactured by Fujifilm and Koichi Chemical Co., Ltd., premium reagent) were dissolved in a plastic beaker and placed in a dropping funnel (2). Then, the mixture in the dropping funnel (1) and the dropping funnel (2) were added dropwise to the above flask simultaneously over 90 minutes. Then, the internal temperature of the flask was raised to 90°C and stirred for another hour. Then, it was cooled to room temperature to obtain a solution of dispersant D1 (methoxy polyethylene glycol (EO9 mol) acrylate / acrylic acid copolymer, Mn: 4,200, acid value: 23 mg KOH / g).

[0201] Synthesis Example 2 (Synthesis of Dispersant D2)

[0202] In Synthesis Example 1, methoxy polyethylene glycol (EO9 mol) acrylate (Shin-Nakamura Chemical) was not used, and 98% acrylic acid was replaced with 100 g. Otherwise, the same synthesis was carried out to obtain a solution of dispersant D2 (polyacrylic acid, Mn: 1,100, acid value: 780 mg KOH / g).

[0203] Manufacturing Example 1 (Manufacturing of Silver Microparticle Dry Powder 1)

[0204] Add 23g of N,N-dimethylethanolamine as a reducing agent to a 100mL glass beaker, and heat it to 40℃ in an oil bath while stirring with a magnetic stirrer.

[0205] Add 140g of silver nitrate as a metal raw material compound, 8g of a substance that makes the dispersant D1 obtained in Synthesis Example 1 in an oven-dry state, and 70g of ion-exchanged water to another 100mL beaker. Stir the mixture at 40°C using a magnetic stirrer until it becomes transparent to the naked eye, and obtain a mixture.

[0206] Next, the above mixture was added to a 1000 mL dropping funnel, and then added dropwise over 30 minutes to N,N-dimethylethanolamine in the glass beaker maintained at 40°C. The reaction mixture was then stirred for 5 hours in an oil bath while maintaining the temperature at 40°C, followed by air cooling to obtain a dark brown dispersion containing dispersed silver particles.

[0207] The total volume of the obtained dispersion was added to a dialysis tube (manufactured by REPLIGEN, trade name: Spectra / por 6, dialysis membrane: regenerated cellulose, molecular weight cutoff (MWCO) = 50K), and the tube was sealed at both ends using a closer. The tube was then immersed in 5L of ion-exchange water in a 5L glass beaker, and the water temperature was maintained at 20-25°C while stirring for 1 hour. This process was repeated three times, with the entire volume of ion-exchange water being exchanged every hour. Samples were then taken every hour, diluted with ion-exchange water, and the standard was reached when the conductivity of the silver particle dispersion was 7 mS / m at a silver concentration of 1%. This resulted in the purified silver particle dispersion.

[0208] The dispersion of refined silver microparticles was freeze-dried using a freeze dryer (Tokyo Rika Kiki Co., Ltd., model: DRC-1000) equipped with a drying chamber (Tokyo Rika Kiki Co., Ltd., model: FDU-2110) under the following drying conditions (freezing at -25°C for 1 hour, reducing pressure at -10°C for 9 hours, and reducing pressure at 25°C for 5 hours, with a pressure reduction of 5 Pa) to obtain silver microparticle dried powder 1 containing dispersant D1.

[0209] Manufacturing Example 2 (Manufacturing of Silver Microparticle Dry Powder 2)

[0210] In manufacturing example 1, dispersant D2 obtained in synthesis example 2 was used instead of dispersant D1, and silver microparticle dry powder 2 containing dispersant D2 was obtained in the same way.

[0211] Manufacturing Example 3 (Manufacturing of Copper Particle Dry Powder 1)

[0212] Add 205g of copper sulfate pentahydrate (manufactured by Fujifilm and Kohden Chemical Co., Ltd., premium reagent) as a metal raw material compound, 8g of a substance that makes the dispersant D1 obtained in Synthesis Example 1 in an oven-dry state as dispersant D, and 1000g of ion-exchanged water to a 2L beaker. Stir the mixture at 40°C using a magnetic stirrer until it becomes transparent to the naked eye, and obtain a mixture.

[0213] Next, 13 g of hydrazine 1-hydrate (manufactured by Fujifilm and Koichi Chemical Co., Ltd., premium grade reagent) was added to a 50 mL dropping funnel, and the hydrazine 1-hydrate was added dropwise to the above mixture in the beaker over 60 minutes at room temperature. Then, the reaction solution was stirred for 5 hours while maintaining the temperature at 40°C in an oil bath, followed by air cooling, to obtain a reddish-brown dispersion containing dispersed copper particles.

[0214] The entire dispersion was added to a dialysis tube (REPLIGEN, trade name: Spectra / por 6, dialysis membrane: regenerated cellulose, molecular weight cutoff (MWCO) = 50K), and the tube was sealed at both ends using a closer. The tube was then immersed in 5L of ion-exchange water in a 5L glass beaker, and the water temperature was maintained at 20-25°C with stirring for 1 hour. This process was repeated three times, with the entire volume of ion-exchange water exchanged every hour. Samples were taken every hour, diluted with ion-exchange water, and the dialysis was terminated when the conductivity of the copper particle dispersion reached 7 mS / m (when the copper concentration was adjusted to 1%), yielding a purified copper particle dispersion.

[0215] The refined copper microparticle dispersion was freeze-dried using a freeze dryer (Tokyo Rika Kiki Co., Ltd., model: DRC-1000) equipped with a drying chamber (Tokyo Rika Kiki Co., Ltd., model: FDU-2110) under the following drying conditions (freezing at -25°C for 1 hour, reducing pressure at -10°C for 9 hours, and reducing pressure at 25°C for 5 hours, with a pressure reduction of 5 Pa) to obtain copper microparticle dried powder 1 containing dispersant D1.

[0216] Example 1

[0217] (1) Manufacturing of metal particle dispersion 1

[0218] 150 g of the dried silver microparticle powder obtained in Manufacturing Example 1 (45 g of silver as metal microparticle A), 45 g of polyethylene glycol dimethyl ether (manufactured by Fujifilm and Koko Pure Chemical Industries, Ltd., number average molecular weight 240, premium grade), 35 g of 1,2-propanediol (manufactured by Fujifilm and Koko Pure Chemical Industries, Ltd., premium grade), and 20 g of deionized water were added to a 500 mL polyethylene beaker. The mixture was dispersed for 1 hour using an ultrasonic disperser (manufactured by Nippon Seiki Co., Ltd., US-3001) while stirring with a magnetic stirrer. Then, the dispersion was filtered using a 5 μm disposable membrane filter (manufactured by Sartorius, Minisart) to obtain metal microparticle dispersion 1. The cumulative average particle size of metal microparticle A (silver microparticles) in metal microparticle dispersion 1 was 21 nm. The obtained metal microparticle dispersion 1 was evaluated using the methods described below.

[0219] (2) Inkjet printing

[0220] The obtained metal particle dispersion 1 was used as ink, and the black cartridge of an inkjet printer (manufactured by Hewlett-Packard Co., model: desktop inkjet 6122, thermal) was reloaded under an environment of 25±1℃ and 30±5% relative humidity. Next, a cleaning operation was performed using the printer's utility program. Starting from a state where all nozzles of the black head could eject without problems, a solid image (204mm x 275mm) created in Photoshop (registered trademark) with RGB set to 0 was printed on a commercially available paper substrate (manufactured by Arjowggings, PowercoatXD) using the inkjet printer. [Printing conditions: Paper type: photo glossy paper, Mode setting: clean, grayscale]

[0221] Next, the paper substrate with the ink coating was heated on a hot plate at 150°C for 10 minutes, and then stored at 25°C and 55% humidity for 24 hours to obtain a printed material with a metallic film. The obtained printed material was then evaluated using the methods described below.

[0222] Examples 2-13 and Comparative Examples 1-5

[0223] In Example 1, metal particle dispersions 2-13 and 51-55 were obtained similarly, except that the formulations were changed to those shown in Table 1. The cumulative average particle size of the metal particles in each metal particle dispersion is shown in Table 1. Using these metal particle dispersions as inks, printed materials were obtained respectively by the same method as in Example 1. The obtained metal particle dispersions and printed materials were respectively evaluated by the methods described below.

[0224] The details of each component in Table 1 are as follows.

[0225] PAGDA-1: Polyethylene glycol dimethyl ether (manufactured by Fujifilm and Kohden Chemical Co., Ltd., number average molecular weight 240, premium grade)

[0226] PAGDA-2: Polypropylene glycol dimethyl ether (manufactured by Fujifilm and Kohden Chemical Co., Ltd., number average molecular weight 250, premium grade)

[0227] PAGDA-3: Tripropylene glycol dipentyl ether (manufactured by Fujifilm and Koko Pure Chemical Industries, Ltd., number average molecular weight 220, premium grade)

[0228] PAGDA-4: Triethylene glycol dimethyl ether (manufactured by Fujifilm and Kazuko Pure Chemical Industries, Ltd., number average molecular weight 178, premium grade)

[0229] PAGDA-5: Polyethylene glycol dimethyl ether (manufactured by Sigma-Aldrich Corporation, number average molecular weight 1100)

[0230] PAGDA-6: Polyethylene glycol dimethyl ether (manufactured by Sigma-Aldrich Corporation, number average molecular weight 600).

[0231] PAG-1: Polyethylene glycol 300 (manufactured by Sigma-Aldrich Corporation, number average molecular weight 300)

[0232] PG: 1,2-Propanediol

[0233] BG: 1,4-Butanediol

[0234] <Evaluation>

[0235] [Evaluation of preservation stability]

[0236] The viscosity of the metal particle dispersions obtained in the examples and comparative examples at 25°C was measured using an E-type viscometer "TV-25" (manufactured by Toki Sangyo Co., Ltd., using a standard conical rotor 1°34'×R24, rotation speed 50 rpm). This measured value was taken as "viscosity before storage stability test (I)". Furthermore, the viscosity of the ink stored in a 60°C oven for 6 weeks was also measured in the same way, and this measured value was taken as "viscosity after storage stability test (II)". Next, the viscosity change rate before and after the storage stability test was calculated using the following formula, which was used as an indicator of storage stability. The results are shown in Table 1. The closer the viscosity change rate is to 100%, the better the storage stability.

[0237] Viscosity change rate (%) = [Viscosity after storage stability test (II) / Viscosity before storage stability test (I)] × 100

[0238] [Evaluation of surface resistivity]

[0239] For the printed materials obtained in the examples and comparative examples, a stainless steel razor (manufactured by Feather Safety Razor Co., Ltd., 76 razor, blade thickness 76μm) was used to cut vertically from the side opposite to the surface on which the metal film was formed, cutting a size of 1cm × 2cm.

[0240] Next, using a resistivity meter (body: Loresta-GP, four-probe detector: PSP probe, both manufactured by Mitsubishi Chemical Analyzer), the surface resistivity (Ω / □) of the cut sample was measured to two decimal places. Measurements were also performed at other locations on the sample, and the surface resistivity ρs (Ω / □) was obtained by arithmetic averaging of 10 measurements. The results are shown in Table 1.

[0241] The lower the surface resistivity ρs, the better the conductivity.

[0242]

[0243] As shown in Table 1, compared with Comparative Examples 1 to 5, Examples 1 to 13 have viscosity change rates close to 100%, excellent storage stability, low surface resistivity, and therefore excellent conductivity.

[0244] Industrial applications

[0245] According to the present invention, a metal particle dispersion with excellent stability even at temperatures above room temperature and an ink containing the metal particle dispersion can be obtained. Furthermore, a printed material having a metal film with low resistivity can be obtained. Therefore, the metal particle dispersion and the ink containing the metal particle dispersion are suitable for use in various fields.

Claims

1. A metal particulate dispersion, wherein, Contains: metal microparticles A, polyalkylene glycol dialkyl ethers B, and polyols C. As the mass ratio of polyalkylene glycol dialkyl ether B to metal particles A, the ratio of polyalkylene glycol dialkyl ether B to metal particles A is 0.5 or more and 1.5 or less. Metal particles A are dispersed using dispersant D. The total content of polyalkylene glycol dialkyl ether B and polyol C in the metal microparticle dispersion is more than 40% by mass and less than 70% by mass.

2. The metal microparticle dispersion according to claim 1, wherein, As the mass ratio of polyol C to metal particle A, the ratio of polyol C / metal particle A is 0.1 or more and 1.3 or less.

3. The metal particle dispersion according to claim 1 or 2, wherein, Polyol C contains at least one selected from 1,2-alkyldiol, polyalkylene glycol, α,ω-alkyldiol and glycerol.

4. The metal particle dispersion according to claim 3, wherein, In polyol C, the total content of 1,2-alkyldiol, polyalkylene diol, α,ω-alkyldiol and glycerol is more than 80% by mass.

5. The metal particle dispersion according to claim 1 or 2, wherein, Polyol C includes at least one selected from ethylene glycol, 1,2-propanediol, 1,4-butanediol and glycerol.

6. The metal particle dispersion according to claim 5, wherein, In polyol C, the total content of ethylene glycol, 1,2-propanediol, 1,4-butanediol and glycerol is more than 80% by mass.

7. The metal microparticle dispersion according to claim 1 or 2, wherein, The content of polyol C in the metal microparticle dispersion is more than 3% by mass and less than 40% by mass.

8. The metal microparticle dispersion according to claim 1 or 2, wherein, The polyalkylene glycol dialkyl ether B comprises at least one of the following: polyoxyethylene dialkyl ethers having 1 or more and 5 or fewer carbon atoms in the alkyl group, and polyoxypropylene dialkyl ethers having 1 or more and 5 or fewer carbon atoms in the alkyl group.

9. The metal particulate dispersion according to claim 1 or 2, wherein, The number average molecular weight of polyalkylene glycol dialkyl ether B is above 100 and below 1,500.

10. The metal particulate dispersion according to claim 1 or 2, wherein, The polyalkylene glycol dialkyl ether B is selected from at least one of polyoxyethylene dialkyl ether and polyoxypropylene dialkyl ether.

11. The metal particulate dispersion according to claim 1 or 2, wherein, Polyoxyethylene dialkyl ether B comprises at least one selected from polyoxyethylene dimethyl ether, polyoxyethylene diethyl ether, polyoxyethylene dipropyl ether, polyoxyethylene dibutyl ether, polyoxyethylene dipentyl ether, and triethylene glycol dimethyl ether.

12. The metal particulate dispersion according to claim 1 or 2, wherein, Polyoxypropylene dialkyl ether B comprises at least one selected from polyoxypropylene dimethyl ether, polyoxypropylene diethyl ether, polyoxypropylene dipropyl ether, polyoxypropylene dibutyl ether, polyoxypropylene dipentyl ether, and tripropylene glycol dipentyl ether.

13. The metal particulate dispersion according to claim 1 or 2, wherein, Polyalkylene glycol dialkyl ether B contains polyoxyethylene dimethyl ether with a number average molecular weight of 160 or higher and 1500 or lower.

14. The metal particulate dispersion according to claim 13, wherein, The total content of polyoxyethylene dimethyl ether with a number average molecular weight of 160 or more and 1500 or less in polyalkylene glycol dialkyl ether B is 80% by mass or more.

15. The metal particulate dispersion according to claim 1 or 2, wherein, The mass ratio of polyalkylene glycol dialkyl ether B to polyol C in the metal microparticle dispersion is 0.3 or more and 2.5 or less.

16. The metal particulate dispersion according to claim 1 or 2, wherein, The content of polyalkylene glycol dialkyl ether B in the metal microparticle dispersion is more than 5% by mass and less than 50% by mass.

17. The metal particulate dispersion according to claim 1 or 2, wherein, Dispersant D contains a vinyl polymer, which comprises structural units derived from a monomer (d-2) having a carboxyl group.

18. The metal particulate dispersion according to claim 1 or 2, wherein, Dispersant D contains a vinyl polymer, which comprises structural units derived from a monomer (d-2) having a carboxyl group and structural units derived from a monomer (d-1) having a polyoxyalkylene group.

19. The metal particulate dispersion according to claim 1 or 2, wherein, Dispersant D is a vinyl polymer, which comprises a structural unit derived from at least one monomer selected from (meth)acrylic acid and maleic acid as monomer (d-2) and a structural unit derived from alkoxy polyalkylene glycol (meth)acrylate as monomer (d-1).

20. The metal particulate dispersion according to claim 17, wherein, Vinyl polymers have an acid value of 5 mg KOH / g or higher and 200 mg KOH / g or lower.

21. The metal particulate dispersion according to claim 17, wherein, The content of structural units derived from monomers (d-2) with carboxyl groups in vinyl polymers is more than 1% by mass and less than 50% by mass.

22. The metal particulate dispersion according to claim 18, wherein, The content of structural units derived from monomers (d-1) with polyoxyalkylene groups in vinyl polymers is more than 50% by mass and less than 99% by mass.

23. The metal particulate dispersion according to claim 18, wherein, The mass ratio of structural units derived from monomers (d-2) having carboxyl groups to structural units derived from monomers (d-1) having polyoxyalkylene groups in vinyl polymers is 0.01 or more and 1 or less.

24. The metal particulate dispersion according to claim 1 or 2, wherein, Dispersant D is polycarboxylic acid.

25. The metal particulate dispersion according to claim 1 or 2, wherein, The content of metal particles A in the metal particle dispersion is more than 10% by mass and less than 50% by mass.

26. The metal particulate dispersion according to claim 1 or 2, wherein, The mass ratio of dispersant D to the total amount of dispersant D and metal particles A in the metal particle dispersion is 0.01 or more and 0.3 or less.

27. The metal microparticle dispersion according to claim 1 or 2, wherein, The metal that makes up the metal particle A includes one or more metals selected from silver and copper.

28. The metal particulate dispersion according to claim 1 or 2, wherein, The cumulative average particle size of metal particles A is greater than 10 nm and less than 100 nm.

29. An ink, wherein, The metal microparticle dispersion contains any one of claims 1 to 28.

30. The ink according to claim 29, wherein, Used for inkjet printing.

31. A method for manufacturing printed matter, wherein, The ink described in claim 29 or 30 is applied to a printing substrate to obtain a printed matter with a metal film formed thereon.

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