JP7217108B2 - Method for producing water-based fine metal particle dispersion - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a water-based fine metal particle dispersion, a metallic printing ink containing the water-based fine metal particle dispersion, and a metallic printing method using the ink.

Metal fine particles are expected to develop a wide variety of industrial applications due to the variety of functions and physical properties that are realized by using metals that have been miniaturized to nanosize.
In order to promote the industrial use of metal fine particles, various methods for producing metal fine particles have been investigated. For example, as chemical methods for producing metal atoms, wet methods such as a method of reducing metal ions eluted from a metal compound in a liquid and a method of extracting metal atoms by thermal decomposition of a metal complex are known. The method using a metal complex requires heat treatment at high temperatures, and the reducing solution used for reducing the metal complex has problems related to the removal of residual organic substances. .

For example, in Patent Document 1, for the purpose of providing colloidal metal particles having excellent storage stability, etc., a metal compound corresponding to metal nanoparticles is mixed with an organic compound having a carboxyl group and a polymer dispersant. A method for producing metal colloid particles composed of metal nanoparticles and a protective colloid covering the metal nanoparticles by reduction in a solvent in the presence of the constituent protective colloid and a reducing agent is described.
Patent Document 2 describes the existence of a metal nanoparticle-protecting polymer having a polyacetylalkyleneimine N-oxide segment and a hydrophilic segment for the purpose of providing a method for producing a metal colloid solution having dispersion stability and the like. Below, a method for producing a metal colloid solution in which metal ions are reduced in a medium to form metal nanoparticles, and the like are described.

JP 2009-74171 A Japanese Patent Application Publication No. 2016-511773

However, in the techniques of Patent Documents 1 and 2, there is a problem that the dispersion stability of the metal fine particles is not sufficient, and the metal fine particles aggregate and settle.
An object of the present invention is to provide a method for producing a water-based fine metal particle dispersion having excellent sedimentation resistance of metal fine particles, a metallic printing ink containing the water-based fine metal particle dispersion, and a metallic printing method using the ink. and
Here, in this specification, the sedimentation resistance of fine metal particles is simply referred to as "sedimentation resistance".

The inventors of the present invention include the step of adding a mixture containing a metal source compound, a polymer having a carboxyl group, and an aqueous solvent to an amine compound that is a reducing agent, and charging the amine compound and the metal source compound. Focusing on the fact that aggregation and sedimentation of fine metal particles can be controlled by setting the molar ratio to a predetermined range, the present inventors have found that the above problems can be solved.

That is, the present invention relates to the following [1] to [3].
[1] A method for producing a water-based fine metal particle dispersion containing fine metal particles a dispersed with a polymer B,
including a step 1 of adding a mixed liquid I containing a metal source compound A, a polymer B, and an aqueous solvent C to an amine compound D;
Polymer B has a carboxy group,
A method for producing a water-based fine metal particle dispersion, wherein the charging molar ratio of amine compound D and metal source compound A [amine compound D/metal source compound A] is 3.0 or more.
[2] A metallic printing ink containing the water-based fine metal particle dispersion obtained by the production method described in [1] above.
[3] A metallic printing method comprising printing on a resin film using the metallic printing ink described in [2] above.

According to the present invention, there are provided a method for producing a water-based fine metal particle dispersion having excellent sedimentation resistance of metal fine particles, a metallic printing ink containing the water-based fine metal particle dispersion, and a metallic printing method using the ink. can be done.

[Method for producing water-based fine metal particle dispersion]
The present invention is a method for producing an aqueous metal fine particle dispersion (hereinafter also referred to as "metal fine particle dispersion") containing metal fine particles a (hereinafter also referred to as "metal fine particle a") dispersed with a polymer B, , a metal source compound A, a polymer B, and an aqueous solvent C, including a step 1 of adding a mixed liquid I containing an aqueous solvent C to an amine compound D, the polymer B having a carboxy group, and the amine compound D and the metal source compound A is charged molar ratio [amine compound D/metal source compound A] of 3.0 or more.

The metal fine particle dispersion obtained by the production method of the present invention is obtained by dispersing metal fine particles a in an aqueous medium. Here, the form of the fine metal particles a is not particularly limited as long as the particles are formed of at least the fine metal particles and the polymer B. For example, a particle form in which the metal fine particles are encapsulated in the polymer B, a particle form in which the metal fine particles are uniformly dispersed in the polymer B, and a particle form in which the metal fine particles are exposed on the particle surface of the polymer B are included. Mixtures are also included.
The term "aqueous" means that water accounts for the maximum proportion in the aqueous medium.

According to the present invention, a fine metal particle dispersion having excellent sedimentation resistance of fine metal particles can be obtained. Although the reason is not clear, it is considered as follows.
In the production method of the present invention, a mixture containing a metal source compound, a polymer, and an aqueous solvent is added to an amine compound as a reducing agent. First, in the mixed solution, a polymer having a carboxyl group that functions as a dispersant adsorbs or coordinates to metal ions, thereby improving the stability of the metal ions. Then, by adding a mixed solution containing metal ions while maintaining stability to the amine compound, and further by adjusting the charging molar ratio of the amine compound and the metal source compound to a predetermined range, in the process of forming metal fine particles by a reduction reaction, , excessive aggregation of metal ions is suppressed, and the generation of coarse metal fine particles is suppressed. As a result, it is considered that a metal fine particle dispersion containing fine metal fine particles can be obtained with high dispersion stability, and sedimentation resistance is improved.

(Step 1)
Step 1 is a step of adding to amine compound D mixed liquid I containing metal source compound A, polymer B, and aqueous solvent C (hereinafter also referred to as “mixed liquid I”). In the mixed liquid I, the polymer B adsorbs or coordinates to the metal ions, and can improve the stability of the metal ions. Then, by adding the mixed liquid I to the amine compound D, the metal ions are reduced by a reductive reaction, the generated metal atoms are moderately aggregated, and fine metal microparticles a are formed.
Mixed liquid I can be obtained by mixing metal source compound A, polymer B and aqueous solvent C by a known method.

<Metal source compound A>
The metals (metal atoms) contained in the metal source compound A include Group 4 transition metals such as titanium and zirconium; Group 5 transition metals such as vanadium and niobium; and Group 6 transition metals such as chromium, molybdenum and tungsten. Metals, 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, 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, germanium, tin, and lead. Group 14 metals such as One of the metals may be used alone, or two or more of them may be used in combination as an alloy. Among them, it is preferably a transition metal of the 4th to 6th periods in Groups 4 to 11, more preferably a noble metal such as copper, gold, silver, platinum, palladium, and more preferably gold, silver and copper. At least one selected, and more preferably silver.

Examples of the metal source compound A include metal salts of inorganic acids or organic acids, metal oxides, metal hydroxides, metal sulfides, metal halides, etc. containing the aforementioned metals. Examples of the metal salt include inorganic acid metal salts such as nitrates, nitrites, sulfates, carbonates, ammonium salts, and perchlorates; and organic acid metal salts such as acetates. The metal source compound A can be used singly or in combination of two or more. Among them, metal salts of inorganic acids or organic acids are preferred, metal salts of inorganic acids are more preferred, metal salts of nitric acid are still more preferred, and silver nitrate is still more preferred.

<Polymer B>
Polymer B according to the present invention has a function as a dispersing agent for fine metal particles.
Polymer B has carboxy groups. The carboxy group also includes a carboxy group exhibiting acidity (--COOM) or its dissociated ionic form ( ^--COO.sup.- ) by dissociating to release hydrogen ions. In the chemical formula, M represents a hydrogen atom, alkali metal, ammonium or organic ammonium. Examples of the polymer B include condensation polymers such as polyester and polyurethane; vinyl polymers and the like.

The carboxy group contained in the molecule of polymer B is preferably introduced into the polymer skeleton by the monomer (b-1) having a carboxy group. That is, the polymer B preferably contains structural units derived from the monomer (b-1) having a carboxy group. Among them, from the viewpoint of improving the sedimentation resistance, a structural unit derived from a monomer (b-1) having a carboxy group (hereinafter also referred to as "monomer (b-1)"), a hydrophobic monomer (b-2) (hereinafter , Also referred to as "monomer (b-2)") derived structural units, and a monomer having a polyalkylene glycol segment (b-3) (hereinafter also referred to as "monomer (b-3)") derived structural units Vinyl-based polymer b (hereinafter also referred to as “polymer b”) is preferred. The polymer b can be obtained by copolymerizing raw material monomers (hereinafter also simply referred to as "raw material monomers") including the monomer (b-1), the monomer (b-2) and the monomer (b-3). Polymer b may be a block copolymer, a random copolymer, or an alternating copolymer.

[Monomer (b-1) having a carboxy group]
The carboxy group contained in the monomer (b-1) is as described above.
Specific examples of the monomer (b-1) include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, and 2-methacryloyloxymethylsuccinic acid; maleic acid, itaconic acid, fumaric acid, citraconic acid, and the like. and unsaturated dicarboxylic acids. The unsaturated dicarboxylic acid may be an anhydride.
Monomer (b-1) may be used alone or in combination of two or more.
Monomer (b-1) is preferably at least one selected from (meth)acrylic acid and maleic acid from the viewpoint of improving sedimentation resistance.
In the present invention, "(meth)acrylic acid" means at least one selected from acrylic acid and methacrylic acid. "(Meth)acrylic acid" below has the same meaning.

[Hydrophobic monomer (b-2)]
Monomer (b-2) is preferably used as a monomer component of polymer b from the viewpoint of improving sedimentation resistance.
In the present invention, the term “hydrophobic” means that the amount of the monomer dissolved in 100 g of deionized water at 25° C. until saturation is less than 10 g. The amount of the monomer (b-2) dissolved is preferably 5 g or less, more preferably 1 g or less, from the viewpoint of improving sedimentation resistance.
The monomer (b-2) is preferably at least one selected from aromatic group-containing monomers and (meth)acrylates having a hydrocarbon group derived from an aliphatic alcohol.
In the present invention, "(meth)acrylate" is at least one selected from acrylate and methacrylate. "(Meth)acrylate" below has the same meaning.

The aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group having 6 or more and 22 or less carbon atoms, which may have a substituent containing a hetero atom, more preferably a styrene-based monomer and an aromatic It is one or more selected from group-containing (meth)acrylates. The molecular weight of the aromatic group-containing monomer is preferably less than 500.
Styrene-based monomers include styrene, α-methylstyrene, 2-methylstyrene, vinyltoluene, divinylbenzene and the like, with styrene and α-methylstyrene being preferred.
As the aromatic group-containing (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate and the like are preferable, and benzyl (meth)acrylate is more preferable.

The (meth)acrylate having a hydrocarbon group derived from an aliphatic alcohol preferably has a hydrocarbon group derived from an aliphatic alcohol having 1 to 22 carbon atoms. For example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, (meth)acrylates having a linear alkyl group such as stearyl (meth)acrylate; isopropyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, isopentyl (meth)acrylate, isooctyl (meth)acrylate, (meth)acrylates having a branched chain alkyl group such as isodecyl (meth)acrylate, isododecyl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl (meth)acrylate; alicyclic alkyl such as cyclohexyl (meth)acrylate group-containing (meth)acrylates, and the like. Among these, those having an alkyl group having 6 to 10 carbon atoms are more preferable.
Monomer (b-2) may be used alone or in combination of two or more.

From the viewpoint of improving sedimentation resistance, the monomer (b-2) is preferably an aromatic group-containing monomer, more preferably a styrenic monomer, and still more preferably styrene, α-methylstyrene, 2-methylstyrene. and vinyltoluene, and more preferably at least one selected from styrene and α-methylstyrene.

[Monomer (b-3) having a polyalkylene glycol segment]
Monomer (b-3) is preferably used as a monomer component of polymer b from the viewpoint of improving sedimentation resistance.
Monomer (b-3) is preferably a monomer capable of introducing a polyalkylene glycol segment as a side chain of polymer b from the viewpoint of improving sedimentation resistance. Examples of the monomer include polyalkylene glycol (meth)acrylates, alkoxypolyalkylene glycol (meth)acrylates, phenoxyalkylene glycol (meth)acrylates, and the like. Monomer (b-3) may be used alone or in combination of two or more.

Monomer (b-3) is preferably at least one selected from polyalkylene glycol (meth)acrylates and alkoxypolyalkyleneglycol (meth)acrylates, more preferably alkoxypolyalkyleneglycol (meth)acrylates. The number of carbon atoms in the alkoxy group of the alkoxypolyalkylene glycol (meth)acrylate is preferably 1 or more and 8 or less, more preferably 1 or more and 4 or less.
Examples of the 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, octoxy Polyalkylene glycol (meth)acrylate and the like are included.

The polyalkylene glycol segment of the monomer (b-3) preferably contains units derived from an alkylene oxide having 2 to 4 carbon atoms. Examples of the alkylene oxide include ethylene oxide, propylene oxide, and butylene oxide.
The number of alkylene oxide-derived units in the polyalkylene glycol segment is preferably 2 or more, more preferably 5 or more, still more preferably 10 or more, and preferably 100 or less, more preferably 70 or less, still more preferably 50 or less.
From the viewpoint of improving sedimentation resistance, the polyalkylene glycol segment is preferably a copolymer containing units derived from ethylene oxide and units derived from propylene oxide. The molar ratio [EO/PO] between ethylene oxide units (EO) and propylene oxide units (PO) is preferably 60/40 or more, more preferably 65/35 or more, still more preferably 70/30 or more, and It is preferably 90/10 or less, more preferably 85/15 or less, still more preferably 80/20 or less.
A copolymer containing ethylene oxide-derived units and propylene oxide-derived units may be a block copolymer, a random copolymer, or an alternating copolymer.

Specific examples of commercially available monomers (b-3) include NK Ester AM-90G, NK Ester AM-130G, AMP-20GY, 230G, M-20G and 40G manufactured by Shin-Nakamura Chemical Co., Ltd. , 90G, 230G, etc.; NOF CORPORATION's Blenmer PE-90, 200, 350, etc., PME-100, 200, 400, 1000, 4000, etc., PP-500, 800, etc. 1000 etc., AP-150, 400, 550 etc., 50PEP-300, 50POEP-800B, 43PAPE-600B and the like.

(Content of each monomer component or structural unit in raw material monomer or polymer b)
The content of the monomers (b-1) to (b-3) in the raw material monomers (the content as the unneutralized amount; the same shall apply hereinafter) or the monomers (b-1) to in the polymer b at the time of producing the polymer b The content of the structural unit derived from (b-3) is as follows from the viewpoint of improving sedimentation resistance.
The content of the monomer (b-1) is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 15 mol% or more, and preferably 40 mol% or less, more preferably 35 mol%. % or less, more preferably 30 mol % or less.
The content of the monomer (b-2) is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 65 mol% or more, and preferably 90 mol% or less, more preferably 85 mol%. % or less, more preferably 80 mol % or less.
The content of the monomer (b-3) is preferably 1 mol% or more, more preferably 5 mol% or more, still more preferably 7 mol% or more, and preferably 30 mol% or less, more preferably 20 mol%. % or less, more preferably 15 mol % or less.

Polymer b includes structural units derived from (meth)acrylic acid and maleic acid as monomer (b-1), structural units derived from styrene monomers as monomer (b-2), and alkoxypolyalkylene as monomer (b-3). It preferably contains a structural unit derived from glycol (meth)acrylate.
Polymer b may be synthesized by a known method, or may be a commercially available product. Commercially available products of polymer b include DISPERBYK-190 and 2015 manufactured by BYK.

The number average molecular weight of polymer B is preferably 1,000 or more, more preferably 2,000 or more, still more preferably 3,000 or more, and preferably 100,000 or less, more preferably 50,000 or less, More preferably 30,000 or less, even more preferably 10,000 or less, still more preferably 7,000 or less. If the number average molecular weight of the polymer B is within the above range, the adsorptive power to the metal fine particles is sufficient and the dispersion stability can be exhibited. The number average molecular weight is measured by the method described in Examples.

The acid value of polymer B is preferably 5 mgKOH/g or more, more preferably 10 mgKOH/g or more, still more preferably 15 mgKOH/g or more, and preferably 200 mgKOH/g or less, more preferably 100 mgKOH/g or less, and further preferably It is preferably 50 mgKOH/g or less, more preferably 30 mgKOH/g or less.
The acid value of polymer B is measured by the method described in Examples.

<Aqueous solvent C>
The water-based solvent C preferably contains water as a main component, and may further contain an organic solvent. Examples of the organic solvent include aliphatic alcohols having 1 to 4 carbon atoms such as ethanol and 2-propanol, ketones having 3 to 8 carbon atoms such as acetone, and ethers such as tetrahydrofuran.
The content of water in the aqueous solvent C is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and even more preferably 95% by mass or more, from the viewpoint of environmental friendliness. .

<Amine compound D>
Examples of the amine compound D include ethanolamine, N-methylethanolamine, N,N-dimethylethanolamine (2-(dimethylamino)ethanol), N,N-diethylethanolamine, diethanolamine, N-methyldiethanolamine, tri alkanolamine such as ethanolamine, propanolamine, N,N-dimethylpropanolamine, triethanolamine, butanolamine, hexanolamine; propylamine, butylamine, hexylamine, diethylamine, dipropylamine, dimethylethylamine, diethylmethylamine, triethylamine Aliphatic amines such as alkylamines such as ethylenediamine, triethylenediamine, tetramethylethylenediamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine, and (poly)alkylenepolyamines such as tetraethylenepentamine; piperidine, pyrrolidine, N-methylpyrrolidine, alicyclic amines such as morpholine; aromatic amines such as aniline, N-methylaniline, toluidine, anisidine and phenetidine; aralkylamines such as benzylamine and N-methylbenzylamine; Amine compound D may be used alone or in combination of two or more.
From the viewpoint of improving sedimentation resistance, the amine compound D is preferably an alkanolamine having 2 to 6 carbon atoms, more preferably a tertiary alkanolamine having 2 to 6 carbon atoms, and still more preferably N , N-dimethylethanolamine.

In step 1, a combination of the amine compound D and another reducing agent may be used as the reducing agent. As other reducing agents, both organic reducing agents and inorganic reducing agents can be used.
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 salts thereof.
Examples of inorganic reducing agents include borohydride salts such as sodium borohydride and ammonium borohydride; aluminum hydride salts such as lithium aluminum hydride and potassium aluminum hydride; hydrazines such as hydrazine and hydrazine carbonate; is mentioned.
In addition, you may use another reducing agent individually by 1 type or in combination of 2 or more types.

(Content of each component in mixed liquid I)
The content of the metal source compound A in the mixed liquid I is preferably 20% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, and preferably 90% by mass or less, more preferably is 80% by mass or less, more preferably 70% by mass or less.
The content of polymer B in mixed liquid I is preferably 0.5% by mass or more, more preferably 1% by mass or more, still more preferably 2% by mass or more, and preferably 10% by mass or less, more preferably is 7% by mass or less, more preferably 5% by mass or less.
The content of the aqueous solvent C in the mixed liquid I is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, and preferably 60% by mass or less, more preferably It is 50% by mass or less, more preferably 40% by mass or less.
The mass ratio of polymer B to metal source compound A in mixed liquid I [polymer B/metal source compound A] is preferably 0.01 or more, more preferably 0.03 or more, and still more preferably 0.05 or more. , and is preferably 0.5 or less, more preferably 0.1 or less, and still more preferably 0.07 or less.

The temperature of the amine compound D when adding the mixed liquid I is preferably 10° C. or higher, more preferably 20° C. or higher, still more preferably 30° C. or higher, and even more preferably 35° C., from the viewpoint of improving sedimentation resistance. and preferably less than 100°C, more preferably 90°C or less, even more preferably 80°C or less, even more preferably 60°C or less, and even more preferably 50°C or less. The reduction reaction may be performed in an air atmosphere or in an inert gas atmosphere such as nitrogen gas.

The method of adding the mixed liquid I to the amine compound D is not particularly limited, and may be added all at once or dividedly, but from the viewpoint of controlling the reduction reaction and improving the sedimentation resistance, the dropping method is preferred.
The dropping speed of the mixed liquid I can be appropriately set according to the scale of production, but the dropping time of the mixed liquid I is preferably 8 hours or less, more preferably 6 hours, from the viewpoint of improving sedimentation resistance. It is more preferably 3 hours or less, still more preferably 1 hour or less, and from the viewpoint of controlling the reduction reaction, it is preferably 0.2 hours or more, more preferably 0.4 hours or more.

(Preparation amount of each component)
The charge amount of each component with respect to the total charge amount of the metal raw material compound A, the polymer B, the aqueous solvent C and the amine compound D when producing the metal fine particle dispersion is determined from the viewpoint of improving the sedimentation resistance and from the viewpoint of productivity. , as follows.
The charge amount of the metal source compound A with respect to the total charge amount of the metal source compound A, the polymer B, the aqueous solvent C, and the amine compound D is preferably 10% by mass or more, more preferably 20% by mass or more, and still more preferably 25% by mass. and preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.
The charged amount of the polymer B with respect to the total charged amount of the metal source compound A, the polymer B, the aqueous solvent C and the amine compound D is preferably 0.5% by mass or more, more preferably 1% by mass or more, and still more preferably 1.5% by mass. % by mass or more, preferably 7% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.
The charged amount of the aqueous solvent C with respect to the total charged amount of the metal source compound A, the polymer B, the aqueous solvent C and the amine compound D is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 13% by mass or more. and is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less.
The charged amount of the amine compound D with respect to the total charged amount of the metal source compound A, the polymer B, the aqueous solvent C and the amine compound D is preferably 20% by mass or more, more preferably 30% by mass or more, and still more preferably 40% by mass or more. and preferably 70% by mass or less, more preferably 65% by mass or less, and even more preferably 60% by mass or less.
The charging molar ratio of amine compound D and metal source compound A [amine compound D/metal source compound A] is 3.0 or more, and preferably 10 or less, more preferably 7 or less, and still more preferably 5 or less. , and more preferably 4 or less.

(Step 2)
In the production method of the present invention, from the viewpoint of removing impurities and improving the dispersion stability of the metal fine particles, a step 2 of further purifying the metal fine particle dispersion obtained in the step 1 (hereinafter, simply referred to as "step 2") is performed. ) is preferably included.
The dispersion of the metal source compound A after the reduction reaction contains impurities such as an unreacted reducing agent, counter ions to the metal ions, excess polymer B that does not contribute to dispersion of the metal fine particles, and the like. Therefore, these impurities can be removed by going through step 2.
The method for purifying the fine metal particle dispersion is not particularly limited, and examples thereof include membrane treatments such as dialysis and ultrafiltration, and methods such as centrifugation. Among them, membrane treatment is preferred, and dialysis is more preferred, from the viewpoint of efficiently removing impurities. As a material for the dialysis membrane used for dialysis, regenerated cellulose is preferable.
From the viewpoint of efficiently removing impurities, the molecular weight cut off of the dialysis membrane is preferably 1,000 or more, more preferably 5,000 or more, still more preferably 10,000 or more, and preferably 100,000 or less. , more preferably 70,000 or less.

For the dialysis treatment, for example, the fine metal particle dispersion obtained in step 1 was put into a cylindrical dialysis tube, both ends of the dialysis tube were sealed, and then the tube was used as a buffer and filled with a large amount of ion-exchanged water. It can be carried out by putting it in a container and leaving it for a predetermined time. As a result, impurity ions having a formula weight equal to or less than the molecular weight cutoff and polymers having a molecular weight equal to or less than the molecular weight cutoff can be removed from the fine metal particle dispersion.
From the viewpoint of treatment efficiency, the temperature of the dialysis treatment is preferably 10° C. or higher, more preferably 15° C. or higher, still more preferably 20° C. or higher, and preferably 60° C. or lower, more preferably 50° C. or lower. It is preferably 40° C. or less.
The electrical conductivity of the fine metal particle dispersion obtained in step 2 is preferably 1 mS/m or more, more It is preferably 3 mS/m or more, more preferably 5 mS/m or more, and preferably 15 mS/m or less, more preferably 13 mS/m or less, still more preferably 10 mS/m or less. Conductivity is measured by the method described in Examples.

(Step 3)
The production method of the present invention preferably further includes step 3 of concentrating the metal fine particle dispersion obtained in step 1 or step 2.
The method for concentrating the fine metal particle dispersion is not particularly limited as long as it can remove the aqueous medium contained in the fine metal particle dispersion. Among them, the method of distilling off the aqueous medium by heating or under reduced pressure is preferable. From the viewpoint of productivity, the heating temperature is preferably 35° C. or higher, more preferably 45° C. or higher, and still more preferably 55° C. or higher. It is preferably 85° C. or lower, more preferably 75° C. or lower, and even more preferably 65° C. or lower. Concentration of the fine metal particle dispersion is preferably carried out while controlling the solid content concentration of the dispersion to be within a desired range.
When the aqueous solvent C contains an organic solvent, it is preferable to remove the organic solvent together with the water in step 3. The organic solvent in the metal fine particle dispersion obtained in step 3 is preferably substantially removed, but may remain as long as the effects of the present invention are not impaired. The amount of residual organic solvent is preferably 0.1% by mass or less, more preferably 0.01% by mass or less.

The form of presence of the polymer B in the metal fine particle dispersion includes a form in which the polymer B is adsorbed to the metal fine particles, a form in which the metal fine particles are contained in the polymer B, and a form in which the metal fine particles are encapsulated (capsule), and a form in which the metal fine particles contain the polymer B. is not adsorbed. From the viewpoint of the dispersion stability of the metal fine particles, a form in which the polymer B contains the metal fine particles is preferable, and a state in which the metal fine particles are contained in the polymer B is more preferable.

In the metal fine particle dispersion obtained by the production method of the present invention, the mass ratio of polymer to the total amount of polymer B and metal [polymer B/(polymer B + metal)] is preferably 0 from the viewpoint of fine metal fine particles. 0.01 or more, more preferably 0.03 or more, still more preferably 0.05 or more, and from the viewpoint of increasing the concentration of metal fine particles, it is preferably 0.3 or less, more preferably 0.2 or less, and further It is preferably 0.1 or less.
The mass ratio [dispersant B/(dispersant B + metal)] is obtained from the mass of dispersant B and metal measured by the method described in Examples using a simultaneous differential thermogravimetric analyzer (TG/DTA). Calculated.

The cumulant average particle size of the metal fine particles a in the metal fine particle dispersion is preferably 2 nm or more, more preferably 5 nm or more, and still more preferably 10 nm, from the viewpoint of improving the dispersion stability of the metal fine particles and improving the sedimentation resistance. As described above, it is more preferably 15 nm or more, and from the viewpoint of miniaturization of metal fine particles, it is preferably 100 nm or less, more preferably 80 nm or less, even more preferably 50 nm or less, still more preferably 40 nm or less, and even more preferably 40 nm or less. 30 nm or less, more preferably 25 nm or less.
The cumulant average particle size is measured by the method described in Examples.

The metal concentration of the fine metal particle dispersion is preferably 20% by mass or more, more preferably 35% by mass or more, still more preferably 40% by mass or more, and even more preferably 45% by mass, from the viewpoint of facilitating the preparation of the ink described later. % or more, and from the viewpoint of improving the dispersion stability of the metal fine particles and improving the sedimentation resistance, the content is preferably 80% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less. , and more preferably 55% by mass or less.
The metal concentration of the fine metal particle dispersion is calculated by the method described in Examples.

The fine metal particle dispersion of the present invention may contain 1% by mass or more and 10% by mass or less of glycerin, triethylene glycol, or the like as a moisturizing agent to prevent drying depending on the application, and an antifungal agent or the like may be added. It may contain an agent. The additive may be added during the reduction reaction, or may be added after obtaining the fine metal particle dispersion.

INDUSTRIAL APPLICABILITY The fine metal particle dispersion of the present invention can be used in a wide range of applications because of its excellent sedimentation resistance of fine metal particles. For example, various inks; conductive materials such as wiring materials, electrode materials, and MLCCs (multilayer ceramic capacitors); bonding materials; various sensors; catalysts;

[Metallic printing ink]
It is preferable that the fine metal particle dispersion according to the present invention is contained in water-based ink (hereinafter also referred to as "water-based ink" or "ink") and used as ink for metallic printing. As a result, it is possible to obtain a water-based ink with excellent storage stability in which sedimentation of fine metal particles is suppressed. In addition, since the metal fine particle dispersion contains fine metal fine particles having excellent dispersion stability, a printed matter having a metal film having a high reflectance can be obtained.
From the viewpoint of storage stability, the water-based ink preferably further contains an organic solvent. The organic solvent preferably contains one or more organic solvents having a boiling point of 90° C. or higher. The weighted average boiling point of the organic solvent is preferably 150° C. or higher, more preferably 180° C. or higher, and is preferably 240° C. or lower, more preferably 220° C. or lower, and still more preferably 200° C. or lower.

Examples of the organic solvent include polyhydric alcohols, polyhydric alcohol alkyl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds. Among them, one or more selected from polyhydric alcohols and polyhydric alcohol alkyl ethers are preferable, and ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, trimethylolpropane, diethylene glycol diethyl ether and diethylene glycol monoisobutyl ether. One or more selected are more preferable, and one or more selected from propylene glycol and diethylene glycol monoisobutyl ether are even more preferable.

Water-based inks may further optionally contain fixation aids such as dispersions of polymer particles, moisturizing agents, wetting agents, penetrants, surfactants, viscosity modifiers, antifoaming agents, and preservatives, which are commonly used in water-based inks. Various additives such as agents, antifungal agents, and antirust agents can be added, and further filtration treatment using a filter or the like can be performed.
The content of each component of the water-based ink and the physical properties of the ink are as follows.

(Content of each component of water-based ink)
The content of the metal in the water-based ink is preferably 1% by mass or more, more preferably 3% by mass or more, and still more preferably 5% by mass or more, from the viewpoint of improving the print density and the reflectance of the metal film, and From the viewpoint of lowering the viscosity of the ink when the solvent is volatilized and improving the storage stability, the content is preferably 20% by mass or less, more preferably 17% by mass or less, and even more preferably 15% by mass or less.
The total content of the metal and polymer B in the water-based ink is preferably 2% by mass or more, more preferably 5% by mass or more, and still more preferably 7% by mass or more, from the viewpoint of fixability. From the viewpoint of lowering the viscosity of the ink at the time and improving the storage stability, the content is preferably 22% by mass or less, more preferably 18% by mass or less, and even more preferably 16% by mass or less.
The content of the organic solvent in the water-based ink is preferably 10% by mass or more, more preferably 20% by mass or more, and still more preferably 30% by mass or more, from the viewpoint of improving the storage stability and fixability of the ink. From the viewpoint of improving the print density and the reflectance of the metal film, the content is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less.
The content of water in the water-based ink is preferably 20% by mass or more, more preferably 30% by mass or more, and still more preferably 40% by mass or more, from the viewpoint of improving the storage stability and fixability of the ink, and , from the viewpoint of improving the print density and the reflectance of the metal film, it is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.
The mass ratio of the metal in the total solid content of the water-based ink [metal/(total solid content of the water-based ink)] is preferably 0.3 or more, more preferably 0.5 or more, still more preferably 0.7 or more, still more preferably 0.8 or more, and from the viewpoint of fixability, preferably 0.98 or less, more preferably It is 0.95 or less, more preferably 0.9 or less.

(Physical properties of water-based ink)
The cumulant average particle size of the fine metal particles a in the water-based ink is preferably the same as the average particle size in the fine metal particle dispersion. It is the same as the preferred embodiment of the diameter.
From the viewpoint of storage stability, the viscosity of the water-based ink at 32° C. is preferably 2 mPa·s or more, more preferably 3 mPa·s or more, still more preferably 5 mPa·s or more, and preferably 12 mPa·s or less. It is more preferably 9 mPa·s or less, still more preferably 7 mPa·s or less. The viscosity of water-based ink can be measured using an E-type viscometer.
The pH of the water-based ink at 20° C. is preferably 7.0 or higher, more preferably 7.2 or higher, and even more preferably 7.5 or higher, from the viewpoint of storage stability. Also, from the viewpoint of member resistance and skin irritation, the pH is preferably 11 or less, more preferably 10 or less, and even more preferably 9.5 or less. The pH of water-based ink can be measured by a conventional method.

[Metallic printing method]
The water-based ink is excellent in storage stability in which sedimentation of fine metal particles is suppressed, and a printed material having a metal film with high reflectance can be obtained. It can be suitably used for metallic printing as an ink for printing. In particular, from the viewpoint of excellent ejection stability, it is more preferable to use it as an ink for inkjet recording.
When the water-based ink is used as ink for inkjet recording, the water-based ink can be loaded into a known inkjet recording apparatus and discharged as ink droplets onto a printing medium to form an image or the like.
There are thermal type and piezo type ink jet recording apparatuses, and the water-based ink of the present invention is more preferably used as a water-based ink for piezo type ink jet recording.

Examples of printing media for the metallic printing method in which water-based ink is used include highly absorbent plain paper, low absorbent coated paper, and non-absorbent resin film. Examples of coated paper include general-purpose glossy paper, multicolor foam gloss paper, and the like. Among them, a resin film is preferable from the viewpoint of obtaining a printed matter on which a metal film having a high reflectance is formed. The resin film is preferably at least one selected from polyester film, polyvinyl chloride film, polypropylene film and polyethylene film. A corona-treated substrate may be used for the resin film.
Examples of commonly available resin films include Lumirror T60 (manufactured by Toray Industries, Inc., polyester), PVC80BP (manufactured by Lintec Corporation, vinyl chloride), DGS-210WH (manufactured by Roland DG Co., Ltd., vinyl chloride), and transparent. PVC RE-137 (manufactured by Mimaki Engineering Co., Ltd., vinyl chloride), Cainus KEE70CA (manufactured by Lintec Corporation, polyethylene), YUPO SG90 PAT1 (manufactured by Lintec Corporation, polypropylene), FOR, FOA (both manufactured by Futamura Chemical Co., Ltd., Polypropylene), Bonyl RX (manufactured by Kohjin Film & Chemicals Co., Ltd., nylon), Emblem ONBC (manufactured by Unitika Ltd., nylon), and the like.

In the following examples and comparative examples, "parts" and "%" are "mass parts" and "mass%" unless otherwise specified.

(1) Measurement of number average molecular weight of polymer B Gel permeation chromatography was performed using a solution obtained by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol/L and 50 mmol/L, respectively, as an eluent. As a standard substance by the graphy method [Tosoh Corporation GPC device (HLC-8320GPC), Tosoh Corporation column (TSKgel Super AWM-H, TSKgel Super AW3000, TSKgel guardcolumn Super AW-H), flow rate: 0.5 mL / min] Monodisperse polystyrene kit with known molecular weight [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].
A sample to be measured was obtained by mixing 0.1 g of polymer with 10 mL of the above eluent in a glass vial, stirring with a magnetic stirrer at 25° C. for 10 hours, and using a syringe filter (DISMIC-13HP PTFE 0.2 μm, Advantech Co., Ltd.). and used after filtration.

(2) Measurement of acid value of polymer B The acid value of polymer B was measured based on the method of JIS K 0070. However, only the measurement solvent was changed from the mixed solvent of ethanol and ether defined in JIS K 0070 to a mixed solvent of acetone and toluene (acetone:toluene=4:6 (volume ratio)).

(3) Measurement of Cumulant Average Particle Diameter of Metal Fine Particles a Cumulant analysis was performed using a laser particle analysis system “ELS-8000” (manufactured by Otsuka Electronics Co., Ltd.) to measure the cumulant average particle diameter. The measurement conditions were a temperature of 25° C., an angle between the incident light and the detector of 90°, and 100 integration times, and the refractive index of water (1.333) was input as the refractive index of the dispersion solvent. The concentration of the sample to be measured was 5×10 ⁻³ % (converted to solid concentration).

(4) Measurement of Solid Content Concentration of Metal Fine Particle Dispersion Into a 30 ml polypropylene container (φ=40 mm, height=30 mm) was weighed 10.0 g of sodium sulfate which had been made constant in a desiccator, and about 1.0 g of a sample was placed therein. After adding 0 g and mixing, weigh accurately, maintain at 105 ° C. for 2 hours to remove volatiles, and after further standing in a desiccator at room temperature (25 ° C.) for an additional 15 minutes, weigh was measured. The mass of the sample after removing the volatile matter was defined as the solid content, and the mass of the added sample was divided to obtain the solid content concentration.

(5) Calculation of Mass Ratio [Polymer B/(Polymer B+Metal)] The obtained metal fine particle dispersion is subjected to a freeze dryer (Tokyo Rika Kikai Co., Ltd., model: FDU-2110), freeze-drying under the drying conditions (freezing at -25 ° C. for 1 hour, reducing pressure at -10 ° C. for 9 hours, reducing pressure at 25 ° C. for 5 hours, degree of pressure reduction 5 Pa), A metal dry powder was obtained.
For this metal dry powder, using a simultaneous differential thermal thermogravimetric analyzer (TG-DTA) (manufactured by Hitachi High-Tech Science Co., Ltd., trade name: STA7200RV), 10 mg of the sample was weighed into an aluminum pan cell, and 10 ° C./min. The temperature was raised from 35° C. to 550° C. at a heating rate of , and the mass reduction was measured under an air flow of 50 mL/min. The mass ratio [polymer B/(polymer B+metal)] was calculated by taking the mass decrease from 35° C. to 550° C. as the mass of polymer B and the residual mass at 550° C. as the mass of metal.

(6) Calculation of Metal Concentration in Fine Metal Particle Dispersion From this, the metal concentration in the fine metal particle dispersion was calculated.

(7) Measurement of conductivity of fine metal particle dispersion The metal fine particle dispersion was diluted with ion-exchanged water so that the metal concentration was 1% by mass, and a portable electrical conductivity meter (manufactured by Horiba, Ltd., model: ES -71) was used to measure conductivity.

Example 1-1
(Step 1)
23 g of N,N-dimethylethanolamine (hereinafter also referred to as "DMAE") was placed in a 100 mL glass beaker, and heated to 40° C. in an oil bath while stirring with a magnetic stirrer.
In a separate 100 mL beaker, 14 g of silver nitrate, acrylic acid/maleic acid/styrene/alkoxy (polyethylene glycol/polypropylene glycol) acrylate (number of alkylene oxide units: 32 mol, molar ratio [EO/PO] = 75/25) were co-polymerized. Coalescence [Aqueous copolymer solution with a solid content of 40% (manufactured by BYK, trade name: DISPERBYK-190, acid value 10 mgKOH/g) was dried to absolute state (number average molecular weight: 4500, acid value 20 mgKOH/g) ] (hereinafter also referred to as “BYK-190dry”) was added to 0.8 g and 7 g of ion-exchanged water was added and stirred at 30 ° C. with a magnetic stirrer until it became visually transparent, and the mixed solution (I-1 ).
Next, mixed solution (I-1) was placed in a 100 mL dropping funnel, and mixed solution (I-1) was added dropwise to DMAE maintained at 40° C. over 30 minutes. Thereafter, the reaction solution was stirred for 5 hours while controlling the temperature of the reaction solution at 40° C. in an oil bath, and then air-cooled to obtain a dark brown silver fine particle dispersion (d1-1) containing dispersed silver fine particles a1. . The entire amount of the dispersion (d1-1) was advanced to the next step 2.

(Step 2)
The silver fine particle dispersion (d1-1) obtained above is put into a dialysis tube (manufactured by Spectrum Laboratories, trade name: Spectra/Pore 6, dialysis membrane: regenerated cellulose, molecular weight cutoff (MWCO) = 50K). Then, the top and bottom of the tube were sealed with a closure. This tube was immersed in 5 L of deionized water in a 5 L glass beaker and stirred for 1 hour while maintaining the water temperature at 20-25°C. After that, after repeating the operation of exchanging the entire amount of ion-exchanged water every hour three times, sampling was performed every hour, and the silver fine particle dispersion when the silver concentration was adjusted to 1% by diluting with ion-exchanged water. The dialysis was terminated when the electrical conductivity of the sample reached 7 mS/m, and a purified fine silver particle dispersion (d2-1) was obtained.

(Step 3)
The fine silver particle dispersion (d2-1) obtained above was concentrated under reduced pressure at 60° C. so that the solid content concentration was 50%, to obtain silver fine particle dispersion (D1). The mass ratio [polymer B/(polymer B+metal)] and metal concentration of the fine silver particle dispersion (D1) were measured and calculated by the methods (5) and (6) above, and the cumulant average particle diameter was measured. Table 2 shows the results.

Reference examples 1-2 and 1-3
A fine silver particle dispersion was prepared in the same manner as in Example 1-1, except that the temperature of DMAE when adding the mixed liquid I was changed to 30° C. ( Reference Example 1-2) and 85° C. ( Reference Example 1-3). (D2) and (D3) were obtained.

Reference Example 1-4, Comparative Example 1-3
Silver fine particle dispersions (D4) and (DC3) were obtained in the same manner as in Example 1-1, except that the amount of amine compound D was changed as shown in Table 1.

Examples 1-5, 1-6
Fine silver particle dispersions (D5) and (D6) were obtained in the same manner as in Example 1-1, except that the silver concentration of the fine silver particle dispersion obtained after step 3 was changed as shown in Table 2.

Examples 1-7, 1-8
Silver fine particle dispersions (D7) and (D8) were obtained in the same manner as in Example 1-1 except that DMAE was replaced with diethanolamine (Example 1-7) and triethylamine (Example 1-8).

Examples 1-9
A fine silver particle dispersion (D9) was obtained in the same manner as in Example 1-1, except that silver nitrate was replaced with silver acetate.

Examples 1-10
A fine silver particle dispersion (D10) was obtained in the same manner as in Example 1-1, except that the time for dropping the mixed liquid I was changed from 30 minutes to 5 hours.

Examples 1-11
In the same manner as in Example 1-1, silver A fine particle dispersion (D11) was obtained.

Comparative Example 1-1
A fine silver particle dispersion (DC1) was obtained in the same manner as in Example 1-1, except that BYK-190dry was replaced with polyvinylpyrrolidone (manufactured by Tokyo Chemical Industry Co., Ltd., product name: PVP K15, reagent).

Comparative Example 1-2
A fine silver particle dispersion (DC2) was obtained in the same manner as in Example 1-1, except that Step 1 of Example 1-1 was changed as follows.
(Step 1')
23 g of DMAE and 0.8 g of BYK-190dry were placed in a 100 mL glass beaker and heated to 40° C. in an oil bath while stirring with a magnetic stirrer.
Separately, 14 g of silver nitrate and 7 g of ion-exchanged water were put into a 100 mL beaker and stirred at 30° C. with a magnetic stirrer until it became visually transparent to obtain a mixed solution (I′-2).
Next, the mixture (I'-2) was placed in a 100 mL dropping funnel, and the mixture (I'-2) was added dropwise to the mixture of DMAE and BYK-190dry maintained at 40° C. over 30 minutes. Thereafter, the reaction solution was stirred for 5 hours while controlling the temperature of the reaction solution at 40° C. in an oil bath, and then air-cooled to obtain a dark brown fine silver particle dispersion (d1-C2) containing fine silver particles aC2. The entire amount of the dispersion (d1-C2) was subjected to the same step as step 2 of Example 1-1.

<Evaluation of sedimentation resistance>
10 mL of the metal fine particle dispersions obtained in Examples and Comparative Examples were placed in a 10 mL glass graduated cylinder with an outer diameter of 14 mm (manufactured by AS ONE Corporation, trade name: high-precision glass graduated cylinder) and sealed with Parafilm. bottom. Then, it was allowed to stand for 24 hours under conditions of a temperature of 23° C. and a humidity of 50%. A 2 mL sample was collected while holding the needle tip of the syringe just below the liquid surface of the fine metal particle dispersion in the graduated cylinder before and after the standing. (polymer + metal)], and the sedimentation resistance was evaluated by the following formula. The higher the numerical value, the better the sedimentation resistance. Table 2 shows the results.
Sedimentation resistance (%) = (metal concentration after standing/metal concentration before standing) x 100

In addition, each notation in Table 1 is as follows.
*1: The charge amount (% by mass) of each component with respect to the total charge amount of the metal source compound A, the polymer B, the aqueous solvent C, and the amine compound D.
*2: Method A is a method of adding mixed liquid I to amine compound D, and method B is a method of adding mixed liquid I′ of metal source compound A and aqueous solvent C to a mixture of amine compound D and polymer B.
*3: The electrical conductivity (mS/m) of the metal fine particle dispersion when the metal concentration is adjusted to 1% by mass.

From Table 2, it can be seen that the fine metal particle dispersions of Examples have smaller cumulant average particle diameters and are superior in sedimentation resistance as compared with Comparative Examples.

<Inks for metallic printing>
Example 2-1
The metal fine particle dispersion (D1) obtained in Example 1-1 was blended so that the total amount of ink was 30 g and the metal content was 10%. The content of isobutyl ether (iBDG) is 1%, the content of polyether-modified silicone surfactant (trade name: KF-6011, manufactured by Shin-Etsu Chemical Co., Ltd., PEG-11 methyl ether dimethicone) is 0.5%, The content of acetylene glycol-based surfactant (trade name: Surfynol 104 (2,4,7,9-tetramethyl-5-decyne-4,7-diol), manufactured by Evonik Industries, active ingredient 100%) Ink 1 was prepared by mixing so that 0.5% and the remainder were deionized water.
The preparation was carried out by charging each component into a 50 mL glass vial while stirring with a magnetic stirrer. After that, filtration was performed using a 25 mL needleless syringe (manufactured by Terumo Corporation) equipped with a 1.2 μm membrane filter (manufactured by Sartorius, trade name “Minizart”) to obtain Ink 1.

Comparative Examples 2-1 to 2-3
Example 2-1 except that the metal fine particle dispersion (D1) in Example 2-1 was changed to the metal fine particle dispersions (DC1) to (DC3) obtained in Comparative Examples 1-1 to 1-3. Inks C1 to C3 were obtained in the same manner.

<Metallic printing>
Using the obtained inks 1 and C1 to C3, metallic printing was performed by the following method, and the specular reflectance of the metal film was evaluated by the following method. Table 3 shows the results.

Inkjet printing evaluation device (Tritech Co., Ltd.) equipped with an inkjet head (manufactured by Kyocera Corporation, KJ4B-QA06NTB-STDV, piezo type, number of nozzles: 2656) in an environment with a temperature of 25 ± 1 ° C and a relative humidity of 30 ± 5% ) was filled with the inks obtained in Examples and Comparative Examples.
Head voltage 26 V, frequency 20 kHz, ejection liquid amount 18 pl, head temperature 32°C, resolution 600 dpi, number of flushes before ejection 200, negative pressure -4.0 kPa. Next, the print medium was fixed to the carriage under reduced pressure. A print command is transferred to the print evaluation device, and the ink is ejected and adhered to the print medium at a duty of 100%, and then the ink on the print medium is dried by heating on a hot plate at 60 ° C. got the print.
A polyester film (Lumirror T60, manufactured by Toray Industries, Inc., thickness 75 μm, water absorption 2.3 g/m ² ) was used as the recording medium.

<Specular reflectance of metal film>
The surface of the metal film formed on the printed matter obtained above was measured with an integrating sphere type spectrophotometer (manufactured by Konica Minolta, model: CM-700d), and the obtained 8 ° gloss (visual amount proportional to the sensitive specular reflectance) was taken as the specular reflectance of the metal film. The higher the number, the higher the reflectance.

From Table 3, it can be seen that the fine metal particle dispersion of Example 2-1 can form a metal film with a higher reflectance than those of Comparative Examples 2-1 to 2-3.

ADVANTAGE OF THE INVENTION According to this invention, the metal fine particle dispersion which is excellent in sedimentation resistance can be obtained, and this metal fine particle dispersion can be suitably used for metallic printing in various fields.

Claims (11)

A method for producing an aqueous metal fine particle dispersion containing metal fine particles a dispersed with a polymer B,
A step 1 of adding a mixed liquid I containing a metal source compound A, a polymer B, and an aqueous solvent C to an amine compound D as a reducing agent to perform a reduction reaction of the metal source compound A;
The metal source compound A is a metal salt of an inorganic acid or an organic acid,
The metal contained in the metal raw material compound A is silver,
Polymer B has a carboxy group, the polymer B is a monomer having a structural unit derived from the monomer (b-1) having a carboxy group, a structural unit derived from the hydrophobic monomer (b-2), and a polyalkylene glycol segment. (b-3) is a vinyl polymer b containing a structural unit derived from
The charging molar ratio of the amine compound D and the metal source compound A [amine compound D/metal source compound A] is 3.0 or more and 4 or less ,
A method for producing a water-based fine metal particle dispersion, wherein the temperature of the amine compound D when adding the mixed liquid I is 35° C. or higher and 50° C. or lower . 2. The water-based fine metal particle dispersion according to claim 1, wherein the charged amount of the metal source compound A with respect to the total charged amount of the metal source compound A, the polymer B, the aqueous solvent C and the amine compound D is 10% by mass or more and 60% by mass or less. manufacturing method. 3. The method for producing a water-based fine metal particle dispersion according to claim 1, wherein the fine metal particles a have a cumulant average particle size of 100 nm or less. 4. The method for producing a water-based fine metal particle dispersion according to claim 1 , wherein the water-based fine metal particle dispersion has a metal concentration of 20% by mass or more and 80% by mass or less. The method for producing a water-based fine metal particle dispersion according to any one of claims 1 to 4 , wherein the amine compound D is an alkanolamine having 2 to 6 carbon atoms. 6. The method for producing a water-based fine metal particle dispersion according to any one of claims 1 to 5 , wherein the metal source compound A is silver nitrate. 7. The production of an aqueous metal fine particle dispersion according to any one of claims 1 to 6 , wherein the metal fine particle dispersion diluted with ion-exchanged water to adjust the metal concentration to 1% by mass has an electrical conductivity of 15 mS/m or less. Method. The method for producing a water-based fine metal particle dispersion according to any one of claims 1 to 7 , wherein the polymer B has an acid value of 10 mgKOH/g or more and 50 mgKOH/g or less. A method for producing an ink for metallic printing, comprising adding an aqueous metal fine particle dispersion obtained by the production method according to any one of claims 1 to 8 and an organic solvent. The method for producing a metallic printing ink according to claim 9 , wherein the organic solvent is one or more selected from polyhydric alcohols and polyhydric alcohol alkyl ethers. A metallic printing method comprising printing on a resin film using the metallic printing ink obtained by the manufacturing method according to claim 9 or 10 .