JP2020033635A - Manufacturing method of aqueous metal fine particle dispersoid - Google Patents

Abstract

To provide a manufacturing method of an aqueous metal fine particle dispersoid excellent in sedimentation resistance of metal fine particles, an ink for metallic printing containing the dispersoid, and a metallic printing method using the ink.SOLUTION: There are provided [1] a manufacturing method of an aqueous metal fine particle dispersoid containing a metal fine particle a dispersed by a polymer B, including a process 1 for adding a mixture I containing a metal raw material compound A, a polymer B and a water-based solvent C to an amine compound D, in which the polymer B has a carboxyl group, and a feed molar ratio [amine compound D/metal raw material compound A] is 3.0 or more, [2] an ink for metallic printing containing the aqueous metal fine particle dispersoid obtained by the manufacturing method according to [1], and [3] a metallic printing method for printing on a resin film using the ink for metallic printing according to [2].SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an aqueous metal fine particle dispersion, an ink for metallic printing containing the aqueous metal fine particle dispersion, and a metallic printing method using the ink.

Metal fine particles are expected to be developed for a wide variety of industrial applications because of the variety of functions and physical properties that are exhibited by using fine metal particles in a nano size.
In order to promote industrial use of metal fine particles, various methods for producing metal fine particles are being studied. For example, as a chemical method for generating a metal atom, a wet method such as a method of reducing a metal ion eluted from a metal compound in a liquid and a method of extracting a metal atom by thermal decomposition of a metal complex is known. The method using a metal complex requires a heat treatment at a high temperature, and the reducing solution used for the reduction of the metal complex has a problem related to the removal of residual organic substances and the like, and industrially practical production methods have been studied. .

For example, Patent Document 1 discloses that a metal compound corresponding to metal nanoparticles is prepared by combining a metal compound corresponding to metal nanoparticles with an organic compound having a carboxyl group and a polymer dispersant in order to provide metal colloid particles having excellent storage stability and the like. A method for producing metal colloid particles composed of metal nanoparticles and a protective colloid covering the metal nanoparticles, which is reduced in a solvent in the presence of the constituted protective colloid and a reducing agent, is described.
Patent Document 2 discloses the existence of a metal nanoparticle protective polymer having a polyacetylalkylenimine 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. A method for producing a metal colloid solution by reducing metal ions in a medium to produce metal nanoparticles is described below.

JP 2009-74171 A JP 2006-511773 A

However, the techniques of Patent Documents 1 and 2 have 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 an aqueous metal fine particle dispersion having excellent sedimentation resistance of metal fine particles, a metallic printing ink containing the aqueous metal fine particle dispersion, and a metallic printing method using the ink. And
Here, in this specification, the sedimentation resistance of the metal fine particles is simply referred to as “sedimentation resistance”.

  The present inventors include a step of adding a mixed solution containing a metal raw material compound, a polymer having a carboxy group, and an aqueous solvent to an amine compound as a reducing agent, and charging the amine compound and the metal raw material compound. By focusing on controlling the aggregation and sedimentation of the metal fine particles by setting the molar ratio within a predetermined range, the inventors have found that the above problem can be solved.

That is, the present invention relates to the following [1] to [3].
[1] A method for producing an aqueous metal fine particle dispersion containing metal fine particles a dispersed in a polymer B,
Step 1 of adding a mixed solution I containing a metal raw material compound A, a polymer B, and an aqueous solvent C to an amine compound D,
Polymer B has a carboxy group,
A process for producing an aqueous metal fine particle dispersion, wherein the charged molar ratio of the amine compound D and the metal raw material compound A [amine compound D / metal raw material compound A] is 3.0 or more.
[2] An ink for metallic printing, containing the aqueous metal fine particle dispersion obtained by the production method according to [1].
[3] A metallic printing method comprising printing on a resin film using the metallic printing ink according to [2].

  According to the present invention, it is possible to provide a method for producing an aqueous metal fine particle dispersion having excellent sedimentation resistance of metal fine particles, a metallic printing ink containing the aqueous metal fine particle dispersion, and a metallic printing method using the ink. Can be.

[Production method of aqueous metal fine particle dispersion]
The present invention relates to 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 particles a”) dispersed in a polymer B. A step of adding a mixed solution I containing a metal raw material compound A, a polymer B, and an aqueous solvent C to an amine compound D, wherein the polymer B has a carboxy group, and the amine compound D and the metal raw material compound A The molar ratio [amine compound D / metal raw material compound A] is 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 metal fine particles a is not particularly limited, as long as the particles are formed by at least the metal fine particles and the polymer B. For example, a particle form in which metal fine particles are included in polymer B, a particle form in which metal fine particles are uniformly dispersed in polymer B, a particle form in which metal fine particles are exposed on the surface of polymer B particles, and the like are included. Mixtures are also included.
In addition, "aqueous" means that water occupies the maximum ratio in the aqueous medium.

According to the present invention, a metal fine particle dispersion having excellent sedimentation resistance of metal fine particles can be obtained. The reason is not clear, but is considered as follows.
In the production method of the present invention, a mixed solution containing a metal raw material 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 carboxy group functioning as a dispersant is adsorbed or coordinated with a metal ion to improve the stability of the metal ion. Then, by adding the mixed solution containing the metal ions maintaining stability to the amine compound, and further adjusting the charged molar ratio of the amine compound and the metal raw material compound to a predetermined range, in the process of forming the metal fine particles by the reduction reaction, It is considered that excessive aggregation of metal ions is suppressed and generation of coarse metal fine particles is suppressed. As a result, it is considered that a metal fine particle dispersion having high dispersion stability and containing fine metal fine particles can be obtained, and sedimentation resistance is improved.

(Step 1)
Step 1 is a step of adding a mixed solution I (hereinafter, also referred to as “mixed solution I”) containing the metal raw material compound A, the polymer B, and the aqueous solvent C to the amine compound D. In the mixed solution I, the polymer B is adsorbed or coordinated to the metal ions, and the stability of the metal ions can be improved. Then, by adding the mixed solution I to the amine compound D, metal ions are reduced by a reduction reaction, and the generated metal atoms are appropriately aggregated to form fine metal fine particles a.
The mixed solution I can be obtained by mixing the metal raw material compound A, the polymer B and the aqueous solvent C by a known method.

<Metal raw material compound A>
The metal (metal atom) contained in the metal raw material compound A is a Group 4 transition metal such as titanium or zirconium, a Group 5 transition metal such as vanadium or niobium, or a Group 6 transition such as chromium, molybdenum or tungsten. Group 7 transition metals such as metals, manganese, technetium and rhenium; Group 8 transition metals such as iron and ruthenium; and Group 9 transition metals such as cobalt, rhodium and iridium; nickel, palladium and platinum. 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 And the like. One of the metals may be used as a single metal, or two or more may be used as an alloy in combination. Among them, preferred are transition metals of Groups 4 to 11 in the fourth to sixth periods, more preferred are noble metals such as copper, gold, silver, platinum and palladium, and further preferred are gold, silver and copper. It is at least one kind selected, and still more preferably silver.

  Examples of the metal raw material compound A include metal salts of inorganic or organic acids, metal oxides, metal hydroxides, metal sulfides, metal halides and the like containing the above-mentioned metals. Examples of the metal salt include metal salts of inorganic acids such as nitrates, nitrites, sulfates, carbonates, ammonium salts and perchlorates; and metal salts of organic acids such as acetates. The metal raw material compound A can be used alone or in combination of two or more. Among them, a metal salt of an inorganic acid or an organic acid is preferable, a metal salt of an inorganic acid is more preferable, a metal salt of nitric acid is more preferable, and silver nitrate is still more preferable.

<Polymer B>
The polymer B according to the present invention has a function as a dispersant for fine metal particles.
Polymer B has a carboxy group. The carboxy group also includes a carboxy group (—COOM) exhibiting acidity by dissociation and release of a hydrogen ion, or a dissociated ion form thereof (—COO ⁻ ). In the above chemical formula, M represents a hydrogen atom, an alkali metal, ammonium or organic ammonium. Examples of the polymer B include condensation polymers such as polyester and polyurethane; and vinyl polymers.

  The carboxy group contained in the molecule of the polymer B is preferably one that is introduced into the polymer skeleton by the monomer (b-1) having a carboxy group. That is, the polymer B preferably contains a structural unit derived from the monomer (b-1) having a carboxy group. Among them, from the viewpoint of improving 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, referred to as a monomer). , A structural unit derived from a monomer (b-2)) and a structural unit derived from a monomer (b-3) having a polyalkylene glycol segment (hereinafter, also referred to as a "monomer (b-3)"). Vinyl-based polymer b (hereinafter also referred to as “polymer b”) is preferred. The polymer b can be obtained by copolymerizing a raw material monomer containing a monomer (b-1), a monomer (b-2) and a monomer (b-3) (hereinafter, also simply referred to as “raw material monomer”). The polymer b may be any of a block copolymer, a random copolymer, and 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 the like. Note that the unsaturated dicarboxylic acid may be an anhydride.
As the monomer (b-1), one type may be used alone, or two or more types may be used in combination.
The 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. In the following, “(meth) acrylic acid” is also synonymous.

[Hydrophobic monomer (b-2)]
The monomer (b-2) is preferably used as a monomer component of the polymer b from the viewpoint of improving sedimentation resistance.
In the present invention, “hydrophobic” means that when the monomer is dissolved in 100 g of ion-exchanged water at 25 ° C. until the monomer is saturated, the dissolved amount is less than 10 g. The amount of the monomer (b-2) to be 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 an aromatic group-containing monomer and a (meth) acrylate having a hydrocarbon group derived from an aliphatic alcohol.
In the present invention, “(meth) acrylate” is at least one selected from acrylates and methacrylates. The “(meth) acrylate” below is also synonymous.

The aromatic group-containing monomer is preferably a vinyl monomer having an aromatic group having 6 to 22 carbon atoms, which may have a substituent containing a hetero atom, and more preferably a styrene monomer and an aromatic monomer. At least one selected from group-containing (meth) acrylates. The molecular weight of the aromatic group-containing monomer is preferably less than 500.
Examples of the styrene-based monomer include styrene, α-methylstyrene, 2-methylstyrene, vinyltoluene, and divinylbenzene, and styrene and α-methylstyrene are 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) acrylate 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, Having a branched alkyl group such as isodecyl (meth) acrylate, isododecyl (meth) acrylate, isostearyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate (meth) Acrylate; and (meth) acrylates having an alicyclic alkyl group, such as cyclohexyl (meth) acrylate. Among them, those having an alkyl group having 6 to 10 carbon atoms are more preferable.
As the monomer (b-2), one type may be used alone, or two or more types may be used in combination.

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

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

The monomer (b-3) is preferably at least one selected from polyalkylene glycol (meth) acrylate and alkoxy polyalkylene glycol (meth) acrylate, and more preferably alkoxy polyalkylene glycol (meth) acrylate. The alkoxy group of the alkoxypolyalkylene glycol (meth) acrylate preferably has 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms.
Examples of the alkoxy polyalkylene glycol (meth) acrylate include methoxy polyalkylene glycol (meth) acrylate, ethoxy polyalkylene glycol (meth) acrylate, propoxy polyalkylene glycol (meth) acrylate, butoxy polyalkylene glycol (meth) acrylate, and octoxy. And polyalkylene glycol (meth) acrylate.

The polyalkylene glycol segment of the monomer (b-3) preferably contains a unit 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 units derived from alkylene oxide 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, and further preferably 50 or less.
The polyalkylene glycol segment is preferably a copolymer containing a unit derived from ethylene oxide and a unit derived from propylene oxide, from the viewpoint of improving sedimentation resistance. The molar ratio [EO / PO] between the ethylene oxide units (EO) and the propylene oxide units (PO) is preferably at least 60/40, more preferably at least 65/35, even more preferably at least 70/30, and It is preferably at most 90/10, more preferably at most 85/15, even more preferably at most 80/20.
The copolymer containing a unit derived from ethylene oxide and a unit derived from propylene oxide may be any of a block copolymer, a random copolymer, and an alternating copolymer.

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

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

The polymer b is a structural unit derived from (meth) acrylic acid and maleic acid as the monomer (b-1), a structural unit derived from a styrene monomer as the monomer (b-2), and an alkoxypolyalkylene as the monomer (b-3). It is preferable to include a structural unit derived from glycol (meth) acrylate.
As the polymer b, a polymer synthesized by a known method may be used, or a commercially available product may be used. Commercial products of the polymer b include DISPERBYK-190 and 2015 manufactured by BYK.

  The number average molecular weight of the polymer B is preferably at least 1,000, more preferably at least 2,000, even more preferably at least 3,000, and preferably at most 100,000, more preferably at most 50,000, More preferably, it is 30,000 or less, still more preferably 10,000 or less, and still more preferably 7,000 or less. When the number average molecular weight of the polymer B is in the above range, the adsorption 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 the 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. Preferably it is 50 mgKOH / g or less, still more preferably 30 mgKOH / g or less.
The acid value of the polymer B is measured by the method described in Examples.

<Aqueous solvent C>
The aqueous solvent C is preferably one containing 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, further preferably 90% by mass or more, and still 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, and triamine. Alkanolamines such as ethanolamine, propanolamine, N, N-dimethylpropanolamine, triethanolamine, butanolamine, hexanolamine; propylamine, butylamine, hexylamine, diethylamine, dipropylamine, dimethylethylamine, diethylmethylamine, triethylamine Such as alkylamine, ethylenediamine, triethylenediamine, tetramethylethylenediamine, diethylenetriamine, dipropylenetriamine, Aliphatic amines such as (poly) alkylenepolyamines such as triethylenetetramine and tetraethylenepentamine; alicyclic amines such as piperidine, pyrrolidine, N-methylpyrrolidine and morpholine; aniline, N-methylaniline, toluidine, anisidine, phenetidine And aralkylamines such as benzylamine and N-methylbenzylamine. The amine compound D may be used alone or in combination of two or more.
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, from the viewpoint of improving sedimentation resistance. , N-dimethylethanolamine.

In step 1, the amine compound D and another reducing agent may be used in combination as the reducing agent. As the other reducing agent, either an organic reducing agent or an inorganic reducing agent can be used.
Examples of the organic reducing agent 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 the inorganic reducing agent 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; hydrogen gas; Is mentioned.
The other reducing agents may be used alone or in combination of two or more.

(Content of each component in mixture I)
The content of the metal raw material compound A in the mixed solution I is preferably 20% by mass or more, more preferably 40% by mass or more, further 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 the polymer B in the mixed solution 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 solution I is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 20% by mass or more, and preferably 60% by mass or less, more preferably It is at most 50% by mass, more preferably at most 40% by mass.
The mass ratio of the polymer B to the metal raw material compound A in the liquid mixture I [Polymer B / metal raw material compound A] is preferably 0.01 or more, more preferably 0.03 or more, and further preferably 0.05 or more. And 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 at the time of adding the mixed solution I is preferably 10 ° C. or higher, more preferably 20 ° C. or higher, still more preferably 30 ° C. or higher, and still more preferably 35 ° C., from the viewpoint of improving sedimentation resistance. The temperature is preferably less than 100 ° C., more preferably 90 ° C. or less, still more preferably 80 ° C. or less, still more preferably 60 ° C. or less, and still more preferably 50 ° C. or less. The reduction reaction may be performed under an air atmosphere or under an inert gas atmosphere such as nitrogen gas.

The method of adding the mixed solution I to the amine compound D is not particularly limited, and may be batch addition or divided addition. However, from the viewpoint of controlling the reduction reaction and improving the sedimentation resistance, the method of dropping is preferable.
The dropping speed of the mixture I can be appropriately set according to the scale of production, but the dropping time of the mixture I is preferably 8 hours or less, more preferably 6 hours, from the viewpoint of improving the sedimentation resistance. Hereinafter, it is more preferably 3 hours or less, further 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.

(Amount of each component)
The charged amount of each component with respect to the total charged 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 from the viewpoint of improving sedimentation resistance, and from the viewpoint of productivity. It is as follows.
The charged amount of the metal raw material compound A based on the total charged amount of the metal raw material 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 further preferably 25% by mass. And preferably at most 60% by mass, more preferably at most 50% by mass, even more preferably at most 40% by mass.
The charged amount of the polymer B based on the total charged amount of the metal raw material 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 or more. % By mass, and preferably 7% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less.
The amount of the aqueous solvent C based on the total amount of the metal raw material 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 preferably 40% by mass or less, more preferably 30% by mass or less, and still more preferably 20% by mass or less.
The charge amount of the amine compound D based on the total charge amount of the metal raw material 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 still more preferably 60% by mass or less.
The charged molar ratio of the amine compound D and the metal raw material compound A [amine compound D / metal raw material compound A] is 3.0 or more, and is preferably 10 or less, more preferably 7 or less, and still more preferably 5 or less. And still 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 fine metal particles, Step 2 of purifying the fine metal particle dispersion obtained in Step 1 (hereinafter, also simply referred to as “Step 2”) ) Is preferable.
The dispersion after the reduction reaction of the metal raw material compound A contains unreacted reducing agents, counter ions of metal ions, and excess impurities such as polymer B that does not contribute to the dispersion of the metal fine particles. Therefore, these impurities can be removed through Step 2.
The method for purifying the metal fine particle dispersion is not particularly limited, and examples thereof include membrane treatment such as dialysis and ultrafiltration; and centrifugal separation. Above all, from the viewpoint of efficiently removing impurities, membrane treatment is preferable, and dialysis is more preferable. As the material of the dialysis membrane used for dialysis, regenerated cellulose is preferable.
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, from the viewpoint of efficiently removing impurities. , More preferably 70,000 or less.

In the dialysis treatment, for example, the metal fine particle dispersion obtained in the step 1 is put into a cylindrical dialysis tube, and after sealing both ends of the dialysis tube, the tube is filled with a large amount of ion-exchanged water using the tube as a buffer. It can be carried out by placing it in a container and leaving it for a predetermined time. This makes it possible to remove impurity ions having a formula weight equal to or less than the cut-off molecular weight and polymers having a molecular weight not more than the cut-off molecular weight from the metal fine particle dispersion.
The temperature of the dialysis treatment is preferably 10 ° C. or higher, more preferably 15 ° C. or higher, further preferably 20 ° C. or higher, and preferably 60 ° C. or lower, more preferably 50 ° C. or lower, from the viewpoint of processing efficiency. Preferably it is 40 ° C. or lower.
The conductivity of the metal fine particle dispersion obtained in the step 2 is preferably 1 mS / m or more, from the viewpoint of improving sedimentation resistance, when the metal concentration of the metal fine particle dispersion is adjusted to 1% by mass. It is preferably at least 3 mS / m, more preferably at least 5 mS / m, and preferably at most 15 mS / m, more preferably at most 13 mS / m, even more preferably at most 10 mS / m. The conductivity is measured by the method described in the examples.

(Step 3)
The production method of the present invention preferably further includes a step 3 of concentrating the fine metal particle dispersion obtained in the step 1 or 2.
The method for concentrating the metal fine particle dispersion is not particularly limited as long as the aqueous medium contained in the metal fine particle dispersion can be removed. Among them, a method of distilling the aqueous medium under heating or reduced pressure is preferable. The heating temperature is preferably 35 ° C. or higher, more preferably 45 ° C. or higher, and still more preferably 55 ° C. or higher, from the viewpoint of productivity, and from the viewpoint of suppressing dispersion stability and thermal decomposition of the metal fine particles, It is preferably at most 85 ° C, more preferably at most 75 ° C, even more preferably at most 65 ° C. The concentration of the metal fine particle dispersion is preferably performed while controlling the solid content concentration of the dispersion to be in a desired range.
When the aqueous solvent C contains an organic solvent, it is preferable to remove the organic solvent together with water in the 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 the residual organic solvent is preferably 0.1% by mass or less, more preferably 0.01% by mass or less.

  The polymer B is present in the metal fine particle dispersion in the form in which the polymer B is adsorbed on the metal fine particles, the metal fine particle encapsulation (capsule) in which the polymer B contains the metal fine particles, and the polymer B in the metal fine particles. Is not adsorbed. From the viewpoint of the dispersion stability of the metal fine particles, the form in which the polymer fine particles are contained in the metal fine particles is preferable, and the metal fine particle containing the polymer fine particles in the polymer B state is more preferable.

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

The cumulant average particle diameter 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. Above, even more preferably 15 nm or more, and from the viewpoint of miniaturization of metal fine particles, preferably 100 nm or less, more preferably 80 nm or less, still more preferably 50 nm or less, still more preferably 40 nm or less, even more preferably It is 30 nm or less, more preferably 25 nm or less.
In addition, the said cumulant average particle diameter is measured by the method described in an Example.

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

  The metal fine particle dispersion of the present invention may contain glycerin, triethylene glycol, or the like as a humectant in an amount of 1% by mass or more and 10% by mass or less as a humectant, depending on the application, An agent may be contained. The additive may be blended at the time of the reduction reaction, or may be blended after obtaining the metal fine particle dispersion.

  The metal fine particle dispersion of the present invention has excellent sedimentation resistance of metal fine particles, and thus can be used for a wide range of applications. For example, various inks; wiring materials, electrode materials, conductive materials such as MLCC (multilayer ceramic capacitors); bonding materials; various sensors; catalysts; optical materials;

[Metallic printing ink]
The metal fine particle dispersion according to the present invention is preferably contained in an aqueous ink (hereinafter, also referred to as “aqueous ink” or “ink”) and used as an ink for metallic printing. Thereby, it is possible to obtain an aqueous ink excellent in storage stability in which sedimentation of metal fine 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 with high reflectivity can be obtained.
The aqueous ink preferably further contains an organic solvent from the viewpoint of storage stability. The organic solvent preferably contains at least one organic solvent 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 preferably 240 ° C. or lower, more preferably 220 ° C. or lower, and further 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 are preferred. One or more selected from the group is more preferable, and one or more selected from propylene glycol and diethylene glycol monoisobutyl ether is further preferable.

The water-based ink may further include a fixing aid such as a dispersion of polymer particles, a humectant, a wetting agent, a penetrant, a surfactant, a viscosity modifier, a defoaming agent, and a preservative, which are generally used in the water-based ink, if necessary. Various additives such as an agent, a fungicide, and a rust inhibitor can be added, and a filtration treatment with a filter or the like can be performed.
The content of each component of the aqueous 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 aqueous ink is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, from the viewpoint of improving the print density and the reflectance of the metal film. From the viewpoint of reducing the viscosity of the ink when the solvent is volatilized and improving the storage stability, it is preferably 20% by mass or less, more preferably 17% by mass or less, and further preferably 15% by mass or less.
The total content of the metal and the polymer B in the aqueous ink is preferably 2% by mass or more, more preferably 5% by mass or more, 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 further preferably 16% by mass or less.
The content of the organic solvent in the aqueous 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 printing 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 further preferably 40% by mass or less.
The content of water in the aqueous ink is preferably 20% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass or more, from the viewpoint of improving the storage stability and fixability of the ink. From the viewpoint of improving the printing density and the reflectance of the metal film, the content is preferably 80% by mass or less, more preferably 70% by mass or less, and further preferably 60% by mass or less.
The mass ratio of the metal in the total solid content of the aqueous ink [metal / (total solid content of the aqueous ink)] is preferably from the viewpoint of improving the storage stability of the aqueous ink, the print density and the reflectance of the metal film. 0.3 or more, more preferably 0.5 or more, still more preferably 0.7 or more, even more preferably 0.8 or more, and from the viewpoint of fixability, preferably 0.98 or less, more preferably 0.95 or less, more preferably 0.9 or less.

(Physical properties of water-based ink)
The average particle size of the cumulant of the metal fine particles a in the aqueous ink is preferably the same as the average particle size in the metal fine particle dispersion, and the preferable mode of the average particle size is also the average particle size in the metal fine particle dispersion. The diameter is the same as the preferred embodiment.
The viscosity of the aqueous 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, from the viewpoint of storage stability. More preferably, it is 9 mPa · s or less, and still more preferably 7 mPa · s or less. The viscosity of the water-based ink can be measured using an E-type viscometer.
The pH at 20 ° C. of the water-based ink is preferably 7.0 or more, more preferably 7.2 or more, and still more preferably 7.5 or more, from the viewpoint of storage stability. Further, from the viewpoints of member resistance and skin irritation, the pH is preferably 11 or less, more preferably 10 or less, and further preferably 9.5 or less. The pH of the aqueous ink can be measured by a conventional method.

[Metallic printing method]
Since the aqueous ink is excellent in storage stability in which sedimentation of metal fine particles is suppressed and a printed matter having a metal film having a high reflectance can be obtained, particularly an ink for flexographic printing, an ink for gravure printing, or inkjet recording. It can be suitably used for metallic printing as an ink for printing. Particularly, 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 an ink for ink-jet recording, the water-based ink can be loaded into a known ink-jet recording apparatus and ejected as ink droplets onto a print medium to form an image or the like.
As the inkjet recording apparatus, there are a thermal type and a piezo type. The aqueous ink of the invention is more preferably used as a piezo type aqueous ink for inkjet recording.

Examples of the printing medium of the metallic printing method for printing using the water-based ink include plain paper having high water absorption, coated paper having low water absorption, and a non-water-absorbing resin film. Examples of the coated paper include general-purpose glossy paper and multicolor foam gloss paper. Above all, a resin film is preferable from the viewpoint of obtaining a printed matter having a metal film having a high reflectance. The resin film is preferably at least one selected from a polyester film, a polyvinyl chloride film, a polypropylene film, and a polyethylene film. The resin film may use a corona-treated base material.
Commonly available resin films include, for example, Lumirror T60 (manufactured by Toray Industries, Inc., polyester), PVC80BP (manufactured by Lintec Corporation, vinyl chloride), DGS-210WH (manufactured by Roland DG Inc., vinyl chloride), transparent PVC-RE-137 (manufactured by Mimaki Engineering Co., Ltd., vinyl chloride), Kinas KEE70CA (manufactured by Lintec Co., polyethylene), YUPO SG90 PAT1 (manufactured by Lintec Co., polypropylene), FOR, FOA (all manufactured by Futamura Chemical Co., Ltd. Polypropylene), Boneal RX (produced by Kojin Film & Chemicals Co., Ltd., nylon), Emblem ONBC (produced by Unitika Ltd., nylon) and the like.

  In the following Examples and Comparative Examples, “parts” and “%” are “parts by mass” and “% by mass” unless otherwise specified.

(1) Measurement of number average molecular weight of polymer B Gel permeation chromatography was performed using a solution in which phosphoric acid and lithium bromide were dissolved in N, N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively, as an eluent. As a standard substance, a lithography method [GPC apparatus (HLC-8320GPC) manufactured by Tosoh Corporation, a column manufactured by Tosoh Corporation (TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guardcolumn Super AW-H), flow rate: 0.5 mL / min] is used as a standard substance. Monodisperse polystyrene kit of 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), east It was measured using a chromatography Co., Ltd.].
For the measurement sample, 0.1 g of the polymer was mixed with 10 mL of the above eluent in a glass vial, and the mixture was stirred with a magnetic stirrer at 25 ° C. for 10 hours, and a syringe filter (DISMIC-13HP PTFE 0.2 μm, manufactured by Advantech Co., Ltd.) 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 K0070. However, only the measurement solvent was changed from a mixed solvent of ethanol and ether prescribed in JIS K 0070 to a mixed solvent of acetone and toluene (acetone: toluene = 4: 6 (volume ratio)).

(3) Measurement of Cumulant Average Particle Size of Metal Fine Particle 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 size. The measurement conditions were a temperature of 25 ° C., an angle between the incident light and the detector of 90 °, and the number of times of integration was 100 times. The concentration of the measurement sample was 5 × 10 ⁻³ % (in terms of solid content concentration).

(4) Measurement of Solids Concentration of Metal Fine Particle Dispersion 10.0 g of sodium sulfate constantized in a desiccator was weighed and placed in a 30 ml polypropylene container (φ = 40 mm, height = 30 mm). After adding 0 g and mixing, weigh accurately, maintain at 105 ° C. for 2 hours to remove volatile components, leave in a desiccator at room temperature (25 ° C.) for further 15 minutes, Was measured. The mass of the sample after the removal of volatile components was defined as a solid content, and divided by the mass of the added sample to obtain a solid content concentration.

(5) Calculation of Mass Ratio [Polymer B / (Polymer B + Metal)] A freeze-dryer (Tokyo Rika) equipped with a dry chamber (model: DRC-1000, manufactured by Tokyo Rika Kikai Co., Ltd.) By freeze-drying under drying conditions (freezing at −25 ° C. for 1 hour, decompressing at −10 ° C. for 9 hours, depressurizing at 25 ° C. for 5 hours, depressurization degree of 5 Pa) using an instrument manufactured by Kikki Co., Ltd. A metal dry powder was obtained.
A 10 mg sample of this metal dry powder was weighed in an aluminum pancel using a differential thermogravimetric simultaneous measurement device (TG-DTA) (trade name: STA7200RV, manufactured by Hitachi High-Tech Science Corporation) and measured at 10 ° C./min. The temperature was raised from 35 ° C. to 550 ° C. at a heating rate of, and the mass loss was measured under an air flow of 50 mL / min. The mass ratio [Polymer B / (Polymer B + Metal)] was calculated using the weight loss of polymer B from 35 ° C. to 550 ° C. as the weight of polymer B and the remaining weight at 550 ° C. as the weight of metal.

(6) Calculation of Metal Concentration in Metal Fine Particle Dispersion Mass Ratio [Polymer B / (Polymer B + Metal)] Obtained in (5) and Solid Content Concentration of Metal Fine Particle Dispersion Obtained in (4) From this, the metal concentration in the metal fine particle dispersion was calculated.

(7) Measurement of Conductivity of Metal Fine Particle Dispersion The metal fine particle dispersion was diluted with ion-exchanged water so as to have a metal concentration of 1% by mass, and a portable electric conductivity meter (manufactured by HORIBA, Ltd., model: ES The conductivity was measured using -71).

Example 1-1
(Step 1)
In a 100 mL glass beaker, 23 g of N, N-dimethylethanolamine (hereinafter, also referred to as "DMAE") was placed, and heated to 40 ° C. in an oil bath while stirring with a magnetic stirrer.
Separately, 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) are placed in a 100 mL beaker. Combined [Aqueous solution of the copolymer having a solid content of 40% (manufactured by BYK, trade name: DISPERBYK-190, acid value 10 mgKOH / g) in an absolutely dried state (number average molecular weight: 4500, acid value 20 mgKOH / g) (Hereinafter, also referred to as “BYK-190dry”), 0.8 g of ion-exchanged water was added, and the mixture was stirred at 30 ° C. using a magnetic stirrer until the mixture became visually transparent. ) Got.
Next, the mixed solution (I-1) was placed in a 100 mL dropping funnel, and the mixed solution (I-1) was dropped into DMAE maintained at 40 ° C. over 30 minutes. Thereafter, the mixture 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 whole 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 (trade name: Spectra / Pore 6, manufactured by Spectrum Laboratories, dialysis membrane: regenerated cellulose, molecular weight cut off (MWCO) = 50K). Then, the top and bottom of the tube were sealed with a closer. This tube was immersed in 5 L of ion exchange water in a 5 L glass beaker, and stirred for 1 hour while maintaining the water temperature at 20 to 25 ° C. Thereafter, the operation of exchanging the total amount of ion-exchanged water every hour was repeated three times, and thereafter, sampling was performed every hour, and the silver fine particle dispersion when the silver concentration was adjusted to 1% by dilution with ion-exchanged water. The dialysis was terminated when the conductivity of the sample became 7 mS / m, to obtain a purified fine silver particle dispersion (d2-1).

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

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

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 the amine compound D charged was changed as shown in Table 1.

Examples 1-5 and 1-6
Silver fine particle dispersions (D5) and (D6) were obtained in the same manner as in Example 1-1, except that the silver concentration of the silver fine 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).

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

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

Example 1-11
The same procedure as in Example 1-1 was carried out except that the end of the dialysis in the step 2 was determined at the time when the conductivity when the silver concentration of the metal fine particle dispersion was adjusted to 1% was 12 mS / m. A fine particle dispersion (D11) was obtained.

Comparative Example 1-1
A silver fine 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 silver fine 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 ')
In a 100 mL glass beaker, 23 g of DMAE and 0.8 g of BYK-190 dry were put, 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 charged into a 100 mL beaker, and the mixture was stirred at 30 ° C. using a magnetic stirrer until the mixture became visually transparent to obtain a mixed solution (I′-2).
Next, the mixed solution (I'-2) was put into a 100 mL dropping funnel, and the mixed solution (I'-2) was dropped into a mixture of DMAE and BYK-190dry kept at 40 ° C over 30 minutes. Thereafter, the mixture 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-C2) containing silver fine particles aC2. The whole amount of the dispersion (d1-C2) was advanced 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 was placed in a 10 mL glass graduated cylinder (manufactured by AS ONE Corporation, trade name: glass high-precision graduated cylinder) having an outer diameter of 14 mm, and sealed with parafilm. did. Then, it was left still for 24 hours under the conditions of a temperature of 23 ° C. and a humidity of 50%. While holding the tip of the syringe needle just below the liquid surface of the metal fine particle dispersion in the measuring cylinder before and after standing, 2 mL was sampled as a sample, and the metal concentration in the sample before and after standing was determined by the aforementioned mass ratio [polymer / polymer]. (Polymer + Metal)], and the sedimentation resistance was evaluated by the following equation. The higher the value, the better the sedimentation resistance. Table 2 shows the results.
Sedimentation resistance (%) = (metal concentration after standing / metal concentration before standing) × 100

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

  From Table 2, it can be seen that the metal fine particle dispersion of the example has a smaller cumulant average particle diameter and is superior in sedimentation resistance as compared with the comparative example.

<Ink for metallic printing>
Example 2-1
The total amount of the ink was 30 g, and the metal fine particle dispersion (D1) obtained in Example 1-1 was blended so that the metal content was 10%. Isobutyl ether (iBDG) content of 1%, polyether-modified silicone surfactant (trade name: KF-6011, Shin-Etsu Chemical Co., Ltd., PEG-11 methyl ether dimethicone) content of 0.5%, The content of an acetylene glycol-based surfactant (trade name: Surfynol 104 (2,4,7,9-tetramethyl-5-decyne-4,7-diol), manufactured by Evonik Industries, effective content 100%) Ink 1 was prepared by mixing 0.5% and the balance with ion-exchanged water.
In addition, preparation was performed by putting each component into a 50 mL glass vial while stirring with a magnetic stirrer. Thereafter, the mixture was filtered with a needle-less syringe (manufactured by Terumo Corporation) having a capacity of 25 mL and equipped with a 1.2 μm membrane filter (manufactured by Sartorius, trade name “Minisart”) to obtain Ink 1.

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

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

Ink jet print evaluation device (Tritech Co., Ltd.) equipped with an ink jet head (KJ4B-QA06NTB-STDV, piezo type, 2656 nozzles, manufactured by Kyocera Corporation) in an environment of a temperature of 25 ± 1 ° C. and a relative humidity of 30 ± 5%. Was filled with the inks obtained in Examples and Comparative Examples.
A head voltage of 26 V, a frequency of 20 kHz, an appropriate amount of ejection liquid of 18 pl, a head temperature of 32 ° C., a resolution of 600 dpi, a number of flushing before ejection of 200, and a negative pressure of −4.0 kPa are set. Then, the print medium was fixed on the carriage under reduced pressure. The 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%. Then, the ink on the print medium is heated and dried at 60 ° C. for 2 minutes on a hot plate, and the metallic material is dried. Printed matter was obtained.
As the recording medium, a polyester film (manufactured by Toray Industries, Inc., Lumirror T60, thickness 75 μm, water absorption 2.3 g / m ² ) was used.

<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). The amount proportional to the regular reflectance) was defined as the regular reflectance of the metal film. The higher the value, the higher the reflectance.

  Table 3 shows that the metal fine particle dispersion of Example 2-1 can form a metal film having a higher reflectance than Comparative Examples 2-1 to 2-3.

  According to the present invention, it is possible to obtain a fine metal particle dispersion having excellent sedimentation resistance, and the fine metal particle dispersion can be suitably used for metallic printing in various fields.

Claims (12)

A method for producing an aqueous metal fine particle dispersion containing metal fine particles a dispersed in a polymer B,
Step 1 of adding a mixed solution I containing a metal raw material compound A, a polymer B, and an aqueous solvent C to an amine compound D,
Polymer B has a carboxy group,
A process for producing an aqueous metal fine particle dispersion, wherein the charged molar ratio of the amine compound D and the metal raw material compound A [amine compound D / metal raw material compound A] is 3.0 or more.   The method for producing an aqueous metal fine particle dispersion according to claim 1, wherein the molar ratio [amine compound D / metal raw material compound A] of the amine compound D and the metal raw material compound A is 10 or less.   The method for producing an aqueous metal fine particle dispersion according to claim 1 or 2, wherein the temperature of the amine compound D at the time of adding the mixed solution I is 10 ° C or higher and lower than 100 ° C.   The charged amount of the metal raw material compound A based on the total charged amount of the metal raw material 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. A method for producing an aqueous metal fine particle dispersion.   The method for producing an aqueous metal fine particle dispersion according to any one of claims 1 to 4, wherein the cumulant average particle diameter of the metal fine particles a is 100 nm or less.   The method for producing an aqueous metal fine particle dispersion according to any one of claims 1 to 5, wherein the metal concentration of the aqueous metal fine particle dispersion is 20% by mass or more and 80% by mass or less.   The method for producing an aqueous metal fine particle dispersion according to any one of claims 1 to 6, wherein the amine compound D is an alkanolamine having 2 to 6 carbon atoms.   The method for producing an aqueous metal fine particle dispersion according to any one of claims 1 to 7, wherein the metal raw material compound A is silver nitrate.   The method for producing an aqueous metal fine particle dispersion according to any one of claims 1 to 8, wherein the electric conductivity of the metal fine particle dispersion in which the metal concentration is adjusted to 1% by mass is 15 mS / m or less.   The polymer B has a structural unit derived from a monomer (b-1) having a carboxy group, a structural unit derived from a hydrophobic monomer (b-2), and a structural unit derived from a monomer (b-3) having a polyalkylene glycol segment. The method for producing a water-based metal fine particle dispersion according to any one of claims 1 to 9, which is a vinyl-based polymer b.   An ink for metallic printing, comprising the aqueous metal fine particle dispersion obtained by the production method according to claim 1.   A metallic printing method, comprising printing on a resin film using the metallic printing ink according to claim 11.