WO2019131435A1 - Method for producing silver nanoparticle dispersion liquid, silver nanoparticle dispersion liquid, inkjet ink and image forming method using same - Google Patents

Method for producing silver nanoparticle dispersion liquid, silver nanoparticle dispersion liquid, inkjet ink and image forming method using same Download PDF

Info

Publication number
WO2019131435A1
WO2019131435A1 PCT/JP2018/046985 JP2018046985W WO2019131435A1 WO 2019131435 A1 WO2019131435 A1 WO 2019131435A1 JP 2018046985 W JP2018046985 W JP 2018046985W WO 2019131435 A1 WO2019131435 A1 WO 2019131435A1
Authority
WO
WIPO (PCT)
Prior art keywords
silver
nanoparticle dispersion
silver nanoparticles
silver nanoparticle
dispersion liquid
Prior art date
Application number
PCT/JP2018/046985
Other languages
French (fr)
Japanese (ja)
Inventor
英也 三輪
中林　亮
禄人 田口
Original Assignee
コニカミノルタ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by コニカミノルタ株式会社 filed Critical コニカミノルタ株式会社
Priority to JP2019561608A priority Critical patent/JPWO2019131435A1/en
Publication of WO2019131435A1 publication Critical patent/WO2019131435A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/16—Making metallic powder or suspensions thereof using chemical processes
    • B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
    • B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
    • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/30—Inkjet printing inks
    • C09D11/32—Inkjet printing inks characterised by colouring agents
    • C09D11/324—Inkjet printing inks characterised by colouring agents containing carbon black
    • C09D11/326—Inkjet printing inks characterised by colouring agents containing carbon black characterised by the pigment dispersant
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D17/00—Pigment pastes, e.g. for mixing in paints

Definitions

  • the present invention relates to a method of producing a silver nanoparticle dispersion, a silver nanoparticle dispersion, an inkjet ink, and an image forming method using the same.
  • metallic gloss colors provide high-class feeling, high designability, strong eye-catching effects, etc., so that an image exhibiting metallic gloss colors is formed, for example, in recorded matter such as labels, packages, advertisement printed matter, and photographs.
  • an image exhibiting high luster and high-definition metallic gloss color can be formed by a digital printing method, particularly an ink jet printing method.
  • an ink containing metallic particles such as aluminum particles, gold particles, and silver particles as metallic gloss pigments is used.
  • the metal particles have a large specific gravity, they are difficult to stably exist in the ink, and there is a problem that aggregation and sedimentation easily occur.
  • the ink jet printing method since an image is formed by spraying a minute droplet of ink from a nozzle head, clogging of the nozzle and a decrease in dispersion stability affect the image, and the ink dispersion stability becomes particularly important. .
  • Patent Document 1 discloses an ink composition in which metal colloid particles containing metal nanoparticles such as gold and silver are dispersed in water or a water-soluble organic solvent.
  • Patent Document 2 discloses, as an aqueous silver colloid liquid having high dispersibility and storage stability, a silver ammine complex as a metal precursor compound, hydrazine as a reducing agent, polyvinyl pyrrolidone and polyvinyl alcohol as a dispersing agent. And an aqueous silver colloid liquid containing the
  • the ink composition of Patent Document 1 contains a large number of coarse metal colloid particles, the dispersion stability is not sufficient.
  • the metal colloid contained in the ink composition of Patent Document 1 is produced by reducing an aqueous silver nitrate solution.
  • the activity of the surface of minute metal nanoparticles is extremely high in the process of metal ions being reduced to precipitate metal nanoparticles, aggregation and coarsening of metal nanoparticles are likely to occur, resulting in coarse particles.
  • Metal colloid particles are easily generated.
  • the ink composition containing such coarse metal colloid particles has poor long-term dispersion stability and ejection stability. As described above, in the image formed by the ink composition having low dispersion stability, the metallic gloss is apt to be remarkably reduced, and the image quality is easily impaired.
  • dispersing agents such as polyvinyl pyrrolidone and polyvinyl alcohol
  • dispersing agents are easy to adsorb
  • the aqueous silver colloid liquid of Patent Document 2 is apt to release the dispersant over time, the dispersion stability tends to be reduced, and is insufficient for use in an inkjet ink.
  • an image formed of such an aqueous silver colloid liquid contains a free dispersing agent, the image may have a yellow or orange color and the design may be impaired.
  • the present invention has been made in view of such circumstances, and it is a method of producing a silver nanoparticle dispersion liquid having a large amount of coarse silver nanoparticles and high dispersion stability, a silver nanoparticle dispersion liquid, an inkjet ink and the use thereof It is an object of the present invention to provide an image forming method.
  • An aqueous solution containing a silver ammine complex, a polymer dispersant having an acidic group and a (poly) alkylene oxide group, and an alkanolamine as a reducing agent are mixed, and the silver ammine complex is reduced to obtain silver nanoparticles. And obtaining an aqueous dispersion containing water and a polymer dispersant adsorbed on at least a part of the surface of the silver nanoparticles, and purifying the aqueous dispersion containing the silver nanoparticles, Method for producing silver nanoparticle dispersion.
  • the polymer dispersant is a structural unit derived from a monomer selected from the group consisting of (meth) acrylic acid, maleic acid and a half ester thereof, an alkylene oxide modified (meth) acrylic ester, and an alkylene oxide modified maleic acid
  • the manufacturing method of the silver nanoparticle dispersion liquid as described in [1] or [2] which contains at least the structural unit derived from the monomer chosen from the group which consists of acid (half) ester.
  • [4] The method for producing a silver nanoparticle dispersion according to any one of [1] to [3], wherein the temperature when reducing the silver ammine complex is 50 ° C. or more and 80 ° C. or less.
  • [5] A silver nanoparticle dispersion containing silver nanoparticles, a polymer dispersant having an acidic group and a polyalkylene oxide group adsorbed on at least a part of the surface of the silver nanoparticles, water, and ammonia.
  • the content of the ammonia is 1 mass ppm or more and 1000 mass ppm or less based on the total mass of the silver nanoparticle dispersion, and the volume-equivalent average particle diameter D50 of the silver nanoparticles is 25 nm or more and 70 nm or less And a half width of a peak in a volume particle size distribution of the silver nanoparticles is 30 nm or more.
  • An inkjet ink comprising silver nanoparticles, a polymer dispersant having an acidic group and a (poly) alkylene oxide group adsorbed on at least a part of the surface of the silver nanoparticles, water, and ammonia.
  • the content of the ammonia is 1 mass ppm or more and 1000 mass ppm or less with respect to the total mass of the inkjet ink, the volume-equivalent average particle diameter D50 of the silver nanoparticles is 25 nm or more and 70 nm or less, The inkjet ink whose half value width of the peak in the volume particle size distribution of the said silver nanoparticle is 30 nm or more.
  • the inkjet ink according to [6] further comprising a water dispersible resin.
  • An image forming method comprising the step of applying the inkjet ink according to [6] or [7] on a substrate to form a metallic gloss layer.
  • the present invention can provide a method for producing a silver nanoparticle dispersion liquid having a large amount of coarse silver nanoparticles and high dispersion stability, a silver nanoparticle dispersion liquid, an inkjet ink, and an image forming method using the same.
  • the present inventors use silver ammine complex as a reaction raw material, and reduce silver ammine complex using a specific reducing agent (alkanolamine) in the presence of a specific polymer dispersant, It has been found that the formation of coarse particles is suppressed, and a silver nanoparticle dispersion having good dispersion stability can be obtained.
  • a specific reducing agent alkanolamine
  • the dispersion stability of the silver nanoparticle dispersion liquid is further enhanced by containing the ammonia derived from the silver ammine complex in the silver nanoparticle dispersion liquid thus obtained.
  • the silver nanoparticle dispersion liquid obtained in this manner has a small average particle diameter D50 of the silver nanoparticles, it is possible to increase the reflectance of the coating film. Furthermore, the obtained silver nanoparticle dispersion has a shape similar to a flat silver foil in the shape of a reflection spectrum of a coating film and has a gloss similar to that of silver, because the half width of the peak in the volume particle size distribution is large. (I.e., can have a silver like silver like bulk silver). Therefore, the coating film excellent in metallic glossiness can be obtained.
  • the supply of silver ions can be relaxed, so 1) the amount of micronucleus in the initial stage can be reduced appropriately, and 2) the surface of the micronucleus is a polymer dispersant. Dispersion stability can be enhanced because it is easily covered. Thereby, aggregation and rapid growth of particles are suppressed, and coarse particles are hardly generated.
  • the silver ion supplied later is not only used for the growth of the initial nucleus, but also easy to be used for the generation of a new nucleus, so the particle size distribution is likely to be broad (the nucleus generated at the initial growth is large And later generated nuclei are likely to become smaller because the time for which they can grow is short). As a result, it is considered that the average particle diameter D50 is small and the half width is large. The present invention has been made based on such findings.
  • the method of producing a silver nanoparticle dispersion liquid of the present invention comprises the steps of: 1) mixing an aqueous solution containing a silver ammine complex, a specific polymer dispersant, and a specific reducing agent; A step of reducing the complex to obtain an aqueous dispersion containing silver nanoparticles, a polymer dispersant adsorbed on at least a part of the surface of the silver nanoparticles, and water (silver nanoparticle production step), 2 And d) purifying the aqueous dispersion containing the obtained silver nanoparticles (purification step).
  • Step 1) (Silver Nanoparticle Generation Step)
  • the silver ammine complex is reduced by mixing an aqueous solution containing a silver ammine complex, a specific polymer dispersant, and a specific reducing agent.
  • silver nanoparticles having a polymeric dispersant adsorbed on at least a part of the surface are produced.
  • An aqueous solution containing a silver ammine complex (hereinafter, also referred to as “silver ammine complex solution”) is obtained by dissolving a silver compound in aqueous ammonia.
  • silver compounds include silver chloride, silver oxide, silver nitrate, silver carbonate and the like. Among them, silver nitrate is preferred. Silver nitrate has a relatively fast reduction reaction and is likely to produce coarse particles compared to other silver compounds, but by forming a complex with ammonia, the reduction reaction can be appropriately delayed, and it is difficult to produce coarse particles. It is from.
  • the content of the silver component in the silver ammine complex solution is preferably 5 g / L or more and 350 g / L or less.
  • the content of the silver component is more preferably 10 g / L or more and 200 g / L or less.
  • the content of ammonia in the silver ammine complex solution may be 1.5 or more and 4 or less (molar ratio) with respect to the total number of moles of the silver component as long as the silver component can sufficiently form a complex with ammonia. Is preferred.
  • the content of ammonia is 1.5 molar ratio or more, the silver component is easily complexed sufficiently, so the reduction reaction rate is easily slowed down and the formation of coarse particles is easily suppressed.
  • the content of ammonia is 4 molar ratio or less, the shape of the silver nanoparticles to be formed is easily stabilized.
  • the content of ammonia is more preferably 1.8 or more and 3 or less (molar ratio) with respect to the total number of moles of the silver component.
  • the polymer dispersant is a polymer dispersant having an acidic group and a (poly) alkylene oxide group.
  • the acidic group can function as an adsorptive group for adsorbing to the surface of silver nanoparticles.
  • the polymeric dispersant When the polymeric dispersant has an acidic group, it can exhibit sufficient performance as a protective colloid of silver nanoparticles.
  • the acidic group include carboxyl group, phosphoric acid group and sulfonic acid group. Among them, a carboxyl group is preferable.
  • the (poly) alkylene oxide group is a group having affinity to a solvent (hydrophilic group), and can function as a group constituting a solvation portion.
  • Examples of the (poly) alkylene oxide group include ethylene oxide group, propylene oxide group, ethylene oxide-propylene oxide containing group and the like.
  • the polymer dispersant having an acidic group and a (poly) alkylene oxide group is preferably a homopolymer or copolymer of a hydrophilic monomer.
  • the copolymer of the hydrophilic monomer may be a copolymer of a hydrophilic monomer and a hydrophobic monomer.
  • the hydrophilic monomer is preferably a monomer having an acid group and / or a (poly) alkylene oxide group and having a radically polymerizable ethylenic unsaturated bond.
  • hydrophilic monomers include monomers having a carboxyl group or an acid anhydride group (for example, (meth) acrylic acids such as acrylic acid and methacrylic acid; unsaturated polyvalent carboxylic acids such as maleic acid or partial esters thereof; Acid anhydrides such as maleic anhydride) or monomers having (poly) alkylene oxide groups (eg, ethylene oxide modified (meth) acrylic acid alkyl ester, acrylic acid diethylene glycol monoethyl ether such as alkylene oxide modified (meth) acrylic acid Ester monomers; alkylene oxide-modified maleic acid (half) ester monomers) and the like are included.
  • (meth) acrylic acids such as acrylic acid and methacrylic acid
  • unsaturated polyvalent carboxylic acids such as maleic acid or partial
  • the hydrophobic monomer is preferably a monomer having no acidic group and no polyalkylene oxide group, and having a radically polymerizable ethylenic unsaturated bond.
  • hydrophobic monomers include (meth) acrylic acid ester monomers such as methyl (meth) acrylate and ethyl (meth) acrylate; maleic acid diester monomers such as dimethyl maleate and diethyl maleate; styrene, ⁇ - Styrene-based monomers such as methylstyrene and vinyltoluene; ⁇ -olefin-based monomers such as ethylene, propylene and 1-butene; and carboxylic acid vinyl ester-based monomers such as vinyl acetate and vinyl butyrate.
  • the polymer dispersant is a structural unit derived from a monomer selected from the group consisting of (meth) acrylic acid, maleic acid or a half ester thereof, an alkylene oxide modified (meth) acrylic ester, and an alkylene oxide modified maleic acid ( It is preferable to include at least a structural unit derived from a monomer selected from the group consisting of a half) ester, and it may further contain a structural unit derived from another monomer as required.
  • a structural unit derived from a monomer selected from the group consisting of an alkylene oxide modified (meth) acrylic acid ester and an alkylene oxide modified maleic acid (half) ester is a group having an affinity to a solvent (solvation portion as described above) Can function as a hydrophilic group).
  • a polymer dispersant having such a group has a molecular structure in which side chains (alkylene oxide groups) are bonded to the main chain as if they were comb teeth. Since the side chains not only contribute to solvation but also cause steric hindrance, aggregation of silver nanoparticles can be more highly suppressed.
  • the copolymer may be any of a random copolymer, an alternating copolymer and a block copolymer.
  • polymeric dispersant examples include a main chain comprising an addition polymer disclosed in JP-A-6-200662 and at least one C1-C4 alkoxy polyethylene or polyethylene-copropylene glycol (meth) acrylate
  • An amphiphilic copolymer comprising a stabilizer unit and having a weight average molecular weight of 2500 to 20000, wherein the main chain comprises 70% by weight in total of 30% by weight or less of nonfunctional structural units
  • An amphiphilic copolymer comprising the following stabilizer unit and functional structural unit, the functional structural unit comprising a substituted or unsubstituted styrene-containing unit, a hydroxyl group-containing unit, and a carboxyl group-containing unit, etc. Can be mentioned.
  • Examples of commercially available polymer dispersants include Solsparse 24000, Solsparse 24000GR, Solsparse 32000, Solsparse 44000, Solsparse 46000 (manufactured by Lubrizol Corporation); Azispar PB 822, Azispar PB 821 and Azispar PB 711 (manufactured by Ajinomoto Fine Techno Co.); DISPERBYK- 102, DISPERBYK-187, DISPERBYK-194N, DISPERBYK-190, DISPERBYK-191, DISPERBYK-199, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2015, DISPERBYK-2015, DISPERBYK-2050, DISPERBYK-2150, and DISPERBYK-2069 (all of which are Big Chemie Company, "DISPER "YK” is a registered trademark of the company; Disparon ED-152
  • the acid value of the polymer dispersant is preferably 5 mg KOH / g or more and 200 mg KOH / g or less.
  • the acid value is 5 mg KOH / g or more, in the case of an acidic group that contributes to the adsorption onto the surface of the silver nanoparticle, the acidic group is adsorbed onto the surface of the silver nanoparticle and the surface of the silver nanoparticle is a polymer dispersant And easy to increase the dispersibility of silver nanoparticles in the ink.
  • the surface of the silver nanoparticle can be rendered hydrophilic to function as an anionic group, and the surface of the silver nanoparticle can be easily charged. And the charge repulsion between the silver nanoparticles is likely to occur, and the dispersibility in the ink is likely to be enhanced.
  • the acid value is 200 mg KOH / g or less
  • one polymer chain is adsorbed to two or more silver nanoparticles, so-called bridged aggregation It can be hard to happen.
  • the acid value of the polymer dispersant is more preferably 5 mgKOH / g or more and 150 mgKOH / g or less, and 10 mgKOH / g or more and 80 mgKOH / g
  • the content is more preferably 20 mg KOH / g or more and 50 mg KOH / g or less.
  • the acid value can be measured according to JIS K 0070.
  • the acid value of the polymer dispersant is determined by the type of polymer dispersant (for example, the product name of the polymer dispersant used for image formation, etc., by Fourier transform infrared spectroscopy (FT-IR).
  • FT-IR Fourier transform infrared spectroscopy
  • the acid value of the same polymer dispersant may be measured according to JIS K 0070.
  • the type of the polymeric dispersant may be specified by 1 H NMR or gas chromatography-mass spectrometry (GC / MS).
  • the molecular weight of the polymer dispersant is preferably 1,000 or more and 100,000 or less, and more preferably 2,000 or more and 50,000 or less. When the molecular weight of the polymer dispersant is within the above range, the surface of the silver nanoparticles can be sufficiently coated with the polymer dispersant, and the storage stability of the ink can be further enhanced.
  • silver nanoparticles having the polymer dispersant adsorbed on at least a part of the surface can be obtained.
  • the compounding quantity of a polymer dispersing agent is 3 to 50 mass% with respect to the total mass of the silver component which comprises a silver ammine complex.
  • the content of the polymer dispersant is 3% by mass or more, the produced silver nanoparticles can be sufficiently covered with the polymer dispersant, so aggregation of the silver nanoparticles is easily suppressed, and coarse particles are reduced.
  • Cheap Thereby, the average particle size D50 of the obtained silver nanoparticles can be made smaller.
  • the amount of the polymer dispersant contained is 50% by mass or less in the resulting silver nanoparticle dispersion, so that the amount of excess polymer dispersant (free polymer dispersant) can be reduced, so that the subsequent purification can be performed.
  • the compounding amount of the polymer dispersant is more preferably 4% by mass or more and 30% by mass or less with respect to the silver component constituting the silver ammine complex.
  • the reducing agent is an alkanolamine.
  • Amines are generally relatively slow in reduction rate compared to other reducing agents, which can make it difficult to produce coarse particles.
  • alkanolamines are readily soluble in water and are suitable for obtaining aqueous silver nanoparticle dispersions.
  • alkanolamines having a primary amino group examples include ethanolamine, propanolamine, butanolamine, hexanolamine, 2- (2-aminoethoxy) ethanol, 1-amino-2-propanol, 2-amino-2-methyl -1-propanol and 2-amino-1-butanol are included.
  • alkanolamines having secondary amino groups include methylaminoethanol, diethanolamine, 2- (3-aminopropylamino) ethanol, diisopropanolamine.
  • alkanolamines having a tertiary amino group examples include dimethylaminoethanol, diethylaminoethanol, 3- (dimethylamino) -1-propanol, triethanolamine, methyldiethanolamine and the like. These may be used alone or in combination of two or more. Among these, an alkanolamine having a tertiary amino group is preferable, and dimethylaminoethanol is more preferable.
  • the compounding amount of the reducing agent is not particularly limited as long as it is not less than the amount necessary to reduce the metal in the metal compound, but 1 to 10 with respect to the total number of moles of the silver component constituting the silver ammine complex It is preferable that it is molar ratio.
  • the compounding amount of the reducing agent is 1 (molar ratio) or more, the reduction rate of the metal ion does not become too slow, so that the production efficiency is hardly impaired. Since the amount of excess reducing agent can be reduced in the obtained silver nanoparticle dispersion liquid when the blending amount of the reducing agent is 10 (molar ratio) or less, not only the load of the subsequent purification step can be easily reduced The hue of the resulting coating (or image) is also less likely to be impaired.
  • the blending amount of the reducing agent is more preferably 1.2 or more and 5 or less (molar ratio) with respect to the total number of moles of the silver component constituting the silver ammine complex.
  • the temperature at the time of mixing the aqueous solution containing a silver ammine complex, a specific polymer dispersing agent, and a specific reducing agent and performing a reduction reaction is 20 ° C. or more and 90 ° C. or less.
  • the temperature is 20 ° C. or higher, the reduction performance of the reducing agent can be increased, so the reduction reaction of the silver ammine complex does not become too slow, and it is easy to suppress the reduction in production efficiency.
  • the half value width of the peak of the particle size distribution of the obtained silver nanoparticle dispersion does not easily decrease. If the temperature is 90 ° C.
  • the temperature for reduction reaction is more preferably 30 ° C. or more and 80 ° C. or less, and still more preferably 50 ° C. or more and 80 ° C. or less.
  • Step 2) (Purification Step)
  • the aqueous dispersion containing the silver nanoparticles produced in the step 1) is purified.
  • the purification method includes electrodialysis, centrifugation, ultrafiltration and the like, and is not particularly limited, but may be a method of filtering and washing the aqueous dispersion containing the produced silver nanoparticles.
  • the method of filtration and washing is not particularly limited, and may be, for example, a method of performing filtration and washing by repeating concentration using an ultrafiltration device and dilution of the obtained concentrate with pure water.
  • impurities such as a polymer dispersant, ammonia, and a reducing agent which are free in the liquid without being adsorbed on the surface of the silver nanoparticles can be sufficiently removed.
  • the purification is carried out to such an extent that impurities such as polymer dispersants, reducing agents, and ammonia released in the solution can be sufficiently removed without being adsorbed to the surface of silver nanoparticles (specifically, the total amount of these impurities) To be in the range described later).
  • the silver nanoparticle dispersion liquid can be obtained by concentrating the solid content concentration of the silver nanoparticle dispersion liquid to, for example, 2% by mass or more and 50% by mass or less.
  • the solid content concentration is substantially the total amount of silver nanoparticles and the polymeric dispersant adsorbed on the surface thereof.
  • the total amount of the aforementioned impurities contained in the silver nanoparticle dispersion is preferably, for example, 1% by mass or less based on the total mass of the silver nanoparticle dispersion.
  • the content of ammonia in the silver nanoparticle dispersion liquid is preferably 1500 mass ppm or less, and more preferably 1000 mass ppm or less.
  • Silver nanoparticle dispersion liquid of the present invention obtained by the method for producing a silver nanoparticle dispersion liquid of the present invention comprises silver nanoparticles, a polymer dispersant adsorbed on the surface of the silver nanoparticles, water, And ammonia.
  • Silver nanoparticles are nano-sized metal particles containing silver.
  • Silver nanoparticles contain silver as a main component.
  • the main component means, for example, a component of 50 atomic% or more with respect to the total of all the atoms constituting the silver nanoparticles.
  • the silver nanoparticles may further contain minor amounts of other components which are inevitably contained (for example, an oxide of silver).
  • the silver nanoparticles may be further surface treated with citric acid or the like to enhance dispersion stability.
  • the volume-equivalent average particle diameter D50 of the silver nanoparticles is preferably 25 nm or more and 70 nm or less.
  • the average particle diameter D50 of the silver nanoparticles is 70 nm or less, the particle diameter is not at least biased to the large particle diameter side, so the dispersion stability is good and the metallic gloss of the coating film tends to be enhanced.
  • the average particle diameter D50 of the silver nanoparticles is more preferably 30 nm or more and 65 nm or less, and still more preferably 35 nm or more and 65 nm or less.
  • the half width of the peak in the volume particle size distribution of the silver nanoparticles is preferably 30 nm or more.
  • the half value width of the peak in the volume particle size distribution of the silver nanoparticles is more preferably 30 nm or more and 120 nm or less, still more preferably 40 nm or more and 100 nm or less, and still more preferably 40 nm or more and 80 nm or less.
  • the half width is 120 nm or less, particles of various different particle sizes can be included in the range that does not include particles that are too coarse, and dispersion stabilization is easy.
  • the full width at half maximum of the peak is the width (full width at half maximum) of the particle diameter which is 1/2 of the peak maximum value in the volume particle size distribution.
  • the “peak” in the volume particle size distribution is a peak at which the volume frequency of the maximum value is 5% or more in the volume particle size distribution measured at intervals of 5 nm. That is, peaks having a volume frequency of maximum less than 5% are not included in the number of peaks in the present invention.
  • the particle size distribution of silver nanoparticles at least one peak having the above-described half width may be present, and a plurality of peaks may be present.
  • a plurality of peaks may be present.
  • another peak may be present.
  • the particle size distribution of silver nanoparticles may be unimodal with one peak or multimodal with two or more peaks.
  • the volume-equivalent average particle diameter D50 of silver nanoparticles and the half width of the peak in the volume particle size distribution can be measured by the following procedure. 1) After applying the dispersion on a glass plate, vacuum degassing is performed to volatilize solvent components to obtain a sample. The obtained sample dispersion is subjected to SEM observation using a measuring apparatus JEOL JSM-7401F to measure the particle diameter of any 300 silver nanoparticles. 2) Based on the obtained measurement data, a particle size distribution based on volume is determined using image processing software Image J, and D50 (median diameter) thereof is defined as an average particle diameter (volume average particle diameter). Also, the half-width of the obtained particle size distribution peak is determined.
  • the particle diameter of the silver nanoparticles is determined as the particle diameter of the silver nanoparticles not containing the polymer dispersing agent.
  • the average particle diameter D50 of the silver nanoparticles and the half width of the peak in the volume particle size distribution are the blending amount and dropping time of the reducing agent, the blending amount of the polymer dispersant and the reduction reaction in the method for producing the silver nanoparticle dispersion described above. It can be adjusted by the temperature of the hour. In order to reduce the average particle diameter D50 of the silver nanoparticles, for example, it is preferable to increase the blending amount of the polymer dispersant and lower the temperature at the reduction reaction.
  • the dropping time of the reducing agent may be shortened, the blending amount of the polymer dispersant may be reduced, and the temperature during the reduction reaction may be increased. preferable.
  • the polymer dispersant contained in the silver nanoparticle dispersion is a component derived from the polymer dispersant used in the method for producing a silver nanoparticle dispersion of the present invention, and at least at the surface of the silver nanoparticles It is adsorbed to a part.
  • the polymeric dispersant is the same as the polymeric dispersant described above.
  • ammonia contained in the silver nanoparticle dispersion liquid is a component derived from the silver ammine complex used in the method for producing a silver nanoparticle dispersion liquid of the present invention. Ammonia may be further added as necessary because it can further enhance the dispersion stability of the silver nanoparticles.
  • the content of ammonia in the silver nanoparticle dispersion liquid is preferably 0.5 mass ppm or more and 1,500 mass ppm or less. That is, in the silver nanoparticle dispersion liquid obtained by the method for producing a silver nanoparticle dispersion liquid of the present invention, the content of ammonia is usually 0.5 mass ppm or more. Furthermore, since ammonia can further enhance the dispersion stability of silver nanoparticles, the content of ammonia is more preferably 1 mass ppm or more and 1000 mass ppm or less.
  • the content of ammonia can be measured, for example, at 25 ° C. by capillary electrophoresis.
  • the content of ammonia can be adjusted mainly by the above-mentioned purification step, but may be adjusted by further adding ammonia in a step separate from the purification step, if necessary.
  • the silver nanoparticle dispersion may further contain other components in addition to the above as required.
  • other components include foreign ions such as nitrate ion derived from raw materials, impurities such as salts generated by reduction and decomposition products of amine, and organic solvents and viscosity modifiers depending on storage stability improvement and purpose of use. , Resins, surfactants, pH adjusters, surface tension adjusters, plasticizers, fungicides, preservatives, moisturizers, evaporation accelerators, antifoaming agents, antioxidants, light stabilizers, antidegradants, oxygen Absorbent, rust inhibitor etc. are included.
  • the silver nanoparticle dispersion liquid of the present invention can be widely used in paints, inks and the like. Among them, the silver nanoparticle dispersion liquid of the present invention can be preferably used as an inkjet ink because the average particle diameter D50 of silver nanoparticles is small and the dispersion stability is high.
  • the inkjet ink of the present invention comprises silver nanoparticles, a polymer dispersant adsorbed on the surface of the silver nanoparticles, water, and ammonia.
  • the content of the polymer dispersant in the inkjet ink with respect to the total mass of silver nanoparticles may be similar to the content of the polymer dispersant in the produced silver nanoparticle dispersion with respect to the total mass of silver nanoparticles.
  • the content of ammonia in the inkjet ink is preferably 0.5 mass ppm or more and 1500 mass ppm or less. That is, since the ammonia derived from the silver ammine complex aqueous solution remains in the silver nanoparticle dispersion liquid of the present invention obtained by the method for producing a silver nanoparticle dispersion liquid of the present invention, the silver nanoparticle dispersion liquid is used In the ink jet ink obtained as a result, ammonia is usually contained in an amount of 0.5 mass ppm or more.
  • the content of ammonia is more preferably 1 mass ppm or more and 1000 mass ppm or less with respect to the total mass of the inkjet ink. More preferably, it is 5 mass ppm or more and 1000 mass ppm or less.
  • the inkjet ink may further contain other components in addition to the above components as long as the effects of the present invention are not impaired.
  • other components include water dispersible resins and solvents, known surfactants (surface conditioners) and the like.
  • the water dispersible resin is a resin dispersed in water or an aqueous solvent, that is, a resin capable of forming a colloidal dispersion in a semi-dissolved particle state or an emulsion or latex in a dispersed particle state in water or an aqueous solvent. And can function as a binder resin.
  • the water dispersible resin interacts with the polymer dispersant adsorbed on the surface of the silver nanoparticles to bind the silver nanoparticles together, form the film of the silver nanoparticles, and adhere the silver nanoparticles to the substrate. It can enhance sex.
  • the water dispersible resin is a polymer having a hydrophilic component as a monomer component, and forms a colloidal dispersion in the form of semi-soluble particles, an emulsion or a latex in the form of dispersed particles, etc. in water or an aqueous solvent.
  • hydrophilic components include anionic groups such as carboxyl group, sulfonic acid group and phosphoric acid group, cationic groups such as primary to tertiary amino groups and quaternary ammonium base, hydroxyl group and polyalkylene oxide group And a monomer component containing a nonionic group such as an amido group.
  • the hydrophilic component may be contained alone or in combination of two or more. Among them, hydrophilic components containing a carboxyl group, a sulfonic acid group, a polyoxyethylene group or a polyoxypropylene group are preferable.
  • the water dispersible resin may be either a forced emulsifying type water dispersible resin obtained by dispersing with an external emulsifier, or a self emulsifying type water dispersible resin in which a hydrophilic component is introduced into the resin skeleton. More preferably, it is a self-emulsifiable water-dispersible resin in which a hydrophilic component is introduced into the resin skeleton.
  • the water-dispersible resin is preferably a resin having high affinity to a polymer dispersant, and examples thereof include acrylic resins, urethane resins, and polyester resins containing the above-mentioned hydrophilic component as a monomer component. And vinyl chloride resins and vinyl acetate resins.
  • an acrylic resin containing a hydrophilic component as a monomer component for example, an acrylic resin containing acrylic acid as a monomer component
  • a hydrophilic component as a monomer component from the viewpoint of improving the water resistance of the metal gloss layer obtained.
  • a urethane resin for example, a polyurethane resin containing dimethylol propionic acid as a monomer component is more preferable.
  • the average particle diameter of the water-dispersible resin is preferably 0.005 ⁇ m or more and 0.5 ⁇ m or less, more preferably 0.01 ⁇ m or more and 0.2 ⁇ m or less, and preferably 0.01 ⁇ m or more and 0.15 ⁇ m or less Is more preferred.
  • the average particle size of the water-dispersible resin can be measured by the same method as the method for measuring the average particle size of silver nanoparticles.
  • M1 / M2 When the content of silver nanoparticles is M1 (% by mass) and the content of the water-dispersible resin is M2 (% by mass), M1 / M2 preferably satisfies 1.3 ⁇ M1 / M2 ⁇ 35.
  • M1 / M2 is 1.3 or more, the content ratio of the resin that easily absorbs light can be reduced, and the content ratio of silver nanoparticles can be increased, so it is easy to increase the reflectance of the metal reflective layer.
  • the M1 / M2 is 35 or less, the content ratio of the resin can be appropriately increased, so the adhesion of the metal reflective layer to the substrate is unlikely to be impaired. More preferably, M1 / M2 satisfies 2 ⁇ M1 / M2 ⁇ 30.
  • the total content (M1 + M2) of the content M1 (mass%) of the silver nanoparticles and the content M2 (mass%) of the water dispersible resin preferably satisfies 1 ⁇ M1 + M2 ⁇ 35.
  • M1 + M2 is 1 or more, the amount of solid content contained in the inkjet ink is appropriately large, so a metal gloss layer having a desired thickness is easily formed, and a sufficient reflectance is easily obtained.
  • M1 + M2 is 35 or less, the solid content in the ink is not too large, so the viscosity does not increase too much, and the ejection stability of the inkjet ink is unlikely to be impaired. It is more preferable that M1 + M2 satisfy 3 ⁇ M1 + M2 ⁇ 30.
  • solvent contains at least water, but may further contain an organic solvent in any proportion.
  • organic solvent examples include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether Ethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol monopropyl ether, tetraethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ester
  • Glycol ethers such as ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether;
  • the solvent preferably includes an organic solvent having a boiling point of 150 ° C. or more from the viewpoint of preventing the ink from drying in the vicinity of the ink jet head and enhancing the dischargeability from the head.
  • organic solvents include glycerin, propylene glycol, triethylene glycol monomethyl ether and the like.
  • surfactants examples include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates and fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols and polyoxy acids
  • anionic surfactants such as ethylene polyoxypropylene block copolymers, cationic surfactants such as alkylamine salts and quaternary ammonium salts, and surfactants of silicone type and fluorine type.
  • silicone surfactants include KF-351A, KF-352A, KF-642 and X-22-4272, Shin-Etsu Chemical Co., Ltd., BYK-307, BYK-345, BYK-347 and BYK -348, manufactured by Big Chemie ("BYK” is a registered trademark of the company), as well as TSF4452, manufactured by Toshiba Silicone Co., Ltd.
  • the content of the surfactant can be, for example, 0.001% by mass or more and less than 1.0% by mass with respect to the total mass of the ink.
  • the viscosity of the inkjet ink of the present invention is preferably 1 cP or more and less than 100 cP, and more preferably 1 cP or more and 50 cP or less, from the viewpoint of further enhancing the ejection stability from the nozzle in image formation by the inkjet method. More preferably, it is 1 cP or more and 15 cP or less.
  • the image forming method of the present invention includes the step of applying the inkjet ink of the present invention on a substrate to form a metallic gloss layer.
  • Step of Forming a Metallic Gloss Layer The above-described inkjet ink is applied onto a substrate and then dried to form a metallic gloss layer.
  • the substrate is not particularly limited, and may be an absorbent substrate or a non-absorbent substrate.
  • absorbent substrates include coated papers such as art papers, coated papers, lightweight coated papers, fine coated papers, and cast papers, and non-coated papers.
  • non-absorbent substrates include polyvinyl chloride (PVC), polyolefins (eg polyethylene (PE), polypropylene (PP) etc.), polyurethane (PU), acrylic resin (PA), polycarbonate (PC), polystyrene PS), Acrylonitrile-Butadiene-Styrene Copolymer (ABS), Polyester (for example, polyethylene terephthalate (PET) or polybutadiene terephthalate (PBT)), resin base material including resin such as nylon (Ny), metals, glass, etc.
  • the application of the ink can be performed by an inkjet method. Specifically, the ink is ejected from the nozzle of the inkjet head to land on the surface of the substrate.
  • the application amount of the ink is such that the thickness of the obtained metallic gloss layer is preferably 0.005 to 10 ⁇ m, more preferably 0.01 to 1.0 ⁇ m, and still more preferably 0.1 to 0.5 ⁇ m. Set to When the thickness of the obtained metallic gloss layer is in the above range, the metallic gloss is easily exhibited sufficiently.
  • the drying of the ink is not particularly limited, and may be performed by a vacuum degassing method, a blast drying method, a heat drying method, or the like.
  • the drying temperature of the ink is preferably less than the glass transition temperature of the water-dispersible resin, for example, preferably from normal temperature to less than 100 ° C., and more preferably from normal temperature to less than 80 ° C.
  • heating may be further performed as needed.
  • the water-dispersible resin in the ink can be easily fused, and the adhesion of the metallic gloss layer to the substrate can be further enhanced.
  • the heating temperature of the ink may be any temperature at which the water-dispersible resin can be heat-fused, and is preferably at least the minimum film-forming temperature (MFT) or glass transition temperature of the water-dispersible resin.
  • MFT minimum film-forming temperature
  • the heating temperature is preferably, for example, 40 ° C. or more, and the upper limit temperature needs to be equal to or less than the heat resistance temperature of the base material and the water-dispersible resin.
  • a film forming aid to the ink, it is also possible to form a film at a Tg or less of the water-dispersible resin.
  • Drying and heating of the ink may be performed sequentially or simultaneously.
  • the drying and heating temperature is preferably at least the minimum film forming temperature (MFT) or the glass transition temperature of the water-dispersible resin.
  • the image forming method of the present invention may further include the step of forming a primer layer on the surface of the substrate before the metallic gloss layer is formed by the above-described steps, if necessary. Further, the image forming method of the present invention may further include the step of forming a coloring material layer or a protective layer on the surface side of the obtained metallic gloss layer.
  • the primer layer can be formed by applying a resin composition containing a binder resin to the surface of the base before the metallic gloss layer is formed. After application of the resin composition, the resin composition may be dried by heating or the like to form a film of binder resin. The drying temperature at this time may be, for example, less than 100 ° C.
  • the binder resin contained in the resin composition may be any resin conventionally used in order to enhance the adhesion of pigments including silver nanoparticles and the like to a substrate.
  • binder resins include acrylic resins, epoxy resins, polysiloxane resins, maleic acid resins, polyolefin resins, vinyl chloride resins, polyamide resins, polyvinyl pyrrolidone, polyhydroxystyrene, polyvinyl alcohol And nitrocellulose, cellulose acetate, ethylcellulose, ethylene-vinyl acetate copolymer, urethane resin, polyester resin, and alkyd resin. These resins may be used alone or in combination of two or more.
  • compositions containing a monomer, oligomer or polymer containing a (meth) acryloyl group, a vinyl group, an epoxy group or an oxetane group are applied to the substrate surface, the composition is cured by energy ray irradiation such as ultraviolet light. It may be allowed to form a primer layer.
  • the color material layer can be formed by applying a resin composition containing known pigments or dyes and a binder resin for fixing them on the metallic gloss layer.
  • the protective layer can be formed by applying a resin composition containing a binder resin on the metallic gloss layer. After application of these resin compositions, the resin composition may be dried by heating or the like to form a binder resin film. The drying temperature at this time may be, for example, less than 100 ° C.
  • the resin contained in these resin compositions can be selected from the same resins as the binder resin contained in the primer layer.
  • compositions containing a monomer, oligomer or polymer containing (meth) acryloyl group, vinyl group, epoxy group or oxetane group is applied onto the metallic gloss layer, and then the composition is irradiated with energy rays such as ultraviolet rays. It may be cured to form a colorant layer or a protective layer.
  • the resin composition may be liquid or film-like. That is, the color material layer and the protective layer may be formed by drying after applying a liquid resin composition, or may be formed by thermocompression bonding of a film-like resin composition.
  • the liquid resin composition can be applied by an inkjet method, a spray method, a roller coating method, an electrophotographic method, or the like. From the viewpoint of facilitating the formation of a fine image, it is preferable to use the inkjet method.
  • the drying temperature after the application of the liquid resin composition is a temperature at which the solvent can be volatilized and the resin can be formed into a film, and may be, for example, less than 100 ° C.
  • thermocompression bonding of the film-like resin composition can be performed by a method of thermocompression bonding by a crimping roller, or a method of thermally transferring a transfer layer previously formed on a sheet by a thermal head or a heat roller.
  • the thermocompression bonding temperature may be in the vicinity of the glass transition temperature of the binder resin.
  • the image-formed article of the present invention obtained by the image-forming method of the present invention comprises a substrate and a metallic gloss layer provided on the substrate.
  • the image-formed product of the present invention may further include a primer layer provided between the substrate and the metallic gloss layer, and a colorant layer and a protective layer provided on the metallic gloss layer, as needed.
  • the metallic gloss layer contains silver nanoparticles and a polymeric dispersant adsorbed on the surface thereof.
  • the composition of the metallic gloss layer is the same as the composition of the solid content of the aforementioned inkjet ink.
  • the composition of the primer layer and the composition of the color material layer and the protective layer are also the same as the composition of the solid content of the resin composition for the primer layer, the color material layer and the protective layer described above.
  • the image-forming material can be preferably used in applications where expression of metallic gloss is required.
  • an image formed article can be used for a recorded matter.
  • the recorded matter may be a single character or a set of characters, and may be an image such as a figure, a picture, a photograph, and the like.
  • Preparation of Silver Nanoparticle Dispersion ⁇ Preparation of Silver Nanoparticle Dispersion 1> 8.3 g of DISPERBYK-190 (manufactured by Big Chemie, solvent: water, solid content (non-volatile component): 40% by mass) as a polymer dispersant in a 1 L separable flask having a flat stirring blade and a baffle plate.
  • Acid value in terms of solid content 100% by mass 25 mg KOH / g, polymer whose main chain contains a structural unit derived from styrene and a structural unit derived from maleic acid and whose side chain has a polyalkylene oxide group, in Table 1 a dispersant A symbol of A) and 260 g of ion exchanged water were added, and stirring was performed to dissolve DISPERBYK-190 to obtain an aqueous dispersant solution. Next, a silver nitrate aqueous solution in which 70 g of silver nitrate was dissolved in 260 g of ion-exchanged water was charged into the separable flask while stirring.
  • the obtained reaction solution was put in a stainless steel cup, and 2 L of ion exchanged water was further added, and then the pump was operated to carry out ultrafiltration (purification step).
  • the solution in the stainless steel cup decreased, ion-exchanged water was again added, and purification was repeated until the conductivity of the filtrate became 100 ⁇ S / cm or less.
  • the filtrate was concentrated to obtain a silver nanoparticle dispersion 1 with a solid content of 30% by mass.
  • the ultrafiltration apparatus used was an ultrafiltration module AHP1010 (Asahi Kasei Co., Ltd., molecular weight cut off: 50000, number of membranes used: 400), and a tube pump (Masterflex Co., Ltd.) connected by a tygon tube. .
  • Silver nanoparticle dispersions 2 to 5 were prepared in the same manner as the silver nanoparticle dispersion 1, except that each material was changed as described in Table 1 and prepared under the conditions described in Table 1.
  • Silver nanoparticles were dispersed similarly to the preparation of silver nanoparticle dispersion 1, except that the reducing agent was changed to diisopropanolamine (represented as reducing agent B in Table 1) and prepared under the conditions described in Table 1 Liquid 6 was prepared.
  • the dispersing agent is Floren G 700 (manufactured by Kyoeisha Chemical Co., Ltd., solid content (non-volatile component): 100% by mass, acid value: 60 mg KOH / g, main chain contains structural unit derived from .alpha.-olefin and structural unit derived from maleic acid, Silver was changed similarly to preparation of the silver nanoparticle dispersion liquid 1 except having changed into the polymer which chain has a polyalkylene oxide group (It is described as dispersing agent B in Table 1), and was prepared on the conditions of Table 1. Nanoparticle dispersion 7 was prepared.
  • Silver Nanoparticle Dispersion 8 The silver nano particles were prepared in the same manner as the silver nanoparticle dispersion liquid 1 except that the reducing agent was changed to hydrazine monohydrate (represented as reducing agent C in Table 1) and prepared under the conditions described in Table 1. A particle dispersion 8 was prepared.
  • Silver Nanoparticle Dispersion 9 The dispersant was changed to polyvinyl pyrrolidone K15 (manufactured by Tokyo Kasei Kogyo Co., Ltd., solid content (nonvolatile component): 100% by mass, having no acidic adsorptive group and alkylene oxide structure, represented as dispersant C in Table 1), and Table 1 A silver nanoparticle dispersion 9 was prepared in the same manner as the silver nanoparticle dispersion 1 except that the preparation was performed under the conditions described in 4.
  • polyvinyl pyrrolidone K15 manufactured by Tokyo Kasei Kogyo Co., Ltd., solid content (nonvolatile component): 100% by mass, having no acidic adsorptive group and alkylene oxide structure, represented as dispersant C in Table 1
  • Table 1 A silver nanoparticle dispersion 9 was prepared in the same manner as the silver nanoparticle dispersion 1 except that the preparation was performed under the conditions described in 4.
  • composition of the solid content of the obtained silver nanoparticle dispersions 1 to 9 and the particle size distribution of the silver nanoparticles were evaluated by the following methods.
  • composition of solid content of silver nanoparticle dispersion A portion of the obtained silver nanoparticle dispersion was collected and vacuum dried at room temperature for 10 hours to obtain a solid containing silver nanoparticles. The obtained solid was subjected to thermogravimetric analysis (Thermoplus TG 8120 manufactured by RIGAKU), and the weight loss at 50 to 500 ° C. was used as the organic component in the solid content, and the residue at 500 ° C. as the Ag content.
  • the average particle diameter D50 of silver nanoparticles and the half-width in the volume particle size distribution were measured by the following procedure. 1) After the dispersion was applied on a glass plate, it was vacuum degassed to evaporate the solvent components to obtain a sample. The obtained sample dispersion was subjected to SEM observation using a measuring apparatus JEOL JSM-7401F, and the particle diameters of 300 arbitrary silver nanoparticles were measured. 2) Based on the obtained measurement data, a particle size distribution based on volume is determined using image processing software Image J, and D50 (median diameter) thereof is defined as an average particle diameter (volume average particle diameter). In addition, the half width of the obtained particle size distribution peak was determined. In addition, in SEM observation, since the dispersing agent adsorbed on the surface of silver nanoparticles can not be observed, the particle diameter of silver nanoparticles was determined as the particle diameter of silver nanoparticles containing no dispersing agent.
  • compositions of the silver nanoparticle dispersions 1 to 9 are shown in Table 1, and the physical properties of the silver nanoparticles (the composition of the solid content and the particle size distribution of the silver nanoparticles) are shown in Table 2.
  • silver nanoparticle dispersions 1 to 3 prepared using an alkanolamine as a reducing agent, a polymer dispersant having an acidic group and a polyalkylene oxide group as a polymer dispersant, and a silver ammine complex aqueous solution It can be seen that the average particle diameter D50 is smaller, the half width of the peak is larger, and a broad particle size distribution is obtained, as compared with the silver nanoparticle dispersion liquid 5 manufactured without using the silver ammine complex aqueous solution.
  • the average particle diameter D50 of the silver nanoparticles can be further decreased while the half width of the peak in the volume particle size distribution is made constant or more by increasing the compounding amount of the polymer dispersant to the silver compound (silver Comparison of nanoparticle dispersions 1 to 4).
  • silver nanoparticle dispersion liquid 8 manufactured using hydrazine monohydrate (reducing agent C) as a reducing agent, and silver nanoparticles manufactured using polyvinyl pyrrolidone (dispersant C) as a polymer dispersing agent
  • reducing agent C hydrazine monohydrate
  • dispersant C polyvinyl pyrrolidone
  • particles were aggregated and precipitated, and a sample for measuring the particle diameter D50 and the half width of the particle size distribution could not be prepared sufficiently.
  • Coarse particles on the order of 100 nm were mainly observed from the SEM image obtained by collecting a part of the mass.
  • a silver nanoparticle dispersion was dropped on a slide glass, applied by a spin coater, and then dried to form a coating film (metallic gloss layer).
  • the reflectance at each wavelength of 10 nm was measured in the range of 450 nm to 650 nm using a spectrophotometer U4100, and the average value thereof was determined. Then, the reflectance was evaluated based on the following criteria. :: The above average value is 50% or more. :: The above average value is less than 50% 40% or more. ⁇ : The above average value is less than 40% 30% or more. ⁇ : The above average value is less than 30%. did.
  • the reflectance of the formed coating film was measured using a spectrophotometer U4100, and the standard deviation of the reflectance of each wavelength for every 20 nm in the range of 460 nm to 780 nm was calculated. And the color was evaluated based on the following criteria. :: Standard deviation of reflectance is less than 2 ⁇ : Standard deviation of reflectance is 2 or more and less than 3 ⁇ : standard deviation of reflectance is 3 or more and less than 4 ⁇ : standard deviation of reflectance is 4 or more ⁇ was evaluated as an allowable range. The smaller the standard deviation, the smaller the difference in reflectance between each wavelength, the closer the shape of the reflection spectrum becomes flat, and the so-called silvery silvery like so-called bulk silver. On the other hand, as the standard deviation is larger, the reflectance difference between each wavelength is more, the reflection spectrum has a peak at a specific wavelength, and silver has a coloring feeling.
  • a silver nanoparticle dispersion liquid 1-4 prepared using an alkanolamine as a reducing agent, a polymer dispersing agent having an acidic group and a polyalkylene oxide group as a polymer dispersing agent, and a silver ammine complex aqueous solution
  • each of Nos. 10 to 13 had good storage stability, and the luster of the resulting coated film (metallic gloss layer) was also good.
  • the reflectance and the color can be further improved by setting the compounding amount of the polymer dispersant in a predetermined range (contrast of dispersion liquids 1 to 4).
  • the reflectance and the color can be further improved by setting the content of ammonia in the dispersion to a predetermined range (contrast of dispersions 2 and 10 to 13).
  • the silver nanoparticle dispersion liquid 5 manufactured without using the silver ammine complex aqueous solution had poor storage stability, and the luster of the obtained coating film (metallic gloss layer) was also low.
  • Polyesterol (molecular weight: 2000) 580 parts by weight obtained by reacting neopentyl glycol, ethylene glycol, terephthalic acid, isophthalic acid, and adipic acid at 56: 4: 1: 21: 18 (mass ratio), and trimethylol 15 parts by mass of propane and 667 parts by mass of methyl ethyl ketone were sufficiently dissolved by stirring. Next, 300 parts by mass of isophorone diisocyanate was added to this solution, and reacted at 75 ° C. for 1 hour.
  • reaction solution After completion of the reaction, the reaction solution is cooled to 60 ° C., 105 parts by mass of dimethylol propionic acid and 59 parts by mass of triethylamine (0.6 mol with respect to dimethylol propionic acid) are added and reacted at 75 ° C. A urethane prepolymer solution having 1.0% of terminal isocyanate groups was obtained. The urethane prepolymer was cooled to 40 ° C., 1857 parts by mass of water was added, and the mixture was stirred at high speed with a homomixer to emulsify.
  • This resin solution was heated under reduced pressure to remove methyl ethyl ketone, thereby obtaining a dispersion containing a polyurethane having a solid concentration of 30% by mass as a water dispersible resin.
  • the average particle diameter D2 of the obtained polyurethane was measured, it was 40 nm.
  • the storage stability and image characteristics of the resulting inkjet inks 1 to 9 were evaluated by the following methods.
  • ⁇ Silver particles were sedimented, but when the container was shaken, they were apparently redispersed. In the discharge evaluation, the line was interrupted halfway. The storage stability of the ink and the dischargeability were evaluated as poor.
  • X Silver particles have settled and do not re-disperse even if the container is shaken. It was evaluated that the ejection stability could not be evaluated, and the storage stability of the ink was extremely bad. ⁇ ⁇ or more was evaluated as an acceptable range.
  • Image formation was performed as follows using the obtained inkjet inks 1 to 9.
  • a metallic gloss layer was formed on the substrate using an inkjet recording apparatus having a piezoelectric inkjet nozzle.
  • the ink jet recording apparatus has an ink tank, an ink supply pipe, an ink supply tank immediately before the ink jet head, a filter, and a piezoelectric ink jet head from the upstream side to the downstream side through which ink flows, in this order.
  • the ink jet head was driven under the condition that the droplet volume was 14 pl, the printing speed was 0.5 m / sec, the ejection frequency was 10.5 kHz, and the printing rate was 100%, and the ink droplets were ejected and landed on each substrate. . After landing, it was dried at 60 ° C. for about 10 minutes to obtain an image-formed product.
  • the reflectance of the obtained image-formed product, the uniformity of metallic glossiness and the color were evaluated by the same method as described above.
  • the compositions of the inkjet inks 1 to 9 and the evaluation results are shown in Table 4.
  • a silver nanoparticle dispersion liquid 1-4 prepared using an alkanolamine as a reducing agent, a polymer dispersing agent having an acidic group and a polyalkylene oxide group as a polymer dispersing agent, and a silver ammine complex aqueous solution
  • the inkjet inks 1 to 4 and 6 to 9 using the above all had good storage stability, and the image characteristics (reflectance, color tone) of the resulting metallic gloss layer were also good.
  • the reflectance and the color can be further improved by setting the compounding amount of the polymer dispersant in a predetermined range (contrast of inkjet inks 1 to 4).
  • the reflectance and the color can be further improved by setting the content of ammonia in the inkjet ink within a predetermined range (contrast of inkjet inks 2, 6 and 7).
  • the inkjet ink 5 using the silver nanoparticle dispersion liquid 5 manufactured without using the silver ammine complex aqueous solution has poor storage stability, and the image characteristics (reflectance, color tone) of the obtained metallic gloss layer It was bad too.
  • the present invention it is possible to provide a method of producing a silver nanoparticle dispersion liquid having a large amount of coarse silver nanoparticles and high dispersion stability, a silver nanoparticle dispersion liquid and an inkjet ink, and an image forming method using the same. .

Abstract

The purpose of the present invention is to provide a method for producing a silver nanoparticle dispersion liquid that contains few coarse silver nanoparticles and has high dispersion stability. A method for producing a silver nanoparticle dispersion liquid according to the present invention comprises: a step wherein an aqueous solution that contains a silver ammine complex, a polymer dispersant that has an acidic group and a polyalkylene oxide group, and an alkanolamine that serves as a reducing agent are mixed with each other, thereby causing reduction of the silver ammine complex and consequently obtaining an aqueous dispersion liquid that contains silver nanoparticles, the polymer dispersant that adheres to at least a part of the surfaces of the silver nanoparticles, and water; and a step wherein the aqueous dispersion liquid that contains silver nanoparticles is purified.

Description

銀ナノ粒子分散液の製造方法、銀ナノ粒子分散液、インクジェットインクおよびそれを用いた画像形成方法Method of producing silver nanoparticle dispersion, silver nanoparticle dispersion, inkjet ink and image forming method using the same
　本発明は、銀ナノ粒子分散液の製造方法、銀ナノ粒子分散液、インクジェットインクおよびそれを用いた画像形成方法に関する。 The present invention relates to a method of producing a silver nanoparticle dispersion, a silver nanoparticle dispersion, an inkjet ink, and an image forming method using the same.
　近年、金属光沢色は、高級感、高意匠性、強いアイキャッチ効果などをもたらすことから、例えばラベルやパッケージ、広告印刷物、写真などの記録物において、金属光沢色を呈する画像が形成されることがある。中でも、光輝性が高く、高精細な金属光沢色を呈する画像を、デジタル印刷方式、特にインクジェット印刷方式で形成できることが望まれている。 In recent years, metallic gloss colors provide high-class feeling, high designability, strong eye-catching effects, etc., so that an image exhibiting metallic gloss colors is formed, for example, in recorded matter such as labels, packages, advertisement printed matter, and photographs. There is. Among them, it is desired that an image exhibiting high luster and high-definition metallic gloss color can be formed by a digital printing method, particularly an ink jet printing method.
　インクジェット印刷方式による金属光沢画像の形成には、金属光沢顔料として、アルミニウム粒子や金粒子、銀粒子などの金属粒子を含むインクが用いられている。しかしながら、金属粒子は比重が大きいため、インク中で安定して存在しにくく、凝集や沈降を生じやすいという問題があった。特に、インクジェット印刷方式では、ノズルヘッドからインクの微小滴を吹き付けて画像を形成するため、ノズルの目詰まりや、分散安定性の低下が画像に影響し、インクの分散安定性は特に重要となる。 In the formation of a metallic gloss image by the inkjet printing method, an ink containing metallic particles such as aluminum particles, gold particles, and silver particles as metallic gloss pigments is used. However, since the metal particles have a large specific gravity, they are difficult to stably exist in the ink, and there is a problem that aggregation and sedimentation easily occur. In particular, in the ink jet printing method, since an image is formed by spraying a minute droplet of ink from a nozzle head, clogging of the nozzle and a decrease in dispersion stability affect the image, and the ink dispersion stability becomes particularly important. .
　これに対して、特許文献１には、水または水溶性有機溶媒中に、金や銀などの金属ナノ粒子を含む金属コロイド粒子を分散させたインク組成物が開示されている。 On the other hand, Patent Document 1 discloses an ink composition in which metal colloid particles containing metal nanoparticles such as gold and silver are dispersed in water or a water-soluble organic solvent.
　また、特許文献２には、高い分散性と保存安定性を有する水性銀コロイド液として、金属前駆体化合物としての銀アンミン錯体と、還元剤としてのヒドラジンと、分散剤としてのポリビニルピロリドンおよびポリビニルアルコールとを含む水性銀コロイド液が開示されている。 Further, Patent Document 2 discloses, as an aqueous silver colloid liquid having high dispersibility and storage stability, a silver ammine complex as a metal precursor compound, hydrazine as a reducing agent, polyvinyl pyrrolidone and polyvinyl alcohol as a dispersing agent. And an aqueous silver colloid liquid containing the
特開２００３－３０６６２５号公報JP 2003-306625 A 特開２０１５－１０５３７２号公報JP, 2015-105372, A
　しかしながら、特許文献１のインク組成物は、粗大な金属コロイド粒子を多く含むことから、分散安定性は十分なものではなかった。具体的には、特許文献１のインク組成物に含まれる金属コロイドは、硝酸銀水溶液を還元して製造される。金属コロイド粒子の製造では、金属イオンが還元されて金属ナノ粒子を析出する過程で、微小な金属ナノ粒子の表面の活性が極めて高いことから、金属ナノ粒子の凝集および粗大化が生じやすく、粗大な金属コロイド粒子が生成されやすい。このような粗大な金属コロイド粒子を含むインク組成物は、長期の分散安定性、吐出安定性が乏しかった。このように、分散安定性が低いインク組成物で形成した画像は、金属光沢が著しく低下しやすく、画像品位を損ないやすかった。 However, since the ink composition of Patent Document 1 contains a large number of coarse metal colloid particles, the dispersion stability is not sufficient. Specifically, the metal colloid contained in the ink composition of Patent Document 1 is produced by reducing an aqueous silver nitrate solution. In the production of metal colloid particles, since the activity of the surface of minute metal nanoparticles is extremely high in the process of metal ions being reduced to precipitate metal nanoparticles, aggregation and coarsening of metal nanoparticles are likely to occur, resulting in coarse particles. Metal colloid particles are easily generated. The ink composition containing such coarse metal colloid particles has poor long-term dispersion stability and ejection stability. As described above, in the image formed by the ink composition having low dispersion stability, the metallic gloss is apt to be remarkably reduced, and the image quality is easily impaired.
　また、特許文献２では、ポリビニルピロリドンやポリビニルアルコールなどの分散剤が銀粒子の表面に吸着および残留しやすく、得られる水性銀コロイド液は分散安定性に優れるとされている。しかしながら、特許文献２の水性銀コロイド液は、経時で分散剤が遊離しやすく、分散安定性が低下しやすく、インクジェットインクに用いるには不十分であった。さらに、このような水性銀コロイド液で形成された画像に、遊離した分散剤が含まれていると、画像が黄色やオレンジ色を呈して、意匠性を損なうことがあった。 Moreover, in patent document 2, dispersing agents, such as polyvinyl pyrrolidone and polyvinyl alcohol, are easy to adsorb | suck and remain on the surface of silver particle, and it is supposed that the aqueous | water-based silver colloid liquid obtained is excellent in dispersion stability. However, the aqueous silver colloid liquid of Patent Document 2 is apt to release the dispersant over time, the dispersion stability tends to be reduced, and is insufficient for use in an inkjet ink. Furthermore, when an image formed of such an aqueous silver colloid liquid contains a free dispersing agent, the image may have a yellow or orange color and the design may be impaired.
　本発明はこのような事情に鑑みてなされたものであり、粗大な銀ナノ粒子が少なく、分散安定性が高い銀ナノ粒子分散液の製造方法、銀ナノ粒子分散液、インクジェットインクおよびそれを用いた画像形成方法を提供することを目的とする。 The present invention has been made in view of such circumstances, and it is a method of producing a silver nanoparticle dispersion liquid having a large amount of coarse silver nanoparticles and high dispersion stability, a silver nanoparticle dispersion liquid, an inkjet ink and the use thereof It is an object of the present invention to provide an image forming method.
　［１］　銀アンミン錯体を含む水溶液と、酸性基および（ポリ）アルキレンオキサイド基を有する高分子分散剤と、還元剤としてアルカノールアミンとを混合し、前記銀アンミン錯体を還元させて、銀ナノ粒子と、前記銀ナノ粒子の表面の少なくとも一部に吸着した高分子分散剤と、水とを含む水分散液を得る工程と、前記銀ナノ粒子を含む水分散液を精製する工程とを有する、銀ナノ粒子分散液の製造方法。
　［２］　前記高分子分散剤の酸価は、５ｍｇＫＯＨ／ｇ以上２００ｍｇＫＯＨ／ｇ以下である、［１］に記載の銀ナノ粒子分散液の製造方法。
　［３］　前記高分子分散剤は、（メタ）アクリル酸、マレイン酸およびそのハーフエステルからなる群より選ばれるモノマー由来の構造単位と、アルキレンオキサイド変性（メタ）アクリル酸エステル、およびアルキレンオキサイド変性マレイン酸（ハーフ）エステルからなる群より選ばれるモノマーに由来する構造単位とを少なくとも含む、［１］または［２］に記載の銀ナノ粒子分散液の製造方法。
　［４］　前記銀アンミン錯体を還元させるときの温度は、５０℃以上８０℃以下である、［１］～［３］のいずれかに記載の銀ナノ粒子分散液の製造方法。
　［５］　銀ナノ粒子と、前記銀ナノ粒子の表面の少なくとも一部に吸着した、酸性基およびポリアルキレンオキサイド基を有する高分子分散剤と、水と、アンモニアとを含む銀ナノ粒子分散液であって、前記アンモニアの含有量は、前記銀ナノ粒子分散液の全質量に対して１質量ｐｐｍ以上１０００質量ｐｐｍ以下であり、前記銀ナノ粒子の体積換算の平均粒径Ｄ５０が２５ｎｍ以上７０ｎｍ以下であり、かつ前記銀ナノ粒子の体積粒度分布におけるピークの半値幅が３０ｎｍ以上である、銀ナノ粒子分散液。
　［６］　銀ナノ粒子と、前記銀ナノ粒子の表面の少なくとも一部に吸着した、酸性基および（ポリ）アルキレンオキサイド基を有する高分子分散剤と、水と、アンモニアとを含むインクジェットインクであって、前記アンモニアの含有量は、前記インクジェットインクの全質量に対して１質量ｐｐｍ以上１０００質量ｐｐｍ以下であり、前記銀ナノ粒子の体積換算の平均粒径Ｄ５０が２５ｎｍ以上７０ｎｍ以下であり、かつ前記銀ナノ粒子の体積粒度分布におけるピークの半値幅が３０ｎｍ以上である、インクジェットインク。
　［７］　水分散性樹脂をさらに含む、［６］に記載のインクジェットインク。
　［８］　基材上に、［６］または［７］に記載のインクジェットインクを付与して、金属光沢層を形成する工程を含む、画像形成方法。 [1] An aqueous solution containing a silver ammine complex, a polymer dispersant having an acidic group and a (poly) alkylene oxide group, and an alkanolamine as a reducing agent are mixed, and the silver ammine complex is reduced to obtain silver nanoparticles. And obtaining an aqueous dispersion containing water and a polymer dispersant adsorbed on at least a part of the surface of the silver nanoparticles, and purifying the aqueous dispersion containing the silver nanoparticles, Method for producing silver nanoparticle dispersion.
[2] The method for producing a silver nanoparticle dispersion liquid according to [1], wherein the acid value of the polymer dispersant is 5 mg KOH / g or more and 200 mg KOH / g or less.
[3] The polymer dispersant is a structural unit derived from a monomer selected from the group consisting of (meth) acrylic acid, maleic acid and a half ester thereof, an alkylene oxide modified (meth) acrylic ester, and an alkylene oxide modified maleic acid The manufacturing method of the silver nanoparticle dispersion liquid as described in [1] or [2] which contains at least the structural unit derived from the monomer chosen from the group which consists of acid (half) ester.
[4] The method for producing a silver nanoparticle dispersion according to any one of [1] to [3], wherein the temperature when reducing the silver ammine complex is 50 ° C. or more and 80 ° C. or less.
[5] A silver nanoparticle dispersion containing silver nanoparticles, a polymer dispersant having an acidic group and a polyalkylene oxide group adsorbed on at least a part of the surface of the silver nanoparticles, water, and ammonia. The content of the ammonia is 1 mass ppm or more and 1000 mass ppm or less based on the total mass of the silver nanoparticle dispersion, and the volume-equivalent average particle diameter D50 of the silver nanoparticles is 25 nm or more and 70 nm or less And a half width of a peak in a volume particle size distribution of the silver nanoparticles is 30 nm or more.
[6] An inkjet ink comprising silver nanoparticles, a polymer dispersant having an acidic group and a (poly) alkylene oxide group adsorbed on at least a part of the surface of the silver nanoparticles, water, and ammonia. The content of the ammonia is 1 mass ppm or more and 1000 mass ppm or less with respect to the total mass of the inkjet ink, the volume-equivalent average particle diameter D50 of the silver nanoparticles is 25 nm or more and 70 nm or less, The inkjet ink whose half value width of the peak in the volume particle size distribution of the said silver nanoparticle is 30 nm or more.
[7] The inkjet ink according to [6], further comprising a water dispersible resin.
[8] An image forming method comprising the step of applying the inkjet ink according to [6] or [7] on a substrate to form a metallic gloss layer.
　本発明は、粗大な銀ナノ粒子が少なく、分散安定性が高い銀ナノ粒子分散液の製造方法、銀ナノ粒子分散液、インクジェットインクおよびそれを用いた画像形成方法を提供することができる。 The present invention can provide a method for producing a silver nanoparticle dispersion liquid having a large amount of coarse silver nanoparticles and high dispersion stability, a silver nanoparticle dispersion liquid, an inkjet ink, and an image forming method using the same.
　本発明者らは、鋭意検討した結果、銀アンミン錯体を反応原料とし、特定の高分子分散剤の存在下で、特定の還元剤（アルカノールアミン）を用いて銀アンミン錯体を還元することで、粗大粒子の生成が抑制され、分散安定性が良好な銀ナノ粒子分散液が得られることを見出した。 As a result of intensive studies, the present inventors use silver ammine complex as a reaction raw material, and reduce silver ammine complex using a specific reducing agent (alkanolamine) in the presence of a specific polymer dispersant, It has been found that the formation of coarse particles is suppressed, and a silver nanoparticle dispersion having good dispersion stability can be obtained.
　この理由は明らかではないが、以下のように推測される。硝酸銀などの銀化合物を、直接、アルカノールアミンなどの還元剤で還元させると、還元反応の速度が速すぎる（還元反応が急激に生じる）ため、生成した銀ナノ粒子の表面が高分子分散剤で覆われないうちに銀ナノ粒子同士が凝集しやすく、粗大粒子が生成されやすい。アルカノールアミンは還元剤のなかでは比較的還元反応速度は遅いものの、まだこのような現象が抑えきれていなかった。
　これに対し、銀化合物をアンモニアによって銀アンミン錯体とすることで（下記式（１）参照）、銀アンミン錯体と当該銀アンミン錯体から遊離した銀イオンとが平衡状態となりやすく（下記式（２）参照）、銀イオンが緩やかに放出されやすい。遊離銀イオンと比べて銀アンミン錯体は直接還元されにくく、また系中の遊離銀イオン量が抑えられているので、その結果、銀イオンの還元反応の速度を適度に遅くすることができる（還元反応を緩やかに生じさせることができる）ため、銀ナノ粒子同士が凝集する前に、銀ナノ粒子の表面が高分子分散剤で覆われやすい。それにより、銀ナノ粒子同士の凝集を低減することができるため、粗大粒子が少なく、分散安定性が良好な銀ナノ粒子分散液を得ることができる。
Figure JPOXMLDOC01-appb-C000001
 Although the reason for this is not clear, it is presumed as follows. When the silver compound such as silver nitrate is directly reduced with a reducing agent such as alkanolamine, the speed of the reduction reaction is too fast (the reduction reaction occurs rapidly), so the surface of the formed silver nanoparticles is a polymer dispersant. Before being covered, the silver nanoparticles tend to aggregate and coarse particles are easily generated. Among the reducing agents, alkanolamines have a relatively slow reduction reaction rate, but such a phenomenon has not been suppressed yet.
On the other hand, when the silver compound is converted to a silver ammine complex by ammonia (see the following formula (1)), the silver ammine complex and the silver ion liberated from the silver ammine complex are easily in equilibrium (the following formula (2)) See note), silver ions are likely to be released slowly. The silver ammine complex is hard to be reduced directly as compared with the free silver ion, and the amount of free silver ion in the system is suppressed. As a result, the speed of the reduction reaction of silver ion can be moderately slowed (reduction Since the reaction can be generated slowly), the surface of the silver nanoparticles is easily covered with the polymer dispersant before the silver nanoparticles aggregate. Thereby, since aggregation of silver nanoparticles can be reduced, it is possible to obtain a silver nanoparticle dispersion liquid with few coarse particles and good dispersion stability.
Figure JPOXMLDOC01-appb-C000001
　また、このようにして得られる銀ナノ粒子分散液は、銀アンミン錯体に由来するアンモニアを含むことで、銀ナノ粒子分散液の分散安定性がさらに高められている。 In addition, the dispersion stability of the silver nanoparticle dispersion liquid is further enhanced by containing the ammonia derived from the silver ammine complex in the silver nanoparticle dispersion liquid thus obtained.
　さらに、このようにして得られる銀ナノ粒子分散液は、銀ナノ粒子の平均粒径Ｄ５０が小さいことから、塗膜の反射率を高めることができる。さらに、得られる銀ナノ粒子分散液は、体積粒度分布におけるピークの半値幅が大きいことから、塗膜の反射スペクトルの形状が平坦な銀箔に類似した形状を有し、銀と類似した光沢性を有しうる（すなわち、バルク銀のような銀らしい銀色を呈しうる）。したがって、金属光沢性の優れた塗膜を得ることができる。 Furthermore, since the silver nanoparticle dispersion liquid obtained in this manner has a small average particle diameter D50 of the silver nanoparticles, it is possible to increase the reflectance of the coating film. Furthermore, the obtained silver nanoparticle dispersion has a shape similar to a flat silver foil in the shape of a reflection spectrum of a coating film and has a gloss similar to that of silver, because the half width of the peak in the volume particle size distribution is large. (I.e., can have a silver like silver like bulk silver). Therefore, the coating film excellent in metallic glossiness can be obtained.
　これは、以下の理由によると考えられる。銀アンミン錯体とすることによって、銀イオンの供給を緩やかにすることができるため、１）初期の微小核の量を適度に少なくすることができ、２）微小核の表面が高分子分散剤で覆われやすくなるため、分散安定性を高めることができる。それにより、粒子の凝集や急激な成長が抑えられ、粗大粒子が生成されにくい。また、後から供給される銀イオンは、初期の核の成長に使われるだけではなく、新たな核発生にも使われやすくなるため、粒度分布は広くなりやすい（初期に発生した核は大きく成長し、後から発生した核は成長できる時間が短いため小さくなりやすい）。その結果、平均粒子径Ｄ５０は小さく、半値幅は大きい粒度分布が得られると考えられる。本発明は、このような知見に基づいてなされたものである。 This is considered to be due to the following reasons. By using a silver ammine complex, the supply of silver ions can be relaxed, so 1) the amount of micronucleus in the initial stage can be reduced appropriately, and 2) the surface of the micronucleus is a polymer dispersant. Dispersion stability can be enhanced because it is easily covered. Thereby, aggregation and rapid growth of particles are suppressed, and coarse particles are hardly generated. In addition, the silver ion supplied later is not only used for the growth of the initial nucleus, but also easy to be used for the generation of a new nucleus, so the particle size distribution is likely to be broad (the nucleus generated at the initial growth is large And later generated nuclei are likely to become smaller because the time for which they can grow is short). As a result, it is considered that the average particle diameter D50 is small and the half width is large. The present invention has been made based on such findings.
　１．銀ナノ粒子分散液の製造方法
　本発明の銀ナノ粒子分散液の製造方法は、１）銀アンミン錯体を含む水溶液と、特定の高分子分散剤と、特定の還元剤とを混合し、銀アンミン錯体を還元させて、銀ナノ粒子と、当該銀ナノ粒子の表面の少なくとも一部に吸着した高分子分散剤と、水とを含む水分散液を得る工程（銀ナノ粒子生成工程）と、２）得られた銀ナノ粒子を含む水分散液を精製する工程（精製工程）とを有する。 1. Method of Producing Silver Nanoparticle Dispersion Liquid The method of producing a silver nanoparticle dispersion liquid of the present invention comprises the steps of: 1) mixing an aqueous solution containing a silver ammine complex, a specific polymer dispersant, and a specific reducing agent; A step of reducing the complex to obtain an aqueous dispersion containing silver nanoparticles, a polymer dispersant adsorbed on at least a part of the surface of the silver nanoparticles, and water (silver nanoparticle production step), 2 And d) purifying the aqueous dispersion containing the obtained silver nanoparticles (purification step).
　１）の工程（銀ナノ粒子生成工程）について
　本工程では、銀アンミン錯体を含む水溶液と、特定の高分子分散剤と、特定の還元剤とを混合し、銀アンミン錯体を還元させる。それにより、表面の少なくとも一部に吸着した高分子分散剤を有する銀ナノ粒子を生成させる。 Step 1) (Silver Nanoparticle Generation Step) In this step, the silver ammine complex is reduced by mixing an aqueous solution containing a silver ammine complex, a specific polymer dispersant, and a specific reducing agent. Thereby, silver nanoparticles having a polymeric dispersant adsorbed on at least a part of the surface are produced.
　（銀アンミン錯体を含む水溶液）
　銀アンミン錯体を含む水溶液（以下、「銀アンミン錯体溶液」ともいう）は、銀化合物を、アンモニア水に溶解させて得られる。 (Aqueous solution containing silver ammine complex)
An aqueous solution containing a silver ammine complex (hereinafter, also referred to as “silver ammine complex solution”) is obtained by dissolving a silver compound in aqueous ammonia.
　銀化合物の例には、塩化銀、酸化銀、硝酸銀、炭酸銀などが含まれる。中でも、硝酸銀が好ましい。硝酸銀は、他の銀化合物と比べて比較的還元反応が速く、粗大粒子が生成しやすいが、アンモニアと錯体を形成することで還元反応を適度に遅くすることができ、粗大粒子が生成されにくいからである。 Examples of silver compounds include silver chloride, silver oxide, silver nitrate, silver carbonate and the like. Among them, silver nitrate is preferred. Silver nitrate has a relatively fast reduction reaction and is likely to produce coarse particles compared to other silver compounds, but by forming a complex with ammonia, the reduction reaction can be appropriately delayed, and it is difficult to produce coarse particles. It is from.
　銀アンミン錯体溶液における銀成分の含有量は、５ｇ／Ｌ以上３５０ｇ／Ｌ以下であることが好ましい。銀成分の含有量が５ｇ／Ｌ以上であると、高い製造効率で銀ナノ粒子を生成させやすく、３５０ｇ／Ｌ以下であると、生成する銀ナノ粒子の形状が安定化しやすい。銀成分の含有量は、１０ｇ／Ｌ以上２００ｇ／Ｌ以下であることがより好ましい。 The content of the silver component in the silver ammine complex solution is preferably 5 g / L or more and 350 g / L or less. When the content of the silver component is 5 g / L or more, silver nanoparticles are easily produced with high production efficiency, and when it is 350 g / L or less, the shape of the produced silver nanoparticles is easily stabilized. The content of the silver component is more preferably 10 g / L or more and 200 g / L or less.
　銀アンミン錯体溶液におけるアンモニアの含有量は、銀成分がアンモニアと錯体を十分に形成しうる程度であればよく、銀成分の全モル数に対して１．５以上４以下（モル比）であることが好ましい。アンモニアの含有量が１．５モル比以上であると、銀成分を十分に錯体化しやすいため、還元反応の速度を適度に遅くしやすく、粗大粒子の生成を抑制しやすい。アンモニアの含有量が４モル比以下であると、生成する銀ナノ粒子の形状が安定化しやすい。アンモニアの含有量は、銀成分の全モル数に対して１．８以上３以下（モル比）であることがより好ましい。 The content of ammonia in the silver ammine complex solution may be 1.5 or more and 4 or less (molar ratio) with respect to the total number of moles of the silver component as long as the silver component can sufficiently form a complex with ammonia. Is preferred. When the content of ammonia is 1.5 molar ratio or more, the silver component is easily complexed sufficiently, so the reduction reaction rate is easily slowed down and the formation of coarse particles is easily suppressed. When the content of ammonia is 4 molar ratio or less, the shape of the silver nanoparticles to be formed is easily stabilized. The content of ammonia is more preferably 1.8 or more and 3 or less (molar ratio) with respect to the total number of moles of the silver component.
　（高分子分散剤）
　高分子分散剤は、酸性基と、（ポリ）アルキレンオキサイド基とを有する高分子分散剤である。 (Polymer dispersant)
The polymer dispersant is a polymer dispersant having an acidic group and a (poly) alkylene oxide group.
　酸性基は、銀ナノ粒子の表面に吸着するための吸着基として機能しうる。高分子分散剤が酸性基を有することにより、銀ナノ粒子の保護コロイドとして十分な性能を発揮することができる。酸性基の例には、カルボキシル基、リン酸基およびスルホン酸基などが含まれる。中でも、カルボキシル基が好ましい。 The acidic group can function as an adsorptive group for adsorbing to the surface of silver nanoparticles. When the polymeric dispersant has an acidic group, it can exhibit sufficient performance as a protective colloid of silver nanoparticles. Examples of the acidic group include carboxyl group, phosphoric acid group and sulfonic acid group. Among them, a carboxyl group is preferable.
　（ポリ）アルキレンオキサイド基は、溶媒に対して親和性を有する基（親水性基）であり、溶媒和部分を構成する基として機能しうる。（ポリ）アルキレンオキサイド基の例には、エチレンオキサイド基やプロピレンオキサイド基、エチレンオキサイド－プロピレンオキサイド含有基などが含まれる。 The (poly) alkylene oxide group is a group having affinity to a solvent (hydrophilic group), and can function as a group constituting a solvation portion. Examples of the (poly) alkylene oxide group include ethylene oxide group, propylene oxide group, ethylene oxide-propylene oxide containing group and the like.
　酸性基と（ポリ）アルキレンオキサイド基とを有する高分子分散剤は、親水性モノマーの単独重合体または共重合体であることが好ましい。親水性モノマーの共重合体は、親水性モノマーと疎水性モノマーとの共重合体であってもよい。 The polymer dispersant having an acidic group and a (poly) alkylene oxide group is preferably a homopolymer or copolymer of a hydrophilic monomer. The copolymer of the hydrophilic monomer may be a copolymer of a hydrophilic monomer and a hydrophobic monomer.
　親水性モノマーは、酸性基および／または（ポリ）アルキレンオキサイド基を有し、かつラジカル重合可能なエチレン性不飽和結合を有するモノマーであることが好ましい。親水性モノマーの例には、カルボキシル基または酸無水物基を有するモノマー（例えば、アクリル酸、メタクリル酸などの（メタ）アクリル酸；マレイン酸などの不飽和多価カルボン酸またはその部分エステル化物；無水マレイン酸などの酸無水物）や；（ポリ）アルキレンオキサイド基を有するモノマー（例えば、エチレンオキサイド変性（メタ）アクリル酸アルキルエステル、アクリル酸ジエチレングリコールモノエチルエーテルなどのアルキレンオキサイド変性（メタ）アクリル酸エステルモノマー；アルキレンオキサイド変性マレイン酸（ハーフ）エステルモノマー）などが含まれる。 The hydrophilic monomer is preferably a monomer having an acid group and / or a (poly) alkylene oxide group and having a radically polymerizable ethylenic unsaturated bond. Examples of hydrophilic monomers include monomers having a carboxyl group or an acid anhydride group (for example, (meth) acrylic acids such as acrylic acid and methacrylic acid; unsaturated polyvalent carboxylic acids such as maleic acid or partial esters thereof; Acid anhydrides such as maleic anhydride) or monomers having (poly) alkylene oxide groups (eg, ethylene oxide modified (meth) acrylic acid alkyl ester, acrylic acid diethylene glycol monoethyl ether such as alkylene oxide modified (meth) acrylic acid Ester monomers; alkylene oxide-modified maleic acid (half) ester monomers) and the like are included.
　疎水性モノマーは、酸性基およびポリアルキレンオキサイド基を有さず、かつラジカル重合可能なエチレン性不飽和結合を有するモノマーであることが好ましい。疎水性モノマーの例には、（メタ）アクリル酸メチル、（メタ）アクリル酸エチルなどの（メタ）アクリル酸エステル系モノマー；マレイン酸ジメチル、マレイン酸ジエチルなどのマレイン酸ジエステルモノマー；スチレン、α－メチルスチレン、ビニルトルエンなどのスチレン系モノマー；エチレン、プロピレン、１－ブテンなどのα－オレフィン系モノマー；酢酸ビニル、酪酸ビニルなどのカルボン酸ビニルエステル系モノマーなどが含まれる。 The hydrophobic monomer is preferably a monomer having no acidic group and no polyalkylene oxide group, and having a radically polymerizable ethylenic unsaturated bond. Examples of hydrophobic monomers include (meth) acrylic acid ester monomers such as methyl (meth) acrylate and ethyl (meth) acrylate; maleic acid diester monomers such as dimethyl maleate and diethyl maleate; styrene, α- Styrene-based monomers such as methylstyrene and vinyltoluene; α-olefin-based monomers such as ethylene, propylene and 1-butene; and carboxylic acid vinyl ester-based monomers such as vinyl acetate and vinyl butyrate.
　中でも、高分子分散剤は、（メタ）アクリル酸、マレイン酸またはそのハーフエステルからなる群より選ばれるモノマーに由来する構造単位と、アルキレンオキサイド変性（メタ）アクリル酸エステル、アルキレンオキサイド変性マレイン酸（ハーフ）エステルからなる群より選ばれるモノマー由来の構造単位とを少なくとも含むことが好ましく、必要に応じて他のモノマー由来の構造単位をさらに含んでいてもよい。 Among them, the polymer dispersant is a structural unit derived from a monomer selected from the group consisting of (meth) acrylic acid, maleic acid or a half ester thereof, an alkylene oxide modified (meth) acrylic ester, and an alkylene oxide modified maleic acid ( It is preferable to include at least a structural unit derived from a monomer selected from the group consisting of a half) ester, and it may further contain a structural unit derived from another monomer as required.
　アルキレンオキサイド変性（メタ）アクリル酸エステル、およびアルキレンオキサイド変性マレイン酸（ハーフ）エステルからなる群より選ばれるモノマー由来の構造単位は、前述の通り、溶媒に対して親和性を有する基（溶媒和部分を構成する親水性基）として機能しうる。このような基を有する高分子分散剤は、側鎖（アルキレンオキサイド基）があたかも櫛の歯のように主鎖に結合されているような分子構造を有する。この側鎖が溶媒和に寄与するだけでなく、立体障害を生じるため、銀ナノ粒子同士の凝集をより高度に抑制しうる。 A structural unit derived from a monomer selected from the group consisting of an alkylene oxide modified (meth) acrylic acid ester and an alkylene oxide modified maleic acid (half) ester is a group having an affinity to a solvent (solvation portion as described above) Can function as a hydrophilic group). A polymer dispersant having such a group has a molecular structure in which side chains (alkylene oxide groups) are bonded to the main chain as if they were comb teeth. Since the side chains not only contribute to solvation but also cause steric hindrance, aggregation of silver nanoparticles can be more highly suppressed.
　共重合体は、ランダム共重合体、交互共重合体、ブロック共重合体のいずれであってもよい。 The copolymer may be any of a random copolymer, an alternating copolymer and a block copolymer.
　高分子分散剤の例には、特開平６－１００６４２号公報に開示されている付加重合体からなる主鎖と、少なくとも１個のＣ１～Ｃ４アルコキシポリエチレンまたはポリエチレン－コプロピレングリコール（メタ）アクリレートからなる安定化剤単位とからなり，かつ２５００～２００００の重量平均分子量を有する両親媒性共重合体であって、主鎖は、３０質量％以下の非官能性構造単位と、合計で７０質量％以下の安定化剤単位および官能性構造単位とを含み、当該官能性構造単位は、置換または無置換のスチレン含有単位、ヒドロキシル基含有単位、およびカルボキシル基含有単位を含む両親媒性共重合体などを挙げることができる。 Examples of the polymeric dispersant include a main chain comprising an addition polymer disclosed in JP-A-6-200662 and at least one C1-C4 alkoxy polyethylene or polyethylene-copropylene glycol (meth) acrylate An amphiphilic copolymer comprising a stabilizer unit and having a weight average molecular weight of 2500 to 20000, wherein the main chain comprises 70% by weight in total of 30% by weight or less of nonfunctional structural units An amphiphilic copolymer comprising the following stabilizer unit and functional structural unit, the functional structural unit comprising a substituted or unsubstituted styrene-containing unit, a hydroxyl group-containing unit, and a carboxyl group-containing unit, etc. Can be mentioned.
　市販の高分子分散剤の例には、ソルスパース２４０００、ソルスパース２４０００ＧＲ、ソルスパース３２０００、ソルスパース４４０００、ソルスパース４６０００（ルーブリゾール社製）；アジスパーＰＢ８２２、アジスパーＰＢ８２１、アジスパーＰＢ７１１（味の素ファインテクノ社製）；ＤＩＳＰＥＲＢＹＫ－１０２、ＤＩＳＰＥＲＢＹＫ－１８７、ＤＩＳＰＥＲＢＹＫ－１９４Ｎ、ＤＩＳＰＥＲＢＹＫ－１９０、ＤＩＳＰＥＲＢＹＫ－１９１、ＤＩＳＰＥＲＢＹＫ－１９９、ＤＩＳＰＥＲＢＹＫ－２０００、ＤＩＳＰＥＲＢＹＫ－２００１、ＤＩＳＰＥＲＢＹＫ－２０１５、ＤＩＳＰＥＲＢＹＫ－２０５０、ＤＩＳＰＥＲＢＹＫ－２１５０、およびＤＩＳＰＥＲＢＹＫ－２０６９（いずれもビックケミー社製、「ＤＩＳＰＥＲＢＹＫ」は同社の登録商標）；ディスパロンＥＤ－１５２、ＥＤ－２１１、ＥＤ－２１２、ＥＤ－２１３、ＥＤ－２１４、ＥＤ－２５１（楠本化成社製）、ＰＬＡＡＤシリーズ（楠本化成社製）；ＥＦＫＡ　６２２０（ＢＡＳＦ社製、「ＥＦＫＡ」は同社の登録商標）、並びにフローレンＴＧ－７５０Ｗ（共栄社化学社製）などが含まれる。 Examples of commercially available polymer dispersants include Solsparse 24000, Solsparse 24000GR, Solsparse 32000, Solsparse 44000, Solsparse 46000 (manufactured by Lubrizol Corporation); Azispar PB 822, Azispar PB 821 and Azispar PB 711 (manufactured by Ajinomoto Fine Techno Co.); DISPERBYK- 102, DISPERBYK-187, DISPERBYK-194N, DISPERBYK-190, DISPERBYK-191, DISPERBYK-199, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2015, DISPERBYK-2015, DISPERBYK-2050, DISPERBYK-2150, and DISPERBYK-2069 (all of which are Big Chemie Company, "DISPER "YK" is a registered trademark of the company; Disparon ED-152, ED-211, ED-212, ED-213, ED-214, ED-251 (manufactured by Kushimoto Chemical Co., Ltd.), PLAAD series (manufactured by Kushimoto Chemical Co., Ltd.); EFKA 6220 (manufactured by BASF, "EFKA" is a registered trademark of the company), Floren TG-750W (manufactured by Kyoeisha Chemical), and the like.
　高分子分散剤の酸価は、５ｍｇＫＯＨ／ｇ以上２００ｍｇＫＯＨ／ｇ以下であることが好ましい。酸価が５ｍｇＫＯＨ／ｇ以上であると、銀ナノ粒子の表面への吸着に寄与する酸性基の場合は、酸性基が銀ナノ粒子の表面に吸着して銀ナノ粒子の表面を高分子分散剤で被覆しやすく、インク中での銀ナノ粒子の分散性を高めやすい。銀ナノ粒子の表面への吸着に寄与しない酸性基の場合は、銀ナノ粒子の表面に親水性を付与してアニオン性基として機能し、銀ナノ粒子の表面に電荷を持たせやすくしうるので、銀ナノ粒子間の電荷反発を起こりやすくし、インク中での分散性を高めやすい。酸価が２００ｍｇＫＯＨ／ｇ以下であると、銀ナノ粒子の表面への吸着に寄与する酸性基の場合は、一つの高分子鎖が２つ以上の銀ナノ粒子に吸着する、いわゆる橋架け凝集が起こりにくくしうる。また、高分子分散剤の銀ナノ粒子表面への吸着に寄与しない酸性基の場合は、銀ナノ粒子の表面の親水性の高まり過ぎによる金属光沢層の耐水性の低下を抑制しやすい。さらに、インクの分散性をより高め、保存安定性をより高める観点では、高分子分散剤の酸価は、５ｍｇＫＯＨ／ｇ以上１５０ｍｇＫＯＨ／ｇ以下であることがより好ましく、１０ｍｇＫＯＨ／ｇ以上８０ｍｇＫＯＨ／ｇ以下であることがさらに好ましく、２０ｍｇＫＯＨ／ｇ以上５０ｍｇＫＯＨ／ｇ以下であることが特に好ましい。 The acid value of the polymer dispersant is preferably 5 mg KOH / g or more and 200 mg KOH / g or less. When the acid value is 5 mg KOH / g or more, in the case of an acidic group that contributes to the adsorption onto the surface of the silver nanoparticle, the acidic group is adsorbed onto the surface of the silver nanoparticle and the surface of the silver nanoparticle is a polymer dispersant And easy to increase the dispersibility of silver nanoparticles in the ink. In the case of an acidic group that does not contribute to adsorption to the surface of the silver nanoparticle, the surface of the silver nanoparticle can be rendered hydrophilic to function as an anionic group, and the surface of the silver nanoparticle can be easily charged. And the charge repulsion between the silver nanoparticles is likely to occur, and the dispersibility in the ink is likely to be enhanced. When the acid value is 200 mg KOH / g or less, in the case of an acidic group that contributes to the adsorption to the surface of silver nanoparticles, one polymer chain is adsorbed to two or more silver nanoparticles, so-called bridged aggregation It can be hard to happen. Moreover, in the case of the acidic group which does not contribute to adsorption | suction to the silver nanoparticle surface of a polymer dispersing agent, it is easy to suppress the water-resistant fall of the metal lustrous layer by the hydrophilicity increase of the surface of silver nanoparticle too much. Furthermore, from the viewpoint of further enhancing the dispersibility of the ink and enhancing the storage stability, the acid value of the polymer dispersant is more preferably 5 mgKOH / g or more and 150 mgKOH / g or less, and 10 mgKOH / g or more and 80 mgKOH / g The content is more preferably 20 mg KOH / g or more and 50 mg KOH / g or less.
　酸価は、ＪＩＳ　Ｋ　００７０に準じて測定することができる。具体的には、高分子分散剤の酸価は、フーリエ変換赤外分光光法（ＦＴ－ＩＲ）により、高分子分散剤の種類（例えば、画像形成に用いた高分子分散剤の製品名等）を特定し、同一の高分子分散剤の酸価をＪＩＳ　Ｋ　００７０に準じて測定すればよい。また、１ＨＮＭＲやガスクロマトグラフィー－質量分析法（ＧＣ／ＭＳ）によって高分子分散剤の種類を特定してもよい。 The acid value can be measured according to JIS K 0070. Specifically, the acid value of the polymer dispersant is determined by the type of polymer dispersant (for example, the product name of the polymer dispersant used for image formation, etc., by Fourier transform infrared spectroscopy (FT-IR). And the acid value of the same polymer dispersant may be measured according to JIS K 0070. In addition, the type of the polymeric dispersant may be specified by 1 H NMR or gas chromatography-mass spectrometry (GC / MS).
　高分子分散剤の分子量は、１０００以上１０００００以下であることが好ましく、２０００以上５００００以下であることがより好ましい。高分子分散剤の分子量が上記範囲内であると、銀ナノ粒子の表面を、高分子分散剤で十分に被覆できるので、インクの保存安定性を一層高めやすい。 The molecular weight of the polymer dispersant is preferably 1,000 or more and 100,000 or less, and more preferably 2,000 or more and 50,000 or less. When the molecular weight of the polymer dispersant is within the above range, the surface of the silver nanoparticles can be sufficiently coated with the polymer dispersant, and the storage stability of the ink can be further enhanced.
　このような高分子分散剤を含む水系溶媒中で、銀イオンを還元することによって、表面の少なくとも一部に吸着した高分子分散剤を有する銀ナノ粒子を得ることができる。 By reducing silver ions in an aqueous solvent containing such a polymer dispersant, silver nanoparticles having the polymer dispersant adsorbed on at least a part of the surface can be obtained.
　高分子分散剤の配合量は、銀アンミン錯体を構成する銀成分の全質量に対して３質量％以上５０質量％以下であることが好ましい。高分子分散剤の配合量が３質量％以上であると、生成した銀ナノ粒子を高分子分散剤で十分に被覆しうるので、銀ナノ粒子同士の凝集を抑制しやすく、粗大粒子を少なくしやすい。それにより、得られる銀ナノ粒子の平均粒子径Ｄ５０をより小さくしうる。高分子分散剤の配合量が５０質量％以下であると、得られる銀ナノ粒子分散液において、余分な高分子分散剤（遊離した高分子分散剤）を少なくすることができるため、後の精製工程の負荷を低減しやすいだけでなく、得られる塗膜（または画像）の色味も損なわれにくい。また、高分子分散剤により安定化しすぎないため、単分散化しすぎず、体積粒度分布におけるピークの半値幅が小さくなりすぎない）。高分子分散剤の配合量は、銀アンミン錯体を構成する銀成分に対して４質量％以上３０質量％以下であることがより好ましい。 It is preferable that the compounding quantity of a polymer dispersing agent is 3 to 50 mass% with respect to the total mass of the silver component which comprises a silver ammine complex. When the content of the polymer dispersant is 3% by mass or more, the produced silver nanoparticles can be sufficiently covered with the polymer dispersant, so aggregation of the silver nanoparticles is easily suppressed, and coarse particles are reduced. Cheap. Thereby, the average particle size D50 of the obtained silver nanoparticles can be made smaller. The amount of the polymer dispersant contained is 50% by mass or less in the resulting silver nanoparticle dispersion, so that the amount of excess polymer dispersant (free polymer dispersant) can be reduced, so that the subsequent purification can be performed. Not only is it easy to reduce the process load, but also the tint of the resulting coating (or image) is less likely to be lost. Moreover, since the polymer dispersant is not excessively stabilized, it is not too monodispersed, and the half width of the peak in the volume particle size distribution does not become too small). The compounding amount of the polymer dispersant is more preferably 4% by mass or more and 30% by mass or less with respect to the silver component constituting the silver ammine complex.
　（還元剤）
　還元剤は、アルカノールアミンである。アミンは、通常、他の還元剤と比べて還元速度が比較的遅いため、粗大粒子を生成しにくくすることができる。アミンの中でもアルカノールアミンは、水に溶けやすく、水系銀ナノ粒子分散液を得るのに適している。 (Reductant)
The reducing agent is an alkanolamine. Amines are generally relatively slow in reduction rate compared to other reducing agents, which can make it difficult to produce coarse particles. Among amines, alkanolamines are readily soluble in water and are suitable for obtaining aqueous silver nanoparticle dispersions.
　１級アミノ基を有するアルカノールアミンの例には、エタノールアミン、プロパノールアミン、ブタノールアミン、ヘキサノールアミン、２－(２－アミノエトキシ)エタノール、１－アミノ－２－プロパノール、２－アミノ－２－メチル－1－プロパノール、２－アミノ－1－ブタノールが含まれる。２級アミノ基を有するアルカノールアミンの例には、メチルアミノエタノール、ジエタノールアミン、２－（３－アミノプロピルアミノ）エタノール、ジイソプロパノールアミンが含まれる。３級アミノ基を有するアルカノールアミンの例には、ジメチルアミノエタノール、ジエチルアミノエタノール、３－（ジメチルアミノ）－１－プロパノール、トリエタノールアミン、メチルジエタノールアミンなどが含まれる。これらは、単独で用いてもよく、２種以上を併用してもよい。これらの中でも、３級アミノ基を有するアルカノールアミンが好ましく、ジメチルアミノエタノールがより好ましい。 Examples of alkanolamines having a primary amino group include ethanolamine, propanolamine, butanolamine, hexanolamine, 2- (2-aminoethoxy) ethanol, 1-amino-2-propanol, 2-amino-2-methyl -1-propanol and 2-amino-1-butanol are included. Examples of alkanolamines having secondary amino groups include methylaminoethanol, diethanolamine, 2- (3-aminopropylamino) ethanol, diisopropanolamine. Examples of alkanolamines having a tertiary amino group include dimethylaminoethanol, diethylaminoethanol, 3- (dimethylamino) -1-propanol, triethanolamine, methyldiethanolamine and the like. These may be used alone or in combination of two or more. Among these, an alkanolamine having a tertiary amino group is preferable, and dimethylaminoethanol is more preferable.
　還元剤の配合量は、上記金属化合物中の金属を還元するのに必要な量以上であれば特に制限されないが、銀アンミン錯体を構成する銀成分の全モル数に対して１以上１０以下（モル比）であることが好ましい。還元剤の配合量が１（モル比）以上であると、金属イオンの還元速度が遅くなりすぎないため、製造効率が損なわれにくい。還元剤の配合量が１０（モル比）以下であると、得られる銀ナノ粒子分散液において、余分な還元剤を少なくすることができるため、後の精製工程の負荷を低減しやすいだけでなく、得られる塗膜（または画像）の色相も損なわれにくい。還元剤の配合量は、銀アンミン錯体を構成する銀成分の全モル数に対して１．２以上５以下（モル比）であることがより好ましい。 The compounding amount of the reducing agent is not particularly limited as long as it is not less than the amount necessary to reduce the metal in the metal compound, but 1 to 10 with respect to the total number of moles of the silver component constituting the silver ammine complex It is preferable that it is molar ratio. When the compounding amount of the reducing agent is 1 (molar ratio) or more, the reduction rate of the metal ion does not become too slow, so that the production efficiency is hardly impaired. Since the amount of excess reducing agent can be reduced in the obtained silver nanoparticle dispersion liquid when the blending amount of the reducing agent is 10 (molar ratio) or less, not only the load of the subsequent purification step can be easily reduced The hue of the resulting coating (or image) is also less likely to be impaired. The blending amount of the reducing agent is more preferably 1.2 or more and 5 or less (molar ratio) with respect to the total number of moles of the silver component constituting the silver ammine complex.
　銀アンミン錯体を含む水溶液と、特定の高分子分散剤と、特定の還元剤とを混合し、還元反応させる際の温度は、２０℃以上９０℃以下であることが好ましい。温度が２０℃以上であると、還元剤による還元性能を高くしうるため、銀アンミン錯体の還元反応が遅くなりすぎず、製造効率の低下を抑制しやすい。また、得られる銀ナノ粒子分散液の粒度分布のピークの半値幅が小さくなりにくい。温度が９０℃以下であると、アンモニアの揮発量が増えすぎず、還元剤による還元性能が高くなりすぎないので、還元速度を適度に遅くしやすく、粗大な銀ナノ粒子を生成しにくくしうる。それにより、得られる銀ナノ粒子分散液の平均粒子径Ｄ５０を小さくしやすい。還元反応させる際の温度は、３０℃以上８０℃以下であることがより好ましく、５０℃以上８０℃以下であることがさらに好ましい。 It is preferable that the temperature at the time of mixing the aqueous solution containing a silver ammine complex, a specific polymer dispersing agent, and a specific reducing agent and performing a reduction reaction is 20 ° C. or more and 90 ° C. or less. When the temperature is 20 ° C. or higher, the reduction performance of the reducing agent can be increased, so the reduction reaction of the silver ammine complex does not become too slow, and it is easy to suppress the reduction in production efficiency. Moreover, the half value width of the peak of the particle size distribution of the obtained silver nanoparticle dispersion does not easily decrease. If the temperature is 90 ° C. or less, the volatilization amount of ammonia does not increase too much, and the reduction performance by the reducing agent does not become too high, so the reduction rate can be easily slowed down and coarse silver nanoparticles can be difficult to form . As a result, the average particle diameter D50 of the resulting silver nanoparticle dispersion can be easily reduced. The temperature for reduction reaction is more preferably 30 ° C. or more and 80 ° C. or less, and still more preferably 50 ° C. or more and 80 ° C. or less.
　２）の工程（精製工程）について
　１）の工程で生成した銀ナノ粒子を含む水分散液を精製する。 Step 2) (Purification Step) The aqueous dispersion containing the silver nanoparticles produced in the step 1) is purified.
　精製方法は、電気透析、遠心分離、限外濾過などがあり、特に制限されないが、生成した銀ナノ粒子を含む水分散液を濾過および洗浄する方法でありうる。濾過および洗浄する方法は、特に制限はなく、例えば限外濾過装置を用いた濃縮と、得られる濃縮液の純水による希釈とを繰り返すことで、濾過および洗浄を行う方法でありうる。それにより、銀ナノ粒子の表面に吸着せずに液中に遊離している高分子分散剤やアンモニア、還元剤などの不純物を十分に除去することができる。 The purification method includes electrodialysis, centrifugation, ultrafiltration and the like, and is not particularly limited, but may be a method of filtering and washing the aqueous dispersion containing the produced silver nanoparticles. The method of filtration and washing is not particularly limited, and may be, for example, a method of performing filtration and washing by repeating concentration using an ultrafiltration device and dilution of the obtained concentrate with pure water. Thereby, impurities such as a polymer dispersant, ammonia, and a reducing agent which are free in the liquid without being adsorbed on the surface of the silver nanoparticles can be sufficiently removed.
　精製は、銀ナノ粒子の表面に吸着せずに液中に遊離している高分子分散剤や還元剤、アンモニアなどの不純物を十分に除去できる程度に（具体的には、これらの不純物の総量が、後述する範囲となるように）行うことが好ましい。 The purification is carried out to such an extent that impurities such as polymer dispersants, reducing agents, and ammonia released in the solution can be sufficiently removed without being adsorbed to the surface of silver nanoparticles (specifically, the total amount of these impurities) To be in the range described later).
　その後、銀ナノ粒子分散液の固形分濃度が、例えば２質量％以上５０質量％以下となるまで濃縮することで、銀ナノ粒子分散液を得ることができる。固形分濃度とは、実質的には、銀ナノ粒子と、その表面に吸着した高分子分散剤の合計量である。 Thereafter, the silver nanoparticle dispersion liquid can be obtained by concentrating the solid content concentration of the silver nanoparticle dispersion liquid to, for example, 2% by mass or more and 50% by mass or less. The solid content concentration is substantially the total amount of silver nanoparticles and the polymeric dispersant adsorbed on the surface thereof.
　銀ナノ粒子分散液に含まれる前述の不純物の総量は、銀ナノ粒子分散液の全質量に対して例えば１質量％以下であることが好ましい。具体的には、銀ナノ粒子分散液におけるアンモニアの含有量は、１５００質量ｐｐｍ以下であることが好ましく、１０００質量ｐｐｍ以下であることがより好ましい。 The total amount of the aforementioned impurities contained in the silver nanoparticle dispersion is preferably, for example, 1% by mass or less based on the total mass of the silver nanoparticle dispersion. Specifically, the content of ammonia in the silver nanoparticle dispersion liquid is preferably 1500 mass ppm or less, and more preferably 1000 mass ppm or less.
　２．銀ナノ粒子分散液
　本発明の銀ナノ粒子分散液の製造方法によって得られる本発明の銀ナノ粒子分散液は、銀ナノ粒子と、銀ナノ粒子の表面に吸着した高分子分散剤と、水と、アンモニアとを含む。 2. Silver nanoparticle dispersion liquid The silver nanoparticle dispersion liquid of the present invention obtained by the method for producing a silver nanoparticle dispersion liquid of the present invention comprises silver nanoparticles, a polymer dispersant adsorbed on the surface of the silver nanoparticles, water, And ammonia.
　２－１．銀ナノ粒子
　銀ナノ粒子は、銀を含むナノサイズの金属粒子である。銀ナノ粒子は、銀を主成分として含む。主成分とは、例えば銀ナノ粒子を構成する全原子の合計に対して５０原子％以上の成分をいう。銀ナノ粒子は、不可避的に含まれる微量の他の成分（例えば銀の酸化物など）をさらに含んでいてもよい。 2-1. Silver Nanoparticles Silver nanoparticles are nano-sized metal particles containing silver. Silver nanoparticles contain silver as a main component. The main component means, for example, a component of 50 atomic% or more with respect to the total of all the atoms constituting the silver nanoparticles. The silver nanoparticles may further contain minor amounts of other components which are inevitably contained (for example, an oxide of silver).
　銀ナノ粒子は、分散安定性を高めるためにクエン酸などでさらに表面処理されていてもよい。 The silver nanoparticles may be further surface treated with citric acid or the like to enhance dispersion stability.
　銀ナノ粒子の体積換算の平均粒子径Ｄ５０は、２５ｎｍ以上７０ｎｍ以下であることが好ましい。銀ナノ粒子の平均粒子径Ｄ５０が７０ｎｍ以下であると、粒子径が、少なくとも大粒子径側には偏っていないため、分散安定性が良く、塗膜の金属光沢性が高まりやすい。銀ナノ粒子の平均粒子径Ｄ５０は、３０ｎｍ以上６５ｎｍ以下であることがより好ましく、３５ｎｍ以上６５ｎｍ以下であることがさらに好ましい。 The volume-equivalent average particle diameter D50 of the silver nanoparticles is preferably 25 nm or more and 70 nm or less. When the average particle diameter D50 of the silver nanoparticles is 70 nm or less, the particle diameter is not at least biased to the large particle diameter side, so the dispersion stability is good and the metallic gloss of the coating film tends to be enhanced. The average particle diameter D50 of the silver nanoparticles is more preferably 30 nm or more and 65 nm or less, and still more preferably 35 nm or more and 65 nm or less.
　銀ナノ粒子の体積粒度分布におけるピークの半値幅は、３０ｎｍ以上であることが好ましい。半値幅が３０ｎｍ以上であると、銀ナノ粒子は、平均粒子径とその近傍の粒子径の粒子のみならず、種々の異なる粒子径の粒子を含んでいるため、種々の波長の光を反射させることができる。その結果、反射光の色味の偏りを少なくすることができる。銀ナノ粒子の体積粒度分布におけるピークの半値幅は、３０ｎｍ以上１２０ｎｍ以下であることがより好ましく、４０ｎｍ以上１００ｎｍ以下であることがさらに好ましく、４０ｎｍ以上８０ｎｍ以下であることがさらに好ましい。半値幅が１２０ｎｍ以下であると、粗大過ぎる粒子を含まない範囲で種々の異なる粒子径の粒子を含むことができ、分散安定化しやすい。 The half width of the peak in the volume particle size distribution of the silver nanoparticles is preferably 30 nm or more. When the half width is 30 nm or more, silver nanoparticles reflect not only particles of average particle diameter and particles of particle diameter in the vicinity but also particles of various particle diameters, and therefore light of various wavelengths is reflected be able to. As a result, it is possible to reduce the bias of the color of the reflected light. The half value width of the peak in the volume particle size distribution of the silver nanoparticles is more preferably 30 nm or more and 120 nm or less, still more preferably 40 nm or more and 100 nm or less, and still more preferably 40 nm or more and 80 nm or less. When the half width is 120 nm or less, particles of various different particle sizes can be included in the range that does not include particles that are too coarse, and dispersion stabilization is easy.
　ピークの半値幅とは、体積粒度分布において、ピークの極大値の１／２の値となる粒径の幅（半値全幅）である。なお、体積粒度分布における「ピーク」とは、５ｎｍ刻みで測定した体積粒度分布において、極大値の体積頻度が５％以上のピークである。すなわち、極大値の体積頻度が５％未満のピークは、本発明においてはピークの数に含めない。 The full width at half maximum of the peak is the width (full width at half maximum) of the particle diameter which is 1/2 of the peak maximum value in the volume particle size distribution. The “peak” in the volume particle size distribution is a peak at which the volume frequency of the maximum value is 5% or more in the volume particle size distribution measured at intervals of 5 nm. That is, peaks having a volume frequency of maximum less than 5% are not included in the number of peaks in the present invention.
　銀ナノ粒子の粒度分布には、前述した半値幅を有するピークが少なくとも１つ存在すればよく、複数存在してもよい。また、平均粒子径が上記範囲内であり、かつ上記範囲内の半値幅を有するピークが少なくとも１つ存在する限り、他のピークが存在してもかまわない。よって、銀ナノ粒子の粒度分布は、ピークが１つの単峰性でもよいし、ピークが２つ以上の多峰性でもよい。 In the particle size distribution of silver nanoparticles, at least one peak having the above-described half width may be present, and a plurality of peaks may be present. In addition, as long as the average particle diameter is in the above range and at least one peak having a half width in the above range, another peak may be present. Thus, the particle size distribution of silver nanoparticles may be unimodal with one peak or multimodal with two or more peaks.
　銀ナノ粒子の体積換算の平均粒子径Ｄ５０および体積粒度分布におけるピークの半値幅は、以下の手順で測定することができる。
　１）ガラス板上に分散液を塗布した後、真空脱気して溶媒成分を揮発させてサンプルを得る。得られたサンプルの分散液について、測定装置ＪＥＯＬ　ＪＳＭ－７４０１Ｆを用いてＳＥＭ観察を行い、任意の３００個の銀ナノ粒子の粒子径をそれぞれ測定する。
　２）得られた測定データに基づいて、画像処理ソフトＩｍａｇｅ Ｊを用いて体積基準の粒度分布を求め、そのＤ５０（メジアン径）を平均粒子径（体積平均粒子径）とする。また、得られた粒度分布のピークの半値幅を求める。 The volume-equivalent average particle diameter D50 of silver nanoparticles and the half width of the peak in the volume particle size distribution can be measured by the following procedure.
1) After applying the dispersion on a glass plate, vacuum degassing is performed to volatilize solvent components to obtain a sample. The obtained sample dispersion is subjected to SEM observation using a measuring apparatus JEOL JSM-7401F to measure the particle diameter of any 300 silver nanoparticles.
2) Based on the obtained measurement data, a particle size distribution based on volume is determined using image processing software Image J, and D50 (median diameter) thereof is defined as an average particle diameter (volume average particle diameter). Also, the half-width of the obtained particle size distribution peak is determined.
　なお、ＳＥＭ観察では、銀ナノ粒子の表面に吸着した高分子分散剤は観察できないことから、銀ナノ粒子の粒子径は、高分子分散剤を含まない銀ナノ粒子の粒子径として求める。 In addition, since the polymer dispersing agent adsorbed on the surface of the silver nanoparticles can not be observed in the SEM observation, the particle diameter of the silver nanoparticles is determined as the particle diameter of the silver nanoparticles not containing the polymer dispersing agent.
　銀ナノ粒子の平均粒子径Ｄ５０および体積粒度分布におけるピークの半値幅は、前述の銀ナノ粒子分散液の製造方法における、還元剤の配合量や滴下時間、高分子分散剤の配合量および還元反応時の温度などによって調整されうる。銀ナノ粒子の平均粒子径Ｄ５０を小さくするためには、例えば高分子分散剤の配合量は多くし、還元反応時の温度は低くすることが好ましい。銀ナノ粒子の体積粒度分布におけるピークの半値幅を大きくするためには、例えば還元剤の滴下時間は短くし、高分子分散剤の配合量は少なくし、還元反応時の温度は高くすることが好ましい。 The average particle diameter D50 of the silver nanoparticles and the half width of the peak in the volume particle size distribution are the blending amount and dropping time of the reducing agent, the blending amount of the polymer dispersant and the reduction reaction in the method for producing the silver nanoparticle dispersion described above. It can be adjusted by the temperature of the hour. In order to reduce the average particle diameter D50 of the silver nanoparticles, for example, it is preferable to increase the blending amount of the polymer dispersant and lower the temperature at the reduction reaction. In order to increase the half width of the peak in the volume particle size distribution of silver nanoparticles, for example, the dropping time of the reducing agent may be shortened, the blending amount of the polymer dispersant may be reduced, and the temperature during the reduction reaction may be increased. preferable.
　２－２．高分子分散剤
　銀ナノ粒子分散液に含まれる高分子分散剤は、本発明の銀ナノ粒子分散液の製造方法で用いた高分子分散剤に由来する成分であり、銀ナノ粒子の表面の少なくとも一部に吸着している。高分子分散剤は、前述の高分子分散剤と同じである。 2-2. Polymeric Dispersant The polymer dispersant contained in the silver nanoparticle dispersion is a component derived from the polymer dispersant used in the method for producing a silver nanoparticle dispersion of the present invention, and at least at the surface of the silver nanoparticles It is adsorbed to a part. The polymeric dispersant is the same as the polymeric dispersant described above.
　２－３．アンモニア
　銀ナノ粒子分散液に含まれるアンモニアは、本発明の銀ナノ粒子分散液の製造方法で用いた銀アンミン錯体に由来する成分である。なお、アンモニアは、銀ナノ粒子の分散安定性をさらに高めうることから、必要に応じてさらに添加されてもよい。 2-3. Ammonia The ammonia contained in the silver nanoparticle dispersion liquid is a component derived from the silver ammine complex used in the method for producing a silver nanoparticle dispersion liquid of the present invention. Ammonia may be further added as necessary because it can further enhance the dispersion stability of the silver nanoparticles.
　銀ナノ粒子分散液におけるアンモニアの含有量は、前述の通り、０．５質量ｐｐｍ以上１５００質量ｐｐｍ以下であることが好ましい。すなわち、本発明の銀ナノ粒子分散液の製造方法で得られる銀ナノ粒子分散液には、通常、アンモニアの含有量が０．５質量ｐｐｍ以上含まれる。さらに、アンモニアは、銀ナノ粒子の分散安定性をさらに高めうることから、アンモニアの含有量は、１質量ｐｐｍ以上１０００質量ｐｐｍ以下であることがより好ましい。 As described above, the content of ammonia in the silver nanoparticle dispersion liquid is preferably 0.5 mass ppm or more and 1,500 mass ppm or less. That is, in the silver nanoparticle dispersion liquid obtained by the method for producing a silver nanoparticle dispersion liquid of the present invention, the content of ammonia is usually 0.5 mass ppm or more. Furthermore, since ammonia can further enhance the dispersion stability of silver nanoparticles, the content of ammonia is more preferably 1 mass ppm or more and 1000 mass ppm or less.
　アンモニアの含有量は、例えばキャピラリー電気泳動法により２５℃にて測定することができる。 The content of ammonia can be measured, for example, at 25 ° C. by capillary electrophoresis.
　アンモニアの含有量は、主に、前述の精製工程によって調整されうるが、必要に応じて精製工程とは別の工程でアンモニアをさらに添加することによって調整してもよい。 The content of ammonia can be adjusted mainly by the above-mentioned purification step, but may be adjusted by further adding ammonia in a step separate from the purification step, if necessary.
　２－４．その他の成分
　銀ナノ粒子分散液は、必要に応じて上記以外の他の成分をさらに含んでいてもよい。他の成分の例には、原料に由来する硝酸イオン等の雑イオン、還元で生じた塩やアミン分解物などの不純物、さらに保存安定性向上や使用目的に応じて、有機溶剤、粘度調整剤、樹脂、界面活性剤、ｐＨ調整剤、表面張力調整剤、可塑剤、防カビ剤、防腐剤、保湿剤、蒸発促進剤、消泡剤、酸化防止剤、光安定剤、劣化防止剤、酸素吸収剤、防錆剤などが含まれる。 2-4. Other Components The silver nanoparticle dispersion may further contain other components in addition to the above as required. Examples of other components include foreign ions such as nitrate ion derived from raw materials, impurities such as salts generated by reduction and decomposition products of amine, and organic solvents and viscosity modifiers depending on storage stability improvement and purpose of use. , Resins, surfactants, pH adjusters, surface tension adjusters, plasticizers, fungicides, preservatives, moisturizers, evaporation accelerators, antifoaming agents, antioxidants, light stabilizers, antidegradants, oxygen Absorbent, rust inhibitor etc. are included.
　３．銀ナノ粒子分散液の用途
　本発明の銀ナノ粒子分散液は、塗料やインクなどに幅広く用いることができる。中でも、本発明の銀ナノ粒子分散液は、銀ナノ粒子の平均粒径Ｄ５０が小さく、分散安定性が高いことから、インクジェットインクとして好ましく用いることができる。 3. Applications of Silver Nanoparticle Dispersion Liquid The silver nanoparticle dispersion liquid of the present invention can be widely used in paints, inks and the like. Among them, the silver nanoparticle dispersion liquid of the present invention can be preferably used as an inkjet ink because the average particle diameter D50 of silver nanoparticles is small and the dispersion stability is high.
　本発明のインクジェットインクは、銀ナノ粒子と、銀ナノ粒子の表面に吸着した高分子分散剤と、水と、アンモニアとを含む。 The inkjet ink of the present invention comprises silver nanoparticles, a polymer dispersant adsorbed on the surface of the silver nanoparticles, water, and ammonia.
　インクジェットインクにおける高分子分散剤の、銀ナノ粒子の全質量に対する含有量は、生成する銀ナノ粒子分散液における高分子分散剤の、銀ナノ粒子の全質量に対する含有量と同様でありうる。 The content of the polymer dispersant in the inkjet ink with respect to the total mass of silver nanoparticles may be similar to the content of the polymer dispersant in the produced silver nanoparticle dispersion with respect to the total mass of silver nanoparticles.
　インクジェットインクにおけるアンモニアの含有量は、前述の通り、０．５質量ｐｐｍ以上１５００質量ｐｐｍ以下であることが好ましい。すなわち、本発明の銀ナノ粒子分散液の製造方法で得られる本発明の銀ナノ粒子分散液は、銀アンミン錯体水溶液に由来するアンモニアが残留していることから、当該銀ナノ粒子分散液を用いて得られるインクジェットインクにも、通常、アンモニアが０．５質量ｐｐｍ以上含まれる。さらに、アンモニアは、インクジェットインクにおける銀ナノ粒子の分散安定性をさらに高める観点から、アンモニアの含有量は、インクジェットインクの全質量に対して１質量ｐｐｍ以上１０００質量ｐｐｍ以下であることがより好ましく、５質量ｐｐｍ以上１０００質量ｐｐｍ以下であることがさらに好ましい。 As described above, the content of ammonia in the inkjet ink is preferably 0.5 mass ppm or more and 1500 mass ppm or less. That is, since the ammonia derived from the silver ammine complex aqueous solution remains in the silver nanoparticle dispersion liquid of the present invention obtained by the method for producing a silver nanoparticle dispersion liquid of the present invention, the silver nanoparticle dispersion liquid is used In the ink jet ink obtained as a result, ammonia is usually contained in an amount of 0.5 mass ppm or more. Furthermore, from the viewpoint of further enhancing the dispersion stability of silver nanoparticles in the inkjet ink, the content of ammonia is more preferably 1 mass ppm or more and 1000 mass ppm or less with respect to the total mass of the inkjet ink. More preferably, it is 5 mass ppm or more and 1000 mass ppm or less.
　インクジェットインクは、本発明の効果を損なわない範囲で、上記成分以外の他の成分をさらに含んでもよい。他の成分の例には、水分散性樹脂や溶媒、公知の界面活性剤（表面調整剤）などが含まれる。 The inkjet ink may further contain other components in addition to the above components as long as the effects of the present invention are not impaired. Examples of other components include water dispersible resins and solvents, known surfactants (surface conditioners) and the like.
　（水分散性樹脂）
　水分散性樹脂は、水または水系溶媒に分散する樹脂、すなわち、水または水系溶媒中で、半溶解粒子状態であるコロイダルディスパージョンや、分散粒子状態であるエマルションまたはラテックスなどを形成しうる樹脂であり、バインダー樹脂として機能しうる。水分散性樹脂は、銀ナノ粒子の表面に吸着した高分子分散剤と相互作用して、銀ナノ粒子同士の結着性、銀ナノ粒子の成膜性および銀ナノ粒子の基材への密着性を高めうる。 (Water-dispersible resin)
The water dispersible resin is a resin dispersed in water or an aqueous solvent, that is, a resin capable of forming a colloidal dispersion in a semi-dissolved particle state or an emulsion or latex in a dispersed particle state in water or an aqueous solvent. And can function as a binder resin. The water dispersible resin interacts with the polymer dispersant adsorbed on the surface of the silver nanoparticles to bind the silver nanoparticles together, form the film of the silver nanoparticles, and adhere the silver nanoparticles to the substrate. It can enhance sex.
　水分散性樹脂は、親水性成分をモノマー成分とする重合体であって、水または水系溶媒中で、半溶解粒子状態であるコロイダルディスパージョンや、分散粒子状態であるエマルションまたはラテックスなどを形成しうる。親水性成分の例には、カルボキシル基、スルホン酸基、リン酸基などのアニオン性基、第１～３級アミノ基、第４級アンモニウム塩基等のカチオン性基や、水酸基、ポリアルキレンオキサイド基、アミド基などのノニオン性基を含むモノマー成分が含まれる。親水性成分は、１種のみが含まれてもよいし、複数種類が含まれていてよい。中でも、カルボキシル基やスルホン酸基、ポリオキシエチレン基、ポリオキシプロピレン基を含む親水性成分が好ましい。 The water dispersible resin is a polymer having a hydrophilic component as a monomer component, and forms a colloidal dispersion in the form of semi-soluble particles, an emulsion or a latex in the form of dispersed particles, etc. in water or an aqueous solvent. sell. Examples of hydrophilic components include anionic groups such as carboxyl group, sulfonic acid group and phosphoric acid group, cationic groups such as primary to tertiary amino groups and quaternary ammonium base, hydroxyl group and polyalkylene oxide group And a monomer component containing a nonionic group such as an amido group. The hydrophilic component may be contained alone or in combination of two or more. Among them, hydrophilic components containing a carboxyl group, a sulfonic acid group, a polyoxyethylene group or a polyoxypropylene group are preferable.
　水分散性樹脂は、外部乳化剤で分散させて得られる強制乳化型の水分散性樹脂や、樹脂骨格中に親水性成分を導入した自己乳化型の水分散性樹脂のいずれであってもよいが、樹脂骨格中に親水性成分を導入した自己乳化型の水分散性樹脂であることがより好ましい。 The water dispersible resin may be either a forced emulsifying type water dispersible resin obtained by dispersing with an external emulsifier, or a self emulsifying type water dispersible resin in which a hydrophilic component is introduced into the resin skeleton. More preferably, it is a self-emulsifiable water-dispersible resin in which a hydrophilic component is introduced into the resin skeleton.
　水分散性樹脂は、高分子分散剤との親和性が高い樹脂であることが好ましく、その例には、前述の親水性成分をモノマー成分として含む、アクリル系樹脂やウレタン系樹脂、ポリエステル系樹脂、塩化ビニル系樹脂、酢酸ビニル系樹脂などが含まれる。中でも、得られる金属光沢層の耐水性を高めうる観点から、親水性成分をモノマー成分として含むアクリル系樹脂（例えばアクリル酸をモノマー成分として含むアクリル系樹脂等）や親水性成分をモノマー成分として含むウレタン樹脂（例えばジメチロールプロピオン酸をモノマー成分として含むポリウレタン系樹脂など）がより好ましい。 The water-dispersible resin is preferably a resin having high affinity to a polymer dispersant, and examples thereof include acrylic resins, urethane resins, and polyester resins containing the above-mentioned hydrophilic component as a monomer component. And vinyl chloride resins and vinyl acetate resins. Among them, an acrylic resin containing a hydrophilic component as a monomer component (for example, an acrylic resin containing acrylic acid as a monomer component) or a hydrophilic component as a monomer component from the viewpoint of improving the water resistance of the metal gloss layer obtained. A urethane resin (for example, a polyurethane resin containing dimethylol propionic acid as a monomer component) is more preferable.
　水分散性樹脂の平均粒子径は、０．００５μｍ以上０．５μｍ以下であることが好ましく、０．０１μｍ以上０．２μｍ以下であることがより好ましく、０．０１μｍ以上０．１５μｍ以下であることがさらに好ましい。水分散性樹脂の平均粒子径は、銀ナノ粒子の平均粒子径の測定方法と同様の方法で測定することができる。 The average particle diameter of the water-dispersible resin is preferably 0.005 μm or more and 0.5 μm or less, more preferably 0.01 μm or more and 0.2 μm or less, and preferably 0.01 μm or more and 0.15 μm or less Is more preferred. The average particle size of the water-dispersible resin can be measured by the same method as the method for measuring the average particle size of silver nanoparticles.
　銀ナノ粒子の含有量をＭ１（質量％）、水分散性樹脂の含有量をＭ２（質量％）としたとき、Ｍ１／Ｍ２は、１．３≦Ｍ１／Ｍ２≦３５を満たすことが好ましい。Ｍ１／Ｍ２が１．３以上であると、光を吸収しやすい樹脂の含有比率を少なくし、銀ナノ粒子の含有比率を高めうるので、金属反射層の反射率を高めやすい。Ｍ１／Ｍ２が３５以下であると、樹脂の含有比率を適度に高めうるので、金属反射層の基材との密着性が損なわれにくい。Ｍ１／Ｍ２は、２≦Ｍ１／Ｍ２≦３０を満たすことがより好ましい。 When the content of silver nanoparticles is M1 (% by mass) and the content of the water-dispersible resin is M2 (% by mass), M1 / M2 preferably satisfies 1.3 ≦ M1 / M2 ≦ 35. When M1 / M2 is 1.3 or more, the content ratio of the resin that easily absorbs light can be reduced, and the content ratio of silver nanoparticles can be increased, so it is easy to increase the reflectance of the metal reflective layer. When the M1 / M2 is 35 or less, the content ratio of the resin can be appropriately increased, so the adhesion of the metal reflective layer to the substrate is unlikely to be impaired. More preferably, M1 / M2 satisfies 2 ≦ M1 / M2 ≦ 30.
　銀ナノ粒子の含有量Ｍ１（質量％）と、水分散性樹脂の含有量Ｍ２（質量％）の合計含有量（Ｍ１＋Ｍ２）は、１≦Ｍ１＋Ｍ２≦３５を満たすことが好ましい。Ｍ１＋Ｍ２が１以上であると、インクジェットインクに含まれる固形分量が適度に多いため、所望の厚みの金属光沢層を形成しやすく、十分な反射率が得られやすい。Ｍ１＋Ｍ２が３５以下であると、インク中の固形分量が多くなりすぎないため、粘度が高まり過ぎず、インクジェットインクの吐出安定性が損なわれにくい。Ｍ１＋Ｍ２は、３≦Ｍ１＋Ｍ２≦３０を満たすことがより好ましい。 The total content (M1 + M2) of the content M1 (mass%) of the silver nanoparticles and the content M2 (mass%) of the water dispersible resin preferably satisfies 1 ≦ M1 + M2 ≦ 35. When M1 + M2 is 1 or more, the amount of solid content contained in the inkjet ink is appropriately large, so a metal gloss layer having a desired thickness is easily formed, and a sufficient reflectance is easily obtained. When M1 + M2 is 35 or less, the solid content in the ink is not too large, so the viscosity does not increase too much, and the ejection stability of the inkjet ink is unlikely to be impaired. It is more preferable that M1 + M2 satisfy 3 ≦ M1 + M2 ≦ 30.
　（溶媒）
　溶媒は、少なくとも水を含むが、任意の割合で有機溶媒をさらに含んでいてもよい。 (solvent)
The solvent contains at least water, but may further contain an organic solvent in any proportion.
　有機溶媒の例には、エチレングリコールモノメチルエーテル、エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、ジエチレングリコールモノメチルエーテル、ジエチレングリコールモノエチルエーテル、ジエチレングリコールモノブチルエーテル、トリエチレングリコールモノメチルエーテル、トリエチレングリコールモノエチルエーテル、トリエチレングリコールモノブチルエーテル、テトラエチレングリコールモノメチルエーテル、テトラエチレングリコールモノエチルエーテル、テトラエチレングリコールモノプロピルエーテル、テトラエチレングリコールモノブチルエーテル、プロピレングリコールモノメチルエーテル、プロピレングリコールモノエチルエーテル、プロピレングリコールモノブチルエーテル、ジプロピレングリコールモノメチルエーテル、ジプロピレングリコールモノエチルエーテル、ジプロピレングリコールモノプロピルエーテルなどのグリコールエーテル類；エチレングリコール、グリセリン、２－エチル－２－（ヒドロキシメチル）－１，３－プロパンジオール、テトラエチレングリコール、トリエチレングリコール、トリプロピレングリコール、１，２，４－ブタントリオール、ジエチレングリコール、プロピレングリコール、ジプロピレングリコール、ブチレングリコール、１，６－ヘキサンジオール、１，２－ヘキサンジオール、１，５－ペンタンジオール、１，２－ペンタンジオール、２，２－ジメチル－１，３－プロパンジオール、２－メチル－２，４－ペンタンジオール、３－メチル－１，５－ペンタンジオール、３－メチル－１，３－ブタンジオール、２－メチルペンタン－２，４－ジオール、２－メチル－１，３－プロパンジオールなどの多価アルコール類；エタノールアミン、２－（ジメチルアミノ）エタノールなどのアミン類；メタノール、エタノール、ブタノールなどの１価アルコール類；２，２′－チオジエタノール；スルホラン；Ｎ，Ｎ－ジメチルホルムアミドなどのアミド類；２－ピロリドン、γブチロラクトン、炭酸プロピレン、炭酸エチレンなどの複素環類；アセトニトリルなどが含まれる。これらを単独または複数混合して用いることもできる。 Examples of the organic solvent include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monoethyl ether Ethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol monopropyl ether, tetraethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ester Glycol ethers such as ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether; ethylene glycol, glycerin, 2-ethyl-2- (hydroxymethyl) -1,3-propanediol, Tetraethylene glycol, triethylene glycol, tripropylene glycol, 1,2,4-butanetriol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, 1,6-hexanediol, 1,2-hexanediol, 1,5 -Pentanediol, 1,2-Pentanediol, 2,2-Dimethyl-1,3-propanediol, 2-Methyl-2,4-Pentanediol, 3-Methyl-1,5-Pen Polyhydric alcohols such as 2-diol, 3-methyl-1,3-butanediol, 2-methylpentane-2,4-diol, 2-methyl-1,3-propanediol; ethanolamine, 2- (dimethylamino) Amines such as ethanol; monohydric alcohols such as methanol, ethanol, butanol; 2,2'-thiodiethanol; sulfolane; amides such as N, N-dimethylformamide; 2-pyrrolidone, γ-butyrolactone, propylene carbonate, carbonate Heterocycles such as ethylene; acetonitrile etc. are included. These may be used alone or in combination of two or more.
　中でも、溶媒は、インクジェットヘッド近傍でのインクの乾燥を防ぎ、当該ヘッドからの吐出性を高める観点などから、沸点１５０℃以上の有機溶媒を含むことが好ましい。そのような有機溶媒の好ましい例には、グリセリンやプロピレングリコール、トリエチレングリコールモノメチルエーテルなどが含まれる。 Among them, the solvent preferably includes an organic solvent having a boiling point of 150 ° C. or more from the viewpoint of preventing the ink from drying in the vicinity of the ink jet head and enhancing the dischargeability from the head. Preferred examples of such organic solvents include glycerin, propylene glycol, triethylene glycol monomethyl ether and the like.
　（界面活性剤）
　界面活性剤の例には、ジアルキルスルホコハク酸塩類、アルキルナフタレンスルホン酸塩類および脂肪酸塩類などのアニオン性界面活性剤、ポリオキシエチレンアルキルエーテル類、ポリオキシエチレンアルキルアリルエーテル類、アセチレングリコール類およびポリオキシエチレン・ポリオキシプロピレンブロックコポリマー類などのノニオン性界面活性剤、アルキルアミン塩類および第四級アンモニウム塩類などのカチオン性界面活性剤、並びにシリコーン系やフッ素系の界面活性剤が含まれる。 (Surfactant)
Examples of surfactants include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates and fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols and polyoxy acids Nonionic surfactants such as ethylene polyoxypropylene block copolymers, cationic surfactants such as alkylamine salts and quaternary ammonium salts, and surfactants of silicone type and fluorine type.
　シリコーン系の界面活性剤の市販品の例には、ＫＦ－３５１Ａ、ＫＦ－３５２Ａ、ＫＦ－６４２およびＸ－２２－４２７２、信越化学工業製、ＢＹＫ－３０７、ＢＹＫ－３４５、ＢＹＫ－３４７及びＢＹＫ－３４８、ビッグケミー製（「ＢＹＫ」は同社の登録商標）、並びにＴＳＦ４４５２、東芝シリコーン社製が含まれる。 Commercially available examples of silicone surfactants include KF-351A, KF-352A, KF-642 and X-22-4272, Shin-Etsu Chemical Co., Ltd., BYK-307, BYK-345, BYK-347 and BYK -348, manufactured by Big Chemie ("BYK" is a registered trademark of the company), as well as TSF4452, manufactured by Toshiba Silicone Co., Ltd.
　界面活性剤の含有量は、例えばインクの全質量に対して０．００１質量％以上１．０質量％未満とすることができる。 The content of the surfactant can be, for example, 0.001% by mass or more and less than 1.0% by mass with respect to the total mass of the ink.
　（物性）
　本発明のインクジェットインクの粘度は、インクジェット法による画像形成において、ノズルからの吐出安定性をより高める観点からは、１ｃＰ以上１００ｃＰ未満であることが好ましく、１ｃＰ以上５０ｃＰ以下であることがより好ましく、１ｃＰ以上１５ｃＰ以下であることがさらに好ましい。 (Physical properties)
The viscosity of the inkjet ink of the present invention is preferably 1 cP or more and less than 100 cP, and more preferably 1 cP or more and 50 cP or less, from the viewpoint of further enhancing the ejection stability from the nozzle in image formation by the inkjet method. More preferably, it is 1 cP or more and 15 cP or less.
　４．画像形成方法
　本発明の画像形成方法は、本発明のインクジェットインクを基材上に付与して、金属光沢層を形成する工程を含む。 4. Image Forming Method The image forming method of the present invention includes the step of applying the inkjet ink of the present invention on a substrate to form a metallic gloss layer.
　４－１．金属光沢層を形成する工程
　前述のインクジェットインクを基材上に付与した後、乾燥させて、金属光沢層を形成する。 4-1. Step of Forming a Metallic Gloss Layer The above-described inkjet ink is applied onto a substrate and then dried to form a metallic gloss layer.
　基材は、特に限定されず、吸収性基材であってもよいし、非吸収性基材であってもよい。吸収性基材の例には、アート紙、コート紙、軽量コート紙、微塗工紙、およびキャスト紙などの塗工紙や、非塗工紙が含まれる。非吸収性基材の例には、ポリ塩化ビニル（ＰＶＣ）、ポリオレフィン（例えばポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）等）、ポリウレタン（ＰＵ）、アクリル樹脂（ＰＡ）、ポリカーボネート（ＰＣ）、ポリスチレン（ＰＳ）、アクリロニトリル－ブタジエン－スチレン共重合体（ＡＢＳ）、ポリエステル（例えばポリエチレンテレフタレート（ＰＥＴ）やポリブタジエンテレフタレート（ＰＢＴ））、ナイロン（Ｎｙ）などの樹脂を含む樹脂基材や、金属類やガラスなどの無機物を含む無機基材が含まれる。 The substrate is not particularly limited, and may be an absorbent substrate or a non-absorbent substrate. Examples of absorbent substrates include coated papers such as art papers, coated papers, lightweight coated papers, fine coated papers, and cast papers, and non-coated papers. Examples of non-absorbent substrates include polyvinyl chloride (PVC), polyolefins (eg polyethylene (PE), polypropylene (PP) etc.), polyurethane (PU), acrylic resin (PA), polycarbonate (PC), polystyrene PS), Acrylonitrile-Butadiene-Styrene Copolymer (ABS), Polyester (for example, polyethylene terephthalate (PET) or polybutadiene terephthalate (PBT)), resin base material including resin such as nylon (Ny), metals, glass, etc. Inorganic base material containing the inorganic substance of
　インクの付与は、インクジェット法にて行うことができる。具体的には、インクをインクジェットヘッドのノズルから吐出して、基材の表面に着弾させる。 The application of the ink can be performed by an inkjet method. Specifically, the ink is ejected from the nozzle of the inkjet head to land on the surface of the substrate.
　インクの付与量は、得られる金属光沢層の厚みが、好ましくは０．００５μｍ以上１０μｍ以下、より好ましくは０．０１μｍ以上１．０μｍ以下、さらに好ましくは０．１μｍ以上０．５μｍ以下となるように設定される。得られる金属光沢層の厚みが上記範囲内であると、金属光沢を十分に発現させやすい。 The application amount of the ink is such that the thickness of the obtained metallic gloss layer is preferably 0.005 to 10 μm, more preferably 0.01 to 1.0 μm, and still more preferably 0.1 to 0.5 μm. Set to When the thickness of the obtained metallic gloss layer is in the above range, the metallic gloss is easily exhibited sufficiently.
　インクの乾燥は、特に制限されず、真空脱気法や送風乾燥法、加熱乾燥法などで行うことができる。インクの乾燥温度は、水分散性樹脂のガラス転移温度未満とすることが好ましく、例えば常温以上１００℃未満であることが好ましく、常温以上８０℃未満であることがより好ましい。 The drying of the ink is not particularly limited, and may be performed by a vacuum degassing method, a blast drying method, a heat drying method, or the like. The drying temperature of the ink is preferably less than the glass transition temperature of the water-dispersible resin, for example, preferably from normal temperature to less than 100 ° C., and more preferably from normal temperature to less than 80 ° C.
　インクジェットインクが水分散性樹脂をさらに含む場合、必要に応じて加熱をさらに行ってもよい。加熱によりインク中の水分散性樹脂を融着させやすくし、金属光沢層の基材との密着性などをさらに高めうる。 When the inkjet ink further contains a water dispersible resin, heating may be further performed as needed. By heating, the water-dispersible resin in the ink can be easily fused, and the adhesion of the metallic gloss layer to the substrate can be further enhanced.
　インクの加熱温度は、水分散性樹脂が熱融着しうる温度であればよく、水分散性樹脂の最低造膜温度（ＭＦＴ）またはガラス転移温度以上とすることが好ましい。具体的には、加熱温度は、例えば４０℃以上とすることが好ましく、上限温度は、基材と水分散性樹脂の耐熱温度以下である必要がある。また、インクに造膜助剤をさらに添加することで、水分散性樹脂のＴｇ以下で造膜させることも可能となる。 The heating temperature of the ink may be any temperature at which the water-dispersible resin can be heat-fused, and is preferably at least the minimum film-forming temperature (MFT) or glass transition temperature of the water-dispersible resin. Specifically, the heating temperature is preferably, for example, 40 ° C. or more, and the upper limit temperature needs to be equal to or less than the heat resistance temperature of the base material and the water-dispersible resin. Further, by further adding a film forming aid to the ink, it is also possible to form a film at a Tg or less of the water-dispersible resin.
　インクの乾燥と加熱は、逐次的に行ってもよいし、同時に行ってもよい。インクの乾燥と加熱とを同時に行う場合、乾燥兼加熱温度は、水分散性樹脂の最低造膜温度（ＭＦＴ）又はガラス転移温度以上とすることが好ましい。 Drying and heating of the ink may be performed sequentially or simultaneously. When the drying and heating of the ink are performed simultaneously, the drying and heating temperature is preferably at least the minimum film forming temperature (MFT) or the glass transition temperature of the water-dispersible resin.
　４－２．その他の層を形成する工程
　本発明の画像形成方法は、必要に応じて、上述した工程によって金属光沢層が形成される前の基材の表面にプライマー層を形成する工程をさらに含んでもよい。また、本発明の画像形成方法は、得られた金属光沢層のより表層側に、色材層または保護層を形成する工程をさらに含んでいてもよい。 4-2. Step of Forming Other Layers The image forming method of the present invention may further include the step of forming a primer layer on the surface of the substrate before the metallic gloss layer is formed by the above-described steps, if necessary. Further, the image forming method of the present invention may further include the step of forming a coloring material layer or a protective layer on the surface side of the obtained metallic gloss layer.
　４－２－１．プライマー層の形成
　プライマー層は、バインダー樹脂を含む樹脂組成物を、金属光沢層が形成される前の基材表面に付与して、形成することができる。樹脂組成物の付与後に、樹脂組成物を加熱などにより乾燥させてバインダー樹脂を成膜させてもよい。このときの乾燥温度は、例えば１００℃未満としうる。 4-2-1. Formation of Primer Layer The primer layer can be formed by applying a resin composition containing a binder resin to the surface of the base before the metallic gloss layer is formed. After application of the resin composition, the resin composition may be dried by heating or the like to form a film of binder resin. The drying temperature at this time may be, for example, less than 100 ° C.
　樹脂組成物に含まれるバインダー樹脂は、銀ナノ粒子などを含む顔料の基材への密着性を高めるために従来から用いられている樹脂であればよい。そのようなバインダー樹脂の例には、アクリル系樹脂、エポキシ系樹脂、ポリシロキサン系樹脂、マレイン酸系樹脂、ポリオレフィン系樹脂、塩化ビニル系樹脂、ポリアミド系樹脂、ポリビニルピロリドン、ポリヒドロキシスチレン、ポリビニルアルコール、ニトロセルロース、酢酸セルロース、エチルセルロース、エチレン－酢酸ビニル共重合体、ウレタン系樹脂、ポリエステル系樹脂、およびアルキド系樹脂などが含まれる。これらの樹脂は、１種単独で用いてもよいし、２種類以上を組み合わせて用いてもよい。 The binder resin contained in the resin composition may be any resin conventionally used in order to enhance the adhesion of pigments including silver nanoparticles and the like to a substrate. Examples of such binder resins include acrylic resins, epoxy resins, polysiloxane resins, maleic acid resins, polyolefin resins, vinyl chloride resins, polyamide resins, polyvinyl pyrrolidone, polyhydroxystyrene, polyvinyl alcohol And nitrocellulose, cellulose acetate, ethylcellulose, ethylene-vinyl acetate copolymer, urethane resin, polyester resin, and alkyd resin. These resins may be used alone or in combination of two or more.
　また、（メタ）アクリロイル基、ビニル基、エポキシ基、またはオキセタン基を含有するモノマー、オリゴマーまたはポリマーを含む組成物を基材表面に付与した後、紫外線などのエネルギー線照射によって当該組成物を硬化させてプライマー層を形成してもよい。 In addition, after a composition containing a monomer, oligomer or polymer containing a (meth) acryloyl group, a vinyl group, an epoxy group or an oxetane group is applied to the substrate surface, the composition is cured by energy ray irradiation such as ultraviolet light. It may be allowed to form a primer layer.
　４－２－２．色材層または保護層の形成
　色材層は、公知の顔料または染料と、それらを定着させるためのバインダー樹脂とを含む樹脂組成物を、金属光沢層上に付与して形成することができる。保護層は、バインダー樹脂を含む樹脂組成物を、金属光沢層上に付与して形成することができる。これらの樹脂組成物の付与後に、当該樹脂組成物を加熱などにより乾燥させてバインダー樹脂を成膜させてもよい。このときの乾燥温度は、例えば１００℃未満としうる。 4-2-2. Formation of Color Material Layer or Protective Layer The color material layer can be formed by applying a resin composition containing known pigments or dyes and a binder resin for fixing them on the metallic gloss layer. The protective layer can be formed by applying a resin composition containing a binder resin on the metallic gloss layer. After application of these resin compositions, the resin composition may be dried by heating or the like to form a binder resin film. The drying temperature at this time may be, for example, less than 100 ° C.
　これらの樹脂組成物に含まれる樹脂は、プライマー層に含まれるバインダー樹脂と同様の樹脂から選択することができる。 The resin contained in these resin compositions can be selected from the same resins as the binder resin contained in the primer layer.
　また、（メタ）アクリロイル基、ビニル基、エポキシ基、またはオキセタン基を含有するモノマー、オリゴマーまたはポリマーを含む組成物を金属光沢層上に付与した後、紫外線などのエネルギー線照射によって当該組成物を硬化させて、色材層または保護層を形成してもよい。 In addition, a composition containing a monomer, oligomer or polymer containing (meth) acryloyl group, vinyl group, epoxy group or oxetane group is applied onto the metallic gloss layer, and then the composition is irradiated with energy rays such as ultraviolet rays. It may be cured to form a colorant layer or a protective layer.
　樹脂組成物は、液状であってもよいし、フィルム状であってもよい。すなわち、色材層や保護層は、液状の樹脂組成物を付与した後、乾燥させて形成してもよいし、フィルム状の樹脂組成物を熱圧着して形成してもよい。 The resin composition may be liquid or film-like. That is, the color material layer and the protective layer may be formed by drying after applying a liquid resin composition, or may be formed by thermocompression bonding of a film-like resin composition.
　液状の樹脂組成物の付与は、インクジェット法、スプレー法、ローラ塗布法、電子写真法などで行うことができる。精細な画像を形成しやすくする観点では、インクジェット法で行うことが好ましい。液状の樹脂組成物の付与した後の乾燥温度は、溶媒を揮発させるとともに樹脂を成膜させうる温度であり、例えば１００℃未満としうる。 The liquid resin composition can be applied by an inkjet method, a spray method, a roller coating method, an electrophotographic method, or the like. From the viewpoint of facilitating the formation of a fine image, it is preferable to use the inkjet method. The drying temperature after the application of the liquid resin composition is a temperature at which the solvent can be volatilized and the resin can be formed into a film, and may be, for example, less than 100 ° C.
　フィルム状の樹脂組成物の熱圧着は、圧着ローラにより熱圧着させる方法や、シート上に予め形成された転写層をサーマルヘッドまたは熱ローラにより熱転写させる方法で行うことができる。熱圧着温度は、バインダー樹脂のガラス転移温度近傍としうる。 The thermocompression bonding of the film-like resin composition can be performed by a method of thermocompression bonding by a crimping roller, or a method of thermally transferring a transfer layer previously formed on a sheet by a thermal head or a heat roller. The thermocompression bonding temperature may be in the vicinity of the glass transition temperature of the binder resin.
　５．画像形成物
　本発明の画像形成方法で得られる本発明の画像形成物は、基材と、当該基材上に設けられた金属光沢層とを含む。本発明の画像形成物は、必要に応じて基材と金属光沢層との間に設けられたプライマー層や、金属光沢層上に設けられた色材層や保護層をさらに含みうる。 5. Image-Formed Article The image-formed article of the present invention obtained by the image-forming method of the present invention comprises a substrate and a metallic gloss layer provided on the substrate. The image-formed product of the present invention may further include a primer layer provided between the substrate and the metallic gloss layer, and a colorant layer and a protective layer provided on the metallic gloss layer, as needed.
　金属光沢層は、銀ナノ粒子と、その表面に吸着した高分子分散剤とを含む。金属光沢層の組成は、前述のインクジェットインクの固形分の組成と同じである。プライマー層の組成や色材層、保護層の組成も、前述のプライマー層用や色材層、保護層用の樹脂組成物の固形分の組成とそれぞれ同じである。 The metallic gloss layer contains silver nanoparticles and a polymeric dispersant adsorbed on the surface thereof. The composition of the metallic gloss layer is the same as the composition of the solid content of the aforementioned inkjet ink. The composition of the primer layer and the composition of the color material layer and the protective layer are also the same as the composition of the solid content of the resin composition for the primer layer, the color material layer and the protective layer described above.
　画像形成物は、金属光沢の発現が求められる用途に好ましく用いることができる。例えば、画像形成物は、記録物に用いることができる。記録物は、単一の文字または文字の集合であってもよく、図形、絵、写真などの画像であってもよい。 The image-forming material can be preferably used in applications where expression of metallic gloss is required. For example, an image formed article can be used for a recorded matter. The recorded matter may be a single character or a set of characters, and may be an image such as a figure, a picture, a photograph, and the like.
　以下、実施例により本発明を具体的に説明するが、本発明はこれらに限定されるものではない。 EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.
　１．銀ナノ粒子分散液の調製
　＜銀ナノ粒子分散液１の調製＞
　平板状の撹拌翼と邪魔板を有する１Ｌのセパラブルフラスコに、高分子分散剤として、８．３ｇのＤＩＳＰＥＲＢＹＫ－１９０（ビッグケミー社製、溶媒：水、固形分（不揮発成分）：４０質量％、固形分１００質量％換算の酸価：２５ｍｇＫＯＨ／ｇ、主鎖がスチレン由来の構造単位とマレイン酸由来の構造単位とを含み、側鎖がポリアルキレンオキサイド基を有する重合体、表１では分散剤Ａと表記）、および２６０ｇのイオン交換水を投入し、撹拌を行ってＤＩＳＰＥＲＢＹＫ－１９０を溶解させて、分散剤水溶液を得た。
　次いで、上記セパラブルフラスコに、２６０ｇのイオン交換水に７０ｇの硝酸銀を溶解させた硝酸銀水溶液を、攪拌しながら投入した。さらに、アンモニア水６８ｇを添加して撹拌し、その後、上記セパラブルフラスコをウォーターバスに入れ、溶液の温度が８０℃に安定するまで加熱撹拌した。その後、還元剤として、１８０ｇのジメチルアミノエタノール（表１では還元剤Ａと表記）をセパラブルフラスコに添加し、さらに、８０℃に保ちながら３時間攪拌を続けて、銀ナノ粒子を含む反応液を得た（銀ナノ粒子生成工程）。 1. Preparation of Silver Nanoparticle Dispersion <Preparation of Silver Nanoparticle Dispersion 1>
8.3 g of DISPERBYK-190 (manufactured by Big Chemie, solvent: water, solid content (non-volatile component): 40% by mass) as a polymer dispersant in a 1 L separable flask having a flat stirring blade and a baffle plate. Acid value in terms of solid content 100% by mass: 25 mg KOH / g, polymer whose main chain contains a structural unit derived from styrene and a structural unit derived from maleic acid and whose side chain has a polyalkylene oxide group, in Table 1 a dispersant A symbol of A) and 260 g of ion exchanged water were added, and stirring was performed to dissolve DISPERBYK-190 to obtain an aqueous dispersant solution.
Next, a silver nitrate aqueous solution in which 70 g of silver nitrate was dissolved in 260 g of ion-exchanged water was charged into the separable flask while stirring. Further, 68 g of ammonia water was added and stirred, and then the separable flask was put into a water bath, and heated and stirred until the solution temperature stabilized at 80 ° C. Thereafter, 180 g of dimethylaminoethanol (represented as reducing agent A in Table 1) as a reducing agent is added to the separable flask, and stirring is continued for 3 hours while maintaining at 80 ° C., a reaction liquid containing silver nanoparticles Were obtained (silver nanoparticle formation step).
　得られた反応液をステンレスカップに入れて、さらに２Ｌのイオン交換水を加えた後、ポンプを稼働して、限外濾過を行った（精製工程）。ステンレスカップ内の溶液が減少した段階で、再びイオン交換水を入れて、ろ液の伝導度が１００μＳ／ｃｍ以下になるまで精製を繰り返し行った。その後、ろ液を濃縮して、固形分３０質量％の銀ナノ粒子分散液１を得た。
　なお、限外濾過装置は、限外濾過モジュールＡＨＰ１０１０（旭化成株式会社製、分画分子量：５００００、使用膜本数：４００本）、チューブポンプ（Ｍａｓｔｅｒｆｌｅｘ社製）をタイゴンチューブでつないだものを使用した。 The obtained reaction solution was put in a stainless steel cup, and 2 L of ion exchanged water was further added, and then the pump was operated to carry out ultrafiltration (purification step). When the solution in the stainless steel cup decreased, ion-exchanged water was again added, and purification was repeated until the conductivity of the filtrate became 100 μS / cm or less. Thereafter, the filtrate was concentrated to obtain a silver nanoparticle dispersion 1 with a solid content of 30% by mass.
The ultrafiltration apparatus used was an ultrafiltration module AHP1010 (Asahi Kasei Co., Ltd., molecular weight cut off: 50000, number of membranes used: 400), and a tube pump (Masterflex Co., Ltd.) connected by a tygon tube. .
　＜銀ナノ粒子分散液２～５の調製＞
　各材料を表１に記載のように変更し、かつ表１に記載の条件で調製した以外は、銀ナノ粒子分散液１の調製と同様に、銀ナノ粒子分散液２～５を調製した。 <Preparation of Silver Nanoparticle Dispersions 2 to 5>
Silver nanoparticle dispersions 2 to 5 were prepared in the same manner as the silver nanoparticle dispersion 1, except that each material was changed as described in Table 1 and prepared under the conditions described in Table 1.
　＜銀ナノ粒子分散液６の調製＞
　還元剤を、ジイソプロパノールアミン（表１では還元剤Ｂと表記）に変更し、かつ表１に記載の条件で調製した以外は、銀ナノ粒子分散液１の調製と同様に、銀ナノ粒子分散液６を調製した。 Preparation of Silver Nanoparticle Dispersion 6
Silver nanoparticles were dispersed similarly to the preparation of silver nanoparticle dispersion 1, except that the reducing agent was changed to diisopropanolamine (represented as reducing agent B in Table 1) and prepared under the conditions described in Table 1 Liquid 6 was prepared.
　＜銀ナノ粒子分散液７の調製＞
　分散剤を、フローレンＧ７００（共栄社化学製、固形分（不揮発成分）：１００質量％、酸価：６０ｍｇＫＯＨ／ｇ、主鎖がαオレフィン由来の構造単位とマレイン酸由来の構造単位とを含み、側鎖がポリアルキレンオキサイド基を有する重合体、表１では分散剤Ｂと表記）に変更し、かつ表１に記載の条件で調製した以外は、銀ナノ粒子分散液１の調製と同様に、銀ナノ粒子分散液７を調製した。 Preparation of Silver Nanoparticle Dispersion 7
The dispersing agent is Floren G 700 (manufactured by Kyoeisha Chemical Co., Ltd., solid content (non-volatile component): 100% by mass, acid value: 60 mg KOH / g, main chain contains structural unit derived from .alpha.-olefin and structural unit derived from maleic acid, Silver was changed similarly to preparation of the silver nanoparticle dispersion liquid 1 except having changed into the polymer which chain has a polyalkylene oxide group (It is described as dispersing agent B in Table 1), and was prepared on the conditions of Table 1. Nanoparticle dispersion 7 was prepared.
　＜銀ナノ粒子分散液８の調製＞
　還元剤を、ヒドラジン一水和物（表１では還元剤Ｃと表記）に変更し、かつ表１に記載の条件で調製した以外は、銀ナノ粒子分散液１の調製と同様に、銀ナノ粒子分散液８を調製した。 Preparation of Silver Nanoparticle Dispersion 8
The silver nano particles were prepared in the same manner as the silver nanoparticle dispersion liquid 1 except that the reducing agent was changed to hydrazine monohydrate (represented as reducing agent C in Table 1) and prepared under the conditions described in Table 1. A particle dispersion 8 was prepared.
　＜銀ナノ粒子分散液９の調製＞
　分散剤を、ポリビニルピロリドンＫ１５（東京化成製、固形分（不揮発成分）：１００質量％、酸性吸着基およびアルキレンオキサイド構造を有しない、表１では分散剤Ｃと表記）に変更し、かつ表１に記載の条件で調製した以外は、銀ナノ粒子分散液１の調製と同様に、銀ナノ粒子分散液９を調製した。 Preparation of Silver Nanoparticle Dispersion 9
The dispersant was changed to polyvinyl pyrrolidone K15 (manufactured by Tokyo Kasei Kogyo Co., Ltd., solid content (nonvolatile component): 100% by mass, having no acidic adsorptive group and alkylene oxide structure, represented as dispersant C in Table 1), and Table 1 A silver nanoparticle dispersion 9 was prepared in the same manner as the silver nanoparticle dispersion 1 except that the preparation was performed under the conditions described in 4.
　ただし、銀ナノ粒子分散液８および９は、粒子は反応終了時点で激しく凝集、沈降しており、限外濾過装置で精製することはできない状態であったため、遠心分離による精製を行った。 However, since the silver nanoparticle dispersion liquids 8 and 9 were in such a state that the particles were strongly aggregated and precipitated at the end of the reaction and could not be purified by an ultrafiltration device, purification was performed by centrifugation.
　得られた銀ナノ粒子分散液１～９の固形分の組成および銀ナノ粒子の粒度分布を、それぞれ以下の方法で評価した。 The composition of the solid content of the obtained silver nanoparticle dispersions 1 to 9 and the particle size distribution of the silver nanoparticles were evaluated by the following methods.
　（銀ナノ粒子分散液の固形分の組成）
　得られた銀ナノ粒子分散液の一部を採取し、室温で１０時間真空乾燥させて、銀ナノ粒子を含む固形物を得た。得られた固形物について、熱重量分析（ＲＩＧＡＫＵ製ＴｈｅｒｍｏｐｌｕｓＴＧ８１２０）を行い、５０～５００℃の重量減少分を固形分中の有機分とし、５００℃での残渣をＡｇ分とした。 (Composition of solid content of silver nanoparticle dispersion)
A portion of the obtained silver nanoparticle dispersion was collected and vacuum dried at room temperature for 10 hours to obtain a solid containing silver nanoparticles. The obtained solid was subjected to thermogravimetric analysis (Thermoplus TG 8120 manufactured by RIGAKU), and the weight loss at 50 to 500 ° C. was used as the organic component in the solid content, and the residue at 500 ° C. as the Ag content.
　（銀ナノ粒子の粒度分布）
　銀ナノ粒子の平均粒子径Ｄ５０および体積粒度分布における半値幅は、以下の手順で測定した。
　１）ガラス板上に分散液を塗布した後、真空脱気して溶媒成分を揮発させてサンプルを得た。得られたサンプルの分散液について、測定装置ＪＥＯＬ　ＪＳＭ－７４０１Ｆを用いてＳＥＭ観察を行い、任意の３００個の銀ナノ粒子の粒子径をそれぞれ測定した。
　２）得られた測定データに基づいて、画像処理ソフトＩｍａｇｅ Ｊを用いて体積基準の粒度分布を求め、そのＤ５０（メジアン径）を平均粒子径（体積平均粒子径）とした。また、得られた粒度分布のピークの半値幅を求めた。
　なお、ＳＥＭ観察では、銀ナノ粒子の表面に吸着した分散剤は観察できないことから、銀ナノ粒子の粒子径は、分散剤を含まない銀ナノ粒子の粒子径として求めた。 (Size distribution of silver nanoparticles)
The average particle diameter D50 of silver nanoparticles and the half-width in the volume particle size distribution were measured by the following procedure.
1) After the dispersion was applied on a glass plate, it was vacuum degassed to evaporate the solvent components to obtain a sample. The obtained sample dispersion was subjected to SEM observation using a measuring apparatus JEOL JSM-7401F, and the particle diameters of 300 arbitrary silver nanoparticles were measured.
2) Based on the obtained measurement data, a particle size distribution based on volume is determined using image processing software Image J, and D50 (median diameter) thereof is defined as an average particle diameter (volume average particle diameter). In addition, the half width of the obtained particle size distribution peak was determined.
In addition, in SEM observation, since the dispersing agent adsorbed on the surface of silver nanoparticles can not be observed, the particle diameter of silver nanoparticles was determined as the particle diameter of silver nanoparticles containing no dispersing agent.
　銀ナノ粒子分散液１～９の組成を表１に示し、銀ナノ粒子の物性（固形分の組成および銀ナノ粒子の粒度分布）を表２に示す。
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
 The compositions of the silver nanoparticle dispersions 1 to 9 are shown in Table 1, and the physical properties of the silver nanoparticles (the composition of the solid content and the particle size distribution of the silver nanoparticles) are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
　表２に示されるように、還元剤としてアルカノールアミン、高分子分散剤として酸性基およびポリアルキレンオキサイド基を有する高分子分散剤、銀アンミン錯体水溶液を用いて製造した銀ナノ粒子分散液１～３は、銀アンミン錯体水溶液を用いずに製造した銀ナノ粒子分散液５よりも、平均粒子径Ｄ５０が小さく、かつピークの半値幅が大きく、ブロードな粒度分布を有することがわかる。 As shown in Table 2, silver nanoparticle dispersions 1 to 3 prepared using an alkanolamine as a reducing agent, a polymer dispersant having an acidic group and a polyalkylene oxide group as a polymer dispersant, and a silver ammine complex aqueous solution It can be seen that the average particle diameter D50 is smaller, the half width of the peak is larger, and a broad particle size distribution is obtained, as compared with the silver nanoparticle dispersion liquid 5 manufactured without using the silver ammine complex aqueous solution.
　また、高分子分散剤の銀化合物に対する配合量を多くすることで、体積粒度分布におけるピークの半値幅を一定以上としつつ、銀ナノ粒子の平均粒子径Ｄ５０をさらに小さくしうることがわかる（銀ナノ粒子分散液１～４の対比）。 In addition, it is understood that the average particle diameter D50 of the silver nanoparticles can be further decreased while the half width of the peak in the volume particle size distribution is made constant or more by increasing the compounding amount of the polymer dispersant to the silver compound (silver Comparison of nanoparticle dispersions 1 to 4).
　また、還元剤として、ヒドラジン一水和物（還元剤Ｃ）を用いて製造した銀ナノ粒子分散液８、および高分子分散剤として、ポリビニルピロリドン（分散剤Ｃ）を用いて製造した銀ナノ粒子分散液９は、粒子は凝集、沈降しており、粒径Ｄ５０、粒度分布半値幅を計測するためのサンプルが十分に調製できなかった。塊の一部を採取したＳＥＭ画像からは、百ｎｍオーダーの粗大粒子が主に観測された。これらのことから、銀アンミン錯体を用い、かつ特定の高分子分散剤を用いても、アルカノールアミンよりも還元力が強い(還元反応が速い)還元剤を用いた場合は、急速な粒子生成による粗大化を抑制できないことがわかる。また、銀アンミン錯体とアルカノールアミンを用いても、特定の高分子分散剤とは異なる分散剤を用いた場合、生成される銀ナノ粒子を十分に被覆安定化できず、凝集、粗大粒子化を抑制できないことがわかる。 Also, silver nanoparticle dispersion liquid 8 manufactured using hydrazine monohydrate (reducing agent C) as a reducing agent, and silver nanoparticles manufactured using polyvinyl pyrrolidone (dispersant C) as a polymer dispersing agent In the liquid dispersion 9, particles were aggregated and precipitated, and a sample for measuring the particle diameter D50 and the half width of the particle size distribution could not be prepared sufficiently. Coarse particles on the order of 100 nm were mainly observed from the SEM image obtained by collecting a part of the mass. From these facts, rapid particle formation occurs when a silver ammine complex is used, and even if a specific polymer dispersant is used, a reducing agent having a stronger reducing power than an alkanolamine (a reduction reaction is faster) is used. It turns out that coarsening can not be suppressed. In addition, even when a silver ammine complex and an alkanolamine are used, when a dispersing agent different from a specific polymer dispersing agent is used, the formed silver nanoparticles can not be sufficiently covered and stabilized, and aggregation and coarsening are achieved. It can be seen that it can not be suppressed.
　２．銀ナノ粒子分散液の調製・評価
　＜銀ナノ粒子分散液１０および１２の調製＞
　銀ナノ粒子分散液２の調製において、限外濾過をさらに繰り返して、分散液に含まれるアンモニアの含有量を表３に示されるように変更した以外は銀ナノ粒子分散液２と同様にして、銀ナノ粒子分散液１０および１２を得た。 2. Preparation and Evaluation of Silver Nanoparticle Dispersion <Preparation of Silver Nanoparticle Dispersions 10 and 12>
In the preparation of silver nanoparticle dispersion 2, the same procedure as silver nanoparticle dispersion 2 is repeated except that ultrafiltration is further repeated to change the content of ammonia contained in the dispersion as shown in Table 3. Silver nanoparticle dispersions 10 and 12 were obtained.
　＜銀ナノ粒子分散液１１および１３の調製＞
　銀ナノ粒子分散液２に、アンモニアの含有量が表３に示される値となるようにアンモニアをさらに添加し、銀ナノ粒子分散液１１および１３を得た。 Preparation of Silver Nanoparticle Dispersions 11 and 13
Ammonia was further added to the silver nanoparticle dispersion liquid 2 so that the content of ammonia became a value shown in Table 3, and silver nanoparticle dispersion liquids 11 and 13 were obtained.
　既に調製した銀ナノ粒子分散液１～５および新たに調製した銀ナノ粒子分散液１０～１３の保存安定性および塗膜の反射率、金属光沢感の均一性および色味を、以下の方法で評価した。 The storage stability of the previously prepared silver nanoparticle dispersions 1 to 5 and the freshly prepared silver nanoparticle dispersions 10 to 13, the reflectance of the coating film, the uniformity of metallic luster and the color tone by the following method evaluated.
　（保存安定性）
　銀ナノ粒子分散液を密閉容器中に入れて、５０℃３０分間と５℃３０分間のヒートサイクルを実施した後、室温で静置して、銀粒子の沈降の様子を肉眼で観察した。そして、以下の基準で評価した。
　○：１０日間以上沈まなかった。
　△：４日～９日後に沈降が観察された。
　×：３日間のうちに沈降が観察された。
　○以上を許容範囲と評価した。 (Storage stability)
The silver nanoparticle dispersion was placed in a closed vessel, heat cycles were carried out at 50 ° C. for 30 minutes and 5 ° C. for 30 minutes, and then allowed to stand at room temperature to observe the precipitation of silver particles visually. And it evaluated by the following criteria.
○: It did not sink for 10 days or more.
Δ: sedimentation was observed after 4 to 9 days.
X: Sedimentation was observed within 3 days.
○ We evaluated the above as an acceptable range.
　（塗膜の評価）
　スライドガラス上に、銀ナノ粒子分散液を滴下して、スピンコーターにて塗布した後、乾燥させて、塗膜（金属光沢層）を形成した。 (Evaluation of coating film)
A silver nanoparticle dispersion was dropped on a slide glass, applied by a spin coater, and then dried to form a coating film (metallic gloss layer).
　（反射率）
　形成した塗膜（金属光沢層）について、分光光度計Ｕ４１００を用いて、４５０ｎｍ～６５０ｎｍの範囲で１０ｎｍおきの各波長での反射率を測定し、それらの平均値を求めた。そして、以下の基準に基づいて、反射率を評価した。
　◎：上記平均値が５０％以上
　〇：上記平均値が５０％未満４０％以上
　△：上記平均値が４０％未満３０％以上
　×：上記平均値が３０％未満
　△以上を実用性ありと評価した。 (Reflectance)
With respect to the formed coating film (metallic gloss layer), the reflectance at each wavelength of 10 nm was measured in the range of 450 nm to 650 nm using a spectrophotometer U4100, and the average value thereof was determined. Then, the reflectance was evaluated based on the following criteria.
:: The above average value is 50% or more. :: The above average value is less than 50% 40% or more. Δ: The above average value is less than 40% 30% or more. ×: The above average value is less than 30%. did.
　（金属光沢感の均一性）
　形成した塗膜（金属光沢層）を目視観察した。そして、金属光沢感の均一性を、以下の基準に基づいて評価した。評価基準は以下のとおりである。
　〇：金属光沢の均一性が優良で、平滑な鏡面のように見える。
　△：金属光沢の均一性が良好。ごく僅かに粒状感があるが実用上問題無し。
　×：金属光沢の均一性劣る。粒状感や白濁して見える部分があり、実用上問題有り。
　△以上を許容範囲と評価した。 (Uniformity of metallic gloss)
The formed coating film (metallic gloss layer) was visually observed. And the uniformity of metallic glossiness was evaluated based on the following references | standards. Evaluation criteria are as follows.
Good: The metallic gloss uniformity is excellent and looks like a smooth mirror surface.
Fair: uniformity of metallic gloss is good. There is a slight grainy feeling, but there is no problem in practical use.
X: The uniformity of metallic gloss is inferior. There is a part that looks grainy or cloudy and there is a problem in practical use.
△ or more was evaluated as an acceptable range.
　（色味）
　形成した塗膜（金属光沢層）について、分光光度計Ｕ４１００を用いて反射率を測定し、４６０ｎｍ～７８０ｎｍの範囲の２０ｎｍごとの各波長の反射率の標準偏差を算出した。そして、以下の基準に基づいて、色味を評価した。
　◎：反射率の標準偏差が２未満 
　○：反射率の標準偏差が２以上３未満 
　△：反射率の標準偏差が３以上４未満
　×：反射率の標準偏差が４以上
　△以上を許容範囲と評価した。
　なお、標準偏差が小さいほど、各波長間の反射率差が少なく、反射スペクトルの形状が平坦に近くなり、所謂バルク銀のような銀色らしい銀色感を持つ。一方で、標準偏差が大きいほど、各波長間の反射率差が多く、反射スペクトルは特定波長でピークを持ち、銀色に着色感がある。 (Color)
The reflectance of the formed coating film (metallic gloss layer) was measured using a spectrophotometer U4100, and the standard deviation of the reflectance of each wavelength for every 20 nm in the range of 460 nm to 780 nm was calculated. And the color was evaluated based on the following criteria.
:: Standard deviation of reflectance is less than 2
○: Standard deviation of reflectance is 2 or more and less than 3
Δ: standard deviation of reflectance is 3 or more and less than 4 ×: standard deviation of reflectance is 4 or more Δ was evaluated as an allowable range.
The smaller the standard deviation, the smaller the difference in reflectance between each wavelength, the closer the shape of the reflection spectrum becomes flat, and the so-called silvery silvery like so-called bulk silver. On the other hand, as the standard deviation is larger, the reflectance difference between each wavelength is more, the reflection spectrum has a peak at a specific wavelength, and silver has a coloring feeling.
　銀ナノ粒子分散液１～５および１０～１３の評価結果を表３に示す。
Figure JPOXMLDOC01-appb-T000004
 The evaluation results of the silver nanoparticle dispersions 1 to 5 and 10 to 13 are shown in Table 3.
Figure JPOXMLDOC01-appb-T000004
　表３に示されるように、還元剤としてアルカノールアミン、高分子分散剤として酸性基およびポリアルキレンオキサイド基を有する高分子分散剤、銀アンミン錯体水溶液を用いて製造した銀ナノ粒子分散液１～４および１０～１３は、いずれも保存安定性が良く、得られる塗膜（金属光沢層）の光輝性も良好であった。 As shown in Table 3, a silver nanoparticle dispersion liquid 1-4 prepared using an alkanolamine as a reducing agent, a polymer dispersing agent having an acidic group and a polyalkylene oxide group as a polymer dispersing agent, and a silver ammine complex aqueous solution And each of Nos. 10 to 13 had good storage stability, and the luster of the resulting coated film (metallic gloss layer) was also good.
　特に、高分子分散剤の配合量を所定の範囲にすることで、反射率や色味を一層良好にしうることがわかる（分散液１～４の対比）。 In particular, it is understood that the reflectance and the color can be further improved by setting the compounding amount of the polymer dispersant in a predetermined range (contrast of dispersion liquids 1 to 4).
　また、分散液中のアンモニアの含有量を所定の範囲にすることで、反射率や色味を一層良好にしうることがわかる（分散液２、１０～１３の対比）。 In addition, it is understood that the reflectance and the color can be further improved by setting the content of ammonia in the dispersion to a predetermined range (contrast of dispersions 2 and 10 to 13).
　これに対して、銀アンミン錯体水溶液を用いずに製造した銀ナノ粒子分散液５は、保存安定性が悪く、得られる塗膜（金属光沢層）の光輝性も低かった。 On the other hand, the silver nanoparticle dispersion liquid 5 manufactured without using the silver ammine complex aqueous solution had poor storage stability, and the luster of the obtained coating film (metallic gloss layer) was also low.
　３．インクジェットインクの調製・評価
　＜材料の調製＞
　（銀ナノ粒子分散液）
　銀ナノ粒子分散液１～５を用いた。 3. Preparation and evaluation of inkjet ink <Preparation of material>
(Silver nanoparticle dispersion liquid)
Silver nanoparticle dispersions 1 to 5 were used.
　（水分散性樹脂の調製）
　ネオペンチルグリコール、エチレングリコール、テレフタル酸、イソフタル酸、およびアジピン酸を、５６：４：１：２１：１８（質量比）で反応させて得られるポリエステルポリオール（分子量２０００）５８０質量部と、トリメチロールプロパン１５質量部と、メチルエチルケトン６６７質量部とを、十分に撹拌溶解させた。次いで、この溶液に、イソホロンジイソシアネート３００質量部を加えて、７５℃で１時間反応させた。反応終了後、６０℃まで冷却し、ジメチロールプロピオン酸１０５質量部と、トリエチルアミン５９質量部（ジメチロールプロピオン酸に対し０．６モル）とを加えて、７５℃で反応させて、ＮＣＯ含量が１．０％の末端イソシアネート基を有するウレタンプレポリマー溶液を得た。このウレタンプレポリマーを４０℃まで冷却して、水１８５７質量部を加え、ホモミキサーで高速撹拌し、乳化させた。この樹脂溶液を加熱減圧下、メチルエチルケトンを留去し、水分散性樹脂として、固形分濃度３０質量％のポリウレタンを含む分散液を得た。得られたポリウレタンの平均粒子径Ｄ２を測定したところ、４０ｎｍであった。 (Preparation of water dispersible resin)
Polyesterol (molecular weight: 2000) 580 parts by weight obtained by reacting neopentyl glycol, ethylene glycol, terephthalic acid, isophthalic acid, and adipic acid at 56: 4: 1: 21: 18 (mass ratio), and trimethylol 15 parts by mass of propane and 667 parts by mass of methyl ethyl ketone were sufficiently dissolved by stirring. Next, 300 parts by mass of isophorone diisocyanate was added to this solution, and reacted at 75 ° C. for 1 hour. After completion of the reaction, the reaction solution is cooled to 60 ° C., 105 parts by mass of dimethylol propionic acid and 59 parts by mass of triethylamine (0.6 mol with respect to dimethylol propionic acid) are added and reacted at 75 ° C. A urethane prepolymer solution having 1.0% of terminal isocyanate groups was obtained. The urethane prepolymer was cooled to 40 ° C., 1857 parts by mass of water was added, and the mixture was stirred at high speed with a homomixer to emulsify. This resin solution was heated under reduced pressure to remove methyl ethyl ketone, thereby obtaining a dispersion containing a polyurethane having a solid concentration of 30% by mass as a water dispersible resin. When the average particle diameter D2 of the obtained polyurethane was measured, it was 40 nm.
　（溶媒）
　水
　プロピレングリコール（ＰＧ、沸点：１８８℃）
　トリエチレングリコールモノメチルエーテル（ＴＥＧＭＥ、沸点：２４８℃） (solvent)
Water Propylene glycol (PG, boiling point: 188 ° C)
Triethylene glycol monomethyl ether (TEGME, boiling point: 248 ° C)
　（添加剤）
　ＢＹＫ－３４８（ビックケミー製）（界面活性剤） (Additive)
BYK-348 (made by BIC Chemie) (surfactant)
　＜インクジェットインク１～９の調製＞
　表４に示されるような組成となるように、各成分（水分散性樹脂、アンモニア、水、プロピレングリコール、トリエチレングリコールモノメチルエーテル、およびＢＹＫ－３４８）を混合した後、ＡＤＶＡＴＥＣ社製テフロン（「テフロン」はデュポン社の登録商標）３μｍメンブランフィルターで濾過して、インクジェットインク１～９を調製した。 Preparation of Inkjet Inks 1 to 9
After mixing each component (water dispersible resin, ammonia, water, propylene glycol, triethylene glycol monomethyl ether, and BYK-348) to obtain the composition as shown in Table 4, Teflon made by ADVATEC (“ The “Teflon” was filtered through a Dupont (registered trademark) 3 μm membrane filter to prepare inkjet inks 1-9.
　得られたインクジェットインク１～９の保存安定性および画像特性を、以下の方法で評価した。 The storage stability and image characteristics of the resulting inkjet inks 1 to 9 were evaluated by the following methods.
　（保存安定性）
　インクを密閉容器中に入れて、５０℃３０分間と５℃３０分間のヒートサイクルを４回繰り返した後、インクの状態を観察した。また、このインクを用いて、線幅０．５ポイントの線を印刷した。そしてその線を目視にて観察して、下記の基準で評価した。
　◎：銀粒子の沈降は見られない。線は、印刷開始時に全くかすれることなく、また印刷途中で途切れることもなく印刷できた。インクの保存安定性、吐出性は良好であると評価した。
　〇：銀粒子の沈降は見られない。線は、印刷開始時にかすれ気味であったが、途中で途切れることなく印刷できた。インクの保存安定性、吐出性は実用レベルに達していると評価した。
　△：銀粒子が沈降しているが、容器を振ると、見かけ上、再分散した。吐出評価は、線が途中で途切れてしまった。インクの保存安定性、吐出性は不良であると評価した。
　×：銀粒子が沈降しており、容器を振っても再分散しない。吐出評価できず、インクの保存安定性は極めて悪いと評価した。
　○以上を、許容範囲と評価した。 (Storage stability)
The ink was placed in a closed container, and heat cycles of 50 ° C. for 30 minutes and 5 ° C. for 30 minutes were repeated four times, and the state of the ink was observed. In addition, a line with a line width of 0.5 point was printed using this ink. And the line was observed visually and evaluated by the following standard.
◎: No sedimentation of silver particles observed. The lines were printed without any blurring at the start of printing and without interruption during printing. The storage stability of the ink and the dischargeability were evaluated as good.
○: No sedimentation of silver particles is observed. The lines were faint at the start of printing but could be printed without interruption. The storage stability of the ink and the dischargeability were evaluated to have reached practical levels.
Δ: Silver particles were sedimented, but when the container was shaken, they were apparently redispersed. In the discharge evaluation, the line was interrupted halfway. The storage stability of the ink and the dischargeability were evaluated as poor.
X: Silver particles have settled and do not re-disperse even if the container is shaken. It was evaluated that the ejection stability could not be evaluated, and the storage stability of the ink was extremely bad.
○ ○ or more was evaluated as an acceptable range.
　（画像特性）
　得られたインクジェットインク１～９を用いて、以下のようにして画像形成を行った。 (Image characteristics)
Image formation was performed as follows using the obtained inkjet inks 1 to 9.
　（基材）
　基材として、コート紙（ラミーコーポレーション、ＷＲＧ３－３６）を準備した。 (Base material)
Coated paper (Rummy Corporation, WRG 3-36) was prepared as a substrate.
　（金属光沢層の形成）
　ピエゾ型インクジェットノズルを有するインクジェット記録装置を用いて、基材に金属光沢層を形成した。インクジェット記録装置は、インクタンク、インク供給配管、インクジェットヘッド直前のインク供給タンク、フィルターおよびピエゾ型のインクジェットヘッドを、インクが流通する上流側から下流側に向けて、この順で有していた。
　インクジェットヘッドは、液滴量１４ｐｌ、印字速度０．５ｍ／ｓｅｃ、射出周波数１０．５ｋＨｚ、印字率１００％となる条件で駆動して、インクの液滴を各基材に吐出して 着弾させた。着弾後、６０℃で１０分ほど乾燥させて、画像形成物を得た。 (Formation of metallic gloss layer)
A metallic gloss layer was formed on the substrate using an inkjet recording apparatus having a piezoelectric inkjet nozzle. The ink jet recording apparatus has an ink tank, an ink supply pipe, an ink supply tank immediately before the ink jet head, a filter, and a piezoelectric ink jet head from the upstream side to the downstream side through which ink flows, in this order.
The ink jet head was driven under the condition that the droplet volume was 14 pl, the printing speed was 0.5 m / sec, the ejection frequency was 10.5 kHz, and the printing rate was 100%, and the ink droplets were ejected and landed on each substrate. . After landing, it was dried at 60 ° C. for about 10 minutes to obtain an image-formed product.
　得られた画像形成物の反射率、金属光沢感の均一性および色味を、前述と同様の方法で評価した。インクジェットインク１～９の組成と評価結果を、表４に示す。
Figure JPOXMLDOC01-appb-T000005
 The reflectance of the obtained image-formed product, the uniformity of metallic glossiness and the color were evaluated by the same method as described above. The compositions of the inkjet inks 1 to 9 and the evaluation results are shown in Table 4.
Figure JPOXMLDOC01-appb-T000005
　表４に示されるように、還元剤としてアルカノールアミン、高分子分散剤として酸性基およびポリアルキレンオキサイド基を有する高分子分散剤、銀アンミン錯体水溶液を用いて製造した銀ナノ粒子分散液１～４を用いたインクジェットインク１～４および６～９は、いずれも保存安定性が良く、得られる金属光沢層の画像特性（反射率、色味）も良好であった。 As shown in Table 4, a silver nanoparticle dispersion liquid 1-4 prepared using an alkanolamine as a reducing agent, a polymer dispersing agent having an acidic group and a polyalkylene oxide group as a polymer dispersing agent, and a silver ammine complex aqueous solution The inkjet inks 1 to 4 and 6 to 9 using the above all had good storage stability, and the image characteristics (reflectance, color tone) of the resulting metallic gloss layer were also good.
　特に、高分子分散剤の配合量を所定の範囲にすることで、反射率や色味を一層良好にしうることがわかる（インクジェットインク１～４の対比）。 In particular, it is understood that the reflectance and the color can be further improved by setting the compounding amount of the polymer dispersant in a predetermined range (contrast of inkjet inks 1 to 4).
　また、インクジェットインク中のアンモニアの含有量を所定の範囲にすることで、反射率や色味を一層良好にしうることがわかる（インクジェットインク２、６および７の対比）。 In addition, it is understood that the reflectance and the color can be further improved by setting the content of ammonia in the inkjet ink within a predetermined range (contrast of inkjet inks 2, 6 and 7).
　これに対して、銀アンミン錯体水溶液を用いずに製造した銀ナノ粒子分散液５を用いたインクジェットインク５は、保存安定性が悪く、得られる金属光沢層の画像特性（反射率、色味）も悪かった。 On the other hand, the inkjet ink 5 using the silver nanoparticle dispersion liquid 5 manufactured without using the silver ammine complex aqueous solution has poor storage stability, and the image characteristics (reflectance, color tone) of the obtained metallic gloss layer It was bad too.
　本出願は、２０１７年１２月２６日出願の特願２０１７－２４９８０３に基づく優先権を主張する。当該出願明細書に記載された内容は、すべて本願明細書に援用される。 This application claims priority based on Japanese Patent Application No. 2017-249803 filed on Dec. 26, 2017. The contents described in the application specification are all incorporated herein by reference.
　本発明によれば、粗大な銀ナノ粒子が少なく、分散安定性が高い銀ナノ粒子分散液の製造方法、銀ナノ粒子分散液およびインクジェットインクおよびそれを用いた画像形成方法を提供することができる。 According to the present invention, it is possible to provide a method of producing a silver nanoparticle dispersion liquid having a large amount of coarse silver nanoparticles and high dispersion stability, a silver nanoparticle dispersion liquid and an inkjet ink, and an image forming method using the same. .

Claims (8)

  1. 　銀アンミン錯体を含む水溶液と、酸性基および（ポリ）アルキレンオキサイド基を有する高分子分散剤と、還元剤としてアルカノールアミンとを混合し、前記銀アンミン錯体を還元させて、銀ナノ粒子と、前記銀ナノ粒子の表面の少なくとも一部に吸着した高分子分散剤と、水とを含む水分散液を得る工程と、
    　前記銀ナノ粒子を含む水分散液を精製する工程と、を有する、
    　銀ナノ粒子分散液の製造方法。     An aqueous solution containing a silver ammine complex, a polymer dispersant having an acidic group and a (poly) alkylene oxide group, and an alkanolamine as a reducing agent are mixed, the silver ammine complex is reduced, and silver nanoparticles are obtained. Obtaining an aqueous dispersion comprising water and a polymer dispersant adsorbed on at least a part of the surface of silver nanoparticles;
    Purifying the aqueous dispersion containing the silver nanoparticles.
    Method for producing silver nanoparticle dispersion.
  2. 　前記高分子分散剤の酸価は、５ｍｇＫＯＨ／ｇ以上２００ｍｇＫＯＨ／ｇ以下である、
    　請求項１に記載の銀ナノ粒子分散液の製造方法。     The acid value of the polymer dispersant is 5 mg KOH / g or more and 200 mg KOH / g or less.
    The manufacturing method of the silver nanoparticle dispersion liquid of Claim 1.
  3. 　前記高分子分散剤は、
    　（メタ）アクリル酸、マレイン酸およびそのハーフエステルからなる群より選ばれるモノマー由来の構造単位と、
    　アルキレンオキサイド変性（メタ）アクリル酸エステル、およびアルキレンオキサイド変性マレイン酸（ハーフ）エステルからなる群より選ばれるモノマーに由来する構造単位とを少なくとも含む、
    　請求項１または２に記載の銀ナノ粒子分散液の製造方法。     The polymer dispersant is
    A structural unit derived from a monomer selected from the group consisting of (meth) acrylic acid, maleic acid and its half ester;
    At least a structural unit derived from a monomer selected from the group consisting of an alkylene oxide-modified (meth) acrylic acid ester, and an alkylene oxide-modified maleic acid (half) ester,
    The manufacturing method of the silver nanoparticle dispersion liquid of Claim 1 or 2.
  4. 　前記銀アンミン錯体を還元させるときの温度は、５０℃以上８０℃以下である、
    　請求項１～３のいずれか一項に記載の銀ナノ粒子分散液の製造方法。     The temperature at which the silver ammine complex is reduced is 50 ° C. or more and 80 ° C. or less.
    The method for producing a silver nanoparticle dispersion liquid according to any one of claims 1 to 3.
  5. 　銀ナノ粒子と、前記銀ナノ粒子の表面の少なくとも一部に吸着した、酸性基および（ポリ）アルキレンオキサイド基を有する高分子分散剤と、水と、アンモニアとを含む銀ナノ粒子分散液であって、
    　前記アンモニアの含有量は、前記銀ナノ粒子分散液の全質量に対して１質量ｐｐｍ以上１０００質量ｐｐｍ以下であり、
    　前記銀ナノ粒子の体積換算の平均粒径Ｄ５０が２５ｎｍ以上７０ｎｍ以下であり、かつ前記銀ナノ粒子の体積粒度分布におけるピークの半値幅が３０ｎｍ以上である、
    　銀ナノ粒子分散液。     A silver nanoparticle dispersion liquid comprising silver nanoparticles, a polymer dispersant having an acidic group and a (poly) alkylene oxide group adsorbed on at least a part of the surface of the silver nanoparticles, water, and ammonia. ,
    The content of the ammonia is 1 mass ppm or more and 1000 mass ppm or less with respect to the total mass of the silver nanoparticle dispersion liquid,
    The volume-equivalent average particle diameter D50 of the silver nanoparticles is 25 nm or more and 70 nm or less, and the half width of the peak in the volume particle size distribution of the silver nanoparticles is 30 nm or more.
    Silver nanoparticle dispersion.
  6. 　銀ナノ粒子と、前記銀ナノ粒子の表面の少なくとも一部に吸着した、酸性基および（ポリ）アルキレンオキサイド基を有する高分子分散剤と、水と、アンモニアとを含むインクジェットインクであって、
    　前記アンモニアの含有量は、前記インクジェットインクの全質量に対して１質量ｐｐｍ以上１０００質量ｐｐｍ以下であり、
    　前記銀ナノ粒子の体積換算の平均粒径Ｄ５０が２５ｎｍ以上７０ｎｍ以下であり、かつ前記銀ナノ粒子の体積粒度分布におけるピークの半値幅が３０ｎｍ以上である、
    　インクジェットインク。     An inkjet ink comprising silver nanoparticles, a polymer dispersant having an acidic group and a (poly) alkylene oxide group, adsorbed on at least a part of the surface of the silver nanoparticles, water, and ammonia,
    The content of the ammonia is 1 mass ppm or more and 1000 mass ppm or less with respect to the total mass of the inkjet ink,
    The volume-equivalent average particle diameter D50 of the silver nanoparticles is 25 nm or more and 70 nm or less, and the half width of the peak in the volume particle size distribution of the silver nanoparticles is 30 nm or more.
    Inkjet ink.
  7. 　水分散性樹脂をさらに含む、
    　請求項６に記載のインクジェットインク。     Further comprising a water dispersible resin,
    The inkjet ink according to claim 6.
  8. 　基材上に、請求項６または７に記載のインクジェットインクを付与して、金属光沢層を形成する工程を含む、
    　画像形成方法。     Applying the inkjet ink according to claim 6 or 7 on a substrate to form a metallic gloss layer,
    Image formation method.
PCT/JP2018/046985 2017-12-26 2018-12-20 Method for producing silver nanoparticle dispersion liquid, silver nanoparticle dispersion liquid, inkjet ink and image forming method using same WO2019131435A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2019561608A JPWO2019131435A1 (en) 2017-12-26 2018-12-20 Method for producing silver nanoparticle dispersion, silver nanoparticle dispersion, inkjet ink and image formation method using it

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2017-249803 2017-12-26
JP2017249803 2017-12-26

Publications (1)

Publication Number Publication Date
WO2019131435A1 true WO2019131435A1 (en) 2019-07-04

Family

ID=67063069

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2018/046985 WO2019131435A1 (en) 2017-12-26 2018-12-20 Method for producing silver nanoparticle dispersion liquid, silver nanoparticle dispersion liquid, inkjet ink and image forming method using same

Country Status (2)

Country Link
JP (1) JPWO2019131435A1 (en)
WO (1) WO2019131435A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021106955A1 (en) * 2019-11-29 2021-06-03 凸版印刷株式会社 Decorative sheet, decorative plate, and inkjet ink for decorative sheets
CN113770373A (en) * 2021-09-28 2021-12-10 长沙新材料产业研究院有限公司 Nano-silver reaction stock solution, preparation method and nano-silver
WO2022167377A1 (en) 2021-02-03 2022-08-11 Basf Se Compositions, comprising silver nanoplatelets
CN115651493A (en) * 2022-10-31 2023-01-31 厦门市金宝源实业有限公司 Antiviral coating composition for coronavirus HCov-229e and preparation process thereof

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1180647A (en) * 1997-07-17 1999-03-26 Nippon Paint Co Ltd Colloidal solution of noble metal or copper and production thereof with paint composition and resin molded material
JP2006328472A (en) * 2005-05-26 2006-12-07 Mitsui Chemicals Inc Production method of silver nanoparticle, silver nanoparticle and application thereof
JP2010229544A (en) * 2008-11-26 2010-10-14 Mitsuboshi Belting Ltd Metal colloid particle, its paste and method for production thereof
JP2013540888A (en) * 2010-08-03 2013-11-07 フラウンホーファー・ゲゼルシャフト・ツール・フェルデルング・デア・アンゲヴァンテン・フォルシュング・エー・ファウ Method for producing nanoparticles from precious metals and use of the produced nanoparticles
JP2017508888A (en) * 2014-08-12 2017-03-30 シュゾー スマート アドバンスト コーティング テクノロジーズ カンパニー リミテッド Method for preparing metal powder

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH1180647A (en) * 1997-07-17 1999-03-26 Nippon Paint Co Ltd Colloidal solution of noble metal or copper and production thereof with paint composition and resin molded material
JP2006328472A (en) * 2005-05-26 2006-12-07 Mitsui Chemicals Inc Production method of silver nanoparticle, silver nanoparticle and application thereof
JP2010229544A (en) * 2008-11-26 2010-10-14 Mitsuboshi Belting Ltd Metal colloid particle, its paste and method for production thereof
JP2013540888A (en) * 2010-08-03 2013-11-07 フラウンホーファー・ゲゼルシャフト・ツール・フェルデルング・デア・アンゲヴァンテン・フォルシュング・エー・ファウ Method for producing nanoparticles from precious metals and use of the produced nanoparticles
JP2017508888A (en) * 2014-08-12 2017-03-30 シュゾー スマート アドバンスト コーティング テクノロジーズ カンパニー リミテッド Method for preparing metal powder

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021106955A1 (en) * 2019-11-29 2021-06-03 凸版印刷株式会社 Decorative sheet, decorative plate, and inkjet ink for decorative sheets
WO2022167377A1 (en) 2021-02-03 2022-08-11 Basf Se Compositions, comprising silver nanoplatelets
CN113770373A (en) * 2021-09-28 2021-12-10 长沙新材料产业研究院有限公司 Nano-silver reaction stock solution, preparation method and nano-silver
CN115651493A (en) * 2022-10-31 2023-01-31 厦门市金宝源实业有限公司 Antiviral coating composition for coronavirus HCov-229e and preparation process thereof
CN115651493B (en) * 2022-10-31 2023-09-05 厦门市金宝源实业有限公司 Antiviral coating composition for coronavirus HCov-229e and preparation process thereof

Also Published As

Publication number Publication date
JPWO2019131435A1 (en) 2020-12-10

Similar Documents

Publication Publication Date Title
WO2019131435A1 (en) Method for producing silver nanoparticle dispersion liquid, silver nanoparticle dispersion liquid, inkjet ink and image forming method using same
JP5214103B2 (en) Metallic pigment, ink composition, and ink jet recording method
WO2006101054A1 (en) Metallic pigment, pigment dispersion liquid, metallic pigment ink composition, and ink jet recording method
TW201443171A (en) White ink
TWI553063B (en) Ink and printing process
JP2011140609A (en) Water-resistant aluminum pigment, water-resistant aluminum pigment dispersion, aqueous ink composition containing them, and method for producing water-resistant aluminum pigment dispersion
WO2019022239A1 (en) Image forming method, image formed article and inkjet ink
JP2011149028A (en) Ink composition, ink set, inkjet recording method, and recorded matter
JP2013064053A (en) Water-resistant aluminum pigment dispersion, method of producing the pigment dispersion, and aqueous ink composition
JP2010202815A (en) Manufacturing method for water resistant aluminum pigment dispersion, water resistant aluminum pigment and aqueous ink composition containing the same
JP2004099800A (en) Aqueous ink composition, process for producing it and method of forming image using aqueous ink composition
JP2005068252A (en) Method for producing ink composition and the resultant ink composition
JP6880686B2 (en) Ink and printed matter
WO2019009047A1 (en) Ink jet recording method
JP2013185028A (en) Water resistance aluminum pigment dispersion, method of manufacturing the same, and aqueous ink composition
JP2009108199A (en) Aqueous dispersion, recording liquid using it, image-forming method and image-forming apparatus, as well as manufacturing method of aqueous dispersion, and ink obtained thereby for use in inkjet
JP6334917B2 (en) Inkjet recording method
JP2000327968A (en) Colored microcapsule-dispersed aqueous jet ink
JP2005120225A (en) Ink composition
JP5154018B2 (en) Method for producing aqueous pigment ink composition and aqueous pigment ink composition
JPH10237368A (en) Production of ink jet ink
JP6232265B2 (en) Method for producing aqueous dispersion for ink jet recording
EP3733793B1 (en) Production method for pigment aqueous dispersion
JP2019026652A (en) Inkjet ink, image forming method, and image formed object
WO2018181080A1 (en) Glitter ink-jet ink and method for forming image using same

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 18895046

Country of ref document: EP

Kind code of ref document: A1

ENP Entry into the national phase

Ref document number: 2019561608

Country of ref document: JP

Kind code of ref document: A

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 18895046

Country of ref document: EP

Kind code of ref document: A1