JPWO2018181080A1 - Glitter inkjet ink and image forming method using the same - Google Patents

Abstract

The brilliant inkjet ink contains metal nanoparticles, a dispersant adsorbed on the surface of the metal nanoparticles, emulsion resin particles, and a solvent, and the metal nanoparticles have an average particle diameter of D1, Assuming that the average particle diameter is D2, 0.05 <D2 / D1 <1 is satisfied.

Description

  The present invention relates to a brilliant inkjet ink and an image forming method using the same.

  Conventionally, in order to form an image that emits a metallic glossy color in a label, a package, a printed matter such as an advertisement printed matter or a photograph, an ink containing a metallic pigment-based glitter pigment such as an aluminum pigment or a pearl pigment may be used. is there. The formation of these images is performed by analog printing such as offset printing, gravure printing, and screen printing.

  In recent years, with the development of digital printing, a method of forming an image emitting a metallic glossy color by an ink jet method has been studied. As an ink used for forming such an image, Patent Document 1 discloses an ink composition for inkjet printing containing silver nanoparticles, a specific organic compound and a polymer dispersant that coats the silver nanoparticles, and a solvent. Is disclosed. Patent Document 2 discloses a glitter pigment ink containing silver nanoparticles (brilliant pigment), a urethane resin, and water.

JP 2009-227736 A JP-A-2013-193721

  However, since the ink of Patent Document 1 does not contain a binder resin, it is difficult to obtain an image having sufficient adhesion to a substrate, especially a non-absorbing substrate. On the other hand, although the ink of Patent Document 2 contains a urethane resin (binder resin), sufficient metallic luster was not obtained.

  The present invention has been made in view of such circumstances, and has an object to provide an inkjet ink having sufficient adhesion to a substrate and capable of forming an image having a sufficient metallic luster. .

[1] The composition includes metal nanoparticles, a dispersant adsorbed on the surface of the metal nanoparticles, emulsion resin particles, and a solvent, wherein the average particle size of the metal nanoparticles is D1, and the average particle size of the emulsion resin particles is Is a glitter inkjet ink that satisfies 0.05 <D2 / D1 <1, where D2 is D2.
[2] Assuming that the content mass of the metal nanoparticles is M1 (%) and the content mass of the emulsion resin particles is M2 (%), 1.3 ≦ M1 / M2 ≦ 35 is further satisfied, [1]. Brilliant inkjet ink.
[3] According to [1] or [2], when the content mass of the metal nanoparticles is M1 (%) and the content mass of the emulsion resin particles is M2 (%), 1 ≦ M1 + M2 ≦ 35 is further satisfied. Brilliant inkjet ink.
[4] The glitter inkjet ink according to any one of [1] to [3], wherein the dispersant is a polymer dispersant.
[5] The glitter according to [4], wherein the dispersant is a comb block copolymer having a main chain containing a structural unit derived from a (meth) acrylic ester and a side chain containing a polyoxyalkyl group. Inkjet ink.
[6] The glitter inkjet ink according to any one of [1] to [5], wherein the emulsion resin particles are urethane resin particles or (meth) acrylic resin particles.
[7] The glitter inkjet ink according to any one of [1] to [6], wherein the solvent includes an organic solvent having a boiling point of 150 ° C. or higher.
[8] The glitter inkjet ink according to any one of [1] to [7], wherein the metal nanoparticles are silver nanoparticles.
[9] After applying the glitter inkjet ink according to any of [1] to [8] on a substrate, a step of volatilizing the solvent, and heating the glitter inkjet ink having the solvent volatilized. Forming a glossy metallic layer.

  The present invention can provide an inkjet ink having sufficient adhesion to a substrate and capable of forming an image having a sufficient metallic luster.

  As described above, with the ink of Patent Document 2, a metallic luster layer having a sufficient metallic luster could not be obtained. The reason is presumed as follows. In the ink of Patent Document 2, the average particle size of the emulsion resin particles is relatively larger than the average particle size of the metal nanoparticles. Therefore, in the obtained metallic gloss layer, a thick resin layer is likely to be formed around the metal nanoparticles, which causes light absorption and a low content ratio of the metallic nanoparticles. Is considered to be easily reduced, that is, the metallic luster is likely to be impaired.

  In Patent Document 2, in order not to impair the metallic luster, it is conceivable to reduce the resin component in the metallic luster layer, that is, to reduce the content of emulsion resin particles in the ink. However, by merely reducing the content of the emulsion resin particles having a relatively large average particle size, the gap between the emulsion resin particles existing around the metal nanoparticles in the ink tends to be large, and the resulting metallic gloss layer , Many voids are likely to be formed around the metal nanoparticles. As a result, the refractive index of the obtained metallic gloss layer tends to increase, and the extinction coefficient tends to decrease. Further, scattered light is also likely to increase. As a result, it is considered that the reflectance of the metallic luster layer tends to decrease (that is, it is difficult to obtain metallic luster).

  On the other hand, the present inventors have made the average particle diameter D2 of the emulsion resin particles relatively smaller than the average particle diameter D1 of the silver metal nanoparticles; specifically, the average particle diameter of the metal nanoparticles. By setting the ratio D2 / D1 of D1 and the average particle diameter D2 of the emulsion resin particles to less than 1, it has high reflectance (that is, has sufficient metallic luster) and good adhesion to the substrate. Has been found to be obtained.

  That is, when D2 / D1 is less than 1, the average particle diameter D2 of the emulsion resin particles is relatively small with respect to the average particle diameter D1 of the metal nanoparticles, so that the content of the emulsion resin particles in the ink is reduced. Even in this case, the surface of the metal nanoparticles can be covered relatively densely (without any gap) in the ink. Thereby, the space around the metal nanoparticles can be reduced in the obtained metallic gloss layer, so that an increase in the refractive index and a decrease in the extinction coefficient of the metallic gloss layer can be reduced. Further, scattered light can be reduced. As a result, the reflectance of the metallic luster layer can be increased, and the metallic luster can be easily obtained. Further, since the space around the metal nanoparticles in the metallic gloss layer can be reduced, the adhesion to the substrate and the film strength can be increased. On the other hand, when D2 / D1 is more than 0.05, the emulsion resin particles have an appropriate size, so that the emulsion resin particles can easily be sufficiently bonded to each other, and the adhesion to the substrate and the high film strength can be improved. Easy to obtain. The present invention has been made based on such findings.

1. Glitter inkjet ink The glitter inkjet ink of the present invention contains metal nanoparticles, a dispersant adsorbed on the surface of the metal nanoparticles, emulsion resin particles, and a solvent.

1-1. Metal nanoparticles Metal nanoparticles are nano-sized metal particles. Examples of the main components of the metal nanoparticles include silver, gold, copper, aluminum, platinum, nickel, chromium, tin, zinc, indium, titanium, bismuth, and the like. These metals may be alloys, mixtures or oxides containing the aforementioned metals. The main component means, for example, 50 atomic% or more of the total of all atoms constituting the metal nanoparticles. Among these metals, gold, silver and aluminum are more preferred from the viewpoint of high gloss and manufacturability, and silver is even more preferred from the viewpoint of stability and color. That is, the metal nanoparticles are preferably silver nanoparticles containing silver as a main component.

  Examples of alloys containing silver include silver magnesium, silver copper, silver palladium, silver palladium copper, silver indium, silver bismuth, and the like. Further, the metal nanoparticles may contain trace amounts of other components that are inevitably contained, or may contain a silver oxide. Commercially available metal nanoparticles may be used.

  The metal nanoparticles may be further surface-treated with citric acid or the like to enhance dispersion stability. Further, the metal nanoparticles contained in the ink may be of one type, or two or more types having different types or compositions may be used in combination.

  The average particle diameter D1 of the metal nanoparticles is not particularly limited as long as D2 / D1 satisfies the range described later, but the dispersion stability in the ink for forming the metallic gloss layer and the reflectance of the metallic gloss layer From the viewpoint of obtaining sufficient smoothness to increase the surface roughness, the thickness is preferably 3 nm or more and 200 nm or less, and more preferably 15 nm or more and 150 nm or less.

The average particle diameter D1 of the metal nanoparticles can be measured by SEM observation. Specifically, it can be measured by the following procedure.
1) SEM observation is performed in a state in which the solvent component is volatilized by applying vacuum without applying heat after applying the ink on the glass substrate, or cryo-SEM observation is performed in a state in which the ink containing the solvent is frozen. In cryo-SEM observation, a cross section of the frozen ink is observed. Then, the particle diameters of arbitrary 300 metal nanoparticles are measured.
2) A volume-based particle size distribution is determined based on the obtained measurement data, and its D50 (median diameter) is defined as an average particle diameter D1 (volume average particle diameter) of the metal nanoparticles.

  In the present invention, the average particle diameter D1 of the metal nanoparticles means the average particle diameter of the metal nanoparticles themselves that do not contain a dispersant (adsorbed on the surface of the metal nanoparticles).

  The average particle diameter D1 of the metal nanoparticles can be adjusted by, for example, the dropping time of the reducing agent during the preparation of the metal nanoparticle dispersion described below.

1-2. Dispersant The dispersant is adsorbed on the surface of the metal nanoparticles. Thereby, the metal nanoparticles are easily dispersed in the solvent, and the dispersant and the emulsion resin particles interact with each other, thereby facilitating uniform mixing of the metal nanoparticles and the emulsion resin particles via the dispersant. be able to. The dispersant is preferably a polymer dispersant from the viewpoint of excellent affinity with the emulsion resin.

  The polymer dispersant is a resin having an adsorbing group for adsorbing on the surface of the metal nanoparticles. Examples of the adsorptive group include a carboxyl group and a thiol group. That is, in the present invention, whether or not the dispersant is adsorbed on the surface of the metal nanoparticle is determined by whether or not the dispersant has an adsorbing group, and the metal nanoparticle has little aggregation and is well dispersed. be able to.

  The resin constituting the polymer dispersant is preferably a homo- or copolymer of a hydrophilic monomer. The copolymer of a hydrophilic monomer may be a copolymer of a hydrophilic monomer and a hydrophobic monomer.

  Examples of the hydrophilic monomer include a monomer containing a carboxyl group or an acid anhydride group ((meth) acrylic acid such as acrylic acid and methacrylic acid, unsaturated polycarboxylic acid such as maleic acid, maleic anhydride, and the like), and alkylene. Oxide-modified (meth) acrylate monomers (e.g., ethylene oxide-modified (meth) acrylate alkyl esters) and the like are included.

  Examples of the hydrophobic monomer include (meth) acrylate-based monomers such as methyl (meth) acrylate and ethyl (meth) acrylate; styrene-based monomers such as styrene, α-methylstyrene, and vinyltoluene; ethylene, propylene And α-olefin monomers such as 1-butene; vinyl carboxylate monomers such as vinyl acetate and vinyl butyrate.

  When the polymer dispersant is a copolymer, it may be any of a random copolymer, an alternating copolymer, a block copolymer, or a comb-type copolymer (or a comb-type graft copolymer). Above all, the polymer dispersant is preferably a comb-type block copolymer in terms of good affinity with the emulsion resin particles described below.

  The comb block copolymer refers to a copolymer including a linear polymer forming a main chain and another type of polymer graft-polymerized to a structural unit derived from a monomer forming the main chain. Preferred examples of the comb-type block copolymer include a main chain containing a structural unit derived from a (meth) acrylic acid ester and a side chain having a polyoxyalkyl group (a long-chain polyoxyalkyl group such as an EO-PO copolymer group). Group). In the comb-type block copolymer, the graft-polymerized side chains cause steric hindrance, so that aggregation of the metal nanoparticles can be more highly suppressed. As a result, the dispersibility of the metal nanoparticles is increased, so that the ejection failure due to the aggregated metal nanoparticles can be more easily suppressed.

  The dispersant preferably has an acid value of 1 mgKOH / g to 80 mgKOH / g. If the acid value is 1 mgKOH / g or more, the dispersant has a tendency to be hydrophilic, so that the dispersibility in an ink (particularly, a water-based ink) is easily increased. When the acid value is 80 mgKOH / g or less, it is easy to suppress a remarkable decrease in durability of the metallic gloss layer due to swelling of the dispersant in the metallic gloss layer. The acid value of the dispersant is more preferably from 1 mgKOH / g to 50 mgKOH / g, further preferably from 2 mgKOH / g to 40 mgKOH / g, and more preferably from 3 mgKOH / g to 30 mgKOH / g. It is particularly preferably from 5 mgKOH / g to 20 mgKOH / g.

The acid value can be measured according to JIS K0070. Specifically, the acid value of the dispersant is determined by Fourier transform infrared spectroscopy (FT-IR) to identify the type of the dispersant (eg, the product name of the polymer dispersant used for image formation). The acid value of the same dispersant may be measured according to JIS K0070. Further, the type of the dispersant may be specified by ¹ HNMR or gas chromatography-mass spectrometry (GC / MS).

  The molecular weight of the dispersant is preferably from 1,000 to 100,000, and more preferably from 2,000 to 50,000.

  Examples of commercially available dispersants include Solsperse 24000, Solsperse 24000GR, Solsperse 32000, Solsperse 44000, Solsperse 46000 (manufactured by Lubrizol Corporation); DISPERBYK-187, DISPERBYK-194N, DISPERBYK-190, DISPERBYK-191, DISPERBYK-199, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2015, DISPERBYK-2050, DISPERBYK-2K, and D-PERBYK-2150K , "DISPERBYK" Dispalon ED-152, ED-211, ED-212, ED-213, ED-214, ED-251 (Kusumoto Kasei Co., Ltd.), PLAAD series (Kusumoto Kasei Co., Ltd.); EFKA 6220 (BASF And “EFKA” are registered trademarks of the same company) and Floren TG-750W (manufactured by Kyoeisha Chemical Co., Ltd.).

  The dispersant adsorbed on the surface of the metal nanoparticles can be obtained, for example, by reducing silver ions (which become metal nanoparticles) in an aqueous solvent containing the dispersant.

1-3. Emulsion resin particles The emulsion resin particles can function as a binder resin, and can interact with a dispersant adsorbed on the surface of the metal nanoparticles to enhance the adhesion of the metal nanoparticles to the base material. Such an emulsion resin particle is preferably a resin having a high affinity for a dispersant, and examples thereof include (meth) acrylic resin, urethane resin, polyolefin resin, polyester resin, and polyvinyl chloride resin (for example, Polyvinyl chloride polymer, vinyl chloride-vinylidene chloride copolymer), epoxy resin, polysiloxane resin, fluororesin, styrene copolymer (for example, styrene-butadiene copolymer, styrene- (meth) acrylate copolymer) Etc.), vinyl acetate copolymers (eg, ethylene-vinyl acetate copolymer, etc.) and the like. Among them, (meth) acrylic resin, urethane resin, polyolefin resin, polyvinyl chloride resin, epoxy resin, polysiloxane resin, fluororesin, styrene copolymer, vinyl acetate Copolymers are preferred, and urethane resins and (meth) acrylic resins are more preferred.

  The urethane resin is obtained, for example, by reacting a sulfonate-containing polyol (a1) with an organic polyisocyanate (a2) in an atmosphere containing an excess of isocyanate groups; and further reacting by adding a low molecular polyol (a3-1) and an aqueous solvent. After that, an emulsion of an isocyanate group-terminated prepolymer is obtained; a low molecular weight polyamine (a3-2) may be added for further reaction.

  Examples of the sulfonate-containing polyol (a1) include a sulfonate-containing polyester polyol, a sulfonate-containing polyether polyol, a sulfonate-containing polycarbonate polyol, and the like.

  Examples of the organic polyisocyanate (a2) include aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate and 1,4-tetramethylene diisocyanate, o-xylene diisocyanate, Examples include araliphatic diisocyanates such as m-xylene diisocyanate and p-xylene diisocyanate, and alicyclic polyisocyanates such as isophorone diisocyanate (hereinafter abbreviated as IPDI).

  The low molecular polyol (a3-1) and the low molecular polyamine (a3-2) can function as a chain extender. Examples of the low molecular polyol (a3-1) include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol and the like; Examples include ethylenediamine, propylenediamine, diethylenetriamine, and the like.

  The aqueous solvent may be a mixed solvent of water and an organic solvent such as N-methylpyrrolidone (NMP) or propylene glycol dimethyl ether (DMPDG).

  The (meth) acrylic resin may be obtained by polymerizing the monomer (b1) using an aqueous initiator (b2) in an aqueous solution containing the polymer emulsifier (b3).

  Examples of the monomer (b1) include alkyl (meth) acrylates such as methyl (meth) acrylate and ethyl (meth) acrylate; alkoxyalkyl (meth) acrylates such as methoxybutyl (meth) acrylate; styrene, α Aromatic vinyl compounds such as methylstyrene; hydrolyzable silane group-containing vinyl compounds such as vinyltriethoxysilane; and (meth) acrylamide compounds such as N-methylolacrylamide.

  Examples of the water-soluble initiator (b2) include sodium persulfate, potassium persulfate, ammonium persulfate and the like.

  The polymer emulsifier (b3) may be a water-soluble resin, and examples thereof include a carboxyl group-containing polymer. The carboxyl group-containing polymer is a homopolymer or a copolymer of a carboxy group-containing unsaturated monomer. Examples of carboxy-containing unsaturated monomers include (meth) acrylic acid; examples of monomers copolymerizable therewith include those similar to monomer (b).

  The ratio D2 / D1 of the average particle diameter D1 of the metal nanoparticles to the average particle diameter D2 of the emulsion resin particles preferably satisfies 0.05 <D2 / D1 <1. When D2 / D1 is less than 1, even if the content of the emulsion resin particles is small, the surface of the metal nanoparticles can be covered with the emulsion resin particles relatively densely (with no gap) in the ink. Even in the metallic luster layer, voids around the metallic nanoparticles can be reduced. Thereby, the increase in the refractive index and the decrease in the extinction coefficient of the metallic gloss layer can be reduced, and the scattered light can also be reduced, so that the reflectance (glossiness) can be increased. In addition, since the space around the metal nanoparticles in the metallic gloss layer can be reduced, the adhesion to the substrate and the film strength can be increased. On the other hand, when D2 / D1 exceeds 0.05, the emulsion resin particles are likely to be sufficiently bonded to each other, so that high adhesion to the substrate and high film strength are easily obtained. The ratio D2 / D1 more preferably satisfies 0.1 <D2 / D1 <1, and even more preferably satisfies 0.2 <D2 / D1 <0.95.

  The average particle diameter D2 of the emulsion resin particles can be measured in the same manner as the method for measuring the average particle diameter D1 of the metal nanoparticles.

  When the emulsion resin particles are urethane resin particles, the average particle diameter D2 is determined by the amount of the chain extender (a3) added and the reaction product of the sulfonate-containing polyol (a1) and the organic polyisocyanate (a2). The reaction time can be adjusted by the reaction time with the chain extender (a3), the composition of the aqueous solvent (such as the DMPDG content ratio), and the like. When the emulsion resin particles are (meth) acrylic resin particles, the average particle diameter D2 may be, for example, the composition of the monomer (b1) (such as the styrene content ratio), the blending amount of the water-soluble initiator (b2), the polymer emulsifier ( It can be adjusted by the composition of b3) and the like.

  By setting D2 / D1 to a certain value or less, as described above, even if the content M2 (%) of the emulsion resin particles is reduced, the periphery of the metal nanoparticles is relatively densely covered with the emulsion resin particles in the ink. Can be covered (relatively without gaps). That is, since the content mass M2 (%) of the emulsion resin particles in the ink can be reduced, the content ratio of the metal nanoparticles in the obtained metallic gloss layer can be increased, and thereby the reflectance can be increased. .

  Specifically, the ratio M1 / M2 between the content M1 (%) of the metal nanoparticles in the ink and the content M2 (%) of the emulsion resin particles in the ink is 1.3 ≦ M1 / M2 ≦ 35. Preferably, it is satisfied. When M1 / M2 is 1.3 or more, the content ratio of the resin that easily absorbs light in the obtained metallic gloss layer can be appropriately reduced, and the content ratio of the metal nanoparticles can be appropriately increased. It is easier to increase reflectivity. When M1 / M2 is 35 or less, the content ratio of the resin in the obtained metallic gloss layer is appropriately high, so that the adhesion of the metallic gloss layer to the substrate and the film strength can be more easily increased. The ratio M1 / M2 more preferably satisfies 1.5 ≦ M1 / M2 ≦ 35, and even more preferably satisfies 2 ≦ M1 / M2 ≦ 30.

  When the above-described content mass ratio M1 / M2 is converted into a volume based on the specific gravity, the ratio V1 (%) between the content volume V1 (%) of the metal nanoparticles in the ink and the content volume V2 (%) of the emulsion resin particles in the ink. / V2 preferably satisfies 0.25 ≦ V1 / V2 ≦ 6. When V1 / V2 is 0.25 or more, the content ratio of the resin that easily absorbs light in the obtained metallic gloss layer can be appropriately reduced, and the content ratio of the metal nanoparticles can be appropriately increased. It is easier to increase reflectivity. When V1 / V2 is 6 or less, the content ratio of the resin in the obtained metallic gloss layer is appropriately high, so that the adhesion of the metallic gloss layer to the substrate and the film strength can be more easily increased. V1 / V2 more preferably satisfies 0.4 ≦ V1 / V2 ≦ 5, and further preferably satisfies 0.6 ≦ V1 / V2 ≦ 4.

  The total amount (M1 + M2) (%) of the content M1 (%) of the metal nanoparticles in the ink and the content M2 (%) of the emulsion resin particles in the ink preferably satisfies 1 ≦ M1 + M2 ≦ 35. When the total amount (M1 + M2) is 1 or more, the amount of solid content contained in the ink is appropriately large, so that it is easy to form a metallic gloss layer having a desired thickness, and it is easy to obtain a sufficient reflectance. If the total amount (M1 + M2) is 35 or less, the amount of solid content contained in the ink is not too large, so that the viscosity does not increase too much and the ejection property from the inkjet head is not easily impaired. The total (M1 + M2) more preferably satisfies 2 ≦ M1 + M2 ≦ 35, and still more preferably satisfies 3 ≦ M1 + M2 ≦ 30.

1-4. Solvent The solvent contains at least water, but may further contain an organic solvent in an arbitrary ratio.

  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, and 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 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-pentane Polyhydric alcohols such as all, 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, and butanol; 2,2'-thiodiethanol; sulfolane; amides such as N, N-dimethylformamide; 2-pyrrolidone, γ-butyrolactone, propylene carbonate, and carbonic acid Heterocycles such as ethylene; acetonitrile and the like are included. These may be used alone or in combination of two or more.

  Above all, the solvent preferably contains an organic solvent having a boiling point of 150 ° C. or higher from the viewpoint of preventing drying of the ink in the vicinity of the ink jet head and improving the dischargeability from the head. Preferred examples of such an organic solvent include glycerin, propylene glycol, triethylene glycol monomethyl ether and the like.

1-5. Other Components The glitter inkjet ink may further contain other components other than the above components as long as the effects of the present invention are not impaired. Examples of other components include a known surfactant (surface conditioner).

  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 Nonionic surfactants such as ethylene-polyoxypropylene block copolymers, cationic surfactants such as alkylamine salts and quaternary ammonium salts, and silicone-based and fluorine-based surfactants are included.

  Examples of commercially available silicone surfactants include KF-351A, KF-352A, KF-642 and X-22-4272, and BYK-307, BYK-345, BYK-347, and BYK manufactured by Shin-Etsu Chemical Co., Ltd. -348, manufactured by Big Chemie ("BYK" is a registered trademark of the company), and 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 based on the total mass of the ink.

1-6. Physical Properties The viscosity of the brilliant 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 improving the ejection stability from the nozzle in image formation by an inkjet method. More preferably, it is 1 cP or more and 15 cP or less.

2. Image forming method using brilliant inkjet ink The image forming method of the present invention includes: 1) a step of applying the brilliant inkjet ink of the present invention on a substrate and then volatilizing a solvent (ink applying / drying step); 2) heating the obtained brilliant inkjet ink to form a metallic gloss layer (heating step).

2-1. Ink Applying / Drying Step After applying the glitter inkjet ink on the substrate, the solvent is volatilized.

  The application of the ink can be performed by an inkjet method. Specifically, the ink is ejected from the nozzles of the inkjet head to land on the surface of the base material.

  The method of volatilizing the solvent is not particularly limited, and may be a vacuum degassing method, a blast drying method, a heating drying method, or the like. The drying temperature is preferably lower than the glass transition temperature of the emulsion resin particles. For example, the drying temperature is preferably normal temperature or higher and lower than 100 ° C, and more preferably normal temperature or higher and lower than 80 ° C.

2-2. Heating step The ink applied on the substrate is heated to form a metallic gloss layer. Specifically, the emulsion resin particles in the ink applied on the base material are thermally fused to form a metallic gloss layer.

  The heating temperature of the ink may be any temperature at which the emulsion resin particles can be thermally fused, and is preferably equal to or higher than the glass transition temperature of the emulsion resin particles. Specifically, the heating temperature is preferably, for example, 40 ° C. or higher, and the upper limit temperature needs to be lower than the heat resistant temperature of the base material and the emulsion resin particles. Further, by further adding a film-forming aid to the ink, it becomes possible to form a film at a Tg or less of the emulsion resin particles.

  The solvent volatilization (drying) step 1) and the heating step 2) may be performed in separate steps or may be performed simultaneously. In the case where the solvent (1) volatilization (drying) and the heating (2) are performed simultaneously, the drying temperature and the heating temperature are preferably equal to or higher than the glass transition temperature of the emulsion resin particles.

2-3. Formation of Other Layers The image forming method of the present invention may further include, if necessary, a step of forming a primer layer on the surface of the substrate before the metallic gloss layer is formed. Further, the image forming method of the present invention may further include a step of forming a coloring material layer or a protective layer on the surface layer side of the obtained metallic gloss layer.

2-3-1. Step of Forming Primer Layer The primer layer can be formed by applying a resin composition containing a binder resin to the surface of the base material before the metallic luster layer is formed. After the application of the resin composition, the resin composition may be dried by heating or the like to form a binder resin. The drying temperature at this time may be, for example, less than 100 ° C.

  The binder resin may be any resin that has been conventionally used to increase the adhesion of a pigment containing metal nanoparticles or the like to a substrate. Examples of such binder resins include (meth) acrylic resin, epoxy resin, polysiloxane resin, maleic acid resin, polyolefin resin, vinyl resin, polyamide resin, polyvinylpyrrolidone, polyhydroxystyrene, polyvinyl alcohol, nitrocellulose, acetic acid Examples include cellulose, ethyl cellulose, ethylene-vinyl acetate copolymer, urethane resin, polyester resin, alkyd resin and the like. These resins may be used alone or in combination of two or more.

2-3-2. Step of Forming Color Material Layer or Protective Layer The color material layer can be formed by applying a resin composition containing a known pigment or dye and a binder resin for fixing the same to the metallic luster layer. . The protective layer can be formed by applying a resin composition containing a binder resin on the metallic luster layer. After applying these resin compositions, the resin compositions may be dried by heating or the like to form a binder resin. The drying temperature at this time may be, for example, less than 100 ° C.

  The resin contained in each resin composition can be selected from the same resins as the binder resin contained in the primer layer.

  The method of applying each resin composition is not particularly limited, but an inkjet method and an electrophotographic method are preferable from the viewpoint of easily forming a fine image.

  Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited thereto.

1. Materials 1-1-1. Preparation of silver nanoparticle dispersion <Silver nanoparticle dispersion 1>
Into a 1 L separable flask having a plate-shaped stirring blade and a baffle plate, 7.2 g of DISPERBYK-190 (manufactured by BYK-Chemie, acid value 10 mgKOH / g) as a dispersant, and 252 g of ion-exchanged water were charged. Stirring was performed to dissolve DISPERBYK-190. Subsequently, 62 g of silver nitrate (manufactured by Toyo Chemical Industry Co., Ltd.) dissolved in 252 g of ion-exchanged water was charged into the separable flask with stirring. Thereafter, the separable flask was placed in a water bath and heated and stirred until the temperature of the solution was stabilized at 70 ° C. Thereafter, using a syringe pump, 157 g of dimethylaminoethanol (manufactured by Wako Pure Chemical Industries, Ltd.) as a reducing agent was dropped into the separable flask over 48 minutes, and stirring was continued for 1 hour while maintaining the temperature at 70 ° C. A reaction solution containing the nanoparticles was obtained.

The obtained reaction solution was put in a stainless steel cup, and 2 L of ion-exchanged water was further added. Then, the pump was operated to perform ultrafiltration. After the solution in the stainless steel cup was reduced, ion-exchanged water was added again, and the purification was repeated until the conductivity of the filtrate became 100 μS / cm. Thereafter, the filtrate was concentrated to obtain a silver nanoparticle dispersion liquid 1 having a solid content of 30% by weight.
The ultrafiltration apparatus used was an ultrafiltration module AHP1010 (manufactured by Asahi Kasei Corporation, molecular weight cut off: 50,000, number of membranes used: 400), and a tube pump (manufactured by Masterflex) connected by a Tygon tube. . When the average particle diameter D1 of the silver nanoparticles in the obtained silver nanoparticle dispersion liquid 1 was measured, it was 55 nm.

<Silver nanoparticle dispersion liquid 2>
Silver nanoparticle dispersion 2 was obtained in the same manner as in preparation of silver nanoparticle dispersion 1, except that the amount of silver nitrate added was changed to 65 g, the dispersant was changed to 6.8 g, and the dropping time of dimethylaminoethanol was changed to 50 minutes. . When the average particle diameter D1 of the silver nanoparticles in the obtained silver nanoparticle dispersion liquid 2 was measured, it was 105 nm.

<Silver nanoparticle dispersion 3>
Silver nanoparticle dispersion 3 was obtained in the same manner as in preparation of silver nanoparticle dispersion 1, except that the amount of silver nitrate added was changed to 58 g, the dispersant was changed to 7.5 g, and the dropping time of dimethylaminoethanol was changed to 45 minutes. . When the average particle diameter D1 of the silver nanoparticles in the obtained silver nanoparticle dispersion liquid 3 was measured, it was 35 nm.

<Silver nanoparticle dispersion 4>
Silver nanoparticle dispersion 4 was obtained in the same manner as in preparation of silver nanoparticle dispersion 1, except that the amount of silver nitrate added was changed to 55 g, the dispersant was changed to 8.0 g, and the dropping time of dimethylaminoethanol was changed to 45 minutes. . When the average particle diameter D1 of the silver nanoparticles in the obtained silver nanoparticle dispersion liquid 4 was measured, it was 20 nm.

<Silver nanoparticle dispersion 5>
Silver nanoparticle dispersion liquid 5 was obtained in the same manner as in preparation of silver nanoparticle dispersion liquid 1, except that the amount of silver nitrate added was changed to 65 g, the dispersant was changed to 6.5 g, and the dropping time of dimethylaminoethanol was changed to 50 minutes. . When the average particle diameter D1 of the silver nanoparticles in the obtained silver nanoparticle dispersion liquid 5 was measured, it was 150 nm.

<Silver nanoparticle dispersion 6>
Silver nanoparticle dispersion 6 was obtained in the same manner as in preparation of silver nanoparticle dispersion 1, except that the amount of silver nitrate added was changed to 69 g, the dispersant was changed to 6.4 g, and the dropping time of dimethylaminoethanol was changed to 55 minutes. . When the average particle diameter D1 of the silver nanoparticles in the obtained silver nanoparticle dispersion liquid 6 was measured, it was 200 nm.

1-1-2. Preparation of gold nanoparticle dispersion <gold nanoparticle dispersion 1>
3.7 g of DISPERBYK-191 (manufactured by BYK-Chemie, acid value: 30 mgKOH / g) and 168 g of ethanol as a dispersant were put into a 1 L separable flask having a plate-like stirring blade and a baffle plate, and 50 ° C. To dissolve DISPERBYK-191. Subsequently, 21 g of chloroauric acid dissolved in 168 g of ethanol was charged into the separable flask while stirring. Thereafter, the separable flask was placed in a water bath and heated and stirred until the temperature of the solution was stabilized at 50 ° C. Thereafter, 19.5 g of dimethylaminoethanol (manufactured by Wako Pure Chemical Industries, Ltd.) as a reducing agent was added, and stirring was continued for 2 hours while maintaining the temperature at 50 ° C. to obtain a reaction solution containing gold nanoparticles.

The obtained reaction solution was placed in a stainless steel cup, and 2 L of ethanol was further added. Then, the pump was operated to perform ultrafiltration. After the solution in the stainless steel cup was reduced, ion-exchanged water was added, and purification was repeated until the conductivity of the filtrate became 30 μS / cm. Thereafter, the filtrate was concentrated to obtain a gold nanoparticle dispersion liquid 1 having a solid content of 30% by weight.
The ultrafiltration apparatus used was an ultrafiltration module AHP1010 (manufactured by Asahi Kasei Corporation, molecular weight cut off: 50,000, number of membranes used: 400), and a tube pump (manufactured by Masterflex) connected by a Tygon tube. . When the average particle diameter D1 of the gold nanoparticles in the obtained gold nanoparticle dispersion liquid 1 was measured, it was 30 nm.

1-2. Preparation of emulsion resin particle dispersion <Emulsion resin particle dispersion 1>
19 g of sodium sulfonate-containing polyester polyol as the sulfonate-containing polyol (a1) and an organic polyisocyanate (a2) were placed in a 200 ml four-necked flask equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen gas inlet pipe. And 8 g of isophorone diisocyanate was reacted at 80 ° C. for 2 hours. Thereafter, 0.8 g of 1,4-butanediol as a low-molecular polyol (a3-1) and 5 g of propylene glycol dimethyl ether (DMPDG) as an aqueous solvent were added thereto, and reacted at 80 ° C. for 2 hours. Thereafter, 60 g of water as an aqueous solvent and 5 g of propylene glycol dimethyl ether were added and emulsified, and an aqueous amine solution obtained by dissolving 0.5 g of ethylenediamine as a low-molecular-weight polyamine (a3-2) in 15 g of water was reacted at 50 ° C. for 3 hours. The obtained emulsion was diluted with water so as to have a solid content concentration of 20% to obtain an emulsion resin particle dispersion 1 (urethane emulsion solution). When the average particle diameter D2 of the emulsion resin particles in the obtained emulsion resin particle dispersion liquid 1 was measured, it was 40 nm.

<Emulsion resin particle dispersion 2>
19 g of sodium sulfonate-containing polyester polyol and 8 g of isophorone diisocyanate were charged into a 200 ml four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, and reacted at 80 ° C. for 2 hours. Thereafter, 0.9 g of 1,4-butanediol and 7 g of propylene glycol dimethyl ether were added and reacted at 80 ° C. for 2 hours. Thereafter, 60 g of water and 7 g of propylene glycol dimethyl ether were added to emulsify, and an aqueous amine solution obtained by dissolving 0.5 g of ethylenediamine in 15 g of water was reacted at 50 ° C. for 4 hours, and the obtained emulsion was solidified at a solid concentration of 20%. To obtain an emulsion resin particle dispersion liquid 2 (urethane emulsion solution). When the average particle diameter D2 of the emulsion resin particles in the obtained emulsion resin particle dispersion liquid 2 was measured, it was 80 nm.

<Emulsion resin particle dispersion 3>
19 g of sodium sulfonate-containing polyester polyol and 8 g of isophorone diisocyanate were charged into a 200 ml four-necked flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen gas inlet tube, and reacted at 80 ° C. for 2 hours. Thereafter, 0.9 g of 1,4-butanediol and 5 g of propylene glycol dimethyl ether were added and reacted at 80 ° C. for 2 hours. Thereafter, 60 g of water and 5 g of propylene glycol dimethyl ether were added to emulsify, and an aqueous amine solution obtained by dissolving 0.5 g of ethylenediamine in 15 g of water was reacted at 50 ° C. for 4 hours, and the obtained emulsion was solidified at a solid concentration of 20%. To obtain an emulsion resin particle dispersion 3 (urethane emulsion solution). When the average particle diameter D2 of the emulsion resin particles in the obtained emulsion resin particle dispersion liquid 3 was measured, it was 20 nm.

<Emulsion resin particle dispersion 4>
In a four-necked flask equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen gas introduction pipe, 140 g of isopropyl alcohol as a solvent was charged, heated to 85 ° C., and then, while introducing nitrogen gas, 12.5 g of methacrylic acid. , 60.5 g of methyl methacrylate, 23 g of 2-ethylhexyl acrylate, and 4 g of a reaction initiator ("ABN-E" manufactured by Nippon Hydrazine Industry Co., Ltd.) were added dropwise over 2 hours. After the dropwise addition, polymerization was continued for 2 hours while maintaining the same temperature, and then the solvent was distilled off under reduced pressure to obtain a water-soluble resin having a glass transition temperature of 50 ° C.
Next, after 96 g of the obtained water-soluble resin was pulverized, it was added to 140 g of water in which an equivalent amount of ammonia was dissolved in the carboxyl group of the water-soluble resin calculated from the monomer composition, mixed with stirring, and heated at 80 ° C. This was dissolved to obtain an aqueous solution (A) of a polymer emulsifier having a solid content of 40%.
In a four-necked flask equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen gas inlet pipe, 240 g of the aqueous solution of the polymer emulsifier (A) and 90 g of water were charged, and the temperature was maintained at 80 to 85 ° C. while introducing nitrogen gas. 86 g of methyl methacrylate, 58 g of 2-ethylhexyl acrylate, and 60 g of a 1% aqueous solution of ammonium persulfate were added dropwise from different dropping ports over 2 hours. After the dropwise addition, the emulsion was further subjected to emulsion polymerization for 2.5 hours while maintaining the same temperature. The obtained emulsion was diluted with water so as to have a solid concentration of 20%, and the emulsion resin particle dispersion 4 (acryl emulsion solution) was diluted. Obtained. The average particle diameter D2 of the emulsion resin particles in the obtained emulsion resin particle dispersion liquid 4 was 45 nm.

<Emulsion resin particle dispersion 5>
In a four-necked flask equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen gas inlet pipe, 220 g of ion-exchanged water and 1.8 g of an emulsifier (“HITENOL 18E” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were ion-exchanged. 8 g of the dissolved emulsifier aqueous solution was charged and heated to 72 ° C. while introducing nitrogen gas. Then, 2.8 g of methacrylic acid, 13 g of methyl methacrylate, 1.9 g of 2-ethylhexyl acrylate and 1.9 g of thioglycolic acid 2 were added. -1 g of ethylhexyl and 13 g of a 5% aqueous solution of ammonium persulfate were charged, and after 15 minutes, 11.2 g of methacrylic acid, 53 g of methyl methacrylate, 7.6 g of 2-ethylhexyl acrylate and 4 g of 2-ethylhexyl thioglycolate were applied for 80 minutes. And dropped. Fifteen minutes after the completion of the dropwise addition, the mixture was heated to 75 ° C., and then 25% aqueous ammonia was added thereto to obtain an aqueous solution (C) of a polymer emulsifier.
Further, the temperature of the aqueous solution (C) of the polymer emulsifier was adjusted to 80 ° C., and 86 g of methyl methacrylate, 58 g of 2-ethylhexyl acrylate, and 100 g of ion-exchanged water were added dropwise over 90 minutes. Thereafter, 7.2 g of a 2% ammonium persulfate aqueous solution was added dropwise over 30 minutes. Aging was performed for 90 minutes while maintaining the temperature, and the obtained emulsion was diluted with water so as to have a solid content concentration of 20% to obtain an emulsion resin particle dispersion liquid 5 (acryl emulsion solution). When the average particle diameter D2 of the emulsion resin particles in the obtained emulsion resin particle dispersion liquid 5 was measured, it was 15 nm.

<Emulsion resin particle dispersion 6>
In a four-necked flask equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen gas introduction pipe, 140 g of isopropyl alcohol as a solvent was charged and heated to 85 ° C., and while introducing nitrogen gas, 3.2 g of methacrylic acid was added. A mixture of 48 g of methyl methacrylate, 12 g of 2-ethylhexyl acrylate, 33 g of styrene, and 4 g of a reaction initiator ("ABN-E" manufactured by Nippon Hydrazine Industry Co., Ltd.) was added dropwise over 2 hours. After the dropwise addition, polymerization was continued for 2 hours while maintaining the same temperature, and then the solvent was distilled off under reduced pressure to obtain a water-soluble resin having a glass transition temperature of 70 ° C.
Next, after 96 g of the obtained water-soluble resin was pulverized, it was added to 140 g of water in which an equivalent amount of ammonia was dissolved in the carboxyl group of the water-soluble resin calculated from the monomer composition, mixed with stirring, and heated at 80 ° C. By dissolving, an aqueous solution (B) of a polymer emulsifier having a solid content of 40% was obtained.
In a four-necked flask equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen gas inlet pipe, 240 g of the aqueous solution of the polymer emulsifier (B) and 90 g of water were charged, and the temperature was maintained at 80 to 85 ° C. while introducing nitrogen gas. 86 g of methyl methacrylate, 58 g of 2-ethylhexyl acrylate, and 60 g of a 1% aqueous solution of ammonium persulfate were added dropwise from different dropping ports over 2 hours. After the dropwise addition, emulsion polymerization was carried out for 3 hours while maintaining the same temperature, and the obtained emulsion was diluted with water so as to have a solid content concentration of 20% to obtain an emulsion resin particle dispersion 6 (acryl emulsion solution). . It was 120 nm when the average particle diameter D2 of the emulsion resin particles in the obtained emulsion resin particle dispersion liquid 6 was measured.

<Emulsion resin particle dispersion 7>
In a four-necked flask equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen gas inlet pipe, 220 g of ion-exchanged water and 1.8 g of an emulsifier (“HITENOL 18E” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were ion-exchanged. 8 g of the dissolved emulsifier aqueous solution was charged and heated to 72 ° C. while introducing nitrogen gas. Then, 2.8 g of methacrylic acid, 13 g of methyl methacrylate, 1.9 g of 2-ethylhexyl acrylate and 1.9 g of thioglycolic acid 2 were added. -1 g of ethylhexyl and 10 g of a 5% aqueous solution of ammonium persulfate were added, and after 10 minutes, 11.2 g of methacrylic acid, 53 g of methyl methacrylate, 7.6 g of 2-ethylhexyl acrylate and 4 g of 2-ethylhexyl thioglycolate were applied for 60 minutes. And dropped. Fifteen minutes after the completion of the dropping, the mixture was heated to 70 ° C., and then 25% aqueous ammonia was added. The temperature was further adjusted to 75 ° C., and 86 g of methyl methacrylate, 58 g of 2-ethylhexyl acrylate, and 100 g of ion-exchanged water were added dropwise over 90 minutes. Thereafter, 6 g of a 2% aqueous solution of ammonium persulfate was added dropwise over 30 minutes. Aging was performed while maintaining the temperature for 60 minutes, and the obtained emulsion was diluted with water so as to have a solid concentration of 20% to obtain an emulsion resin particle dispersion 7 (acryl emulsion solution). When the average particle diameter D2 of the emulsion resin particles in the obtained emulsion resin particle dispersion liquid 7 was measured, it was 6 nm.

  The average particle diameter D1 of silver nanoparticles in the obtained silver nanoparticle dispersions 1 to 6, the average particle diameter D1 of gold nanoparticles in gold nanoparticle dispersion 1, and the emulsion resin particles in emulsion resin particle dispersions 1 to 7 Was measured by the following methods.

<Measurement of average particle size>
The average particle diameter D1 of the metal nanoparticles and the average particle diameter D2 of the emulsion resin particles were measured by SEM observation. Specifically, it measured by the following procedures.
1) After applying the dispersion onto a glass plate, the sample was obtained by degassing in vacuo to volatilize the solvent component. The dispersion of the obtained sample was subjected to SEM observation using a measuring device JEOL JSM-7401F, and the particle diameter of arbitrary 300 metal nanoparticles or emulsion resin particles was measured.
2) Based on the obtained measurement data, a volume-based particle size distribution was determined using image processing software Image J, and its D50 (median diameter) was defined as an average particle diameter (volume average particle diameter).
Since the dispersant adsorbed on the surface of the metal nano was not observed by SEM observation, the particle size of the metal nano was determined as the particle size of the metal nano not containing the dispersant.

1-3. Solvent Water Propylene glycol (boiling point: 188 ° C)
Triethylene glycol monomethyl ether (boiling point: 248 ° C)

1-4. Additive BYK-348 (by Big Chemie) (surfactant)

2. Preparation of Ink According to the composition shown in Table 1 or 2, after mixing each component, the mixture was filtered through a Teflon (“Teflon” is a registered trademark of DuPont) 3 μm membrane filter manufactured by ADVATEC, and Examples 1 to 20 and Comparative Examples 1 to 5 inks were prepared.

3. Evaluation of Inks Using the inks of Examples 1 to 20 and Comparative Examples 1 to 5, images were formed on the following substrates.

(Base material)
Coated paper: Ramie Corporation, WRG3-36

(Image forming conditions)
An image was formed on each substrate using an inkjet recording apparatus having a piezo-type inkjet nozzle. The ink jet recording apparatus had an ink tank, an ink supply pipe, an ink supply tank immediately before the ink jet head, a filter, and a piezo type ink jet head in this order from the upstream side where the ink flows to the downstream side. . The inkjet head was driven under the conditions of a droplet volume of 14 pl, a printing speed of 0.5 m / sec, an ejection frequency of 10.5 kHz, and a printing rate of 100%, and ejected and landed ink droplets on each base material. . After landing, drying was performed at 60 ° C. for about 10 minutes to obtain an image.

  Then, the reflectance and adhesion of the obtained image, and the ejection stability of the ink were evaluated by the following methods.

(Reflectance)
Using a spectrophotometer U4100, the reflectance at each wavelength of 450 nm, 550 nm, and 650 nm was measured, and the average value thereof was obtained and evaluated according to the following criteria.
：: The average value is 50% or more 〇: The average value is less than 50% 40% or more △: The average value is less than 40% 30% or more ：: The average value is less than 30% 20% or more XX: The average A value of less than 20% Δ or more was evaluated as practical.
However, in Example 20, the reflectance at each of the wavelengths of 600 nm and 650 nm was measured, and the average value was evaluated.

(Adhesion)
On the surface of the obtained image, cuts were made in a grid pattern so that the number of grids became 100, and a grid tape peeling test was performed. And it evaluated by the following criteria.
○: No peeling at 100/100 grids △: No peeling at 99 / 100-95 / 100 grids ×: No peeling at 94 / 100-0 / 100 grids △ or more Was evaluated as practical.

(Discharge stability)
The obtained ink is filled in an ink supply tank of an inkjet image forming apparatus, and at room temperature, under conditions that a droplet amount is 42 pl, a printing speed is 0.5 m / sec, an ejection frequency is 10.5 kHz, and a printing rate is 100%. Ink droplets were continuously discharged for 8 hours to land on the base material.
During continuous ejection for 8 hours, the number of occurrences of missing dots, flight bends, and ink scattering on the substrate was visually observed, and based on the total number, the ejection stability of the ink composition was evaluated based on the following criteria. did.
○ The number of missing dots, flight bending and ink scattering is less than 15 times △ The number of missing dots, flying bending and ink scattering is 15 or more and less than 20 times × The number of missing dots, flight bending and ink scattering is 20 The number of times Δ or more was evaluated as practical.

Tables 1 and 2 show the obtained evaluation results.

  As shown in Table 1, the images obtained using the inks of Examples 1 to 20 in which D2 / D1 is more than 0.05 and less than 1 all have high reflectance and also have good adhesion to the base material. It turns out that it is favorable.

  In particular, by setting M1 / M2 to be 1.3 or more and 35 or less, it can be seen that the reflectance of the obtained image can be higher and the adhesion to the base material can be higher (with the inks of Examples 3 and 8 to 11). And the inks of Examples 16 to 17). Further, it is understood that the reflectance of the obtained image can be further increased by setting M1 / M2 to 2 or more (comparison between the ink of Example 8 and the ink of Example 16).

  Further, it can be seen that by setting M1 + M2 to 1 or more, the reflectance of the obtained image is easily increased, and when it is set to 35 or less, the ejection stability is easily obtained (the inks of Examples 3 and 10 to 11). And the inks of Examples 18 to 19). It is considered that the reason that the reflectance is increased by setting M1 + M2 to 1 or more is that the solid content concentration is appropriately high, so that a film thickness sufficient to enhance the reflectance is easily obtained. It is considered that the reason why the ejection stability is improved by setting M1 + M2 to 35 or less is that the solid content concentration is not too high and the rise in ink viscosity is small.

  In contrast, it can be seen that the image obtained using the ink of Comparative Example 1 containing no emulsion resin particles has low adhesion to the substrate. On the other hand, it can be seen that the images obtained using the inks of Comparative Examples 2 to 4, which contain emulsion resin particles but have D2 / D1 of 1 or more, both have low reflectance and low adhesion to the substrate. In particular, from the comparison between Comparative Examples 2 and 3, when the average particle diameter D2 of the emulsion resin particles is relatively too large, many voids around the metal nanoparticles are formed when the content of the emulsion resin particles is reduced. Therefore, the refractive index extinction coefficient of the obtained metallic gloss layer is increased and the scattering factor is increased, which indicates that the reflectance and the adhesion are further reduced. In addition, it can be seen that the image obtained using the ink of Comparative Example 5 containing the emulsion resin particles but having D2 / D1 of less than 0.05 has particularly low adhesion to the substrate. This is considered to be because the average particle diameter D2 of the emulsion resin particles is relatively too small, and the binding between the resin particles is insufficient, and sufficient film strength cannot be obtained.

  This application claims the priority based on Japanese Patent Application No. 2017-065900 filed on Mar. 29, 2017. The contents described in the specification of this application are all incorporated herein by reference.

ADVANTAGE OF THE INVENTION According to this invention, it can provide the inkjet ink which has sufficient adhesiveness with a base material and can form the image which has sufficient metallic luster.

Claims (9)

Metal nanoparticles, a dispersant adsorbed on the surface of the metal nanoparticles, emulsion resin particles, and a solvent,
A glitter inkjet ink that satisfies 0.05 <D2 / D1 <1, where D1 is the average particle diameter of the metal nanoparticles and D2 is the average particle diameter of the emulsion resin particles.   The brilliancy according to claim 1, further satisfying 1.3 ≦ M1 / M2 ≦ 35, where M1 (%) is the content mass of the metal nanoparticles and M2 (%) is the content mass of the emulsion resin particles. Inkjet ink.   The glitter inkjet ink according to claim 1 or 2, further satisfying 1 ≦ M1 + M2 ≦ 35 when the content mass of the metal nanoparticles is M1 (%) and the content mass of the emulsion resin particles is M2 (%). .   The glitter ink according to any one of claims 1 to 3, wherein the dispersant is a polymer dispersant.   The glitter inkjet according to claim 4, wherein the polymer dispersant is a comb-type block copolymer having a main chain containing a structural unit derived from a (meth) acrylate and a side chain containing a polyoxyalkyl group. ink.   The glitter inkjet ink according to any one of claims 1 to 5, wherein the emulsion resin particles are urethane resin particles or (meth) acrylic resin particles.   The glitter ink according to any one of claims 1 to 6, wherein the solvent includes an organic solvent having a boiling point of 150 ° C or higher.   The brilliant inkjet ink according to any one of claims 1 to 7, wherein the metal nanoparticles are silver nanoparticles. After applying the glitter inkjet ink according to any one of claims 1 to 8 on a substrate, a step of volatilizing a solvent,
Heating the glitter inkjet ink in which the solvent has been volatilized to form a metallic glossy layer.