JP2019162741A - Image-formed article, ink set, and image forming method - Google Patents

Abstract

To provide an image-formed article having high gradation recognition properties since an image-formed article formed by a prior method for printing by an inkjet method using a luster ink has a problem that gradation is hard to be recognized, an ink set for forming the image-formed article, and an image forming method.SOLUTION: The image-formed article includes: a substrate; a ground layer formed on a surface of the substrate; and an ink layer formed by contacting the ground layer, where the ink layer having a film thickness of 100 nm or more is constituted by aggregating a plurality of dots containing a metal nano-particle, and a plurality of the dots have an average value of maximum values Δ1 of differences of dot heights in a region having a radius of 1/4 dot diameter defined in a dot peripheral direction from a dot center of 20 nm or less.SELECTED DRAWING: None

Description

  The present invention relates to an image formed product, an ink set, and an image forming method.

  In recent years, there has been an increasing demand for metallic glossy prints on recorded materials such as labels, packages, printed advertisements and photographs. Conventionally, analog printing such as offset printing, gravure printing, or screen printing has been used as a metallic glossy printing technique. On the other hand, the technical development of an ink jet method capable of forming a finer image and capable of digital printing has been advanced. In addition, technical development of a method for forming an image-formed product having a metallic luster by an ink jet method using an ink jet ink containing a glitter pigment is also in progress.

  In Patent Document 1, in order to obtain glitter on a recording medium with low smoothness such as plain paper, a resin component is dispersed or dissolved in a solvent component in advance in the area of the recording medium where the glitter pigment ink is ejected. An ink jet recording method in which a resin ink is applied to fill in irregularities on the surface of a recording medium to form an undercoat layer having high smoothness, and an aqueous glitter ink in which an effect pigment is dispersed is recorded on the formed underlayer Has been proposed.

  Further, Patent Document 2 proposes a method in which a material having an ink absorbing function such as fumed silica is previously applied to a recording medium, and glitter pigment ink is applied by an ink jet method for recording.

JP 2012-35591 A Japanese Patent Laying-Open No. 2015-193721

  However, the conventional image formed product formed by printing the glitter ink by the ink jet method has a problem that it is difficult to visually recognize gradation (density difference). Accordingly, an object of the present invention is to provide an image formed product with high gradation visibility, and an ink set and an image forming method for forming the image formed product.

The above problem is solved by the following means.
[1] A base material, a base layer formed on the surface of the base material, and an ink layer formed in contact with the base layer, the ink layer having a thickness of 100 nm or more A plurality of dots including nanoparticles are aggregated, and the plurality of dots is a maximum value of a difference in dot height in a region having a radius of ¼ of the dot diameter defined in the direction from the dot center to the dot periphery. An image formed product having an average value of Δ1 of 20 nm or less.
[2] The image formed product according to [1], wherein the plurality of dots have an average value of a maximum difference Δ1 of the dot height of 15 nm or less.
[3] The image formed product according to [1] or [2], wherein the plurality of dots have an average dot diameter of 45 μm or more and 55 μm or less.
[4] The image formed product according to any one of [1] to [3], wherein the underlayer includes a polymer of a hydrophilic monomer.
[5] The image formed product according to any one of [1] to [4], wherein the metal nanoparticles are particles having an average particle diameter of 100 nm or less.
[6] The image formed product according to any one of [1] to [5], wherein the metal nanoparticles are silver nanoparticles.
[7] The image formed product according to any one of [1] to [6], which is an image formed product having gradation.
[8] An ink set comprising: a first pretreatment liquid containing a hydrophilic monomer; a second pretreatment liquid containing a flocculant and a surfactant; and a metal ink containing metal nanoparticles and water.
[9] A step of applying a first pretreatment liquid containing a hydrophilic monomer on a substrate, a step of curing the applied first pretreatment liquid by irradiation with actinic rays, and the first A step of applying a second pretreatment liquid containing a flocculant and a surfactant to the surface of the cured film obtained by curing the pretreatment liquid, and the second pretreatment liquid on the base material. Applying a metal ink containing metal nanoparticles to the region by an ink jet method.
[10] The image forming method according to [9], wherein the first pretreatment liquid is applied onto the substrate by an inkjet method.
[11] The image forming method according to [9] or [10], wherein the second pretreatment liquid is applied to the surface of the cured film by an inkjet method.

  According to the present invention, an image formed product with high gradation visibility, an ink set for forming the image formed product, and an image forming method are provided.

  The present inventors have intensively studied in view of the above problems, and exhibit a metallic luster by an ink layer in which dots derived from ink droplets formed by an inkjet method using an inkjet ink containing metal nanoparticles are assembled. At that time, it was found that the gradation of the image formed product can be more easily recognized by making the ink layer thickness 100 nm or more and making the surface of the dot flatter, and further studies are made. The present invention has been completed.

  In other words, in an image formed product in which gloss is expressed by the glitter pigment, a part of the light incident on the image formed product becomes specularly reflected light, and the other part becomes diffusely reflected light. Of these, specularly reflected light enhances the visibility of the metallic luster strength, but diffusely reflected light weakens the visibility of the metallic luster strength. For this reason, it is considered that the intensity of the metallic luster of the region can be more accurately visually recognized by making more of the light incident on a certain region in the image-formed product into regular reflection light.

  It is considered that the ratio of specular reflection light is greatly influenced by the shape of the glitter pigment and the shape of the dots.

  When the shape of the glitter pigment approaches a spherical shape, the light incident on the glitter pigment is more likely to be regularly reflected, but when the shape of the glitter pigment approaches an irregular shape rather than a spherical shape, the light incident on the glitter pigment is more Easy to diffuse reflection. For this reason, it is considered that a larger amount of light incident on the image-formed product can be regularly reflected by using metallic nanoparticles closer to a spherical shape as a bright pigment.

  Further, when the surface shape of the dot becomes smoother, the light incident on the dot is more likely to be regularly reflected, but when the surface shape of the dot is roughened, the light incident on the dot is more easily diffusely reflected. Therefore, it is considered that more smooth reflection of the surface shape of the dots allows regular reflection of more of the light incident on the image forming object.

  According to the knowledge of the present inventors, ink pinning deficiency and coffee ring (dot coalescence) tend to occur particularly in an area where dots are densely formed, particularly when an image having gradation is to be formed. If the shape of the dots collapses due to the occurrence of these, the surface shape of the dots becomes rougher and diffuse reflected light increases, or the shapes of the dots differ greatly and the light incident on the image formation varies. The light is reflected in a different direction and the apparent diffuse reflection light increases, so the visibility of the metallic luster strength is weakened.

  Based on these findings, the present invention uses metal nanoparticles as a bright pigment, and adjusts the surface shape of the dots constituting the ink layer and the film thickness of the ink layer to the above ranges, so that the incident light is incident on the image formed product. The proportion of regularly reflected light among the received light is increased, while the proportion of diffusely reflected light that is incident on the image forming object is lowered. As a result, in the image formed product, more specular reflection light is generated in a region where the density is high and dots are denser, and less specular reflection light is generated in a region where the density is low and dots are present more sparsely. It is considered that the visibility of the intensity of the gloss is increased by the amount of the regular reflection light according to the density difference (gradation) between the areas of the image formed product.

  Based on these findings, it is considered that the ink layer having the above characteristics can be formed by increasing the pinning property of the ink or by reducing the contact angle to make it difficult to produce a coffee ring.

  Based on the above findings, the present invention relates to the above-described image formed product, an ink set for forming the image formed product, and an image forming method.

1 Image-formed product An image-formed product according to an embodiment of the present invention is an image-formed product having a substrate, a base layer, and an ink layer.

1-1 Substrate The substrate is not particularly limited as long as a base layer can be formed, and may be a paper substrate having high water absorption, or a substrate having low water absorption such as gravure or coated paper for offset printing. Alternatively, it may be a non-water-absorbing substrate such as a film, a plastic board (soft vinyl chloride, hard vinyl chloride, acrylic plate, polyolefin, etc.), glass, tile and rubber.

1-2 Underlayer The underlayer is a layer containing a monomer polymer formed on the surface of the substrate. By forming the base layer on the surface of the base material, it is possible to create a smooth surface by filling the unevenness of the surface of the base material, and the surface shape of the dots constituting the ink layer formed thereon is smoother Can be The monomer for forming the underlayer is not particularly limited as long as it can form the underlayer, but a hydrophilic monomer is preferable from the viewpoint of improving the adhesion with the ink layer.

  The film thickness of the underlayer is not particularly limited as long as a smooth surface can be produced regardless of the unevenness of the surface of the base material, but can be 10 μm or more and 40 μm or less, and preferably 20 μm or more and 30 μm or less.

  The underlayer may be formed on the entire surface of the substrate, although it may be formed in the region where at least the ink layer is to be formed and the metallic luster should be developed in the surface of the substrate.

1-3 Ink Layer The ink layer is a layer in which a plurality of dots derived from ink droplets formed by an ink jet method are formed in contact with the surface of the base layer. The plurality of dots include metal nanoparticles.

  The thickness of the ink layer is 100 nm or more. If the film thickness is 100 nm or more, it is considered that the influence of the surface shape of the dots on the ratio of specular reflection light can be reduced and the ratio of specular reflection light can be increased. The upper limit of the film thickness is not particularly limited as long as it can be formed by an inkjet method, but is preferably 400 nm.

  The plurality of dots constituting the ink layer are dots in which the average value of the maximum difference Δ1 of the dot heights in the region having a radius of ¼ of the dot diameter defined from the dot center to the dot peripheral direction is 20 nm or less. It is. If the average value of Δ1 is 20 nm or less, the surface of the dot is sufficiently smoothed, and thus it is considered that a sufficient proportion of the light incident on the dot can be regularly reflected. The average value of Δ1 is preferably 18 nm or less, more preferably 15 nm or less, and more preferably 12 nm or less from the viewpoint of increasing the smoothness of the dot surface and increasing the proportion of specularly reflected light. More preferably, it is 10 nm or less. The lower limit of the average value of Δ1 is not particularly limited, but ideally it is preferably 0 nm.

  Δ1 is a base layer in the range of ¼ of the dot diameter from the dot center to the dot peripheral direction for each dot in the image obtained by observing the cross section of the image formed product with a transmission electron microscope (TEM). It is obtained by measuring the height from the surface of the dot to the surface of the dot and calculating the difference between the maximum value and the minimum value of the measured height. In the present embodiment, the average value of Δ1 calculated for some arbitrarily defined dots (for example, five dots) among the plurality of dots included in the image obtained by the TEM is 20 nm or less. I just need it.

  From the viewpoint of increasing the gradation visibility by reducing the ratio of diffusely reflected light, the average dot diameter of the plurality of dots is preferably 45 μm or more and 55 μm or less, and 47 μm or more and 53 μm or less. More preferred.

  The average dot diameter is obtained by observing the surface of the ink layer with a TEM and, for some dots (for example, 15 dots) arbitrarily determined among a plurality of dots included in each dot in the obtained image. It is obtained by calculating the dot diameter and calculating the average value of the calculated dot diameters.

  It is preferable that the ink layer includes a plurality of regions having different dot densities to constitute an image formed product having gradation. At this time, in the present embodiment, a stronger gloss is visually recognized in an area where the dot density is high, and a weaker gloss is visually recognized in an area where the dot density is low, so that the gradation of the image formed product is better recognized. The The arrangement of the plurality of dots is not particularly limited, but is preferably an arrangement by a systematic dither method or an error diffusion method.

  The metal contained in the metal nanoparticles may be any metal that can exhibit a metallic luster when the ink layer is formed.

  Examples of the above metals include gold, silver, copper, nickel, palladium, platinum, aluminum, zinc, chromium, iron, cobalt, molybdenum, zirconium, ruthenium, iridium, tantalum, mercury, indium, tin, lead, and tungsten. Is included. Of these, gold, silver, copper, nickel, cobalt, tin, lead, chromium, zinc and aluminum are preferred because they can express high gloss and are inexpensive. Gold, silver, copper, tin, Chromium, lead and aluminum are more preferred, gold and silver are more preferred, and silver is particularly preferred. These metals can be used singly or in combination of two or more as an alloy or a mixture. Moreover, you may use combining the 2 or more types of metal nanoparticle from which the kind or composition of a metal differs. The metal nanoparticles only need to contain these metals as main components, may contain a small amount of other components inevitably contained, and are surface-treated with citric acid or the like to improve dispersion stability. Also good. Moreover, these metals may contain an oxide.

  The average particle diameter of the metal nanoparticles is not particularly limited, but is preferably 3 nm or more and 100 nm or less from the viewpoint of enhancing dispersion stability and storage stability in the metal ink and from the viewpoint of gradation visibility. It is more preferably 80 nm or less, still more preferably 10 nm or more and 60 nm or less, particularly preferably 15 nm or more and 55 nm or less, and particularly preferably 20 nm or more and 30 nm or less.

  The average particle diameter of the metal nanoparticles is determined by observing the metal nanoparticle dispersion with SEM and determining the volume average particle diameter of the nanoparticles, and specifically, the following procedure is performed.

1) After applying the dispersion on a glass plate, vacuum degassing to volatilize the solvent component to obtain a sample. The obtained sample dispersion is subjected to SEM observation using a scanning electron microscope JSM-7401F (manufactured by JEOL Ltd.), and the particle diameters of arbitrary 300 metal nanoparticles are measured.
2) Based on the obtained measurement data, the image processing software Image J is used to obtain a volume-based particle size distribution, and D50 (median diameter) is defined as a volume-converted average particle diameter (volume average particle diameter).

  Each of the plurality of dots constituting the ink layer may include a resin such as a fixing resin in addition to the metal nanoparticles.

2 Ink Set An ink set according to another embodiment of the present invention is an exemplary ink set for forming the image formed product, and includes a first pretreatment liquid and a second pretreatment liquid for forming the base layer. A pretreatment liquid and a metal ink for forming the ink layer.

2-1 First Pretreatment Liquid The first pretreatment liquid contains a monomer for forming a base layer on the base material by polymerization when applied on the base material and irradiated with actinic rays. What is necessary is just an actinic-light curable type processing liquid. The monomer is preferably a hydrophilic monomer from the viewpoint of further increasing the affinity with a metal ink that is a water-based ink. Further, the first pretreatment liquid may contain a polymerization initiator, a surfactant and the like as optional components as necessary.

2-1-1 Hydrophilic monomer The underlayer formed by polymerizing the hydrophilic monomer has a high affinity with the second treatment liquid, which is an aqueous liquid, and the metal ink. Therefore, the base layer formed by polymerizing the hydrophilic monomer enhances the adhesion of the flocculant contained in the second treatment liquid and further enhances the effect of improving the pinning property of the ink by the flocculant.

  The hydrophilic monomer is a monomer that is cured by polymerization and crosslinking upon irradiation with actinic rays. The hydrophilic monomer only needs to have a solubility in water at 25 ° C. of 0.1 g / L or more, for example. A hydrophilic monomer may be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of the hydrophilic monomer include a styrene monomer, a monomer having a sulfonic acid group, a monomer having a carboxy group, a monomer having a hydroxy group, and a structure having polarity such as an amino group, an oxyalkylene chain and a cyano group in the structure. The monomer which has is included.

  Examples of the monomer having a sulfonic acid group include styrene sulfonic acid and 2- (meth) acrylamidopropyl sulfonic acid.

  Examples of the monomer having a carboxy group include (meth) acrylic acid, fumaric acid, maleic acid, itaconic acid, cinnamic acid, maleic acid monobutyl ester, and maleic acid monooctyl ester.

  Examples of the monomer having a hydroxy group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 2-hydroxy-3-phenoxypropyl (meth) acrylate. 4-hydroxybutyl (meth) acrylate, hydroxyethylacrylamide and the like are included.

  Examples of the monomer having an amino group in the structure include dimethylaminoethyl (meth) acrylate, diethylaminopropyl (meth) acrylate, 3-dimethylaminophenyl (meth) acrylate, dimethylaminopropyl acrylamide, and salts thereof. It is.

  Examples of monomers having an oxyalkylene chain in the above structure include polyethylene glycol di (meth) acrylate and ethylene oxide modified such as trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate and bisphenol A diacrylate Products or propylene oxide modified products.

  Examples of the monomer having a cyano group in the structure include (meth) acrylonitrile.

  The content of the hydrophilic monomer in the first treatment liquid is not particularly limited as long as a base layer having a sufficiently smooth surface is formed, but is 80% by mass with respect to the total mass of the first pretreatment liquid. It is preferably 100% or less by mass.

2-1-2 Polymerization initiator The polymerization initiator may be a known polymerization initiator. Examples of the polymerization initiator include bis (2,4,6-trimethylbenzoyl-phenylphosphine oxide, benzoin methyl ether, benzoin ethyl ether, isopropyl benzoin ether, isobutyl benzoin ether, 1-phenyl-1,2-propanedione- Examples include 2- (o-ethoxycarbonyl) oxime, benzyl, diethoxyacetophenone, benzophenone, chlorothioxanthone, 2-chlorothioxanthone, isopropylthioxanthone, 2-methylthioxanthone, polychlorinated polyphenyl, hexachlorobenzene, and the like. An agent may be used individually by 1 type and may be used in combination of 2 or more type.

  The content of the polymerization initiator in the first treatment liquid is not particularly limited as long as the polymerization of the hydrophilic monomer can be started by irradiation with actinic rays, but is 0.1 mass with respect to the total mass of the first pretreatment liquid. % To 10% by mass is preferable.

2-1-3 Surfactant The surfactant may be 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. These surfactants may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the surfactant in the first treatment liquid is not particularly limited as long as the base layer is formed, but is 0.01% by mass or more and 10% by mass or less with respect to the total mass of the first pretreatment liquid. It is preferable that

2-2 Second Pretreatment Liquid The second pretreatment liquid is applied to the surface of the base layer formed by polymerization of the monomers contained in the first pretreatment liquid, and is applied to the surface of the base layer by an inkjet method. The dot shape of the applied metal ink is adjusted. The second pretreatment liquid includes water as a solvent, a flocculant, and a surfactant.

2-2-1 Flocculant The flocculant, when applied to the metal ink, diffuses into the metal ink and acts on the metal nanoparticles and the anionic resin to agglomerate them. What is necessary is just to improve pinning property. Although not particularly limited, examples of the flocculant include a cationic resin, a polyvalent metal salt, and an organic acid. These flocculants can be used individually by 1 type or in combination of 2 or more types.

  Examples of the cationic resin include polyallylamine, polyvinylamine, polyethyleneimine, and polydiallyldimethylammonium chloride.

  Examples of the polyvalent metal salt include water-soluble salts such as calcium salt, magnesium salt, aluminum salt, and zinc salt.

  Examples of the organic acids include formic acid, acetic acid, propionic acid, isobutyric acid, oxalic acid, fumaric acid, malic acid, citric acid, malonic acid, succinic acid, maleic acid, benzoic acid, 2-pyrrolidone-5-carboxylic acid , Lactic acid, acrylic acid and derivatives thereof, methacrylic acid and derivatives thereof, and compounds having a carboxyl group including acrylamide and derivatives thereof, sulfonic acid derivatives, and phosphoric acid and derivatives thereof.

  The flocculant is preferably a polyvalent metal salt or an acid because it has a low molecular weight and easily diffuses into the metal ink, and the components in the metal ink can be aggregated at a higher speed. Furthermore, since the safety is higher and the compatibility with the anionic resin is higher, the flocculant is more preferably an acid.

  The range of the content (attachment amount) of the flocculant applied to the substrate is not limited, and can be appropriately set according to the composition of the metal ink, the amount of the metal ink, the type of the flocculant, and the like. For example, the mass of the flocculant is preferably 3% by mass or more and 50% by mass or less with respect to the mass of the image to be formed.

  In addition, when using an acid, it is preferable that the addition amount of an acid is an amount which adjusts the pH of a process liquid to below the neutralization equivalent of the anion component contained in a metal ink. Further, when the anion component is a compound having a carboxyl group, the first dissociation constant of the acid is preferably 3.5 or less from the viewpoint of making image bleeding more difficult.

2-2-2 Surfactant The surfactant has an action of lowering the surface tension of the surface of the base layer to which the metal ink is applied and reducing the contact angle of the applied metal ink. As a result, ink coffee ring or the like is less likely to occur, and it becomes easier to form an ink layer in which dots having the above-described characteristics are gathered.

  The surfactant may be a known surfactant (surface conditioning agent). Examples of the surfactant include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates and fatty acid salts, polyoxyethylene, and the like. Nonionic surfactants such as alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols and polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts As well as silicone and fluorine surfactants. These surfactants may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the surfactant in the second treatment liquid is not particularly limited as long as the ink layer formed by collecting the dots having the above-described shape by adjusting the dot shape of the metal ink is formed. It is preferable that it is 0.01 mass% or more and 10 mass% or less with respect to the total mass of a pre-processing liquid.

2-3 Metal Ink The metal ink contains water as a solvent and the metal nanoparticles described above. The metal nanoparticles are preferably dispersed with a polymer dispersant. The metal ink may contain an anionic resin emulsion, a surfactant, and a dispersant as optional components as required.

2-3-1 Metal Nanoparticles The metal contained in the metal nanoparticles and the average particle diameter of the metal nanoparticles are as described above.

  The content of the metal nanoparticles in the metal ink is not particularly limited, but is preferably 0.5% by mass or more and 15% by mass or less, and preferably 0.75% by mass or more and 12.5% by mass with respect to the total mass of the metal ink. % Or less is more preferable, and 1% by mass or more and 10% by mass or less is further preferable.

2-3-2 Polymer Dispersant The polymer dispersant is a compound having an adsorbing group that can be adsorbed on the surface of the metal nanoparticles and a hydrophilic structure.

  The polymer dispersant has an adsorbing group that can be adsorbed on the surface of the metal nanoparticles. Examples of the adsorbing group include a hydroxy group, a carboxyl group, and a thiol group.

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

  Examples of hydrophilic monomers include monomers containing carboxyl groups or acid anhydride groups (such as (meth) acrylic acid, unsaturated polyvalent carboxylic acids such as maleic acid, and maleic anhydride), and alkylene oxide modified (meta). ) Acrylic acid ester monomers (such as ethylene oxide-modified (meth) acrylic acid alkyl esters). In the present invention, (meth) acryl means both or one of acrylic and methacrylic.

  Examples of hydrophobic monomers include (meth) acrylate monomers such as methyl (meth) acrylate and ethyl (meth) acrylate, styrene monomers such as styrene, α-methylstyrene and vinyltoluene, ethylene, propylene And α-olefin monomers such as 1-butene, and carboxylic acid vinyl ester monomers such as vinyl acetate and vinyl butyrate.

  When the polymer dispersant is a copolymer, it may be a random copolymer, an alternating copolymer, a block copolymer, a comb copolymer, or the like. Among these, from the viewpoint of further improving the dispersibility of the metal nanoparticles, the polymer dispersant is preferably a comb block copolymer.

  The comb-type block copolymer means a copolymer containing a linear polymer forming a main chain and another kind of polymer graft-polymerized to a structural unit derived from a monomer constituting the main chain. Preferable examples of the comb block copolymer include a long chain containing a structural unit derived from a (meth) acrylic acid ester and a side chain containing a polyalkylene oxide group (such as an ethylene oxide-propylene oxide copolymer group). Comb-type block copolymers containing a chain polyalkylene oxide group). In the comb-type block copolymer, since the graft-polymerized side chain causes steric hindrance, aggregation of metal nanoparticles can be further suppressed. Thereby, the dispersibility of the metal nanoparticles is increased, and thus it is easier to suppress ejection failure due to the aggregated metal nanoparticles.

  The polymer dispersant preferably has an acid value of 1 mgKOH / g or more and 100 mgKOH / g or less. When the acid value is 1 mgKOH / g or more, a sufficient size is provided between the cationic flocculant and the metal ink due to the application of the second pretreatment liquid to enhance the pinning property of the metal ink. Interaction occurs. Further, when the acid value is 1 mgKOH / g or more, the polymer dispersant has a hydrophilic tendency, so that the dispersibility of the metal nanoparticles in the metal ink can be improved, and the ejection stability of the metal ink. Can be even higher. On the other hand, when the acid value is 100 mgKOH / g or less, the charge of the anion component of the metal ink is sufficiently canceled by the cationic pretreatment layer, so that the pinning property of the metal ink is improved. Therefore, a sufficiently large cohesive force acts. In addition, when the acid value is 100 mgKOH / g or less, it is possible to suppress a remarkable decrease in ejection stability from the inkjet head due to swelling of the polymer dispersant in the inkjet head. From the above viewpoint, the acid value of the polymer dispersant is preferably 3 mgKOH / g or more and 80 mgKOH / g or less, more preferably 5 mgKOH / g or more and 60 mgKOH / g or less, and 7 mgKOH / g or more and 50 mgKOH / g. More preferably, it is as follows.

  The acid value of the polymer dispersant can be measured according to JIS K 0070. Specifically, the acid value of the dispersant is determined by the type of the dispersant (for example, the product name of the polymer dispersant used for the production of the laminate) by Fourier transform infrared spectroscopy (FT-IR). The acid value of the same dispersant may be specified according to JIS K 0070. Further, the type of the dispersant may be specified by 1H-NMR and gas chromatography-mass spectrometry (GC / MS).

  The polymer dispersant preferably has a polyalkylene oxide structure in the molecule, and more preferably the above-described comb block copolymer having a polyalkylene oxide group in the side chain. The polyalkylene oxide structure moderately reduces the cohesiveness of the metal nanoparticles due to steric hindrance. Thereby, it is considered that the metal ink (or metal nanoparticles in the metal ink) spreads moderately on the base material, and can form a smoother and higher gloss image.

  The polyalkylene oxide structure is preferably a polyalkylene oxide structure (polyethylene oxide structure and porpropylene oxide structure) having 3 to 6 carbon atoms. The polymer dispersant preferably has 3 or more and 80 or less polyalkylene oxide structures per molecule.

  The polymer dispersant preferably has a weight average molecular weight of 1,000 to 100,000, more preferably 2,000 to 50,000.

  Examples of commercially available polymer dispersants having an acid value of 1 mgKOH / g or more and 100 mgKOH / g or less include DISPERBYK-102, DISPERBYK-187, DISPERBYK-190, DISPERBYK-191, DISPERBYK-194N, DISPERBYK-199, DISPERBYK- 2015, and DISPERBYK-2069 (both manufactured by Big Chemie, “DISPERBYK” is a registered trademark of the company), EFKA 6220 (manufactured by BASF, “EFKA” is a registered trademark of the company), and Solsperse 32000, Solsperse 44000, Solsperse 46000 ( Lubrizol Co., Ltd.), Florene TG-750W (Kyoeisha Chemical Co., Ltd.) and the like are included.

  The content of the polymer dispersant in the metal ink is not particularly limited, but from the viewpoint of sufficiently enhancing the dispersibility of the metal nanoparticles in the metal ink and the adhesion to the substrate, the total mass of the metal nanoparticles On the other hand, it is preferably 1% by mass or more and 15% by mass or less, more preferably 2% by mass or more and 10% by mass or less, and further preferably 3% by mass or more and 8% by mass or less.

2-3-3 Anionic resin emulsion The anionic resin emulsion acts as a fixing resin, interacts with the polymer dispersant adsorbed on the surface of the metal nanoparticles, and adheres the metal nanoparticles to the substrate. Can increase sex.

  The anionic resin is preferably a resin having high affinity with the polymer dispersant, and is a (meth) acrylic resin, urethane resin, polyolefin resin, polyester resin, 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), and vinyl acetate A copolymer (for example, ethylene-vinyl acetate copolymer) can be appropriately selected and used. From the viewpoint of further improving the water resistance of the formed image, the anionic resin is composed of (meth) acrylic resin, urethane resin, polyolefin resin, polyvinyl chloride resin, epoxy resin, polysiloxane resin, fluorine resin, styrene copolymer. It is preferably selected from a coalescence, a vinyl acetate copolymer and the like, and preferably selected from a urethane resin and a (meth) acrylic resin.

  The anionic urethane resin is prepared by, for example, reacting a sulfonate-containing polyol (a1) and an organic polyisocyanate (a2) in an isocyanate group-excess atmosphere, and then adding a low-molecular polyol (a3-1) and an aqueous solvent. To obtain an emulsion of an isocyanate group-terminated prepolymer, and a low-molecular polyamine (a3-2) is added to the emulsion for further reaction.

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

  Examples of the organic polyisocyanate (a2) include aromatic diisocyanates including 4,4′-diphenylmethane diisocyanate, aliphatic diisocyanates including 1,6-hexamethylene diisocyanate, 1,4-tetramethylene diisocyanate, and the like, o Examples include araliphatic diisocyanates including xylene diisocyanate, m-xylene diisocyanate, and p-xylene diisocyanate, and alicyclic polyisocyanates including isophorone diisocyanate.

  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, and 1,4-butanediol. Examples of the low molecular weight polyamine (a3-2) include ethylenediamine, propylenediamine, and diethylenetriamine.

  The aqueous solvent can be a mixed solvent of an organic solvent containing N-methylpyrrolidone (NMP) and propylene glycol dimethyl ether (DMPDG) and water.

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

  Examples of the monomer (b1) include (meth) acrylic acid alkyl ester containing methyl (meth) acrylate and ethyl (meth) acrylate, (meth) acrylic acid alkoxyalkyl ester containing methoxybutyl (meth) acrylate and the like. , Aromatic vinyl compounds including styrene and α-methylstyrene, hydrolyzable silane group-containing vinyl compounds including vinyltriethoxysilane, and (meth) acrylamide compounds including N-methylolacrylamide.

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

  The polymer emulsifier (b3) may be a water-soluble resin, and a carboxyl group-containing polymer can be used. The carboxyl group-containing polymer is a homopolymer of a carboxy group-containing unsaturated monomer or a copolymer of a carboxy group-containing unsaturated monomer and another monomer. Examples of the carboxy group-containing unsaturated monomer include (meth) acrylic acid. Examples of the monomer copolymerizable with the carboxy group-containing unsaturated monomer include those similar to the monomer (b).

  The emulsion resin may be a commercially available water-dispersed resin. Examples of the above-mentioned commercially available water-dispersed resins include acrylic resin water dispersions SE841E and SE1658 (manufactured by Taisei Fine Chemical Co., Ltd.), polyester resin water dispersions Vironal MD1200, Vironal MD1245, and Vironal MD2000 (all of which are Toyobo Co., Ltd.). And “Vylonal” are registered trademarks of the company, and Superflex 210 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., “Superflex” is a registered trademark of the company) is a polyurethane resin aqueous dispersion.

  The average particle diameter of the anionic resin emulsion is preferably 10 nm or more and 200 nm or less, and more preferably 30 nm or more and 100 nm or less. The average particle size of the emulsion can be a volume average particle size determined using a particle size distribution measuring apparatus based on a dynamic light scattering method.

  The solid content of the emulsion in the water-based ink is preferably 0.01% by mass or more and 0.1% by mass or less based on the total mass of the metal nanoparticles and the polymer dispersant. When the solid content is 0.01% by mass or more, the abrasion resistance of the formed image can be further improved. When the solid content is 0.1% by mass or less, the glitter (reflectance) of the formed image can be further increased. From the above viewpoint, the solid content of the emulsion in the water-based ink is more preferably 0.02% by mass or more and 0.1% by mass or less, and 0.03% by mass or more and 0.1% by mass or less. It is more preferable.

2-3-4 Surfactant Examples of the surfactant that the metal ink composition may contain include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates and fatty acid salts, polyoxyethylene, and the like. Nonionic surfactants such as alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols and polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts As well as silicone and fluorine surfactants.

  Examples of commercially available silicone surfactants include KF-351A, KF-352A, KF-642 and X-22-4272, manufactured by Shin-Etsu Chemical, BYK307, BYK345, BYK347 and BYK348, manufactured by Big Chemie ("BYK "Is a registered trademark of the same company), as well as TSF4452, manufactured by Toshiba Silicone.

  The content of the surfactant can be, for example, 0.001% by mass or more and less than 1.0% by mass relative to the total mass of the ink composition.

2-4 Solvent The second pretreatment liquid and the metal ink in the ink set are water-based liquids and contain water as a solvent. The solvent may optionally contain a known organic solvent for viscosity adjustment and the like.

  Examples of organic solvents include polyhydric alcohols, polyhydric alcohol derivatives, alcohols, amides, ketones, keto alcohols, ethers, nitrogen-containing solvents, sulfur-containing solvents, propylene carbonate, ethylene carbonate, and 1,3-dimethyl-2- Includes imidazolidinone. Examples of the polyhydric alcohol include glycerin, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, hexylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, trimethylolpropane, 1, 3-butanediol, 1,5-pentanediol, 1,2,6-hexanetriol and the like are included. Examples of the polyhydric alcohol derivatives include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol-n-propyl. Ether, diethylene glycol-n-butyl ether, diethylene glycol-n-hexyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol-n-propyl ether, triethylene glycol-n-butyl ether, propylene glycol monomethyl ether, Propylene glycol monoethyl ether, propylene Recall-n-propyl ether, propylene glycol-n-butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol-n-propyl ether, dipropylene glycol-n-butyl ether, tripropylene glycol monomethyl ether, Examples include tripropylene glycol monoethyl ether, tripropylene glycol-n-propyl ether, and tripropylene glycol-n-butyl ether. Examples of the alcohol include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, and benzyl alcohol. Examples of the amide include dimethylformamide, dimethylacetamide and the like. Examples of the ketone include acetone. Examples of the keto alcohol include diacetone alcohol. Examples of the ether include tetrahydrofuran, dioxane and the like. Examples of the nitrogen solvent include pyrrolidone, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, and triethanolamine. Examples of the sulfur-containing solvent include thiodiethanol, thiodiglycol, thiodiglycerol, sulfolane, dimethyl sulfoxide, and the like. These organic solvents may be used individually by 1 type, and may be used in combination of 2 or more type.

  From the viewpoint of suppressing nozzle clogging due to drying of the second pretreatment liquid or metal ink in the vicinity of the nozzle during ejection from the inkjet head, the organic solvent preferably contains a polyhydric alcohol. At this time, the content of the polyhydric alcohol in the second pretreatment liquid or the metal ink is preferably 1% by mass or more and 10% by mass or less with respect to the total mass of the aqueous ink.

  In addition, the content of the organic solvent in the second pretreatment liquid or the metal ink is preferably 20% by mass to 50% by mass with respect to the total mass of the aqueous ink, and is preferably 30% by mass. More preferably, it is 50 mass% or less.

2-5 Physical Properties The viscosity of the first pretreatment liquid, the second pretreatment liquid, and the metal ink is preferably 1 cP or more and less than 100 cP from the viewpoint of further improving the discharge stability from the nozzles of the inkjet head. It is more preferably 1 cP or more and 50 cP or less, and further preferably 1 cP or more and 15 cP or less.

  From the viewpoint of enhancing the ejection stability from the nozzles of the inkjet head, the surface tensions of the first pretreatment liquid, the second pretreatment liquid, and the metal ink are preferably 20 mN / m or more and 50 mN / m or less. From the viewpoint of improving the wettability with respect to the substrate and making the formed image higher definition, the surface tension of the water-based ink is more preferably 20 mN / m or more and 35 mN / m or less.

3 Image Forming Method An image forming method according to another embodiment of the present invention is an exemplary image forming method for forming the above-mentioned image formed product, and is a first pretreatment liquid containing a hydrophilic monomer on a substrate. A step of curing the applied first pretreatment liquid by irradiation of actinic rays, and a flocculant and an interface on the surface of the cured film obtained by curing the first pretreatment liquid. A step of applying a second pretreatment liquid containing an activator, and a step of applying a metal ink containing metal nanoparticles to the region of the substrate to which the second pretreatment liquid has been applied by an inkjet method. Have.

3-1 Step of Applying First Pretreatment Liquid The method of applying the first pretreatment liquid is not particularly limited, and the first pretreatment liquid is applied to the surface of the substrate using a roll coater, a spin coater, or the like. The first pretreatment liquid may be applied to the surface of the base material by a method such as spray coating, dipping method, screen printing, gravure printing, offset printing, or the first method by an ink jet method. The pretreatment liquid may be landed on the surface of the substrate. Among these, the inkjet method is preferable from the viewpoint of forming a finer recorded matter.

  The amount of the first pretreatment liquid applied is not particularly limited, but it is preferably adjusted so that the film thickness of the underlayer is 10 μm or more and 40 μm or less, preferably 20 μm or more and 30 μm or less.

3-2 Step of Curing First Pretreatment Liquid The step of curing the first pretreatment liquid is performed by irradiation with actinic rays. The actinic ray is not particularly limited as long as the hydrophilic monomer can be cured, and includes α ray, γ ray, X ray, ultraviolet ray, visible ray, electron beam and the like.

3-3 Step for Applying Second Pretreatment Liquid The second pretreatment liquid is applied to the surface of the cured film formed by curing the first pretreatment liquid. Since the cured film is smooth, the second pretreatment liquid is applied to a smooth surface.

  The method for applying the second pretreatment liquid may be the same as the application of the first pretreatment liquid.

The amount of the second pretreatment liquid is not particularly limited and can be adjusted as appropriate. For example, when the flocculant is a polyvalent metal salt, the amount of the polyvalent metal salt is preferably 0.1 g / m ² or more and 20 g / m ² or less. When the aggregating agent is an acid, the amount of acid is preferably equal to or less than the neutralization equivalent of the anion component in the metal ink.

3-4 Step of Applying Metal Ink by Inkjet Method Metal ink is applied to the region to which the second pretreatment liquid has been applied by the inkjet method.

  The metallic ink is applied so as to form an image having gradation by changing the density of dots for each region. For example, although the metal ink is not particularly limited, it is preferable that the position where each droplet reaches is adjusted by a systematic dither method or an error diffusion method.

3-5 Others The substrate may be dried after application of the second treatment liquid or after application of the metal ink. Drying can be performed by known methods such as infrared lamp drying, hot air drying, back heat drying, and reduced pressure drying. From the viewpoint of further increasing the efficiency of drying, the substrate may be dried by combining two or more of these drying methods.

  The drying may be performed both after the application of the second treatment liquid and after the application of the metal ink. However, from the viewpoint of more sufficiently aggregating the water-based ink with the second pretreatment liquid, the application of the pretreatment liquid is performed. It is preferable that drying is not performed later, and drying is performed insufficiently (to the extent that moisture remains), and after the metal ink is applied, it is preferably dried completely.

  The on-demand method or the continuous method may be used as the discharge method from the ink jet head by the ink jet method. On-demand inkjet heads include electro-mechanical conversion systems such as single cavity type, double cavity type, bender type, piston type, shear mode type and shared wall type, as well as thermal inkjet type and bubble jet. Any of electric-thermal conversion methods such as Canon Inc. (registered trademark) type may be used.

  According to the above-described method, since the metal ink is applied to the surface smoothed by the application and curing of the first pretreatment liquid, an ink layer in which dots with smoother surface shapes are gathered is formed. Can do. In addition, the contact angle of the metal ink droplet is reduced by the surfactant, and further, the pinning property is imparted to the metal ink droplet by the flocculant adhered by the underlayer formed by polymerization of the hydrophilic monomer. For this reason, it is considered that an ink layer in which dots having the above-described shape are assembled is formed.

Hereinafter, specific examples of the present embodiment will be described together with comparative examples. However, the technical scope of the present invention is not limited only to the following examples.
(Example 1)

1 Preparation of metal ink 1-1 Preparation of metal nanoparticle dispersion (silver nanoparticle dispersion 1)
Into a 1 L separable flask having a flat stirring blade and baffle plate, 8.6 g of DISPERBYK-190 (manufactured by Big Chemie) and 269 g of ion-exchanged water were added and stirred to dissolve DISPERBYK-190. . Subsequently, 55 g of silver nitrate dissolved in 269 g of ion exchange water was added to the separable flask while stirring. Furthermore, 70 g of 30% aqueous ammonia was added and stirred, and then the separable flask was placed in a water bath and heated and stirred until the temperature of the solution was stabilized at 80 ° C. Thereafter, 144 g of dimethylaminoethanol was added to the separable flask, and the mixture was further stirred for 6 hours while maintaining at 80 ° C. to obtain a reaction solution containing silver nanoparticles.

  The obtained reaction liquid was put into a stainless steel cup, and 2 L of ion exchange water was further added, and then the pump was operated to perform ultrafiltration. When the solution in the stainless cup decreased, ion-exchanged water was added again, and purification was repeated until the filtrate had a conductivity of 100 μS / cm or less. Thereafter, the filtrate was concentrated to obtain a silver nanoparticle dispersion 1 having a solid content of 30 wt%.

  The ultrafiltration device used was an ultrafiltration module AHP1010 (manufactured by Asahi Kasei Co., Ltd., molecular weight cut off: 50000, number of membranes used: 400), and a tube pump (manufactured by Masterflex) connected by a Tygon tube. .

  The obtained silver nanoparticle dispersion was observed by SEM, and the volume average particle diameter of the nanoparticles was determined. Specifically, the procedure was as follows.

1) After applying the dispersion on a glass plate, vacuum degassing was performed to volatilize the solvent component to obtain a sample. The obtained sample dispersion was subjected to SEM observation using a scanning electron microscope JSM-7401F (manufactured by JEOL Ltd.), and the particle diameters of arbitrary 300 silver nanoparticles were measured.
2) Based on the obtained measurement data, the image processing software Image J was used to obtain a volume-based particle size distribution, and D50 (median diameter) was defined as an average particle diameter (volume average particle diameter) in terms of volume.

  According to the result of the above measurement, the average particle diameter of the silver nanoparticles in the silver nanoparticle dispersion 1 was 20 nm.

(Silver nanoparticle dispersion 2)
In the preparation of silver nanoparticle dispersion 1, silver nanoparticle dispersion was performed in the same manner except that the amount of silver nitrate added was changed to 70 g, DISPERBYK-190 was changed to 7.6 g, ammonia water was changed to 89 g, and dimethylaminoethanol was changed to 183 g. Liquid 2 was obtained.

  In the same manner as in the silver nanoparticle dispersion liquid 1, the average particle diameter of silver nanoparticles in the silver nanoparticle dispersion liquid 2 was determined. As a result, the average particle size was 50 nm.

(Gold nanoparticle dispersion 1)
As the gold nanoparticles, a commercially available particle dispersion (manufactured by Sigma-Aldrich, Gold nanoparticles) was used. In the same manner as in the silver nanoparticle dispersion 1, the average particle size of the gold nanoparticles in the gold nanoparticle dispersion was determined. As a result, the average particle size was 50 nm.

1-2 Preparation of Resin Emulsion (Resin Emulsion 1)
In a flask equipped with a dehydrator, 10 parts by mass of terephthalic acid as an acid component, 190 parts by mass of isophthalic acid and 170 parts by mass of adipic acid, 32 parts by mass of ethylene glycol and 510 parts by mass of neopentyl glycol as glycol components After adding 0.2 parts by mass of tetraisopropyl titanate as a reaction catalyst, polyester glycol 1 was obtained by performing a condensation reaction at 220 ° C. until the acid value became 1.0 or less and the water content became 0.05% or less.

  In a four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen blowing tube, 488 parts by mass of the polyester glycol 1 obtained above, 13 parts by mass of trimethylolpropane, 88 parts by mass of dimethylolpropionic acid, 252 parts by mass of isophorone diisocyanate and 670 parts by mass of methyl ethyl ketone were added and reacted at 75 ° C. for 4 hours to obtain a methyl ethyl ketone solution of a urethane prepolymer. This solution was cooled to 40 ° C. and neutralized by adding 40 parts by mass of triethylamine. Thereafter, 1850 parts by mass of ion-exchanged water was gradually added, emulsified and dispersed using a homogenizer, and stirred for 1 hour. The solvent was removed at 50 ° C. under reduced pressure, and ion-exchanged water was further added to obtain a resin emulsion 1 made of polyurethane having a nonvolatile content of about 20%. It was 40 nm when the average particle diameter of the obtained resin particle was measured similarly to the said silver nanoparticle dispersion liquid 1.

1-3 Preparation of metal ink (silver nanoparticle-containing ink M1)
Using the silver nanoparticle dispersion 1 and the emulsion resin dispersion 1 obtained as described above, the mixture was mixed with the following composition to prepare a silver nanoparticle-containing ink M1.
Silver nanoparticle dispersion 1 5 parts by weight Resin emulsion 1 0.35 parts by weight Water 59.2 parts by weight Propylene glycol 10 parts by weight Triethylene glycol monomethyl ether 25.4 parts by weight Surfactant (BYK-348: manufactured by Big Chemie) 0.1 parts by mass

(Silver nanoparticle-containing ink M2)
In preparing the silver nanoparticle-containing ink M1, a silver nanoparticle-containing ink M2 was prepared in the same manner except that the silver nanoparticle dispersion 2 was used instead of the silver nanoparticle dispersion 1.

(Gold nanoparticle-containing ink M3)
In preparing the silver nanoparticle-containing ink 1, a metal nanoparticle-containing ink M3 was similarly prepared except that the gold nanoparticle dispersion 1 was used instead of the silver nanoparticle dispersion 1.

2 Preparation of first pretreatment liquid The following were used as monomers, surfactants, and initiators contained in the first pretreatment liquid.

2-1 Monomer The following monomers were used.
4HBA (Osaka Organic Chemical Industry Co., Ltd.): 4-hydroxybutyl acrylate HPA (Osaka Organic Chemical Industry Co., Ltd.): hydroxypropyl acrylate A-BPE-30 (Shin Nakamura Chemical Co., Ltd.): Ethoxylated bisphenol A di Acrylate-A600 (manufactured by Shin-Nakamura Chemical Co., Ltd.): Polyethylene glycol # 600 diacrylate-ACMO (manufactured by KJ Chemicals): acryloylmorpholine-HEAA (manufactured by KJ Chemicals): hydroxyethylacrylamide-Aron DA (manufactured by Toagosei Co., Ltd.) ): Dimethylaminoethyl acrylate A-DCP (manufactured by Shin-Nakamura Chemical Co., Ltd.): Tricyclodecane dimethanol diacrylate M360 (manufactured by Miramer): Trimethylolpropane triacrylate APG-200 (Shin-Nakamura Chemical Co., Ltd.) ): Tripropylene glycol diacrylate · MPD-A (manufactured by Kyoeisha Chemical Co., Ltd.): 3-methyl-1,5-pentanediol diacrylate

2-2 Surfactant The following surface conditioner was used as the surfactant.
・ BYK-307 (by Big Chemie)

2-3 Initiator The following initiator was used.
IRGACURE819 (manufactured by BASF): bis (2,4,6-trimethylbenzoyl-phenylphosphine oxide)

2-4 Composition of first pretreatment liquid According to the composition described in Table 1 below, after the monomer, surfactant and initiator were mixed, the mixed solution was heated at 80 ° C. for 1 hour, and then ADVANTEC Teflon (“ Teflon was filtered through a DuPont 3 μm membrane filter to prepare first pretreatment liquids P1 to P11.

3 Preparation of second pretreatment liquid 3-1 Flocculant The following flocculants were used in the second pretreatment liquid.
PAA-05 (manufactured by Toyobo Co., Ltd.): polyallylamine Unisense KHP10P (manufactured by Senka): dicyandiamide-diethylenetriamine condensate Malonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.)
・ Kachio Master PD-7 (manufactured by Yokkaichi Gosei Co., Ltd.): Amine / Epichlorohydrin condensation polymer

3-2 Composition of second pretreatment liquid (second pretreatment liquid Q1)
In order to obtain the 2nd pretreatment liquid Q1, it mixed by the following compositions and obtained the mixed solution.
PAA-05 5 parts by mass Water 59.5 parts by mass Propylene glycol 10 parts by mass Triethylene glycol monomethyl ether 25.4 parts by mass Surfactant (BYK-348: manufactured by BYK Chemie) 0.1 part by mass

  The obtained mixed solution was heated at 80 ° C. for 1 hour and then filtered through a 3 μm membrane filter manufactured by ADVANTEC (“Teflon” is a registered trademark of DuPont) to obtain a second pretreatment solution.

(Second pretreatment liquid Q2)
A second pretreatment liquid Q2 was prepared in the same manner as in the preparation of the second pretreatment liquid Q1, except that Unisense KHP10P was used instead of PAA-05.

(Second pretreatment liquid Q3)
In preparing the second pretreatment liquid Q1, a second pretreatment liquid Q3 was prepared in the same manner except that malonic acid was used instead of PAA-05.

(Second pretreatment liquid Q4)
A second pretreatment liquid Q4 was prepared in the same manner as in the preparation of the second pretreatment liquid Q1, except that Kathiomaster PD-7 was used instead of PAA-05.

4 Production of Glossy Image Formation 4-1 Substrate Images were formed on the following substrates using the metal ink prepared above, the first pretreatment liquid, and the second pretreatment liquid.
・ OK top coat paper (128g / m2) (Oji Paper Co., Ltd.)
・ POD matte coated paper (128 g / m2) (Oji Paper Co., Ltd.)

4-2 Preparation conditions of image-formed product Using an inkjet recording apparatus having a piezo-type inkjet nozzle, recording on a recording medium (base material) was performed. The ink supply system was composed of an original tank, supply piping, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head, and heat insulation and heating were performed from the ink supply tank to the inkjet head portion. The temperature sensor is provided in the vicinity of the ink supply tank and the nozzle of the inkjet head, respectively, and the nozzle portion is 80 ° C. ± 2 ° C. when using the first pretreatment liquid that is UV-based ink, and metal ink that is water-based ink When the second pretreatment liquid was used, temperature control was performed at 25 ° C. ± 2 ° C. The piezo-type inkjet head was driven under the conditions that the droplet amount was 14 pL, the printing speed was 0.5 m / sec, the ejection frequency was 10.5 kHz, and the printing rate was 60% to 100% and changed every 10%. After landing of the first pretreatment liquid that is UV-based ink, UV light is condensed to an exposure surface illuminance of 1200 mW / cm ² , and irradiation is performed 0.1 seconds after the first pretreatment liquid has landed on the recording medium. The exposure system, main scanning speed and injection frequency were adjusted to begin.

  Further, the exposure time was variable, and exposure energy was irradiated. An LED lamp (manufactured by GS Yuasa Corporation) was used as the ultraviolet lamp.

  In the drying process, the IR heater is dried after the first pretreatment liquid is discharged and exposed, the IR heater is dried after the second pretreatment liquid is discharged, and the IR is dried after the metal ink is discharged. Heater drying was performed.

  Using the metal inks M1 to M3 prepared above, the first pretreatment liquids P1 to P11, and the second pretreatment liquids Q1 to Q4, an image is formed on any of the substrates under the image forming conditions. did. Driving was performed at a printing rate of 60% to 100% under conditions that change every 10% / cm to form gradation image portions (image formations 1 to 18) of 5 cm × 5 cm.

  Under the above conditions, a gradation image formed product was formed by the following procedure.

  First, the first pretreatment liquid was subjected to inkjet discharge / UV irradiation on the substrate to obtain a cured film. Next, the second treatment liquid was ejected by inkjet onto the surface of the obtained cured film, and the second pretreatment liquid was applied to the surface of the cured film. Finally, a gradation image formed product was obtained by ink-jetting metal ink to the region to which the second pretreatment liquid was applied.

5 Evaluation The gradation image formation 1 to the image formation 18 were evaluated according to the following criteria, and the results are shown in Table 2.

5-1 Appearance Evaluation The produced gradation image formations 1 to 18 are placed on a flat plate having an illuminance of 1000 lux in a room where a natural fluorescent lamp (FLR40S / N-SDN / M; manufactured by Panasonic) is installed. Arranged. Then, the produced gradation image formation 1 to image formation 18 were observed by 20 people extracted at random, and evaluated according to the following criteria.
(Double-circle): All 20 people evaluated that it was glossy and the gradation image was visible even if the printing rate was 60%.
○: 18 to 19 out of 20 people evaluated that there was glossiness even when the printing rate was 60% and a gradation image could be seen.
Δ: 1 to 17 out of 20 people evaluated that there was glossiness even when the printing rate was 60% and that a gradation image could be seen.
X: It was evaluated that 0 out of 20 people had glossiness even when the printing rate was 60% and a gradation image could be seen.

5-2 Δ1
Select any 5 dots of gradation image with 60% coverage, and etch the metallic luster layer with focused ion beam (FIB) (2050SMI, manufactured by SII), and transmission electron microscope (TEM) (2010F, JEOL Ltd.) Made by cross-section TEM observation. The surface of the dot-like metallic luster layer is obtained for a 5 dot difference Δ1 between the maximum value and the minimum value of the vertical dot height within a range having a radius of ¼ of the dot diameter from the center of the dot, The average value was calculated.

5-3 Film thickness of ink layer The film thickness of the ink layer was measured in the same manner using the above apparatus.

  As apparent from Table 2 above, in the image formed products 1 to 14 having Δ1 of 20 nm or less, the appearance evaluation was excellent.

  The image formed product of the present invention has high gloss visibility while having gloss. Therefore, the present invention is expected to expand the range of application of glittering recorded materials and contribute to the advancement and spread of technology in the same field.

Claims (11)

A substrate;
An underlayer formed on the surface of the substrate;
An ink layer formed in contact with the base layer,
The ink layer is a collection of a plurality of dots including metal nanoparticles having a thickness of 100 nm or more,
In the plurality of dots, the average value of the maximum value Δ1 of the difference in dot height in an area having a radius of ¼ of the dot diameter defined in the direction from the dot center to the dot periphery is 20 nm or less. .   2. The image-formed product according to claim 1, wherein the plurality of dots have an average value of a maximum value Δ1 of the difference in dot height of 15 nm or less.   The image forming product according to claim 1, wherein the plurality of dots have an average dot diameter of 45 μm or more and 55 μm or less.   The image formation product according to claim 1, wherein the underlayer includes a polymer of a hydrophilic monomer.   The image formed product according to claim 1, wherein the metal nanoparticles are particles having an average particle diameter of 100 nm or less.   The image-formed product according to claim 1, wherein the metal nanoparticles are silver nanoparticles.   The image formed article according to any one of claims 1 to 6, which is an image formed article having gradation. A first pretreatment liquid containing a hydrophilic monomer;
A second pretreatment liquid comprising a flocculant and a surfactant;
A metal ink comprising metal nanoparticles and water;
Including ink set. Providing a first pretreatment liquid containing a hydrophilic monomer on a substrate;
Curing the applied first pretreatment liquid by irradiation with actinic rays;
Applying a second pretreatment liquid containing a flocculant and a surfactant to the surface of the cured film obtained by curing the first pretreatment liquid;
Applying a metal ink containing metal nanoparticles to the region to which the second pretreatment liquid has been applied on the substrate by an inkjet method;
An image forming method.   The image forming method according to claim 9, wherein the first pretreatment liquid is applied onto the substrate by an inkjet method.   The image forming method according to claim 9 or 10, wherein the second pretreatment liquid is applied to the surface of the cured film by an inkjet method.