JP7367672B2 - Image forming method - Google Patents

Description

The present invention relates to an image forming method.

BACKGROUND ART Aluminum pigments, pearl pigments, and the like are used for the purpose of imparting metallic luster to recorded materials such as labels, packages, printed publications, and photographs. These pigments are applied as ink compositions onto a substrate by analog printing techniques, including offset printing, gravure printing, screen printing, and the like, to form areas in the imaged product that develop a metallic luster color.

In recent years, nano-sized particles containing metals such as gold, silver, and copper (hereinafter also simply referred to as "metal nanoparticles") have been used to create recorded materials with higher definition areas that emit metallic luster colors. A method has been developed for forming a metallic luster layer containing the metal nanoparticles on the surface of the substrate by applying the metal nanoparticles to the surface of the substrate.

Further, Patent Document 1 describes a method of forming a plurality of metallic lusters having different degrees of gloss on one image formed object in one printing process using an inkjet method. According to Patent Document 1, an ink composition discharged by an inkjet method is deposited on a base material to change the arithmetic roughness (Ra) of the base material surface for each region, thereby roughening the surface to a different degree for each region. It is said that by attaching a glossy ink composition containing tabular particles to a base material that has been coated, it is possible to develop different degrees of gloss in each region.

Japanese Patent Application Publication No. 2010-030139

According to the method described in Patent Document 1, as the amount of the ink composition (precoat agent) applied to the surface of the substrate increases, the surface of the substrate becomes rougher, and the glossiness of the image formed product decreases. It is said that then. However, metallic luster has various degrees of luster, from bright luster to dull luster, and even if the glossiness is changed using the method described in Patent Document 1, the various degrees of luster mentioned above cannot be sufficiently reproduced. I couldn't get enough of it.

Furthermore, in the method described in Patent Document 1, in which the surface of the base material is roughened, the degree of gloss can only be changed according to the thickness of one dot, and the image that can be formed by the image forming apparatus is It is not possible to fine-tune the roughness of the base material surface more finely than the resolution of . Therefore, when it is desired to further finely adjust the surface roughness, there is no choice but to use a base material with fine surface roughness. However, when trying to adjust the surface roughness by changing the base material, it is not possible to change the gloss for each area in the image. Thus, conventionally, it has been difficult to form an image-formed product in which the gloss is minutely changed in the image.

The present invention was made in view of the above-mentioned problems, and it is possible to form an image-formed product that is capable of expressing a more diverse range of metallic luster, and in which the gloss is minutely changed in images formed on the surface of the same base material. The purpose is to provide a possible image forming method.

One form of the present invention for solving the above problems includes a step of applying a precoat agent to the surface of a base material to form a precoat layer, and applying a glitter ink containing a glitter pigment to the surface of the precoat layer by inkjet jetting. A method of forming an image includes a step of forming an ink layer formed by aggregation of dots formed by the glitter ink. In the above method, the thickness of the precoat layer or the ink layer corresponding to one dot included in the ink layer, and the thickness of the precoat layer or the ink layer corresponding to another dot included in the ink layer. and, with different thicknesses, the height of the peak of the brightness or reflection intensity of the reflected light reflected by the formed image and the height of the baseline, the area containing the one dot and the area containing the other dot. and have different values.

Another form of the present invention for solving the above problem is to apply a glitter ink containing a glitter pigment to the surface of a base material by an inkjet method, and to collect dots formed by the glitter ink. A method for forming an image includes the steps of: forming an ink layer consisting of an ink layer; and applying an overcoat agent to the surface of the dots constituting the ink layer to form an overcoat layer. In the above method, the thickness of the ink layer and the overcoat layer corresponds to one dot included in the ink layer, and the thickness of the ink layer and the overcoat layer corresponds to another dot included in the ink layer. The film thickness and the height of the peak of the brightness or reflection intensity of the reflected light reflected by the formed image and the size of the half width of the peak are determined by the area containing the one dot and the other The value is different for the area containing the dots.

ADVANTAGE OF THE INVENTION The present invention provides an image forming method that is capable of expressing a more diverse range of metallic luster and that can form an image formed product in which the gloss is minutely changed in images formed on the surface of the same base material.

FIG. 1A is a schematic diagram showing how a part of the incident light incident on an object becomes specularly reflected light and the other part becomes diffusely reflected light, and FIG. 1B shows the state of FIG. FIG. 2 is a schematic diagram illustrating a graph of distribution information in which the light receiving angle (θ) is plotted on the vertical axis and the lightness (L ^* ) is plotted on the vertical axis. FIG. 2 is a flowchart of an image forming method according to the first embodiment of the present invention. FIG. 3 is a flowchart of an image forming method according to the second embodiment of the present invention. FIG. 4 is a flowchart of another image forming method according to the second embodiment of the present invention.

The present inventors have conducted extensive studies in view of the above-mentioned problems, and found that the gloss perceived from an image-formed object is determined by the specular reflection component and the diffuse reflection component when perceiving the light reflected by the image-formation object. It was found that it is influenced by the contribution that contributes to

That is, compared to ordinary colors, glossy colors reflect more of the light incident on an object in a directionally manner as specularly reflected light. Therefore, there is a large directivity in the spatial distribution of the light that is reflected and perceived by the glossy color, and it is thought that this directivity has a large influence on the tone of the glossy color that a person visually perceives.

Specifically, the degree of gloss of an object perceived by an observer is determined by the degree to which the brightness or reflection intensity of the reflected light that is incident on the object is concentrated at the angle of regular reflection ( (directionality of spatial distribution). As shown in Figure 1A, incident light I that has entered an object becomes light P that is partly specularly reflected, and light B that is partly diffusely reflected. The brightness or reflection intensity of light B is determined by the distance from point L where incident light I enters (the length of the solid arrow indicating specularly reflected light P and the length of the dashed arrow indicating diffusely reflected light B). Note that the brightness or reflection intensity of light P and light B has been adjusted for ease of understanding, and does not accurately reflect the brightness or reflection intensity that is actually measured and calculated.)

Figure 1B shows the distribution information of brightness or reflection intensity (reflectance or brightness) based on data of multiple different light receiving angles and the radiation intensity measured at the light receiving angles, and the light receiving angle is plotted on the horizontal axis. , is a graph in which brightness or reflection intensity is plotted on the vertical axis. At this time, the directivity of the spatial distribution is expressed by the peak height (H), baseline height (B), and peak half-width (W) in the distribution information shown in FIG. 1B. Glossiness can also be expressed by the peak height (H), baseline height (B), and peak half width (W). For example, the greater the difference between the peak height (H) and the baseline height (B), the stronger the perceived gloss, and the smaller the half width (W) of the peak, the sharper the perceived gloss. According to the above findings, if an image is formed so that the height (H) of the peak, the height (B) of the baseline, and the half-width (W) of the peak are changed, the perceived The gloss applied can also be varied accordingly.

According to further studies by the present inventors, in an image formed product having a precoat layer and an ink layer containing a glittering pigment, by independently changing the thickness of the precoat layer and the ink layer, , the peak height (H) and the baseline height (B) can be varied. In addition, in an image formed product having a precoat layer, an ink layer containing a glitter pigment, and an overcoat layer, by independently changing the thickness of the overcoat layer, the peak height (H) and The half width (W) of the peak can be further changed.

The present invention was made based on the above new findings, and by independently changing the film thicknesses of the precoat layer, ink layer, and overcoat layer, the height (H) of the peak and the baseline The height (B) and the half width (W) of the peak are changed, thereby changing the gloss perceived from the formed image.

1. First Embodiment In the first embodiment of the present invention, a precoat layer is formed on the surface of a base material using a precoat agent, and a glitter ink containing a glitter pigment is applied to the surface of the precoat layer. The present invention relates to an image forming method for forming a layer. The pre-coat agent may be any water-based, solvent-based, or actinic radiation-curable pre-coat agent, but by curing the pre-coat agent before it wets and spreads too much, the film thickness can be easily controlled and the film thickness can be reduced. From the viewpoint of making it easier to increase the thickness, it is preferable to use an actinic ray-curable precoat agent that can form a plurality of layers by repeating the step of applying it to the surface of the base material and curing it. The glitter ink may be any ink such as a water-based ink, a solvent-based ink, or an actinic radiation-curable ink, but from the viewpoint of suppressing the reduction in gloss caused by the inclusion of components other than the glitter pigment in the ink layer. It is preferable that the ink be a water-based ink.

The method of applying the precoating agent is not particularly limited, and the precoating agent may be applied to the surface of the base material using a roll coater, a spin coater, etc., or may be applied by spray coating, dipping, screen printing, gravure printing, offset printing, etc. The precoat agent may be applied to the surface of the base material by a method such as printing, or the precoat agent may be applied to the surface of the base material using an inkjet method. Among these, from the viewpoint of forming finer recorded matter, screen printing and inkjet methods are preferred, and inkjet methods are more preferred.

On the other hand, the glitter ink is applied to the surface of the precoat layer by an inkjet method. Thereafter, dots formed with the glitter ink are formed by drying the glitter ink to remove the liquid component, or by applying actinic rays to the glitter ink and curing the glitter ink. An ink layer is formed by aggregation of the ink.

At this time, by independently changing the film thickness of the precoat layer or ink layer formed by the applied precoat agent or glitter ink for each dot constituting the ink layer, the gloss of the image formed object can be improved. Change each dot independently. In this way, the film thickness of the precoat layer (specifically, the portion of the precoat layer located directly under the one dot) or the ink layer corresponding to one dot included in the ink layer is determined. , the thickness of the precoat layer corresponding to other dots included in the ink layer (specifically, the portion of the precoat layer located directly below the other dots) or the thickness of the ink layer is different. By setting the peak height (H) and the baseline height (B) in the distribution information to different values between the area containing the one dot and the area containing the other dot, Different degrees of gloss can be perceived from each of the regions. By applying the glitter ink by an inkjet method, it is possible to change the thickness of the ink layer for each dot and form an image in which the perceived gloss is changed with higher precision. Furthermore, if a precoat agent is also applied by an inkjet method, it is possible to change the thickness of the precoat layer for each dot, thereby forming an image in which the perceived gloss is changed with even higher precision. Note that the one dot and the other dots are included in an ink layer formed on the same surface of the same base material. At that time, it is also possible to form an image having a fine gloss gradation by forming an area formed by a plurality of the above-mentioned dots and an area formed by a plurality of other dots adjacent to each other. It is.

Specifically, the thickness of the precoat layer is determined by the solid content concentration (concentration of resin, etc.) in the precoat agent, the number of times the precoat agent is applied to form the precoat layer, and the thickness of the precoat agent discharged from the nozzle of the inkjet head. It can be adjusted by the size of the droplets (droplet amount) and the number of droplets applied for each dot (droplet number) when applying the droplets to the surface of the base material. For example, by changing the number of times the precoat layer is formed or the droplet volume and number of droplets for each area in the image, the thickness of the precoat layer can be changed for each corresponding dot included in the ink layer. can. In addition, the film thickness of the ink layer is determined by the size (droplet volume) of the glitter ink droplets discharged from the nozzle of the inkjet head and the solid content of the glitter ink when the droplets are applied to the surface of the precoat layer. It can be adjusted by adjusting the concentration (concentration of bright pigment, fixing resin, etc.).

The amount of droplets of the pre-coat agent (when applied by inkjet method) or glitter ink is preferably adjusted within the range of 0.5 pl or more and 50 pl or less, in order to form a high-definition image. is more preferably adjusted in the range of 0.5 pl or more and 20 pl or less, and even more preferably adjusted in the range of 0.5 pl or more and 10 pl or less.

The number of droplets of the pre-coat agent (when applied by inkjet method) is preferably adjusted within the range of 0 to 10 drops, more preferably adjusted within the range of 0 to 5 drops. .

In addition, when forming an embossed image, etc., the number of droplets of the precoat agent applied by the inkjet method is adjusted in the range of 0 to 5 drops, and the precoat applied by the inkjet method. By forming in an image an area in which the number of agent droplets is adjusted within the range of 6 to 10, minute irregularities can be formed in the image.

The driving frequency when ejecting the pre-coat agent (when applied by an inkjet method) or glitter ink from the nozzle of an inkjet head is preferably adjusted in the range of 5kHz or more and 100kHz, and adjusted in the range of 5kHz or more and 20kHz. It is more preferable that

Note that when forming an image that includes multiple areas with different densities, the number of dots formed per unit area included in each area can be increased by changing the driving frequency independently for each area. It may be changed. Increasing the driving frequency to increase the number of dots formed per unit area will result in the formation of areas with lower density, and decreasing the driving frequency to increase the number of dots formed per unit area. A smaller value creates a more dense region.

In addition, the base material is not particularly limited, and includes art paper, coated paper, lightweight coated paper, coated paper including slightly coated paper and cast paper, and absorbent media including uncoated paper, polyester, polyvinyl chloride, Non-absorbent recording media (plastic substrates) composed of plastics containing polyethylene, polyurethane, polypropylene, acrylic resin, polycarbonate, polystyrene, acrylonitrile-butadiene-styrene copolymer, polyethylene terephthalate and polybutadiene terephthalate, as well as metals and It can be a non-absorbing inorganic recording medium such as glass. Among these, substrates with low surface smoothness (substrates with rough surfaces), such as the above-mentioned absorptive media, have conventionally been difficult to align glitter pigments, resulting in a significantly large amount of diffuse reflection components. Therefore, it was difficult to adjust the degree of gloss. However, according to the present embodiment, even with such a base material with low surface smoothness, the diffuse reflection component can be adjusted by adjusting the surface smoothness, and the degree of gloss can be easily adjusted.

In this embodiment, the above distribution information is obtained by independently changing the thickness of the precoat layer to which the precoat agent is applied and the thickness of the ink layer to which the glittering ink is applied, each dot by dot. The peak height (H) and baseline height (B) are changed for each dot.

Specifically, in the case of a substrate with a low surface smoothness such as the above-mentioned absorbent medium, the roughness of the surface of the substrate can be adjusted to make it smoother by increasing the thickness of the precoat layer. This makes it easier to arrange the bright pigments more densely, increasing the specular reflection component to raise the peak height (H), and decreasing the diffuse reflection component to raise the baseline height (B). You can adjust the gloss to lower it.

The thickness of the precoat layer may be set for each area (or for each dot included in the area) depending on the degree of gloss to be formed in each area of the image formed object. In addition, in the case of a substrate with a low surface smoothness such as the above-mentioned absorbent medium, it is preferable to adjust the amount of the precoat agent applied so that the precoat layer does not completely cover the surface of the substrate. In this way, in the area containing the one dot or the other dot, the precoat layer does not completely cover the surface of the substrate, but exposes a part of the surface of the substrate. The peak height (H) and baseline height (B) can be adjusted over a wider range by adjusting the roughness of the base material surface with the precoat layer while leaving some of the original surface roughness. be able to.

In addition, by increasing the thickness of the ink layer, the amount of glittering pigment contained in the dots can be increased, and the peak height (H) and base height (B) can be adjusted to be higher. I can do it.

The thickness of the ink layer may be set for each dot included in the area according to the degree of gloss to be formed in each area of the image formed object.

The thickness of the precoat layer and ink layer depends on the composition of the precoat agent and glitter ink, as well as the time from when the actinic ray-curable precoat agent is discharged and lands on the substrate surface to when it is irradiated with actinic rays. , etc. can also be changed. Based on these conditions, the amounts of the precoat agent and glitter ink to be applied may be adjusted so as to obtain the desired level of gloss.

According to the method described in Patent Document 1, by changing the amount of the ink composition (precoat agent) applied to the surface of the substrate and changing the surface roughness of the substrate, multiple areas with different glossiness can be formed. can be formed on an image-formed article. Specifically, it is said that as the amount of the ink composition applied increases, the surface of the substrate becomes rougher and the glossiness of the image-formed product decreases. However, the applicable substrates of this method are almost limited to substrates with smooth surfaces (for example, resin sheets made of vinyl chloride, etc.). On a substrate with a rough surface such as a paper substrate, the amount of the ink composition applied does not necessarily correspond to the glossiness of the image formed, and it is impossible to form an image with the desired gloss. In contrast, according to the present invention, it is possible to form an image having a desired level of gloss, regardless of the surface roughness of the base material.

Furthermore, in the method described in Patent Document 1, in which the surface of the base material is roughened, the degree of gloss can only be changed according to the thickness of one dot, and the image that can be formed by the image forming apparatus is It is not possible to fine-tune the roughness of the base material surface more finely than the resolution of . Therefore, when it is desired to further finely adjust the surface roughness, there is no choice but to use a base material with fine surface roughness. However, when trying to adjust the surface roughness by changing the base material, it is not possible to change the gloss for each area in the image. Thus, conventionally, it has been difficult to form an image-formed product in which the gloss is minutely changed in the image. In contrast, in the present invention, by changing the film thickness of each layer, it is possible to more finely adjust the gloss. Furthermore, according to the present invention, since it is possible to control the expression of metallic luster without relying solely on the surface roughness of the base material, it is possible to express different metallic lusters on surfaces with the same surface roughness, or to express different metallic lusters on surfaces with the same surface roughness. It becomes possible to express the same metallic luster on the surface.

1-1. Precoat Agent The precoat agent may be an ink composition that can be applied to the surface of the base material to form a layer on the surface.

For example, when the precoat agent is a water-based ink, it can contain water, a resin, and optionally a water-soluble organic solvent. Moreover, when the precoat agent is a solvent-based ink, it can contain an organic solvent and a resin. Further, when the precoating agent is an actinic ray-curable ink, it can contain a photopolymerizable compound that polymerizes and crosslinks upon irradiation with actinic rays, and optionally a photopolymerization initiator.

The precoating agent may further contain a surfactant, a polymerization inhibitor, an ultraviolet absorber, and the like, if necessary. The above-mentioned other components may be contained in the precoat agent alone or in combination of two or more.

The precoat agent is applied to the surface of the base material and cured from the viewpoint of making it easier to control the film thickness by curing the precoat agent before it wets and spreads too much, and also making it easier to increase the film thickness. Preferably, it is an actinic radiation-curable precoating agent that can form a plurality of layers by repeating the process.

Examples of the water-soluble organic solvent when the precoating agent is a water-based ink include alcohols including methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol and t-butanol, ethylene glycol, diethylene glycol, and triethylene. Glycols, including polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, and pentanediol, glycerin, hexanetriol, thiodiglycol, 1,2-butanediol, 1,3-butanediol, 1 , 2-pentanediol, 1,2-hexanediol and 1,2-heptanediol, polyhydric alcohols, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine Amines, including formamide, N,N-dimethylformamide and N,N-dimethylacetamide, 2 - Heterocyclic compounds including pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone and 1,3-dimethyl-2-imidazolidinone, sulfoxides including dimethyl sulfoxide, and ethylene glycol monomethyl ether, ethylene glycol mono Ethyl ether, ethylene glycol monobutyl ether, ethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol monomethyl Ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol diethyl ether , ethylene glycol monomethyl acetate, ethylene glycol monoethyl acetate, ethylene glycol monobutyl acetate, diethylene glycol monomethyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol mono Included are glycol ethers including ethyl ether acetate, diethylene glycol monoethyl acetate, diethylene glycol monobutyl acetate, and triethylene glycol monobutyl ether.

When the precoat agent is a water-based ink, the content of the water-soluble organic solvent can be, for example, 5.0% by mass or more and 30% by mass or less based on the total mass of the precoat agent.

In addition, when applying a precoating agent to a substrate by an inkjet method, from the viewpoint of suppressing the occurrence of nozzle clogging due to drying of the water-based ink near the nozzle during ejection from the inkjet head, the water-soluble organic solvent is Preferably, it contains a polyhydric alcohol. At this time, the content of polyhydric alcohol in the precoat agent is preferably 1% by mass or more and 10% by mass or less based on the total mass of the precoat agent.

Examples of the resin when the precoating agent is a water-based ink include polyester resins, polyurethane resins, acrylic resins, polyurethane-acrylic resins, vinyl chloride resins, and vinyl acetate resins. The resin may be a latex that is dispersed in the ink to form a dispersion, or a soluble resin (water-soluble resin or organic solvent-soluble resin) that dissolves in the ink with water or an organic solvent. Good too.

When the precoat agent is a water-based ink, the content of the resin can be, for example, 1% by mass or more and 20% by mass or less based on the total mass of the precoat agent as a solid content. The content of the resin may be adjusted depending on the thickness of the precoat layer formed by one application and the thickness of the precoat layer formed by one liquid applied by an inkjet method. .

Examples of the organic solvent when the precoating agent is a solvent-based ink include water-soluble organic solvents and water-insoluble organic solvents that can be used in the water-based ink.

Examples of the water-insoluble organic solvent include aliphatic hydrocarbons having 5 to 15 carbon atoms, including pentane, hexane, i-hexane, heptane, i-heptane, octane, i-octane, and decane, and cyclopentane. , cyclohexane, methylcyclohexane, dimethylcyclohexane, ethylcyclohexane, cycloheptane, and alicyclic hydrocarbons containing 5 to 15 carbon atoms, cyclohexene, cycloheptene, cyclooctene, 1,1,3,5,7 - Cyclic unsaturated hydrocarbons having 5 to 15 carbon atoms, including cyclooctatetraene and cyclododecene, and 6 to 12 carbon atoms, including benzene, toluene, ethylbenzene, cumene, o-xylene, m-xylene, and p-xylene. The following aromatic hydrocarbons, heptanol, hexanol, methylhexanol, ethylhexanol, heptanol, octanol, decanol, undecyl alcohol, and monohydric alcohols with 5 to 15 carbon atoms, including lauryl alcohol, methyl-i-butyl ketone , di-i-butyl ketone, cyclohexanone, methylcyclohexanone, cycloheptanone, and alicyclic ketones having 5 to 15 carbon atoms, including cyclooctanone, methyl acetate, ethyl acetate, propyl acetate, i-propyl acetate, Butyl acetate, hexyl acetate, amyl acetate, i-amyl acetate, 2-ethylhexyl acetate, methyl propionate, ethyl propionate, butyl propionate, hexyl propionate, amyl propionate, ethyl valerate, ethyl hexanoate, heptanoic acid Contains ethyl, ethyl octoate, ethyl decanoate, cyclohexyl acetate, cyclooctyl acetate, phenyl acetate, phenyl propionate, methyl benzoate, ethyl benzoate, butyl benzoate, dimethyl phthalate, diethyl phthalate, and dibutyl phthalate. Includes ester compounds, nitro compounds including nitroethane, nitropropane, nitropentane, nitrobenzene, dinitrobenzene, nitrotoluene, and nitroxylene, nitriles including acetonitrile, benzonitrile, and lactones including γ-butyrolactone and ε-caprolactone. It will be done.

When the precoat agent is a solvent-based ink, the content of the water-insoluble organic solvent can be, for example, 1.0% by mass or more and 98% by mass or less, based on the total mass of the precoat agent, and 20% by mass. It is more preferably 95% by mass or less, and even more preferably 40% by mass or more and 90% by mass or less.

Examples of the resin when the precoat agent is a solvent-based ink include polyester resins, polyurethane resins, acrylic resins, polyurethane-acrylic resins, vinyl chloride resins, and vinyl acetate resins. The resin may be a latex that is dispersed in the ink to form a dispersion, or a soluble resin (water-soluble resin or organic solvent-soluble resin) that dissolves in the ink with water or an organic solvent. Good too.

When the precoat agent is a solvent-based ink, the content of the resin can be, for example, 1% by mass or more and 20% by mass or less based on the total mass of the precoat agent as a solid content. The content of the resin may be adjusted depending on the thickness of the precoat layer formed by one application and the thickness of the precoat layer formed by one liquid applied by an inkjet method. .

Examples of the photopolymerizable compound when the precoating agent is an actinic radiation curable ink include radically polymerizable compounds and cationic polymerizable compounds. The photopolymerizable compound may be a monomer, a polymerizable oligomer, a prepolymer, or a mixture thereof.

The radically polymerizable compound is preferably an unsaturated carboxylic acid ester compound, and more preferably a (meth)acrylate. In addition, in this specification, "(meth)acrylate" means acrylate or methacrylate, "(meth)acrylic" means acrylic or methacryl, and "(meth)acryloyl" means acryloyl or methacryloyl. means.

Examples of monofunctional (meth)acrylates include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomylstyl (meth)acrylate, isostearyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate ) acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxy Ethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethylsuccinic acid, 2-(meth)acryloyloxyethyl phthalate The acids include 2-(meth)acryloyloxyethyl-2-hydroxyethyl-phthalic acid and t-butylcyclohexyl (meth)acrylate.

Examples of polyfunctional (meth)acrylates include triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate. (meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, Dimethylol-tricyclodecane di(meth)acrylate, PO adduct di(meth)acrylate of bisphenol A, neopentyl hydroxypivalate glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, polyethylene glycol diacrylate and Bifunctional (meth)acrylates including tripropylene glycol diacrylate, as well as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate , ditrimethylolpropane tetra(meth)acrylate, glycerin propoxytri(meth)acrylate, and pentaerythritol ethoxytetra(meth)acrylate.

The radically polymerizable compound preferably contains (meth)acrylate modified with ethylene oxide or propylene oxide (hereinafter also simply referred to as "modified (meth)acrylate"). Modified (meth)acrylates have higher photosensitivity. Furthermore, modified (meth)acrylates are more easily compatible with other components even at high temperatures. Furthermore, since modified (meth)acrylates have less curing shrinkage, printed matter is less likely to curl when irradiated with actinic light.

Examples of cationically polymerizable compounds include epoxy compounds, vinyl ether compounds, and oxetane compounds.

Examples of the above epoxy compounds include 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene monoepoxide, ε-caprolactone-modified 3, 4-Epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate, 1-methyl-4-(2-methyloxiranyl)-7-oxabicyclo[4,1,0]heptane, 2-(3,4 - cycloaliphatic epoxy resins such as epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexanone-meta-dioxane and bis(2,3-epoxycyclopentyl) ether, diglycidyl ether of 1,4-butanediol , diglycidyl ether of 1,6-hexanediol, triglycidyl ether of glycerin, triglycidyl ether of trimethylolpropane, diglycidyl ether of polyethylene glycol, diglycidyl ether of propylene glycol, ethylene glycol, propylene glycol, and glycerin. Aliphatic epoxy compounds including polyglycidyl ethers of polyether polyols obtained by adding one or more alkylene oxides (such as ethylene oxide and propylene oxide) to aliphatic polyhydric alcohols, and bisphenol A or Di- or polyglycidyl ethers of alkylene oxide adducts thereof, di- or polyglycidyl ethers of hydrogenated bisphenol A or its alkylene oxide adducts, and aromatic epoxy compounds including novolak-type epoxy resins.

Examples of the vinyl ether compounds include ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl Monovinyl ether compounds, including ether-o-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether, as well as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether , butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, trimethylolpropane trivinyl ether, and the like.

Examples of the oxetane compounds include 3-hydroxymethyl-3-methyloxetane, 3-hydroxymethyl-3-ethyloxetane, 3-hydroxymethyl-3-propyloxetane, 3-hydroxymethyl-3-n-butyloxetane, -Hydroxymethyl-3-phenyloxetane, 3-hydroxymethyl-3-benzyloxetane, 3-hydroxyethyl-3-methyloxetane, 3-hydroxyethyl-3-ethyloxetane, 3-hydroxyethyl-3-propyloxetane, 3 -Hydroxyethyl-3-phenyloxetane, 3-hydroxypropyl-3-methyloxetane, 3-hydroxypropyl-3-ethyloxetane, 3-hydroxypropyl-3-propyloxetane, 3-hydroxypropyl-3-phenyloxetane, 3 -Hydroxybutyl-3-methyloxetane, 1,4bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane and di[1- Includes ethyl(3-oxetanyl)]methyl ether and the like.

The content of the photopolymerizable compound in the precoat agent can be, for example, 1.0% by mass or more and 97% by mass or less, and 30% by mass or more and 90% by mass or less based on the total mass of the precoat agent. It is preferable.

The precoat agent may further contain a photopolymerization initiator. The photopolymerization initiator may be any one as long as it can initiate polymerization of the photopolymerizable compound. For example, when the precoat agent has a radically polymerizable compound, the photopolymerization initiator can be a radical photoinitiator, and when the precoat agent has a cationic polymerizable compound, the photopolymerization initiator can be a photocationic initiator ( photoacid generator).

The content of the photopolymerization initiator can be arbitrarily set within a range where curing of the precoat agent is initiated by irradiation with actinic rays, and for example, 0.1% by mass with respect to the total mass of the precoat agent. The content can be 20% by mass or less, preferably 1.0% by mass or more and 12% by mass or less. Note that the photopolymerization initiator is not necessary when curing of the precoat agent is started even without the photopolymerization initiator, such as when semi-curing the precoat agent by irradiation with an electron beam.

The precoat agent may contain components that precipitate or aggregate the glitter pigment contained in the glitter ink, such as polyvalent metal ions and polyvalent organic acids. These components can precipitate or aggregate the glitter pigment in the glitter ink to further stabilize the dot diameter of the glitter ink.

When applying a precoat agent to a substrate by an inkjet method, from the viewpoint of further increasing the stability of ejection from the nozzle of an inkjet head, the viscosity of the precoat agent is preferably 1 cP or more and less than 100 cP, and 1 cP or more and 50 cP or less. More preferably, it is 1 cP or more and 15 cP or less.

1-2. Glittering Ink The glittering ink may be any ink composition that contains a glittering pigment and can be ejected by an inkjet method.

For example, when the glitter ink is a water-based ink, it can contain water and optionally a water-soluble organic solvent. Furthermore, when the glitter ink is a solvent-based ink, it can contain an organic solvent. Furthermore, when the glitter ink is an actinic ray-curable ink, it can contain a photopolymerizable compound that polymerizes and crosslinks upon irradiation with actinic rays, and optionally a photopolymerization initiator. The types and contents of the water, water-soluble organic solvent, organic solvent, photopolymerizable compound, and photopolymerization initiator that the glitter ink may contain may be the same as those of the precoat agent described above.

The glitter ink further contains a dispersant for dispersing the glitter pigment, a fixing resin for fixing the glitter pigment to the base material, a surfactant, a polymerization inhibitor, an ultraviolet absorber, etc., as necessary. May be contained. The above-mentioned other components may be contained in the glitter ink alone or in combination of two or more.

The above-mentioned glitter pigment may be any known pigment used to give an image gloss, such as an aluminum pigment or a pearl pigment, but from the viewpoint of aligning the pigments and controlling light reflection more precisely , metal particles are preferred.

The metal particles are particles whose main component is metal, and are not particularly limited as long as they can exhibit metallic luster. Examples of metals that make up the metal particles include gold, silver, copper, nickel, palladium, platinum, aluminum, zinc, chromium, iron, cobalt, molybdenum, zirconium, ruthenium, iridium, tantalum, mercury, indium, tin, and lead. , and tungsten. Among these, gold, silver, copper, nickel, cobalt, tin, lead, chromium, zinc and aluminum are preferred because they can produce high gloss and are inexpensive; gold, silver, copper, and tin are preferred. , chromium, lead and aluminum are more preferred, gold and silver are even more preferred, and silver is particularly preferred. These metals can be used alone or as an alloy or mixture of two or more. Furthermore, two or more types of metal particles having different metal types or compositions may be used in combination. The metal particles may have these metals as their main components, may also contain small amounts of other unavoidable components, or may be surface-treated with citric acid or the like to improve dispersion stability. good. Moreover, these metals may contain oxides.

The average particle diameter of the metal particles is not particularly limited, but from the viewpoint of increasing dispersion stability and storage stability in the metal ink, and from the viewpoint of increasing the visibility of gradation, the average particle diameter of the metal particles is nano-sized. Certain metal nanoparticles are preferred. The average particle diameter of the metal particles is preferably 3 nm or more and 100 nm or less, more preferably 5 nm or more and 80 nm or less, even more preferably 10 nm or more and 60 nm or less, and particularly preferably 15 nm or more and 55 nm or less. .

The average particle diameter of the metal particles is determined by observing the metal particle dispersion using a SEM and determining the volume average particle diameter of the nanoparticles. Specifically, the measurement is carried out by the following procedure.

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

The content of metal nanoparticles in the glitter ink is not particularly limited, but it is preferably 0.5% by mass or more and 15% by mass or less based on the total mass of the glitter ink, and 0.75% by mass or more.12. It is more preferably 5% by mass or less, and even more preferably 1% by mass or more and 10% by mass or less.

The dispersant may be used as long as it can sufficiently disperse the glitter pigment. In particular, when the glitter pigment is a metal nanoparticle, the dispersant is preferably a polymer dispersant.

The polymer dispersant is a compound that has an adsorption group that can be adsorbed onto the surface of the metal nanoparticles and a hydrophilic structure. Examples of the adsorption groups include carboxyl groups and thiol groups.

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

Examples of hydrophilic monomers include monomers containing carboxyl or acid anhydride groups (such as (meth)acrylic acid, unsaturated polycarboxylic acids such as maleic acid, and maleic anhydride), as well as alkylene oxide-modified (meth) ) Acrylic acid ester monomers (ethylene oxide-modified (meth)acrylic acid alkyl esters, etc.). In the present invention, (meth)acrylic means both or either of acrylic and methacryl.

Examples of hydrophobic monomers include (meth)acrylate monomers such as methyl (meth)acrylate and ethyl (meth)acrylate, styrenic 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 polymeric dispersant is a copolymer, it can 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 metal nanoparticles, the polymer dispersant is preferably a comb-shaped block copolymer.

A comb-shaped block copolymer means a copolymer containing a linear polymer forming a main chain and another type of polymer graft-polymerized to a constitutional unit derived from a monomer forming the main chain. Preferred examples of the comb-shaped block copolymer include a main chain containing a structural unit derived from (meth)acrylic acid ester, and a long side chain containing a polyalkylene oxide group (such as an ethylene oxide-propylene oxide copolymer group). comb-shaped block copolymers containing chain polyalkylene oxide groups). The comb-shaped block copolymer can suppress aggregation of metal nanoparticles to a higher degree because the graft-polymerized side chains cause steric hindrance. This increases the dispersibility of the metal nanoparticles, making it easier to suppress discharge failures due to agglomerated metal nanoparticles.

The content of the polymer dispersant in the glitter ink is not particularly limited, but from the viewpoint of sufficiently increasing the dispersibility of the metal nanoparticles in the glitter ink and the adhesion to the base material, the content of the metal nanoparticles is not particularly limited. 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 even more preferably 3% by mass or more and 8% by mass or less, based on the total mass.

Examples of the fixing resin include (meth)acrylic resin, epoxy resin, polysiloxane resin, maleic acid resin, vinyl resin, polyamide resin, nitrocellulose, cellulose acetate, ethylcellulose, ethylene-vinyl acetate copolymer, urethane resin, Includes polyester resins and alkyd resins.

Among these, the fixing resin should be an anionic resin emulsion from the viewpoint of interacting with the polymer dispersant adsorbed on the surface of the metal nanoparticles and increasing the adhesion of the metal nanoparticles to the base material. is preferred.

The anionic resin is preferably a resin that has high affinity with the polymer dispersant, such as (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 (e.g. styrene-butadiene copolymer, styrene-(meth)acrylate copolymer, etc.), and vinyl acetate It can be appropriately selected and used from copolymers (eg, ethylene-vinyl acetate copolymers, etc.). From the viewpoint of further increasing the water resistance of the formed image, the above-mentioned anionic resins include (meth)acrylic resins, urethane resins, polyolefin resins, polyvinyl chloride resins, epoxy resins, polysiloxane resins, fluororesins, and styrene copolymers. The resin is preferably selected from polyurethane resins, vinyl acetate copolymers, and vinyl acetate copolymers, and is preferably selected from urethane resins and (meth)acrylic resins.

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

The solid content of the emulsion in the glitter 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 brightness (reflectance) of the formed image can be further improved. From the above viewpoint, the solid content of the emulsion in the glitter 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 that there be.

Examples of the above-mentioned surfactants include anionic surfactants including dialkyl sulfosuccinates, alkylnaphthalene sulfonates and fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols and Includes nonionic surfactants including oxyethylene polyoxypropylene block copolymers, cationic surfactants including alkylamine salts and quaternary ammonium salts, silicone surfactants, and fluorine surfactants. It will be done.

The content of the surfactant is preferably 0.001% by mass or more and less than 1.0% by mass based on the total mass of the glitter ink.

From the viewpoint of further increasing the reflectance of the ink layer, the glitter ink consists essentially of metal nanoparticles to which the polymer dispersant is adsorbed, an emulsion of the anionic resin and a solvent, and optionally a required amount of surfactant. It is preferable to consist of. The total content of the metal nanoparticles to which the polymer dispersant is adsorbed, the emulsion of the anionic resin, and the solvent is preferably 90% by mass or more and 100% by mass or less based on the total mass of the glitter ink, More preferably, it is 95% by mass or more and 100% by mass or less.

From the viewpoint of further enhancing ejection stability from the nozzles of the inkjet head, the viscosity of the glitter ink is preferably 1 cP or more and less than 100 cP, more preferably 1 cP or more and 50 cP or less, and 1 cP or more and 15 cP or less. is even more preferable.

1-3. Image Forming Method FIG. 2 is a flowchart of the image forming method according to this embodiment. In this embodiment, a precoat layer is formed in contact with the surface of the base material using the above precoat agent (step S110), and an ink layer is formed in contact with the surface of the precoat layer formed using the above glitter ink. (Step S120).

1-3-1. Formation of precoat layer (step S110)
First, the precoat agent is applied to the surface of a base material to form a precoat layer.

For example, droplets of the precoating agent are ejected from a nozzle of an inkjet head onto the surface of a base material that is being transported and moved along a transport path. The ejected droplets land on the surface of the base material. Alternatively, a precoat agent is applied to the surface of the base material by a known method such as screen printing.

At this time, the film thickness of the pre-coat layer to be formed is determined by adjusting the thickness of the pre-coat layer in the area containing the corresponding dots included in the ink layer (specifically, the dots of the ink layer formed in contact with the relevant portion of the pre-coat layer). Adjust according to the desired gloss level. The thickness of the precoat layer is determined based on the relationship between the degree of gloss to be developed and the thickness of the precoat layer and ink layer to be formed, which is determined in advance according to the type of precoat agent and glitter ink used. This can be determined by referring to the obtained correspondence table. Alternatively, the thickness of the pre-coat layer can be determined by having a processing device using machine learning etc. calculate the relationship between the degree of gloss to be developed and the thickness of the pre-coat layer and ink layer to be formed. can do.

Specifically, when applying droplets of precoat agent discharged from the nozzle of an inkjet head to the surface of a substrate, the size of the droplets (droplet volume) and the number of droplets applied per dot (droplets) are determined. The thickness of the precoat layer to be formed may be adjusted by adjusting the number of droplets) or the number of times screen printing is repeated.

The conveyance speed of the base material is not particularly limited, but may be set, for example, between 1 m/s or more and 1000 m/s or less. The faster the conveyance speed is, the faster the image forming speed is.

When applying the precoating agent to the base material by an inkjet method, the ejection method from the inkjet head may be either an on-demand method or a continuous method. On-demand inkjet heads include electro-mechanical conversion methods 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 (bubble jet is Any electric-to-thermal conversion method such as the Canon Inc. (registered trademark) type may be used.

At this time, the temperature of the precoat agent to be discharged may be adjusted by heating the ink flow path. The temperature of the precoat agent to be discharged is not particularly limited, but is preferably 50°C or more and 90°C or less.

Further, by adjusting the ejection conditions of the precoat agent, the resolution of the image to be formed can also be adjusted. The resolution of the formed image can be 600 dpi or more and 1440 dpi or less, but from the viewpoint of forming a higher definition image, it is preferably 1200 dpi or more and 1440 dpi or less.

Thereafter, droplets of the precoat agent applied to the base material are irradiated with actinic rays or the precoat agent applied to the base material is dried to form a precoat layer in which the precoat agent is cured.

The actinic light is preferably ultraviolet light from an ultraviolet LED. A metal halide lamp is known as a general ultraviolet light source, but by using an ultraviolet LED as a light source, it is possible to suppress curing defects on the surface of the cured film due to melting of the cured film by the radiant heat of the light source. From the viewpoint of appropriately curing the droplets, the peak wavelength of the ultraviolet LED is preferably 385 nm or more and 400 nm or less. An example of a light source having an ultraviolet LED includes a water-cooled ultraviolet irradiation unit (peak wavelength: 395 nm) manufactured by Phoseon Technology.

The irradiation conditions of actinic rays can be appropriately set depending on the composition of the precoating agent and the like. For example, a light source having an ultraviolet LED is used so that the maximum illuminance on the surface of the droplet on the substrate is 0.5 W/cm ² or more and 10.0 W/cm ^{2 or} less, more preferably 1 W/cm ² or more and 5 W/cm ² or less. Just set it up so that it is.

1-3-2. Formation of ink layer (step S120)
Next, the glitter ink is applied dot by dot by an inkjet method to the surfaces of the dots on which the precoat agent constituting the precoat layer has been cured. After that, depending on the type of glitter ink, for example, if the glitter ink is water-based ink or solvent-based ink, the liquid component may be removed by drying, or if the glitter ink is actinic light-curable ink, the liquid component may be removed. The glitter ink is cured by irradiation with actinic light to form an ink layer in which dots formed by the glitter ink are aggregated. The drying conditions and the actinic ray irradiation conditions may be determined as appropriate depending on the composition of the glitter ink. For example, the irradiation conditions for the actinic rays may be the same as the conditions for curing droplets of the precoating agent.

Further, the ejection method from the inkjet head is not particularly limited, and may be the same as the conditions used when forming the precoat layer.

At this time, the thickness of the ink layer to be formed is adjusted depending on the degree of gloss to be exhibited in the area including the dots formed by the applied glitter ink. The thickness of the ink layer is determined in advance based on the relationship between the degree of gloss to be developed and the thickness of the precoat layer and ink layer to be formed, which is determined in advance according to the type of precoat agent and glitter ink used. This can be determined by referring to the obtained correspondence table. Alternatively, the thickness of the ink layer can be determined by having a processing device using machine learning etc. calculate the relationship between the degree of gloss to be developed and the thickness of the pre-coat layer and ink layer to be formed. can do.

Specifically, depending on the solid content concentration of the glitter ink, the size of the dots to be formed, etc., when applying droplets of the precoat agent discharged from the nozzle of the inkjet head to the surface of the base material, The thickness of the formed ink layer may be adjusted by changing the size of the droplets (droplet amount) and the number of droplets applied for each dot (droplet number).

Further, at this time, the amount of applied glitter ink may be adjusted so that the size of the dots formed by the applied glitter ink is approximately the same as the size of the dots formed by the precoat agent.

2. Second Embodiment In the second embodiment of the present invention, after forming a precoat layer and an ink layer in the same manner as in the first embodiment, the surface of the ink layer is overcoated with an overcoat agent. The present invention relates to an image forming method for forming a coat layer. The overcoat agent may be any type of overcoat agent, such as water-based, solvent-based, or actinic radiation-curable, but the film thickness can be easily controlled by curing the overcoat before the overcoat spreads too much. From the viewpoint of easily increasing the film thickness, it must be an actinic radiation-curable overcoat agent that can form multiple layers by repeating the process of applying it to the surface of the base material and curing it. is preferred.

The method of applying the overcoat agent is not particularly limited, and the overcoat agent may be applied to the surface of the ink layer using a roll coater, a spin coater, etc., or spray coating, dipping, screen printing, or gravure printing. The overcoat agent may be applied to the surface of the ink layer by a method such as offset printing, or the overcoat agent may be applied to the surface of the ink layer by an inkjet method. Among these, from the viewpoint of forming finer recorded matter, screen printing and inkjet methods are preferred, and inkjet methods are more preferred.

At this time, by independently changing the thickness of the overcoat layer formed by the applied overcoat agent for each dot, the gloss of the image formed material can be further changed independently for each dot. , it is possible to form an image whose gloss is changed with higher precision. In this way, the thickness of the overcoat layer (specifically, the portion of the overcoat layer located directly under the one dot) corresponding to one dot included in the ink layer, and the thickness of the overcoat layer corresponding to one dot included in the ink layer, By making the film thickness of the overcoat layer (specifically, the portion of the overcoat layer located directly below the other dots) different from that corresponding to the other dots included in the ink layer. , the peak height (H) and the peak half-width (W) in the distribution information are set to different values between the area containing the one dot and the area containing the other dot, and from each area. , different degrees of gloss can be perceived. Furthermore, by applying the overcoat agent by an inkjet method, it is also possible to change the thickness of the overcoat layer for each dot to form an image in which the perceived gloss is changed with higher precision.

Specifically, the film thickness of the overcoat layer is determined by the number of times the precoat agent is applied to form the precoat layer, as well as the number of times the overcoat agent is applied to the surface of the ink layer by droplets of the overcoat agent discharged from the nozzle of the inkjet head. can be adjusted by the size of the droplets (droplet amount) and the number of droplets applied for each dot (droplet number). For example, by changing the number of times the precoat layer is formed or the droplet volume and number of droplets for each area in the image, the thickness of the precoat layer can be changed for each corresponding dot included in the ink layer. can.

The amount of droplets of the overcoat agent (when applied by inkjet method) is preferably adjusted within a range of 0.5 pl or more and 50 pl or less, and in order to form a high-definition image, 0.5 pl or more is required. It is more preferable that the amount is adjusted within a range of 20 pl or less, and even more preferably within a range of 0.5 pl or more and 10 pl or less.

The number of droplets of the overcoat agent (when applied by inkjet method) is preferably adjusted within the range of 0 to 10 drops, more preferably adjusted within the range of 0 to 5 drops. preferable.

The driving frequency when ejecting the above-mentioned overcoat agent (when applied by an inkjet method) from a nozzle of an inkjet head is preferably adjusted in the range of 5kHz or more and 100kHz, and preferably adjusted in the range of 5kHz or more and 20kHz. is more preferable.

In this embodiment, the height (H) of the peak in the above distribution information is changed by independently changing the film thickness of the overcoat layer, which is formed by applying an overcoat agent and being cured by irradiation with actinic light, for each dot. and the half width (W) of the peak is changed for each dot.

Specifically, by increasing the thickness of the overcoat layer, the amount of specularly reflected light emitted from the dots can be reduced, and the gloss can be adjusted so as to slightly reduce the peak height (H). Furthermore, by increasing the thickness of the overcoat layer, the surface of the dots is adjusted to be rougher, making it difficult for the light emitted from the dots to concentrate on specularly reflected light, and increasing the half-width (W) of the peak. It can be adjusted to widen.

The thickness of the overcoat layer may be set depending on the degree of gloss to be formed by the dots.

The thickness of the overcoat layer can also be changed depending on the time from when the overcoat agent is ejected and lands on the substrate surface to when it is irradiated with actinic rays, the composition of the precoat agent and the glitter ink, etc. can. Based on these conditions, the amount of overcoat agent applied may be adjusted so as to obtain the desired level of gloss.

The overcoat layer may contain a non-glare coloring material. Non-glare colorants can be pigments or dyes known in the art used to form images exhibiting yellow, red or magenta, blue or cyan and black, and other distinctive colors. By containing a non-glitter coloring material in the overcoat layer, it is possible to impart a color to the formed gloss and to develop various gloss colors such as red silver, blue silver, and gold.

2-1. Precoat Agent and Overcoat Agent As the precoat agent and overcoat agent, the same ones as the precoat agent used in the first embodiment can be used, so a detailed explanation will be omitted.

Note that the precoat agent and overcoat agent used to form the same dot may have the same composition or may have different compositions from each other.

The overcoat agent may contain a non-glare coloring material.

The non-glitter coloring materials include non-glitter dyes and non-glitter pigments.

From the viewpoint of obtaining an image with good weather resistance, the non-glitter coloring material is preferably a non-glitter pigment. The non-glare pigment can be selected from, for example, a yellow pigment, a red or magenta pigment, a blue or cyan pigment, a green pigment, and a black pigment, depending on the color of the image to be formed. Pigments such as pink, green, and orange may also be used to form other special colors.

Examples of yellow pigments include C. I. Pigment Yellow (hereinafter also simply referred to as "PY") 1, PY3, PY12, PY13, PY14, PY17, PY34, PY35, PY37, PY55, PY74, PY81, PY83, PY93, PY94, PY95, PY97, PY108, PY109 , PY110, PY137, PY138, PY139, PY153, PY154, PY155, PY157, PY166, PY167, PY168, PY180, PY185, and PY193.
Examples of red or magenta pigments include C. I. Pigment Red (hereinafter also simply referred to as "PR") 3, PR5, PR19, PR22, PR31, PR38, PR43, PR48:1, PR48:2, PR48:3, PR48:4, PR48:5, PR49:1 , PR53:1, PR57:1, PR57:2, PR58:4, PR63:1, PR81, PR81:1, PR81:2, PR81:3, PR81:4, PR88, PR104, PR108, PR112, PR122, PR123 , PR144, PR146, PR149, PR166, PR168, PR169, PR170, PR177, PR178, PR179, PR184, PR185, PR208, PR216, PR226, and PR257, C. I. Pigment Violet (hereinafter also simply referred to as "PV") 3, PV19, PV23, PV29, PV30, PV37, PV50, and PV88, and C. I. Pigment Orange (hereinafter also simply referred to as "PO") 13, PO16, PO20, PO36, and the like.
Examples of blue or cyan pigments include C.I. I. Pigment Blue (hereinafter also simply referred to as "PB") 1, PB15, PB15:1, PB15:2, PB15:3, PB15:4, PB15:6, PB16, PB17-1, PB22, PB27, PB28, PB29 , PB36, and PB60.
Examples of green pigments include C. I. Pigment Green (hereinafter also simply referred to as "PG") 7, PG26, PG36, and PG50.
Examples of black pigments include C. I. Pigment Black (hereinafter also simply referred to as "PBk") 7, PBk26, and PBk28.

2-2. Glitter Ink The same glitter ink as the glitter ink used in the first embodiment can be used as the glitter ink, so a detailed explanation will be omitted.

2-3. Image Forming Method FIG. 3 is a flowchart of the image forming method according to this embodiment. In this embodiment, a precoat layer is formed in contact with the surface of the base material using the precoat agent (step S110), and an ink layer is formed in contact with the surface of the precoat layer using the glitter ink (step S120). ), and further, an ink layer is formed using the overcoat agent (step S130).

2-3-1. Formation of precoat layer (step S110)
Since the precoat layer can be formed in the same manner as in the first embodiment, detailed explanation will be omitted.

Note that at this time, the thickness of the precoat layer to be formed is adjusted depending on the degree of gloss that should be developed in the area containing the corresponding dots included in the ink layer. The thickness of the precoat layer is determined in advance according to the type of precoat agent, glitter ink, and overcoat agent used, and the degree of gloss to be developed and the precoat agent, glitter ink, and overcoat agent to be formed. This can be determined by referring to a correspondence table obtained in advance to determine the relationship between the amount of provision and the amount of . Alternatively, the thickness of the precoat layer can be determined by having a processing device using machine learning calculate the relationship between the degree of gloss to be developed and the thickness of the precoat agent, glitter ink, and overcoat agent to be formed. After that, it can be determined by calculating the amount of the precoat agent to be applied to form a precoat layer having the thickness.

Specifically, when applying droplets of precoat agent discharged from the nozzle of an inkjet head to the surface of a substrate, the size of the droplets (droplet volume) and the number of droplets applied per dot (droplets) are determined. The thickness of the precoat layer to be formed may be adjusted by adjusting the number of droplets) or the number of times screen printing is repeated.

2-3-2. Formation of ink layer (step S120)
Since the ink layer can also be formed in the same manner as in the first embodiment, detailed explanation will be omitted.

Note that, at this time, the thickness of the ink layer to be formed is adjusted depending on the degree of gloss to be exhibited in the area including the dots formed by the applied glitter ink. The thickness of the ink layer is determined in advance according to the type of precoat agent, glitter ink, and overcoat agent used, and the degree of gloss to be developed and the precoat agent, glitter ink, and overcoat agent to be formed. This can be determined by referring to a correspondence table obtained in advance to determine the relationship between the amount of provision and the amount of . Alternatively, the thickness of the ink layer can be determined by using a processing device that uses machine learning to calculate the relationship between the degree of gloss that should be developed and the thickness of the precoat agent, glitter ink, and overcoat agent that should be formed. After that, it can be determined by calculating the amount of the precoat agent to be applied to form a precoat layer having the thickness.

Specifically, depending on the solid content concentration of the glitter ink, the size of the dots to be formed, etc., when applying droplets of the precoat agent discharged from the nozzle of the inkjet head to the surface of the base material, The thickness of the formed ink layer may be adjusted by changing the size of the droplets (droplet amount) and the number of droplets applied for each dot (droplet number).

Further, at this time, the amount of applied glitter ink may be adjusted so that the size of the dots formed by the applied glitter ink is approximately the same as the size of the dots formed by the precoat agent.

2-3-3. Formation of overcoat layer (step S130)
Thereafter, the overcoat agent is applied to the surface of the dots formed by the glitter ink constituting the ink layer to form an overcoat layer.

At this time, the thickness of the overcoat layer to be formed is adjusted depending on the degree of gloss that should be expressed in the area containing the corresponding dots included in the ink layer. The thickness of the overcoat layer is determined in advance according to the type of precoat agent, glitter ink, and overcoat agent used, and the degree of gloss to be developed and the precoat agent, glitter ink, and overcoat to be formed. The relationship between the applied amount of the agent and the amount of the agent can be determined by referring to a correspondence table determined in advance. Alternatively, the thickness of the overcoat layer can be determined by using a processing device that uses machine learning to calculate the relationship between the degree of gloss that should be developed and the thickness of the precoat agent, glitter ink, and overcoat agent that should be formed. After that, it can be determined by calculating the amount of precoat agent to be applied to form a precoat layer having the thickness.

Specifically, when applying droplets of overcoat agent discharged from the nozzle of an inkjet head to the surface of a substrate, the size of the droplets (droplet amount) and the number of droplets applied for each dot ( The thickness of the overcoat layer formed may be adjusted by adjusting the number of droplets) or the number of times screen printing is repeated.

When applying the overcoat agent to the base material by an inkjet method, the ejection method from the inkjet head may be either an on-demand method or a continuous method. On-demand inkjet heads include electro-mechanical conversion methods 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 (bubble jet is Any electric-to-thermal conversion method such as the Canon Inc. (registered trademark) type may be used.

At this time, the temperature of the overcoat agent to be discharged may be adjusted by heating the ink flow path. The temperature of the overcoat agent to be discharged is not particularly limited, but is preferably 50°C or more and 90°C or less.

Further, by adjusting the discharge conditions of the overcoat agent, the resolution of the formed image can also be adjusted. The resolution of the formed image can be 600 dpi or more and 1440 dpi or less, but from the viewpoint of forming a higher definition image, it is preferably 1200 dpi or more and 1440 dpi or less.

After that, the droplets of the overcoat agent that landed on the surface of the ink layer are irradiated with actinic rays, or the precoat agent applied to the base material is dried, and the overcoat agent is cured to form an overcoat layer. form.

The actinic light is preferably ultraviolet light from an ultraviolet LED. A metal halide lamp is known as a general ultraviolet light source, but by using an ultraviolet LED as a light source, it is possible to suppress curing defects on the surface of the cured film due to melting of the cured film by the radiant heat of the light source. From the viewpoint of appropriately curing the droplets, the peak wavelength of the ultraviolet LED is preferably 385 nm or more and 400 nm or less. An example of a light source having an ultraviolet LED includes a water-cooled ultraviolet irradiation unit (peak wavelength: 395 nm) manufactured by Phoseon Technology.

The irradiation conditions of actinic rays can be appropriately set depending on the composition of the overcoat agent and the like. For example, a light source having an ultraviolet LED is used so that the maximum illuminance on the surface of the droplet on the substrate is 0.5 W/cm ² or more and 10.0 W/cm ^{2 or} less, more preferably 1 W/cm ² or more and 5 W/cm ² or less. Just set it up so that it is.

Note that in this embodiment, an image having a precoat layer, an ink layer, and an overcoat layer was formed, but depending on the gloss of the image to be formed, it may be possible to form an image having an ink layer and an overcoat layer without forming a precoat layer. An image may also be formed (see FIG. 4). At this time, by independently changing the thickness of the overcoat layer for each dot, the peak height (H) and peak half-width (W) in the above distribution information can be changed for each dot. .

Hereinafter, specific examples of the present invention will be described together with comparative examples, but the present invention is not limited thereto.

1. Preparation of glitter ink 1-1. Preparation of silver nanoparticle dispersion 8.6 g of DISPERBYK-190 (manufactured by BYK Chemie) and 269 g of ion-exchanged water were put into a 1 L separable flask equipped with a flat stirring blade and a baffle plate, and stirred. to dissolve DISPERBYK-190. Subsequently, 55 g of silver nitrate dissolved in 269 g of ion-exchanged water was charged into the separable flask with stirring. Further, 70 g of 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 stabilized at 80°C. Thereafter, 144 g of dimethylaminoethanol was added to the separable flask, and stirring was continued for 6 hours while maintaining the temperature at 80° C. to obtain a reaction solution containing silver nanoparticles.

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

The ultrafiltration device used was an ultrafiltration module AHP1010 (manufactured by Asahi Kasei Corporation, molecular weight cutoff: 50,000, number of membranes used: 400) and a tube pump (manufactured by Masterflex) connected with a Tygon tube. .

1-2. Preparation of emulsion resin particle dispersion In a flask equipped with a dehydrator, 10 parts by mass of terephthalic acid, 190 parts by mass of isophthalic acid and 170 parts by mass of adipic acid as acid components, and 32 parts by mass of ethylene as a glycol component. Glycol and 510 parts by mass of neopentyl glycol were charged, and after adding 0.2 parts by mass of tetraisopropyl titanate as a reaction catalyst, a condensation reaction was carried out at 220°C until the acid value was 1.0 or less and the water content was 0.05% or less. was carried out to obtain polyester glycol.

In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen blowing tube, 488 parts by mass of the polyester glycol obtained above, 13 parts by mass of trimethylolpropane, 88 parts by mass of dimethylolpropionic acid, and 252 parts by mass were added. 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 solution of urethane prepolymer in methyl ethyl ketone. This solution was cooled to 40°C, and 40 parts by mass of triethylamine was added thereto to neutralize it. 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 added to obtain an emulsion resin particle dispersion consisting of polyurethane with a non-volatile content of about 20%.

1-3. Preparation of Glitter Ink 1 to Glitter Ink 3 (Glitter Ink 1)
Glitter ink 1 was obtained by mixing the following components in the following composition.
Silver nanoparticle dispersion 5 parts by mass Emulsion resin particle dispersion 0.35 parts by mass Water 59.2 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 parts by mass

(Glitter ink 2)
Glitter Ink 2 was obtained in the same manner as Glitter Ink 1 except that the amount of silver nanoparticle dispersion was 2.5 parts by weight and the amount of emulsion resin particle dispersion was 0.18 parts by weight. .

(Glitter ink 3)
Glitter Ink 3 was obtained in the same manner as Glitter Ink 1 except that the amount of the silver nanoparticle dispersion was 1.2 parts by weight and the amount of the emulsion resin particle dispersion was 0.09 parts by weight. .

(Glitter ink 4)
Glitter ink 4 containing aluminum pigment was obtained by the method described in JP-A-2005-123456.

2. Preparation of precoat agent and overcoat agent (Precoat agent 1 and Overcoat agent 1)
Precoat agent 1 and overcoat agent 1 were obtained by mixing the following components in the following compositions. Precoat agent 1 and overcoat agent 1 have the same composition.
Polyethylene glycol #400 diacrylate 34 parts by weight 4EO-modified pentaerythritol tetraacrylate 23 parts by weight 6EO-modified trimethylolpropane triacrylate 31 parts by weight Photoinitiator (diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide (DAROCUR TPO, Manufactured by BASF))
7 parts by weight Sensitizing aid (p-dimethylaminobenzoic acid ethyl ester (Kayacure EPA, manufactured by Nippon Kayaku Co., Ltd.))
2 parts by weight Surfactant (KF-352: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.1 parts by weight

(Precoat agent 2)
Precoat agent 2 was obtained by mixing the following components in the following composition.
Polyester emulsion (manufactured by Toyobo Co., Ltd., Vylonal MD1500 (solid content 30 wt%))
17.5 parts by weight Triethylene glycol monomethyl ether 8 parts by weight Propylene glycol 2 parts by weight Water 12.5 parts by weight

(Overcoat agent 2)
9 parts by mass of Ajisper PB824 and 71 parts by mass of tripropylene glycol diacrylate were placed in a stainless steel beaker and heated and stirred for 1 hour on a hot plate at 65° C. to dissolve them.

After the solution was cooled to room temperature, 20 parts by mass of Pigment Yellow 180 (Chromofine Yellow 6280JC, manufactured by Dainichiseika Chemical Co., Ltd.) was added, and the mixture was placed in a glass bottle with 200 g of zirconia beads having a diameter of 0.5 mm and sealed. After dispersing this in a paint shaker for a predetermined time (pigment: 1:5 hours), the zirconia beads were removed to obtain a pigment dispersion.

12 parts by weight of the pigment dispersion obtained above was added to Overcoat Agent 1, heated to 80°C and stirred. The obtained solution was filtered with a Teflon (registered trademark) 3 μm membrane filter manufactured by ADVATEC under heating to obtain an overcoat agent 2.

3. Image formation 3-1. Substrate Images were formed on the following substrates.
Base material 1: OK top coat paper (surface roughness Ra: 0.25 μm)
Base material 2: Coated paper (surface roughness Ra: 0.43 μm)
Base material 3: PET film (surface roughness Ra: 0.05 μm)

3-2. Formation of Precoat Layer Precoat agent 1 or precoat agent 2 was loaded into an inkjet recording apparatus having an inkjet head equipped with a piezo type inkjet nozzle. The inkjet recording device had an ink tank, an ink supply pipe, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head, in this order from the upstream side where the ink flows to the downstream side. . Using an inkjet head with a droplet volume of 7 pl, the droplets of the precoat agent were ejected and landed on the substrate by driving at a printing speed of 0.5 m/sec and an ejection frequency of 10.5 kHz.

Regarding precoat agent 1, after landing, actinic light (395 nm, 8W/cm ² ) was irradiated from an LED lamp equipped with a water cooling unit manufactured by Phoseon Technology, and a precoat layer was formed by aggregating dots of the precoat agent. . The distance from the lamp to the surface of the precoat agent that landed was 20 mm.

Regarding precoat agent 2, after landing, it was dried at 60° C. for 1 minute to form a precoat layer in which dots of the precoat agent were cured.

At this time, the number of times the droplets of the precoat agent were ejected (the number of droplets) was varied between 0 and 7 times. When the number of times the droplets of the precoating agent were ejected (the number of droplets) was 0, irradiation with actinic light was not performed.

3-3. Formation of Ink Layer Any of the glittering inks 1 to 3 was loaded into the same inkjet recording device used when forming the precoat layer. Using an inkjet head with a droplet volume of 7 pl, driving at a printing speed of 0.5 m/sec and an injection frequency of 10.5 kHz, a droplet of glitter ink was ejected once and landed on the precoat layer. Ta.

After landing, the glitter ink was dried at 60° C. for about 10 minutes to form an ink layer made up of dots formed by the glitter ink.

3-4. Formation of Overcoat Layer Either of the above-mentioned Overcoat Agent 1 and Overcoat Agent 2 was loaded into the same inkjet recording device as that used when forming the above-mentioned precoat layer. Using an inkjet head with a droplet volume of 7 pl, the overcoat agent droplets were ejected and landed on the ink layer by driving at a printing speed of 0.5 m/sec and an ejection frequency of 10.5 kHz.

After landing, actinic light (395 nm, 8 W/cm ² ) was irradiated from an LED lamp equipped with a water cooling unit manufactured by Phoseon Technology, to form an overcoat layer consisting of aggregation of dots in which the overcoat agent had been cured. The distance from the lamp to the surface of the landed overcoat agent was 20 mm.

3-5. Conditions for forming each layer 3-5-1. Sample 1 to sample 4
Glitter ink 1 was used as the glitter ink, base material 1 was used as the base material, the thickness of the ink layer was fixed at 0.2 μm, and the ejection conditions of precoat agent 1 were set at 4 levels from 0 drop (not ejected) to 3 drops. Images were formed by changing the conditions, and Samples 1 to 4 were obtained, respectively.

3-5-2. Sample 5 ~ Sample 6
Sample 5 and Sample 6 were obtained in the same manner as Sample 3 except that Glitter Ink 2 and Glitter Ink 3 were used as the glitter ink and the thickness of the ink layer was changed.

3-5-3. Sample 7 ~ Sample 8
Sample 7 and Sample 8 were obtained in the same manner as Sample 3 except that Overcoat Agent 1 was used as the overcoat agent and the discharge conditions for the overcoat agent were 1 drop and 2 drops, respectively.

3-5-4. Sample 9 ~ Sample 10
Sample 9 and Sample 10 were obtained in the same manner as Sample 1 except that Overcoat Agent 1 was used as the overcoat agent and the discharge conditions for the overcoat agent were 1 drop and 2 drops, respectively.

3-5-5. Sample 11 ~ Sample 14
Samples 11 to 14 were obtained in the same manner as Samples 1 to 4, respectively, except that Base Material 2 was used as the base material.

3-5-6. Sample 15 to Sample 17
Samples 15 to 17 were obtained in the same manner as Samples 1 to 3, respectively, except that Base Material 3 was used as the base material.

3-5-7. Sample 18 ~ Sample 20
Images were formed adjacent to each other in the same manner as Samples 1 to 3 on three areas set on the same surface of the same base material (Substrate 1) to obtain gradation images. Of the three areas in which images were formed on the same base material, the area in which the image was formed in the same way as Sample 1 was Sample 18, the area in which the image was formed in the same manner as in Sample 2 was Sample 19, and the area in which the image was formed in the same way as Sample 3 was used. The area where the image was formed was designated as sample 20.

3-5-8. Sample 21 ~ Sample 23
Samples 21 to 23 were obtained in the same manner as Sample 2, Sample 3, and Sample 7, except that Glitter Ink 4 was used as the glitter ink.

3-5-9. Sample 24 ~ Sample 25
Samples 24 to 25 were prepared in the same manner as Sample 9 except that Overcoat Agent 2 was used as the overcoat agent, the discharge conditions for Precoat Agent 1 were 1 drop and 2 drops, and the discharge conditions for Overcoat Agent 2 were 2 drops. I got it.

3-5-10. sample 26
Sample 26 was obtained in the same manner as Sample 1 except that the discharge conditions for Precoat Agent 1 were 9 drops.

3-5-11. Sample 27 ~ Sample 28
Samples 27 and 28 were obtained in the same manner as Samples 5 and 6, respectively, except that the driving frequency was 21 kHz.

3-5-12. sample 29
Sample 29 was obtained in the same manner as Sample 1 except that a precoat layer having a thickness of 10 μm was formed by screen printing.

3-5-13. Sample 30 ~ Sample 31
Sample 30 and Sample 31 were obtained in the same manner as Sample 2 except that Precoat Agent 2 was used as the precoat agent and the discharge conditions for Precoat Agent 1 were 1 drop and 2 drops, respectively.

Note that samples 1 to 17 and samples 21 to 31 are samples in which each image is formed on the surface of a different base material, and one image is formed on one base material. Samples 18 to 20 are samples in which three images (samples) are formed on one base material by forming images in different areas set on the surface of one base material.

4. Evaluation The image in each sample was cut into a size of 15 mm x 50 mm. Using a variable angle photometer (manufactured by Murakami Color Research Institute Co., Ltd., product name GCMS-4), each gloss value measurement method sample was irradiated with incident light at an incident angle of 45° while changing the receiving angle. The reflection intensity from 0° to 50° was measured every 5°. The reflectance was calculated from the reflection intensity obtained at each light receiving angle, and a reflection spatial distribution profile showing the relationship between the light receiving angle and the reflectance was obtained.

The shape of the obtained spatial distribution profile of reflection is fitted to one Lorentz function, and the peak height (H), peak The half width (W) and the baseline height (B) were determined.

Tables 1 and 2 show the formation conditions and evaluation results for each sample. In Tables 1 and 2, "PC agent" refers to the type of precoat agent used for image formation, "ink" refers to the type of glitter ink used for image formation, and "OC agent" refers to the type of glitter ink used for image formation. The types of overcoat agents used are shown below.

By changing the film thickness of the precoat layer and the ink layer, the above-mentioned information on the distribution of brightness or reflection intensity with respect to the light reception angle obtained by measuring the reflected light obtained by reflecting the measurement light irradiated on the formed image. The peak height (H) and baseline height (B) of brightness or reflection intensity could be varied. Specifically, by changing the amount of precoat agent applied and increasing the thickness of the precoat layer formed, the height of the peak (H) in the above distribution information becomes higher and the height of the base (B) becomes higher. (Samples 1 to 4). In addition, by changing the solid content concentration of the glitter ink and increasing the thickness of the ink layer formed, the height of the peak (H) in the above distribution information will become higher and the height of the base (B) will become higher. (Sample 3, Sample 5, Sample 6).

Furthermore, by changing the thickness of the overcoat layer, it was possible to change the peak height (H) and half-width (W) of the brightness or reflection intensity peak in the distribution information. Specifically, by changing the amount of overcoat agent applied to increase the thickness of the overcoat layer formed, the height (H) of the peak in the above distribution information becomes lower and the half width (W) of the peak decreases. ) could be made wider. This tendency was the same when a precoat layer was formed (Sample 3, Sample 7, Sample 8) and when a precoat layer was not formed (Sample 1, Sample 9, Sample 10).

Note that even if images are similarly formed on substrates with different surface roughnesses Ra, if the amount of applied precoat agent is changed to increase the thickness of the precoat layer formed, the height of the peak in the above distribution information will increase. (H) higher and the base height (B) lower (Samples 11 to 17).

Furthermore, by forming a plurality of adjacent regions with different thicknesses of the precoat layer in different regions included on the same surface of the same base material, it is possible to form a plurality of adjacent regions with different gloss. Completed (sample 18 to sample 20).

In addition, when using not only metal nanoparticles but also known aluminum pigments, increasing the thickness of the precoat layer formed will increase the peak height (H) in the above distribution information and increase the base height. (B) can be lowered (Sample 21, Sample 22), and by increasing the thickness of the overcoat layer formed, the height (H) of the peak in the above distribution information can be lowered and half of the peak can be lowered. The value range (W) could be made wider (Sample 22, Sample 23).

Furthermore, by including a coloring material in the overcoat layer, it was possible to form a glossy image colored yellow. Also at this time, if the thickness of the precoat layer to be formed is increased by changing the amount of precoat agent applied, the height of the peak (H) in the above distribution information will become higher and the height of the base (B) will become higher. (Sample 24, Sample 25).

Furthermore, by changing the thickness of the precoat layer, the height from the base material to the image surface could be changed to form an embossed image (Sample 26).

In addition, by changing the injection frequency and changing the number of dots formed per unit area, it was possible to form images with varying density and gloss (Sample 3, 27, sample 28).

Furthermore, when the pre-coat layer was formed by screen printing, an image with the same gloss as when the pre-coat layer was formed with approximately the same thickness using the inkjet method (sample 14) could be obtained (sample 29). .

Also, when a precoat layer is produced by an inkjet method using a water-based ink as a precoat agent, increasing the thickness of the precoat layer to be formed increases the peak height (H) in the above distribution information and increases the base height. (B) could be lowered (Samples 30 to 31). Note that the gloss index (especially the peak height (H) and base height in the above distribution information (B)) is different because the thickness of the precoat layer formed per drop of these precoat agents is different.

This application is an application claiming priority based on Japanese Application No. 2018-112756 filed on June 13, 2018, and the contents described in the claims, specification, and drawings of this application are Incorporated into the application.

The image forming method of the present invention can produce various metallic luster depending on the formed image. Therefore, the present invention is expected to expand the range of applications for recorded materials having glitter, and contribute to the advancement and popularization of technology in the field.

Claims (14)

A step of applying a precoat agent to the surface of the base material to form a precoat layer;
A step of applying a glitter ink containing a glitter pigment to the surface of the pre-coat layer by an inkjet method to form an ink layer made up of aggregation of dots formed by the glitter ink;
An image forming method comprising:
At least the thickness of the ink layer is changed independently for each dot included in the ink layer,
a thickness of the precoat layer or the ink layer corresponding to one dot included in the ink layer;
The thickness of the precoat layer or the ink layer corresponding to other dots included in the ink layer is different ,
The thickness of the ink layer and the thickness of the precoat layer are adjusted independently according to the difference in the degree of gloss developed,
The peak height and baseline height of the brightness or reflection intensity of the reflected light reflected by the formed image are set to different values in the area including the one dot and the area including the other dot,
Image forming method. The step of forming the precoat layer is a step of applying the precoat agent to the surface of the base material by an inkjet method to form a precoat layer in which dots formed by the applied precoat agent are aggregated. ,
The step of forming the ink layer is a step of applying the glitter ink to the surface of the dots forming the precoat layer.
The image forming method according to claim 1 . 3. The image forming method according to claim 2 , wherein the thickness of the precoat layer is changed independently for each dot forming the precoat layer. The image forming method according to any one of claims 1 to 3 , wherein the precoat agent is an actinic ray-curable precoat agent. Further, the step of applying an overcoat agent to the surface of the dots constituting the ink layer to form an overcoat layer,
a thickness of the overcoat layer corresponding to forming the one dot;
The thickness of the overcoat layer corresponding to the formation of the other dots is different,
The height of the peak of the brightness or reflection intensity and the size of the half-width of the peak are set to different values in the area including the one dot and the area including the other dot,
The image forming method according to any one of claims 1 to 4 . A step of applying a glitter ink containing a glitter pigment to the surface of a base material by an inkjet method to form an ink layer made up of aggregation of dots formed by the glitter ink;
applying an overcoat agent to the surface of the dots constituting the ink layer to form an overcoat layer;
An image forming method comprising:
At least the thickness of the ink layer is changed independently for each dot included in the ink layer,
a film thickness of the ink layer and the overcoat layer corresponding to one dot included in the ink layer;
The thicknesses of the ink layer and the overcoat layer corresponding to other dots included in the ink layer are different,
The thickness of the ink layer and the thickness of the overcoat layer are independently adjusted depending on the difference in the degree of gloss developed,
The height of the peak of the brightness or reflection intensity of the reflected light reflected by the formed image and the size of the half-value width of the peak are set to different values in the area containing the one dot and the area containing the other dot. and
Image forming method. In the step of forming the overcoat layer, the overcoat agent is applied to the surface of the dots constituting the ink layer by an inkjet method, and the dots formed by the applied overcoat agent are aggregated. This is a step of forming an overcoat layer,
The image forming method according to claim 5 or 6 . 8. The image forming method according to claim 7 , wherein the thickness of the overcoat agent is changed independently for each dot forming the overcoat layer. The image forming method according to any one of claims 5 to 8 , wherein the overcoat agent is an actinic radiation-curable overcoat agent. The image forming method according to any one of claims 5 to 9 , wherein the overcoat agent contains a non-glare coloring material. The image forming method according to claim 1 , wherein the one dot and the other dot are applied to the same surface of the same base material. forming a plurality of regions in which the number of dots formed per unit area differs;
The image forming method according to any one of claims 1 to 11 . a region in which a plurality of the first dots are formed and has a gloss developed by the plurality of the first dots;
another area in which a plurality of the other dots are formed and has a gloss developed by the plurality of other dots;
forming adjacent
The image forming method according to any one of claims 1 to 12 . The image forming method according to any one of claims 1 to 13 , wherein the bright pigment is a metal nanoparticle.

Images