JP2021151742A - Image forming method - Google Patents

Abstract

To provide an image forming method capable of suppressing strike-through and oozing-out of ink in forming an image by using active ray-curable ink.SOLUTION: An image forming method includes: a process for applying pretreatment liquid to a recording medium 110; a process for applying active ray-curable ink to a surface of the recording medium to which the pretreatment liquid is applied; and a process for irradiating the applied active ray-curable ink with an active ray. The pretreatment liquid includes water and resin, and the active ray-curable ink includes a two-functional monomer or a polyfunctional monomer. The active ray-curable ink is applied to the surface of the recording medium to which the pretreatment liquid set to a temperature lower than a glass transition temperature (Tg) of the resin is applied.SELECTED DRAWING: Figure 1

Description

The present invention relates to an image forming method.

Since the inkjet method can produce an image easily and inexpensively, it is applied to various printing fields including special printing such as various printing, marking, fine line formation, and color filter. Since the inkjet method enables digital printing without using a plate, it is particularly suitable for applications in which various images are formed little by little.

When an image is formed on a recording medium that absorbs ink such as paper by the inkjet method, components (for example, active ray polymerizable compound, coloring material, etc.) in the ink ejected from the inkjet head and landed on the recording medium are recorded. Since it is easily absorbed into the inside of the medium, strike-through of the landed ink, ink bleeding, and uneven density of the formed image are likely to occur. Therefore, in order to prevent ink from being absorbed inside the recording medium, a method of applying a pretreatment liquid to the surface of the recording medium to form a pretreatment layer and applying ink to the surface has been studied. There is.

For example, Patent Document 1 describes an image forming method in which an oil-based ink is applied onto a recording medium coated with a pretreatment liquid containing polyolefin-based resin particles. According to Patent Document 1, the solvent in the oil-based ink is absorbed by the polyolefin-based resin particles, and the permeation into the recording medium is suppressed, so that the coloring material stays on the surface of the recording medium, so that the ink strikes through. And it is said that bleeding can be suppressed.

Further, Patent Document 2 describes a step of forming a pretreatment layer on the surface of a recording medium using a pretreatment layer forming material containing a resin, and applying ink on the pretreatment layer formed by the ink applying means. An image forming method including the steps to be performed is described. According to Patent Document 2, since the ink applying means is heated to a temperature higher than the glass transition temperature of the resin contained in the pretreatment layer, a part of the ink component is impregnated inside the pretreatment layer. Therefore, it is said that the ink is quickly fixed on the pretreatment layer, so that the ink bleeding is suppressed.

Further, Patent Document 3 describes a step of applying a reaction liquid containing a flocculant for aggregating the components of an aqueous ink composition to the surface of a recording medium, and a reaction of applying an aqueous ink to the surface of the recording medium. An image forming method including a step of applying the liquid to the surface of the liquid is described. According to Patent Document 3, since the water-based ink contains the surface treatment pigment, the reactivity with the coagulant contained in the reaction liquid is improved, so that sufficient image quality can be obtained even if the coating amount of the reaction liquid is reduced. It is said that it will be done.

JP 2015-104872 Japanese Unexamined Patent Publication No. 2018-138347 Japanese Unexamined Patent Publication No. 2018-165029

As described in Patent Documents 1 to 3, when forming an image on a recording medium, it is required to suppress ink strike-through and bleeding. Here, the methods described in Patent Documents 1 and 3 are intended for oil-based inks and water-based inks, respectively. However, strike-through and bleeding of the ink also occur when forming an image using the active ray-curable ink, and the methods described in these documents suppress the strike-through and bleeding of the active ray-curable ink. Can not do it.

On the other hand, according to the method described in Patent Document 2, it is expected that strike-through and bleeding of the active ray-curable ink can be suppressed. However, according to the study by the present inventors, even with the method described in Patent Document 2, the strike-through and bleeding of the active ray-curable ink could not be completely suppressed.

The present invention has been made in view of this point, and provides an image forming method capable of suppressing strike-through and bleeding of ink when forming an image using an active ray-curable ink. The purpose.

In order to solve the above problems, the image forming method according to the embodiment of the present invention includes a step of applying a pretreatment liquid to a recording medium and active ray curing on a surface of the recording medium to which the pretreatment liquid is applied. The pretreatment liquid includes water and a resin, and the active ray-curable ink comprises a step of applying the mold ink and a step of irradiating the applied active ray-curable ink with active rays. The active ray-curable ink containing a bifunctional monomer or a polyfunctional monomer is applied to the surface of the recording medium set to a temperature lower than the glass transition temperature (Tg) of the resin.

According to the present invention, it is possible to provide an image forming method capable of suppressing strike-through and bleeding of ink when forming an image using an active ray-curable ink.

FIG. 1 is a schematic view showing a configuration of an image forming apparatus for carrying out an image forming method according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail.

1. 1. Image forming method The image forming method according to the embodiment of the present invention includes (1) a step of applying a pretreatment liquid to a recording medium, and (2) an active ray on a surface of the recording medium to which the pretreatment liquid is applied. It has a step of applying a curable ink and (3) a step of irradiating the applied active ray curable ink with an active ray. Hereinafter, each step will be described.

1-1. Step of Applying Pretreatment Liquid The step of applying the pretreatment liquid is a step of applying the pretreatment liquid to the surface of the recording medium.

[Pretreatment liquid]
The pretreatment liquid according to the embodiment of the present invention is a liquid containing water and a resin. Further, the pretreatment liquid may contain a water-soluble organic solvent and, as an additive, a surfactant, a preservative, an antifungal agent and the like.

(resin)
Examples of the above resins include water-soluble resins and water-based resin emulsions. The types of the water-soluble resin and the water-based resin emulsion are not particularly limited, and known or commercially available water-soluble resins and water-based resin emulsions can be used. The water-soluble resin and the water-based resin emulsion can also be used in combination.

Examples of water-soluble resins include polyacrylic acid, acrylic acid-acrylic nitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, and styrene. -Methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene -Maleic acid copolymer, styrene-maleic anhydride copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid Polymers, vinyl acetate-acrylic acid copolymers, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, saccharides and the like, and salts thereof are included. Only one type of the water-soluble resin may be used alone, or two or more types may be used in combination. Further, as the form of the copolymer, any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer can be used.

Examples of commercially available water-soluble acrylic resins include John Krill 63J (weight average molecular weight (Mw): 12500, acid value: 213) and John Krill 67 (weight average molecular weight (Mw): 12,500) manufactured by BASF. , Acid value: 213), John krill 678 (weight average molecular weight (Mw): 8,500, acid value: 215), John krill 586 (weight average molecular weight (Mw): 4,600, acid value: 108), John Krill 611 (weight average molecular weight (Mw): 8,100, acid value: 53), John Krill 680 (weight average molecular weight (Mw): 4,900, acid value: 215), John Krill 682 (weight average molecular weight (Mw)) ): 1,700, Acid Value: 238), John Krill 683 (Weight Average Molecular Weight (Mw): 8,000, Acid Value: 160), John Krill 690 (Weight Average Molecular Weight (Mw): 16,500, Acid Value) : 240) ("John Krill" is a registered trademark of the company), Julimer AT-210, AT-510, AT-613, ARUFON series manufactured by Toa Synthetic Co., Ltd. ("Jurimer" and "ARUFON" are registered trademarks of the same company) , X-1, X-200, X-205, X-220, YS-1274, VS-1047, RS-1191, TS-1315, RS-1190 and the like manufactured by Seikou PMC Co., Ltd. are included. These include solid resins, which can be used by being neutralized and dissolved in water or the like with a base or dissolved in a solvent as appropriate.

Examples of the aqueous resin emulsion include (meth) acrylic resin emulsion, urethane resin emulsion, polyester resin emulsion, polyolefin resin emulsion and the like.

Examples of commercially available (meth) acrylic resin emulsions include Vinibran 2580, Vinibran 2585, Vinibran 2680, Vinibran 2682, Vinibran 2864, Vinibran 2685, Vinibran 2678, and Vinibran GA-6610 (all of which are Nisshin Kagaku Kogyo Co., Ltd.). ), John Krill 741, John Krill 790, John Krill 537J (all manufactured by BASF, "John Krill" is a registered trademark of the company) and the like. As the (meth) acrylic resin emulsion, only one type may be used alone, or two or more types may be used in combination.

Examples of the urethane resin emulsion include WBR-016U (manufactured by Taisei Fine Chemical Co., Ltd.), Superflex 150HS, Superflex 620, Superflex 650, Superflex 500M, and Superflex E-2000 (all of which are manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.). Company-made, "Superflex" is a registered trademark of the company), Permarin UC-20 (manufactured by Sanyo Kasei Kogyo Co., Ltd., "Permarin" is a registered trademark of the company), Parasurf UP-22 (manufactured by Ohara Palladium Chemical Co., Ltd.), etc. included. As for the urethane resin emulsion, only one type may be used alone, or two or more types may be used in combination.

Examples of commercially available polyester resin emulsions include Elitel KA-5034, Elitel KA-5071S, Elitel KA-1449, Elitel KA-0134, Elitel KA-3556, Elitel KA-6137, Elitel KZA-6034, and Elitel KT. -8803, Elitel KT-8701, Elitel KT-9204, Elitel KT-8904, Elitel KT-0507, Elitel KT-9511, etc. (all manufactured by Unitika Ltd., "Elitel" is a registered trademark of the same company). The polyester resin emulsion may be used alone or in combination of two or more.

Examples of the above-mentioned polyolefin-based resin emulsion include Arrow Base SB-1200 (manufactured by Unitika Co., Ltd., "Arrow Base" is a registered trademark of the same company), Auroran 150A, Auroralen AE-301 (manufactured by Nippon Paper Industries, Ltd., "Au". "Lauren" is a registered trademark of the company), Supercron E-415 (manufactured by Nippon Paper Industries, Ltd., "Supercron" is a registered trademark of the company), Hardren Na-1001 (manufactured by Toyobo Co., Ltd., "Hardren" is a registered trademark of the company) ) Etc. are included. As the polyolefin resin emulsion, only one type may be used alone, or two or more types may be used in combination.

The weight average molecular weight (Mw) of the water-soluble resin is preferably 1000 or more and 100,000 or less, and more preferably 3000 or more and 50,000 or less. When the weight average molecular weight (Mw) of the water-soluble resin is within the above range, the storage stability of the pretreatment liquid can be kept good, and the pretreatment liquid is uniformly spread on the recording medium due to appropriate fluidity. Since the ink can be applied to the surface of the recording medium, the ink can be retained on the surface of the recording medium, and the decrease in image density can be suppressed.

Among the above resins, an aqueous resin emulsion is preferable. Further, among the above-mentioned aqueous resin emulsions, a (meth) acrylic resin emulsion, a styrene- (meth) acrylic resin emulsion, and a urethane resin emulsion are preferable. When a (meth) acrylic resin emulsion, a styrene- (meth) acrylic resin emulsion, or a urethane resin emulsion is used as the aqueous resin emulsion, the adhesion of the pretreatment liquid to the recording medium is improved and the emulsion is less likely to settle. It also has excellent storage stability.

Further, the water-soluble resin and the resin contained in the water-based resin emulsion preferably have a glass transition temperature (Tg).

The water-soluble resin and the resin contained in the aqueous resin emulsion according to the embodiment of the present invention preferably have a glass transition temperature (Tg) of 15 ° C. or higher and 90 ° C. or lower, and a glass transition temperature (Tg) of 45 ° C. or higher. It is more preferably 65 ° C. or lower. When the glass transition temperature (Tg) of the resin is 15 ° C. or higher and 90 ° C. or lower, ink is suppressed from penetrating into the recording medium or the resin, so that there is almost no density unevenness on the image surface and a high density image is formed. In addition, it is possible to prevent the ink from penetrating into the back surface of the recording medium and strike through. Further, when the glass transition temperature (Tg) of the resin is 45 ° C. or higher and 65 ° C. or lower, the resin is less likely to soften at room temperature, so that the scratchability of the formed image can be improved.

The glass transition temperature (Tg) of the water-soluble resin and the resin contained in the water-based resin emulsion can be measured using, for example, a commercially available measuring device such as "Diamond DSC" (manufactured by PerkinElmer).

The content of the resin contained in the pretreatment liquid is more preferably 5% by mass or more and 20% by mass or less as a solid content with respect to the total mass of the pretreatment liquid, and is 10% by mass or more and 15% by mass or less. Is more preferable. When the content of the resin contained in the pretreatment liquid is 5% by mass or more, the surface of the recording medium set to a temperature lower than the glass transition temperature (Tg) of the resin is coated with the resin contained in the pretreatment liquid. .. Therefore, the active ray-curable ink is less likely to be absorbed by the recording medium, so that strike-through of the active ray-curable ink can be suppressed. Further, when the content of the resin contained in the pretreatment liquid is 20% by mass or less, it is easy to eject even when an inkjet method, a spray coating or the like is used as the coating method, and in the case of an aqueous resin emulsion, it is easy to eject. Since the resin can be prevented from aggregating and precipitating, the storage stability is improved.

(Water-soluble organic solvent)
The pretreatment liquid according to the embodiment of the present invention may contain a water-soluble organic solvent.

Examples of the above water-soluble organic solvent include glycerins such as glycerin, diglycerin and polyglycerin; ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol and polypropylene. Glycosyls such as glycols, neopentyl glycol glycerin, trimethylolethane, trimethylolpropane, tributylolpropane, pentaerythritol, and polyfunctional glycols containing sorbitol; methanol, ethanol, propanol, isopropanol, butanol, 2-butanol, tert -Butanol, Isobutanol, Pentanol, Isopentanol, Hexanol, Isohexanol, Octanol, Isooctanol, 2-Ethylhexyl alcohol, Nonyl alcohol, Isononyl alcohol, tert-Nonyl alcohol, Decanol, Dodecanol, Dodecahexanol, Dodecaoctanol, Monoalcohols such as allyl alcohol, oleyl alcohol, 1-methoxy-1-propanol, 3-methoxy-1-butanol, cyclohexyl alcohol, benzyl alcohol, 3-phenylpropanol; 1,2-butanediol, 1,3-propane Diol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentane Diol, 1,6-hexanediol, 1,2-hexanediol, 1,8-octanediol, 1,2-octanediol, 1,9-nonandiol, 3-methyl-1,5-pentanediol, 2- Methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-dibutyl-1,3-propanediol, Alcohol diols such as 2-methyl-2,4-pentanediol, 2-methyl-1,8-octanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol; 1,3-dimethyl-2- Imidazolidinones such as imidazolidinone; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol mono Isopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monodiethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether , Propropylene glycol monopropyl ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, 3-methoxy-3-methyl-butanol and other glycols Ethers; ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, Amines such as tetramethylpropylenediamine; amides such as formamide, N, N-dimethylformamide, N, N-dimethylacetamide are included.

Among the water-soluble organic solvents, glycerins and glycols are preferable. Among glycerins and glycols, glycerin and propylene glycol are preferable. By using a water-soluble organic solvent having two or more hydroxyl groups in one molecule contained in glycerins and glycols, the hydrophilicity of the pretreatment liquid is enhanced, and the active rays imparted to the surface of the pretreatment liquid. It can be difficult to be compatible with curable ink. Therefore, the active ray-curable ink applied to the surface of the pretreatment liquid is less likely to permeate into the pretreatment liquid, so that strike-through of the active ray-curable ink can be suppressed. In addition, since the active ray-curable ink tends to stay on the surface of the pretreatment liquid, bleeding of the ink can be suppressed.

The water-soluble organic solvent is preferably 0% by mass or more and 80% by mass or less, and more preferably 50% by mass or more and 80% by mass or less with respect to the total mass of the pretreatment liquid. By setting the content of the water-soluble organic solvent to 50% by mass or more with respect to the total mass of the pretreatment liquid, the water-soluble organic solvent and the resin contained in the pretreatment liquid are well compatible with each other and are homogeneous. The above resin can be applied to the surface of the recording medium. Therefore, since the voids existing on the surface of the recording medium can be filled with the resin contained in the pretreatment layer, it is possible to prevent the active ray-curable ink from being absorbed by the recording medium and strike through. Further, by setting the content of the water-soluble organic solvent to 80% by mass or less with respect to the total mass of the pretreatment liquid, it is possible to suppress a decrease in fluidity, and when an aqueous resin emulsion is contained, it is possible to suppress the decrease in fluidity. , Aggregation and sedimentation of aqueous resin emulsion can be suppressed.

[Other ingredients]
The pretreatment liquid according to one embodiment of the present invention may contain a surfactant, a preservative, and an antifungal agent.

(Surfactant)
Examples of surfactants include anionic surfactants including dialkyl sulfosuccinates, alkylnaphthalene sulfonates and fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols and polyoxy. Includes nonionic surfactants including ethylene-polyoxypropylene block copolymers, cationic surfactants including alkylamine salts and quaternary ammonium salts, silicone-based surfactants, and fluorine-based surfactants. ..

The surfactant is preferably 0% by mass or more and 5% by mass or less with respect to the total mass of the pretreatment liquid, and is 0% by mass or more and 2% by mass or less with respect to the total mass of the pretreatment liquid. Is more preferable.

(Preservatives / fungicides)
Examples of preservatives or fungicides include aromatic halogen compounds (eg, Preventol CMK from Ranks), methylene dithiocyanate, halogenated nitrogen-sulfur compounds, 1,2-benzisothiazolin-3-one (eg, Lonza). PROXELGXL) manufactured by the company is included.

The preservative or fungicide is preferably 0.1% by mass or more and 1% by mass or less, and 0.1% by mass or more and 0.5% by mass or less, based on the total mass of the pretreatment liquid. Is more preferable.

(Physical characteristics of pretreatment liquid)
The viscosity of the pretreatment liquid is preferably 1000 cPs or more and 10000 cPs or less at 20 ° C. When the viscosity of the pretreatment liquid is 1000 Ps or more, the pretreatment liquid can be uniformly applied to the entire surface of the recording medium or to the portion to which the surface treatment liquid is to be applied. The viscosity of the pretreatment liquid at 20 ° C. can be measured with a stress-controlled rheometer "Physica MCR301" (manufactured by Antonio Par, cone plate diameter: 75 mm, cone angle: 1.0 °).

[Method of applying pretreatment liquid]
As the pretreatment liquid, known liquid coating methods such as spray coating, spiral coating using a nozzle or slit, dipping coating, roll coater coating, gravure coating, flexographic coating, and inkjet coating can be used.

The amount of the pretreatment liquid ^{applied is preferably 1 g / m 2} or more and 50 g / m ² or less, and more preferably 2 g / m ² or more and 30 g / m ² or less. When the amount of the pretreatment liquid applied is 1 g / m ² or more, the voids existing on the surface of the recording medium can be filled with the resin contained in the pretreatment layer. When the amount of the pretreatment liquid applied is 50 g / m ² or less, the amount of resin contained in the pretreatment layer increases, and the voids in the pretreatment layer also decrease. It becomes difficult to penetrate and the strike-through of ink can be suppressed.

[recoding media]
The recording medium according to the embodiment of the present invention is not particularly limited, and a known recording medium can be used.

Examples of the recording medium include paper having no surface layer such as an ink receiving layer and a film layer, for example, copy paper, high-quality paper, recycled paper, and the like. Examples of the above copy paper, woodfree paper, and recycled paper include Xerox 4200, Xerox 4024 (all manufactured by Xerox), GeoCycle (Gerogia-Pacific), Recycle Cut R-100 (manufactured by Oji Paper Co., Ltd.), 55PW ( (Made by Lintec Corporation), etc. are included.

Further, medium quality paper, stencil paper, coated paper, art paper, cast coated paper and the like may be used.

As the absorbent recording medium, the absorption amount of water contained in the pretreatment liquid within 30 ^{msec 1/2} from the start of contact with the pretreatment liquid in the Bristow method ^{is 10 ml / m 2} or more and 30 ml / m ² or less. Is preferable.

The amount of water absorbed in the pretreatment liquid is the standard No. of "JAPAN TAPPI Paper and Pulp Test Method" adopted by the Japan Technical Association of the Pulp and Paper (JAPANTAPPI). It can be obtained in accordance with 51 "Paper and Paperboard-Liquid Absorption Test Method-Bristow Method".

1-2. Step of Applying Active Ray Curable Ink for Inkjet The step of applying active ray curable ink for inkjet (hereinafter, also simply referred to as “ink application step”) is a process of applying a pretreatment liquid to the surface of a recording medium. This is a step of applying active ray-curable ink to the surface to form an intermediate image.

In the ink application step according to the embodiment of the present invention, the active ray-curable ink is applied to the surface of a recording medium set to a temperature lower than the glass transition temperature (Tg) of the resin contained in the pretreatment liquid. .. By setting the temperature of the recording medium in this way, the ink is applied to the surface in which the resin applied by the pretreatment liquid is not so softened and the gaps between the resin molecules are less likely to occur due to the movement of the resin. It is considered that the resin can sufficiently suppress the unintended diffusion of the ink, thereby sufficiently suppressing the strike-through and bleeding of the ink. From the above viewpoint, the temperature of the recording medium is preferably 10 ° C. or higher and 30 ° C. or lower lower than the glass transition temperature (Tg) of the resin contained in the pretreatment liquid, and more preferably 10 ° C. or higher and 20 ° C. or lower. ..

In the present invention, "the temperature is set lower than the glass transition temperature (Tg) of the resin contained in the pretreatment liquid" means that, when there are a plurality of resins contained in the pretreatment liquid, the inside of the resin is included. In, it means that the glass transition temperature is set to a temperature lower than the maximum value.

Further, the temperature lower than the glass transition temperature (Tg) of the resin contained in the pretreatment liquid may be lower than the glass transition temperature (Tg) of the resin contained most in the pretreatment liquid. preferable. Further, it is preferably lower than the glass transition temperature (Tg) of all the resins contained in the pretreatment liquid.

In the present invention, it is preferable to further have a step of drying the pretreatment liquid applied to the surface of the recording medium after the step of applying the pretreatment liquid to the recording medium. Examples of the method for drying the pretreatment liquid include a method using a non-contact heating type drying device such as a drying furnace and a hot air blower, and a contact heating type drying device such as an infrared heater, a hot plate, and a hot roller. Methods etc. are included. The above method can be appropriately selected depending on the type of the water-soluble organic solvent contained in the pretreatment liquid and the like.

[Active ray curable ink]
The active ray-curable ink according to an embodiment of the present invention is an ink containing an active ray-polymerizable compound, and the active ray-polymerizable compound is polymerized and crosslinked and cured by irradiation with active rays.

The active ray-polymerizable compound contained in the active ray-curable ink according to the embodiment of the present invention is preferably a monomer having a solubility parameter (SP value) of 20 or less, and a monomer having an SP value of 17 or more and 20 or less. More preferably. When the SP value is 17 or more and 20 or less, the difference from the SP value of the resin contained in the pretreatment liquid can be increased. Therefore, the monomer contained in the active ray-curable ink and the resin contained in the pretreatment liquid are less likely to be compatible with each other, so that strike-through due to penetration of the active ray-curable ink can be suppressed. In addition, since the active ray-curable ink tends to stay on the surface of the pretreatment liquid, bleeding of the ink can be suppressed.

In addition, the active ray-polymerizable compound contained in the active ray-curable ink according to the embodiment of the present invention may include a monofunctional monomer, a bifunctional monomer, and a polyfunctional monomer.

The active ray-curable ink preferably contains a bifunctional monomer or a polyfunctional monomer. The bifunctional monomer or the polyfunctional monomer is preferably contained in an amount of 30% by mass or more and 80% by mass or less, more preferably 50% by mass or more and 80% by mass or less, based on the total mass of the active ray-curable ink. By containing the above bifunctional monomer or the polyfunctional monomer in an amount of 30% by mass or more with respect to the total mass of the active ray curable ink, when the ink is cured by irradiating the active ray, the ink is cured. Since the object forms a network structure, the surface thereof becomes hard, so that the scratchability of the formed image can be improved. Further, by containing the bifunctional monomer and the polyfunctional monomer in an amount of 80% by mass or less based on the total mass of the active ray-curable ink, the cured product obtained by curing the ink does not become too hard, so that the cured product is fixed to the recording medium. The sex is not easily impaired.

(Active ray-polymerizable compound)
The active ray-polymerizable compound is a compound that is crosslinked or polymerized by irradiation with active rays. Examples of active rays include electron beams, ultraviolet rays, α rays, γ rays, X-rays and the like. Among the above active rays, ultraviolet rays or electron beams are preferable, and ultraviolet rays are more preferable. Examples of the active ray-polymerizable compound include radical-polymerizable compounds, cationically polymerizable compounds, or mixtures thereof. Among the active ray-polymerizable compounds, a radical-polymerizable compound is preferable. The active ray-polymerizable compound may be any of a monomer, a polymerizable oligomer, a prepolymer, and a mixture thereof.

The radically polymerizable compound is a compound having an ethylenically unsaturated double bond group in the molecule. The radically polymerizable compound can be a monofunctional or polyfunctional compound. Examples of radically polymerizable compounds include (meth) acrylates, which are unsaturated carboxylic acid ester compounds. In the present invention, "(meth) acrylate" means acrylate or methacrylate, "(meth) acryloyl group" means acryloyl group or methacryloyl group, and "(meth) acrylic" means acrylic or methacrylic. Means.

Examples of monofunctional (meth) acrylates include isoamyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, benzyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, and isomil still (meth). Meta) 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, methoxydiethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) ) Acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinic acid, 2- (meth) ) Acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl-2-hydroxyethyl-phthalic acid and t-butylcyclohexyl (meth) acrylate are included. As the monofunctional (meth) acrylate, only one type may be used alone, or two or more types may be used in combination.

Examples of bifunctional and polyfunctional (meth) acrylates include triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, Polypropylene glycol di (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 ) Acrylate, dimethylol-tricyclodecanedi (meth) acrylate, PO adduct di (meth) acrylate of bisphenol A, neopentyl glycol di (meth) acrylate of hydroxypivalate, polytetramethylene glycol di (meth) acrylate, polyethylene glycol Bifunctional (meth) acrylates such as di (meth) acrylates, dipropylene glycol di (meth) acrylates, and tripropylene glycol di (meth) acrylates; trimethylol propanthry (meth) acrylates, pentaerythritol tri (meth) acrylates. Trifunctional (meth) acrylates such as pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylolpropanetetra (meth) acrylate, glycerin propoxytri (meth) acrylate and pentaerythritol ethoxytetra (meth). ) Trifunctional or higher functional (meth) acrylates such as acrylates; oligomers having a (meth) acryloyl group containing polyester acrylate oligomers, and modified products thereof. Examples of the modified product include ethylene oxide-modified (EO-modified) (meth) acrylate in which an ethylene oxide group is inserted, and propylene oxide-modified (PO-modified) (meth) acrylate in which propylene oxide is inserted. As the bifunctional and polyfunctional (meth) acrylates, only one type may be used alone, or two or more types may be used in combination.

The cationically polymerizable compound is a compound having a cationically polymerizable group in the molecule. Examples of cationically polymerizable compounds include epoxy compounds, vinyl ether compounds, oxetane compounds and the like.

Examples of the above epoxy compounds include 3,4-epoxycyclohexylmethyl-3', 4'-epoxycyclohexanecarboxylate, bis (3,4-epoxycyclohexylmethyl) adipate, vinylcyclohexene monoepoxyside, ε-caprolactone modified 3, 4-Epoxycyclohexylmethyl 3', 4'-epoxycyclohexanecarboxylate, 1-methyl-4- (2-methyloxylanyl) -7-oxabicyclo [4,1,0] heptane, 2- (3,4) -Epoxy Cyclohexyl-5,5-Spiro-3,4-Epoxy) Cyclohexanone-Meta-dioxane and alicyclic epoxy resins such as bis (2,3-epoxycyclopentyl) ether, diglycidyl ether of 1,4-butanediol , 1,6-Hexanediol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, ethylene glycol, propylene glycol, and glycerin, etc. An aliphatic epoxy compound containing polyglycidyl ether, which is a polyether polyol obtained by adding one or more kinds of alkylene oxides (such as ethylene oxide and propylene oxide) to an aliphatic polyhydric alcohol, and bisphenol A or Included are di or polyglycidyl ethers of the alkylene oxide adduct, di or polyglycidyl ethers of hydrogenated bisphenol A or the alkylene oxide adducts thereof, aromatic epoxy compounds including novolak type epoxy resins and the like.

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, and 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 ethers, hexanediol divinyl ethers, cyclohexanedimethanol divinyl ethers, and di or trivinyl ether compounds including trimethylrol propantrivinyl ethers and the like.

Examples of the above oxetane compounds include 3-hydroxymethyl-3-methyloxetane, 3-hydroxymethyl-3-ethyloxetane, 3-hydroxymethyl-3-propyloxetane, 3-hydroxymethyl-3-normalbutyloxetane, 3 -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, 1,4 bis {[(3-ethyl-3-oxetanyl) methoxy] methyl} benzene, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane and di [1- Ethyl (3-oxetanyl)] Includes methyl ether and the like.

Among the radically polymerizable compound and the cationically polymerizable compound, it is preferable to include the radically polymerizable compound.

(Polymerization initiator)
The active ray-curable ink according to one embodiment of the present invention may contain a polymerization initiator. The polymerization initiator may be any one capable of initiating the polymerization of the active ray-polymerizable compound by irradiation with active rays. For example, when the active ray-curable ink has a radically polymerizable compound, the polymerization initiator can be a photoradical initiator, and when the active ray curable ink has a cationically polymerizable compound, polymerization initiation The agent can be a photocation initiator (photoacid generator).

The radical polymerization initiator includes an intramolecular bond cleavage type radical polymerization initiator and an intramolecular hydrogen abstraction type radical polymerization initiator.

Examples of intramolecular bond cleavage type radical polymerization initiators include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1- (4-isopropylphenyl) -2. -Hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4) Acetphenone-based initiators including −methylthiophenyl) propan-1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, benzoin, benzoin methyl ether, benzoin isopropyl ether, etc. Includes benzoins, including 2,4,6-trimethylbenzoindiphenylphosphine oxides, acylphosphine oxide-based initiators, benzyl and methylphenylglycoesters, and the like.

Examples of intramolecular hydrogen abstraction-type radical polymerization initiators include benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl. 2-Isopropyl, a benzophenone-based initiator containing sulfide, acrylated benzophenone, 3,3', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, and 3,3'-dimethyl-4-methoxybenzophenone. A thioxanthone-based initiator containing thioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, etc., an aminobenzophenone-based initiator containing Michler ketone, 4,4'-diethylaminobenzophenone, etc. Includes 10-butyl-2-chloroacrydone, 2-ethylanthraquinone, 9,10-phenanslenquinone, and camphorquinone.

Examples of cationic polymerization initiators include photoacid generators. Examples of photoacid generators include diazonium, ammonium, iodonium, sulfonium, and phosphonium and aromatic onium compound containing ^{_{B (C 6 F 5) 4}} -, PF 6 -, AsF 6 -, SbF 6 -, CF Includes sulfonates that generate sulfonic acids, halides that photogenerate hydrogen halides, such as ₃ SO ₃ ^{-salts, and iron allen complexes.}

(Gel agent)
The active ray-curable ink according to an embodiment of the present invention may contain a gelling agent. The gelling agent is an organic substance that is solid at room temperature but becomes liquid when heated, so that the active ray-curable ink can undergo a sol-gel phase transition in response to a temperature change.

Further, the gelling agent is preferably crystallized in the ink at a temperature equal to or lower than the gelation temperature of the ink. Here, the gelling temperature refers to a temperature at which the ink undergoes a phase transition from the sol to the gel when the solified or liquefied ink is cooled by heating, and the viscosity of the ink suddenly changes. Specifically, the solified or liquefied ink is cooled while measuring the viscosity with, for example, a rheometer "MCR300" (manufactured by AntonioPaar), and the temperature at which the viscosity rises sharply is gelled. Can be temperature.

When the gelling agent crystallizes in the ink, a structure in which the active ray-polymerizable compound is contained in the three-dimensional space formed by the gelling agent and the wax crystallized in a plate shape may be formed (. Such a structure is hereinafter referred to as a "card house structure"). When the card house structure is formed, the liquid active ray-polymerizable compound is retained in the space, so that the active ray-polymerizable compound and the resin contained in the pretreatment liquid are less likely to be compatible with each other. The linear curable ink is less likely to permeate into the pretreatment liquid, and strike-through of the ink can be suppressed.

Examples of gelling agents include dipentadecyl ketone, diheptadecyl ketone (stealon), dilignoceryl ketone, dibehenyl ketone, distearyl ketone, dieicosyl ketone, dipalmityl ketone, dimyristyl ketone, lauryl myristyl. Aliphatic ketone waxes such as ketones, lauryl palmityl ketones, myristyl palmityl ketones, myristyl stearyl ketones, myristyl behenyl ketones, palmityl stearyl ketones, balmityl behenyl ketones and stearyl behenyl ketones; cetyl palmitate, stearyl stearate, behenic acid. Behenyl, icosyl icosate, behenyl stearate, palmityl stearate, lauryl stearate, stearyl palmitate, myristyl myristate, cetyl myristate, octyldodecyl myristate, stearyl oleate, stearyl erucate, stearyl linoleate, behenyl oleate And aliphatic ester waxes such as arachidyl linoleate; amide compounds such as N-lauroyl-L-glutamate dibutylamide, N- (2-ethylhexanoyl) -L-glutamate dibutylamide; 1,3: 2,4-bis Divendilidene sorbitols such as -O-benziliden-D-glucitol; petroleum waxes such as paraffin wax, microcrystallin wax, petrolactam; candelilla wax, carnauba wax, rice wax, wood wax, jojoba oil, jojoba solid wax , And plant waxes such as jojoba ester; animal waxes such as beeswax, lanolin and whale wax; mineral waxes such as montan wax and hydrogenated wax; hardened bean oil or hardened bean oil derivative; montan wax derivative, paraffin wax Modified waxes such as derivatives, microcrystalin wax derivatives or polyethylene wax derivatives; higher fatty acids such as bechenic acid, arachidic acid, stearic acid, palmitic acid, myristic acid, lauric acid, oleic acid, and erucic acid; stearyl alcohol, behenyl alcohol, etc. Higher alcohols; hydroxystearic acids such as 12-hydroxystearic acid; 12-hydroxystearic acid derivatives; lauric acid amides, stearic acid amides, behenic acid amides, oleic acid amides, erucic acid amides, ricinolic acid amides, 12-hydroxystearic acids Fatty acid amides such as amides; Ami N-stearyl stearate N-substituted fatty acid amides such as de, N-oleyl palmitate amide; N, N'-ethylenebisstearylamide, N, N'-ethylenebis-12-hydroxystearylamide, and N, N'-xylylene bisstearyl. Special fatty acid amides such as amides; higher amines such as dodecylamine, tetradecylamine or octadecylamine; stearyl stealic acid, oleyl palmitic acid, glycerin fatty acid esters, sorbitan fatty acid esters, propylene glycol fatty acid esters, ethylene glycol fatty acid esters, polyoxyethylene Fatty acid ester compounds such as fatty acid esters; sucrose fatty acid esters such as sucrose stearic acid and sucrose palmitic acid; synthetic waxes such as polyethylene wax and α-olefin maleic anhydride copolymer wax; polymerizable wax; dimer acid; dimer Includes diols and the like. Only one type of these waxes may be used alone, or two or more types may be used in combination.

Of these, from the viewpoint of further enhancing the pinning property of the ink, aliphatic ketone wax, aliphatic ester wax, higher fatty acid, higher alcohol and fatty acid amide are preferable, and carbons arranged on both sides of the keto group or ester group are preferable. More preferably, an aliphatic ketone wax or an aliphatic ester wax having 9 or more and 25 or less carbon atoms in the chain is preferable.

The content of the gelling agent is preferably 0.5% by mass or more and less than 10.0% by mass with respect to the total mass of the active ray-curable ink, and is 1 with respect to the total mass of the active ray-curable ink. It is more preferably 0.0% by mass or more and less than 10.0% by mass, and further preferably 2.0% by mass or more and 7.0% by mass or less with respect to the total mass of the active ray-curable ink.

(Polymerization inhibitor)
The active ray-curable ink may contain a polymerization inhibitor.

Examples of the polymerization inhibitor include (alkyl) phenol, hydroquinone, catechol, resorcin, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiline, p-. Benzoquinone, nitrosobenzene, 2,5-di-t-butyl-p-benzoquinone, dithiobenzoyldisulfide, picric acid, cuperon, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, N- (3-oxyanilino) -1,3-Dimethylbutylidene) Aniline oxide, dibutyl cresol, cycloquinone oxime cresol, guayacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxim, cycloquinone oxime are included.

The content of the polymerization inhibitor can be 0.05% by mass or more and 0.2% by mass or less with respect to the total mass of the ink.

(Color material)
The active ray-curable ink may contain a coloring material. Coloring materials include pigments and dyes. From the viewpoint of improving the dispersion stability of the active ray-curable ink and forming an image having high weather resistance, the coloring material is preferably a pigment. Examples of pigments include organic pigments and inorganic pigments. Examples of dyes include various oil-soluble dyes.

The pigment can be selected from, for example, red or magenta pigments, yellow pigments, green pigments, blue or cyan pigments and black pigments described in the color index, depending on the color of the image to be formed and the like.

The content of the pigment or dye is preferably 0.1% by mass or more and 20.0% by mass or less, and more preferably 0.4% by mass or more and 10.0% by mass or less with respect to the total mass of the ink. preferable. When the content of the pigment or dye is 0.1% by mass or more with respect to the total mass of the ink, the color development of the obtained image is sufficient. When the content of the pigment or dye is 20.0% by mass or less with respect to the total mass of the ink, the viscosity of the ink does not increase too much.

(Dispersant)
The pigment may be dispersed with a dispersant. The dispersant only needs to be able to sufficiently disperse the pigment. Examples of dispersants include hydroxyl group-containing carboxylic acid esters, long-chain polyaminoamide and high molecular weight acid ester salts, high molecular weight polycarboxylic acid salts, long chain polyaminoamide and polar acid ester salts, and high molecular weight unsaturated acid esters. , Polymer copolymer, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, naphthalene sulfonic acid formalin condensate salt, aromatic sulfonic acid formalin condensate salt, polyoxyethylene alkyl phosphate ester, polyoxyethylene Includes nonylphenyl ether, and stearylamine acetate.

(Fixing resin)
The active ray-curable ink may contain a fixing resin in order to further enhance the scratch resistance and blocking resistance of the coating film.

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

The content of the fixing resin can be, for example, 1.0% by mass or more and 10.0% by mass or less with respect to the total mass of the active ray-polymerizable compound.

(Surfactant)
The active ray-curable ink may contain a surfactant.

The surfactant can adjust the surface tension of the ink to adjust the wettability of the ink after application to the substrate and suppress the coalescence between adjacent droplets.

Examples of surfactants include silicone-based surfactants, acetylene glycol-based surfactants, and fluorine-based surfactants having a perfluoroalkenyl group.

The content of the surfactant is preferably 0.001% by mass or more and 10% by mass or less, and 0.001% by mass or more and 1.0% by mass or less, based on the total mass of the active ray-curable ink. Is more preferable.

(Other ingredients)
In addition to the above components, the active ray-curable ink includes polysaccharides, viscosity modifiers, resistivity modifiers, film forming agents, ultraviolet absorbers, antioxidants, antifading agents, fungicides, etc., as required. It may contain a rust preventive or the like. As for the other components, only one kind may be contained in the above composition, or two or more kinds may be contained.

In the present invention, the active ray-curable ink can be used as an inkjet ink.

(Physical characteristics of active ray curable ink)
From the viewpoint of further enhancing the ejection property from the inkjet head, the viscosity of the active ray-curable ink is 40 ° C. of the active ray-curable ink when the active ray-curable ink is an ink containing no gelling agent. The viscosity in is preferably 3 mPa · s or more and 20 mPa · s or less. When the active ray-curable ink is an ink containing a gelling agent, the viscosity of the active ray-curable ink at 80 ° C. is preferably 3 mPa · s or more and 20 mPa · s or less. When the viscosity at 80 ° C. is 3 mPa · s or more and 20 mPa · s or less, the active ray-curable ink is less likely to gel when the active ray-curable ink is injected from the inkjet head, so that the active ray-curable ink is more stable. Ink can be ejected. When the active ray-curable ink contains a gelling agent, the viscosity of the active ray-curable ink at 25 ° C. is from the viewpoint of sufficiently gelling the ink when it lands and cools to room temperature. Is preferably 1000 mPa · s or more. When the viscosity at 25 ° C. is 1000 mPa · s or more, it is difficult for the ink droplets applied to the recording medium having the pretreatment layer to spread, and it is difficult for the droplets to coalesce with each other.

The viscosity of the active ray-curable ink at 40 ° C. and the viscosity at 80 ° C. are measured by heating the active ray-curable ink to 100 ° C. with a rheometer and measuring the viscosity with a stress-controlled rheometer "Physica MCR301" (manufactured by Antonio Par). At the same time, the viscosity at 40 ° C. and 80 ° C. was determined in the temperature change curve of the viscosity obtained by cooling the ink to 40 ° C. under the conditions of a shear rate of 11.7 (1 / s) and a temperature lowering rate of 0.1 ° C./s. Obtained by reading each.

[Preparation method for active ray curable ink]
The active ray-curable ink can be prepared by mixing the above-mentioned active ray-polymerizable compound, a polymerization initiator, a polymerization inhibitor, a coloring material, and any other component under heating. At this time, it is preferable to filter the obtained mixed solution with a predetermined filter. When preparing an ink containing a pigment, it is preferable to prepare a pigment dispersion liquid containing the pigment and an active ray-polymerizable compound, and then mix the pigment dispersion liquid with other components. The pigment dispersion may further contain a dispersant.

The pigment dispersion liquid can be prepared by dispersing the pigment in an active ray-polymerizable compound. The pigment may be dispersed by using, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like. At this time, a dispersant may be added.

[Method of applying active ray curable ink]
The method of applying the active ray-curable ink to the surface of the liquid pretreatment layer is not particularly limited, and known methods such as spray coating, dipping method, screen printing, gravure printing, offset printing, and inkjet method can be used. Can be used. According to one embodiment of the present invention, in the step of applying the active ray-curable ink to the surface of the liquid pretreatment layer to form an intermediate image, the active ray-curable ink is ejected from the inkjet head. Therefore, it is preferable to use an inkjet method that is applied to the surface of the liquid pretreatment layer.

The inkjet head used in the inkjet method may be either an on-demand method or a continuous method inkjet head. Examples of on-demand inkjet heads include electro-mechanical conversion methods including single cavity type, double cavity type, bender type, piston type, shared mode type and shared wall type, and thermal inkjet type and bubble jet ( "Bubble jet" includes an electric-heat conversion method including a registered trademark of Canon Inc.).

Further, the inkjet head may be either a scan type or a line type inkjet head.

At this time, in order to improve the ejection property of the droplets of the active ray-curable ink, the active ray-curable ink in the inkjet head is heated to 40 to 90 ° C., and the heated active ray-curable ink is ejected. Is preferable.

When the active ray-curable ink contains a gelling agent, the temperature of the active ray-curable ink in the inkjet head is 10 ° C. or higher than the gelling temperature of the gelling agent contained in the active ray-curable ink. It is preferable to set the temperature lower than ° C. By setting the temperature of the active ray-curable ink in the inkjet head to the gelation temperature + 10 ° C or higher, the active ray-curable ink does not gel in the inkjet head or on the nozzle surface, and the active ray-curable ink is good. Can be ejected to. Further, by setting the temperature of the active ray-curable ink in the inkjet head to less than the gelation temperature of the active ray-curable ink + 40 ° C., the thermal load of the inkjet head can be reduced. In particular, in an inkjet head using a piezo element, performance deterioration is likely to occur due to a thermal load, so it is particularly preferable to keep the temperature of the active ray-curable ink within the above range.

When the active ray-curable ink contains a gelling agent, the active ray-curable ink applied to the surface of the recording medium is pinned by crystallizing the gelling agent. Therefore, the applied ink stays on the surface of the pretreatment layer formed on the surface of the recording medium, so that the strike-through of the ink can be remarkably suppressed.

1-3. Step of irradiating active ray-curable ink with active rays In the step of irradiating active ray-curable ink with active rays, active rays (for example, ultraviolet rays) are applied to the active ray-curable ink (intermediate image) applied to the surface of a recording medium. This is a step of completely curing the active ray-curable ink (intermediate image) by irradiating the ink. The wavelength of the active ray irradiated in the step is preferably 350 nm or more and 450 nm or less, and more preferably 380 nm or more and less than 430 nm. As a result, the active ray-curable ink can be main-cured to improve the fixability between the recording medium and the active ray-curable ink.

2. Image forming apparatus FIG. 1 is a schematic view showing an exemplary configuration of an image forming apparatus 100 for inkjet according to an embodiment of the present invention.

The image forming apparatus 100 according to an embodiment of the present invention includes a recording medium 110, a pretreatment liquid application unit 120 that applies a pretreatment liquid to the surface of the recording medium 110, and an active ray on a surface to which the pretreatment liquid is applied. An ink applying unit 130 for applying curable ink, an active ray irradiating unit 140 for irradiating the surface to which the active ray curable ink is applied with active rays, and a temperature adjusting unit 150 for adjusting the temperature of the recording medium. And have.

In FIG. 1, the pretreatment liquid application unit 120, the ink application unit 130, and the active ray irradiation unit 140 are arranged in this order from the upstream side along the transfer direction of the base material (the direction of the arrow in the figure).

The pretreatment liquid application unit 120 may be configured to be able to apply the pretreatment liquid to a region wider than the region on the recording medium 110 on which the droplets of the active ray-curable ink are landed. For example, the pretreatment liquid application unit 120 may include a dispenser 122 that supplies the pretreatment liquid to the coating roller 121, and a coating roller 121 that applies the supplied pretreatment liquid in the form of a film. In the pretreatment liquid application unit 120, a method using a bar coater, an inkjet method, or the like may be used.

In one embodiment of the present invention, the ink-applying unit 130 is an ink-applying unit that forms an image by an inkjet method, and is active in each color of Y (yellow), M (magenta), C (cyan), and K (black), respectively. It has inkjet heads 132Y, 132M, 132C and 132K for ejecting a linear curable composition (inkjet ink) from a nozzle 131 and applying it onto a pretreatment layer formed on the surface of a recording medium 110. The inkjet heads 132Y, 132M, 132C and 132K apply the active ray-curable inks of the above colors to positions on the pretreatment layer formed on the surface of the recording medium 110 according to the image to be formed. Form an image.

The active ray irradiation unit 140 is arranged on the downstream side of the ink application unit 130 in the transport direction of the recording medium 110, and the active line is directed toward the surface of the recording medium 110 to which the pretreatment liquid and the active ray curable ink are applied. Irradiate (ultraviolet rays). As a result, the active ray irradiation unit 140 irradiates the pretreatment liquid and the active ray curable ink applied to the surface of the recording medium 110 with the active rays to cure the pretreatment liquid and the active ray curable ink.

The temperature adjusting unit 150 is for adjusting the temperature of the recording medium 110. As the temperature adjusting unit 150, a known device capable of adjusting to a temperature lower than the glass transition temperature (Tg) of the resin contained in the pretreatment liquid can be used. Examples of the temperature adjusting unit 150 include a heater, a cooling device, and a blower.

Further, in the above description, an image is formed on the surface of the pretreatment liquid applied to the surface of the recording medium by the inkjet method, but the method of forming the image is not particularly limited, and spray coating, dipping method, and screen printing are used. , Known methods such as gravure printing and offset printing can be used.

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

1. 1. Preparation of pretreatment liquid (preparation of pretreatment liquids 1 to 16)
Each component shown in Table 1 was mixed and stirred with a stirrer for 1 hour. The obtained solution was filtered through a 5 μm membrane filter to obtain pretreatment liquids 1 to 16. The unit of the numerical values shown in Table 1 is the mass part, the resin content is a solid content conversion value, and the additive is a preservative (Proxel GXL (S), manufactured by Lonza Japan Co., Ltd.). Water is ion-exchanged water. The numerical values shown in Table 1 are values in which the total amount is 100 parts by mass.

The abbreviations shown in Table 1 are as follows.
(resin)
Resin 1: Water-dispersible acrylic resin emulsion "John Krill 790" (manufactured by BASF)
Resin 2: Styrene-acrylic acid copolymer "John Krill 63J"
Resin 3: Water-dispersible acrylic resin emulsion "John Krill 537J"
Resin 4: Polyurethane aqueous dispersion "Superflex 150HS" (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)
Resin 5: Water-dispersible acrylic resin emulsion "John Krill 741"

The glass transition temperatures (Tg) of the resins 1 to 5 shown in Table 1 are listed in the catalog values.

(Water-soluble organic solvent)
Gly: Glycerin PG: Propylene glycol (surfactant)
E1010: Acetylene glycol-based surfactant "Orfin E1010" (manufactured by Nissin Chemical Industry Co., Ltd.)

2. Preparation of active ray-curable ink The active ray-curable ink was prepared by the following procedure.

2-1. Preparation of pigment dispersion liquid (preparation of cyan pigment dispersion liquid 1)
72.7 parts by mass of lauryl acrylate "Light Acrylate LA" (manufactured by Kyoeisha Chemical Co., Ltd.) and 7.0 parts by mass of pigment dispersant "BYKJET-9151" (manufactured by Big Chemie Japan Co., Ltd., "BYKJET" The company's registered trademark) and 0.3 parts by mass of the polymerization inhibitor "Igastab UV-10" (BASF, "Igastab" is the company's registered trademark) are placed in a stainless steel beaker at 65 ° C. The mixture was stirred for 1 hour while heating on a hot plate. After cooling the obtained solution to room temperature, 20.0 parts by mass of cyan pigment "Chromofine Blue 6332JC" (Pigment Blue 15: 4, manufactured by Dainichiseika Kogyo Co., Ltd.) and 200 g of zirconia beads having a diameter of 0.5 mm were added. , Was placed in a plastic container, sealed, and dispersed in a paint shaker for 3 hours. Zirconia beads were removed from the dispersion to obtain a cyan pigment dispersion 1.

(Preparation of Cyan Pigment Dispersion Liquid 2)
A cyan pigment dispersion 2 was obtained in the same manner as the cyan pigment dispersion 1 except that the lauryl acrylate was changed to tripropylene glycol diacrylate.

2-2. Preparation of active ray-curable ink (preparation of active ray-curable ink 1)
33.3 parts by mass of cyanide pigment dispersion 1, 33.6 parts by mass of active ray-polymerizable compound "lauryl acrylate", 20 parts by mass of tripropylene glycol diacrylate, and 8 parts by mass of dipropylene glycol diacrylate. , 5 parts by mass of polymerization initiator "IRGACURE 819" (manufactured by BASF, "IRGACURE" is a registered trademark of the company) and 0.15 parts by mass of polymerization inhibitor "Irgastab UV-10" in a stainless steel beaker. The mixture was added, stirred at 105 ° C. for 45 minutes, and then filtered through a Teflon (registered trademark) 3 μm polymer filter manufactured by ADVATEC to obtain an active ray-curable ink 1.

(Preparation of active ray curable inks 2 to 4)
Table 2 shows the contents (unit: parts by mass) of each component of the active ray-curable ink 1 and the active ray-curable inks 2 to 4. The total amount of the bifunctional and polyfunctional monomers includes the bifunctional and polyfunctional monomers contained in the dispersion liquid 1 and the dispersion liquid 2.

The abbreviations shown in Table 2 are as follows.
(Cyan pigment dispersion)
Dispersion liquid 1: Cyan pigment dispersion liquid 1
Dispersion liquid 2: Cyan pigment dispersion liquid 2
(Monofunctional monomer)
LA: Lauryl acrylate BA: Benzyl acrylate (bifunctional monomer)
TPGDA: Tripropylene glycol diacrylate (SP value: 17.5)
DPGDA: Dipropylene glycol diacrylate (SP value: 17.7)
1,9-NDDA: 1,9-nonanediol diacrylate (SP value: 17.1)
(Polyfunctional monomer)
TMP (EO) 9TA: Trimethylolpropane EO-modified (9) Triacrylate (SP value: 19.0)
TMP (EO) 3TA: Trimethylolpropane EO-modified (3) Triacrylate (SP value: 17.7)
(Polymerization initiator)
819: IRGACURE 819
(Polymerization inhibitor)
UV-10: Irgastab UV-10
(Gel agent)
SS: Stearyl stearate

3. 3. Image formation was performed using the evaluation pretreatment liquids 1 to 16 and inks 1 to 4, and the image density, strike-through, bleeding, and scratch resistance were evaluated under the following conditions.

3-1. Image formation method (application method of pretreatment liquid)
Bar coater No. Pretreatment liquids 1 to 16 were applied to the surface of the recording medium "Xerox 4024" (copy paper, basis weight 105 g / m ^{2, manufactured by Xerox) so that the wet film thickness (18 μm) was obtained at 8.} It was dried with.

(Image formation method)
Ink 1 was loaded into a single-pass inkjet image forming apparatus having an inkjet head equipped with a piezo-type inkjet nozzle. The ink supply system includes an ink tank, an ink flow path, a sub ink tank immediately before the inkjet head, a pipe with a filter, and an inkjet head, and the temperature of the inkjet head is set to 80 ° C. As the inkjet head, a piezo head having a nozzle diameter of 20 μm and 1024 nozzles (512 nozzles x 2 rows, staggered arrangement, 1 row nozzle pitch 600 dpi) was used. Inks 1 to 4 were ejected at a droplet speed of about 6 m / s under discharge conditions where the appropriate amount of one drop of liquid was 3.0 pl. The transport unit of the recording medium was set so that the temperature of the recording medium to which the pretreatment liquid was applied was 82 ° C., and was arranged on the active ray curable ink landing on the recording medium on the downstream side of the inkjet head. A solid image was obtained by irradiating an LED lamp (manufactured by Phoseon Technology, 395 nm, water-cooled LED) with ultraviolet rays (resolution: 1200 dpi × 1200 dpi). The image formation was performed in an environment of 23 ° C. and 55% RH.

Further, a solid image was formed in the same manner as the image forming method using the ink 1 except that the ink 1 was changed to the inks 2 to 4 and the temperature of the recording medium shown in Table 3 was changed.

3-2. Evaluation of image density (evaluation method)
The solid images obtained by the above image forming method were visually observed.

(Evaluation criteria)
A: There is almost no density unevenness on the image surface and the density is high. B: There is a little density unevenness on the image surface and the density is felt to be slightly low. C: There is density unevenness on the image surface and the density is low.

3-3. Evaluation of strike-through (evaluation method)
An image having a printing rate of 70% was formed at a resolution of 1200 dpi × 1200 dpi, and was visually observed from the back surface side.

(Evaluation criteria)
A: No strike-through is observed B: Ink bleeding and strike-through are slightly observed on the back surface C: Ink bleeding and strike-through are observed on the back surface

3-4. Evaluation of bleeding (evaluation method)
At a resolution of 1200 dpi × 1200 dpi, 8-point alphanumeric characters were printed, and the characters were visually observed for fatness.

(Evaluation criteria)
A: The characters can be read clearly without blurring B: The characters are slightly thick but the characters can be read C: The characters are thick and difficult to read D: The characters are blurred and difficult to read

3-5. Evaluation of scratchability (evaluation method)
In accordance with JIS K5701-1 6.2.3, a recording paper of an appropriate size is placed on the solid image obtained by the above image forming method, and a load is applied to rub the recording paper and the solid image. rice field. The degree of density of the image after rubbing was visually observed.

(Evaluation criteria)
A: No change in image is observed when rubbed 100 times or more B: Decrease in image density is observed when rubbed 100 times or more, but there is no problem in practical use C: Obvious when rubbed less than 50 times Decreased image density is observed, and there is a problem in practical use.

The above evaluation results are shown in Table 3.

From the above evaluation results, it was found that by lowering the temperature of the recording medium to the glass transition temperature of the resin, it is possible to suppress the occurrence of ink strike-through, bleeding, and image density unevenness. This is because even if the heated ink is applied to the surface of the recording medium having the pretreatment layer, the resin contained in the pretreatment layer is difficult to soften, so that the ink does not penetrate into the pretreatment layer and the surface thereof. It is thought that this is because it becomes easier to stay in.

It was also found that by using an ink containing a gelling agent, strike-through of the ink can be remarkably suppressed. This is because the gelling agent of the ink applied to the surface of the pretreatment layer whose temperature of the recording medium is lower than the glass transition temperature of the resin (below the gelation temperature) rapidly crystallizes in the ink. In order to form a three-dimensional space called a card house structure and hold the active ray-polymerizable compound contained in the active ray-curable ink in the space, the active ray-polymerizable compound and the resin contained in the pretreatment liquid are combined. It becomes difficult to be compatible. Therefore, it is considered that the active ray-curable ink is less likely to permeate into the pretreatment liquid, and the strike-through of the ink can be suppressed.

Further, it was found that the scratchability of the image was improved by setting the total amount of the bifunctional monomer and the polyfunctional monomer to 30% by mass or more with respect to the total mass of the active ray-curable ink. It is considered that this is because when the ink is cured by irradiating the active rays, the cured product formed by curing the ink forms a network structure, so that the surface thereof becomes hard and dense.

By using the pretreatment liquid of the present invention, even if the active ray-curable ink is used as the absorbent recording medium, the strike-through of the ink and the bleeding of the ink can be suppressed, so that the density unevenness of the formed image can be prevented. It can be suppressed. Therefore, the present invention is expected to broaden the range of applications of image forming methods using active ray-curable inks and contribute to the advancement and popularization of technologies in the same field.

100 Image forming device 110 Recording medium 120 Pretreatment liquid application unit 121 Coating roller 122 Dispenser 130 Ink application unit 131 Nozzle 132 Inkjet head 140 Active ray irradiation unit 150 Temperature adjustment unit

Claims (8)

The process of applying the pretreatment liquid to the recording medium and
A step of applying the active ray-curable ink to the surface of the recording medium to which the pretreatment liquid is applied, and
The step of irradiating the applied active ray curable ink with active rays, and
Have,
The pretreatment liquid contains water and a resin, and contains water and a resin.
The active ray curable ink contains a bifunctional monomer or a polyfunctional monomer and contains.
An image forming method in which the active ray-curable ink is applied to the surface of a recording medium to which the pretreatment liquid set to a temperature lower than the glass transition temperature (Tg) of the resin is applied. The image forming method according to claim 1, wherein the pretreatment liquid contains a resin having a glass transition temperature (Tg) of 15 ° C. or higher and 90 ° C. or lower. The image forming according to claim 1 or 2, wherein the active ray-curable ink is applied to the surface of the recording medium set to a temperature lower than the glass transition temperature (Tg) of the resin by 10 ° C. or more. Method. The image forming method according to any one of claims 1 to 3, wherein the pretreatment liquid further contains a water-soluble organic solvent. The image forming method according to any one of claims 1 to 4, further comprising a step of drying the pretreatment liquid applied to the surface of the recording medium. The image according to any one of claims 1 to 5, wherein the active ray-curable ink contains the bifunctional monomer or the polyfunctional monomer in an amount of 30% by mass or more based on the total mass of the active ray-curable ink. Forming method. The image forming method according to any one of claims 1 to 6, wherein the active ray-curable ink contains a gelling agent. In the recording medium to which the pretreatment liquid is applied, the amount of water absorbed in the pretreatment liquid within 30 ^{msec 1/2} from the start of contact with the pretreatment liquid in the Bristow method of the recording medium ^{is 10 ml / m 2.} The image forming method according to any one of claims 1 to 7, wherein the image forming method is 30 ml / m ^{2 or less.}

Images