JP2022016981A - Image formation method - Google Patents

Abstract

To provide an image formation method which can suppress strike-through of ink and folding cracks of a formed image when an image is formed using active ray-curable ink.SOLUTION: An image formation method includes a step of imparting a pretreatment liquid onto a recording medium 110, a step of imparting active ray-curable ink onto a surface to which the pretreatment liquid of the recording medium is imparted, and a step of irradiating the imparted active ray-curable ink with active rays. The pretreatment liquid contains water, a water-soluble organic solvent, and a resin. A content of the water-soluble organic solvent is 50 mass% or more and 80 mass% or less with respect to the total mass of the pretreatment liquid. The water-soluble organic solvent contains at least glycol ether, and uses alkanediol in combination depending on the type of the glycol ether. The active ray-curable ink contains a polyfunctional active ray-polymerizable compound.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 various printing, marking, fine line forming, and special printing such as a color filter. Since the inkjet method enables digital printing without using a plate, it is particularly suitable for applications such as forming various images little by little.

When an image is formed on a recording medium that absorbs ink such as paper by the inkjet method, components in the ink ejected from the inkjet head and landed on the recording medium (for example, an active ray polymerizable compound, a coloring material, etc.) are recorded. Since it is easily absorbed into the inside of the medium, strike-through of the landed ink and uneven density of the formed image are likely to occur. Therefore, in order to suppress the absorption of ink into 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 a step of applying a pretreatment liquid containing a polyvalent metal salt and 3-methoxy-3-methyl-1-butanol to a recording medium, and a surface of the recording medium to which the pretreatment liquid is applied. Describes an inkjet recording method including a step of applying a water-based ink. According to Patent Document 1, both the pretreatment liquid and the ink have good permeability to plain paper, and the pretreatment liquid can rapidly aggregate the pigment contained in the ink, so that a high-concentration image can be obtained. It is said that it will be done.

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 rapidly immobilized on the pretreatment layer, so that the ink bleeding is suppressed.

Japanese Unexamined Patent Publication No. 2009-20596 Japanese Unexamined Patent Publication No. 2018-138347

The method described in Patent Document 1 targets water-based inks. However, even if the method described in Patent Document 1 is tried when the active ray-curable ink is used, the components in the ink permeate into the recording medium, the ink strikes out, and an image having sufficient image density is obtained. I couldn't. On the other hand, the method described in Patent Document 2 targets active ray-curable ink, suppresses the penetration of components in the ink into the recording medium, and reduces the strike-through of the ink and the decrease in image density. I was able to. However, according to the study by the present inventors, when the image formed by the method described in Patent Document 2 is curved, creases may occur.

The present invention has been made in view of this point, and when an image is formed using an active ray-curable ink, image formation capable of suppressing ink strike-through and cracking of the formed image can be suppressed. The purpose is to provide a method.

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 comprises a step of applying a mold ink and a step of irradiating the applied active ray-curable ink with an active ray, and the pretreatment liquid contains water, a water-soluble organic solvent and a resin, and the active ray. The curable ink contains a polyfunctional active ray-polymerizable compound, and the content of the water-soluble organic solvent is 50% by mass or more and 80% by mass or less with respect to the total mass of the pretreatment liquid, and the water-soluble ink is described. The sex organic solvent contains any of the glycol ethers represented by the following general formulas (3) to (5), where the glycol ether represented by the general formula (3) is described by the following general formula (3). It is contained together with 1) or an alkanediol represented by the following general formula (2).

General formula (1) R ₁ -CH (OH) -CH (OH) -CH ₂ -R ₂
(In formula (1), R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom, a methyl group, an ethyl group or a propyl group.)
General formula (2) R ₃ -CH (OH) -CH ₂ -CH (OH) -R ₄
(In formula (2), R ₃ represents a hydrogen atom or a methyl group, and R ₄ represents a hydrogen atom, a methyl group, an ethyl group or a propyl group.)
General formula (3) CH ₃ -OR ₅ -OH
(In formula ( ₃ ), R5 represents a divalent saturated hydrocarbon group having a branched chain.)
General formula (4) R ₆ -O- (EO) _m -H
(In formula (4), R ₆ represents a methyl group, an ethyl group, a butyl group or an isopropyl group, EO represents an ethylene oxide group, and m represents an integer of 1 to 3.)
General formula (5) R ₇ -O- (PO) _n -H
(In the formula, R ₇ represents a methyl group, an ethyl group, a butyl group or an aryl group, PO represents a propylene oxide group, and n represents an integer of 1 to 3).

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

FIG. 1 is a schematic diagram 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 curing type on a surface to which the pretreatment liquid of the recording medium is applied. It has a step of applying ink and (3) a step of irradiating the applied active ray-curable ink with active rays. Hereinafter, each step will be described.

1-1. Step of applying the 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 contains water, a water-soluble organic solvent and a resin.

(Water-soluble organic solvent)
The water-soluble organic solvent contains glycol ethers represented by the following general formulas (3) to (5). However, the glycol ether represented by the following general formula (3) is included together with the alkanediol represented by the following general formula (1) or the following general formula (2).

General formula (1) R ₁ -CH (OH) -CH (OH) -CH ₂ -R ₂
(In formula (1), R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom, a methyl group, an ethyl group or a propyl group.)
General formula (2) R ₃ -CH (OH) -CH ₂ -CH (OH) -R ₄
(In formula (2), R ₃ represents a hydrogen atom or a methyl group, and R ₄ represents a hydrogen atom, a methyl group, an ethyl group or a propyl group.)
General formula (3) CH ₃ -OR ₅ -OH
(In the formula (3), R ₅ represents a divalent saturated hydrocarbon group having a branched chain. The carbon number of R ₅ is not particularly limited, but is preferably 2 or more and 10 or less, and 3 or more and 5 It is more preferable that it is as follows.
General formula (4) R ₆ -O- (EO) _m -H
(In formula (4), R ₆ represents a methyl group, an ethyl group, a butyl group or an isopropyl group, EO represents an ethylene oxide group, and m represents an integer of 1 to 3.)
General formula (5) R ₇ -O- (PO) _n -H
(In the formula, R ₇ represents a methyl group, an ethyl group, a butyl group or an aryl group, and among the aryl groups, a phenyl group is more preferable. PO represents a propylene oxide group, and n represents 1 to 3 Represents an integer.)

By containing the glycol ether represented by the general formula (3) to the above general formula (5) as the water-soluble organic solvent in the pretreatment liquid, the cracking of the image portion when the coating film is bent is reduced. be able to. This is because the glycol ether represented by the general formula (3) to the above general formula (5) is a polyfunctional active ray-polymerizable compound (the polyfunctional active ray-polymerizable compound is an oligomer and an oligomer other than the monomer. Although it is a concept including a prepolymer and the like, for the sake of simplicity, it is also referred to as a "polyfunctional monomer" below) and has a structure similar to that of a functional group (for example, an ester group) (for example, an ether group, etc.). It is considered that this is because it has a large number of ethylene oxide groups, propylene oxide groups, etc.) and therefore has a high affinity with the polyfunctional monomer. That is, the glycol ethers represented by the general formulas (3) to (5) have a high affinity when the active ray-curable ink is applied to the surface of the pretreatment liquid. Easy to get in between functional monomers. The glycol ethers represented by the general formulas (3) to (5) that have entered between the polyfunctional monomers maintain an appropriate distance between the monomers in the active ray-curable ink, and crosslink the monomers. It suppresses the reaction from proceeding excessively and imparts flexibility to the coating film. Therefore, even if the coating film is formed with an ink containing a polyfunctional monomer, it is considered that the coating film is unlikely to become excessively hard and cracks are unlikely to occur.

Although the glycol ether represented by the general formula (3) has an ether group, it is considered that the affinity with the polyfunctional monomer is not so high because the number thereof is small. On the other hand, the alkanediol represented by the above general formula (1) or the above general formula (2) has an intermolecular interaction between its hydroxy group and the carbonyl group of the polyfunctional monomer contained in the active ray-curable ink. Therefore, it is easy to enter between the polyfunctional monomers. Further, the alkanediol represented by the general formula (1) or the general formula (2) has a high affinity with the glycol ether represented by the general formula (3). Therefore, the alkanediol represented by the general formula (1) or the general formula (2) has an action of entering between the polyfunctional monomers and the glycol ether represented by the general formula (3) is polyfunctional. It is thought to have an action of assisting the entry between the monomers. Due to these actions, the alkanediol represented by the general formula (1) or the general formula (2) itself imparts flexibility to the coating film, and the flexibility due to the glycol ether of the general formula (3). It is considered that the application of the coating film is promoted to further increase the flexibility of the coating film.

The polyfunctional monomer having a hydrophilic functional group such as an ethylene oxide group, a propylene oxide group and a hydroxy group is represented by the above general formula (1) or the above general formula (2) because the intermolecular interaction is stronger. It is easy to allow alkanediol to enter between polyfunctional monomers. Therefore, it is considered that the effect of imparting flexibility to the coating film is more remarkable when these polyfunctional monomers having a hydrophilicity are used.

Examples of the alkanediol represented by the general formula (1) include 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 2,3-butanediol, and 2,3-pentane. Diols, 1,2-hexanediol, 2,3-hexanediol and the like are included. Among the alkanediols represented by the general formula (1), 1,2-butanediol and 1,2-hexanediol are preferable.

Examples of the alkanediol represented by the general formula (2) include 1,3-propanediol, 1,3-butanediol, 2,4-pentanediol and the like. Among the alkanediols represented by the general formula (2), 1,3-butanediol is preferable.

Examples of the glycol ether represented by the general formula (3) include 3-methoxy-1-butanol, 3-methoxy-3-methyl-1-butanol, 2-methoxy-1-propanol and the like. Among the glycol ethers represented by the general formula (3), 3-methoxy-3-methyl-1-butanol is preferable.

Examples of the glycol ether represented by the general formula (4) include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol mono. Includes butyl ether, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether and the like. Among the glycol ethers represented by the general formula (4), triethylene glycol monobutyl ether is preferable.

Examples of the glycol ether represented by the general formula (5) include propylene glycol monomethyl ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether and the like. Among the glycol ethers represented by the general formula (5), tripropylene glycol monomethyl ether is preferable.

Further, the water-soluble organic solvent according to the embodiment of the present invention may contain other water-soluble organic solvents other than the water-soluble organic solvents represented by the general formulas (1) to (5). Examples of the above other water-soluble organic solvents include glycerins such as glycerin, diglycerin, and polyglycerin, ethylene glycol, diethylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol. , Neopentyl glycol, trimethylolethane, trimethylolpropane, tributylolpropane, pentaerythritol, and glycols such as polyfunctional glycols including sorbitol.

The content of the water-soluble organic solvent (including the water-soluble organic solvent represented by the general formulas (1) to (5) and other water-soluble organic solvents) is based on the total mass of the pretreatment liquid. It is preferably 50% by mass or more and 80% by mass or less, and preferably 55% by mass or more and 75% by mass or less. By setting the content of the water-soluble organic solvent to 50% by mass or more and 80% by mass or less with respect to the total mass of the pretreatment liquid, it is possible to suppress a decrease in image density, and more cracking and strike-through occur. It can be made difficult. It is considered that this is because the resin contained in the pretreatment liquid can be uniformly applied to the recording medium by improving the viscosity and wettability with an appropriate amount of the water-soluble organic solvent, so that the decrease in image density and strike-through are suppressed. .. Further, since a sufficient amount of the water-soluble organic solvent can enter the polyfunctional monomer contained in the ink, it is considered that the cured film of the ink is kept flexible and cracking is less likely to occur.

The content of the alkanediol represented by the general formula (1) or the general formula (2) is preferably 45% by mass or more and 70% by mass or less with respect to the total mass of the pretreatment liquid. It is more preferably 50% by mass or more and 65% by mass or less. By setting the content of the alkanediol to 45% by mass or more, it is possible to make cracking less likely to occur. It is considered that this is because the above-mentioned effect of imparting flexibility to the coating film is more sufficiently exerted. Further, by setting the content to 70% by mass or less, the storage stability of the pretreatment liquid can be ensured.

The content of glycol ether represented by the general formula (3) is preferably 5% by mass or more and 15% by mass or less with respect to the total mass of the pretreatment liquid, and is 5% by mass or more and 10% by mass or less. The following is more preferable. By setting the content of the glycol ether to 5% by mass or more, it is possible to make cracking less likely to occur. It is considered that this is because the above-mentioned effect of imparting flexibility to the coating film is more sufficiently exerted. Further, by setting the content to 15% by mass or less, the storage stability of the pretreatment liquid can be ensured.

The content of glycol ether represented by the general formula (4) or the general formula (5) is preferably 15% by mass or more and 30% by mass or less with respect to the total mass of the pretreatment liquid. It is more preferably 20% by mass or more and 25% by mass or less. By setting the content of the glycol ether to 15% by mass or more, it is possible to make cracking less likely to occur. It is considered that this is because the above-mentioned effect of imparting flexibility to the coating film is more sufficiently exerted. Further, by setting the content to 30% by mass or less, it is possible to prevent the pretreatment liquid from excessively permeating into the recording medium.

In one embodiment of the present invention, the water contained in the pretreatment liquid is not particularly limited, and may be ion-exchanged water, distilled water, or pure water.

(resin)
The pretreatment liquid contains a resin. The resin limits the movement of the active ray-curable ink to the surface side of the recording medium through the pretreatment agent, and suppresses a decrease in image density and strike-through.

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

Examples of the water-soluble resin 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 the like. Styline-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 Includes copolymers, vinyl acetate-acrylic acid copolymers, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, carboxymethyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, saccharides and the like, and salts thereof. 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 commercial products of the above water-soluble resin include John Krill 63J, John Krill 67, John Krill 678, John Krill 586, John Krill 611, John Krill 680, John Krill 682, John Krill 683, and John Krill manufactured by BASF. 690, John Krill 780 ("John Krill" is a registered trademark of the company), Toagosei Corporation's Julimer AT-210, AT-510, AT-613, ARUFON series ("Jurimer", "ARUFON" are registered by the company) Trademark), X-1, X-200, X-205, X-220, YS-1274, VS-1047, RS-1191, TS-1315, RS-1190 and the like manufactured by Seiko PMC Corporation. 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 commercial products of the above (meth) acrylic resin emulsion include Aron A-104 and 106 manufactured by Toagosei Co., Ltd. (“Aron” is a registered trademark of the company), Viniblanc 2580 manufactured by Nisshin Chemical Industry Co., Ltd., Includes Vinibran 2585, Vinibran 2680, Vinibran 2682, Vinibran 2648, Vinibran 2685, Vinibran 2687, Vinibran GA-6610, BASF's John Krill 741, John Krill 790, John Krill 537J and the like. As for the above (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 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. "Superflex" is a registered trademark of the company), Permarin UC-20 manufactured by Sanyo Kasei Kogyo Co., Ltd. ("Parmarin" is a registered trademark of the company), Parasurf UP-22 manufactured by Ohara Palladium Chemical Co., Ltd., etc. are included. As for the urethane-based 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 Unitika Ltd.'s Elitel KA-5034, Elitel KA-5071S, Elitel KA-1449, Elitel KA-0134, Elitel KA-3556, Elitel KA-6137, Elitel KZA. -6034, Elitel KT-8803, Elitel KT-8701, Elitel KT-9204, Elitel KT-8904, Elitel KT-0507, Elitel KT-9511, etc. ("Elitel" is a registered trademark of the company). The polyester resin emulsion may be used alone or in combination of two or more.

Examples of the above-mentioned polyolefin resin emulsion include Arrowbase SB-1200 manufactured by Unitika Ltd. (“Arrowbase” is a registered trademark of the company), Auroralen 150A, Auroralen AE-301 manufactured by Nippon Paper Industries, Ltd., and Supercron. E-415 (“Auroren” and “Supercron” are registered trademarks of the same company), Hardlen Na-1001 manufactured by Toyobo Co., Ltd. (“Hardren” is a registered trademark of the company), etc. are included. As the polyolefin-based 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 distributed 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, (meth) acrylic resin emulsions and urethane resin emulsions are preferable. When a (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 also excellent in storage stability such as being difficult to settle.

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

The resin contained in the pretreatment agent according to the embodiment of the present invention preferably has a glass transition temperature (Tg) of 15 ° C. or higher and 90 ° C. or lower, and more preferably 30 ° C. or higher and 60 ° C. or lower. When the glass transition temperature (Tg) of the resin is 15 ° C. or higher, ink can be applied to a surface in which the resin does not soften so much and gaps between resin molecules due to the movement of the resin are unlikely to occur. Therefore, the resin sufficiently suppresses the unintended diffusion of the ink, whereby the strike-through of the ink can be sufficiently suppressed. Further, when the glass transition temperature (Tg) of the resin is 15 ° C. or higher, the resin is difficult 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 by using 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 can be 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 it is possible to suppress a decrease in density and strike-through of the active ray-curable ink. 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.

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

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

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 and fungicides)
Examples of the above-mentioned preservatives or fungicides include aromatic halogen compounds (eg, Presidentol CMK manufactured by Lonza), methylene dithiosianate, halogen-containing nitrogen-sulfur compounds, 1,2-benzisothiazolin-3-one (eg, for example). PROXELGXL) manufactured by Lonza.

The preservative or fungicide is preferably 0.1% by mass or more and 1% by mass or less, and preferably 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, diameter of cone plate: 75 mm, cone angle: 1.0 °).

[Pretreatment liquid application method]
The pretreatment liquid can be applied by a known liquid coating method such as spray coating, spiral coating using a nozzle or slit, dipping coating, roll coater coating, gravure coating, flexographic coating, and inkjet coating.

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 Bristol method shall be 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 the "JAPAN TAPPI Paper and Pulp Test Method" adopted by the Japan Technical Association of the Pulp and Paper (JAPAN TAPPI). 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 The step of applying active ray-curable ink (hereinafter, also simply referred to as “ink applying step”) is an active ray-curable type on the surface of the pretreatment liquid applied to the surface of the recording medium. This is a process of applying ink 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. It is preferable, and it is more preferable that the liquid 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. 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 does not soften so much and the gaps between the resin molecules due to the movement of the resin are unlikely to occur. Therefore, it is considered that the resin sufficiently suppresses the unintended diffusion of the ink, thereby sufficiently suppressing the strike-through of the ink.

In the present invention, "the temperature is set to be 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 (for example, ultraviolet rays).

(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, gamma 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 a monomer, a polymerizable oligomer, a prepolymer, or a mixture thereof.

The active ray-curable ink contains a polyfunctional active ray-polymerizable compound. The "polyfunctional active ray-polymerizable compound" includes a bifunctional monomer and a trifunctional or higher functional monomer.

The content of the polyfunctional monomer is preferably 25% by mass or more, more preferably 25% by mass or more and 90% by mass or less, and 50% by mass or more and 85% by mass with respect to the total mass of the active ray-curable ink. It is more preferably mass% or less. When the content of the polyfunctional monomer is 25% by mass or more with respect to the total mass of the active ray-curable ink, the ink is irradiated with active rays to further improve the curability of the ink, and the ink is cured. The surface of the cured product can be hardened to improve the scratch resistance of the formed image. Further, since the content of the polyfunctional monomer is 90% by mass or less with respect to 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 fixing property to the recording medium is not too hard. Is not easily damaged.

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, bifunctional 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 methacrylic acid group, and "(meth) acrylic" means acrylic or methacrylic. Means.

Examples of bifunctional (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. (Meta) 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-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 di (meth) ) Bifunctional (meth) acrylates such as acrylates, dipropylene glycol di (meth) acrylates, and tripropylene glycol di (meth) acrylates. As the bifunctional (meth) acrylate, only one type may be used alone, or two or more types may be used in combination.

Examples of trifunctional or higher functional (meth) acrylates include trifunctional (meth) acrylates such as trimethylolpropanetri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, and dipentaerythritol. Includes trifunctional or higher functional (meth) acrylates such as hexa (meth) acrylate, ditrimethylol propanetetra (meth) acrylate, glycerin propoxytri (meth) acrylate and pentaerythritol ethoxytetra (meth) acrylate, polyester acrylate oligomers (meth). It includes oligomers having an acryloyl group 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 polyfunctional (meth) acrylate, 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 polyfunctional epoxy compounds, polyfunctional vinyl ether compounds and polyfunctional oxetane compounds.

Examples of the above-mentioned polyfunctional epoxy compounds include 3,4-epoxycyclohexylmethyl-3', 4'-epoxycyclohexanecarboxylate, bis (3,4-epoxycyclohexylmethyl) adipate, and ε-caprolactone-modified 3,4-. Epoxycyclohexylmethyl 3', 4'-epoxycyclohexanecarboxylate, 1-methyl-4- (2-methyloxylanyl) -7-oxabicyclo [4,1,0] heptane, 2- (3,4-epoxy) Alicyclic epoxy resins such as cyclohexyl-5,5-spiro-3,4-epoxy) cyclohexanone-meth-dioxane and bis (2,3-epoxycyclopentyl) ethers, diglycidyl ethers 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 aliphatics such as glycerin. 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 a polyhydric alcohol, and bisphenol A or an alkylene thereof. Included are di or polyglycidyl ethers of oxide adducts, di or polyglycidyl ethers of hydrogenated bisphenol A or alkylene oxide adducts thereof, aromatic epoxy compounds including novolak type epoxy resins and the like.

Examples of the polyfunctional vinyl ether compound include 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, and cyclohexanedimethanol. Divinyl ethers, and di- or trivinyl ether compounds including trimethylolpropane trivinyl ethers and the like are included.

Examples of the polyfunctional oxetane compound include 1,4 bis {[(3-ethyl-3-oxetanyl) methoxy] methyl} benzene, di [1-ethyl (3-oxetanyl)] methyl ether and the like. ..

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

The active ray-curable ink may contain a monofunctional active ray-polymerizable compound. Examples of the monofunctional active ray polymerizable compound include monofunctional (meth) acrylates, monofunctional epoxy compounds, monofunctional vinyl ether compounds, monofunctional oxetane compounds and the like.

Examples of the 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. (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 ( Meta) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- (meth) acryloyloxyethyl succinic acid, 2- ( Includes meta) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl-2-hydroxyethyl-phthalic acid, t-butylcyclohexyl (meth) acrylate and the like. As the monofunctional (meth) acrylate, only one type may be used alone, or two or more types may be used in combination.

Examples of the monofunctional epoxy compound include vinylcyclohexene monoepoxiside and the like.

Examples of the monofunctional vinyl ether compound 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, and isopropyl vinyl ether. , Isopropenyl ether-o-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether and the like.

Examples of the monofunctional oxetane compound include 3-hydroxymethyl-3-methyloxetane, 3-hydroxymethyl-3-ethyloxetane, 3-hydroxymethyl-3-propyloxetane, and 3-hydroxymethyl-3-normalbutyl. Oxetane, 3-Hydroxymethyl-3-phenyloxetane, 3-Hydroxymethyl-3-benzyloxetane, 3-Hydroxyethyl-3-methyloxetane, 3-Hydroxyethyl-3-ethyloxetane, 3-Hydroxyethyl-3-propyl Oxetane, 3-Hydroxyethyl-3-phenyloxetane, 3-Hydroxypropyl-3-methyloxetane, 3-Hydroxypropyl-3-ethyloxetane, 3-Hydroxypropyl-3-propyloxetane, 3-Hydroxypropyl-3-phenyl Includes oxetane, 3-hydroxybutyl-3-methyloxetane and 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane.

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 the SP value of the monomer is 17 or more and 20 or less. It is more preferable to have. 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.

(Polymer 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 as long as it can initiate 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, the polymerization initiator can be used. 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 the above-mentioned intramolecular bond cleavage type radical polymerization initiator include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethylketal, 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 ( Acetphenone-based initiators, such as 4-methylthiophenyl) propan-1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone, benzoin, benzoin methyl ether, and benzoin isopropyl ether. Includes benzoins, including 2,4,6-trimethylbenzoindiphenylphosphine oxide, acylphosphine oxide-based initiators, and benzyl and methylphenylglycoesters.

Examples of the above-mentioned intramolecular hydrogen abstraction type radical polymerization initiator include benzophenone, o-benzoylmethylbenzoate, 4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-. Benzophenone-based initiators, including diphenylsulfide, acrylicized benzophenone, 3,3', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, and 3,3'-dimethyl-4-methoxybenzophenone, 2- Thioxanthone-based initiators including isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, etc., Michlerketone, aminobenzophenone-based initiators including 4,4'-diethylaminobenzophenone, etc. Includes 10-butyl-2-chloroacrydone, 2-ethylanthraquinone, 9,10-phenanslenquinone, as well as camphorquinone and the like.

Examples of the cationic polymerization initiator include a photoacid generator. Examples of photoacid generators include B (C ₆ F ₅ ) _4- ^, PF _6- ^, AsF _6- ^, SbF _6- ^, CF of aromatic onium compounds including diazonium, ammonium, iodonium, sulfonium, and phosphonium. ₃ SO ₃ ^- salts and other sulfonates that generate sulfonic acids, halides that photogenerate hydrogen halides, iron allen complexes, and the like are included.

(Gelling 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 a liquid when heated, so that the active ray-curable ink can undergo a sol-gel phase transition in response to a temperature change. The gelling agent immediately gels and temporarily fixes (pinning) the activated ray-curable ink, which has become liquid by heating, immediately when the temperature drops due to landing on the recording medium. As a result, the gelling agent suppresses the excessive spread of the ink that has landed on the recording medium, and enables the formation of a higher-definition image.

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 and the viscosity of the ink suddenly changes when the ink that has been solified or liquefied by heating is cooled. Specifically, the solified or liquefied ink is cooled while measuring the viscosity with, for example, a rheometer "MCR300" (manufactured by Antonio Par), and the temperature at which the viscosity rises sharply is set to the gel of the ink. It can be a sol.

The gelling agent can retain the active ray-polymerizable compound during crystallization. The gelling agent makes it difficult for the active ray-polymerizable compound and the resin contained in the pretreatment liquid to be compatible with each other, suppresses the penetration of the active ray-polymerizable compound into the pretreatment liquid, and strikes through the ink. Can be suppressed. In particular, when the gelling agent forms a structure (cardhouse structure) in which the active ray-polymerizable compound is contained in the three-dimensional space, a large amount of the active ray-polymerizable compound is likely to be contained in the three-dimensional space, and the above-mentioned action. The effect of suppressing strike-through is remarkable.

Examples of the gelling agent include dipentadecyl ketone, diheptadecyl ketone (stealon), dilignoceryl ketone, dibehenyl ketone, distearyl ketone, dieicosyl ketone, dipalmityl ketone, dimyristyl ketone, and lauryl. Adipose ketone waxes such as myristyl ketone, lauryl palmityl ketone, myristyl palmityl ketone, myristyl stearyl ketone, myristyl behenyl ketone, palmityl stearyl ketone, balmityl behenyl ketone and stearyl behenyl ketone, cetyl palmitate, stearyl stearate, behenin. Behenyl acid, icosyl icosanoate, behenyl stearate, palmityl stearate, lauryl stearate, stearyl palmitate, myristyl myristate, cetyl myristine, stearyl octyldodecyl myristate, stearyl oleate, stearyl erucate, stearyl linoleate, oleic acid Aliphatic ester waxes such as behenyl and arachidyl linoleate, amide compounds such as N-lauroyl-L-glutamate dibutylamide, N- (2-ethylhexanoyl) -L-glutamate dibutylamide, 1,3: 2,4- Divendilidene sorbitols such as bis-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 Rows and vegetable waxes such as jojoba ester, animal waxes such as honey wax, lanolin and whale wax, monttan wax, and mineral waxes such as hydride wax, hardened castor oil or hardened castor oil derivative, montane wax derivative, paraffin. Modified waxes such as wax derivatives, microcrystallin wax derivatives or polyethylene wax derivatives, higher fatty acids such as behenic 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, ricinoleic acid amides, 12-hydroxystearic Fatty acid amides such as acid amides, N-stearyl stealic acid N-substituted fatty acid amides such as amides, N-oleyl palmitate amides, N, N'-ethylene bisstearyl amides, N, N'-ethylene bis-12-hydroxystearyl amides, and N, N'-xylylene bisstearyl amides. Special fatty acid amides such as amides, higher amines such as dodecylamine, tetradecylamine or octadecylamine, stearylstearic 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 anhydride maleic acid copolymer wax, polymerizable waxes, dimer acids and dimers. Includes diol 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% 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 1% by mass or more and less than 10% by mass, and further preferably 1% by mass or more and 5% by mass or less with respect to the total mass of the active ray curable ink.

(Polymerization inhibitor)
The active ray-curable ink according to one embodiment of the present invention may contain a polymerization inhibitor.

Examples of the polymerization inhibitors 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, methylethylketoxim, cyclohexanone 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 according to an embodiment of the present invention 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% by mass or less, and more preferably 0.4% by mass or more and 10% by mass or less with respect to the total mass of the ink. 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% 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 may be sufficient to 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 according to one embodiment of the present invention may contain a fixing resin. By containing the fixing resin, the scratch resistance and blocking resistance of the coating film can be further enhanced.

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% by mass or more and 10% by mass or less with respect to the total mass of the active ray-polymerizable compound.

(Surfactant)
The active ray-curable ink according to one embodiment of the present invention 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 can suppress the coalescence between adjacent droplets.

Examples of the above-mentioned 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 more preferably 0.001% by mass or more and 1% by mass or less, based on the total mass of the active ray-curable ink. preferable.

(Other ingredients)
In addition to the above components, the active ray-curable ink according to an embodiment of the present invention has a polysaccharide, a viscosity modifier, a resistivity adjuster, a film-forming agent, an ultraviolet absorber, an antioxidant, a fading inhibitor, and an antifungal agent. It may contain an agent, a rust preventive, and the like. The above other components may contain only one kind or two or more kinds in the above composition.

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

(Physical characteristics of active ray curable ink)
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 from the viewpoint of further enhancing the ejection property from the inkjet head. The viscosity in the above 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 ejected 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 80 ° C. is measured by heating the active ray curable ink to 100 ° C. with a rheometer and measuring the viscosity with a stress control type rheometer "Physica MCR301" (manufactured by Antonio Par). However, 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, the viscosities at 40 ° C. and 80 ° C. are shown, respectively. Obtained by reading.

[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 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 colloidal 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. In 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 electrical-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) type 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 + 40 ° C. of the active ray-curable ink, the thermal load of the inkjet head can be reduced. In particular, in an inkjet head using a piezo element, performance deterioration tends 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 the 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. 2. Image Forming Device FIG. 1 is a schematic diagram showing an exemplary configuration of an image forming device 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 applying unit 120 for applying 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 (direction of 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 be configured to 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 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 ray 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 adjusts the temperature of the recording medium 110. As the temperature adjusting unit 150, a known device capable of adjusting the surface of the recording medium 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 control unit 150 include a heater, a cooling device, and a blower.

Further, in the above description, the 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 the spray coating method, the dipping method, and the screen printing method 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 26)
Each component shown in Tables 1 to 3 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 26. The units of the numerical values shown in Tables 1 to 3 are parts by mass, the resin content is a solid content conversion value, and the surfactant is Orfin E1010 manufactured by Nissin Chemical Industry Co., Ltd. ”. The preservative is Proxel GXL (S) manufactured by Lonza Japan Co., Ltd. Further, the numerical values shown in Tables 1 to 3 are values in which the total amount is 100 parts by mass.

The abbreviations of the resins shown in Tables 1 to 3 are as follows.

A-1: Water-dispersible acrylic resin emulsion "John Krill 790"
A-2: Styrene-acrylic acid copolymer "John Krill 63J"
A-3: Water-dispersible acrylic resin emulsion "John Krill 537J"
A-4: Polyurethane aqueous dispersion "Superflex 150HS"
A-5: Water-dispersible acrylic resin emulsion "John Krill 741"
A-6: Water-dispersible acrylic resin emulsion "Aron A-106"
A-7: Water-dispersible acrylic resin emulsion "John Krill 780"

The water-dispersible acrylic resin emulsion "John Krill 790, 63J, 537J, 741 and 780" is manufactured by BASF, and the polyurethane water dispersion "Superflex 150HS" is manufactured by Daiichi Kogyo Seiyaku Co., Ltd. The water-dispersible acrylic resin emulsion "Aron A-106" is manufactured by Toa Synthetic Co., Ltd.

Further, the glass transition temperature (Tg) of the resins (A-1 to A-7) shown in Tables 1 to 3 is the catalog value.

The water-soluble organic solvents shown in Tables 1 to 3 are as follows. Further, the abbreviations of glycol ethers represented by the general formula (4) and the general formula (5) are shown below.

(Alkanediol represented by the general formula (1))
1,2-Propanediol 1,2-Butanediol 1,2-Pentanediol 1,2-Hexanediol 2,3-Butanediol

(Alkanediol represented by the general formula (2))
1,3-Propanediol 1,3-Butanediol

(Glycol ether represented by the general formula (3))
3-Methoxy-1-butanol 3-Methoxy-3-methyl-1-butanol

(Glycol ether represented by the general formula (4))
TEGBE: Triethylene Glycol Monobutyl Ether

(Glycol ether represented by the general formula (5))
TPGME: Tripropylene glycol monomethyl ether

(Other water-soluble organic solvents)
Glycerin dipropylene glycol

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

2-1. Preparation of pigment dispersion (preparation of cyan pigment dispersion 1)
Polymerization of 72.7 parts by mass of lauryl acrylate and 7.0 parts by mass of pigment dispersant "BYKJET-9151" (manufactured by Big Chemie Japan Co., Ltd., "BYKJET" is a registered trademark of the same company) and 0.3 parts by mass. The inhibitor "Igastab UV-10" (manufactured by BASF, "Igastab" is a registered trademark of the same company) was placed in a beaker made of stainless steel and stirred for 1 hour while heating on a hot plate at 65 ° C. 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 lauryl acrylate, 10 parts by mass of tripropylene glycol diacrylate, 8 parts by mass of dipropylene glycol diacrylate, and 10 parts by mass of 1 , 9-Nonandiol diacrylate, 5 parts by mass of polymerization initiator "IRGACURE 819" (BASF, "IRGACURE" is a registered trademark of the same company), and 0.15 parts by mass of polymerization inhibitor "Irgastab UV-10". Was placed in a stainless steel beaker, stirred at 105 ° C. for 45 minutes, and then filtered through an ADVATEC Teflon (registered trademark) 3 μm membrane filter to obtain an active ray-curable ink 1.

(Preparation of active ray curable inks 2 to 5)
Table 4 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 5. 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 4 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 DPGDA: Dipropylene Glycol Diacrylate 1,9-NDDA: 1,9-Nonanediol Diacrylate

(Polyfunctional monomer)
TMP (EO) 9TA: Trimethylolpropane EO-modified (9) Triacrylate TMP (EO) 3TA: Trimethylolpropane EO-modified (3) Triacrylate

(Polymer initiator)
819: IRGACURE 819

(Polymerization inhibitor)
UV-10: Irgastab UV-10

(Gelling agent)
SS: Stearyl stearate

3. 3. Evaluation Image formation was performed using pretreatment liquids 1 to 26 and inks 1 to 5, and image density, strike-through, bending 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 26 are 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) is 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 × 2 rows, staggered arrangement, 1 row nozzle pitch 600 dpi) was used. Ink 1 was ejected at a droplet speed of about 6 m / s under ejection conditions where the appropriate amount of one drop of liquid was 3.0 pl. The transport section of the recording medium was set so that the temperature of the recording medium to which the pretreatment liquid was applied was 50 ° 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 ultraviolet rays from an LED lamp (395 nm, water-cooled LED manufactured by Phoseon Technology) (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 5 and the temperature of the recording medium was changed to the temperature shown in Table 5.

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. D: The density is low on the image surface. Concentration unevenness is clearly felt and the concentration is low

3-3. Evaluation of folding cracks (evaluation method)
The solid image obtained by the above image forming method was folded in half (mountain fold), and the folded portion was visually observed.

(Evaluation criteria)
A: No change is observed B: The color of the bent part changes, but no cracks are observed C: Slight cracks occur in the bent part, but there is no practical problem D: When folded , The coating film peels off from the cracked part E: Cracks and the coating film fall off just by bending

3-4. Evaluation of strike-through (evaluation method)
The backside density of the solid image obtained by the above image forming method was measured using a 938 spectrodensitometer (manufactured by X-Rite). In addition, the density of the non-recording portion of the recording medium on which the solid image was formed was also measured in the same manner. Next, the density difference was obtained from (concentration of the back surface of the cyan image portion)-(concentration of the non-image portion), and strike-through was evaluated according to the following evaluation criteria.

(Evaluation criteria)
A: Concentration difference is less than 0.05 B: Concentration difference is 0.05 or more and less than 0.08 C: Concentration difference is 0.08 or more and less than 0.12 D: Concentration difference is 0.12 or more Less than 0.15 E: Concentration difference is 0.15 or more

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 after rubbing more than 100 times B: Decrease in image density is observed after rubbing 100 times, but there is no practical problem C: Clear image density after rubbing 80 times There is no problem in practical use. D: A clear decrease in image density is observed at the stage of rubbing less than 50 times, and there is a problem in practical use.

The above evaluation results are shown in Table 5.

From the above evaluation results, the pretreatment liquid contains glycol ethers represented by the general formulas (3) to (5) as the water-soluble organic solvent, so that the coating film is irradiated with active rays (for example, ultraviolet rays). It was found that the flexibility was imparted to the image, and the cracking of the image portion when the coating film was bent could be reduced. This has a structure similar to that of the glycol ether represented by the general formulas (3) to (5) and the polyfunctional monomer contained in the active ray-curable ink (for example, an ether group, an ethylene oxide group, a propylene oxide group, etc.). ), The affinity between the polyfunctional monomer and the glycol ethers represented by the general formulas (3) to (5) is enhanced, so that the glycol ether can easily enter between the polyfunctional monomers, and the recording medium can be used. It is considered that this is because the distance between the monomers in the active ray-curable ink applied to the surface can be kept appropriate and the cross-linking reaction of the monomers can be suppressed from progressing excessively.

Further, the glycol ether represented by the general formula (3) is contained together with the alkane diol represented by the general formula (1) or the general formula (2), so that the image portion is cracked when the coating film is bent. Was found to be able to be further reduced. This is because the glycol ether represented by the general formula (3) has an ether group, but the number thereof is small, so that it is considered that the affinity with the polyfunctional monomer is not so high. On the other hand, the alkanediol represented by the general formula (1) or the general formula (2) has an intermolecular interaction between its hydroxy group and the carbonyl group of the polyfunctional monomer contained in the active ray-curable ink. Easy to get in between polyfunctional monomers. Further, the alkanediol represented by the general formula (1) or the general formula (2) has a high affinity with the glycol ether represented by the general formula (3). Therefore, the alkanediol represented by the general formula (1) or the general formula (2) has an action of entering between the polyfunctional monomers by itself, and the glycol ether represented by the general formula (3) is between the polyfunctional monomers. It is thought to have an action that assists in entering. Due to these actions, the alkanediol represented by the general formula (1) or the general formula (2) imparts flexibility to the coating film by itself, and also imparts flexibility by the glycol ether of the general formula (3). It is believed to promote and increase the flexibility of the coating film.

It was also found that by lowering the temperature of the recording medium to lower than the glass transition temperature of the resin, it is possible to suppress the occurrence of ink strike-through and image density unevenness. This is because by setting the temperature of the recording medium in this way, even if the heated ink is applied to the surface of the recording medium to which the pretreatment liquid is applied, the resin applied by the pretreatment liquid does not soften so much. In addition, since the ink can be applied to the surface in which gaps between the molecules of the resin are unlikely to occur due to the movement of the resin, it is considered that the resin sufficiently suppresses the unintended diffusion of the ink.

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 retain 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 separated from each other. 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 polyfunctional monomers 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 it with 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, it is possible to suppress the strike-through of the ink and the folding of the image. 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 control unit

Claims (12)

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,
Have,
The pretreatment liquid contains water, a water-soluble organic solvent and a resin, and contains.
The active ray-curable ink contains a polyfunctional active ray-polymerizable compound and contains.
The content of the water-soluble organic solvent is 50% by mass or more and 80% by mass or less with respect to the total mass of the pretreatment liquid.
The water-soluble organic solvent contains any of the glycol ethers represented by the following general formulas (3) to (5), except that the glycol ether represented by the general formula (3) is described below. An image forming method included with an alkanediol represented by the formula (1) or the following general formula (2).
General formula (1) R ₁ -CH (OH) -CH (OH) -CH ₂ -R ₂
(In formula (1), R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a hydrogen atom, a methyl group, an ethyl group or a propyl group.)
General formula (2) R ₃ -CH (OH) -CH ₂ -CH (OH) -R ₄
(In formula (2), R ₃ represents a hydrogen atom or a methyl group, and R ₄ represents a hydrogen atom, a methyl group, an ethyl group or a propyl group.)
General formula (3) CH ₃ -OR ₅ -OH
(In formula ( ₃ ), R5 represents a divalent saturated hydrocarbon group having a branched chain.)
General formula (4) R ₆ -O- (EO) _m -H
(In formula (4), R ₆ represents a methyl group, an ethyl group, a butyl group or an isopropyl group, EO represents an ethylene oxide group, and m represents an integer of 1 to 3.)
General formula (5) R ₇ -O- (PO) _n -H
(In the formula, R ₇ represents a methyl group, an ethyl group, a butyl group or an aryl group, PO represents a propylene oxide group, and n represents an integer of 1 to 3). The pretreatment liquid according to claim 1, wherein the pretreatment liquid contains glycol ether represented by the general formula (3) and an alkane diol represented by the general formula (1) or the general formula (2). Image formation method. The claim that the total content of the alkanediol represented by the general formula (1) and the general formula (2) is 45% by mass or more and 70% by mass or less with respect to the total mass of the pretreatment liquid. 2. The image forming method according to 2. The image according to claim 2 or 3, wherein the content of the glycol ether represented by the general formula (3) is 5% by mass or more and 15% by mass or less with respect to the total mass of the pretreatment liquid. Forming method. The pretreatment liquid according to any one of claims 2 to 4, wherein the pretreatment liquid contains an alkanediol selected from the group consisting of 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol. Image formation method. The image forming method according to any one of claims 2 to 5, wherein the glycol ether represented by the general formula (3) is 3-methoxy-3-methyl-1-butanol. The image forming method according to any one of claims 1 to 6, wherein the pretreatment agent contains glycol ether represented by the general formula (4) or the general formula (5). The image forming method according to any one of claims 1 to 7, wherein the resin has a glass transition temperature (Tg) of 15 ° C. or higher and 90 ° C. or lower. The invention according to any one of claims 1 to 8, wherein the active ray-curable ink contains 30% by mass or more of the polyfunctional active ray-polymerizable compound with respect to the total mass of the active ray-curable ink. Image formation method. The image forming method according to any one of claims 1 to 9, wherein the active ray-curable ink contains a gelling agent. The image forming method according to any one of claims 1 to 10, wherein the active ray-curable ink is an inkjet ink. In the 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 Bristol method of the recording medium is 10 ml / m ² or more and 30 ml / m ² or less. The image forming method according to any one of claims 1 to 11.

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