JP5566722B2 - Ink set and image forming method - Google Patents

Description

  The present invention relates to an ink set and an image forming method using the ink set.

  In recent years, various methods have been proposed as image recording methods for recording color images. In any case, there is a high demand for the quality of recorded matter, such as image quality, texture, and curl after recording.

  For example, ink jet technology has been applied to the fields of office printers, home printers, and the like, but in recent years, it has been applied in the field of commercial printing. In this commercial printing field, a printing texture like general-purpose printing paper is required rather than having a photograph-like surface that completely shuts out the penetration of the ink solvent into the base paper. Here, when the solvent absorption layer in the recording medium is as thick as 20 to 30 μm, the surface gloss, texture, stiffness, and the like of the recording medium are limited. Therefore, the application of inkjet technology in the commercial printing field is limited to posters, form printing, and the like that are allowed to be limited in terms of surface gloss, texture, stiffness, etc., on the recording medium.

  In addition, the recording medium dedicated for ink jet recording is expensive due to the solvent absorption layer and the water-resistant layer, and this also contributes to the limitation of the ink jet technology application to the commercial printing field.

  On the other hand, a pigment is widely used as a colorant which is one of the components of the ink material, and the pigment is used by being dispersed in a medium such as water. When pigments are used in a dispersed manner, the dispersed particle size when dispersed, the stability after dispersion, size uniformity, etc., and ejection properties from the ejection head are important. It is done.

  Furthermore, since inks containing pigments generally do not penetrate the recording medium and remain on the surface, sufficient performance may not be obtained in terms of fixability (for example, scratch resistance), water resistance, and stain resistance. is there.

  Therefore, an ink-jet ink composition containing self-dispersing polymer particles has been disclosed in order to give good water resistance and stain resistance to an ink containing a pigment (see, for example, Patent Document 1).

  In addition, as a method for imparting good scratch resistance and water resistance to an ink containing a pigment, a method of applying a solution containing a polar polymer onto the recording medium in combination with the pigment ink is disclosed. (For example, refer to Patent Document 2). Furthermore, an image is formed using a reaction liquid that reacts with an ink composition such as a polyvalent metal salt or polyamylamine, and an ink containing a pigment and a thermoplastic resin emulsion, and is fixed at a temperature higher than the softening temperature of the thermoplastic resin. A method is disclosed (for example, see Patent Document 3).

  In relation to the above, a technique (UV inkjet) that uses an ink in which a polymerizable monomer is used in combination with a pigment and is cured with ultraviolet rays is widely known and commonly used. Such UV ink jets show good scratch resistance, but generally are solvent-based inks, which is not environmentally preferable. Also, when inks before curing come into contact with each other, the inks coalesce (landing interference). Not suitable for high-speed recording.

  In addition, environmentally preferable water-based pigment inks have also been studied to improve scratch resistance by containing a polymerizable monomer and cured. For example, a recording medium is contacted with an ink composition to form an aggregate. An ink jet recording method is disclosed in which printing is performed by adhering a reaction liquid containing a reaction agent that generates a photopolymerization initiator and an ink composition containing an acrylate monomer or a resin emulsion (see, for example, Patent Document 4). ). In addition, a one-component ink is disclosed that is used for ink jet recording including a specific cationic oligomer and a photopolymerization initiator together with a coloring material and water (see, for example, Patent Document 5).

In addition, it is disclosed that the image is fixed by a two-liquid reaction including a reaction liquid containing a reactive agent and an ink composition, as landing interference is further suppressed and a higher quality image can be obtained (for example, And Patent Document 6).
Further, in order to realize the formation of a high-quality image and the improvement of film physical properties after curing, the content of the polymerizable compound is 30 to 70% by mass, and the viscosity is 1 to 30 mPa · s (35 ° C. or higher). An ink composition is disclosed (for example, see Patent Document 7).

Japanese Patent No. 3069543 Japanese Patent No. 3217486 Japanese Patent No. 3206797 Japanese Patent No. 3642152 Japanese Patent No. 3576862 JP-A-10-287035 JP 2004-189930 A

However, the methods described in Patent Documents 1 to 5 are expected to improve fixability and water resistance to some extent, but cannot be expected to improve cockling and strength.
In both Patent Documents 6 and 7, since the ink composition uses water as a main solvent, it is not preferable that the droplet ejection portion is cuckled. In addition, this system, which is characterized by the UV effect, cures the image in accordance with the shape of the cockling. Therefore, distortion is accumulated in the image area as the cockling is eased over time after image formation. As a result, the image intensity is reduced.

  The present invention has been made in view of the above, and an object thereof is to provide an ink set and an image forming method capable of forming an image having excellent cuckling and film strength, and to achieve the object.

<1> An ink composition containing a pigment and a water-soluble polymerizable compound that is polymerized by active energy rays, an aggregating agent for aggregating the components in the ink composition, and 25% by mass or more based on the total mass of the liquid 60 A treatment liquid containing an organic solvent having a solubility in 100 g of water (25 ° C.) of 30% or less by mass or less ,
Ink set containing.
<2> The ink set according to <1>, wherein the organic solvent is at least one selected from fatty oil and fat.
<3> The ink set according to <2>, wherein the fatty oil is a non-drying oil.
<4> The ink set according to <3>, wherein the non-drying oil is at least one selected from rapeseed oil, olive oil, peanut oil, and camellia oil.
<5> The ink set according to any one of <1> to <4>, wherein the pigment is a water-dispersible pigment in which at least a part of a surface thereof is coated with a polymer dispersant.
<6> The ink set according to <5>, wherein the polymer dispersant has a carboxyl group.
<7> The ink set according to any one of <1> to <6>, wherein the flocculant is an organic acid.
<8> The ink set according to any one of <1> to <7>, wherein at least one of the ink composition and the treatment liquid further includes a polymerization initiator that initiates polymerization of the polymerizable compound.
<9> The ink set according to any one of <1> to <8>, wherein the ink composition further contains polymer particles.
<10> The treatment liquid is further ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether Any one of <1> to <9>, comprising an aqueous solvent mixed with at least one water selected from the group consisting of triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and ethylene glycol monophenyl ether The ink set according to item.
<1 1 > an ink application step of applying an ink composition containing a pigment and a water-soluble polymerizable compound polymerized by active energy rays to a recording medium by an inkjet method;
A treatment comprising an aggregating agent for aggregating the components in the ink composition, and an organic solvent having a solubility in 100 g of water (25 ° C.) of 25 % by mass or more and 60% by mass or less with respect to the total mass of the liquid. A treatment liquid application step for applying the liquid to the recording medium;
An image forming method comprising:
<1 2 > The image forming method according to <1 1 >, wherein the recording medium is a coated paper having a base paper and a coating layer containing an inorganic pigment.

  According to the present invention, it is possible to provide an ink set and an image forming method capable of forming an image excellent in cockling and film strength.

It is a schematic block diagram which shows the structural example of the inkjet recording device used for implementation of the image forming method of this invention.

Hereinafter, the ink set of the present invention and an image forming method using the ink set will be described in detail.
<Ink set>
The ink set of the present invention includes an ink composition containing a pigment and a polymerizable compound that is polymerized by active energy rays, an aggregating agent that aggregates the components in the ink composition, and 25% by mass to 60 % by mass of the total liquid. And a treatment liquid containing an organic solvent having a solubility in 100 g of water (25 ° C.) of 30% or less by mass or less .

In the present invention, in particular, the ink composition for forming an ink image contains a pigment and a polymerizable compound that is polymerized by active energy rays, and the aggregate liquid is 25% by mass or more and 60 % by mass with respect to the total mass of the liquid. % or less, water (25 ° C.) solubility in 100g is by including an organic solvent is 30% or less, it is possible to effectively suppress the Kac ring. This is presumed to be effective in suppressing cockling by forming an oil film on the recording medium to which the treatment liquid is applied. In addition, when contacted with the treatment liquid, the image is fixed by agglomeration reaction of components (particularly pigment) in the ink composition, and the polymerized and cured in a state where the polymerizable compound is uniformly taken into the gaps of the pigment. Therefore, the intensity of the image is increased. In particular, it is more effective when an image is formed on a coated paper in which the polymerizable compound easily penetrates into the recording medium while the pigment tends to remain on the surface.

-Ink composition-
The ink composition in the present invention comprises a pigment and a polymerizable compound that is polymerized by active energy rays, and preferably contains polymer particles. If necessary, a dispersant, a surfactant, and other components. Can be used.

(Pigment)
The ink composition in the present invention contains at least one pigment as a color material component. There is no restriction | limiting in particular as a pigment, According to the objective, it can select suitably, For example, any of an organic pigment and an inorganic pigment may be sufficient. The pigment is preferably a pigment that is almost insoluble or hardly soluble in water from the viewpoint of ink colorability.

Examples of organic pigments include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are more preferable. Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black. Among these, carbon black is particularly preferable.
A pigment may be used individually by 1 type, or may be used in combination of 2 or more type.

  Although the volume average particle diameter of the pigment in the present invention is not particularly limited, it is preferably 10 to 200 nm, more preferably 10 to 150 nm, from the viewpoints of suppression of cockling and ejection properties. Further, the particle size distribution of the pigment is not particularly limited, and may be either a wide particle size distribution or a monodispersed particle size distribution. Two or more pigments having a monodispersed particle size distribution may be mixed and used.

Here, the volume average particle diameter of the pigment indicates the volume average particle diameter in an ink state, but the same applies to a so-called concentrated ink dispersion at a stage before ink conversion.
In addition, the volume average particle diameter and the particle size distribution of the pigment in the dispersed state are measured using a dynamic light particle size distribution measuring apparatus (Version 10.1.2-211BH (trade name), manufactured by Nikkiso Co., Ltd.). It is obtained by the scattering method.

  In the present invention, the volume average particle diameter of the pigment can be adjusted by a commonly used method. For example, the volume average particle diameter of the pigment can be adjusted to a desired range by appropriately selecting a dispersion time or the like when preparing a pigment dispersion using a dispersant described later.

  The pigment content is preferably from 1 to 25 mass%, more preferably from 2 to 20 mass%, still more preferably from 5 to 20 mass%, particularly preferably from 5 to 15 mass%, based on the total mass of the ink composition. preferable.

~ Dispersant ~
The ink composition of the present invention can contain at least one dispersant. The pigment dispersant may be either a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.

  The low molecular surfactant type dispersant can stably disperse the pigment in the aqueous solvent while keeping the ink at a low viscosity. The low molecular surfactant type dispersant is a low molecular dispersant having a molecular weight of 2,000 or less. The molecular weight of the low molecular surfactant type dispersant is preferably 100 to 2,000, and more preferably 200 to 2,000.

  The low molecular surfactant type dispersant has a structure including a hydrophilic group and a hydrophobic group. Moreover, the hydrophilic group and the hydrophobic group should just be independently contained 1 or more in 1 molecule, respectively, and may have multiple types of hydrophilic group and hydrophobic group. In addition, a linking group for linking a hydrophilic group and a hydrophobic group can be appropriately included.

  The hydrophilic group is anionic, cationic, nonionic, or a betaine type that combines these. The anionic group may be any one as long as it has a negative charge, and may be a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, or a carboxylic acid group. Preferably, it is a phosphoric acid group or a carboxylic acid group, and more preferably a carboxylic acid group. The cationic group may be any one having a positive charge, but is preferably an organic cationic substituent, and more preferably a nitrogen or phosphorus cationic group. Further, it is more preferably a pyridinium cation or an ammonium cation. Examples of the nonionic group include polyethylene oxide, polyglycerin, and a part of a sugar unit.

  The hydrophilic group is preferably an anionic group. The anionic group is preferably a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, or a carboxylic acid group, and more preferably a phosphoric acid group or a carboxylic acid group. Preferably, it is a carboxylic acid group.

  When the low molecular surfactant type dispersant has an anionic hydrophilic group, the pKa is preferably 3 or more from the viewpoint of promoting the aggregation reaction by contacting with an acidic treatment liquid. The pKa of the low molecular surfactant type dispersant is titrated with a solution of 1 mmol / L of the low molecular surfactant type dispersant in a tetrahydrofuran-water (3: 2 = V / V) solution with an acid or alkaline aqueous solution. The value obtained experimentally from the titration curve. When the pKa of the low-molecular surfactant type dispersant is 3 or more, 50% or more of the anionic groups are in a non-dissociated state when in contact with a liquid having a theoretical pH of about 3. Therefore, the water solubility of the low-molecular surfactant type dispersant is remarkably lowered, and an agglomeration reaction occurs. That is, the aggregation reactivity is improved. From this viewpoint, the low molecular surfactant type dispersant preferably has a carboxylic acid group as an anionic group.

The hydrophobic group has a hydrocarbon-based, fluorocarbon-based, silicone-based or the like structure, and is particularly preferably a hydrocarbon-based group. Further, the hydrophobic group may have a linear structure or a branched structure. Further, the hydrophobic group may have a single chain structure or a chain structure of more than this, and in the case of a structure of two or more chains, it may have a plurality of types of hydrophobic groups.
The hydrophobic group is preferably a hydrocarbon group having 2 to 24 carbon atoms, more preferably a hydrocarbon group having 4 to 24 carbon atoms, and further preferably a hydrocarbon group having 6 to 20 carbon atoms.

  Among the polymer dispersants, examples of the water-soluble dispersant include hydrophilic polymer compounds. For example, natural hydrophilic polymer compounds include plant polymers such as gum arabic, tragan gum, guar gum, karaya gum, locust bean gum, arabinogalactone, pectin, quince seed starch, seaweeds such as alginic acid, carrageenan and agar. Examples include molecules, animal polymers such as gelatin, casein, albumin and collagen, and microorganism polymers such as xanthene gum and dextran.

  In addition, in hydrophilic polymer compounds modified from natural products, fiber polymers such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, starch such as sodium starch glycolate and sodium starch phosphate And seaweed polymers such as sodium alginate, propylene glycol alginate, and the like.

  Further, synthetic hydrophilic polymer compounds include vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl methyl ether, non-crosslinked polyacrylamide, polyacrylic acid or alkali metal salts thereof, water-soluble styrene acrylic resins, and the like. Acrylic resin, water-soluble styrene maleic acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleic resin, polyvinyl pyrrolidone, polyvinyl alcohol, alkali metal salts of β-naphthalene sulfonic acid formalin condensate, quaternary ammonium and amino And polymer compounds having a salt of a cationic functional group such as a group in the side chain, natural polymer compounds such as shellac, and the like.

  Among these, water-soluble dispersants introduced with carboxyl groups are hydrophilic polymers such as homopolymers of acrylic acid, methacrylic acid, styrene acrylic acid, and copolymers with monomers having other hydrophilic groups. Preferred as a compound.

  Among the polymer dispersants, as the water-insoluble dispersant, a polymer having both a hydrophobic portion and a hydrophilic portion can be used. For example, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, (meth) acrylic acid ester- (meth) acrylic acid copolymer, polyethylene glycol ( Examples thereof include (meth) acrylate- (meth) acrylic acid copolymers, vinyl acetate-maleic acid copolymers, and styrene-maleic acid copolymers.

  The weight average molecular weight of the polymer dispersant is preferably 3,000 to 100,000, more preferably 5,000 to 50,000, still more preferably 5,000 to 40,000, and particularly preferably 10,000. 000 to 40,000.

  The acid value of the polymer dispersant is preferably 130 mgKOH / g or less from the viewpoint of good aggregation when the treatment liquid comes into contact. Furthermore, the acid value is more preferably 25 to 120 mgKOH / g, and further preferably 25 to 100 mgKOH / g. When the acid value of the polymer dispersant is 130 mgKOH / g or less, and further 100 mgKOH / g or less, the pigment becomes relatively hydrophobic and the water resistance of the image is improved. When the acid value of the polymer dispersant is 25 mgKOH / g or more, the stability of self-dispersibility is improved.

  The polymer dispersant preferably contains a polymer having a carboxyl group from the viewpoint of self-dispersibility and the aggregation rate when the treatment liquid comes into contact. The polymer dispersant has a carboxyl group and an acid value of 25 to 100 mgKOH / g. More preferably.

  The mixing mass ratio (p: s) between the pigment (p) and the dispersant (s) is preferably in the range of 1: 0.06 to 1: 3, more preferably in the range of 1: 0.125 to 1: 2. Preferably, it is 1: 0.125 to 1: 1.5.

In the present invention, a pigment is used as a coloring material, but a dye can be used as long as the effects of the present invention are not impaired.
In the present invention, when a dye is used as the coloring material, a material in which the dye is held on a water-insoluble carrier can be used as the water-insoluble colored particles. As the dye, known dyes can be used without particular limitation. For example, the dyes described in JP-A-2001-115066, JP-A-2001-335714, JP-A-2002-249677 and the like can be used in the present invention. It can be used suitably. The carrier is not particularly limited as long as it is insoluble in water or hardly soluble in water, and inorganic materials, organic materials, and composite materials thereof can be used. Specifically, the carriers described in JP-A-2001-181549, JP-A-2007-169418, etc. can be suitably used in the present invention.
The carrier holding the dye (water-insoluble colored particles) can be used as an aqueous dispersion using a dispersant. As the dispersant, the above-described dispersants can be suitably used.

  In the present invention, from the viewpoint of the light resistance and quality of an image, it is preferable to contain a pigment and a dispersant, more preferably an organic pigment and a polymer dispersant, and a polymer dispersant containing an organic pigment and a carboxyl group. It is particularly preferred that In addition, the pigment is preferably a water-dispersible pigment in which at least a part of the surface thereof is coated with a polymer dispersant from the viewpoint of aggregability, and the pigment is coated with a polymer dispersant having a carboxyl group, More preferably, it is insoluble.

The average particle size of the pigment in the dispersed state is preferably 10 to 200 nm, more preferably 10 to 150 nm, and still more preferably 10 to 100 nm. When the average particle size is 200 nm or less, the color reproducibility is good, the droplet ejection characteristics when droplets are ejected by the ink jet method are good, and when it is 10 nm or more, the light resistance is good. Further, the particle size distribution of the color material is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Two or more color materials having a monodisperse particle size distribution may be mixed and used.
Here, the average particle diameter of the pigment in the dispersed state indicates the average particle diameter in the ink state, but the same applies to the so-called concentrated ink dispersion in the previous stage before the ink is formed.

  The average particle size of the pigment in the dispersed state and the average particle size and particle size distribution of the polymer particles were measured using a dynamic light scattering method using a nanotrack particle size distribution measuring device UPA-EX150 (manufactured by Nikkiso Co., Ltd.). It is calculated | required by measuring a volume average particle diameter.

The pigments may be used alone or in combination of two or more.
The content of the pigment in the ink composition is preferably 1 to 25% by mass, more preferably 2 to 20% by mass, and more preferably 5 to 20% by mass with respect to the ink composition from the viewpoint of image density. Is more preferable, and 5 to 15% by mass is particularly preferable.

(Polymer particles)
The ink composition of the present invention preferably contains at least one polymer particle. The polymer particles have a function of fixing the ink composition by destabilizing and agglomerating and aggregating the ink to increase the viscosity of the ink when the polymer particles come into contact with a treatment liquid described later or a dried region thereof. The fixing property to the recording medium and the scratch resistance (image strength) of the image can be further improved.
Examples of the polymer particles or polymer latex that can be used in the present invention include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, styrene resins, Cross-linked acrylic resins, cross-linked styrene resins, benzoguanamine resins, phenol resins, silicone resins, epoxy resins, urethane resins, paraffin resins, fluorine resins, and the like can be used. Preferred examples include acrylic resins, acrylic-styrene resins, styrene resins, cross-linked acrylic resins, and cross-linked styrene resins.

The weight average molecular weight of the polymer particles is preferably 10,000 or more and 200,000 or less, more preferably 100,000 or more and 200,000 or less.
The average particle diameter of the polymer particles is preferably in the range of 10 nm to 1 μm, more preferably in the range of 10 to 200 nm, still more preferably in the range of 20 to 100 nm, and particularly preferably in the range of 20 to 50 nm.
The glass transition temperature Tg of the polymer particles is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, and further preferably 50 ° C. or higher.

The addition amount of the polymer particles is preferably 0.5 to 20% by mass, more preferably 3 to 20% by mass, and further preferably 5 to 15% by mass with respect to the ink.
Moreover, there is no restriction | limiting in particular regarding the particle size distribution of a polymer particle, What has a wide particle size distribution or a thing with a monodispersed particle size distribution may be sufficient. Two or more polymer particles having a monodispersed particle size distribution may be mixed and used.

(Polymerizable compound)
The ink composition in the present invention contains at least one water-soluble polymerizable compound having a polymerizable group (hereinafter also referred to as a polymerizable monomer) and polymerizes when irradiated with active energy rays. This polymerizable compound is used in combination with the pigment, and is taken in between the particles when agglomerating in contact with the processing liquid, and the image is enhanced by subsequent polymerization and curing. Furthermore, it is more preferable from the viewpoint of image enhancement that the polymerizable compound is used in combination with the pigment and polymer particles.

  The term “water-soluble” means that it can be dissolved in water at a certain concentration or higher, and it can be dissolved in water-based ink (preferably uniformly). Further, the solubility may be increased by adding a water-soluble organic solvent to be described later, and it may be dissolved (desirably uniformly) in the ink. Specifically, the solubility in water is 10% by mass or more, and preferably 15% by mass or more.

  As the polymerizable compound, a nonionic polymerizable compound or a cationic polymerizable compound is preferable in that it does not hinder the reaction between the flocculant and the pigment (further, the reaction between the flocculant, the pigment, and the polymer particles). A polymerizable compound having a solubility in 10% by mass or more (more preferably 15% by mass or more) is preferable.

  Examples of nonionic polymerizable monomers include polymerizable compounds such as (meth) acrylic monomers.

Examples of the (meth) acrylic monomers include (meth) acrylic acid ester of polyhydric alcohol, (meth) acrylic acid ester of polyglycol glycidyl ether, (meth) acrylic acid ester of polyethylene glycol, polyhydric alcohol UV curable monomers and oligomers such as (meth) acrylic acid esters of ethylene oxide addition compounds, and reaction products of polybasic acid anhydrides and hydroxyl group-containing (meth) acrylic acid esters.
The polyhydric alcohol may be chain-extended with an ethylene oxide chain by addition of ethylene oxide.

  Hereinafter, specific examples (nonionic compounds 1 to 4) of the nonionic polymerizable compound are shown. However, the present invention is not limited to these.

  An acrylic acid ester having two or more acryloyl groups in one molecule derived from a polyhydroxyl compound can also be used. Examples of the polyhydroxyl compound include condensates of glycols, oligoethers, oligoesters, and the like.

Furthermore, examples of nonionic polymerizable compounds include acrylic acid esters or methacrylic acid esters of polyols having two or more hydroxyl groups such as monosaccharides and disaccharides; triethanolamine, diethanolamine, trishydroxyaminomethane, trishydroxyaminoethane, and the like. Also suitable are (meth) acrylic acid esters. Furthermore, acrylamides can also be suitably used as the nonionic polymerizable compound. These can be obtained by reaction of acrylic acid chloride with polyvalent amines. Nonionic compounds a to k are shown. However, the present invention is not limited to these. Also, acrylates or methacrylates of polyols having two or more hydroxyl groups such as monosaccharides and disaccharides; (meth) acrylates with triethanolamine, diethanolamine, trishydroxyaminomethane, trishydroxyaminoethane, etc. Is preferred.
Specific examples of these (nonionic compounds a to k) are shown below. However, the present invention is not limited to these.

The cationic polymerizable compound is a compound having a cationic group and a polymerizable group such as an unsaturated double bond, and for example, epoxy monomers and octacene monomers can be suitably used. When the cationic polymerizable compound is contained, the cationic property of the ink composition is increased due to the presence of the cationic group, and color mixing when an anionic ink is used is more effectively prevented.
Examples of the cationic polymerizable compound include N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminopropyl methacrylate, N, N-dimethylaminopropyl acrylate, N, N-dimethylaminoacrylamide, N, N-dimethylaminomethacrylamide, N, N-dimethylaminoethylacrylamide, N, N-dimethylaminoethylmethacrylamide, N, N-dimethylaminopropylacrylamide, N, N-dimethylaminopropyl Examples include methacrylamide and quaternized compounds thereof.
Examples of the epoxy monomers include glycidyl ethers of polyhydric alcohols, glycidyl esters, and aliphatic cyclic epoxides.
Furthermore, what has the following structure can be mentioned as an example of a cationic polymerizable compound.

In the structure, R represents a polyol residue. Further, X represents a hydrogen atom or a methyl group, A ^- is ^Cl -, HSO ₃ ^- or _CH 3 COO ^- represents a. Examples of the compound for introducing the polyol include glycerin, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol, trimethylolpropane, trimethylolmethane, Examples thereof include trimethylolethane, pentaerythritol, bisphenol A, alicyclic bisphenol A, and condensates thereof.
Hereinafter, specific examples (cationic compounds 1 to 11) of the polymerizable compound having a cationic group are listed.

  As the polymerizable compound in the present invention, a polyfunctional monomer is preferable from the viewpoint of enhancing scratch resistance, and a bifunctional to hexafunctional monomer is preferable, and from the viewpoint of compatibility between solubility and scratch resistance, bifunctional to 4 Functional monomers are preferred.

A polymeric compound can be contained individually by 1 type or in combination of 2 or more types.
As content in the ink composition of a polymeric compound, 20-800 mass% is preferable with respect to a pigment, and 25-600 mass% is more preferable. When the content of the polymerizable compound is 20% by mass or more, the image strength is further improved and the image has excellent scratch resistance, and when it is 800% by mass or less, it is advantageous in terms of pile height.
The content of the polymerizable compound in the ink composition in the case where the ink composition has polymer particles (preferably self-dispersing polymer particles) is 30 to 300% by mass with respect to the solid content of the pigment. Is preferable, and 50-200 mass% is more preferable. When the content of the polymerizable compound is 30% by mass or more, the image strength is further improved and the image has excellent scratch resistance, and when it is 300% by mass or less, it is advantageous in terms of pile height.

(Polymerization initiator)
In the present invention, it is preferable that at least one of the ink composition and the treatment liquid described later contains a polymerization initiator that initiates polymerization of the polymerizable compound by active energy rays. A polymerization initiator can be used individually by 1 type or in mixture of 2 or more types or using together with a sensitizer.

  The polymerization initiator can contain a compound capable of initiating a polymerization reaction by active energy rays as appropriate. For example, it generates active species (radicals, acids, bases, etc.) by radiation or light, or electron beams. An initiator (for example, a photopolymerization initiator) can be used.

  Examples of the photopolymerization initiator include acetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophene, p-dimethylaminopropiophenone, benzophenone, 2-chlorobenzophenone, p, p′-dichlorobenzophene, p, p'-bisdiethylaminobenzophenone, Michler's ketone, benzyl, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin isobutyl ether, benzoin n-butyl ether, benzyldimethyl ketal, tetramethylthiuram mono Sulfide, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, azobisisobutyronitrile, benzoin peroxide, -Tert-butyl peroxide, 1-hydroxycyclohexyl phenyl ketone, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-2 -Methyl-1-phenyl-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, methylbenzoyl formate. Furthermore, for example, aromatic diazonium salts, aromatic halonium salts, aromatic sulfonium salts, metallocene compounds such as triphenylsulfonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate and the like can be mentioned.

  When the polymerization initiator is contained, the content of the polymerization initiator in the ink composition is preferably 1 to 40% by mass and more preferably 5 to 30% by mass with respect to the polymerizable compound. When the content of the polymerization initiator is 1% by mass or more, the scratch resistance of the image is further improved, which is advantageous for high-speed recording, and when it is 40% by mass or less, it is advantageous in terms of ejection stability.

Examples of the sensitizer include amines (aliphatic amines, amines containing aromatic groups, piperidine, etc.), ureas (allylic, o-tolylthiourea, etc.), sulfur compounds (sodium diethyldithiophosphate, aromatic sulfinic acid). Soluble salts, etc.), nitrile compounds (N, N, di-substituted p-aminobenzonitrile, etc.), phosphorus compounds (tri-n-butylphosphine, netium diethyldithiophos feed, etc.), nitrogen compounds (Michler ketone, N-nitriso) Hydroxylamine derivatives, oxazolidine compounds, tetrahydro 1,3-oxazine compounds, formaldehyde, acetaldehyde and diamine condensates, etc.), chlorine compounds (carbon tetrachloride, hexachloroethane, etc.), polymerized amines of reaction products of epoxy resins and amines , Triethanolamine Acrylate, and the like.
A sensitizer can be contained in the range which does not impair the effect of this invention.

(Water-soluble organic solvent)
The ink composition in the invention may contain at least one water-soluble organic solvent. The water-soluble organic solvent can obtain the effect of preventing drying, wetting or promoting penetration. In order to prevent drying, the ink adheres to and drys at the ink discharge port of the ejection nozzle and is used as an anti-drying agent to prevent clogging. For drying prevention and wetting, the vapor pressure is lower than that of water. A water-soluble organic solvent is preferred. Further, for penetration promotion, it can be used as a penetration enhancer that enhances ink permeability to paper.

The drying inhibitor is preferably a water-soluble organic solvent having a vapor pressure lower than that of water. Specific examples of such water-soluble organic solvents include ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propanediol, 1,2,6-hexane. Polyols represented by triols, acetylene glycol derivatives, glycerin, trimethylolpropane, etc., ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monoethyl (or butyl) ether, etc. Lower alkyl ethers of polyhydric alcohols, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, heterocyclic rings such as N-ethylmorpholine, sulfolane, Methyl sulfoxide, sulfur-containing compounds such as 3-sulfolene, diacetone alcohol, polyfunctional compounds such as diethanolamine, and urea derivatives.
Of these, polyhydric alcohols such as glycerin and diethylene glycol are preferred as the drying inhibitor.
Anti-drying agents may be used alone or in combination of two or more. The content of the drying inhibitor is preferably in the range of 10 to 50% by mass in the ink composition.

As a penetration accelerator, it is suitable for the purpose of allowing the ink composition to permeate the recording medium (such as printing paper) better. Specific examples of such water-soluble organic solvents include alcohols such as ethanol, isopropanol, butanol, di (tri) ethylene glycol monobutyl ether, 1,2-hexanediol, sodium lauryl sulfate, sodium oleate, and nonionic interfaces. An activator or the like can be preferably used.
A penetration enhancer may be used individually by 1 type, or may be used together 2 or more types. The content of the penetration enhancer is preferably in the range of 5 to 30% by mass in the ink composition. Moreover, it is preferable to use the penetration enhancer within a range that does not cause image bleeding and paper loss (print-through).

  The water-soluble organic solvent is used for adjusting the viscosity in addition to the above. Specific examples of water-soluble organic solvents that can be used to adjust the viscosity include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, t-butanol, pentanol, hexanol, cyclohexanol). Benzyl alcohol), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodi) Glycol), glycol derivatives (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether) , Ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, tri Ethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monophenyl ether), amine (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethyl) Diamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine) and other polar solvents (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone). Also in this case, the water-soluble organic solvent may be used alone or in combination of two or more.

(water)
The ink composition contains water, but the amount of water is not particularly limited. Especially, the preferable content of water is 10 to 99% by mass, more preferably 30 to 80% by mass, and still more preferably 50 to 70% by mass.

(Other additives)
The ink composition in the present invention can be constituted using other additives in addition to the above components. Other additives include, for example, polymerization inhibitors, anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, anti-fungal agents, pH adjusters, surface tension. Well-known additives, such as a regulator, an antifoamer, a viscosity modifier, a dispersing agent, a dispersion stabilizer, a rust inhibitor, a chelating agent, are mentioned. These various additives are generally added directly to the ink in the case of an ink composition, and when a pigment is used as a dispersion, it is generally added to the dispersion after the preparation of the pigment dispersion. May be.

-Treatment liquid-
The treatment liquid includes at least an aggregating agent for aggregating the components in the ink composition described above and an organic solvent having a solubility in 100 g of water (25 ° C.) of 25% by mass or more with respect to the total mass of the liquid of 30% or less. It can be configured using other components as necessary. By using the treatment liquid together with the ink composition, it is possible to increase the speed of ink jet recording, and an image with excellent density and resolution can be obtained even when recording at high speed (for example, reproducibility of fine lines and fine portions).

The aggregating agent is preferably a compound that can change the pH of the ink composition. As a compound that can lower the pH of the ink composition, an organic acid is preferable.
Examples of the organic acid include polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, pyrrolidonecarboxylic acid, and pyronecarboxylic acid. Preferable examples include acids, pyrrole carboxylic acids, furan carboxylic acids, pyridine carboxylic acids, coumaric acids, thiophene carboxylic acids, nicotinic acids, derivatives of these compounds, or salts thereof.
An organic acid may be used individually by 1 type, and may use 2 or more types together.
In addition to the organic acid, other acidic substances may be added as long as the effects of the present invention are not impaired. As other acidic substances, for example, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, sulfonic acid, orthophosphoric acid, or salts thereof are preferably exemplified.

When the treatment liquid in the present invention contains an organic acid, the pH (25 ° C.) of the treatment liquid is preferably 6 or less, more preferably 4 or less. Especially, pH (25 degreeC) has the preferable range of 1-4, Especially preferably, pH is 1-3. At this time, the pH (25 ° C.) of the ink composition is preferably 7.5 or more (more preferably 8.0 or more).
Among them, from the viewpoint of image density, resolution, and speedup of inkjet recording, the pH (25 ° C.) of the ink composition is 8.0 or more, and the pH (25 ° C.) of the treatment liquid is 0.5 to 4. Some cases are preferred.

  Among these, as the flocculant in the present invention, an organic acid is preferable in terms of enhancing the cohesiveness and fixing the entire ink, but a divalent or higher valent organic acid is preferable, and a divalent or higher valent organic acid is particularly preferable. preferable. The divalent or higher organic acid is preferably an organic acid having a first pKa of 3.5 or less, more preferably an organic acid of 3.0 or less. Specific examples include oxalic acid, malonic acid, and citric acid.

A flocculant can be used individually by 1 type or in mixture of 2 or more types.
The content of the flocculant in the treatment liquid for aggregating the ink composition is preferably 1 to 50% by mass, more preferably 3 to 45% by mass, and still more preferably 5 to 40% from the viewpoint of improving the aggregation property. It is the range of mass%.

(Organic solvent with water solubility of 30% or less)
The treatment liquid in the present invention contains an organic solvent (hereinafter also referred to as “organic poor solvent”) having a solubility in 100 g of water (25 ° C.) of 25% by mass or more based on the total mass of the liquid. To do. By containing 25% by mass or more of the organic poor solvent in the processing liquid, it is possible to effectively suppress the cuckling in the image after the image formation and to improve the decrease in the film strength at the same time.
If the content of the organic poor solvent in the treatment liquid is less than 25% by mass, large unevenness (cuckling) occurs in the entire image.
Here, the “organic poor solvent” refers to an organic solvent having a solubility in 100 g of water (25 ° C.) of 30% or less. As an organic poor solvent, from the viewpoint of suppressing cockling, the solubility in 100 g of water (25 ° C.) is preferably 20% or less, and more preferably 10% or less.

Specific examples of such organic poor solvents include rapeseed oil (preferably canola oil), olive oil, peanut oil, salad oil, white squeezed oil, corn oil, soybean oil, sesame oil, rice bran oil, coconut oil, coconut oil, safflower Oil (safflower oil), palm kernel oil, palm oil, cottonseed oil, sunflower oil, coconut oil, peanut oil, almond oil, avocado oil, hazelnut oil, walnut oil, grape seed oil, mustard oil, lettuce oil, fish oil, whale oil , Fatty oils (liquid at normal temperature), cocoa butter, palm oil, lard (pig fat), het (beef tallow), chicken oil, rosin, sheep fat, horse fat, Schmalz, shortening , Fats represented by milk fat, butter, margarine, ghee, hydrogenated oil and the like (solid at normal temperature). Here, normal temperature means 5-35 degreeC.
Among these, rapeseed oil (preferably canola oil), olive oil, peanut oil, corn oil, and sesame oil are the semi-represented from the viewpoint of improving suppression of image cockling, coating properties, and liquid stability. Dry oils and non-dry oils are preferred, and non-dry oils such as rapeseed oil (preferably canola oil) and olive oil are more preferred.

An organic poor solvent may be used individually by 1 type, or may be used together 2 or more types.
The content of the organic poor solvent is 25% by mass or more and 60% by mass or less in the treatment liquid, but is preferably 30% by mass to 60% by mass, more preferably 40% by mass to 55% by mass from the viewpoint of more effective suppression of occurrence of cockling. Is more preferable.

(Aqueous solvent mixed with water)
The treatment liquid in the present invention contains at least one aqueous solvent mixed with water (hereinafter also referred to as “aqueous solvent mixed with water”) having a solubility in 100 g of water (25 ° C.) of 50% or more. be able to. By containing the aqueous solvent mixed with water in the treatment liquid, the aggregation reaction of the ink component by the aggregating agent can be effectively caused.
The content of the aqueous solvent mixed with the water in the treatment liquid is preferably 30% by mass or more, and more preferably 40% by mass or more. If the content of the aqueous solvent to be mixed with water in the treatment liquid is less than 30% by mass, the agglomeration reaction may be suppressed, and the image may impact and cause blurring. That is, when the content is 30% by mass or more, the aggregation reaction is suppressed, and there is no case where the image is subjected to landing interference to cause bleeding.
Here, the “aqueous solvent mixed with water” refers to an aqueous solvent having a solubility in 100 g of water (25 ° C.) of 50% or more. The solubility of the aqueous solvent mixed with water in 100 g of water (25 ° C.) is more preferably 70% or more from the viewpoint of effectively supplying the flocculant to the image, and further preferably arbitrarily mixed with water. It is.

Examples of the aqueous solvent mixed with water include the solvents mixed with water among the water-soluble organic solvents described in the ink composition.
For example, alcohol (for example, methanol, ethanol, propanol, isopropanol), polyhydric alcohol (for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexane Triols, thiodiglycols), glycol derivatives (eg ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene Glycol monomethyl ester Ter, triethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monophenyl ether), amines (eg, ethanolamine, diethanolamine, triethanol) Amines, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine), and other polar solvents (eg, formamide, N, N- Dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxy , Sulfolane, 2-pyrrolidone, N- methyl-2-pyrrolidone, N- vinyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone).
Among these, glycol derivatives are preferable, for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol. Monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and ethylene glycol monophenyl ether are preferred.

  The treatment liquid can further contain other additives as other components within a range not impairing the effects of the present invention. Other additives include, for example, anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, UV absorbers, preservatives, anti-fungal agents, pH adjusters, surface tension adjusters, anti-foaming agents. Well-known additives, such as a foaming agent, a viscosity modifier, a dispersing agent, a dispersion stabilizer, a rust preventive agent, a chelating agent, are mentioned.

  Among the above, the ink set of the present invention includes a water-dispersible pigment coated with a polymer dispersant having a carboxyl group and an acid value of 130 mgKOH / g or less, an acid value of 120 mgKOH / g or less, a glass transition temperature (Tg ) Is a self-dispersing polymer particle having a volume average particle diameter of 50 nm or less, and an ink composition containing a nonionic or cationic trifunctional to pentafunctional water-soluble monomer as a polymerizable compound; A combination mode with a treatment liquid containing an organic acid is preferable, and further, a water-dispersible pigment having a carboxyl group and coated with a polymer dispersant having an acid value of 30 to 110 mgKOH / g, an acid value of 25 to 100 mgKOH / g, Self-dispersing polymer having a glass transition temperature (Tg) of 100 ° C. or higher and a volume average particle diameter of 2 to 60 nm (more preferably 2 to 30 nm) More preferred is a combination of particles and an ink composition containing a nonionic trifunctional to tetrafunctional water-soluble acrylate monomer or acrylamide monomer as a polymerizable compound and a treatment liquid containing a divalent or higher organic acid. In addition to these, it is particularly preferred that the self-dispersing polymer particles are acrylic resin particles containing structural units derived from a (meth) acrylate monomer.

<Image forming method>
The image forming method of the present invention uses the above-described ink set of the present invention, and an ink composition containing a pigment and a water-soluble polymerizable compound polymerized by active energy rays is applied to a recording medium by an inkjet method. An ink application step for application, an aggregating agent for aggregating the components in the ink composition, and an organic solvent having a solubility in 100 g of water (25 ° C.) of 25% by mass or more based on the total mass of the liquid is 30% or less. And a treatment liquid application step for applying a treatment liquid containing a liquid to a recording medium. The image forming method of the present invention can be configured by further providing other steps as necessary.

  In the present invention, the ink composition for forming an ink image contains a water-soluble polymerizable compound that can be polymerized and cured together with the pigment, so that the image is fixed by the aggregation reaction of the pigment when contacted with the processing liquid. It becomes. Since the polymerizable compound is polymerized and cured between the pigment particles, the strength of the final image can be increased.

In the present invention, it is preferable that the ink composition further contains polymer particles. This is because an ink composition for forming an ink image contains a water-soluble polymerizable compound that can be polymerized and cured together with a pigment together with the pigment, thereby agglomerating the pigment and / or polymer particle when contacted with the treatment liquid. The image is fixed by the reaction, and polymer particles are present between the pigment particles, and the polymer is cured while the polymerizable compound is taken in between the pigment and polymer particle particles in the fixed image. Therefore, the intensity of the final image can be increased.
In this case, first, the components in the ink composition are aggregated at high speed using the treatment liquid, thereby preventing the mixing between inks (such as bleeding and color mixing between colors) and improving the high-speed recording suitability that enables high-speed recording.
In addition, the hue and image drawability during high-speed recording (reproducibility of fine lines and fine parts in the image) are improved, and the polymerizable compound is moderately placed in the gap between the pigment particles and the polymer particles forming the aggregated state. Since it is polymerized and cured in a state where it enters, image strength is remarkably improved, and both high-speed recording suitability and improved image scratch resistance can be achieved.
In particular, it is more effective when an image is recorded on coated paper where the pigment tends to remain on the surface of the recording medium.

Hereafter, each process which comprises the image forming method of this invention is demonstrated.
-Ink application process-
In the ink application step, an ink composition containing a pigment and a water-soluble polymerizable compound that is polymerized by active energy rays is applied to a recording medium by an inkjet method. In this step, the ink composition can be selectively applied onto the recording medium, and a desired visible image can be formed. The ink composition contains at least a pigment and a water-soluble polymerizable compound, and details of the ink composition such as details and preferred embodiments of each component are as described above.

  Specifically, the image recording using the ink-jet method is performed by supplying energy to obtain a desired recording medium, that is, plain paper, resin-coated paper, for example, JP-A-8-169172 and JP-A-8-27693. Publication No. 2-276670, No. 7-276789, No. 9-323475, No. JP-A-62-238783, JP-A-10-153898, No. 10-217473, No. 10- No. 235995, No. 10-337947, No. 10-217597, No. 10-337947, etc. Ink composition for ink jet paper, film, electrophotographic co-paper, cloth, glass, metal, ceramics, etc. This can be done by discharging objects. As a preferable ink jet recording method for the present invention, the method described in paragraph Nos. 0093 to 0105 of JP-A No. 2003-306623 can be applied.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method that discharges ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses vibration pressure of a piezoelectric element, an electric method An acoustic ink jet system that converts a signal into an acoustic beam, irradiates the ink with ink and ejects the ink using radiation pressure, and a thermal ink jet (bubble jet (registered trademark)) that heats the ink to form bubbles and uses the generated pressure. )) Any method may be used. As an ink jet method, in particular, the method described in Japanese Patent Application Laid-Open No. Sho 54-59936 causes an abrupt volume change of the ink subjected to the action of thermal energy, and the ink is ejected from the nozzle by the action force due to this state change. Ink jet method can be used effectively.
The ink jet method includes a method of ejecting many low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent inks. The method using is included.

In addition, an ink jet head used in the ink jet method may be an on-demand method or a continuous method. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, a thermal type) Specific examples include an ink jet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.) and a discharge type (for example, a spark jet type). However, any discharge method may be used.
There are no particular restrictions on the ink nozzles used when recording by the ink jet method, and they can be appropriately selected according to the purpose.

Specific examples of the ink jet recording method are shown below.
As an inkjet recording method, there is (1) a method called an electrostatic attraction method. In the electrostatic suction method, a strong electric field is applied between the nozzle and the acceleration electrode arranged in front of the nozzle, and droplet-like ink is continuously ejected from the nozzle, and the ink droplet passes between the deflection electrodes. In the meantime, by supplying a printing information signal to the deflection electrode, the ink droplets are blown onto the recording medium to fix the ink on the recording medium, and the image is recorded or printing is performed without deflecting the ink droplets. In this method, an image is fixed on a recording medium by ejecting ink droplets from a nozzle toward the recording medium in accordance with an information signal. In addition, (2) there is a method of forcibly ejecting ink droplets from a nozzle by applying pressure to the ink liquid with a small pump and mechanically vibrating the ink jet nozzle with a crystal resonator or the like. The ink droplet ejected from the nozzle is charged at the same time as it is ejected, and while the ink droplet passes between the deflection electrodes, a print information signal is given to the deflection electrode to fly the ink droplet toward the recording medium, This is a method for recording an image on a recording medium. Next, (3) A method of recording an image on a recording medium (piezo) by simultaneously applying pressure and a printing information signal to the ink liquid by a piezoelectric element and ejecting ink droplets from the nozzle toward the recording medium (4) A method for recording an image on a recording medium by injecting the ink liquid from a nozzle toward a recording medium by expanding the bubbles by heating the ink liquid using microelectrodes in accordance with print signal information (bubble Jet (registered trademark).

  As an inkjet head, a short serial head is used, and a shuttle system that performs recording while scanning the head in the width direction of the recording medium, and a line head in which recording elements are arranged corresponding to the entire area of one side of the recording medium There is a line system using. In the line system, an image can be recorded on the entire surface of the recording medium by scanning the recording medium in a direction orthogonal to the arrangement direction of the recording elements, and a carriage system such as a carriage for scanning a short head is not necessary. Further, since complicated scanning control of the carriage movement and the recording medium is not required, and only the recording medium is moved, the recording speed can be increased as compared with the shuttle system. The image forming method of the present invention can be applied to any of these, but generally, when applied to a line system that does not use a dummy jet, the effect of improving ejection accuracy and image scratch resistance is great.

  The amount of ink droplets ejected from the inkjet head is preferably 1 to 10 pl (picoliter) and more preferably 1.5 to 6 pl from the viewpoint of obtaining a high-definition image. In addition, from the viewpoint of improving the unevenness of the image and the continuous gradation, it is also effective to discharge different amounts of liquids in combination, and even in such a case, the present invention can be suitably used.

-Treatment liquid application process-
The treatment liquid application step includes an aggregating agent for aggregating components in the ink composition and an organic solvent having a solubility in 100 g of water (25 ° C.) of 25% by mass or more based on the total mass of the liquid and 30% or less. The treatment liquid is applied to the recording medium, and the treatment liquid is brought into contact with the ink composition to form an image. In this case, the dispersed particles including the pigment and polymer particles in the ink composition are aggregated, and the image is fixed on the recording medium. The treatment liquid contains at least a flocculant, and details and preferred embodiments of each component are as described above.

  The treatment liquid can be applied by applying a known method such as a coating method, an ink jet method, or an immersion method. As a coating method, a known coating method using a bar coater, an extrusion die coater, an air doctor coater, a blade coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, a bar coater or the like can be used. The details of the inkjet method are as described above.

  The treatment liquid application step may be provided either before or after the ink application step using the ink composition. In the present invention, an embodiment in which an ink application step is provided after applying the treatment liquid in the treatment liquid application step is preferable. Specifically, a treatment liquid for aggregating pigment and / or self-dispersing polymer particles in the ink composition is applied in advance to the recording medium before applying the ink composition, and the recording medium is applied. An embodiment in which an ink composition is applied so as to come into contact with the treatment liquid applied above to form an image is preferable. Thereby, inkjet recording can be speeded up, and an image with high density and resolution can be obtained even at high speed recording.

The amount of treatment liquid applied is not particularly limited as long as the ink composition can be agglomerated, but the amount of aggregating agent applied is preferably an amount such that the amount of the aggregating agent is 0.1 g / m ² or more. Especially, the quantity from which the provision amount of a flocculant will be 0.2-0.7 g / m < ² > is preferable. When the applied amount of the flocculant is 0.1 g / m ² or more, good high-speed flocculence can be maintained according to various usage forms of the ink composition. Further, it is preferable that the amount of the flocculant applied is 0.7 g / m ² or less because the surface properties of the applied recording medium are not adversely affected (such as a change in gloss).

  In the present invention, an ink application step is provided after the treatment liquid application step, and the treatment liquid on the recording medium is heated and dried after the treatment liquid is applied on the recording medium and before the ink composition is applied. It is preferable to further provide a heat drying step. By heating and drying the treatment liquid in advance before the ink application step, ink colorability such as bleeding prevention is improved, and a visible image with good color density and hue can be recorded.

  Heating and drying can be performed by known heating means such as a heater, air blowing means using air blowing such as a dryer, or a combination of these. As the heating method, for example, a method of applying heat with a heater or the like from the side opposite to the treatment liquid application surface of the recording medium, a method of applying warm air or hot air to the treatment liquid application surface of the recording medium, or an infrared heater was used. The heating method etc. are mentioned, You may heat combining these two or more.

-Recording media-
The image forming method of the present invention records an image on a recording medium.
The recording medium is not particularly limited, and general printing paper mainly composed of cellulose, such as so-called high-quality paper, coated paper, and art paper, used for general offset printing and the like can be used. General printing paper mainly composed of cellulose is relatively slow in ink absorption and drying in image recording by a general ink jet method using water-based ink, and color material movement is likely to occur after droplet ejection, and image quality is likely to deteriorate. However, according to the image forming method of the present invention, it is possible to record a high quality image excellent in color density and hue by suppressing the movement of the color material.

  As the recording medium, commercially available media can be used. For example, “OK Prince fine quality” manufactured by Oji Paper Co., Ltd., “Shiorai” manufactured by Nippon Paper Industries Co., Ltd., and Nippon Paper Industries ( Fine coated paper such as “New NPI fine quality” manufactured by Co., Ltd., “OK Everlight Coat” manufactured by Oji Paper Co., Ltd., and “Aurora S” manufactured by Nippon Paper Industries Co., Ltd., Oji Lightweight coated paper (A3) such as “OK Coat L” manufactured by Paper Industries Co., Ltd. and “Aurora L” manufactured by Nippon Paper Industries Co., Ltd. “OK Top Coat +” manufactured by Oji Paper Co., Ltd. and Nippon Paper Industries Co., Ltd. ) Coated paper (A2, B2) such as “Aurora Coat” manufactured by Oji Paper Co., Ltd. Art paper (A1) such as “OK Kanfuji +” manufactured by Oji Paper Co., Ltd. and “Tokuhishi Art” manufactured by Mitsubishi Paper Industries Co., Ltd. Is mentioned. It is also possible to use various photographic papers for ink jet recording.

  Among the recording media, so-called coated paper used for general offset printing is preferable. The coated paper is obtained by applying a coating material to the surface of high-quality paper, neutral paper, or the like that is mainly surface-treated with cellulose as a main component and is not surface-treated. The coated paper is liable to cause quality problems such as glossiness and scratch resistance of the image in normal aqueous inkjet image formation. However, in the image forming method of the present invention, gloss unevenness is suppressed and glossiness and resistance to abrasion are reduced. An image having good rubbing properties can be obtained. In particular, a coated paper having a base paper and a coat layer containing an inorganic pigment is preferably used, and a coated paper having a base paper and a coat layer containing kaolin and / or calcium bicarbonate is more preferably used. Specifically, art paper, coated paper, lightweight coated paper, or finely coated paper is more preferable.

-Inkjet recording device-
Next, an example of an ink jet recording apparatus suitable for carrying out the image forming method of the present invention will be specifically described with reference to FIG. FIG. 1 is a schematic configuration diagram illustrating a configuration example of the entire inkjet recording apparatus.

  As shown in FIG. 1, the ink jet recording apparatus includes a processing liquid application unit 12 including a processing liquid discharge head 12S that sequentially discharges a processing liquid in the recording medium conveyance direction (the arrow direction in the figure); A treatment liquid drying zone 13 provided with a heating means (not shown) for drying the applied treatment liquid, an ink ejection part 14 for ejecting various ink compositions, and an ink drying zone 15 for drying the ejected ink composition. Are arranged. Further, an ultraviolet irradiation unit 16 including an ultraviolet irradiation lamp 16S is disposed on the downstream side of the ink drying zone 15 in the conveyance direction of the recording medium.

  The recording medium supplied to the ink jet recording apparatus includes a processing liquid application unit 12, a processing liquid drying zone 13, and an ink discharging unit by a conveying roller from a paper feeding unit that feeds the recording medium from a case loaded with the recording medium. 14, the ink drying zone 15, and the ultraviolet irradiation unit 16 are sequentially sent and accumulated in the accumulation unit. In addition to the method using a conveyance roller, the conveyance may be performed by a drum conveyance method using a drum-shaped member, a belt conveyance method, a stage conveyance method using a stage, or the like.

  Among the plurality of transport rollers, at least one roller may be a driving roller to which the power of a motor (not shown) is transmitted. By rotating a driving roller rotated by a motor at a constant speed, the recording medium is conveyed in a predetermined direction by a predetermined conveyance amount.

  The treatment liquid application unit 12 is provided with a treatment liquid discharge head 12S connected to a storage tank that stores the treatment liquid. The treatment liquid ejection head 12S can eject the treatment liquid from ejection nozzles arranged to face the recording surface of the recording medium, and can apply the treatment liquid on the recording medium. The treatment liquid application unit 12 is not limited to a method of discharging from a nozzle-shaped head, and an application method using an application roller can also be adopted. In this coating method, the treatment liquid can be easily applied to almost the entire surface including the image area where the ink droplets land on the recording medium by the ink discharge unit 14 disposed on the downstream side. In order to make the thickness of the processing liquid on the recording medium constant, for example, an air knife or a member having a sharp corner is provided with a gap corresponding to the specified amount of the processing liquid provided between the recording medium and the recording medium. You may provide the method of doing.

  A treatment liquid drying zone 13 is disposed downstream of the treatment liquid application unit 12 in the recording medium conveyance direction. The treatment liquid drying zone 13 can be configured by using a known heating means such as a heater, an air blowing means using air blowing such as a dryer, or a combination of these. The heating means may be a method of installing a heating element such as a heater on the side opposite to the barrier layer forming surface of the recording medium (for example, below the conveyance mechanism that carries the recording medium when the recording medium is automatically conveyed) Examples include a method of applying warm air or hot air to the surface of the medium on which the barrier layer is formed, a heating method using an infrared heater, and the like.

In addition, since the surface temperature of the recording medium changes depending on the type (material, thickness, etc.) of the recording medium, the environmental temperature, etc., the measuring unit for measuring the surface temperature of the recording medium and the surface of the recording medium measured by the measuring unit It is preferable to provide a control mechanism that feeds back the temperature value to the heating control unit to form the blocking layer while controlling the temperature. As a measurement part which measures the surface temperature of a recording medium, a contact or non-contact thermometer is preferable.
Further, the solvent may be removed using a solvent removal roller or the like. As another embodiment, a method of removing excess solvent from the recording medium with an air knife is also used.

  The ink discharge unit 14 is disposed downstream of the treatment liquid drying zone 13 in the recording medium conveyance direction. The ink discharge section 14 includes a recording head (ink discharge head) 30K connected to each of the ink storage sections that store black (K), cyan (C), magenta (M), and yellow (Y) color inks. 30C, 30M, and 30Y are arranged. Each ink storage section (not shown) stores an ink composition containing a pigment corresponding to each hue, resin particles, a water-soluble organic solvent, and water, and ejects each ink as necessary when recording an image. The heads 30K, 30C, 30M, and 30Y are supplied. Further, as shown in FIG. 1, a recording head 30A for spot color ink discharge is provided on the downstream side in the transport direction of the ink discharge heads 30K, 30C, 30M, and 30Y so that spot color ink can be discharged as needed. 30B can be further provided.

  The ink ejection heads 30K, 30C, 30M, and 30Y each eject ink corresponding to an image from ejection nozzles arranged to face the recording surface of the recording medium. Thus, each color ink is applied on the recording surface of the recording medium, and a color image is recorded.

  Each of the treatment liquid ejection head 12S and the ink ejection heads 30K, 30C, 30M, 30Y, 30A, and 30B has a large number of ejection openings over the maximum recording width (maximum recording width) of an image recorded on the recording medium. It is a full line head in which (nozzles) are arranged. Compared to the serial type in which recording is performed while reciprocating a short shuttle head in the width direction of the recording medium (direction perpendicular to the conveying direction on the recording medium conveying surface), it is possible to record an image on the recording medium at a higher speed. it can. In the present invention, either a serial type recording or a method capable of relatively high-speed recording, for example, a method capable of recording by ejecting in the main scanning direction by a single pass forming one line in one scan. However, according to the image recording method of the present invention, a high-quality image with high reproducibility can be obtained even by a single-pass method.

  Here, the treatment liquid discharge head 12S and the ink discharge heads 30K, 30C, 30M, 30Y, 30A, and 30B all have the same structure.

  The application amount of the treatment liquid and the application amount of the ink composition are preferably adjusted as necessary. For example, the application amount of the treatment liquid may be changed according to the recording medium in order to adjust the physical properties such as the viscoelasticity of the aggregate formed by mixing the treatment liquid and the ink composition.

  The ink drying zone 15 is disposed downstream of the ink discharge unit 14 in the recording medium conveyance direction. The ink drying zone 15 can be configured in the same manner as the treatment liquid drying zone 13.

The ultraviolet irradiation unit 16 is arranged further downstream in the recording medium conveyance direction of the ink drying zone 15, and is irradiated with ultraviolet rays by an ultraviolet irradiation lamp 16S provided in the ultraviolet irradiation unit 16, and in the image after image drying. The monomer component is polymerized and cured. The ultraviolet irradiation lamp 16S irradiates the entire recording surface with a lamp disposed opposite to the recording surface of the recording medium, so that the entire image can be cured. The ultraviolet irradiation unit 16 is not limited to the ultraviolet irradiation lamp 16S, and a halogen lamp, a high-pressure mercury lamp, a laser, an LED, an electron beam irradiation device, or the like can also be employed.
The ultraviolet irradiation unit 16 may be installed either before or after the ink drying zone 15, or may be installed both before and after the ink drying zone 15.

  Further, in the ink jet recording apparatus, a heating unit that performs a heat treatment on the recording medium can be arranged in a conveyance path from the paper feeding unit to the stacking unit. For example, the temperature of the recording medium is raised to a desired temperature by disposing a heating unit at a desired position such as the upstream side of the treatment liquid drying zone 13 or between the ink discharge unit 14 and the ink drying zone 15. Thus, drying and fixing can be effectively performed.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “part” and “%” are based on mass.

[Preparation of ink composition]
<< Preparation of Cyan Ink C-1 >>
-Preparation of polymer dispersant 1 solution-
In a reaction vessel, 6 parts of styrene, 11 parts of stearyl methacrylate, 4 parts of styrene macromer AS-6 (manufactured by Toa Gosei Co., Ltd.), 5 parts of Bremer PP-500 (manufactured by NOF Corporation), 5 parts of methacrylic acid, 2 -0.05 part of mercaptoethanol and 24 parts of methyl ethyl ketone were added to prepare a mixed solution.

  Meanwhile, in a dropping funnel, 14 parts of styrene, 24 parts of stearyl methacrylate, 9 parts of styrene macromer AS-6 (manufactured by Toa Gosei Co., Ltd.), 9 parts of Blenmer PP-500 (manufactured by NOF Corporation), 10 parts of methacrylic acid 2-mercaptoethanol (0.13 parts), methyl ethyl ketone (56 parts), and 2,2′-azobis (2,4-dimethylvaleronitrile) (1.2 parts) were added to prepare a mixed solution.

  And under nitrogen atmosphere, it heated up to 75 degreeC, stirring the mixed solution in reaction container, and the mixed solution in a dropping funnel was dripped gradually over 1 hour. Two hours after the completion of the dropwise addition, a solution prepared by dissolving 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) in 12 parts of methyl ethyl ketone was added dropwise over 3 hours. Aged at 80 ° C. for 2 hours to obtain a polymer dispersant 1 solution.

  A part of the obtained polymer dispersant 1 solution was isolated by removing the solvent, and the obtained solid content was diluted to 0.1% by mass with tetrahydrofuran to obtain a high-speed GPC (gel permeation chromatography) HLC. Three TSKgeL SuperHZM-H, TSKgeL SuperHZ4000, and TSKgeL SuperHZ2000 (manufactured by Tosoh Corporation) were connected in series at -8220 GPC, and the weight average molecular weight was measured. As a result, the weight average molecular weight was 25,000 in terms of polystyrene. The acid value was 99 mgKOH / g.

-Preparation of Cyan Dispersion C1-
Next, 5.0 g of the above polymer dispersant solution in terms of solid content, 10.0 g of cyan pigment Pigment Blue 15: 3 (manufactured by Dainichi Seika Kogyo Co., Ltd.), 40.0 g of methyl ethyl ketone, 1 mol / L (liter; In the same manner, 8.0 g of sodium hydroxide and 82.0 g of ion-exchanged water were supplied to the vessel together with 300 g of 0.1 mm zirconia beads and dispersed at 1000 rpm for 6 hours with a ready mill disperser (manufactured by Imex). The obtained dispersion was concentrated under reduced pressure using an evaporator until methyl ethyl ketone could be sufficiently distilled off, and further concentrated until the pigment concentration became 10% to prepare cyan dispersion C1 in which a water-dispersible pigment was dispersed.
The volume average particle size (secondary particles) of the obtained cyan dispersion liquid C1 was measured by a dynamic light scattering method using a Microtorac particle size distribution measuring device (Version 10.1.2-211BH (trade name), manufactured by Nikkiso Co., Ltd.). Was 78 nm.

-Synthesis of self-dispersing polymer particles 1-
360.0 g of methyl ethyl ketone was charged into a 2-liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the temperature was raised to 75 ° C. Then, 180.0 g of phenoxyethyl acrylate, 162.0 g of methyl methacrylate, 18.0 g of acrylic acid, 72 g of methyl ethyl ketone, and “V-601” (manufactured by Wako Pure Chemical Industries, Ltd.) while maintaining the temperature in the flask at 75 ° C. A mixed solution consisting of 1.44 g was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, a solution composed of 0.72 g of “V-601” and 36.0 g of methyl ethyl ketone was added thereto, stirred at 75 ° C. for 2 hours, and further a solution composed of 0.72 g of “V-601” and 36.0 g of isopropanol. And stirred at 75 ° C. for 2 hours. Thereafter, the temperature was raised to 85 ° C., and stirring was further continued for 2 hours to obtain a resin solution of a phenoxyethyl acrylate / methyl methacrylate / acrylic acid (= 50/45/5 [mass ratio]) copolymer.
The weight average molecular weight (Mw) measured in the same manner as described above of the obtained copolymer was 64,000 (calculated in terms of polystyrene by gel permeation chromatography (GPC)), and the acid value was 38.9 mgKOH / g. there were.

  Next, 668.3 g of the obtained resin solution was weighed, 388.3 g of isopropanol and 145.7 ml of 1 mol / L NaOH aqueous solution were added thereto, and the temperature in the reaction vessel was raised to 80 ° C. Next, 720.1 g of distilled water was added dropwise at a rate of 20 ml / min to disperse in water, and then the reaction vessel internal temperature was 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours under atmospheric pressure. After maintaining, the inside of the reaction vessel was depressurized, and 913.7 g of isopropanol, methyl ethyl ketone and distilled water were distilled off in total to obtain an aqueous dispersion of self-dispersing polymer particles 1 having a solid content concentration of 28.0% by mass.

  After preparing the cyan dispersion C1 as described above, each of the above-described self-dispersing polymer particle 1 aqueous dispersion, organic solvent, surfactant, and ion-exchanged water was used to obtain the following composition. After mixing the components, coarse particles were removed through a 5 μm filter to obtain cyan ink C1.

<Composition of cyan ink C1>
Cyan pigment (Pigment Blue 15: 3, manufactured by Dainichi Seika Co., Ltd.)
... 3%
・ Polymer dispersant 1 ・ ・ ・ 1.35%
・ Aqueous dispersion of self-dispersing polymer particles 1 2%
・ The following polymerizable compound 1 15%
・ 1,2-Hexanediol 3%
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1%
・ Irgacure 2959 (Ciba Japan) 3%
・ Ion exchange water

<< Preparation of Cyan Ink C2 >>
Cyan ink C2 was prepared in the same manner as described above except that in the preparation of cyan ink C1, Irgacure 2959 was removed from the composition of cyan ink C1.

[Preparation of treatment solution]
(Preparation of treatment liquid 1)
The component of the following composition was mixed and the processing liquid 1 was prepared.

<Composition of treatment liquid 1>
・ Canola oil: 26% by mass
・ Diethylene glycol monobutyl ether: 64% by mass
・ 4-Methylphthalic acid: 10% by mass

(Preparation of treatment liquid 2)
The component of the following composition was mixed and the processing liquid 2 was prepared.

<Composition of treatment liquid 2>
・ Canola oil: 26% by mass
・ Tetraethylene glycol monomethyl ether: 64% by mass
・ 4-Methylphthalic acid: 10% by mass

(Preparation of treatment liquid 3)
The component of the following composition was mixed and the processing liquid 3 was prepared.

<Composition of treatment liquid 3>
・ Canola oil: 45% by mass
・ Diethylene glycol monobutyl ether: 45% by mass
・ 4-Methylphthalic acid: 10% by mass

(Preparation of treatment liquid 4)
The component of the following composition was mixed and the processing liquid 4 was prepared.

<Composition of treatment liquid 4>
・ Olive oil: 26% by mass
・ Diethylene glycol monobutyl ether: 64% by mass
・ 4-Methylphthalic acid: 10% by mass

(Preparation of treatment liquid 5)
The component of the following composition was mixed and the processing liquid 5 was prepared.

<Composition of treatment liquid 5>
・ Peanut oil: 26% by mass
・ Diethylene glycol monobutyl ether: 64% by mass
・ 4-Methylphthalic acid: 10% by mass

(Preparation of treatment liquid 6)
The component of the following composition was mixed and the processing liquid 6 was prepared.

<Composition of treatment liquid 6>
・ Canola oil: 20% by mass
・ Diethylene glycol monobutyl ether: 80% by mass
・ 4-Methylphthalic acid: 10% by mass

(Preparation of treatment liquid 7)
The component of the following composition was mixed and the processing liquid 7 was prepared.

<Composition of treatment liquid 7>
・ Citric acid: 25% by mass
・ Diethylene glycol monobutyl ether: 20% by mass
・ Ion exchange water: 55% by mass

[Image recording and evaluation]
Using the cyan ink C1 obtained above and the treatment liquids 1 to 7 shown in Table 1 in combination, an image is recorded as follows, and the following method is used to evaluate the cockling of the recorded image. did. The evaluation results are shown in Table 1 below.

<Recording images>
First, as shown in FIG. 1, a treatment liquid application unit 12 including a treatment liquid ejection head 12S that ejects an aqueous treatment liquid sequentially in the conveyance direction of the recording medium (the arrow direction in the drawing) is applied. A treatment liquid drying zone 13 for drying the aqueous treatment liquid, an ink ejection section 14 for ejecting various aqueous inks, an ink drying zone 15 for drying the ejected aqueous ink, and UV irradiation capable of irradiating ultraviolet rays (UV). An ink jet apparatus provided with a UV irradiation unit 16 provided with a lamp 16S was prepared.
Although not shown, the processing liquid drying zone 13 is provided with a blower for drying by sending dry air to the recording surface side of the recording medium, and an infrared heater on the non-recording surface side of the recording medium. The temperature and the air volume are adjusted to evaporate (dry) 70% by mass or more of water in the aqueous treatment liquid until 900 msec after the application of the treatment liquid is started in the application unit. The ink discharge unit 14 includes a black ink discharge head 30K, a cyan ink discharge head 30C, a magenta ink discharge head 30M, and a yellow ink discharge head 30Y, which are sequentially arranged in the transport direction (arrow direction). Each head is a 1200 dpi / 10 inch wide full-line head (driving frequency: 25 kHz, recording medium conveyance speed 530 mm / sec), and can record by discharging each color in the main scanning direction by a single pass.

In the storage tanks (not shown) connected to the treatment liquid ejection head 12S and the cyan ink ejection head 30C of the inkjet apparatus configured as shown in FIG. 1, the treatment liquids 1 to 7 and the ink composition C1 obtained above are respectively stored. And a solid image and a 1200 dpi line image were recorded on the recording medium. The amount of the aqueous treatment liquid applied to the recording medium was 5 ml / m ² . As recording media, “OK Topcoat + ” (basis weight 104.7 g / m ² ) manufactured by Oji Paper Co., Ltd. and “Xerox 4024” manufactured by Fuji Xerox Co., Ltd. were used.
In recording an image, the aqueous treatment liquid and cyan ink were ejected at a resolution of 1200 dpi × 600 dpi, an ink droplet amount of 3.5 pl, and a maximum ink application amount of 10 ml / m ² . At this time, the solid image was formed as a solid image by ejecting ink on the entire surface of a sample obtained by cutting the recording medium into A5 size.
First, after the processing liquid is discharged from the processing liquid discharge head 12S onto the recording medium by a single pass (discharge amount 5 ml / m ² ), the processing liquid is dried in the processing liquid drying zone 13. It passed through the drying zone by 900 msec from the start of discharge of the aqueous treatment liquid. In the treatment liquid drying zone 13, 120 ° C. is applied to the recording surface by a blower while heating the deposited aqueous treatment liquid from the back side (rear side) of the landing surface with an infrared heater so that the film surface temperature is 40 to 45 ° C. The warm air was applied to adjust the air volume to a predetermined dry amount. Subsequently, after cyan ink is ejected in a single pass by the cyan ink ejection head 30C and an image is recorded, the ink drying zone 15 is heated with an infrared heater from the back side (back surface) of the ink landing surface as described above. Then, warm air at 120 ° C. and 5 m / sec was applied to the recording surface for 15 seconds with a blower and dried. After drying the image, the UV irradiation unit 16 irradiated UV light (a metal halide lamp, maximum irradiation wavelength 365 nm, manufactured by Eye Graphics Co., Ltd.) so that the integrated irradiation amount was 3 J / cm ² , and the image was cured.

<Evaluation>
-Evaluation of cockling-
As described above, a solid image of the maximum discharge amount was output on the OK top coat + , and after standing in an environment of 50% RH for 1 hour, the image was visually observed for cuckling and evaluated according to the following criteria. . The evaluation results are shown in Table 1 below.
<Evaluation criteria>
1: There is almost no unevenness in the image.
2: Slight irregularities are observed at the periphery of the image.
3: Unevenness occurs in the entire image.
4: Large unevenness occurs in the entire image.

-Evaluation of film strength (abrasion resistance)-
As described above, the ink composition C1 and the treatment liquids 1 to 7 are combined on the OK topcoat + to output a solid image (sample) with the maximum discharge amount and left for 1 hour in an environment of 25 ° C. and 50% RH. After that, the printing screen is overlapped with the non-printed OK top coat +, and with the weight of 500 g applied, the printing screen is rubbed 10 reciprocations (moving amount 5 cm at a time) to evaluate the destruction behavior of the image surface. did. In this evaluation method, 3 or less is an acceptable level as a product, and a lower score is more preferable.

<Evaluation criteria>
1: No change is observed on the image surface.
2: Although no broken part is observed on the image surface, the surface glossiness is partially changed.
3: A part of the image is transferred to the non-image part, but there is no part where the image is missing on the image surface. 4: A part of the image is missing, and a part where there is no image appears.
5: The image is missing over the entire surface, and a large area with no image appears.

  As is apparent from Table 1, it was found that in the present invention, the cuckling is suppressed and the image quality is remarkably improved. Further, the obtained image was obtained as a uniform solid image without buffering the landing, and the image intensity was sufficient.

In addition, as a recording medium, “Xerox 4024” manufactured by Fuji Xerox Co., Ltd. conducted a similar experiment. As a result, the obtained image was obtained as a uniform solid image without impact buffering, and the image intensity was sufficient. there were.
Further, when the ink composition C2 is used in place of the ink composition C1 and the processing liquid 8 is used in place of the processing liquid 1, like the combination of the ink composition C1 and the processing liquid 1, cuckling occurs. The image quality was remarkably improved, and the obtained image was obtained as a uniform solid image without buffering the landing, and the image intensity was sufficient.

DESCRIPTION OF SYMBOLS 12 ... Treatment liquid provision part 12S ... Treatment liquid discharge head 13 ... Treatment liquid drying zone 14 ... Ink discharge part 15 ... Ink drying zone 16 ... Ultraviolet irradiation part 16S ... Ultraviolet irradiation lamps 30K, 30C, 30M, 30Y... Ink discharge head

Claims (12)

An ink composition comprising a pigment and a water-soluble polymerizable compound that is polymerized by active energy rays;
A treatment comprising an aggregating agent for aggregating the components in the ink composition, and an organic solvent having a solubility in 100 g of water (25 ° C.) of 25 % by mass or more and 60% by mass or less with respect to the total mass of the liquid. Liquid,
Ink set containing. The ink set according to claim 1, wherein the organic solvent is at least one selected from fatty oil and fat. The ink set according to claim 2, wherein the fatty oil is a non-drying oil. The ink set according to claim 3, wherein the non-drying oil is at least one selected from rapeseed oil, olive oil, peanut oil, and camellia oil. The ink set according to any one of claims 1 to 4, wherein the pigment is a water-dispersible pigment having at least a part of a surface thereof coated with a polymer dispersant. The ink set according to claim 5, wherein the polymer dispersant has a carboxyl group. The ink set according to claim 1, wherein the flocculant is an organic acid. The ink set according to any one of claims 1 to 7, wherein at least one of the ink composition and the treatment liquid further includes a polymerization initiator that initiates polymerization of the polymerizable compound. The ink set according to claim 1, wherein the ink composition further contains polymer particles. The treatment liquid is further ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene. The aqueous solvent mixed with at least 1 sort (s) of water selected from the group of glycol monomethyl ether, a triethylene glycol monoethyl ether, and ethylene glycol monophenyl ether of any one of Claims 1-9. Ink set. An ink application step of applying an ink composition containing a pigment and a water-soluble polymerizable compound polymerized by active energy rays to a recording medium by an inkjet method;
A treatment comprising an aggregating agent for aggregating the components in the ink composition, and an organic solvent having a solubility in 100 g of water (25 ° C.) of 25 % by mass or more and 60% by mass or less with respect to the total mass of the liquid. A treatment liquid application step for applying the liquid to the recording medium;
An image forming method comprising: The recording medium, the image forming method according to claim 1 1 which is a coated paper having a base paper and a coating layer containing inorganic pigments.