JP2008093858A - Ink jet printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet printing method for obtaining a printed matter superior in print density and glossiness, and to provide an ink set for use therein. <P>SOLUTION: (1) In the printing method, a recording medium is coated with coating ink containing metal oxide secondary particles formed by combining a plurality of primary particles, and then aqueous ink containing a coloring agent is printed on the coated part by ink jet recording system. (2) The ink set is composed of the coating ink containing metal oxide secondary particles formed by combining a plurality of primary particles, and the aqueous ink containing a coloring agent, wherein a recording medium is coated with the coating ink and then the aqueous ink is printed on the coated part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet printing method and an ink set capable of obtaining a printed matter having excellent print density and glossiness.

The ink jet recording method is a recording method in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle onto a recording member and attaching them. This method is easily spread at full color, is inexpensive, has a number of advantages in that a recording medium can be used as a recording member, and is non-contact with respect to an object to be printed.
Regarding the ink jet recording method, for example, Patent Document 1 discloses a liquid adhesion process in which a liquid containing colorless fine particles is adhered to a recording material, and pigment, water, resin fine particles, and a water-soluble solvent are added to the liquid adhesion portion. A recording liquid discharge process for discharging the recording liquid to be included. In the liquid adhesion process, the surface roughness (Ra) of the recording material is adjusted to a specific range, and the surface tension is 25 to 50 mN / m. An ink jet recording method is disclosed in which the dynamic contact angle of the recording liquid to the surface of a recording material is set to 30 ° / sec or more.

Regarding ink jet recording ink, for example, Patent Document 2 discloses a liquid composition containing light or white water-insoluble fine particles (resin emulsion), a water-soluble organic solvent and water, a colorant, a water-soluble organic solvent and water. And an ink containing an ink.
With respect to the ink set, for example, Patent Document 3 discloses an ink set having black, yellow, magenta, and cyan inks, and at least one kind of ink contains a water-insoluble colorant. An ink set is disclosed which is an aqueous ink containing an encapsulated color material coated with a weight percent organic polymer.
Patent Document 4 discloses an ink set composed of a recording liquid containing a coloring material and a processing liquid containing a component having reactivity with the coloring material, and the processing liquid and the recording liquid are ejected from an inkjet head. Thus, the cross section of the recording portion formed by being overlaid on the recording medium is formed separately into a layer formed with the components constituting the recording liquid and a layer formed with the components constituting the processing liquid. An ink set having a thickness of those layers of 0.01 to 10 μm is disclosed.
However, with the ink jet recording method, ink, and ink set disclosed in the patent document, it has been impossible to obtain a printed matter with excellent print density and glossiness.

JP 2005-1182 A JP 2000-034342 A JP 2001-152060 A Japanese Patent Laying-Open No. 2005-138502

  An object of the present invention is to provide an ink jet printing method and an ink set that can obtain a printed matter with excellent print density and gloss.

The present inventors have found that a printed matter and a photograph having excellent gloss can be obtained by using a coating ink containing a specific metal oxide.
That is, the present invention provides the following (1) and (2).
(1) An ink jet printing method in which the following steps 1 and 2 are sequentially performed on a recording medium using a coating ink and a water-based ink.
Step 1: A step of coating a coating ink containing metal oxide secondary particles in which a plurality of primary particles are connected to all or part of the recording medium by an inkjet recording method. Step 2: Step 1 (2) A metal oxide secondary in which a plurality of primary particles are connected to each other by applying an aqueous ink containing a colorant to the coated portion of the recording medium obtained in step 2 by an inkjet recording method. An ink set composed of a coating ink containing particles and a water-based ink containing a colorant, wherein the coating ink is coated on a recording medium by an inkjet recording method, and the coating treatment portion An ink set for printing the water-based ink on top of the other.

  According to the ink jet printing method and ink set of the present invention, a printed matter (printed matter, photograph) having excellent print density and gloss can be obtained even if plain paper or copy paper is used as a recording medium.

The ink jet printing method of the present invention is characterized by sequentially performing the following steps 1 and 2 on a recording medium using a coating ink and an aqueous ink.
Step 1: A step of applying a coating ink containing metal oxide secondary particles in which a plurality of primary particles are connected to all or part of a recording medium by an inkjet recording method. Step 2: Obtained in Step 1 Step of printing a water-based ink containing a colorant on the coated portion of the recording medium by using an ink jet recording method. Each component used in the printing method of the present invention will be described below.

(Coating ink)
The coating ink used in the present invention is an aqueous coating ink containing metal oxide secondary particles (hereinafter simply referred to as “metal oxide secondary particles”) in which a plurality of primary particles are connected.
The metal oxide used for the metal oxide secondary particles is preferably at least one selected from the group consisting of silicon oxide (silica), titanium oxide, and cerium oxide. Among these, silica is preferable from the viewpoint of dispersion stability.
In the present invention, the metal oxide secondary particles are used from the viewpoint of improving printing density and gloss.

The metal oxide secondary particles are obtained by continuously connecting a plurality of metal oxide primary particles. “Linked” means that a plurality of bonds are continuously formed by chemical bonds. For example, in the case of silica, a siloxane bond or the like is meant. The “metal oxide primary particles” constituting the metal oxide secondary particles are metal oxide fine particles before joining which are constituent units of the metal oxide secondary particles. Colloidal particles are usually used as the metal oxide fine particles. The shape is not particularly limited, and may be spherical or elongated. When producing the metal oxide secondary particles, other metal oxides may be used as a substance interposed for bonding the metal oxide primary particles. Examples of such metals include divalent metals such as Ba, Ca, and Mg, and trivalent metals such as Al.
The bonding site where the metal oxide primary particles are bonded to each other may be the case where the portion of the formed metal oxide secondary particle has a constriction or not, and this is a problem in the manufacturing method. Dependent on either form. When it has a constriction, it becomes a bead-shaped metal oxide particle, and this includes a plurality of primary particles connected in a bead shape, dumbbell shape, necklace shape, etc. It becomes metal oxide particles.

  There is no particular limitation on the shape or degree of constriction at the joints of the beaded metal oxide particles, from those that can finally be recognized to those having a large constriction, for example, those having a thread-like joint. Are also included. In addition, the shape of the constriction includes any shape such as a partial circle such as a semicircle, a trapezoidal shape, and other quadrangular shapes. In the present invention, from the viewpoint of gloss and the like, any of beaded metal oxide particles formed by connecting a plurality of primary particles in a bead shape, and elongated metal oxide particles formed by connecting a plurality of primary particles in an elongated shape, Are also preferably used.

The shape of the metal oxide secondary particles may be a linearly extended shape, a two-dimensionally or three-dimensionally curved shape. Moreover, it may be linear or branched.
In the present invention, “a plurality of primary particles” refers to two or more metal oxide primary particles, and preferably 2 to 100 metal oxide primary particles, more preferably 5 to 50, from the viewpoint of gloss. Metal oxide primary particles.
About the shape of the said metal oxide secondary particle, the shape of primary particle which comprises a metal oxide secondary particle, a number, etc. can be confirmed by methods, such as an electron micrograph. The number can be obtained as an average value of the number of primary particles constituting 50 metal oxide secondary particles observed in an electron micrograph.

The average particle size of the primary particles constituting the metal oxide secondary particles is preferably 1 to 30 nm, more preferably 3 to 25 nm, from the viewpoint of gloss, and 50 metal oxides observed in an electron micrograph. It is expressed by the average diameter of the primary particles. Specifically, it can be measured by the method described in the examples described later.
When the metal oxide secondary particles have an elongated shape, the average diameter of the primary particles is obtained as an average value of thicknesses (diameters) measured at any 50 locations of the metal oxide secondary particles in the electron micrograph. When the metal oxide secondary particles have a constriction and a bead shape, it can be obtained as an average value of the diameters of 50 bead beads in an electron micrograph. When each rosary has a major axis and a minor axis, that is, when each rosary has an elongated shape, the minor axis is measured.
The average particle size of the metal oxide secondary particles is preferably 40 to 300 nm, more preferably 40 to 200 nm, and still more preferably 60 to 200 nm, from the viewpoint of gloss. The average particle diameter can be measured by a dynamic light scattering method, and specifically, can be measured by the method described in the examples described later.

  When the metal oxide is silica, the silica secondary particles are obtained by the method described in claim 2 of WO 00/15552 and the disclosure part of the related specification, Patent No. 2803134, Patent No. 2926915. Can be produced by the method described in claim 2 of the specification and the disclosure of the specification related thereto, or a method analogous thereto.

Specific examples of the silica secondary particles that can be used in the present invention include “Snowtex-OUP” (average secondary particle size: 40 to 100 nm) manufactured by Nissan Chemical Industries, Ltd., and “Snowtex-UP”. (Average secondary particle size: 40 to 100 nm), the same “Snowtex PS-M” (average secondary particle size: 80 to 150 nm), the same “Snowtex PS-MO” (average secondary particle size: 80 to 150 nm), “Snowtex PS-S” (average secondary particle size: 80-120 nm), “Snowtex PS-SO” (average secondary particle size: 80-120 nm), “IPA-ST-UP” (Average secondary particle size: 40 to 100 nm), “Quartron PL-7” (average secondary particle size: 130 nm) manufactured by Fuso Chemical Industry Co., Ltd., and the like.
Specific examples of the titanium oxide secondary particles include “PW-6030” (average secondary particle size: 93 nm) manufactured by Catalyst Kasei Kogyo Co., Ltd., and specific examples of the cerium oxide secondary particles include Taki Chemical Co., Ltd. “Nidoral P-10” (average secondary particle size: 49 nm).

Although the said metal oxide secondary particle may be used individually by 1 type, it can also be used in combination of 2 or more type.
When the metal oxide secondary particles used in the present invention are ejected from the nozzle as a coating ink component onto the recording paper, the metal oxide secondary particles are caught on the paper fiber of the recording paper, so that the penetration into the recording paper is suppressed. It is considered that the glossiness of the paper is improved and the print density of the printed matter is improved by suppressing the penetration of the colorant in the water-based ink.
In the present invention, when the metal oxide secondary particles are added to the dispersion, the form thereof is not particularly limited, but is usually a sol form.
The solid content of the metal oxide secondary particles in the coating ink is preferably 5 to 70 wt. From the viewpoint of increasing the solid content to prevent wrinkling of the recording medium and the dispersion stability of the fine particles. %, More preferably 10 to 50% by weight, particularly preferably 10 to 30% by weight.
The content of water in the coating ink is preferably 20 to 90% by weight, more preferably 30 to 80% by weight, from the viewpoint of preventing wrinkling of the recording medium and dispersion stability of the fine particles.

The viscosity (20 ° C.) of the coating ink is preferably 2 to 12 mPa · s, more preferably 2.5 to 10 mPa · s, in order to maintain good ejection properties.
The coating ink may contain additives such as a wetting agent, a dispersing agent, an antifoaming agent, an antifungal agent, a chelating agent, and an anti-wrinkle agent that are usually used in water-based inks.

(Coloring agent)
The colorant is not particularly limited, and pigments, hydrophobic dyes, water-soluble dyes (acid dyes, reactive dyes, direct dyes, etc.) can be used, but from the viewpoint of water resistance, dispersion stability, and scratch resistance. Pigments and hydrophobic dyes are preferred.
When the pigment and the hydrophobic dye are used in an aqueous ink, it is necessary to use a surfactant and a polymer to form fine particles that are stable in the ink. In particular, from the viewpoint of bleeding resistance, water resistance, and the like, it is preferable to include a pigment and / or a hydrophobic dye in the water-insoluble polymer particles.
The pigment may be either an inorganic pigment or an organic pigment.
Examples of the inorganic pigment include carbon black, metal sulfide, metal chloride and the like. Of these, carbon black is preferred particularly for black aqueous inks. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.
Examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthoraquinone pigments, and quinophthalone pigments.
Specific examples of preferred organic pigments include C.I. I. Pigment yellow, C.I. I. Pigment Red, C.I. I. Pigment violet, C.I. I. Pigment blue, and C.I. I. One or more types of products selected from the group consisting of pigment green are listed.

The hydrophobic dye is not particularly limited as long as it can be contained in the polymer particles. The hydrophobic dye is dissolved in an amount of 2 g / L or more, preferably 20 to 500 g / L (25 ° C.) with respect to the organic solvent (preferably methyl ethyl ketone) used in the production of the polymer from the viewpoint of efficiently containing the dye in the polymer. What to do is desirable.
Examples of the hydrophobic dye include oil-soluble dyes and disperse dyes. Among these, oil-soluble dyes are preferable.
Examples of the oil-soluble dye include C.I. I. Solvent Black, C.I. I. Solvent Yellow, C.I. I. Solvent Red, C.I. I. Solvent Violet, C.I. I. Solvent Blue, C.I. I. Solvent Green, C.I. I. Examples are products of various product numbers such as Solvent Orange, which are commercially available from Orient Chemical Co., Ltd., BASF Co., etc.
The above colorants can be used alone or in admixture of two or more at any ratio.

(Water-based ink containing colorant)
The aqueous ink containing the colorant used in the present invention preferably contains the following dispersions (1) to (3).
(1) Dispersion in which colorant is dispersed in water with surfactant, pigment derivative or water-soluble polymer (2) Self-dispersed pigment in which hydrophilic group is bonded to pigment directly or through other atomic groups (3) Water dispersion of water-insoluble polymer particles containing a colorant The surfactant used in the dispersion (1) includes an anionic surfactant, a cationic surfactant, and a nonionic interface. Activators and amphoteric surfactants are all included, and pigment derivatives include ionic functional groups or salts of ionic functional groups, azo derivatives, diazo derivatives, phthalocyanine derivatives, quinacridone derivatives, isoindolinone derivatives, dioxazines. Derivatives, perylene derivatives, perinone derivatives, thioindigo derivatives, anthraquinone derivatives, quinophthalone derivatives, and the like.
The water-soluble polymer is a polymer having a dissolution amount exceeding 10 g, preferably 20 g or more, more preferably 30 g or more when dissolved in 100 g of water at 25 ° C. When the water-soluble polymer has a salt-forming group such as a carboxy group or an ammonium group, the amount dissolved is determined by neutralizing the salt-forming group of the water-soluble polymer with acetic acid or sodium hydroxide according to the type of the water-soluble polymer. The amount of dissolution.

Examples of the water-soluble polymer include (i) a water-soluble polymer obtained by subjecting a sulfonated product obtained by sulfonating a polynuclear aromatic compound or a mononuclear aromatic compound to formalin condensation, and then preferably neutralizing; (ii) carboxy A water-soluble polymer having a group is preferred. Specific examples of the polymer (i) include polynaphthalene sulfonic acid (salt) typified by sodium salt of β-naphthalene sulfonic acid formalin condensate. Commercial products such as Demall MS (trade name) can be used. Examples of the polymer (ii) include (meth) acrylic acid (salt) polymers represented by polyacrylic acid and copolymers thereof, sodium salts of styrene and maleic acid copolymers, diisobutylene and maleic acid copolymer. A maleic acid (salt) polymer represented by a combined sodium salt and a copolymer thereof may be mentioned, and specifically, Pois 520, Pois 521, Pois 530 and the like manufactured by Kao Corporation are preferable.
The water-soluble polymer preferably has a weight average molecular weight of 2,000 to 50,000 from the viewpoint of dispersibility. The weight average molecular weight of the water-soluble polymer was measured using polystyrene as a standard substance by gel chromatography using dimethylformamide in which 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide were dissolved as a solvent. can do.

The self-dispersing pigment used in the dispersion (2) binds one or more salt-forming groups which are an anionic hydrophilic group or a cationic hydrophilic group to the surface of the pigment directly or via another atomic group. This means a pigment that can be dispersed in an aqueous medium without using a surfactant or a resin.
Here, as other atomic groups, an alkylene group having 1 to 24 carbon atoms, preferably an alkylene group having 1 to 12 carbon atoms, an optionally substituted phenylene group, or an optionally substituted naphthylene group. Etc.
Any anionic hydrophilic group may be used as long as it is sufficiently hydrophilic so that the pigment particles can be stably dispersed in the aqueous medium. Specific examples thereof include a carboxy group (-COOM ^1), a sulfonic acid group (-SO ₃ M ^1), phosphoric acid group _{^{(-PO 3 M 1 2),}} - SO 2 NH 2, -SO 2 NHCOR 1 or their The dissociated ionic form (—COO ⁻ , —SO ₃ ⁻ , —PO ₃ ²⁻ , —PO ₃ ⁻ M ¹ ), and the like. In the chemical formula, M ¹ may be the same or different and is a hydrogen atom, an alkali metal, ammonium, or organic ammonium. R ¹ is an alkyl group which may have an optionally substituted phenyl group or a substituted naphthyl group having 1 to 12 carbon atoms.
Among these anionic hydrophilic groups, a carboxy group (—COOM ¹ ) and a sulfonic acid group (—SO ₃ M ¹ ) are particularly preferable.
Examples of the cationic hydrophilic group include an ammonium group and an amino group.
Among these, as the water-based ink used in the present invention, (3) an aqueous dispersion of water-insoluble polymer particles containing a colorant is used from the viewpoint of improving excellent ejection reliability and gloss of printed matter. Preferably, it will be described below.

(Water-insoluble polymer)
Examples of the water-insoluble polymer constituting the water-insoluble polymer particles include a water-insoluble vinyl polymer, a water-insoluble ester polymer, and a water-insoluble urethane polymer. Among these, a water-insoluble vinyl polymer is preferable from the viewpoint of the stability of the aqueous dispersion.
Here, the water-insoluble polymer is a polymer having a dissolution amount of 10 g or less, preferably 5 g or less, more preferably 1 g or less, after being dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C. Say. In the case where the water-insoluble polymer has a salt-forming group, the dissolution amount is a dissolution amount when the salt-forming group of the water-insoluble polymer is neutralized 100% with acetic acid or sodium hydroxide depending on the type.

The water-insoluble polymer is preferably a water-insoluble graft polymer containing a structural unit derived from the macromer (b) from the viewpoint of sufficient printing density and improvement in dispersion stability. In particular, the water-insoluble polymer has a polymer containing a structural unit derived from the salt-forming group-containing monomer (a) and a structural unit derived from the hydrophobic monomer (c) in the main chain, and the structural unit derived from the macromer (b). A water-insoluble graft polymer having a side chain is preferred.
Examples of such a water-insoluble graft polymer include a salt-forming group-containing monomer (a) (hereinafter sometimes referred to as “(a) component”), a macromer (b) (hereinafter sometimes referred to as “(b) component”), And a water-insoluble vinyl polymer obtained by copolymerizing a monomer mixture (hereinafter also referred to as “monomer mixture”) containing a hydrophobic monomer (c) (hereinafter also referred to as “component (c)”) is preferable.

(Salt-forming group-containing monomer (a))
The component (a) is used from the viewpoint of enhancing the dispersion stability of the resulting dispersion, and examples thereof include a cationic monomer and an anionic monomer. Specifically, those described in JP-A-9-286939, page 5, column 7, line 24 to page 8, column 8 line 29 can be used. Examples of the salt-forming group include a carboxy group, a sulfonic acid group, a phosphoric acid group, an amino group, and an ammonium group.
Representative examples of the cationic monomer include unsaturated amine-containing monomers and unsaturated ammonium salt-containing monomers. Among these, N, N-dimethylaminoethyl (meth) acrylate, N- (N ′, N '-Dimethylaminopropyl) (meth) acrylamide is preferred.

Representative examples of anionic monomers include unsaturated carboxylic acid monomers, unsaturated sulfonic acid monomers, unsaturated phosphoric acid monomers, and the like.
Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid.
Examples of unsaturated sulfonic acid monomers include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, and bis- (3-sulfopropyl) -itaconate.
Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxy Examples thereof include ethyl phosphate.
Among the anionic monomers, unsaturated carboxylic acid monomers are preferable, and acrylic acid or methacrylic acid is more preferable from the viewpoints of dispersion stability, ejection reliability, and the like.

(Macromer (b))
The component (b) is used from the viewpoint of improving the dispersion stability of the water-insoluble polymer particles and improving the printing density, and has a number average molecular weight of 500 to 100,000, preferably 1,000 to 10,000. Examples thereof include a macromer which is a monomer having a polymerizable functional group such as an unsaturated group at the terminal.
The number average molecular weight of the component (b) can be measured by gel permeation chromatography using polystyrene as a standard substance and tetrahydrofuran containing 50 mmol / L acetic acid as a solvent.
Specifically, as the macromer of the component (b), the following (b-1) styrene-based macromer, (b-2) alkyl (meth) acrylate-based macromer, (b-3) aromatic ring-containing (meth) acrylate-based Macromers, (b-4) silicone-based macromers, and the like.

(B-1) Styrenic Macromer The styrene macromer means a macromer having a styrene monomer (referred to as a b-1 monomer) such as styrene, α-methylstyrene, vinyltoluene and the like. Of the styrenic monomers, styrene is preferred.
Examples of the styrenic macromer include a styrene homopolymer having a polymerizable functional group at one end, and a copolymer of styrene and another monomer having a polymerizable functional group at one end. The polymerizable functional group present at one end is preferably an acryloyloxy group or a methacryloyloxy group, and by copolymerizing these, a water-insoluble graft polymer having a structural unit derived from a styrenic macromer can be obtained. Examples of the other monomer include acrylonitrile, an alkyl (meth) acrylate (b-2 monomer) described later, and an aromatic ring-containing (meth) acrylate (b-3 monomer) other than styrene.
The content of the structural unit derived from the styrene monomer in the side chain or styrene macromer is preferably 60% by weight or more, more preferably 70% by weight or more, and particularly preferably 90% by weight from the viewpoint of improving the printing density. % Or more.
Examples of commercially available styrenic macromers include Toa Gosei Co., Ltd. trade name, AS-6 (S), AN-6 (S), HS-6 (S), and the like.

(B-2) Alkyl (meth) acrylate-based macromer An alkyl (meth) acrylate-based macromer has an alkyl group that may have a hydroxy group, preferably 1 to 22 carbon atoms, preferably 1 to 18 carbon atoms. , Means a macromer having an alkyl (meth) acrylate (b-2 monomer).
Specifically, as the b-2 monomer, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (iso or tertiary) butyl ( Examples include (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) stearyl (meth) acrylate, and the like.
The side chain containing the structural unit derived from the b-2 monomer is obtained by copolymerizing an alkyl (meth) acrylate macromer having a polymerizable functional group at one end, for example, methyl methacrylate macromer, butyl acrylate macromer. , Isobutyl methacrylate-based macromer, lauryl methacrylate-based macromer, and the like.
The alkyl (meth) acrylate-based macromer is composed of an alkyl (meth) acrylate homopolymer having a polymerizable functional group at one end, and an alkyl (meth) acrylate having another polymerizable functional group at one end and another monomer. A copolymer may be mentioned, and the polymerizable functional group is preferably an acryloyloxy group or a methacryloyloxy group. Examples of the other monomer include the styrene monomer (b-1 monomer) and aromatic ring-containing (meth) acrylate (b-3 monomer) other than styrene described below.
In the side chain or in the alkyl (meth) acrylate macromer, the content of the structural unit derived from the (meth) acrylic acid ester is the largest, and preferably 60% by weight or more, more preferably from the viewpoint of improving the printing density. It is 70% by weight or more, particularly preferably 90% by weight or more.

(B-3) Aromatic ring-containing (meth) acrylate-based macromer The aromatic ring-containing (meth) acrylate-based macromer means a macromer having an aromatic ring-containing (meth) acrylate (b-3 monomer). As an aromatic ring containing (meth) acrylate, the monomer represented by following formula (1) is preferable.
CH ₂ = CR ² COOR ³ (1)
(In the formula, R ² represents a hydrogen atom or a methyl group, and R ³ represents an arylalkyl group having 7 to 22 carbon atoms or an aryl group having 6 to 22 carbon atoms, which may have a substituent. )
Specifically, benzyl (meth) acrylate, phenyl (meth) acrylate, 2-phenylethyl (meth) acrylate, phenoxyethyl (meth) acrylate, 1-naphthyl acrylate, 2-naphthyl (meth) acrylate, phthalimidomethyl (meta ) Acrylate, p-nitrophenyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, 2-acryloyloxyethyl phthalate, and the like. Among these, benzyl (meth) acrylate is particularly preferable. These can be used alone or in admixture of two or more.

A side chain containing a structural unit derived from an aromatic ring-containing (meth) acrylate can be obtained by copolymerizing an aromatic ring-containing (meth) acrylate-based macromer having a polymerizable functional group at one end.
An aromatic ring-containing (meth) acrylate-based macromer is a homopolymer of an aromatic ring-containing (meth) acrylate having a polymerizable functional group at one end, and an aromatic ring-containing (meth) acrylate having a polymerizable functional group at one end And other monomers, and the polymerizable functional group is preferably an acryloyloxy group or a methacryloyloxy group. Examples of the other monomer include the styrene monomer (b-1 monomer) and (meth) acrylic acid ester (b-2 monomer).
In the side chain or the aromatic ring-containing (meth) acrylate macromer, the content of the structural unit derived from the aromatic ring-containing (meth) acrylate is the largest.

(B-4) Silicone Macromer The water-insoluble graft polymer used in the present invention may have an organopolysiloxane chain as a side chain. This side chain can be obtained, for example, by copolymerizing a silicone macromer having a polymerizable functional group at one end, preferably represented by the following formula (2).
_{CH 2 = C (CH 3)} -COOC 3 H 6 - [Si (CH _{3) 2} -O] _{t -Si (CH 3) 3 (} 2)
(Wherein t represents a number of 8 to 40)
When the polymer used in the present invention is a water-insoluble graft polymer, the weight ratio of [main chain / side chain] is 1/1 to 20/1 from the viewpoint of improving printing density and storage stability. Is preferable, 3/2 to 15/1 is more preferable, and 2/1 to 10/1 is particularly preferable. The weight ratio is calculated assuming that the polymerizable functional group is contained in the side chain.
Among the above, a styrenic macromer having a polymerizable functional group at one end is preferable from the viewpoint of high affinity with the pigment and improving storage stability.

(Hydrophobic monomer (c))
The component (c) is used from the viewpoint of improving the printing density, and examples thereof include alkyl (meth) acrylate, alkyl (meth) acrylamide, and aromatic ring-containing monomers.
Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, Cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) cetyl (meth) acrylate, (Meth) acrylic acid ester having an alkyl group having 1 to 30 carbon atoms, such as (iso) stearyl (meth) acrylate and (iso) behenyl (meth) acrylate. Among these, a (meth) acrylate having a long-chain alkyl group having 8 to 30 carbon atoms, preferably 12 to 22 carbon atoms is preferable from the viewpoint of dispersion stability, and (iso) lauryl (meth) acrylate, ( Iso) stearyl (meth) acrylate and (iso) behenyl (meth) acrylate are preferred.

As alkyl (meth) acrylamide, carbon number such as dimethyl (meth) acrylamide, diethyl (meth) acrylamide, dibutyl (meth) acrylamide, t-butyl (meth) acrylamide, octyl (meth) acrylamide, dodecyl (meth) acrylamide, etc. Examples include (meth) acrylamide having 1 to 22 alkyl groups.
Examples of the aromatic ring-containing monomer include styrene monomers (c-1) such as styrene, 2-methylstyrene and vinyltoluene, aryl esters of (meth) acrylic acid such as benzyl (meth) acrylate and phenoxyethyl (meth) acrylate, Preferred examples include an aromatic group-containing vinyl monomer (c-2) having 6 to 22 carbon atoms such as ethyl vinyl benzene, 4-vinyl biphenyl, 1,1-diphenyl ethylene, vinyl naphthalene and chlorostyrene. Among these, benzyl (meth) acrylate is particularly preferable.
In the present specification, “(iso or tertiary)” and “(iso)” mean that both of these groups are present and not present, and these groups are present. If not, it indicates normal. In addition, “(meth) acrylate” indicates that both acrylate and methacrylate are included.
The component (c) is preferably a (meth) acrylate and / or an aromatic ring-containing monomer having a long-chain alkyl group having 8 to 30 carbon atoms from the viewpoint of improving the printing density.
The components (a) to (c) can be used alone or in combination of two or more.

In the present invention, the monomer mixture containing the components (a), (b), and (c) further contains a hydroxyl group-containing monomer (d) (hereinafter sometimes referred to as “component (d)”). Is preferred.
The component (d) enhances dispersion stability. As the component (d), for example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polyethylene glycol (n = 2 to 30, n represents the average number of moles of oxyalkanediyl group added. The same shall apply hereinafter.) (Meth) acrylate, polypropylene glycol (n = 2 to 30) (meth) acrylate, poly (ethylene glycol (n = 1 to 15) / propylene glycol (n = 1 to 15)) (meth) acrylate, etc. Is mentioned. Among these, 2-hydroxyethyl (meth) acrylate, polyethylene glycol monomethacrylate, and polypropylene glycol methacrylate are preferable.

The monomer mixture may further contain a monomer (e) represented by the following formula (3) (hereinafter sometimes referred to as “component (e)”).
^{_{CH 2 = C (R 4)}} COO (R 5 O) p R 6 (3)
Wherein R ⁴ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ⁵ is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ⁶ is a hetero atom. The monovalent hydrocarbon group having 1 to 30 carbon atoms that may be present, p represents the average number of moles added, and is 1 to 60, preferably 1 to 30.)
The component (e) exhibits excellent effects such as enhancing the ejection reliability of the water-based ink and suppressing the occurrence of twisting even when continuous printing is performed.
In the formula (3), examples of the hetero atom that R ⁵ or R ⁶ may have include a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom.
Typical examples of the group represented by R ⁵ or R ⁶ include aromatic groups having 6 to 30 carbon atoms, heterocyclic groups having 3 to 30 carbon atoms, alkanediyl groups having 1 to 30 carbon atoms, and the like. May have a substituent. These groups may be a combination of two or more. Examples of the substituent include an aromatic group, a heterocyclic group, an alkyl group, a halogen atom, and an amino group.

As R ⁵ , a phenylene group optionally having a substituent having 1 to 24 carbon atoms, an aliphatic alkanediyl group having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, or a carbon having an aromatic ring. Preferred examples include an alkanediyl group having 7 to 30 carbon atoms and an alkanediyl group having 4 to 30 carbon atoms having a heterocyclic ring. Particularly preferred specific examples of the R ⁵ O group include an oxyethylene group, an oxy (iso) propylene group, an oxytetramethylene group, an oxyheptamethylene group, an oxyhexamethylene group, or a carbon composed of one or more of these oxyalkanediyl groups. The oxyalkanediyl group and oxyphenylene group of several 2-7 are mentioned.
R ⁶ is a phenyl group, an aliphatic alkyl group having 1 to 30 carbon atoms, preferably a branched chain having 1 to 20 carbon atoms, or an alkyl group having 7 to 30 carbon atoms having an aromatic ring. Or a C4-C30 alkyl group which has a heterocyclic ring is mentioned preferably. More preferable examples of R ⁶ include alkyl groups having 1 to 12 carbon atoms such as methyl group, ethyl group, (iso) propyl group, (iso) butyl group, (iso) pentyl group, and (iso) hexyl group, phenyl Groups and the like.

Specific examples of the component (e) include methoxypolyethylene glycol (p in formula (3) is 1 to 30) (meth) acrylate, methoxypolytetramethylene glycol (p = 1 to 30) (meth) acrylate, and ethoxypolyethylene. Glycol (p = 1-30) (meth) acrylate, (iso) propoxypolyethylene glycol (p = 1-30) (meth) acrylate, butoxypolyethylene glycol (p = 1-30) (meth) acrylate, octoxypolyethylene glycol (P = 1-30) (meth) acrylate, methoxypolypropylene glycol (p = 1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol copolymer) (p = 1-30, ethylene glycol moiety therein 1 to 29) (meta Acrylate, and the like. Among these, methoxypolyethylene glycol (p = 2 to 20) (meth) acrylate and octoxypolyethylene glycol (p = 2 to 20) (meth) acrylate are preferable.
Specific examples of the commercially available component (d) and component (e) include polyfunctional acrylate monomers (NK ester) M-40G, 90G, 230G, and EH-4E from Shin-Nakamura Chemical Co., Ltd. Blemmer series of Nippon Oil & Fat Co., Ltd., PE-90, 200, 350, PME-100, 200, 400, 1000, PP-500, 800, 1000, AP-150, 400, 550, 800, 50 PEP-300, 50POEP-800B, and the like.
The component (d) and the component (e) can be used alone or in combination of two or more.

Components (a) to (e) in the monomer mixture of the components (a) to (e) at the time of water-insoluble polymer production (contents as unneutralized amounts; the same applies hereinafter) or water-insoluble polymers The content of the structural unit derived from is as follows.
The content of the component (a) is preferably 1 to 50% by weight, more preferably 2 to 40% by weight, more preferably 3 to 30% by weight, particularly preferably from the viewpoint of dispersion stability of the resulting dispersion. Is 5 to 20% by weight.
The content of the component (b) is preferably 1 to 50% by weight, more preferably 3 to 40% by weight, and particularly preferably 5 to 35% by weight from the viewpoint of dispersion stability of the obtained dispersion, improvement in printing density, and the like. %.
The content of the component (c) is preferably 5 to 90% by weight, more preferably 5 to 80% by weight, and still more preferably 10 to 60% by weight from the viewpoint of printing density and the like.
The weight ratio ((a) / [(b) + (c)]) of the content of the component (a) and the total content of the components (b) and (c) is the long-term storage of the resulting water-based ink. From the viewpoints of stability, ejection reliability, etc., it is preferably 0.01 to 1, more preferably 0.02 to 0.7, and still more preferably 0.05 to 0.5.

The content of the component (d) is preferably 1 to 40% by weight, more preferably 2 to 30% by weight, and further preferably 3 to 15% by weight from the viewpoints of redispersibility and dispersion stability.
The content of the component (e) is preferably 1 to 50% by weight, more preferably 2 to 30% by weight, and further preferably 5 to 30% by weight from the viewpoints of ejection reliability, dispersion stability, and the like.
The total content of the component (a) and the component (d) is preferably 5 to 60% by weight, more preferably 7 to 50% by weight, and still more preferably 10 from the viewpoints of stability in water and water resistance. -40% by weight.
The total content of the component (a) and the component (e) is preferably 5 to 75% by weight, more preferably 7 to 50% by weight, from the viewpoints of dispersion stability in water, ejection reliability, and the like. More preferably, it is 10 to 40% by weight.
The total content of the component (a), the component (d), and the component (e) is preferably 5 to 60% by weight, more preferably 7 to 50% by weight from the viewpoints of dispersion stability in water and ejection reliability. %, More preferably 10 to 40% by weight.

(Production of water-insoluble polymer)
The water-insoluble polymer constituting the water-insoluble polymer particles is produced by copolymerizing the monomer mixture by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, Among these polymerization methods, effects such as high gloss and high printing density can be suitably obtained in the case of the solution polymerization method.
The solvent used in the solution polymerization method is preferably a polar organic solvent having a high affinity with the water-insoluble polymer, and preferably has a solubility in water of 20% by weight or less, preferably 5% by weight or more. Examples of the polar organic solvent include aliphatic alcohols such as butoxyethanol; aromatics such as toluene and xylene; ketones such as methyl ethyl ketone and methyl isobutyl ketone; esters such as ethyl acetate. Among these, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, butoxyethanol, or a mixed solvent of one or more of these with water is preferable.

In the polymerization, azo compounds such as 2,2′-azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile), tert-butyl peroxyoctoate, dibenzoyl oxide, etc. Known polymerization initiators such as organic peroxides can be used.
The amount of the polymerization initiator is preferably 0.001 to 5 mol, more preferably 0.01 to 2 mol, per mol of the monomer mixture.
In the polymerization, a known polymerization chain transfer agent such as mercaptans such as octyl mercaptan and 2-mercaptoethanol and thiuram disulfide can be further added.
The polymerization conditions of the monomer mixture vary depending on the type of polymerization initiator, monomer, and solvent used, but the polymerization temperature is usually 30 to 100 ° C., preferably 50 to 80 ° C., and the polymerization time is 1 to 20 hours. is there. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
After completion of the polymerization reaction, the produced polymer can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. Further, the obtained polymer can be purified by repeating reprecipitation or by removing unreacted monomers and the like by membrane separation, chromatographic method, extraction method and the like.

  The weight average molecular weight of the obtained water-insoluble polymer is preferably from 5,000 to 500,000, more preferably from 8,000 to 400,000, from the viewpoint of dispersion stability of the colorant, water resistance, ejection reliability and the like. 1,000 to 300,000 are particularly preferred. In addition, the weight average molecular weight of a water-insoluble polymer is measured by the same measuring method as the above-mentioned water-soluble polymer.

  When the water-insoluble polymer has a salt-forming group derived from the salt-forming group-containing monomer (a), it is neutralized with a neutralizing agent. As the neutralizing agent, an acid or a base can be used depending on the kind of the salt-forming group in the polymer. For example, hydrochloric acid, acetic acid, propionic acid, phosphoric acid, sulfuric acid, lactic acid, succinic acid, glycolic acid, Examples include acids such as gluconic acid and glyceric acid, bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, triethanolamine, and tributylamine It is done.

The degree of neutralization of the salt-forming group is preferably 10 to 200%, more preferably 20 to 180%, and particularly preferably 50 to 150%. Here, the degree of neutralization can be determined by the following formula when the salt-forming group is an anionic group.
{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [acid value of polymer (KOH mg / g) × polymer weight (g) / (56 × 1000)]} × 100
When the salt-forming group is a cationic group, it can be determined by the following formula.
{[Weight of neutralizer (g) / equivalent of neutralizer] / [amine value of polymer (HCL mg / g) × polymer weight (g) / (36.5 × 1000)]} × 100
The acid value and amine value can be calculated from the structural unit of the polymer, but can also be determined by a method of titrating by dissolving the polymer in an appropriate solvent (for example, methyl ethyl ketone).

(Production of water-insoluble polymer particles containing a colorant)
The water-insoluble polymer particles containing the colorant are preferably obtained as an aqueous dispersion by the following steps (a) and (b).
Step (a): A step of dispersing a mixture containing a water-insoluble polymer, an organic solvent, a colorant, water and, if necessary, a neutralizing agent Step (b): a step of removing the organic solvent In the step (a) First, the water-insoluble polymer is dissolved in an organic solvent, and then a colorant, water, and, if necessary, a neutralizing agent, a surfactant and the like are added to the organic solvent and mixed to obtain an oil-in-water dispersion. It is preferable to obtain a body. In the mixture, the colorant is preferably 5 to 50% by weight, the organic solvent is preferably 10 to 70% by weight, the water-insoluble polymer is preferably 2 to 40% by weight, and the water is preferably 10 to 70% by weight. . When the water-insoluble polymer has a salt-forming group, it is preferable to use a neutralizing agent, but the degree of neutralization is not particularly limited. Usually, it is preferable that the liquid dispersion of the finally obtained water dispersion is neutral, for example, pH is 4.5 to 10. The pH can also be determined by the desired degree of neutralization of the water-insoluble vinyl polymer.

Preferred examples of the organic solvent include alcohol solvents, ketone solvents, and ether solvents, and those having a solubility in water of 50% by weight or less and 10% by weight or more at 20 ° C. are preferable.
Examples of alcohol solvents include ethanol, isopropanol, n-butanol, tertiary butanol, isobutanol, diacetone alcohol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like. Among these solvents, isopropanol, acetone and methyl ethyl ketone are preferable, and methyl ethyl ketone is particularly preferable. These solvents can be used alone or in admixture of two or more.
As the neutralizing agent, an acid or a base can be used depending on the kind of the salt-forming group in the water-insoluble polymer. As the neutralizing agent, those described above can be used.

  There is no restriction | limiting in particular in the dispersion method of the mixture in the said process (a). It is preferable to carry out the main dispersion by applying a shear stress after preliminarily dispersing. In step (b), atomization is performed so that water-insoluble polymer particles having a desired average particle diameter are obtained.

  In the step (b), water of the water-insoluble polymer particles containing a colorant having a desired average particle size is obtained by distilling the organic solvent from the dispersion obtained in the step (a) into an aqueous system. Obtain a dispersion. The organic solvent contained in the aqueous dispersion can be removed by a general method such as distillation under reduced pressure. The organic solvent in the aqueous dispersion containing the obtained water-insoluble polymer particles is substantially removed, and the amount of the organic solvent is preferably 0.1% by weight or less, more preferably 0.01% by weight or less. is there. It is preferable to remove coarse particles by filtering the obtained aqueous dispersion containing water-insoluble polymer particles. Coarse particles are not present or few if present, but the filter particle size is preferably 0.5 to 10 μm, more preferably 0.8 to prevent clogging of the printer nozzles. 7 μm.

The water dispersion of water-insoluble polymer particles containing a colorant is a dispersion in which a solid content of a water-insoluble polymer containing a colorant is dispersed in water as a main medium. Here, the form of the water-insoluble polymer particles containing the colorant is not particularly limited as long as the particles are formed of at least the colorant and the water-insoluble polymer. For example, a particle form in which a colorant is included in a water-insoluble polymer, a particle form in which a colorant is uniformly dispersed in a water-insoluble polymer, a particle form in which a colorant is exposed on the surface of a water-insoluble polymer particle, and the like are included.
The average particle diameter of the water-insoluble polymer particles containing the colorant is preferably 50 to 200 nm, more preferably 70 to 170 nm, and particularly preferably 70 to 150 nm, from the viewpoints of dispersion stability and dischargeability.
The average particle size was measured using a laser particle analysis system ELS-8000 (cumulant analysis) manufactured by Otsuka Electronics Co., Ltd., at a temperature of 25 ° C., an incident light-detector angle of 90 °, an integration count of 200 times, and a dispersion. The refractive index of water (1.333) is input as the refractive index of the solvent, and the measurement concentration is about 5 × 10 ⁻³ wt%.
D90 of water-insoluble polymer particles containing a colorant (cumulative value of 90% calculated from the small particle side in the frequency distribution of scattering intensity) is a viewpoint and recording medium that increases the storage stability of the dispersion by reducing coarse particles From the viewpoint of improving the glossiness, it is preferably 800 nm or less, more preferably 500 nm or less, particularly preferably 300 nm or less, and the lower limit thereof is preferably 100 nm or more, more preferably 120 nm or more. From these viewpoints, the D90 is preferably 100 to 800 nm, more preferably 100 to 500 nm, and particularly preferably 120 to 300 nm.

An aqueous dispersion of water-insoluble polymer particles containing a colorant may be used as it is as a water-based ink containing water as a main medium, but a wetting agent, a penetrating agent, a dispersant, a viscosity usually used in water-based inks for inkjet recording. You may add a regulator, an antifoamer, an antifungal agent, an antirust agent, etc.
The content of the colorant in the water-based ink is preferably 1 to 20% by weight, more preferably 3 to 10% by weight from the viewpoint of improving dispersion stability, printing density, and the like.
In the case where the colorant is contained in the water-insoluble polymer, the weight ratio of the water-insoluble polymer and the colorant is preferably a weight ratio of [colorant / water-insoluble polymer] from the viewpoint of increasing the printing density. It is 50-90 / 10, More preferably, it is 50 / 50-80 / 20, More preferably, it is 55 / 45-78 / 22.
The water content in the water-based ink is preferably 30 to 90% by weight, more preferably 40 to 80% by weight.

(recoding media)
The recording medium used in the present invention is not particularly limited as long as it can be applied to the ink jet recording method, and examples thereof include paper, plastic, and composites thereof.
The paper is a sheet-like material obtained by dispersing pulp fibers in water and wet papermaking, containing pulp fibers as the main component, and pulp fibers that are in a state of being bonded to each other by hydrogen bonds or binders Sheets are preferred. Specifically, pulp sheets obtained from pulp of chemical pulp, mechanical pulp, waste paper pulp, etc., for example, high-quality paper, medium-quality paper, top-up paper, re-paper, book paper, Kent paper, color high-quality paper, gravure paper Copy paper, type paper, copy paper, glassine paper and the like. According to the present invention, it is possible to obtain photographic printed matter and printed matter with excellent gloss even on plain paper, so that the effect of the present invention is not exerted, it is not necessary to have an ink receiving layer, a high quality paper, a medium quality Non-coated paper, usually referred to as plain paper, such as paper and copy paper is suitable.
Specific examples of the recording medium that can be suitably used in the present invention include commercially available ordinary products such as trade names of Xerox Co., Ltd., Xerox 4024, PB paper manufactured by Canon Inc., and PPC paper My Paper manufactured by Ricoh Co., Ltd. Paper is an example.
As the recording medium, those usually referred to as glossy paper and photographic paper having a void type ink receiving layer and an alumina-based ink receiving layer can also be used.

(Inkjet printing method)
The present invention is an inkjet printing method in which the following steps 1 and 2 are sequentially performed on a recording medium using a coating ink and a water-based ink.
Step 1: A step of coating a coating ink containing metal oxide secondary particles in which a plurality of primary particles are connected to all or part of the recording medium by an inkjet recording method. Step 2: Step 1 A step of printing a water-based ink containing a colorant on the coated part of the recording medium obtained in step 2 by an inkjet recording method.

In step 1, a coating ink containing metal oxide secondary particles is coated on a recording medium by an ink jet recording method. The coating amount of the metal oxide secondary particles is preferably ² g / m ² or more, more preferably 3 g / m ² or more from the viewpoint of printing density and gloss of the printed matter, and the upper limit is 40 g / m ² or less. Is preferable, 30 g / m ² or less is more preferable, and 25 g / m ² or less is particularly preferable. From the point of view, its coating amount is preferably from 2 to 40 g / m ^2, more preferably ^{2~30g / m 2, 3~25g / m} 2 is particularly preferred.
The 60 ° gloss (25 ° C.) of the coated portion of the recording medium obtained in step 1 is preferably 4.5 to 30, and more preferably 5 to 25.
The area to be coated may be the entire recording medium, that is, the entire surface, or a part of the recording medium, and can be determined according to the gloss requirement of the print screen obtained in step 2. For example, when a photographic image is printed in step 2, only that portion can be applied in step 1 in advance.

In step 2, a water-based ink containing a colorant is printed over the portion of the recording medium obtained in step 1 that has been coated by an ink jet recording method. In this case, after coating the coating ink on the recording medium, the aqueous ink containing the colorant may be continuously printed on the coated portion, and after coating the coating ink, After a certain time, a water-based ink containing a colorant may be printed on the coated part.
As for 60 degree glossiness (25 degreeC) of the printing part of the recording medium obtained at the process 2, 4.5-50 are preferable and 5-30 are still more preferable.
In the present invention, the ink jet recording method is not limited, but is particularly suitable for a piezo ink jet printer.

(Ink set)
The ink set of the present invention is an ink set composed of a coating ink containing metal oxide secondary particles formed by connecting a plurality of primary particles and a water-based ink containing a colorant, and an ink jet recording method Thus, the coating ink is applied on the recording medium, and the water-based ink is printed over the coating processing portion.
The ink set preferably includes two or more different colors, preferably chromatic inks, as the water-based ink. Here, the “different color” means that the reflected light is measured at a wavelength of light of D65 / 2 using a spectral color difference meter SE-2000 manufactured by Nippon Denshoku Industries Co., Ltd., and L ^* a ^* b ^{* A} color in which a ^* (chromaticity in the red-green direction) and b ^* (chromaticity in the yellow-blue direction) are not the same when displayed in the color system. Examples thereof include two or more chromatic colors selected from the group consisting of cyan, yellow, magenta, light cyan, dark yellow, and light magenta.
The ink set of the present invention preferably includes a combination of two or more water-based inks selected from these chromatic colors. A three-color ink set, a four-color ink set, a five-color ink set, a six-color ink set, and seven colors Any of ink set and higher may be used.
More preferably, the ink set includes two or more different colors of water-based inks selected from magenta ink, yellow ink, and cyan ink, which are the three subtractive primary colors, and the ink set including these three colors of ink is provided. Particularly preferred. The ink set of the present invention may further include black ink such as self-dispersing carbon black.

In the following production examples, preparation examples, examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified.
Preparation Example 1 (Preparation of coating ink 1)
Anionic colloidal silica secondary particles (manufactured by Nissan Chemical Industries, Ltd., trade name: Snowtex PS-M, solid content (pure content) 20%, average particle diameter of silica secondary particles 115 nm, average particle diameter of silica primary particles 38 nm , Silica secondary particle shape: beaded) 75 parts, 2- {2- (2-butoxyethoxy) ethoxy} ethanol 5 parts, hexanediol 2 parts, acetylene glycol EO adduct (average number of moles added: 10) ( Kawaken Fine Chemical Co., Ltd., trade name: Acetylenol E100) 0.5 part and ion-exchanged water 17.5 parts were mixed, and the resulting liquid mixture was added to a 1.2 μm membrane filter (Sartorius, trade name: Minisart). The aqueous coating ink 1 was obtained. The shape of the metal oxide (silica) secondary particles was confirmed by an electron micrograph (TEM).

Preparation Example 2 (Preparation of coating ink 2)
Anionic colloidal silica (manufactured by Nissan Chemical Industries, Ltd., trade name: MP2040, solid content (pure content) 40%, average particle diameter 221 nm, shape: spherical) 50 parts, 2- {2- (2-butoxyethoxy) ethoxy } 5 parts of ethanol, 2 parts of hexanediol, 0.5 part of the acetylene glycol EO adduct and 42.5 parts of ion-exchanged water were mixed, and the resulting mixture was filtered with the membrane filter to obtain an aqueous coating ink 2 Got.

The average particle size of the metal oxide (silica) primary particles and the average particle size of the metal oxide (silica) secondary particles were measured by the following methods.
(1) Average particle diameter of metal oxide (silica) primary particles In a photograph taken with a transmission electron microscope JEM2100FX manufactured by JEOL, the particle diameters of 50 primary particles were measured visually, and the average value was calculated as the average particle size. The diameter.
(2) Method for Measuring Metal Oxide (Silica) Secondary Particles The average particle size was measured with a laser particle analysis system ELS-8000 (cumulant analysis) manufactured by Otsuka Electronics Co., Ltd. The measurement conditions are a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and an integration count of 100. The refractive index of water (1.333) is input as the refractive index of the dispersion solvent. The measurement concentration was usually about 5 × 10 ⁻³ wt%.

Production Example 1 (Production of aqueous dispersion of pigment-containing particles and aqueous ink)
In a reaction vessel, 20 parts of methyl ethyl ketone, 0.25 part of a polymerization chain transfer agent (2-mercaptoethanol), and (a) methacrylic acid / (b) styrene macromer (trade name: AS-6S: manufactured by Toa Gosei Co., Ltd.) / (C) benzyl methacrylate / (e) NK ester EH-4E (Octoxypolyethylene glycol monomethacrylate manufactured by Shin-Nakamura Chemical Co., Ltd., average added mole number of ethylene oxide: 4) = 15/30/50/5 ( 10% of 250 parts of the monomer mixture (effective weight ratio) was added and mixed, and nitrogen gas substitution was sufficiently performed to obtain a mixed solution.
On the other hand, the remaining 90% of the monomer mixture was charged into a dropping funnel, and 2.25 parts of the polymerization chain transfer agent, 40 parts of methyl ethyl ketone and a radical polymerization initiator (2,2′-azobis (2,4-dimethylvaleronitrile). )) 2.5 parts were added and mixed, and nitrogen gas substitution was sufficiently performed to obtain a mixed solution.
Under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 65 ° C. while stirring, and the mixed solution in the dropping funnel was gradually dropped over 3 hours. After 2 hours at 65 ° C. from the end of dropping, a solution in which 3 parts of the radical polymerization initiator was dissolved in 30 parts of methyl ethyl ketone was added, and further aged at 65 ° C. for 3 hours and at 70 ° C. for 2 hours to obtain a polymer solution. Next, an appropriate amount of methyl ethyl ketone was added to the polymer solution and stirred to obtain a polymer solution having a solid content (effective content) of 50%. The weight average molecular weight of the obtained polymer was about 20,000 by the above-mentioned method.

25 parts of the polymer obtained by drying the polymer solution under reduced pressure was dissolved in 71 parts of methyl ethyl ketone, and a neutralizing agent (5N aqueous sodium hydroxide solution) was 65% (7 parts) with respect to the acid value. 211 parts of exchange water is added simultaneously with stirring to neutralize the salt-forming group, and further, a magenta pigment [C.I. I. Pigment Violet 19, Clariant, trade name: Hostaperm Red E5B02], 75 parts, and after sufficient stirring, using a microfluidizer (manufactured by Microfluidics), 180 MPa, 15-pass high-pressure dispersion treatment Thus, water-insoluble vinyl polymer particles containing pigment (hereinafter referred to as pigment-containing particles) were obtained.
The obtained paste is diluted with ion-exchanged water (about 10%) and stirred sufficiently, and then methyl ethyl ketone and water are distilled off using an evaporator to obtain a pigment having a solid content (effective content) of 20%. An aqueous dispersion of contained particles was obtained.
25 parts aqueous dispersion of pigment-containing particles obtained above, 10 parts glycerin, 5 parts 2- {2- (2-butoxyethoxy) ethoxy} ethanol, 2 parts hexanediol, acetylene glycol EO adduct (average addition mole) Number: 10) (product of Kawaken Fine Chemical Co., Ltd., trade name: acetylenol E100) 0.5 part and 57.5 parts of ion-exchanged water were mixed, and the resulting liquid mixture was a 1.2 μm membrane filter [manufactured by Sartorius Co., Ltd. And trade name: Minisart] to obtain an aqueous magenta ink.
For cyan ink, cyan pigment [C.I. I. Pigment Blue 15: 4, manufactured by Dainichi Seika Co., Ltd., trade name: Chromofine Blue 4965], and yellow ink [C.I. I. Pigment Yellow 74, manufactured by Sanyo Dye Co., Ltd., trade name: First Yellow 7414] was used to obtain aqueous cyan ink and aqueous yellow ink in the same manner.
The average particle diameter of the obtained polymer particles was 99 nm for magenta, 81 nm for cyan, and 111 nm for yellow, and D90 was 157 nm for magenta, 130 nm for cyan, and 218 nm for yellow.

Examples 1-3 and Comparative Examples 1-2
As shown in Table 1, the black ink of a commercially available Seiko Epson ink jet printer (product number: EM-930C, piezo method) is replaced with the coating inks 1 and 2, and coating and printing are performed on the recording medium. Went. In Comparative Example 1, no coating ink was used.
As the recording medium, plain paper “Xerox 4024” manufactured by Xerox Co., Ltd. was prepared, and the coating ink was solid-printed in the plain paper photo mode (bidirectional printing off) to perform coating. The coating amount was changed by repeating the coating. The coating amount of silica in the coating ink (g / m ² ) (the coating amount per unit area) is the same as the OHP sheet (trade name: MJOHPS1N, manufactured by Seiko Epson Corporation) under the same printing conditions. ), And the remaining amount obtained by evaporating water (20 ° C., 12 hours) (the weight of the OHP sheet from which water was evaporated after coating−the weight of the OHP sheet before coating) was obtained by the following formula. .
Coating amount (g / m ² ) = residual amount (g) × (silica content in coating ink (% by weight)) × [1 / [100-water content in coating ink (% by weight) ]]] × [1 / area of coated OHP sheet (m ² )]

Printing was performed by the printer using the water-based ink (yellow ink, magenta ink, cyan ink) obtained in Production Example 1, and printing on the recording medium in a photo mode, overlaid on the coated portion.
Using the gloss meter HANDY GLOSSMETER PG-1M (manufactured by Nippon Denshoku Industries Co., Ltd.), the surface of the plain paper coated part obtained as described above or the surface of the solid printed part is 60 ° gloss ( 25 ° C.). The glossiness after printing was the average value of the glossiness of the color ink single-color solid printing portion.

The print density of the printed material is the same printer, using the water-based ink (yellow ink, magenta ink, cyan ink) obtained in Production Example 1, and the recording medium in the plain paper photo mode (bidirectional printing off). A solid printing was performed on the printed part, and the print density of the printed part obtained as described above was measured with a Macbeth densitometer (product number: RD914, manufactured by Gretag Macbeth).
The printing density in Table 1 was the average printing density of the color ink single-color solid printing part. The results are shown in Table 1.

  From Table 1, it can be seen that the printed materials obtained in Examples 1 to 3 are superior in print density and gloss compared to the printed materials obtained in Comparative Examples 1 and 2.

Claims (6)

An inkjet printing method in which the following steps 1 and 2 are sequentially performed on a recording medium using a coating ink and a water-based ink.
Step 1: A step of coating a coating ink containing metal oxide secondary particles in which a plurality of primary particles are connected to all or part of the recording medium by an inkjet recording method. Step 2: Step 1 A step of printing a water-based ink containing a colorant on the coated part of the recording medium obtained in step 2 by an inkjet recording method.   The ink-jet printing method according to claim 1, wherein the metal oxide secondary particles are beaded or elongated.   The inkjet printing method of Claim 1 or 2 whose average particle diameter of the said metal oxide secondary particle obtained by measuring by the dynamic light scattering method is 40-300 nm.   The inkjet printing method according to any one of claims 1 to 3, wherein the metal oxide is silica.   The inkjet printing method according to any one of claims 1 to 4, wherein the water-based ink contains an aqueous dispersion of water-insoluble polymer particles containing a colorant.   An ink set comprising a coating ink containing metal oxide secondary particles in which a plurality of primary particles are connected, and a water-based ink containing a colorant, wherein the ink set is formed on a recording medium by an inkjet recording method. An ink set in which a coating ink is applied and the water-based ink is printed over the coating portion.