JP5166845B2 - Ink set for inkjet recording - Google Patents

Description

  The present invention relates to an ink set for inkjet recording.

The ink jet recording system is a recording system in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle and attaching them to a recording member. This method is widely spread because it is easy to make full color and is inexpensive, and has many advantages such as the ability to use plain paper as a recording member and non-contact with the object to be printed.
Among them, from the viewpoint of weather resistance and water resistance of printed materials, those using pigment-based ink as a colorant have become mainstream.

With respect to the ink jet recording method, for example, Patent Document 1 discloses recording an image on a recording medium using an ink containing water, a coloring material, a resin emulsion, and sugar, and recording the color ink in a printing area. An ink jet recording method is disclosed in which clear ink having a difference in refractive index with respect to the ink within 0.1 is recorded in a void portion that is not formed.
Patent Document 2 discloses an ink jet recording method in which an image is formed by ejecting a recording ink containing a color material and a colorless ink for improving glossiness onto a recording medium by a recording head.
Patent Document 3 discloses an ink jet which discharges a pigment ink composition and a clear ink composition containing a resin component and records it on a recording medium, and adjusts the discharge amount of the pigment ink composition and / or the clear ink composition. A recording method and an ink set for an inkjet recording method comprising the pigment ink composition and the clear ink composition are disclosed.
However, the above ink jet recording method and ink set are not satisfactory in glossiness and image clarity.

JP-A-8-85218 International Publication No. 04/69543 Pamphlet International Publication No. 02/87886 Pamphlet

  An object of the present invention is to provide an ink set for ink-jet recording and a clear ink capable of obtaining a printed matter excellent in glossiness and image clarity when printed on dedicated paper.

  The present invention relates to an ink set for inkjet recording, and a crosslinked polymer particle (B) containing a colored ink containing a crosslinked polymer particle (A) containing a colorant and a clear ink containing the crosslinked polymer particle (B). A clear ink for inkjet recording comprising a water-insoluble organic compound is provided.

  The ink set for ink-jet recording and the clear ink of the present invention can give a printed matter excellent in glossiness and image clarity when printed on dedicated paper.

The ink set for inkjet recording of the present invention is characterized by containing a colored ink containing a crosslinked polymer particle (A) containing a colorant and a clear ink containing a crosslinked polymer particle (B). Here, the clear ink is ink that does not substantially contain a colorant. In ink-jet recording water-based ink, when printing on dedicated paper, there may be a difference in the dot height between the high print area rate portion and the low print area rate portion, or the print portion and the non-print portion. The difference affects glossiness and image clarity.
By using the ink set for inkjet recording of the present invention, the difference in dot height can be eliminated, and glossiness and image clarity can be improved. Further, in the present invention, the cross-linked polymer particles are used for the colored ink and the clear ink, and the stability of the particles is high. Even when the colored ink and the clear ink overlap with each other, the ink is contained in the ink. The increase in the viscosity of the ink is suppressed for a time sufficient for the polymer particles to be fused together, so that the print surface is smoothed and the glossiness and image clarity are further improved. Hereinafter, each component used in the ink set of the present invention will be described. In the present specification, a crosslinked polymer particle containing a colorant may be referred to as a “colorant-containing crosslinked polymer particle”, and a crosslinked product containing a colorant. The colored ink containing the polymer particles (A) may be simply referred to as “colored ink”, and the clear ink containing the crosslinked polymer particles (B) may be simply referred to as “clear ink”.

(Coloring agent)
The colorant used in the colored ink constituting the ink set of the present invention is not particularly limited, but pigments, hydrophobic dyes and the like can be used, but from the viewpoint of water resistance, dispersion stability and scratch resistance. Pigments and hydrophobic dyes are preferred. Among them, it is preferable to use a pigment in order to express the high weather resistance which has been recently demanded.
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 viewpoints of bleeding resistance, water resistance, and the like, it is preferable to include a pigment and / or a hydrophobic dye in the polymer particles.
The pigment may be either an inorganic pigment or an organic pigment. If necessary, they can be used in combination with extender pigments.
Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. 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 crosslinked 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, and C.I. I. One or more types of products selected from the group consisting of Solvent Orange are listed, which are commercially available from Orient Chemical Co., Ltd., BASF Corp. and others.
The above colorants can be used alone or in admixture of two or more at any ratio.
The weight ratio of the amount of the polymer and the amount of the colorant [colorant / polymer] is preferably 10/90 to 90/10, more preferably 50/50, from the viewpoints of glossiness, image clarity, and dispersion stability. It is -85/15, More preferably, it is 60 / 40-80 / 20.

(polymer)
The polymer used in the colorant-containing crosslinked polymer particles (A) and the crosslinked polymer particles (B) used in the present invention is preferably a water-insoluble polymer. Here, the water-insoluble polymer means that when the polymer is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., the dissolution amount is 10 g or less, preferably 5 g or less, more preferably 1 g or less. Is a polymer. When the polymer has a salt-forming group, the dissolution amount is a dissolution amount when the salt-forming group of the polymer is neutralized 100% with acetic acid or sodium hydroxide depending on the type.
Examples of the polymer to be used include polyester, polyurethane, and vinyl polymer. From the viewpoint of dispersion stability, a vinyl polymer obtained by addition polymerization of a vinyl monomer (vinyl compound, vinylidene compound, vinylene compound) is preferable.

(Vinyl polymer)
As the vinyl polymer, (a) a salt-forming group-containing monomer (hereinafter sometimes referred to as “(a) component”), (b) a macromer (hereinafter sometimes referred to as “(b) component”) and / or (c ) A vinyl polymer obtained by copolymerizing a monomer mixture (hereinafter also referred to as “monomer mixture”) containing a hydrophobic monomer (hereinafter also referred to as “component (c)”) is preferable. This vinyl polymer has a structural unit derived from the component (a), a structural unit derived from the component (b) and / or a structural unit derived from the component (c). A more preferable vinyl polymer has a structural unit derived from the component (a) or a structural unit derived from the components (a) and (c) as a main chain, and a graft having a structural unit derived from the component (b) as a side chain. It is a polymer, More preferably, it is a graft polymer which has the structural unit derived from (a) component and (c) component as a main chain, and has the structural unit derived from (b) component as a side chain.

((A) salt-forming group-containing monomer)
(A) The salt-forming group-containing monomer is used from the viewpoint of enhancing the dispersion stability of the resulting dispersion. 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.
Examples of the salt-forming group-containing monomer include cationic monomers and anionic monomers described in JP-A-9-286939, paragraph [0022].
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 and vinylpyrrolidone are preferable.
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 the unsaturated sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, bis- (3-sulfopropyl) -itaconic acid ester, and the like. Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, etc. Is mentioned.
Among the anionic monomers, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable from the viewpoints of dispersion stability and ejection stability.

((B) Macromer)
(B) The macromer is used from the viewpoint of enhancing the dispersion stability of the crosslinked polymer particles. The macromer includes a macromer which is a monomer having a polymerizable unsaturated group having a number average molecular weight of 500 to 100,000, preferably 1,000 to 10,000. In addition, the number average molecular weight of (b) macromer is measured using polystyrene as a standard substance by gel chromatography using tetrahydrofuran containing 50 mmol / L acetic acid as a solvent.
Among the macromers, a styrene macromer and an aromatic group-containing (meth) acrylate macromer having a polymerizable functional group at one end are preferable from the viewpoint of dispersion stability of the crosslinked polymer particles.
Examples of the styrenic macromer include a styrene monomer homopolymer or a copolymer of a styrene monomer and another monomer. Examples of the styrene monomer include styrene, 2-methylstyrene, vinyl toluene, ethyl vinyl benzene, vinyl naphthalene, chlorostyrene, and the like.

Examples of the aromatic group-containing (meth) acrylate-based macromer include a homopolymer of an aromatic group-containing (meth) acrylate or a copolymer thereof with another monomer. As an aromatic group-containing (meth) acrylate, an arylalkyl having 7 to 22 carbon atoms, preferably 7 to 18 carbon atoms, more preferably 7 to 12 carbon atoms, which may have a substituent containing a hetero atom. (Meth) acrylate having an aryl group having 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms, which may have a group or a substituent containing a hetero atom In addition, examples of the substituent containing a hetero atom include a halogen atom, an ester group, an ether group, and a hydroxy group. Examples include benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, and benzyl (meth) acrylate is particularly preferable.
The polymerizable functional group present at one end of the macromer is preferably an acryloyloxy group or a methacryloyloxy group, and the other monomer to be copolymerized is preferably acrylonitrile.
The content of the styrene monomer in the styrene macromer or the aromatic group-containing (meth) acrylate in the aromatic group-containing (meth) acrylate macromer is preferably 50% by weight from the viewpoint of increasing the affinity with the pigment. Above, more preferably 70% by weight or more.

(B) The macromer may have a side chain composed of another structural unit such as an organopolysiloxane. This side chain can be obtained, for example, by copolymerizing a silicone macromer having a polymerizable functional group at one end represented by the following formula (1).
_{CH 2 = C (CH 3)} -COOC 3 H 6 - [Si (CH _{3) 2} O] _{t -Si (CH 3) 3 (} 1)
(In the formula, t represents a number of 8 to 40).
Examples of commercially available styrenic macromers as component (b) include Toa Gosei Co., Ltd. trade names, AS-6 (S), AN-6 (S), HS-6 (S), and the like. It is done.

((C) hydrophobic monomer)
(C) The hydrophobic monomer is used from the viewpoint of improving the printing density. Examples of the hydrophobic monomer include alkyl (meth) acrylates and aromatic group-containing monomers.
As the alkyl (meth) acrylate, those having an alkyl group having 1 to 22 carbon atoms, preferably 6 to 18 carbon atoms are preferable. For example, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meta) ) Acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) Examples include decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, and (iso) stearyl (meth) acrylate.
In the present specification, “(iso or tertiary)” and “(iso)” mean both the case where these groups are present and the case where these groups are not present. Indicates. “(Meth) acrylate” indicates acrylate, methacrylate, or both.

The aromatic group-containing monomer has an aromatic group having 6 to 22 carbon atoms, preferably 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms, which may have a substituent containing a hetero atom. Vinyl monomers are preferable, and examples thereof include the styrene monomer (c-1 component) and the aromatic group-containing (meth) acrylate (c-2 component). The above-mentioned thing is mentioned as a substituent containing a hetero atom.
Among the components (c), a styrene monomer (c-1 component) is preferable from the viewpoint of improving printing density, and styrene and 2-methylstyrene are particularly preferable as the styrene monomer. The content of the component (c-1) in the component (c) is preferably 10 to 100% by weight, more preferably 20 to 80% by weight, from the viewpoint of improving printing density.
Moreover, as an aromatic group containing (meth) acrylate (c-2) component, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, etc. are preferable. The content of the component (c-2) in the component (c) is preferably 10 to 100% by weight, more preferably 20 to 80% by weight, from the viewpoint of improving printing density, glossiness, and image clarity. . Moreover, it is also preferable to use (c-1) component and (c-2) component together.

((D) hydroxyl group-containing monomer)
The monomer mixture may further contain (d) a hydroxyl group-containing monomer (hereinafter sometimes referred to as “component (d)”). (D) A hydroxyl group-containing monomer is used to further increase the 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 added moles of oxyalkylene group. The same)) (meth) acrylate, polypropylene glycol (n = 2-30) (meth) acrylate, poly (ethylene glycol (n = 1-15) / propylene glycol (n = 1-15)) (meth) acrylate, etc. Can be mentioned. Among these, 2-hydroxyethyl (meth) acrylate, polyethylene glycol monomethacrylate, and polypropylene glycol methacrylate are preferable.

((E) Monomer represented by the following formula (2))
The monomer mixture may further contain (e) a monomer represented by the following formula (2) (hereinafter sometimes referred to as “(e) component”).
CH ₂ = C (R ¹⁰ ) COO (R ²⁰ O) _q R ³⁰ (2)
Wherein R ¹⁰ is a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, R ²⁰ is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ³⁰ is , A monovalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, q means an average number of added moles, and represents a number of 1 to 60, preferably 1 to 30. )
The component (e) is used for further improving the dischargeability.
Excellent effect of improving.
In the formula (2), examples of the hetero atom include a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom.
Preferable examples of R ¹⁰ include a methyl group, an ethyl group, and an (iso) propyl group.
Preferred examples of the R ²⁰ O group include oxyethylene group, oxytrimethylene grave, oxypropane-1,2-diyl group, oxytetramethylene group, oxyheptamethylene group, oxyhexamethylene group, and two or more kinds thereof. Examples thereof include oxyalkanediyl groups having 2 to 7 carbon atoms (oxyalkylene groups).
Preferable examples of R ³⁰ include an aliphatic alkyl group having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms, an alkyl group having 7 to 30 carbon atoms having an aromatic ring, and A C4-C30 alkyl group and a C6-C12 aryl group which have a heterocyclic ring are mentioned.

  Specific examples of the component (e) include methoxypolyethylene glycol (1 to 30: the value of q in the formula (2), the same applies hereinafter) (meth) acrylate, methoxypolytetramethylene glycol (1 to 30) ( (Meth) acrylate, ethoxy polyethylene glycol (1-30) (meth) acrylate, octoxy polyethylene glycol (1-30) (meth) acrylate, polyethylene glycol (1-30) (meth) acrylate 2-ethylhexyl ether, (iso) Propoxy polyethylene glycol (1-30) (meth) acrylate, butoxy polyethylene glycol (1-30) (meth) acrylate, methoxypolypropylene glycol (1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol) Polymerization) (1 to 30, ethylene glycol therein: 1-29) (meth) acrylate. Among these, octoxypolyethylene glycol (1-30) (meth) acrylate and polyethylene glycol (1-30) (meth) acrylate 2-ethylhexyl ether are preferable.

Specific examples of commercially available (d) and (e) components include Shin-Nakamura Chemical Co., Ltd. polyfunctional acrylate monomer (NK ester) M-40G, 90G, 230G, and Nippon Oil & Fats Co., Ltd. BLEMMER series, PE-90, 200, 350, PME-100, 200, 400, 1000, PP-500, 800, 1000, AP-150, 400, 550, 800 , 50PEP-300, 50POEP-800B, 43PAPE600B, and the like.
The components (a) to (e) can be used alone or in admixture of two or more.

The content of the components (a) to (e) in the monomer mixture at the time of vinyl polymer production (content as an unneutralized amount; the same applies hereinafter) or derived from the components (a) to (e) in the vinyl polymer The content of the structural unit is as follows.
The content of component (a) is preferably 2 to 40% by weight, more preferably 2 to 30% by weight, and particularly preferably 3 to 20% by weight from the viewpoint of dispersion stability of the resulting dispersion.
The content of the component (b) is preferably 1 to 25% by weight, more preferably 5 to 20% by weight, particularly from the viewpoint of enhancing the interaction with the colorant.
The content of the component (c) is preferably 5 to 98% by weight, more preferably 10 to 60% by weight, from the viewpoint of improving print density.
The content of component (d) is preferably 5 to 40% by weight, more preferably 7 to 20% by weight, from the viewpoint of dispersion stability of the resulting dispersion.
The content of the component (e) is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, from the viewpoint of improving dischargeability.
The total content of [component (a) + component (d)] in the monomer mixture is preferably 6 to 60% by weight, more preferably 10 to 50% by weight, from the viewpoint of dispersion stability of the resulting dispersion. is there. The total content of [component (a) + component (e)] is preferably 6 to 75% by weight, more preferably 13 to 50% by weight, from the viewpoint of dispersion stability and dischargeability of the resulting dispersion. . Moreover, the total content of [(a) component + (d) component + (e) component] is preferably 6 to 60% by weight, more preferably from the viewpoint of dispersion stability and dischargeability of the resulting dispersion. 7 to 50% by weight.
The weight ratio of [(a) component / [(b) component + (c) component]] is preferably 0.01 to 1, more preferably from the viewpoint of dispersion stability and print density of the resulting dispersion. Is 0.02 to 0.67, more preferably 0.03 to 0.50.

(Manufacture of polymers)
The polymer used in the present invention is produced by copolymerizing a monomer mixture by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method or an emulsion polymerization method. Among these polymerization methods, the solution polymerization method is preferable.
The solvent used in the solution polymerization method is not particularly limited, but a polar organic solvent is preferable. When the polar organic solvent is miscible with water, it can be used by mixing with water. Examples of the polar organic solvent include aliphatic alcohols having 1 to 3 carbon atoms such as methanol, ethanol, and propanol; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; esters such as ethyl acetate. Among these, methanol, ethanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, or a mixed solvent of one or more of these and water are preferable.
In the polymerization, azo compounds such as 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), t-butyl peroxyoctate, dibenzoyl oxide, etc. Known radical polymerization initiators such as organic peroxides can be used.
The amount of the radical 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 may be further added.

Since the polymerization conditions of the monomer mixture vary depending on the type of radical polymerization initiator, monomer, and solvent used, it cannot be determined unconditionally. Usually, the polymerization temperature is preferably 30 to 100 ° C, more preferably 50 to 80 ° C, and the polymerization time is preferably 1 to 20 hours. 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 polymer is preferably 5,000 to 500,000, more preferably 10,000 to 400,000, and more preferably 10,000 to 300,000 from the viewpoints of printing density, gloss, image clarity, and dispersion stability of the colorant. Is more preferable, and 20,000 to 300,000 is particularly preferable. In addition, the weight average molecular weight of the polymer was measured by the method shown in the Examples.
When the vinyl polymer has a salt-forming group derived from (a) a salt-forming group-containing monomer, it is neutralized with a neutralizing agent. As the neutralizing agent, an acid or a base can be used depending on the type 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, gluconic acid, glyceric acid and other acids, lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, methylamine, dimethylamine , Bases such as trimethylamine, ethylamine, diethylamine, triethylamine, triethanolamine, and tributylamine.

The degree of neutralization of the salt-forming group is preferably 10 to 200%, more preferably 20 to 150%, and particularly preferably 50 to 150%.
Here, the degree of neutralization can be determined by the following formulas (3) and (4) 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 (3)
When the salt-forming group is a cationic group, it can be determined by the following formula.
{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [amine value of polymer (HCL mg / g) × polymer weight (g) / (36.5 × 1000)]} × 100 (4)
The acid value and amine value can be calculated from the structural unit of the polymer. Alternatively, it can also be determined by a method in which a polymer is dissolved in an appropriate solvent (for example, methyl ethyl ketone) and titrated. The acid value or amine value of the polymer is preferably 50 to 200, more preferably 50 to 150.

(Crosslinking agent)
The crosslinking agent used in the production of (A) the colorant-containing crosslinked polymer particles and (B) the crosslinked polymer particles has two or more reactive functionalities in the molecule from the viewpoint of appropriately crosslinking the polymer and improving the storage stability. A compound having a group (hereinafter also simply referred to as “crosslinking agent”) is preferred.
The molecular weight of the crosslinking agent is preferably 120 to 2000, more preferably 125 to 1500, still more preferably 130 to 1000, and more preferably 150 to 1000, from the viewpoint of easy reaction and storage stability of the resulting crosslinked polymer particles. Particularly preferred.
The number of reactive functional groups is preferably 2 to 6, more preferably 2 to 4, from the viewpoint of controlling the molecular weight to improve glossiness and image clarity. Preferred examples of the reactive functional group include one or more selected from the group consisting of a hydroxyl group, an epoxy group, an aldehyde group, an amino group, a carboxy group, an oxazoline group, and an isocyanate group.

Specific examples of such a crosslinking agent include the following (a) to (g).
(A) Compound having two or more hydroxyl groups in the molecule: for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, 1,4-butanediol, 1,5-pentane Polyhydric alcohols such as diol, 1,6-hexanediol, neopentyl alcohol, diethanolamine, tridiethanolamine, polypropylene glycol, polyvinyl alcohol, pentaerythritol, sorbitol, sorbitan, glucose, mannitol, mannitan, sucrose, and glucose.
(B) Compound having two or more epoxy groups in the molecule: for example, polyglycol such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin triglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether Glycidyl ether.
(C) Compounds having two or more aldehyde groups in the molecule: for example, polyaldehydes such as glutaraldehyde and glyoxal.
(D) Compounds having two or more amino groups in the molecule: for example, polyamines such as ethylenediamine and polyethyleneimine.
(E) Compounds having two or more carboxy groups in the molecule: for example, polyvalent carboxylic acids such as oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid and adipic acid.
(F) Compound having two or more oxazoline groups in the molecule: for example, a compound in which 2 or more, preferably 2 to 3 oxazoline groups are bonded to an aliphatic group or an aromatic group, more specifically 2 , 2′-bis (2-oxazoline), 1,3-phenylenebisoxazoline, bisoxazoline compounds such as 1,3-benzobisoxazoline, and terminal oxazoline groups obtained by reacting the compound with a polybasic carboxylic acid A compound having
(G) Compound having two or more isocyanate groups in the molecule: for example, organic polyisocyanate or isocyanate group-terminated prepolymer.
Among these, (b) a compound having two or more epoxy groups in the molecule is preferable, and trimethylolpropane polyglycidyl ether is particularly preferable.

The polymer has a reactive group (crosslinkable functional group) capable of reacting with the crosslinking agent, and a suitable combination example of both is as follows.
When the reactive group of the polymer is an acidic group such as a carboxy group, a sulfonic acid group, or a phosphoric acid group, the crosslinking agent is preferably the compounds (a), (b), (d), and (f).
Moreover, when the reactive group of a polymer is an amino group and a hydroxyl group, the said (b), (c) and (e) compound are preferable for a crosslinking agent.
When the reactive group of the polymer is an isocyanate group or an epoxy group, the crosslinking agent is preferably the compounds (a), (d) and (e).
Among the above combinations, from the viewpoint of controlling the polymer so as to give an appropriate cross-linked structure, at least one selected from an acidic group (carboxy group, sulfonic acid group, phosphoric acid group, etc.), amino group and hydroxyl group. A combination of a polymer having a reactive group and (b) a compound having two or more epoxy groups in the molecule is particularly preferred.

As the reactive group (crosslinkable functional group) capable of reacting with the crosslinking agent, a polymer having an acidic group such as a carboxy group, a sulfonic acid group, or a phosphoric acid group, an amino group, a hydroxyl group, an isocyanate group, an epoxy group, etc. In the production of the polymer, it can be produced by copolymerizing a polymerizable monomer composition containing the monomer having the reactive group.
As the polymer having a reactive group capable of reacting with the crosslinking agent, the polymer having a salt-forming group such as an acidic group or an amino group can be a polymer obtained by copolymerizing the aforementioned salt-forming group-containing monomer. As the polymer having, a polymer obtained by copolymerizing the above-mentioned hydroxyl group-containing monomer can be used.
As the polymer having an epoxy group, a monomer having an epoxy group, specifically, a polymer obtained by copolymerizing glycidyl (meth) acrylate can be used. As the polymer having an isocyanate group, (i) a monomer having an isocyanate group, for example, a polymer copolymerized with isocyanate ethyl (meth) acrylate, (ii) an isocyanate-terminated prepolymer obtained from an unsaturated polyester polyol and isocyanate was copolymerized. A polymer or the like can be used.

(Crosslinkable monomer)
From the viewpoint of improving glossiness and image clarity in the production of (A) a colorant-containing crosslinked polymer particle and (B) a crosslinked polymer particle, a crosslinkable monomer having 2 or more reactive unsaturated groups in the molecule (hereinafter referred to as “crosslinkable monomer”) It is preferable to simply use a “crosslinkable monomer”.

As the crosslinkable monomer, (1) ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polypropylene Glycol di (meth) acrylate, 1,2-butylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, glycerin di (meth) acrylate, glycerin tri ( (Meth) acrylate compounds of polyhydric alcohols such as (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate; ) Acrylamide compounds such as N-methylallylacrylamide, N-vinylacrylamide, N, N′-methylenebis (meth) acrylamide, bisacrylamideacetic acid; (3) Divinyl compounds such as divinylbenzene, divinyl ether, divinylethyleneurea; ) Polyallyl compounds such as diallyl phthalate, diallyl malate, diallylamine, triallylamine, triallyl ammonium salt, allyl etherified product of pentaerythritol, allyl etherified product of sucrose having at least two allyl ether units in the molecule, etc. Can be mentioned.
Among these, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, divinylbenzene, pentaerythritol triallyl ether, pentaerythritol tetraallyl ether, and methylenebisacrylamide are particularly preferable.

((A) Crosslinked polymer particles containing colorant)
In the present invention, (A) the colorant-containing crosslinked polymer particles improve the storage stability in the water-based ink as the crosslinked polymer particles for the colored ink, and (B) improve the glossiness and image clarity of the crosslinked polymer particles. Used to make
(A) As a manufacturing method of a coloring agent containing crosslinked polymer particle, (i) The process I which obtains the polymer particle containing a coloring agent using a coloring agent and a polymer, and the coloring agent containing polymer particle obtained by the process I And a step II of obtaining a colorant-containing crosslinked polymer particle by mixing a polymer and a crosslinking agent, and (ii) a step III of obtaining a crosslinked polymer by crosslinking the polymer with a crosslinking agent, The method of manufacturing by the process IV which obtains a coloring agent containing crosslinked polymer particle using the crosslinked polymer and colorant which were obtained at the process III is mentioned. Among these, the method according to (i) is preferable from the viewpoint of glossiness, image clarity, and ease of production.

The manufacturing method by said (i) can be performed by the following process (1)-(3), for example.
Step (1): Step of obtaining a dispersion of polymer particles containing a colorant by dispersing a mixture containing a polymer, an organic solvent, a colorant, water and, if necessary, a neutralizing agent Step (2): Step Step of removing the organic solvent from the dispersion obtained in (1) to obtain an aqueous dispersion of polymer particles containing a colorant Step (3): containing the colorant obtained in Step (2) A step of obtaining a colorant-containing crosslinked polymer particle (A) by crosslinking the polymer of the polymer particle with a crosslinking agent.

In step (1), the polymer is first dissolved in an organic solvent, and then a colorant, water, and, if necessary, a neutralizing agent and a surfactant are added to and mixed with the obtained organic solvent solution. A method for obtaining an oil-in-water type dispersion is preferred. In the mixture, the colorant is preferably 5 to 50 wt%, more preferably 10 to 40 wt%, the organic solvent is preferably 10 to 70 wt%, more preferably 10 to 50 wt%, and the polymer is 2 to 2 wt%. It is preferably 40% by weight, more preferably 3 to 20% by weight, and water is preferably 10 to 70% by weight, more preferably 20 to 70% by weight.
When the polymer has a salt-forming group, it is preferable to use a neutralizing agent. There is no particular limitation on the degree of neutralization when neutralizing with a neutralizer. 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 polymer. Examples of the neutralizing agent include those described above. Further, the polymer may be neutralized in advance.

  Examples of the organic solvent include alcohol solvents such as ethanol, isopropanol and isobutanol, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and diethyl ketone, and ether solvents such as dibutyl ether, tetrahydrofuran and dioxane. Preferably, the amount dissolved in 100 g of water is preferably 5 g or more at 20 ° C., more preferably 10 g or more, more specifically preferably 5 to 80 g, more preferably 10 to 50 g, particularly methyl ethyl ketone. And methyl isobutyl ketone are preferred.

There is no restriction | limiting in particular in the dispersion method of the mixture in process (1). Although the average particle size of the polymer particles can be atomized only by the main dispersion until the desired particle size is reached, it is preferably pre-dispersed and then subjected to further dispersion by applying a shear stress to obtain the average particle size of the polymer particles. It is preferable to control the diameter to a desired particle diameter. 5-50 degreeC is preferable and dispersion | distribution of a process (1) has more preferable 10-35 degreeC.
When preliminarily dispersing the mixture, a commonly used mixing and stirring device such as an anchor blade can be used. Among the mixing and stirring devices, Ultra Disper [Asada Steel Corporation, product name], Ebara Milder [Ebara Manufacturing Co., Ltd., product name], TK Homomixer, TK Pipeline Mixer, TK Homojetter, TK Homomic Line Flow, High-speed agitating and mixing devices such as Filmix [above, Primix Co., Ltd., trade name], Clear Mix [M Technique Co., Ltd., trade name], and KD Mill [Kinetic Dispersion Co., Ltd., trade name] are preferred.
As means for applying the shear stress of this dispersion, for example, a kneader such as a roll mill, a bead mill, a kneader, an extruder, a high-pressure homogenizer (Izumi Food Machinery Co., Ltd., trade name), a minilab 8.3H type (Rannie Co., trade name) Representative homo-valve type high-pressure homogenizer, microfluidizer (Microfluidics, trade name), nanomizer (Nanomizer, trade name), optimizer (Sugino machine, trade name), Genus PY (Shiramizu Chemical Co., Ltd.) Product name], DeBEE2000 [Japan EE Co., Ltd., product name] and the like chamber type high-pressure homogenizer. A plurality of these devices can be combined. Among these, when a pigment is used as the colorant, a high-pressure homogenizer is preferable from the viewpoint of reducing the particle size of the pigment.

In the step (2), an aqueous dispersion of polymer particles containing a colorant can be obtained by distilling off the organic solvent from the obtained dispersion by a known method to form an aqueous system. The organic solvent in the aqueous dispersion containing the polymer particles obtained is preferably substantially removed, but may remain as long as the object of the present invention is not impaired. do it. The amount of the residual organic solvent is preferably 0.1% by weight or less, and more preferably 0.01% by weight or less.
The obtained aqueous dispersion of polymer particles containing the colorant is one in which the solid content of the polymer containing the colorant is dispersed in water as the main solvent. Here, the form of the polymer particles is not particularly limited as long as the particles are formed of at least a colorant and a polymer. For example, a particle form in which a colorant is included in a polymer, a particle form in which a colorant is uniformly dispersed in a polymer, a particle form in which a colorant is exposed on the surface of a polymer particle, and the like are included.

In the step (3), the polymer particles containing the obtained colorant can be crosslinked with a crosslinking agent to obtain crosslinked polymer particles. In the step (3), from the viewpoint of glossiness, image clarity, and ease of production, an aqueous dispersion of the colorant-containing polymer particles and a crosslinking agent are mixed to crosslink the polymer to obtain the colorant-containing crosslinked polymer particles. The production method obtained is preferred. The catalyst, solvent, reaction temperature, and reaction time can be appropriately selected and determined depending on the crosslinking agent used. The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 5 hours, and the reaction temperature is preferably 40 to 95 ° C.
The amount of the crosslinking agent used is preferably from 0.5 to 15 parts by weight, more preferably from 0.6 to 12 parts by weight, more preferably from 0.7 to 100 parts by weight based on 100 parts by weight of the polymer, from the viewpoints of glossiness and image clarity. 12 parts by weight is more preferable, 0.75 to 10 parts by weight is still more preferable, 0.75 to 8 parts by weight is particularly preferable, and 0.8 to 6 parts by weight is most preferable.
Further, as the polymer crosslinking step, the dispersion of the colorant-containing polymer particles obtained in the step (1) and the crosslinking agent can be mixed to crosslink the polymer. In this case, an aqueous dispersion of crosslinked polymer particles containing a colorant is obtained by performing the step of removing the organic solvent from the dispersion of crosslinked polymer particles obtained in the crosslinking step in the same manner as in the step (2). Can be obtained.

The crosslinking rate (mol%) of the crosslinked polymer is preferably 1 to 80 mol%, more preferably 1 to 60 mol%, and more preferably 2.5 to 2.5% from the viewpoint of improving printing density, glossiness, and image clarity. It is 45 mol%, more preferably 3 to 40 mol%, particularly preferably 5 to 35 mol%. Here, the crosslinking rate (mol%) of the crosslinked polymer refers to a value determined by the following formula (5).
Crosslink rate (mol%) = [number of moles of crosslinker to be reacted with 1 mole of polymer × 100 / number of moles of reactive group capable of reacting with crosslinker of 1 mole of polymer] (5)
Here, “the number of molar equivalents of the crosslinking agent to be reacted with 1 mol of the polymer” is a value obtained by multiplying the number of moles of the crosslinking agent to be reacted with 1 mol of the polymer by the number of reactive groups in one molecule of the crosslinking agent.

((B) Crosslinked polymer particles)
The crosslinked polymer particle (B) used in the present invention is used as a crosslinked polymer particle for clear ink in order to improve glossiness and image clarity.
The crosslinked polymer particles (B) are obtained by (i) polymer particles obtained by crosslinking the polymer with a crosslinking agent (polymer particles obtained by the same production method as the crosslinked polymer particles (A) except that no colorant is contained). ) Or (ii) polymer particles obtained by polymerizing a monomer mixture containing a crosslinkable monomer and (c) a hydrophobic monomer. In the case of (i), the use amount of the crosslinking agent and the crosslinking rate are preferably in the same range as the crosslinked polymer particles (A). In the case of (ii), the use amount of the crosslinkable monomer is from 0.5 to 100 parts by weight with respect to 100 parts by weight of the total amount of the hydrophobic monomer and the crosslinkable monomer from the viewpoint of improving glossiness and image clarity. 15 parts by weight, more preferably 0.7 to 13 parts by weight, still more preferably 1.0 to 11 parts by weight, particularly preferably 1.5 to 9 parts by weight.

(A) Colorant-containing crosslinked polymer particles, and (B) Crosslinked polymer particles, from the viewpoint of improving glossiness and image clarity, the polymer in (A) the colorant-containing crosslinked polymer particles and (B) the crosslinked polymer particles From the group consisting of (a) a salt-forming group-containing monomer, (b) a macromer, (c) a hydrophobic monomer, (d) a hydroxyl group-containing monomer, and (e) a component described in the above-mentioned vinyl polymer column. Among the selected monomer types, it is preferable to include structural units derived from two or more same monomer types, and it is more preferable to include structural units derived from three or more same monomer types, (a) to (e) It is particularly preferable that the structural unit is derived from the five monomer species. In the case where (A) the colorant-containing crosslinked polymer particle and (B) the crosslinked polymer particle are a core-shell polymer to be described later, the constitutional unit of the polymer in the shell part is derived from two or more of the same monomer species as described above. Preferably it contains units.
Thus, the polymer contained in the clear ink has two or more structural units derived from the same monomer species as the polymer contained in the colored ink, so that the miscibility of the polymers when printed on the dedicated paper becomes good. Further, glossiness and image clarity can be further improved.

(Cross-linked core-shell polymer particles)
(A) The crosslinked polymer particle containing a colorant and (B) the crosslinked polymer particle may be a crosslinked core-shell polymer particle having a core-shell structure.
In the present invention, the crosslinked core-shell polymer particles used in (A) and (B) are polymers having a structure in which a polymer constituting the shell part is physically or chemically bonded to a polymer constituting the core part. In addition, it means a polymer obtained by crosslinking at least one of the polymer in the core part and the polymer in the shell part.
Here, the polymer of the core part and the polymer of the shell part include, in addition to crosslinking, from the viewpoint of the required performance, the type of constituent unit (type of monomer as a raw material) and / or the weight ratio of constituent unit (monomer The weight ratio is different.

(A) When the colorant-containing cross-linked polymer particles are core-shell polymer particles, the cross-linked polymer in the core part improves the affinity with the colorant, and the cross-linked polymer in the shell part serves as an aqueous dispersion of the cross-linked core-shell polymer particles. It has a function of stability and is used to improve glossiness and image clarity due to (B) crosslinked polymer particles.
When the crosslinked polymer particles (B) used in the clear ink are crosslinked core-shell polymer particles, from the viewpoint of glossiness and image clarity, if the core portion is a crosslinked core-shell polymer particle, the shell portion is crosslinked. Although not necessarily required, from the viewpoint of improving glossiness, image clarity, and storage stability, a crosslinked core-shell polymer particle composed of a polymer in which the core polymer and the shell polymer are both crosslinked is provided. preferable.

  The core part of the crosslinked core-shell polymer particles used in (A) and (B) is preferably obtained by polymerizing a crosslinking monomer and the hydrophobic monomer (c), and the shell part of the crosslinked core-shell polymer particles is A polymer having the polymer structure described in the vinyl polymer, which is obtained by copolymerizing a monomer mixture containing (a) a salt-forming group-containing monomer, (b) a macromer and / or (c) a hydrophobic monomer, It is preferably obtained by crosslinking with an agent.

Although there is no restriction | limiting in particular in the manufacturing method of a coloring agent containing bridge | crosslinking core-shell polymer particle, According to the method which has the following processes 1-3, it can manufacture efficiently.
Step 1: Polymer particles containing a colorant, a crosslinkable monomer having two or more reactive unsaturated groups, and a hydrophobic monomer are mixed, and at least a part of the crosslinkable monomer and the hydrophobic monomer is colored. Step 2 for inclusion in the polymer particles containing the agent: Step 3 for obtaining core-shell polymer particles in which the core part is crosslinked by polymerizing the crosslinkable monomer and the hydrophobic monomer. A process of obtaining a crosslinked core-shell polymer particle in which both the core part and the shell part are crosslinked by reacting the core-shell polymer particle having a crosslinked core part with a crosslinking agent.

In step 1, the dispersion of the colorant-containing polymer particles is mixed with a crosslinkable monomer, a hydrophobic monomer, water, and a surfactant as necessary. There is no restriction | limiting in particular in the dispersion method of the obtained mixture. The dispersion in step 1 is preferably 5 to 50 ° C, more preferably 10 to 35 ° C.
The dispersion of the colorant-containing polymer particles can be obtained by the same method as in the step (1) described in the column (A) Colorant-containing crosslinked polymer particles.
As the mixing and stirring device for dispersing the mixture and the means for giving the shear stress, the same ones as described in the column (A) Colorant-containing crosslinked polymer particles can be used.
The amount of the hydrophobic monomer used is preferably such that the weight ratio of the polymer particles containing the hydrophobic monomer / colorant is from 0.1 to 1, from the viewpoint of improving printing density, glossiness, and image clarity, and from 0.2 to 0.5 is more preferable.

In step 2, the crosslinkable monomer and the hydrophobic monomer in the obtained dispersion are polymerized to obtain a dispersion of core-shell polymer particles having a core portion crosslinked. The initiator for polymerization may be added in Step 1 or after Step 1. The initiators described above can be used. The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 5 hours, and the reaction temperature is preferably 40 to 95 ° C.
The core-shell polymer particles obtained in this step 2 include a core part in which a polymer having a structural unit derived from a hydrophobic monomer is cross-linked by a cross-linkable monomer, and a shell part consisting of a polymer derived from a polymer particle containing a colorant. Have.
An aqueous dispersion of core-shell polymer particles in which the core part containing a pigment having a desired average particle diameter is crosslinked can be obtained by distilling off the organic solvent from the obtained dispersion to form an aqueous system. The removal of the organic solvent contained in the aqueous dispersion is the same as that described in the column (A) Colorant-containing crosslinked polymer particles. The organic solvent may be removed after Step 2 or may be removed in Step 3.

In step 3, the core-shell polymer particles obtained by crosslinking the core part obtained in step 2 are reacted with a crosslinking agent to obtain crosslinked core-shell polymer particles. In this step 3, the polymer as the shell part is cross-linked by a cross-linking agent to obtain cross-linked core-shell polymer particles in which both the core part and the shell part are cross-linked.
The catalyst, solvent, reaction temperature, and reaction time in the reaction can be appropriately determined in consideration of the crosslinking agent to be used. The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 5 hours, and the reaction temperature is preferably 40 to 95 ° C.
It is preferable to remove coarse particles by filtering the aqueous dispersion containing the obtained colorant-containing crosslinked core-shell polymer particles. The aqueous dispersion of the colorant-containing crosslinked core-shell polymer particles is one in which the solid content of the crosslinked core-shell polymer containing the colorant is dispersed in water as a main medium. Here, the form of the colorant-containing crosslinked core-shell polymer particles is not particularly limited as long as the particles are formed of at least the colorant and the crosslinked core-shell polymer. For example, particle forms in which a coloring agent is encapsulated in the crosslinked core-shell polymer, particle forms in which the coloring agent is uniformly dispersed in the crosslinked core-shell polymer, and particle forms in which the coloring agent is exposed on the surface of the crosslinked core-shell polymer particle are included. It is.

Although there is no restriction | limiting in particular in the manufacturing method of the crosslinked core-shell polymer particle used for clear ink, According to the method which has the following process I and II, it can manufacture efficiently.
Step I: A dispersion of a core-shell polymer particle obtained by polymerizing a hydrophobic monomer and a crosslinkable monomer having two or more reactive unsaturated groups in the presence of water, an organic solvent and a polymer to crosslink the core part. Step II: Cross-linked core-shell polymer particles obtained by cross-linking the core-shell polymer particles obtained in Step I using a cross-linking agent having two or more reactive functional groups, and the core portion and the shell portion are both cross-linked. The process of obtaining

  In step I, it is preferable to first polymerize the polymer dissolved in an organic solvent, a hydrophobic monomer and a crosslinkable monomer in an aqueous medium and emulsified and dispersed. At this time, it is preferable to use a neutralizing agent to neutralize the polymer having a salt-forming group, but the polymer may be previously neutralized with a neutralizing agent. There is no particular limitation on the degree of neutralization of the polymer. Usually, it is preferable to neutralize so that the finally obtained dispersion has neutral liquidity, for example, pH of 4.5 to 10 (20 ° C.). The pH can also be determined by the desired degree of neutralization of the polymer.

As an organic solvent, the thing of the above-mentioned process (1) can be used.
Although there is no restriction | limiting in particular in the emulsification method in the process I, It is preferable to fully emulsify the monomer mixture B by the ultrasonic dispersion method etc. The ultrasonic disperser preferably has a frequency of 20 to 2000 kHz and a wattage per liter of the total reaction liquid amount of preferably 20 to 1000 W, more preferably 50 to 800 W. It is commercially available from companies such as Nippon Seiki Seisakusho and Alex. As for the emulsification conditions of Step I, the temperature is preferably 5 to 50 ° C., and the time is preferably about 0.5 to 3 hours.

The weight ratio of [total amount of hydrophobic monomer and crosslinkable monomer having two or more reactive unsaturated groups / polymer amount] is preferably 2/10 to 10/2, more preferably 3/10 to 10/3. preferable. As the polymerization initiator, those described above can be used.
The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 5 hours, and the reaction temperature is preferably 40 to 95 ° C.
The dispersion of the core-shell polymer particles obtained by crosslinking the core part obtained in Step I is composed of a polymer having a salt-forming group as a crosslinked polymer particle obtained by polymerizing a hydrophobic monomer and a crosslinking monomer. The core-shell polymer particles contained in the shell part are dispersed in water as a main medium.

In Step II, the core-shell polymer particles obtained by crosslinking the core part obtained in Step I are reacted with a crosslinking agent to obtain a dispersion of crosslinked core-shell polymer particles.
The catalyst, solvent, temperature, and time in the above reaction can be appropriately determined in consideration of the crosslinking agent to be used. The reaction time is preferably 0.5 to 10 hours, more preferably 1 to 5 hours, and the reaction temperature is preferably 40 to 95 ° C. Step II has the same conditions as step 3 described above.
It is preferable to remove coarse particles by filtering the aqueous dispersion containing the obtained crosslinked core-shell polymer particles. The aqueous dispersion of the crosslinked core-shell polymer particles obtained in step II is a dispersion in which the solid content of the crosslinked core-shell polymer obtained by crosslinking both the core and shell is dispersed in water as the main medium. .

Hereinafter, it is described in common for the crosslinked polymer particles or the crosslinked core-shell polymer particles used in the colored ink and the clear ink.
In the crosslinked core-shell polymer particles, the degree of crosslinking of the core part represented by the following formula (6) is preferably 0.5 to 15% by weight, more preferably from the viewpoint of printing density, glossiness, and image clarity. It is 0.7-13 weight%, More preferably, it is 1.0-11 weight%, Most preferably, it is 1.5-9 weight%.
Cross-linking degree of core part (% by weight) = (Amount of crosslinkable monomer / Amount of polymer of cross-linking core part) × 100 (6)
In the formula (6), the polymer amount of the cross-linked core part is the amount of cross-linked polymer, and is the total charge calculation amount of the cross-linkable monomer and the hydrophobic monomer.

Moreover, the crosslinking degree of the shell part represented by the following formula (7) is preferably 0.5 to 15% by weight, more preferably 0.7 to 13% by weight from the viewpoints of printing density, glossiness, and image clarity. %, More preferably 1.0 to 11% by weight, and particularly preferably 1.5 to 9% by weight.
Cross-linking degree of shell part (% by weight) = (Amount of cross-linking agent / Amount of polymer of shell part) × 100 (7)
In (7), the polymer amount of the shell portion is the amount of polymer before crosslinking, and does not include the amount of crosslinking agent.

The crosslinking rate (mol%) of the shell part of the crosslinked core-shell polymer particles is preferably 1 to 80 mol%, more preferably 3 to 60 mol%, particularly preferably from the viewpoints of glossiness, image clarity, and storage stability. 5 to 50 mol%. Here, the crosslinking rate (mol%) of the shell portion refers to a value obtained by the following formula (8).
Crosslinking rate (mol%) = [number of moles of crosslinking agent to be reacted with 1 mole of polymer in shell portion × 100 / number of moles of reactive group capable of reacting with crosslinking agent of 1 mole of polymer in shell portion] (8)

  (A) Colorant-containing crosslinked core-shell polymer particles and (B) crosslinked core-shell polymer particles, in any case, the weight ratio of the core part to the shell part excluding the colorant (core part / shell part) is preferably 0.00. It is 3-15, More preferably, it is 0.4-13, More preferably, it is 0.5-10, Most preferably, it is 0.5-8. In the case of cross-linking, the calculation of the weight ratio between the core part and the shell part includes the amount of cross-linkable monomer and the amount of cross-linking agent, respectively, and the weight of the core part is the hydrophobic monomer and cross-linkable monomer used for forming the core part. The weight of the shell portion is the total amount of charge of the polymer forming the shell portion and the crosslinking agent.

(A) Colorant-containing crosslinked polymer particle, (B) When the crosslinked polymer particle is a core-shell polymer particle or not a core-shell polymer particle, the crosslinked polymer represented by the following formula (9) The crosslinking degree is preferably 0.5 to 15% by weight, more preferably 0.7 to 13% by weight, still more preferably 1 to 11% by weight, particularly preferably, from the viewpoints of glossiness and image clarity. Is 1 to 9% by weight.
Crosslinking degree of entire crosslinked polymer (% by weight) = [(crosslinking monomer amount + crosslinking agent amount) / crosslinked polymer total amount] × 100 (9)
The total amount of crosslinked polymer is the amount of polymer after crosslinking.
Specifically, in the case of the core-shell polymer particles, the total amount of the crosslinked polymer is a total charge calculation amount including the crosslinking monomer, the crosslinking agent, the polymer forming the shell portion, and the hydrophobic monomer used for forming the core portion. Yes, when the crosslinking is only the core or the shell, either the amount of the crosslinkable monomer or the amount of the crosslinking agent is zero.
When the particles are not core-shell polymer particles, the total amount of the crosslinked polymer is a total charge calculation amount including the polymer and the crosslinking agent, or a total charge calculation amount including the hydrophobic monomer and the crosslinkable monomer used to form the polymer particles.
Both a crosslinking monomer and a crosslinking agent can be used.

(Water-insoluble organic compound)
In the present invention, a water-insoluble organic compound can be used from the viewpoint of improving the flexibility of the crosslinked polymer particles and improving the glossiness and image clarity of the printed matter. The water-insoluble organic compound can be added during or after the production process of the colorant-containing crosslinked polymer particles (A) and the crosslinked polymer particles (B).
The water-insoluble organic compound preferably has a molecular weight of 100 to 2,000, more preferably a molecular weight of 100 to 1,200, from the viewpoint of improving the glossiness and image clarity of the water-based ink.
The maximum weight (20 ° C.) of the water-insoluble organic compound that can be dissolved in 100 g of water is preferably 5 g or less, more preferably 3 g or less, still more preferably 1 g or less, and particularly preferably 0.5 g or less.
The water-insoluble organic compound improves the glossiness and image clarity of the printed matter when printed on special paper, and also improves its storage stability of the water dispersion from its LogP value (1 of the water-insoluble organic compound). -Logarithm of octanol / water partition coefficient) is preferably 4 to 16, more preferably 5 to 16, and particularly preferably 6 to 15.

  Here, “Log P value” means the logarithmic value of the 1-octanol / water partition coefficient of water-insoluble organic compounds, calculated by the fragment approach by SRC's LOGKOW / KOWWIN Program of KowWin (Syracuse Research Corporation, USA). The KowWin Program methodology is described in the following journal article: Meylan, WM and PH Howard. 1995. Atom / fragment contribution method for using octanol-water partition coefficients. J. Pharm. Sci. 84: 83-92 .). The fragment approach is based on the chemical structure of the compound and takes into account the number of atoms and the type of chemical bond. The LogP value is a numerical value generally used for relative evaluation of the hydrophilicity / hydrophobicity of an organic compound.

The water-insoluble organic compound is preferably an ester compound, an ether compound, or a sulfonic acid amide compound so as to be easily contained in the (crosslinked) polymer particle, and an ester having two or more ester or ether bonds in the molecule. Or an ether compound (f) and / or one or more ester or ether bonds in the molecule, a carboxy group, a sulfuric acid group, a sulfonic acid group, a phosphoric acid residue, a phosphonic acid group, a carbonyl group, an epoxy group, and An ester or ether compound (g) having at least one functional group selected from the group consisting of hydroxyl groups is more preferred. The ester or ether bond of the compound (f) is preferably 2 to 3, and may have an ester bond and an ether bond. The number of ester or ether bonds in the compound (g) is preferably 1 to 3. The number of functional groups is preferably 1 to 3. In addition, a phosphoric acid residue means the remaining phosphoric acid group in which a part of phosphoric acid was esterified.
Among the ester compounds, esters obtained from monovalent carboxylic acids or salts thereof and polyhydric alcohols, polyacids (polycarboxylic acids, phosphoric acids) or esters obtained from salts thereof and monohydric alcohols are preferred, and ether compounds Of these, polyhydric alcohol ethers are preferred. Examples of the salt include alkali metal salts, alkanolamine salts, ammonium salts and the like.

Examples of monovalent carboxylic acids include linear or branched aliphatic carboxylic acids having 1 to 18 carbon atoms, preferably 2 to 10 carbon atoms, and aromatic carboxylic acids having 6 to 12 carbon atoms (for example, benzoic acid). Can be mentioned. Examples of the polyvalent acid include aliphatic carboxylic acids having 2 to 12 carbon atoms such as maleic acid, fumaric acid, itaconic acid, succinic acid, adipic acid and sebacic acid, and 6 to 12 carbon atoms such as phthalic acid and trimellitic acid. Aromatic carboxylic acid, phosphoric acid and the like can be mentioned.
As the monohydric alcohol, a linear or branched aliphatic alcohol having 1 to 18 carbon atoms, preferably 2 to 10 carbon atoms (for example, ethyl alcohol, butyl alcohol, hexyl alcohol, octyl alcohol, dodecyl alcohol), carbon number 6-12 aromatic alcohol (for example, phenol), these alkylene oxide compounds, etc. are mentioned.
Examples of the polyhydric alcohol include polyhydric alcohols having 2 to 12 carbon atoms such as ethylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, pentaerythritol, and glycerin, and alkylene oxide compounds thereof. A saturated or unsaturated fatty acid or alcohol can be used.

Specific examples of the water-insoluble organic compound include (1) aliphatic carboxylic acid ester, (2) aromatic carboxylic acid ester, (3) cycloalkane (ken) carboxylic acid ester, (4) phosphoric acid ester, (5) Oxy acid ester, (6) glycol ester, (7) epoxy ester, (8) sulfonamide, (9) polyester, (10) glyceryl alkyl ether, (11) glyceryl alkyl ester, (12) glycol alkyl ether, etc. Can be mentioned.
Among these, from the viewpoints of improving glossiness and image clarity, the compounds of (1) to (5), (8) and (10) are preferred, (1) aliphatic carboxylic acid ester, (2) aromatic It is more preferably at least one selected from the group consisting of aromatic carboxylic acid esters, (3) cycloalkane (ken) carboxylic acid esters, and (4) phosphoric acid esters, and aliphatic dicarboxylic acid esters, aromatic di- or tricarboxylic acids. Particularly preferred is at least one selected from the group consisting of acid esters, cycloalkane (ken) dicarboxylic acid esters, and phosphate esters.
(1) Aliphatic carboxylic acid ester, (2) aromatic carboxylic acid ester, and (3) cycloalkane (ken) carboxylic acid ester are preferably compounds represented by the following formula (11).

(.R wherein, R ¹ and R ² are each independently a hydrogen atom, or a hydrocarbon group having 1 to 22 carbon atoms, R ³ is showing a divalent hydrocarbon group having 1 to 18 carbon atoms ¹ and R ² may be the same or different, except when R ¹ and R ² are both hydrogen atoms, R ^{1 to} R ³ may have a substituent, and m and n are Each independently represents an average addition mole number of 0 to 30, and AO represents an alkanediyloxy group.)

R ¹ and R ² are preferably a linear or branched alkyl or alkenyl group having 2 to 18 carbon atoms, more preferably 4 to 12 carbon atoms, from the viewpoint of improving glossiness and image clarity of printed matter. , An aralkyl group having 7 to 23 carbon atoms, preferably 7 to 11 carbon atoms, or an aryl group having 6 to 22 carbon atoms, preferably 6 to 10 carbon atoms. Specifically, a methyl group, an ethyl group, and propyl group Group, isopropyl group, butyl group, hexyl group, 2-ethylhexyl group, octyl group, dodecyl group, cetyl group, phenyl group, benzyl group and the like. The same applies to the following equations.

R ³ is preferably a divalent aliphatic hydrocarbon group, a cyclic hydrocarbon group or an aromatic hydrocarbon group, preferably 2 to 15 carbon atoms, more preferably 2 to 12 carbon atoms, particularly preferably 2 carbon atoms. An alkanediyl group (alkylene group) or an alkenylene group having 8 to 8 carbon atoms, an arylene group having 6 to 10 carbon atoms, more preferably a phenylene group, or a cyclic saturated or unsaturated hydrocarbon group having 3 to 8 carbon atoms. Specifically, ethylene group, trimethylene group, propane-1,2-diyl group, tetramethylene group, heptamethylene group, hexamethylene group, pentane-1,5-diyl group, octamethylene group, dodecamethylene group, phenylene Groups and the like. The same applies to the following equations.
m and n are each independently preferably 0 to 20, more preferably 0 to 15, still more preferably 1 to 15, particularly preferably 2 to 14, and most preferably 2 to 12.

AO is the number of carbon atoms such as ethyleneoxy group (EO), propyleneoxy group (trimethyleneoxy group or propane-1,2-diyloxy group) (PO), butyleneoxy group (tetramethyleneoxy group etc.) (BO), etc. 2 to 4 alkanediyloxy groups (alkyleneoxy groups), and when m and n are 2 or more, AO may be the same or different, and when they are different, AO may be added in blocks or randomly. It may be.
Examples of the substituent that R ^{1 to} R ³ may have include halogen atoms such as fluorine, chlorine and bromine atoms, alkoxy groups having 1 to 12 carbon atoms such as methoxy, ethoxy and isopropoxy groups, phenyloxy Aryloxy groups such as oxycarbonyl groups such as methoxycarbonyl groups, acyl groups such as acetyl and benzoyl groups, acyloxy groups such as acetyloxy groups, cyano groups, nitro groups, hydroxyl groups, carboxy groups, oxo groups, epoxy groups , Ether groups, ester groups and the like (these are collectively referred to as “substituents”). These substituents may be one or a combination of two or more.
The substituent that R ³ may have is preferably —CO (O) — (AO) _L —R ⁴ . In the formula, AO is the same as described above. L has the same meaning as m described above, and the preferred range is also the same. R ⁴ has the same meaning as R ¹ described above, and the preferred range is also the same. In this case, R ³ is preferably an aromatic hydrocarbon group.

(1) The aliphatic carboxylic acid ester is more specifically a compound in which, in the formula (11), R ³ is a divalent aliphatic hydrocarbon group which may have a substituent. preferable. Examples of this substituent include the above-described substituents.
Specific examples of the aliphatic carboxylic acid ester include dimethyl adipate, diethyl adipate, dibutyl adipate, diisobutyl adipate, bis (2-ethylhexyl) adipate, diisononyl adipate, diisodecyl adipate, bis (butyldiethylene glycol) adipate, dimethyl sebacate, diethyl sebacate Examples thereof include aliphatic dibasic acid esters such as keto, dibutyl sebacate, bis (2-ethylhexyl) sebacate, diethyl succinate and bis (2-ethylhexyl) azelate. Among these, diethyl adipate, dibutyl adipate, diisobutyl adipate, bis (butyldiethylene glycol) adipate, bis (octoxypolyethylene glycol) adipate (R ¹ and R ² are both 2-ethylhexyl, EO average addition moles m and n = 1 to 4), bis (octoxypolypropylene glycol) adipate (R ¹ and R ² are both 2-ethylhexyl, average added moles of PO and n = 1 to 6), bis (octoxypolyethyleneglycol / polypropylene) Propylene glycol) adipate (R ¹ and R ² are both 2-ethylhexyl, EO and PO total average addition moles m and n = 4-12, block addition), bis [octoxypoly (ethylene glycol propylene glycol)] adipate (R ¹ and R ² are both 2 -Ethyl hexyl, EO and PO total average addition moles m and n = 4-12, random addition), diethyl sebacate, dibutyl sebacate, diisobutyl sebacate, etc. Diesters are particularly preferred.

  (2) More specifically, the aromatic carboxylic acid ester is more preferably a compound represented by the following formula (12).

(In the formula, R ¹ and R ² have the same meaning as described above, and may be the same or different. AO, m and n have the same meaning as described above, and m and n are 2 or more. AO may be the same or different.)
Specific examples of the aromatic carboxylate include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisobutyl phthalate, bis (2-ethylhexyl) phthalate, di-n-octyl phthalate, diisodecyl phthalate, butyl benzyl phthalate, octyl benzyl phthalate, nonyl Phthalate esters such as benzyl phthalate, stearyl benzyl phthalate, octyl decyl phthalate, dicyclohexyl phthalate, diphenyl phthalate, bis (dimethylcyclohexyl) phthalate, bis (t-butylcyclohexyl) phthalate, ethyl phthalyl ethyl glycolate, tributyl trimellitate, Trimellitic acid esters such as triisobutyl trimellitate and tri (2-ethylhexyl) trimellitate It is below. Among these, carbon number 3 such as phthalic acid diester having an aliphatic alcohol residue having 1 to 5 carbon atoms such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diisobutyl phthalate, octyl benzyl phthalate, nonyl benzyl phthalate, stearyl benzyl phthalate Benzyl phthalate having -18 alkyl groups, bis (octoxypolyethylene glycol) phthalate (R ¹ and R ² are both 2-ethylhexyl, average addition number m of EO and n = 1-5), bis (octoxy Polypropylene glycol) phthalate (R ¹ and R ² are both 2-ethylhexyl, average added moles m and n of PO = 1 to 4), bis (octoxypolyethylene glycol / polypropylene glycol) phthalate (R ¹ and R ² Are both 2-Echi Hexyl, each total average addition mole number m and n = 4 to 12 of EO and PO, block addition), bis [Okutokishipori (ethylene glycol-propylene glycol) phthalate (R ¹ and R ² are both 2-ethylhexyl, EO and The total average number of moles of PO added m and n = 4 to 12, random addition) and the like, and phthalic acid esters such as tributyl trimellitate and triisobutyl trimellitate, The trimellitic acid diester is particularly preferred.

  (3) More specifically, the cycloalkane (ken) carboxylic acid ester is more preferably a cyclohexane (cene) carboxylic acid ester represented by the following formula (13). Examples of the cycloalkane (ken) group include a cyclic hydrocarbon group which may have one unsaturated group having 3 to 8 carbon atoms.

(In the formula, R ¹ and R ² have the same meaning as described above, and may be the same or different. AO, m and n have the same meaning as described above, and m and n are 2 or more. AO may be the same or different.)
Specific examples of the cycloalkane (ken) carboxylic acid ester include cyclohexane carboxylic acid esters such as 1,2-cyclohexanedicarboxylic acid dibutyl ester, 1,2-cyclohexanedicarboxylic acid diisononyl ester, and 3,4-cyclohexene dicarboxylic acid dibutyl ester. And cyclohexene carboxylic acid esters such as 3,4-cyclohexene carboxylic acid diisononyl ester.
(4) The phosphate ester is preferably a compound represented by the following formula (14).

(In the formula, R ¹ and R ² have the same meaning as described above and may be the same or different.)
Specific examples of phosphate esters include tributyl phosphate, tris (2-ethylhexyl) phosphate, tris (butoxyethyl) phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, 2-ethylhexyl diphenyl A phosphate etc. are mentioned. Among these, phosphate esters having a C5-C9 alkoxyalkyl group such as tris (butoxyethyl) phosphate, phosphate esters having a C4-12 aliphatic hydrocarbon group such as tributyl phosphate, tris ( Butoxyethyl) phosphates, tricresyl phosphates, trixylenyl phosphates, cresyl diphenyl phosphates, and other phosphate esters having an aromatic hydrocarbon group of 7 to 12 carbon atoms are particularly preferred. The phosphate ester is preferably a phosphoric acid di- or triester.

  (5) The oxyacid ester is preferably a compound represented by the following formula (15).

(In the formula, R ¹ , R ² and R ³ have the same meaning as described above. R ¹ and R ² may be the same or different.)
Specific examples of the oxyester include triethyl acetylcitrate, tributyl acetylcitrate, methyl acetylricinoleate and the like.

(6) Specific examples of glycol esters include diethylene glycol dibenzoate and triethylene glycol di (2-ethylhexoate).
(7) Specific examples of the epoxy ester include butyl epoxy stearate and octyl epoxy stearate.

  (8) The sulfonamide is preferably a compound represented by the following formula (16).

(In the formula, R ¹ and R ² have the same meaning as described above and may be the same or different.)
Specific examples of the sulfonamide include o- and p-toluenesulfonamide, N-butylbenzenesulfonamide and the like.

(9) Specific examples of polyester include poly (1,2-butanediol adipate), poly (1,3-butanediol adipate) and the like.
(10) Specific examples of the glyceryl alkyl ether include glyceryl monoether, glyceryl diether, and glyceryl triether. In these, the glyceryl monoether which has a C8-C30 linear or branched alkyl group is preferable. The alkyl group has 8 to 30 carbon atoms, preferably 8 to 22 carbon atoms, and more preferably 8 to 14 carbon atoms.
Examples of the alkyl group include 2-ethylhexyl, (iso) octyl, (iso) decyl, (iso) dodecyl, (iso) myristyl, (iso) cetyl, (iso) stearyl, and (iso) behenyl groups.
There is no restriction | limiting in particular about the position of an alkyl group, Either 1-alkyl glyceryl monoether and 2-alkyl glyceryl monoether may be sufficient.

(11) Examples of glyceryl alkyl esters include monoalkyl esters, dialkyl esters, and trialkyl esters. Among these, linear or branched aliphatic carboxylic acids having 1 to 18 carbon atoms, preferably 2 to 10 carbon atoms. Esters of acids (for example, straight chain aliphatic carboxylic acids such as acetic acid, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, and palmitic acid, and branched aliphatic carboxylic acids such as pivalic acid) are preferred. More specifically, glyceryl triacetate, glyceryl diacetate, glyceryl monoacetate and the like can be mentioned.
(12) Examples of glycol alkyl ether include monoalkyl ether and dialkyl ether, and examples of glycol include ethylene glycol and neopentyl glycol. Moreover, as an alkyl group, C1-C22, Preferably it is C6-C20, More preferably, a C8-C18 linear or branched alkyl group is mentioned.

(Colored ink containing colorant-containing crosslinked polymer particles (A) / Clear ink containing crosslinked polymer particles (B))
For the colored ink containing the colorant-containing crosslinked polymer particles (A), an aqueous dispersion of the colorant-containing crosslinked polymer particles (A) can be used as the colored ink as it is. The aqueous dispersion of the colored ink can be obtained preferably in the steps (1) to (3) or steps 1 to 3. Similarly, for the clear ink containing the crosslinked polymer particles (B), the aqueous dispersion of the crosslinked polymer particles (B) can be used as it is as the clear ink. The aqueous dispersion of clear ink can be obtained preferably in the steps (1) to (3) or the steps I and II. A wetting agent, a penetrating agent, a dispersing agent, a viscosity modifier, an antifoaming agent, an antifungal agent, a rust preventing agent, and the like that are usually used for water-based inks for inkjet recording may be added to the aqueous dispersion.

The content of the colorant-containing crosslinked polymer particles, the colorant, water, and the water-insoluble organic compound in the water dispersion and the colored ink is as follows from the viewpoint of improving glossiness and image clarity.
The content of the colorant-containing crosslinked polymer particles is preferably 1 to 20% by weight, more preferably 1.5 to 15% by weight, and preferably 1.5 to 12% by weight.
The content of water is preferably 40 to 90% by weight, more preferably 50 to 80% by weight, and still more preferably 60 to 80% by weight.
The content of the colorant is preferably 1 to 15% by weight, more preferably 2 to 10% by weight.
The content of the water-insoluble organic compound is preferably 0.03 to 3% by weight, more preferably 0.05 to 2% by weight, and particularly preferably 0.1 to 1.5% by weight.
The content of the crosslinked polymer particles, water, and the water-insoluble organic compound in the aqueous dispersion and the clear ink is as follows from the viewpoint of improving glossiness and image clarity.
The content of the crosslinked polymer particles is preferably 0.3 to 20% by weight, more preferably 0.5 to 12% by weight, and particularly preferably 0.7 to 10% by weight. About preferable content of water and a water-insoluble organic compound, it is the same as the said description about the colored ink.

The average particle size of the (A) colorant-containing crosslinked polymer particles in the obtained colored ink and the (B) crosslinked polymer particles in the clear ink is preferably 10 to 10 from the viewpoint of preventing clogging of the nozzles of the printer and dispersion stability. The thickness is 500 nm, more preferably 30 to 300 nm, and particularly preferably 50 to 200 nm. In addition, an average particle diameter can be measured on condition of the following using laser particle analysis system ELS-8000 (cumulant analysis) of Otsuka Electronics Co., Ltd., for example.
Measurement conditions: temperature 25 ° C., incident light / detector angle 90 °, integration count 100 times, water refractive index (1.333) as the refractive index of the dispersion solvent, measured concentration, typically 5 × 10 ⁻³ weight About% The surface tension (20 ° C.) of the colored ink and the clear ink is preferably 25 to 50 mN / m, more preferably 27 to 45 mN / m.
The viscosity (20 ° C.) of the colored ink and the clear ink is preferably 2 to 12 mPa · s, more preferably 2.5 to 10 mPa · s, from the viewpoint of maintaining good dischargeability. The pH of the water-based ink is preferably 4-10.
The viscosity (20 ° C.) at a solid content of 10% by weight of the aqueous dispersion is preferably 2 to 6 mPa · s, more preferably 2 to 5 mPa · s in order to obtain a favorable viscosity when a colored ink or a clear ink is used. . Further, the viscosity (20 ° C.) of the water-based ink is preferably 2 to 12 mPa · s, and more preferably 2.5 to 10 mPa · s, in order to maintain good ejection properties. The pH of the colored ink and clear ink is preferably 4-10.

(Ink set for inkjet recording)
The ink set for inkjet recording of the present invention is an ink set containing a colored ink containing a colorant-containing crosslinked polymer particle (A) and a clear ink containing a crosslinked polymer particle (B).
The colored ink is preferably provided with one or more colors, more preferably two or more different colors, and still more preferably two or more chromatic inks. Here, “different color” means that the reflected light is measured at a wavelength of light of D65 / 2 using a spectroscopic color difference meter SE-2000 manufactured by Nippon Denshoku Industries Co., Ltd., and L ^* a ^*. When displayed in the b ^* color system, a ^* (red-green chromaticity) and b ^* (yellow-blue chromaticity) are not the same color. 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 one or more color inks selected from these chromatic colors and the like, and a clear ink, and a two-color ink set, a three-color ink set, a four-color ink set, and a five-color ink set. Any of a color ink set, a 6-color ink set, and a 7-color ink set may be used.
More preferably, it is an ink set comprising one or more colored inks selected from the group consisting of magenta ink, yellow ink and cyan ink, which are three subtractive primary colors, and a clear ink. An ink set including the above colored inks is more preferable, and an ink set including three colored inks is particularly preferable. The ink set of the present invention may further include black ink.

(Inkjet printing method)
The ink set of the present invention can be printed by filling each color ink cartridge of the inkjet printer with clear ink and colored ink, and ejecting ink droplets from each minute nozzle corresponding to each ink cartridge. In this case, the portion where the colored ink is printed at a printing area ratio (duty, DUTY) of 10 to 80% is not entirely covered with the colored ink on the dedicated paper printing surface, and the dot height derived from the colored ink is formed. A step with the paper surface occurs. A method of printing with clear ink so as to fill the step is preferable. There is no particular limitation on the order of printing the colored ink and the clear ink. That is, even if the color ink is printed in advance and then the clear ink is superimposed and printed, the clear ink can be printed in advance and the color ink can be printed thereafter.
The ink jet system to which the ink set of the present invention is applied is not limited, but is particularly suitable for a piezoelectric ink jet printer.

In the following production examples, examples , reference examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified. The weight average molecular weight of the polymer was measured by the following method.
(1) Weight average molecular weight of polymer Gel chromatography using N, N-dimethylformamide containing 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as a solvent [GPC apparatus (HLC- 8120GPC), a column manufactured by Tosoh Corporation (TSK-GEL, α-M × 2), flow rate: 1 mL / min], using polystyrene as a standard substance.

Production Example 1 (Production of water-insoluble polymer)
In a reaction vessel, 20 parts of methyl ethyl ketone, 0.03 part of a polymerization chain transfer agent (2-mercaptoethanol), and 10% of 200 parts of each monomer shown in Table 1 were mixed and thoroughly replaced with nitrogen gas. A mixed solution was obtained.
On the other hand, the remaining 90% of the monomers shown in Table 1 were charged into a dropping funnel, and 0.27 part of the polymerization chain transfer agent, 60 parts of methyl ethyl ketone and a radical polymerization initiator (2,2′-azobis (2,4-dimethyl) were added. Valeronitrile)) 1.2 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 obtained by dissolving 0.3 part of the radical polymerization initiator in 5 parts of methyl ethyl ketone was added, and further aged at 65 ° C. for 2 hours and 70 ° C. for 2 hours to obtain a polymer solution. It was. The weight average molecular weight of the polymer was measured by the method shown above. The results are shown in Table 1.

The details of the compounds shown in Table 1 are as follows.
(B) Styrene macromer: manufactured by Toa Gosei Co., Ltd., trade name: AS-6 (S) (50% toluene solution, solid content 15 parts), number average molecular weight: 6000, polymerizable functional group: methacryloyloxy group (d) polypropylene Glycol monomethacrylate (propylene oxide average added mole number = 9, terminal: hydroxyl group): manufactured by NOF Corporation, trade name: BLEMER PP-500
(E) Polyethylene glycol monomethacrylate (average number of added moles of ethylene oxide = 9, terminal: methyl group): Shin-Nakamura Chemical Co., Ltd., trade name: NK ester M-90G

Preparation Example 1 [Preparation of Clear Ink]
(Production of aqueous dispersion of crosslinked polymer particles for clear ink)
Into the reaction vessel, 73.99 parts of Liquid A (ion exchange water of sodium hydroxide 0.1%) was added, and while stirring (about 100 rpm), a styrene solution [styrene, divinylbenzene (100 parts of styrene) at room temperature. 6.4 parts by weight, pure content of divinylbenzene: 81% by weight, trade name: DVB-810, manufactured by Nippon Steel Chemical Co., Ltd.), and 2,2′-azobis (2,4- Dimethylvaleronitrile) (2.2 parts for 100 parts of styrene, trade name: V-65, manufactured by Wako Pure Chemical Industries, Ltd.)] 11.4 parts and 35% methyl ethyl ketone of the polymer obtained in Production Example 1 After dropping 22.11 parts of B liquid mixed with 11.14 parts of the solution, ultrasonic dispersion was performed for 1 hour using an ultrasonic dispersion apparatus (manufactured by Nippon Seiki Seisakusho, Ultrasonic Generater Nissei Model USS-300T, 300 μA). Emulsified in Ukoto, then the temperature was raised to 75 ° C., subjected to polymerization for 3 hours, while stirring, then the organic solvent was removed to obtain an aqueous dispersion of crosslinked core-shell polymer particles that the core portion is crosslinked. 0.156 parts of a crosslinking agent (Denacol EX-321: epoxy equivalent 140: manufactured by Nagase ChemteX Corporation) (crosslinking agent / polymer weight ratio 4 / 100) is further added and stirred at 90 ° C. for 1.5 hours to crosslink, then cooled and adjusted with ion exchange water to obtain a crosslinked core-shell polymer particle for clear ink having a solid content concentration of 10% ( An aqueous dispersion having a crosslinking ratio of the shell portion: 17 mol%, a core-shell weight ratio of 2.81, and a crosslinking degree of the entire crosslinked polymer: 4.6 wt% was obtained.

The crosslinking rate of the shell part was calculated based on the following formula (8).
Crosslinking rate (mol%) = [number of mole equivalents of crosslinking agent to be reacted with 1 mole of polymer in shell portion × 100 / number of moles of reactive group capable of reacting with crosslinking agent contained in 1 mole of polymer in shell portion] (8)
In the formula (8), “the number of molar equivalents of the crosslinking agent to be reacted with 1 mol of the polymer in the shell portion” means the number of moles of the crosslinking agent to be reacted with 1 mol of the polymer in the shell portion. The value multiplied by the number of.

In the production of the crosslinked core-shell polymer particles for clear ink, the polymer (weight average molecular weight 180,000) was obtained by reacting 0.156 parts (epoxy equivalent 140) of the crosslinking agent (Denacol EX-321) with 3.90 parts of the polymer in the shell part. ) The number of molar equivalents of the crosslinking agent reacted with 1 mole is
(0.156 / 140) / (3.90 / 18000) = 51.
Here, since the crosslinking agent (Denacol EX-321) reacts with a carboxy group and a hydroxyl group, the number of moles of the reactive group capable of reacting with the crosslinking agent possessed by 1 mol of the polymer is methacrylic acid (molecular weight 86) possessed by 1 mol of the polymer. ), Polypropylene glycol monomethacrylate (PP-500, molecular weight 612).
180000 × 0.12 / 86 + 18000 × 0.15 / 612 = 295 mol Accordingly, the cross-linking ratio of the shell portion is 51 × 100/295 = 17 mol%.

(Preparation of clear ink)
In 15.00 parts of the obtained aqueous dispersion of crosslinked core-shell polymer particles for clear ink, 25 parts of glycerin, 7 parts of triethylene glycol monobutyl ether (TEGMBE), 1 part of Surfinol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), 1 part of triethanolamine, 0.3 part of Proxel XL2 (manufactured by Avicia Co., Ltd.) and 50.70 parts of ion-exchanged water were mixed, and the resulting mixture was filtered with a 1.2 μm filter (acetylcellulose membrane, outer diameter: A clear ink shown in Table 2 was obtained by filtering with a syringe having a capacity of 25 mL equipped with 2.5 cm, manufactured by Fuji Film Co., Ltd., and removing coarse particles.

Preparation Example 2 (Preparation of clear ink)
In the same manner as in Preparation Example 1, an aqueous dispersion of crosslinked core-shell polymer particles for clear ink having a solid content concentration of 10% was obtained. To 10.00 parts of the resulting aqueous dispersion of crosslinked core-shell polymer particles for clear ink, a water-insoluble organic compound [(i) ethylene oxide adduct of phthalic acid and 2-ethylhexyl alcohol (average added mole number 4, Japan Emulsifier Stock) Made from company, trade name: New Coal 1004) 25 parts of diester and (ii) 75 parts of triester with trimellitic acid and ethylene oxide adduct of lauryl alcohol (average added mole number 4, Nippon Emulsifier Co., Ltd.) 0.05 parts were mixed and stirred to contain a water-insoluble organic compound in the polymer particles. In this mixed solution, 27 parts of glycerin, 7 parts of triethylene glycol monobutyl ether (TEGMBE), 1 part of Surfinol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), 1 part of triethanolamine, Proxel XL2 (manufactured by Avicia Co., Ltd.) 0 3 parts and 53.65 parts of ion-exchanged water were mixed, and the obtained mixed solution was a volume of 25 mL to which a 1.2 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by FUJIFILM Corporation) was attached. The clear ink shown in Table 2 was obtained by filtering with a needleless syringe and removing coarse particles.

Preparation Example 3 (Preparation of clear ink)
A clear ink shown in Table 2 was obtained in the same manner as in Preparation Example 2 except that the amount of the ink component was changed to the amount shown in Table 2.

Preparation Example 4 (Preparation of ink containing cyan pigment-containing crosslinked polymer particles)
(Preparation of base dispersion)
68 parts of the polymer obtained by drying the polymer solution obtained in Production Example 1 under reduced pressure was dissolved in 281 parts of methyl ethyl ketone, and then 12.4 parts of neutralizer 1 (5N aqueous sodium hydroxide solution) (neutralization degree 55%) ) And neutralizing agent 2 (25% aqueous ammonia solution) 6.5 parts (neutralization degree 100%) and ion-exchanged water 975 parts to neutralize the salt-forming groups, and copper phthalocyanine pigment (Pigment Blue 15: 3) 157 parts were added, and a dispersion treatment was performed for 2 hours at a peripheral speed of 15 m / s using a pico mill manufactured by Asada Tekko. The obtained mixture was subjected to a 5-pass dispersion treatment with a microfluidizer (trade name, manufactured by Microfluidics) at a pressure of 150 MPa.

(Reaction of cross-linked core)
To 200 parts of the obtained dispersion (solid content concentration 14%), 9.3 parts of styrene, 0.49 parts of divinylbenzene (purity 81%: trade name: DVB-810: manufactured by Nippon Steel Chemical Co., Ltd.), radical A solution in which 0.2 part of a polymerization initiator (2,2′-azobis (2,4-dimethylvaleronitrile)) was mixed was added and mixed with a disper blade for 1 hour at 20 ° C. The resulting mixture was mixed with a microfluidizer ( Microfluidics, product name) was subjected to a 5-pass dispersion treatment at a pressure of 150 MPa.
The obtained dispersion was put into a reaction vessel under a nitrogen atmosphere and reacted at 77 ° C. for 3 hours with stirring to obtain a dispersion of polymer particles containing a cyan pigment and having a crosslinking site in the core. .

(Dispersion processing)
Methyl ethyl ketone was removed from the obtained dispersion at 60 ° C. under reduced pressure, a part of water was further removed, and a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Film Co., Ltd.) was attached. Filtration was performed with a syringe having no capacity of 25 mL (manufactured by Terumo Corporation) to remove coarse particles, thereby obtaining an aqueous dispersion of cyan pigment-containing water-insoluble polymer particles having a solid content concentration of 22%.

(Crosslinking reaction of shell part)
200 parts of the obtained aqueous dispersion (9.8 parts of polymer in the shell part) was put into a reaction vessel under a nitrogen atmosphere, and further, a crosslinking agent (trimethylolpropane polyglycidyl ether, manufactured by Nagase ChemteX Corporation, Denacol). EX-321, epoxy equivalent 140) 0.40 part, ion exchange water 47.4 parts, react with stirring at 90 ° C. for 1.5 hours, adjust the concentration with ion exchange water, Cross-linked (crosslink rate: 17.8 mol%) cyan pigment-containing cross-linked core-shell polymer particle dispersion (solid content concentration 20%, core-shell weight ratio: 1.1, cross-linking degree of the entire cross-linked polymer: 4.0 wt%) Obtained.

(Preparation of ink)
In Preparation Example 1, the aqueous dispersion of the crosslinked core-shell polymer particles for clear ink was changed to the cyan pigment-containing crosslinked core-shell polymer particle dispersion obtained above, and the blending amount of the ink components was changed to the amounts shown in Table 3. Except for this, the same procedure as in Preparation Example 1 was carried out to obtain the colored ink shown in Table 3.

Preparation Example 5 (Preparation of ink containing a magenta pigment-containing crosslinked polymer particle dispersion)
(Preparation of base dispersion)
200 parts of the polymer obtained by drying the polymer solution obtained in Production Example 1 under reduced pressure was dissolved in 400 parts of methyl ethyl ketone, and 16 parts of the neutralizing agent (5N aqueous sodium hydroxide solution) (neutralization degree 60%) and Add 1600 parts of ion-exchanged water to neutralize the salt-forming groups, and add 680 parts of quinacridone pigment (CI Pigment Violet 19, Clariant Japan Co., Ltd., trade name: Hostaperm Red E5B02). The mixture was dispersed at 20 ° C. for 2 hours. The obtained dispersion was further subjected to 10-pass dispersion treatment at a pressure of 200 MPa with a microfluidizer (trade name, manufactured by Microfluidics).
After adding 250 parts of ion-exchanged water to the obtained dispersion and stirring, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was removed, and a 5 μm filter (acetylcellulose membrane, outer diameter: 2). Polymer particles containing a magenta pigment with a solid content concentration of 18% by filtering with a 25 mL needleless syringe (Terumo Corporation) attached with a 5 cm, Fujifilm Corporation) and removing coarse particles. An aqueous dispersion was obtained.
Next, 0.11 part of Denacol EX-810 (molecular weight: 216, manufactured by Nagase ChemteX Corporation, epoxy equivalent 113) as a crosslinking agent was added to 80 parts of the dispersion (of which 3.3 parts of the polymer), and ion exchange was performed. 0.80 parts of water was added and stirred at 80 ° C. for 3 hours, and a magenta pigment-containing crosslinked polymer particle dispersion having a solid content concentration of 18% (crosslinking ratio: 18 mol%, the degree of crosslinking of the entire crosslinked polymer: 3. 2% by weight) was obtained.

(Preparation of ink)
In Preparation Example 2, the aqueous dispersion of the crosslinked core-shell polymer particles for clear ink was changed to the magenta pigment-containing crosslinked polymer particle dispersion obtained above, and the blending amount of the ink components was changed to the amounts shown in Table 3. Was carried out in the same manner as in Preparation Example 2 to obtain colored inks shown in Table 3.

Preparation Example 6
(Preparation of ink)
In Preparation Example 2, the aqueous dispersion of the crosslinked core-shell polymer particles for clear ink was changed to the cyan pigment-containing crosslinked core-shell polymer particle dispersion obtained in Preparation Example 4, and the blending amounts of the ink components were those shown in Table 3. The same procedure as in Preparation Example 2 was repeated except that the color inks shown in Table 3 were obtained.

Preparation Example 7 (Preparation of clear ink)
351.63 parts of solution A (sodium hydroxide 0.1% ion-exchanged water) was charged into the reaction vessel, stirred (about 100 rpm) and cooled, while the polymer obtained in Production Example 1 was 35% methyl ethyl ketone. After dripping 28.57 parts of the solution, the mixture was emulsified by performing ultrasonic dispersion (manufactured by Nippon Seiki Seisakusho, Ultrasonic Generater Nissei Model USS-300T, 300 μA) for 1 hour. Thereafter, the organic solvent was removed, cooled, and adjusted with ion exchange water to obtain an aqueous dispersion of uncrosslinked polymer particles for clear ink having a solid content of 10%.

  The same procedure as in Preparation Example 1 was performed except that the aqueous dispersion of the crosslinked core-shell polymer particles for clear ink was changed to the uncrosslinked polymer particle dispersion obtained above in Preparation Example 1, and the clear ink shown in Table 2 was obtained. It was.

Preparation Examples 8 to 11 (Preparation of clear ink)
In the production of an aqueous dispersion of a crosslinked core-shell polymer particle in which both the core and the shell of Preparation Example 1 are crosslinked, the core is crosslinked in the same manner as in Preparation Example 1 except that the shell is not crosslinked by a crosslinking agent. An aqueous dispersion was obtained.
Next, except that the blending amount of the ink component was changed to the amount shown in Table 2, Preparation Examples 8 and 9 were performed in the same manner as Preparation Example 1, and Preparation Examples 10 and 11 were performed in the same manner as Preparation Example 2. The clear ink shown in Table 2 was obtained.

Preparation Examples 12 and 13 (Preparation of clear ink)
A clear ink shown in Table 2 was obtained in the same manner as in Preparation Example 2 except that the amount of the ink component was changed to the amount shown in Table 2 in Preparation Example 2.

Preparation Example 14 (Preparation of colored ink containing cyan pigment-containing crosslinked polymer particles)
A color ink shown in Table 3 was obtained in the same manner as in Preparation Example 4 except that the amount of the ink component was changed to the amount shown in Table 3 in Preparation Example 4.

Preparation Example 15 (Preparation of colored ink containing cyan pigment-containing crosslinked polymer particles)
A colored ink shown in Table 3 was obtained in the same manner as in Preparation Example 6 except that the amount of the ink component was changed to the amount shown in Table 3 in Preparation Example 6.

Preparation Example 16 (Preparation of colored ink containing magenta pigment-containing crosslinked polymer particles)
A color ink shown in Table 3 was obtained in the same manner as in Preparation Example 5 except that the amount of the ink component was changed to the amount shown in Table 3 in Preparation Example 5.

Preparation Example 17 (Preparation of colored ink containing yellow pigment-containing crosslinked polymer particles)
In Preparation Example 5, the quinacridone pigment used was changed to an azo pigment (C.I. Pigment Yellow 74, manufactured by Sanyo Dye Co., Ltd., trade name: FY7413), and the amount of the ink component was changed to the amount shown in Table 3. Except having changed, it carried out similarly to the preparation example 5, and obtained the colored ink shown in Table 3.

Glossiness evaluation of Examples 1 to 4 and Comparative Example 1 As shown in Table 4, clear ink and colored ink were used, clear ink was set on the yellow head, and colored ink was set on the magenta or cyan head. The secondary color red (RGB values are R: 255, G: 0, B: 0) or green (RGB values are R: 0, G: 255, B: 0) is printed on the Sex was evaluated. The results are shown in Table 4.
For example, Example 1 indicates that clear ink is printed from the yellow head and cyan ink is printed from the cyan head. In that case, the mixing of the clear ink and the cyan ink may be instructed to print green. By measuring the glossiness at the printed portion, the glossiness of the mixed portion of the clear ink and the cyan ink can be evaluated. Since the yellow head uses clear ink, the printed matter is actually printed at a print density equivalent to DUTY 50%.

Evaluation of glossiness of Examples 9 to 10, Reference Examples 5 to 8 and 11 to 14 and Evaluation of image clarity of Examples 1 to 4, 9 and 10, Reference Examples 5 to 8 and 11 to 14, and Comparative Example 1 As shown in Tables 4 and 5, using the clear ink and the colored ink, the clear ink is set on the yellow head and the colored ink is set on the magenta head, and the secondary color red (RGB value is R: 255, G: 0, B: 0) were printed, and glossiness and image clarity were evaluated by the following methods. The results are shown in Tables 4 and 5.
Note that the clear ink is set on the magenta head from the yellow head, and the red ink is instructed to be printed. It is possible to evaluate the glossiness and image clarity of the mixed portion with the ink. The printed matter actually shows a print density equivalent to 50% Duty.

(1) Evaluation of 20 ° Gloss Using a commercially available inkjet printer (manufactured by Seiko Epson Corporation, model number: PX-A650, piezo method), commercially available inkjet photo paper (manufactured by Seiko Epson Corporation, trade name: photographic paper <glossy) > Printed in solid on [Model No .: KA450PSK] (Printing condition = Paper type: EPSON photo paper, Mode setting: Photo), left at 25 ° C for 24 hours, and then glossiness of 20 ° (Nippon Denshoku Industries Co., Ltd.) Product, product name: HANDY GLOSSMETER, product number: PG-1), and the average value was obtained. The larger the value, the higher the glossiness.

(2) Evaluation of 45 ° image clarity Using a commercially available inkjet printer (Seiko Epson Corporation model number: PX-A650, piezo method), commercially available inkjet photographic paper (Seiko Epson Corporation brand name: photographic paper <glossy > Solid printing on model number: KA450PSK [printing condition = paper type: EPSON photo paper, mode setting: photo], left at 25 ° C for 24 hours, and then a 45 ° image clarity measuring device (Suga Test Instruments Co., Ltd.) The product was measured three times by a company, product name: image clarity measuring instrument, product number: ICM-1T), and the average value was obtained. The larger the value, the higher the glossiness.

The criteria for glossiness and image clarity differ depending on the color, but compared to Comparative Example 1 in Table 4, the ink sets of Examples 1-4, 9 and 10 have glossiness and image clarity when printed on dedicated paper. It can be seen that an excellent image can be obtained. The images obtained in the examples of the present invention are also excellent in gloss uniformity.

Claims (10)

An ink set for ink-jet recording comprising a colored ink containing crosslinked polymer particles (A) containing a colorant and a clear ink containing crosslinked polymer particles (B), wherein the crosslinked polymer particles (B) in the clear ink Is a crosslinked core-shell polymer particle having a core-shell structure, the crosslinked core-shell polymer particle core part is a polymer particle crosslinked, and the shell part is crosslinked with a compound having two or more reactive functional groups in the molecule those ink set for ink jet recording.   The ink set for inkjet recording according to claim 1, wherein the colorant is at least one selected from the group consisting of magenta, cyan, and yellow.   The ink set for ink jet recording according to claim 1 or 2, wherein the degree of crosslinking of the entire crosslinked polymer of the crosslinked polymer particles (A) containing a colorant is 0.5 to 15% by weight.   The structural unit of the polymer of the crosslinked polymer particle (A) containing the colorant and the structural unit of the polymer of the crosslinked polymer particle (B) include structural units derived from two or more same monomer species. 4. An ink set for ink jet recording according to any one of 3 above.   At least one of the polymer of the crosslinked polymer particle (A) containing the colorant and the polymer of the crosslinked polymer particle (B) is a structural unit derived from the salt-forming group-containing monomer (a) and the hydrophobic monomer (c). The ink set for inkjet recording according to any one of claims 1 to 4, which is a graft polymer having a structural unit derived from a main chain and a structural unit derived from a macromer (b) in a side chain.   The cross-linked polymer particle (A) containing a colorant is a cross-linked polymer particle obtained by mixing a polymer particle containing a colorant and a cross-linking agent, and the polymer is cross-linked. Ink set for inkjet recording.   The crosslinked polymer particles (A) containing a colorant are polymer particles crosslinked using 0.5 to 15 parts by weight of a crosslinking agent with respect to 100 parts by weight of the polymer of the polymer particles containing a colorant. Item 7. The ink set for inkjet recording according to Item 6.   The ink set for inkjet recording according to claim 6 or 7, wherein the crosslinking agent is a compound having two or more reactive functional groups in the molecule. The inset for inkjet recording according to any one of claims 1 to 8 , wherein a weight ratio (core part / shell part) of the core part to the shell part of the crosslinked core-shell polymer particles is 0.3 to 15. The inset for inkjet recording according to any one of claims 1 to 9, wherein the crosslinked polymer particles (B) in the clear ink are produced by a method having the following steps I and II.
Step I: A dispersion of a core-shell polymer particle obtained by polymerizing a hydrophobic monomer and a crosslinkable monomer having two or more reactive unsaturated groups in the presence of water, an organic solvent and a polymer to crosslink the core part. Obtaining process
Step II: Cross-linked core-shell polymer particles obtained by cross-linking the core-shell polymer particles obtained in Step I using a compound having two or more reactive functional groups in the molecule and both the core portion and the shell portion are cross-linked The process of obtaining