JP2009046595A - Water-based ink for inkjet recording - Google Patents

Abstract

A water-based ink for ink-jet recording containing a quinacridone solid solution pigment that satisfies saturation and has excellent storage stability, an aqueous dispersion used in the ink, and crosslinked polymer particles are provided.
(1) Crosslinked polymer particles for ink jet recording containing a quinacridone solid solution pigment (A) containing two or more kinds of quinacridone compounds, wherein the anionic group is neutralized with a base per 1 g of the crosslinked polymer. And 0.2 mmol / g or more of crosslinked polymer particles for inkjet recording, and (2) an aqueous dispersion and an aqueous ink containing them.
[Selection figure] None

Description

  The present invention relates to crosslinked polymer particles for inkjet recording, and an aqueous dispersion and aqueous ink containing the same.

  The ink jet recording method is a recording method in which ink droplets are directly ejected and adhered to a recording member from very fine nozzles to obtain characters and images. 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.

Patent Document 1 discloses an ink for a jet printer containing a quinacridone solid solution pigment composed of two or more quinacridone compounds.
Patent Document 2 discloses a water-based ink for ink jet recording containing an aqueous dispersion of water-insoluble vinyl polymer particles containing a solid solution magenta pigment, wherein the water-insoluble vinyl polymer contains at least an alicyclic (meth) acrylate (A) and An aqueous ink for ink-jet recording, which is a water-insoluble vinyl polymer copolymerized with a salt-forming group-containing monomer (B), is disclosed.
Patent Document 3 discloses an ink jet recording pigment in which a mixture containing a quinacridone solid solution pigment, a salt-forming group-containing polymer, a neutralizing agent, an organic solvent and water is kneaded and then diluted and dispersed by adding water and / or an organic solvent. An aqueous dispersion is disclosed.
However, the above-described pigment dispersion or water-based ink is not satisfactory in terms of storage stability and saturation.

JP-A-10-219166 JP 2005-29597 A JP 2006-104367 A

  An object of the present invention is to provide a water-based ink for inkjet recording containing a quinacridone solid solution pigment, which satisfies saturation and has excellent storage stability, an aqueous dispersion used in the ink, and crosslinked polymer particles. .

Compared to quinacridone pigments, quinacridone solid solution pigments are excellent in chroma, but are difficult to use in practice because of poor storage stability in ink.
The present inventors have found that the storage stability can be improved while satisfying the saturation by incorporating the quinacridone solid solution pigment into the crosslinked polymer particles having an anionic group neutralized with a base.
That is, the present invention provides the following (1) to (3).
(1) Crosslinked polymer particles containing a quinacridone solid solution pigment (A) containing two or more quinacridone compounds, wherein 0.2 g / g or more of anionic groups neutralized with a base per 1 g of the crosslinked polymer Containing crosslinked polymer particles for inkjet recording.
(2) An aqueous dispersion for inkjet recording containing the crosslinked polymer particles of (1).
(3) A water-based ink for ink-jet recording containing the aqueous dispersion of (2).

  The aqueous ink containing the aqueous dispersion of crosslinked polymer particles for inkjet recording of the present invention is excellent in storage stability while satisfying the saturation.

The aqueous dispersion for inkjet recording and the aqueous ink of the present invention are crosslinked polymer particles containing a quinacridone solid solution pigment (A) containing two or more quinacridone compounds, and are neutralized with a base per 1 g of the crosslinked polymer. It includes a crosslinked polymer particle for inkjet recording containing 0.2 mmol / g or more of an anionic group.
Hereinafter, each component used in the present invention will be described.

[Quinacridone solid solution pigment containing two or more quinacridone compounds (A)]
The quinacridone solid solution pigment (A) (hereinafter also referred to simply as “quinacridone solid solution pigment (A)”) containing two or more quinacridone compounds used in the present invention is excellent by using two or more quinacridone compounds. It is a pigment showing physical properties such as color tone, weather resistance and solvent resistance.
Examples of the quinacridone compound include compounds represented by the following general formula (1).
_{X n -Q-Y m (1} )
(In the formula, Q represents a quinacridone residue or a quinacridonequinone residue, X and Y represent a hydrogen atom, a methyl group, a chloro group, or a methoxy group, and n and m represent an integer of 1 to 4.)
Specific examples thereof include unsubstituted quinacridone, 2,9-dimethylquinacridone, 2,9-dichloroquinacridone, 2,9-dimethoxyquinacridone, 3,10-dimethylquinacridone, 3,10-dichloroquinacridone, 3,10 -Dimethoxyquinacridone, 4,11-dimethylquinacridone, 4,11-dichloroquinacridone, 4,11-dimethoxyquinacridone, quinacridonequinone and the like.

Preferable examples of the quinacridone solid solution pigment (A) include solid solution pigments containing two kinds selected from the group consisting of unsubstituted quinacridone, dimethyl-substituted quinacridone and dichloro-substituted quinacridone. More specifically, (1) a solid solution pigment of unsubstituted quinacridone and dimethyl-substituted quinacridone such as 2,9-dimethylquinacridone, (2) unsubstituted quinacridone and 2,9-dichloroquinacridone, 3,10-dichloro Solid solution pigments with dichloro-substituted quinacridone such as quinacridone, (3) Solid solution pigments with dimethyl-substituted quinacridone such as 2,9-dimethylquinacridone and dichloro-substituted quinacridone such as 2,9-dichloroquinacridone and 3,10-dichloroquinacridone A solid solution pigment comprising a combination of the above is preferred.
Among the above, (1) a solid solution pigment comprising a combination of unsubstituted quinacridone and dimethyl substituted quinacridone and (2) a solid solution pigment comprising a combination of unsubstituted quinacridone and dichloro substituted quinacridone are preferred. More specifically, from the viewpoint of hue, a solid solution pigment comprising a combination of unsubstituted quinacridone (CI Pigment Violet 19 and the like) and 2,9-dimethylquinacridone (CI Pigment Red 122 and the like). And a solid solution pigment composed of a combination of unsubstituted quinacridone (CI Pigment Violet 19 and the like) and 2,9-dichloro substituted quinacridone (CI Pigment Red 202 and the like), and unsubstituted quinacridone (C Pigment Violet 19 etc.) and 2,9-dichloro substituted quinacridone (C.I. Pigment Red 202 etc.) are more preferred.
As the unsubstituted quinacridone, any of α-type, β-type, and γ-type can be used, but β-type or γ-type unsubstituted quinacridone is preferable from the viewpoint of storage stability. For example, a solid solution magenta pigment disclosed in JP-A-10-219166 can also be used.

In the quinacridone solid solution pigment (A), the weight ratio of [unsubstituted quinacridone / dimethyl substituted quinacridone], the weight ratio of [unsubstituted quinacridone / dichloro substituted quinacridone], and the weight ratio of [dimethyl substituted quinacridone / dichloro substituted quinacridone] From the viewpoint of reliability, print density, saturation, etc., the ratio is preferably 5/95 to 95/5, more preferably 10/90 to 90/10.
The quinacridone solid solution pigment (A) can be produced by a known method. For example, (i) a method in which a crude unsubstituted quinacridone and a quinacridone compound are dissolved in an aprotic polar organic solvent in the presence of caustic alkali and neutralized and reprecipitated with an acid (see JP-A-60-35055),
(Ii) A method of pulverizing a crude or auxiliary pigment quinacridone compound in the presence of solubilizing amounts of alcohol and base and isolating the resulting solid solution (see JP-A-2-38463), and (iii) two types Examples include a method of subjecting the above 2,5-diarylaminoterephthalic acid derivative to condensation cyclization, followed by pigmentation treatment (control of crystal form, size, crystal form) (see JP-A-10-219166). It is done.
The form of the quinacridone solid solution pigment (A) may be a powdery, granular, or massive dry pigment, or a wet cake or slurry.
The average particle size of the quinacridone solid solution pigment (A) is preferably 0.01 to 0.3 μm, more preferably 0.03 to 0.2 μm, from the viewpoint of storage stability. In addition, an average particle diameter can be calculated | required from the average value of the long diameter of 100 pigments by the image analysis (20,000 times) by an electron microscope (TEM).

[Crosslinked polymer]
The crosslinked polymer used in the present invention is preferably a crosslinked polymer obtained by crosslinking the polymer with a crosslinking agent (B), and the polymer 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 polymers. From the viewpoint of storage stability, vinyl polymers obtained by addition polymerization of vinyl monomers (vinyl compounds, vinylidene compounds, vinylene compounds) are used. preferable.

[Vinyl polymer (hereinafter also simply referred to as “vinyl polymer”)]
The vinyl polymer includes (a) a salt-forming group-containing monomer (hereinafter also referred to as “(a) component”), (b) a macromer (hereinafter also referred to as “(b) component”) and / or (c) a hydrophobic monomer. A vinyl polymer obtained by copolymerizing a monomer mixture (hereinafter also referred to simply as “monomer mixture”) containing (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 water having a structural unit derived from the component (b) as a side chain. Insoluble vinyl graft polymer.

[(A) salt-forming group-containing monomer]
(A) The salt-forming group-containing monomer is used from the viewpoint of enhancing the storage 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 storage stability and ejection stability.

[(B) Macromer]
(B) The macromer is used from the viewpoint of enhancing the storage stability of the crosslinked polymer particles containing the quinacridone solid solution pigment (A). The macromer is preferably 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 chloroform containing 1 mmol / L of dodecyldimethylamine as a solvent.
(B) Among the macromers, from the viewpoint of the storage stability of the crosslinked polymer particles containing the quinacridone solid solution pigment (A), a styrenic macromer having a polymerizable functional group at one end, containing an aromatic group (meth) One or more selected from the group consisting of acrylate macromers and silicone macromers are preferred.
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 (2).
_{CH 2 = C (CH 3)} -COOC 3 H 6 - [Si (CH _{3) 2} O] _{t -Si (CH 3) 3 (} 2)
(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 and saturation. Moreover, it is also preferable to use (c-1) component and (c-2) component together.

[(D) Hydroxyl-containing monomer]
The monomer mixture may further contain (d) a hydroxyl group-containing monomer (hereinafter also referred to as “component (d)”). (D) The hydroxyl group-containing monomer exhibits an excellent effect of enhancing storage 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 to 30) (meth) acrylate, poly (ethylene glycol (n = 1 to 15) / propylene glycol (n = 1 to 15)) (meth) acrylate, and the like. It is done. Among these, 2-hydroxyethyl (meth) acrylate, polyethylene glycol monomethacrylate, and polypropylene glycol methacrylate are preferable.

[(E) Monomer Represented by Formula (6)]
The monomer mixture may further contain (e) a monomer represented by the following formula (3) (hereinafter also referred to as “component (e)”).
^{_{CH 2 = C (R 1)}} COO (R 2 O) q R 3 (3)
Wherein R ¹ is a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, R ² is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ³ is A monovalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom or a phenyl group optionally having an alkyl group having 1 to 9 carbon atoms, q means the average number of moles added. , 1 to 60, preferably 1 to 30.)
(E) component expresses the outstanding effect of improving discharge property.
As a hetero atom contained in the monomer of Formula (3), a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom are mentioned, for example.
Preferable examples of R ¹ include methyl group, ethyl group, (iso) propyl group and the like.
Preferred examples of the R ² O group include an oxyethylene group, an oxytrimethylene grave, an oxypropane-1,2-diyl group, an oxytetramethylene group, an oxyheptamethylene group, an 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 ³ 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 Preferable examples include an alkyl group having 4 to 30 carbon atoms having a heterocycle and an optionally substituted alkyl group having 1 to 8 carbon atoms.

  Specific examples of the component (e) include methoxypolyethylene glycol (1 to 30: the value of q in the formula (3). 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, butoxypolyethylene 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 3 to 40% by weight, more preferably 4 to 30% by weight, and particularly preferably 5 to 25% by weight from the viewpoint of storage 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 pigment.
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 storage 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 storage 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 storage stability and dischargeability of the resulting dispersion. . The total content of [(a) component + (d) component + (e) component] is preferably 6 to 60% by weight, more preferably from the viewpoint of storage 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.

(Production of polymer)
The polymer 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 and methyl ethyl ketone; esters such as ethyl acetate and the like. Among these, methanol, ethanol, acetone, methyl ethyl ketone, or a mixed solvent of one or more of these and water is 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 used in the present invention is preferably from 5,000 to 500,000, more preferably from 10,000 to 400,000, from the viewpoint of the storage stability of the chroma and the quinacridone solid solution pigment (A), and preferably from 10,000 to 300,000 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 polymer used in the present invention has (a) a salt-forming group derived from 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 formula when the salt-forming group is an anionic group.
{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [acid value of polymer (KOH mg / g) × polymer weight (g) / (56 × 1000)]} × 100
When the salt-forming group is a cationic group, it can be determined by the following formula.
{[Weight of neutralizer (g) / equivalent of neutralizer] / [amine value of polymer (HCL mg / g) × polymer weight (g) / (36.5 × 1000)]} × 100
The acid value and amine value can be calculated from the structural unit of the polymer. 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.

[Crosslinking agent (B)]
In the present invention, as the crosslinking agent (B), a compound having two or more reactive functional groups in the molecule is preferably used in order to appropriately crosslink the polymer. The molecular weight of the crosslinking agent (B) is preferably 120 to 2000, more preferably 150 to 1500, and particularly preferably 150 to 1000, from the viewpoint of easy reaction and storage stability of the resulting crosslinked polymer particles.
The number of reactive functional groups contained in the crosslinking agent (B) is preferably 2 to 4, and most preferably 2 or 3, from the viewpoint of improving the storage stability by controlling the molecular weight. 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, and an oxazoline group.
The crosslinking agent (B) is preferably 50 g or less, more preferably 40 g or less when dissolved in 100 g of water at 25 ° C. from the viewpoint of efficiently crosslinking the surface of the polymer and enhancing the storage stability. More preferably, it is 30 g or less.

Specific examples of the crosslinking agent (B) include the following (a) to (e).
(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-pentanediol 1,6-hexanediol, neopentyl alcohol, diethanolamine, tridiethanolamine, polypropylene glycol, polyvinyl alcohol, pentaerythritol, sorbitol, sorbitan, glucose, mannitol, mannitan, sucrose, glucose and the like.
(B) Compound having two or more epoxy groups in the molecule: for example, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin triglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether Polyglycidyl ethers such as trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, hydrogenated bisphenol A type diglycidyl 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.
Among these, (b) a compound having two or more epoxy groups in the molecule is preferable, and ethylene glycol diglycidyl ether and trimethylolpropane polyglycidyl ether are particularly preferable.
(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

The polymer used in the present invention has a reactive group (crosslinkable functional group) capable of reacting with the crosslinking agent (B), and a suitable combination example of both is as follows.
When the reactive group of the polymer is an anionic group such as a carboxy group, a sulfonic acid group, a sulfuric acid group, a phosphonic acid group, or a phosphoric acid group, the crosslinking agent (B) is the above (a), (b), (d) And (f) compounds are preferred.
When the reactive group of the polymer is an amino group, the crosslinking agent (B) is preferably the compounds (b), (c) and (e).
When the reactive group of the polymer is a hydroxyl group, the crosslinking agent (B) is preferably the compounds (c) and (e).
When the reactive group of the polymer is an isocyanate group or an epoxy group, the crosslinking agent (B) is preferably the compounds (a), (d) and (e).
Among the above combinations, from the viewpoint of controlling the polymer so as to impart an appropriate cross-linked structure, the cross-linking agent (B) preferably has a functional group that reacts with the anionic group of the polymer. A combination with a compound having two or more epoxy groups therein is particularly preferred.

Polymer having an anionic group such as a carboxy group, a sulfonic acid group, and a phosphoric acid group, an amino group, a hydroxyl group, an isocyanate group, and an epoxy group as a reactive group (crosslinkable functional group) that can react with the crosslinking agent (B) Can be produced by copolymerizing a polymerizable monomer composition containing the monomer having a reactive group in the production of the above-described polymer.
As the polymer having a salt-forming group such as an anionic group or an amino group as a reactive group capable of reacting with the crosslinking agent (B), a polymer obtained by copolymerizing the above-mentioned monomer having a salt-forming group can be used. Moreover, as a polymer which has a hydroxyl group as a reactive group which can react with a crosslinking agent (B), the polymer which copolymerized the above-mentioned hydroxyl-containing monomer can be used.
As a polymer having an epoxy group as a reactive group capable of reacting with the crosslinking agent (B), a monomer having an epoxy group, specifically, a polymer obtained by copolymerizing glycidyl (meth) acrylate can be used. Examples of the polymer having an isocyanate group as a reactive group capable of reacting with the crosslinking agent (B) include (i) a polymer having an isocyanate group, for example, a polymer copolymerized with isocyanate ethyl (meth) acrylate, and (ii) an unsaturated polyester polyol. And a polymer obtained by copolymerizing an isocyanate-terminated prepolymer obtained from an isocyanate.

[Crosslinked polymer particles containing quinacridone solid solution pigment (A)]
The crosslinked polymer particles containing the quinacridone solid solution pigment (A) (hereinafter also referred to as “solid solution pigment-containing crosslinked polymer particles”) are used to improve storage stability while satisfying the saturation.
The crosslinked polymer particles for ink jet recording containing the quinacridone solid solution pigment (A) containing two or more kinds of quinacridone compounds of the present invention have 0.2 mmol / anionic group neutralized with a base per 1 g of the crosslinked polymer. g or more.
Specific examples of the anionic group neutralized with a base include carboxy ion (—COOM ¹ ), sulfonate ion (—SO ₃ M ¹ ), phosphate ion (—PO ₃ M ¹ ₂ ) and the like.
In the above chemical formula, M ¹ may be the same or different, and alkali metals such as lithium, sodium and potassium; ammonium; monomethylammonium group, dimethylammonium group, trimethylammonium group; monoethylammonium group; Organic ammonium and the like.
Examples of the base include alkali hydroxides such as sodium hydroxide, alkaline earth hydroxides, organic amines such as amines and triethanolamine, basic amino acids, and the like.
The anionic group neutralized with a base is considered to dissociate and contribute to the stability of the crosslinked polymer particles by charge repulsion between ions of the anion.

From the viewpoint of improving the stability due to charge repulsion between the crosslinked polymer particles for ink jet recording containing the quinacridone solid solution pigment (A) containing two or more kinds of quinacridone compounds, it is neutralized with a base per 1 g of the crosslinked polymer. The content of the anionic group (anion) is 0.2 mmol / g or more, preferably 0.5 mmol / g or more, more preferably 1.1 mmol / g or more, and the upper limit thereof is preferably 5 mmol or less, More preferably, it is 3 mmol or less, More preferably, it is 1.7 mmol or less. From these viewpoints, the content is preferably 0.2 to 5 mmol / g, more preferably 0.5 to 5 mmol / g, still more preferably 0.5 to 3 mmol / g, and particularly preferably 1.1 to 3 mmol. / G, most preferably 1.1 to 1.7 mmol / g.
As the method for producing the crosslinked polymer particles, from the viewpoint of storage stability, the polymer particles containing the quinacridone solid solution pigment (A) are obtained by using the quinacridone solid solution pigment (A) and the polymer. A method of producing the crosslinked polymer particles by mixing the polymer particles containing the obtained quinacridone solid solution pigment (A) and the crosslinking agent (B) and crosslinking the polymer to obtain crosslinked polymer particles is preferable.

The manufacturing method by the said process I and the process II can be performed by the following process (1)-(3), for example.
Step (1): Dispersion of a polymer, an organic solvent, a quinacridone solid solution pigment (A), water, and, if necessary, a mixture containing a neutralizer to disperse polymer particles containing the quinacridone solid solution pigment (A) Step (2): A step of removing the organic solvent from the dispersion obtained in step (1) to obtain an aqueous dispersion of polymer particles containing the quinacridone solid solution pigment (A) Step (3) Step of cross-linking polymer of polymer particles containing quinacridone solid solution pigment (A) obtained in step (2) with cross-linking agent (B) to obtain solid solution pigment-containing cross-linked polymer particle aqueous dispersion

In the step (1), the polymer is first dissolved in an organic solvent, and then the quinacridone solid solution pigment (A), water, and, if necessary, a neutralizing agent and a surfactant are added to the obtained organic solvent solution. In addition, a method of mixing to obtain an oil-in-water dispersion is preferred. In the mixture, the quinacridone solid solution pigment (A) is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, and the organic solvent is preferably 10 to 70% by weight, more preferably 10 to 50% by weight. Is preferably 2 to 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 at 20 ° C. is preferably 5 g or more, more preferably 10 g or more, more specifically preferably 5 to 80 g, more preferably 10 to 50 g, especially 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. The dispersion in the step (1) is preferably 5 to 50 ° C, more preferably 5 to 35 ° C, and the dispersion time is preferably 1 to 30 hours, more preferably 2 to 25 hours.
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 apparatuses, high-speed stirring and mixing apparatuses such as Ultra Disper [Asada Steel Co., Ltd., trade name], Ebara Milder [Ebara Manufacturing Co., Ltd., trade name], TK Homomixer [Primix Co., Ltd., trade name] are preferable. .
As means for giving 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) Examples thereof include chamber type high-pressure homogenizers such as homo-valve type high-pressure homogenizers, microfluidizers (trade name), and nanomizers (trade name). A plurality of these devices can be combined. Among these, 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 the quinacridone solid solution pigment (A) can be obtained from the obtained dispersion by distilling off the organic solvent by a known method to form an aqueous system. . The organic solvent in the aqueous dispersion containing the obtained polymer particles is preferably substantially removed, but may remain as long as the object of the present invention is not impaired, and may be removed again after crosslinking as necessary. . 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 quinacridone solid solution pigment (A) is one in which the solid content of the polymer containing the quinacridone solid solution pigment (A) 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 the quinacridone solid solution pigment (A) and the polymer. For example, a particle form in which the quinacridone solid solution pigment (A) is included in the polymer, a particle form in which the quinacridone solid solution pigment (A) is uniformly dispersed in the polymer, and a particle in which the quinacridone solid solution pigment (A) is exposed on the polymer particle surface The form etc. are included.

In the step (3), from the viewpoint of saturation and storage stability, the polymer particles containing the quinacridone solid solution pigment (A) and the crosslinking agent (B) are mixed to crosslink the polymer, thereby solid polymer pigment-containing crosslinked polymer particles. More specifically, an aqueous dispersion of polymer particles containing the quinacridone solid solution pigment (A) and the crosslinking agent (B) are mixed to crosslink the polymer, and the solid polymer pigment-containing crosslinked polymer particles A method of obtaining an aqueous dispersion is preferred. At that time, it is preferable from the viewpoint of crosslinking efficiency and storage stability due to surface crosslinking that the polymer is water-insoluble and the amount of the crosslinking agent dissolved in water is as described above.
In step (3), the catalyst, solvent, temperature, and time can be appropriately selected and determined depending on the crosslinking agent (B) to be used. The crosslinking reaction time is preferably 0.5 to 10 hours, more preferably 1 to 5 hours, and the crosslinking reaction temperature is preferably 40 to 95 ° C.
The amount of the crosslinking agent (B) (compound having two or more reactive functional groups in the molecule) is 0.3 / 100 by weight ratio of [crosslinking agent (B) / polymer] from the viewpoint of storage stability. -35/100 are preferable, 2 / 100-30 / 100 are more preferable, 5 / 100-25 / 100 are still more preferable, and 5 / 100-20 / 100 are especially preferable.
From the viewpoint of improving the stability of the cross-linked polymer particles, the cross-linking agent (B) has a functional group that reacts with the anionic group of the polymer, and the amount of the cross-linking agent (B) used per 1 g of the polymer is The amount reacting with 0.1 to 3 mmol / g of the functional group is preferred, the amount reacting with 0.2 to 3 mmol / g is more preferred, the amount reacting with 0.4 to 2.5 mmol / g is more preferred, An amount that reacts with 7 to 2.5 mmol / g is particularly preferred.
In addition, the polymer crosslinking step can be performed by mixing the polymer particle dispersion containing the quinacridone solid solution pigment (A) obtained in the step (1) and the crosslinking agent (B). In this case, an aqueous dispersion of the solid solution pigment-containing crosslinked polymer particles is obtained by performing the step of removing the organic solvent from the dispersion of the crosslinked polymer particles obtained in the crosslinking step in the same manner as in the step (2). be able to.

Here, the crosslinking rate (mol%) of the crosslinked polymer particles obtained from the following formula (4) is preferably 10 to 80 mol%, more preferably 20 to 80 mol%, and still more preferably, from the viewpoint of storage stability. 30 to 60 mol%. The crosslinking rate is calculated from the amount of crosslinking agent (B) used and the number of moles of reactive groups, the amount of polymer used and the number of moles of reactive groups of the polymer that can react with the reactive group of crosslinking agent (B). It is a value that can be.
Crosslinking rate (mol%) = [number of moles of reactive group of crosslinking agent × 100 / number of moles of reactive group capable of reacting with crosslinking agent of polymer] (4)
In the formula (4), “the number of moles of the reactive group of the crosslinking agent” is a value obtained by dividing the weight of the crosslinking agent used by the equivalent of the reactive group. That is, the number of moles of the crosslinking agent used is multiplied by the number of reactive groups in one molecule of the crosslinking agent.

[Aqueous dispersion containing solid solution pigment-containing crosslinked polymer particles and aqueous ink]
The aqueous dispersion for inkjet recording of the present invention is an aqueous dispersion containing solid solution pigment-containing crosslinked polymer particles, and can be preferably obtained by the steps (1) to (3).
The content of the quinacridone solid solution pigment (A) in the aqueous dispersion and aqueous ink of the present invention is preferably 1 to 30% by weight, and 2 to 20% by weight from the viewpoint of increasing storage stability, saturation and printing density. More preferred is 2 to 15% by weight.
The weight ratio of the polymer to the quinacridone solid solution pigment (A) used in the present invention [polymer / quinacridone solid solution pigment (A)] is preferably 10/90 to 90/10 from the viewpoint of enhancing storage stability. 20/80 to 80/20 is more preferable, and 20/80 to 50/50 is particularly preferable.
The aqueous dispersion of the present invention may be used as it is as a water-based ink, but a wetting agent, a penetrating agent, a dispersant, a viscosity modifier, an antifoaming agent, an antifungal agent, and a rust-preventing agent that are commonly used in water-based inks for inkjet recording. Etc. may be added.

The solid solution pigment-containing crosslinked polymer particles and the water content in the aqueous dispersion for inkjet recording and the water-based ink are as follows from the viewpoints of saturation and storage stability.
The content of the solid solution pigment-containing crosslinked polymer particles is preferably 5 to 40% by weight, more preferably 5 to 35% by weight.
The content of water is preferably 40 to 80% by weight, and more preferably 50 to 80% by weight.
Even if the aqueous dispersion and aqueous ink containing the solid solution pigment-containing crosslinked polymer particles of the present invention have a high concentration, they can be printed at a high printing density because of excellent storage stability.
The content of the pigment in the aqueous dispersion for inkjet recording is preferably 10 to 40% by weight, more preferably 15 to 35% by weight, from the viewpoints of printing density and storage stability.
The content of the pigment in the water-based ink for inkjet recording is preferably 4 to 20% by weight, more preferably 5 to 15% by weight, from the viewpoint of printing density and storage stability.
The average particle size of the solid solution pigment-containing crosslinked polymer particles in the obtained water dispersion and water-based ink is preferably 10 to 500 nm, more preferably 30 to 300 nm, particularly from the viewpoint of preventing clogging of the printer nozzle and storage stability. Preferably it is 50-200 nm. The average particle size is measured by the method described in the examples.
The preferred surface tension (20 ° C.) of the aqueous dispersion and aqueous ink of the present invention is preferably 30 to 70 mN / m, more preferably 35 to 68 mN / m, and more preferably aqueous ink. Is 25-50 mN / m, more preferably 27-45 mN / m.
The viscosity (20 ° C.) at a solid content of 10% by weight of the aqueous dispersion is preferably 2 to 6 mPa · s, and more preferably 2 to 5 mPa · s, in order to obtain a good viscosity when used as a water-based ink. 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 water-based ink is preferably 4-10.
The ink jet method to which the water-based ink of the present invention is applied is not limited, but is particularly suitable for a piezo ink jet printer.

In the following production examples, examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified. In addition, the measuring method of a weight average molecular weight, a viscosity, and an average particle diameter is as follows.
(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.
(2) Viscosity measurement Using a RE80 viscometer manufactured by Toki Sangyo Co., Ltd., using a standard rotor (1 ° 34 ′ × R24), measuring temperature 20 ° C., measuring time 1 minute, rotation speed 100 rpm It measured on condition of this.
(3) Measurement of average particle diameter of solid solution pigment-containing crosslinked polymer particles Measurement was performed using a laser particle analysis system ELS-8000 (cumulant analysis) manufactured by Otsuka Electronics Co., Ltd. The measurement conditions are a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and an integration count of 100. The refractive index of water (1.333) is input as the refractive index of the dispersion solvent. The measurement concentration was about 5 × 10 ⁻³ wt%.

Production Examples 1-3
In a reaction vessel, 20 parts of MEK, 0.03 part of a polymerization chain transfer agent (2-mercaptoethanol) and 10% of 200 parts of the monomer mixture shown in Table 1 are mixed and mixed, and nitrogen gas replacement is sufficiently performed and mixed. A solution was obtained.
On the other hand, the remaining 90% of the monomer mixture shown in Table 1 was charged into a dropping funnel, and 0.27 part of the polymerization chain transfer agent, 60 parts of MEK, and a radical polymerization initiator (2,2′-azobis (2,4-dimethyl). 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 in which 0.3 part of the radical polymerization initiator was dissolved in 5 parts of MEK was added, and further aged at 65 ° C. for 2 hours and at 70 ° C. for 2 hours to obtain a polymer solution. . Table 1 shows the weight average molecular weight and acid value of the obtained polymer. The acid value (KOHmg / g) of the polymer can be calculated from the ratio of methacrylic acid and the molecular weight.

The details of the monomers shown in Table 1 are as follows.
Styrene macromer: manufactured by Toa Gosei Co., Ltd., trade name: AS-6S, number average molecular weight: 6000, polymerizable functional group: methacryloyloxy group / polyethylene glycol monomethacrylate (ethylene oxide average added mole number = 9, terminal methyl group) : Shin-Nakamura Chemical Co., Ltd., trade name: NK ester M-90G
Polypropylene glycol monomethacrylate (propylene oxide average added mole number = 9, terminal hydroxyl group): manufactured by NOF Corporation, trade name: BLEMMER PP-500

Example 1
<Water dispersion manufacturing process>
25 parts of the polymer obtained by drying the polymer solution obtained in Production Example 1 under reduced pressure was mixed with 50 parts of MEK (methyl ethyl ketone). I. Pigment violet 19 and C.I. 100 parts of CI Pigment Red 202 quinacridone solid solution pigment (CI Pigment Violet 19 / C.I. Pigment Red 202 (weight ratio) = 20/80) was added and mixed well, and further 5% sodium hydroxide aqueous solution and 25% 4.6 parts and 3.9 parts (neutralization degree 60%) of ammonia aqueous solution were added, respectively, and stirred for 60 minutes at 5 ° C. and 7000 rpm using a TK homomixer (Primix Co., Ltd., trade name). The obtained mixture was diluted with ion-exchanged water so as to be a 20% aqueous solution, and it was 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, MEK was completely removed at 60 ° C. under reduced pressure, a part of water was further removed, and a 5 μm filter (acetylcellulose membrane, outer Diameter: 2.5cm, manufactured by Fuji Photo Film Co., Ltd.) Filtered with a 25 mL needleless syringe (made by Terumo Co., Ltd.), and removed coarse particles to contain solid solution pigment with a solid content concentration of 20% An aqueous dispersion of vinyl polymer particles was obtained.

<Aqueous dispersion production process of solid solution pigment-containing crosslinked polymer particles>
A crosslinking agent (manufactured by Nagase ChemteX Corp., trade name: Denacol EX-321, epoxy equivalent 140, amount dissolved in 100 g of water with respect to 100 parts of the aqueous dispersion (4 parts of polymer) of the obtained pigment-containing vinyl polymer particles 0.07 part (about 27 g (25 ° C.)) was added and stirred well at 90 ° C. for 1 hour. After 1 hour, it was cooled to room temperature and filtered with a 25 mL needleless syringe (Terumo Corporation) with a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.) An aqueous dispersion of solid solution pigment-containing crosslinked polymer particles having a solid content concentration of 20% was obtained.

Calculation of the crosslinking rate (mol%) of the crosslinked polymer particles was performed by the following formula (4).
Crosslinking rate (mol%) = [number of moles of reactive group of crosslinking agent × 100 / number of moles of reactive group capable of reacting with crosslinking agent of polymer] (4)
In the formula (4), “the number of moles of the reactive group of the crosslinking agent” is a value obtained by dividing the weight of the crosslinking agent used by the epoxy equivalent.
In Example 1, 0.07 part of a crosslinking agent (Denacol EX-321, epoxy equivalent 140) is reacted with 4 parts of a water-insoluble polymer. Therefore, the number of moles of the reactive group of the cross-linking agent is 0.07 / 140 = 0.0005.
Here, since the crosslinking agent (Denacol EX-321) reacts with the carboxy group, the number of moles of the reactive group that can react with the crosslinking agent that the polymer has is the number of moles of methacrylic acid (molecular weight 86) that the polymer has. ,
4 × 0.1 / 86 = 0.0006
Therefore, the crosslinking rate of the water-insoluble crosslinked polymer particles is 0.0005 × 100 / 0.0046 = 10.9 (mol%).
The amount of anionic groups (mmol / g) neutralized with a base is 72/56 × 0.6 × (4 / 4.07) because the acid value of the polymer is 72 and the neutralization rate is 60%. = 0.76 mmol / g
The amount of the crosslinking agent used per 1 g of polymer is an amount that reacts with 0.0005 / 4 × 1000 = 0.125 mmol / g in terms of anionic group amount.

<Ink manufacturing process>
To 40 parts of an aqueous dispersion of the obtained solid solution pigment-containing crosslinked polymer particles, 7 parts of triethylene glycol monobutyl ether, 1 part of Surfynol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), Proxel XL2 (manufactured by Avicia Corporation) 3 parts and 36 parts of ion-exchanged water were mixed, and glycerin and water were added so that the viscosity at 20 ° C. was 4 mPa · s to prepare a total of 100 parts. The obtained mixture was filtered with a 25 mL needleless syringe equipped with a 5 μm filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.) to remove coarse particles. Ink was obtained.

Comparative Example 1
In Example 1, a water-based ink was obtained in the same manner as in Example 1 except that the crosslinking was not performed in the aqueous dispersion production step of the solid solution pigment-containing crosslinked polymer particles.
Comparative Example 2
In Example 1, C.I. I. A water-based ink was obtained in the same manner as in Example 1 except that CI Pigment Red 122 was used and crosslinking was not performed.
Example 2
A water-based ink was obtained in the same manner as in Example 1 except that 0.14 part of the crosslinking agent was used in Example 1.
Example 3
In Example 1, the polymer of Production Example 2 was used, the degree of neutralization in the aqueous dispersion production process was 49%, and the cross-linking ratio of the polymer in the aqueous dispersion production process of the solid solution pigment-containing crosslinked polymer particles was 51 mol%. Thus, a water-based ink was obtained in the same manner as in Example 1 except that the crosslinking agent was used.
Example 4
Example 1 is the same as Example 1 except that the polymer of Production Example 3 was used and a crosslinking agent was used so that the crosslinking rate of the polymer in the aqueous dispersion production process of the solid solution pigment-containing crosslinked polymer particles was 36 mol%. A water-based ink was obtained in the same manner.
Example 5
In Example 1, using the polymer of Production Example 2, the degree of neutralization in the aqueous dispersion production process is 10%, and the crosslinking rate of the polymer in the aqueous dispersion production process of the solid solution pigment-containing crosslinked polymer particles is 90 mol%. Thus, a water-based ink was obtained in the same manner as in Example 3 except that the crosslinking agent was used.

Example 6
In Example 1, the pigment is C.I. I. Pigment violet 19 and C.I. Pigment Red 122 quinacridone solid solution pigment (CI Pigment Violet 19 / CI Pigment Red 122 (weight ratio) = 90/10), except that 0.14 parts of a crosslinking agent was used. A water-based ink was obtained in the same manner as in Example 1.
Example 7
In Example 1, the pigment is C.I. I. Pigment violet 19 and C.I. Pigment Red 122 quinacridone solid solution pigment (CI Pigment Violet 19 / C.I. Pigment Red 122 (weight ratio) = 80/20), except that 0.14 part of cross-linking agent was used. A water-based ink was obtained in the same manner as in Example 1.

Next, the storage stability and saturation of the water-based inks obtained in Examples 1 to 7 and Comparative Examples 1 and 2 were evaluated by the following methods. The results are shown in Table 2.
(1) Storage stability The sealed ink described in Examples was allowed to stand at 70 ° C. for one week, and the rate of change was measured by the above-described method for measuring the average particle diameter of the solid solution pigment-containing crosslinked polymer particles.
The evaluation was evaluated as ◎ if the rate of change in average particle size was within ± 5%, ○ if it was within ± 10%, Δ if it was within ± 20%, and × if it exceeded ± 20%. More than Δ is the area that can be actually used.
(2) Saturation Using a printer (model number: EM-930C) manufactured by Seiko Epson Corporation, solid printing (printing condition = paper type: plain paper) on commercially available high-quality plain paper (Xerox Corporation, trade name: XEROX4024) , Mode setting: Fine], and left at 25 ° C. for 24 hours, then set the optical densitometer SpectroEye (manufactured by Gretag Macbeth) to the measurement mode L ^* a ^* b ^* and print (5.1 cm × 8.0 cm) An average value was obtained by measuring a total of five points at the center and four corners, and saturation was calculated from the average value. Saturation is a scale that represents the degree of vividness of a color, and is represented by the distance from an achromatic color of equal brightness. Here, as shown in the following equation, the saturation is represented by the L ^* a ^* b ^* color system (where L ^* is lightness, a ^* is chromaticity in the red-green direction, and b ^* is in the yellow-blue direction). ) And the distance from the center (position where both a ^* b ^* are 0: achromatic color).
Saturation = {(a ^* ) ² + (b ^* ) ² } ^1/2
The saturation is preferably 58 or more.

  From Table 2, it can be seen that the water-based inks of Examples 1 to 7 are superior in storage stability to the water-based ink of Comparative Example 1 and have better chroma than the water-based ink of Comparative Example 2. In particular, the storage stability of Examples 3 and 4 is excellent.

Claims (10)

  Crosslinked polymer particles containing a quinacridone solid solution pigment (A) containing two or more quinacridone compounds, and containing 0.2 mmol / g or more of an anionic group neutralized with a base per 1 g of the crosslinked polymer. Crosslinked polymer particles for inkjet recording.   The crosslinked polymer particles for inkjet recording according to claim 1, wherein the content of the anionic group neutralized with a base is 0.2 to 5 mmol / g.   The crosslinked polymer particles for inkjet recording according to claim 1 or 2, obtained by mixing polymer particles containing the quinacridone solid solution pigment (A) and the crosslinking agent (B) and crosslinking the polymer.   The crosslinking agent (B) has a functional group that reacts with the anionic group of the polymer, and the amount of the crosslinking agent (B) used per 1 g of the polymer reacts with 0.1 to 3 mmol / g of the anionic group of the polymer. The crosslinked polymer particles for inkjet recording according to claim 3, wherein   The crosslinked polymer particle for inkjet recording according to any one of claims 1 to 4, wherein a crosslinking rate of the crosslinked polymer is 10 to 80 mol%.   The ink jet recording according to any one of claims 1 to 5, wherein the quinacridone solid solution pigment (A) is a solid solution pigment of unsubstituted quinacridone and dimethyl-substituted quinacridone and / or a solid solution pigment of unsubstituted quinacridone and dichloro-substituted quinacridone. Cross-linked polymer particles.   The crosslinked polymer particles for inkjet recording according to any one of claims 1 to 6, wherein the polymer is a water-insoluble vinyl graft polymer.   An aqueous dispersion for inkjet recording, comprising the crosslinked polymer particles for inkjet recording according to any one of claims 1 to 7.   A water-based ink for ink-jet recording, comprising the water dispersion according to claim 8.   The water-based ink for inkjet recording according to claim 9, wherein the pigment content is 4 to 20% by weight.