JP2010265398A - Aqueous ink for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aqueous dispersion and aqueous ink for inkjet recording having high print density, excellent storage stability, and high chroma saturation and a method for producing the aqueous dispersion for inkjet recording. <P>SOLUTION: (1) The aqueous dispersion for inkjet recording containing anionic polymer particles including a solid solution pigment containing dichloroquinacridone and cationic polymer, wherein a polymer constituting the polymer particles includes 30-80 wt.% of a constituent unit derived from benzyl methacrylate and/or benzyl acrylate, (2) the aqueous ink for inkjet recording containing the aqueous dispersion, and (3) the method for producing the aqueous dispersion for inkjet recording are provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an aqueous dispersion for inkjet recording, an aqueous ink containing the same, and a method for producing an aqueous dispersion 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.
In recent years, inks using pigments as colorants have been widely used in order to impart weather resistance and water resistance to printed matter. Particularly for magenta and red inks, quinacridone pigments having excellent weather resistance are used. However, since the structure is simple, there is a drawback that there are few types of hues. Thus, attempts have been made to obtain various hues by using a solid solution with two or more quinacridones or other organic pigments, so-called solid solution pigments. The solid solution pigment has a characteristic that it has a unique hue and a vivid color tone while maintaining the weather resistance unique to quinacridone.

For example, Patent Document 1 discloses crosslinked polymer particles containing a quinacridone solid solution pigment containing two or more kinds of quinacridone compounds for the purpose of improving saturation and storage stability, and neutralized with a base per 1 g of the crosslinked polymer. A water-based ink containing crosslinked polymer particles for inkjet recording, containing 0.2 mmol / g or more of the anionic group formed is disclosed.
Patent Document 2 includes a magenta solid solution pigment and a polymer capable of dispersing the pigment in an ink composition for the purpose of improving color developability and ink reliability, and the polymer includes a styrene macromer and a salt. An ink composition is disclosed which is obtained by copolymerizing a monomer composition containing a product group-containing monomer.
Patent Document 3 includes an aqueous dispersion of water-insoluble vinyl polymer particles containing a solid solution magenta pigment for the purpose of improving long-term storage reliability, and the water-insoluble vinyl polymer is at least an alicyclic (meth) acrylate (A). And a water-based ink for inkjet recording, which is a water-insoluble vinyl polymer obtained by copolymerization of a monomer (B) containing a salt-forming group.

On the other hand, as an example using a cationic polymer, Patent Document 4 discloses a cationic water-soluble polymer such as a pigment, an anionic dispersant, or polyethyleneimine for the purpose of improving the saturation, density, etc. in plain paper printing. An aqueous pigment ink comprising a compound and an aqueous medium is disclosed.
Further, as an example using a benzyl acrylate monomer, Patent Document 5 describes that 50% by weight or more of benzyl acrylate, 10% by weight or more of styrene monomer and the like for the purpose of improving storage stability, ejection stability, color developability and the like. Ink jet recording inks containing a pigment in which a styrene macromonomer and 15% by weight or less of (meth) acrylic acid are polymerized and dispersed using a polymer having a specific acid value are disclosed.

JP 2009-46595 A International Publication No. 2006/137414 Pamphlet JP 2005-29597 A JP 2004-123865 A JP 2007-99922 A

When quinacridone pigments are used in water-based inks for ink jet recording, simply increasing the amount of pigment in the ink to improve the printing density will improve the printing density but lower the saturation and improve the storage stability of the ink. There was a problem of lowering. Further, when a solid solution pigment containing dichloroquinacridone is used, the chroma is improved to some extent, but higher chroma is required, and the solid solution pigment has a problem that the storage stability of the ink tends to be lowered.
An object of the present invention is to provide an aqueous dispersion for inkjet recording and an aqueous ink having a high printing density, excellent storage stability, and high saturation, and a method for producing an aqueous dispersion for inkjet recording.

The present invention provides the following (1) to (3).
(1) An anionic polymer particle containing a solid solution pigment containing dichloroquinacridone, and an aqueous dispersion for inkjet recording containing a cationic polymer, wherein the polymer constituting the anionic polymer particle is benzyl methacrylate and / or benzyl An aqueous dispersion for ink-jet recording, comprising 30 to 80% by weight of a structural unit derived from acrylate.
(2) A water-based ink for ink jet recording containing the water dispersion of (1).
(3) The method for producing an aqueous dispersion for inkjet recording according to (1), comprising the following step I.
Step I: A step of obtaining a water dispersion (A) by adding a cationic polymer to an aqueous dispersion (a) containing anionic polymer particles containing a solid solution pigment containing dichloroquinacridone.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the aqueous dispersion for inkjet recording and aqueous ink which have high printing density, is excellent in storage stability, and is high in saturation, and the aqueous dispersion for inkjet recording can be provided.

The aqueous dispersion for inkjet recording and the aqueous ink of the present invention are anionic polymer particles containing a solid solution pigment containing dichloroquinacridone, and an aqueous dispersion for inkjet recording containing a cationic polymer, and constitutes the anionic polymer particles. The polymer is characterized in that it contains 30 to 80% by weight of structural units derived from benzyl methacrylate and / or benzyl acrylate.
The inventors of the present invention have examined the cause of poor storage stability and insufficient saturation when a solid solution pigment containing dichloroquinacridone is used in an aqueous ink for inkjet recording. As a result, since the solid solution pigment is obtained by crystallizing molecules having different structures, the crystal is disordered. Therefore, it is considered that aggregates are formed by recrystallization in dispersion or in a solvent. Thus, it has been found that by adopting the above configuration, not only the storage stability and saturation but also the printing density can be improved. Hereafter, each component etc. which are used for this invention are demonstrated.

[Anionic polymer particles]
The aqueous dispersion for ink jet recording and the water-based ink of the present invention are anionic polymer particles containing a solid solution pigment containing dichloroquinacridone, wherein the polymer constituting the polymer particles is derived from benzyl methacrylate and / or benzyl acrylate It contains anionic polymer particles containing 30 to 80% by weight of units.
Here, “anionic” in the present specification means that when an unneutralized substance is dispersed or dissolved in pure water, the pH becomes less than 7, or the substance is insoluble in pure water and has a pH of When it cannot be measured clearly, it means that the zeta potential of the dispersion dispersed in pure water becomes negative.
The average particle diameter of the anionic polymer particles containing the solid solution pigment is preferably 50 to 300 nm, more preferably 60 to 200 nm, and still more preferably 70 to 150 nm from the viewpoints of dispersibility and printing density. The average particle diameter is measured by a dynamic light scattering method, and specifically measured by the method of the example.
The anionic polymer particles used in the present invention are formed of a solid solution pigment containing at least dichloroquinacridone and a polymer containing 30 to 80% by weight of a structural unit derived from benzyl methacrylate and / or benzyl acrylate. Examples of the polymer particle form include a particle form in which a pigment is included in a polymer, a particle form in which a pigment is uniformly dispersed in a polymer, and a particle form in which a pigment is exposed on the surface of a polymer particle.
From the viewpoint of improving the storage stability, the anionic polymer particles are more preferably used in the form of crosslinked polymer particles obtained by crosslinking the polymer in the polymer particles with a crosslinking agent.

[Solid solution pigment]
The solid solution pigment used in the present invention contains at least dichloroquinacridone.
Dichloroquinacridone, when used as one component of a solid solution pigment, exhibits the effect of increasing the transparency and saturation of the solid solution pigment itself due to a change in the electronic state derived from the chlorine group, and therefore is used from the viewpoint of color development.
Examples of dichloroquinacridone include 2,9-dichloroquinacridone, 3,10-dichloroquinacridone, and 4,11-dichloroquinacridone.
Examples of the pigment to be in solid solution with dichloroquinacridone include unsubstituted quinacridone such as β-type and γ-type, and dimethylquinacridone.
Among the solid solution pigments, a solid solution pigment composed of a combination of 2,9-dichloroquinacridone (CI Pigment Red 202) and unsubstituted quinacridone (CI Pigment Violet 19) is more preferable.
In the solid solution pigment, the content of dichloroquinacridone is preferably 5 to 95% by weight, more preferably 10 to 90% by weight, and still more preferably 15 to 85% by weight.
Said solid solution pigment can be used individually or in mixture of 2 or more types in arbitrary ratios, and may use together with another coloring agent, for example, a pigment, in the range which does not impair the effect of this invention.

[Anionic polymer]
The anionic polymer used for the anionic polymer particles containing the solid solution pigment containing dichloroquinacridone (hereinafter, also simply referred to as “anionic polymer particles” or “polymer particles”) includes the print density of the aqueous dispersion and the water-based ink, and From the viewpoint of improving storage stability, a water-insoluble polymer is preferable.
Here, the water-insoluble polymer is a polymer having a dissolution amount of 10 g or less when 100 g of polymer solid content is dried at 105 ° C. for 2 hours, reaching a constant weight, and then dissolved in 100 g of water at 25 ° C. The amount of dissolution is preferably 5 g or less, more preferably 1 g or less. The dissolution amount is the dissolution amount when the anionic group of the polymer is neutralized 100% with sodium hydroxide.
The polymer constituting the anionic polymer particles contains 30 to 80% by weight of a structural unit derived from benzyl methacrylate and / or benzyl acrylate from the viewpoint of saturation, storage stability and printing density, preferably 40 to 80%. % By weight, more preferably 50 to 75% by weight, still more preferably 60 to 75% by weight.
The polymer is preferably composed of structural units derived from monomers having the same polymerizable group, and more preferably the same polymerizable group is a methacryloyl group, from the viewpoint of printing density and storage stability. . This is because the polymerization rate of monomers having the same polymerizable group is almost the same, so that the composition of the obtained polymer molecule becomes uniform, and the monomer can be introduced into the polymer molecule at the designed ratio. It is believed that there is.
In the present invention, it is possible to achieve both the adsorptivity to the solid solution pigment by the structural unit derived from benzyl methacrylate and / or benzyl acrylate and the interaction with the cationic polymer by the anionic group, so that the print density and the storage stability can be achieved. Is thought to improve.

From the viewpoint of improving the printing density, the anionic polymer includes a structural unit derived from the anionic monomer (a) (hereinafter also referred to as “component (a)”), benzyl methacrylate and / or benzyl acrylate monomer (b) (hereinafter referred to as “( A polymer having a structural unit derived from b) component ") is preferred. Furthermore, it is preferable that the structural unit derived from the monomer copolymerizable with (a) component and (b) component is included. Preferred examples of the monomer copolymerizable with the component (a) and the component (b) include the macromer (c) and the nonionic monomer (d), and the macromer (c) is more preferable.
This anionic polymer can be produced by copolymerizing a component (a), a component (b), and a monomer mixture containing monomers copolymerizable therewith (hereinafter also simply referred to as “monomer mixture”). .

[Anionic monomer (a)]
The anionic monomer (a) is used from the viewpoint of the storage stability of the polymer particles.
Examples of the anionic monomer include a carboxylic acid monomer having a carboxy group, a sulfonic acid monomer having a sulfonic acid group, and a phosphoric acid monomer. Examples of the 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 sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, bis- (3-sulfopropyl) -itaconate, and the like. Examples thereof include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, and the like.
Among the anionic monomers, a carboxylic acid monomer is preferable from the viewpoint of storage stability, and acrylic acid and methacrylic acid are more preferable.

[Macromer (c)]
Macromer (c) (hereinafter also referred to as “component (c)”) is a compound having a polymerizable functional group at one end and a number average molecular weight of 500 to 100,000, and is used from the viewpoint of storage stability of polymer particles. . The polymerizable functional group present at one end is preferably an acryloyloxy group or a methacryloyloxy group, and more preferably a methacryloyloxy group. The number average molecular weight is preferably 500 to 100,000, more preferably 1,000 to 10,000. The number average molecular weight is measured using polystyrene as a standard substance by gel chromatography using chloroform containing 1 mmol / L dodecyldimethylamine as a solvent.
As the macromer (c), a styrene macromer, an aromatic group-containing (meth) acrylate macromer, and a silicone macromer are preferable from the viewpoint of dispersion stability of polymer particles.
Examples of the styrenic macromer include a styrene monomer homopolymer or a copolymer of a styrene monomer and another monomer. In the case of a copolymer, from the viewpoint of dispersion stability, the content of the styrene monomer is preferably 50% by weight or more, and more preferably 70% by weight or more. Examples of the styrene monomer include styrene, 2-methylstyrene, vinyl toluene, ethyl vinyl benzene, vinyl naphthalene, chlorostyrene, and the like. Other monomers to be copolymerized include aromatic group-containing (meth) acrylates or acrylonitrile. Examples of commercially available styrenic macromers include AS-6 (S), AN-6 (S), HS-6 (S) (trade name of Toagosei Co., Ltd.), 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. In the case of a copolymer, from the viewpoint of dispersion stability, the content of the aromatic group-containing (meth) acrylate monomer is preferably 50% by weight or more, and more preferably 70% by weight or more.
As an aromatic group-containing (meth) acrylate, an arylalkyl group having 7 to 22 carbon atoms which may have a substituent containing a heteroatom, or a carbon number which may have a substituent containing a heteroatom. Examples include (meth) acrylates having 6 to 22 aryl groups. Specific examples thereof include benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, and the like, and benzyl (meth) Acrylate is preferred. Examples of other monomers to be copolymerized include styrene monomers and acrylonitrile.
Examples of the silicone macromer include organopolysiloxane having a polymerizable functional group at one end.

[Nonionic monomer (d)]
Nonionic monomers (d) (hereinafter also referred to as “component (d)”) include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polyethylene glycol (n = 2 to 30, n is oxy) The average number of added moles of an alkylene group is shown below (the same applies hereinafter) (meth) acrylate, polypropylene glycol (n = 2 to 30) (meth) acrylate, poly (ethylene glycol (n = 1-15) / propylene glycol (n = 1) -15)) (meth) acrylate, methoxypolyethylene glycol (1-30) (meth) acrylate, ethoxypolyethylene glycol (1-30) (meth) acrylate, octoxypolyethylene glycol (1-30) (meth) acrylate, polyethylene Glycol (1-30) (meta) Chryrate 2-ethylhexyl ether, (iso) propoxypolyethylene glycol (1-30) (meth) acrylate, methoxypolypropylene glycol (1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol copolymer) (1-30, Among them, ethylene glycol: 1 to 29) (meth) acrylate and the like can be mentioned.
Examples of commercially available products of component (d) include NK Ester M-20G, 40G, 90G, and 230G from Shin-Nakamura Chemical Co., Ltd., Bremer PE-90, 200, 350, and PME from NOF Corporation. -100, 200, 400, 1000, PP-500, 800, 1000, AP-150, 400, 550, 800, 50 PEP-300, 50POEP-800B, 43PAPE-600B, etc. .
The components (a) to (d) can be used alone or in admixture of two or more.

The content of the components (a) to (c) in the monomer mixture (content as an unneutralized amount; the same shall apply hereinafter) or the preceding structural unit constituting the anionic polymer (a The content of the structural units derived from the components (c) to (c) is as follows from the viewpoints of storage stability and print density of the resulting aqueous dispersion and aqueous ink.
The content of the component (b) is 30 to 80% by weight, preferably 40 to 80% by weight, more preferably 50 to 75% by weight, and still more preferably 60 to 75% by weight.
The content of the component (a) is preferably 3 to 40% by weight, more preferably 4 to 30% by weight, still more preferably 5 to 25% by weight, and the content of the component (c) is preferably 5 to 67%. % By weight, more preferably 10 to 60% by weight.
Further, the weight ratio of [(a) component / [(b) component + (c) component]] is preferably 0.01 to 1, more preferably 0.02 to 0.67, and still more preferably 0.03. ~ 0.50.

(Production of anionic polymer)
The anionic polymer is produced by copolymerizing the monomer mixture by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method. Among these polymerization methods, the solution polymerization method is preferable.
As the solvent used in the solution polymerization method, 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.

Although the polymerization conditions of the monomer mixture vary depending on the type of radical polymerization initiator, monomer, and solvent to be used, the polymerization temperature is usually 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 an inert gas atmosphere such as nitrogen or 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. In addition, unreacted monomers and the like can be removed from the obtained polymer by reprecipitation, membrane separation, chromatographic methods, extraction methods and the like.

The weight average molecular weight of the anionic polymer is preferably from 5,000 to 500,000, more preferably from 10,000 to 400,000, from the viewpoints of the print density and storage stability of the resulting aqueous dispersion and aqueous ink, and preferably from 10,000 to 30 Is more preferable, and 20,000 to 300,000 is more preferable. In addition, the weight average molecular weight of a polymer is measured by the method shown in an Example.
When the anionic polymer has an anionic group derived from (a) an anionic monomer, the anionic polymer is preferably neutralized with a neutralizing agent. Examples of the neutralizing agent include bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and various amines.
From the viewpoint of dispersion stability, the neutralization degree of the anionic group of the anionic polymer is preferably 10 to 300%, more preferably 20 to 200%, and still more preferably 30 to 150%.
When the anionic polymer is crosslinked, from the viewpoint of dispersion stability and crosslinking efficiency, the degree of neutralization of the anionic group of the polymer before crosslinking is preferably 10 to 90%, and preferably 20 to 80%. More preferably, it is 30 to 70%.
Here, the neutralization degree can be obtained by the following equation.
{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [acid value of anionic polymer (KOH mg / g) × weight of anionic polymer (g) / (56 × 1000)]} × 100
The acid value can be calculated from the structural unit of the anionic polymer. Alternatively, it can also be determined by a method in which a polymer is dissolved in a suitable solvent (for example, methyl ethyl ketone) and titrated.

[Production of Anionic Polymer Particles Containing Solid Solution Pigment Containing Dichloroquinacridone]
An aqueous dispersion of anionic polymer particles containing a solid solution pigment containing dichloroquinacridone contained in an aqueous dispersion and an aqueous ink of the present invention can be efficiently produced by a method having the following steps (1) and (2). Can be manufactured.
Step (1): A step of dispersing a mixture containing an anionic polymer, an organic solvent, a solid solution pigment, and water to obtain a dispersion of anionic polymer particles containing a solid solution pigment Step (2): Step (1) The organic solvent is removed from the dispersion obtained in step 1) to obtain an aqueous dispersion of anionic polymer particles containing a solid solution pigment.

Process (1)
In the step (1), first, an anionic polymer is dissolved in an organic solvent to obtain an organic solvent solution of the polymer. In this organic solvent solution, a solid solution pigment, water, and a neutralizer, a surfactant and the like as required. Is preferably added and mixed to obtain an oil-in-water dispersion. Although there is no restriction | limiting in the order added to the organic solvent solution of an anionic polymer, It is preferable to add in order of a neutralizing agent, water, and a coloring agent. As the organic solvent solution of the polymer, a polymer solution obtained by polymerizing the polymer may be used as it is or further diluted with an organic solvent.
In the mixture, the solid solution pigment is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, the organic solvent is preferably 10 to 70% by weight, more preferably 10 to 50% by weight, and the polymer is 2 to 2% by weight. 40 weight% is preferable, 3-20 weight% is more preferable, 10-70 weight% is preferable and, as for water, 20-70 weight% is more preferable.
The weight ratio of the solid solution pigment amount to the anionic polymer amount [solid solution pigment / anionic polymer] is preferably 1.0 to 9.0, more preferably 2.3 to 5.7, from the viewpoint of dispersion stability.
When the anionic polymer is neutralized with a neutralizing agent, the pH of the finally obtained aqueous dispersion is preferably 7 to 11. 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. You may use these individually or in combination of 2 or more types.
The amount of the organic solvent dissolved in 100 g of water is preferably 5 g or more, more preferably 10 g or more at 20 ° C., and 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). The average particle size of the anionic polymer particles can be atomized only by the main dispersion until the desired particle size is reached, but preferably after pre-dispersion, the main dispersion is further carried out by applying shear stress to obtain the average particle size. Is preferably controlled to have a desired particle size. The temperature in 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 pre-dispersing the mixture, commonly used mixing and stirring devices such as anchor blades, such as Ultra Disper, Desperm (Asada Tekko Co., Ltd., trade name), Milder (Ebara Corporation, Taiheiyo Kiko) Co., Ltd., trade name), TK homomixer, TK pipeline mixer, TK homo jetter, TK homomic line flow, Filmix (above, Primix Corporation, trade name) and the like are preferred.
Examples of means for applying the shear stress of this dispersion include, for example, a kneader such as a roll mill, a kneader, and an extruder, a high pressure homogenizer represented by a high pressure homogenizer (Izumi Food Machinery Co., Ltd., trade name), and a microfluidizer (Microfluidics). Company name, Nanomizer (Yoshida Kikai Kogyo Co., Ltd., trade name), Optimizer, Starburst (Sugino Machine Co., Ltd., trade name) and other chamber type high-pressure homogenizers, paint shakers, bead mills and other media-type dispersers Is mentioned. Commercially available media type dispersers include Star Mill (manufactured by Ashizawa Finetech Co., Ltd., trade name), Ultra Apex Mill (manufactured by Kotobuki Industries Co., Ltd., trade name), Pico Mill (manufactured by Asada Tekko Co., Ltd., trade name), MSC mill (trade name) manufactured by Mitsui Mining Co., Ltd., dyno mill (trade name, manufactured by Shinmaru Enterprises Co., Ltd.), etc. A plurality of these devices can be combined. Among these, from the viewpoint of reducing the particle size of the solid solution pigment, it is preferable to use a media-type disperser and a high-pressure homogenizer in combination.

Process (2)
In the step (2), an aqueous dispersion of anionic polymer particles containing a solid solution pigment 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 obtained anionic polymer particles is preferably substantially removed, but may remain as long as the object of the present invention is not impaired. When performing, if necessary, it may be removed again after crosslinking. The amount of the residual organic solvent is preferably 0.1% by weight or less, and more preferably 0.01% by weight or less.
If necessary, the dispersion can be heated and stirred before the organic solvent is distilled off.

[Cationic polymer]
The aqueous dispersion and aqueous ink of the present invention contain a cationic polymer from the viewpoint of improving the printing density.
Here, the “cationic” of the cationic polymer means that when an unneutralized polymer is dispersed or dissolved in pure water, the pH is higher than 7, or a polymer having a quaternary ammonium salt or the like. When the counter ion is dispersed or dissolved in pure water as a hydroxide ion, the pH becomes higher than 7, or the polymer or the like is insoluble in pure water, and the pH cannot be measured clearly. It means that the zeta potential of the dispersion dispersed in pure water becomes positive.
The cationic polymer is preferably a polymer having a cationic group such as a primary to tertiary amino group, a quaternary ammonium base, or hydrazine, and the polymer is a homopolymer of a monomer having a cationic group or other monomer. And a copolymer or a condensation polymer.
The cationic polymer is preferably water-soluble from the viewpoint of efficiently causing interaction with anionic polymer particles and improving the print density of the aqueous dispersion or ink. Here, the “water-soluble polymer” is a polymer in which the cationic polymer is dried at 105 ° C. for 2 hours, and when the polymer that has reached a constant weight is dissolved in 100 g of water at 25 ° C., the dissolved amount exceeds 10 g. The dissolution amount is preferably 20 g or more, more preferably 100 g or more.

Examples of the cationic polymer include polyethyleneimine, polyallylamine, polyvinylamine, polyvinylpyridine, polyethyleneimine-epichlorohydrin reaction product, polyamide-polyamine resin, polyamide-epichlorohydrin resin, chitosan, cationized starch, polyaminesulfone, polyvinylimidazole, polyamidine, diamidine. cyan amide polyalkylene polyamine condensate, polyalkylene polyamine dicyandiamide ammonium salt condensate, dicyandiamide formalin condensate, epichlorohydrin-dialkylamine polycondensate, diallyl dimethyl ammonium chloride-SO ₂ copolymer, vinylpyrrolidone-vinylimidazole copolymers, Vinylbenzyltrimethylammonium chloride polymer, dimethylaminoethyl Methacrylate polymers or their acid neutralization products, and the like. These can be used alone or in combination of two or more.
Among the above cationic polymers, from the viewpoint of improving the print density of the aqueous dispersion or ink, a cationic polymer having an amino group is preferred, and specific examples thereof include polyethyleneimine, polyallylamine, Polyvinylamine, polyvinylpyridine, polyethyleneimine-epichlorohydrin reactant, polyamide-polyamine resin, polyamide-epichlorohydrin resin and the like can be mentioned. Among these, polyethyleneimine is particularly preferable.

(Polyethyleneimine)
Polyethyleneimine is represented by — (CH ₂ CH ₂ NH) _n —, and is a water-soluble polymer compound in which ethyleneimine units are polymerized in a branched, linear or network form. Polyethyleneimine is present as a polycation in the aqueous dispersion, and is considered to interact with anionic groups of anionic polymer particles containing a solid solution pigment, thereby connecting the polymer particles in a chain form.
The number average molecular weight of polyethyleneimine is preferably 600 to 100,000, more preferably 800 to 70,000, and still more preferably 1,000 to 50,000. When the number average molecular weight is 600 or more, the fixability of the pigment on the surface of the printing paper is further improved and the effect of improving the printing density is increased. When the number average molecular weight is 100,000 or less, the viscosity of the aqueous dispersion or ink is low. The dispersion stability is excellent. The number average molecular weight of polyethyleneimine can be determined by the boiling point raising method or the like.
The production method of polyethyleneimine is not particularly limited, and can be produced by a known polymerization method. For example, [1] a method of ring-opening polymerization of ethyleneimine using carbon dioxide, hydrochloric acid, hydrobromic acid or the like as a catalyst, [2] a method of polycondensation of ethylene chloride and ethylenediamine, [3] a method of heating oxazolidone-2 Etc.
Polyethyleneimine can be used individually or in combination of 2 or more types.
The content of polyethyleneimine in the aqueous dispersion is preferably 0.01 to 3% by weight, based on the anionic polymer particles containing the solid solution pigment, from the viewpoint of achieving both the basic physical properties of the water-based ink and the improvement in printing density. More preferably 0.05 to 2% by weight, still more preferably 0.1 to 1% by weight.

[Production of water dispersion for inkjet recording]
The method for producing an aqueous dispersion for inkjet recording of the present invention is a method having the following step I. According to this method, the aqueous dispersion for inkjet recording of the present invention can be efficiently produced.
Step I: A step of adding a cationic polymer to an aqueous dispersion (a) containing anionic polymer particles containing a solid solution pigment containing dichloroquinacridone to obtain an aqueous dispersion (A) for ink jet recording. The method for producing an aqueous dispersion for inkjet recording of the present invention preferably further includes the following step II.
Step II: A step of adding a crosslinking agent to the aqueous dispersion (A) obtained in Step I and crosslinking the anionic polymer in the aqueous dispersion (A) to obtain an aqueous dispersion (B) for inkjet recording.

Process I
In Step I, a cationic polymer is added to an aqueous dispersion (a) containing anionic polymer particles containing a solid solution pigment containing dichloroquinacridone obtained by the above production method to obtain an aqueous dispersion (A).
In order to uniformly disperse the cationic polymer in the aqueous dispersion (a) and to react uniformly with the anionic polymer particles containing the solid solution pigment, when adding the cationic polymer, shearing is performed with a stirrer or a disperser. It is preferable to add while applying. The aqueous dispersion (A) containing anionic polymer particles containing the obtained solid solution pigment is excellent in storage stability and printing density.

Process II
In Step II, by adding a crosslinking agent to the aqueous dispersion (A) containing the polymer particles containing the solid solution pigment obtained in Step I, the anionic polymer in the aqueous dispersion (A) is subjected to a crosslinking treatment. It can be obtained as an aqueous dispersion (B) containing polymer particles in a form in which crosslinked anionic polymer particles containing a solid solution pigment are linked in a chain form by the action of a cationic polymer.
The storage stability of the aqueous dispersion can be improved by crosslinking the anionic polymer. The crosslinking treatment of the anionic polymer may be performed before removing the organic solvent in the step (2), but is preferably performed after the step I from the viewpoint of improving storage stability.
By cross-linking after Step I, cross-linking between the anionic polymer particles connected in a chain occurs, and it is considered that the storage stability of the aqueous dispersion and aqueous ink of the present invention can be further improved. .
Here, as a crosslinking agent, the compound which has a functional group which reacts with the anionic group of an anionic polymer is preferable, and the compound which has this functional group in 2 or more, Preferably 2-6 in a molecule | numerator is more preferable.
The crosslinking agent used here is preferably 50 g or less, more preferably dissolved when dissolved in 100 g of water at 25 ° C. from the viewpoint of efficiently crosslinking the surface of an anionic polymer, particularly a water-insoluble anionic polymer. Is 40 g or less, more preferably 30 g or less. The molecular weight is preferably 120 to 2000, more preferably 150 to 1500, and still more preferably 150 to 1000, from the viewpoint of easy crosslinking reaction and storage stability of the aqueous dispersion.

(Crosslinking agent)
Preferable examples of the crosslinking agent include the following (i) to (iii).
(I) 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.
(Ii) Compounds having two or more oxazoline groups in the molecule: for example, bisoxazoline compounds such as 2,2′-bis (2-oxazoline), 1,3-phenylenebisoxazoline, 1,3-benzobisoxazoline, A compound having a terminal oxazoline group obtained by reacting the compound with a polybasic carboxylic acid.
(Iii) Compound having two or more isocyanate groups in the molecule: for example, organic polyisocyanate or isocyanate group-terminated prepolymer.
Among these, (i) a compound having two or more epoxy groups in the molecule is preferable, and ethylene glycol diglycidyl ether and trimethylolpropane polyglycidyl ether are more preferable.

The amount of the crosslinking agent used is preferably 0.3 / 100 to 50/100, and preferably 1/100 to 40/100, in terms of the weight ratio of [crosslinking agent / anionic polymer], from the viewpoint of storage stability of the aqueous dispersion. More preferably, 2/100 to 30/100 is more preferable, and 5/100 to 25/100 is still more preferable.
Further, the amount of the crosslinking agent used is preferably an amount that reacts with 0.1 to 20 mmol of anionic groups of the polymer in terms of anionic group amount per gram of anionic polymer from the viewpoint of storage stability. The amount reacting with 0.5 to 15 mmol is more preferable, and the amount reacting with 1 to 10 mmol is more preferable.
The anionic crosslinked polymer obtained by crosslinking treatment preferably contains 0.5 mmol or more of an anionic group (preferably carboxy group) neutralized with a base per 1 g of the polymer. Such a crosslinked polymer is considered to contribute to the stability of the crosslinked polymer particles containing the solid solution pigment by dissociating in the aqueous dispersion and charge repulsion between anions.
Here, the crosslinking rate (mol%) of the anionic crosslinked polymer obtained from the following formula (1) is preferably 10 to 80 mol%, more preferably 20 to 70 mol%, further preferably, from the viewpoint of storage stability. Is 30 to 60 mol%. The crosslinking rate can be calculated from the amount of crosslinking agent used and the number of moles of reactive groups, the amount of anionic polymer used and the number of moles of reactive groups of the anionic polymer that can react with the reactive group of the crosslinking agent. .
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 anionic polymer] (1)
In the formula (1), “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.

The aqueous dispersion of the anionic (crosslinked) polymer particles containing the solid solution pigment obtained by the above production method is a dispersion in which the solid content of the anionic polymer containing the solid solution pigment is contained in water as a main medium. .
The average particle diameter of the anionic (crosslinked) polymer particles containing the solid solution pigment obtained by the above production method is preferably 50 to 300 nm, more preferably 60 to 200 nm, and more preferably 70 to 150 nm from the viewpoint of dispersibility and printing density. Further preferred. The average particle diameter is measured by a dynamic light scattering method, and specifically measured by the method of the example.

[Water dispersion for inkjet recording]
The aqueous dispersion of the present invention is an anionic polymer particle containing a solid solution pigment containing dichloroquinacridone, and an aqueous dispersion for inkjet recording containing a cationic polymer, wherein the polymer constituting the polymer particle is benzyl methacrylate and / or Although it contains 30 to 80% by weight of a structural unit derived from benzyl acrylate, a moisturizing agent and an organic solvent can be added to prevent drying, and it can also be used as an aqueous ink as it is.
The content of each component in the aqueous dispersion of the present invention is as follows.
The content of the solid solution pigment contained in the anionic polymer particles used in the aqueous dispersion of the present invention in the aqueous dispersion is preferably from 1 to 25% by weight, more preferably from 2 to 20 from the viewpoint of increasing the printing density. % By weight, more preferably 4 to 15% by weight, still more preferably 4 to 8% by weight.
The ratio of the anionic polymer particles to the cationic polymer [anionic polymer particles / cationic polymer] is preferably 5000 to 40, more preferably 2000 to 80, from the viewpoint of increasing the printing density of the aqueous dispersion. Preferably it is 1000-100.
The water content is preferably 20 to 90% by weight, more preferably 30 to 80% by weight, and still more preferably 40 to 70% by weight.
The preferred surface tension (20 ° C.) of the aqueous dispersion of the present invention is 30 to 70 mN / m, more preferably 35 to 65 mN / m.
The viscosity (20 ° C.) of 20% by weight (solid content) of the aqueous dispersion of the present invention is preferably 1 to 12 mPa · s, more preferably 1 to 9 mPa · s, more preferably 2 to 6 mPa · s, and still more preferably. Is 2 to 5 mPa · s.

[Water-based ink for inkjet recording]
An aqueous ink for inkjet recording of the present invention is an anionic polymer particle containing a solid solution pigment containing dichloroquinacridone, and an aqueous dispersion for inkjet recording containing a cationic polymer, wherein the polymer constituting the polymer particle is benzyl methacrylate and It contains 30 to 80% by weight of a structural unit derived from benzyl acrylate, but wetting agents, penetrants, dispersants, surfactants, viscosity modifiers, antifoaming agents, preservatives usually used in water-based inks, An antifungal agent, an antirust agent, etc. can be added.
The content of each component in the aqueous ink of the present invention is as follows.
The content of the solid solution pigment contained in the anionic polymer particles used in the aqueous ink of the present invention in the ink is preferably 1 to 25% by weight in the aqueous ink from the viewpoint of increasing the printing density of the aqueous ink. Preferably it is 2-20 weight%, More preferably, it is 4-15 weight%, More preferably, it is 5-12 weight.
The water content is preferably 20 to 90% by weight, more preferably 30 to 80% by weight, and still more preferably 40 to 70% by weight.
The preferred surface tension (20 ° C.) of the water-based ink of the present invention is 23 to 50 mN / m, more preferably 23 to 45 mN / m, and still more preferably 25 to 40 mN / m.
In order to maintain good ejection reliability, the viscosity (20 ° C.) of the aqueous ink of the present invention is preferably 2 to 20 mPa · s, more preferably 2.5 to 16 mPa · s, and still more preferably 2. 5 to 12 mPa · s.
The ink jet method to which the water-based ink of the present invention is applied is not limited, but is suitable for a piezo ink jet printer suitable for discharging a dispersion containing a dispersible colorant such as a pigment.

In the following examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified. The weight average molecular weight of the polymer and the average particle diameter of the polymer particles are measured by the following methods. The aqueous inks obtained in Examples and Comparative Examples are evaluated for storage stability and printed by the following printing method. Then, the print density and the saturation were evaluated.
(1) Measurement of weight average molecular weight of anionic polymer Gel chromatography using a solution obtained by dissolving phosphoric acid and lithium bromide in N, N-dimethylformamide so as to have concentrations of 60 mmol / L and 50 mmol / L, respectively. It was measured using polystyrene as a standard substance by the method [GPC apparatus (HLC-8120GPC) manufactured by Tosoh Corporation, column (TSK-GEL, α-M × 2), manufactured by Tosoh Corporation, flow rate: 1 mL / min].
(2) Measurement of average particle diameter of anionic polymer particles containing solid solution pigment and anionic crosslinked polymer particles Measurement was performed using a laser particle analysis system ELS-8000 (cumulant analysis) of Otsuka Electronics Co., Ltd. A dispersion diluted with water so that the concentration of particles to be measured was about 5 × 10 ⁻³ wt% was used. The measurement conditions were a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and the number of integrations of 100. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent.

(3) Storage stability A water-based ink is filled in a glass sealed container and stored at 70 ° C. for 14 days. The viscosity of the water-based ink before and after storage is measured using an E-type viscometer (RE80L, rotor 1 manufactured by Toki Sangyo Co., Ltd.). Was used, and the viscosity was measured under the conditions of 20 ° C. and 50 r / min.
Using the measured viscosity value, the viscosity change rate was calculated from the following formula, and the storage stability was evaluated based on the following evaluation criteria. The smaller the absolute value of the viscosity change rate, the better the storage stability.
Viscosity change rate (%) = (([viscosity after storage] − [viscosity before storage]) / [viscosity before storage]) × 100

(4) Printing method Ink is filled into the ink injection port at the upper part of the black head of an ink jet printer (manufactured by Seiko Epson Corporation, model number: EM-930C, piezo method) through a silicon tube. Next, a solid print pattern (width 204 mm x length 275 mm) is created by Photoshop (product name, manufactured by Adobe), and test print is performed by changing the solid duty (print condition = paper type: plain paper) , Mode setting: black, fine, bidirectional), and the duty was adjusted so that the actual discharge amount was 0.75 ± 0.01 mg / cm 2. The discharge amount was measured by changing the weight of the screw tube containing the ink. Printing was performed on commercially available plain paper (trade name: XEROX 4200, manufactured by XEROX, high-quality plain paper) using the adjusted solid image of Duty.

(5) Measurement of printing density After the printed matter was left at 25 ° C. and 50% humidity for 24 hours, the printing density on the printing surface was measured. The print density was measured using a Macbeth densitometer (manufactured by Gretag Macbeth, SpectroEye, trade name). The measurement conditions were an observation light source of D65, an observation field of view of 2 degrees, a density reference of DIN16536, and a magenta color. The numerical value of the concentration component was read. The number of times of measurement was changed, and 5 points were selected at random from the portion printed in the forward path of bidirectional printing, and 5 points were selected from the portion printed on the return path, and an average value of a total of 10 points was obtained.
The higher the numerical value, the better the print density.

(6) Saturation measurement After leaving the printed matter for 24 hours at 25 ° C and 50% humidity, using the Macbeth densitometer, set the measurement mode to L ^* a ^* b ^* , set the observation light source to D65, and observe the field of view. Was set to 2 degrees, and the a ^* value and b ^* value of the printed surface were measured based on CIELAB, and the saturation (metric saturation) was calculated. The number of times of measurement was changed, and 5 points were selected at random from the portion printed in the forward path of bidirectional printing, and 5 points were selected from the portion printed on the return path, and an average value of a total of 10 points was obtained.
Saturation is represented by a distance from the center (a position where both a ^* and b ^* are 0: achromatic color) in the L ^* a ^* b ^* color system and the following formula. As the saturation value is larger, the color is brighter and better.
Saturation = [(a ^* ) ² + (b ^* ) ² ] ^1/2

Example 1 (Preparation of aqueous dispersion for inkjet recording)
(1) Synthesis of anionic polymer 142 parts of benzyl methacrylate, 38 parts of methacrylic acid, 40 parts of styrene macromer having a methacryloyl group at the end (trade name: AS-6S, manufactured by Toagosei Co., Ltd.) (solid content 50%) Then, a monomer mixed solution was prepared.
In a reaction vessel, 18 parts of methyl ethyl ketone, 0.03 part of a polymerization chain transfer agent (2-mercaptoethanol) and 10% of the monomer mixture were mixed and sufficiently substituted with nitrogen gas.
Meanwhile, in the dropping funnel, the remaining 90% of the monomer mixture, 0.27 part of the polymerization chain transfer agent, 42 parts of methyl ethyl ketone, and a polymerization initiator (trade name: V-65, 2, manufactured by Wako Pure Chemical Industries, Ltd.) A mixture of 1.2 parts of 2′-azobis (2,4-dimethylvaleronitrile) was added, and the mixture was heated to 75 ° C. while stirring the mixed solution in the reaction vessel under a nitrogen atmosphere. The mixed solution was added dropwise over 3 hours. After 2 hours at 75 ° C. from the end of the dropwise addition, a solution in which 0.3 part of the polymerization initiator was dissolved in 5 parts of methyl ethyl ketone was added and further aged at 75 ° C. for 2 hours and at 80 ° C. for 2 hours to obtain benzyl methacrylate. An anionic polymer solution (polymer weight average molecular weight: 90000) containing 71% by weight of the structural unit was obtained.

(2) Preparation of aqueous dispersion of solid solution pigment-containing anionic polymer particles 45 parts of anionic polymer obtained by drying the anionic polymer solution obtained in (1) above under reduced pressure were dissolved in 300 parts of methyl ethyl ketone, Are added with 10.2 parts of a neutralizing 5N aqueous sodium hydroxide solution, 12.2 parts of 25% aqueous ammonia and 1150 parts of ion-exchanged water, and a magenta pigment (a solid solution pigment comprising 2,9-dichloroquinacridone and unsubstituted quinacridone). After adding 180 parts of Ciba Japan Co., Ltd., trade name: Chromophthaljet Magenta 2BC) and mixing with Disper blade 7000 rpm at 20 ° C. for 1 hour, a bead mill type disperser (manufactured by Kotobuki Kogyo Co., Ltd., Ultra Apex) Mill, model UAM-05, media particles: zirconia beads, particle size: 0.05mm) It was mixed and dispersed for 40 minutes at 20 ° C. using. The obtained dispersion was further subjected to a 5-pass dispersion treatment at a pressure of 180 MPa using a microfluidizer (manufactured by Microfluidics, high-pressure homogenizer, trade name, model M-140K).
Methyl ethyl ketone was removed from the obtained dispersion at 60 ° C. under reduced pressure, a part of water was further removed, and the mixture was centrifuged, and the filter (manufactured by Sartorius, mini-Salto syringe filter, pore size: 5 μm, material: cellulose acetate) ) To remove coarse particles, and an aqueous dispersion of anionic polymer particles containing a solid solution pigment (solid content concentration: 30.0%, average particle size of 80 nm) was obtained.

(3) Preparation of aqueous dispersion for inkjet recording 50 g of the aqueous dispersion of solid solution pigment-containing anionic polymer particles obtained in (2) above was placed in a beaker, immersed in a 0 ° C. water bath, and dispersed at 7000 rpm with a homogenizer. 9.5 g of a 0.3% aqueous solution of polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., Epomin SP-200, number average molecular weight 10,000) was added dropwise at a rate of 20 ml / min. The obtained dispersion was filtered through the filter (manufactured by Sartorius, pore size: 5 μm) to remove coarse particles, thereby obtaining an aqueous dispersion for inkjet recording having an average particle size of 110 nm. Furthermore, 0.47 g of an epoxy-based crosslinking agent (manufactured by Nagase ChemteX Corporation, trade name: Denacol EX321, epoxy equivalent 140) and 1.07 g of ion-exchanged water were added to 40 g of the obtained water dispersion, and a 90 ° C. warm bath And held for 1 hour with stirring. After cooling, it is filtered through the filter (manufactured by Sartorius, pore size: 5 μm) to remove coarse particles, and anionic crosslinked polymer particles containing a solid solution pigment with an average particle size of 115 nm (crosslinking rate of the crosslinked polymer according to the formula (1)) : 56.8 mol%) and a polyethyleneimine-containing aqueous dispersion for ink jet recording.

Example 2 (Preparation of aqueous dispersion for inkjet recording)
(1) Synthesis of anionic polymer In Example 1 (1), an anionic polymer solution (polymer weight average molecular weight: 90000) was obtained in the same manner as in Example 1 (1) except that benzyl methacrylate was replaced with benzyl acrylate. )
(2) Preparation of aqueous dispersion of solid solution pigment-containing anionic polymer particles In Example 1 (2), the anionic polymer solution obtained in Example 1 (1) was obtained in Preparation Example 2 (1). An aqueous dispersion of anionic polymer particles containing a solid solution pigment (solid content concentration: 30.0%, average particle size of 80 nm) was obtained in the same manner as in Example 1 (2) except that the anionic polymer solution was used. Obtained.
(3) Preparation of aqueous dispersion for inkjet recording In Example 1 (3), the aqueous dispersion of solid solution pigment-containing anionic polymer particles obtained in Example 1 (2) was obtained in Preparation Example 2 (2). An aqueous dispersion for inkjet recording was obtained in the same manner as in Example 1 (3) except that the solid dispersion pigment-containing anionic polymer particle was replaced with an aqueous dispersion.

Comparative Example 1 (Preparation of water dispersion for inkjet recording)
(1) Synthesis of anionic polymer Anionic polymer solution (weight average molecular weight of the polymer: 90000) in the same manner as in Example 1 (1) except that benzyl methacrylate was replaced with styrene in Example 1 (1). Got.
(2) Preparation of aqueous dispersion of solid solution pigment-containing anionic polymer particles In Example 1 (2), the anionic polymer solution obtained in Example 1 (1) was obtained in Comparative Example 1 (1). An aqueous dispersion of anionic polymer particles containing a solid solution pigment (solid content concentration: 30.0%, average particle size 85 nm) was prepared in the same manner as in Example 1 (2) except that the anionic polymer solution was used. Obtained.
(3) Preparation of Inkjet Recording Water Dispersion In Example 1 (3), an aqueous dispersion of pigment-containing anionic polymer particles obtained in Example 1 (2) was obtained in Comparative Example 1 (2). An aqueous dispersion for inkjet recording was obtained in the same manner as in Example 1 (3) except that the solid dispersion pigment-containing anionic polymer particle was replaced with an aqueous dispersion.

Comparative Example 2 (Preparation of water dispersion for inkjet recording)
(1) Synthesis of anionic polymer An anionic polymer solution (weight average molecular weight of polymer: 90000) was obtained in the same manner as in Example 1 (1).
(2) Preparation of Aqueous Dispersion of Solid Solution Pigment-Containing Anionic Polymer Particles In Example 1 (2), the solid solution pigment was a solid solution pigment composed of 2,9-dimethylquinacridone and unsubstituted quinacridone (manufactured by DIC Corporation, trade name: An aqueous dispersion of anionic polymer particles containing a solid solution pigment (solid content concentration: 30.0%, average particle size of 85 nm), except that it was changed to Fastgen Super Magenta RY). )
(3) Preparation of aqueous dispersion for ink jet recording In Example 1 (3), Example 1 (3) was used except that the aqueous dispersion of solid solution pigment-containing anionic polymer particles obtained in Comparative Example 2 (2) was used. ) To obtain an aqueous dispersion for inkjet recording.

Comparative Example 3 (Preparation of water dispersion for inkjet recording)
(1) Synthesis of anionic polymer An anionic polymer solution (weight average molecular weight of polymer: 90000) was obtained in the same manner as in Example 1 (1).
(2) Preparation of aqueous dispersion of quinacridone pigment-containing anionic polymer particles In Example 1 (2), the solid solution pigment was a pigment made of 2,9-dimethylquinacridone (manufactured by DIC Corporation, trade name: Fastgen Super Magenta RG). An aqueous dispersion of anionic polymer particles containing a quinacridone pigment (solid content concentration: 30.0%, average particle size of 90 nm) was obtained in the same manner as in Example 1 (2) except that was replaced with.
(3) Preparation of Inkjet Recording Water Dispersion Example 1 (3) except that the aqueous dispersion of quinacridone pigment-containing anionic polymer particles obtained in Comparative Example 3 (2) was used in Example 1 (3). ) To obtain an aqueous dispersion for inkjet recording.

Comparative Example 4 (Preparation of water dispersion for inkjet recording)
(1) Synthesis of anionic polymer An anionic polymer solution (weight average molecular weight of polymer: 90000) was obtained in the same manner as in Example 1 (1).
(2) Preparation of aqueous dispersion of quinacridone pigment-containing anionic polymer particles In the same manner as in Example 1 (2), an aqueous dispersion of anionic polymer particles containing a solid solution pigment (solid content concentration: 30.0%, An average particle size of 80 nm) was obtained.
(3) Preparation of aqueous dispersion for inkjet recording An aqueous dispersion for inkjet recording was obtained in the same manner as in Example 1 (3) except that polyethyleneimine was not added in Example 1 (3).

Example 3 [Production of ink]
1,2-hexanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) 2.0 parts, 2-pyrrolidone (manufactured by Wako Pure Chemical Industries, Ltd.) 2.0 parts, Surfynol 465 (manufactured by Nissin Chemical Industry Co., Ltd.) 0.5 Part, Olphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 0.5 part, 2.0 parts of glycerin (manufactured by Kao Corporation), triethylene glycol monobutyl ether (trade name: butyl triglycol, manufactured by Nippon Emulsifier Co., Ltd.) 10 0.0 part, 0.3 part of Proxel XL2 (manufactured by Avicia Co., Ltd.) and ion-exchanged water were mixed while stirring with a magnetic stirrer, and further stirred at room temperature for 15 minutes to obtain a mixed solution. Here, the blending amount of the ion exchange water is an amount adjusted so that the total amount of the mixed solution and the water dispersion for ink jet recording obtained in Example 1 is 100 parts.
Next, the mixed solution was added while stirring 41.7 parts (12.5 parts in terms of solid content, 10.0 parts in terms of pigment content) of the aqueous dispersion for ink jet recording obtained in Example 1 with a magnetic stirrer. And a 1.2 μm filter (cellulose acetate membrane, manufactured by Sartorius) to obtain a water-based ink.

Example 4 [Production of ink]
In Example 3, a water-based ink was obtained in the same manner as in Example 3 except that the aqueous dispersion prepared in Example 2 was used.
Comparative Example 5 [Ink Production]
In Example 3, a water-based ink was obtained in the same manner as in Example 3 except that the aqueous dispersion prepared in Comparative Example 1 was used.
Comparative Example 6 [Ink Production]
In Example 3, a water-based ink was obtained in the same manner as in Example 3 except that the aqueous dispersion prepared in Comparative Example 2 was used.
Comparative Example 7 [Production of ink]
In Example 3, a water-based ink was obtained in the same manner as in Example 3 except that the aqueous dispersion prepared in Comparative Example 3 was used.
Comparative Example 8 [Production of ink]
In Example 3, a water-based ink was obtained in the same manner as in Example 3, except that the aqueous dispersion prepared in Comparative Example 4 was used.

  From Table 1, it can be seen that the inks of Examples 3 to 4 are superior in printing density and storage stability and have high chroma as compared with the inks of Comparative Examples 5 to 8.

Claims (9)

  An anionic polymer particle containing a solid solution pigment containing dichloroquinacridone, and an aqueous dispersion for inkjet recording containing a cationic polymer, wherein the polymer constituting the anionic polymer particle is derived from benzyl methacrylate and / or benzyl acrylate An aqueous dispersion for inkjet recording, comprising 30 to 80% by weight of the structural unit.   The aqueous dispersion for ink jet recording according to claim 1, wherein the solid solution pigment comprises dichloroquinacridone and unsubstituted quinacridone.   The aqueous dispersion for inkjet recording according to claim 1, wherein the cationic polymer is polyethyleneimine.   The aqueous dispersion for inkjet recording according to any one of claims 1 to 3, wherein the polymer constituting the anionic polymer particles is crosslinked by a crosslinking agent.   The aqueous dispersion for inkjet recording according to any one of claims 1 to 4, wherein the polymers constituting the anionic polymer particles are all composed of structural units derived from monomers having the same polymerizable group.   The aqueous dispersion for inkjet recording according to claim 5, wherein the polymerizable group of the monomer is a methacryloyl group.   An aqueous ink for inkjet recording, comprising the water dispersion according to any one of claims 1 to 6. The manufacturing method of the aqueous dispersion for inkjet recording of Claim 1 which has the following process I.
Step I: A step of obtaining a water dispersion (A) by adding a cationic polymer to an aqueous dispersion (a) containing anionic polymer particles containing a solid solution pigment containing dichloroquinacridone. The manufacturing method of the aqueous dispersion for inkjet recording of Claim 4 which has the following process I and process II.
Step I: Step of obtaining a water dispersion (A) by adding a cationic polymer to an aqueous dispersion (a) containing anionic polymer particles containing a solid solution pigment containing dichloroquinacridone Step II: obtained in Step I A step of adding a crosslinking agent to the aqueous dispersion (A) and crosslinking the anionic polymer in the aqueous dispersion (A) to obtain an aqueous dispersion for inkjet recording