JP5683143B2 - Ink set for inkjet recording - Google Patents

Description

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

The ink jet recording method is a recording method in which characters and images are obtained by ejecting and adhering ink droplets directly from a very fine nozzle to a recording member. This method is remarkably widespread because it has many advantages that full color is easy and inexpensive, plain paper can be used as a recording member, and there is no contact with the object to be printed. Among these, pigment-based inks have become mainstream from the viewpoint of light resistance and water resistance of printed matter, and are preferably used in home inkjet printers.
In recent years, the range of use of ink jet printers has been expanded from home use to office use and commercial printing use, and the trend of technology is colorization and high speed. As a method for realizing high speed, a method of increasing the printing speed by reducing the number of printings by increasing the volume of ink droplets or improving the print head is employed.
The problem with high-speed printing is that, since conventional printing cannot be performed twice or three times, sufficient dispersion stability and ejection stability are imparted so as not to cause deterioration in printing quality such as blurring or missing. There has been a demand for an ink and ink set that can suppress the penetration of the colorant into the paper, particularly when printing on plain paper, so that the colorant is highly colored so that a high printing density can be obtained by one-time printing.

In particular, in colorization, inks of two colors with different hues are mixed to produce color, so the mixing of inks, hue error of mixed ink as a secondary color, turbidity, storage stability, bleed resistance, light absorption Characteristic changes and fixability to recording paper are important issues.
In Patent Document 1, for the purpose of improving color developability and abrasion resistance, each of a plurality of light-colored inks and a plurality of dark-colored inks contains a pigment and a solvent. Each of which contains polymer fine particles, and each of the multiple color dark inks does not contain the polymer fine particles or contains a smaller amount of the polymer fine particles than the light color ink. And it is disclosed that it is preferable to use a self-dispersing pigment as the pigment of each ink.
In Patent Document 2, for the purpose of suppressing secondary color image deformation, an ink composition containing polymer particles having 65% by mass or more of a structural unit derived from a methacrylic acid derivative and a coloring material, and contact with the ink composition Ink jet recording ink sets containing a treatment liquid capable of forming an aggregate when it is used, and it is disclosed that it is preferable to use a pigment in which each ink is coated with a polymer dispersant. .

Japanese Patent Laid-Open No. 2002-3768 JP 2010-31267 A

However, it has been found that conventional ink sets are insufficient for recent demands for higher image quality and higher speed.
An object of the present invention is to provide an ink set for ink jet recording that has little change in light absorption characteristics, excellent bleed resistance, and excellent storage stability even when secondary color inks having different hues are used. .

The present inventors obtained polymer particles (A) containing a colorant having no self-dispersibility obtained by dispersing a pigment having no self-dispersibility with a water-soluble polymer (x) and a water-insoluble polymer (y). It has been found that an ink set comprising an aqueous ink containing and an aqueous ink containing a self-dispersing pigment can solve the above problems.
That is, the present invention is an ink set comprising two or more kinds of colored inks, wherein the first kind of colored ink contains a pigment having no self-dispersibility, a water-soluble polymer (x) and a water-insoluble polymer (y). A water-based ink (I) containing polymer particles (A) containing a pigment that does not have self-dispersibility obtained by dispersing in a water-insoluble polymer (x) in a weight ratio of the water-insoluble polymer (y) [ (Y) / (x)] is 2.0 to 5.0, and an ink set for inkjet recording is provided, wherein the second type of colored ink is a water-based ink (II) containing a self-dispersing pigment.

  According to the present invention, it is possible to provide an ink set for ink jet recording that has little change in light absorption characteristics, excellent bleed resistance, and excellent storage stability even when secondary color inks having different hues are used. .

The ink set for inkjet recording of the present invention is an ink set comprising two or more kinds of colored inks, wherein the first kind of colored ink contains a pigment having no self-dispersibility, a water-soluble polymer (x) and a water-insoluble polymer. A water-based ink (I) containing polymer particles (A) containing pigments having no self-dispersibility obtained by dispersing with a polymer (y), the water-insoluble polymer (y) with respect to the water-soluble polymer (x) The weight ratio [(y) / (x)] is 2.0 to 5.0, and the second type of colored ink is an aqueous ink (II) containing a self-dispersing pigment.
In the ink set of the present invention, in the water-based ink (I), a pigment having no self-dispersibility obtained by dispersing a pigment having no self-dispersibility with a water-soluble polymer (x) and a water-insoluble polymer (y). By using the contained polymer particles (A), it is easy to control the wettability and adsorptivity between the pigment and the polymer, and the pigment coverage is increased and stably dispersed. As a water-based ink (II), self-dispersion Although the detailed reason is unclear by using the water-based ink containing the type pigment, the water-soluble polymer (x) existing on the surface of the pigment having no self-dispersibility used in the water-based ink (I) and water-insoluble Because of the interaction between the polymer (y) and the surface of the self-dispersing pigment used in the water-based ink (II), the mixing property of both inks is increased, the optical property change is small, and the bleed resistance is excellent. And excellent storage stability, and further, it is considered possible to provide an excellent ink jet recording ink set fixability on the recording paper without hue error and turbidity.
Hereafter, each component etc. which are used for this invention are demonstrated.

<Pigment>
The pigment used in the present invention may be either an organic pigment or an inorganic pigment. If necessary, extender pigments can be used in combination.
Among these pigments, a pigment having no self-dispersibility is selected for the water-based ink (I), and a self-dispersing pigment is selected for the water-based ink (II).

  In the present invention, the self-dividing powder pigment is defined as a pigment having an acidic group amount of 200 μmol / g or more in the case of an achromatic pigment, and a pigment having an acidic group amount of 40 μmol / g or more in the case of a chromatic pigment. In addition, the self-dispersing pigment has one or more anionic hydrophilic functional groups on the surface of the pigment directly or through other atomic groups, so that it can be used in an aqueous medium without using a surfactant or a resin. It means a pigment that is dispersible. Here, “dispersible” means that it is stable for 90 days in water (25 ° C., solid content 10% by weight) without a dispersant (with a change in the particle size of the pigment within +/− 30%). . Further, as other atomic groups, an alkanediyl group having 1 to 24 carbon atoms, preferably 1 to 12 carbon atoms, a phenylene group which may have a substituent, or a naphthylene group which may have a substituent. Is mentioned. On the other hand, the pigment having no self-dispersibility in the present invention means a pigment other than the self-dividing powder.

Examples of the anionic hydrophilic functional group include the following acidic groups. Any acidic group may be used as long as the hydrophilicity is high enough to stably disperse the pigment particles in the aqueous medium. Specific examples thereof include a carboxylic acid group (—COOM ¹ ), a sulfonic acid group (—SO ₃ M ¹ ), a phosphonic acid group (—PO ₃ M ¹ ₂ ), —PO ₃ HM ¹ , —SO ₂ M ¹ , _{-SO 2 NH 2, -SO 2 NHCOR} 1, or their dissociated ionic form _{^{(-COO -, -SO 3 -,}} -PO 3 2-, -PO 3 - H) 1 kind selected from the group consisting of such Or 2 or more types of acidic groups are mentioned.
In the above chemical formula, M ¹ may be the same or different, hydrogen atom; alkali metal such as lithium, sodium and potassium; alkaline earth metal; ammonium; monomethylammonium group, dimethylammonium group, trimethylammonium group; monoethylammonium Group, diethylammonium group, triethylammonium group; organic ammonium such as monomethanolammonium group, dimethanolammonium group, trimethanolammonium group.
R ¹ is an alkyl group which may have an optionally substituted phenyl group or a substituted naphthyl group having 1 to 12 carbon atoms. Among these, from the viewpoint of dispersion stability in the ink, a carboxyl group (—COOM ¹ ) and a sulfonic acid group (—SO ₃ M ¹ ) are preferable.
The acidic group amount can be measured by the method described in the examples.

For the self-dispersing pigment, for example, the necessary amount of the anionic hydrophilic functional group may be chemically bonded to a pigment that is not a self-dispersing pigment. Any known method can be used as such a method. For example, U.S. Pat. Nos. 5,571,311, 5,630,868, 5,707,432, JE Johnson, Imaging Science and Technology's 50th Annual Conference (1997), Yuan Yu, Imaging Science and Technology's 53th Annual Conference (2000). ), Polyfile, 1248 (1996), and the like.
More specifically, acids having oxidizing properties such as nitric acid, sulfuric acid, persulfuric acid, peroxodisulfuric acid, hypochlorous acid, chromic acid and salts thereof, or oxidation of hydrogen peroxide, nitrogen oxide, ozone, etc. There are a method of introducing a carboxy group by an agent, a method of introducing a sulfone group by thermal decomposition of a persulfate compound, a method of introducing the acidic group by a diazonium salt compound having a carboxy group, a sulfone group, etc. Among them, the liquid phase oxidation method using the oxidizing acid is preferable from the viewpoint of improving the printing density of the water-based ink.

Examples of self-dispersing pigments and pigments that do not have self-dispersing properties include organic pigments and inorganic pigments.
Examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments.
Specific examples of preferred organic pigments include C.I. I. Pigment yellow, C.I. I. Pigment Red, C.I. I. Pigment violet, C.I. I. Pigment blue, and C.I. I. One or more types of products selected from the group consisting of pigment green are listed. Moreover, solid solution pigments, such as a quinacridone solid solution pigment, can also be used.
Examples of the inorganic pigment include carbon black, metal oxide, metal sulfide, and metal chloride. Of these, carbon black is preferred particularly for black aqueous inks. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.
Examples of extender pigments include silica, calcium carbonate, and talc.
Among the pigments, for example, C.I. I. An azo pigment such as CI Pigment Yellow 74 is more preferable.

(CI Pigment Yellow 74)
C. I. Examples of the pigment yellow 74 (hereinafter, also referred to as “PY74 (A)”) include an acetoacetyl allylide monoazo pigment. Its chemical name is 2-[(2-methoxy-4-nitrophenyl) azo] -N- (2-methoxyphenyl) -3-oxobutanamide and has a structure represented by the following formula (1). A compound.
PY74 (A) is available from manufacturers such as DIC Corporation, Dainichi Seika Kogyo Co., Ltd., Sanyo Pigment Co., Ltd., Toyo Ink Manufacturing Co., Ltd.

(Other azo pigments (B))
In the present invention, in order to refine PY74 (A) and improve the storage stability of the aqueous dispersion, the azo pigment (B) represented by the following formula (2) (hereinafter simply referred to as “azo pigment (B)”) Can also be used in combination with PY74 (A).

(Wherein R ¹⁰ and R ²⁰ each independently represents an aryl group optionally having a substituent selected from a methoxy group and a nitro group, and at least one of R ¹⁰ and R ²⁰ is a sulfonic acid group. And a sulfonic acid amide group.)
From the viewpoint of improving the dispersibility of PY74 (A), the azo pigment (B) is (i) R ¹⁰ is a phenyl group having a sulfonic acid group and a sulfonamide group, and R ²⁰ is a phenyl group. or compound is a phenyl group having one or more substituents selected from methoxy and nitro groups, (ii) R ¹⁰ is either a phenyl group, or a substituted one or more kinds selected from methoxy and nitro groups And a compound in which R ²⁰ is a phenyl group having a sulfonic acid group and a sulfonamide group.
In the case of (i), R ²⁰ is preferably a phenyl group having a methoxy group at the ortho position.
In the case of (b), an azo pigment represented by the following formula (3) is preferable.

(In the formula, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms or an aminoalkyl group optionally having a substituent, and R ³ represents a single bond, methylene. Group or ethylene group.)
The azo pigment (B) represented by the formula (3) has a structure in which a sulfonamide group (—SO ₂ NR ¹ R ² ) and a sulfonic acid group (—R ³ —SO ₃ H) are substituted.
Here, R ¹ and R ² are each independently a hydrogen atom or a C 1-12 alkyl having a substituent, from the viewpoint of improving printing density, storage stability, and versatility. Although it is a group or an aminoalkyl group, examples of the substituent include a sulfonic acid group, a carboxy group, and a hydroxy group.
As an alkyl group which is R < ¹ > and R < ² >, C1-C3 alkyl groups, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, are preferable.
As the aminoalkyl group as R ¹ and R ² , those represented by — (CH ₂ ) _k NR ⁴ R ⁵ are preferable. Here, k is an integer of 1 to 4, R ⁴ and R ⁵ independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Moreover, the alkyl group of R < ⁴ > and R < ⁵ > shows a C1-C3 methyl group, an ethyl group, a propyl group, and an isopropyl group.

That is, in the sulfonamide group (—SO ₂ NR ¹ R ² ), as an amine residue represented by —NR ¹ R ² , the viewpoint of improving the printing density and storage stability, the viscosity when used as an ink. From the viewpoint of suppressing the change in light absorption characteristics and the above-described —NH (CH ₂ ) _k NR ⁴ R ⁵ is preferable.
Specific examples of the amine residue include N-aminoethyl group (derived from ethylenediamine), N-aminopropyl group (derived from 1,3-propanediamine), N-methyl-aminoethyl group (derived from N-methylethylenediamine), N-methyl-aminopropyl group (derived from N-methylpropanediamine), N, N-dimethylaminoethyl group (derived from N, N-dimethylethylenediamine), 3-aminopropyl group, N- (2-aminoethyl) -3 -Aminopropyl group, N- (2-dimethylaminoethyl) -3-aminopropyl group, N-alkyl (C1-12) -3-aminopropyl group, N, N-dimethylaminopropyl group (N, N -Dimethyl-1,3-propanediamine), N, N-bis (2-hydroxyethyl) -3-aminopropyl group and the like.
Among these, N-alkyl (1 to 3 carbon atoms) -3-aminopropyl group and N, N-dialkyl (carbon number) from the viewpoint of reducing the viscosity when ink is used and suppressing changes in light absorption characteristics. 1-3) A 3-aminopropyl group is preferred.
Examples of the sulfonic acid group (—R ³ —SO ₃ H) include a sulfonic acid group (—SO ₃ H), a methylene sulfonic acid group (—CH ₂ —SO ₃ H), and an ethylene sulfonic acid group (—CH ₂ CH ₂ —). SO ₃ H) but may be mentioned, sulfonic acid group (-SO ₃ H) is more preferable. When R ³ is a single bond, it means that a sulfonic acid group (—SO ₃ H) is directly bonded to the benzene ring.

In the present invention, when a pigment mixture of PY74 (A) and an azo pigment (B) is used, the amount of sulfur in the pigment mixture reduces the viscosity when used in ink from the viewpoint of improving printing density and storage stability. From the viewpoint of suppressing the change in light absorption characteristics, it is preferably 0.25 to 0.7% by weight, more preferably 0.25 to 0.5% by weight, still more preferably 0.3 to 0.5% by weight. The amount of the azo pigment (B) in the pigment mixture is preferably 0.5 to 7 mol% from the viewpoint of improving the printing density and storage stability, and from the viewpoint of suppressing the change in the light absorption characteristics when the ink is used. More preferably, it is 1 to 5 mol%.
The average primary particle size of the pigment mixture is preferably 10 to 50 nm, more preferably 15 to 40 nm, and still more preferably 20 to 35 nm, from the viewpoint of reducing the printing density and viscosity when ink is used. Measurement of the amount of sulfur in the pigment mixture and the average primary particle diameter can be carried out by the methods described in the Examples.
The pigments, except for carbon black, are not self-dispersible. However, as described above, these pigments are hydrophilic functional groups (anionic hydrophilic groups such as carboxy groups and sulfonic acid groups, or A self-dispersing pigment can be obtained by bonding one or more of cationic hydrophilic groups such as a quaternary ammonium group to the surface of the pigment directly or via another atomic group.

In the water-based ink (II) of the present invention, a self-dispersing pigment is used. However, the viewpoint of improving the dispersion stability of the ink and the mixing property between the water-based ink (I) and the water-based ink (II) are improved. From the viewpoint of reducing hue error and turbidity as a color ink and improving storage stability, carbon black is particularly preferable for water-based black ink, and water-based chromatic pigment ink is hydrophilic via a phenyl group on the surface. A chromatic pigment having a functional group is preferred, and among the chromatic pigments, a cyan pigment or a magenta pigment is preferred.
The amount of the hydrophilic functional group is not particularly limited, but is preferably 40 to 3,000 μmol per 1 g of the self-dispersing pigment, and preferably 80 to 800 μmol per 1 g of the self-dispersing pigment when the hydrophilic functional group is a carboxy group.
Examples of self-dispersing carbon black that can be used include CAB-O-JET 200, 300 (above, manufactured by Cabot), BONJET CW-1 (500 μmol / g as a carboxy group), and CW-2 (470 μmol as a carboxy group). / G) (as described above, manufactured by Orient Chemical Co., Ltd.), Aqua-Black 162 (about 800 μmol / g as a carboxy group) from Tokai Carbon Co., Ltd., and the like.
The pigments can be used alone or in admixture of two or more at any ratio.

<Polymer>
In the water-based ink (I) used in the present invention, a water-insoluble polymer (y) and a water-soluble polymer (x) are used as polymers.
Here, the “water-insoluble polymer (y)” and the “water-soluble polymer (x)” mean that when the polymer has a salt-forming group, the salt-forming group of the polymer is converted into acetic acid or hydroxylated according to the type of the polymer. When 100 g of pure water at 25 ° C. is added to 10 g of 100% neutralized with sodium and sufficiently stirred, the polymer is “water-soluble polymer (x)” in the present invention. In addition, when using a commercially available polymer, or when using a polymer neutralized with a neutralizing agent other than acetic acid or sodium hydroxide at the time of synthesis, if the degree of neutralization is not 100%, acetic acid or sodium hydroxide is used. In addition, the solubility is judged as 100% neutralization.
When the solubility test is performed and the polymer has a portion that does not dissolve, it is difficult for pure water to penetrate into the polymer. Therefore, in the following procedure, it is determined whether the water-soluble polymer (x) or the water-insoluble polymer (y). Determine. That is, the polymer is previously dissolved in an organic solvent such as methyl ethyl ketone, the salt-forming group of the polymer is neutralized with acetic acid or sodium hydroxide, and dropped into pure water, and the organic solvent is removed to adjust the concentration. The dispersion having a concentration of 10% by weight is separated by centrifugation, membrane filtration or the like, and then the polymer dissolved in water is referred to as “water-soluble polymer ((x)”), and the remaining polymer is referred to as “water-insoluble polymer (y)”. Determine.

(Water-insoluble polymer (y))
In the present invention, a water-insoluble polymer (y)) is used from the viewpoint of atomizing a pigment, improving dispersibility, mainly improving storage stability and increasing printing density.
As the water-insoluble polymer (y), a vinyl polymer obtained by addition polymerization of a vinyl monomer or a urethane polymer having a urethane bond is preferable, and a salt-forming group-containing monomer (a) (hereinafter also referred to as “component (a)”). A vinyl polymer comprising a structural unit derived from and a structural unit derived from a hydrophobic monomer (b) (hereinafter also referred to as “component (b)”) and / or macromer (c) (hereinafter also referred to as “component (c)”) Are more preferable, and those including all the structural units derived from the components (a) to (c) are more preferable. Such a water-insoluble polymer (y) can be obtained by copolymerization of a monomer mixture containing the component (a) and the component (b) and / or the component (c) (hereinafter also simply referred to as “monomer mixture”). .

[Salt-forming group-containing monomer (a)]
The salt-forming group-containing monomer (a) is used from the viewpoint of enhancing the dispersibility of the resulting polymer particles.
Examples of the salt-forming group-containing monomer (a) include cationic monomers and anionic monomers, with anionic monomers being preferred.
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, and among them, a carboxy group is preferable.

Representative examples of the cationic monomer include amine-containing monomers and ammonium salt-containing monomers. Among these, N, N-dimethylaminoethyl (meth) acrylate, N- (N ′, N′-dimethylaminopropyl) (meth) acrylamide and vinylpyrrolidone are preferable.
Examples of the anionic monomer include a carboxylic acid monomer, a sulfonic acid monomer, 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, and bis- (3-sulfopropyl) -itaconate.
Examples of phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, and the like. It is done.
Among the anionic monomers, a carboxylic acid monomer is preferable and acrylic acid and methacrylic acid are more preferable from the viewpoint of improving the dispersibility of the polymer particles.

[Hydrophobic monomer (b)]
The hydrophobic monomer (b) is used from the viewpoint of increasing the affinity of the polymer for the pigment mixture. Examples of the hydrophobic monomer (b) include alkyl (meth) acrylates and aromatic group-containing monomers. From the viewpoint of increasing affinity with the pigment mixture, and improving dispersibility and storage stability, aromatic group-containing monomers. Is preferred.
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 and / or methacrylate.
Examples of the aromatic group-containing monomer include styrene monomers and aromatic group-containing (meth) acrylates. As the styrenic monomer, styrene and 2-methylstyrene are preferable, and as the aromatic group-containing (meth) acrylate, benzyl (meth) acrylate and phenoxyethyl (meth) acrylate are preferable.
Among the components (b), styrene and benzyl (meth) acrylate are preferable, and styrene is more preferable from the viewpoint of increasing the affinity of the polymer for the pigment mixture.
Further, from the viewpoint of increasing the affinity with the water-insoluble polymer (y), the component (b) in the water-insoluble polymer (y) and the water-soluble polymer (x) described later is preferably the same.

[Macromer (c)]
The macromer (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 increasing the affinity of the polymer for the pigment mixture.
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 500 to 100,000, 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 styrenic macromer, an aromatic group-containing (meth) acrylate macromer, and a silicone macromer are preferable from the viewpoint of increasing the affinity of the polymer to PY74 (A).
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, the content of the styrenic monomer is preferably 50% by weight or more and more preferably 70% by weight or more from the viewpoint of increasing the affinity of the polymer for the pigment mixture. Other monomers to be copolymerized include aromatic group-containing (meth) acrylates or acrylonitrile. Examples of the styrenic monomer include styrene and 2-methylstyrene.
Specific examples of the styrenic macromer 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, the content of the aromatic group-containing (meth) acrylate is preferably 50% by weight or more and more preferably 70% by weight or more from the viewpoint of increasing the affinity of the polymer for the pigment mixture. The aromatic group-containing (meth) acrylate is a (meth) acrylate having an arylalkyl group having 7 to 12 carbon atoms or an aryl group, which may have a substituent containing a hetero atom, such as benzyl (meth). Examples include acrylate and phenoxyethyl (meth) acrylate, and benzyl (meth) acrylate is preferred. Examples of other monomers to be copolymerized include styrene monomers and acrylonitrile.
The macromer may be a silicone macromer, and examples of the silicone macromer include organopolysiloxane having a polymerizable functional group at one end.
As the macromer (c) in the water-insoluble polymer (y), the weight of the same monomer as the hydrophobic monomer (b) in the water-soluble polymer (x) is increased from the viewpoint of increasing the affinity with the water-soluble polymer (x) described later. It is preferable to use a coalescence, more preferably a styrene macromer.

[Nonionic monomer (d)]
The monomer mixture may further contain a nonionic monomer (d) (hereinafter also referred to as “component (d)”).
(D) As a component, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polyethyleneglycol (n = 2-30, n shows the average addition mole number of an oxyalkylene group. The same hereafter). (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, methoxypolyethylene glycol ( n = 1-30) (meth) acrylate, methoxypolytetramethylene glycol (n = 1-30) (meth) acrylate, ethoxypolyethylene glycol (n = 1-30) (meth) acrylate, octoxypolyethylene glycol (n = 1-30) (meth) acrylate, Liethylene glycol (n = 1-30) (meth) acrylate 2-ethylhexyl ether, (iso) propoxypolyethylene glycol (n = 1-30) (meth) acrylate, butoxypolyethylene glycol (n = 1-30) (meth) acrylate , Methoxypolypropylene glycol (n = 1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol copolymer) (n = 1-30, ethylene glycol: 1-29 therein) (meth) acrylate, phenoxypolyethylene Glycol (n = 1-15) -polypropylene glycol (n = 1-15) -methacrylate and the like.

Specific examples of the commercially available component (d) include NK Esters M-40G, 90G, and 230G from Shin-Nakamura Chemical Co., Ltd., Bremer PE-90, 200, and 350 from NOF Corporation. PME-100, 200, 400, 1000, PP-500, 800, 1000, AP-150, 400, 550, 800, 50PEP-300, 50POEP-800B, 43PAPE-600B, etc. Can be mentioned.
The components (a) to (d) can be used alone or in admixture of two or more.

The content of the structural unit derived from the components (a) to (d) in the water-insoluble polymer (y) is as follows.
The content of the structural unit derived from the component (a) is preferably 4 to 40% by weight, more preferably 5 to 30% by weight, still more preferably 10 to 30% by weight, from the viewpoint of enhancing the dispersibility of the polymer particles. Particularly preferred is 10 to 25% by weight.
The content of the structural unit derived from the component (b) is preferably 5 to 98% by weight, more preferably 10 to 60% by weight, from the viewpoint of increasing the affinity of the polymer for the pigment mixture.
The content of the structural unit derived from the component (c) is preferably 1 to 25% by weight, more preferably 5 to 20% by weight, from the viewpoint of increasing the affinity of the polymer for the pigment mixture.
The content of the structural unit derived from the component (d) is preferably 5 to 60% by weight, more preferably 17 to 50% by weight, from the viewpoint of enhancing the dispersibility of the polymer particles.
Moreover, 50-200 are preferable and, as for the acid value in case (a) component is an anionic monomer, 50-160 are more preferable.
The weight average molecular weight of the water-insoluble polymer (y) is preferably 5,000 to 500,000, more preferably 10,000 to 400,000, and 10,000 to 300,000 from the viewpoint of the storage stability of the aqueous dispersion and the water-based ink. More preferred is 20,000 to 300,000. In addition, the weight average molecular weight of this polymer can be measured by the method as described in an Example.

(Water-soluble polymer (x))
In the present invention, the water-insoluble polymer (x) is used together with the water-insoluble polymer (y) from the viewpoint of atomizing the pigment, improving dispersibility, mainly reducing the viscosity of the ink, and suppressing the change in the light absorption characteristics of the pigment. Used.
The water-soluble polymer (x) is preferably a vinyl polymer obtained by addition polymerization of a vinyl monomer or a urethane polymer having a urethane bond, and a salt-forming group-containing monomer (a) (same as the component (a) above) And a vinyl polymer obtained by copolymerizing a monomer mixture (same as the above “monomer mixture”) containing a hydrophobic monomer (b) (same as the above component (b)).

[Salt-forming group-containing monomer (a)]
Specific examples and preferred examples of the salt-forming group-containing monomer (a) in the water-soluble polymer (x) are the same as described above. Among them, a carboxylic acid monomer is preferable from the viewpoint of improving the dispersibility of the polymer particles, acrylic acid and methacrylic acid are more preferable, and acrylic acid is further preferable from the viewpoint of increasing solubility in water.

[Hydrophobic monomer (b)]
Specific examples and preferred examples of the hydrophobic monomer (b) in the water-soluble polymer (x) are the same as described above. Among them, styrene and benzyl (meth) acrylate are preferable, and styrene is more preferable from the viewpoint of increasing the affinity of the polymer for the pigment mixture.
Further, as described above, from the viewpoint of increasing the affinity with the water-insoluble polymer (y), the component (b) in the water-insoluble polymer (y) and the water-soluble polymer (x) is preferably the same.

The water-soluble polymer (x) preferably contains 5 to 80% by weight, more preferably 10 to 60% by weight, and still more preferably 15 to 40% by weight of the structural unit derived from the component (a). The structural unit derived from the component is preferably 15 to 95% by weight, more preferably 25 to 90% by weight, still more preferably 50 to 80% by weight, and the structural unit derived from the component (b) is a styrene monomer. The structural unit derived from is preferably contained, and the structural unit derived from the styrene monomer is contained in the total amount of the water-soluble polymer (x), preferably 50 to 90% by weight, more preferably 50 to 80% by weight.
The water-soluble polymer (x) has a weight average molecular weight of preferably 1000 to 300,000, more preferably 10,000 to 200,000, from the viewpoint of improving dispersibility. In addition, the weight average molecular weight of this polymer can be measured by the method as described in an Example.
The acid value when component (a) is an anionic monomer is preferably 150 to 300 KOHmg / g, more preferably 170 to 250 KOHmg / g.
Examples of commercially available water-soluble polymers (x) include BASF Japan's Jonkrill (registered trademark) 57J, 60J, 61J, 63J, 70J, PD-96J, and 501J. . These commercially available polymers are neutralized, and a neutralizing agent may be added separately as necessary.

(Production of polymer)
The water-insoluble polymer (y) and the water-soluble polymer (x) (hereinafter collectively referred to as “polymer”) used in the present invention are bulk polymerization, solution polymerization, suspension polymerization, emulsification. It is produced by copolymerizing the monomer mixture by a known polymerization method such as a polymerization method. Among these polymerization methods, the solution polymerization method is preferable.
The solvent used in the solution polymerization method is preferably a polar organic solvent. When the polar organic solvent is miscible with water, it can be used by mixing with water. As the polar organic solvent, for example, aliphatic alcohols having 1 to 3 carbon atoms; ketones having 3 to 8 carbon atoms; esters such as ethyl acetate; or a mixed solvent of one or more of these with water.
In the polymerization, a known radical polymerization initiator such as an azo compound or an organic peroxide 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, solvent, etc. used, it cannot be generally stated, but usually the polymerization temperature is preferably 30 to 100 ° C, more preferably 50 to 80 ° C. 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 polymer produced by a known method can be isolated. Further, the obtained polymer can be purified by removing the unreacted monomer and the like by re-precipitation by membrane separation, chromatographic method, extraction method or the like.

The polymer used in the present invention is preferably used after neutralizing the salt-forming group derived from the salt-forming group-containing monomer (a) with a neutralizing agent. When the salt-forming group is an anionic group, examples of the neutralizing agent include bases such as sodium hydroxide, potassium hydroxide and various amines.
The degree of neutralization of the salt-forming groups of the polymer is preferably 10 to 300%, more preferably 20 to 200%, from the viewpoint of improving the dispersion stability of the polymer particles (A) in the ink. More preferably, ˜150%.
Here, the degree of neutralization when the salt-forming group is an anionic group can be determined by the following formula.
{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [acid value of polymer (KOH mg / g) × polymer weight (g) / (56 × 1000)]} × 100
The acid value can be calculated by calculation from the structural unit of the polymer, or can be determined by a method in which the polymer is dissolved in an appropriate solvent (for example, methyl ethyl ketone) and titrated.

[Polymer particles containing pigment]
In the water-based ink (I) used in the present invention, a pigment that does not have self-dispersibility is dispersed with a polymer, but a pigment that does not have self-dispersibility is contained in the polymer. It is preferable that the polymer particles contain “a polymer particle containing” or “a crosslinked polymer particle containing a pigment having no self-dispersibility”.
Polymer particles containing a pigment (hereinafter also simply referred to as “polymer particles (A)”) can be obtained by dispersing a pigment with a water-insoluble polymer (y) and a water-soluble polymer (x).
By using a water-soluble polymer (x) and a water-insoluble polymer (y) in combination as a pigment dispersant, it is possible to obtain an aqueous ink for ink-jet recording having high storage density and excellent storage stability even when the solid content concentration is high. At the same time, when mixed with water-based ink (II), which is a water-based ink containing a self-dispersing pigment, and used as a secondary color, it is possible to preserve the ink without any hue error or turbidity, because the mixing property of both inks increases. An ink set for ink jet recording can be obtained which has excellent stability and bleed resistance, little change in light absorption characteristics, and excellent fixability to recording paper. This is because, in part, the water-insoluble polymer (y) can coat the surface of the pigment and finely disperse the pigment, and the water-insoluble polymer (x) stabilizes the water-insoluble polymer particles containing the pigment. Further, it is considered that the use of the water-based ink containing the self-dispersing pigment as the water-based ink (II) makes it possible to improve the mixing property of both inks although the detailed reason is unknown.

The weight ratio of the pigment to the water-insoluble polymer (y) [pigment / water-insoluble polymer (y)] is compatible with both the print density and the storage stability, and the mixing property between the water-based ink (I) and the water-based ink (II). 1 to 20, preferably 1 to 10, more preferably 2 to 6, more preferably from the viewpoint of improving color stability, reducing hue error and turbidity as a secondary color ink, and improving storage stability.
The weight ratio of the pigment to the water-soluble polymer (x) [pigment / water-soluble polymer (x)] reduces the viscosity of the ink and suppresses the change in the light absorption characteristics of the pigment, and the water-based ink (I) and water-based ink (II 15 to 25, preferably 25 to 25, more preferably 17 to 25, and more preferably 17 to 23, from the viewpoint of improving the mixing property with the above) and lowering the viscosity of the ink as a secondary color ink and suppressing the change in light absorption characteristics of the pigment. .
The weight ratio [pigment / [(y) + (x)]] of the pigment to the total amount [(y) + (x)] of the water-insoluble polymer (y) and the water-soluble polymer (x) used for dispersion is the print density. In addition to compatibility with storage stability, the ink is reduced in viscosity to suppress changes in the light absorption characteristics of the pigment, and the mixing property of the water-based ink (I) and water-based ink (II) is improved, so that the secondary color ink From the viewpoint of reducing the viscosity of the ink and suppressing changes in the light absorption characteristics of the pigment, 50/50 to 95/5 are preferable, 60/40 to 95/5 are more preferable, and 70/30 to 95/5 are further preferable.
The weight ratio [(y) / (x)] of the water-insoluble polymer (y) to the water-soluble polymer (x) reduces the viscosity of the ink and suppresses changes in the light absorption characteristics of the pigment in addition to the print density and storage stability. From the viewpoint of doing, it is 2.0 to 5.0, preferably 2.5 to 5.0, and more preferably 3.0 to 5.0.
The polymer particles (A) are efficiently and preferably produced as an aqueous dispersion by a method having the steps (i) and (ii) described in the method for producing an aqueous dispersion described later.

[Crosslinked polymer particles containing pigment]
In the water-based ink (I) used in the present invention, while maintaining the viscosity low, the viewpoint of improving the print density and the mixing property between the water-based ink (I) and the water-based ink (II) are improved, and the secondary color ink is used. From the viewpoint of reducing the viscosity of the ink and reducing the hue error and turbidity, the water-insoluble polymer (y) or the water-soluble polymer (x) and the water-insoluble polymer (y) should contain a cross-linked polymer. Is preferred.
The crosslinking rate (mol%) of the crosslinked polymer is preferably 10 to 90 mol%, more preferably 20 to 80 mol%, and even more preferably 30 to 70 mol%. The crosslinking rate is determined by the method described later. Can do.
The crosslinked polymer particles are preferably produced as an aqueous dispersion by the method having the step (iii) described in the method for producing an aqueous ink described later.

[Method for producing aqueous dispersion for inkjet recording]
The aqueous dispersion for ink-jet recording of the present invention can efficiently produce an aqueous dispersion used for the aqueous ink (I) according to the method having the following steps (i) and (ii). Furthermore, by having the following step (iii), an aqueous dispersion for inkjet recording containing crosslinked polymer particles containing a crosslinked polymer obtained by crosslinking a water-soluble polymer (x) and a water-insoluble polymer (y) is efficiently produced. can do.
Step (i): Dispersing the pigment with the water-soluble polymer (x) and water to obtain an aqueous dispersion Step (ii): Adding the water-insoluble polymer (y) to the aqueous dispersion obtained in step (i) Step of obtaining a dispersion containing pigment-containing polymer particles (A) Step (iii): The dispersion obtained in step (ii), or obtained by removing the solvent from the dispersion Step of performing a crosslinking treatment on the aqueous dispersion The aqueous ink (I) used in the present invention is the step (i) to (ii) or the step (i) to
The dispersion obtained in (iii) can be obtained by adding an additive such as a wetting agent ordinarily used in water-based ink as necessary.

Process (i)
Step (i) is a step of dispersing the pigment with the water-soluble polymer (x) to obtain an aqueous dispersion. First, the water-soluble polymer (x), the pigment, water, and, if necessary, a neutralizing agent, A method of mixing a surfactant or the like to obtain the mixture and dispersing the mixture with a disperser is preferred.
In the mixture, the pigment 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, and the water-soluble polymer (x) 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.
The preferred weight ratio between the water-soluble polymer (x) and the pigment is as described above.
When neutralizing with a neutralizing agent, it is preferable to neutralize so that the finally obtained aqueous dispersion has a pH of 7-11. Examples of the neutralizing agent include bases such as sodium hydroxide, potassium hydroxide, and various amines. Further, the water-soluble polymer (x) may be neutralized in advance.
Examples of the organic solvent are the same as described above.

There is no restriction | limiting in particular in the dispersion method of the mixture in process (i). Although the average particle size of the pigment particles can be atomized only by the main dispersion until the desired particle size is obtained, preferably the pre-dispersion is performed, and then the main dispersion is further performed by applying a shear stress to obtain the average particle size of the pigment particles. It is preferable to control the diameter to a desired particle diameter. The temperature in the dispersion in the step (i) is preferably 5 to 50 ° C, more preferably 5 to 35 ° C, and the dispersion time is preferably 1 to 30 hours, more preferably 1 to 25 hours.
When pre-dispersing the mixture, commonly used mixing and stirring devices such as anchor blades and disper blades, such as Ultra Disper, Desperm (Asada Tekko Co., Ltd., trade name), Milder (Ebara Manufacturing Co., Ltd.) High-speed agitation and mixing devices such as TK Homomixer, TK Pipeline Mixer, TK Homojetter, TK Homomic Line Flow, and Fillmix (hereinafter, Primix Co., Ltd., trade name) are preferred.
Examples of means for applying the shear stress of this dispersion include a kneader such as a roll mill, a kneader, and an extruder, and a high pressure homogenizer represented by a high pressure homogenizer (Izumi Food Machinery Co., Ltd., trade name), 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 Ultra Apex Mill (manufactured by Kotobuki Kogyo Co., Ltd., trade name), Picomill (manufactured by Asada Tekko Co., Ltd., trade name), Dino Mill (manufactured by Shinmaru Enterprises Co., Ltd., trade name), etc. Is mentioned. A plurality of these devices can be combined. Among these, a high-pressure homogenizer is preferable from the viewpoint of improving the stability of the pigment.
Among these, from the viewpoint of reducing the particle size of pigment particles and stabilizing the dispersion, it is also preferable to use a high-pressure homogenizer and a media-type disperser in combination.

Step (ii)
Step (ii) is a step of adding a water-insoluble polymer (y) to the water dispersion obtained in step (i) and further dispersing it to obtain a dispersion containing polymer particles (A) containing a pigment. A method of preparing and dispersing a mixture containing the water dispersion obtained in step (i), the water-insoluble polymer (y), an organic solvent, water, and, if necessary, a neutralizing agent and a surfactant. It is preferable to use a dispersion of a water-insoluble polymer (y) containing a water-insoluble polymer (y), an organic solvent and water.
In the mixture, the pigment 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, and the water-insoluble polymer (y ) 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.
The preferred weight ratio between the water-insoluble polymer (y) and the pigment is as described above.
When neutralizing with a neutralizing agent, it is preferable to neutralize so that the finally obtained aqueous dispersion has a pH of 7-11. Further, the anionic 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.

The method for dispersing the mixture obtained by adding the water-insoluble polymer (y) to the water dispersion obtained in step (i) in step (ii) is not particularly limited, as in step (i). After the dispersion, the main dispersion may be performed by further applying a shear stress. However, the average particle diameter of the polymer particles can be atomized only by the main dispersion until a desired particle diameter is obtained. The temperature in the dispersion in the step (ii) is preferably 5 to 50 ° C, more preferably 5 to 35 ° C, and the dispersion time is preferably 1 to 30 hours, more preferably 1 to 25 hours.
When preliminarily dispersing the mixture, the above-described mixing and stirring device or the like is preferably used.
Examples of means for imparting the shear stress of this dispersion include the kneader, the high-pressure homogenizer, and the media-type disperser. Among these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle diameter of the polymer particles (A) and stabilizing the dispersion.

Step (iii)
Step (iii) is a step of performing a crosslinking treatment on the dispersion containing the polymer particles (A) obtained in step (ii), or the aqueous dispersion obtained by removing the solvent from the dispersion. When the dispersion containing the polymer particles (A) obtained in the step (ii) or the dispersion obtained in the step (ii) contains a solvent, the dispersion is obtained by removing the solvent from the dispersion. By adding a crosslinking agent to the aqueous dispersion of polymer particles (A), an aqueous dispersion containing crosslinked polymer particles obtained by crosslinking the water-insoluble polymer (y) and the water-soluble polymer (x) can be obtained. In step (iii), the viscosity of the water-based ink is reduced, the printing density is improved, and the mixing property of the water-based ink (I) and the water-based ink (II) is improved. From the viewpoint of reducing hue error and turbidity.

(Solvent removal step)
In the method for producing the water-based ink, as an optional step, after the step (ii), the organic solvent is distilled off from the dispersion containing the polymer particles (A) obtained in the step (ii) by a known method. By making an aqueous system, an aqueous dispersion of polymer particles (A) can be obtained.
The organic solvent in the aqueous dispersion of the obtained polymer particles (A) is preferably substantially removed, but may remain as long as the object of the present invention is not impaired, and the crosslinking step is performed later. In such a case, it may be additionally removed after cross-linking if necessary. The amount of the residual organic solvent in the aqueous dispersion of the polymer particles (A) finally obtained 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.
The obtained aqueous dispersion of polymer particles (A) is one in which the solid content of the polymer is dispersed in water as a main medium. Here, the form of the polymer particles (A) is not particularly limited as long as the particles are formed of at least a pigment and a polymer. For example, a particle form in which the pigment is included in the polymer, a particle form in which the pigment is uniformly dispersed in the polymer, a particle form in which the pigment is exposed on the polymer particle surface, and the like are included.
When the polymer is crosslinked by mixing the dispersion of the polymer particles (A) containing the pigment obtained in the step (ii) and a crosslinking agent, the dispersion of the crosslinked polymer particles obtained in the crosslinking step is performed. An aqueous dispersion can also be obtained by performing the step of removing the organic solvent from the body in the same manner as the solvent removal step.

(Crosslinking agent)
Preferable examples of the crosslinking agent include the following (a) to (c).
(A) 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.
(B) 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.
(C) Compound having two or more isocyanate groups in the molecule: for example, organic polyisocyanate or isocyanate group-terminated prepolymer.
Among these, (a) 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.

The amount of the crosslinking agent used is to lower the viscosity of the polymer particles (A) in the ink and to improve the mixing property of the water-based ink (I) and the water-based ink (II). From the viewpoint of reducing the hue error and turbidity, the weight ratio of [crosslinking agent / polymer (total of water-soluble polymer (x) and water-insoluble polymer (y))] is 5/100 to 25/100. Is preferable, 7/100 to 25/100 is more preferable, 10/100 to 25/100 is still more preferable, and 16/100 to 20/100 is still more preferable.
The amount of the crosslinking agent used is preferably an amount that reacts with 0.05 to 10 mmol as the number of moles of the reactive group of the crosslinking agent per 1 g of the polymer, and is 0.1 to 5 mmol. It is more preferable that the amount reacts with 0.1 to 2 mmol.

The conditions during the crosslinking reaction are preferably 60 to 95 ° C. and 0.5 to 7 hours.
The crosslinked polymer in the aqueous dispersion of crosslinked polymer particles obtained in the step (iii) preferably contains 0.5 mmol or more of neutralized salt-forming groups (preferably carboxy groups) per 1 g of the crosslinked polymer. Such a crosslinked polymer is considered to contribute to the stability of the crosslinked polymer particles containing the pigment by dissociating in the aqueous dispersion and charge repulsion between the salt-forming groups.
Here, the crosslinking rate (mol%) of the crosslinked polymer obtained from the following calculation formula (3) is preferably 10 to 90 mol%, more preferably 20 to 80 mol%, and still more preferably 30 to 70 mol%. . The crosslinking rate can be determined by calculation from the amount of the crosslinking agent used and the number of moles of the reactive group, the amount of polymer used and the number of moles of the reactive group of the polymer that can react with the reactive group of the crosslinking agent.
Crosslinking rate (mol%) = [number of moles of reactive group of crosslinking agent / number of moles of reactive group capable of reacting with crosslinking agent of polymer] × 100 (3)
In the calculation formula (3), “the number of moles of the reactive group of the crosslinking agent” is obtained by multiplying the number of moles of the crosslinking agent to be used by the number of reactive groups in one molecule of the crosslinking agent.

[Water-based ink for ink-jet recording (I)]
The aqueous dispersion used in the aqueous ink (I) used in the present invention is obtained by the above production method, and may be used as it is as an aqueous ink using water as a main medium.
The content of each component in the aqueous dispersion of the present invention is as follows.
The content of the pigment is preferably 1 to 25% by weight, more preferably 2 to 20% by weight, still more preferably 4 to 15% by weight, and particularly preferably 4 to 12% by weight from the viewpoint of increasing the printing density. 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 water-based ink (I) contains the above-mentioned aqueous dispersion. Here, “water-based” means that water accounts for the largest proportion in the medium contained in the water-based ink. In some cases, the medium is water alone, and a mixed solvent of water and one or more organic solvents is also included. To this water-based ink, wetting agents, penetrants, dispersants, viscosity modifiers, antifoaming agents, antifungal agents, rust preventive agents and the like that are usually used in water-based inks can be added.
The content of each component in the aqueous ink of the present invention is as follows.
The content of the pigment is from the viewpoints of both the print density and storage stability, and the secondary color ink comprising the water-based ink (I) and the water-based ink (II), such as the ink print density and the storage stability. The content is preferably 3 to 30% by weight, more preferably 4 to 20% by weight, still more preferably 4 to 15% by weight, and particularly preferably 4 to 12% by 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 average particle size of the water-based ink (I) is preferably 30 nm to 300 nm, more preferably 50 nm to 200 nm, from the viewpoints of high-speed printer suitability and printing performance.
The water content in the water-based ink is compatible with both the print density and storage stability, and as the secondary color ink consisting of the water-based ink (I) and water-based ink (II), the ink print density and storage stability, etc. From the viewpoint of compatibility, it is 60% by weight or less, preferably 20 to 60% by weight, more preferably 30 to 60% by weight, still more preferably 30 to 57% by weight, and particularly preferably 30 to 55% by weight.
The content of the hydrophilic organic solvent in the water-based ink (I) is composed of both the water-based ink (I) and the water-based ink (II), while suppressing the increase in viscosity and achieving both printing density and storage stability. As a secondary color ink, 10% by weight or more is preferable, 10 to 80% by weight is more preferable, 15 to 50% by weight is further more preferable, and 15 to 35% by weight is preferable from the viewpoint of coexistence of ink printing density and storage stability. Even more preferred.
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.

[Water-based ink for ink-jet recording (II)]
The aqueous ink (II) used in the present invention is the same as the aqueous ink (I) except that the pigment used is a self-dispersing pigment. However, since the pigment is a self-dispersing pigment, it is not necessary to use a polymer or a surfactant as a dispersant, and it is not necessary to coat the pigment with a polymer. In the present invention, the mixing with the water-based ink (I) is improved, the hue error and turbidity of the secondary color ink are reduced, the storage stability and bleed resistance are improved, the change in light absorption characteristics is reduced, and From the viewpoint of obtaining fixing properties on recording paper, it is preferable that the water-based ink (II) does not use a polymer or a surfactant as a dispersant.
Further, from the viewpoint of improving the bleed resistance and the fixing property to the recording paper, the water base ink (II) for ink jet recording preferably contains a resin emulsion. Known resin emulsions can be used.

[Resin emulsion]
The resin emulsion has the effect of improving the fixability of the image portion of the recorded matter because the resin particles and the resin particles and the coloring component are fused to each other as the ink is dried to fix the colorant to the recording medium. .
These resin particles are preferably one or more selected from the group consisting of acrylic resins, methacrylic resins, styrene resins, urethane resins, acrylamide resins, and epoxy resins. These resins may be used as homopolymers or as copolymers.
In the present invention, resin particles having a single particle structure can be used. On the other hand, in the present invention, it is also possible to use resin particles having a core / shell structure including a core portion and a shell portion surrounding the core portion. The “core / shell structure” means “a form in which two or more kinds of polymers having different compositions exist in phase separation in particles”. Therefore, the shell portion may not only cover the core portion completely, but may cover a portion of the core portion. Moreover, it can obtain by well-known emulsion polymerization. That is, it can be obtained by emulsion polymerization of an unsaturated vinyl monomer (unsaturated vinyl monomer) in water in the presence of a polymerization catalyst and an emulsifier.

As unsaturated vinyl monomers, acrylic acid ester monomers, methacrylic acid ester monomers, aromatic vinyl monomers, vinyl ester monomers, vinyl, which are generally used in emulsion polymerization Cyanide monomers, halogenated monomers, olefin monomers, diene monomers and the like can be mentioned.
Further, specific examples include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, dodecyl acrylate. Acrylic esters such as octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, glycidyl acrylate; methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl Methacrylate, 2-ethyl Methacrylic esters such as hexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, glycidyl methacrylate; and vinyl esters such as vinyl acetate; vinyl such as acrylonitrile, methacrylonitrile Cyanogen compounds; halogenated monomers such as vinylidene chloride and vinyl chloride; aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, chlorostyrene, vinylanisole and vinylnaphthalene Olefins such as ethylene and propylene, dienes such as butadiene and chloroprene, vinyl ether, vinyl ketone, vinyl pyrrolidone Vinyl monomers such as; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid; acrylamides such as acrylamide and N, N′-dimethylacrylamide; 2-hydroxyethyl acrylate, 2 -Hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and hydroxyl group-containing monomers such as 2-hydroxypropyl methacrylate.

  Moreover, in this invention, what has the structure bridge | crosslinked by the crosslinkable monomer which has two or more polymerizable double bonds can be used as a molecule | numerator derived from the said monomer. Examples of the crosslinkable monomer having two or more polymerizable double bonds include polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 1,9-nonanediol diacrylate, polypropylene glycol diacrylate, 2,2′-bis (4-acryloxypropyloxyphenyl) propane, 2,2 ′ -Diacrylate compounds such as bis (4-acryloxydiethoxyphenyl) propane, triacrylate compounds such as trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate Tetraacrylate compounds such as ditrimethylol tetraacrylate, tetramethylol methane tetraacrylate, pentaerythritol tetraacrylate, hexaacrylate compounds such as dipentaerythritol hexaacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol di Methacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polybutylene glycol dimethacrylate Methacrylate, 2, Examples include dimethacrylate compounds such as 2′-bis (4-methacryloxydiethoxyphenyl) propane, trimethacrylate compounds such as trimethylolpropane trimethacrylate and trimethylolethane trimethacrylate, methylenebisacrylamide, and divinylbenzene. Or 2 or more types can be mixed and used.

Moreover, the polymerization initiator, the emulsifier, and the molecular weight modifier used in the emulsion polymerization can be used according to a conventional method.
As the polymerization initiator, those used for normal radical polymerization are used, for example, potassium persulfate, ammonium persulfate, hydrogen peroxide, azobisisobutyronitrile, benzoyl peroxide, dibutyl peroxide, Examples include peracetic acid, cumene hydroperoxide, t-butyl hydroxy peroxide, paramentane hydroxy peroxide, and the like. In particular, as described above, when the polymerization reaction is performed in water, a water-soluble polymerization initiator is preferable.
Examples of the emulsifier include sodium lauryl sulfate, those generally used as anionic surfactants, nonionic surfactants, or amphoteric surfactants, and mixtures thereof. These may be used alone or in combination of two or more. Can be used as a mixture.
When the resin particles are produced by emulsion polymerization, particularly when a polymer emulsion composed of anionic resin particles is produced by emulsion polymerization, negative polar groups such as carboxyl groups and sulfonic acid groups are formed on the resin particle surface. Is present, the pH is inclined to the acidic side, and viscosity increases and aggregation tends to occur. Therefore, neutralization with a basic substance is usually performed. As this basic substance, ammonia, organic amines, inorganic hydroxides and the like can be used. Of these, monovalent inorganic hydroxides (potassium hydroxide, sodium hydroxide, lithium hydroxide) are particularly preferred from the viewpoints of long-term storage stability and ejection stability of the polymer emulsion and aqueous ink composition. The addition amount of the neutralizing agent is appropriately determined so that the pH of the polymer emulsion is in the range of 7.5 to 9.5, preferably in the range of 7.5 to 8.5.

From the viewpoints of long-term storage stability and ejection stability of the ink composition, the resin particles preferably used in the present invention have a particle size in the range of 5 to 400 nm, more preferably in the range of 50 to 200 nm.
The addition amount of these resin emulsions may be appropriately determined in consideration of fixability and the like, but each ink composition preferably contains 1% by weight or more in terms of solid content.
The weight ratio (self-dispersing pigment / resin particles) of the self-dispersing pigment in the water-based ink (II) and the resin particles in the resin emulsion (solid content of the resin emulsion) improves bleed resistance and fixability to recording paper. In view of the above, 10/1 to 1/1 is preferable, 7/1 to 2/1 is more preferable, and 5/1 to 2/1 is more preferable.

<Ink set for inkjet recording>
The ink set for inkjet recording of the present invention is an ink set comprising two or more kinds of colored inks, wherein the first kind of colored ink is a water-based ink (I) containing a pigment having no self-dispersibility, The two colored inks are water-based ink (II) containing a self-dispersing pigment.
The ink set of the present invention may be any of a two-color ink set selected from chromatic pigments, a three-color ink set, a four-color ink set, a five-color ink set, a six-color ink set, a seven-color ink set or more. Good. Examples thereof include water-based inks containing two or more pigments selected from cyan, yellow, magenta, light cyan, dark yellow, light magenta, red, green, and blue. More preferably, the ink set includes one or more colored inks selected from magenta ink, yellow ink, and cyan ink, which are three subtractive primary colors, and two or more kinds of colored inks are provided as these colored inks. An ink set is more preferable, and an ink set including three kinds of colored inks is still more preferable. The ink set of the present invention can further include black ink.

In the ink set for ink jet recording of the present invention, the mixing property of the water-based ink (I) and the water-based ink (II) is improved, the hue error and turbidity of the secondary color ink are reduced, and the storage stability and bleed resistance are reduced. As a pigment that does not have self-dispersibility for use in the water-based ink (I), an azo pigment is preferable, for example, in the case of yellow ink. Is C.I. I. Pigment Yellow 74 is preferable. Further, as a self-dispersing pigment used in the water-based ink (II), for example, in black ink, carbon black having a hydrophilic functional group on the surface, or in chromatic ink other than yellow ink, for example, via a phenyl group on the surface. A chromatic pigment having a hydrophilic functional group is preferable, carbon black having a hydrophilic functional group on the surface, or a cyan pigment having a hydrophilic functional group on the surface via a phenyl group is more preferable, and a phenyl group is formed on the surface. C. having a hydrophilic functional group via I. Pigment Blue 15: 3 is more preferable.
That is, in the present invention, from the viewpoint of obtaining an ink set with little change in optical characteristics, excellent bleed resistance and storage stability, and excellent fixability to recording paper without hue error and turbidity, water-based ink (I The pigment having no self-dispersibility used in the above) is a yellow pigment, and the self-dispersing pigment used in the water-based ink (II) is preferably a cyan pigment. The self-dispersibility used in the water-based ink (I) is preferably As a pigment not having C.I. I. Pigment Yellow 74, a self-dispersing pigment used for water-based ink (II), C.I. I. More preferred is an ink set comprising CI Pigment Blue 15: 3. Further, from the viewpoint of enhancing the storage stability as a secondary color, the aqueous ink (I) preferably contains the azo pigment (B).

In the following production examples, examples and comparative examples, “parts” and “%” are “parts by weight” and “% by weight” unless otherwise specified.
In addition, the weight average molecular weight of the polymer obtained by the manufacture example, the Example, and the comparative example, the average particle diameter, various physical properties of the aqueous dispersion and the water-based ink were measured and evaluated by the following methods.

1. Measurement of the amount of acidic groups The amount of acidic groups can be determined by the following method as the amount reacted with a strong alkali such as NaOH or KOH.
(Measurement condition)
Apparatus: Kyoto Denshi Kogyo Co., Ltd., potentiometric automatic titrator, AT-610
Titration conditions: 0.01 N HCl, titration 0.02 ml, intermittent time 30 seconds, 25 ° C.
0.01N-NaOH used was 0.01 mol / L sodium hydroxide (for volumetric analysis) manufactured by Wako Pure Chemical Industries, and 0.01N-HCl used 0.01 mol / L hydrochloric acid (for volumetric analysis) manufactured by Wako Pure Chemical Industries.
(Measurement procedure)
By accurately weighing an aqueous dispersion of carbon black to a solid content of 0.05 g, adding ion-exchanged water to 50 ml, adding 1.5 ml (excess amount) of 0.01 N NaOH and stirring for 30 minutes. All acid groups were Na salts. To this alkaline dispersion, 0.02 g of 0.01N HCl is added dropwise at 30 second intervals while stirring, and the pH is measured. Starting from the neutralization point (inflection point 1) where the excess alkali is neutralized, and the neutralization point from the most acidic (final inflection point 2) among the subsequent neutralization inflection points From the final inflection point 2 to the inflection point 1, the amount of acidic groups of the particles was calculated from the amount of 0.01 N HCl used, and the equivalent per 1 g of solid content was calculated. The measurement was performed at 20 ° C.

2. Evaluation of polymer (1) Measurement of weight average molecular weight of polymer Gel chromatography method using N, N-dimethylformamide containing 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as a solvent [manufactured by Tosoh Corporation Measurement was performed using polystyrene as a standard substance with a GPC apparatus (HLC-8120GPC), a column (TSK-GEL, α-M × 2) manufactured by Tosoh Corporation, and a flow rate of 1 mL / min.

3. Evaluation of Ink as Ink Set The following evaluation is an evaluation of a mixed ink in which the ink (I) and the ink (II) shown in Table 2 are uniformly mixed at 1: 1.
(1) Measurement of average particle diameter It measured using the laser particle analysis system "ELS-8000" (cumulant analysis) of Otsuka Electronics Co., Ltd. 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. The measurement concentration was usually about 5 × 10 ⁻³ wt%.
(2) Measurement of viscosity The viscosity was measured at 20 ° C using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., RE80L).
(3) Evaluation of storage stability The screw tube was filled with a water dispersion of a pigment mixture-containing (crosslinked) polymer particle having a solid content of 30% and water-based ink, sealed, and stored in a thermostatic bath at 70 ° C. for 1 week. The average particle size and viscosity before and after storage were measured by the above (1) and (2), respectively, and the average particle size change rate (%) and viscosity change rate (%) were determined by the following calculation formulas. evaluated.
Average particle diameter change rate (%) = 100 − [[average particle diameter after storage] / [average particle diameter before storage]] × 100
When the average particle size change rate and viscosity change rate are close to 100%, the storage stability is excellent, that is, the ink (I) and the ink (II) are excellent in the mixing property as the secondary color and excellent in the ink. Indicates that it will be a set.
(Evaluation criteria)
A: Change rate of average particle size is within ± 10% B: Change rate of average particle size exceeds ± 10% and within ± 15% C: Change rate of average particle size exceeds ± 15% Viscosity change rate (%) = 100 − [[viscosity after storage] / [viscosity before storage]] × 100
(Evaluation criteria)
A: Viscosity change rate is within ± 10% B: Viscosity change rate exceeds ± 10%, within ± 15% C: Viscosity change rate exceeds ± 15%

(4) Evaluation of change in light absorption characteristics (3) The water-based ink used in the storage stability evaluation was diluted 10,000 times with water, and the absorption spectrum of the diluted solution was spectrophotometer (manufactured by Hitachi, Ltd., model number : U-3010), and measured over an absorption wavelength range of 370 to 800 nm. The amount of change with respect to the maximum absorption wavelength of the absorption spectrum before storage at 70 ° C. for one week was calculated and evaluated according to the following criteria. The smaller the change in the light absorption characteristic, the better the compatibility between the ink (I) and the ink (II), and the better the ink set.
(Evaluation criteria)
A: Change in maximum absorption wavelength is 1 nm or less B: Change in maximum absorption wavelength exceeds 1 nm to 3 nm or less C: Change in maximum absorption wavelength exceeds 3 nm

(5) Hue error and turbidity evaluation Solid images are printed on plain paper "4024" (manufactured by Fuji Xerox Co., Ltd.) using a commercially available Seiko Epson inkjet printer (part number: EM-930C, piezo method). Then, after being left for one day, an optical densitometer SpectroEye (manufactured by Gretag Macbeth Co., Ltd.) was used to measure any 10 locations over almost the entire surface, and the average value of all the concentrations was obtained.
The numerical expression in the concentration was in accordance with the following formula according to GATF (Graphic Art Technical Foundation) regulations.
Hue error: ((ML) / (HL)) × 100 (%)
Grayness: (L / H) x 100 (%)
H: highest density, M: average density at 10 locations, L: lowest density Hue error indicates that there is no hue error as the value is higher, and turbidity indicates that there is no turbidity as the value is smaller.

(6) Bleeding between color inks Using the printer, solid printing was performed with yellow ink in each ink set on recycled paper for PPC, and immediately after that, solid printing of each color ink was performed with cyan ink so as to be adjacent thereto. The border portion of the obtained solid print was visually observed, and bleeding between color inks was evaluated in four stages.
A: Bleeding is not recognized at all boundaries.
B: Slight bleeding is observed.
C: Some bleeding is observed.
D: Bleeding at almost all boundaries is recognized.

(7) Evaluation of Fixability Using the printer, a solid image having a size of 20 mm × 20 mm is printed on the same plain paper “4024” as in the above (5), and is separated from the printed image after 10 seconds. The surface of the plain paper P was overlapped, and the surface of the solid image was moved in a state where a load of 490 g (load area 43 mm × 30 mm) was applied from above, and the stain on the stacked paper was measured. Evaluation was performed according to the following criteria.
(Evaluation criteria)
A: The printed image is hardly peeled off and the unprinted image portion is not stained.
B: The printed image is hardly peeled off and the surroundings are slightly stained.
C: Printed material is peeled off and the surroundings are very dirty.

Production Examples 1 to 3 (Preparation of water-insoluble polymer solution)
In a reaction vessel, 10 parts of methyl ethyl ketone, 0.01 part of a polymerization chain transfer agent (2-mercaptoethanol), and the initial charge monomer (shown in parts by weight) shown in Table 1 are mixed and thoroughly replaced with nitrogen gas. A mixed solution was obtained.
On the other hand, in the dropping funnel, the dropping monomer shown in Table 1 (parts by weight) was charged, and then 0.09 part of the polymerization chain transfer agent, 80 parts of methyl ethyl ketone and the polymerization initiator [2,2′-azobis (2, 4-dimethylvaleronitrile)] 1.0 part was added and mixed, and nitrogen gas substitution was sufficiently performed to obtain a mixed solution.
Under a nitrogen atmosphere, the temperature of the initially charged monomer mixed solution in the reaction vessel was raised to 75 ° C. while stirring, and then the mixed solution in the dropping funnel was gradually dropped into the reaction vessel over 3 hours. After completion of the dropping, the liquid temperature of the mixed solution is maintained at 75 ° C. for 2 hours, and then a solution obtained by dissolving 0.6 part of the polymerization initiator in 10 parts of methyl ethyl ketone is added to the mixed solution, and further at 75 ° C. for 1 hour. Was repeated 3 times and then aged at 85 ° C. for 2 hours to obtain a water-insoluble polymer solution.
A part of the obtained water-insoluble polymer solution was dried at 105 ° C. under reduced pressure for 2 hours, and the water-insoluble polymer was isolated by removing the solvent, and its weight average molecular weight was measured. The results are shown in Table 1. In addition, the numerical value of each monomer in Table 1 shows the weight part of an effective part.

Production Example 4 (Production of pigment mixture of PY74 and derivative pigment (A))
(1) 168 parts (1 mol) of 2-methoxy-4-nitroaniline was dissolved in a solution consisting of 2000 parts of water and 260 parts of 35% hydrochloric acid, and 1000 parts of ice was added thereto and cooled to 0 ° C. A solution consisting of 200 parts of water and 70 parts of sodium nitrite was added and stirred at 3 ° C. or lower for 60 minutes to obtain a diazo component.
(2) On the other hand, 200 parts (0.966 mol) of 2-methoxyacetoacetanilide and 7.9 parts (0.019 mol) of a compound represented by the following formula (4) were added to 5000 parts of water and 10 parts of sodium hydroxide. Was dissolved in a solution consisting of To this, 200 parts of 80% acetic acid was added little by little to obtain a suspension, which was a coupler component.

(3) To the coupler component obtained in (2) above, the diazo component obtained in (1) above was added over 60 minutes. The coupling reaction during this period was kept at about 20 ° C. The obtained pigment mixture slurry was heated to 90 ° C. and held for 30 minutes, then filtered, washed with water, pressed, dried at 90 ° C. for 15 hours, and 500 parts of monoazo pigment, Pigment Yellow 74 (A), and the following formula (5 The pigment mixture of the azo derivative pigment (A) represented by this was obtained. This pigment mixture was pulverized into a pigment mixture powder (the amount of acidic groups of Pigment Yellow 74 (A) was 0 μmol / g, and the amount of acidic groups of the azo derivative pigment (A) was below the detection limit).

Preparation Example 1
(1) Preparation of water dispersion containing pigment having no self-dispersibility and water-insoluble polymer / water-soluble polymer 25 parts of polymer obtained by drying the polymer solution obtained in Production Examples 1 to 3 under reduced pressure ( Water-insoluble polymer / water-soluble polymer = 19.7 / 5.3) was dissolved in 71.5 parts of methyl ethyl ketone, and 209.7 parts of ion-exchanged water and a neutralizing agent (5N-sodium hydroxide aqueous solution) were added to the acid. The salt-forming group was neutralized with a mixture added by 65% of the valence, and 75 parts of the pigment mixture obtained in Production Example 4 was added and dispersed using a disper. The obtained mixture was subjected to 15-pass dispersion treatment at a pressure of 150 MPa using a microfluidizer (trade name, manufactured by Microfluidics). Methyl ethyl ketone is removed from the obtained dispersion at 60 ° C. under reduced pressure using an evaporator, and water dispersion containing water-insoluble polymer particles (I) containing a pigment having no self-dispersibility (solid content 20%) Got.

(2) Preparation of a cyan self-dispersing pigment dispersion in which a hydrophilic group is bonded via a phenyl group A 4L stainless steel beaker is attached to a rotor-stator type high shear mixer (Silverson L4RT-A) and iced. Immerse in the bath. In this beaker, C.I. I. Pigment Blue 15: 4 About 75 g and 1000 g of water were added and homogenized at 7200 rpm for 15 minutes. To this was added 20 ml of an isopropanol solution in which 2.07 g (0.01 mol) of o-acetaniside was dissolved, and the mixture was further stirred for 15 minutes.
In a separate container, 4.35 g (0.025 mol) of sulfanilic acid, 30 mL of 1N HCl and 1.73 g (0.025 mol) of sodium nitrite were mixed at 5-10 ° C. to form a diazonium salt. It was. Next, this is referred to as C.I. I. Pigment Blue 15: 3 and o-acetaniside were added with stirring to maintain the temperature at about 10 ° C. This mixture was adjusted to pH 5-6 by dropwise addition of 5M NaOH solution, and further stirred for 2 hours while confirming the progress of the reaction based on the presence or absence of a diazonium salt. When a diazonium salt is present, when the reaction mixture and a 1M Na ₂ CO ₃ solution in which 0.1% aminosalicylic acid is dissolved are dropped on a filter paper one by one, when the spread of these two drops touches, Become.
The mixture was transferred to a Telsonic flow sonicator and sonicated for 2 hours, and the resulting pigment dispersion was purified using a 50 nm diafiltration membrane column and then concentrated to a solids content of 20% Thus, a cyan self-dispersing pigment dispersion (1) was obtained (the acidic group amount of the cyan self-dispersing pigment was 93 μmol / g).

(3) Preparation of yellow self-dispersing pigment dispersion having a hydrophilic group bonded via a phenyl group In the cyan self-dispersing pigment dispersion of (2) above, C.I. I. Pigment Blue 15: 3 to C.I. I. A yellow self-dispersing pigment dispersion (2) was obtained in the same manner except that the pigment yellow 74 was used (the acidic group amount of the yellow self-dispersing pigment was 80 μmol / g).
(I) Preparation of Resin Emulsion A reaction vessel equipped with a stirrer, a reflux condenser, and a dropping device was charged with 900 g of ion exchange water and 1 g of sodium lauryl sulfate, and the temperature was raised to 70 ° C. while purging with nitrogen under stirring. Maintaining the internal temperature at 70 ° C., adding 4 g of potassium persulfate as a polymerization initiator and dissolving it, 450 g of ion-exchanged water, 3 g of sodium lauryl sulfate, 385 g of styrene, 545 g of butyl acrylate, and 30 g of methacrylic acid are stirred in advance In addition, the prepared emulsion was continuously dropped into the reaction solution over 4 hours. After completion of dropping, aging was performed for 3 hours. The obtained resin emulsion was cooled to room temperature (25 ° C.), and then ion-exchanged water and an aqueous sodium hydroxide solution were added to adjust the solid content to 40% and pH 8 to obtain a resin emulsion. The glass transition temperature of the resin particles in the obtained resin emulsion was −6 ° C.
(Ii) Production of aqueous dispersion containing cyan self-dispersing pigment Into 40 g of cyan self-dispersing pigment dispersion (1) obtained in (2) above, 5 g of resin emulsion obtained in (3) (i) above was added. Were mixed to obtain an aqueous dispersion (II) containing a cyan self-dispersing pigment containing a resin emulsion.

(4) Preparation of water-based ink containing pigment having no self-dispersibility Water dispersion 5 containing water-insoluble polymer particles (I) containing the pigment obtained in (1) above
3.4 parts, 10 parts of glycerin, 5 parts of 2- {2- (2-butoxyethoxy) ethoxy} ethanol, 2 parts of hexanediol, 0.5 part of acetylene glycol EO adduct (n = 10) and ion-exchanged water 29 .1 part was mixed, and the obtained mixed solution was filtered through a 1.2 μm membrane filter (trade name: Minisart, manufactured by Sartorius) to obtain an aqueous ink (I) containing a pigment having no self-dispersibility. .

Preparation Examples 2-4
An aqueous dispersion and an aqueous ink were obtained in the same manner as in Preparation Example 1 except that the raw materials and blending amounts in Preparation Example 1 were changed to the raw materials and blending amounts shown in Table 2.

Comparative Preparation Examples 1 and 2
A water-based ink was obtained in the same manner as in Preparation Example 1 except that 75 g of PY74 alone was used as the pigment in Preparation Example 1 and the water-soluble polymer and water-insoluble polymer were changed to those shown in Table 2.

Examples 1-4 and Comparative Examples 1-3 (ink set and inkjet recording)
The water-based ink (I) obtained in the preparation example and the water-based ink (II) containing a cyan self-dispersing pigment dispersion are mounted on the ink jet printer as an ink set, and ink jet recording is performed by the method described above. A printed matter was obtained. The results are shown in Table 2.
As a water-based ink (I), a yellow self-dispersing pigment dispersion (2) is used in Comparative Example 3, and as a water-based ink (II), a water-based ink containing a cyan self-dispersing pigment containing a resin emulsion in Examples 1 and 3. As the dispersion liquid (1), in Examples 2, 4 and Comparative Examples 1 to 3, only the aqueous dispersion liquid (1) containing a cyan self-dispersing pigment was used.

  From Table 2, the ink sets of Examples 1 to 4 have little change in light absorption characteristics, excellent bleed resistance, excellent storage stability, reduced hue error and turbidity, excellent print density, and recording paper. It can be seen that the fixing property is excellent. On the other hand, it can be seen that the ink set of Comparative Example 1 is significantly inferior in characteristics as compared with the ink sets of Examples 1 to 4.

Claims (6)

  An ink set including two or more kinds of colored inks, wherein the first kind of colored ink is obtained by dispersing a pigment having no self-dispersibility with a water-soluble polymer (x) and a water-insoluble polymer (y). A water-based ink (I) containing polymer particles (A) containing a pigment having no self-dispersibility, wherein the weight ratio of the water-insoluble polymer (y) to the water-soluble polymer (x) [(y) / (x )] Is 2.0 to 5.0, and the second colored ink is an aqueous ink (II) containing a self-dispersing pigment.   The pigment of the water-based ink (I) is C.I. I. The ink set for ink-jet recording according to claim 1, wherein the ink set is an azo pigment containing CI Pigment Yellow 74. The ink set for inkjet recording according to claim 2, wherein the azo pigment further contains an azo pigment (B) represented by the following formula (2).

(Wherein R ¹⁰ And R ²⁰ Each independently represents an aryl group optionally having a substituent selected from a methoxy group and a nitro group; ¹⁰ And R ²⁰ At least one of them has a sulfonic acid group and a sulfonic acid amide group. ) The self-dispersing pigment of the water-based ink (II) is carbon black having a hydrophilic functional group on the surface or a chromatic pigment having a hydrophilic functional group on the surface via a phenyl group . The ink set for inkjet recording as described in 2. The ink set for inkjet recording according to any one of claims 1 to 4 , wherein the water-based ink (II) contains a resin emulsion. Water-insoluble polymer comprises a structural unit derived from a salt-forming group-containing monomer (a), a constitutional unit derived from the hydrophobic monomer (b) and / or macromer (c), according to any one of claims 1 to 5 Ink set for inkjet recording.