JP2009227853A - Method for manufacturing pigment dispersion, pigment dispersion liquid, ink for use in inkjet-recording, and ink set - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a pigment dispersion which can provide an inkjet-recording ink which is excellent in the light resistance as well as in the after-thermo droplet landing position accuracy and which can prevent the image deformation from occuring. <P>SOLUTION: The method for manufacturing a pigment dispersion comprises a process of making a dispersant contained in at least one of the pigment dissolving solution, which dissolves an azo pigment (a) and at least one basic-group-bearing derivative (b) selected from the group consisting of a pigment derivative formed by introducing a basic group into an organic pigment, a basic group-bearing anthraquinone derivative, a basic group-bearing acridone derivative and a basic group-bearing triazine derivative, and an aqueous solvent, and then of mixing the above pigment dissolving solution and the above aqueous solvent, and thus of depositing the pigment. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a pigment dispersion, a pigment dispersion, an inkjet recording ink, and an ink set.

  The ink jet recording method has advantages such as high-speed recording, high degree of freedom in drawing patterns, low noise during recording, image recording at low cost, and easy color recording. It is rapidly spreading and developing further. Conventionally, a dye ink in which a water-soluble dye is dissolved in an aqueous medium has been widely used as the ink for ink jet recording. However, since this dye ink is inferior in water resistance and weather resistance of printed matter, a pigment ink capable of improving this has been studied.

However, pigments are often inferior in ink liquid stability and ejectability from nozzles of inkjet heads as compared to dyes. In addition, since pigments are particles rather than individual pigment molecules such as dyes, the absorption spectrum becomes broader than that of dyes due to scattering and reflection by pigments, and images formed with pigment inks are images of dye inks. In comparison, the transparency is generally low and the color developability tends to be low. As one of means for solving such problems of pigment ink, a method of miniaturizing the pigment is known.
Usually, the pigment is finely divided by a mechanical force using a disperser such as a sand mill, a roll mill, or a ball mill. A method of finely dispersing organic pigment aggregated particles with a pulverizer or a disperser is disclosed (for example, see Patent Document 1).
On the other hand, recently, a method has been proposed in which a pigment is dissolved once and then precipitated again to form pigment fine particles (see, for example, Patent Document 2).
JP-A-10-110111 JP 2002-322404 A

In the method of Patent Document 1, it is difficult to reduce the pigment to about 100 nanometers near the primary particles, and it is difficult to cope with the case where further finer particles are required. In addition, the smaller the particle size, the longer the dispersion takes, and the higher the cost, the more difficult it becomes to obtain a uniform quality. Further, the problem that the light resistance deteriorates due to the formation of fine particles remains unsolved.
In addition, since the organic pigment particle dispersion obtained as described in Patent Document 2 can obtain a more uniform nanometer-order fine particle dispersion compared to a dispersion prepared by an ordinary pulverization method, It shows high transparency with little scattering and improved light resistance.
However, the fine particle dispersion has a problem in landing position accuracy after a lapse of time, and further long-term liquid stabilization and prevention of deformation of the printed image are strongly demanded with the recent popularization of the ink jet recording method. .

The present invention has been made in view of the above, and is a method for producing a pigment dispersion capable of providing an ink for ink jet recording that has excellent light resistance, excellent post-thermo landing position accuracy, and can prevent image deformation, And a pigment dispersion.
Furthermore, an object of the present invention is to provide an ink for ink jet recording and an ink set which are excellent in post-thermo landing position accuracy and can prevent image deformation.

<1> From the group of an azo pigment (a), a pigment derivative obtained by introducing a basic group into an organic pigment, an anthraquinone derivative having a basic group, an acridone derivative having a basic group, and a triazine derivative having a basic group A pigment-dissolved solution in which a derivative (b) having at least one selected basic group is dissolved;
Containing a dispersant in at least one of the aqueous solvents,
A method for producing a pigment dispersion, comprising a step of mixing the pigment-dissolved solution and the aqueous solvent to precipitate a pigment.

<2> The method for producing a pigment dispersion according to <1>, wherein the derivative (b) is 0.5 to 20 parts by mass with respect to 100 parts by mass of the azo pigment (a).
<3> The above <1> or <2>, wherein the dispersant is a polymer compound having one or more kinds selected from a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group as a hydrophilic group. The manufacturing method of the pigment dispersion liquid of description.
<4> The method for producing a pigment dispersion according to any one of <1> to <3>, wherein the phase transfer base is added.
<5> The azo pigment (a) is C.I. I. The method for producing a pigment dispersion according to any one of <1> to <4>, wherein the pigment (Y) is Pigment Yellow 74, and the derivative (b) has an azo skeleton.

<6> The method for producing a pigment dispersion according to any one of <1> to <5>, wherein the pigment has an average particle diameter of 5 to 50 nm.
<7> The method for producing a pigment dispersion according to any one of <1> to <6>, wherein the monodispersity of the pigment particle size is 1.5 or less.
<8> An ink for ink jet recording comprising a pigment dispersion prepared by the production method according to any one of <1> to <7>.
<9> An ink set comprising the ink according to <8> and a colorless ink containing an aggregation accelerator that promotes aggregation of the ink.
<10> From the group of the azo pigment (a), a pigment derivative obtained by introducing a basic group into an organic pigment, an anthraquinone derivative having a basic group, an acridone derivative having a basic group, and a triazine derivative having a basic group. The pigment comprising the selected derivative (b) having at least one basic group and a dispersant has an average particle size of 5 to 50 nm, and the monodispersity of the pigment particle size is 1.5 or less. A pigment dispersion characterized by the above.

<11> An ink for inkjet recording comprising the pigment dispersion according to <10> above.
<12> An ink set comprising the ink for inkjet recording according to the above <11> and a colorless ink containing an aggregation accelerator that promotes aggregation of the ink for inkjet recording.

According to the present invention, there are provided a method for producing a pigment dispersion capable of providing an ink for inkjet recording that has excellent light resistance, has excellent post-thermo landing position accuracy, and can prevent image deformation, and a pigment dispersion. Can do.
Furthermore, according to the present invention, it is possible to provide an ink for ink jet recording and an ink set that are excellent in light resistance, excellent in post-thermo landing position accuracy, and capable of preventing image deformation.

  Below, the manufacturing method of the pigment dispersion of this invention, a pigment dispersion, the ink for inkjet recording, and an ink set are demonstrated.

<Method for producing pigment dispersion>
The method for producing a pigment dispersion of the present invention comprises a pigment derivative obtained by introducing a basic group into an azo pigment (a) organic pigment, an anthraquinone derivative having a basic group, an acridone derivative having a basic group, and a basic group. A pigment-dissolving solution in which at least one derivative (b) having at least one basic group selected from the group of triazine derivatives having a dispersant is contained in at least one of an aqueous solvent, the pigment-dissolving solution, It includes a step of mixing the aqueous solvent to precipitate a pigment.
Here, the deposited pigment contains at least the azo pigment (a) and the derivative (b).
The method for producing a pigment dispersion of the present invention is excellent in dispersion stability and light resistance of the liquid, having excellent landing position accuracy after thermo and having little image deformation by adopting the above-described configuration. This is a method capable of producing a pigment dispersion that can be an ink.

<Pigment dissolving solution>
The pigment-dissolving solution comprises at least one basic group selected from the group consisting of an azo pigment (a), a pigment derivative, an anthraquinone derivative having a basic group, an acridone derivative having a basic group, and a triazine derivative having a basic group. It is a solution in which the derivative (b) having
The preparation of the pigment solution is not particularly limited, but it is preferable to dissolve the azo pigment (a) that is difficult to dissolve before the derivative (b) and then add the derivative (b) to prepare the dissolved solution. .
As a method for dissolving the azo pigment (a), it is preferable to use a solvent having strong dissolving power and water miscibility, and examples thereof include a method using sulfuric acid.
The solvent is preferably a mixture of an aprotic polar organic solvent, water, and an alkali. Specific examples of the aprotic polar organic solvent include dimethyl sulfoxide, dimethylformamide, N-methyl-2-pyrrolidone, 2-pyrrolidone, and tetramethylurea. The amount of the aprotic polar organic solvent used is suitably 5 to 20 times the amount of the azo pigment (a). The ratio of the aprotic polar organic solvent to water (organic solvent / water) is preferably 97/3 to 70/30 (mass ratio). When water is not present or small, it is difficult to completely dissolve the azo pigment, and when the amount of water is too large, it is difficult to dissolve again. The amount of alkali used is preferably 1.5 moles or more, preferably 2 to 3 moles per mole of the azo pigment.

(Azo pigment (a))
Examples of the azo pigment (A) used in the present invention include C.I. I. Pigment Yellow 1, 2, 3, 5, 6, 10, 12, 13, 14, 17, 49, 55, 60, 63, 65, 73, 74, 75, 81, 83, 87, 90, 97, 98 , 106, 111, 113, 114, 116, 121, 124, 126, 127, 130, 136, 152, 154, 165, 167, 170, 171, 172, 174, 176, 188, etc., C. I. And condensed azo pigments such as CI Pigment Yellow 93, 94, 95, 128, and 166. These can be used alone or in combination of two or more.
Among these, C.I. from the viewpoint of colorability and clear hue. I. Pigment yellow 74, C.I. I. Pigment yellow 128, C.I. I. Pigment Yellow 155 is preferred, and C.I. I. Pigment Yellow 74 is particularly preferable.

  The addition amount of the azo pigment (a) is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and particularly preferably 12 to 20% by mass in the pigment dispersion from the viewpoint of dispersion stability and production cost. .

(Derivative formed by introducing a basic group (b))
The derivative (b) is obtained by introducing a basic group into an organic pigment, anthraquinone, acridone or triazine. Examples of the basic group include at least one group selected from the groups represented by the following general formula (1), general formula (2), general formula (3), and general formula (4). .

In the general formula (1), J represents (on the side bonded to the organic pigment) —SO ₂ —, —CO—, —CH ₂ NHCOCH ₂ —, —CH ₂ —, or a single bond, and f represents 1 to R ¹ and R ² each independently represent an alkyl group, an alkenyl group, an aryl group, or a heterocyclic ring formed by R ¹ and R ² together with the nitrogen atom in the formula. The alkyl group and alkenyl group preferably have 1 to 10 carbon atoms. In addition, the alkyl group, alkenyl group, aryl group, and heterocyclic ring may be independently substituted. The heterocyclic ring may contain a nitrogen atom, an oxygen atom, or a sulfur atom in the ring.

In a preferred form of the group represented by the general formula (1), J is —SO ₂ — or —CO—, f is 1 to 5 (more preferably 2 to 4), and R ¹ and R ² Are each independently an alkyl group having 1 to 4 carbon atoms (methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group), or R ¹ and R ² This is the case where morpholine is formed together with the nitrogen atom in the formula.

In general formula (2), R ¹ and R ² are each independently synonymous with the above general formula (1).

In a preferred form of the group represented by the general formula (2), R ¹ and R ² are each independently an alkyl group having 1 to 4 carbon atoms (methyl group, ethyl group, n-propyl group, iso-propyl group). , N-butyl group, iso-butyl group).

In general formula (3), J has the same meaning as J in general formula (1).
R ³ represents an alkyl group, an alkenyl group, or an aryl group. The alkyl group and alkenyl group preferably have 1 to 10 carbon atoms.
R ⁴ , R ⁵ , R ⁶ , and R ⁷ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group. As for carbon number of the alkyl group and alkenyl group in R < ⁴ > -R < ⁷ >, 1-5 are preferable. The alkyl group, alkenyl group, or aryl group in R ^{3 to} R ⁷ may be further substituted.

In a preferred form as the group represented by the general formula (3), J is —CH ₂ NHCOCH ₂ —, and R ³ is an alkyl group having 1 to 4 carbon atoms (methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group or iso-butyl group), and R ^{4 to} R ⁷ are hydrogen atoms.

In the general formula (4), J has the same meaning as J in the general formula (1).
K represents —NR ⁸ —Z—NR ⁹ — or a single bond, and R ⁸ and R ⁹ each independently represent a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group, and the alkyl group, alkenyl group Or the aryl group may be further substituted. The alkyl group in R ⁸ and ^{R 9,} the number of carbon atoms in the alkylene group is 1 to 5 is preferred.
Z represents an alkylene group, an alkenylene group, or an arylene group, and the alkylene group, alkenylene group, or arylene group may be further substituted. The alkyl group and alkenyl group preferably have 1 to 10 carbon atoms.
W represents a substituent represented by the general formula (1) or a substituent represented by the general formula (3), and Q represents a hydroxyl group, an alkoxyl group, or the general formula (1). Or a substituent represented by the general formula (3). As for carbon number of an alkoxyl group, 1-10 are preferable.

In a preferred form as the group represented by the general formula (4), J is —SO ₂ — or a single bond, K is a single bond or —NH—Z—NH—, Z is a phenylene group, Q is a hydroxyl group, an alkoxyl group having 1 to 4 carbon atoms (methoxy group, ethoxy group, propoxy group or butoxy group), W is a group represented by the general formula (1), and J in the W is —SO ₂ — or —CO—, wherein f in W is 1 to 5 (more preferably 2 to 4), and R ¹ and R ^{2 in} W each independently have 1 to 4 carbon atoms. Of the alkyl group (methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group).

  Examples of amine compounds used to form the groups represented by the general formula (1) to the general formula (4) include secondary or tertiary monoamines, diamines, cyclic amines, and carboxyl group-containing cyclic amines. , Hydroxyl group-containing cyclic amines, and cyclic diamines. Specifically, dimethylamine, diethylamine, methylethylamine, N, N-ethylisopropylamine, N, N-ethylpropylamine, N, N-methylbutylamine, N, N-methylisobutylamine, N, N-butylethylamine N, N-tert-butylethylamine, diisopropylamine, dipropylamine, N, N-sec-butylpropylamine, dibutylamine, di-sec-butylamine, diisobutylamine, N, N-isobutyl-sec-butylamine, diamylamine , Diisoamylamine, dihexylamine, dicyclohexylamine, di (2-ethylhexyl) amine, dioctylamine, N, N-methyloctadecylamine, didecylamine, diallylamine, N, N-ethyl-1,2-dimethylpro Ruamine, N, N-methylhexylamine, dioleylamine, distearylamine, N, N-dimethylaminomethylamine, N, N-dimethylaminoethylamine, N, N-dimethylaminoamylamine, N, N-dimethylaminobutylamine N, N-diethylaminoethylamine, N, N-diethylaminopropylamine, N, N-diethylaminohexylamine, N, N-diethylaminobutylamine, N, N-diethylaminopentylamine, N, N-dipropylaminobutylamine, N, N-dibutylaminopropylamine, N, N-dibutylaminoethylamine, N, N-dibutylaminobutylamine, N, N-diisobutylaminopentylamine, N, N-methyl-laurylaminopropylamine, N, N-ethyl-hex Ruaminoethylamine, N, N-distearylaminoethylamine, N, N-dioleylaminoethylamine, N, N-distearylaminobutylamine, piperidine, 2-pipecoline, 3-pipecoline, 4-pipecoline, 2,4-lupetidine 2,6-lupetidine, 3,5-lupetidine, 3-piperidinemethanol, pipecolic acid, isonipecotic acid, methyl isonicopetinate, ethyl isonicopetinate, 2-piperidineethanol, pyrrolidine, 3-hydroxypyrrolidine, N-aminoethylpiperidine, N-aminoethyl-4-pipecholine, N-aminoethylmorpholine, N-aminopropylpiperidine, N-aminopropyl-2-pipecholine, N-aminopropyl-4-pipecoline, N-aminopropylmorpholine, N-methylpipecoline Razine, N-butylpiperazine, N-methylhomopiperazine, 1-cyclopentylpiperazine, 1-amino-4-methylpiperazine, 1-cyclopentylpiperazine and the like can be mentioned. Of these, dimethylamine, diethylamine, dipropylamine, dibutylamine, N-methylpiperazine, and N-butylpiperazine are preferable.

  The pigment part constituting the “pigment derivative having a basic group in the organic pigment” includes, for example, diketopyrrolopyrrole dyes, azo dyes such as azo, disazo, polyazo, phthalocyanine dyes, diaminodianthraquinone, anthrapyrimidine, Anthraquinone dyes such as flavantron, anthanthrone, indanthrone, pyranthrone, violanthrone, quinacridone dye, dioxazine dye, perinone dye, perylene dye, thioindigo dye, isoindoline dye, isoindolinone dye, quinophthalone And pigments derived from organic dyes such as azo dyes, selenium dyes, and metal complex dyes. Azo dyes and quinacridone dyes are preferable, and an azo skeleton is more preferable.

  Further, “anthraquinone derivative having a basic group” or “acridone derivative having a basic group” includes, on the anthraquinone ring or acridone ring, in addition to the basic group, an alkyl group such as a methyl group or an ethyl group, an amino group It may have a substituent such as an alkoxy group such as a group, a nitro group, a hydroxyl group, a methoxy group or an ethoxy group, or a halogen such as chlorine.

  Further, the triazine moiety constituting the “triazine derivative having a basic group” includes, in addition to the basic group, an alkyl group (for example, a methyl group, an ethyl group, a butyl group, etc.), an amino group, an alkylamino group (for example, Dimethylamino group, diethylamino group, dibutylamino group, etc.), nitro group, hydroxyl group, alkoxy group (eg methoxy group, ethoxy group, butoxy group etc.), halogen atom (eg chlorine atom, bromine atom etc.), phenyl group (For example, an alkyl group, an amino group, an alkylamino group, a nitro group, a hydroxyl group, an alkoxy group, a halogen atom and the like may be substituted) and a phenylamino group (for example, an alkyl group, an amino group, an alkylamino group, It may have a substituent such as a nitro group, a hydroxyl group, an alkoxy group, or a halogen atom. Preferred triazine moieties are derived from 1,3,5-triazine.

  Specific examples of the “derivative (b) having a basic group” include the following derivatives.

  The derivative (b) in the present invention may be used alone or in combination of two.

The “derivative (b) having a basic group” used in the present invention can be synthesized by a known method. For example, after introducing a substituent represented by the following formula (7) to the following formula (10) into an organic dye, anthraquinone or acridone, it reacts with these substituents to give the above general formula (1) to the above general formula. An amine compound capable of forming the group represented by (4), for example, N, N-dimethylaminopropylamine, N-methylpiperazine, diethylamine or 4- [4-hydroxy-6- [3- (dibutylamino) ) Propylamino] -1,3,5-triazin-2-ylamino] aniline and the like.
Formula (7): —SO ₂ Cl
Formula (8): -COCl
Formula (9): —CH ₂ NHCOCH ₂ Cl
Formula (10): —CH ₂ Cl

  In addition, the substituent represented by the general formula (1) to the general formula (4) is previously introduced into a diazo component (for example, a compound having a diazo group) or a coupling component (for example, a compound having an acetamide group), Subsequently, an azo pigment derivative can be produced by performing a coupling reaction.

It is preferable that the addition amount of a derivative (b) is 0.5-20 mass parts with respect to 100 mass parts of azo pigments (a), 7.5-20 mass parts is more preferable, 7.5-12 .5 parts by mass is particularly preferred.
By making it the range of the addition amount, the post-thermo landing position accuracy is good and the light resistance tends to be excellent, which is preferable.

<Aqueous solvent>
The aqueous solvent includes water or a mixture of water and an aqueous solvent. In the case of a mixture, a liquid containing 50% or more, preferably 80% or more of water as a volume% is preferable. Specific examples of the aqueous solvent include water-soluble organic solvents described later.

<Dispersant>
At least one of the pigment solution and the aqueous solvent contains a dispersant.
The dispersant has an action of (1) quickly adsorbing on the surface of the pigment that has been deposited to form fine pigment particles, and (2) preventing these particles from aggregating again.
As the dispersant, a surfactant, a polymer, a pigment derivative into which a polar substituent different from the pigment derivative (b) is introduced, a nonionic, anionic, cationic, or amphoteric compound may be used. it can. These dispersants can be used singly or in combination of two or more. A preferable embodiment includes an embodiment in which a polymer and / or an anionic surfactant is contained in the pigment solution.

Examples of the surfactant include an anionic surfactant such as acylmethyl taurine salt, fatty acid salt, alkyl sulfate ester salt, alkylbenzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl phosphate ester salt, naphthalene. Examples thereof include sulfonic acid formalin condensate and polyoxyethylene alkyl sulfate ester salt. Of these, acylmethyl taurine salts are preferred. An anionic surfactant can be used individually by 1 type or in combination of 2 or more types.
Nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin fatty acid ester, etc. Can do. Among these, polyoxyethylene alkyl aryl ether is preferable. A nonionic surfactant can be used individually by 1 type or in combination of 2 or more types.

  Examples of the polymer include polyvinyl pyrrolidone, polyvinyl alcohol, polyvinyl methyl ether, polyethylene oxide, polyethylene glycol, polypropylene glycol, polyacrylamide, vinyl alcohol-vinyl acetate copolymer, polyvinyl alcohol-partial formalized product, polyvinyl alcohol-partial butyralized product. , Vinylpyrrolidone-vinyl acetate copolymer, polyethylene oxide / propylene oxide block copolymer, polyacrylate, polyvinyl sulfate, poly (4-vinylpyridine) salt, polyamide, polyallylamine salt, condensed naphthalene sulfonate, Styrene-acrylate copolymer, styrene-methacrylate copolymer, acrylate ester-acrylate copolymer, acrylate ester-methacrylic acid Copolymer, Methacrylate-acrylate copolymer, Methacrylate-methacrylate copolymer, Styrene-itaconate copolymer, Itaconic acid-itaconate copolymer, Vinylnaphthalene-acrylic Examples thereof include an acid salt copolymer, a vinyl naphthalene-methacrylate salt copolymer, a vinyl naphthalene-itaconate salt copolymer, a cellulose derivative, and a starch derivative. In addition, natural polymers such as alginate, gelatin, albumin, casein, gum arabic, tonganto gum and lignin sulfonate are also included. The polymer can be used alone or in combination of two or more.

In addition to the above, examples of the nonionic compound, the anionic compound, the cationic compound, and the amphoteric compound include a copolymer of a monomer having an α, β-ethylenically unsaturated group.
Examples of monomers having an α, β-ethylenically unsaturated group include ethylene, propylene, butene, pentene, hexene, vinyl acetate, allyl acetate, acrylic acid, methacrylic acid, crotonic acid, crotonic acid ester, itaconic acid, itacone Acid monoester, maleic acid, maleic acid monoester, maleic acid diester, fumaric acid, fumaric acid monoester, vinyl sulfonic acid, styrene sulfonic acid, sulfonated vinyl naphthalene, vinyl alcohol, acrylamide, methacryloxyethyl phosphate, bismethacryloxy Styrene derivatives such as ethyl phosphate, methacryloxyethyl phenyl acid phosphate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, styrene, α-methylstyrene, vinyltoluene , Vinylcyclohexane, vinylnaphthalene, vinylnaphthalene derivatives, alkyl acrylates that may be substituted with aromatic groups, phenyl esters of acrylate, alkyl methacrylates that may be substituted with aromatic groups, phenyl esters of methacrylic acid, methacryl Acid cycloalkyl ester, crotonic acid alkyl ester, itaconic acid dialkyl ester, maleic acid dialkyl ester, vinyl alcohol, and derivatives of the above compounds.

A copolymer obtained by copolymerizing one or more monomers having the α, β-ethylenically unsaturated group is used as a polymer dispersant. Specifically, acrylic acid alkyl ester-acrylic acid copolymer, methacrylic acid alkyl ester-methacrylic acid copolymer, styrene-acrylic acid alkyl ester-acrylic acid copolymer, styrene-methacrylic acid phenyl ester-methacrylic acid copolymer. Polymer, styrene-methacrylic acid cyclohexyl ester-methacrylic acid copolymer, styrene-styrene sulfonic acid copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid copolymer, vinyl Naphthalene-maleic acid copolymer, vinyl naphthalene-methacrylic acid copolymer, vinyl naphthalene-acrylic acid copolymer, polystyrene, polyester, polyvinyl alcohol and the like can be mentioned.
Among these, a polymer compound having one or more kinds selected from a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group as a hydrophilic group is preferable. Specifically, an acrylic acid alkyl ester-acrylic acid copolymer is preferable. Polymer, methacrylic acid alkyl ester-methacrylic acid copolymer, styrene-acrylic acid alkyl ester-acrylic acid copolymer, styrene-methacrylic acid phenyl ester-methacrylic acid copolymer, styrene-methacrylic acid cyclohexyl ester-methacrylic acid copolymer Polymers, styrene-styrene sulfonic acid copolymers, styrene-maleic acid copolymers, vinyl naphthalene-maleic acid copolymers, vinyl naphthalene-methacrylic acid copolymers, vinyl naphthalene-acrylic acid copolymers, etc. are preferred, Acrylic acid alkyl ester-acrylic acid Polymers, alkyl methacrylate - methacrylic acid copolymer, styrene - acrylic acid alkyl ester - acrylic acid copolymer, styrene - methacrylic acid copolymer, styrene - acrylic acid copolymer is more preferable.

The average molecular weight of the dispersant is preferably in the range of 2,000 to 60,000 in terms of weight average molecular weight.
The amount of the dispersant added to the azo pigment (a) is preferably 10 to 100% by mass, more preferably 20 to 70% by mass, and still more preferably 30 to 50% by mass.

-Method for producing pigment dispersion-
The method for producing a pigment dispersion of the present invention includes a step of precipitating a pigment by mixing the pigment solution and the aqueous solvent (hereinafter referred to as “build-up method”).
For example, a pigment solution containing a dispersing agent is injected from a nozzle into an aqueous solvent at a predetermined rate (for example, at a high speed), and fine particles are continuously precipitated to obtain a pigment dispersion in which pigment particles are finely dispersed. .
According to this method, since the surface of the pigment particle is covered and stabilized simultaneously with the formation of the particle, it is possible to form a finer particle having a narrow particle size distribution. In other words, if a dispersant is present when the dissolved pigment is precipitated, it is considered that the fine organic pigment particles can be stably present because the dispersant is quickly adsorbed on the surface of the precipitated pigment.
As a method of mixing the pigment-dissolved solution and the aqueous solvent, the other liquid may be added to one liquid and mixed, or both liquids may be supplied simultaneously and then stirred and mixed. The addition speed, the strength of stirring, and the like can be appropriately selected depending on the purpose.

In the method for producing the pigment dispersion of the present invention, the average particle diameter of the pigment particles in the pigment dispersion is preferably 5 to 50 nm, more preferably 5 to 30 nm, and more preferably 10 to 20 nm. It is particularly preferable to do so.
When Mv exceeds 50 nm, ink jet recording ink containing the dispersion may not be able to prevent image bleeding and image deformation, and extremely small particles are often difficult to produce in a stable manner at 5 nm or more. Preferably there is.
The monodispersity of the particle size of the pigment particles in the pigment dispersion is preferably 1.5 or less, and more preferably 1.3 or less.

Here, the average particle diameter and monodispersity of the pigment will be described.
~ Average particle size ~
In the present invention, the average particle diameter of the pigment refers to the volume average particle diameter (Mv), and is measured using a Microtrac particle size distribution analyzer (Version 10.1.2-211BH (trade name), manufactured by Nikkiso Co., Ltd.). It is measured by a dynamic light scattering method. That is, the dispersion state of the pigment can be evaluated by a dynamic light scattering method, and thereby the average particle diameter can be calculated. The principle is as follows.
The pigment particles having a particle diameter in the range of about 1 nm to 5 μm change their position and orientation from moment to moment by Brownian motion such as translation and rotation in the liquid. Therefore, when these pigment particles are irradiated with laser light and the scattered light emitted is detected, fluctuations in the scattered light intensity depending on the Brownian motion are observed. By observing the fluctuation of the scattered light intensity over time, the speed (diffusion coefficient) of the Brownian motion of the particles can be obtained, and further the size of the particles can be known.

~ Monodispersity ~
The monodispersity is an index for evaluating the dispersibility of the dispersion, and the ratio (Mv / Mn) of the volume average particle diameter (Mv) and the number average particle diameter (Mn) obtained by the dynamic light scattering method. It is represented by The volume average particle size (Mv) and the number average particle size (Mn) are determined by a dynamic light scattering method using a Microtorac particle size distribution analyzer (Version 10.1.2-211BH (trade name), manufactured by Nikkiso Co., Ltd.). Measured by

  The monodispersity of the pigment in the pigment dispersion in the present invention is such that the value of Mv / Mn of the pigment particles is 1.5 or less, and preferably 1.3 or less. When the value of Mv / Mn exceeds 1.5, image bleeding and image deformation cannot be prevented.

  In the present invention, the adjustment of the average particle diameter and monodispersity of the pigment can be achieved, for example, when the pigment is dispersed by the above-described pigment production method, for example, the speed at which the solution containing the organic pigment is brought into contact with the aqueous solvent ( The injection rate when the liquid is injected into the other liquid), the temperature, the addition ratio of the dispersant, the pH adjustment of the aqueous medium, and the like.

The pigment dispersion may further have a purification step.
The purification step can be achieved by washing with ion exchange water, a water-soluble organic solvent or the like. Specifically, after adjusting the pH to 2 to 4 with the acid of the pigment dispersion and aggregating the pigment particles from the pigment dispersion, the paste in which the pigment in the pigment dispersion is aggregated is filtered to obtain ion-exchanged water. Alternatively, it can be purified by washing with a water-soluble organic solvent. After purification, ion-exchanged water is added to the paste and the pH is adjusted to 7 to 10 with an alkali or the like to obtain a purified pigment dispersion.
Known acids and alkalis can be used.

  As described above, by adding a purification step, the solvent used in the production of the pigment dispersion can be removed, the crystallinity of the pigment is improved (strong crystals are formed), and prepared using such a pigment dispersion. The weather resistance of the image recorded with the prepared ink is remarkably improved.

(Phase transfer type base)
In the method for producing a pigment dispersion of the present invention, it is preferable from the viewpoint of pigment dispersion stability that a phase transfer base is added during the production process.
Addition of the phase transfer type base is preferable because the dispersion stability of the pigment tends to be improved by electrostatic repulsion derived from the anion group of the polymer compound and the phase transfer type group.
In the preparation of the pigment dispersion, the phase transfer base is used in the form contained in the pigment dissolving solution or added to the aqueous solvent to prepare the pigment dispersion. They may be added after the purification step or after the purification step, or they may be used in combination, but it is preferably used at least when the pigment is dissolved.

  Examples of the phase transfer base used in the present invention include alkylammonium derivatives, alkylsulfonium derivatives, alkylphosphonium derivatives and the like. Of these, alkylammonium derivatives are preferred.

Examples of the alkylammonium derivatives include choline hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrapropylammonium hydroxide, and tetramethylammonium hydroxide and tetraethylammonium hydroxide are particularly preferable.
The phase transfer base used in the present invention is not limited to this. The phase transfer bases may be used alone or in combination of two.

In addition, the alkylammonium derivative, alkylsulfonium derivative, and alkylphosphonium derivative used in the present invention preferably have a structure with a negative ClogP value, and more preferably more negative than −2, from the viewpoint of dispersion stability. .
Here, the ClogP value refers to a common logarithm value of 1-octanol / water partition coefficient P indicating the ratio between the equilibrium concentrations of the compound in 1-octanol and in water.
This ClogP value is determined by a fragment approach based on the chemical structure of the compound (A. Leo, Comprehensive Medical Chemistry, Vol. 4; C. Hansch, P. G. Sammens, J. B. Taylor and C. A. Ramden. , P. 295, Pergramon Press, 1990), etc., and can be defined by values calculated with the “CLOGP” program available from Daylight Chemical Information Systems. In the present invention, this definition is adopted.

The addition amount of the phase transfer type base is preferably 0.5 to 50 molar equivalents, more preferably 1.0 to 20 molar equivalents with respect to the pigment from the viewpoint of co-dissolution with the pigment and the polymer dispersant. 1.5 to 10 molar equivalents are particularly preferred.
By setting the amount within the above range, it is preferable that co-dissolution with the pigment and the polymer dispersant is easy and the dispersion stability is good.

<Pigment dispersion>
The pigment dispersion of the present invention has an azo pigment (a), a pigment derivative obtained by introducing a basic group into an organic pigment, an anthraquinone derivative having a basic group, an acridone derivative having a basic group, and a basic group. The average particle size of the pigment comprising the derivative (b) having at least one basic group selected from the group of triazine derivatives and a dispersant is 5 to 50 nm, and the monodispersity of the pigment particle size Is 1.5 or less.
The pigment dispersion of the present invention is a pigment dispersion capable of providing an ink for ink jet recording that has excellent light resistance and has excellent post-thermo landing position accuracy and can prevent image deformation by adopting the above-described configuration. it can.
In addition, by using an ink set for ink jet recording containing the pigment dispersion, the pigment dispersed in the ink for ink jet recording is aggregated by the action of a colorless ink described later (for example, the pH is changed to the acidic side). When an image is recorded, image blurring is suppressed, image deformation such as cracking that easily occurs due to evaporation of a solvent or the like is suppressed, and light resistance of the image is improved. As a result, it is possible to increase the speed of inkjet recording, and it is possible to record an image having excellent image quality and light fastness, for example, at a high speed by a single pass method.
The pigment dispersion of the present invention can be produced using the same material by the above-described method for producing the pigment dispersion of the present invention.

<Ink for inkjet recording>
The ink for inkjet recording of the present invention (hereinafter also referred to as an ink composition) is characterized by including a pigment dispersion prepared by the method for manufacturing a pigment dispersion of the present invention, and further contains a water-soluble organic solvent. It is preferable to contain.

-Water-soluble organic solvent-
The water-soluble organic solvent is used for the purpose of an anti-drying agent, a wetting agent or a penetration enhancer. The anti-drying agent is used for the purpose of preventing the ink from adhering and drying to form aggregates and clogging at the ink discharge port of the ejection nozzle, and the anti-drying agent and wetting agent have a vapor pressure lower than that of water. Low water-soluble organic solvents are preferred. Moreover, as a penetration accelerator, it is used for the purpose of improving the ink permeability to paper.

The water-soluble organic solvent contained in the ink composition of the present invention is a known water-soluble organic solvent considering its function as a drying inhibitor, wetting agent or penetration enhancer from the viewpoint of compatibility with water. Can be appropriately selected.
Examples of water-soluble organic solvents include glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, 2- Butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol Alkanediols (polyhydric alcohols) such as 4-methyl-1,2-pentanediol; glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, maltose, cellobiose, lact Sugars such as sucrose, trehalose and maltotriose; sugar alcohols; hyaluronic acids; so-called solid wetting agents such as ureas; alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol and isopropanol Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol Mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, Tylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl Glycol ethers such as ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether; 2 -Pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, formamide, aceto Toamide, dimethyl sulfoxide, sorbit, sorbitan, acetin, diacetin, triacetin, sulfolane and the like can be mentioned, and one or more of these can be used.

  For the purpose of drying inhibitors and wetting agents, polyhydric alcohols are useful, such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-butanediol. 2,3-butanediol, 1,4-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, tetraethylene glycol, 1,6-hexanediol, 2-methyl-2, Examples include 4-pentanediol, polyethylene glycol, 1,2,4-butanetriol, 1,2,6-hexanetriol, and the like. These may be used individually by 1 type and may use 2 or more types together.

  For the purpose of the penetrant, a polyol compound is preferable, and examples of the aliphatic diol include 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, 2,2- Diethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, Examples include 5-hexene-1,2-diol and 2-ethyl-1,3-hexanediol. Among these, preferred examples include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.

A water-soluble organic solvent can be used individually by 1 type or in mixture of 2 or more types.
As content in the ink composition of a water-soluble organic solvent, 1-60 mass% is preferable, More preferably, it is 5-40 mass%.

-Water-
The ink composition in the present invention contains water, but the amount of water is not particularly limited. Especially, the preferable content of water is 10 to 99% by mass, more preferably 30 to 80% by mass, and still more preferably 50 to 70% by mass.

-Others-
In addition to the above components, the ink composition in the present invention includes, for example, resin fine particles or polymer latex, a surfactant, an ultraviolet absorber, an antifading agent, an antifungal agent, a pH adjuster, and a rust preventive, as necessary. , Antioxidants, emulsion stabilizers, preservatives, antifoaming agents, viscosity modifiers, dispersion stabilizers, chelating agents and other components may be contained.

Examples of the resin fine particles include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, styrene resins, crosslinked acrylic resins, and crosslinked styrene resins. , Benzoguanamine resin, phenol resin, silicone resin, epoxy resin, urethane resin, paraffin resin, fluorine resin, or polymer latex containing these.
Preferable examples include acrylic resins, acrylic-styrene resins, styrene resins, cross-linked acrylic resins, fine particles of cross-linked styrene resins, or polymer latex containing these.

When preparing an ink composition by adding resin fine particles or polymer latex, it is preferable to add the resin fine particles or polymer latex at the same time as the pigment or the like when preparing the pigment dispersion in terms of enhancing fixability.
The weight average molecular weight of the resin fine particles is preferably 10,000 or more and 200,000 or less, more preferably 100,000 or more and 200,000 or less.
The average particle size of the resin fine particles is preferably in the range of 10 nm to 1 μm, more preferably in the range of 10 to 200 nm, still more preferably in the range of 20 to 100 nm, and particularly preferably in the range of 20 to 50 nm.
The addition amount of the resin fine particles is preferably 0.5 to 20% by mass, more preferably 3 to 20% by mass, and further preferably 5 to 15% by mass with respect to the ink.
The glass transition temperature (Tg) of the resin fine particles is preferably 30 ° C. or higher, more preferably 40 ° C. or higher, and further preferably 50 ° C. or higher.
Moreover, there is no restriction | limiting in particular regarding the particle size distribution of a polymer particle, Any of what has a wide particle size distribution or a monodispersed particle size distribution may be sufficient. Further, two or more kinds of polymer fine particles having a monodispersed particle size distribution may be mixed and used.

The pH adjuster is not particularly limited as long as it adjusts the pH to a desired value without adversely affecting the prepared ink composition, and can be appropriately selected according to the purpose.
Examples of the pH adjuster include alcohol amines (eg, diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol), alkali metal hydroxides (eg, lithium hydroxide, hydroxide) Sodium, potassium hydroxide, etc.), ammonium hydroxide (for example, ammonium hydroxide, quaternary ammonium hydroxide), phosphonium hydroxide, alkali metal carbonate and the like.

The surfactant is used as a surface tension adjusting agent, and examples thereof include nonionic surfactants, cationic surfactants, anionic surfactants, and betaine surfactants.
The surfactant preferably contains an amount capable of adjusting the surface tension of the ink composition to 20 to 60 mN / m in order to eject droplets favorably by the ink jet method. Especially, content of surfactant is the quantity which can adjust surface tension to 20-45 mN / m, More preferably, it is quantity which can be adjusted to 25-40 mN / m.

  As the surfactant, a compound having a structure having both a hydrophilic part and a hydrophobic part in the molecule can be used effectively. Anionic surfactant, cationic surfactant, amphoteric surfactant, nonionic surfactant Any of the surfactants can be used.

Specific examples of the anionic surfactant include, for example, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium alkyldiphenyl ether disulfonate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate, sodium stearate, potassium oleate, Sodium dioctyl sulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, sodium dialkyl sulfosuccinate, sodium stearate, sodium oleate, t-octylphenoxyethoxypoly Examples include sodium ethoxyethyl sulfate, etc., and select one or more of these Rukoto can.
Specific examples of the nonionic surfactant include, for example, polyoxyethylene lauryl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene oleyl phenyl ether, polyoxyethylene nonyl phenyl ether, oxyethylene / oxypropylene block copolymer, t- Examples include octylphenoxyethyl polyethoxyethanol, nonylphenoxyethyl polyethoxyethanol, and the like, and one or more of these can be selected.
Examples of the cationic surfactant include tetraalkylammonium salts, alkylamine salts, benzalkonium salts, alkylpyridium salts, imidazolium salts, and the like. Specific examples thereof include dihydroxyethyl stearylamine and 2-heptadecenyl. -Hydroxyethyl imidazoline, lauryl dimethyl benzyl ammonium chloride, cetyl pyridinium chloride, stearamide methyl pyridium chloride and the like.

  There is no restriction | limiting in particular in content in the ink composition of surfactant, 1 mass% or more is preferable, More preferably, it is 1-10 mass%, More preferably, it is 1-3 mass%.

  Examples of the ultraviolet absorber include a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylate ultraviolet absorber, a cyanoacrylate ultraviolet absorber, and a nickel complex ultraviolet absorber.

"
As the anti-fading agent, various organic and metal complex anti-fading agents can be used. Organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, etc. Complex, zinc complex and the like.

  Examples of the antifungal agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, ethyl p-hydroxybenzoate, 1,2-benzisothiazolin-3-one, sodium sorbate, sodium pentachlorophenol Etc. These are preferably used in the ink in an amount of 0.02 to 1.00% by mass.

  Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

  Examples of the antioxidant include phenol-based antioxidants (including hindered phenol-based antioxidants), amine-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

  Examples of the chelating agent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate, and the like.

-Physical properties of ink composition-
The surface tension (20 ° C.) of the ink composition in the invention is preferably 20 mN / m or more and 60 mN / m or less. More preferably, it is 20 mN or more and 45 mN / m or less, More preferably, it is 25 mN / m or more and 40 mN / m or less.
The surface tension is a value measured at a liquid temperature of 20 ° C. and 60% RH by a Wilhelmy method using a surface tension meter (manufactured by Kyowa Interface Science Co., Ltd., surface tension meter CBVP-Z, etc.).

Further, the viscosity at 20 ° C. of the ink composition in the present invention is preferably 1.2 mPa · s or more and 15.0 mPa · s or less, more preferably 2 mPa · s or more and less than 13 mPa · s, and still more preferably. Is 2.5 mPa · s or more and less than 10 mPa · s.
The viscosity is measured using a VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD) under the condition of 20 ° C. of a water-based ink.

The ink composition in the present invention can be used when forming a multicolor image (for example, a full color image). In forming a full-color image, an ink composition having a yellow color tone, a magenta color tone, and a cyan color tone is used. The ink composition according to the present invention is preferably used as a magenta color tone ink composition.
In order to further adjust the color tone, a black tone ink composition can be used.
In addition, ink compositions having red (R), green (G), blue (B), and white (W) tones other than yellow (Y), magenta (M), and cyan (C), and so-called printing fields. Ink-colored ink compositions and the like can be used.
The ink composition of each color tone can be prepared by changing the hue of the pigment used as the colorant as desired.

When the average particle diameter of the pigment particles between the magenta liquid, cyan liquid, yellow liquid, and black liquid is close, the image may be easily blurred or deformed. The color liquid is used as the ink composition of the present invention described above, and as a black ink composition, the average particle diameter (Mv) is 30 nm or more larger than that of the ink composition of the present invention described above. Use in combination with a black liquid containing a color pigment is preferred. The average particle diameter here is the volume average particle diameter as described above.
Among them, a magenta color-based liquid, the average particle diameter Mv ¹ of the pigment particles in the cyan-based liquid, and a yellow color-based liquid, the difference between the average particle diameter Mv ² of the pigment particles of the black color system liquid (Mv ² -mv ¹ ) is preferably in the range of 30 to 100 nm, and more preferably in the range of 50 to 100 nm, in that high resolution with suppressed occurrence of bleeding and cracks can be obtained.

<Ink set>
The ink set of the present invention includes the ink for ink jet recording and a colorless ink containing an aggregation promoter that promotes aggregation of the ink for ink jet recording.
When the ink set of the present invention has the above-described configuration, aggregation can be caused and an image can be formed when ink for inkjet recording and a colorless ink described later are brought into contact with each other.

(Colorless ink)
The colorless ink in the ink set for ink-jet recording of the present invention comprises at least an aggregating agent that agglomerates the ink composition when in contact with the ink for ink-jet recording, and is configured using other components as necessary. Can do. As the aggregating agent for aggregating the ink composition, for example, changing the pH of the ink composition to the acidic side can be used.

-Flocculant-
The colorless ink in the present invention contains at least one flocculant for aggregating the ink composition. When the colorless ink is mixed with the ink composition ejected by the ink jet method, the pigment particles in the ink composition change from the dispersion stable region to the unstable region. Thereby, aggregation of the pigment stably dispersed in the ink composition is promoted.

At this time, the pH (25 ° C.) of the colorless ink is preferably in the range of 1 to 6, more preferably in the range of 2 to 5, and still more preferably in the range of 3 to 5. In this case, the pH (25 ° C.) of the ink composition is preferably 7.5 or more, and more preferably 8.5 or more.
Among these, in the present invention, from the viewpoint of image density, resolution, and speedup of inkjet recording, the pH (25 ° C.) of the ink composition is 7.5 or more, and the pH (25 ° C.) of the colorless ink is high. The case of 5 or less is preferable. Further, it is desirable that the pH (25 ° C.) of the ink composition can be changed to an acid side of 3.5 or more with colorless ink, and more preferably 4.5 or more.

  As the flocculant, an organic acid is preferably exemplified. Examples of organic acids include polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid, It is preferably selected from pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof. . These compounds may be used alone or in combination of two or more.

  The content of the flocculant in the colorless ink is preferably about 1 to about 10% by mass, more preferably about 1.5 to about 7% by mass, and still more preferably about 2 to about 6% by mass. is there.

<Image recording method>
The image recording method of the present invention is to record an image using the ink-jet recording ink set of the present invention described above. Preferably, the image recording method of the present invention comprises an ink applying step for applying an ink for ink jet recording and a step of applying a colorless ink using the ink set for ink jet recording of the present invention described above. The Specifically, an ink composition application step for applying an ink composition onto a recording medium, and an aggregating agent for aggregating the ink composition on the recording medium, the ink composition from a dispersion stable region of pigment particles A colorless ink applying step for applying a colorless ink to be changed to an unstable region is provided, and an image is formed by bringing the ink composition into contact with the colorless ink.
More preferably, the image recording method of the present invention includes a step of applying an ink composition after the step of applying a colorless ink.

  In the ink composition application step, the ink composition is applied by an inkjet method. Specifically, by supplying energy, a desired recording medium, that is, plain paper, resin-coated paper, for example, JP-A-8-169172, JP-A-8-27693, JP-A-2-276670, JP-A-7-276789, JP-A-9-323475, JP-A-62-238783, JP-A-10-153789, JP-A-10-217473, JP-A-10-235995, and JP-A-10-337947. 10-217597, 10-337947, etc., ink-jet exclusive paper, film, electrophotographic co-paper, fabric, glass, metal, ceramics, etc., discharge the ink composition to form a colored image . As a preferable ink jet recording method for the present invention, the method described in paragraph Nos. 0093 to 0105 of JP-A No. 2003-306623 can be applied.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method that discharges ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses vibration pressure of a piezoelectric element, an electric method An acoustic ink jet system that converts a signal into an acoustic beam, irradiates the ink with ink and ejects the ink using radiation pressure, and a thermal ink jet (bubble jet (registered trademark)) that heats the ink to form bubbles and uses the generated pressure. )) Any method may be used. As an ink jet method, in particular, the method described in Japanese Patent Application Laid-Open No. Sho 54-59936 causes an abrupt volume change of the ink subjected to the action of thermal energy, and the ink is ejected from the nozzle by the action force due to this state change. Ink jet method can be used effectively.
The ink jet method includes a method of ejecting a large number of low-density inks called photo inks in a small volume, a method of improving the image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent inks. The method using is included.

In addition, an ink jet head used in the ink jet method may be an on-demand method or a continuous method. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, a thermal type) Specific examples include an ink jet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.) and a discharge type (for example, a spark jet type). However, any discharge method may be used.
There are no particular restrictions on the ink nozzles used when recording by the ink jet method, and they can be appropriately selected according to the purpose.

  In the colorless ink application step, the colorless ink is applied on the recording medium before or after the ink composition is applied. The colorless ink can be applied by applying a known method such as a coating method, an ink jet method, or an immersion method. As a coating method, a known coating method using a bar coater, an extrusion die coater, an air doctor coater, a bread coater, a rod coater, a knife coater, a squeeze coater, a reverse roll coater, a bar coater or the like can be used. The details of the inkjet method are as described above.

  In this invention, the aspect which provides an ink composition provision process after giving a colorless ink by a colorless ink provision process is preferable. That is, before applying the ink composition on the recording medium, a colorless ink that changes the ink composition from the dispersion stable region of the pigment particles to the unstable region (for example, agglomerates the pigment) is applied in advance. An embodiment in which an image is formed by applying an ink composition so as to come into contact with colorless ink applied on a recording medium is preferable. Thereby, inkjet recording can be speeded up, and an image with high density and resolution can be obtained even at high speed recording.

During image recording, a polymer latex compound may be used in combination for the purpose of imparting glossiness or water resistance or improving weather resistance. The timing for applying the polymer latex compound may be before or after applying the ink composition, or may be applied simultaneously. Therefore, the polymer latex compound may be used in an embodiment applied to a recording medium, may be used in an embodiment added to the ink composition, or may be used in an embodiment in which the polymer latex compound is used as another liquid material. Good.
Specifically, Japanese Patent Application Laid-Open No. 2002-166638 (Japanese Patent Application No. 2000-363090), Japanese Patent Application Laid-Open No. 2002-121440 (Japanese Patent Application No. 2000-315231), Japanese Patent Application Laid-Open No. 2002-154201 (Japanese Patent Application No. 2000-354380), The methods described in JP-A No. 2002-144696 (Japanese Patent Application No. 2000-343944) and JP-A No. 2002-080759 (Japanese Patent Application No. 2000-268952) can be preferably used.

  In addition to the ink composition applying step for applying the ink composition and the colorless ink applying step for applying the colorless ink, the image forming method may further include other steps. There is no restriction | limiting in particular as another process, According to the objective, it can select suitably. For example, a drying and removing step for drying and removing the organic solvent in the ink composition applied to the recording medium, a heat fixing step for melting and fixing resin fine particles or polymer latex contained in the ink composition, and the like can be mentioned.

As another example of the image forming method, an intermediate transfer member is used as a recording medium for image formation first, and the intermediate transfer member includes a water-soluble organic solvent, water, and a pigment, and the average particle diameter of the pigment An ink composition applying step of applying an ink composition (ink composition) having a monodispersity of 1.5 or less by an ink jet method, and an ink composition on the intermediate transfer member A colorless ink application step that includes a component that changes the pH to the acidic side and that imparts a colorless ink that changes the ink composition from a dispersion stable region to an unstable region of the pigment particles is provided to contact the ink composition and the colorless ink. Then, after forming an image on the intermediate transfer member, a method of providing a transfer step of transferring the image formed on the intermediate transfer member to a desired final recording medium can be mentioned.
In this case as well, other processes such as a drying removal process and a heat fixing process can be further provided in the same manner as described above. Moreover, the aspect which provides an ink composition provision process after giving a colorless ink at a colorless ink provision process in an ink composition provision process and a colorless ink provision process is preferable.

  The present invention will be described more specifically with reference to the following examples. The scope of the present invention is not limited to the specific examples shown below. Unless otherwise specified, “part” and “%” are based on mass.

-Polymer synthesis-
(Synthesis Example 1)
The inside of a 2000 ml separable flask equipped with a stirrer, a reflux tube, a thermometer, and a dropping funnel was purged with nitrogen, and then 200.0 parts of diethylene glycol monomethyl ether was added to the separable flask and heated to 80 ° C. while stirring. . Next, 200.0 parts of diethylene glycol monomethyl ether, 453.5 parts of benzyl acrylate, 131.3 parts of acrylic acid, and 4.8 parts of t-butylperoxy (2-ethylhexanoate) are put into a dropping funnel. It was made to react by dripping at 80 degreeC over 4 hours in a separable flask. After completion of the dropwise addition, the mixture was kept at 80 ° C. for 1 hour, 0.8 parts of t-butylperoxy (2-ethylhexanoate) was added, and the reaction was further carried out at 80 ° C. for 1 hour. Thereafter, diethylene glycol monomethyl ether was removed by distillation under reduced pressure. Then, 600.0 parts of methyl ethyl ketone was added to prepare a polymer composition solution having a resin solid content of 50% by mass.
A portion of the polymer composition solution thus obtained was taken and dried for 1 hour in a high-temperature dryer at 105 ° C., and then the acid value and weight average molecular weight of the solid matter of the polymer composition obtained were measured. However, the acid value was 180 mgKOH / g and the weight average molecular weight was 28000.
The weight average molecular weight was detected by a differential refractometer with a solvent THF using a GPC analyzer using columns of TSKgel GMHxL, TSKgel G4000HxL, TSKgel G2000HxL (all manufactured by Tosoh Corporation), and polystyrene was used as a standard substance. It was calculated by using.

(Synthesis Example 2)
A polymer composition solution was prepared in the same manner as in Synthesis Example 1 except that 77.4 parts of acrylic acid was used instead of 100.8 parts of acrylic acid in Synthesis Example 1.
A part of the polymer composition solution thus obtained was taken and dried for 1 hour in an ignition dryer at 105 ° C., and then the acid value and the weight average molecular weight of the solid content of the polymer composition were measured. However, the acid value was 98 mgKOH / g, and the weight average molecular weight was 34,000. The weight average molecular weight was measured in the same manner as described above.

-Preparation of latex-
(Synthesis Example 3)
To 120 g of water, latemul ASK (manufactured by Kao Corporation, carboxylate emulsifier) 19.7 g, 6 g of 5 mol / L sodium hydroxide aqueous solution, and 2,2′-azobis (2-amidinopropane) dihydrochloride 3 g was added and dissolved uniformly. This was heated to 70 ° C., and a monomer mixture of 25.8 g of styrene, 26.4 g of butyl acrylate, and 5.1 g of acrylic acid was added over 2 hours under a nitrogen stream. Then, it heated at 70 degreeC for 2 hours and 80 degreeC for 3 hours. After cooling to room temperature, a 1 mol / L aqueous sodium hydroxide solution was added with stirring so that the pH was around 9, thereby obtaining a latex dispersion LX-1. The solid content of the latex dispersion was 33% by mass.

-Preparation of basic group-containing pigment derivatives-
(Preparation of pigment derivative Y1)
The following pigment derivative (Y1) having a basic group was obtained by reacting 50 parts of a naphthol pigment with 28 parts of N, N-diethylaminopropylamine as an amine component.

(Preparation of pigment derivative Y2)
A pigment derivative (Y2) having the following basic group was obtained by reacting 50 parts of copper phthalocyanine as a pigment component with 40 parts of dibutylamine as an amine component.

(Preparation of pigment derivative Y3)
After chloroacetamidomethylation of 50 parts of quinacridone as a pigment component, it was reacted with 38 parts of N-methylpiperazine as an amine component to obtain a pigment derivative (Y3) having the following basic group.

(Preparation of triazine derivative Y4)
Triazine was reacted with N, N-dimethylaminopropylamine, which is an amine component, to obtain a triazine derivative having the following basic group (Y4 was obtained).

-Preparation of anion group-containing pigment derivatives-
(Preparation of pigment derivative Y5)
Under a low temperature condition of 5 to 10 ° C., 2,9-dimethylquinacridone pigment (CI Pigment Red 122, manufactured by Ciba Specialty Chemicals Co., Ltd.) was added to the fuming sulfuric acid and reacted, Poured into ice water. The obtained suspension was filtered, further washed, and the resulting product was dried to obtain sulfonated-2,9-dimethylquinacridone (Y5).

[Example 1]
-Preparation of water-based ink (yellow ink) 101-
First, pigment dispersion A was prepared by the following method (build-up method).
As a dispersant, 4 parts of a solid (dried product) of the polymer composition solution prepared in Synthesis Example 1 was dissolved in 80 parts of dimethyl sulfoxide. I. 10 parts of Pigment Yellow 74 (azo pigment) was suspended in a flask at 25 ° C. in an air atmosphere. Next, a 25% tetramethylammonium hydroxide methanol solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise little by little to dissolve the azo pigment to obtain a red-violet pigment solution. After stirring this pigment solution for 1 hour, 0.05 part of pigment derivative (Y1) was added and further stirred for 15 minutes, and then this was cooled and kept warm with stirring by an impeller type stirring blade (700 rpm). A system dispenser (manufactured by Musashi Engineering Co., Ltd., needle inner diameter: 0.58 mm, discharge pressure: 4.0 kgf / cm ² ) 2 in ion-exchanged water (amount that becomes 400 parts of ion-exchanged water with respect to 10 parts of pigment) The group was quickly charged to obtain a transparent, slightly orange-yellow pigment dispersion.
When the average volume particle diameter of this pigment dispersion was determined by the following dynamic light scattering method, it was 49.8 nm (TEM average particle diameter: 35.5 nm), and the degree of monodispersity [volume Ratio of average particle diameter Mv / number average particle diameter Mn] was 1.50.

  Next, hydrochloric acid was added dropwise to the pigment dispersion to adjust the pH to 3.5, and pigment particles were aggregated from the pigment dispersion. Thereafter, the agglomerate was filtered under reduced pressure using a membrane filter having an average pore size of 0.2 μm, and washed twice with ion-exchanged water to obtain a paste of a dispersion of pigment particles that has been desalted and desolvated.

  Next, 100 parts of acetone was added to the paste, followed by stirring and ultrasonic treatment. Then, it filtered under reduced pressure using the membrane filter with an average hole diameter of 0.2 micrometer. The filtered paste was washed with ion-exchanged water and filtered under reduced pressure again using a membrane filter having an average pore size of 0.2 μm to obtain a dispersion paste containing pigment particles.

  Next, a small amount of ion-exchanged water was added to the obtained dispersion paste, and a 15% tetramethylammonium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) was added. Was done. Thereafter, ion-exchanged water was added so that the pigment content was 10% by mass. Further, 15% tetramethylammonium hydroxide aqueous solution was added to adjust the pH to 9.0, and then pigment dispersion A was obtained.

Using this pigment dispersion A, yellow ink 101 (pH = 8.8 (25 ° C.)) having the following composition was produced.
After the yellow ink 101 was diluted 50 times with ultrapure water, the average volume particle size Mv determined by the dynamic light scattering method by the method shown below was 50.1 nm (TEM average particle size: 35.0 nm). The degree of monodispersity [ratio of volume average particle diameter Mv / number average particle diameter Mn], which is an index of monodispersibility, was 1.5 (the particle diameter was measured by a method similar to that for yellow ink 101 and latex It is the value which produced and measured the liquid which does not contain the dispersion liquid LX-1. No change was observed in the particle size after storage for 2 weeks, no sediment was observed, and no discoloration was observed.

<Composition>
・ Pigment dispersion A ... 40.0g
・ Diethylene glycol: 9.0g
・ Glycerin ... 18.0g
・ Latex dispersion LX-1 ... 18.2g
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) ... 1.0g
・ Water: Amount of 100g in total

-Preparation of water-based inks 102-105 (ink of the present invention) and 106-107 (comparative ink)-
In the preparation of the water-based ink 101, yellow-colored water-based inks 102 to 107 were obtained by changing the amount and type of the pigment derivative as shown in Table 1 below. The pH of each of the obtained water-based inks at 25 ° C. was 8.8. The methods for measuring the average particle size and monodispersity of the pigment are as follows.

-Preparation of water-based ink 108 (comparative ink)-
First, pigment dispersion B was prepared by the following method (hereinafter referred to as “breakdown method”).
To 120.0 parts of the polymer composition solution prepared in Synthesis Example 2, 3.0 parts of 30% aqueous sodium hydroxide solution was added, and yellow pigment C.I. I. 480.0 parts of Pigment Yellow 74 and 36 parts of a basic group-containing pigment derivative (Y1) were added, and Picomil (dispersion medium: zirconia, temperature: 20 ° C., dispersion media / liquid separation mass) manufactured by Asada Steel Corporation. The pigment dispersion slurry was obtained by dispersion treatment for 10.5 hours at a peripheral speed of 8 m / s using a ratio of 8/2). Then, this pigment dispersion slurry was continuously dispersed 10 times at a pressure of 200 MPa by an ultrahigh pressure homogenizer (Microfluidizer, manufactured by Mizuho Kogyo Co., Ltd.) to obtain a pigment dispersion.

  Further, methyl ethyl ketone and a part of water were distilled off from the pigment dispersion obtained as described above by vacuum distillation using an evaporator, and the mixture was centrifuged for 30 minutes using a centrifuge (05P-21, manufactured by Hitachi, Ltd.). After centrifugal separation at 5000 rpm, ion-dispersed water was added so that the pigment concentration was 16% by mass to prepare pigment dispersion B. Then, pressure filtration was performed using a 2.5 μm membrane filter (manufactured by Advantech).

Using the filtered pigment dispersion B, a yellow ink 108 (pH = 8.8 (25 ° C.)) having the following composition was produced.
After the yellow ink 108 was diluted 500 times with ultrapure water, the average volume particle size Mv determined by the dynamic light scattering method was 63.0 nm (TEM average particle size: 37.2 nm), and it was monodisperse. The monodispersity [ratio of volume average particle size Mv / number average particle size Mn] as an index of 1.80 was 1.80 (measurement of particle size was performed using latex dispersion LX-1 by the same production method as yellow ink 108). It is the value which produced and measured the liquid which does not contain.

<Composition>
・ Pigment dispersion B ... 25.0g
・ Diethylene glycol: 9.0g
・ Glycerin ... 18.0g
・ Latex dispersion LX-1 ... 18.2g
・ Orphine E1010 (Nissin Chemical Industry Co., Ltd.) ... 1.0g
・ Water: Amount of 100g in total

-Preparation of water-based ink 109 (comparative ink)-
In the preparation of the water-based ink 108, water-based inks 109 having different average particle diameters Mv of pigments as shown in Table 1 were obtained by changing the dispersion time. The pH of the obtained water-based ink at 25 ° C. was 8.8. The methods for measuring the average particle size and monodispersity of the pigment are as follows.

-Measurement of average particle size and monodispersity-
[1. Volume average particle diameter (Mv)]
About the obtained water-based ink, the volume average particle diameter (secondary particle) was measured by a dynamic light scattering method using a Microtrac particle size distribution measuring device (Version 10.1.2-211BH (trade name), manufactured by Nikkiso Co., Ltd.). Was measured. In order to eliminate the influence of LX, the pigment particle size is measured by adding 10 ml of ion exchange water to 10 μl of water-based ink not containing LX-1 to prepare a sample solution for measurement, and adjusting the temperature to 25 ° C. It was done. The measurement results are shown in the following tables.

[2. Monodispersity]
For the obtained water-based ink, similarly to the measurement of Mv, using a measurement sample liquid (25 ° C.) prepared by adding 10 ml of ion-exchanged water to 10 μl of water-based ink, a Microtorac particle size distribution measuring device (Version 10) was used. 1.2-211BH (trade name), manufactured by Nikkiso Co., Ltd., by a dynamic light scattering method, the volume average particle size (Mv) and the number average particle size (Mn) are measured. The ratio of number average particle diameter (Mv / Mn) was determined. The measurement results are shown in the following tables.

-Preparation of aqueous coagulation liquid 1-
Components of the following composition were mixed and adjusted to pH 3.3 using a sodium hydroxide solution to prepare an aqueous aggregate 1 (colorless ink).

<Composition>
・ Citric acid ・ ・ ・ 15 parts ・ Ion-exchanged water ・ ・ ・ 84 parts ・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.)

  An ink set as shown in Table 1 below was prepared by combining the aqueous inks 101 to 109 prepared as described above and the aqueous aggregation liquid 1.

-Evaluation of ink set-
The following evaluation was performed on the ink set obtained above. The evaluation results are shown in Table 1 below.
<1. Dispersion stability>
50 ml of ink is put in a sealed sample container so as not to evaporate, and left in a constant temperature bath at 60 ° C. for 2 W, and a Microtorac particle size distribution measuring device (Version 10.1.2-211BH (trade name), Nikkiso Co., Ltd.) The change rate of the volume average particle diameter (Mv) measured by the dynamic light scattering method was obtained and evaluated.
<Evaluation criteria>
A: Change rate of particle size is less than 10% B: Change rate of particle size is 10-30%
C: The particle size change rate exceeds 30% and is unacceptable for practical use.

<2. Post-thermo landing position accuracy>
As an inkjet recording device,
・ Head: 1,200 dpi / 20 inch width full line head ・ Discharged droplet amount: 4-value recording of 0, 2.0, 3.5, 4.0 pL ・ Drive frequency: 30 kHz (recording medium conveyance speed 635 mm / sec)
An image recording apparatus equipped with a prototype print head was prepared so that liquid could be supplied from the outside. This apparatus is loaded with the ink set obtained above, and the resulting aqueous aggregating liquid and aqueous ink are each supplied from separate discharge nozzles in this order on fine paper (product name: Shirai, 76.5 g / m, ² products, Japan The ink was discharged onto paper (manufactured by Paper Manufacturing Co., Ltd.) to draw a yellow dot line. After drying, the image was fixed by fixing and heating at 100 ° C. for 10 seconds. Then, the linearity of the line was visually evaluated according to the following evaluation criteria.

<Evaluation criteria>
A: Line bending does not occur.
B: Line bending is slightly seen.
C: Line bending is observed, but it is within a practically allowable range.
D: Line bending is large and practically unacceptable.
E: Line bending was remarkable.

<3. Light resistance>
<2. A yellow image was recorded on inkjet paper (photo paper <gloss>, manufactured by Epson Corporation) in the same manner as in the evaluation of the post-thermo landing position accuracy>, and the yellow image was naturally dried for 24 hours. The image density Ci was measured using Gretag Spectrolino (trade name: manufactured by Gretag). After the measurement, using an Atlas weather meter, the image was continuously irradiated with xenon light (100,000 lux) for 30 days, and then the image of the region where the reflection density before the xenon irradiation was 1.0 was again in the same manner. The density Cf was measured, and the dye residual ratio (%) was determined by the following formula and evaluated according to the following evaluation criteria.
Dye remaining rate (%) = Cf / Ci × 100
<Evaluation criteria>
A: The residual ratio of the dye was 90% or more.
B: Dye residual ratio was 75 or more and less than 90%.
C: Dye remaining rate was less than 75%.

[Example 2]
-Preparation of water-based inks 201-203-
The same water-based ink 201 as that of the water-based ink 102 was used.
By changing the amount of the polymer composition solution and the amount of 25% tetramethylammonium hydroxide methanol solution (manufactured by Wako Pure Chemical Industries, Ltd.) with respect to the water-based ink 201, the water-based inks 202 to 203 are changed to the following Table 2. As shown in Fig. 5, yellow water-based inks 202 to 203 having different average particle diameters Mv and monodispersities of the pigments were obtained. The average particle diameter and monodispersity were measured in the same manner as in Example 1.

  An ink set as shown in Table 2 below was prepared by combining the aqueous inks 201 to 203 prepared as described above and the aqueous aggregation liquid 1.

-Evaluation of ink set-
For the ink set obtained above, the same method as in Example 1 was used. 2. Post-thermo landing position accuracy, and 3. Image deformation was evaluated.

<3. Image transformation>
<1. After recording a yellow image of 5 cm × 5 cm on high-quality paper (product name: Shiraoi, 76.5 g / m ² product, manufactured by Nippon Paper Industries Co., Ltd.) in the same manner as the evaluation of post-thermo landing position accuracy> After drying, the image was fixed by heating at 100 ° C. for 10 seconds. Then, the image part was observed visually and evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: Almost no cracking or unevenness occurred in the image area.
B: There were few cracks and unevenness.
C: Although cracks and unevenness were observed, they were practically acceptable.
D: A lot of cracks and unevenness was observed, which was unacceptable for practical use.
E: Generation of cracks and unevenness was remarkable.

  In the present invention, it was found that the smaller the average pigment particle diameter, the better the image deformation, and the smaller the value of the monodispersity of the pigment particles, the better.

[Example 3]
As shown in Table 3 below, by changing the amount of the polymer composition solution and the amount of 25% tetramethylammonium hydroxide methanol solution (manufactured by Wako Pure Chemical Industries, Ltd.) in the same manner as the preparation of the ink 101, In addition, four types of water-based inks 301 to 304 having different pigment derivative types were obtained by combining the average particle diameter Mv and monodispersity of the pigment.

  An ink set as shown in Table 3 below was prepared by combining the water-based inks 301 to 304 prepared as described above and the water-based aggregate liquid 1.

-Evaluation of ink set-
For the ink set obtained above, the post-thermo landing position accuracy and the following image deformation were evaluated in the same manner as in Example 2.

  As apparent from Table 3 above, the present invention using different pigment derivatives was excellent in post-thermo landing position accuracy and image deformation. In particular, the ink set 301 similar to the structure of the azo pigment was very good in the evaluation.

Claims (12)

At least selected from the group consisting of an azo pigment (a), a pigment derivative obtained by introducing a basic group into an organic pigment, an anthraquinone derivative having a basic group, an acridone derivative having a basic group, and a triazine derivative having a basic group A pigment solution in which a derivative (b) having one kind of basic group is dissolved;
Containing a dispersant in at least one of the aqueous solvents,
A method for producing a pigment dispersion, comprising the step of mixing the pigment-dissolved solution and the aqueous solvent to precipitate a pigment.   The method for producing a pigment dispersion according to claim 1, wherein the derivative (b) is 0.5 to 20 parts by mass with respect to 100 parts by mass of the azo pigment (a).   The pigment dispersion according to claim 1 or 2, wherein the dispersant is a polymer compound having one or more kinds selected from a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group as a hydrophilic group. Liquid manufacturing method.   The method for producing a pigment dispersion according to any one of claims 1 to 3, wherein the correlation transfer base is added.   The azo pigment (a) is C.I. I. It is a pigment yellow 74, Comprising: The said derivative | guide_body (b) has an azo skeleton, The manufacturing method of the pigment dispersion liquid of any one of Claims 1-4 characterized by the above-mentioned.   The method for producing a pigment dispersion according to any one of claims 1 to 5, wherein the average particle diameter of the pigment is 5 to 50 nm.   The method for producing a pigment dispersion according to any one of claims 1 to 6, wherein the monodispersity of the pigment particle diameter is 1.5 or less.   An ink for inkjet recording, comprising a pigment dispersion prepared by the production method according to any one of claims 1 to 7.   An ink set comprising the ink according to claim 8 and a colorless ink containing an aggregation accelerator that promotes aggregation of the ink. At least selected from the group consisting of an azo pigment (a), a pigment derivative obtained by introducing a basic group into an organic pigment, an anthraquinone derivative having a basic group, an acridone derivative having a basic group, and a triazine derivative having a basic group The average particle size of the pigment comprising the derivative (b) having one kind of basic group and the dispersant is 5 to 50 nm, and the monodispersity of the pigment particle size is 1.5 or less. A pigment dispersion characterized by   An ink for ink-jet recording comprising the pigment dispersion according to claim 10.   An ink set comprising: the ink for ink jet recording according to claim 11; and a colorless ink containing an aggregation accelerator that promotes aggregation of the ink for ink jet recording.