JP2009298933A - Water-based pigment dispersion, ink composition and ink-jet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based pigment dispersion that has excellent dispersion stability, especially excellent solvent resistance of dispersibility to an ether-based solvent liable to cause dispersion destruction. <P>SOLUTION: The water-based pigment dispersion comprises a water-based medium (a), a pigment (b) and a cationic polymer (c) in which the cationic polymer (c) has at least an aromatic ring and a quaternary ammonium base and a number-average molecular weight in terms of a polyethylene glycol measured by GPC of ≥14,000. The cationic polymer (c) is obtained by copolymerizing a monomer mixture preferably containing one or more aromatic group-containing monomers and one or more quaternary ammonium base-containing monomers. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an aqueous pigment dispersion excellent in dispersion stability, storage stability and solvent resistance, a method for producing the same, an ink composition containing the aqueous pigment dispersion, and an ink jet recording method using the ink composition. .

  Inkjet printers are rapidly used for both personal use and business use due to the ease of full color, low noise, high-resolution images at a low price, and high-speed printing. It is becoming popular. At present, aqueous recording liquids are mainly used as recording liquids for ink jet printers, and printed materials with high resolution are being obtained.

  Conventionally, the aqueous recording liquid mainly contains a water-soluble dye and a liquid medium. However, the printed matter obtained with this aqueous recording liquid has insufficient water resistance, light resistance, ozone resistance and the like because the aqueous recording liquid contains a water-soluble dye. Therefore, in recent years, instead of such a dye, a pigment dispersion in which a pigment is dispersed in an aqueous medium has been developed.

  As a method for preparing a pigment dispersion by dispersing a pigment in an aqueous medium, a method using a polymer dispersant such as a water-soluble polymer or a water-dispersible polymer is known. For example, an example in which a polymer containing a cationic group such as a tertiary amino group or a quaternary ammonium salt is used as a polymer dispersing agent for pigment dispersion is disclosed (see Patent Documents 1 and 2).

  For example, in Patent Document 1, a water-soluble resin containing at least one monomer specifically selected from styrenes and alkyl (meth) acrylates and a cationic group-containing monomer and having a number average molecular weight of 1000 to 10,000 is used. The water-based pigment ink used has been proposed, and is said to be effective in long-term storage stability, ejection properties, and the like.

  Patent Document 2 proposes a dispersible color material having chargeable resin pseudo fine particles smaller than the color material, in which the color material and the charge resin pseudo fine particles are fixed to each other. It is said that it is effective in properties and ejection properties. In Patent Document 2, a cationic polymer is used as one of the resin components constituting the chargeable pseudo fine particles.

  In recent years, with the improvement in image quality of inkjet printers and the improvement in resolution of printed matter, the amount of ink ejected from an ink ejection nozzle has been reduced to several picoliters. In addition, with the increase in printing speed, the discharge speed of ink from the discharge nozzle is remarkably increased. In order to achieve such high image quality and high printing speed, it is important to prevent clogging of the ink discharge nozzle, storage stability, discharge stability, etc. Therefore, pigment dispersion with excellent dispersion stability Liquid has been needed.

  In addition, aqueous pigment dispersions used for inkjet printers include penetration enhancers, surface tension modifiers, hydrotropic agents, pH adjusters, chelating agents, preservatives, viscosity modifiers, humectants, antifungal agents, Various additives such as rust preventives are added to prepare the recording liquid, but the aqueous pigment dispersion must maintain sufficient dispersion stability even when such additives are added. It is said. When the dispersion stability in the recording liquid is reduced, the printer head is clogged, the printing quality is lowered, and the recording liquid cannot be stored stably for a long period of time.

  In particular, recently, in order to improve the wettability and penetrability of ink with respect to media, many of them contain ether solvents, and there is a strong demand for long-term storage stability of recording liquids containing these solvents. . Examples of ether solvents include carbitols such as ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, and triethylene glycol monobutyl ether. However, when these are added to the pigment dispersion, they are more heated than other solvents. In particular, it tends to cause dispersion failure.

For these reasons, there has been a demand for further development of an aqueous pigment dispersion that is excellent not only in dispersion stability but also in dispersibility with respect to ether solvents that are liable to cause dispersion failure as described above.
Japanese Patent Laid-Open No. 6-122846 JP 2004-331946 A

  The present invention has been made in view of the above-described conventional situation, and is an aqueous pigment dispersion that has excellent dispersion stability, in particular, excellent dispersibility and solvent resistance to an ether-based solvent that easily causes dispersion failure. The issue is to provide.

  In order to solve this problem, the present inventors have conducted extensive studies on an aqueous pigment dispersion. As a result, the present inventors have (a) an aqueous medium, (b) a pigment, and (c) at least an aromatic ring and a quaternary ammonium base. In addition, an aqueous pigment dispersion containing a cationic polymer having a number average molecular weight of 14000 or more measured by GPC as measured by GPC is excellent in dispersion stability, storage stability, particularly solvent resistance to ether solvents. The present invention has been found to be excellent, and the present invention has been completed.

  That is, the gist of the present invention is that an aqueous pigment dispersion comprising (a) an aqueous medium, (b) a pigment, and (c) a cationic polymer, wherein (c) the cationic polymer is at least an aromatic ring and a quaternary ammonium base. And an aqueous pigment dispersion (Claim 1) characterized by being a polymer having a number average molecular weight in terms of polyethylene glycol measured by GPC of 14,000 or more.

  Another aspect of the present invention is a method for producing this aqueous pigment dispersion by subjecting a mixture containing (a) an aqueous medium, (b) a pigment, and (c) a cationic polymer to a dispersion treatment, (A) A method for producing an aqueous pigment dispersion characterized in that only water is used as an aqueous medium (claim 7).

  Still another subject matter of the present invention includes an ink composition comprising the aqueous pigment dispersion (Claim 8), and the aqueous pigment dispersion produced by the method for producing the aqueous pigment dispersion. The present invention resides in an ink composition (claim 9).

  Still another subject matter of the present invention resides in an ink jet recording method (claim 10), characterized in that a droplet of the ink composition is ejected from an ink jet head and the droplet is adhered to a recording medium.

  The aqueous pigment dispersion of the present invention is excellent in dispersion stability, storage stability and solvent resistance, and has a low viscosity. In particular, the aqueous pigment dispersion of the present invention exhibits good dispersion stability even when an ether solvent is used. Therefore, such an aqueous pigment dispersion of the present invention can be suitably used particularly for an ink composition as a recording liquid for an inkjet printer or the like, and has excellent storage stability including the aqueous pigment dispersion of the present invention. By using the obtained ink composition, it is possible to obtain a high-quality inkjet recorded matter without causing problems such as clogging of the printer head.

  Hereinafter, embodiments of the present invention will be described in detail. However, the description of the constituent elements described below is an example (representative example) of the embodiments of the present invention, and the present invention does not exceed the gist thereof. These contents are not specified.

  In the following, “(meth) acrylate” means “acrylate and / or methacrylate”, and “(meth) acryl” means “acryl and / or methacryl”. The same applies to “(meth) acrylo”.

  In the present invention, “aromatic ring” includes “aromatic hydrocarbon ring” and “aromatic heterocycle”, and “heterocycle” means “aromatic heterocycle” and “aromatic heterocycle”. And “non-aromatic heterocycle”.

[1] Aqueous Pigment Dispersion The aqueous pigment dispersion of the present invention is an aqueous pigment dispersion containing (a) an aqueous medium, (b) a pigment, and (c) a cationic polymer. A polymer having at least an aromatic ring and a quaternary ammonium base and having a number average molecular weight in terms of polyethylene glycol measured by GPC of 14,000 or more is used.

  In the present invention, (c) a cationic polymer having at least an aromatic ring and a quaternary ammonium base and having a number average molecular weight in terms of polyethylene glycol measured by GPC of 14,000 or more is used as a polymer dispersant. As a result, an aqueous pigment dispersion having significantly improved dispersion stability and an ink composition having excellent storage stability can be obtained.

  Although the details of the mechanism of action of the dispersion stability improving effect by this specific (c) cationic polymer are not clear, it is considered as follows.

  The basic design of the polymer dispersant for the aqueous pigment dispersion includes affinity for the pigment, affinity for the aqueous dispersion medium, and imparting repulsion between the dispersions at the time of dispersion. It is important to arrange in a balanced manner.

The cationic polymer (c) having an aromatic ring having a large affinity for the pigment from the viewpoint of hydrophobicity and electronic environment and a quaternary ammonium base having a high affinity for the aqueous dispersion medium from the viewpoint of the degree of dissociation Is used, an aqueous pigment dispersion having high dispersion stability can be obtained.
In addition, a polymer having a low molecular weight exhibits a high mobility due to a short polymer chain, and thus has a large excluded volume space. In particular, in a state where an ink additive containing an aqueous organic solvent, particularly an ether solvent, is added, and under the condition of being heated, the motility of the polymer is further increased, so that the excluded volume space is expanded. Under such conditions, the polymer adsorbed on the pigment is gradually peeled off, and not only the stability of the recording liquid is lowered but also the viscosity is increased and the dischargeability is also deteriorated. Accordingly, the polymer dispersant needs to have a certain degree of molecular weight.

  In the present invention, as the dispersant, (c) a cationic polymer having at least an aromatic ring and a quaternary ammonium base and having a number average molecular weight of 14,000 or more in terms of polyethylene glycol measured by GPC is used. It is considered that an aqueous pigment dispersion having solvent resistance and a recording liquid excellent in storage stability can be obtained.

[(C) Cationic polymer]
In the present invention, (b) a cationic polymer used as a polymer dispersant for dispersing the pigment in an aqueous medium has at least an aromatic ring and a quaternary ammonium base.

{Aromatic rings and quaternary ammonium bases}
(C) As a substituent of the nitrogen atom which comprises the quaternary ammonium base of a cationic polymer, the following are mentioned, for example.
Alkyl group: methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, etc. sec-butyl group, isobutyl group, tert-butyl group, isopentyl group, neopentyl group, tert-pentyl group, 1-ethylpropyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, neopentyl group, etc. Cyclic type cyclopentyl group, cyclohexyl group, 1-methylcyclohexyl group, etc. Aromatic ring group (especially aromatic hydrocarbon ring group) Substituted alkyl group: optionally substituted benzyl group, phenethyl group (for example, 2-phenylethyl group) ), 3-phenylpropyl group, 4-phenylbutyl group, 5-phenylpentyl group, 6-phenyl Aralkyl group such as xyl group Aromatic ring group (especially aromatic hydrocarbon ring group): aryl group such as optionally substituted phenyl group, tolyl group, o-xylyl group, naphthyl group, anthranyl group, pyrenyl group, A condensed aromatic ring group such as a phenanthryl group, etc. Heterocyclic group: a group derived from a heterocyclic ring such as pyridine, pyrrole, indole, quinoline, pyrrolidine, piperidine, etc. Here, examples of the substituent of the phenyl group and benzyl group include linear, Alkyl group which may be branched or cyclic, alkoxyl group which may be linear, branched or cyclic, hydroxyl group, carboxyl group, carboxyl base, sulfonyl group, sulfonyl base, phosphonyl group, phosphonyl base, cyano group, halogen Groups and the like. Examples of the salt include alkali metal salts and alkaline earth metal salts.

  The four substituents of the quaternary ammonium base may be the same as or different from each other, and are composed of any one to four of the above substituents.

  Examples of the ammonium salt of the quaternary ammonium base include halide salt, acetate salt, sulfate salt, sulfite salt, alkyl sulfate salt, aryl sulfate salt, carbonate salt, bicarbonate salt, alkyl carbonate salt, nitrate salt and the like. It is done. Here, examples of the alkyl sulfate, the alkyl group of the alkyl carbonate, and the aryl group of the aryl sulfate include those exemplified above as the substituent of the nitrogen atom of the quaternary ammonium base.

  Among them, the alkyl group is preferable as the substituent of the quaternary ammonium base, and the halide salt and the alkyl sulfate are preferable as the form of the ammonium salt.

  (C) Since the cationic polymer has at least an aromatic ring and a quaternary ammonium base, all the nitrogen atom substituents in the quaternary ammonium base are aromatic ring groups and aromatic rings among the above-mentioned substituents. When the group-substituted alkyl group and the heterocyclic group are other than the aromatic heterocyclic group, and the ammonium salt is other than the aryl sulfate, a functional group having an aromatic ring is further required.

Examples of the functional group having an aromatic ring include an aryl group such as an optionally substituted phenyl group, tolyl group and o-xylyl group, an optionally substituted benzyl group, a 2-phenylethyl group, and a 3-phenylpropylene group. And condensed aromatic ring groups such as an aralkyl group such as an alkyl group, a naphthyl group, an anthranyl group, a pyrenyl group, and a phenanthryl group.
Here, examples of the substituent of the phenyl group and the benzyl group include an alkyl group which may be linear, branched or cyclic, an alkoxyl group which may be linear, branched or cyclic, a hydroxyl group, a carboxyl group, Examples include a carboxyl base, a sulfonyl group, a sulfonyl base, a phosphonyl group, a phosphonyl base, a cyano group, and a halogen group. Examples of the salt include alkali metal salts and alkaline earth metal salts.

Among the above, the functional group having an aromatic ring is preferably the following from the viewpoint of the affinity for the pigment.
Unsubstituted phenyl group; alkyl group which may be linear, branched or cyclic, alkoxyl group which may be linear, branched or cyclic, hydroxyl group, carboxyl group, sulfonyl group, phosphonyl group, cyano group, Or a phenyl group substituted with a halogen group; an aryl group such as a tolyl group or an o-xylyl group;
An unsubstituted benzyl group; an alkyl group that may be linear, branched, or cyclic; an alkoxyl group that may be linear, branched, or cyclic; a hydroxyl group, a carboxyl group, a sulfonyl group, a phosphonyl group, a cyano group, Or a benzyl group substituted with a halogen group; an aralkyl group such as a 2-phenylethyl group and a 3-phenylpropyl group;
Condensed aromatic ring groups such as naphthyl group, anthranyl group, pyrenyl group, phenanthryl group:

  Among the above, the functional group having an aromatic ring is preferably an aryl group or an aralkyl group, and particularly an unsubstituted phenyl group or benzyl group; an alkyl group that may be linear, branched, or cyclic, linear, branched A phenyl group or a benzyl group substituted with an alkoxyl group, a hydroxyl group, a carboxyl group, a sulfonyl group, a phosphonyl group, a cyano group, or a halogen group, which may be in the form of a ring or a ring, is particularly preferable.

{Water-soluble and water-dispersible}
The cationic polymer (c) of the present invention is preferably a water-soluble or water-dispersible cationic polymer.

  As used herein, “water-soluble” refers to a substance that dissolves in water and / or an aqueous medium at 25 ° C. in an amount of 2% by weight or more, more preferably 10% by weight or more. Further, “water dispersibility” means that no precipitation occurs in a dispersion of water and / or an aqueous medium having a concentration of 2% by weight or more.

  Examples of the aqueous medium include lower alcohols having 1 to 4 carbon atoms such as ethanol and propanol; ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1 , 3-propylene glycol, isopropylene glycol, polypropylene glycol, pentamethylene glycol, trimethylene glycol, butylene glycol, isobutylene glycol, thiodiglycol, 1,2-hexanediol, 1,6-hexanediol, 2-ethyl-1 , 3-hexanediol, 1,2-pentanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 1,3-propane Polyols such as all, 1,4-butanediol, 1,7-heptanediol, 1,8-octanediol, 2-butene-1,4-diol, glycerin; ethylene glycol monomethyl ether, ethylene glycol monoethyl Ether, ethylene glycol monobutyl ether, ethylene glycol mono-t-butyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monophenyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono Isopropyl ether, diethylene glycol monobutyl ether, diethylene glycol -T-butyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol-t-butyl ether, propylene glycol monopropyl ether, propylene glycol iso Polyhydric alcohol ethers such as propylene ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoisopropyl ether; acetone , Methyl ethyl ke And ketones such as acetonylacetone; esters such as γ-butyrolactone, diacetin and triethyl phosphate; lower alkoxy alcohols such as 2-methoxyethanol and 2-ethoxyethanol; ethanolamine, diethanolamine, triethanolamine, N -Amines such as methyldiethanolamine, N-ethyldiethanolamine, triethylenetetramine, tetraethylenepentamine, pentamethyldiethylenetriamine; Amides such as formamide, N, N-dimethylformamide, N-methylformamide, N, N-dimethylacetamide 2-pyrrolidone, N-ethylpyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, morpholine, N-ethylmorpholine, 2-oxazolidone, 1,3-dimethyl Heterocycles such as 2-imidazolidinone, imidazole, methylimidazole, hydroxyimidazole, dimethylaminopyridine, 1,3-propane sultone, hydroxyethylpiperazine, piperazine; sulfoxides such as dimethyl sulfoxide; sulfones such as sulfolane These organic solvents are mentioned. As the aqueous medium, one of the above may be used alone, or two or more may be mixed and used.

{Polymer structure}
(C) The cationic polymer according to the present invention preferably comprises at least one or more types of aromatic ring monomers and one or more types of quaternary ammonium base monomers as constituent units. In the case of a synthetic polymer, the structural unit here is a unit derived from a monomer molecule used for production of the polymer by polymerization or copolymerization, or a unit in which they are modified by modification. In the case of a natural polymer, it is a repeating unit or a unit modified by modification or the like.

  The polymer structure of the (c) cationic polymer according to the present invention may be a random copolymer, a diblock copolymer, a triblock or more multiblock copolymer, a gradient copolymer, a graft copolymer, a star copolymer, etc. Is preferred.

{Molecular weight}
The number average molecular weight (Mn) of the (c) cationic polymer used in the present invention is 14000 or more, preferably 15000 or more. Further, it is preferably 100,000 or less, more preferably 50,000 or less, and particularly preferably 30,000 or less.
The weight average molecular weight (Mw) is preferably 25000 or more, more preferably 30000 or more, preferably 200,000 or less, more preferably 100,000 or less, and particularly preferably 60,000 or less.

  When the molecular weight is larger than this range, the viscosity of the pigment dispersion increases. When the molecular weight is smaller, the polymer as a dispersant is easily peeled off from the pigment surface, and the dispersion becomes unstable.

  In addition, the value of molecular weight here is a value in terms of polyethylene glycol measured by GPC (gel permeation chromatography).

{(C) Cationic polymer synthesis method}
The method for synthesizing the cationic polymer (c) used in the present invention is not particularly limited. For example, a known polymerization method such as radical polymerization or ionic polymerization can be selected, and (c) the cationic polymer is selected from these known methods. The derivative | guide_body and modified body of the polymer synthesize | combined by the method may be sufficient. Among these, a cationic polymer synthesized using a radical polymerization method is preferable because the synthesis method is simple.

  In particular, the cationic polymer according to the present invention contains at least a cationic polymer synthesized by radical polymerization of an aromatic ring monomer described below and a quaternary ammonium base monomer, or at least an aromatic ring monomer described below. After radical polymerization with a tertiary amino group monomer, it is preferably a cationic polymer in which the tertiary amino group moiety is converted to a quaternary ammonium salt using a quaternizing agent. Among them, the former, that is, a cationic polymer synthesized by performing radical polymerization of at least an aromatic ring-containing monomer and a quaternary ammonium base monomer is preferable in terms of dispersion stability, storage stability of recording liquid, and viscosity. To preferred. In the copolymerization of the aromatic ring monomer and the quaternary ammonium base monomer, one or more of the aromatic ring monomers and the quaternary quaternary may be added in the reaction system in the presence of other monomers as described below if necessary. A cation composed of an aromatic ring-containing monomer constituent unit, a quaternary ammonium base monomer constituent unit, and other monomer constituent units by copolymerizing one or more ammonium base monomers with one or more other monomers. A functional polymer can also be synthesized.

<Quaternary ammonium base monomer>
(C) Examples of the quaternary ammonium base monomer serving as the structural unit of the cationic polymer include the following.
(Meth) acryloyloxyethyldimethyloctylammonium chloride, (meth) acryloyloxyethyldimethyloctylammonium bromide, (meth) acryloyloxyethyldimethyldodecylammonium chloride, (meth) acryloyloxyethyldimethyldodecylammonium bromide, (meth) acryloyloxyethyl Dimethyl hexadecyl ammonium chloride, (meth) acryloyloxyethyl dimethyl hexadecyl ammonium bromide, (meth) acryloyloxyethyl diethyl octyl ammonium chloride, (meth) acryloyloxyethyl diethyl octyl ammonium bromide, (meth) acryloyloxyethyl diethyl dodecyl ammonium chloride , (Meta) a Liloyloxyethyl diethyl dodecyl ammonium bromide, (meth) acryloyloxyethyl diethyl hexadecyl ammonium chloride, (meth) acryloyloxyethyl diethyl hexadecyl ammonium bromide, (meth) acryloylaminopropyldimethyloctylammonium chloride, (meth) acryloylamino Propyldimethyloctylammonium bromide, (meth) acryloylaminopropyldimethyldodecylammonium chloride, (meth) acryloylaminopropyldimethyldodecylammonium bromide, (meth) acryloylaminopropyldimethylhexadecylammonium chloride, (meth) acryloylaminopropyl Dimethylhexadecyl ammonium bromide, (meth) ac Royloxyethyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloyloxyethyltrimethylammonium methylsulfate, (meth) acryloyloxyethyldimethylethylammonium ethyl sulfate, (meth) acryloyloxyethyl Trimethylammonium p-toluenesulfonate, (meth) acryloylaminopropyltrimethylammonium chloride, (meth) acryloylaminopropyldimethylbenzylammonium chloride, (meth) acryloylaminopropyltrimethylammonium methyl sulfate, (meth) acryloylaminopropyldimethylethylammonium ethyl Sulfae Pass, (meta) aqua Liloylaminopropyltrimethylammonium p-toluenesulfonate

  These may be used alone or in combination of two or more.

  Examples of the quaternary ammonium-containing monomer include (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloyloxyethyltrimethylammonium methyl sulfate, and (meth) acryloyloxyethyl. Dimethylethylammonium ethyl sulfate is preferred, and (meth) acryloyloxyethyltrimethylammonium chloride is particularly preferred.

<Contained tertiary amino group monomer / quaternizing agent>
In addition, (c) the cationic polymer is subjected to radical polymerization of at least an aromatic ring-containing monomer and a tertiary amino group monomer, and then the tertiary amino group portion is converted to a quaternary ammonium salt using a quaternizing agent. Although it may be a cationic polymer, examples of the tertiary amino group monomer in this case include the following.
N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-di-t-butylaminoethyl (meth) acrylate N, N-dialkylaminoalkyl (meth) acrylates such as N, N-dimethylaminobutyl (meth) acrylate; N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N N, N-dialkylaminoalkyl (meth) acrylamide, such as N, N-dimethylaminopropyl (meth) acrylamide

  These may be used alone or in combination of two or more.

  Among them, as the tertiary amino group monomer, N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate are preferable.

The quaternizing agent is not particularly limited and known ones can be used. For example, alkyl halides such as alkyl chloride such as methyl chloride, benzyl halides such as benzyl chloride, epichlorohydrin, dimethyl sulfate, diethyl sulfate, etc. Etc.
These may be used alone or in combination of two or more.

<Aromatic ring monomer>
(C) Although it does not specifically limit as a aromatic ring monomer which comprises a cationic polymer, A well-known thing can be used, For example, the following are mentioned.
Benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxyethylene glycol (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, phenoxypropylene glycol (meth) acrylate, phenoxypolypropylene glycol (meth) acrylate , Phenoxypoly (ethylene glycol-propylene glycol) (meth) acrylate, nonylphenoxyethylene glycol (meth) acrylate, nonylphenoxypolyethylene glycol (meth) acrylate, nonylphenoxypolypropylene glycol (meth) acrylate, nonylphenoxypoly (ethylene glycol-propylene) Glycol) (meth) acrylate, 2-naphthyl (Meth) acrylate, 9-anthracenyl (meth) acrylate, 1-pyrenylmethyl (meth) acrylate, o-phenylphenol (meth) acrylate, o-phenylphenol glycidyl ether (meth) acrylate, 2- (meth) acryloyloxyethyl phthalate Acid, 2- (meth) acryloyloxyethyl 2-hydroxyethyl phthalate, 2- (meth) acryloyloxyethyl 2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- (meth) Acryloyloxyethyl 2-hydroxyethyl phthalate, 2- (meth) acryloyloxyethyl 2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, neopentyl glycol (me ) Having an aromatic ring such as acrylic acid ester (meth) acrylate;
Styrene, vinyl naphthalene, α-methyl styrene, t-butyl styrene, p-methyl styrene, o-methoxy styrene, m-methoxy styrene, p-methoxy styrene, ot-butoxy styrene, mt-butoxy styrene, p -T-butoxystyrene, o-chloromethylstyrene, m-chloromethylstyrene, p-chloromethylstyrene, vinyltoluene, ethylvinylbenzene, 4-vinylbiphenyl, 1,1-diphenylethylene, vinylphenol, vinyl benzoate, Styrenic monomers such as benzyl vinyl ether;
Aromatic rings such as N-phenyl (meth) acrylamide, N-benzyl (meth) acrylamide, N-2-naphthyl (methacryl) amide, N- (N-phenyl-N-methyl) -aminoethyl (meth) acrylamide, etc. Amide monomer:

  These may be used alone or in combination of two or more.

As the aromatic ring-containing monomer, in particular, from the viewpoint of affinity for the pigment, as the (meth) acrylate having an aromatic ring, benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2-naphthyl ( (Meth) acrylate, 9-anthracenyl (meth) acrylate, 1-pyrenylmethyl (meth) acrylate, o-phenylphenol (meth) acrylate, o-phenylphenol glycidyl ether (meth) acrylate, 2- (meth) acryloyloxyethyl phthalate Acid, 2- (meth) acryloyloxyethyl 2-hydroxyethyl phthalate, 2- (meth) acryloyloxyethyl 2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- (meth) A Acryloyloxyethyl 2-hydroxyethyl phthalate, 2- (meth) acryloyloxyethyl 2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, neopentyl glycol (meth) acrylic acid benzoate As styrene monomers, styrene, vinyl naphthalene, α-methyl styrene, t-butyl styrene, p-methyl styrene, o-methoxy styrene, m-methoxy styrene, p-methoxy styrene, ot-butoxy styrene, mt-butoxystyrene, pt-butoxystyrene, o-chloromethylstyrene, m-chloromethylstyrene, p-chloromethylstyrene, vinyltoluene, ethylvinylbenzene, 4-vinylbiphenyl, 1,1-diphenylethylene , Vinylphenol, vinyl benzoate, benzyl vinyl is preferred.
As the aromatic ring-containing monomer, benzyl (meth) acrylate and styrene are particularly preferable.

<Other monomers>
The monomer constituent unit constituting the cationic polymer (c) according to the present invention may contain components other than the aromatic ring-containing monomer constituent unit and the quaternary ammonium base monomer constituent unit. Although it does not specifically limit as these monomers, For example, cationic monomers other than a monomer which has an aliphatic hydrocarbon group, a quaternary ammonium base monomer, a nonionic monomer, etc. are mentioned.

(Monomer having an aliphatic hydrocarbon group)
Although the following are mentioned as a monomer which has an aliphatic hydrocarbon group, It is not limited to the following illustrations, A conventionally well-known thing can be used.
The aliphatic hydrocarbon group contained in the aliphatic hydrocarbon group-containing monomer may be linear, cyclic, or branched.

  Examples of the monomer having a linear or branched aliphatic hydrocarbon group include the following.

Olefins such as ethylene, propylene, 1-butene and isobutene;
Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, i-propyl (meth) acrylate, butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, amyl ( (Meth) acrylate, i-amyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, i-octyl (meth) acrylate, decyl (meth) acrylate, i-decyl (meth) acrylate, dodecyl ( (Meth) acrylate esters such as (meth) acrylate, i-dodecyl (meth) acrylate, stearyl (meth) acrylate, i-stearyl (meth) acrylate, and behenyl (meth) acrylate;
Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether;
Nitriles such as acrylonitrile and methacrylonitrile;
Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride;
Allyl compounds such as allyl acetate and allyl chloride;
Dicarboxylic acid ester derivatives such as maleic acid ester and itaconic acid ester;
Vinylsilyl compounds such as vinyltrimethoxysilane;
Vinyl esters such as vinyl acetate and isopropenyl acetate:

As a monomer having a cyclic aliphatic hydrocarbon group, for example,
Cyclopropyl (meth) acrylate, cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclononyl (meth) acrylate, cyclodecyl (meth) acrylate (Meth) acrylate esters such as isobornyl (meth) acrylate, norbornyl (meth) acrylate, adamantyl (meth) acrylate;
Cyclopentene, cycloheptene, cyclooctene, cyclododecene, 1,5-cyclooctadiene, cyclopentadiene, 1,5,9-cyclododecatriene, 1-chloro-1,5-cyclooctadiene, dicyclopentadiene, ethylidene norbornene, 5 -Cyclic olefins such as methyl norbornene-2-carboxylate and dimethyl 5-norbornene-2,3-dicarboxylate;
Etc.

(Cationic monomers other than quaternary ammonium base monomers)
Examples of the cationic monomer other than the quaternary ammonium base monomer include the following tertiary amino group-containing polymerizable unsaturated monomers, but are not limited to the following examples, and conventionally known ones are used. be able to.
N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-di-t-butylaminoethyl (meth) acrylate N, N-dialkylaminoalkyl (meth) acrylates such as N, N-dimethylaminobutyl (meth) acrylate;
N, N-dialkylaminoalkyl (meth) acrylamides such as N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide and N, N-dimethylaminopropyl (meth) acrylamide:

(Nonionic monomer)
Nonionic monomers include the following, but are not limited to the following examples, and conventionally known monomers can be used.
Monomers having primary amino groups such as aminoethyl (meth) acrylate and aminopropyl (meth) acrylate;
Secondary such as methylaminoethyl (meth) acrylate, methylaminopropyl (meth) acrylate, ethylaminoethyl (meth) acrylate, ethylaminopropyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine A monomer having an amino group;
(Meth) acrylamide, N-alkyl (meth) acrylamide having 1 to 6 carbon atoms in the alkyl group, N, N-dialkyl (meth) acrylamide, C 1-3 in carbon number in the alkyl group, diacetone (meth) acrylamide, N -Methylol (meth) acrylamide, N-2-hydroxyethyl (meth) acrylamide, N, N-diethanol (meth) acrylamide, N-vinylacetamide, N-methyl-N-vinylacetamide, N-vinylformamide, N-methyl Amide group-containing monomers such as -N-vinylformamide, N- (2- (polyethylene glycol) ethyl) (meth) acrylamide, N, N- (2,2 '-(polyethylene glycol) diethyl) (meth) acrylamide;
2-vinylpyridine, 4-vinylpyridine, 1-vinylimidazole, N-vinylpyrrolidone, 2-vinyl-2-oxazoline, 5-methyl-2-vinyl-2-oxazoline, N-vinyloxazolidone, 2-N-pyrrolidoneethyl Monomers having a heterocycle such as (meth) acrylate, N-vinylcaprolactam, 9-vinylcarbazole, N-vinylphthalimide, glycidyl (meth) acrylate, aziridine ring-containing monomer;
Monomers containing a hydroxyl group such as 2-hydroxyethyl (meth) acrylic acid ester, 2-hydroxypropyl (meth) acrylic acid ester, 2,3-dihydroxypropyl (meth) acrylate, 2-hydroxyethyl vinyl ether;
Polyethylene glycol (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, ethoxy polyethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, lauroxy polyethylene glycol (meth) acrylate, stearoxy polyethylene glycol (meth) acrylate, nonylphenoxy Polyethylene glycol (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, poly (ethylene glycol-propylene glycol) (meth) acrylate, polyethylene glycol-polypropylene glycol (meth) acrylate, poly (ethylene glycol- Tetramethylene glycol) (meta Acrylate, poly (propylene glycol-tetramethylene glycol) (meth) acrylate, propylene glycol-polybutylene glycol (meth) acrylate, octoxy polyethylene glycol-polypropylene glycol (meth) acrylate, stearoxy polyethylene glycol-polypropylene glycol (meth) acrylate Oxyalkylene chain monomers such as allyloxy polyethylene glycol-polypropylene glycol (meth) acrylate, nonylphenoxy poly (ethylene glycol-propylene glycol) (meth) acrylate;
Glucose, mannose, galactose, glucosamine, mannosamine, galactosamine, etc., hexoses, arabinose, xylose, ribose, etc. Disaccharides such as mannobiose and sophorose, other oligosaccharides such as maltotriose, isomaltotriose, maltotetraose, maltopentaose, mannotriose and manninotriose, polysaccharides such as cellulose and modified cellulose A monomer having a structure as derived and having a glycosyl group, such as a monomer such as glucosylethyl methacrylate;
Monomers having a polyvinyl alcohol structure:

  These other monomers may be used alone or in a combination of two or more.

  Among these monomers, among these, from the viewpoint of dispersion stability, storage stability of the recording liquid, and viscosity, monomers having an aliphatic hydrocarbon group having a linear or branched structure, monomers containing a hydroxyl group, An oxyalkylene chain monomer, a monomer having a primary amino group, a monomer having a secondary amino group, a monomer having a tertiary amino group, or a monomer having a tehero ring is preferred, and an aliphatic having a linear or branched structure A monomer having a hydrocarbon group is particularly preferred. Most preferred are butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate in terms of storage stability of the recording liquid.

<(C) Ratio of monomer structural unit in cationic polymer>
The ratio of the aromatic ring monomer constituent unit constituting the cationic polymer (c) and the quaternary ammonium base monomer constituent unit constituting the cationic polymer according to the present invention in the cationic polymer is the aromatic content relative to all monomer constituent units constituting the cationic polymer. The total of the cyclic monomer structural unit and the quaternary ammonium base monomer structural unit is usually 100 mol% or less, usually 10 mol% or more, preferably 50 mol% or more, more preferably 80 mol% or more.

  In addition, the ratio of the aromatic ring monomer constituent unit to the total of the monomer constituent units constituting the cationic polymer (c) is usually 10 mol% or more, preferably 20 mol% or more, more preferably 30 mol% or more, particularly preferably. Is 40 mol% or more, usually 90 mol% or less, preferably 80 mol% or less, more preferably 70 mol% or less, and particularly preferably 60 mol% or less.

  In addition, the ratio of the quaternary ammonium base monomer constituent unit to the sum of the monomer constituent units constituting the cationic polymer (c) is usually 10 mol% or more, preferably 20 mol% or more, and usually 80 mol% or less, preferably Is 60 mol% or less, more preferably 50 mol% or less.

  (C) If the total content of the aromatic ring monomer constituent unit and the quaternary ammonium base monomer constituent unit in the cationic polymer is too small, the electrostatic repulsion between the pigments and the adsorptive power between the polymer and the pigment decrease. , Dispersion becomes unstable.

  In addition, (c) if the amount of the aromatic ring-containing monomer constituent unit is excessive with respect to the sum of the monomer constituent units constituting the cationic polymer, the polymer becomes water-insoluble, and pigment dispersion in an aqueous medium is impossible. The water solubility of the polymer is too high so that the polymer cannot be adsorbed on the pigment surface and the dispersion becomes unstable.

  (C) If the amount of the quaternary ammonium base monomer is too large relative to the sum of the monomer constitution units constituting the cationic polymer, the water solubility of the polymer is so high that the polymer cannot be adsorbed on the pigment surface and the dispersion is unstable. If the amount is too small, the polymer becomes water-insoluble and pigment dispersion in an aqueous medium becomes impossible.

  The content ratio of the aromatic ring monomer constituent unit and the quaternary ammonium base monomer constituent unit in (c) the cationic polymer is not particularly limited, but the above-mentioned effects due to the inclusion of both are effectively obtained. Above, it is preferable that it is 20 / 80-90 / 10 by the molar ratio of aromatic ring monomer structural unit / quaternary ammonium base monomer structural unit, especially 30 / 70-80 / 20.

  In addition, when (c) the cationic polymer contains other monomer constituent units other than the aromatic ring-containing monomer constituent unit and the quaternary ammonium base monomer constituent unit, the effect of the present invention may be impaired if the content is too large. Therefore, the content is preferably 50 mol% or less, particularly preferably 40 mol% or less, based on the total of monomer constituent units constituting (c) the cationic polymer.

  In the present invention, the content and content ratio of monomer constituent units such as (c) the aromatic ring-containing monomer structural unit and the quaternary ammonium base monomer structural unit contained in the cationic polymer are as follows: Was obtained by calculation from the charged amount of raw material monomer when producing the (c) cationic polymer was obtained by analysis according to the analysis method described in the Examples section below, It is the content and content ratio in the actual (c) cationic polymer.

<Polymerization reaction solvent>
(C) The radical polymerization reaction for synthesizing the cationic polymer can be carried out without solvent or in the presence of a solvent.

  Examples of the polymerization reaction solvent include ethers such as diethyl ether, tetrahydrofuran, diphenyl ether, anisole and dimethoxybenzene, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, acetonitrile, propionitrile and benzonitrile. Nitriles, acetone, methyl ethyl ketone, methyl isobutyl ketone, carbonyl compounds such as ethyl acetate, butyl acetate, ethylene carbonate, propylene carbonate, alcohols such as methanol, ethanol, propanol, isopropanol, n-butyl alcohol, t-butyl alcohol, isoamyl alcohol , Aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene, methylene chloride, chloroform, chlorobenzene, carbon tetrachloride Include halogenated hydrocarbons it is.

  Among these, an aqueous solvent is preferable as the polymerization reaction solvent.

  The aqueous solvent refers to a solvent obtained by mixing 100% water or water and a polar organic solvent at an arbitrary ratio. The polar organic solvent is not limited as long as it can be mixed with water in an arbitrary ratio. Specifically, the solvent is a protic solvent such as methanol, ethanol, or isopropanol, or an aprotic solvent such as acetonitrile, acetone, dimethylformamide, or dityl sulfoxide. Is exemplified. Of these, methanol, ethanol, and isopropanol are particularly preferable. These solvents may be a single solvent composed of only one kind or a mixed solvent composed of two or more kinds.

<Polymerization initiator>
(C) A known radical polymerization initiator can be used for the radical polymerization reaction in the synthesis of the cationic polymer. As the polymerization initiator, either a water-soluble polymerization initiator or an oil-soluble polymerization initiator can be used.

(Water-soluble polymerization initiator)
Examples of the water-soluble polymerization initiator include 2,2′-azobis (2-amidinopropane) dihydrochloride, 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis [2- (2-Imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, 2,2′-azobis [ N- (2-carboxyethyl) -2-methylpropionamide], 2,2′-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl) propane} dihydrochloride, 2, 2′-azobis (1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis {2-methyl-N- [2- (1-hydroxybutyl)] propionamide}, 2 , 2′-azobis [2- (5-methyl- Midazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (3,4,5,6, -tetrahydropyrimidin-2-yl) propane] dihydrochloride and other azo compound initiators , Oxidizing agents such as potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, etc., or aqueous solutions of sodium sulfite, sodium hyposulfite, ferrous sulfate, ferrous nitrate, sodium formaldehyde sulfoxylate, thiourea, etc. And redox initiators combined with an organic reducing agent.

  These may be used alone or in combination of two or more.

(Oil-soluble polymerization initiator)
Examples of oil-soluble polymerization initiators include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobiscyclohexane 1-carbonitrile, , 2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, dimethyl-2,2′-azobis (2-methylpropionate), Azo compound-based initiators such as 1,1′-azobis (1-acetoxy-1-phenylethane) and 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), acetylcyclohexylsulfonyl peroxide, Isobutyryl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, 2,4-dichloroben Ile peroxide, t-butyl peroxypivalate, 3,5,5-trimethylhexanonyl peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, stearoyl peroxide, propionitrile peroxide, succinic Acid peroxide, acetyl peroxide, t-butylperoxy-2-ethylhexanoate, benzoyl peroxide, parachlorobenzoyl peroxide, t-butylperoxyisobutyrate, t-butylperoxymaleic acid, t -Butylperoxylaurate, cyclohexanone peroxide, t-butylperoxyisopropyl carbonate, 2,5-dimethyl-2,5-dibenzoylperoxyhexane, t-butyl Peroxyacetate, t-butylperoxybenzoate, diisobutyldiperoxyphthalate, methyl ethyl ketone peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, t-butylcumyl peroxide , T-butyl hydroperoxide, di-t-butyl peroxide, diisopropylbenzene hydroperoxide, paramentane hydroperoxide, pinane hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide and cumene peroxide Peroxide polymerization initiators such as hydroperoxide (tret-butylhydroxyperoxide, cumenehydroxyperoxide, etc.), dialkyl peroxide (e.g. lauroyl peroxide) and peroxide Oil-soluble peroxides such as diacyl fluoride (benzoyl peroxide, etc.), tertiary amines (triethylamine, tributylamine, etc.), naphthenates, mercaptans (mercaptoethanol, lauryl mercaptan, etc.), organometallic compounds (triethylaluminum, triethyl) And an oil-soluble redox polymerization initiator used in combination with an oil-soluble reducing agent such as boron and diethyl zinc.

  These may be used alone or in combination of two or more.

<Additives such as chain transfer agents>
In the radical polymerization reaction, in addition to the above polymerization initiator, known materials such as a chain transfer agent, a chain terminator, and a polymerization accelerator can be added and used in order to adjust the resulting polymer to a preferred molecular weight.

<Polymerization conditions>
When performing the polymerization reaction, the order of addition of the raw material monomer, the polymerization reaction solvent, the polymerization initiator, etc. is arbitrary. For example, the temperature after the raw material monomer, the polymerization reaction solvent, and the polymerization initiator are charged into the reaction vessel all at once. And a method of conducting a polymerization reaction by raising the ratio. As another method, after the raw material monomer and the polymerization reaction solvent are charged into the reaction vessel and the temperature is increased, the monomer solution containing the polymerization initiator, the polymerization reaction solvent, or a mixture thereof is continuously added. Or the method etc. which add by dividing | segmenting and performing a polymerization reaction are mentioned. Among these, from the viewpoint of simplicity of operation, a method of conducting a polymerization reaction by raising the temperature after charging raw materials such as a raw material monomer, a polymerization reaction solvent, and a polymerization initiator all at once is preferable.

  Although the usage-amount of a polymerization reaction solvent is not specifically limited, It is normally 1 weight part or more with respect to 100 weight part of raw material monomers, Usually 2000 weight part or less, Preferably it is 1000 weight part or less.

  The amount of the polymerization initiator used varies depending on the type of polymerization initiator used and is not particularly limited, but is usually 0.5 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the raw material monomer.

  The polymerization temperature is not particularly limited, but is usually 0 ° C or higher, preferably 20 ° C or higher, and the upper limit is usually 200 ° C or lower, preferably 150 ° C or lower.

<Purification>
Although there is no particular problem even if the polymer obtained by polymerization is used as it is, it is preferably purified according to a conventional method and subjected to the subsequent pigment dispersion step. Purification methods include dropping the polymer solution into a solvent in which the polymer is insoluble and the monomer and polymerization initiator are soluble, reprecipitation purification by repeating the precipitation and filtration of the polymer, and the polymer and the polymer insoluble in the polymer solution and the polymerization initiator. Add a solvent that is soluble in water, remove the unreacted monomer and reaction solvent by fractional precipitation purification, heating distillation, vacuum distillation, etc. that repeat polymer precipitation and filtration, and then replace the solvent with water and / or aqueous solvent And a method of removing low molecular impurities and low molecular weight oligomer components using an ultrafiltration membrane or a dialysis membrane.

{(B) About pigment}
The (b) pigment used in the present invention is not particularly limited as long as it is appropriately selected from general pigments for each application. The following are representative examples of pigments.

Extender pigments such as calcium carbonate, kaolin clay, talc, bentonite, mica;
Metal oxide pigments typified by titanium oxide, zinc oxide, goethite, magnetite, chromium oxide, etc .;
Complex oxide pigments such as titanium yellow, titanium buff, antimony yellow, vanadium tin yellow, cobalt green, cobalt chrome green, manganese green, cobalt blue, cerulean blue, manganese blue, tungsten blue, Egyptian blue, cobalt black and the like;
Sulfide pigments such as litbon, cadmium red yellow and cadmium red;
Phosphate pigments typified by mineral violet, cobalt violet, lithium cobalt phosphate, sodium cobalt phosphate, potassium potassium phosphate, cobalt ammonium phosphate, nickel phosphate, copper phosphate;
Chromate pigments such as yellow lead and molybdate orange;
Metal complex pigments typified by ultramarine and Prussian blue;
Metal powder pigments such as aluminum paste, bronze powder, zinc powder, stainless steel flakes and nickel flakes;
Carbon black, bismuth oxychloride, basic carbonate, titanium dioxide, coated mica, ITO (indium tin oxide), ATO (antimony tin oxide) and other inorganic pigments such as pearlescent pigments and nacreous conductive pigments ;
Quinacridone pigment, quinacridone quinone pigment, dioxazine pigment, phthalocyanine pigment, anthrapyrimidine pigment, ansanthrone pigment, indanthrone pigment, flavanthrone pigment, perylene pigment, diketopyrrolopyrrole pigment, perinone Organic pigments such as pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, metal complex pigments, azomethine pigments or azo pigments:

  Specific examples of the pigment include pigments having the following pigment numbers and known carbon blacks generally used in the color material field. Note that terms such as “CI Pigment Red 2” mentioned below mean a color index (CI).

  Red colorant: C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 14, 15, 16, 17, 21, 22, 23, 31, 32, 37, 38, 41, 47, 48, 48: 1, 48: 2, 48: 3, 48: 4, 49, 49: 1, 49: 2, 50: 1, 52: 1, 52: 2, 53, 53: 1, 53: 2, 53: 3, 54, 57, 57: 1, 57: 2, 58, 58: 4, 60, 63, 63: 1, 63: 2, 64, 64: 1, 68, 69, 81, 81: 1, 81: 2, 81: 3, 81: 4, 83, 88, 90: 1, 101, 101: 1, 104, 108, 108: 1, 109, 112, 113, 114, 122, 123, 144, 146, 147, 149, 151, 166, 168, 169, 170, 172, 173, 174, 175, 176, 177, 78, 179, 181, 184, 185, 187, 188, 190, 193, 194, 200, 202, 206, 207, 208, 209, 210, 214, 216, 220, 221, 224, 230, 231, 232, 233, 235, 236, 237, 238, 239, 242, 243, 245, 247, 249, 250, 251, 253, 254, 255, 256, 257, 258, 259, 260, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276;

  Blue colorant: C.I. I. Pigment Blue 1, 1: 2, 9, 14, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17, 19, 25, 27, 28, 29, 33, 35, 36, 56, 56: 1, 60, 61, 61: 1, 62, 63, 66, 67, 68, 71, 72, 73, 74, 75, 76, 78, 79;

  Green colorant: C.I. I. Pigment Green 1, 2, 4, 7, 8, 10, 13, 14, 15, 17, 18, 19, 26, 36, 45, 48, 50, 51, 54, 55;

  Yellow colorant: C.I. I. Pigment Yellow 1, 1: 1, 2, 3, 4, 5, 6, 9, 10, 12, 13, 14, 16, 17, 23, 24, 31, 32, 34, 35, 35: 1, 36, 36: 1, 37, 37: 1, 40, 41, 42, 43, 48, 53, 55, 61, 62, 62: 1, 63, 65, 73, 74, 75, 81, 83, 87, 93, 94, 95, 97, 100, 101, 104, 105, 108, 109, 110, 111, 116, 119, 120, 126, 127, 127: 1, 128, 129, 133, 134, 136, 138, 139, 142, 147, 148, 150, 151, 153, 154, 155, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 172, 173 174, 175, 176, 180, 181, 182, 183, 184, 185, 188, 189, 190, 191, 191: 1, 192, 193, 194, 195, 196, 197, 198, 199, 200, 202, 203, 204, 205, 206, 207, 208, 215;

  Orange colorant: C.I. I. Pigment Orange 1, 2, 5, 13, 16, 17, 19, 20, 21, 22, 23, 24, 34, 36, 38, 39, 43, 46, 48, 49, 61, 62, 64, 65, 67, 68, 69, 70, 71, 72, 73, 74, 75, 77, 78, 79;

  Violet colorant: C.I. I. Pigment Violet 1, 1: 1, 2, 2: 2, 3, 3: 1, 3: 3, 5, 5: 1, 14, 15, 16, 19, 23, 25, 27, 29, 31, 32, 37, 39, 42, 44, 47, 49, 50

  Brown colorant: C.I. I. Pigment Brown 1, 6, 11, 22, 23, 24, 25, 27, 29, 30, 31, 33, 34, 35, 37, 39, 40, 41, 42, 43, 44, 45

  Black colorant: C.I. I. Pigment Black 1, 31, 32

  Among the above pigments, red pigments preferably include quinacridone pigments, xanthene pigments, perylene pigments, antanthrone pigments, and monoazo pigments. I. Pigment Red-5, -7, -12, -112, -81, -122, -123, 146, -147, -168, -173, -202, -206, -207, -209, C.I. I. And CI Pigment Violet-19. Among these, the solid solution which consists of a quinacridone-type pigment and two or more types of quinacridone-type pigments is more preferable from the surface of a pigment's stability and hue.

  Of the above-mentioned pigments, monoazo pigments and disazo pigments are preferable as yellow pigments because color development as printed matter is better than other pigments. Among them, C.I. I. Pigment-1, -3, -16, -17, -74, -95, -120, -128, -151, -155, -175, -215 are particularly preferred from the viewpoint of the color, and among them, C . I. CI Pigment Yellow-74 and -155 are non-halogen compounds, and are particularly preferable from the viewpoint of little influence on the environment and hue.

  Of the above-mentioned pigments, a blue pigment is preferable, and a copper phthalocyanine pigment is preferable because color development as a printed matter is better than other pigments. Among them, C.I. I. Pigment Blue-15: 3 is preferable from the viewpoints of stability and hue.

  Further, as the carbon black used in the present invention, various carbon blacks such as acetylene black, channel black and furnace black can be used. Among these, channel black or furnace black is preferable, and furnace black is particularly preferable.

The DBP oil absorption amount of the carbon black is preferably 40 ml / 100 g or more, more preferably 50 ml / 100 g or more, and particularly preferably 60 ml / 100 g or more from the viewpoint of printing density.
The volatile content is preferably 8% by weight or less, particularly preferably 4% by weight or less.
From the viewpoint of storage stability of the recording liquid, the pH is preferably 3 or more, more preferably 6 or more, and the upper limit is preferably 11 or less, particularly preferably 9 or less.
Further, the BET specific surface area of carbon black is usually 100 m ² / g or more, preferably 150 m ² / g or more, and the upper limit is preferably 700 m ² / g or less, particularly preferably 600 m ² / g or less.

  Here, the DBP oil absorption is a value measured by the method of JISK6221A, the volatile content is a value measured by the method of JISK6221, pH is a value measured by a glass electrode meter with a mixture of carbon black and distilled water, and the BET specific surface area is that of JISK6217. It is the value measured by the method.

  Further, from the viewpoint of safety, carbon black in which functional groups on the surface of the carbon black are reduced by baking at 600 to 1500 ° C. or washing with water, warm water, a solvent, or the like can also be used.

  Specific examples of the carbon black include products shown in the following (1) to (4).

(1) # 2700B, # 2650, # 2650B, # 2600, # 2600B, 2450B, 2400B, # 2350, # 2300, # 2300B, # 2200B, # 1000, # 1000B, # 990, # 990B, # 980, # 980B, # 970, # 960, # 960B, # 950, # 950B, # 900, # 900B, # 850, # 850B, MCF88, MCF88B, MA600, MA600B, # 750B, # 650B, # 52, # 52B, # 50, # 47, # 47B, # 45, # 45B, # 45L, # 44, # 44B, # 40, # 40B, # 33, # 33B, # 32, # 32B, # 30, # 30B, # 25, # 25B, # 20, # 20B, # 10, # 10B, # 5, # 5B, CF9, CF9B, # 95, # 260, MA77 MA77B, MA7, MA7B, MA8, MA8B, MA11, MA11B, MA100, MA100B, MA100R, MA100RB, MA100S, MA230, MA220, MA200RB, MA14, # 3030B, # 3040B, # 3050B, # 3230B, # 3350B (and above, Mitsubishi Chemical company product).

(2) Monarch 1400, Black Pearls 1400, Monarch 1300, Black Pearls 1300, Monarch 1100, Black Pearls 1100, Monarch 1000, Black Pearls 1000, Monarch 900, Black Pearl 900 800, Monarch 700, Black Pearls 700, Black Pearls 2000, Vulcan XC72R, Vulcan XC72, Vulcan PA90, Vulcan 9A32, Mogul L, Black Pearls L, Regal 660R, R gal 660, Black Pearls 570, Black Pearls 520, Regal 400R, Regal 400, Regal 330R, Regal 330, Regal 300R, Black Pearls 490, Black Pearls 480, Black Pearls 480, Black Pearls 480, Black Pearls 480, Black Pearls 480, Black Pearls 480 Black Pearls 420, Black Pearls 410, Regal 350R, Regal 350, Regal 250R, Regal 250, Regal 99R, Regal 99I, Elftex Pellets 115, Elftex 8, Elftex 5, Elftex 12, Mftex 12 ch 280, Black Pearls 280, Black Pearls 170, Black Pearls 160, Black Pearls 130, Monarch 120, Black Pearls 120 (above, products of Cabot Corporation).

(3) Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Special Black 4, Special Black 4A, Special Black 4A, Special Black 4W, Color Black FW2V, Color Black FW2V, Color Black FW2 V, Printex 150T, Printex 140U, Printex 140V, Printex 95, Printex 90, Printex 85, Printex 80, Printex 75, Printex 55, Printex 45, Printex 40, Printex 40, Princex ntex 60, Printex XE, Printex L6, Printex L, Printex 300, Printex 30, Printex 3, Printex 35, Printex 25, Printex 200, Printex A, Printex G, Stex 100 (above, Degussa product).

(4) Raven 7000, Raven 5750, Raven 5250, Raven 5000 ULTRA, Raven 3500, Raven 2000, Raven 1500, Raven 1250, Raven 1250, Raven 10R, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170, Raven 1170 Raven 1000, Raven 890H, Raven 890, Raven 850, Raven 790 ULTRA, Raven 760 ULTRA, Raven 520, Raven 500, Raven 450, Raven 430, Raven 420, Raven 420, Raven 420, Raven 420, Raven 420 ULTRA, Raven H2O, Raven C ULTRA (or more, Columbia's products).

  As the pigment according to the present invention, one of the above pigments may be used alone, or two or more of them may be used in combination. It can also be used in combination with other color materials.

  The shape of the pigment may be any form such as paste, powder, solid solution and the like.

The primary particle size of these pigments may be arbitrarily set according to the purpose, but is usually 10 nm or more, and preferably 500 nm or less, more preferably 300 nm or less, still more preferably 200 nm or less, particularly Preferably it is 100 nm or less.
Here, the primary particle diameter of the pigment is an arithmetic average diameter (number average) measured by an electron microscope.

The average dispersed particle size of the pigment in the aqueous pigment dispersion of the present invention is usually 500 nm or less, preferably 300 nm or less, and particularly preferably 200 nm or less. Moreover, as a minimum, it is 20 nm or more normally.
The average dispersed particle size can be measured using an electron microscope such as SEM or TEM, or can be measured using a commercially available dynamic light scattering measurement device.

  As the above-mentioned pigments, those that are not chemically modified and that do not contain impurities other than pigments, such as a crystallization inhibitor for promoting the reduction in the particle size of pigments, adsorb pigments onto polymers. It is preferable because it does not inhibit. However, in order to impart self-dispersibility to the pigment, a pigment that has been subjected to a known chemical modification in advance, or a pigment and a dye having a specific physical adsorptivity to the pigment are dispersed in an aqueous medium. Thus, a pigment having self-dispersibility in which the dye is physically adsorbed on the surface can also be used.

  The pigment used in the aqueous pigment dispersion of the present invention may be an untreated pigment that has not been subjected to such treatment, or a pigment that has been chemically decorated on the surface, or a pigment that has adsorbed a dye on the surface to provide self-dispersibility. Any of them may be used, and one or more kinds of arbitrary pigments can be used.

{(A) About aqueous medium}
Examples of the aqueous medium (a) used in the aqueous pigment dispersion of the present invention include water and / or a water-soluble organic solvent. Although it will not specifically limit if it is generally used for this use as a water-soluble organic solvent, Specifically, it is a thing with a vapor pressure smaller than water, and the following are mentioned.

Ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propylene glycol, isopropylene glycol, polypropylene glycol, pentamethylene glycol, trimethylene glycol, butylene Glycol, isobutylene glycol, thiodiglycol, 1,2-hexanediol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, 1,2-pentanediol, 1,5-pentanediol, 2- Methyl-2,4-pentanediol, 1,3-propanediol, 1,4-butanediol, 1,7-heptanediol, 1,8-octanediol, 2 Butene-1,4-diol, polyhydric alcohols such as glycerin;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol mono-t-butyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monophenyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl Ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, Lopylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol-t-butyl ether, propylene glycol monopropyl ether, propylene glycol isopropyl ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene Polyhydric alcohol ethers such as glycol monobutyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoisopropyl ether;
Ketones such as acetonylacetone;
Esters such as γ-butyrolactone, diacetin, triethyl phosphate;
Lower alkoxy alcohols such as 2-methoxyethanol and 2-ethoxyethanol;
Amines such as ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, triethylenetetramine, tetraethylenepentamine, pentamethyldiethylenetriamine;
Amides such as formamide, N, N-dimethylformamide, N-methylformamide, N, N-dimethylacetamide;
2-pyrrolidone, N-ethylpyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, morpholine, N-ethylmorpholine, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, imidazole, methylimidazole, hydroxyimidazole , Heterocycles such as dimethylaminopyridine, 1,3-propane sultone, hydroxyethylpiperazine, piperazine;
Sulfoxides such as dimethyl sulfoxide;
Sulfones such as sulfolane:

  These may be used alone or in combination of two or more.

  The aqueous medium used in the present invention is preferably water or a mixture of water and a water-soluble organic solvent as described above.

{Aqueous pigment dispersion composition}
The aqueous pigment dispersion of the present invention comprises the above-mentioned (a) aqueous medium, (b) a pigment and (c) a cationic polymer as a dispersant.

  In the aqueous pigment dispersion of the present invention, one (c) cationic polymer may be included singly or two or more may be included.

  The pigment concentration (b) of the aqueous pigment dispersion of the present invention is usually 30% by weight or less, preferably 20% by weight or less, because if it is too high, there is a risk of poor dispersion. If the pigment concentration is too low, there is a problem that it takes a lot of time and effort during preparation of the recording liquid. Therefore, it is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more.

  In the aqueous pigment dispersion of the present invention, the concentration of the cationic polymer (c) is usually 0.05% by weight or more, preferably 0.25% by weight or more, more preferably 0.5% by weight or more. is there. On the other hand, the upper limit of the content of the (c) cationic polymer is usually 20% by weight or less, preferably 10% by weight or less. (C) If the concentration of the cationic polymer is too low, sufficient dispersion stability cannot be obtained, and if it is too high, the viscosity of the aqueous pigment dispersion increases.

  The weight ratio of (b) pigment to (c) cationic polymer may be appropriately selected and determined, but in general, (c) cationic polymer is 0 per 1 part by weight of pigment. It is preferably 0.01 parts by weight or more, especially 0.05 parts by weight or more, and particularly preferably 0.1 parts by weight or more, and the upper limit is usually 2 parts by weight or less, preferably 1.5 parts by weight or less.

{About viscosity}
The viscosity of the aqueous pigment dispersion of the present invention is preferably 10 cp or less, more preferably 5 cp or less, and particularly preferably 3 cp or less at a pigment concentration of 8% by weight.
If the viscosity of the aqueous pigment dispersion is too high, the viscosity increases even when a recording liquid is prepared, which is not suitable for inkjet printer applications. The lower limit of the viscosity is usually 0.1 cp or more, preferably 0.5 cp or more, more preferably 1.0 cp or more.

{About manufacturing method}
The mixing method and order of addition of (a) the aqueous medium, (b) the pigment, and (c) the cationic polymer that is the polymer dispersant in the production of the aqueous pigment dispersion of the present invention are arbitrary. (C) a cationic polymer, (b) a pigment, and (a) an aqueous medium containing an aqueous medium as a main component may be dispersed using a general disperser. In the present invention, this ( c) When a mixture containing a cationic polymer, (b) a pigment, and (a) an aqueous medium is subjected to a dispersion treatment, (a) the dispersion treatment using only water as the aqueous medium is carried out. It is preferable in terms of storage stability.

  As the disperser used for the dispersion treatment, various dispersers that are generally used for pigment dispersion can be used.

  The disperser is not particularly limited, and a paint shaker, ball mill, sand mill, attritor, pearl mill, coball mill, homomixer, homogenizer, wet jet mill, ultrasonic homogenizer, and the like can be used. Glass beads, zirconia beads, alumina beads, magnetic beads, and styrene beads can be used for those using media as a disperser. Among these, a particularly preferable dispersion treatment method is a method in which beads are dispersed with a mill using a medium and then dispersed with an ultrasonic homogenizer.

  A method for obtaining an aqueous pigment dispersion having a preferred dispersed particle diameter is not particularly limited, but the pigment in the dispersion system can be used to reduce the size of the dispersion media of the disperser and increase the filling rate of the dispersion media. Examples thereof include a method of increasing the concentration, extending the treatment time, classifying with a filter, a centrifuge, etc. after dispersion, or a combination of these methods.

  Moreover, you may perform the process which removes at least one part of the unadsorbed polymer dispersing agent contained in the obtained pigment dispersion using an ultrafiltration membrane or a microfiltration membrane. If the amount of unadsorbed polymer dispersant is large, it may adversely affect the ejection stability and re-dissolvability of the head, cause clogging, and increase the viscosity when the recording liquid is stored for a long period of time. Or cause it. Of these, use of a cross-flow type ultrafiltration membrane or a microfiltration membrane is preferable because the treatment is simple.

[2] Ink composition (recording liquid)
The ink composition of the present invention comprising the aqueous pigment dispersion of the present invention containing the above-mentioned (c) cationic polymer as a dispersant exhibits particularly excellent effects as a recording liquid, particularly an inkjet recording liquid.

  The ink composition of the present invention used as a recording liquid (hereinafter referred to as “recording liquid of the present invention”) adjusts the colorant concentration of the above-described aqueous pigment dispersion of the present invention as necessary, and further uses Depending on the conditions, various additives are added.

  As the colorant, in addition to the pigment in the aqueous pigment dispersion of the present invention described above, it is further dispersed with a self-dispersing pigment surface-treated for purposes such as toning, a dye, a surfactant, a polymer dispersant, etc. It may also contain added pigments or dyes.

  The concentration of the total colorant in the recording liquid of the present invention is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and the upper limit is 15% by weight with respect to the total amount of the recording liquid. Hereinafter, it is preferably 10% by weight or less, particularly preferably 8% by weight or less. If the colorant concentration is too high, the viscosity is increased and the discharge properties are deteriorated. If the colorant concentration is too low, the printing density is too low. On the other hand, the amount of the colorant added to the aqueous pigment dispersion is usually 100 parts by weight or less, preferably 75 parts by weight or less, more preferably 50 parts by weight or less, with respect to 100 parts by weight of the pigment in the aqueous pigment dispersion. The amount is particularly preferably 25 parts by weight or less. If the additional amount of the colorant is too large, the effect of the present invention is reduced.

  The solvent used in the recording liquid of the present invention preferably contains water and a water-soluble organic solvent, and can further contain other components as desired.

  The concentration of the water-soluble organic solvent in the recording liquid of the present invention may be appropriately selected and determined. Usually, it is preferably 1% by weight or more and 45% by weight or less, more preferably 40% by weight or less with respect to the recording liquid. In addition, the content of water in the recording liquid may be an amount that can appropriately set the concentration of the above-described colorant, water-soluble organic solvent, and optional additive components described below.

  As the water-soluble organic solvent, those exemplified as the aqueous medium (a) of the aqueous pigment dispersion of the present invention described above can be used.

  In particular, the aqueous pigment dispersion of the present invention is excellent in solvent resistance against ether-based solvents that easily cause dispersion failure such as carbitols such as ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, and triethylene glycol monobutyl ether. When these ether solvents are included, the effects of the present invention are effectively exhibited. When the recording liquid of the present invention contains such an ether solvent, the content thereof is preferably 0.1 to 20% by weight with respect to the total amount of the recording liquid. If the ether solvent content is too small, the leakage and penetrability improvement effects due to the addition of the solvent cannot be sufficiently obtained, and if it is too much, the storage stability is impaired. However, the recording liquid of the present invention is not limited to the one containing an ether solvent.

  The recording liquid of the present invention may contain various additives as necessary within the range not impairing the effects of the present invention.

  Examples of such additives include recording liquids such as penetration enhancers, surface tension modifiers, hydrotropic agents, pH adjusters, chelating agents, preservatives, viscosity modifiers, humectants, antifungal agents, and rust inhibitors. Known additives can be used.

  The content of these additives in the recording liquid of the present invention is generally 30% by weight or less, particularly preferably 15% by weight or less, based on the total amount of the recording liquid.

  Examples of penetration enhancers include lower alcohols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol and pentanol, carbitols such as ethylene glycol monobutyl ether and triethylene glycol monobutyl ether glycol ether, and surfactants 1 A seed | species or 2 or more types is mentioned.

  As the surfactant, any one or more of nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, polymer surfactants and the like can be used. Can be used. Of these, nonionic surfactants, anionic surfactants and polymer surfactants are preferred.

  Nonionic surfactants include, for example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene derivatives, oxyethylene / oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid Examples thereof include esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, acetylene glycols, and acetylene alcohols.

  Examples of the anionic surfactant include fatty acid salts, alkyl sulfate esters, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether sulfonates, alkyl phosphates, polyoxyethylene alkyl sulfates. Examples include ester salts, polyoxyethylene alkylaryl sulfate esters, alkane sulfonates, naphthalene sulfonate formalin condensates, polyoxyethylene alkyl phosphates, α-olefin sulfonates, and the like.

  Polymeric surfactants include polyacrylic acid, styrene / acrylic acid copolymer, styrene / acrylic acid / acrylic acid ester copolymer, styrene / maleic acid copolymer, styrene / maleic acid / acrylic acid ester copolymer, styrene / methacrylic acid. Examples include copolymers, styrene / methacrylic acid / acrylic acid ester copolymers, styrene / maleic acid half ester copolymers, styrene / styrene sulfonic acid copolymers, vinyl naphthalene / maleic acid copolymers, vinyl naphthalene / acrylic acid copolymers, and salts thereof.

  Examples of the cationic surfactant include, but are not limited to, tetraalkylammonium salts, alkylamine salts, benzalkonium salts, alkylpyridium salts, imidazolium salts, and the like.

  In addition, silicone surfactants such as polysiloxane oxyethylene adducts, fluorine surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, oxyethylene perfluoroalkyl ethers, rhamnolipids, lysolecithins, etc. Surfactants such as biosurfactants can also be used.

  The content of these surfactants may be selected and determined as appropriate. Usually, by adding in the range of 0.001 wt% or more and 5 wt% or less with respect to the recording liquid, the quick drying property and the print quality of the printed matter can be further improved.

  Examples of the surface tension adjusting agent include alcohols such as diethanolamine, triethanolamine, glycerin, and diethylene glycol, nonions, cations, anions, and amphoteric surfactants.

  As the hydrotropic agent, one or more of urea, alkylurea, ethyleneurea, propyleneurea, thiourea, guanidate, tetraalkylammonium halide and the like are preferable.

  As a humectant, 1 type (s) or 2 or more types, such as glycerol and diethylene glycol, can also be added as what also serves as a water-soluble organic solvent.

  Furthermore, a solid moisturizing agent (a water-soluble substance having a water retaining function and solid at 25 ° C.) can also be added. Preferred solid humectants include saccharides, sugar alcohols, hyaluronate, trimethylolpropane, 1,2,6-triol and the like. Examples of the saccharide include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), and polysaccharides. Specifically, glucose, fructose, ribose, xylose, arabinose, galactose, sorbit, maltose, and lactose. , Sucrose, trehalose and the like. Examples of sugar alcohols include maltitol, sorbitol, xylitol, and the like, and one or more of these solid humectants can be added.

  Although it does not specifically limit as a chelating agent, 1 type (s) or 2 or more types, such as a sodium salt of ethylenediaminetetraacetic acid, a diammonium salt of ethylenediaminetetraacetic acid, are used. These are preferably used in the range of 0.005 wt% to 0.5 wt% with respect to the recording liquid.

  The antifungal agent is not particularly limited, but sodium dehydroacetate, dichlorophen, sorbic acid, sodium benzoate, p-hydroxybenzoate, 1,2-Benzisothiazoline-3-one (product name: Proxel) GXL (manufactured by Arch Chemicals)) or the like is used. These are preferably contained in the range of 0.05 wt% to 1 wt% with respect to the recording liquid.

  Further, the pH of the recording liquid is adjusted to prevent the stability of the recording liquid or the corrosion of the recording liquid piping in the recording apparatus. However, the pH adjustment of sodium hydroxide, nitric acid, ammonia, etc. is not particularly limited. A buffer such as an agent and phosphoric acid can be used.

  The pH of the recording liquid is usually in the neutral to alkaline range, and is preferably adjusted to about pH 6 to 11.

  Further, the recording liquid of the present invention may contain a polymer other than the above-mentioned (c) cationic polymer as long as the effects of the present invention are not impaired. Specific examples of such polymers include vinyl resins, such as acrylic resins, styrene-acrylic resins, polyvinyl alcohol resins, vinyl acetate resins, and polyester resins, polyamide resins, polyurethane resins, and epoxy resins. And known resins such as butadiene-based resins, petroleum-based resins, and fluorine-based resins.

  In the recording liquid of the present invention, the content of all the polymers including the above-mentioned (c) cationic polymer and the polymer other than the above-mentioned (c) cationic polymer is usually 0.05% by weight or more, preferably It is 0.25% by weight or more, more preferably 0.5% by weight or more, and the upper limit is usually 20% by weight or less, and preferably 10% by weight or less. The ratio of (c) the cationic polymer to the other polymer is determined by appropriately selecting the weight ratio of (c) the cationic polymer to the other polymer in the range of 99: 1 to 1:99. (C) In order to effectively exhibit the above-described improvement effect by the cationic polymer, specifically, (c) 30 parts by weight of the other polymer with respect to 1 part by weight of the total amount of the cationic polymer. In particular, the amount is preferably 20 parts by weight or less, particularly preferably 10 parts by weight or less.

  In addition, polymer fine particles may be added to the recording liquid of the present invention in order to further improve the fixability and abrasion resistance of an image on a recording medium. The polymer fine particles are not particularly limited, but those having an ionic group on the surface and a particle diameter of 10 to 150 nm are preferable.

  The amount of the polymer fine particles used may be appropriately selected and determined within a range not impairing the effects of the present invention. Specifically, it is 1 to 100% by weight, preferably 10 to 80%, based on the pigment in the recording liquid. % By weight, more preferably 10 to 50% by weight.

  Hereinafter, the present invention will be described more specifically with reference to synthesis examples, examples, and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

In the following examples, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured under the following conditions using gel permeation chromatography (GPC).
Column packing: Styrene-divinylbenzene copolymer Solvent: Dimethyl sulfoxide (including 50 mM LiBr (lithium bromide))
Flow rate: 0.27 ml / min
Temperature: 50 ° C
Calibration was performed using polyethylene glycol.
In addition, this time, it measured using the following apparatuses, a detector, and a column, and the calibration was performed using the thing by Polymer Laboratories.
Apparatus: Waters 2695 manufactured by Nippon Waters Co., Ltd.
Detector: Waters 2414 manufactured by Nippon Waters Co., Ltd.
Column: Showa Denko Co., Ltd.
Shodex GPC KF-G + KF-604 + KF-603
The structure of the obtained cationic copolymer was confirmed by ¹ H-NMR using d-DMSO (dimethyl sulfoxide) as a solvent, and the composition ratio of the monomer structural units was calculated from NMR data.
In the following notation, “co” means “co” of copolymer.

[Synthesis Example 1] (Synthesis of Cationic Copolymer I)
8.9 g of 2,2′-azobisisobutyronitrile was charged as a polymerization initiator into a separable flask equipped with a nitrogen-substituted condenser, a nitrogen introduction tube, a stirrer, and a thermometer, and then as a solvent. Solmix A-11 (mixed solvent of ethanol 85.5% by weight, methanol 13.4% by weight and IPA (isopropyl alcohol) 1.1% by weight, manufactured by Nippon Alcohol Sales Co., Ltd.) 1300.0 g, distilled water 175. The above flask was charged with 0 g, 327.3 g of styrene as a monomer, and 349.7 g of acrylate ester DMC (80% by weight aqueous solution of 2-methacryloyloxyethyltrimethylammonium chloride, manufactured by Mitsubishi Rayon Co., Ltd.).

  The separable flask was immersed in an oil bath, the bath temperature was raised from room temperature to 78 ° C. over 45 minutes, and polymerization was carried out at 78 ° C. for 10 hours. After the completion of the polymerization, the polymerization solution was concentrated under reduced pressure using an evaporator, and then the polymer formed by dropping twice the polymerization solution concentrated in an isopropanol / tetrahydrofuran (1/2 = v / v) mixed solvent was precipitated. The supernatant was removed by decantation, 7000 g of distilled water was added and mixed, and then the residual organic solvent was removed by atmospheric distillation to obtain an aqueous polymer solution. The obtained polymer aqueous solution was dried to obtain a random copolymer: cationic copolymer I of poly (styrene-co-2-methacryloyloxyethyltrimethylammonium chloride).

The composition ratio of the styrene structural unit and 2-methacryloyloxyethyltrimethylammonium chloride structural unit in the cationic copolymer I was 58:42 (molar ratio).
This cationic copolymer I had a number average molecular weight (Mn) of 22,000 and a weight average molecular weight (Mw) of 39,900.

[Synthesis Example 2] (Synthesis of Cationic Copolymer II)
6.92 g of 2,2′-azobisisobutyronitrile as a polymerization initiator was charged into a separable flask equipped with a nitrogen-substituted condenser, a nitrogen introducing tube, a stirrer, and a thermometer, and then as a solvent. 1053 g of Solmix A-11, 219.4 g of styrene as a monomer, 202.5 g of n-butyl acrylate, and 410.1 g of acrylate ester DMC were charged into the flask.

  The separable flask was immersed in an oil bath, the bath temperature was raised from room temperature to 78 ° C. over 45 minutes, and polymerization was carried out at 78 ° C. for 7 hours. After completion of the polymerization, a crude polymer aqueous solution was obtained by adding water while removing the organic solvent with an evaporator. After removing impurities from the crude polymer aqueous solution by ultrafiltration membrane treatment, the polymer aqueous solution is concentrated and dried to obtain a random copolymer of poly (styrene-co-n-butylacrylate-co-2-methacryloyloxyethyltrimethylammonium chloride). : Cationic copolymer II was obtained.

The composition ratio of the styrene constituent unit, the n-butyl acrylate constituent unit, and the 2-methacryloyloxyethyltrimethylammonium chloride constituent unit in the cationic copolymer II was 45:25:30 (molar ratio).
This cationic copolymer II had a number average molecular weight (Mn) of 17,000 and a weight average molecular weight (Mw) of 37400.

[Synthesis Example 3] (Synthesis of Cationic Copolymer III)
2.4 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was charged as a polymerization initiator into a separable flask equipped with a nitrogen-substituted condenser, a nitrogen introducing tube, a stirrer, and a thermometer. 253.0 g of methanol as a solvent, 81.2 g of styrene as a monomer, 110.3 g of 2-ethylhexyl acrylate, and 97.3 g of N, N-dimethylaminoethyl acrylate were charged into the flask.

The separable flask was immersed in an oil bath, the bath temperature was raised from room temperature to 69 ° C. over 30 minutes, and polymerization was carried out at 69 ° C. for 8 hours.
493.7 g of the above polymerization solution was weighed, 98.7 g of dimethyl sulfate as a quaternizing agent, 653.0 g of tetrahydrofuran and 223.0 g of methanol were added as a solvent, and the mixture was stirred at room temperature for 4 hours to be reacted. After completion of the reaction, the reaction solution was dropped into tetrahydrofuran to precipitate the produced polymer. The supernatant was removed by decantation, 2000 g of distilled water was added and mixed, and then the residual organic solvent was removed by atmospheric distillation to obtain an aqueous polymer solution. The obtained aqueous polymer solution was dried to obtain poly (styrene-co-2-ethylhexyl acrylate-co-2-methacryloyloxyethyltrimethylammonium methylsulfate) random copolymer: cationic copolymer III.

  The composition ratio of the styrene structural unit, 2-ethylhexyl acrylate structural unit, and 2-methacryloyloxyethyltrimethyl sulfate structural unit in the cationic copolymer III was 54/20/26 (molar ratio). This cationic copolymer III had a number average molecular weight (Mn) of 15,500 and a weight average molecular weight (Mw) of 30,700.

[Synthesis Example 4] (Synthesis of Cationic Copolymer IV)
2.4 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was charged as a polymerization initiator into a separable flask equipped with a nitrogen-substituted condenser, a nitrogen introducing tube, a stirrer, and a thermometer. In addition, 258.0 g of methanol as a solvent, 81.2 g of styrene as a monomer, 73.5 g of 2-ethylhexyl acrylate, and 128.6 g of N, N-dimethylaminoethyl methacrylate were charged into the flask.

The separable flask was immersed in an oil bath, the bath temperature was raised from room temperature to 69 ° C. over 30 minutes, and polymerization was carried out at 69 ° C. for 8 hours.
522.7 g of the above polymerization solution was weighed, 119.3 g of benzyl chloride as a quaternizing agent, 681.0 g of tetrahydrofuran and 433.0 g of methanol were added as solvents, and the mixture was reacted at room temperature for 4 hours with stirring. After completion of the reaction, the produced polymer was precipitated by dropping the reaction solution into a tetrahydrofuran / n-hexane (2/1 = v / v) mixed solvent. The supernatant was removed by decantation, 2000 g of distilled water was added and mixed, and then the residual organic solvent was removed by atmospheric distillation to obtain an aqueous polymer solution. The obtained aqueous polymer solution was dried to obtain poly (styrene-co-2-ethylhexyl acrylate-co-2-methacryloyloxyethyldimethylbenzylammonium chloride) random copolymer: cation copolymer IV.

The composition ratio of the styrene structural unit, 2-ethylhexyl acrylate structural unit, and 2-methacryloyloxyethyldimethylbenzylammonium chloride structural unit in the cationic copolymer IV was 52/14/34 (molar ratio).
This cationic copolymer IV had a number average molecular weight (Mn) of 16000 and a weight average molecular weight (Mw) of 30,800.

[Synthesis Example 5] (Synthesis of Cationic Copolymer V)
Into a separable flask equipped with a nitrogen-substituted condenser, nitrogen introduction tube, stirrer and thermometer, 24.3 g of 2,2′-azobisisobutyronitrile was charged as a polymerization initiator, and then as a solvent. 3885 g of Solmix A-11, 578 g of distilled water, 727 g of styrene as a monomer, and 775 g of acrylate ester DMC, and 61.5 g of lauryl mercaptan as a thiol compound were charged into the flask.

  The separable flask was immersed in an oil bath, the bath temperature was raised from room temperature to 78 ° C. over 1 hour, and polymerization was carried out at 78 ° C. for 10 hours. After the completion of the polymerization, the polymerization solution was concentrated under reduced pressure using an evaporator, and then the polymer formed by dropping twice the polymerization solution concentrated in an isopropanol / tetrahydrofuran (1/2 = v / v) mixed solvent was precipitated. The supernatant was removed by decantation, 7000 g of distilled water was added and mixed, and then the residual organic solvent was removed by atmospheric distillation to obtain an aqueous polymer solution. The obtained aqueous polymer solution was dried to obtain a random copolymer: cation copolymer V of poly (styrene-co-2-methacryloyloxyethyltrimethylammonium chloride).

The composition ratio of the styrene structural unit and 2-methacryloyloxyethyltrimethylammonium chloride structural unit in the cationic copolymer V was 70:30 (molar ratio).
This cationic copolymer V had a number average molecular weight (Mn) of 7500 and a weight average molecular weight (Mw) of 11,000.

[Example 1] (Black pigment dispersion and recording liquid using cationic polymer I)
<Preparation of pigment dispersion>
Firing product carbon black (# 960B (manufactured by Mitsubishi Chemical Corporation) at 1200 ° C. for 1 month in a nitrogen atmosphere; powder; solid content 100% by weight) 28.0 g, cationic polymer I aqueous solution (cationic copolymer I concentration 36) .2 wt.%) 46.4 g and distilled water 205.6 g are mixed, 0.5 mmφ zirconia beads are used as a medium and dispersed at 60 ° C. for 7 hours using a self-made bead mill, and further dispersed at 40 ° C. for 1 hour. After removing the beads, the pigment concentration was adjusted to 8% by weight to obtain a dispersion.

  The dispersion was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 90 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain pigment dispersion a.

  Distilled water was added to this pigment dispersion a to dilute it twice, and after ultrafiltration membrane treatment, it was concentrated to obtain dispersion A having a pigment concentration of 8% by weight.

<Preparation of recording liquid>
Using dispersion A, an ink was produced according to the following formulation.
Pigment dispersion A: 5.0 g
Distilled water: 3.4g
Olfine E1010 (Surfactant manufactured by Air Products): 0.1 g
Triethylene glycol mono-n-butyl ether: 0.5 g
Glycerin: 1.0g

The above components were mixed, stirred for 15 minutes, adjusted to pH 9 with an aqueous sodium hydroxide solution, and then subjected to ultrasonic dispersion treatment for 30 minutes to obtain recording liquid A.
This recording liquid A was evaluated by the following method.
The results are shown in Table 1.

(I) Measurement of average dispersion particle diameter of pigment in recording liquid Recording liquid A was diluted 10,000 times with distilled water, a diluted probe was attached to Otsuka Electronics FPAR-1000, and the particle diameter was measured. The value of the dispersed particle size was calculated by the Cumulant method.

(Ii) Measurement of viscosity of recording liquid Recording liquid A was measured using a rheometer (REOLOGICA AB Instruments; VAR-100; cone 1 ° / 55φ), and the value at a shear rate of 100 / sec was read.

(Iii) Stability of recording liquid The average dispersed particle diameter of the pigment after holding the recording liquid A at 70 ° C. for 15 hours was measured in the same manner as in (i). The smaller the increase in particle size, the more stable.
Further, the viscosity after holding the recording liquid A at 70 ° C. for 15 hours was measured in the same manner as in (ii). The viscosity change is small or stable so that no increase in viscosity is observed.

[Example 2] (Black pigment dispersion and recording liquid using cationic polymer II)
Firing product carbon black (# 960B (manufactured by Mitsubishi Chemical Corporation) at 1200 ° C. for 1 month in a nitrogen atmosphere; powder; solid content: 100% by weight) 28.0 g, cationic copolymer II aqueous solution (cation copolymer II concentration 18) 89.4% by weight) and 162.6 g of distilled water were mixed and dispersed using a self-made bead mill with 0.5 mmφ zirconia beads as a medium at 40 ° C. for 8 hours. After removing the beads, the pigment concentration A dispersion was obtained by adjusting to 8% by weight.

  The dispersion was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 90 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain a pigment dispersion b.

Distilled water was added to this pigment dispersion b to dilute it twice, and after ultrafiltration membrane treatment, it was concentrated to obtain dispersion B having a pigment concentration of 8% by weight.
Using this dispersion B, a recording liquid B was prepared in the same manner as in Example 1, and the recording liquid B was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

[Example 3] (Cyan pigment dispersion and recording liquid using cationic polymer II)
Pigment Blue-15: 3 (manufactured by Dainichi Seika Kogyo Co., Ltd .; powder; solid content: 100.0% by weight) 28.0 g, cationic copolymer II aqueous solution (cation copolymer II concentration 18.8% by weight), 89.3 g, and Mix 162.7g of distilled water, disperse the zirconia beads of 0.5mmφ as a medium at 25 ° C for 2 hours using a self-made bead mill, remove the beads, adjust the pigment concentration to 8% by weight, and disperse the dispersion. Obtained.

  The dispersion was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 120 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; chip used: 36 mmφ) to obtain pigment dispersion c.

Distilled water was added to this pigment dispersion c to dilute it twice, and after ultrafiltration membrane treatment, it was concentrated to obtain dispersion c having a pigment concentration of 8% by weight.
Using this dispersion C, a recording liquid C was prepared in the same manner as in Example 1, and the recording liquid C was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

[Example 4] (Magenta pigment dispersion and recording liquid using cationic polymer II)
Pigment Red-122 (manufactured by Dainichi Seika Kogyo Co., Ltd .; paste; solid content 27.0 wt%) 103.7 g, aqueous cation copolymer II (cation copolymer II concentration 18.8 wt%) 89.3 g, and distilled water 87.0 g was mixed, 0.5 mmφ zirconia beads were used as a medium, dispersed at 60 ° C. for 7 hours using a self-made bead mill, and further dispersed at 40 ° C. for 1 hour. After removing the beads, the pigment concentration was 8% by weight. To obtain a dispersion.

  The dispersion was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 90 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain a pigment dispersion d.

Distilled water was added to the pigment dispersion d to dilute it twice, and after ultrafiltration membrane treatment, it was concentrated to obtain a dispersion D having a pigment concentration of 8% by weight.
Using this dispersion D, a recording liquid D was prepared in the same manner as in Example 1, and the recording liquid D was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

[Example 5] (Magenta pigment dispersion and recording liquid using cationic polymer III)
Pigment Red-122 (manufactured by Dainichi Seika Kogyo Co., Ltd .; paste; solid content 27.0% by weight) 103.7 g, cationic copolymer III aqueous solution (cationic copolymer IV concentration 10.7% by weight) 157.2 g, and distilled water 19.1 g was mixed, 0.5 mmφ zirconia beads were used as a medium, dispersed at 60 ° C. for 7 hours using a self-made bead mill, and further dispersed at 40 ° C. for 1 hour. After removing the beads, the pigment concentration was 8% by weight. To obtain a dispersion.

  The dispersion was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) for 60 minutes to obtain a pigment dispersion e.

Distilled water was added to this pigment dispersion e to dilute it twice, and after ultrafiltration membrane treatment, it was concentrated to obtain dispersion E having a pigment concentration of 8% by weight.
Using this dispersion E, a recording liquid E was prepared in the same manner as in Example 1, and the recording liquid E was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

[Example 6] (Magenta pigment dispersion and recording liquid using cationic polymer IV)
Pigment Red-122 (manufactured by Dainichi Seika Kogyo Co., Ltd .; paste; solid content: 27.0% by weight) 103.7 g, cationic copolymer IV aqueous solution (cationic copolymer IV concentration 12.1% by weight) 139.4 g, and distilled water 36.9 g was mixed, 0.5 mmφ zirconia beads were used as a medium, dispersed at 60 ° C. for 7 hours using a self-made bead mill, and further dispersed at 40 ° C. for 1 hour. After removing the beads, the pigment concentration was 8% by weight. To obtain a dispersion.

  The dispersion was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 90 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain a pigment dispersion f.

Distilled water was added to this pigment dispersion f to dilute it twice, and after ultrafiltration membrane treatment, it was concentrated to obtain dispersion F having a pigment concentration of 8% by weight.
Using this dispersion F, a recording liquid F was prepared in the same manner as in Example 1, and the recording liquid F was evaluated in the same manner as in Example 1.
The results are shown in Table 1.

[Comparative Example 1] (Black pigment dispersion and recording liquid using cationic polymer V)
Firing product carbon black (# 960B (manufactured by Mitsubishi Chemical Corporation) at 1200 ° C. for 1 month in a nitrogen atmosphere; powder; solid content: 100% by weight) 28.0 g, cation copolymer V aqueous solution (cation copolymer V concentration 18) .4 wt%) 91.3 g and distilled water 160.7 g were mixed, and 0.5 mmφ zirconia beads were used as media to disperse at 60 ° C. for 7 hours and then at 40 ° C. for 1 hour. After removing the beads, the pigment concentration was adjusted to 8% by weight to obtain a dispersion.

  The dispersion was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 120 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain a pigment dispersion g.

Distilled water was added to this pigment dispersion g to dilute it twice, and after ultrafiltration membrane treatment, it was concentrated to obtain dispersion G having a pigment concentration of 8% by weight.
Using this dispersion G, a recording liquid G was prepared in the same manner as in Example 1, and the recording liquid G was evaluated in the same manner as in Example 1.
The results are shown in Table 1.
In this recording liquid G, an increase in the dispersed particle diameter of the pigment was observed in the stability test.

[Comparative Example 2] (Cyan Pigment Dispersion and Recording Solution Using Cationic Polymer V)
Pigment Blue-15: 3 (manufactured by Dainichi Seika Kogyo Co., Ltd .; powder; solid content 100.0% by weight) 28.0 g, cationic copolymer V aqueous solution (cation copolymer V concentration 18.4% by weight) 91.4 g, and Mix 160.7g of distilled water, disperse 0.5mmφ zirconia beads as a medium at 25 ° C for 2 hours using a self-made bead mill, remove the beads, adjust the pigment concentration to 8% by weight, and disperse the dispersion. Obtained.

  The dispersion was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed for 120 minutes with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) to obtain a pigment dispersion h.

Distilled water was added to the pigment dispersion h to dilute it twice, and after ultrafiltration membrane treatment, it was concentrated to obtain a dispersion H having a pigment concentration of 8% by weight.
Using this dispersion H, a recording liquid H was prepared in the same manner as in Example 1, and the recording liquid H was evaluated in the same manner as in Example 1. The results are shown in Table 1.
In this recording liquid H, an increase in the dispersed particle diameter and viscosity of the pigment was observed in the stability test.

[Comparative Example 3] (Magenta pigment dispersion and recording liquid using cationic polymer V)
Pigment Red-122 (manufactured by Dainichi Seika Kogyo Co., Ltd .; paste; solid content 27.0 wt%) 103.7 g, cationic copolymer V aqueous solution (cation copolymer V concentration 18.4 wt%) 91.4 g, and distilled water 84.9 g was mixed, and 0.5 mmφ zirconia beads were used as media to disperse at 25 ° C. for 8 hours using a self-made bead mill. After removing the beads, the pigment concentration was adjusted to 8% by weight to obtain a dispersion. .

  The dispersion was placed in a 500 ml tall beaker, the beaker was immersed in ice water, and dispersed with an ultrasonic homogenizer (Nippon Seiki Seisakusho; US-600T; used chip 36 mmφ) for 90 minutes to obtain pigment dispersion i.

Distilled water was added to this pigment dispersion i to dilute it twice, and after ultrafiltration membrane treatment, it was concentrated to obtain dispersion I having a pigment concentration of 8% by weight.
Using this dispersion I, a recording liquid I was prepared in the same manner as in Example 1, and the recording liquid I was evaluated in the same manner as in Example 1.
The results are shown in Table 1.
This recording liquid I showed an increase in the dispersed particle diameter and viscosity of the pigment in the stability test.

  From Table 1, the following is clear.

  Comparative Examples 1, 2, and 3 are those using a cationic copolymer V having a small number average molecular weight (Mn). In the stability test of the recording liquid, an increase in the dispersed particle diameter and viscosity of the pigment was observed. Insufficient sex.

  In contrast, in Examples 1 to 6 using the cationic copolymers I to IV which are (c) cationic polymers according to the present invention, good dispersion stability is obtained.

  From the above results, the aqueous pigment dispersion of the present invention using a cationic polymer having at least an aromatic ring and a quaternary ammonium base and having a number average molecular weight of 14,000 or more in terms of polyethylene glycol measured by GPC as a dispersant. It is apparent that the body has higher stability when used as a recording liquid and higher durability against ether solvents than a pigment dispersion prepared with a dispersant having a small number average molecular weight.

Claims (10)

  In an aqueous pigment dispersion comprising (a) an aqueous medium, (b) a pigment, and (c) a cationic polymer, (c) the cationic polymer has at least an aromatic ring and a quaternary ammonium base, and GPC ( A water-based pigment dispersion characterized by being a polymer having a number average molecular weight in terms of polyethylene glycol measured by gel permeation chromatography) of 14,000 or more.   The aqueous pigment dispersion according to claim 1, wherein the cationic polymer (c) is water-soluble or water-dispersible.   The aqueous pigment dispersion according to claim 1 or 2, wherein the cationic polymer (c) comprises one or more aromatic ring monomers and one or more quaternary ammonium base monomers as constituent units. .   The aqueous pigment dispersion according to claim 3, wherein the ratio of the quaternary ammonium base monomer constituent unit to the sum of the monomer constituent units constituting the (c) cationic polymer is 10 to 80 mol%.   (B) The aqueous pigment dispersion according to any one of claims 1 to 4, wherein the pigment has an average dispersed particle diameter of 500 nm or less.   6. The cationic polymer (c) obtained by copolymerizing a monomer mixture containing one or more kinds of aromatic ring monomers and one or more kinds of quaternary ammonium base monomers. The aqueous pigment dispersion according to any one of the above.   A method for producing an aqueous pigment dispersion according to any one of claims 1 to 6, wherein the mixture comprising (a) an aqueous medium, (b) a pigment, and (c) a cationic polymer is subjected to a dispersion treatment. (A) A method for producing an aqueous pigment dispersion, wherein only water is used as an aqueous medium.   An ink composition comprising the aqueous pigment dispersion according to any one of claims 1 to 6.   An ink composition comprising an aqueous pigment dispersion produced by the method for producing an aqueous pigment dispersion according to claim 7.   10. An ink jet recording method comprising ejecting droplets of the ink composition according to claim 8 or 9 from an ink jet head and attaching the droplets to a recording medium.