JP2006206665A - Inkjet ink and inkjet recording method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet ink having excellent ejection stability and improved feathering resistance on plain paper and giving an image and a printed material having high scratch resistance even on a low absorption recording medium and provide an inkjet recording method using the ink. <P>SOLUTION: The inkjet ink at least contains a pigment, water, a water-soluble solvent and polymer particulates. The polymer particulate has a shell structure composed of a core part and a shell part and the shell part contains a monomer having a group expressed by general formula (1) or (2). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel inkjet ink and an inkjet recording method using the same.

  In recent years, an inkjet recording method can easily and inexpensively create an image, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as a color filter. In particular, inkjet recording equipment that emits and controls fine dots, and ink ink with improved color reproduction range, durability, and emission suitability, and ink absorbency, coloring of color materials, surface gloss, etc. are dramatically improved. Using specially made paper, we have reached an image quality comparable to silver halide photography.

  However, in an inkjet image recording system that requires dedicated paper, there are problems in that the recording media that can be used are limited and the cost of the recording media is increased. In the office, recording media such as plain paper and coated paper are used. In addition, there is an increasing need for a system that can perform high-speed and sharp full-color printing without being restricted by art paper and plain paper double-sided printing.

  However, one of the problems with plain paper in inkjet recording is that a phenomenon called so-called feathering, in which irregular bleeding occurs along the fiber of the paper, is a factor that reduces character quality. It has become.

  In order to prevent this feathering, various methods have been proposed in the past, and one method is a method of aggregating the color material of the ink with an aggregating agent. For example, an ink jet recording medium (for example, refer to Patent Document 1) that incorporates a means for aggregating and fixing a color material on the ink jet recording medium, a colorless ink that insolubilizes the color material is attached to the recording medium from an ink jet nozzle, An ink jet recording method for recording a material (for example, see Patent Document 2), an ink set composed of a pigment ink containing carboxymethyl cellulose and a pigment ink containing a cationic dispersant (for example, see Patent Document 3). Etc. have been proposed. However, it is necessary to apply the flocculant to the ink jet recording medium separately from the ink by using other means, which not only complicates the configuration of the ink jet recording apparatus but is also insufficient in preventing feathering. It was in a state.

  Another method for preventing feathering is to add a temperature-sensitive polymer whose viscosity changes depending on the temperature to the ink, and after landing on the ink jet recording medium, increase the ink viscosity to prevent feathering. Has been proposed. For example, a water-based ink containing a high-molecular substance that is thermoreversibly gelled at a temperature higher than the transition temperature and becomes water-insoluble by drying (see, for example, Patent Document 4), or lower critical eutectic temperature (LCST) A method using a temperature-sensitive colored polymer obtained by reacting a temperature-sensitive polymer with an anionic dye (see, for example, Patent Document 5) has been proposed. However, these proposed methods have apparatus loads such as heating or cooling the ink jet head or the ink jet recording medium, and the suppression effect on feathering is still insufficient, so that feathering is sufficient. The current situation is that it has not yet been reduced.

  As another method, a method for preventing feathering by adding an additive to the ink has been proposed. For example, a method of adding a urethane oligomer having a surfactant group into an ink (for example, see Patent Document 6), a method of using a water-soluble polymer such as hydroxypropylcellulose, polyisopropylacrylamide and a monohydric alcohol (for example, , See Patent Document 7). Like these proposed methods, if a large amount of additives are added to prevent feathering, when printing using an inkjet head, there is a drawback that the inkjet head is clogged and cannot be ejected, It was difficult to achieve both feathering and discharge stability.

  In addition, an ink-jet ink using polymer fine particles using an oil-soluble dye, a monomer having a carboxylic acid, a monomer having a glycidyl group, and another monomer is disclosed (for example, see Patent Document 8), and has excellent bleeding resistance. The nozzle is not clogged. Furthermore, as an example of acrylamide as another monomer, a method of adding polyvinylpyrrolidone to an anionic dye-containing ink has been proposed (for example, see Patent Document 9). According to this method, it is said that the ink ejection stability is improved as a result of preventing the precipitation of the dye. However, in any of the methods proposed in Patent Documents 8 and 9, the coloring material to be used is a dye system, there is no suggestion about the pigment, and simply adding acrylamide or polyvinylpyrrolidone to the pigment ink, The clogging of the inkjet head and the feathering could not be made compatible.

Furthermore, in order to improve water fastness, a method using a polymer having a glass transition point lower than room temperature in the core part and a core-shell type polymer fine particle using a polymer higher than room temperature in the shell part has been proposed (for example, In addition, it is said that polyvinyl pyrrolidone can be used in the shell portion in the same manner as polystyrene and polymethyl methacrylate. However, by using polystyrene, polymethyl methacrylate, or the like for the shell portion, solid matter is deposited by drying and clogs the ink jet head, so that the ink ejection failure cannot be improved.
JP 55-84992 A JP-A-1-63185 JP 2002-309132 A Japanese Patent Laid-Open No. 9-12947 JP 2001-114820 A Japanese Patent Laid-Open No. 6-279718 JP-A-6-248208 JP 2001-323290 A JP 2003-113334 A JP-A-10-195362

  The present invention has been made in view of the above problems, and its object is to provide high scratch resistance even in a recording medium that has excellent ejection stability, improved feathering resistance to plain paper, and is difficult to absorb ink. It is another object of the present invention to provide an inkjet ink capable of obtaining a printed image and a printed matter and an inkjet recording method using the inkjet ink.

  The above object of the present invention is achieved by the following configurations.

(Claim 1)
In an inkjet ink containing at least a pigment, water, a water-soluble solvent and polymer fine particles, the polymer fine particles have a shell structure composed of a core part and a shell part, and the shell part is represented by the following general formula (1) or ( An ink-jet ink comprising a monomer having a group represented by 2).

[In General Formulas (1) and (2), R represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and R ₁ , R ₂ , and R ₃ represent a hydrogen atom and a carbon atom number, respectively. 1 to 12 linear or branched alkyl group, alkenyl group, or linear or branched aryl group having 6 to 12 carbon atoms, and R ₁ and R ₂ are bonded to each other to contain a 5- or 6-membered group. Nitrogen heterocycles may be formed. X represents an oxygen atom or NR ₄ , and R ₄ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms. n represents 0 or 1. ]
(Claim 2)
The content of the monomer having the group represented by the general formula (1) or (2) in the shell part is 50% by mass or more of the total mass of the shell part. Inkjet ink.

(Claim 3)
3. The inkjet ink according to claim 1, wherein a mass ratio of the shell part to the core part (shell part mass / core part mass) is 0.5 to 100. 4.

(Claim 4)
In an inkjet ink containing at least a pigment, water, a water-soluble solvent, and polymer fine particles, the polymer fine particles contain a monomer having a group represented by the following general formula (1) or (2) An inkjet ink, which is a crosslinked gel.

[In General Formulas (1) and (2), R represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and R ₁ , R ₂ , and R ₃ represent a hydrogen atom and a carbon atom number, respectively. 1 to 12 linear or branched alkyl group, alkenyl group, or linear or branched aryl group having 6 to 12 carbon atoms, and R ₁ and R ₂ are bonded to each other to contain a 5- or 6-membered group. Nitrogen heterocycles may be formed. X represents an oxygen atom or NR ₄ , and R ₄ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms. n represents 0 or 1. ]
(Claim 5)
The content of the hydrophilic partially crosslinked gel containing the monomer having the group represented by the general formula (1) or (2) in the polymer fine particle is 50% by mass or more of the total mass of the polymer fine particle. The inkjet ink according to claim 4, wherein the inkjet ink is provided.

(Claim 6)
The inkjet ink according to any one of claims 1 to 5, wherein the group represented by the general formula (1) is a group represented by the following general formula (1-A).

[Wherein, R represents a hydrogen atom or a methyl group, and R ₁ and R ₂ represent a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, an alkenyl group, or a straight chain having 6 to 12 carbon atoms, respectively. It represents a chain or branched aryl group, and R ₁ and R ₂ may be further bonded to form a 5- or 6-membered nitrogen-containing heterocycle. ]
(Claim 7)
The inkjet ink according to any one of claims 1 to 5, wherein the group represented by the general formula (2) is a group represented by the following general formula (2-A).

[Wherein, R represents a hydrogen atom or a methyl group, and R ₁ and R ₃ represent a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, an alkenyl group, or a linear chain having 6 to 12 carbon atoms. Alternatively, it represents a branched aryl group. ]
(Claim 8)
The inkjet ink according to claim 1, comprising at least one other polymer fine particle together with the polymer fine particle.

(Claim 9)
An ink-jet recording method comprising forming an image by ejecting the ink-jet ink according to claim 1 onto a recording medium using an ink-jet head.

(Claim 10)
10. The ink jet recording method according to claim 9, wherein the recording medium is at least one selected from plain paper, art paper, and coated paper.

  According to the present invention, an inkjet ink having excellent ejection stability, improved feathering resistance to plain paper, and capable of obtaining an image and printed matter having high scratch resistance even on a recording medium that hardly absorbs ink, and An ink jet recording method using the same can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventors have found that in inkjet ink (hereinafter also simply referred to as ink) containing at least a pigment, water, a water-soluble solvent and polymer fine particles, 1) An ink-jet ink having a core-shell structure and containing a monomer having a group represented by the general formula (1) or (2) in the shell portion, or 2) a polymer fine particle having the general formula By using an inkjet ink characterized by being a hydrophilic partially crosslinked gel containing a monomer having the group represented by (1) or (2), it has excellent ejection stability and feathering on plain paper Ink jet ink capable of obtaining images and printed matter with high scratch resistance even on a recording medium with improved resistance and difficult to absorb ink Heading, is up which led to the present invention.

  Conventionally, for example, JP 2004-217930 A proposes to act as an anti-curl agent by attaching a low molecular compound having an amide group and a hydroxyl group to cellulose fibers. The present inventors presume that feathering can be prevented by adsorbing to the color material by applying the above characteristics to the ink containing the color material and also effectively adsorbing the cellulose fiber. As a result of searching for various additives, polymer fine particles containing a monomer (hydrophilic gel) having a core-shell structure and having a group represented by the general formula (1) or (2) in the shell part, Alternatively, by applying polymer fine particles containing a hydrophilic partially cross-linked gel containing a monomer having a group represented by the general formula (1) or (2) to a pigment ink, clogging in an inkjet head is prevented. It has been found that feathering can be effectively prevented even when printing on a water-absorbing recording medium such as plain paper without causing it.

  The reason for the above improvement effect is not clear, but is presumed as follows.

  That is, in the ink, the polymer fine particles according to the present invention are dispersed in a stable state because hydrophilic amide groups or urea groups are present on the surface. Therefore, the viscosity of the ink can be kept low, and as a result, clogging in the inkjet head is less likely to occur. As soon as the ink is ejected by the head and penetrates into the plain paper, strong hydrogen bonds are formed between the amide groups, urea groups, etc. of the fine polymer particles and the cellulose fibers constituting the plain paper, and the nitrogen atoms are replaced. Since the pigment is adsorbed by the hydrophobic portion and the hydrophobic portion of the polymer chain, the pigment is fixed to the cellulose fiber and feathering is prevented. Further, since the polymer fine particles serve to protect the pigment, it is considered that the scratch resistance such as scratches could be improved.

  Details of the present invention will be described below.

  In the ink of the present invention, polymer fine particles containing a monomer (hydrophilic gel) having a group represented by the following general formula (1) or (2) in the shell portion, or the following general formula (1) or It contains polymer fine particles containing a hydrophilic partially crosslinked gel containing a monomer having a group represented by (2).

  In the groups represented by the general formulas (1) and (2), R represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms (for example, methyl, ethyl, n-propyl, i-propyl). , Sec-butyl, i-hexyl and the like).

R ₁ , R ₂ and R ₃ are each a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms (for example, methyl, ethyl, n-propyl, i-propyl, sec-butyl, i-hexyl, Each group such as dodecyl), alkenyl group (each group such as allyl, hexenyl, dodecyl), or straight or branched aryl group having 6 to 12 carbon atoms (each group such as phenyl, benzyl, tolyl, xylyl). To express. In the general formula (1), R ₁ and R ₂ may combine to form a 5- or 6-membered nitrogen-containing heterocyclic ring (for example, each group such as piperidino, morpholino, N-methylpiperazino). Good. X represents an oxygen atom or NR ₄ , and R ₄ represents a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms (for example, methyl, ethyl, n-propyl, i-propyl, sec-butyl, i -Respective groups such as hexyl). n represents 0 or 1.

In addition, the group represented by the general formula (1) is preferably a group represented by the general formula (1-A) from the viewpoint of further achieving the object effect of the present invention. In the general formula (1-A), R represents a hydrogen atom or a methyl group, and R ₁ and R ₂ are a hydrogen atom and a linear or branched alkyl group having 1 to 12 carbon atoms (for example, methyl, ethyl). , N-propyl, i-propyl, sec-butyl, i-hexyl, dodecyl, etc.), alkenyl group (allyl, hexenyl, dodecyl, etc.) or straight or branched chain having 6 to 12 carbon atoms Represents an aryl group (groups such as phenyl, benzyl, tolyl, xylyl, etc.), and R ₁ and R ₂ are further bonded to form a 5- or 6-membered nitrogen-containing heterocyclic ring (for example, piperidino, morpholino, N-methylpiperazino, etc.) Each group) may be formed.

In addition, the group represented by the general formula (2) is preferably a group represented by the general formula (2-A) from the viewpoint of further achieving the object effect of the present invention. In the general formula (2-A), R represents a hydrogen atom or a methyl group, R ₁ and R ₃ represent a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms (for example, methyl, ethyl, n-propyl, i-propyl, sec-butyl, i-hexyl, dodecyl, etc.), alkenyl group (allyl, hexenyl, dodecyl, etc.) or straight or branched aryl having 6 to 12 carbon atoms Represents a group (groups such as phenyl, benzyl, tolyl, xylyl, etc.).

  Specific examples of the groups represented by the general formulas (1), (1-A), (2), and (2-A) according to the present invention are shown below, but the present invention is not limited thereto. Absent.

  The polymer fine particles according to the present invention containing the monomer having the group represented by the general formula (1) or (2) are used as an adhesive between pigment particles and cellulose fibers in a recording medium. Therefore, feathering on plain paper can be prevented, and as a result, a clear character image and line drawing can be provided. Furthermore, since the polymer fine particles according to the present invention are excellent in dispersion stability and can be present at a high concentration in the ink, it is possible to provide images and printed matter with high scratch resistance.

  The form of the polymer fine particle according to the present invention is not limited as long as it is a water-affinity gel having at least a part of the group represented by the general formula (1) or (2). The surface is preferably composed of a monomer having a group represented by the general formula (1) or (2). In the present invention, the term water affinity is used, which means that a polymer that is not crosslinked is at least water-soluble at a certain temperature.

  One feature of the polymer fine particles according to the present invention is that the shell portion contains a monomer (hydrophilic gel) having a group represented by the general formula (1) or (2).

  The polymer constituting the core part is not particularly limited. For example, polystyrene, poly (meth) acrylic ester (for example, polymethyl (meth) acrylate, polyethyl (meth) acrylate, polybutyl (meth) acrylate, poly 2-ethylhexyl) (Meth) acrylate, polystearyl (meth) acrylate), polyvinyl butyral, polyvinyl formal, polyethylene, polypropylene, polyester, polyurethane, or a copolymer thereof can be used.

  The shell part is characterized by containing a monomer having a group represented by the general formula (1) or (2). A coalescence may be formed, or a copolymer may be formed with other monomers. Monomers that may be copolymerized include monomers having an acidic group such as acrylic acid and methacrylic acid, styrene, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2- Examples include (meth) acrylate monomers such as ethylhexyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate.

  In the polymer fine particles having a core-shell structure according to the present invention, the content of the monomer having a group represented by the general formula (1) or (2) in the shell portion is approximately 40% by mass of the total mass of the shell. Although it is above, it is preferable that it is 50 mass% or more of shell total mass from a viewpoint which can exhibit the objective effect of this invention effectively. When the content of the monomer having the group represented by the general formula (1) or (2) in the shell portion is less than 40% by mass, the adsorptive power to the cellulose fiber is weak and the effect of preventing feathering is insufficient. is there.

  In the polymer fine particles according to the present invention, the method for forming the shell portion is not particularly limited. However, in the case of copolymerization, the groups represented by the general formula (1) or (2) are adjacent to each other. The copolymer polymer fine particles can be obtained by, for example, blocking by a cation living polymerization method, an anion living polymerization, or a graft polymerization method. However, in the case of synthesizing only the monomer having the group represented by the general formula (1) or (2), radical polymerization that is usually used can be applied.

  The molecular weight of the shell portion is preferably 2000 or more and 200000 or less, more preferably 5000 or more and 70000 or less as a weight average molecular weight. When the molecular weight of the shell part is small, the effect of preventing the decap is weak, and when the molecular weight of the shell is too large, the viscosity of the polymer fine particle itself becomes too high and stable emission becomes difficult.

  In the core-shell type polymer fine particles according to the present invention, the mass ratio between the core portion and the shell portion is not particularly limited, and the mass ratio (S / C) of the shell portion S to the core portion C is the object effect of the present invention. Is preferably 0.5 to 100, and more preferably 0.5 to 30 from the viewpoint that can be more exhibited. If S / C is less than 0.5, the shrinkage effect is small and the desired decap prevention effect cannot be obtained. On the contrary, if it exceeds 100, it will be entangled between the particles when shrinking, causing coarse particles to be formed.

  Specific examples and synthesis methods of the polymer fine particles according to the present invention include, for example, compound examples and synthesis examples described in JP-A-7-33224, JP-A-2000-26795, JP-A-2003-40916, and the like. Can be mentioned.

  One feature of the polymer fine particles according to the present invention is that it contains a hydrophilic partially crosslinked gel containing a monomer having a group represented by the general formula (1) or (2).

  In the present invention, it is possible to use polymer fine particles formed by partially cross-linking the water affinity gel used in the shell portion of the core shell. The term “partial crosslinking” as used herein means that the gel is not completely crosslinked and can be swelled and shrunk under certain conditions. As for the degree of cross-linking, if the cross-linking is weak, it cannot exist as polymer fine particles. Conversely, if the cross-linking is too strong, it becomes difficult to adsorb with cellulose, so the cross-linking agent is naturally limited. Therefore, the hydrophilic partially cross-linked gel particles according to the present invention contain a crosslinking monomer amount of approximately 0.01% by mass to 10.0% by mass with respect to the total mass. From the viewpoint of exhibiting, it is preferable to contain 0.05 to 5.0 mass%.

Crosslinkers include polymerizable unsaturated dimers in the molecule such as ethylene glycol di (meth) acrylate, ethylene glycol bisacrylamide, polyethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and allyl (meth) acrylate. A monomer having two or more heavy bonds can be used.
The inkjet ink of the present invention contains at least a pigment and a water-soluble solvent together with the above-described polymer fine particles according to the present invention.

  Examples of the water-soluble solvent according to the present invention include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, Triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol), polyhydric alcohol ethers (eg, ethylene glycol monomethyl ether, ethylene Glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl Ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl Ether, propylene glycol monophenyl ether), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, Traethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocyclics (eg, 2-pyrrolidone) N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone), sulfoxides (for example, dimethyl sulfoxide) and the like.

  In the present invention, the water-soluble organic solvent is preferably a water-soluble solvent having a boiling point higher than 100 ° C. and having a hydroxyl group. For example, the polyhydric alcohols and polyhydric alcohol ethers can be preferably used.

  In the ink of the present invention, amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine are used for the purpose of adjusting the pH of the ink. , Diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine) can be added to the solvent.

  In the inkjet ink of the present invention, the fixability after printing is improved together with the polymer fine particles containing the monomer having the group represented by the general formula (1) or (2) according to the present invention described above. For this purpose, it is preferable to use other polymer fine particles in combination. In the present application, these polymer fine particles are referred to as fixing polymer fine particles.

  The fixing fine polymer particles that can be used in the present invention are not particularly limited, and examples thereof include styrene-butadiene copolymer, polystyrene, acrylonitrile-butadiene copolymer, acrylate copolymer, polyurethane, and silicon-acrylic. Examples thereof include latex such as a copolymer and an acrylic-modified fluororesin. The latex may be obtained by dispersing polymer particles using an emulsifier, or may be dispersed without using an emulsifier. A surfactant is often used as an emulsifier, but a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer in which a solubilizing group is graft-bonded, a single group having a solubilizing group). It is also preferable to use a polymer obtained from a monomer and a monomer having an insoluble part.

  In the ink of the present invention, soap-free latex can be used. Soap-free latex is a latex that does not use an emulsifier and a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer in which a solubilizing group is graft-bonded, a solubilizing group) A polymer obtained from a monomer having an insoluble part and a monomer having an insoluble part).

  In recent years, there are latexes in which core-shell type polymer particles having different compositions at the center and outer edge of the particles are dispersed in addition to the latex in which the polymer particles are uniformly dispersed throughout the polymer particles. This type of latex can also be preferably used.

  In the present invention, the average particle size of the fixing fine polymer particles can be measured by light scattering, and is preferably 10 nm or more and 300 nm or less, more preferably 10 nm or more and 200 nm or less. When the average particle diameter of the fixing fine polymer particles by light scattering exceeds 300 nm, the gloss of the image is deteriorated, and when it is less than 10 nm, the water resistance and scratch resistance become insufficient.

  The fixing fine polymer particles used in the present invention have a glass transition point of −20 ° C. or higher and 80 ° C. or lower, preferably −10 ° C. or higher and 60 ° C. or lower. As the glass transition point is lower, the scratch resistance is improved, but conversely, if the images are left on top of each other, adhesion occurs and the image portion is peeled off. Moreover, when the glass transition point is too high, the scratch resistance is poor.

  The total amount of the polymer fine particles according to the present invention and the fixing polymer fine particles in the ink of the present invention is preferably in the range of 3 to 30% by mass from the viewpoint of fixability. If it is less than 3%, a printed matter with insufficient scratch resistance and high fastness cannot be obtained, and if it exceeds 30% by mass, the ink viscosity before drying is too high, making it difficult to emit from the inkjet head. .

The ink of the present invention is characterized by using a pigment as a color material.
As the pigment, conventionally known organic and inorganic pigments can be used, for example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxanes. Polycyclic pigments such as gin pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, dye lakes such as basic dye-type lakes and acid dye-type lakes, nitro pigments, nitroso pigments, aniline black, daylight fluorescent pigments And organic pigments such as carbon black and inorganic pigments such as carbon black.

  Specific organic pigments are exemplified below.

  Examples of pigments for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the orange or yellow pigment include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, pigment yellow 180, and the like.

Examples of pigments for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment Green 7 and the like are used. The pigment content in the ink of the present invention is 1 to 20% by mass.

  The pigment to be applied in the ink of the present invention is usually dispersed by a known dispersing means using a dispersant, and as an applicable dispersant, an anionic surfactant, a nonionic surfactant, or a water-soluble surfactant is used. A polymeric dispersant can be mentioned.

  Examples of the dispersing means that can be used in the present invention include a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, and a high-pressure homogenizer. Various dispersers can be used. It is also preferable to use a centrifugal separator or a filter for the purpose of removing the coarse particles of the pigment dispersion.

  In the ink of the present invention, a surfactant is preferably used in order to adjust the surface tension of the ink to a desired condition.

  The surfactant is not particularly limited, but examples thereof include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene. Nonionic surfactants such as glycols and polyoxyethylene / polyoxypropylene block copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. In particular, an anionic surfactant and a nonionic surfactant can be preferably used.

  Furthermore, a polymeric surfactant can also be used, for example, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer, styrene. -Maleic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene- A maleic acid copolymer etc. can be mentioned.

  In the ink of the present invention, in addition to the above description, if necessary, the output stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performance improvement objectives are known. Various additives such as a viscosity modifier, a specific resistance modifier, a film forming agent, an ultraviolet absorber, an antioxidant, a fading inhibitor, an antifungal agent, a rust inhibitor, etc. can be appropriately selected and used. Oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476; -74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc. Anti-fading agents, fluorescent whitening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-242871, and JP-A-4-219266. be able to.

  The viscosity of the ink of the present invention is preferably 3 mPa · s or more and 300 mPa · s or less. If the viscosity of the ink is less than 3 mPa · s, the ink fluidity during ink jet recording is too high, and the image sharpness is deteriorated. On the other hand, if it exceeds 300 mPa · s, the ink viscosity is too high and it becomes difficult to emit from the head.

  The inkjet recording method of the present invention is characterized in that an image is formed by ejecting the inkjet ink of the present invention onto a recording medium using an inkjet head.

  The ink jet head used in the ink jet recording method of the present invention may be an on-demand system or a continuous system. As the discharge method, an electro-mechanical conversion method (for example, single cavity type, double cavity type, bender type, piston type, shear mode type, shared wall type, etc.), electro-thermal conversion method (for example, thermal ink jet) Specific examples include a mold, a bubble jet (registered trademark) type, an electrostatic attraction method (for example, an electric field control type, a slit jet type, etc.), and a discharge method (for example, a spark jet type). However, any discharge method may be used. Further, as a printing method, a serial head method, a line head method, etc. can be used without limitation, but among them, it is particularly preferable for an ink jet recording method using an ink jet head having a line head method with severe requirements for clogging. Can also be used.

  In the inkjet recording method of the present invention, it is preferable to use at least one selected from plain paper, art paper, and coated paper as a recording medium from the viewpoint that the effects of the ink of the present invention can be exhibited.

  As the recording paper that can be applied in the ink jet recording method of the present invention, for example, plain paper, fine paper, art paper, coated paper, cast coated paper, glossy paper, ink jet exclusive paper, and the like can be widely used. An ink jet recording method using plain paper, art paper, or coated paper, which is a conductive support, is preferable because the excellent properties of the ink of the present invention can be exhibited.

The paper, coated paper, there is a non-coated paper, as the coated paper, the coating amount per 1m ² is one side 20g before and after of art paper, 1m ² per coated amount on one side 10g before and after the coated paper Examples include a light-weight coated paper having a coating amount per 1 m ^{2 of} about 5 g on one side, a finely coated paper, a mat-like finished mat-coated paper, a dull-like finished dull-coated paper, and a newsprint. Non-coated paper includes printing paper A using 100% chemical pulp, printing paper B using 70% or more chemical pulp, printing paper C using 40% or more and less than 70% chemical pulp, and printing using less than 40% chemical pulp. Examples thereof include paper D, gravure paper containing mechanical pulp and subjected to calendar treatment. More details are described in detail in “Latest Paper Processing Handbook” edited by the Paper Processing Handbook Editorial Committee, published by Tech Times, “Printing Engineering Handbook” edited by the Japan Printing Society.

  The plain paper is 80 to 200 μm uncoated paper belonging to a part of uncoated paper, special printing paper and information paper. The plain paper used in the present invention includes, for example, high-grade printing paper, intermediate-grade printing paper, low-grade printing paper, thin-like printing paper, fine-coating printing paper, special printing paper such as fine-quality printing paper, foam paper, PPC paper, and others There are information sheets and the like. Specifically, there are the following sheets and various modified / processed sheets using these sheets, but the present invention is not particularly limited thereto.

  High quality paper and colored high quality paper, recycled paper, copy paper / colored paper, OCR paper, carbonless paper / colored paper, synthetic paper such as YUPO 60, 80, 110 microns, YUPO COAT 70, 90 microns, etc. Coated paper 90kg, Foam mat paper 70, 90, 110kg, Foamed PET 38 microns, Mitsuori-kun (above, Kobayashi recording paper), OK fine paper, New OK fine paper, Sunflower, Phoenix, OK Royal White, Export fine paper ( NPP, NCP, NWP, Royal White) OK Book Paper, OK Cream Book Paper, Cream Premium Paper, OK Map Paper, OK Ishikari, Cucumber, OK Foam, OKH, NIP-N (above, Shin Oji Paper), Gold Wang, Toko, export quality paper, special demand quality paper, book paper, book paper L, light cream book paper, elementary textbook Paper, continuous slip paper, high quality NIP paper, silver ring, gold yang, gold yang (W), bridge, capital, silver ring book, harp, harp cream, SK color, securities paper, opera cream, opera, KYP medical record, silvia HN, Excellent Foam, NPI Foam DX (Nippon Paper), Pearl, Kinryo, Uscream fine paper, Special Book Paper, Super Book Paper, Book Paper, Diamond Foam, Inkjet Foam (Mitsubishi Paper), Carpet V, carpet SW, white elephant, luxury publication paper, cream carpet, cream white elephant, securities / voucher paper, book paper, map paper, copy paper, HNF (above, Hokuetsu), phone book cover, Book paper, cream shirairai, cream shirairaifu, cream shirairaifu, DSK (above, Daishowa Paper), Sendai MP fine paper, Jiang, Thunderbird fine, hanging paper, colored paper base, dictionary paper, cream book, white book, cream fine paper, map paper, continuous slip paper (above, Chuetsu Pulp), OP gold cherry (Chuetsu), gold sand, reference book paper, Replacement certificate paper (white), form printing paper, KRF, white foam, color foam, (K) NIP, fine PPC, Kishu inkjet paper (above, made by Kishu Paper), Taiou, Bright Foam, Kant, Kant White, Dante , CM paper, Dante Comic, Heine, paperback book paper, Heine S, New AD paper, Utrilo Excel, Excel Super A, Kant Excel, Excel Super B, Dante Excel, Heine Excel, Excel Super C, Excel Super D, AD Excel, Excel Super E, New Bright Foam, New Bright NI P (above, made by Daio Paper), Sun Ring, Moon Ring, Cloud Pass, Galaxy, Baiyun, Wyeth, Moon Ring Ace, Baiyun Ace, Cloud Pass Ace (above, Nippon Paper Industries), Taiou, Bright Foam, Bright Nip (Nagoya Pulp), Peony A, Golden Pigeon, Special Peony, White Peony A, White Peony C, Silver Pigeon, Super White Peony A, Light Cream White Peony, Special Medium Quality Paper, White Pigeon, Super Medium Quality Paper, Blue Pigeon, Red Pigeon, Gold Pigeon M Snow Vision, Snow Vision, Gold Pigeon Snow Vision, White Pigeon M, Super DX, Hamanasu O, Red Pigeon M, HK Super Printing Paper (above, Honshu Paper), Stalinden (A・ AW), Star Elm, Star Maple, Star Laurel, Star Poplar, MOP, Star Cherry I, Cherry I Super, Cherry II Super, Star Cherry III, Star Cherry IV, Cherry III Super, Cheri -IV Super (above, made by Maruzumi Paper), SHF (above, made by Toyo Pulp), TRP (above, made by Tokai Pulp) and the like.

  Typical printing papers include Mitsubishi Paper's Tokuhishi Art and Oji Paper's OK Top Coat N.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<Preparation of polymer fine particles>
[Preparation of polymer fine particle 1]
A monomer solution prepared by mixing 10 parts of styrene, 10 parts of butyl methacrylate, and 0.2 part of ethylene glycol dimethacrylate was prepared. Next, 0.5 parts of dodecyl sulfate and 100 parts of ion-exchanged water were dissolved in a four-necked flask, and then the atmosphere was replaced with nitrogen. In this, 3 parts of monomer solutions were added, and it heated up at 60 degreeC, stirring. After the temperature rise, 1 part of 2.0% ammonium persulfate aqueous solution was added dropwise, and the temperature was further raised to 80 ° C., and the remaining monomer solution and 20 parts of 2.0% ammonium persulfate aqueous solution were added dropwise over 4 hours. The core part was prepared by aging for time.

  While maintaining this reaction liquid at 80 ° C., a mixed liquid of 100 parts of N-isopropylacrylamide and 800 parts of ion-exchanged water and 24 parts of 2.0% ammonium persulfate were dropped over 3 hours, After aging for 4 hours, coarse particles were removed using a centrifugal separator, and ion-exchanged water was added so that the solid content concentration was 10% to obtain polymer fine particles 1 having an average particle size of 143 nm.

[Preparation of polymer fine particles 2 to 7]
In the preparation of the polymer fine particle 1, 10 parts of styrene (abbreviation: St) used for forming the core part, 10 parts of butyl methacrylate (abbreviation: BMA), and N-isopropylacrylamide ( Abbreviations: NIPAM) were changed in the same manner except that the total amount added to each monomer listed in Table 1 was the same, and polymer fine particles 2 to 7 were prepared.

[Preparation of polymer fine particle 8]
A solution of 12 parts of polyvinyl butyral (BL-1 manufactured by Sekisui Chemical Co., Ltd.) in 100 parts of ethyl acetate was added to 800 m of a 0.3% aqueous solution of sodium dodecyl sulfate, dispersed with ultrasonic waves, and then evaporated with ethyl acetate. Core particles were prepared by removing 100 ml.

  Next, 8 parts of N, N-diethylacrylamide was added and stirred for 1 hour. After heating to 80 ° C., 5 parts of 2.0% ammonium persulfate aqueous solution was added, and then N, N-diethylacrylamide was added. 80 parts were slowly added dropwise over 2 hours. After completion of the dropping, the reaction was continued at 80 ° C. for 3 hours, and then core-shell type polymer fine particles 8 having a core part made of polyvinyl butyral and a shell part made of N, N-diethylacrylamide were prepared.

[Preparation of polymer fine particles 9]
A monomer solution was prepared by mixing 100 parts of N-isopropylacrylamide and 0.1 part of ethylene glycol dimethacrylate. Next, 2.0 parts by mass of dodecyl sulfate and 800 parts by mass of ion-exchanged water were dissolved in the four-necked flask, and then the atmosphere was replaced with nitrogen. 3 parts of the monomer solution was added to this, and the temperature was raised to 60 ° C. while stirring. After raising the temperature, 1 part of a 2% aqueous ammonium persulfate solution was added dropwise, and the temperature was further raised to 80 ° C., 20 parts of the remaining monomer solution and 2% aqueous ammonium persulfate solution were added dropwise over 3 hours, and aged for 2 hours. Coarse particles were removed using a centrifugal separator, and ion-exchanged water was added so that the solid concentration was 10% to prepare partially crosslinked polymer fine particles 9.

[Preparation of polymer fine particles 10, 11]
In the preparation of the polymer fine particles 9, polymer fine particles 10 and 11 were prepared in the same manner except that the addition amount of ethylene glycol dimethacrylate as a crosslinking agent was changed to 1.0 part and 10.0 parts, respectively. .

[Preparation of polymer fine particles 12]
After adding 0.5 part of dodecyl sulfate and 100 parts of ion-exchanged water to a four-necked flask and dissolving, it was purged with nitrogen. Next, after raising the temperature to 80 ° C., a mixed solution of 100 parts of N-isopropylacrylamide and 800 parts of ion-exchanged water and 24 parts of 2.0% ammonium persulfate were added dropwise over 3 hours and aged for 4 hours. Then, ion-exchanged water was added so that the solid content concentration was 10% to prepare comparative polymer fine particles 12.

[Preparation of Resin Solution A]
Resin solution A was prepared in the same manner as in the preparation of the polymer fine particles 12 except that acrylamide was used instead of N-isopropylacrylamide. In the above method, resin fine particles were not formed, and a viscous resin solution was obtained.

[Preparation of resin solution B]
Resin solution B was prepared in the same manner as in the preparation of the polymer fine particles 12 except that N-vinylpyrrolidone was used instead of N-isopropylacrylamide. In the above method, resin fine particles were not formed, and a viscous resin solution was obtained.

[Preparation of polymer fine particles 13]
In the preparation of the polymer fine particles 1, polymer fine particles 13 were prepared in the same manner except that butyl acrylate was used instead of N-isopropylacrylamide.

  In addition, the detail of each additive used for preparation of each said polymer fine particle and resin solution and having described in Table 1 with the abbreviation is as follows.

St: Styrene BMA: n-butyl methacrylate NIPAM: N-isopropylacrylamide AM: Acrylamide BA: n-butyl acrylate VA: N-vinylacetamide EAM: N-ethylacrylamide BL-1: Polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd.)
<Preparation of ink>
(Preparation of carbon black dispersion)
Carbon Black: Talker Black # 8500 (Tokai Carbon Co., Ltd.) 120g
Jongkrill 62 (Johnson Polymer Co., Ltd.) 59g
Lebenol WX (Kao Corporation) 3g
Diethylene glycol 100g
Ion exchange water 300g
The above additives were mixed, dispersed using a sand grinder filled with 50% by volume of 0.5 mm zirconia beads, and coarse particles were removed with a centrifuge. Subsequently, it diluted with water so that carbon black content might be 20 mass%, and the carbon black pigment dispersion liquid was prepared.

(Preparation of inks 1 to 15: the present invention)
Carbon black dispersion (carbon black content: 20%) 40 parts Polymer fine particles or resin solution (types listed in Table 1) 40 parts Ethylene glycol 10 parts Triethylene glycol monobutyl ether 10 parts Olfine E1010 (Nonshin Chemical nonion) System Surfactant) 0.3 part Proxel GXL (manufactured by Avicia) 0.1 part The above additives were mixed in order to prepare inks 1 to 15 as black pigment inks.

<Image printing and characteristic evaluation>
[Evaluation of output stability]
In an environment of 25 ° C. and 60% RH, a piezo head having a nozzle diameter of 23 μm, a driving frequency of 5 kHz, a number of nozzles of 128 per color, and a nozzle density of 90 dpi of the same color is mounted, and the maximum recording density is 720 × 720 dpi. Each ink prepared above is set in an on-demand type ink jet printer set to have a droplet volume of 8 pl, and Konica Minolta Copy Paper NR-A80 (manufactured by Konica Minolta Business Technology Co., Ltd.) as copy paper is set as plain paper Then, the line drawing and the solid image were printed continuously at intervals of 9 sheets. Next, printing was stopped in the same environment for 10 minutes, and then the 10th print was performed. In the present invention, dpi represents the number of dots per 2.54 cm.

  The emission state of the inkjet nozzle at the time of printing the tenth sheet was visually observed, and the emission stability was evaluated according to the following criteria.

  A: No change is observed in the emission state for all nozzles.

○: Diagonal emission can be seen with 1 and 2% nozzles, but there is no ink deficit Δ: Ink deficient with 3% or more and less than 10% nozzles ×: Nozzle with 10% or more ink deficiency In the above evaluation, it was determined that it was practically acceptable if the rank was Δ or higher.

[Evaluation of feathering resistance]
About the 10th print created by the above-mentioned evaluation of the emission stability, the state of bleeding at the boundary between the printed portion and the non-printed portion was visually observed, and the feathering resistance was evaluated according to the following evaluation.

◎: No blurring is observed in the contour region. ○: Slightly irregular blurring is observed in the contour region, but there is no effect on the layer quality. △: Irregular bleeding in the contour region is totally absent. About 10 to 30% is recognized, but is practically acceptable. ×: Irregular bleeding is recognized by 30% or more in the outline region, and the image quality is deteriorated. In other words, it was determined to be within a practically acceptable range.

[Evaluation of scratch resistance]
Each solid image created in the above evaluation of the emission stability was reciprocated five times on the surface with an office eraser (manufactured by MONON Tonbo Pencil Co., Ltd.), and visual evaluation of the residual concentration by 20 general evaluators. The scratch resistance was evaluated according to the following criteria.

A: 16 or more people who evaluated that the density of the original image remained almost: ○: 12 to 15 people who evaluated that the density of the original image remained almost △: The density of the original image was almost 8 to 11 people evaluated as remaining ×: 7 or less people who evaluated that the density of the original image remained substantially In the above evaluation, if the rank was Δ or higher, the practically acceptable range It was determined that

  The results obtained as described above are shown in Table 1.

  As is apparent from the results shown in Table 1, polymer fine particles having a core-shell structure and containing a monomer having a group represented by the general formula (1) or (2) in the shell portion, or a general formula ( The ink of the present invention containing polymer fine particles containing a hydrophilic partially cross-linked gel containing a monomer having a group represented by 1) or (2) is superior in ejection stability and feathering resistance to the comparative example. In addition, it was confirmed that an excellent effect was exhibited in both the properties of scratch resistance.

  Moreover, in the polymer fine particles of the present invention having a core-shell structure, the content of the monomer having a group represented by the general formula (1) or (2) in the shell portion is set to 50% or more. It turns out that the outstanding effect is acquired.

Example 2
<< Preparation of inks 21 to 35 >>
Carbon black dispersion 50 parts Polymer fine particles or resin solution (types listed in Table 2) 10 parts Johncrill 450 (fixing polymer fine particles, solid content concentration 42%, manufactured by Johnson Polymer Co., Ltd.) 12 parts Ethylene glycol 10 parts Triethylene glycol Monobutyl ether 10 parts Orphine E1010 (manufactured by Nissin Chemical) 0.3 part Proxel GXL (manufactured by Avicia) 0.1 part Ion-exchanged water is added to make 100 parts in total to contain two types of polymer fine particles Inks 21 to 35 were prepared.

<Image printing and characteristic evaluation>
The prepared inks 21 to 35 were evaluated for ejection stability, feathering resistance and scratch resistance in the same manner as in Example 1, and the obtained results are shown in Table 2.

  As is apparent from the results shown in Table 3, the fixing fine polymer particles were contained together with the fine polymer particles containing the monomer having the group represented by the general formula (1) or (2) of the present invention. It can be seen that the ink of the present invention maintains excellent ejection stability and feathering resistance, and further improves the scratch resistance.

Example 3
<Preparation of polymer fine particles>
In the preparation of the polymer fine particles 1 described in Example 1, the polymer fine particles 21 were similarly prepared except that the amount of N-isopropylacrylamide added during the shell formation was changed to the shell mass described in Table 3. -26 was prepared.

<Preparation of ink>
Inks 41 to 46 were prepared in the same manner as in the preparation of the ink 1 described in Example 1, except that the polymer fine particles 21 to 26 prepared above were used instead of the polymer fine particles 1.

<Image printing and characteristic evaluation>
For the inks 41 to 46 prepared above and the ink 1 prepared in Example 1, the ejection stability, feathering resistance and scratch resistance were evaluated in the same manner as described in Example 1, and obtained. The results are shown in Table 3.

  As is apparent from the results shown in Table 3, the ink containing a polymer fine particle having a core-shell structure and having a core / shell ratio in the range of 0.5 to 100 has ejection stability, feathering resistance and resistance. It can be seen that the scratching property is further improved.

Example 4
<Preparation of polymer fine particles>
In the preparation of the polymer fine particles 9 described in Example 1, instead of 100 parts of N-isopropylacrylamide, the addition amounts of N-isopropylacrylamide and butyl methacrylate were appropriately changed so that the mixing ratio described in Table 4 was obtained. Except for the above, polymer fine particles 31 to 36 were prepared in the same manner.

<Preparation of ink>
Inks 51 to 56 were prepared in the same manner as in the preparation of the ink 9 described in Example 1, except that the polymer fine particles 31 to 36 prepared above were used instead of the polymer fine particles 9.

<Image printing and characteristic evaluation>
For the inks 31 to 36 prepared above and the ink 9 prepared in Example 1, the ejection stability, the feathering resistance and the scratch resistance were evaluated in the same manner as in the method described in Example 1. The results are shown in Table 4.

  As is clear from the results shown in Table 4, by setting the ratio of the hydrophilic partially crosslinked gel containing the monomer having the group represented by the general formula (1) or (2) to 50% by mass or more. It can be seen that the ejection stability, the feathering resistance and the scratch resistance are further improved.

Example 5
In Examples 1 to 4, the color material was changed from carbon black to C.I. I. Pigment red 122, C.I. I. Pigment blue 15: 3, C.I. I. Each ink was prepared in the same manner except that it was changed to CI Pigment Yellow 128, and the same evaluation as in Examples 1 to 4 was performed. As a result, in magenta pigment ink, cyan pigment ink and yellow pigment ink, Tables 1 to Similar to the results described in No. 4, it was confirmed that ejection stability, feathering resistance and scratch resistance were all improved.

Example 6
In Examples 1-4, instead of Konica Minolta Copy Paper NR-A80 (manufactured by Konica Minolta Business Technology Co., Ltd.), which is a plain paper as a recording medium, art paper (Tokuhishi Art, manufactured by Mitsubishi Paper Industries Co., Ltd.) Basis weight: 127 g / m ² ) and coated paper for printing (artpost Yasutsubo: 256 g, manufactured by Hokuetsu Paper Co., Ltd.) as the coated paper, image formation was performed in the same manner, and the feathering resistance and scratch resistance of the obtained image were evaluated in the same manner. As in the case of using plain paper, it was confirmed that the image formed using the ink of the present invention has excellent feathering resistance and scratch resistance on any recording medium.

Claims (10)

In an inkjet ink containing at least a pigment, water, a water-soluble solvent and polymer fine particles, the polymer fine particles have a shell structure composed of a core part and a shell part, and the shell part is represented by the following general formula (1) or ( An ink-jet ink comprising a monomer having a group represented by 2).

[In General Formulas (1) and (2), R represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and R ₁ , R ₂ , and R ₃ represent a hydrogen atom and a carbon atom number, respectively. 1 to 12 linear or branched alkyl group, alkenyl group, or linear or branched aryl group having 6 to 12 carbon atoms, and R ₁ and R ₂ are bonded to each other to contain a 5- or 6-membered group. Nitrogen heterocycles may be formed. X represents an oxygen atom or NR ₄ , and R ₄ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms. n represents 0 or 1. ] The content of the monomer having the group represented by the general formula (1) or (2) in the shell part is 50% by mass or more of the total mass of the shell part. Inkjet ink. 3. The inkjet ink according to claim 1, wherein a mass ratio of the shell part to the core part (shell part mass / core part mass) is 0.5 to 100. 4. In an inkjet ink containing at least a pigment, water, a water-soluble solvent, and polymer fine particles, the polymer fine particles contain a monomer having a group represented by the following general formula (1) or (2) An inkjet ink, which is a crosslinked gel.

[In General Formulas (1) and (2), R represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and R ₁ , R ₂ , and R ₃ represent a hydrogen atom and a carbon atom number, respectively. 1 to 12 linear or branched alkyl group, alkenyl group, or linear or branched aryl group having 6 to 12 carbon atoms, and R ₁ and R ₂ are bonded to each other to contain a 5- or 6-membered group. Nitrogen heterocycles may be formed. X represents an oxygen atom or NR ₄ , and R ₄ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms. n represents 0 or 1. ] The content of the hydrophilic partially crosslinked gel containing the monomer having the group represented by the general formula (1) or (2) in the polymer fine particle is 50% by mass or more of the total mass of the polymer fine particle. The inkjet ink according to claim 4, wherein the inkjet ink is provided. The inkjet ink according to any one of claims 1 to 5, wherein the group represented by the general formula (1) is a group represented by the following general formula (1-A).

[Wherein, R represents a hydrogen atom or a methyl group, and R ₁ and R ₂ represent a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, an alkenyl group, or a straight chain having 6 to 12 carbon atoms, respectively. It represents a chain or branched aryl group, and R ₁ and R ₂ may be further bonded to form a 5- or 6-membered nitrogen-containing heterocycle. ] The inkjet ink according to any one of claims 1 to 5, wherein the group represented by the general formula (2) is a group represented by the following general formula (2-A).

[Wherein, R represents a hydrogen atom or a methyl group, and R ₁ and R ₃ represent a hydrogen atom, a linear or branched alkyl group having 1 to 12 carbon atoms, an alkenyl group, or a linear chain having 6 to 12 carbon atoms. Alternatively, it represents a branched aryl group. ] The inkjet ink according to claim 1, comprising at least one other polymer fine particle together with the polymer fine particle. An ink-jet recording method comprising forming an image by ejecting the ink-jet ink according to claim 1 onto a recording medium using an ink-jet head. 10. The ink jet recording method according to claim 9, wherein the recording medium is at least one selected from plain paper, art paper, and coated paper.