JP2007161848A - Inkjet ink, inkjet ink set and recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide inkjet ink which is excellent in storage stability, prevents bleeding on a recording medium such as art paper, coated paper and plain paper and yields an image showing high scratch resistance and high optical density, an inkjet ink set, and an inkjet recording method using the same. <P>SOLUTION: The inkjet ink contains a color material, a polymer compound, a photopolymerization initiator and a thermal polymerization initiator, wherein the polymer compound has a plurality of side chains on a hydrophilic main chain, wherein the side chains are crosslinkable with each other when exposed to an active energy ray irradiation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inkjet ink containing a polymer compound that can be cross-linked by irradiation with active energy rays, an inkjet ink set, and an inkjet recording method using them.

  The ink jet recording method is capable of recording high-definition images with a relatively simple apparatus, and has been rapidly developed in various fields. In addition, there are various uses, and a recording medium or ink suitable for each purpose is used.

  In particular, in recent years, the recording speed has been greatly improved, and printers having performance capable of withstanding light printing applications have been developed. However, in order to bring out the performance of the ink jet printer, an ink jet dedicated paper having ink absorbability is required.

  When recording on coated paper or art paper that does not absorb much ink, or on plastic film that does not absorb ink at all, different color ink liquids mix on the recording medium and cause color turbidity. There is a problem, and it has been a problem to give diversity to the recording medium by inkjet recording.

  In order to solve the above problem, an ink for ink jet recording and an ink jet recording method which are cured by irradiating ultraviolet rays have been proposed (see Patent Document 1). In addition, a so-called non-aqueous ink using a triacrylate or higher polyacrylate, a ketone, and an alcohol as main solvents as a pigment and a polymerizable material has been proposed (see Patent Document 2).

  In the above proposed method, since the ink itself is cured with a curing component, it is possible to record even on a non-absorbent recording medium, but it contains a large amount of a curing component other than a coloring material, and Since it does not volatilize, the recorded image surface is swelled by ink dots, and there is a problem that unnaturalness of image quality, particularly glossiness, occurs.

  A water-soluble photopolymerization inkjet ink diluted with water using a water-soluble photopolymerizable monomer or oligomer instead of the non-aqueous ink is disclosed (see Patent Documents 3 and 4).

  Surely, by using these proposed water-soluble photopolymerization inkjet inks, a flat image without image swell can be obtained, but as long as the disclosed aqueous photopolymerizable monomer or oligomer is used, In order to cause gelation capable of preventing bleeding, a large amount of energy is required, and even if a light amount capable of sufficient gelation is given, a photopolymerizable monomer or oligomer having a low molecular weight is essentially added. Therefore, when the formed images are overlapped due to the stickiness of the image due to the uncured component remaining in a trace amount, there is a drawback that the images stick to each other and peel off.

  In order to improve that point, the inventors of the present invention have proposed that at least one of the water-soluble polymers has a plurality of side chains in the hydrophilic main chain and is irradiated with active energy rays to crosslink between the side chains. Ink jet inks using various polymer compounds are proposed, the amount of energy required to achieve bleed prevention can be reduced, and photopolymerizable monomers or oligomers used in water-containing photopolymerizable inks described in the above-mentioned patent documents Therefore, it has been proposed that stickiness can be prevented and sticking in superimposed images can be prevented (see Patent Document 5).

However, in black ink, due to the absorption of light, the photopolymerization initiator alone does not sufficiently cure no matter how much light is applied, and when recording on art paper, coated paper, plain paper on a recording medium, Even if the bleeding can be prevented to some extent, there is a drawback that the optical density is lowered.
U.S. Pat. No. 4,228,438 Japanese Patent Publication No. 5-64667 JP-A-7-224241 JP 2004-285161 A JP 2005-019659 A

  The present invention has been made in view of the above problems, and its object is to prevent bleeding on a recording medium such as art paper, coated paper, plain paper, and the like, and to have high scratch resistance and high optical density. An object of the present invention is to provide an ink-jet ink, an ink-jet ink set, and an ink-jet recording method using the ink-jet ink, in which an image is obtained and the ink storage stability is excellent.

The above object of the present invention is achieved by the following configurations.
1. Contains a coloring material, a polymer compound having a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays, a photopolymerization initiator, and a thermal polymerization initiator An ink jet ink characterized by comprising:
2. 2. The ink-jet ink according to 1, wherein a content of the thermal polymerization initiator is 5% by mass or more and less than 60% by mass with respect to the photopolymerization initiator. 3. The inkjet ink according to 1 or 2, wherein the polymer compound is contained in an amount of 0.8% by mass or more and 5.0% by mass or less based on the total mass of the ink.
4). The inkjet according to any one of 1 to 3, wherein a partial structure of a portion having the hydrophilic main chain and the side chain of the polymer compound is represented by the following general formula (A): For ink.

Formula (A)
Poly-{(X1) m- [B- (Y1) n] p}
[In the formula, Poly represents a hydrophilic main chain, {} represents a side chain, X1 represents a (p + 1) -valent linking group, B represents a crosslinkable group, Y1 represents a hydrogen atom or a substituent. To express. m represents 0 or 1, n represents 0 or 1, and p represents a positive integer. When p is 2 or more, a plurality of B and Y1 may be the same or different. ]
5. The hydrophilic main chain is a saponified product of polyvinyl acetate, the saponification degree is 77% or more and 99% or less, and the polymerization degree is 200 or more and 4000 or less, Item 2. An ink-jet ink according to item 1.
6). 6. The inkjet ink according to any one of 1 to 5, wherein a modification rate of the side chain with respect to the hydrophilic main chain is 1.0 mol% or more and 4.0 mol% or less.
7). The inkjet ink according to any one of 1 to 6, wherein the photopolymerization initiator is water-soluble.
8. An ink-jet ink set comprising ink-jet inks of two or more colors, wherein at least one of the ink-jet inks is the ink-jet ink according to any one of 1 to 7.
Use of the inkjet ink set according to recording method 10.8, wherein the inkjet ink according to any one of 9.1 to 7 is ejected from a nozzle onto a recording medium and recorded. A characteristic recording method.

  According to the present invention, bleeding of art paper, coated paper, and plain paper is prevented, an image having high optical density, high scratch resistance, and excellent ink storage stability can be provided. Ink sets and ink jet recording methods using them can be provided.

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

  The present invention relates to a color material, a polymer compound having a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays, and photopolymerization. It contains an initiator and a thermal polymerization initiator.

  By using this ink-jet ink, it is possible to obtain an ink-jet ink that is prevented from bleeding on art paper, coated paper, and plain paper, and has an image with a high optical density, high scratch resistance, and excellent ink storage stability.

  When the polymer compound according to the present invention, a photopolymerization initiator, and a thermal polymerization initiator are used in combination, the optical density becomes sufficiently high, and a photopolymerization initiator and a thermal polymerization initiator are added to a conventional water-soluble polymerizable compound. The reason why the effect does not appear so much even when used in combination is not clear, but the polymer compound according to the present invention has a sufficiently high degree of polymerization even before crosslinking. In order to reach a high degree of polymerization that does not penetrate from the surface in a much shorter time than when a water-soluble polymerizable compound is used, it is presumed that a high optical density can be obtained.

<Active energy ray crosslinkable polymer compound>
The polymer compound having a plurality of side chains in the hydrophilic main chain according to the present invention and capable of crosslinking between the side chains by irradiating with active energy rays is a saponified product of polyvinyl acetate, polyvinyl acetal, polyethylene Oxide, polyalkylene oxide, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, or a derivative of the hydrophilic resin, and at least one hydrophilic selected from the group consisting of these copolymers In the resin, a modified group such as a photodimerization type, a photodecomposition type, a photopolymerization type, a photomodification type, or a photodepolymerization type is introduced into the side chain. Photopolymerizable crosslinkable groups are desirable from the viewpoints of sensitivity and performance of the generated image.

  There is a preferable combination between the ionicity of the coloring material according to the present invention and the ionicity of the side chain of the polymer compound. It is preferable from the viewpoint of excellent image fastness, ink storage stability, and continuous emission properties by selecting anionic as the color material and combining nonionicity or anionicity with the side chain. The side chain is most preferably nonionic.

  What the partial structure of the hydrophilic principal chain and side chain of the active energy ray crosslinkable polymer compound of the present invention is represented by the following general formula (A) is preferable.

Formula (A)
Poly-{(X1) m- [B- (Y1) n] p}
In the above general formula (A), Poly represents a hydrophilic main chain, and is a saponified product of polyvinyl acetate, polyvinyl acetal, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid, hydroxyethyl cellulose, methyl cellulose, hydroxy Propyl cellulose, or a derivative of the hydrophilic resin, and a copolymer thereof are preferable.

  {} Represents a side chain. In the side chain, X1 represents a (p + 1) -valent linking group. p represents a positive integer, preferably an integer of 1 to 5. Specifically, when p = 1, X1 represents a divalent linking group, for example, an alkylene group, an arylene group, a heteroarylene group, an ether group, a thioether group, an imino group, an ester group, an amide group, or a sulfonyl group. These may be combined to form one divalent or higher group. When p = 2 or more, a plurality of B and Y1 described later may be the same or different.

  X1 is preferably an alkylene oxide or a divalent or higher linking group in which an aromatic group is combined at least.

  B represents a crosslinking group. Specifically, it is a group containing a double bond or a triple bond, and represents, for example, an acryl group, a methacryl group, a vinyl group, an allyl group, a diazo group, or an azide group. An acrylic group and a methacryl group are preferable.

  Y1 represents a hydrogen atom or a substituent. Specifically, the substituent is a halogen atom (for example, fluorine atom, chlorine atom, etc.), an alkyl group (for example, methyl, ethyl, butyl, pentyl, 2-methoxyethyl, trifluoromethyl, 2-ethylhexyl, cyclohexyl, etc.) , Aryl groups (eg, phenyl, p-tolyl, naphthyl, etc.), acyl groups (eg, acetyl, propionyl, benzoyl, etc.), alkoxy groups (eg, methoxy, ethoxy, butoxy, etc.), alkoxycarbonyl groups (eg, methoxycarbonyl) I-propoxycarbonyl etc.), acyloxy group (eg acetyloxy, ethylcarbonyloxy etc.), carbamoyl group (eg methylcarbamoyl, ethylcarbamoyl, butylcarbamoyl, phenylcarbamoyl etc.), sulfamoyl group (eg sulfayl) Yl, methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl etc.), alkylthio groups (eg methylthio, ethylthio, octylthio etc.), arylthio groups (eg phenylthio, p-tolylthio etc.), alkylureido groups (eg , Methylureido, ethylureido, methoxyethylureido, dimethylureido, etc.), arylureido groups (eg, phenylureido etc.), alkylsulfonamide groups (eg, methanesulfonamide, ethanesulfonamide, butanesulfonamide, trifluoromethylsulfone) Amide, 2,2,2-trifluoroethylsulfonamide, etc.), arylsulfonamide groups (eg, phenylsulfonamide, tolylsulfonamide, etc.), alkylaminosulfonylamino groups (eg, Methylaminosulfonylamino, ethylaminosulfonylamino, etc.), arylaminosulfonylamino groups (eg, phenylaminosulfonylamino, etc.), hydroxy groups, heterocyclic groups (eg, pyridyl, pyrazolyl, imidazolyl, furyl, thienyl, etc.), etc. In addition, these may have a substituent.

  m represents 0 or 1, and n represents 0 or 1.

  In the hydrophilic main chain, a saponified product of polyvinyl acetate is preferable from the viewpoint of convenience for introduction of side chains and handling, and the polymerization degree is preferably 200 or more and 4000 or less, and 200 or more and 2000 or less is a viewpoint of handling. From the viewpoint of ejection stability, it is more preferably from 200 to 500. The modification rate of the side chain with respect to the main chain is preferably 1.0 mol% or more and 4.0 mol% or less, and 1.0 mol% or more and 3.0 mol% or less in terms of reactivity and film strength. More preferred.

  In the active energy ray crosslinkable polymer compound according to the present invention, as a more preferable structure, a photosensitive resin described in JP-A-56-67309 is represented by the following general formula (1) in a polyvinyl alcohol structure. The side chain of 2-azido-5-nitrophenylcarbonyloxyethylene structure (nonionic) or the 4-azido-3-nitrophenylcarbonyloxyethylene structure (nonionic) represented by the following general formula (2) A resin composition having a side chain.

  A side chain of a modifying group (anionic) represented by the following general formula (3) is also preferably used.

  In the formula, R represents an alkylene group or an aromatic ring. A benzene ring is preferred.

  As the photopolymerization type modifying group, for example, a resin (nonionic) represented by the following general formula (4) disclosed in JP-A Nos. 2000-181062 and 2004-189841 is preferable from the viewpoint of reactivity.

In the formula, R ₂ represents a methyl group or a hydrogen atom, n represents 1 or 2, X represents — (CH 2) m —COO— or —O—, Y represents an aromatic ring or a single bond, and m represents 0 to Represents an integer up to 6.

  Moreover, it is also preferable to use the photopolymerization type | mold modified group (nonionic property) represented by following General formula (5) described in Unexamined-Japanese-Patent No. 2004-161942 for a conventionally well-known water-soluble resin.

  In the formula, R3 represents a methyl group or a hydrogen atom, and R4 represents a linear or branched alkylene group having 2 to 10 carbon atoms.

  Furthermore, modified groups (nonionic) represented by the following general formulas (6) to (8) are also preferably used.

  Such an active energy ray-crosslinking polymer compound is preferably contained in an amount of 0.8% by mass to 5.0% by mass with respect to the total mass of the ink. The presence of 0.8% by mass or more improves cross-linking efficiency, and beading and color bleeding are more preferable due to a rapid increase in ink viscosity after cross-linking. In the case of 5.0% by mass or less, it is difficult to adversely affect the ink physical properties and the state in the ink head, which is preferable from the viewpoint of the light emission property and the ink storage property.

  In the active energy ray cross-linking polymer compound according to the present invention, the main chain originally having a certain degree of polymerization is cross-linked via a cross-linking bond between side chains, and therefore through a general chain reaction. The effect of increasing the molecular weight per photon is remarkably great for the active energy ray-curable resin that polymerizes. On the other hand, in the conventionally known active energy ray curable resins, the number of crosslinking points cannot be controlled, so the physical properties of the cured film cannot be controlled, and the film tends to be hard and brittle.

  In the active energy ray-crosslinking polymer compound according to the present invention, the number of crosslinking points can be completely controlled by the length of the hydrophilic main chain and the amount of side chains introduced, and the physical properties of the ink film can be controlled according to the purpose. It is.

  Furthermore, in the conventionally known active energy ray-curable ink, almost all of the ink other than the color material is a curing component, so that the dots after curing rise and the image quality represented by gloss is inferior. The amount required for the line-crosslinking polymer compound is small, and since there are many dry components, the image quality after drying can be improved and the fixing property is also good.

<< Thermal polymerization initiator >>
The thermal polymerization initiator according to the present invention is a compound capable of initiating crosslinking of the polymer compound according to the present invention by heat generated by irradiation of active energy.

  The thermal polymerization initiator is not particularly limited. Various peroxides such as ammonium persulfate, sodium persulfate, and potassium persulfate are used as the water-soluble thermal polymerization initiator, and benzoyl peroxide is used as the oil-soluble thermal polymerization initiator. Various peroxides, such as di-t-butyl peroxide, cumene hydroperoxide, t-butyl peroxide or 2-ethylhexanoate; or various compounds such as azobisisobutyronitrile or azobisisovaleronitrile An azo compound etc. can be mentioned. As a form to be added, it can be added in dissolved or dispersed state in the ink. As the thermal polymerization initiator, a water-soluble thermal polymerization initiator is preferably used.

<< Photopolymerization initiator >>
The photopolymerization initiator according to the present invention is a compound capable of initiating crosslinking of the polymer compound according to the present invention upon irradiation with active energy.
The photopolymerization initiator according to the present invention may be dissolved or dispersed in a solvent, or may be chemically bonded to the photosensitive resin. The photosensitizer that may be used is not particularly limited, and a conventionally known photosensitizer can be used, but a water-soluble compound is preferable from the viewpoint of mixing property and reaction efficiency. In particular, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone (HMPK), thioxanthone ammonium salt (QTX), and benzophenone ammonium salt (ABQ) are preferable from the viewpoint of miscibility with an aqueous solvent.

  Furthermore, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) represented by the following general formula (9) from the viewpoint of compatibility with the active energy ray-crosslinking polymer compound according to the present invention. ) Ketone (n = 1, HMPK) and its ethylene oxide adduct (n = 2 to 5) are more preferable.

  In the said General formula (9), n represents the integer of 1-5.

In addition, as an example,
1) Benzophenones such as benzophenone, hydroxybenzophenone, bis-N, N-dimethylaminobenzophenone, bis-N, N-diethylaminobenzophenone, 4-methoxy-4'-dimethylaminobenzophenone,
2) Thioxanthones such as thioxatone, 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, isopropoxychlorothioxanthone,
3) Anthraquinones such as ethyl anthraquinone, benzanthraquinone, aminoanthraquinone, chloroanthraquinone,
4) Acetophenones,
5) Benzoin ethers such as benzoin methyl ether,
6) 2,4,6-trihalomethyltriazines,
7) 1-hydroxycyclohexyl phenyl ketone, 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di (m-methoxyphenyl) imidazole dimer 2- (o-fluorophenyl) -4,5-phenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-phenylimidazole dimer, 2- (p-methoxyphenyl) -4, 5-diphenylimidazole dimer, 2, -di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl) -4,5-diphenylimidazole dimer, 2, Imidazoles such as 4,5-triarylimidazole dimer,
8) Benzyldimethyl ketal, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-1- Propanone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one Benzoins such as phenanthrenequinone, 9,10-phenanthrenequinone, methylbenzoin, ethylbenzoin,
9) Acridine derivatives such as 9-phenylacridine, 1,7-bis (9,9'-acridinyl) heptane,
10) Bisacylphosphine oxide,
And mixtures thereof are preferably used, and the above may be used alone or in combination.

  In addition to these photopolymerization initiators, accelerators and the like can also be added. Examples of these include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethanolamine, diethanolamine, triethanolamine and the like.

  These photopolymerization initiators are preferable even if they are grafted to the side chain with respect to the hydrophilic main chain.

<Ratio of thermal polymerization initiator to photopolymerization initiator>
The ratio of the thermal polymerization initiator and the photopolymerization initiator is not particularly limited, but preferably the thermal polymerization initiator is 5% by mass or more and less than 60% by mass with respect to the photopolymerization initiator. From the standpoint of the effect of addition and storage stability.

  More preferably, this ratio is preferably changed depending on the type of color material contained in the ink. In particular, when an achromatic color material that absorbs or reflects light such as black or white is used, the content of the thermal polymerization initiator is 30% by mass or more and less than 60% by mass, and colored inks such as cyan, magenta, and yellow are used. I need to do more.

  Further, the amount of the photopolymerization initiator used is 1% or more and 100% or less, preferably 5% or more and 50% or less of the polymer compound used in the present invention.

《Coloring material》
As the coloring material used in the ink-jet ink of the present invention, various dyes or pigments known in ink-jetting can be used. From the combination with the ionicity of the side chain of the active energy ray-crosslinking resin, it is anionic. Preferably there is.

〔dye〕
There is no restriction | limiting in particular as dye which can be used by this invention, Water-soluble dyes, such as an acid dye, a direct dye, and a reactive dye, a disperse dye, etc. are mentioned, It is an anionic dye.

(Water-soluble dye)
Examples of the anionic water-soluble dye that can be used in the present invention include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, diphenylmethane dyes, and the like. The specific compound is shown below. However, it is not limited to these exemplified compounds.

<C. I. Acid Yellow>
1, 3, 11, 17, 18, 19, 23, 25, 36, 38, 40, 42, 44, 49, 59, 61, 65, 67, 72, 73, 79, 99, 104, 110, 114, 116, 118, 121, 127, 129, 135, 137, 141, 143, 151, 155, 158, 159, 169, 176, 184, 193, 200, 204, 207, 215, 219, 220, 230, 232, 235, 241, 242, 246,
<C. I. Acid Orange>
3, 7, 8, 10, 19, 24, 51, 56, 67, 74, 80, 86, 87, 88, 89, 94, 95, 107, 108, 116, 122, 127, 140, 142, 144, 149, 152, 156, 162, 166, 168,
<C. I. Acid Red>
88, 97, 106, 111, 114, 118, 119, 127, 131, 138, 143, 145, 151, 183, 195, 198, 211, 215, 217, 225, 226, 249, 251, 254, 256, 257, 260, 261, 265, 266, 274, 276, 277, 289, 296, 299, 315, 318, 336, 337, 357, 359, 361, 362, 364, 366, 399, 407, 415,
<C. I. Acid Violet>
17, 19, 21, 42, 43, 47, 48, 49, 54, 66, 78, 90, 97, 102, 109, 126,
<C. I. Acid Blue>
1, 7, 9, 15, 23, 25, 40, 62, 72, 74, 80, 83, 90, 92, 103, 104, 112, 113, 114, 120, 127, 128, 129, 138, 140, 142, 156, 158, 171, 182, 185, 193, 199, 201, 203, 204, 205, 207, 209, 220, 221, 224, 225, 229, 230, 239, 249, 258, 260, 264, 278, 279, 280, 284, 290, 296, 298, 300, 317, 324, 333, 335, 338, 342, 350,
<C. I. Acid Green>
9, 12, 16, 19, 20, 25, 27, 28, 40, 43, 56, 73, 81, 84, 104, 108, 109,
<C. I. Acid Brown>
2, 4, 13, 14, 19, 28, 44, 123, 224, 226, 227, 248, 282, 283, 289, 294, 297, 298, 301, 355, 357, 413,
<C. I. Acid Black>
1, 2, 3, 24, 26, 31, 50, 52, 58, 60, 63, 107, 109, 112, 119, 132, 140, 155, 172, 187, 188, 194, 207, 222,
<C. I. Direct yellow>
8, 9, 10, 11, 12, 22, 27, 28, 39, 44, 50, 58, 79, 86, 87, 98, 105, 106, 130, 132, 137, 142, 147, 153,
<C. I. Direct orange>
6, 26, 27, 34, 39, 40, 46, 102, 105, 107, 118,
<C. I. Direct Red>
2, 4, 9, 23, 24, 31, 54, 62, 69, 79, 80, 81, 83, 84, 89, 95, 212, 224, 225, 226, 227, 239, 242, 243, 254,
<C. I. Direct Violet>
9, 35, 51, 66, 94, 95,
<C. I. Direct Blue>
1, 15, 71, 76, 77, 78, 80, 86, 87, 90, 98, 106, 108, 160, 168, 189, 192, 193, 199, 200, 201, 202, 203, 218, 225, 229, 237, 244, 248, 251, 270, 273, 274, 290, 291,
<C. I. Direct Green>
26, 28, 59, 80, 85,
<C. I. Direct Brown>
44, 106, 115, 195, 209, 210, 222, 223,
<C. I. Direct Black>
17, 19, 22, 32, 51, 62, 108, 112, 113, 117, 118, 132, 146, 154, 159, 169,
<C. I. Reactive Yellow>
2, 3, 7, 15, 17, 18, 22, 23, 24, 25, 27, 37, 39, 42, 57, 69, 76, 81, 84, 85, 86, 87, 92, 95, 102, 105, 111, 125, 135, 136, 137, 142, 143, 145, 151, 160, 161, 165, 167, 168, 175, 176,
<C. I. Reactive Orange>
1, 4, 5, 7, 11, 12, 13, 15, 16, 20, 30, 35, 56, 64, 67, 69, 70, 72, 74, 82, 84, 86, 87, 91, 92, 93, 95, 107,
<C. I. Reactive Red>
2, 3, 5, 8, 11, 21, 22, 23, 24, 28, 29, 31, 33, 35, 43, 45, 49, 55, 56, 58, 65, 66, 78, 83, 84, 106, 111, 112, 113, 114, 116, 120, 123, 124, 128, 130, 136, 141, 147, 158, 159, 171, 174, 180, 183, 184, 187, 190, 193, 194, 195, 198, 218, 220, 222, 223, 228, 235,
<C. I. Reactive Violet>
1, 2, 4, 5, 6, 22, 23, 33, 36, 38,
<C. I. Reactive Blue>
2, 3, 4, 5, 7, 13, 14, 15, 19, 21, 25, 27, 28, 29, 38, 39, 41, 49, 50, 52, 63, 69, 71, 72, 77, 79, 89, 104, 109, 112, 113, 114, 116, 119, 120, 122, 137, 140, 143, 147, 160, 161, 162, 163, 168, 171, 176, 182, 184, 191, 194, 195, 198, 203, 204, 207, 209, 211, 214, 220, 221, 222, 231, 235, 236,
<C. I. Reactive Green>
8, 12, 15, 19, 21,
<C. I. Reactive Brown>
2, 7, 9, 10, 11, 17, 18, 19, 21, 23, 31, 37, 43, 46,
<C. I. Reactive Black>
5, 8, 13, 14, 31, 34, 39,
<C. I. Food Black>
1, 2,
Etc.

[Pigment]
As the pigment that can be used in the present invention, conventionally known organic and inorganic pigments can be used, but they are anionic pigments. For example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, polycyclic rings such as phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Examples include formula pigments, dye lakes such as acid dye lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, 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. And CI Pigment Yellow 138.

  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. And CI Pigment Green 7.

<Dispersant>
As the water-soluble polymer dispersant for stably dispersing the pigment in the ink, the following water-soluble resin can be used, which is preferable from the viewpoint of ejection stability.

  As the water-soluble resin, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer are preferably used. Polymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer It is a water-soluble resin such as.

  The content of the water-soluble resin with respect to the total amount of the ink is preferably 0.1 to 10% by mass, and more preferably 0.3 to 5% by mass.

  Two or more of these water-soluble resins can be used in combination.

<Anionic pigment>
The form of the anionic pigment used in the present invention is preferably a pigment in which the pigment is dispersed with an anionic polymer dispersant or an anion-modified self-dispersing pigment from the viewpoint of dispersion stability.

  The anionic polymer dispersant refers to a dispersant having an anionic group obtained by neutralizing an acidic group in a molecule with a basic compound. Examples of the basic compound used at this time include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amines such as ammonia, alkylamine, and alkanolamine. In the present invention, amines are particularly preferable. .

  The anionic polymer dispersant preferably used in the present invention is not particularly limited as long as the molecular weight is 1000 or more. For example, polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, and acrylic acid-acrylonitrile copolymers , Acrylic resins such as potassium acrylate-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer Styrene-acrylic resins such as styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, Styrene-maleic acid copolymer, styrene-maleic anhydride Rain acid copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer Polymers, vinyl acetate copolymers such as vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer, and copolymers or resins thereof such as carboxylic acids, sulfonic acids or phosphones Includes homopolymers, copolymers and terpolymers with acid functionality. Monomers that give acid functionality are, for example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, mesaconic acid, fumaric acid, citraconic acid, vinyl acetic acid, acryloxypropionic acid, vinyl sulfonic acid, Styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, allylsulfonic acid, allylphosphonic acid, vinylphosphonic acid and vinylsulfonic acid.

  The anion-modified self-dispersing pigment preferably used in the present invention refers to a pigment having an anionic group on the surface and capable of being dispersed without a dispersant. An anionic self-dispersing pigment refers to a pigment in which an acidic group is modified and neutralized with a basic compound, thereby making the anionic group dispersible in water without a dispersant.

  The pigment particle having an acidic group on the surface means a pigment directly modified with an acidic group on the surface of the pigment particle, or an organic substance having an organic pigment mother nucleus and having an acidic group bonded directly or through a joint. .

  Examples of the acidic group (also referred to as polar group) include a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a boric acid group, and a hydroxyl group, preferably a sulfonic acid group and a carboxylic acid group, and more preferably a sulfone group. It is an acid group.

  Acid group modifiers include sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, sulfonated pyridine salt, sulfamic acid and other treatments containing sulfur atoms, and the pigment particle surface is oxidized. Carboxylating agents such as sodium hypochlorite and potassium hypochlorite that introduce carboxylic acid groups can be mentioned. Among them, a sulfonating agent such as sulfur trioxide, sulfonated pyridine salt or sulfamic acid, or a carboxylating agent is preferable. Examples of basic compounds that neutralize acidic groups include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amines such as ammonia, alkylamines, and alkanolamines. In the present invention, amines are used. Is particularly preferred.

  In the present invention, the polar group may be free or in a salt state, or may have a counter salt. Examples of the counter salt include inorganic salts (lithium, sodium, potassium, magnesium, calcium, aluminum, nickel, ammonium) and organic salts (triethylammonium, diethylammonium, pyridinium, triethanolammonium, etc.), preferably 1 A counter salt having a valence.

  The average particle size of the pigment dispersion used in the inkjet ink of the present invention is preferably 500 nm or less, preferably 10 nm or more and 200 nm or less, and more preferably 10 nm or more and 150 nm or less. If the average particle size of the pigment dispersion exceeds 500 nm, the dispersion becomes unstable. In addition, even when the average particle size of the pigment dispersion is less than 10 nm, the stability of the pigment dispersion tends to deteriorate, and the storage stability of the ink tends to deteriorate.

  The particle size of the pigment dispersion can be determined by a commercially available particle size measuring device using a light scattering method, an electrophoresis method, a laser Doppler method or the like. It is also possible to obtain a particle image with a transmission electron microscope on at least 100 particles and perform statistical processing on the image using image analysis software such as Image-Pro (manufactured by Media Cybernetics). Is possible.

  Various methods such as 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, and a paint shaker can be used as a pigment dispersion method.

  The content of the color material that can be dispersed or dissolved in water used in the inkjet ink of the present invention is preferably 1 to 10% by mass relative to the total mass of the ink.

《Water-soluble solvent》
In the inkjet ink of the present invention, a water-soluble solvent is preferably used, and as the water-soluble solvent, a mixed solvent such as water and a water-soluble organic solvent is more preferably used. Examples of water-soluble organic solvents that are preferably used include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol), polyhydric alcohols (eg, 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 Nomethyl 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 (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetra) , Tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocycles (eg, 2 -Pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone), sulfoxides (for example, dimethyl sulfoxide) and the like.

<Surfactant>
Surfactants preferably used in the ink of the present invention include alkyl sulfates, alkyl ester sulfates, dialkyl sulfosuccinates, alkyl naphthalene sulfonates, alkyl phosphates, polyoxyalkylene alkyl ether phosphates, fatty acids. Anionic surfactants such as salts, nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyalkylene alkyl phenyl ethers, acetylene glycols, polyoxyethylene-polyoxypropylene block copolymers, glycerin esters, sorbitan Activators such as esters, polyoxyethylene fatty acid amides and amine oxides, and cationic surfactants such as alkylamine salts and quaternary ammonium salts.

  These surfactants can also be used as pigment dispersants, and in particular, anionic and nonionic surfactants can be preferably used.

<Inkjet ink set>
The ink-jet ink set of the present invention is composed of two or more ink-jet inks, and at least one of the ink-jet inks is the ink-jet ink of the present invention.

  The ink-jet ink set of the present invention comprises the ink-jet ink described in the claims. Preferably, two or more kinds of inks are the ink-jet ink of the present invention, and particularly preferably all the inks of the present invention. By being an ink jet ink, the effects of the present invention are remarkably exhibited.

  As inks having different hues constituting the inkjet ink set of the present invention, it is preferable to use an ink set composed of inkjet inks of yellow, magenta, cyan, and black.

  Further, in addition to the four color inks, a light cyan ink, a light magenta ink, a dark yellow ink, and a light black ink (gray ink) may be used. It is also possible to use so-called special color inks such as blue, red, green, orange and violet.

(Dark ink)
In the ink-jet ink set of the present invention, it is desirable to use an ink-jet ink set composed of at least two inks of the same color having different densities in at least one color ink. Further, it is more preferable to use an ink jet ink set composed of at least two inks of the same color having different densities in two or more colors. In particular, at least two inks of the same color having different densities are used. It is preferable to use an ink-jet ink set composed of ink.

  This is because by using a low-density ink jet ink, it is possible to reduce graininess and form a high-quality image without so-called “roughness”. In particular, it is preferable to use at least two inks having different densities in magenta ink or cyan ink having high human visibility.

  The density ratio of the ink jet ink sets having different densities may be any value. However, in order to achieve smooth gradation reproduction, the ratio of the high density ink to the low density ink (color material density / high density of the low density ink) The color material density of the density ink is preferably between 0.1 and 1.0, more preferably between 0.2 and 0.5, and between 0.25 and 0.4. It is particularly preferred.

<< Other Additives for Inkjet Inks >>
In the ink of the present invention, if necessary, various known additives such as ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other performance improvement purposes, for example, , Viscosity modifier, Surface tension modifier, Specific resistance modifier, Film forming agent, Dispersant, Surfactant, Ultraviolet absorber, Antioxidant, Anti-fading agent, Antifungal agent, Rust inhibitor, etc. For example, polystyrene, polyacrylates, polymethacrylates, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, urea resin, or melamine Organic latex such as resin, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil and other oil droplets, ON or nonionic surfactants, UV absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192, JP-A-57-87989, 60-72785, 61-146591, anti-fading agents described in JP-A-1-95091 and 3-13376, JP-A-59-42993, 59-52689, 62- 280069, 61-242871, and JP-A-4-219266, etc., optical brighteners, pH adjusters such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, etc. Can be mentioned.

(latex)
In the inkjet ink of the present invention, latex may be added to the ink. Examples thereof include latex such as styrene-butadiene copolymer, polystyrene, acrylonitrile-butadiene copolymer, acrylic ester copolymer, polyurethane, silicon-acrylic copolymer, and 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.

  Moreover, it is particularly preferable to use soap-free latex in the ink jet ink of the present invention. 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, as latex polymer particles, there are also 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 uniform throughout. However, this type of latex can also be preferably used.

  In the inkjet ink of the present invention, the average particle size of the polymer particles in the latex is preferably 10 nm or more and 300 nm or less, and more preferably 10 nm or more and 100 nm or less. When the average particle size of the latex exceeds 300 nm, the glossiness of the image is deteriorated, and when it is less than 10 nm, the water resistance and scratch resistance become insufficient. The average particle size of the polymer particles in the latex can be determined by a commercially available particle size measuring instrument using a light scattering method, an electrophoresis method, or a laser Doppler method.

  In the inkjet ink of the present invention, the latex is preferably added so that the solid content is 0.1% by mass or more and 20% by mass or less with respect to the total mass of the ink. It is particularly preferable that the content be 0.5 mass% or more and 10% mass% or less. If the amount of latex solids added is less than 0.1% by mass, it is difficult to exert a sufficient effect on the weather resistance, and if it exceeds 20% by mass, the ink viscosity increases over time and the ink storage stability is increased. There are many problems that arise.

(Outgoing stabilizer for thermal)
The ink jet ink of the present invention may be used in a thermal ink jet printer. At this time, in order to solve the clogging of the head called gogging, (M1) 2SO4, CH3COO (M1), Ph-COO (M1), (M1) NO3, ( A salt selected from M1) Cl, (M1) Br, (M1) I, (M1) 2SO3 and (M1) 2CO3 may be added. Here, M1 represents an alkali metal, ammonium or organic ammonium, and Ph represents a phenyl group. Examples of the alkali metal include Li, Na, K, Rb, and Cs. Examples of organic ammonium include methylammonium, dimethylammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, trihydroxymethylamine, dihydroxymethylamine, monohydroxymethylamine, monoethanolammonium, diethanolammonium, and triethanol. Ammonium, N-methylmonoethanolammonium, N-methyldiethanolammonium, monopropanolammonium, dipropanolammonium, tripropanolammonium, etc. are mentioned.

(Crosslinking agent)
The inkjet ink of the present invention may contain a crosslinking agent. Specific examples of the crosslinking agent include, for example, epoxy curing agents (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N-diglycidyl- 4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde curing agents (formaldehyde, glioxal, etc.), active halogen curing agents (2,4-dichloro-4-hydroxy-1,3,5) , -S-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), aluminum alum, boric acid or a salt thereof.

(Anti-fading agent)
In the ink-jet ink of the present invention, a known anti-fading agent can be used in conventional ink-jet inks. This anti-fading agent suppresses fading caused by light irradiation and fading caused by various oxidizing gases such as ozone, active oxygen, NOx, and SOx. Examples of such anti-fading agents include antioxidants described in JP-A-57-74192, JP-A-57-87989, and JP-A-60-72785, and ultraviolet absorbers described in JP-A-57-74193. Hydrazides described in JP-A-61-154989, hindered amine-based antioxidants described in JP-A-61-146591, nitrogen-containing heterocyclic mercapto-based compounds described in JP-A-61-177279, The thioether antioxidants described in 1-115677 and 1-36479, the hindered phenol antioxidants having a specific structure described in JP-A-1-36480, JP-A-7-195824 and 8-150773. Ascorbic acids described in JP-A-7-149037, zinc sulfate described in JP-A-7-314882, Phosphates such as thiourea derivatives described in JP-A-7-314883, saccharides described in JP-A-7-276790 and 8-108617, and phosphate-based antioxidants described in JP-A-8-118791 Examples of the anti-fading agent include nitrites, sulfites, and thiosulfates described in JP-A-8-300807, and hydroxylamine derivatives described in JP-A-9-267544. Furthermore, polycondensates of dicyandiamide and polyalkylene polyamine described in JP-A No. 2000-266928 and the like are also effective anti-fading agents in inkjet.

(PH buffer)
In the inkjet ink of the present invention, a pH buffer agent may be added to the ink. For example, organic acids and inorganic acids. Examples of the organic acid include nonvolatile phthalic acid, terephthalic acid, salicylic acid, benzoic acid, sebacic acid, lauric acid, palmitic acid, ascorbic acid, citric acid, malic acid, lactic acid, succinic acid, succinic acid, and polyacrylic acid. And various organic acids such as benzylic acid.

(Defoamer)
In the inkjet ink of the present invention, an antifoaming agent can be added, and a commercially available product can be used without particular limitation as the antifoaming agent. Examples of such commercially available products include KF96, 66, 69, KS68, 604, 607A, 602, 603, KM73, 73A, 73E, 72, 72A, 72C, 72F, 82F, 70, 71 manufactured by Shin-Etsu Silicone. 75, 80, 83A, 85, 89, 90, 68-1F, 68-2F (trade name), and the like. Although there is no restriction | limiting in particular in the compounding quantity of these compounds, It is preferable to mix | blend 0.001-2 mass% in the ink of this invention. If the compounding amount of the compound is less than 0.001% by mass, bubbles are likely to be generated at the time of preparing the ink, and it is difficult to remove small bubbles in the ink. During printing, repellency may occur in the ink and the print quality may be deteriorated.

(impurities)
In the present invention, when using colorant particles in which pigments and the like are dispersed, it is preferable to reduce the amount of impurities such as ions in the ink in order to inhibit dispersion stability due to the influence of impurities such as ions. . The amount of ions that may be present in monovalent cations such as sodium and potassium, and monovalent anions such as chlorine ions and bromine ions is preferably 2000 ppm or less, more preferably 500 ppm or less. In the case of divalent cations such as calcium ions and magnesium and divalent anions such as sulfate ions, the total amount of each is preferably 50 ppm or less, more preferably 20 ppm or less. The total amount of trivalent or more cation such as aluminum and iron and trivalent or more anion such as phosphoric acid is preferably 5 ppm or less, more preferably 2 ppm or less.

<Preparation of ink>
There is no particular limitation on the preparation of the ink-jet ink of the present invention. However, when an ink containing a dispersion such as a pigment, a disperse dye, inorganic fine particles, or resin fine particles is prepared, no aggregation or sedimentation occurs in the preparation process. Thus, it is preferable to prepare the ink. If necessary, a preparation method such as adjusting the order of addition of the dispersion, solvent, water, photosensitive resin and other additives, and the addition rate can be taken. In addition, for the purpose of stabilizing the dispersion and redispersing the agglomeration generated during the blending of the ink during or after the blending, a dispersion process using a bead mill or ultrasonic waves, a heating process, or the like may be performed.

《Ink physical properties》
(surface tension)
The surface tension of the inkjet ink of the present invention is not particularly limited, but is preferably 24 mN / m or more and 50 mN / m or less. Specific surface tension adjusting means can be adjusted to a desired surface tension by appropriately selecting and adjusting the type and addition amount of the following surfactant or the type and addition amount of the water-soluble organic solvent. .

(viscosity)
The viscosity of the inkjet ink of the present invention is not particularly limited, but is preferably 2 mPa · s or more and 100 mPa · s or less. Moreover, it is preferable that the viscosity of the inkjet ink of the present invention has no speed dependency.

  The ink viscosity (mPa · s) in the present invention is not particularly limited as long as it is tested with a standard solution for calibration of a viscometer specified in JIS Z 8809, and is measured at 25 ° C. according to a known method. As the viscosity measuring device, a rotary, vibration or capillary type viscometer can be used, for example, a Saybolt viscometer, a Redwood viscometer, etc., for example, a cone plate type manufactured by Tokimec E type viscometer, Toki Sangyo E Type Viscometer (rotary viscometer), Tokyo Keiki B type viscometer BL, Yamaichi Denki FVM-80A, Nametor Kogyo Viscoliner VISCO MATE MODEL VM-1A, DD-1 manufactured by Denki Co., Ltd. can be exemplified.

(Electrical conductivity)
In the inkjet ink of the present invention, when a pigment is used as the coloring material, the electrical conductivity is preferably 1 mS / m or more and 500 mS / m or less, more preferably 1 mS / m, from the viewpoint of ink storage stability. m or more and 200 mS / m or less, more preferably 10 mS / m or more and 100 mS / m or less. When the electric conductivity of the ink exceeds 500 mS / m, an emission defect due to deposition of a coloring material occurs. Moreover, if it is 1 ms / m or less, sufficient electrostatic repulsion for allowing the dispersion to exist stably cannot be obtained, and it will also aggregate. Therefore, the dispersion can be stably present by setting the electric conductivity to 1 mS / m or more and 500 mS / m.

  In the ink according to the present invention, there is no particular limitation as a means for achieving a desired electric conductivity. In the present invention, a pigment is used as a coloring material, and a polymer compound (polymer dispersing agent) is used as a pigment dispersant. The method used or a method using an electrical conductivity modifier, for example, an inorganic salt such as potassium chloride, ammonium chloride, sodium sulfate, sodium nitrate, or sodium chloride, or an aqueous amine such as triethanolamine is appropriately selected or combined. Can be achieved.

  The electrical conductivity of the ink can be easily measured according to the method described in JIS K 0400-13-10 (1999) or the method disclosed in Japanese Patent Application Laid-Open No. 61-61164.

(Ion concentration adjustment)
In preparing the inkjet ink of the present invention, it is preferable to adjust the ion concentration as appropriate.

  An aqueous dye solution having a predetermined concentration is measured by ICP-AES, and the ion concentration of the ink state is calculated in terms of the dye concentration used in the ink. By using distilled water or ion-exchanged water, the ion concentration at the time of ink formation can be estimated.

  Next, other additives are added to prepare an ink, and the ion concentration in the ink is measured by ICPAES. When the target ion concentration is exceeded, the ion concentration can be lowered by passing the aqueous dye solution through an ion exchange resin. Ion exchange can be performed a plurality of times to further reduce the ion concentration. If the desired ion concentration is not reached, the additives other than the dye are also subjected to treatment such as ion exchange. Moreover, you may add processes, such as filtration by an activated carbon process or an ultrafiltration membrane, as needed.

(Deaeration treatment)
The dissolved oxygen concentration in the inkjet ink of the present invention is preferably 2 ppm or less, more preferably 1 ppm or less. If the dissolved oxygen concentration in the ink-jet ink exceeds 2 ppm, cavitation occurs when ink is ejected, and emission defects are likely to occur.

  The method for adjusting the dissolved oxygen concentration is not particularly limited. However, as described in JP-A-11-209670, a method for degassing an inkjet ink under reduced pressure, a method for degassing by irradiating ultrasonic waves, and a method for degassing. Examples include a degassing method using a hollow fiber membrane. In particular, degassing with a degassing hollow fiber membrane is preferred.

  Examples of the method for measuring the dissolved oxygen concentration include the Ostwald method (see Experimental Chemistry Course 1, Basic Operation [I], page 241, 1975, Maruzen), the method of measuring by the mass spectrum method, the galvanic cell type, and the polarograph. It can be measured using a simple oxygen concentration meter such as a mold or a colorimetric analysis method. The dissolved oxygen concentration can also be easily measured using a commercially available dissolved oxygen concentration meter (DO-30A type manufactured by Toa Denpa Kogyo Co., Ltd.).

"recoding media"
As the recording medium applicable to the ink jet recording method of the present invention, various papers, various films, various cloths, various woods, various ink jet recording media and the like can be used, but the recording medium is art paper or coated paper, or ordinary paper. If it is paper, the effect is more obtained.

Art paper is coated paper having a coating amount of about 20 g / m ^{2 on} one side, and is generally prepared by applying a pigment to the paper surface and then applying a calendar treatment. There are special art, average art, matte (matte) art, single art (single side coating), double art (double side coating), and more specifically, OK Kanto N, Satin Kanto N, SA Kanou, Ultra Satin Kinto N, OK Ultra Aqua Satin, OK Kanto Single Side, N Art Post, NK Special Side Art, Thunderbird Super Art N, Thunderbird Super Art MN, Thunderbird Art N, Thunderbird Dull Art N, Hi McKinley Art, Hi McKinley Mat, High McKinley Pure Dull Art, Hi McKinley Super Dal, Hi McKinley Mat Elegance, Hi McKinley Deep Mat, etc.

The coated paper is a coated paper having a coating amount of about 10 g / m ^{2 on} one side, and is generally produced by processing with a coating apparatus provided in the middle of the paper machine. The coating amount is smaller than that of art paper, and the smoothness is slightly reduced, but the advantages are low cost and light weight. There is also a type of coated paper with a smaller coating amount, such as a light-weight coat and a finely coated paper. Specific examples of these coated papers include POD gloss coat, OK top coat +, OK top coat S, aurora coat, mu coat, mu white, thunderbird coat N, utrilo coat, pearl coat, white pearl coat, POD mat coat, New Age, New Age W, OK top coat mat N, OK royal coat, OK top coat dull, Z coat, Silver diamond, Ulite, Neptune, Mu mat, White mu mat, Thunderbird mat coat N, Utrilogros mat, New V mat, white new V mat, etc. are mentioned.

  Examples of plain paper include advanced printing paper, intermediate printing paper, lower printing paper, thin printing paper, fine-coating printing paper, special printing paper such as fine-quality printing paper, foam paper, PPC paper, and other information paper. Specifically, there are the following papers and various modified / processed papers using them, but the present invention is not particularly limited to these.

  The paper used as the recording medium according to the present invention includes high-quality paper and colored high-quality paper, recycled paper, copy paper / colored paper, OCR paper, carbonless paper / colored paper, YUPO 60, 80, 110 microns, YUPO COAT 70, Synthetic paper such as 90 microns, other single-sided art paper 68kg, coated paper 90kg, foam mat paper 70, 90, 110kg, foamed PET 38micron, Mitsuori-kun (above, Kobayashi recording paper), OK fine paper, new OK fine paper, Sunflower, Phoenix, OK Royal White, Export Quality Paper (NPP, NCP, NWP, Royal White) OK Book Paper, OK Cream Book Paper, Cream Quality Paper, OK Map Paper, OK Ishikari, Cucumber, OK Form, OKH , NIP-N (above, Shin Oji Paper), Kim Wang, Toko, export quality paper, special demand quality paper, Register paper, book paper L, light cream book paper, small 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 chart, Sylvia HN, excellent form, NPI form DX (above, Nippon Paper), Pearl, Kinryo, Uscream high quality paper, special book paper, super book paper, book paper , Diamond form, inkjet form (Mitsubishi Paper), carpet V, carpet SW, white elephant, high-grade publication paper, cream carpet, cream white elephant, securities / voucher paper, book paper, map paper, copy paper, HNF (above, Hokuetsu Paper) Shirai, phone book cover, book paper, cream shirairai, cream shirairairu, cream shirairaira , DSK (above, Daishowa Paper), Sendai MP fine paper, Nishiki, 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 (Chews), gold sand, reference book paper, replacement paper (white), form printing paper, KRF, white foam, color foam, (K) NIP, fine PPC, Kishu inkjet paper (Kishu Paper) ), Taito, Bright Form, Kant, Kant White, Dante, CM Paper, Dante Comic, Heine, Bunko 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 Sue Par E, New Bright Foam, New Bright NIP (made by Daio Paper), Sun Ring, Moon Ring, Unzen, Galaxy, Baiyun, Weiss, Moon Ring Ace, Baiyun Ace, Unzen Ace (above Nippon Paper Industries), Tai Oh, 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 (Honshu Paper) , Starlinden (A / AW), Star Elm, Star Maple, Star Laurel, Star Poplar, MOP, Star Cherry I, Cherry I Super, Cherry II Super, Star Cherry I I, Star Cherry IV, Cherry III Super, Cherry IV Super (Maruzumi Paper), SHF (Toyo Pulp), TRP (Tokai Pulp), Konica Copy Paper NR-A100 (Konica Minolta Business Technology) ) And the like.

<Inkjet recording method>
The inkjet recording method of the present invention is a method for recording by ejecting the inkjet ink or inkjet ink set of the present invention onto a recording medium. In the present invention, a method in which the ink is further cured by irradiating with active energy rays after being ejected and then dried and recorded is a preferred embodiment.

  Hereinafter, a method for irradiating an inkjet ink with an active energy ray will be described.

[Active energy ray irradiation]
(Active energy rays)
Examples of the active energy rays in the present invention include electron beams, ultraviolet rays, α rays, β rays, γ rays, X-rays, etc., but they are dangerous to the human body and easy to handle. Electron beams and ultraviolet rays that are widely used are preferred. In the present invention, ultraviolet rays are particularly preferable.

  When using an electron beam, the amount of the electron beam to be irradiated is preferably in the range of 0.1 to 30 Mrad. If it is less than 0.1 Mrad, a sufficient irradiation effect cannot be obtained, and if it exceeds 30 Mrad, the support or the like may be deteriorated.

  When ultraviolet rays are used, the light source is, for example, a low pressure, medium pressure, high pressure mercury lamp, metal halide lamp, xenon lamp having a light emission wavelength in the ultraviolet region, cold cathode tube, hot cathode tube having an operating pressure of several hundred Pa to 1 MPa. A conventionally well-known thing, such as LED, is used.

(Light irradiation conditions after ink landing)
As the irradiation condition of the active energy ray, it is preferable that the active energy ray is irradiated for 0.001 to 1.0 seconds after the ink has landed on the recording medium, and more preferably 0.001 to 0.00. 5 seconds. In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible.

(Irradiation method of active energy rays)
As a method for irradiating active energy rays, a basic method is disclosed in Japanese Patent Application Laid-Open No. 60-132767. According to this, the light source is provided on both sides of the head unit, and the head and the light source are scanned by the shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In US Pat. No. 6,145,979, as an irradiation method, a method using an optical fiber or a method of irradiating a recording unit with ultraviolet rays by applying a collimated light source to a mirror surface provided on the side surface of the head unit is disclosed. . Any of these irradiation methods can be used in the inkjet recording method of the present invention.

  Also preferred is a method in which the irradiation of active energy rays is divided into two stages, and the active energy rays are first irradiated by the above-described method within 0.001 to 2.0 seconds after ink landing, and further the active energy rays are irradiated. It is one of. By dividing the irradiation of the active energy ray into two stages, it is possible to further suppress the shrinkage of the recording material that occurs during ink curing.

(Drying after curing)
In the inkjet recording method of the present invention, it is preferable that the inkjet ink discharged onto the recording medium is cured by irradiating with active energy rays and then dried for the purpose of removing unnecessary water-soluble organic solvent. It is.

  The ink drying means is not particularly limited. For example, a method of drying the recording medium by bringing the back surface of the recording medium into contact with a heating roller or a flat heater, a means of blowing hot air on the printing surface with a dryer, or a decompression process. A method for removing volatile components and the like can be appropriately selected or combined.

(Recording head)
The recording head (ink jet print head) to be used may be an on-demand system or a continuous system. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, a thermal type) Examples thereof include an ink jet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.), and a discharge type (for example, a spark jet type). The electro-mechanical conversion method is preferable, but any discharge method may be used.

  Examples of the present invention will be described below.

Example 1
<< Preparation of polymer compound 1 >>
After 100 g of polyacrylic acid (weight average molecular weight 800,000) was dissolved in 750 g of methanol by heating, 16 g of 4-hydroxybutyl acrylate glycidyl ether and 11 g of pyridine as a catalyst were added and stirred for 24 hours while maintaining at 60 ° C. did. Next, the temperature of the system was raised to 95 ° C., and methanol was distilled off while dropping water, followed by treatment with an ion exchange resin (manufactured by Mitsubishi Chemical Corporation, PK-216H). After removing pyridine, diluted with ion exchange water. As a result, a 10% aqueous solution of the polymer compound 1 was obtained.

[Preparation of polymer compound 2]
56 g of glycidyl methacrylate, 48 g of p-hydroxybenzaldehyde, 2 g of pyridine and 1 g of N-nitroso-phenylhydroxyamine ammonium salt were placed in a reaction vessel and stirred in a hot water bath at 80 ° C. for 8 hours. Next, 45 g of a polyvinyl acetate saponified product having a degree of polymerization of 500 and a saponification rate of 88% was dispersed in 225 g of ion-exchanged water, and then 4.5 g of phosphoric acid was added to this solution and p- (3- Methacryloxy-2-hydroxypropyloxy) benzaldehyde was added so that the modification rate was 2 mol% with respect to polyvinyl alcohol, and the mixture was stirred at 90 ° C. for 6 hours. After cooling the obtained solution to room temperature, 30 g of basic ion exchange resin was added and stirred for 1 hour. Thereafter, the ion exchange resin was filtered, and then diluted with ion exchange water to obtain a 10% aqueous solution of polymer compound 2. This polymer compound 2 has a degree of polymerization of 500 and a side chain modification rate of 2 mol%.

[Preparation of polymer compounds 3 to 10]
In the preparation of the polymer compound 2, the degree of polymerization of the polyvinyl acetate saponified product was changed, and the modification rate was adjusted by changing the addition amount of p- (3-methacryloxy-2-hydroxypropyloxy) benzaldehyde. Polymer compounds 3 to 10 having a polymerization degree and a modification rate described in Table 1 were prepared.

[Preparation of polymer compound A-11]
Polymer compound A-11 was prepared in the same manner as in the preparation of polymer compound 2, except that the degree of saponification of the polyvinyl acetate saponified product was 98%.

Preparation of pigment dispersion << Preparation of pigment dispersion >>
(Preparation of black pigment dispersion)
The following additives were mixed and dispersed using a sand grinder filled with 50% by volume of 0.5 mm zirconia beads to prepare a black pigment dispersion having a black pigment content of 12 parts.

  The average particle diameter of the black pigment particles contained in this black pigment dispersion was 72 nm. The particle size was measured using a Zetasizer 1000HS manufactured by Malvern.

Carbon black (manufactured by Mitsubishi Chemical Corporation, MA-7) 12 parts by mass Jonkrill 60 (acrylic styrene resin dispersant, solids by Johnson Co., Ltd., 34% solids) 9 parts by mass Diethylene glycol 15 parts by mass Pure water is added and 100 parts by mass did.

<Preparation of black ink>
[Preparation of black ink 1: pigment ink]
Black pigment dispersion (pigment concentration: 12%) 24 parts by mass 10% aqueous solution of polymer compound 1 20 parts by mass Diethylene glycol 20 parts by mass Diethylene glycol monobutyl ether 8 parts by mass Olphine E1010 (manufactured by Nissin Chemical) 0.2 parts by mass Irgacure (Irg) 2959 (Ciba Specialty Chemicals)
0.3 part by mass 10% aqueous solution of potassium persulfate (KPS) 1 part by mass Pure water was added to make 100 parts by mass.

[Preparation of Black Ink 2: Pigment Ink]
Black ink 2 was prepared in the same manner except that 1 part by mass of a 10% aqueous solution of ammonium persulfate (APS) was used instead of potassium persulfate in the preparation of black ink 1.

[Preparation of black ink 3: pigment ink]
1 g of azoisobutyronitrile (AIBN) is dissolved in 5 g of ethyl acetate, added to 10 g of a 0.1% aqueous solution of sodium dodecyl sulfate, dispersed by ultrasonic dispersion, and then ethyl acetate is removed under reduced pressure. A 10% aqueous dispersion of butyronitrile was prepared. Black ink 3 was prepared in the same manner as in black ink 1 except that 1 part by mass of this dispersion was used instead of potassium persulfate in the preparation of black ink 1.
[Preparation of Black Inks 4 to 6: Pigment Ink]
Black inks 4, 5, and 6 were prepared in the same manner except that polymer compound 2 was used instead of polymer compound 1 in the preparation of black inks 1, 2, and 3.

[Preparation of black ink 7: Pigment ink]
Instead of Irgacure 2959 of black ink 4, Irgacure 500, 0.5 g (manufactured by Ciba Specialty Chemicals) and Irgacure 819W, 0.5 g (manufactured by Ciba Specialty Chemicals) were mixed with 2 g of an ultrasonic dispersion in 10 g of water. The black ink 5 was obtained in the same manner as the black ink 4.

[Preparation of black ink 8-26: pigment ink]
The black ink 8 was added in the same manner as the black ink 4 except that the polymer compound addition amount, the photopolymerization initiator addition amount, and the thermal polymerization initiator addition amount were changed to the amounts shown in Table 1. 26 was prepared.

[Preparation of Black Inks 27 to 29: Pigment Ink]
In addition to changing the polymer compound 2 of the black ink 4 to A-400 (manufactured by Shin-Nakamura Chemical Co., Ltd.), the addition amount of the photopolymerization initiator and the addition amount of the thermal polymerization initiator were adjusted to the amounts shown in Tables 1 and 2. Except for the change, the same procedure was performed as for the black ink 4 to prepare black inks 27 to 29.

[Preparation of Black Inks 30 to 32: Pigment Ink]
The black inks 30 to 32 were used in the same manner as the black inks 27 to 29 except that the black inks 27 to 29 were replaced with UA-W2A (manufactured by Shin Nakamura Chemical Co.) instead of A-400 (manufactured by Shin Nakamura Chemical Co., Ltd.). Prepared.

(Preparation of magenta pigment dispersion)
The following additives were mixed and dispersed using a sand grinder filled with 0.5% zirconia beads at a volume ratio of 50% to prepare a black pigment dispersion having a magenta pigment content of 12 parts. The average particle diameter of the magenta pigment particles contained in this magenta pigment dispersion was 78 nm. The particle size was measured using a Zetasizer 1000HS manufactured by Malvern.

Pigment Red 122 12 parts by mass Jonkrill 70 (acrylic styrene resin dispersant, manufactured by Johnson, solid content 30%) 13 parts by mass Diethylene glycol 15 parts by mass Pure water was added to make 100 parts by mass.

<Preparation of magenta ink>
[Preparation of magenta ink 2: Pigment ink]
Magenta pigment dispersion (pigment concentration: 12%) 24 parts by mass 10% aqueous solution of polymer compound 2 20 parts by mass Diethylene glycol 20 parts by mass 1,2-hexanediol 9 parts by mass Olphine E1010 (manufactured by Nisshin Chemical Co., Ltd.) 0.2 Parts by mass Irgacure 2959 (manufactured by Ciba Specialty Chemicals) 0.3 parts by mass 1 part by mass of a 10% aqueous solution of potassium persulfate Pure water was added to make 100 parts by mass.

[Preparation of magenta ink 2: Pigment ink]
Magenta ink 2 was prepared in the same manner as in the preparation of magenta ink 1, except that 1 part by mass of a 10% aqueous solution of ammonium persulfate was used instead of potassium persulfate.

[Preparation of magenta ink 3: pigment ink]
1 g of azoisobutyronitrile is dissolved in 5 g of ethyl acetate, added to 10 g of a 0.1% aqueous solution of sodium dodecyl sulfate, dispersed by ultrasonic dispersion, ethyl acetate is removed under reduced pressure, and azoisobutyronitrile is removed. A 10% aqueous dispersion was prepared. Magenta ink 3 was prepared in the same manner as magenta ink 1 except that 1 part by mass of this dispersion was used instead of potassium persulfate in the preparation of magenta ink 1.

[Preparation of magenta inks 4 to 6: pigment ink]
Magenta inks 4, 5, and 6 were prepared in the same manner except that polymer compound 2 was used instead of polymer compound 1 in the preparation of magenta inks 1, 2, and 3.

[Preparation of magenta ink 7: Pigment ink]
Instead of magenta ink 4 Irgacure 2959, Irgacure 500, 0.5 g (manufactured by Ciba Specialty Chemicals) and Irgacure 819W 0.5 g (manufactured by Ciba Specialty Chemicals) were mixed with 2 g of ultrasonic dispersion in 10 g of water. Were performed in the same manner as magenta ink 4 to obtain magenta ink 5.

[Preparation of magenta ink 8-26: pigment ink]
The magenta ink 4 was added in the same manner as the magenta ink 4 except that the addition amount of the polymer compound, the addition amount of the photopolymerization initiator, and the addition amount of the thermal polymerization initiator were changed to the amounts shown in Table 1. 26 was prepared.

[Preparation of magenta inks 27 to 29: pigment ink]
In addition to changing the polymer compound 2 of the magenta ink 4 to A-400 (manufactured by Shin-Nakamura Chemical Co., Ltd.), the addition amount of the photopolymerization initiator and the addition amount of the thermal polymerization initiator were adjusted to the amounts shown in Tables 1 and 2. Except for the change, the same procedure was performed as for the black ink 4 to prepare black inks 27 to 29.

[Preparation of Black Inks 30 to 32: Pigment Ink]
The black inks 30 to 32 were used in the same manner as the black inks 27 to 29 except that the black inks 27 to 29 were replaced with UA-W2A (manufactured by Shin Nakamura Chemical Co.) instead of A-400 (manufactured by Shin Nakamura Chemical Co., Ltd.). Prepared.

[Dye ink]
Instead of black ink 2, C.I. I. Food black 2 3 parts by mass, magenta ink 2 instead of C.I. I. In the same manner except that 3 parts by mass of Direct Red 227 was used, black inks 33 to 45 magenta inks 33 to 45 using dyes were prepared using the polymer compounds shown in Table 2.

  The obtained images were evaluated according to the following criteria.

<Image formation>
A piezo head having a nozzle diameter of 25 μm, a driving frequency of 12 kHz, a nozzle number of 128, and a nozzle density of 180 dpi (dpi represents the number of dots per 2.54 cm) is mounted, and 120 W / cm metal halide lamps at both ends of the piezo head. An on-demand ink jet printer having a maximum recording density of 720 × 720 dpi was prepared by arranging (MAL400NL manufactured by Nippon Battery Co., Ltd., power supply power 3 kW · hr). While illuminating a metal halide lamp, on art paper (POD gloss coat made by Oji Paper Co., Ltd.) and fine paper (First Class paper made by Konica Minolta Business Technology Co., Ltd.) After recording the five-step density pattern, it was dried with warm air for 2 minutes using a dryer.

(Bleed evaluation)
An image of a black thin line having a width of 1 mm was observed on a magenta solid surface using a 10 × magnifier, and the following three-level evaluation was performed.

○: The boundary between the fine line and the solid part is clear. △: The blur is observed at the boundary part, but the quality is within the allowable limit for practical use. Poor tolerance (image density)
The black density of the image density at the third stage of each of the five-stage density patterns of the produced art paper and fine paper was measured using X-rite 938 (manufactured by X-rite).

○: Black density of art paper 1.1 or more and black density of fine paper 0.7 or more Δ: Black density of art paper 0.9 to 1.1 or black density of fine paper 0.6 to 0.7
X: Black density of art paper is less than 0.9 and black density of fine paper is less than 0.6 (evaluation of scratch resistance)
In the same manner as the above bleed resistance evaluation, the recording papers were overlapped and rubbed 10 times, and the scratch resistance was evaluated according to the following criteria.

○: No change in the printed image Δ: A small amount of scratches is observed, but the quality is within the practically acceptable limit ×: The formed black thin line image peels off from the recording paper, and the quality is not acceptable at all (Ink storage Sex assessment)
Place 100 ml of black ink in a sealed sample bottle so that it does not evaporate, leave it in a thermostatic bath at 30 ° C. for 3 months, determine the rate of change in the viscosity of the ink, and perform a three-stage evaluation of ○, Δ, × It was. The viscosity of the ink was measured using VISCO MATE MODEL VM-1A manufactured by Yamaichi Electric Co., Ltd.

○: Particle size change rate is 4% or less △: Particle size change rate is 4-8%
X: Particle size change rate is 8% or more. The results are shown in Tables 1 and 2. From Tables 1 and 2, when the ink of the present invention is used, ink storage stability is high, bleeding of art paper, coated paper and plain paper is prevented, and an image having high optical density and high scratch resistance can be obtained. I understand.

Example 2
<Preparation of ink set>
[Preparation of yellow pigment dispersion and cyan pigment dispersion]
In the preparation of the black pigment dispersion of Example 1, C.I. I. Pigment yellow 128, C.I. I. A yellow pigment dispersion and a cyan pigment dispersion were prepared in the same manner except that CI Pigment Blue 15: 3 was used.

[Preparation of ink set 1]
In the same manner as the preparation of the black ink 4 described in Example 1, yellow ink 4 and cyan ink 4 were prepared using a yellow pigment dispersion and a cyan pigment dispersion, respectively.

[Preparation of ink set 2]
Ink set 2 containing no potassium persulfate was prepared in the same manner as ink set 1 except that potassium persulfate was removed from each ink in ink set 1.

[Preparation of ink set 3]
Ink set 3 was prepared in the same manner except that UA-W2A (manufactured by Shin-Nakamura Chemical Co., Ltd.) was used instead of polymer 2 of each ink in ink set 1.

<Image formation>
A piezo head having a nozzle diameter of 25 μm, a driving frequency of 12 kHz, a nozzle number of 128, and a nozzle density of 180 dpi (dpi represents the number of dots per 2.54 cm) is mounted, and 120 W / cm metal halide lamps at both ends of the piezo head. An on-demand ink jet printer having a maximum recording density of 720 × 720 dpi was prepared by arranging (MAL 400NL manufactured by Nippon Battery Co., Ltd., power supply power 3 kW · hr). “High-definition color digital standard image (XYZ / SCID)”, “N3 / fruit” on art paper (POD gloss coat made by Oji Paper) and fine paper (First Class paper made by Konica Minolta Business Technology) while irradiating a metal halide lamp The basket was recorded (issued in 1995 by the Japan Planning Association) and dried in warm air for 2 minutes.

<Evaluation of formed image>
Each image formed using each of the ink sets prepared above was subjected to various evaluations with prevention of bleeding, and the results obtained are shown in Table 3.
(Image density)
The created art paper and high-quality paper color images were shown to 20 panelists to test whether images with contrast could be recognized.

○: More than 80% of panelists recognized as images with sufficient contrast for both art paper and high-quality paper images Δ: Panelers recognized as images with sufficient contrast for both art paper and high-quality paper images %
×: Panel images recognized as sufficiently contrasted images for both art paper and high-quality paper images are less than 40% (density unevenness)
The flatness of apple images of “high-definition color digital standard image (XYZ / SCID)” and “N3 fruit basket” was visually evaluated, and density unevenness was evaluated according to the following criteria.

○: An image having no density unevenness and excellent uniformity Δ: Slight density unevenness is slightly recognized, but is in an acceptable range for practical use ×: Density unevenness is remarkably recognized and not acceptable (Abrasion resistance Evaluation of)
In the same manner as the bleed resistance evaluation, the front and back of each recording paper were overlapped and rubbed 10 times, and the scratch resistance was evaluated according to the following criteria.

○: No change in the printed image Δ: A small amount of scratches is observed, but the quality is within the practically acceptable limit ×: The formed black thin line image is peeled off from the recording paper, and the quality is not acceptable at all. 3 shows. From Table 3, when the ink set of the present invention is used, the ink storage stability is high, bleeding of art paper, coated paper and plain paper is prevented, optical density is high, there is no density unevenness, and images with high scratch resistance are obtained. I can see that

Claims (10)

Contains a coloring material, a polymer compound having a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays, a photopolymerization initiator, and a thermal polymerization initiator An ink jet ink characterized by comprising: 2. The inkjet ink according to claim 1, wherein a content of the thermal polymerization initiator is 5% by mass or more and less than 60% by mass with respect to the photopolymerization initiator. The inkjet ink according to claim 1, wherein the polymer compound is contained in an amount of 0.8% by mass or more and 5.0% by mass or less based on the total mass of the ink. The partial structure of the part which has the said hydrophilic principal chain and the said side chain of the said high molecular compound is represented by the following general formula (A), The any one of Claims 1-3 characterized by the above-mentioned. Inkjet ink.
Formula (A)
Poly-{(X1) m- [B- (Y1) n] p}
[In the formula, Poly represents a hydrophilic main chain, {} represents a side chain, X1 represents a (p + 1) -valent linking group, B represents a crosslinkable group, Y1 represents a hydrogen atom or a substituent. To express. m represents 0 or 1, n represents 0 or 1, and p represents a positive integer. When p is 2 or more, a plurality of B and Y1 may be the same or different. ] The hydrophilic main chain is a saponified product of polyvinyl acetate, having a saponification degree of 77% or more and 99% or less, and a polymerization degree of 200 or more and 4000 or less. The ink for inkjet of any one of Claims. The inkjet ink according to any one of claims 1 to 5, wherein a modification rate of the side chain with respect to the hydrophilic main chain is 1.0 mol% or more and 4.0 mol% or less. . The inkjet ink according to any one of claims 1 to 6, wherein the photopolymerization initiator is water-soluble. An ink-jet ink set comprising ink-jet inks of two or more colors, wherein at least one of the ink-jet inks is the ink-jet ink according to any one of claims 1 to 7. A recording method comprising: recording the ink jet ink according to claim 1 from a nozzle onto a recording medium. A recording method using the inkjet ink set according to claim 8.