JP2007144759A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method which can decide a drying condition in a simple method in forming an image on a recording medium using an aqueous active energy curing ink and can obtain an image having image flatness without luster unevenness. <P>SOLUTION: In the image forming method which is provided with a drying process after a printing process for printing on a recording medium 2 by ejecting an active ray curing ink on the recording medium with an inkjet recording head 3, a luster sensor 1 is used to detect a kind of the recording medium, allowing drying temperature or wind force to be controlled corresponding to the kind of the recording medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming method, and more particularly to an image forming method for recording an image by curing ink by irradiating an aqueous active energy ray.

  The ink jet recording method is a relatively simple apparatus and can record high-definition images, 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 problems, a solventless ultraviolet curable inkjet ink and an inkjet recording method that are cured by irradiating ultraviolet rays have been proposed (for example, see Patent Document 1). In addition, a solvent-based ultraviolet curable ink using a pigment, trifunctional or higher polyacrylate, ketone, and alcohol as main solvents has been proposed (for example, see Patent Document 2).

  In the proposed solvent-free UV curable inkjet ink, since the ink itself is cured, it is possible to record on a non-absorbent recording medium, but it contains a large amount of a curing component other than a coloring material, Moreover, since they do not volatilize, the recorded image surface is raised, and there is a problem that unnaturalness of image quality, particularly glossiness, is caused. Further, the solvent-based ultraviolet curable ink has a problem that it contains a large amount of a volatile organic solvent harmful to the body.

An aqueous ultraviolet curable inkjet ink diluted with water using a water-soluble photopolymerizable monomer or oligomer instead of the solventless ultraviolet curable inkjet ink and solvent-based ultraviolet curable is disclosed (see Patent Documents 3 and 4). . By using these proposed water-soluble UV-curable ink-jet inks, a flat image without image swell can be obtained and a glossy image can be obtained. On the other hand, since it contains water, it has penetrability. Depending on the type of recording medium, the drying time differs between the recording medium and the non-permeable recording medium, and the gloss differs even when dried under the same conditions. It was necessary to change the conditions, and a simple method for determining the drying conditions was awaited.
U.S. Pat. No. 4,228,438 Japanese Patent Publication No. 5-64667 JP-A-7-224241 JP 2004-285161 A

  An image forming method in which drying conditions can be determined by a simple method when forming an image on a recording medium using an aqueous active energy curable ink, and an image having high gloss and no curling can be obtained. Is to provide. It is another object of the present invention to provide an image forming method capable of obtaining an image having good light emission and preventing bleeding when an ink to which a specific polymer compound is further added is used.

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

  1. An image forming method in which an actinic ray curable ink is ejected onto a recording medium from an ink jet recording head and printing is performed on the recording medium, and then a drying process is provided. The gloss sensor detects the type of the recording medium, An image forming method comprising controlling a drying temperature or wind force according to a type of a recording medium.

  2. 2. The image forming method according to 1 above, wherein the gloss sensor makes the drying temperature of the recording medium with high glossiness, the wind force higher than the drying temperature of the recording medium with low glossiness, or the wind speed.

  3. 3. The image forming method according to 1 or 2 above, wherein the total ink film thickness after the actinic ray curable ink is landed and cured by irradiation with a lamp is 0.2 to 2 μm.

  4). Use at least a colorant, water, a polymer having a plurality of side chains in the hydrophilic main chain, and a polymer compound and a photopolymerization initiator that can be cross-linked between the side chains by irradiation with active energy rays. 4. The inkjet image forming method according to any one of 1 to 3 above.

  5. 5. The image forming method as described in 4 above, wherein the partial structure of the hydrophilic main chain and the side chain is represented by the following general formula (A).

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. ]
That is, as a result of sincerity studies, the present inventor determined the type of the recording medium by the gloss sensor when the actinic ray curable ink was ejected from the ink jet recording head onto the recording medium and printed on the recording medium. By detecting and controlling the drying temperature or wind force according to the type of the recording medium, it was found that an image having no gloss unevenness and maintaining image flatness can be obtained regardless of the type of the recording medium.

  In the image forming method according to the present invention, when forming an image on a recording medium using a water-based active energy curable ink, drying conditions can be determined by a simple method, and there is no unevenness of gloss, and image flatness. Is obtained, and an excellent effect is obtained.

  Hereinafter, the present invention will be described in detail.

  In the present invention, when the type of the recording medium is detected by the gloss sensor and an image is formed on the recording medium by inkjet, the gloss flatness is maintained and the image flatness is maintained according to the type of the recording medium. It is characterized by controlling the drying temperature or wind power.

《Gloss sensor》
A gloss sensor is a detector that measures the glossiness of a recording medium.For example, if the reflectance is high by applying light to the surface of the recording medium and measuring the reflectance, the gloss sensor is not a non-coated material such as a polyester film. If it is a permeable recording medium and the reflectance is low, it can be determined as a permeable recording medium such as plain paper or high-quality paper. A specific example of the sensor is a fiber gloss sensor E3X-NL manufactured by OMRON.

  The position where the gloss sensor is attached is not particularly limited from the paper feed unit to immediately before the dryer, but is preferably between the paper feed unit and the ink jet nozzle.

  When the gloss sensor recognizes that the recording medium is a non-permeable recording medium, the drying temperature and the wind speed are made higher than the drying conditions of the permeable recording medium. Preferably, the drying temperature is 40 ° C. or higher and the wind speed is high, and conversely, when it is recognized that the recording medium is permeable, the drying temperature is lower than that of the non-permeable recording medium. Reduce the wind speed. It is preferable to select conditions where the drying temperature is 30 ° C. or lower and the wind speed is low.

<Water-based actinic ray curable ink>
The water-based actinic ray curable ink as used in the present application is defined as an ink containing water as a main component and containing at least a compound capable of being cross-linked or polymerized by irradiation with active energy rays and a coloring material.

  A compound that can be cross-linked or polymerized by irradiation with active energy rays is a water-soluble compound, for example, a compound having a water-soluble skeleton as a repeating unit such as vinyl alcohol, acrylamide, acrylic acid, ethylene glycol, etc. It is a compound having an acryl group, a methacryl group, an azide group, a diazo group, or the like that crosslinks between side chains when irradiated with active energy rays. Specific examples include UA-W2A, A-Gly-20E manufactured by Shin-Nakamura Chemical Co., Ltd., or polyvinyl alcohol in which an acrylic group, a methacryl group, or an azide group is pendant. With respect to the molecular weight, if it has the above repeating units, a molecular weight of 800 or more can provide a sufficient effect, but it is preferably 2000 or more.

  The compound that can be crosslinked or polymerized by irradiation with active energy rays according to the present invention is preferably contained in an amount of 0.8% by mass to 20% 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. When the content is 20% 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 viewpoints of light emission properties and ink storage stability.

Moreover, it is preferable that the total ink film thickness after irradiating and hardening | curing with a lamp | ramp is 0.2-2 micrometers. When the thickness is 0.2 μm or less, the permeable recording medium among the recording media does not allow the ink to remain on the surface, so that the effect of improving the gloss is hardly recognized. Among these active energy ray crosslinkable or polymerizable compounds, the load becomes large and becomes impractical. The hydrophilic main chain has a plurality of side chains, and crosslinks between the side chains by irradiating active energy rays. A possible polymer compound (hereinafter abbreviated as an active energy ray crosslinkable polymer) is preferable. This active energy ray crosslinkable polymer is a saponified product of polyvinyl acetate, polyvinyl acetal, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, or the hydrophilic Photodimerization type, photodecomposition type, photopolymerization type, photomodification type, photodepolymerization type, etc. in the side chain for resin derivatives and at least one hydrophilic resin selected from the group consisting of these copolymers The modified group is introduced. Photopolymerizable crosslinkable groups are desirable from the viewpoints of sensitivity and performance of the generated image.

  There is a preferred combination between the ionicity of the colorant and the ionicity of the side chain of the polymer compound. An anionic colorant is selected as the coloring material, and a nonionic or anionic property is combined with the side chain, which is preferable from the viewpoints of image fastness, ink storage stability, and continuous emission. The side chain is most preferably nonionic.

  What the partial structure of the hydrophilic main 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 particularly preferable.

Formula (A)
Poly-{(X1) m- [B- (Y1) n] p}
In the general formula (A), Poly represents a hydrophilic main chain. Saponified product of polyvinyl acetate, polyvinyl acetal, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, or a derivative of the hydrophilic resin, and copolymers thereof Is preferred.

  {} 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 more preferably 1.0 mol% or more and 3.0 mol% or less from the viewpoint of reactivity. If it is less than 1.0 mol%, the crosslinkability is insufficient and the effect of the present invention is reduced. If it is more than 4.0 mol%, the crosslink density increases and the film becomes hard and brittle, resulting in a decrease in film strength.

  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, R ₃ represents a methyl group or a hydrogen atom, and R ₄ 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.

  Why, when inks using these active energy ray crosslinkable polymer compounds and gloss sensors are used to form images by changing the drying conditions for each recording medium, the light emission is good, bleeding is prevented, and uneven gloss The reason why an image with image flatness can be obtained is not clear, but since the active energy ray-crosslinkable polymer compound has a sufficiently large molecular weight before cross-linking, it is slightly affected by irradiation with the active energy ray. Even cross-linking causes a large increase in ink viscosity, prevents bleeding and makes it difficult to penetrate into the recording medium, thus maintaining image flatness. For this reason, it is thought that the maximum effect can be obtained by grasping the permeability of the recording medium in advance using a gloss sensor and selecting a drying method suitable for the recording medium.

<< Photopolymerization initiator, sensitizer >>
In the present invention, it is also preferable to add a photopolymerization initiator or a sensitizer. These compounds may be dissolved or dispersed in a solvent, or may be chemically bonded to the photosensitive resin.

  There is no restriction | limiting in particular about the photoinitiator and photosensitizer which are applied, A conventionally well-known thing can be used.

1) Benzophenones such as benzophenone, hydroxybenzophenone, bis-N, N-dimethylaminobenzophenone, bis-N, N-diethylaminobenzophenone, 4-methoxy-4'-dimethylaminobenzophenone, and salts thereof 2) Thioxanthone, 2 Thioxanthones such as 4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, isopropoxychlorothioxanthone, and salts thereof 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, bisphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide 11) 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-) Propyl) ketone, and these ethylene oxide adducts and mixtures thereof are preferably used, and the above may be used alone or in combination. Moreover, the form added to an ink can be added as a dissolved material or a dispersion.

  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.

《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 the ink 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 agent)
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 Silicon. 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》
(Ink 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 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 measurement of the electrical conductivity of the ink in the present invention should be easily performed according to the method described in JIS K 0400-13-10 (1999) or the method disclosed in JP-A-61-61164. Can do.

(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.).

(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 high-definition images, it is especially important that the irradiation timing is as early as possible (drying after curing)
In the inkjet recording method of the present invention, the inkjet ink ejected onto the recording medium is cured by irradiating it with active energy rays, and then dried for the purpose of removing unnecessary water-soluble organic solvents and the like.

  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.

(recoding media)
The recording medium used in the present invention is a recording medium made of a material such as plain paper, recycled paper, glossy paper, etc., various fabrics, various non-woven fabrics, resin, metal, glass, etc., applied to a normal ink jet image recording apparatus. The medium 4 is applicable. Moreover, as a form of the recording medium 4, a roll shape, a cut sheet shape, a plate shape, or the like is applicable. In particular, as the recording medium 4 used in the present embodiment, a transparent or opaque non-absorbent resin film used for soft packaging can be applied. Specific resin types of resin films include polyethylene terephthalate, polyester, polyolefin, polyamide, polyesteramide, polyether, polyimide, polyamideimide, polystyrene, polycarbonate, poly-ρ-phenylene sulfide, polyether ester, polyvinyl chloride. , Poly (meth) acrylic acid ester, polyethylene, polypropylene, nylon and the like are applicable, and further, copolymers of these resins, mixtures of these resins, and those obtained by crosslinking these resins are also applicable. Above all, as the type of resin of the resin film, one of stretched polyethylene terephthalate, polystyrene, polypropylene, and nylon is selected because of the transparency, dimensional stability, rigidity, environmental load, cost, etc. of the resin film. It is preferable to use a resin film having a thickness of 2 μm to 100 μm (preferably 6 μm to 50 μm). Moreover, you may perform surface treatments, such as a corona discharge process and an easily bonding process, on the surface of the support body of resin films. Further, as the recording medium 4 used in the present embodiment, a known opaque recording medium 4 such as various papers whose surfaces are coated with a resin, a film containing a pigment, and a foamed film can be applied.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited to these examples.

Example 1
<< Preparation of polymer compound >>
[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, after raising the temperature of the system to 95 ° C. and distilling off methanol while dripping water, an ion exchange resin (manufactured by Mitsubishi Chemical Corporation, PK-216H) treatment is performed to remove pyridine and the non-volatile concentration is reduced. A 15% aqueous solution was obtained. As a photopolymerization initiator, 0.5 g of Irgacure 500 and 0.5 g of Irgacure 819W (manufactured by Ciba Specialty Chemicals) were mixed in an ultrasonic dispersion in 10 g of water, and then diluted with ion-exchanged water. As a result, a 10% aqueous solution of 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. As a photopolymerization initiator, 0.5 g of Irgacure 500 and 0.5 g of Irgacure 819W (manufactured by Ciba Specialty Chemicals) were mixed in an ultrasonic dispersion in 10 g of water, and then diluted with ion-exchanged water. As a result, a 10% aqueous solution of polymer compound 2 was obtained. This polymer compound 2 has a degree of polymerization of 500 and a side chain modification rate of 2 mol%.

[Preparation of polymer compound 3]
Polymer 3 was synthesized in the same manner as in the synthesis method of polymer compound 2, except that the degree of polymerization was changed to 300 and the modification rate of the side chain was changed to 3 mol%.

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 76 nm. The particle size was measured using a Zetasizer 1000HS manufactured by Malvern.

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

<Preparation of black ink>
[Preparation of Black Ink 1: Pigment Ink]
Black pigment dispersion (pigment concentration: 12%) 24 parts by weight 10% aqueous solution of polymer compound 1 20 parts by weight Ethylene glycol 10 parts by weight Glycerin 5 parts by weight Diethylene glycol monobutyl ether 10 parts by weight Olphine E1010 0.2 parts by weight Pure water In addition, the amount was 100 parts by mass.

[Preparation of yellow pigment dispersion, cyan pigment dispersion, and magenta pigment dispersion]
In the preparation of the black pigment dispersion of Example 1, C.I. I. Pigment yellow 128, C.I. I. Pigment red 122, C.I. I. A yellow pigment dispersion, a cyan pigment dispersion, and a magenta pigment dispersion were prepared in the same manner except that CI Pigment Blue 15: 3 was used.

(Ink set 1)
A yellow ink, a cyan ink, and a magenta ink were prepared using a yellow pigment dispersion, a cyan pigment dispersion, and a magenta pigment dispersion, respectively, instead of the black pigment dispersion of the black ink 1 to prepare ink set 1.

(Ink set 2)
Ink set 2 was prepared in the same manner except that polymer compound 2 was used instead of polymer compound 1 prepared in ink set 1.

(Ink set 3)
Ink set 3 was prepared in the same manner except that polymer compound 3 was used instead of polymer compound 1 prepared in ink set 1 (ink set 4).
Ink set 4 was prepared in the same manner except that UA-W2A (manufactured by Shin-Nakamura Chemical Co., Ltd.) (manufactured by Shin-Nakamura Chemical Co., Ltd.) was used in place of polymer compound 1 prepared in ink set 1.

<Image formation>
(recoding media)
The following recording media having different glossiness were prepared.

Plain paper: KM250A4MP manufactured by Konica Minolta Business Technology
Fine paper: CF paper manufactured by Konica Minolta Business Technology Co., Ltd. Cast coated paper: Esprit coat manufactured by Nippon Paper Industries Co., Ltd. Pet film: Toyobo Co., Ltd. Ester film E5000 thickness 75 μm
As a result of measuring the gloss of each recording medium, the gloss was plain paper <high quality paper <art paper <pet film.
(Image forming method)
As shown in FIG. 1, an Omron fiber gloss sensor E3X-NL is installed between the paper feed unit and the head. The head has a nozzle diameter of 25 μm, a driving frequency of 12 kHz, a number of nozzles of 128, a nozzle density of 180 dpi (note that dpi is Piezo head that represents the number of dots per 2.54 cm). A printer in which 120 W / cm metal halide lamps (MAL400NL power supply power 3 kW · hr manufactured by Nippon Battery Co., Ltd.) were arranged on both ends of the piezo head was produced. The dryer produced the warm air fan heater using the heater provided with the heating wire, and the propeller type fan.

  Based on this information, while irradiating a metal halide lamp, each recording medium was imaged of a magenta thin line having a width of 150 μm on a yellow solid, “high-definition color digital standard image (XYZ / SCID)”, “N3 fruit When recording and drying the “Cage” (issued in 1995 by the Japan Planning Association), the signal detected by the gloss sensor is divided into 5 levels from the smallest, as shown in the table, dryer temperature and fan speed. Controlled.

Stage Dryer temperature Fan speed 1 30 ° C 100rpm
2 30 ° C 300rpm
3 45 ° C 300rpm
4 45 ° C 600rpm
5 60 ° C 600rpm
The obtained images were evaluated according to the following criteria.
(Emission evaluation)
Using the ink prepared above, intermittent operation of continuous ejection for 10 seconds → pause for a fixed time → continuous emission was performed by the above recording method. At this time, since whether or not the discharge direction is disturbed at the beginning after the discharge pause is determined by the length of the pause time, the stability of intermittent emission was measured by changing the length of the discharge pause time stepwise. .

  ○: All inks were stably emitted even after a pause of 20 seconds or longer.

  Δ: Stable emission even after 10 seconds to 30 seconds pause, but disturbance occurred in the emission direction when at least one ink was paused for 30 seconds or more.

  X: When it was allowed to stand for 10 seconds, it could not be stably emitted with at least one ink.

(Bleed evaluation)
A black thin line image with a width of 150 μm is visually evaluated on a yellow solid area. ○: The boundary line between the thin line and the solid line is clear. △: Blur is observed at the boundary part, but the quality is within the practically acceptable limit. ×: The quality of the boundary between the thin line and the solid part is unclear, and the bleed resistance is poor (gloss unevenness)
The flatness of apple images of “high-definition color digital standard image (XYZ / SCID)” and “N3 fruit basket” was visually evaluated, and gloss unevenness was evaluated according to the following criteria.

A: An image having no gloss unevenness and excellent uniformity. Δ: A slight gloss unevenness is observed, but in a practically acceptable range.

  X: Gloss unevenness is noticeable and is not acceptable.

(Evaluation of image flatness)
The flatness of the images of “high-definition color digital standard image (XYZ / SCID)” and “N3 / fruit basket” was visually evaluated. ○: The recording medium was kept flat and no wrinkles were observed.

  Δ: A small amount of wrinkles and twists are observed.

  X: Wrinkles and twists are clearly observed, and a plurality of sheets cannot be stacked uniformly.

  In addition, as a dye instead of a pigment, C.I. I. Food Black 2, C.I. I. Acid Yellow 23, C.I. I. Direct Red 227, C.I. I. Ink was prepared using Direct Blue 199, and similar results were obtained.

  As is clear from the above results, when the image recording method of the present invention is used, appropriate drying conditions are selected depending on the type of the recording medium, so that the emission stability is stable, and regardless of the recording medium, It can also be seen that bleeding can be prevented, and glossy unevenness and an image maintaining the flatness of the recording medium can be easily obtained.

It is the schematic which occupies an example which irradiates an optical sensor to the recording medium of this invention, and controls the temperature of a dryer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gloss sensor 2 Recording medium 3 Head 4 Light source 5 Dryer

Claims (5)

An image forming method in which an actinic ray curable ink is ejected onto a recording medium from an ink jet recording head and printing is performed on the recording medium, and then a drying process is provided. The gloss sensor detects the type of the recording medium, An image forming method comprising controlling a drying temperature or wind force according to a type of a recording medium. 2. The image forming method according to claim 1, wherein the gloss sensor makes the drying temperature of the recording medium with high glossiness and the wind force higher than the drying temperature of the recording medium with low glossiness or the wind speed. The image forming method according to claim 1, wherein the total ink film thickness after the actinic ray curable ink has landed and cured by irradiation with a lamp is 0.2 to 2 μm. Use at least a colorant, water, a polymer having a plurality of side chains in the hydrophilic main chain, and a polymer compound and a photopolymerization initiator that can be cross-linked between the side chains by irradiation with active energy rays. The inkjet image forming method according to any one of claims 1 to 3. The image forming method according to claim 4, wherein the partial structure of the hydrophilic main chain and the side chain is represented by the following general formula (A).
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. ]

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