JP4525574B2 - Inkjet recording method and inkjet ink set - Google Patents

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 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 ultraviolet monomer or oligomer instead of the solventless ultraviolet curable ink or the solvent-based ultraviolet curable ink is disclosed (for example, Patent Documents 3 and 4). reference.). Certainly, by using these proposed aqueous UV curable inkjet inks, a flat image without image swell can be obtained, but as long as the disclosed water-soluble UV curable monomer or oligomer is used, bleeding prevention is achieved. In order to cause possible gelation, a large amount of energy is required, and even if a sufficient amount of light that can be gelled is applied, a low molecular weight UV curable monomer or oligomer is used, The stickiness of the image due to the uncured component remaining in a trace amount was generated, and when the formed images were overlapped, the defect that the images were peeled off could not be solved.

  The present inventors have disclosed an inkjet ink that uses a polymer compound in which at least one of the water-soluble polymers has a plurality of side chains in the hydrophilic main chain and is crosslinked between the side chains by irradiation with active energy rays. The amount of energy required to achieve bleed prevention can be reduced, and the molecular weight is higher than that of the monomer or oligomer used in the aqueous ultraviolet curable inkjet ink described in the above-mentioned patent document. It has been proposed that it has the characteristics that it can prevent the occurrence and sticking in the superimposed images.

However, the crosslinking reaction between polymer compounds having a plurality of side chains in the hydrophilic main chain related to the present invention and cross-linking between the side chains by irradiating with active energy rays is a radical such as a photopolymerization initiator. Since the cross-linking is generated, problems such as cavitation may occur due to the fact that the reaction is inhibited by oxygen and the repeated pressurization and depressurization generated in the ink jet nozzle. As a countermeasure, it is known that solvent-free ultraviolet curable ink-jet ink, solvent-based ultraviolet curable ink, and aqueous ultraviolet curable ink-jet ink remove dissolved oxygen and dissolved air in the ink. In addition, there is a proposal that the emission performance is improved by removing dissolved oxygen and dissolved air in the ink. (For example, refer to Patent Document 5.)
Therefore, in order to reduce dissolved oxygen, it is generally performed to reduce the oxygen concentration of the gas around the ink. Therefore, the oxygen concentration in the atmosphere between the time when the ink lands on the recording medium and the time when the ink is cured with actinic rays is reduced. It is self-evident that oxygen inhibition is reduced and curing becomes easier.

However, when using a polymer compound having a plurality of side chains in the hydrophilic main chain used in the present invention and capable of cross-linking between side chains by irradiating active energy rays, oxygen is excessively removed. As a result, a phenomenon occurs in which the glossiness of the image, particularly the image clarity (hereinafter referred to as image clarity gloss), deteriorates.
U.S. Pat. No. 4,228,438 Japanese Patent Publication No. 5-64667 JP-A-7-224241 JP 2004-285161 A JP 2004-196936 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an ink jet recording method capable of obtaining an image having excellent light-emitting properties, excellent image clarity and excellent bleed resistance.

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

1. In an inkjet recording method in which an inkjet ink containing a coloring material, water, and a polymer compound is ejected from at least one nozzle for recording, the polymer compound has a plurality of side chains in a hydrophilic main chain, and an active energy It is a polymer compound that can be cross-linked between side chains by irradiating a line, and the inkjet ink contains the polymer compound 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. And an atmosphere in which actinic rays are irradiated to the recording medium on which the ink has landed is maintained at an oxygen concentration of 0.5% to 12% (v / v). Recording method.
2. In an inkjet recording method in which an inkjet ink containing a coloring material, water, and a polymer compound is ejected from at least one nozzle for recording, the polymer compound has a plurality of side chains in a hydrophilic main chain, and an active energy The atmosphere in which actinic rays are irradiated onto a recording medium that is a polymer compound that can be cross-linked between side chains by irradiation of an ink and that has landed on an ink is 0.5% to 12% (v / V), and the oxygen concentration at the time of curing is higher than the oxygen concentration at the time of landing.
3. 3. The ink jet recording method according to 2, wherein the polymer compound is contained in an amount of 0.8% by mass to 5.0% by mass with respect to the total mass of the ink.
4). The inkjet recording method according to any one of 1 to 3, 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. ]
5. The hydrophilic main chain is a saponified product of polyvinyl acetate, the saponification degree is 77 mol% or more and 99 mol% or less, and the polymerization degree is 200 or more and 4000 or less, The inkjet recording method according to any one of the above.
6). 6. The inkjet recording method 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 water-soluble photopolymerization initiator is contained, The inkjet recording method of any one of 1-6 characterized by the above-mentioned.
8. An ink jet ink comprising two or more ink jet inks, wherein at least one of the ink jet inks is an ink used in the ink jet recording method according to any one of 1 to 7. set.

  According to the present invention, there is provided an ink jet recording method which has excellent light-emitting properties, glossiness, image glossiness, image uniformity (reduction in gloss difference between image areas and non-image areas), sharpness (edge sharpness), and bleed resistance. Can be provided.

As a result of intensive studies in view of the above problems, the present inventor has a plurality of side chains in at least a coloring material, water, and a hydrophilic main chain, and crosslinks between the side chains by irradiating active energy rays. The atmosphere in which the actinic ray is irradiated onto the recording medium landed with the ink jet ink using a possible polymer compound is maintained at an oxygen concentration of 0.5% to 12% (v / v) ; and At that time, the inkjet ink contains the polymer compound 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, or the oxygen concentration at the time of curing rather than the oxygen concentration at the time of landing. By adjusting so that the image quality becomes higher, it is possible to realize an ink jet image with excellent emission characteristics, excellent bleeding resistance and image gloss, and excellent image uniformity (reduction in gloss difference between the image area and the non-image area). Heading, present invention Led was is up.

  Hereinafter, the present invention will be described in more detail.

  In the present invention, it is not clear whether the image gloss is improved when the oxygen concentration is adjusted to this range, but it has a plurality of side chains in water and the hydrophilic main chain, and by irradiating active energy rays, When a polymer compound that can be cross-linked between chains is used, the molecular weight before cross-linking is already sufficiently large, so that a large increase in viscosity occurs even when cross-linking is performed at a small number of places. When excessively dissolved oxygen is removed, a rapid crosslinking reaction occurs on the surface by irradiation with active energy rays. On the other hand, since the crosslinking is slowed by absorption of active energy rays inside, the crosslinking speed is different between the surface and the inside, and as a result, irregularities are formed on the surface, resulting in poor image clarity. Under moderate oxygen concentration atmosphere, it causes moderate oxygen inhibition in the vicinity of the surface and slows the curing rate of the surface. As a result of deep absorption due to absorption of active energy rays, the curing rate is canceled and it cures uniformly. I think it will be like that.

  More preferably, the atmosphere should be maintained at an oxygen concentration of 2% to 8% (v / v).

  As a means for controlling the oxygen concentration in the atmosphere, a method in which all the image forming apparatuses are closed to make a nitrogen atmosphere, or a method in which nitrogen, carbon dioxide, water vapor or the like is ejected from a nozzle to lower the oxygen concentration in the vicinity. There is no particular limitation such as a method in which air is separated and ejected from the difference in transmittance with respect to the hollow fiber membrane, but from the viewpoint of a simple printer, a method in which the oxygen concentration in the vicinity is lowered by ejecting from the nozzle is preferable. More preferably, the oxygen concentration in the vicinity of the active energy ray irradiating device is made smaller than the oxygen concentration at the ink landing location by a method such as disposing a nitrogen gas ejection nozzle near the active energy ray irradiating device. Is preferred. Since the oxygen in the air is in an equilibrium state with the oxygen in the ink, the oxygen distribution in the landed ink dots is lower than the reverse when the oxygen concentration in the air gradually decreases. I think it is because it has become uniform.

  The oxygen concentration can be easily measured using a commercially available oxygen concentration meter. For example, a digital oximeter XO-326AL manufactured by New Cosmos Electric Co., Ltd. may be used.

<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 preferred combination between the ionicity of the colorant 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 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. Represents an integer of ~ 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 ink head, which is preferable from the viewpoint of the emission property and the ink storage property.

<< 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, However, It is preferable from a viewpoint of mixing property and reaction efficiency that it is a water-soluble compound. 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 thioxanthone, 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.

《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. 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. The content is particularly preferably 0.5% by mass or more and 10% by 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) 2SO ₄ , CH ₃ COO (M1), Ph-COO (M1), (M1) disclosed in JP 2001-81379 A A salt selected from NO ₃ , (M1) Cl, (M1) Br, (M1) I, (M1) 2SO ₃ and (M1) 2CO ₃ 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》
(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 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, the electrostatic repulsion for making a dispersion exist stably is not fully obtained, but 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.

(Ink safety)
The active energy ray-reactive compound used in the present invention preferably has low or no mutagenicity, acute toxicity, sensitization and the like.

"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. Or coated paper) or a non-absorbent recording medium.

[Coated paper for printing]
Coated paper for printing is coated paper often used in printing. Generally, high-quality paper or medium-quality paper is used as the base paper, and after applying a pigment such as clay on the surface of the paper, smoothness is improved. Therefore, it is produced by applying a calendar process. Such processing improves whiteness, smoothness, print ink acceptability, halftone dot reproducibility, print gloss, print opacity, and the like. Depending on the amount of coating, there are classifications such as art paper, coated paper, lightweight coated paper, etc., and it is classified into glossy, dull, matte, etc. depending on the gloss of the paper. From the perspective that can be demonstrated without
Art paper or coated paper is preferred.

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 less 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.

[Non-absorbent recording medium]
As the non-absorbable recording medium, all commonly used various films can be used. For example, there are a polyester film, a polyolefin film, a polyvinyl chloride film, a polyvinylidene chloride film, and the like. Resin-coated paper that is photographic printing paper or YUPO paper that is synthetic paper can also be used.

<Inkjet recording method>
The inkjet recording method of the present invention is characterized in that the inkjet ink or inkjet ink set of the present invention is ejected onto a recording medium, the active energy rays are irradiated to cure the ink, and then dried.

  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, 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, 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.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, the embodiment of this invention is not limited to these examples. In the examples, “%” represents mass% unless otherwise specified.

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. Here, n = 1 Irgacure 2959 (manufactured by Ciba Specialty Chemicals Co., Ltd.) of the general formula (9) as a photopolymerization initiator was mixed at a ratio of 0.1 g with respect to 100 g of a 15% aqueous solution, and then mixed with ion-exchanged water. To obtain a 10% aqueous solution of polymer compound 1.

[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. Here, as a photopolymerization initiator, n = 1 Irgacure 2959 (manufactured by Ciba Specialty Chemicals Co., Ltd.) of general formula (9) was mixed at a rate of 0.1 g with respect to 100 g of a 15% aqueous solution, and then ion-exchanged water was used. Dilution was performed 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, except that the degree of modification was adjusted by changing the polymerization degree and saponification degree of the polyvinyl acetate saponified product and further changing the addition amount of p- (3-methacryloxy-2-hydroxypropyloxy) benzaldehyde. In the same manner, polymer compounds 3 to 10 having the polymerization degree and the modification rate shown in Table 1 were prepared.

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 0.5% zirconia beads at a volume ratio of 50% to prepare a black pigment dispersion having a black pigment content of 16 parts. The average particle diameter of the black pigment particles contained in this black pigment dispersion was 96 nm. The particle size was measured using a Zetasizer 1000HS manufactured by Malvern.

Carbon black (manufactured by Mitsubishi Chemical Corporation, MA-7) 16 parts by mass Jonkrill 63 (acrylic styrene resin dispersant, manufactured by Johnson, solid content 30%)
15 parts by mass Diethylene glycol Pure water was added to the remaining 15 parts by mass to make 100 parts by mass << Preparation of Black Ink >>
[Preparation of Black Ink 2: Pigment Ink]
Black pigment dispersion (pigment concentration: 16%) 24 parts by mass 10% aqueous solution of polymer compound 2 20 parts by mass Diethylene glycol 20 parts by mass 1,2-pentanediol 8 parts by mass Olphine E1010 (manufactured by Nisshin Chemical Co., Ltd.) 0.2 Part by mass Pure water was added to make 100 parts by mass.

(Preparation of magenta 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 pigment content of 12 parts. The particle size was measured with a Zetasizer 1000HS manufactured by Malvern.

Pigment Red 122 12 parts by weight Jonkrill 70 (acrylic styrene resin dispersant, manufactured by Johnson) 3 parts by weight Diethylene glycol 15 parts by weight Pure water was added to the rest to make 100 parts by weight << 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-pentanediol 8 parts by mass Olphine E1010 (manufactured by Nisshin Chemical Co., Ltd.) 0.2 Part by mass Pure water was added to make 100 parts by mass.

  Similarly, as shown in Table 2, aqueous ultraviolet curable black inks 1 and 3 to 13 and aqueous ultraviolet curable magenta inks 1 and 3 to 13 in which only the polymer compound was changed were prepared.

  Black ink and magenta ink are paired in the same manner except that NK ester A-400 (manufactured by Shin-Nakamura Chemical Co., Ltd.) or UA-W2A (manufactured by Shin-Nakamura Chemical Co., Ltd.) is used instead of polymer compound 2. Water-based UV curable inks 14 to 15 were prepared.

[Dye ink]
Instead of black ink 2, C.I. I. 4 parts by weight of food black 2, C. instead of magenta ink 2 I. Except for using 3 parts by mass of Direct Red 227, similarly, the polymer compounds shown in Table 1 were used to produce water-based UV curable black inks 16 to 23 and water-based UV curable magenta inks 16 to 23 using dyes. did.

  Similar to black ink 16 and magenta ink 16 except that NK ester A-400 (manufactured by Shin-Nakamura Chemical Co., Ltd.) or UA-W2A (manufactured by Shin-Nakamura Chemical Co., Ltd.) was used instead of polymer compound 2. Thus, black ink 24.25 and magenta ink 24.25 were respectively produced.

<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 a MAL400NL power supply power (3 kW · hr, manufactured by Nippon Battery Co., Ltd.) and a hot air dryer (60 ° C. fan 700 rpm). Also, as shown in the figure, the nitrogen release nozzle was set to face the metal halide lamp between the metal halide lamp and the dryer.

  While irradiating the metal halide lamp, each magenta ink was discharged, and a magenta solid image and a magenta thin line image were recorded on art paper (NK Art Kanfuji N, manufactured by Oji Paper).

  The amount of nitrogen gas ejected from the nitrogen nozzle was controlled to control the oxygen concentration directly under the metal halide lamp. The oxygen concentration immediately under irradiation was measured with a digital oximeter XO-326AL manufactured by New Cosmos Electric Co., Ltd.

(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. .

  ○: Stable light was emitted even after a pause of 30 seconds or more.

  (Triangle | delta): Although it radiate | emitted stably even if it pauses for 15 seconds or more and 30 seconds, disorder | damage | failure occurred in the radiation | emission direction when it paused for 30 seconds or more.

  X: When it was left for 15 seconds, it could not be emitted stably.

(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 (evaluation of mapping gloss)
Evaluation Magenta solid sample images were measured for image clarity (C value) with a reflection angle of 60 ° and an optical comb of 2 mm using an ICM-1DP (manufactured by Suga Test Instruments Co., Ltd.). A stage evaluation was performed.

○: C value greater than 68 Δ: C value greater than 60, 68 or less ×: C value 60 or less (Abrasion resistance evaluation)
The image portion and the back surface of each magenta solid image produced above were overlapped and rubbed 10 times, and the degree of density reduction of the image portion was classified as follows.

○: There is almost no color fading. Δ: Color fading can be confirmed, and the image quality is degraded.

X: The color fading is large and the influence on the image quality is great. As shown in Table 1, when the ink of the present invention is used, as shown in Table 1, the emission property is excellent, the bleeding is excellent, and the image clarity is good. It can be seen that the gloss is excellent and scratch resistance is obtained.

Example 2
<Preparation of ink set>
[Preparation of yellow pigment dispersion and cyan pigment dispersion]
Instead of preparing the magenta 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]
An ink set 1 was prepared in the same manner as in Example 1, except that the magenta pigment dispersion of magenta ink 2 described in Example 1 was replaced with a yellow pigment dispersion or a cyan pigment dispersion.

[Preparation of ink set 2]
Ink set 2 was produced in the same manner except for NK ester A-400 (manufactured by Shin-Nakamura Chemical Co., Ltd.) instead of polymer compound 2 used in ink set 1.

<Image formation>
Using the same light emitting device as in Example 1, on a piece of art paper (NK Art Kanfuji N, manufactured by Oji Paper), a black thin line image with a width of 1 mm on a magenta solid and a high-definition color digital standard data “N5 bicycle (Japan Planning Association, issued in December 1995).

  The same image evaluation as in Example 1 was performed.

  However, only the image uniformity was performed by the following method.

(Evaluation of image uniformity)
The image part and non-image part of the produced color image “N5 / bicycle” were visually observed, and the image uniformity was evaluated according to the following criteria.

○: There is no difference in gloss between the printed part and the non-printed part, and the image is excellent in uniformity. △: A slight difference in gloss is recognized between the printed part and the non-printed part, but the image is almost uniform. Yes: There is a sense of incongruity between the printed part and the non-printed part, and the image is uneven

  As described above, it can be seen that when the ink of the present invention is used, it is possible to obtain an image having good light emission properties, good bleeding prevention, good image clarity and good scratch resistance.

It is the schematic which shows an example of the method of manufacturing the recording medium of this invention.

Explanation of symbols

1 Nozzle 2 UV irradiation device 3 Nitrogen release nozzle 4. Dryer

Claims (8)

In an inkjet recording method in which an inkjet ink containing a coloring material, water, and a polymer compound is ejected from at least one nozzle for recording, the polymer compound has a plurality of side chains in a hydrophilic main chain, and an active energy It is a polymer compound that can be cross-linked between side chains by irradiating a line, and the inkjet ink contains the polymer compound 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. And an atmosphere in which actinic rays are irradiated to the recording medium on which the ink has landed is maintained at an oxygen concentration of 0.5% to 12% (v / v). Recording method. In an inkjet recording method in which an inkjet ink containing a coloring material, water, and a polymer compound is ejected from at least one nozzle for recording, the polymer compound has a plurality of side chains in a hydrophilic main chain, and an active energy The atmosphere in which actinic rays are irradiated onto a recording medium that is a polymer compound that can be cross-linked between side chains by irradiation of an ink and that has landed on an ink is 0.5% to 12% (v / V), and the oxygen concentration at the time of curing is higher than the oxygen concentration at the time of landing. The inkjet recording method according to claim 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. The inkjet recording method according to any one of claims 1 to 3, 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. ] The hydrophilic main chain is a saponified product of polyvinyl acetate, the saponification degree is 77 mol% or more and 99 mol% or less, and the polymerization degree is 200 or more and 4000 or less. 5. The ink jet recording method according to any one of 4 above. The inkjet recording method 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 recording method according to claim 1, further comprising a water-soluble photopolymerization initiator. An ink jet ink comprising two or more ink jet inks, wherein at least one of the ink jet inks is an ink used in the ink jet recording method according to any one of claims 1 to 7. set.

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