JP2007138072A - Inkjet ink, inkjet ink set and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain inkjet ink that has printability on various recording media, forms an image having excellent color bleeding resistance, beading resistance and image gloss and does not cause paper undulation in recording on a paper medium such as coated paper for printing, etc., and an inkjet ink set and to provide an inkjet recording method. <P>SOLUTION: The inkjet ink comprises at least water, a thiol and a polymer compound that has a plurality of side chains on a hydrophilic main chain and is crosslinkable and bondable between side chains by irradiation with an active energy ray. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inkjet ink containing an active energy ray-reactive polymer compound, an inkjet ink set, and an inkjet recording method using the inkjet ink set.

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

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

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

  In response to the above problems, a hot melt ink composition made of a solid wax or the like at room temperature is used, liquefied by heating or the like, sprayed with some energy applied, cooled and solidified while adhering to the recording medium, and recorded A hot melt type ink jet recording method for forming dots has been proposed (see Patent Documents 1 and 2). Since this hot melt ink is solid at room temperature, it does not get dirty during handling, and since there is substantially no ink evaporation during melting, nozzle clogging does not occur. Furthermore, it is said to be an ink composition that provides good print quality regardless of paper quality because it solidifies immediately after adhesion and has little color bleeding. However, an image recorded by such a method has problems such as deterioration in quality due to the rising of the dots and insufficient scratch resistance because the ink dots are in the form of soft wax.

  On the other hand, an inkjet recording ink that is cured by irradiation with active energy rays has been disclosed (see Patent Document 3). In addition, a so-called non-aqueous ink containing a pigment as a coloring material, a triacrylate or higher polyacrylate as a polymerizable material, and having a ketone or alcohol as a main solvent has been proposed (see Patent Document 4). . An aqueous active energy ray-curable ink jet recording ink composition containing a polyurethane compound, a basic compound, a colorant, a water-soluble organic solvent and water containing a group having an active energy ray-curable unsaturated double bond Has been proposed (see Patent Document 5). Furthermore, a water-based inkjet ink comprising a self-dispersing pigment having one or more hydrophilic groups bonded to the surface of pigment particles, an ultraviolet curable monomer made of a vinyl compound, a photopolymerization initiator, and water. It has been proposed (see Patent Document 6).

In these proposed active energy ray reactive inks, since the ink itself is cured by a curing component, it is possible to record on a non-absorbent recording medium, but the image forming portion and the non-image portion (white background portion) ) Produces an unnatural and uncomfortable image quality due to a difference in glossiness from the above), and as a result, the image uniformity is impaired. Furthermore, when a part of these proposed active energy ray reactive inks is recorded on a paper-based medium such as coated paper for printing, swell (cockling) occurs in the recording medium, and in some cases, conveyance failure occurs. It turns out that it causes, and immediate improvement is required.
US Pat. No. 4,391,369 U.S. Pat. No. 4,484,948 U.S. Pat. No. 4,228,438 Japanese Patent Publication No. 5-64667 JP 2002-80767 A JP 2002-275404 A

  The present invention has been made in view of the above problems, and an object of the present invention is to have printability on various recording media, and an image excellent in color bleed resistance, beading resistance and image gloss can be obtained. It is another object of the present invention to provide an inkjet ink, an inkjet ink set, and an inkjet recording method that do not cause paper swell even when recording on a paper medium such as coated paper for printing.

  The above object of the present invention can be achieved by the following constitution.

  1. An ink-jet ink comprising at least water, thiol, and a polymer compound having a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays.

  2. 2. The inkjet ink according to 1, wherein the thiol content is 0.1% by mass or more and 10% by mass or less.

  3. 3. The inkjet ink according to 1 or 2, wherein the hydrophilic main chain of the polymer compound capable of crosslinking between the side chains is a saponified product of polyvinyl acetate.

  4). Any one of 1 to 3, wherein a modification rate of the side chain with respect to the hydrophilic main chain of the polymer compound capable of cross-linking between the side chains is 0.8 mol% or more and 4.0 mol% or less. The inkjet ink of Claim 1.

  5. The inkjet ink according to any one of claims 1 to 4, wherein the polymer compound capable of cross-linking between the side chains has a degree of polymerization of a hydrophilic main chain of 200 or more and 500 or less.

  6). The ink-jet ink according to any one of 1 to 5, wherein the content of the polymer compound capable of crosslinking between the side chains is 0.8% by mass or more and less than 5% by mass.

  7. An inkjet ink set comprising two or more inkjet inks, wherein at least one of the inkjet inks is the inkjet ink according to any one of 1 to 6.

  8. An ink jet recording method comprising discharging the ink jet ink according to any one of 8.1 to 6 onto a recording medium, irradiating the ink jet ink with active energy rays, and drying the ink.

  An inkjet recording method comprising: discharging an inkjet ink constituting the inkjet ink set according to 9.7 onto a recording medium, irradiating the inkjet ink with active energy rays, and drying the inkjet ink.

  10. 10. The ink jet recording method according to 8 or 9, wherein the apparatus for irradiating the active energy ray is a low pressure mercury lamp.

  11. 10. The ink jet recording method according to 8 or 9, wherein the device for irradiating the active energy ray is an LED.

  12 The inkjet recording method according to any one of 8 to 11, wherein the recording medium is a paper medium.

  13. 13. The inkjet recording method according to 12, wherein the paper medium is a coated paper for printing.

  14 10. The ink jet recording method according to 8 or 9, wherein the device for irradiating the active energy ray is a low-pressure mercury lamp or LED, and recording is performed on a coated paper for printing.

  According to the present invention, an image having printability on various recording media and excellent in color bleeding resistance, beading resistance and image gloss can be obtained, and further recorded on a paper medium such as a coated paper for printing. In some cases, it is possible to provide an inkjet ink, an inkjet ink set, and an inkjet recording method that do not cause undulation of paper.

  Hereinafter, although the best mode for carrying out the present invention will be described, the present invention is not limited to these.

  As a result of intensive studies in view of the above problems, the present inventor has a plurality of side chains in water, thiol, and hydrophilic main chain, and can be crosslinked between the side chains by irradiating active energy rays. An ink jet ink containing at least a polymer compound, or an ink jet ink set including the ink jet ink and an ink jet recording method using the ink jet ink have printability on various recording media, color bleed resistance, beading resistance and image It has been found that an image having excellent gloss can be obtained, and that an ink jet ink, an ink jet ink set, and an ink jet recording method that do not cause paper swell even when recorded on a paper medium such as coated paper for printing can be realized. It is up to the present invention.

  Details of the present invention will be described below.

  The inventor has studied various ink-jet inks and processing methods thereof. Water, thiol, and a hydrophilic main chain have a plurality of side chains and are irradiated with active energy rays to crosslink between the side chains. It has been found that an ink jet ink containing at least a bondable polymer compound has excellent ink curability, no color bleeding and beading, and an excellent gloss image.

The cause of the dramatic improvement in ink curability is not limited to the following estimation,
1. The active energy ray-crosslinking type polymer compound has a significantly larger effect on increasing the molecular weight per photon than the conventionally known active energy ray-curable resin produced by polymerizing monomers through a general chain reaction. 2. Since the ink contains thiol, which is a chain transfer agent, it is considered that the two effects of preventing the inhibition of the curing reaction by oxygen work synergistically in the ink curing process during irradiation with active energy rays. It is done.

  In addition, the ink using a conventionally known active energy ray curable compound is a component that is involved in curing almost all of the materials other than the color material, so the dots after curing rise, and the image quality represented by gloss is significantly deteriorated. On the other hand, the ink used in the present invention is considered to exhibit excellent gloss due to high smoothness after drying because the amount of the crosslinkable polymer compound used is small and there are many dry components.

  Furthermore, the inventor also applied the ink-jet ink, ink-jet ink set, and ink-jet ink recording of the present invention to the swell of paper that occurs when recording the active energy ray-curable ink on a paper medium such as coated paper for printing, so-called cockling. It was found that this can be prevented by the method.

  As a result of inventor's various analyzes on the cause of cockling that occurs when recording on coated paper for printing, the high-intensity high-pressure mercury lamp often used in conventionally known active energy ray-curable inks It was found that it contributed greatly to. That is, the high-pressure mercury lamp is a light source that generates a large amount of heat with respect to the amount of irradiation light, and particularly when a high-intensity mercury lamp is used, the amount of heat applied to the recording medium becomes very large. As a result, it has been estimated that water contained in the applied ink or water originally contained in the coated paper for printing is volatilized and cockling occurs due to deformation of the paper fibers.

  Based on the above analysis, when the active energy ray to be irradiated was changed to a high-pressure mercury lamp with low illuminance, or a low-pressure mercury lamp or LED with little heat generation, it was found that cockling of the coated paper for printing was reduced. However, these light sources have drawbacks that the ink curability is greatly lowered due to factors such as low output and the fact that the wavelength region of the light source overlaps with the absorption wavelength of the color material contained in the ink. . In response to this problem, the inventor combined the inkjet ink having the excellent curability with the light source, and recorded on the coated paper for printing. It was discovered that the record that does not occur is possible.

  As described above, the recording method using the inkjet ink of the present invention and irradiating the light source is particularly effective for recording on the coated paper for printing, but the recording method of the present invention is not necessarily limited thereto. . The ink-jet ink of the present invention having excellent curability may be used in combination with various conventionally known light sources, and the recording medium may be plain paper, film, cloth, etc. other than coated paper for printing. I do not care.

  Next, the inkjet ink according to the present invention will be described. In the inkjet ink of the present invention (hereinafter, also simply referred to as ink), a polymer compound having a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays (hereinafter, referred to as “ink”). It is also characterized by containing a crosslinkable polymer compound).

<Crosslinkable polymer compound>
By applying the crosslinkable polymer compound according to the present invention to ink, it exhibits sufficient curability by irradiation with low energy active energy rays, the resolution of the formed image is high, the gloss is good, and the color An ink-jet ink can be obtained with less bleeding.

  Next, the crosslinkable polymer compound according to the present invention will be described.

  The hydrophilic main chain of the crosslinkable polymer compound according to the present invention includes saponified polyvinyl acetate, polyvinyl acetal, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid, hydroxyethyl cellulose, methyl cellulose, hydroxy And propyl cellulose.

  Among these, when the hydrophilic main chain is a saponified product of polyvinyl acetate, the introduction of the side chain is simplified and the handleability is improved. The degree of polymerization of the main chain is preferably in the range of 200 or more and 2000 or less, but the degree of polymerization is particularly preferably 200 or more and 500 or less from the viewpoint of sufficiently achieving the object effect of the present invention. If the degree of polymerization is 200 or more, a moderate increase in viscosity during the crosslinking reaction can be imparted, and color bleed and beading described later can be sufficiently prevented. If the degree of polymerization is 2000 or less, an increase in viscosity when added to the ink can be suppressed, and good emission stability can be obtained.

  For the side chain, a modifying group such as a photodimerization type, a photodecomposition type, a photopolymerization type, a photomodification type, and a photodepolymerization type can be introduced. From the viewpoint of reactivity with the color material to be combined, the side chain is preferably nonionic, anionic, or amphoteric (betaine compound). Particularly, when the color material is combined with an anionic dye or an anionic pigment, the side chain is It is preferably nonionic or anionic, and particularly preferably nonionic.

  The modification rate of the side chain with respect to the hydrophilic main chain is preferably 0.8 mol% or more and 4.0 mol% or less, and more preferably 1.5 mol% or more and 3.0 mol% or less. More preferable from the viewpoint of reactivity. If the modification rate of the side chain with respect to the hydrophilic main chain is 0.8 mol% or more, it has sufficient crosslinkability, and the object effect of the present invention can be obtained. On the other hand, if it is 4.0 mol% or less, the crosslinking density is appropriate, so that a flexible image film can be easily obtained and the film strength is particularly good.

  As the photodimerization-type modifying group, those in which a diazo group, a cinnamoyl group, a stilbazonium group, a stilquinolium group or the like is introduced are preferable. For example, a photosensitive resin described in JP-A-60-129742 (Composition).

  The photosensitive resin described in JP-A-60-129742 is a compound represented by the following general formula (1) in which a stilbazonium group is introduced into a polyvinyl alcohol structure.

In the formula, R ₁ represents an alkyl group having 1 to 4 carbon atoms, and A ⁻ represents a counter anion.

  The photosensitive resin described in JP-A-56-67309 includes a 2-azido-5-nitrophenylcarbonyloxyethylene structure represented by the following general formula (2) in the polyvinyl alcohol structure, or the following general formula. This is a resin composition represented by (3) and having a 4-azido-3-nitrophenylcarbonyloxyethylene structure.

  Further, a modifying group represented by the following general formula (4) 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 represented by the following general formula (5) shown 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—, and Y represents an aromatic ring or a single bond. And m represents an integer from 0 to 6.

  Moreover, it is also preferable to use the photopolymerization type | mold modified group represented by following General formula (6) 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.

  In such an active energy ray-crosslinked polymer compound, the main chain originally having a certain molecular weight is cross-linked between the side chains through a cross-linking bond. The effect of increasing the molecular weight per photon is remarkably large compared to a conventionally known active energy ray-curable resin produced by polymerization.

  Furthermore, since ink using a conventionally known active energy ray-curable resin is a component that is involved in curing almost all of the materials other than the color material, the dots after curing rise and the image quality represented by gloss is significantly deteriorated. On the other hand, the ink-jet ink according to the present invention requires a small amount of the crosslinkable polymer compound and has a large amount of dry components, so that the image quality after drying is improved and the fixability is also good.

  The addition amount in the ink of 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 0.8% by mass or more. 5.0% by mass or less is preferable.

  If the addition amount is within this range, the crosslinking efficiency is improved, and the ink is ejected from the head and adhered to the base material, and then crosslinked, so that the viscosity of the ink after crosslinking is rapidly increased and the beading resistance and color bleed resistance are increased. Will improve. When the addition amount is less than 0.8%, the objective effect of the present invention obtained due to insufficient crosslinkability is reduced, and when it exceeds 5.0%, the ink viscosity increases and affects intermittent emission stability. Sometimes.

  In the inkjet ink of the present invention, when using a polymer compound having a photopolymerizable modifying group, it is preferable to use a known photopolymerization initiator, and it is particularly preferable to use a water-soluble photopolymerization initiator.

  As a water-soluble photopolymerization initiator applicable to the ink jet ink of the present invention, a compound represented by the following general formula (7) is preferable from the viewpoint of compatibility with a polymer compound and sensitivity.

In the formula, n represents an integer of 1 to 5.
The photopolymerization initiator is preferably grafted to the side chain with respect to the hydrophilic main chain of the polymer compound according to the present invention.

  Next, the thiol contained in the inkjet ink of the present invention will be described.

《Thiol》
Any thiol may be used in the present invention, but polyfunctional thiol is preferable from the viewpoint of improving ink curability. Moreover, what shows solubility with respect to water and a water-soluble organic solvent is preferable. Examples of such thiol compounds include 1,2-ethanedithiol, 2-mercaptoethyl ether, 2,3-dimercapto-1-propanol, 1,5-pentanedithiol, 1,6-hexanedithiol, 3,6 -Dioxa-1,8-octanedithiol, triglycol dimercaptan, α, ω-dimercaptopolyethylene oxide, trimethylolpropane tris (3-mercaptopropionate), trimethylolpropane tris (2-mercaptoacetate), pentaerythritol Examples thereof include tetrakis (3-mercaptopropionate), pentaerythritol tetrakis (2-mercaptoacetate), 1,2,6-hexanetriol trithioglycolate and the like.

  The amount of thiol to be added is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% with respect to the total amount of ink. If the amount is less than 0.1% by mass, the effects of the present invention may not be sufficiently obtained. If the amount exceeds 10% by mass, problems such as deterioration in film physical properties of images and generation of odor derived from low-molecular thiols contained as impurities may occur. There is a fear.

  Next, other components of the inkjet ink of the present invention will be described.

《Coloring material》
As the coloring material used in the inkjet ink of the present invention, a dye or a pigment can be used.

  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.

  Specific examples of dyes applicable to the ink jet ink of the present invention are listed below, but the present invention is not limited to these exemplified dyes.

  Examples of water-soluble dyes that can be used in the present invention include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, and diphenylmethane dyes.

<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.

  Furthermore, examples of the dye include a compound represented by the following general formula (8) or a compound represented by the general formula (9).

In the general formula (8), R ₁ represents a hydrogen atom or a substitutable substituent, and is preferably a hydrogen atom or a phenylcarbonyl group. R ₂ may be different and represents a hydrogen atom or a substitutable substituent, and is preferably a hydrogen atom. R ₃ represents a hydrogen atom or a substitutable substituent, and is preferably a hydrogen atom or an alkyl group. R ₄ represents a hydrogen atom or a substitutable substituent, preferably a hydrogen atom or an aryloxy group. R ₅ may be different and represents a hydrogen atom or a substitutable substituent, and is preferably a sulfonic acid group. n represents an integer of 1 to 4, and m represents an integer of 1 to 5.

In the general formula (9), X represents a phenyl group or a naphthyl group, may be substituted with a substitutable substituent, and is preferably substituted with a sulfonic acid group or a carboxyl group. Y represents hydrogen ion, sodium ion, potassium ion, lithium ion, ammonium ion or alkylammonium ion. R ₆ may be different and represents a hydrogen atom or a substituent that can be substituted on the naphthalene ring. q represents 1 or 2. p represents an integer of 1 to 4. However, q + p = 5. Z represents a substitutable substituent, and represents a carbonyl group, a sulfonyl group or a group represented by the following general formula (10), and particularly preferably a group represented by the following general formula (10).

In the general formula (10), W ₁ and W ₂ each independently represent a halogen atom, amino group, hydroxyl group, alkylamino group or arylamino group, preferably a halogen atom, hydroxyl group or alkylamino group.

(Disperse dye)
As the disperse dye, various disperse dyes such as azo disperse dyes, quinone disperse dyes, anthraquinone disperse dyes, quinophthalone disperse dyes can be used, and specific compounds thereof are listed below.

<C. I. Disperse Yellow>
3, 4, 5, 7, 9, 13, 23, 24, 30, 33, 34, 42, 44, 49, 50, 51, 54, 56, 58, 60, 63, 64, 66, 68, 71, 74, 76, 79, 82, 83, 85, 86, 88, 90, 91, 93, 98, 99, 100, 104, 108, 114, 116, 118, 119, 122, 124, 126, 135, 140, 141, 149, 160, 162, 163, 164, 165, 179, 180, 182, 183, 184, 186, 192, 198, 199, 202, 204, 210, 211, 215, 216, 218, 224, 227, 231, 232,
<C. I. Disperse Orange>
1, 3, 5, 7, 11, 13, 17, 20, 21, 25, 29, 30, 31, 32, 33, 37, 38, 42, 43, 44, 45, 47, 48, 49, 50, 53, 54, 55, 56, 57, 58, 59, 61, 66, 71, 73, 76, 78, 80, 89, 90, 91, 93, 96, 97, 119, 127, 130, 139, 142,
<C. I. Disperse Red>
1, 4, 5, 7, 11, 12, 13, 15, 17, 27, 43, 44, 50, 52, 53, 54, 55, 56, 58, 59, 60, 65, 72, 73, 74, 75, 76, 78, 81, 82, 86, 88, 90, 91, 92, 93, 96, 103, 105, 106, 107, 108, 110, 111, 113, 117, 118, 121, 122, 126, 127, 128, 131, 132, 134, 135, 137, 143, 145, 146, 151, 152, 153, 154, 157, 159, 164, 167, 169, 177, 179, 181, 183, 184, 185, 188, 189, 190, 191, 192, 200, 201, 202, 203, 205, 206, 207, 210, 221, 224, 225, 227, 229, 23 , 240,257,258,277,278,279,281,288,298,302,303,310,311,312,320,324,328,
<C. I. Disperse Violet>
1, 4, 8, 23, 26, 27, 28, 31, 33, 35, 36, 38, 40, 43, 46, 48, 50, 51, 52, 56, 57, 59, 61, 63, 69, 77,
<C. I. Disperse Green>
9,
<C. I. Disperse Brown>
1, 2, 4, 9, 13, 19,
<C. I. Disperse Blue>
3, 7, 9, 14, 16, 19, 20, 26, 27, 35, 43, 44, 54, 55, 56, 58, 60, 62, 64, 71, 72, 73, 75, 79, 81, 82, 83, 87, 91, 93, 94, 95, 96, 102, 106, 108, 112, 113, 115, 118, 120, 122, 125, 128, 130, 139, 141, 142, 143, 146, 148, 149, 153, 154, 158, 165, 167, 171, 173, 174, 176, 181, 183, 185, 186, 187, 189, 197, 198, 200, 201, 205, 207, 211, 214, 224, 225, 257, 259, 267, 268, 270, 284, 285, 287, 288, 291, 293, 295, 297, 301, 315, 3 0,333,
<C. I. Disperse Black>
1, 3, 10, 24
Etc.

  These dyes listed above are described in “Dyeing Note 21st Edition” (published by Color Dyeing Co., Ltd.) and the like.

  In addition, chelate dyes and azo dyes used for silver dye bleach (silver dye bleaching) photosensitive materials (for example, Cibachrome manufactured by Ciba Geigy) can be used.

  Chelating dyes are described, for example, in British Patent No. 1,077,484. As for azo dyes for silver dye bleaching photosensitive materials, for example, British Patent Nos. 1,039,458, 1,004,957, 1,077,628, U.S. Pat. 612,448.

  Examples of the pigment that can be used in the present invention include conventionally known organic or inorganic pigments. For example, azo pigments such as azo lake pigments, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc. Polycyclic pigments, dye lakes such as basic dye type lakes and acid dye type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, daylight fluorescent pigments, and inorganic pigments such as carbon black .

  Hereinafter, specific examples of the pigment applicable to the ink-jet ink of the present invention will be listed, but the present invention is not limited only to these exemplified pigments.

  Examples of magenta or red pigments 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 orange or yellow pigments include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150, pigment yellow 180, and the like.

  Examples of green or cyan pigments 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 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  Examples of the pigment for black include carbon black.

(Self-dispersing pigment)
In the ink-jet ink of the present invention, a self-dispersing pigment can also be used as a pigment. The self-dispersing pigment refers to a pigment that can be dispersed without a dispersant, and particularly preferably pigment particles having a polar group on the surface.

  Pigment particles having a polar group on the surface are pigments directly modified with a polar group on the surface of the pigment particle, or organic substances having an organic pigment mother nucleus and having a polar group bonded directly or via a joint , Referred to as pigment derivative).

  Examples of the 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 sulfonic acid group.

  Examples of a method for obtaining pigment particles having a polar group on the surface include WO97 / 48769, JP-A-10-110129, JP-A-11-246807, JP-A-11-57458, and 11-189739. By making the surface of pigment particles described in JP-A-11-323232, JP-A-2000-265094, etc. with an appropriate oxidizing agent, polarities such as sulfonic acid groups or salts thereof are formed on at least a part of the pigment surface. The method of introduce | transducing group is mentioned. Specifically, it is prepared by oxidizing carbon black with concentrated nitric acid or, in the case of color pigments, by oxidizing with sulfamic acid, sulfonated pyridine salt, amidosulfuric acid, etc. in sulfolane or N-methyl-2-pyrrolidone. can do. In these reactions, the pigment dispersion can be obtained by removing and purifying the substance that has been excessively oxidized and becomes water-soluble. Moreover, when a sulfonic acid group is introduced onto the surface by oxidation, the acidic group may be neutralized with a basic compound as necessary.

  Other methods include a method of adsorbing the pigment derivative described in JP-A-11-49974, JP-A-2000-273383, JP-A-2000-303014, etc. on the pigment particle surface by a treatment such as milling, and the like. Examples include a method of dissolving the pigment described in 2002-179777, 2002-201401, etc. together with a pigment derivative in a solvent and then crystallization in a poor solvent, and any method can easily polarize the surface. Pigment particles having groups can be obtained.

  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 (eg, lithium, sodium, potassium, magnesium, calcium, aluminum, nickel, ammonium) and organic salts (eg, triethylammonium, diethylammonium, pyridinium, triethanolammonium, etc.). A counter salt having a monovalent valence is preferable.

(Method for producing pigment dispersion)
As a method for dispersing the pigment, for example, various dispersing machines 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. It is also preferable to use a centrifugal separator or a filter for the purpose of removing the coarse particles of the pigment dispersion.

(Surfactant applicable to pigment dispersion)
In preparing the pigment dispersion, if necessary, a surfactant or a polymer dispersant may be contained as a pigment dispersant. The type of surfactant and polymer dispersant is not particularly limited. Examples of the surfactant include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, and naphthalene sulfonates. , Alkyl phosphate, polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide and the like As the polymer dispersant, a water-soluble resin is preferably used from the viewpoint of ejection stability. For example, styrene, a styrene derivative, a vinyl naphthalene derivative, acrylic acid, an acrylic acid derivative, maleic acid, maleic acid. acid Examples include conductors, itaconic acid, itaconic acid derivatives, fumaric acid, block copolymers composed of two or more monomers selected from fumaric acid derivatives, random copolymers, and salts thereof. Styrene-acrylic acid-alkyl acrylate ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid-alkyl acrylate copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid-acrylic acid Examples thereof include an alkyl ester copolymer, a styrene-methacrylic acid copolymer, a styrene-maleic acid half ester copolymer, a vinyl naphthalene-acrylic acid copolymer, and a vinyl naphthalene-maleic acid copolymer.
The amount of each polymer dispersant added to the total amount of the ink is preferably 0.1 to 10% by mass, more preferably 0.3 to 5% by mass. Two or more of these polymer dispersants can be used in combination.

(Particle size of pigment particles)
The particle size of the pigment particles includes the particle size (primary particle size) obtained by directly observing the particles with an electron microscope, and the dispersed particle size (secondary particle size) using a particle size measuring device utilizing light scattering. There is a viscosity-converted particle size obtained from the intrinsic viscosity.

  The primary particle diameter of the pigment in the ink of the present invention is preferably 10 nm or more and 1000 nm or less, more preferably 10 nm or more and 70 nm, from the viewpoint of light resistance and dispersion stability. If the thickness is smaller than 10 nm, the light resistance is not deteriorated. If the thickness is larger than 100 nm, the head is clogged due to aggregation. Here, in order to obtain primary particles, the major axis of 1000 pigment particles is measured with a transmission electron microscope, and the average value (number average) can be obtained.

"solvent"
In the inkjet ink of the present invention, it is preferable to use a water-soluble organic solvent. Examples of the water-soluble organic solvent that can be used in the present invention include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl). Alcohol), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol Etc.), polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, ethylene glycol) Ether monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl 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, etc.), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, mole) Phosphorus, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N , N-dimethylacetamide, etc.), heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides ( For example, dimethyl sulfoxide etc.), sulfones (for example, sulfolane etc.), urea, acetonitrile, acetone etc. are mentioned. Preferable water-soluble organic solvents include polyhydric alcohols. Furthermore, it is particularly preferable to use a polyhydric alcohol and a polyhydric alcohol ether in combination.

  The water-soluble organic solvent may be used alone or in combination. The total amount of the water-soluble organic solvent added to the ink is 5 to 60% by mass, preferably 10 to 35% by mass.

<Inkjet ink set>
The inkjet ink set of the present invention is composed of inkjet inks of three colors or four colors or more.

  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, an ink jet ink set composed of at least two inks of the same color having different densities in at least one color ink may be used. Furthermore, in two or more inks, an ink jet ink set composed of at least two same color inks having different densities may be used. In particular, in three or more color inks, at least two inks having the same color having different densities may be used. It is preferable from the point of gradation property to use the inkjet ink set comprised. 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 inkjet ink sets having different densities may be any value. However, in order to achieve smooth gradation reproduction, the ratio of high density ink to low density ink (color density of low density ink / high density) The ink colorant density) 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.

(White ink)
In the inkjet ink set of the present invention, a white ink containing a white pigment may be used in addition to the colored pigment. The white pigment used is not particularly limited as long as it makes the inkjet ink white, and examples thereof include inorganic white pigments, organic white pigments, and white hollow polymer fine particles.

  Examples of inorganic white pigments include sulfates of alkaline earth metals such as barium sulfate, carbonates of alkaline earth metals such as calcium carbonate, silicas such as fine silicate, synthetic silicate, calcium silicate, alumina , Alumina hydrate, titanium oxide, zinc oxide, talc, clay and the like. In particular, since titanium oxide has a high refractive index, it is fine and has high concealability and colorability, and can be preferably used.

  Examples of the organic white pigment include organic compound salts disclosed in JP-A No. 11-129613 and alkylene bismelamine derivatives disclosed in JP-A Nos. 11-14365 and 2001-234093. Specific examples of the white pigment include Shigenox OWP, Shigenox OWPL, Shigenox FWP, Shigenox FWG, Shigenox UL, and Shigenox U (all trade names manufactured by Hackol Chemical Co., Ltd.).

  Examples of the white hollow polymer fine particles include thermoplastic fine particles substantially made of an organic polymer disclosed in US Pat. No. 4,089,800.

  In the present invention, the white pigment may be used alone or in combination. For the dispersion of the pigment, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like can be used. It is also possible to add a dispersant when dispersing the pigment.

  A normal dispersant can be used as the dispersant, but a polymer dispersant is preferably used.

  In the dispersion of the pigment, the average particle diameter is preferably 0.05 to 1.0 μm, more preferably 0.08 to 0.3 μm.

(Colorless ink)
In the inkjet ink set of the present invention, a colorless ink (also referred to as a transparent ink) that does not substantially contain a color material can be used in combination.

  In the present invention, the colorless ink containing substantially no color material means a state in which the content of the color material is 0.1% or less with respect to the total ink mass, and preferably contains no color material. is there.

  The component contained in the colorless ink according to the present invention may be either uniformly dissolved or present in a non-uniform dispersion system. Examples of the resin that can be added include a water-based dissolved resin, a water-based dispersed resin, an organic solvent-based dissolved resin, an organic solvent-based dispersed resin, and the like. A resin dispersed in an aqueous system is preferred. Although colorless inks obtained by removing only the color material from the ink-jet ink used can be used, it is preferable to add the following additives in order to add various functions.

  Examples of resins that are dissolved in water include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, color ginnan (κ, ι, λ, etc.), agar, pullulan, water-soluble Polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like can be added.

  As the resin dispersed in an aqueous system, it is particularly preferable to add fine particles of a thermoplastic resin because the glossiness of the image is improved. As the thermoplastic resin fine particles, the thermoplastic resin that can be added to the surface layer of the recording medium or the kind described in the description of the fine particles can be used. In particular, it is preferable to apply those which do not cause thickening or precipitation even when added to the ink. The average particle size of the thermoplastic resin particles is preferably 0.5 μm or less. The fine particles of the thermoplastic resin to be added are preferably those that melt and soften in the range of 0 to 150 ° C.

<< Other additives for inkjet ink >>
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, acrylate copolymer, polyurethane, silicon-acrylic copolymer, and acrylic-modified fluorine-fatting. The latex may be obtained by dispersing polymer particles using an emulsifier, or may be dispersed without using an emulsifier. A surfactant is often used as an emulsifier, but a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer in which a solubilizing group is graft-bonded, a single group having a solubilizing group). It is also preferable to use a polymer obtained from a monomer and a monomer having an insoluble part.

  In the ink-jet ink of the present invention, it is particularly preferable to use soap-free latex. 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 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 kogation, (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph-COO (M1), ( A salt selected from M1) NO ₃ , (M1) Cl, (M1) Br, (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO 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, NO _x , and SO _x . 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 any 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.

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

<Preparation of ink>
There is no particular limitation on the preparation of the inkjet 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, aggregation and settling do not occur in the preparation process. It is preferable to prepare an 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》
(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.

  In the inkjet ink of this invention, it is preferable that the viscosity in 25 degreeC is 15 mPa * s or less, More preferably, it is 2-15 mPa * s.

  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.

(surface tension)
Moreover, in the inkjet ink used in the recording method of the present invention, the surface tension is preferably 40 mN / m or less, more preferably 20 to 35 mN / m.

  The surface tension (mN / m) of the ink referred to in the present invention is a value obtained by measuring the surface tension measured at 25 ° C., and the measurement method is described in general interface chemistry, colloid chemistry reference books, etc. For example, New Experimental Chemistry Course Volume 18 (Interface and Colloid), The Chemical Society of Japan, published by Maruzen Co., Ltd. 68-117 can be referred to. Specifically, it can be determined using a ring method (Dunoi method) or a platinum plate method (Wilhelmy method), but in the present invention, it is represented by a surface tension value (mPa · s) measured by the platinum plate method. For example, it can be measured using a surface tension meter CBVP-Z manufactured by Kyowa Interface Science.

(Electrical conductivity)
In the inkjet ink of the present invention, from the viewpoint of ink storage stability, the electrical conductivity is preferably 1 mS / m or more and 500 mS / m or less, more preferably 1 mS / m or more and 200 mS / m or less, More preferably, they are 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.

"recoding media"
As a 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. When using a paper medium such as a printing coated paper as the recording medium, as described above, the active energy ray to be irradiated is a low-illuminance high-pressure mercury lamp, low-pressure mercury lamp, LED or the like that generates a small amount of heat, It is preferable from the viewpoint of cockling.

[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. The paper is classified into art paper, coated paper, lightweight coated paper, etc., depending on the coating amount, and is classified into glossy, dull, matte, etc., depending on the gloss of the paper.

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

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

[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>
In the ink jet recording method of the present invention, the ink jet ink according to the present invention is ejected onto a recording medium by an ink jet head, and the ink is cured by irradiating active energy rays. Furthermore, it is preferable to introduce a drying step after the ink is cured.

  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.

  In particular, when a paper-based medium such as a coated paper for printing is used as the recording medium, as described above, the amount of heat generated by the low-intensity high-pressure mercury lamp, low-pressure mercury lamp, LED, etc. is used as the active energy ray to be irradiated. A small one is preferable from the viewpoint of cockling.

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

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

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

(Drying after curing)
In the ink jet recording method of the present invention, it is preferable that drying is performed for the purpose of removing unnecessary water-soluble organic solvent after the ink for ink jetting onto the recording medium is cured by irradiation with active energy rays.

  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.

(Printer parts)
As a member used in the ink jet printer used in the ink jet recording method of the present invention, in order to prevent irradiation of the head surface due to irregular reflection of actinic rays, for example, ultraviolet rays, a material having a low transmittance or reflectance with respect to active energy rays is preferable. .

  The irradiation unit preferably has a shutter mounted. For example, when ultraviolet rays are used, the ratio of illuminance when opening and closing the shutter is preferably shutter open / shutter close = 10 or more, more preferably 100 or more. Preferably it is 10,000 or more.

  Next, an inkjet printer used in the inkjet image recording method of the present invention will be described.

〔inkjet printer〕
As an ink jet printer that can be used in the present invention, for example, image formation is arranged horizontally, and the back surface of the recording medium in a predetermined range on the upper surface (the surface opposite to the image forming surface side) is driven by the suction device. Equipped with a platen that is sucked and supported by a recording head, a recording head that discharges ink from a nozzle outlet toward a recording medium, and an irradiation unit that includes these recording head and actinic rays, and moves in the scanning direction during image formation A carriage, a drive circuit board mounted on the carriage and for driving the carriage, a guide member extending along the scanning direction to guide the movement of the carriage, and extending along the scanning direction; In the longitudinal direction, the linear scale on which the optical pattern is arranged and the optical pattern that is mounted on the carriage and arranged on the linear scale are read. Device configured by a linear encoder sensor that outputs a clock signal and the like.

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

Example 1
<< Preparation of crosslinkable polymer compound >>
56 g of glycidyl methacrylate, 48 g of p-hydroxybenzaldehyde, 2 g of pyridine and 1 g of N-nitroso-phenylhydroxyamine ammonium salt were put in a reaction vessel, respectively, and stirred in a hot water bath at 80 ° C. for 8 hours.

  Next, 45 g of polyvinyl acetate saponified product having a degree of polymerization of 300 and a saponification rate of 98% was dispersed in 225 g of ion-exchanged water, and then 4.5 g of phosphoric acid was added to this solution to obtain p- (3 -Methacryloxy-2-hydroxypropyloxy) benzaldehyde was added to polyvinyl alcohol so that the modification rate was 2.8 mol%, 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. The ion exchange resin was filtered and then diluted with pure water to obtain a 15% by mass aqueous solution of the crosslinkable polymer compound. A crosslinkable polymer compound is a polymer compound that has a plurality of side chains in a saponified polyvinyl acetate that is a hydrophilic main chain, and can be crosslinked between side chains by irradiating active energy rays. is there.

<Preparation of ink set>
[Preparation of ink set 1]
Ink set 1 composed of yellow ink 1, magenta ink 1, cyan ink 1 and black ink 1 was prepared according to the following method.

(Preparation of yellow ink 1)
The following compositions were sequentially mixed, dispersed using a bead mill, and then filtered through a # 3000 metal mesh filter to prepare yellow ink 1.

Crosslinkable polymer compound 2 parts as solid content Ethylene glycol 10 parts 2-pyrrolidinone 8 parts 1,2-hexanediol 5 parts Thiol: 1,2-ethanedithiol 1 part Activator: Olphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1 part Polymerization initiator: Irgacure 2959 1 part Pigment: Cab-O-Jet270 (Yellow self-dispersing pigment manufactured by Cabot)
3 parts as solid content Antifungal agent: Proxel GXL (manufactured by Avicia) 0.2 parts Ion exchange water was added to each of the above compositions to finish 100 parts.

(Preparation of magenta ink 1, cyan ink 1, black ink 1)
In the preparation of the yellow ink 1, the pigment was replaced with Cab-O-Jet 270, Cab-O-Jet 260 (magenta self-dispersing pigment manufactured by Cabot), Cab-O-Jet 250 (cyan self-dispersing pigment manufactured by Cabot), respectively. Magenta ink 1, cyan ink 1, and black ink 1 were prepared in the same manner except that Cab-O-Jet 300 (black self-dispersing pigment manufactured by Cabot) was used.

[Preparation of ink set 2]
Ink set 2 composed of yellow ink 2, magenta ink 2, cyan ink 2 and black ink 2 was prepared according to the following method.

(Preparation of yellow ink 2)
The following compositions were sequentially mixed, dispersed using a bead mill, and then filtered through a # 3000 metal mesh filter to prepare yellow ink 2.

Crosslinkable polymer compound 2 parts as solid content Propylene glycol 10 parts Triethylene glycol monobutyl ether 10 parts Thiol: 2-mercaptoethyl ether 3 parts Activator: Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1 part Polymerization initiator: Irgacure 2959 1 part Pigment: Cab-O-Jet270 (Yellow self-dispersing pigment manufactured by Cabot)
3 parts as solid content Antifungal agent: Proxel GXL (manufactured by Avicia) 0.2 parts Ion exchange water was added to each of the above compositions to finish 100 parts.

(Preparation of magenta ink 2, cyan ink 2, black ink 2)
In the preparation of the yellow ink 2, in place of the Cab-O-Jet 270, Cab-O-Jet 260 (magenta self-dispersing pigment manufactured by Cabot), Cab-O-Jet 250 (cyan self-dispersing pigment manufactured by Cabot), respectively, Magenta ink 2, cyan ink 2, and black ink 2 were prepared in the same manner except that Cab-O-Jet 300 (black self-dispersing pigment manufactured by Cabot) was used.

[Preparation of ink set 3]
Ink set 3 (comparative example) composed of yellow ink 3, magenta ink 3, cyan ink 3 and black ink 3 was prepared according to the following method.

(Preparation of yellow ink 3)
The following compositions were sequentially mixed and dispersed using a bead mill, and then filtered through a # 3000 metal mesh filter to prepare yellow ink 3.

Crosslinkable polymer compound 2 parts as solid content Ethylene glycol 10 parts 2-pyrrolidinone 8 parts 1,2-hexanediol 5 parts Activator: Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1 part Polymerization initiator: Irgacure 2959 1 part Pigment: Cab-O-Jet270 (Yellow self-dispersing pigment manufactured by Cabot)
3 parts as solid content Antifungal agent: Proxel GXL (manufactured by Avicia) 0.2 parts Ion exchange water was added to each of the above compositions to finish 100 parts.

(Preparation of magenta ink 3, cyan ink 3, and black ink 3)
In the preparation of the yellow ink 3, instead of the Cab-O-Jet 270, Cab-O-Jet 260 (magenta self-dispersing pigment manufactured by Cabot), Cab-O-Jet 250 (cyan self-dispersing pigment manufactured by Cabot), respectively, Magenta ink 3, cyan ink 3, and black ink 3 were prepared in the same manner except that Cab-O-Jet 300 (black self-dispersing pigment manufactured by Cabot) was used.

[Preparation of ink set 4]
Ink set 4 (comparative example) composed of yellow ink 4, magenta ink 4, cyan ink 4 and black ink 4 was prepared according to the following method.

(Preparation of yellow ink 4)
The following compositions were sequentially mixed and dispersed using a bead mill, and then pre-dispersed for 1 hour using a dissolver. Further, the mixture was kneaded using a bead mill and filtered through a # 3000 metal mesh filter to prepare yellow ink 4.

Active energy ray reactive compound: NK-ester A-200 10 parts Ethylene glycol 15 parts 2-pyrrolidinone 10 parts Thiol: 2-mercaptoethyl ether 4 parts Activator: Olphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1 part Polymerization start Agent: Irgacure 2959 1 part Pigment: C.I. I. Pigment Yellow 74 3 parts Pigment dispersant: Solsperse 20000 (manufactured by Avicia) 1 part Antifungal agent: Proxel GXL (manufactured by Abyssia) 0.2 part Ion exchange water was added to each of the above compositions to finish 100 parts.

(Preparation of magenta ink 4, cyan ink 4, and black ink 4)
In the preparation of the yellow ink 4, the pigment is C.I. I. In place of Pigment Yellow 74, C.I. I. Pigment red 122, C.I. I. Magenta ink 4, cyan ink 4 and black ink 4 were prepared in the same manner except that CI pigment blue 15: 3 and carbon black were used.

[Preparation of ink set 5]
Ink set 5 (comparative example) composed of yellow ink 5, magenta ink 5, cyan ink 5 and black ink 5 was prepared according to the following method.

(Preparation of yellow ink 5)
The following compositions were sequentially mixed and dispersed using a bead mill, and then pre-dispersed for 1 hour using a dissolver. Further, the mixture was kneaded using a bead mill and filtered through a # 3000 metal mesh filter to prepare yellow ink 5.

Pigment: C.I. I. Pigment Yellow 74 5 parts Pigment dispersant: Ajisper PB821 (manufactured by Ajinomoto Fine Techno) 3 parts Aronix M5700 (manufactured by Toagosei Co., Ltd.) 12 parts Ethylene oxide added 1,6-hexanediol acrylate 63 parts 3-methoxybutyl acrylate 12 parts Thiol: 2 -Mercaptoethyl ether 5 parts Polymerization initiator: Irgacure 369 5 parts (Preparation of magenta ink 5, cyan ink 5, black ink 5)
In the preparation of the yellow ink 5, the pigment is C.I. I. In place of Pigment Yellow 74, C.I. I. Pigment red 122, C.I. I. Magenta ink 5, cyan ink 5, and black ink 5 were prepared in the same manner except that CI pigment blue 15: 3 and carbon black were used.

  The ink-jet ink sets 1 to 5 obtained above were image-formed and evaluated as shown below.

<< Production of images 1 to 5 >>
A piezo head having a nozzle diameter of 23 μm, a driving frequency of 15 kHz, a nozzle number of 256, a minimum liquid amount of 5 pL, and a nozzle density of 180 dpi (where dpi represents the number of dots per 2.54 cm) is mounted on both ends of the piezo head. A 120 W / cm metal halide lamp (MAL 400NL power supply power 3 kW · hr manufactured by Nihon Batteries Co., Ltd.) was arranged, and an on-demand type ink jet printer having a maximum recording density of 1440 × 720 dpi was prepared. While irradiating a metal halide lamp, ink sets 1 to 5 were discharged to record an image on a polyethylene terephthalate film. The recorded image is a pattern in which a solid image of 5 cm × 5 cm of red and blue, which are intermediate colors, is arranged adjacent to each other. The print ratio of yellow ink and magenta ink in the red image is 100%, and magenta ink in the blue image. The printing rate of cyan ink is 100%. After image recording, it was dried with warm air for 30 seconds with a dryer and then naturally dried for 24 hours.

<< Evaluation of images 1-5 >>
Images 1 to 5 produced with ink sets 1 to 5 were evaluated according to the following methods. In all cases, the performance of ◯ or higher was regarded as an acceptable level.

(Evaluation of ink curability)
The boundary between the red image and the blue image was visually observed, and the ink curability was evaluated according to the following criteria.

○: No blur between colors occurs at the color boundary part Δ: Some blur occurs at the color boundary part, and color mixing with a width of several millimeters occurs ×: The color boundary part almost blurs Each solid image is also mixed with each other's color (evaluation of image gloss)
Images 1 to 5 produced with ink sets 1 to 5 were visually observed, and gloss was evaluated according to the following criteria.

○: The gloss of the solid image is very good, and there is little difference in gloss between the printed part and the non-printed part. △: The gloss of the solid image is moderately good, but the printed part and the non-printed part are slightly glossy. X: Solid image has no gloss and large difference in gloss between printed and non-printed areas is felt Table 1 shows the results obtained as described above.

  As is apparent from the results shown in Table 1, the ink set of the present invention composed of the ink jet ink composed of the composition defined in the present invention has better ink curability and superior gloss than the comparative example. I understand that.

Example 2
<< Production of images 6 to 11 >>
Image 6 was produced according to the following method. A piezo head having a nozzle diameter of 23 μm, a driving frequency of 15 kHz, a nozzle number of 256, a minimum liquid amount of 5 pL, and a nozzle density of 180 dpi (where dpi represents the number of dots per 2.54 cm) is mounted on both ends of the piezo head. A low-pressure mercury lamp (L251US manufactured by Nihon Battery Co., Ltd.) was arranged, and an on-demand type ink jet printer having a maximum recording density of 1440 × 720 dpi was prepared. While irradiating the low-pressure mercury lamp, the ink set 1 was discharged, and a color image composed of a landscape photograph was recorded on NK special art paper (manufactured by Nippon Processing Paper Co., Ltd.), which is a coated paper for printing. After image recording, it was dried with warm air for 30 seconds with a dryer and then naturally dried for 24 hours.

  For images 7, 8, 10, and 11, images were prepared in the same manner as image 6 except that ink sets 2, 3, 4, and 5 were used instead of ink set 1, respectively.

  For image 9, an image was produced in the same manner as image 6 except that the light source mounted on both ends of the head was changed to an 80 W / cm high-pressure mercury lamp (HI-20, manufactured by Nihon Battery Co., Ltd.).

<< Evaluation of images 6-11 >>
Images 6 to 11 produced with ink sets 1 to 5 were evaluated according to the following methods. In all cases, the performance of ◯ or higher was regarded as an acceptable level.

(Evaluation of ink curability)
The ink image was evaluated visually according to the following criteria by visually observing a large portion of the color change in the landscape image.

○: Bleeding or mottle between colors is not generated at all, and the image is good. Δ: Bleeding between colors, mottled slightly occurs. ×: Bleeding between colors, mottled occurs, and clearly reproducibility. The image is inferior to (Evaluation of image gloss)
The image was visually observed and gloss was evaluated according to the following criteria.

○: The glossiness of the image is very good, and the difference in glossiness between the high density portion and the low density portion is small. Δ: The glossiness of the image is moderately good, but the glossiness is slightly high and low density portions. X: There is no gloss in the image, and there is a large difference in gloss between the high and low density areas (cockling)
◎: The recording medium hardly swells. ○: Swelling occurs in a part of the recording medium. X: The recording medium swells, causing the head surface and the recording medium to rub, resulting in image contamination. Table 2 shows the results obtained.

  As is apparent from the results shown in Table 2, the ink set of the present invention composed of the ink jet ink composed of the composition defined in the present invention has better ink curability and better gloss than the comparative example. I understand that. Furthermore, it can be seen that in the inkjet recording method of the present invention using a low-pressure mercury lamp, there is little cockling of the coated paper for printing.

Claims (14)

An ink-jet ink comprising at least water, thiol, and a polymer compound having a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays. 2. The inkjet ink according to claim 1, wherein the thiol content is 0.1 mass% or more and 10 mass% or less. The inkjet ink according to claim 1 or 2, wherein the hydrophilic main chain of the polymer compound capable of cross-linking between the side chains is a saponified product of polyvinyl acetate. The modification rate of the side chain with respect to the hydrophilic main chain of the polymer compound capable of cross-linking between the side chains is 0.8 mol% or more and 4.0 mol% or less. The inkjet ink according to any one of the above. The inkjet ink according to any one of claims 1 to 4, wherein the degree of polymerization of the hydrophilic main chain of the polymer compound that can be cross-linked between the side chains is 200 or more and 500 or less. 6. The inkjet ink according to claim 1, wherein the content of the polymer compound that can be cross-linked between the side chains is 0.8% by mass or more and less than 5% by mass. . An ink-jet ink set comprising two or more ink-jet inks, wherein at least one of the ink-jet inks is the ink-jet ink according to any one of claims 1 to 6. An ink jet recording method comprising: discharging the ink jet ink according to claim 1 onto a recording medium; irradiating the ink jet ink with active energy rays; An ink jet recording method comprising: discharging an ink jet ink constituting the ink jet ink set according to claim 7 onto a recording medium, irradiating the ink jet ink with active energy rays, and drying the ink. 10. The ink jet recording method according to claim 8, wherein the device for irradiating the active energy ray is a low pressure mercury lamp. 10. The ink jet recording method according to claim 8, wherein the device for irradiating the active energy ray is an LED. The inkjet recording method according to any one of claims 8 to 11, wherein the recording medium is a paper medium. The inkjet recording method according to claim 12, wherein the paper medium is a coated paper for printing. The inkjet recording method according to claim 8 or 9, wherein the device for irradiating the active energy ray is a low-pressure mercury lamp or LED, and recording is performed on a coated paper for printing.