JP2007138092A - Inkjet ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide inkjet ink excellent in dispersion stability and ejection stability and capable of giving high-quality good-gloss characters on plain paper. <P>SOLUTION: The inkjet ink is inkjet ink containing a pigment, a dispersant, and water, wherein a polymer compound composed of a hydrophilic skeleton and a plurality of side chains attached thereto and being capable of being crosslinked among the side chains when irradiated with an actinic radiation is contained, and the acid number of the dispersant is larger than its amine value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inkjet ink.

  The ink jet recording method is capable of recording a high-definition image with a relatively simple device, 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 draw 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 at all, there is a problem such as so-called bleeding, where different color ink liquids mix on the recording medium and cause color turbidity. In addition, there has been a problem in providing a variety of recording media to the inkjet.

  In the above problems, a hot-melt ink composition made of a wax that is solid at room temperature is used, liquefied by heating, etc., sprayed with some energy applied, cooled and solidified while adhering to the recording medium, and recorded A hot-melt ink jet recording method for forming dots has been proposed. However, an image recorded by such a method has problems such as deterioration in quality and lack of scratching performance due to the rising of the dots because the ink dots are in the form of soft wax.

  On the other hand, an inkjet recording ink that is cured by exposure to ultraviolet rays is disclosed (for example, see Patent Document 1). In addition, a so-called non-aqueous ink containing a pigment as an essential component and a triacrylate or higher polyacrylate as a polymerizable material and using a ketone or an alcohol as a main solvent has been proposed (for example, Patent Document 2). reference.). Further, an ink using a water-based ultraviolet polymerization monomer has been proposed (for example, see Patent Document 3).

  In these methods, since the ink itself is cured with a curing component, recording is possible even on a non-absorbing medium. However, since the curing component other than the colorant is contained in a large amount and does not volatilize, the recording surface is reduced. The ink dots swelled up, causing unnaturalness in image quality, especially gloss. Furthermore, there is a safety concern for the conventionally known curable components, and there is a problem that even if the safety is cleared, there is a narrow selection of substances, and the material and physical properties cannot be designed freely. .

In the actinic ray curable inkjet ink containing a photopolymerizable compound, a pigment, and a dispersant, the photopolymerizable compound is a radical polymerizable compound (cationic polymerizable compound), and the acid value is higher than the amine value in the dispersion of the pigment. Actinic ray curable inkjet ink using a large dispersant, or actinic ray curing using a pigment whose photopolymerizable compound is a radical polymerizable compound (cationic polymerizable compound) and whose amine value is larger than the acid value Type ink-jet inks are disclosed (see, for example, Patent Documents 4 and 5), but in these inks, the polymerizable component is used in an ink composition ratio of 50% or more, so that the printed portion is raised and glossy. There will be no image. Also, due to the solvent-based ink (low surface tension), there is a problem that plain paper causes feathering and back-through.
U.S. Pat. No. 4,228,438 Japanese Patent Publication No. 5-64667 JP-A-7-224241 JP 2005-187725 A JP 2005-194356 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink-jet ink having excellent dispersion stability and emission stability, good gloss, and excellent character quality on plain paper.

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

  1. An inkjet ink containing a pigment, a dispersant, and water contains a polymer compound having a plurality of side chains in the hydrophilic main chain and capable of crosslinking between the side chains by irradiating active energy rays. An ink for ink-jet recording, wherein the acid value of the dispersant is greater than the amine value.

  2. An inkjet ink containing a pigment, a dispersant, and water contains a polymer compound having a plurality of side chains in the hydrophilic main chain and capable of crosslinking between the side chains by irradiating active energy rays. An ink for ink jet printing, wherein the amine value of the pigment is higher than the acid value.

  3. 2. The ink-jet ink as described in 1 above, wherein the amine value of the pigment is larger than the acid value.

  4). 4. The inkjet ink according to any one of 1 to 3, wherein the polymer compound is contained in an amount of 0.8 to 5.0% by mass with respect to the total mass of the ink.

  According to the present invention, it was possible to provide an ink-jet ink having excellent dispersion stability and emission stability, good gloss, and excellent character quality on plain paper.

  The ink-jet ink of the present invention is characterized in that a dispersant having an acid value larger than the amine value is used as the dispersant, and that the amine value of the pigment is larger than the acid value.

  The acid value or amine value referred to in the present invention can be determined by potentiometric titration, and can be measured by, for example, the method described in Color Material Association Journal 61, [12] 692-698 (1988). When a plurality of pigments and dispersants are used, the weight average can be displayed.

  In the inkjet ink of the present invention, the acid value of the dispersant is preferably larger than the amine value, and the difference is preferably 1 mg / g KOH or more and less than 30 mg / g KOH. If the difference between the acid value and the amine value is less than 1 mg / g KOH, the objective effect of the present invention cannot be obtained, and if it is 30 mg / g KOH or more, there is a concern that the heat reaction will cause curing.

  As the dispersant that can be used in the present invention, any of a low molecular weight dispersant and a high molecular dispersant can be used as long as the conditions specified in the present invention are satisfied. Agents are preferred. Preferable specific examples of the dispersant include, for example, Ajisper PB822 manufactured by Ajinomoto Fine Techno Co., and Ajisper PB821 manufactured by Ajinomoto Fine Techno Co., but the present invention is of course not limited thereto.

  In the inkjet ink of the present invention, it is preferable to select a pigment having an amine value larger than the acid value as the dispersoid pigment together with the dispersant, and the difference between the amine value and the acid value is 1 mg / g KOH or more, It is preferably less than 10 mg / g. If the difference between the amine value and the acid value is less than 1 mg / g KOH, the intended effect of the present invention cannot be obtained, and if it is 10 mg / g KOH or more, it is necessary to perform basic treatment excessively, resulting in an increase in cost. It is not preferable.

  In the present invention, the specific dispersant or specific pigment not only contributes to the dispersibility, but also improves the gloss after the ink has landed. The coexistence of the dispersant or pigment according to the present invention and the polymer compound reduces the cohesiveness of the pigment after the ink has landed, and a preferable leveling state is achieved even on the landed recording medium. It is estimated that the performance has improved.

  Hereinafter, the ink-jet ink of the present invention will be described.

(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.

  In the hydrophilic main chain, a saponified product of polyvinyl acetate is preferable from the viewpoint of ease of handling and introduction of side chains, and the degree of polymerization is preferably 200 or more and 4000 or less, and more preferably 200 or more and 2000 or less from the viewpoint of handling. . The modification rate of the side chain with respect to the main chain is preferably 0.3 mol% or more and 4 mol% or less, and more preferably 0.8 mol% or more and 4 mol% or less from the viewpoint of reactivity. If it is less than 0.3 mol%, the crosslinkability is insufficient and the effect of the present invention is reduced. If it is more than 4 mol%, the crosslink density is increased and the film is hard and brittle, and the strength of the film is lowered.

  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 No. 56-67309 contains a 2-azido-5-nitrophenylcarbonyloxyethylene structure represented by the following general formula (2) or the following general formula ( It 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.

  Such an active energy ray crosslinkable 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 bleed 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 physical properties of the ink and the state in the ink head, which is preferable from the viewpoint of the light emission property and the ink storage property. Further, crosstalk in the recording method is less likely to occur. Further, since printing and swell are reduced, it is preferable in terms of gloss.

  In such an active energy ray crosslinkable polymer compound, the main chain originally having a certain degree of polymerization is crosslinked via a crosslink between side chains, and thus polymerized via a general chain reaction. The effect of increasing the molecular weight per photon is significantly greater than the active energy ray-curable resin. On the other hand, in the conventionally known active energy ray curable resins, the number of crosslinking points cannot be controlled, so the physical properties of the cured film cannot be controlled, and the film tends to be hard and brittle.

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

  In addition, conventionally known active energy ray-curable inks (radical polymerizable compounds and cationic polymerization compounds) are almost all components other than the colorant, so that the dots after curing rise and the image quality typified by gloss is inferior. On the other hand, the active energy ray crosslinkable polymer compound used in the present invention requires a small amount, and since there are many dry components, the image quality after drying can be improved and the fixing property is also good. In addition, since the conventionally known active energy ray-curable ink is also a solvent-based ink, there are problems such as difficulty in feathering and density with respect to plain paper, but the inkjet ink of the present invention is a water-based ink. Therefore, such a fault is also eliminated.

(Photopolymerization initiator, photosensitizer)
In the present invention, it is also preferable to add a photopolymerization initiator or a photosensitizer. 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. Although there is no restriction | limiting in particular about the photoinitiator and photosensitizer which are applied, A water-soluble thing is preferable from a viewpoint of mixing property and reaction efficiency. In particular, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone (HMPK), thioxanthone ammonium salt (QTX), and benzophenone ammonium salt (ABQ) are preferable from the viewpoint of miscibility with an aqueous solvent.

  Furthermore, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone (n = 1, HMPK) represented by the following general formula (7) from the viewpoint of compatibility with the resin, An ethylene oxide adduct (n = 2 to 5) is more preferable.

  In the formula, n represents an integer of 1 to 5.

  In addition, benzophenones such as benzophenone, hydroxybenzophenone, bis-N, N-dimethylaminobenzophenone, bis-N, N-diethylaminobenzophenone, 4-methoxy-4'-dimethylaminobenzophenone. Thioxanthones such as thioxatone, 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, and isopropoxychlorothioxanthone. Anthraquinones such as ethyl anthraquinone, benzanthraquinone, aminoanthraquinone and chloroanthraquinone. Acetophenones. Benzoin ethers such as benzoin methyl ether. 2,4,6-trihalomethyltriazines, 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, 2,4-di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl) -4, 2,4,5-triarylimidazole dimer of 5-diphenylimidazole dimer, benzyldimethyl ketal, 2-benzyl-2-dimethyl Ruamino-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, phenanthrenequinone, 9,10-phenanthrenequinone, Benzoins such as methylbenzoin and ethylbenzoin, 9-phenylacridine, acridine derivatives such as 1,7-bis (9,9'-acridinyl) heptane, bisacylphosphine oxide, and mixtures thereof are preferably used. 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.

  Even if these photoinitiators are grafted to the side chain with respect to the hydrophilic main chain.

(Active energy rays, irradiation method)
Examples of active energy rays in the present invention include electron beams, ultraviolet rays, α rays, β rays, γ rays, and X-rays. However, there are dangers to the human body, and handling is easy and industrial use. Electron beams and ultraviolet rays are widely used.

  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 may be deteriorated, which is not preferable.

  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 having an operating pressure of 0.1 kPa to 1 MPa. Conventionally known materials such as tubes and LEDs are used.

(Light irradiation conditions after ink landing)
As the irradiation condition of actinic rays, actinic rays are preferably irradiated between 0.001 and 1.0 seconds after ink landing, and more preferably 0.001 to 0.5 seconds. In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible.

(Installation of lamp)
As a method for irradiating actinic rays, the basic method is disclosed in JP-A-60-132767. According to this, a 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 UV light by applying a collimated light source to a mirror surface provided on the side of the head unit is disclosed. ing. Any of these irradiation methods can be used in the image forming method according to the present invention.

  In another preferred embodiment, irradiation with actinic rays is divided into two stages, and actinic rays are first irradiated by the above-described method between 0.001 and 2.0 seconds after ink landing, and further irradiated with actinic rays. It is. By dividing the irradiation of actinic rays into two stages, it is possible to further suppress the shrinkage of the recording material that occurs during ink curing.

  As the pigment that can be used in the present invention, various pigments can be used as long as the amine value is larger than the acid value.

  Specific examples of the pigment that can be used in the present invention are illustrated below. In the pigments listed below, a pigment having an amine value larger than the acid value can be used, but the present invention is not limited thereto. .

<C. I. Pigment Yellow>
1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 109, 114, 120, 128, 129, 138, 151, 154
<C. I. Pigment Red>
5, 7, 12, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 101, 112, 122, 123, 144, 146, 168, 184, 185, 202
<C. I. Pigment Violet>
19, 23
<C. I. Pigment Blue>
1, 2, 3, 15: 1, 15: 2, 15: 3, 15: 4, 18, 22, 27, 29, 60
<C. I. Pigment Green>
7, 36
<C. I. Pigment White>
6, 18, 21
<C. I. Pigment Black>
7
The pigment used in the present invention may be subjected to various known surface treatments as necessary.

  For the dispersion of the pigment, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like can be used. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid if necessary. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment. The dispersion medium is used using a solvent or a polymerizable compound. In the inkjet ink of the present invention, an actinic ray is irradiated and reacted and cured immediately after ink landing, so that it is preferably solventless. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable in view of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.

  The pigment is preferably dispersed so that the average particle size of the pigment particles is 0.08 to 0.5 μm, and the maximum particle size is 0.3 to 10 μm, preferably 0.3 to 3 μm. Selection of the dispersion medium, dispersion conditions, and filtration conditions are appropriately set. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.

  The pigment concentration is preferably 1% by mass to 10% by mass of the entire composition.

  The ink-jet ink of the present invention can be used in an ink-jet ink set having at least a yellow ink-jet ink, a magenta ink-jet ink, a cyan ink-jet ink, and a black ink-jet ink, and is generally used for so-called color ink-jet prints. It can be an ink set in which a plurality of inks are set. In the present invention, it is preferable that all of the ink-jet inks of the ink-jet ink set are the ink-jet inks of the present invention. When an ink-jet image is formed using this ink set, an image in which color mixing has been solved is obtained. Can be formed.

(Water-soluble solvent)
A water-soluble solvent is preferably used as the solvent according to the present invention, and a mixed solvent such as water and a water-soluble organic solvent is more preferably used as the water-soluble solvent. Water is preferably added in an amount of 10 to 45% by mass in the ink, and the water-soluble organic solvent is preferably added in an amount of 50 to 90% by mass in the ink. This is presumed that the hydrophilicity and hydrophobicity of the ink itself are preferable for pigment dispersion stability by adjusting the water and the water-soluble organic solvent in this range.

  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 inkjet ink of the present invention include alkyl sulfates, alkyl ester sulfates, dialkyl sulfosuccinates, alkyl naphthalene sulfonates, alkyl phosphates, and 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 , Surfactants such as sorbitan esters, polyoxyethylene fatty acid amides and amine oxides, and cationic surfactants such as alkylamine salts and quaternary ammonium salts.

(Various additives)
In the present invention, other conventionally known additives can be contained. For example, fluorescent brighteners, antifoaming agents, lubricants, preservatives, thickeners, antistatic agents, matting agents, water-soluble polyvalent metal salts, acid bases, pH adjusters such as buffers, antioxidants, surfaces These are tension modifiers, non-resistance modifiers, rust inhibitors, inorganic pigments, and the like.

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

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

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

(Various films)
As the various films, all commonly used 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.

(Various ink jet recording media)
As the various ink jet recording media, an ink receiving layer is formed on the surface using an absorbent support or a non-absorbent support as a base material. Examples of the ink receiving layer include a coating layer, a swelling layer, and a fine void layer.

  The swelling layer absorbs ink when the ink receiving layer made of a water-soluble polymer swells. The fine void layer is composed of inorganic or organic fine particles having a secondary particle size of about 20 to 200 nm and a binder, and fine voids of about 100 nm absorb ink.

  In recent years, an ink jet recording medium in which the fine void layer is provided using RC paper in which both surfaces of a paper base material are coated with an olefin resin is preferably used in terms of a photographic image.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
(Synthesis of polymer compound 1)
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 and stirred in a hot water bath at 80 ° C. for 8 hours.

  Next, 45 g of saponified polyvinyl acetate having a polymerization degree of 300 and a saponification degree of 88% was dispersed in 225 g of ion-exchanged water, and then 4.5 g of phosphoric acid and p- (3-methacryloxy-2) obtained by the above reaction were added to this solution. -Hydroxypropyloxy) benzaldehyde was added to PVA so that the modification rate was 3 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. Thereafter, the ion exchange resin is filtered, and Irgacure 2959 (manufactured by Ciba Specialty Chemicals) is mixed as a photopolymerization initiator at a ratio of 0.1 g with respect to 100 g of a 15% aqueous solution, and then diluted with ion exchange water. As a result, a 10% aqueous solution of polymer compound 1 was obtained.

(Synthesis of polymer compounds 2 to 4)
In addition, the modification rate was adjusted by changing the polymerization degree and the saponification degree of the polyvinyl acetate saponified product as needed and changing the amount of p- (3-methacryloxy-2-hydroxypropyloxy) benzaldehyde charged.

<< Preparation of yellow, magenta, cyan, and black pigment dispersions >>
<< Preparation of Cyan Pigment Dispersion >>
The following additives were mixed and dispersed using a sand grinder filled with 0.5 mm zirconia beads at a volume ratio of 50% to prepare a pigment dispersion having a cyan pigment content of 20%.

Cyanine 4044 (Sanyo Dye, Pigment Blue 15: 4, amine value 8.0 mg / g KOH, acid value 0.0 mg / g KOH) 20 parts PB822 (Ajinomoto Fine Techno Co., polymer dispersant, acid value 18. 5 mg / g KOH, amine value 15.9 mg / g KOH) 10 parts Ethylene glycol 60 parts Ion-exchanged water 10 parts << Preparation of yellow, magenta and black pigment dispersions >>
Instead of Cyanine Blue 4044, yellow is Pariotool Yellow D0960 (manufactured by BASF, Pigment Yellow 138, amine value 5.8 mg / g KOH, acid value 2.6 mg / g KOH), magenta is amine value 6.1 mg / g KOH, acid Pigment Red 122 adjusted to 4.1 mg / g KOH, black was similarly dispersed with carbon black adjusted to amine value 3.1 mg / g KOH, acid value adjusted to 1.1 mg / g KOH, and magenta and black The agent was changed to PB821 (manufactured by Ajinomoto Fine Techno Co., Ltd., polymer dispersant, acid value 30.4 mg / g KOH, amine value 10.2 mg / g KOH) to prepare yellow, magenta and black pigment dispersions.

[Preparation of ink set-1]
10% aqueous solution of polymer compound 1 10 parts Cyan pigment dispersion 20 parts Diethylene glycol 50 parts Surfinol 465 (manufactured by Air Products) 0.5 part Add ion-exchanged water to 100 parts in total, and add 1-C ink. Prepared.

  A 1-M ink, a 1-Y ink, and a 1-K ink were similarly prepared using a magenta pigment dispersion, a yellow pigment dispersion, and a black pigment dispersion instead of the cyan pigment dispersion (Y, M, C and K combined ink set-1).

[Preparation of ink sets-2 to 6]
An ink was prepared in the same manner as in the preparation of ink set-1, except that the kind and amount of 10% aqueous solution of polymer compound 1 were changed.

[Preparation of Comparative Ink Set-1]
In the preparation of ink set-1, Comparative 1-C, Comparative 1-Y, Comparative 1-M, and Comparative 1-K were prepared in the same manner except that polymer compound 1 was not contained. did.

[Preparation of Comparative Ink Set-2]
Comparative 2-C having the following composition containing a solvent-based UV curable cationic polymerization monomer was prepared.

Cyanine Blue 4044 (Sanyo Dye, Pigment Blue 15: 4, amine value 8.0 mg / g KOH, acid value 0.0 mg / g KOH) 4 parts PB822 (Ajinomoto Fine Techno Co., polymer dispersant, acid value 18. 10 parts Cationic polymerization monomer OXT221 (Oxetane Toagosei Co., Ltd.) 80 parts Photoacid generator CS5102 (Nippon Soda Co., Ltd.) 5 parts Initiator assistant C17001 (Nippon Soda Co., Ltd.) 1 In place of part Cyanine Blue 4044, yellow is Pariotol Yellow D0960 (manufactured by BASF, Pigment Yellow 138, amine value 5.8 mg / g KOH, acid value 2.6 mg / g KOH), magenta is amine value 6.1 mg / g KOH, Acid value 4 Pigment Red 122 adjusted to 1 mg / g KOH, black was similarly dispersed with carbon black adjusted to an amine value of 3.1 mg / g KOH and an acid value of 1.1 mg / g KOH, and the magenta and black dispersants were PB821 ( The product was changed to Ajinomoto Fine Techno Co., Ltd., polymer dispersant, acid value 30.4 mg / g KOH, amine value 10.2 mg / g KOH) to prepare Comparative 2-Y, Comparative 2-M, and Comparative 2-K.

[Preparation of Comparative Ink Set-3]
Comparative ink set-3 was prepared in the same manner except that the dispersant was changed as follows in the preparation of ink set-1.

  For the cyan and yellow dispersions, Disperbyk 161 (manufactured by Big Chemie, polymer dispersant, acid value 4.4 mg / g KOH, amine value 10.9 mg / g KOH) was changed, and for the masse and black dispersions, Solspers 32000 (manufactured by Avicia, polymer dispersant, acid value 24.8 mg / g KOH, amine value 27.1 mg / g KOH).

<Measurement of amine value of dispersant>
The dispersant was dissolved in methyl isobutyl ketone, potentiometric titration was performed with a 0.01 mol / L methyl isobutyl ketone perchlorate solution, and the value converted to KOH mg / g was used as the amine value of the dispersant. Potentiometric titration was measured using an automatic titrator COM-1500 manufactured by Hiranuma Sangyo Co., Ltd.

<Measurement of acid value of dispersant>
Dispersing the dispersant in methyl isobutyl ketone, performing potentiometric titration with 0.01 mol / L potassium methoxide-methyl isobutyl ketone / methanol (4: 1) solution, and converting to KOH mg / g, the acid value of the dispersant It was. Potentiometric titration was measured using an automatic titrator COM-1500 manufactured by Hiranuma Sangyo Co., Ltd.

<Measurement of amine value of pigment>
0.01 mol / L methyl butyl ketone perchlorate solution was added to the pigment, and ultrasonic dispersion was performed. Thereafter, the supernatant was subjected to potentiometric titration with a 0.01 mol / L potassium methoxide-methylisobutyl ketone / methanol (4: 1) solution by centrifugation, and the amount of perchloric acid reduced by the pigment was converted to KOH mg / g. Was the amine value of the pigment. Potentiometric titration was measured using an automatic titrator COM-1500 manufactured by Hiranuma Sangyo Co., Ltd.

<Measurement of acid value of pigment>
A 0.01 mol / L tetrabutylammonium hydroxide-methylbutylketone solution was added to the pigment, and ultrasonic dispersion was performed. Thereafter, the supernatant was subjected to potentiometric titration with a 0.01 mol / L methyl isobutyl ketone perchlorate solution by centrifugation, and the 0.01 mol / L tetrabutylammonium hydroxide reduction amount by the pigment was converted to KOH mg / g. This was the acid value of the pigment. Potentiometric titration was measured using an automatic titrator COM-1500 manufactured by Hiranuma Sangyo Co., Ltd.

  Table 2 shows the measurement results of the acid value, amine value, pigment acid value, and amine value of the dispersant.

[Evaluation of ink]
(Storage stability)
Each of the inks prepared above was put in a glass bottle, sealed, and allowed to stand at 60 ° C. for 7 days, and the sedimentation state of the pigment was visually observed, and the storability of the ink was evaluated according to the following criteria.

○: No pigment settling is observed Δ: No settling is observed, but when the liquid is shaken, some aggregates of pigment particles are observed on the wall surface of the glass bottle ×: Clear sediment is observed at the bottom of the glass bottle.

(Evaluation of output stability)
In an environment of 20 ° C. and 30% RH, each ink set was mounted on an ink jet printer equipped with a piezo-type head having a nozzle hole diameter of 20 μm, a driving frequency of 10 kHz, and a nozzle number of 128, and under the condition of discharging 12 pl per drop, The state after the discharge was continuously continued for 1 hour without cleaning was visually observed, and the discharge stability was evaluated according to the following criteria.

◎: Normal emission from all nozzles ○: Clogging is observed in 1 to 3 nozzles, but recovered by suction cleaning from the nozzle surface △: Clogging occurs in 4 or more nozzles and cannot be recovered by suction cleaning Clogging occurs in one nozzle, but is in a practically acceptable range. X: Clogging occurs in 7 or more nozzles, and clogging that cannot be recovered by suction cleaning occurs in 2 nozzles. Xx: Clogging in 10 or more nozzles. Occurred, and clogging that cannot be recovered by suction cleaning occurs for 3 nozzles or more.

  From Table 3, it can be seen that the inkjet ink of the present invention is excellent in storage stability and emission stability.

[Evaluation of inkjet image]
(Color bleed)
An on-demand ink jet with a maximum recording density of 720 × 720 dpi using a piezo head having a nozzle diameter of 25 μm, a drive frequency of 12 kHz, a nozzle count of 128, and a nozzle density of 180 dpi (dpi represents the number of dots per 2.54 cm). Using a printer, black fine lines having a width of 100 μm were printed on art paper (NK Art Kinfuji N, manufactured by Oji Paper Co., Ltd.) on a magenta solid, and then visually observed, and color bleed resistance was evaluated according to the following criteria. Each ink was continuously ejected, and 0.1 seconds after landing, a 120 W / cm metal halide lamp (MAL 400NL, manufactured by Nihon Battery Co., Ltd., power supply power 3 kW · hr) was irradiated.

◎: The boundary between the fine line and the solid is clear. ○: The boundary is slightly blurred, but the quality has no practical problem. △: The boundary is blurred, but practically acceptable. ×: Obvious bleeding is observed at the boundary, and the line width is about 1.5 times, which is a quality that is a practical problem. XX: The boundary between the thin line and the solid part is unclear. Quality and bleed resistance is extremely poor.

(Glossy)
Using an on-demand type ink jet printer with a maximum recording density of 720 × 720 dpi, using a piezo head having a nozzle diameter of 25 μm, a drive frequency of 12 kHz, a nozzle number of 128, and a nozzle density of 180 dpi, art paper (NK Art Kongo N, manufactured by Oji Paper) ) Was printed with a solid black of 10 cm × 10 cm, visually observed, and glossiness was evaluated according to the following criteria. Each ink was continuously ejected, and 0.1 seconds after landing, a 120 W / cm metal halide lamp (MAL 400NL, power supply power 3 kW · hr, manufactured by Nihon Battery Co., Ltd.) was irradiated.

◎: Natural difference between glossiness of recording surface and background is almost natural ○: Glossiness of recording surface and background is slightly different, but acceptable level Δ: Visual observation that glossiness of recording surface and background is slightly different And the glossiness of the recording surface is remarkably higher than that of the background. X: It is possible to visually observe that the glossiness of the recording surface and the background is clearly different, and the glossiness of the recording surface is remarkably higher than that of the background. It can be visually observed that the glossiness of the recording medium is different, and the glossiness of the recording surface is significantly lower than that of the base.

(Feathering)
Using a piezo-type head with a nozzle diameter of 25 μm, a drive frequency of 12 kHz, a nozzle number of 128, and a nozzle density of 180 dpi, using an on-demand type ink jet printer with a maximum recording density of 720 × 720 dpi, high-quality paper (first manufactured by Konica Minolta Business Technology, Inc.) A black thin line having a width of 250 μm and a length of 5 cm was printed on (Class paper), visually observed, and evaluated for feathering according to the following criteria. Each ink was continuously ejected and landed, and 0.1 seconds after landing, a 120 W / cm metal halide lamp (MAL 400NL power supply power 3 kW · hr, manufactured by Nippon Battery Co., Ltd.) was irradiated.

◎: Thin lines are reproduced without blurring due to bleeding ○: Lines are not thickened due to bleeding, but less than 5 spots, ink bleeding along the paper fiber is observed Δ: Lines are thickened due to bleeding No, but less than 10 places, ink bleeding along the paper fiber is observed. X: The line is slightly thickened due to bleeding, and more than 10 ink bleeding along the paper fiber is observed.

XX: Line thickening due to bleeding is intense, and ink bleeding along paper fibers is observed at 20 or more locations. Among these, XX and XX are levels that are problematic as products.

(concentration)
Using a piezo-type head with a nozzle diameter of 25 μm, a drive frequency of 12 kHz, a nozzle count of 128, and a nozzle density of 180 dpi, using an on-demand type ink jet printer with a maximum recording density of 720 × 720 dpi, plain paper (full color PPC paper type manufactured by Ricoh) 6000) was printed with a black solid of 10 cm × 10 cm, and the black density was measured with a reflection densitometer of X-Rite, and evaluated according to the following criteria. Each ink was continuously ejected and landed, and 0.1 seconds later, 120 W / cm metal halide lamps (MAL 400NL power supply power 3 kW · hr, manufactured by Nippon Battery Co., Ltd.) disposed at both ends of the piezo-type head were irradiated.

◎: Black density 1.5 or more ○: Black density 1.4 or more, less than 1.5 △: Black density 1.2 or more, less than 1.4 ×: Black density 0.8 or more, less than 1.2 XX: Black density less than 0.8.

  From the above results, the inkjet ink of the present invention is excellent in the storage stability and emission stability of the ink, and the image from the inkjet ink of the present invention is also excellent in color bleeding, glossiness, and feathering, and a high image. It was confirmed that the concentration could be obtained.

Claims (4)

An inkjet ink containing a pigment, a dispersant, and water contains a polymer compound having a plurality of side chains in the hydrophilic main chain and capable of crosslinking between the side chains by irradiating active energy rays. An ink for ink-jet recording, wherein the acid value of the dispersant is greater than the amine value. An inkjet ink containing a pigment, a dispersant, and water contains a polymer compound having a plurality of side chains in the hydrophilic main chain and capable of crosslinking between the side chains by irradiating active energy rays. An ink for ink jet printing, wherein the amine value of the pigment is higher than the acid value. The inkjet ink according to claim 1, wherein an amine value of the pigment is larger than an acid value. The ink-jet ink according to any one of claims 1 to 3, wherein the polymer compound is contained in an amount of 0.8 to 5.0 mass% with respect to the total mass of the ink.