JP2005105227A - Aqueous ink for inkjet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide aqueous ink for inkjet, excellent in dispersion stability and improved with the gloss and feathering resistance of an obtained image. <P>SOLUTION: This aqueous ink for inkjet containing at least water, a dispersed coloring material and water-soluble organic solvent is characterized by containing ≥2.0 mass % 1,2-pentane diol as the water-soluble organic solvent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel ink-jet water-based ink, and more particularly to an ink-jet water-based ink having improved dispersion stability, gloss and feathering resistance of the obtained image.

  In recent years, with the widespread use of digital cameras or computers, hard copy image recording technology for recording these images on paper has been rapidly developed. The ultimate goal of these hard copies is to bring the image quality closer to that of a silver halide photograph. In particular, the color reproducibility, color density, texture, resolution, glossiness, light resistance, etc. should be closer to that of a silver halide photograph. It is a development goal.

  A wide variety of recording methods have been proposed and put to practical use as such hard copy recording methods, but among them, the ink jet printer has the advantage of being easy to make full color and having less printing noise. It has been rapidly spreading in recent years.

  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.

  Ink-jet recording media used in the ink-jet recording method have an ink-absorbing layer on a support that also serves as an absorber, such as coated paper, or an ink-receptive layer, such as plain paper. There are those coated with a layer, and those coated with an ink absorbing layer on a non-absorbing support such as a resin-coated paper or a polyester film. Among them, the recording medium of the type in which an ink absorbing layer is coated on a non-absorbing support is a silver salt such as gloss, gloss, and depth because the support has a high surface smoothness and little swell. It is preferably used for an output that requires a high quality texture such as a photograph.

  On the other hand, the ink is roughly classified into a dye ink in which a color material is dissolved in a solvent and a dispersed ink in which the color material is dispersed in a solvent. Since the dye ink is dissolved in a solvent, it tends to have good color developability and high chroma and is preferably used for outputting silver salt photographic images and the like. However, dye inks are basically prone to light fading, and when posting for a certain period of time, such as signboards and posters, there is a problem that if the surface is not laminated, it will fade immediately. It was. On the other hand, the dispersed ink generally does not easily cause light fading and is preferably used for the creation of a poster or the like. In the past, dispersed inks had a large dispersed particle size, mainly from the viewpoint of ensuring dispersion stability, and were completely unsuitable for silver salt photographic-like printing. The grain size was reduced, and silver salt photographic printing was also performed. Here, as the color material of the dispersed ink, for example, colored fine particles obtained by coating an organic pigment, an inorganic pigment, or a color material with a polymer or the like are used.

  In particular, in the ink jet recording method using the dispersed ink, in addition to the above-described improvement in the image quality similar to the silver salt photograph such as glossiness, the mottle pattern due to the absorbability of the printed dispersed ink into the ink jet recording medium is obtained. A higher level of resistance to generation (beading) and mixing between colors (bleeding) has been demanded. Furthermore, the print quality of plain paper such as copy paper, which is non-inkjet paper, is also required, and irregular bleeding (feathering) in the contour of the image is also a problem.

As a method for adjusting the penetrability of the ink into the ink jet recording medium and improving the print quality on the ink jet exclusive paper or plain paper, for example, triethylene glycol monobutyl ether or 1,2-hexanediol A method has been proposed in which a water-soluble organic solvent is used in dispersed ink to improve ink absorbability (see, for example, Patent Document 1). However, in the case of dispersed inks, particularly pigment inks containing dispersed pigment particles and inks containing colored fine particles, when the proposed water-soluble organic solvent is used, the dispersion stability of the dispersed particles is reduced. As a result, it has been found that the method does not satisfy both ink permeability and dispersion stability.
JP 2001-181547 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a water-based inkjet ink having excellent dispersion stability and improved gloss and feathering resistance of the obtained image.

The above object of the present invention is achieved by the following configurations.
(Claim 1)
An inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, wherein the water-soluble organic solvent contains 2.0% by mass or more of 1,2-pentanediol. Water based ink.
(Claim 2)
An inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, wherein the water-soluble organic solvent contains 2.0% by mass or more of 1,6-hexanediol. Water based ink.
(Claim 3)
An aqueous inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, wherein the water-soluble organic solvent contains 3.0% by mass or more of 2-methyl-2,4-pentanediol. An inkjet water-based ink.
(Claim 4)
An aqueous inkjet ink containing at least 3.0% by mass of triacetin as the aqueous organic solvent in an aqueous inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent.
(Claim 5)
In the water-based inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, the water-soluble organic solvent contains 1.0% by mass or more of 2- (2-n-butoxyethoxy) ethanol. A water-based ink for ink jet.
(Claim 6)
In the water-based inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, the water-soluble organic solvent contains 2.0% by mass or more of 2,5-dimethyl-2,5-hexanediol. An aqueous inkjet ink characterized by
(Claim 7)
An aqueous inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, wherein the water-soluble organic solvent contains 3.0% by mass or more of 2-methyl-1,3-propanediol. An inkjet water-based ink.
(Claim 8)
An inkjet water-based ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, wherein the water-soluble organic solvent contains 3.0% by mass or more of ethylene glycol isopropyl ether. .
(Claim 9)
An aqueous inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, wherein the aqueous water-soluble organic solvent contains 3.0% by mass or more of tripropylene glycol monomethyl ether as the water-soluble organic solvent. ink.
(Claim 10)
In the water-based inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, the water-soluble organic solvent includes triethylene glycol monobutyl ether, 1,2-hexanediol, 1,2-pentanediol, 1, 6-hexanediol, 2-methyl-2,4-pentanediol, triacetin, 2- (2-n-butoxyethoxy) ethanol, 2,5-dimethyl-2,5-hexanediol, 2-methyl-1,3 -Containing two or more solvents selected from propanediol, ethylene glycol isopropyl ether and tripropylene glycol monomethyl ether, the total content of the two or more solvents being 3.0 mass% or more, and triethylene Total content of glycol monobutyl ether and 1,2-hexanediol Aqueous ink-jet ink, characterized in that but less than 3.0 wt%.
(Claim 11)
The aqueous ink for inkjet according to any one of claims 1 to 10, wherein a volume maximum particle size measured by a laser scattering method of the colorant-containing particles in the colorant dispersion is less than 400 nm. ink.
(Claim 12)
The aqueous inkjet ink according to any one of claims 1 to 11, wherein the pH is 5.0 or more and less than 10.0.
(Claim 13)
The water-based ink for ink jet according to claim 1, wherein the color material contained in the color material dispersion is a pigment.
(Claim 14)
The water-based ink for ink-jet recording according to any one of claims 1 to 12, wherein the colorant dispersion contains polymer particles that are compatible or impregnated with a dye.

  ADVANTAGE OF THE INVENTION According to this invention, the aqueous ink for inkjets which was excellent in the dispersion stability and the glossiness and feathering tolerance of the image which were obtained can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

  In the present invention, a specific water-soluble organic solvent is used in a specific ratio in a water-based ink for ink-jet including a colorant dispersion, for example, a dispersion containing pigment particles or a dispersion containing polymer particles compatible or impregnated with a dye. It has been found that by containing it, it is possible to realize an aqueous inkjet ink having excellent dispersion stability and improved image gloss and feathering resistance regardless of the material of the inkjet recording medium.

  Hereinafter, the details of the water-based ink for inkjet according to the present invention will be described.

  First, the water-soluble organic solvent according to the present invention will be described.

  The aqueous inkjet ink according to the present invention is characterized by containing 1.0% by mass or more of 2- (2-n-butoxyethoxy) ethanol, and the content is preferably 1.0 to 10% by mass. In addition, the aqueous inkjet ink according to the present invention contains 1,2-pentanediol, 1,6-hexanediol, or 2,5-dimethyl-2,5-hexanediol in an amount of 2.0% by mass or more. Preferably, each content is 2.0 to 15% by mass. Further, in the aqueous inkjet ink of the present invention, 2-methyl-2,4-pentanediol, triacetin, 2-methyl-1,3-propanediol, ethylene glycol isopropyl ether or tripropylene glycol monomethyl ether is 3.0. It is the characteristic to contain more than mass%, Preferably each content is 3.0-20 mass%.

  Furthermore, in the water-based inkjet ink of the present invention, as the water-soluble organic solvent, triethylene glycol monobutyl ether, 1,2-hexanediol, 1,2-pentanediol, 1,6-hexanediol, 2-methyl-2 , 4-pentanediol, triacetin, 2- (2-n-butoxyethoxy) ethanol, 2,5-dimethyl-2,5-hexanediol, 2-methyl-1,3-propanediol, ethylene glycol isopropyl ether and tri It is characterized in that it contains two or more solvents selected from propylene glycol monomethyl ether, and the total content of the two or more solvents is 3.0% by mass or more, preferably the total content is 3. It is 0-20 mass%. At this time, the total content of triethylene glycol monobutyl ether and 1,2-hexanediol is less than 3% by mass, and preferably less than 3.0% by mass including 0% by mass.

  In the aqueous inkjet ink of the present invention, a known water-soluble organic solvent can be used in combination as long as the conditions specified in the present invention are satisfied and the object effects of the present invention are not impaired.

  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 , Ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenedia) , Diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.) Heterocycles (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides (for example, dimethyl sulfoxide, etc.), Examples include sulfones (for example, sulfolane), urea, acetonitrile, acetone, and the like.

  Next, the color material dispersion according to the present invention will be described.

  The color material dispersion referred to in the present invention refers to color material particles in which the color material itself is dispersed, or color material-containing fine particles (hereinafter also referred to as colored fine particles) formed by dissolving or impregnating a color material in a polymer or the like. It means what is contained in the medium.

  In the present invention, a pigment dispersion containing pigment particles in which a pigment is dispersed, or a colored fine particle dispersion formed by dissolving or impregnating a dye in a polymer or the like is preferable.

  First, the pigment dispersion will be described.

  As the pigment that can be used in the present invention, conventionally known organic and inorganic pigments can be used. For example, azo pigments such as azo lakes, 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. Examples include cyclic pigments, dye lakes such as basic dye lakes, and acid dye lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as carbon black.

  Specific organic pigments are exemplified below.

  Examples of pigments for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the orange or yellow pigment include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. And CI Pigment Yellow 138.

  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 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  The content of the pigment used in the water-based ink is preferably 1 to 10% by mass with respect to the total mass of the ink.

  In the present invention, a pigment dispersant may be used in preparing the pigment dispersion. Examples of the pigment dispersant that can be used include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, Sulfosuccinate, naphthalene sulfonate, alkyl phosphate, polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, Activators such as amine oxide, or selected from styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives Block copolymers of two or more monomers, mention may be made of the random copolymer and the salts thereof.

  As a dispersion method used for preparing the pigment dispersion, various types 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 coarse particles of the pigment dispersion obtained by the dispersion method using the pigment and the pigment dispersant.

  Next, the colored fine particle dispersion according to the present invention will be described.

  In the present invention, the color material is preferably an oil-soluble dye. Oil-soluble dyes are usually dyes that are soluble in organic solvents that do not have water-soluble groups such as carboxylic acids and sulfonic acids and are insoluble in water, but by salting water-soluble dyes with long-chain bases, Dyes that exhibit oil solubility are also included. For example, acid dyes, direct dyes, and salt-forming dyes of reactive dyes and long chain amines are known. The oil-soluble dye is not limited to the following, but particularly preferable specific examples include, for example, Valifast Yellow 4120, Valifast Yellow 3150, Varifast Yellow 3108, Varifast Yellow 2310N, and Valifast Y from Orient Chemical Industry Co., Ltd. 1101, Variast Red 3320, VariFast Red 3304, VariFast Red 1306, VariFast Blue 2610, VariFast Blue 2606, VariFast Blue 1603, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yell 29G ow 105, Oil Scallet 308, Oil Red RR, Oil Red OG, Oil Red 5B, Oil Pin 312, Oil Blue BOS, Oil Blue 613, Oil Blue 2N, Oil Black BY, Oil Black BS, Oil Black 60, Oil Black BS, Oil 70 , Oil Black 5906, Oil Black 5905, Kayset Yellow SF-G, Kayase Yellow K-CL, Kayase Yellow AG, Kayset Yellow A-G, Kayase Yellow 2G, Kayset Yellow 2G K-BL, Kayset Red A-BR , Kayset Magenta 312, Kayset Blue K-FL, FS Yellow 1015, FS Magenta 1404, FS Cyan 1522, FS Blue 1504, C.I. I. Solvent Yellow 88, 83, 82, 79, 56, 29, 19, 16, 14, 04, 03, 02, 01, C.I. I. Solvent Red 84: 1, C.I. I. Solvent Red 84, 218, 132, 73, 72, 51, 43, 27, 24, 18, 01, C.I. I. Solvent Blue 70, 67, 44, 40, 35, 11, 02, 01, C.I. I. Solvent Black 43, 70, 34, 29, 27, 22, 7, 3, C.I. I. Solvent Violet 3, C.I. I. Solvent Green 3 and 7, Plast Yellow DY352, Plast Red 8375, MS Yellow HD-180 manufactured by Mitsui Chemicals, MS Red G, MS Magenta HM-1450H, MS Blue HM-1384, ES Red 3001 manufactured by Sumitomo Chemical Co., Ltd. ES Red 3002, ES Red 3003, TS Red 305, ES Yellow 1001, ES Yellow 1002, TS Yellow 118, ES Orange 2001, ES Blue 6001, TS Turq Blue Yellow GE, Bayer's MACROLEL Yellow N 75E Yellow 6G , Ceres Blue GN, MACROLEX Re d Violet R and the like.

  In addition, metal complex dyes such as those disclosed in JP-A Nos. 9-277893, 10-20559, and 10-30061 are also preferably used. Preferred structures are those represented by the following general formula (1). is there.

General formula (1)
M (Dye) _p (A) _m
In the formula, M represents a metal ion, and Dye represents a dye capable of coordinating with a metal. A represents a ligand other than a dye, p represents 1 to 3, and m represents 0, 1, 2, or 3. When m is 0, p represents 2 or 3, in which case Dye may be the same or different.

  Examples of the metal ion represented by M include metals belonging to Groups 1 to 17 of the periodic table. Various dye structures are conceivable as the dye capable of coordinating with the metal represented by Dye, but conjugated methine dyes, azomethine dyes, and those having a coordination group in the azo dye skeleton are preferred.

  A disperse dye can be used as the oil-soluble dye, and the disperse dye is not limited to the following, but as a particularly preferred specific example, C.I. I. Disperse Yellow 5, 42, 54, 64, 79, 82, 83, 93, 99, 100, 119, 122, 124, 126, 160, 184: 1, 186, 198, 199, 204, 224 and 237; C . I. Disperse Orange 13, 29, 31: 1, 33, 49, 54, 55, 66, 73, 118, 119 and 163; C.I. I. Disperse Red 54, 60, 72, 73, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167: 1, 177 , 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356 and 362; I. Disperse violet 33; C.I. I. Disperse Blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165: 1, 165: 2, 176, 183, 185, 197, 198, 201, 214, 224, 225 257, 266, 267, 287, 354, 358, 365 and 368 and C.I. I. Disperse Green 6: 1 and 9 etc. are mentioned.

  Other oil-soluble dyes include phenols, naphthols, cyclic methylene compounds such as pyrazolone and pyrazolotriazole, or so-called couplers such as open-chain methylene compounds, p-phenylenediamines or p-diaminopyridines, and the like. Also preferred are azomethine dyes, indoaniline dyes and the like obtained by oxidative coupling of compounds. An azomethine dye having a pyrazolotriazole ring is particularly preferable as a magenta dye.

  Next, a polymer (resin) that is compatible or impregnated with the coloring material according to the present invention will be described.

  As the polymer according to the present invention, a generally known polymer can be used, but a polymer obtained by radical polymerization of a vinyl monomer having a polymerizable ethylenically unsaturated double bond is preferably used. .

  The polymer obtained by radical polymerization of a vinyl monomer having a polymerizable ethylenically unsaturated double bond preferably used in the present invention is preferably an acrylic polymer or a styrene-acrylic polymer, such as an acrylic ester, styrene- A copolymer such as an acrylic ester is preferred.

  Specific monomers that give the above polymers include vinyl acetate, methyl acrylate, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, dodecyl acrylate, Octadecyl acrylate, 2-phenoxyethyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, methacryl Cyclohexyl acid, stearyl methacrylate, benzyl methacrylate, glycidyl methacrylate, phenyl methacrylate, styrene, α-methylstyrene, acrylonitrile, etc., acetoacetoxyethyl Methacrylate, glycidyl methacrylate of soybean oil fatty acid modified products: include (Blenmer G-FA manufactured by NOF Corporation) and the like.

  More preferable combinations include styrene or methyl methacrylate as a main component, acetoacetoxyethyl methacrylate, glycidyl methacrylate modified with soybean oil fatty acid (Blemmer G-FA: manufactured by NOF Corporation), and n-butyl acrylate, methacrylic acid. Add at least one selected from long-chain (meth) acrylates such as stearyl acid and 2-ethylhexyl acrylate, and add acrylonitrile, divinylbenzene, diethylene glycol dimethacrylate, etc. as necessary to improve physical properties. The copolymer which can be mentioned can be mentioned.

  The above polymer may have a substituent, and the substituent may have a linear, branched, or cyclic structure. Various polymers having the above functional groups are commercially available, but can also be synthesized by a conventional method. These copolymers can also be obtained, for example, by introducing an epoxy group into one polymer molecule and then performing polycondensation with another polymer or graft polymerization using light or radiation.

  The weight average molecular weight of the polymer according to the present invention is preferably in the range of 2,000 to 50,000, more preferably 2,000 to 30,000, still more preferably 2,000. ~ 15,000.

  The method for measuring the weight average molecular weight of the polymer according to the present invention is determined by measurement by GPC (gel permeation chromatography) using THF (tetrahydrofuran) as a solvent.

  The Tg of the polymer according to the present invention can be variously used, but it is preferable to use at least one polymer having a Tg of 10 ° C. or higher among the polymers to be used. Moreover, from the viewpoint of improving the dispersion stability of the colored fine particles according to the present invention, the Tg of the polymer is preferably in the range of 0 ° C to 100 ° C.

  Next, the colored fine particles according to the present invention will be described.

  The colored fine particle dispersion according to the present invention is prepared by dissolving the above-described polymer (may be used in plural) and an oil-soluble dye in an organic solvent, and adding the reactive emulsifier thereto to emulsify in water. Thereafter, it is obtained by copolymerizing with a polymerizable monomer.

  Such a colored fine particle dispersion can be used to form an ink-jet ink. However, the colored fine particle dispersion can be prevented from agglomerating for a long period of time, and the stability of the fine particle as an ink suspension can be improved. In order to provide image fastness such as color tone and gloss when printed on a medium, and further light fastness, in the present invention, the core-shell type in which the colored fine particles are used as a core and a shell made of an organic polymer is formed. Colored fine particles are preferable.

  As a method for forming the shell, there is a method in which a polymer dissolved in an organic solvent is gradually dropped and adsorbed on the surface of the colored fine particle core at the same time as precipitation. In the present invention, a core containing a colorant and a resin is used. After forming colored fine particles, a monomer having a polymerizable unsaturated double bond is added, emulsion polymerization is performed in the presence of an activator, and a shell is formed by depositing on the core surface simultaneously with polymerization. Even when formed by this method, for example, when a dye is used as a color material, there is some phase mixing at the core / shell interface, and the color material content in the shell is not necessarily zero. However, less mixing is preferable, and the color material content (concentration) in the shell is preferably 0.8 or less of the color material content (concentration) in the core not subjected to core / shell formation, More preferably, it is 0.5 or less.

  Examples of the monomer having a polymerizable unsaturated double bond that forms a polymer covering the colorant particle as a shell include ethylene, propylene, butadiene, vinyl chloride, vinylidene chloride, vinyl acetate, styrene, (meth) acrylic acid esters, Compounds selected from (meth) acrylic acid, acrylamides, and the like, (meth) acrylic acid esters such as special styrene, ethyl (meth) acrylate, butyl (meth) acrylate, and ethylhexyl (meth) acrylate are preferred. In addition to these monomers, polymerizable unsaturated monomers containing a hydroxyl group in the molecule, for example, esters such as hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate, other ethylenic monomers It may be used in combination with a monomer having an unsaturated double bond. . In addition, for reasons such as increasing the stability of the shell, an ethylenic group containing a dissociable group having a pKa value of 3 to 7 such as a monomer containing a carboxylic acid such as acrylic acid or methacrylic acid or a monomer containing a sulfonic acid. You may use 10% or less of unsaturated monomers. By using these monomer components having hydroxyl groups (specifically, monomers having a hydration layer forming group such as acrylic acid or methacrylic acid) for shell formation, the core / shell colored fine particles are dispersed in water. Body stability is greatly improved.

  In the present invention, it is preferable that a dissociation group is present on the surface of the colored fine particles. With this configuration, good dispersion stability of the colored fine particle dispersion can be realized.

  It is important to evaluate whether it is actually a core shell. In the present invention, since the individual particle diameter is as very small as 200 nm or less, the analysis method is limited from the viewpoint of resolution. TEM, TOF-SIMS, etc. can be applied as an analysis method that meets such a purpose. When observing fine particles that have been core-shelled by TEM, the dispersion can be applied on a carbon support film, dried and observed. In the observation image of TEM, since the difference in contrast may be small only by the kind of polymer that is an organic substance, in order to evaluate whether it is a core-shell, fine particles are obtained by osmium tetroxide, ruthenium tetroxide, chlorosulfonic acid / It is preferable to dye using uranyl acetate, silver sulfide or the like. Dye the fine particles of the core only, observe the TEM, and compare with the one provided with a shell. Further, after mixing the fine particles provided with the shell and the fine particles not provided with the dye, the particles are dyed, and it is confirmed whether or not the proportion of the fine particles having different dyeing degree matches the presence or absence of the shell.

  In the colored fine particle dispersion according to the present invention, in order to obtain an appropriate particle size, optimization of the formulation and selection of an appropriate emulsification method are important. Although it differs depending on the colorant and polymer to be used, it is a suspension in water. Therefore, it is generally necessary that the polymer constituting the core is more hydrophilic than the polymer constituting the core. Further, the color material contained in the polymer constituting the shell is preferably less than the polymer constituting the core as described above, and the color material is also required to be less hydrophilic than the polymer constituting the shell. . The hydrophilicity and hydrophobicity can be estimated using, for example, the solubility parameter (SP) described above.

  The colored fine particle dispersion according to the present invention and the colored fine particles having a more preferable core / shell form are preferably in the range of 1: 0.1 to 1: 5 as the ratio of the coloring material to the polymer. The amount is preferably 0.5 to 50% by mass and more preferably 0.5 to 30% by mass in the aqueous ink of the present invention. If the blending amount of the polymer is less than 0.5% by mass, the color material cannot be sufficiently protected. If it exceeds 50% by mass, the storage stability of the suspension as a water-based ink may be reduced, or the tip of the nozzle The printer head may be clogged due to ink thickening or suspension agglomeration that accompanies evaporation of the ink in the above range.

  On the other hand, the colorant is preferably blended in the ink in an amount of 1 to 30% by mass, more preferably 1.5 to 25% by mass. If the blending amount of the coloring material is less than 1% by mass, the printing density is insufficient, and if it exceeds 30% by mass, the suspension stability with time decreases and the particle size tends to increase due to aggregation. It is preferable to be within the range.

  Next, an emulsification method used for producing the colored fine particle dispersion according to the present invention will be described. For the colored fine particle dispersion according to the present invention, various emulsification methods can be used, for example, in the production of the colorant particles serving as the core. These emulsification methods are summarized, for example, in the description on page 86 of “Progress of Functional Emulsifiers / Emulsification Technology and Application Development CMC”. In the present invention, it is particularly preferable to use an emulsifying and dispersing apparatus using ultrasonic waves, high-speed rotational shearing, and high pressure for forming the dye core.

  In the emulsification dispersion using ultrasonic waves, two types of so-called batch type and continuous type can be used. The batch method is suitable for producing a relatively small amount of sample, and the continuous method is suitable for producing a large amount of sample. In the continuous type, for example, a device such as UH-600SR (manufactured by SMT Co., Ltd.) can be used. In the case of such a continuous system, the ultrasonic wave irradiation time can be obtained by the volume of the dispersion chamber / flow velocity × the number of circulations. In the case where there are a plurality of ultrasonic irradiation apparatuses, the total irradiation time is obtained. The irradiation time of ultrasonic waves is practically 10000 seconds or less. Further, if it is necessary for 10000 seconds or more, the load on the process is large, and in practice, it is necessary to shorten the emulsification dispersion time by reselecting the emulsifier. Therefore, more than 10,000 seconds are not necessary. More preferably, it is 10 seconds or more and 2000 seconds or less.

  As an emulsifying and dispersing apparatus by high-speed rotational shearing, it is described in a disper mixer as described in pages 255 to 256 of "Functional emulsifier / emulsification technology and application development CMC", or page 251. Such a homomixer and an ultramixer as described on page 256 can be used. These types can be properly used depending on the liquid viscosity at the time of emulsification dispersion. In the emulsification disperser using these high-speed rotary shears, the rotational speed of the stirring blade is important. In the case of an apparatus having a stator, the clearance between the stirring blade and the stator is usually about 0.5 mm and cannot be made extremely narrow, so the shearing force mainly depends on the peripheral speed of the stirring blade. If the peripheral speed is 5 m / S or more and 150 m / S or less, it can be used for emulsification and dispersion of the present invention. This is because when the peripheral speed is low, it is often impossible to reduce the particle size even if the emulsification time is extended, and in order to achieve 150 m / S, it is necessary to extremely improve the performance of the motor. More preferably, it is 20-100 m / S.

For emulsification and dispersion by high pressure, LAB2000 (manufactured by SMT) can be used, but the emulsification and dispersion ability depends on the pressure applied to the sample. The pressure is preferably in the range of 10 ⁴ kPa to ⁵ × 10 ⁵ kPa. Moreover, it can emulsify and disperse | distribute several times as needed, and can obtain the target particle size. If the pressure is too low, the desired particle size cannot be achieved in many cases by carrying out emulsification and dispersion many times, and in order to make the pressure 5 × 10 ⁵ kPa, the apparatus is heavily loaded and is not practical. . More preferably, it is the range of 5 * 10 < ⁴ > kPa-2 * 10 < ⁵ > kPa.

  These emulsifying / dispersing devices may be used alone or in combination as necessary. Colloid mills, flow jet mixers, etc. alone cannot achieve the object of the present invention, but by combining with the apparatus of the present invention, it is possible to enhance the effects of the present invention, such as enabling emulsification and dispersion in a short time. is there.

  In the inkjet ink of the present invention, the volume maximum particle size measured by the laser scattering method of the color material-containing particles contained in the color material dispersion is preferably less than 400 nm, more preferably 10 nm or more and 400 nm. Is less than. When the volume maximum particle size is 10 nm or less, the surface area per unit volume becomes very large, so that the effect of encapsulating the coloring material in the core-shell polymer becomes small. On the other hand, if particles larger than 400 nm are present, the head tends to be clogged, and sedimentation in the ink tends to occur, so that the stagnation stability is deteriorated.

  In particular, in the present invention, the effect of dispersion stability in the present invention is more remarkable when the volume maximum particle size measured by the laser scattering method of the color material-containing particles contained in the color material dispersion is less than 400 nm. In addition, it is possible to obtain an ink exhibiting good glossiness on glossy paper which is a dedicated inkjet recording medium. Examples of the method for controlling the maximum particle size within the range specified in the present invention include a method for adjusting dispersion conditions such as dispersion time and dispersion medium size, a method for removing coarse particles by a centrifugal separation operation, and a filtration operation.

  The volume maximum particle diameter according to the present invention is measured by a laser scattering method, and can be measured by using, for example, a Zeta Sizer 1000 (manufactured by Malvern) based on a dynamic laser scattering method.

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

  The ink of the present invention is mainly composed of the above-described water-soluble organic solvent and a colorant dispersion using water as a medium. Further, various conventionally known additives, for example, wetting agents such as polyhydric alcohols, inorganic Salt, surfactant, antiseptic, antifungal agent, pH adjuster, silicone-based antifoaming agent, viscosity adjusting agent or chelating agent such as EDTA, oxygen absorber such as sulfite, etc. as necessary It may be added.

  Examples of the wetting agent that can be used in the present invention include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerin, diethylene glycol diethyl ether, diethylene glycol mono n-butyl ether, ethylene glycol monomethyl ether, Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methyl carbitol, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, diethyl carbitol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, etc. Polyhydric alcohols and their ethers, Use one or more of cetates, nitrogen-containing compounds such as N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, triethanolamine, formamide, dimethylformamide, and dimethylsulfoxide. Can do. Although there is no restriction | limiting in particular in the compounding quantity of these wetting agents, Preferably 0.1-50 mass% can be mix | blended in the said water-based ink, More preferably, 0.1-30 mass% can be mix | blended.

  In addition, an inorganic salt may be added to the ink in order to keep the viscosity of the ink stable and improve color development. Examples of inorganic salts include sodium chloride, sodium sulfate, magnesium chloride, magnesium sulfide and the like. When implementing this invention, it is not limited to these.

  Further, the emulsifier and the dispersant are not particularly limited, but the HLB value of 8 to 18 is preferable from the viewpoint of manifesting the effect or from the effect of suppressing the increase in the particle diameter of the suspension. .

  As the surfactant, any of cationic, anionic, amphoteric and nonionic can be used.

  The emulsifier or dispersant is preferably an anionic surfactant or a polymer surfactant, and an anionic surfactant is particularly preferable.

  The activator for adjusting the surface tension of the ink is preferably a nonionic surfactant.

  Examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts, and the like. Examples of the anionic surfactant include fatty acid soap, N-acyl-N-methylglycine salt, N-acyl-N-methyl-β-alanine salt, N-acyl glutamate, alkyl ether carboxylate, acyl Peptide, alkyl sulfonate, alkyl benzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α-olefin sulfonate, N-acylmethyl taurine, sulfated oil, higher alcohol Sulfate, secondary higher alcohol sulfate, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkyl phenyl ether sulfate, monoglyculate, fatty acid alkylolamide sulfate, alkyl ether phosphorus Acid Examples include stealth salts and alkyl phosphate ester salts. Examples of amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine and the like. Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether (eg, Emulgen 911), polyoxyethylene sterol ether, polyoxyethylene lanolin derivative, Polyoxyethylene polyoxypropylene alkyl ether (for example, Newpol PE-62), polyoxyethylene glycerin fatty acid ester, polyoxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyethylene Glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid Ester, sucrose fatty acid esters, fatty acid alkanolamides, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amines, alkyl amine oxides, acetylene glycol, acetylene alcohol, and the like. In addition, as the surfactant, for example, Dispersant Demol SNB, MS, N, SSL, ST, and P (trade name) manufactured by Kao Corporation can be given.

  When these surfactants are used, they can be used singly or as a mixture of two or more kinds. By adding 0.001 to 1.0% by mass with respect to the total amount of the ink, the surface of the ink can be used. Tension can be adjusted arbitrarily. When implementing this invention, it is not limited to these. In order to maintain the long-term storage stability of the ink, an antiseptic and an antifungal agent may be added to the ink.

  Moreover, the following water-soluble resins can be used as the polymer surfactant, which is preferable from the viewpoint of ejection stability. As the water-soluble resin, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid copolymer are preferably used. Polymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer Etc. Other examples of the polymer surfactant include Jonkrill, an acrylic-styrene resin (Johnson Corporation). Two or more of these polymer surfactants can be used in combination.

  The addition amount of each of the above polymer surfactants with respect to the total amount of the dispersed ink is preferably 0.1 to 10% by mass, more preferably 0.3 to 5% by mass. If the blending amount is less than 0.01% by mass, it is difficult to reduce the particle size of the suspension, and if it exceeds 10% by mass, the particle size of the suspension may increase or the suspension stability may decrease and gelation may occur. .

  Examples of the antiseptic / antifungal agent include aromatic halogen compounds (eg, Preventol CMK, chloromethylphenol, etc.), methylene dithiocyanate, halogen-containing nitrogen sulfur compounds, 1,2-benzisothiazolin-3-one (eg, PROXEL). GXL) and the like can be mentioned, but the present invention is not limited to these.

  In order to keep the inside of the ink stable, a pH adjusting agent may be added to the ink. As the pH adjuster, hydrochloric acid, acetic acid, citric acid, sodium hydroxide, potassium hydroxide or the like can be diluted with water or used as it is.

  Moreover, as said antifoamer, a commercial item can be used without a restriction | limiting in particular. 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 which concerns on 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.

  In the aqueous inkjet ink according to the present invention, the pH is preferably 5.0 or more and less than 10.0. By setting the pH within this range, the dispersion stability can be further improved.

  When an image is formed by ejecting the ink of the present invention, the inkjet 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, thermal ink jet) Any discharge method such as a mold, a bubble jet (R) type, or the like may be used.

  Next, an image forming method using the aqueous inkjet ink of the present invention will be described.

  In the image forming method that can be used in the present invention, it is preferable that ink is ejected as droplets from an inkjet head based on a digital signal by a printer or the like loaded with the ink of the present invention and deposited on an inkjet recording medium.

  As the inkjet recording medium, for example, any of plain paper, coated paper, cast coated paper, glossy paper, glossy film, and OHP film can be used. Among them, for example, a porous layer is formed on a support. An ink jet recording medium having an ink absorbing layer having a so-called void layer is preferable. The material or shape of the support described above is not particularly limited, and for example, it may have a three-dimensional structure other than those formed in a sheet shape.

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

<< Preparation of colorant dispersion >>
[Preparation of Pigment Dispersion P1]
According to the following method, a pigment dispersion P1 was prepared in which pigment particles were dispersed in a medium containing water as a main component.

(Preparation of polymer dispersant P)
A 3 liter four-necked flask is equipped with a dripping device, thermometer, nitrogen gas inlet tube, stirring device and reflux condenser. While heating and refluxing 1000 g of ethyl acetate, 500 g of styrene, 200 g of stearyl methacrylate, acrylic A mixed solution containing 300 g of acid and 20 g of N, N′-azobisisovaleronitrile was added dropwise over 2 hours. Subsequently, after making it react at 80 degreeC for 5 hours, ethyl acetate was distilled and 1000g of methanol was added. Thereafter, an equivalent amount of sodium hydroxide was added for neutralization, and then methanol was distilled to obtain a polymer dispersant P.

(Preparation of pigment dispersion)
C. I. Pigment Blue 15: 3 (150 g), Polymer Dispersant P (45 g), Methanol (25 g), ion-exchanged water (780 g) were mixed, and dispersed using a sand grinder filled with 50% by volume of 1 mm zirconia beads. Dispersion P1 was obtained.

  After this pigment dispersion was diluted 5000 times, the particle size measurement was performed five times by measuring the scattering intensity distribution of Zetasizer 1000 (Malvern), and the volume average particle size was calculated by arithmetically averaging the measured values. The maximum particle size was 420 nm.

[Preparation of Pigment Dispersion P2]
In the preparation of the pigment dispersion P1, a part of the pigment dispersion P1 is subjected to a 1600 G centrifuge, and the centrifugal treatment is performed until the volume maximum particle size of the 50% by volume supernatant liquid dispersion is about 300 nm from the top of the centrifuge tube. Was given. After completion of the centrifugation, the supernatant dispersion liquid was collected, and this was used as a pigment dispersion P2. The volume maximum particle size was measured by the same method as for the dispersion P1, and as a result, it was 315 nm.

(Preparation of colored fine particle dispersion)
A core-shell type colored fine particle dispersion in which a polymer and a dye are compatible was prepared according to the following method.

(Preparation of core polymer CP)
A 3 liter four-necked flask is equipped with a dripping device, thermometer, nitrogen gas inlet tube, stirring device and reflux condenser. While heating and refluxing 1000 g of ethyl acetate, 500 g of styrene, 200 g of stearyl methacrylate, acetoacetoxy A mixed solution containing 300 g of methacrylate and 20 g of N, N′-azobisisovaleronitrile was dropped over 2 hours and reacted at the same temperature for 5 hours, and then a core polymer CP having a solid content of 50% by mass was obtained. It was.

(Preparation of colored fine particle dispersion D)
In a pot of Cleamix CLM-0.8S (M Technic Co., Ltd.), 18 g of FS Blue 1504 (Arimoto Chemical Co., Ltd.) as a dye, 140 g of the above core polymer CP and ethyl acetate of 15 g in solid content, A dye solution was prepared by stirring to completely dissolve the dye. Next, a solution obtained by adding 9 g of Aqualon KH-05 (Daiichi Kogyo Seiyaku Co., Ltd.) to 258 g of pure water was added to the dye solution, followed by emulsification for 5 minutes at a rotational speed of 20000 rpm. Thereafter, ethyl acetate was removed under reduced pressure to obtain a colored fine particle core dispersion.

260 g of this colored fine particle core dispersion was transferred to a three-separable flask, the inside of the flask was replaced with N ² , and then heated to 80 ° C. with a heater. Next, a mixed liquid containing 1 g of methyl methacrylate and 0.5 g of N, N′-azobisisovaleronitrile is dropped over 1 hour, and further reacted for 6 hours to obtain a core-shell type colored fine particle dispersion D. It was.

<Preparation of ink>
[Preparation of Ink 1]
Pigment dispersion P1 15g
1,2-pentanediol 5g
Ethylene glycol 13g
Glycerin 15g
Surfactant: Olfine E1010 (Nisshin Chemical Co., Ltd.) 0.5g
Preservative: Proxel GXL (Avecia) 0.1g
The above additives were mixed and pure water was added to make 100 g. Subsequently, it filtered with a 0.8 micrometer membrane filter, and removed the dust and the coarse particle, and prepared the ink 1 which is a water-based ink for inkjet.

[Preparation of inks 2 to 23]
In the preparation of the ink 1, inks 2 to 23 were prepared in the same manner except that the type of the colorant dispersion and the type of the water-soluble organic solvent were changed according to the combinations shown in Table 1.

  Table 1 shows the configuration of each ink obtained as described above.

  In addition, the detail of the abbreviation of each water-soluble organic solvent described in Table 1 is as follows.

1,2-PD: 1,2-pentanediol (water-soluble organic solvent according to the present invention)
1,2-HD: 1,2-hexanediol (water-soluble organic solvent according to the present invention)
1,6-HD: 1,6-hexanediol (water-soluble organic solvent according to the present invention)
TA: Triacetin (water-soluble organic solvent according to the present invention)
EG: ethylene glycol DEG: diethylene glycol Gly: glycerin Solv-1: 2- (2-n-butoxyethoxy) ethanol (water-soluble organic solvent according to the present invention)
Solv-2: 2-methyl-2,4-pentanediol (water-soluble organic solvent according to the present invention)
Solv-3: 2,5-dimethyl-2,5-hexanediol (water-soluble organic solvent according to the present invention)
Solv-4: 2-methyl-1,3-propanediol (water-soluble organic solvent according to the present invention)
Solv-5: ethylene glycol isopropyl ether (water-soluble organic solvent according to the present invention)
Solv-6: Tripropylene glycol monomethyl ether (water-soluble organic solvent according to the present invention)
Solv-7: Triethylene glycol monobutyl ether (water-soluble organic solvent according to the present invention)

<Measurement of ink characteristic values>
After each ink prepared above was diluted 1000 times with pure water, the particle size was measured five times by measuring the scattering intensity distribution of Zetasizer 1000 (manufactured by Malvern), and the measured value was arithmetically averaged to obtain the maximum volume particle size. Was calculated. Moreover, about each prepared said ink, pH of the ink in 25 degreeC was measured using pH electrode GTS-5221C by Toa DKK Corporation.

<< Image formation and evaluation >>
[Image formation]
Each of the inks prepared above is packed in a genuine color ink cartridge and filled in an ink jet printer CL-750 (manufactured by Seiko Epson Corporation). Characters were printed on copy paper Xerox 4024 (manufactured by Xerox Co., Ltd.), and images 1 to 23 were created.

[Evaluation of gloss]
The degree of gloss of each image formed on inkjet paper photo-like QP was visually observed, and the gloss was evaluated according to the following criteria.

A: The formed image is glossy and has a very good gloss. ○: The glossy and glossy is good. B: The formed image lacks a glossy feeling. Glossiness is felt ×: The formed image has poor glossiness and lacks glossiness (evaluation of feathering resistance)
Feathering of printed characters was visually observed for each image on which characters were printed on copy paper Xerox 4024 (manufactured by Xerox Co., Ltd.), which is plain paper, and feathering resistance was evaluated according to the following criteria.

○: Feathering was not recognized at all, and the character quality was very good. △: Slight feathering was observed. ×: Clear feathering occurred and the outline of the character was unclear [Dispersion stability. Evaluation of〕
Each of the inks prepared above was packed in a glass sample bottle and stored for one month in a thermostatic bath at 60 ° C. Thereafter, similarly to the above method, each color solid image was printed on the inkjet paper photo-like QP using the inkjet printer CL-750. When printing, visually observe the ejection state of the ink droplets from the nozzles of the recording head of the ink jet printer, and visually check the image (pre-storage image) created by the gloss evaluation above. Comparison was made and dispersion stability was evaluated according to the following criteria.

◎: Ink can be ejected without any problem, and the printed image has exactly the same image quality as the image before the storage process. ○: The ink can be ejected without any problem, and the printed image is slightly uneven compared to the image before the storage process. It can be determined that the image quality is within the same range. △: Nozzles with missing nozzles or poor emission occurred sporadically, and white streaks were observed in the printed image compared with the pre-storage image. ×: Inkjet printer cleaning Table 2 shows the results obtained as described above.

  As is apparent from the results in Table 2, the ink containing the pigment dispersion and the water-soluble organic solvent according to the present invention in a specified amount has excellent dispersion stability and good gloss and feathering resistance compared to the comparative example. I understand that there is. Furthermore, it was confirmed that the ink having the volume maximum particle size of the colorant-containing particles of less than 400 nm is more excellent in dispersion stability and gloss.

Claims (14)

An inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, wherein the water-soluble organic solvent contains 2.0% by mass or more of 1,2-pentanediol. Water based ink. An inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, wherein the water-soluble organic solvent contains 2.0% by mass or more of 1,6-hexanediol. Water based ink. An aqueous inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, wherein the water-soluble organic solvent contains 3.0% by mass or more of 2-methyl-2,4-pentanediol. An inkjet water-based ink. An aqueous inkjet ink containing at least 3.0% by mass of triacetin as the aqueous organic solvent in an aqueous inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent. In the water-based inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, the water-soluble organic solvent contains 1.0% by mass or more of 2- (2-n-butoxyethoxy) ethanol. A water-based ink for ink jet. In the water-based inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, the water-soluble organic solvent contains 2.0% by mass or more of 2,5-dimethyl-2,5-hexanediol. An aqueous inkjet ink characterized by An aqueous inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, wherein the water-soluble organic solvent contains 3.0% by mass or more of 2-methyl-1,3-propanediol. An inkjet water-based ink. An inkjet water-based ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, wherein the water-soluble organic solvent contains 3.0% by mass or more of ethylene glycol isopropyl ether. . An aqueous inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, wherein the aqueous water-soluble organic solvent contains 3.0% by mass or more of tripropylene glycol monomethyl ether as the water-soluble organic solvent. ink. In the water-based inkjet ink containing at least water, a colorant dispersion, and a water-soluble organic solvent, the water-soluble organic solvent includes triethylene glycol monobutyl ether, 1,2-hexanediol, 1,2-pentanediol, 1, 6-hexanediol, 2-methyl-2,4-pentanediol, triacetin, 2- (2-n-butoxyethoxy) ethanol, 2,5-dimethyl-2,5-hexanediol, 2-methyl-1,3 -Containing two or more solvents selected from propanediol, ethylene glycol isopropyl ether and tripropylene glycol monomethyl ether, the total content of the two or more solvents being 3.0 mass% or more, and triethylene Total content of glycol monobutyl ether and 1,2-hexanediol Aqueous ink-jet ink, characterized in that but less than 3.0 wt%. The aqueous ink for inkjet according to any one of claims 1 to 10, wherein a volume maximum particle size measured by a laser scattering method of the colorant-containing particles in the colorant dispersion is less than 400 nm. ink. The aqueous inkjet ink according to any one of claims 1 to 11, wherein the pH is 5.0 or more and less than 10.0. The water-based ink for ink jet according to claim 1, wherein the color material contained in the color material dispersion is a pigment. The water-based ink for ink-jet recording according to any one of claims 1 to 12, wherein the colorant dispersion contains polymer particles that are compatible or impregnated with a dye.