JP2005089554A - Water-based ink, its ink set, ink jet recording method and recorded image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based ink which gives prints having high chroma, high concentration and excellent water resistance, even when printed on plain paper, to provide an ink set, to provide an ink jet recording method, and to provide a recorded image. <P>SOLUTION: This water-based ink is characterized in that the surface tension of the water-based ink containing colored fine particles having a colorant and a polymer is 37 to less than 55 mN/m. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a water-based ink, an ink set thereof, an ink jet recording method, and a recorded image.

  In recent years, the ink jet recording system can create images easily and inexpensively, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters. In particular, a recording device that emits and controls fine dots, ink that has improved color reproduction gamut, durability, and emission suitability, and ink absorbability, coloring material color development, surface gloss, etc. have been dramatically improved. It is also possible to obtain image quality comparable to silver halide photography using special paper. The image quality improvement of today's ink jet recording system is achieved only when all of the recording apparatus, ink, and special paper are available.

  As water-based recording materials used for ink jet recording, those mainly composed of an aqueous solution of a water-soluble dye and those mainly composed of a fine dispersion of a pigment are widely used.

  Water-based inks that use water-soluble dyes are mainly water-soluble dyes classified as acidic dyes, direct dyes, and some food dyes. Glycols, alkanolamines, and moisturizers are used to adjust surface tension. In addition, a surfactant added with a thickener or the like as required is used. Water-based inks using these water-soluble dyes are most commonly used because of their reliability against clogging at the tip of a pen or printer, but they tend to bleed on recording paper, forcing limited use and lowering of recording quality. Has been. In other words, it is difficult to say that a water-soluble dye that has only penetrated into recording paper and has been dry-fixed is “dyed”. .

  On the other hand, water-based inks using dispersed pigments as coloring materials and using solvents and additives similar to water-soluble dyes are also used. Such a pigment ink is excellent in light fastness and water resistance in plain paper printing. Furthermore, a pigment ink having a surface tension at 20 ° C. of 45 mN / m or more is disclosed as a pigment ink from which a high-resolution image can be obtained (see, for example, Patent Document 8). However, since pigment ink uses solid color material in a dispersed state, it does not dissolve like dye ink, but color material tends to aggregate, and even if the amount of ink applied is increased, the concentration may be saturated. In many cases, the saturation of the image was impaired. In particular, when the surface tension of the ink is increased, regardless of whether the color material is a water-soluble dye or pigment, it tends to localize near the surface layer of the recording material, and saturation is a more serious problem. It was.

  In order to solve the problem of low water fastness and light fastness of water-based inks using water-soluble dyes, proposals for coloring water-dispersible resins with oil-soluble dyes or hydrophobic dyes (see, for example, Patent Documents 1 to 7). ) Has been made. In addition to coloring water-dispersible resins with oil-soluble dyes and hydrophobic dyes, color materials and colored fine particles composed of resins coated therewith, and color material particles composed of colorants and resins are further coated with a film-forming resin. Attempts have also been made to use colored fine particles.

As an example using these colored fine particles, there is a description of colored resin fine particles using a vinyl polymer (for example, see Patent Document 9). However, the surface tension of the ink exemplified here is 31.5 mN / m to 36.2 mN / m, and the concept of adjusting the surface tension for plain paper applications is not shown.
JP 55-139471 A JP 58-45272 A Japanese Patent Laid-Open No. 3-250069 JP-A-8-253720 (Claim 1) JP-A-8-92513 (Claim 1) JP-A-8-183920 (Claims) JP 2001-11347 A (Claims) Japanese Patent Laid-Open No. 5-171082 (Claims, Table 8 of Examples) JP-A-11-61017 (Claim 1, page 11)

  An object of the present invention is to provide a water-based ink having high saturation and density and no image blur even when printed on plain paper, an ink set thereof, an ink jet recording method, and a recorded image.

The above object of the present invention can be achieved by the following configuration.
(Claim 1)
A water-based ink characterized in that the surface tension of a water-based ink containing colored fine particles having a coloring material and a polymer is 37 mN / m or more and less than 55 mN / m.
(Claim 2)
The water-based ink according to claim 1, wherein the surface tension is 40 mN / m or more and less than 45 mN / m.
(Claim 3)
The water-based ink according to claim 1 or 2, wherein the coloring material is impregnated or compatible with the polymer.
(Claim 4)
The water-based ink according to any one of claims 1 to 3, wherein the volume average particle diameter of the colored fine particles measured by a laser scattering method is less than 150 nm, and the volume maximum particle diameter is less than 400 nm.
(Claim 5)
The water-based ink according to any one of claims 1 to 4, wherein the volume average particle diameter of the colored fine particles measured by a laser scattering method is less than 50 nm, and the volume maximum particle diameter is less than 250 nm.
(Claim 6)
The water-based ink according to any one of claims 1 to 5, wherein the colored fine particles contain a vinyl polymer.
(Claim 7)
The water-based ink according to claim 1, wherein the coloring material of the colored fine particles is an oil-soluble dye.
(Claim 8)
An ink set, wherein at least one of yellow, magenta, cyan, and black is the water-based ink according to any one of claims 1 to 7.
(Claim 9)
The ink set according to claim 8, wherein the black ink is the water-based ink according to any one of claims 1 to 7.
(Claim 10)
An ink set, wherein each of the colors yellow, magenta, cyan, and black is the water-based ink according to any one of claims 1 to 7.
(Claim 11)
An ink-jet recording method comprising printing the water-based ink according to any one of claims 1 to 7 on plain paper.
(Claim 12)
An inkjet recording image obtained by printing the water-based ink according to any one of claims 1 to 7 on plain paper.

  According to the present invention, it is possible to provide water-based ink, an ink set thereof, an ink jet recording method, and a recorded image having high saturation and density and no image blur even when printed on plain paper.

  The present invention will be described in more detail. In a general pigment ink, aggregation occurs when a color material is localized on the surface layer of a recording material, resulting in a decrease in saturation and saturation of density. Also in the dye ink, particularly when the surface tension is increased, the dye is deposited on the surface layer of the recording material, which causes the same problem as that of the pigment ink. On the other hand, the ink of the present invention also has a high surface tension, and localization of dispersed particles on the surface layer is considered to occur similarly to the pigment ink. However, since the color material is coated with a polymer, the color materials are aggregated. Be inhibited. It is considered that an aqueous ink having a high density and saturation is obtained while having the advantage of a high surface tension ink that a high-definition image can be obtained by such an effect of preventing the colorant aggregation of the polymer.

  The surface tension of the ink of the present invention is 37 mN / m or more and less than 55 mN / m, more preferably 40 mN / m or more and less than 45 mN / m. If the surface tension is lower than this range, the ink dots spread and a high-definition image cannot be obtained, and the print density is insufficient. On the other hand, when the surface tension is higher than this range, the wettability with respect to the ink flow path is deteriorated, and it is difficult to discharge the bubbles accumulated in the flow path. As a result, the emission stability is deteriorated. When a dispersion is prepared by emulsifying and dispersing colored fine particles with an activator and a dispersant, the excess activator / dispersant may decrease the surface tension, making it difficult to adjust the surface tension of the ink. . Also, the surface tension may be lowered by unreacted monomers or dyes which are not impregnated in the polymer and are released. In order to avoid this problem, it is preferable to perform adsorption purification using a resin or activated carbon or purification using an ultrafiltration membrane after the preparation of the dispersion or after the preparation.

  Examples of the adsorbent include activated carbon, ion exchange resin, and synthetic resin. Specific examples of activated carbon products include Futamura K, S, M, P, A, SG, SGP, etc. manufactured by Nimura Chemical Industry Co., Ltd., Takeda Pharmaceutical Co., Ltd., Shirahama A, M, C, P, carborafine, strong white birch, etc. Can be mentioned.

  The ion exchange resin and synthetic resin are Diaion SK1B, SK104, PK208, PK212, SA10A, SA20A, PA306, PA308, PA316, PA406, WK10, WK20, WA10, WA10, WA20, CR11, CR20, HP10, HP20, manufactured by Mitsubishi Chemical Corporation. HP30, SP800, SP825, SP850, SP205, SP206, HP1MG, HP2MG and the like. Moreover, Amberlite IR120B-Na, IR124-Na, IRC50, IRC76, IRA400J-Cl, 4400Cl, IRA900J-Cl, IRA67, Amberlist 15DRY, 15JWET, etc. manufactured by Organo Corporation can be mentioned.

  Furthermore, as an ultrafiltration membrane which can be used in the present invention, Nitto Denko Corporation NTU-2020, 2120, 3520, 3150, 3006, 3050, 3250, 3550, 4208, 4220, NFS-100, 101, 103, NTM-9002 etc. Asahi Kasei Kogyo Co., Ltd. AIV-3010, 5010, ACV-3010, 3050, 5010, 5050, SIW-3054, SEP-1013, SAP-1013, SIP-1013, SLP-1053, etc. can be mentioned.

  The polymer used in the present invention has a number average molecular weight of 500 to 100,000, particularly 1,000 to 30,000, in terms of film-forming properties after printing, durability and suspension formability. To preferred.

  As the polymer used in 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. Examples thereof include copolymers such as acrylic acid esters, styrene-acrylic acid esters, and vinyl acetate-acrylic acid esters.

  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 water in which the colored fine particles of the present invention are dispersed (also referred to as a colored fine particle aqueous dispersion) is obtained by dissolving the polymer (which may be used in plural) and a coloring material (dye or pigment) in an organic solvent (or Dispersed) and emulsified in water, and then formed by a method of removing the organic solvent. Alternatively, for example, a method in which an aqueous dispersion of polymer fine particles is formed in advance by emulsion polymerization, an organic solvent solution in which a dye is dissolved is mixed with the aqueous dispersion of polymer fine particles, and then the polymer fine particles are impregnated with the dye. Can be obtained by various methods.

  Such an aqueous dispersion of colored fine particles can be used to form a water-based 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 impart fastness to the image, such as the color tone and gloss of the image printed on the medium, and light resistance, it is preferable to form a shell made of an organic polymer with the colored fine particles as a core.

  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 the precipitation. In the present invention, a core containing a coloring material and a polymer 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. 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, a raw material for forming a shell from a polymerizable unsaturated monomer containing a hydroxyl group in the molecule, for example, an ester such as hydroxyalkyl (meth) acrylate such as hydroxyethyl (meth) acrylate Up to 50% of total monomer, other ethylenic unsaturation It is preferably used in admixture with monomers having a 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. The unsaturated monomer may be used in an amount of 10% or less and less than the monomer containing the hydroxyl group. Furthermore, what melt | dissolves 50 mass% or more in ethyl acetate is preferable as a core polymer.

  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 a mass spectrometer such as TOF-SIMS, it is confirmed that the amount of color material in the vicinity of the surface is reduced by providing a shell on the particle surface as compared with the case of only the core. When there is an element not contained in the polymer of the core shell in the color material, it can be confirmed whether or not a shell having a small color material content is provided using the element as a probe.

  In the absence of such an element, the colorant content in the shell can be compared with that without the shell using an appropriate dye. For example, the core-shell formation can be observed more clearly by embedding the core-shell particles in an epoxy resin, preparing an ultrathin section with a microtome, and performing staining. As described above, when there is an element that can be a probe in a polymer or a color material, the composition of the core shell and the distribution amount of the color material to the core and shell can be estimated by TOF-SIMS or TEM.

  In order to obtain the necessary particle size in the colored fine particles of the present invention, it is important to optimize the formulation and select an appropriate emulsification method. The formulation differs depending on the color material and polymer used, but since it is a suspension in water, 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).

  In the present invention, the average particle size of the colored fine particles measured by the laser scattering method is preferably less than 150 nm, more preferably less than 50 nm, and the maximum particle size is preferably less than 400 nm, more preferably less than 250 nm. By setting the particle size within this range, an image with higher saturation can be obtained.

  The particle size distribution can be measured using the laser scattering method, for example, using a laser particle size analysis system manufactured by Otsuka Electronics or a Zetasizer manufactured by Malvern.

  As the hue of the color material used in the present invention, yellow, magenta, cyan, black, blue, green, and red are preferably used, and yellow, magenta, cyan, and black dyes are particularly preferable. 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. However, oil-soluble dyes are oil-soluble by salting water-soluble dyes with long-chain bases. The dye which shows is 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, and particularly preferable specific examples include, for example, Valifast Yellow 4120, Valifast Yellow 3150, Varifast Yellow 3108, Varifast Yellow 2310N, and Valifast Yell 1101 manufactured by Orient Chemical Industry Co., Ltd. , Variast Red 3320, Variast Red 3304, Variast Red 1306, Variast Blue 2610, Variast Blue 2606, Variast Blue 1603, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow GG-S, Oil Yellow w 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 BS, Oil 70 Bac , Oil Black 5906, Oil Black 5905, Kayset Yellow SF-G, Kayase Yellow K-CL, Kayase Yellow AG, Kayset Yellow A-G, Kayset Yellow A-G, Kayset Yellow 2G, Kayset Yellow 2K -BL, Kayset Red A-BR, K ayase Magenta 312, Kayase Blue K-FL, Kayase Pink FN, Kayase Red A-5B, FS Yellow 1015, FS Magenta 1404, FS Cyan 1522, FS Blue 1504, FS Blue 1504. 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, Mitsui Chemicals MS Yellow HD-180, MS Red G, MS Magenta HM-1450H, MS Blue HM-1384, Sumitomo Chemical ES Red 3001, 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 618 Ner Elu Yellow 6G, Cer GB Yellow Nlu 6G GN, MACROLEX Red V olet 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.

  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.

  The colored fine particle dispersion according to the present invention and the colored fine particles having a more preferable core / shell form are preferably blended in an amount of 0.5 to 50% by mass in the aqueous ink of the present invention as a polymer amount. More preferably, 5 to 30% by mass is blended. If the blending amount of the polymer is less than 0.5% by mass, the color material cannot be protected sufficiently. 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, it is preferable that 1-30 mass% is mix | blended in this ink as coloring materials, such as the said dye and a pigment, and it is still more preferable that 1.5-25 mass% is mix | blended. 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.

  The water-based ink of the present invention comprises a suspension of a polymer containing water as a medium and encapsulating the coloring material, and the suspension includes various conventionally known additives, for example, wetting agents such as polyhydric alcohols, inorganic salts, surface activity. Additives, preservatives, antifungal agents, pH adjusters, antifoaming agents such as silicones, viscosity modifiers or chelating agents such as EDTA, oxygen absorbers such as sulfites, etc. may be added as necessary Good.

  Here, as the wetting agent, for example, 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 Polyhydric alcohols such as 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 And its ethers, acetates, N Can be used methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, triethanolamine, formamide, nitrogen-containing compounds such as dimethyl formamide, dimethyl monkey sulfoxide one or two or more kinds. 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-system 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 anionic surfactants include fatty acid soap, N-acyl-N-methylglycine salt, N-acyl-N-methyl-β-alanine salt, N-acyl glutamate, alkyl ether carboxylate, acylated peptide , Alkyl sulfonate, alkyl benzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α-olefin sulfonate, N-acylmethyl taurine, sulfated oil, higher alcohol sulfate Salts, secondary higher alcohol sulfates, alkyl ether sulfates, secondary higher alcohol ethoxy sulfates, polyoxyethylene alkylphenyl ether sulfates, monoglyculates, fatty acid alkylolamide sulfates, alkyl ether phosphates Salt, alkyl phosphate ester salt and the like.

  Examples of amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine and the like.

  Nonionic surfactants 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, New Pole 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, examples of the surfactant include dispersants Demol SNB, MS, N, SSL, ST, and P (trade names) manufactured by Kao Corporation.

  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 (for example, Preventol CMK, chloromethylphenol), methylene dithiocyanate, halogen-containing nitrogen sulfur compounds, 1,2-benzisothiazolin-3-one (for example, PROXEL GXL). However, 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 water-system ink of this invention. If the compounding amount of the compound is less than 0.001% by mass, bubbles are likely to be generated at the time of preparing the ink, and it is difficult to remove small bubbles in the ink. During printing, repellency may occur in the ink and the print quality may be deteriorated.

  Next, the emulsification method used in the production of the ink of the present invention will be described. In the ink of the present invention, various emulsification methods can be used, for example, in the production of core color material particles or in the production of core-shell colored fine particles directly from pigment particles and a polymer. Various methods can be used as the emulsification method. Examples thereof are summarized in the description on page 86 of “Advances in Functional Emulsifier / 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. For pigments, a media disperser is preferred.

  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.

  When forming an image by ejecting the water-based ink for ink-jet recording of the present invention, the ink-jet 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.

  In the image forming method using the water-based ink for ink-jet recording of the present invention, for example, the ink is ejected as droplets from the ink-jet head based on the digital signal by a printer loaded with the water-based ink for ink-jet recording and attached to the ink receptor. By doing so, for example, an inkjet print in which an inkjet recording image is formed on an inkjet image recording medium is obtained.

  As the inkjet image recording medium, for example, any of plain paper, coated paper, cast coated paper, glossy paper, glossy film, and OHP film can be used, and for example, a so-called void layer in which a porous layer is formed, for example. It is preferable if the recording medium has It is not particularly limited to the material or shape of the support described above, and for example, it may have a three-dimensional structure other than those formed in a sheet shape.

  The water-based ink of the present invention can be used as ink for writing instruments such as general fountain pens, ballpoint pens, sign pens, etc., in addition to ink for inkjet recording. The suspension of the present invention can be dried to obtain a fine powder. The obtained powder can be used for toner for electrophotography.

  Hereinafter, the present invention will be described in more detail with reference to synthesis examples and examples, but the present invention is not limited to the scope of these examples.

(Method for synthesizing polymers P-1 to P-3)
A dropping device, a thermometer, a nitrogen gas introduction tube, a stirring device, and a reflux condenser were attached to a 3 liter four-necked flask, and 1000 g of ethyl acetate was heated to reflux. The mixture was weighed so that the total amount of monomers was 1000 g at the ratio shown in Table 1, and then a mixed solution obtained by adding 20 g of N, N′-azobisisovaleronitrile to the monomer was added dropwise over 2 hours. After reacting for a period of time, polymers P-1 to P-3 in Table 1 having a solid content of 50% by mass were obtained. For the pigment dispersion polymer P-3, ethyl acetate was distilled after synthesis and 1000 g of methanol was added. Further, an equivalent amount of sodium hydroxide was added for neutralization, and then methanol was distilled to obtain a pigment-dispersing polymer P-3.

(Manufacturing colored fine particles)
In a pot of Creamix CLM-0.8S (M Technic Co., Ltd.), 15 g of the following Y dye, 7.5 g of polymer P-1 in terms of solid content, 7.5 g of polyvinyl butyral BL-S (Sekisui Chemical Co., Ltd.) And 140 g of ethyl acetate were added and stirred to completely dissolve the dye. 4.5 g of Aqualon KH-05 (Daiichi Kogyo Seiyaku Co., Ltd.) was added to 250 g of pure water, added to the dye solution, and emulsified for 5 minutes at a rotational speed of 20000 rpm. Thereafter, ethyl acetate was removed under reduced pressure to obtain core fine particles Y1.

260 g of the Y1 core fine particle 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. A mixed solution of 6.7 g of methyl methacrylate and 0.5 g of N, N′-azobisisovaleronitrile was added dropwise over 1 hour, and the mixture was further reacted for 6 hours to obtain core-shell colored fine particles Y1.

  In accordance with the formulation shown in Table 2 for M1, C1, K1, Y2, M2, C2, and K2, core-shell colored fine particles were produced by the same method.

(Concentration process of colored fine particles)
Colored fine particles obtained by concentrating 250 g of the C1 core-shell colored fine particle dispersion to a 2.5-fold concentration using an ultrafiltration membrane device RUM-2 / C10-T (manufactured by Nitto Denko Corporation / ultrafiltration membrane: NTU-3150) C1 was obtained.

  Regarding C2, K1, and K2, the dispersion was concentrated in the same manner according to the concentration ratio shown in Table 2.

(Purification process of colored fine particles)
40 g of activated carbon (Shirakaba C, manufactured by Takeda Pharmaceutical Company Limited) was added to 100 g of the colored fine particle dispersion of Y1, and the mixture was stirred at room temperature until the surface tension of the dispersion reached approximately 50 mN / m. Thereafter, the activated carbon was filtered using a 0.8 μ membrane filter (ADVANTEC). The dispersions of M1, C1, K1, Y2, M2, C2, and K2 were also subjected to adsorption purification by the same method.

FSB1504: FS Blue 1504 (Arimoto Chemical Co., Ltd.)
Oil Black 860: Oil Black 860 (manufactured by Orient Chemical)
Oil Yellow 129: Oil Yellow 129 (manufactured by Orient Chemical Co., Ltd.)
(Manufacture of pigment dispersion)
C. I. Pigment Yellow 128 (150 g), Polymer P-3 (45 g), Methanol (25 g), and ion-exchanged water (780 g) were mixed and dispersed using a sand grinder filled with 1 mm zirconia beads at a volume ratio of 50%. Got. The pigment dispersions m, c, and k were also prepared according to the formulation described in Table 3.

(Ink production)
45 g of the colored fine particle dispersion Y1 prepared by the above method, 10 g of ethylene glycol, 15 g of glycerin, 0.4 g of Olphine E1010 (manufactured by Nissin Chemical), and 0.1 g of the preservative Proxel GXL (manufactured by Avecia) After mixing, pure water was added to make 100 g. Subsequently, it filtered with the 0.8 micrometer membrane filter, and removed the dust and the coarse particle, and produced the ink 1 which is an inkjet ink. Inks 2 to 12, inks A to D, and inks a to d were prepared in the same manner as ink 1 according to the formulation shown in Table 4. The unit in the table is% by mass.

(Ink performance evaluation)
(Ink physical property measurement)
The viscosity of the ink at 25 ° C. using a vibration viscometer Viscomate VM-1A-L (manufactured by Yamaichi Electronics Co., Ltd.) and the viscosity at 25 ° C. using an automatic surface tension meter CBVP-Z type (manufactured by Kyowa Interface Science) The surface tension of each ink was measured and the results are shown in Table 5.

(Particle size measurement)
After each ink was diluted 1000 times, the measurement was carried out five times by the scattering intensity distribution measurement of Zetasizer 1000 (manufactured by Malvern), and the average value was measured by arithmetically averaging the measured values.

(Concentration evaluation)
Each ink is packed in a genuine color ink cartridge, filled in an inkjet printer CL-750 (manufactured by Seiko Epson Corporation), and printed on a copy sheet Xerox 4024 (manufactured by Xerox Co., Ltd.), which is a plain paper, with a wedge pattern consisting of 10 patches. did. The wedge pattern is obtained by changing the density between patches in increments of 10% with a maximum density of 100%. Each patch density was measured with an X-Rite 900 densitometer (manufactured by Nippon Flat Equipment Co., Ltd.), and the maximum density is shown in Table 5.

(Saturation evaluation)
Ink set 1 is composed of inks 1 to 4, ink set 2 is composed of inks 5 to 8, ink set 3 is composed of inks 9 to 12, ink set 4 is composed of inks A to D, and ink set 5 is composed of inks a to d. Then, the ink cartridge was packed, and a color image was printed on copy paper Xerox 4024 (manufactured by Xerox Co., Ltd.) using an ink jet printer CL-750 (manufactured by Seiko Epson Corporation). The saturation of the created image was subjected to sensory evaluation according to the following criteria.
◎: Image with high saturation and very vivid sharpness ○: Vivid image ×: Image with no sharpness in color and lack of saturation (Water resistance evaluation)
The image created in the saturation evaluation was immersed in water for 10 seconds and then pulled up, and the image bleeding was visually evaluated according to the following criteria.
○: Image is hardly blurred x: Image is blurred, color is mixed, and details are blurred

  When images of the same color are compared, an image created with the ink of the example shows a higher density than the image of the comparative example. Furthermore, ink sets 1, 2, and 3 configured with the inks of the examples have high saturation and vivid images can be obtained, and images created from the ink sets 1, 2, and 3 configured with the inks of the examples are It was excellent in water resistance.

Claims (12)

A water-based ink characterized in that the surface tension of a water-based ink containing colored fine particles having a colorant and a polymer is 37 mN / m or more and less than 55 mN / m. The water-based ink according to claim 1, wherein the surface tension is 40 mN / m or more and less than 45 mN / m. The water-based ink according to claim 1 or 2, wherein the coloring material is impregnated or compatible with the polymer. The water-based ink according to any one of claims 1 to 3, wherein the volume average particle diameter of the colored fine particles measured by a laser scattering method is less than 150 nm, and the volume maximum particle diameter is less than 400 nm. The water-based ink according to any one of claims 1 to 4, wherein the volume average particle diameter of the colored fine particles measured by a laser scattering method is less than 50 nm, and the volume maximum particle diameter is less than 250 nm. The water-based ink according to any one of claims 1 to 5, wherein the colored fine particles contain a vinyl polymer. The water-based ink according to claim 1, wherein the coloring material of the colored fine particles is an oil-soluble dye. 8. An ink set, wherein at least one of yellow, magenta, cyan, and black is the water-based ink according to any one of claims 1 to 7. The ink set according to claim 8, wherein the black ink is the water-based ink according to any one of claims 1 to 7. An ink set, wherein each of the colors yellow, magenta, cyan, and black is the water-based ink according to any one of claims 1 to 7. An ink-jet recording method comprising printing the water-based ink according to any one of claims 1 to 7 on plain paper. An inkjet recording image obtained by printing the water-based ink according to any one of claims 1 to 7 on plain paper.