JP2007009014A - Ink composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition excellent in printing quality in various recording media, and particularly excellent in reliability when applied to inkjet printers, such as reliability in ink storage stability, recovery from clogging and continuous printing stability, and can obtain both color development properties to regular paper and gloss to glossy paper. <P>SOLUTION: The ink composition at least contains a quinacridone pigment, two or more water-insoluble vinyl polymers and water. One of the water-insoluble vinyl polymers is obtained by polymerizing a monomer composition comprising an amide group-containing monomer. The other of the water-insoluble vinyl polymers is obtained by polymerizing a monomer composition comprising a monomer containing no amide group. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

Background of the Invention

Field of the Invention The present invention is excellent in print quality on various recording media, particularly reliability such as storage stability of ink, and reliability when applied to an ink jet printer such as clogging recovery and continuous printing stability. The present invention relates to an ink composition for ink-jet recording, which is excellent in color, and capable of achieving both color development on plain paper and gloss on glossy paper, a recording method using the ink composition, and a recorded matter.

BACKGROUND ART An ink jet recording method is a method of recording characters and figures on the surface of a recording medium such as paper by ejecting ink droplets from a fine nozzle head. As an ink jet recording method, an electric signal is converted into a mechanical signal using an electrostrictive element, and ink droplets stored in the nozzle head portion are intermittently ejected to record characters and symbols on the surface of the recording medium. A part of the ink liquid is rapidly heated near the discharge part of the head to generate bubbles, and ink droplets are intermittently discharged by the volume expansion caused by the bubbles, and characters and symbols are printed on the surface of the recording medium. A recording method has been put to practical use.

  As the ink for inkjet recording, a water-based ink in which a colorant composed of a dye or a pigment is dispersed in water may be used. In such an aqueous ink, it is generally performed to disperse a colorant in an aqueous dispersion medium using a dispersing agent such as a surfactant or a polymer dispersing agent. Proposals have been made. For example, Japanese Patent Application Laid-Open No. 2000-219841 (Patent Document 1) discloses an ink excellent in pigment dispersion stability by using two types of anionic group-containing organic polymers having different solubility parameters. JP-A-2005-41994 (Patent Document 2) and the like disclose that a pigment is included in a water-insoluble vinyl polymer obtained by polymerizing a monomer containing a nonionic (meth) acrylamide monomer, thereby stabilizing the dispersion of the pigment. Ink has been disclosed which is excellent in color and excellent in color developability and glossiness.

However, even with the above ink, depending on the pigment used, the reliability of the ink may be insufficient, or the print density and glossiness may be inferior.
JP 2000-219841 A Japanese Patent Laid-Open No. 2005-41994

Summary of the Invention

  The present inventors have now added two types of vinyl polymers, an insoluble vinyl polymer containing an amide group and a water-insoluble vinyl polymer containing no amide group, in an ink composition using a specific magenta pigment. By this, it is excellent in print quality in various recording media, in particular, reliability such as ink storage stability, and excellent reliability when applied to an ink jet printer such as clogging recovery and continuous printing stability, The inventor has obtained the knowledge that both color development on plain paper and gloss on glossy paper can be achieved. The present invention is based on this finding.

  Accordingly, the object of the present invention is excellent in print quality on various recording media, and in particular, reliability such as ink storage stability and reliability when applied to an ink jet printer such as clogging recovery and continuous printing stability. Another object of the present invention is to provide an ink composition that has both excellent colorability and can achieve both color development on plain paper and gloss on glossy paper.

The ink composition according to the present invention is an ink composition comprising at least a quinacridone pigment, two or more water-insoluble vinyl polymers, and water,
One water-insoluble vinyl polymer is a water-insoluble vinyl polymer containing an amide group,
The other water-insoluble vinyl polymer is a water-insoluble vinyl polymer containing no amide group.

  According to the present invention, by using a quinacridone pigment as a colorant and adding two different water-insoluble vinyl polymers as described above, the ink has excellent storage stability, clogging recovery and other reliability, and is usually It is possible to achieve both color development on paper and gloss on glossy paper.

Detailed description of the invention

  The ink composition according to the present invention comprises at least a quinacridone pigment, two or more water-insoluble vinyl polymers, and water. Each component constituting the ink composition will be described.

Water-insoluble vinyl polymer The ink composition according to the present invention contains two or more water-insoluble vinyl polymers. One water-insoluble vinyl polymer is a water-insoluble vinyl polymer containing an amide group, and the other water-insoluble vinyl polymer. The vinyl polymer is a water-insoluble vinyl polymer containing no amide group. Here, the “water-insoluble vinyl polymer containing an amide group” is obtained by polymerizing a monomer composition containing an amide group-containing monomer, and the “water-insoluble vinyl polymer containing no amide group” is , And obtained by polymerizing a monomer composition comprising a monomer not containing an amide group.

  In the present invention, in an ink composition using a quinacridone pigment, by adding both a water-insoluble vinyl polymer containing an amide group and a water-insoluble vinyl polymer containing no amide group, the storage stability and target of the ink are increased. It is possible to realize an ink composition that is excellent in reliability such as clogging recovery and can achieve both color development on plain paper and gloss on glossy paper. The reason for this is not clear, but is considered as follows. That is, the quinacridone pigment is a pigment having an NH group and a C═O group as described below, and is easily adsorbed with an organic polymer having an amide group. However, when only a polymer having an amide group is used, aggregation occurs in a state where the pigment and the polymer are adsorbed, and the dispersion stability of the ink is impaired. In the present invention, it is considered that by using a vinyl polymer containing no amide group in combination, the dispersion stability of the pigment is improved, and further, the color developability on plain paper and the glossiness on glossy paper are also improved.

(1) Water-insoluble vinyl polymer containing an amide group The water-insoluble vinyl polymer containing an amide group used in the present invention is a vinyl polymer having an amide group. The vinyl polymer having an amide group includes (A) an aromatic-containing monomer, (B) an anionic salt-forming group-containing monomer, (C) an amide group-containing monomer, and (D) the monomers (A) to (C). It is preferable that it is a thing obtained by copolymerizing the monomer composition which comprises four types of monomers of the polymerizable monomer.

  As the aromatic-containing monomer (A), various monomers containing aromatics can be used. Styrene, vinyl naphthalene, α-methylstyrene, vinyl toluene, ethyl vinyl benzene, 4-vinyl biphenyl, 1,1-diphenyl ethylene , Benzyl acrylate, benzyl methacrylate, phenoxyethyl (meth) acrylate, 2-hydroxy-3phenoxypropyl acrylate, 2-methacryloyloxyethyl-2hydroxypropyl phthalate, 2-acryloyloxyethyl phthalate and neopentyl glycol acrylic One or more selected from the group consisting of acid benzoates are preferred. By using these aromatic-containing monomers, the water resistance of the recorded matter can be improved. Furthermore, among the above aromatic monomers, it is preferable to use one or more selected from the group consisting of styrene, α-methylstyrene, vinyl toluene, vinyl naphthalene, benzyl acrylate, and benzyl methacrylate. By using these monomers, in addition to improving the water resistance of the recorded matter, the scratch resistance of the recorded matter is improved.

  Examples of the anionic salt-forming group-containing monomer (B) include one or more selected from the group consisting of unsaturated carboxylic acid monomers, unsaturated sulfonic acid monomers, and unsaturated phosphoric acid monomers.

  Specific examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinate. These can be used alone or in admixture of two or more.

  Examples of unsaturated sulfonic acid monomers include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and the like. Can be mentioned. These can be used alone or in admixture of two or more.

  Examples of the unsaturated phosphoric acid monomer include vinyl sulfonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-4 methacryloyloxyethyl phosphate, dibutyl-2- Examples include acryloyloxyethyl phosphate. These can be used alone or in admixture of two or more.

  Among the anionic monomers, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable from the viewpoint of ink viscosity and ink reliability.

  Examples of the amide group-containing monomer (C) include acrylamide, N-methyl acrylamide, N-ethyl acrylamide, N-propyl acrylamide, N-dimethyl acrylamide, N-diethyl acrylamide, N-dipropyl acrylamide, N- (2- Aminoethyl) acrylamide, N- (2-aminopropyl) acrylamide, N- (3-aminopropyl) acrylamide, N- [2- (methylamino) ethyl] acrylamide, N- [2- (methylamino) propyl] acrylamide N- [3- (methylamino) propyl] acrylamide, N- [2- (dimethylamino) ethyl] acrylamide, N- [2- (dimethylamino) propyl] acrylamide, N- [3- (dimethylamino) propyl ] Acrylamides, metac Luamide, N-methylmethacrylamide, N-ethylmethacrylamide, N-propylmethacrylamide, N-dimethylmethacrylamide, N-diethylmethacrylamide, N-dipropylmethacrylamide, N- (2-aminoethyl) methacrylamide N- (2-aminopropyl) methacrylamide, N- (3-aminopropyl) methacrylamide, N- [2- (methylamino) ethyl] methacrylamide, N- [2- (methylamino) propyl] methacrylamide N- [3- (methylamino) propyl] methacrylamide, N- [2- (dimethylamino) ethyl] methacrylamide, N- [2- (dimethylamino) propyl] methacrylamide, N- [3- (dimethyl Amino) propyl] methacrylamide, maleamide, N, N Dimethyl maleate amide, Fumaramido, N, N-dimethyl-off Mara bromide include unsaturated fatty acid amides and the like.

  Examples of the monomer (D) copolymerizable with the monomers (A) to (C) include (meth) acrylic acid esters and long chain alkyl group-containing monomers. By using such a monomer, it is possible to suppress a change in the viscosity of the ink due to a wetting agent or a dispersant added at the time of preparing the ink, and thus it is possible to improve the storage stability of the ink.

  Examples of (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meta) ) Acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, Examples include (meth) acrylic acid esters in which an ester moiety such as (iso) stearyl (meth) acrylate is an alkyl group having 1 to 18 carbon atoms. These can be used alone or in admixture of two or more. In addition, (iso or tertiary) and (iso) mean both the case where these groups are present and the case where these groups are not present, and means the normal when these groups are not present.

上記式中、Ｒ１は水素原子または炭素数１〜４の低級アルキル基を表し、Ｒ２はヘテロ原子を有してもよい炭素数１６〜３０の一価の炭化水素基を表す。Ｒ２は、炭素数１８〜３０が好ましく、より好ましくは１８〜２２である。 As the long-chain alkyl group-containing monomer, a monomer having a long-chain alkyl group with a chain length of 16 to 30 carbon atoms is preferably used, and a monomer having 18 to 22 carbon atoms is more preferable. Specifically, the following formula:

In said formula, R1 represents a hydrogen atom or a C1-C4 lower alkyl group, R2 represents the C1-C30 monovalent hydrocarbon group which may have a hetero atom. R2 preferably has 18 to 30 carbon atoms, more preferably 18 to 22 carbon atoms.

  In the amide group-containing vinyl polymer, the content of each monomer described above is such that the aromatic-containing monomer (A) is 5 to 80% by weight, the anionic salt-forming group-containing monomer (B) is 3 to 30% by weight, and the amide group is contained. It is preferable that the monomer is 1 to 10% by weight and the copolymerizable monomer (D) is 5 to 50% by weight.

(2) Amide group-free water-insoluble vinyl polymer As the water-insoluble vinyl polymer used in the present invention, as the other vinyl polymer used together with the above-mentioned amide group-containing vinyl polymer, a vinyl monomer having no amide group was polymerized. If it is a thing, it will not be limited. In the present invention, as a vinyl polymer not containing an amide group, (E) an aromatic-containing monomer, (F) an anionic salt-forming group-containing monomer, and (G) the monomers (E) and (F) can be copolymerized. Monomers,
What is obtained by polymerizing a monomer composition comprising can be suitably used.

  As the aromatic-containing monomer, the anionic salt-forming group-containing monomer, and the monomer copolymerizable with the two types of monomers, the same monomers as described above can be preferably used.

  In the vinyl polymer containing no amide group, the content of each monomer described above is 5 to 80% by weight of the aromatic-containing monomer (E), 3 to 30% by weight of the anionic salt-forming group-containing monomer (F), The polymerizable monomer (G) is preferably 5 to 50% by weight.

  In the ink composition of the present invention, it is preferable that the water-insoluble vinyl polymer containing no amide group is contained more than the water-insoluble vinyl polymer containing an amide group. By increasing the content of the water-insoluble vinyl polymer not containing an amide group as compared with the water-insoluble vinyl polymer containing an amide group, ink storage stability, clogging recovery property, and continuous printing stability are improved.

  The content of the water-insoluble vinyl polymer containing no amide group is preferably 100 parts by weight or more, particularly 200 parts by weight or more with respect to 100 parts by weight of the water-insoluble vinyl polymer containing an amide group.

Synthesis of water-insoluble vinyl polymer A water-insoluble vinyl polymer can be synthesized by polymerizing a composition containing the above-described monomer by the following method.

  The water-insoluble vinyl polymer is produced by polymerizing the monomer composition by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, or an emulsion polymerization method. Among these polymerization methods, the solution polymerization method is preferable.

  The solvent used in the solution polymerization method is preferably a polar organic solvent. When the polar organic solvent is miscible with water, it can be used by mixing with water.

  Examples of the polar organic solvent include aliphatic alcohols having 1 to 3 carbon atoms such as methanol, ethanol and propanol; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate and the like. Among these, methanol, ethanol, acetone, methyl ethyl ketone, or a mixed solution of these with water is preferable.

  In the polymerization of the monomer composition, a radical polymerization initiator can be used. Examples of the radical polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), dimethyl-2,2′-azobisbutyrate, 2, Azo compounds such as 2′-azobis (2-methylbutyronitrile), 1,1′-azobis (1-cyclohexanecarbonitrile); t-butyl peroxyoctate, di-t-butyl peroxide, dibenzoyl oxide, etc. Organic peroxides can be used.

  The amount of the polymerization initiator added per mole of the monomer composition is preferably 0.001 to 5 moles, and more preferably 0.01 to 2 moles.

  In the polymerization of the monomer composition, a polymerization chain transfer agent may be added in addition to the radical polymerization initiator. Examples of the polymerization chain transfer agent include mercaptans such as octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-tetradecyl mercaptan and 2-mercaptoethanol; xanthogen disulfides such as dimethylxanthogen disulfide and diisopropylxanthogen disulfide; Thiuram disulfides such as methylthiuram disulfide and tetrabutylthiuram disulfide; Halogenated hydrocarbons such as carbon tetrachloride and ethylene bromide; Hydrocarbons such as pentaphenylethane; Acrolein, methacrolein, allyl alcohol, 21-ethylhexylthio Glycolate, terbinolene, α-terpinene, γ-terpinene, dipentene, α-methylstyrene dimer, 9,10-dihydroanthracene, 1, - dihydronaphthalene, indene, 1,4-cyclohexadiene unsaturated cyclic hydrocarbon compounds of a diene and the like; 2,5-unsaturated heterocyclic compounds dihydrofuran like can be used. These polymerization chain transfer agents can be used alone or in admixture of two or more.

  The polymerization conditions of the composition containing the monomer described above vary depending on the type of radical polymerization initiator, monomer, and solvent used. Usually, the polymerization temperature is preferably 30 to 100 ° C, more preferably 50 to 80 ° C, and the polymerization time is preferably 1 to 20 hours. The polymerization atmosphere is preferably an inert gas atmosphere such as nitrogen gas.

  After completion of the polymerization reaction, the produced vinyl polymer is isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. Further, the obtained vinyl polymer can be purified by repeating reprecipitation or removing unreacted monomers by membrane separation, chromatographic method, extraction method or the like.

Quinacridone Pigment The ink composition according to the present invention uses a quinacridone magenta pigment as a colorant. As quinacridone pigments, quinacridone magenta pigments may be C.I. I. Pigment red 122, C.I. I. Pigment red 202, C.I. I. Pigment red 209, and C.I. I. Pigment violet 19 may be used, and one or more of these may be used in combination. In particular, C.I. I. Pigment red 122 or C.I. I. Pigment Violet 19 is preferable.

Water and other components (1) Water The water contained in the ink composition of the present invention functions as the main solvent of the ink, and is pure water such as ion exchange water, ultrafiltered water, reverse osmosis water, and distilled water. Or it is preferable to use ultrapure water. In particular, the use of water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is preferable because it prevents mold and bacteria from being generated and allows the ink composition to be stored for a long period of time.

(2) Water-soluble organic solvent The ink composition according to the present invention preferably contains a water-soluble organic compound. Examples of the water-soluble organic compound include glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, 2 -Butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol, 4 -Alkanediols (polyhydric alcohols) such as methyl-1,2-pentanediol, glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, (sorbitol), maltose Sugars such as cellobiose, lactose, sucrose, trehalose, maltotriose, so-called solid wetting agents such as sugar alcohols, hyaluronic acids, ureas, etc., alkyls having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol, isopropanol Alcohols, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether , Diethylene glycol mono-iso-propyl ether, ethylene glycol mono n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono Glycols such as n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether Ethers, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidino , Formamide, acetamide, dimethyl sulfoxide, sorbit, sorbitan, acetin, diacetin, triacetin, sulfolane and the like, and one or more of these can be used. These water-soluble organic solvents are used in the ink composition. From the viewpoints of ensuring appropriate physical property values (viscosity, etc.), printing quality, and reliability, the ink composition preferably contains 10 to 50% by weight.

  Of the water-soluble organic compounds, alkanediol is preferably contained in the composition in order to improve the gloss of the recorded matter.

  Specific examples of the alkanediol used include propanediol, butanediol, pentanediol, and octanediol. Among these alkanediols, 1,2-alkanediol is preferable, and among these, 1,2-pentanediol is particularly preferable. And 1,2-hexanediol are particularly preferred.

(3) pH adjuster A pH adjuster may be added to the ink composition of the present invention. As the pH adjuster, it is possible to use alkali metal hydroxides such as lithium hydroxide, potassium hydroxide and sodium hydroxide, amines such as ammonia, triethanolamine, tripropanolamine, diethanolamine and monoethanolamine. it can. If necessary, collidine, imidazole, phosphoric acid, 3- (N-morpholino) propanesulfonic acid, tris (hydroxymethyl) aminomethane, boric acid and the like can be used as a pH buffering agent.

(4) Surfactant A surfactant may be further added to the ink composition of the present invention. As the surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant and a nonionic surfactant can be contained. A nonionic surfactant is particularly preferable from the viewpoint of obtaining an ink composition with less foaming and foaming.

  Specific examples of nonionic surfactants include acetylene glycol surfactants, acetylene alcohol surfactants, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl Ethers such as allyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene oleic acid, polyoxyethylene oleic acid ester, polyoxyethylene distearic acid ester , Sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene Nmonooreeto, polyoxyethylene stearate, etc. esters, silicone surface active agents dimethylpolysiloxane, other fluorine alkyl esters, fluorine-containing surfactants such as perfluoroalkyl carboxylic acid salts, and the like. Among these nonionic surfactants, acetylene glycol-based surfactants and acetylene alcohol-based surfactants are particularly preferable in that they have little foaming and have excellent antifoaming performance.

  Specific examples of the acetylene glycol surfactant and the acetylene alcohol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne- 3,6-diol, 3,5-dimethyl-1-hexyne-3ol and the like can be mentioned. Commercially available products can also be used. For example, Surfynol 104, 82, 465, 485, TG manufactured by Air Products, or Olfin STG, Olphine E1010 manufactured by Nissin Chemical Co., Ltd. can be preferably used.

(5) Antioxidant / Ultraviolet Absorber An antioxidant or an ultraviolet absorber may be added to the ink composition of the present invention. Antioxidants and ultraviolet absorbers include allophanates such as allophanate and methyl allophanate, biurets such as biuret, dimethylbiuret and tetramethylbiuret, L-ascorbic acid and its salts, etc. Tinuvin 328, 900 manufactured by Ciba Geigy 1130, 384, 292, 123, 144, 622, 770, 292, Irgacor 252, 153, Irganox 1010, 1076, 1035, MD1024, or the like, or a lanthanide oxide or the like is used.

(6) Antiseptic / antifungal agent An antiseptic or fungicide can be further added to the ink composition of the present invention. Examples of antiseptics and fungicides include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazolin-3-one ( Avecia's Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN) and the like.

Preparation of pigment dispersion The pigment dispersion can be prepared, for example, in the order of the following steps (1) to (4).

(1) Mixing process Mixing quinacridone pigment and each water-insoluble vinyl polymer with an organic solvent solution, water, and a neutralizing agent used as necessary, using a normal mixing and stirring device such as an anchor blade or a turbine blade. To prepare a raw material mixture. In mixing, it is preferable to knead the mixture using a kneader in order to sufficiently atomize the mixture. As kneaders for kneading, there are a batch type and a continuous type. The former includes a double-arm kneader, and the latter includes a self-cleaning kneader. Among these, the former double-armed kneader is preferable from the viewpoint of product type switching, washing in the tank, and the like.

(2) Dispersing step Next, the obtained raw material mixture is diluted to a desired solid content concentration and subjected to a dispersion treatment. When performing the dispersion treatment, a ball mill, a roll mill, a bead mill, a high-pressure homogenizer, a high-speed stirring disperser, or the like can be used. Among these, a high-pressure homogenizer with less inorganic impurities is preferable. Examples of the high-pressure homogenizer include those having a chamber in which the flow path of the processing liquid is fixed, and those having a homogeneous valve capable of adjusting the width of the flow path of the processing liquid. As a high-pressure homogenizer having a chamber in which the flow path of the processing solution is fixed, a microfluidizer (trade name, manufactured by Microfluidics), a nanomizer (trade name, manufactured by Nanomizer), an optimizer (manufactured by Sugino Machine, product) Name). Examples of high-pressure homogenizers that have a homogeneous valve include high-pressure homogenizers (trade name, manufactured by Lani), high-pressure homogenizers (trade name, manufactured by Mimaru Machinery Co., Ltd.), and high-pressure homogenizers (trade name, manufactured by Izumi Food Machinery Co., Ltd.). Can be mentioned. The pressure when dispersing with a high-pressure homogenizer is preferably 50 MPa or more, and more preferably 80 MPa or more because polymer particles having a desired particle diameter can be easily obtained in a short time.

(3) Solvent Removal Step Next, the organic solvent and a predetermined amount of water are removed from the raw material mixture that has been subjected to the dispersion treatment, whereby a pigment dispersion having a desired concentration is obtained. Either the organic solvent removal step or the dispersion step may be performed first. As a method for removing the organic solvent, a vacuum distillation method, particularly a thin-film vacuum distillation method is preferable. In addition, the removal amount of the organic solvent is not particularly limited, but it is preferable that the entire amount of the organic solvent is removed.

(4) Coarse particle removal process After removing a solvent, you may remove a coarse particle as needed. For example, the ink composition obtained as described above is subjected to pressure filtration through a filter or treated with a centrifuge, and is preferably 2 μm or more, more preferably 1 μm or more, particularly preferably 0.5 μm or more. By removing the particles, a pigment dispersion having high dispersion stability can be obtained.

  Hereinafter, the mixing step (1) will be described in more detail. The organic solvent used in the mixing step is preferably an alcohol solvent, a ketone solvent, an ether solvent, an aromatic hydrocarbon solvent, an aliphatic hydrocarbon solvent, or a halogenated aliphatic hydrocarbon solvent, and a hydrophilic organic solvent Is more preferable.

  Examples of the alcohol solvent include methanol, ethanol, isopropanol, n-butanol, tertiary butanol, isobutanol, diacetone alcohol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of the ether solvent include dibutyl ether, tetrahydrofuran, dioxane and the like. Examples of the aromatic hydrocarbon solvent include benzene and toluene. Examples of the aliphatic hydrocarbon solvent include heptane, hexane, cyclohexane and the like. Examples of the halogenated aliphatic hydrocarbon solvent include methylene chloride, 1,1,1-trichloroethane, chloroform, carbon tetrachloride, 1,2-dichloroethane and the like. Among these, acetone and methyl ethyl ketone are preferable.

  If necessary, an organic solvent and a high-boiling hydrophilic organic solvent may be used in combination. Examples of the high boiling hydrophilic organic solvent include phenoxyethanol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether and the like.

  A base can be used as the neutralizing agent. Examples of the base include tertiary amines such as trimethylamine and triethylamine, ammonia, sodium hydroxide, potassium hydroxide and the like. The degree of neutralization is not particularly limited, but the obtained ink composition is preferably close to neutrality, and specifically, the pH of the ink composition is preferably 4.5 to 10.

  The content of the quinacridone pigment is preferably 100 to 700 parts by weight, more preferably 200 to 600 parts by weight, particularly preferably from 100 parts by weight of the resin solid content of each water-insoluble vinyl polymer in terms of printing density. Is 300 to 500 parts by weight.

  The content of the organic solvent is preferably 20 parts by weight or more, more preferably 30 parts by weight or more, and more preferably 50 parts by weight with respect to 100 parts by weight of the resin solid content of the total amount of each vinyl polymer from the viewpoint of ease of compatibility with the pigment. Part or more is particularly preferable. Further, the content of the organic solvent is preferably 500 parts by weight or less, based on 100 parts by weight of the resin solid content of the total amount of each vinyl polymer, from the viewpoint of obtaining effective shearing force when kneading the mixture, Part or less is more preferable, and 200 parts by weight or less is particularly preferable. Therefore, the content of the organic solvent is preferably 20 to 500 parts by weight, more preferably 30 to 300 parts by weight, and particularly preferably 50 to 200 parts by weight with respect to 100 parts by weight of the resin solid content of the total amount of each vinyl polymer. It is.

  The water content is preferably 50 to 1000 parts by weight, more preferably 100 to 500 parts by weight with respect to 100 parts by weight of the organic solvent, from the viewpoint of ease of compatibility with the pigment.

  The solid content concentration in the mixture is preferably 50% by weight or more, more preferably 65% by weight from the viewpoint of obtaining an effective shearing force when the mixture is kneaded. Further, the solid content concentration is preferably 80% by weight in order to avoid the viscosity of the obtained kneaded product from becoming too high to prevent uniform kneading and to avoid the kneaded product from collapsing into particles. Hereinafter, it is more preferably 75% by weight or less. Therefore, the solid content concentration in the mixture is preferably 50% by weight or more, more preferably 50 to 80% by weight, still more preferably 65 to 80% by weight, and particularly preferably 65 to 75% by weight.

  In addition, solid content in a mixture means the total amount of solid content of a pigment, a polymer, and a neutralizer.

Preparation of Ink Composition An ink composition according to the present invention comprises a dispersion / mixer comprising a pigment dispersion of the quinacridone pigment obtained as described above and two or more water-insoluble vinyl polymers, and the components described above. It may be prepared by supplying (for example, ball mill, sand mill, attritor, basket mill, roll mill) and dispersing. According to a preferred embodiment of the present invention, it is preferable to filter the ink stock solution obtained by the above-described dispersing / mixing device using a filter such as a membrane filter or a mesh filter to remove coarse particles.

  The content of the pigment in the ink composition is not particularly limited as long as a sufficient printing density is obtained, but is preferably 1 to 30% by weight from the viewpoint of imparting sufficient ejection properties and printing density. 2 to 10% by weight is more preferable, and 4 to 8% by weight is particularly preferable.

Inkjet recording method and apparatus An inkjet recording method in which the ink composition according to the present invention is used discharges ink composition droplets and attaches the droplets to a recording medium for printing. As an example of a method for ejecting ink composition droplets, for example, an electrostrictive element is used to convert an electrical signal into a mechanical signal, and ink stored in the nozzle head portion is intermittently ejected onto the surface of the recording medium. A method of recording characters and symbols, ink heated in the nozzle head portion is heated rapidly at a location very close to the discharge portion, bubbles are generated, and the ink is intermittently discharged by the volume expansion caused by the bubbles, and characters are printed on the surface of the recording medium. And a method of recording symbols. According to a preferred embodiment of the present invention, the ink composition according to the present invention is preferably used in an ink jet recording method using an electrostrictive element. The ejection of the ink composition droplets is preferably performed by a recording head that ejects ink droplets using the mechanical action of the piezoelectric element.

  Further, according to the present invention, a recorded matter recorded by the recording method is also provided.

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but these do not limit the scope of the present invention.

Preparation of water-insoluble vinyl polymer Water-insoluble vinyl polymers containing amide groups and water-insoluble vinyl polymers containing no amide groups were prepared as follows.

  A synthetic reaction vessel containing 20 parts by weight of methyl ethyl ketone, 10% by weight of each monomer in the amount (parts by weight) shown in Table 1 below, and a polymerization chain transfer agent (2-mercaptoethanol) in the amount shown in Table 1 below. The mixture was mixed and nitrogen gas substitution was sufficiently performed to obtain a mixed solution.

  On the other hand, the remaining 90% by weight of each monomer in the amount (parts by weight) shown in Table 1 below was charged into the dropping funnel, and then the polymerization chain transfer agent (2-mercaptoethanol) in the amount shown in Table 1 below. Then, 60 parts by weight of methyl ethyl ketone and 1.2 parts by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) were mixed and mixed, and nitrogen gas substitution was sufficiently performed to obtain a mixed solution. Under a nitrogen atmosphere, the temperature was raised to 65 ° C. while damaging the mixed solution in the reaction vessel, and the mixed solution in the dropping funnel was gradually dropped into the reaction vessel over 3 hours. After completion of the dropwise addition, the mixed solution was allowed to stand at 65 ° C. for 2 hours, and then a solution in which 0.3 part by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) was dissolved in 5 parts by weight of methyl ethyl ketone was prepared. The polymer solution was aged at 65 ° C. for 2 hours and then at 70 ° C. for 2 hours.

A portion of the resulting polymer solution was isolated by drying at 105 ° C. under reduced pressure for 2 hours and removing the solvent, polystyrene as the standard, 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as the solvent. The weight average molecular weight was measured by gel permeation chromatography using dimethylformamide containing. The results are shown in Table 1 below.

Preparation of pigment dispersion Each polymer solution (Product Nos. 1 to 8) obtained by drying under reduced pressure was dissolved in methyl ethyl ketone, and a neutralizing agent (20% aqueous sodium hydroxide solution) was placed therein. The salt-forming group was completely neutralized by adding a fixed amount, and the quinacridone pigment [C.I. I. Pigment Red 122, manufactured by Dainippon Ink & Chemicals, Inc., trade name: Fastgen Super Magenta R], or phthalocyanine pigment [C.I. I. Pigment Blue 15: 4, manufactured by Toyo Ink Manufacturing Co., Ltd., trade name: LIONOL BLUE FG-7400-G], and kneaded in a bead mill for 2 hours. The amount of each component used was as shown in Table 2 below.

  After adding 120 parts by weight of ion-exchanged water to the kneaded material thus obtained and stirring, methyl ethyl ketone is removed at 60 ° C. under reduced pressure, and a part of the water is further removed, so that the solid content concentration is reduced. A pigment dispersion (A to L) containing 20% by weight of pigment-containing vinyl polymer particles was obtained. The average particle size of the dispersion in the pigment dispersion was 100 nm as a result of measurement using a Coulter Counter N4 (trade name, manufactured by Coulter, Inc.).

Preparation of ink Each pigment dispersion (A to L) thus obtained was mixed so as to have the composition shown in Table 3 below, and the obtained mixture was mixed with a 0.5 μm filter (acetylcellulose membrane). The outer diameter: 2.5 cm, manufactured by Fuji Photo Film Co., Ltd.) and filtered through a 25 ml needle-free syringe (manufactured by Terumo Co., Ltd.) to remove coarse particles, Examples 1 to 8 and Inks of Comparative Examples 1 to 4 were obtained.

Evaluation of ink (1) Evaluation of glossiness Printing was performed using an ink jet printer PX-A550 (manufactured by Seiko Epson Corporation). Magenta ink cartridges for this printer (model number ICM31, manufactured by Seiko Epson Corporation) are filled with the inks of Examples and Comparative Examples, respectively, and PM photographic paper (trade name, manufactured by Seiko Epson Corporation, model number: KA420PSK) On the other hand, a solid image with gradation was printed at a resolution of 1440 × 720 dpi to obtain a recorded matter. The obtained recorded matter was allowed to stand at room temperature for 1 day, and then the 20 ° gloss of the highest density portion was measured using a gloss meter GM-268 (manufactured by Konica Minolta). The measurement results were evaluated based on the following criteria.
A: 20 ° gloss is 60 or more B: 20 ° gloss is 50 or more and less than 60 C: 20 ° gloss is 40 or more and less than 50 D: 20 ° gloss is less than 40 The results are shown in Table 4 below. It was as shown.

(2) Print Density Evaluation Using a printer similar to the above, a solid image with gradation was printed on a Xerox 4024 with a resolution of 720 × 720 dpi to obtain a recorded matter. The obtained recorded matter was allowed to stand at room temperature for 1 day, and then the print density was measured by measuring the highest density portion of the recording surface using Spectrolino manufactured by Gretag. A value obtained by averaging five times for each recording paper was calculated and evaluated based on the following criteria.
A: Print density is 1.1 or more B: Print density is 1.0 or more and less than 1.1 C: Print density is 0.9 or more and less than 1.0 The results are as shown in Table 4 below.

(3) Evaluation of ink storage stability The ink was left in a 70 ° C. environment for 1 week with 50 g of ink in an aluminum pack. After leaving, the presence or absence of foreign matter (sediment) was confirmed. Moreover, changes in physical properties (viscosity, surface tension, pH, particle diameter of resin particles) were further confirmed for those in which no foreign matter was generated. Evaluation was performed based on the following criteria.
A: No foreign matter is generated, and there is no change in physical properties.
B: No foreign matter is generated, but the physical properties slightly change.
C: Foreign matter is generated or the physical properties are remarkably changed.
The results were as shown in Table 4 below.

(4) Clogging recovery evaluation Using the same inkjet printer and cartridge as described above, printing was continued for 10 minutes, and after confirming that all nozzles were ejected normally, the drying state at the nozzles was accelerated. For this purpose, the ink cartridge was removed and the recording head was removed from the head cap and left in an environment of 40 ° C. and 20% RH for one week. After leaving, the cleaning operation was repeated until all nozzles ejected at the same level as the initial stage, and the ease of recovery was evaluated according to the following criteria.
A: Recovered to the same level as the initial stage by one or two cleaning operations.
B: Recovered to the same level as the initial stage after 3 or 4 cleaning operations.
C: Recovered to the same level as the initial stage after 4 or 5 cleaning operations.
D: It does not recover after a realistic number of cleaning operations.
The results were as shown in Table 4 below.

(5) Evaluation of continuous printing stability Using an ink jet printer and a cartridge similar to those described above, solid and line patterns were continuously printed at room temperature. The number of times the printer nozzle was cleaned as an operation for returning to normal printing in the case of ink dot missing or flying bending within 100 pages of printing was measured and evaluated based on the following criteria.
A: Cleaning 0 times B: Cleaning 1 or 2 times C: Cleaning 3 or 4 times D: Cleaning 5 times or more The results were as shown in Table 4 below.

  As is clear from the results shown in Table 4 above, the ink containing the amide group-containing vinyl polymer and the amide group-free vinyl polymer (Examples 1 to 8) is an ink containing no two or more types of vinyl polymers (Examples 1 to 8). Compared to Comparative Examples 1 to 3), the ink was excellent in the reliability of the ink and also in the printing density and glossiness of plain paper.

  Further, the ink containing two kinds of vinyl polymers not containing an amide group (Comparative Example 4) is more stable than the ink in which one vinyl polymer contains an amide group (Examples 1 to 8). In addition, the continuous printing stability was poor.

  Further, when Example 4 and Example 5 were compared, the ink composition (Example 5) in which the water-insoluble vinyl polymer containing no amide group was contained more than the water-insoluble vinyl polymer containing the amide group, It can be seen that the overall performance is excellent as compared with the ink composition (Example 4) having a small content of the water-insoluble vinyl polymer containing no amide group.

Also, the following formula:
CH ₂ = CR ₁ CONHR ₂
The ink compositions using the monoalkyl acrylamide group-containing monomer represented by the formula (Examples 3 and 5) were compared with the ink compositions using the acrylamide and dialkyl acrylamide group-containing monomers (Examples 2 and 6). Excellent overall.

  Further, the ink composition (Example 5) having an amide group-containing monomer content in the range of 1 to 10 parts by weight has an amide group-containing monomer content of less than 1 important part (Example 7) or 10 parts by weight. As compared with an ink composition exceeding that (Example 8), clogging recovery and continuous printing stability are excellent.

Claims (10)

An ink composition comprising at least a quinacridone pigment, two or more water-insoluble vinyl polymers, and water,
One water-insoluble vinyl polymer is a water-insoluble vinyl polymer containing an amide group,
The ink composition, wherein the other water-insoluble vinyl polymer is a water-insoluble vinyl polymer containing no amide group. The water-insoluble vinyl polymer containing the amide group is
(A) an aromatic-containing monomer (B) an anionic salt-forming group-containing monomer (C) an amide group-containing monomer, and (D) a monomer copolymerizable with the monomers (A) to (C),
Is obtained by polymerizing a monomer composition comprising
The water-insoluble vinyl polymer containing no amide group is
(E) an aromatic-containing monomer (F) an anionic salt-forming group-containing monomer, and (G) a monomer copolymerizable with the monomers (E) and (F),
The ink composition according to claim 1, wherein the ink composition is obtained by polymerizing a monomer composition comprising   The ink composition according to claim 1 or 2, wherein the water-insoluble vinyl polymer containing no amide group is contained more than the water-insoluble vinyl polymer containing the amide group. The amide group-containing monomer (C) has the following formula:
CH ₂ = CR ₁ CONHR ₂
(Wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents a substituted or unsubstituted alkyl group.)
The ink composition according to claim 2, which is a monomer represented by:   5. The water-insoluble vinyl polymer containing the amide group is obtained by polymerizing a monomer composition containing 1 to 10 parts by weight of the amide group-containing monomer. Ink composition.   The ink composition according to any one of claims 1 to 5, wherein the quinacridone pigment and the two or more water-insoluble vinyl polymers are in a weight ratio of 6: 4 to 9: 1.   The aromatic compound-containing monomer is one or more selected from the group consisting of styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, benzyl acrylate, and benzyl methacrylate, according to any one of claims 2 to 6. The ink composition as described.   The quinacridone pigment is C.I. I. Pigment red 122, C.I. I. Pigment red 202, C.I. I. Pigment red 209, and C.I. I. The ink composition according to claim 1, which is selected from the group consisting of CI Pigment Violet 19.   An ink jet recording method for performing printing by discharging droplets of an ink composition and attaching the droplets to a recording medium, wherein the ink composition according to any one of claims 1 to 8 is used. An ink jet recording method using   A recorded matter recorded by the ink jet recording method according to claim 9.