JP5393940B2 - Ink composition and ink jet recording method using the ink composition - Google Patents

Description

Background of the Invention

FIELD OF THE INVENTION The present invention has high gloss on glossy paper, high color development on plain paper, and has excellent fixability while ensuring ink reliability such as clogging recovery and ink deposition. The present invention relates to an ink composition used in an improved ink jet recording method.

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 an ink for inkjet recording, an ink in which a colorant composed of a dye or a pigment is dispersed in water is provided. In such inks, it is common to disperse a colorant in an aqueous dispersion medium using a dispersant such as a surfactant or a polymer dispersant, and many proposals have been made regarding the ink composition. Has been made.

  For example, Japanese Patent Application Laid-Open No. 11-209671 discloses an ink that can increase the printing density by including a pigment dispersant and monodispersed fine particles in a predetermined ratio (Patent Document 1). Japanese Patent Application Laid-Open No. 2001-123098 discloses excellent dispersion stability and ejection stability by adding polymer fine particles to a pigment dispersion containing a specific surfactant, and excellent color development on plain paper. Ink is disclosed (Cited document 2). Furthermore, Japanese Patent Application Laid-Open No. 2005-41994 discloses an ink that has excellent dispersion stability and can achieve high gloss and high print density by including a water-insoluble polymer having a specific structure containing a pigment. (Patent Document 3).

  However, when a magenta pigment is used as the pigment, the ink containing the pigment dispersant and resin fine particles described above may not have sufficient fixability. If the resin content is increased to improve the fixability, clogging will be recovered. There is a risk that the reliability of the ink such as property may be lowered.

Further, when special paper is used as a recording medium, glossiness may be lowered, and print density may be lowered even with plain paper.
JP-A-11-209671 JP 2001-123098 A Japanese Patent Laid-Open No. 2005-41994

Summary of the Invention

  The present inventors have a high gloss on glossy paper in a magenta pigment ink by adding a dispersion resin capable of dispersing the pigment in the ink and a water-insoluble vinyl polymer having a specific structure different from the resin. At the same time, it has been found that it has high color developability even on plain paper and can improve the fixability while ensuring the reliability of the ink such as clogging recovery and ink deposition. The present invention is based on this finding.

  Accordingly, an object of the present invention is to provide a magenta pigment ink having high gloss on glossy paper, high color development on plain paper, and ensuring ink reliability such as clogging recovery and ink accumulation. However, an object is to provide an ink composition capable of improving the fixing property.

The ink composition according to the present invention comprises at least a magenta pigment, a polymer capable of dispersing the pigment in the ink composition, a water-insoluble vinyl polymer different from the polymer, and water. Because
The water-insoluble vinyl polymer is a polymer obtained by polymerizing a monomer composition containing [1] an aromatic vinyl monomer and [2] a monomer copolymerizable with the aromatic vinyl monomer. The membrane temperature is below 20 ° C,
The water-insoluble vinyl polymer has an average particle size of 30 to 70 nm.

  According to the present invention, high gloss is obtained on glossy paper, high color developability on plain paper, clogging recovery, and ink is deposited on the ink discarding portion during ink waste liquid portion and borderless printing. Fixability can be improved while ensuring ink reliability such as ink accumulation.

Detailed description of the invention

  The ink composition according to the present invention contains a magenta pigment, a polymer capable of dispersing the pigment in the ink composition, a water-insoluble vinyl polymer different from the polymer, and water as essential components. Hereinafter, each component of the ink composition according to the present invention will be described.

<Water-insoluble vinyl polymer>
The water-insoluble vinyl polymer used in the ink composition according to the present invention is obtained by polymerizing a monomer composition containing an aromatic vinyl monomer and a monomer copolymerizable with the aromatic vinyl monomer.

  Examples of the aromatic vinyl monomer include styrene, p-methylstyrene, α-methylstyrene, 2-methylstyrene, t-butylstyrene, chlorostyrene, vinylxylene, vinylnaphthalene, vinylanthracene, vinylanisole, and divinylbenzene. Of these, styrene is preferred.

  Monomers copolymerizable with aromatic vinyl monomers include acrylic acid esters, methacrylic acid esters, unsaturated carboxylic acids, unsaturated sulfonic acids, hydroxyl group-containing vinyl compounds, aromatic vinyl compounds, unsaturated amides, Aminoalkyl acrylates or aminoalkyl methacrylates, or quaternary chlorides thereof such as methyl halides, ethyl halides, benzyl halides, N-aminoalkylacrylamides or N-aminoalkylmethacrylamides, or methyl halides thereof And quaternary chlorides, vinyl esters, vinylidene halides, diacrylates, dimethacrylates, and the like with ethyl halide, benzyl halide, and the like.

  As acrylic esters, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, Examples thereof include alkyl esters of 1 to 12 carbon atoms of acrylic acid such as decyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, and benzyl acrylate.

  Methacrylic acid esters include ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 21-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, Examples thereof include alkyls having 1 to 12 carbon atoms and esters of methacrylic acid such as dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, and benzyl methacrylate.

  Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, acrylic anhydride, methacrylic anhydride, maleic anhydride, itaconic anhydride, and fumaric anhydride.

  Examples of the unsaturated sulfonic acids include 2-sulfoethyl methacrylate, t-butyl acrylamide sulfonic acid, styrene sulfonic acid, and salts thereof.

  Examples of hydroxyl-containing vinyl compounds include 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, polyethylene glycol monomethacrylate, polypropylene Examples include glycol monomethacrylate, polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, and glycerol monomethacrylate.

  Examples of aromatic vinyl compounds include 2-methylstyrene, t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene, and divinylbenzene.

  As unsaturated amides, acrylamide, methacrylamide, N-isopropylacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N, N-diethylmethacrylamide, N-methylol Examples include methacrylamide, N-methylol acrylamide, diacetone acrylamide, and maleic amide.

  As aminoalkyl acrylates or aminoalkyl methacrylates, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropyl acrylate, N, N-dimethylaminopropyl methacrylate, N, N -T-butylaminoethyl acrylate, N, N-t-butylaminoethyl methacrylate, N, N-monomethylaminoethyl acrylate, N, N-monomethylaminoethyl methacrylate and the like can be mentioned.

  Examples of N-aminoalkyl acrylamide or N monoaminoalkyl methacrylamide include N, N-dimethylaminopropyl acrylamide, N, N-dimethylaminopropyl methacrylamide, N, N-dimethylaminoethyl acrylamide, N, N- And dimethylaminoethyl methacrylamide.

  Examples of vinyl esters include vinyl acetate and vinyl propionate.

  Examples of vinylidene halides include vinylidene chloride and vinylidene fluoride.

  Examples of diacrylates include polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene glycol diacrylate, and polypropylene glycol diacrylate.

  Dimethacrylates include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6- Hexanediol dimethacrylate, neopentyl glycol dimethacrylate and the like can be mentioned.

  In addition to the above monomers, other monomers include trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetramethylolmethane triacrylate, tetramethylolmethane tetraacrylate, allyl medaacrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl. Acrylate, vinyl chloride, vinyl ether, vinyl ketone, vinyl amide, chloroprene, ethylene, propylene, isoprene, butadiene, vinyl pyrrolidone, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, acrylonitrile, Methacrylonitrile, isopropenyl-α, α-dimethylben Examples include diisocyanate and allyl mercaptan.

  As said other monomer, only 1 type may be sufficient and it can use 2 or more types together. Among these monomers, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl acrylate, 2- Alkyl esters or hydroxyalkyl esters of acrylic acid or methacrylic acid such as hydroxyethyl methacrylate are preferred.

  Monomers that can be copolymerized with the aromatic vinyl monomer described above may be used alone or in combination of two or more.

  In the present invention, among the monomers described above as monomers that can be copolymerized with an aromatic vinyl monomer, unsaturated amide compounds are preferred. By adding a water-insoluble vinyl polymer obtained by copolymerizing an aromatic vinyl monomer and an unsaturated amide compound monomer to the ink, the redispersibility of the water-insoluble vinyl polymer is improved. That is, even when the ink composition is once solidified, if the liquid ink composition is supplied, the solidified water-insoluble vinyl polymer is easily redispersed in the ink composition. As a result, when the ink composition according to the present invention is used in an ink jet printer, ink can be prevented from accumulating in the waste liquid portion of the ink or the portion of the ink discarded during the borderless printing, and when the ink jet head is clogged. The recoverability is also good.

  The addition amount of the unsaturated amide compound is preferably 3 to 8 parts by weight when the entire monomer composition is 100 parts by weight. By using such an addition amount, it is possible to further suppress ink accumulation and improve clogging recovery properties while suppressing an increase in ink viscosity. When the addition amount of the unsaturated amide compound exceeds 8% by weight, the ink viscosity increases, and the optimum physical property value as an ink composition for inkjet recording may not be obtained.

  Further, the water-insoluble vinyl polymer used in the present invention can further improve the clogging recovery property by containing unsaturated carboxylic acids in addition to the unsaturated amide compound.

  The amount of the unsaturated carboxylic acid added is preferably 1 to 10 parts by weight when the entire monomer composition is 100 parts by weight.

  If the amount of the unsaturated carboxylic acid added is less than 1 part by weight, the effect on clogging recovery may be reduced, and if it exceeds 10 parts by weight, the ink viscosity may increase.

  In the present invention, the monomer copolymerizable with the aromatic vinyl monomer preferably further comprises one or more monomers having at least two double bonds polymerizable in at least one molecule. In addition to the unsaturated amide compound and unsaturated carboxylic acid monomer described above, the inclusion of such a monomer further improves ink redispersibility, ink deposition suppression ability, and clogging recovery.

  Diacrylates and dimethacrylates are preferably used as monomers having two or more polymerizable double bonds in one molecule, and polyvalent esters of polyhydric alcohols and unsaturated carboxylic acids are particularly preferably used. . As the polyvalent ester of a polyhydric alcohol and an unsaturated carboxylic acid, a compound obtained by esterification reaction between a compound having a skeleton of ethylene oxide and (meth) acrylic acid can be preferably used. Specifically, It is preferable to use one or more selected from the group consisting of polyethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate.

  When the total amount of the monomer composition is 100 parts by weight, the addition amount of the monomer having two or more polymerizable double bonds in one molecule to the monomer composition is preferably 0.3 to 10 parts by weight. More preferred are parts by weight. By adding in such a range, the ink viscosity change rate when the ink is stored at a high temperature can be suppressed. If the amount of the monomer having two or more polymerizable double bonds in one molecule is less than 0.3 part by weight, the dispersion stability of the polymer particles is lowered, and the ink is used when used as an ink for ink jet recording. There is a case where the ink ejection of the cartridge is clogged, and the printing stability tends to be inferior. On the other hand, when the addition amount of the monomer having two or more polymerizable double bonds in one molecule exceeds 10 parts by weight, unreacted monomer may remain and odor may be generated.

  In the present invention, a sulfonic acid group and / or a sulfonic acid group may be introduced into the water-insoluble vinyl polymer. By introducing a sulfonic acid group and / or a sulfonic acid base, ink deposition is suppressed and clogging recovery is further improved. As a method for introducing a sulfonic acid group, an unsaturated sulfonic acid can be used as a monomer constituting the water-insoluble vinyl polymer. Further, a surfactant, a radical initiator, a chain transfer agent or the like that can bring a sulfonic acid group and / or a sulfonate group to the water-insoluble vinyl polymer may be used. These introduction methods can be arbitrarily combined and are not particularly limited.

<Production of water-insoluble vinyl polymer>
The water-insoluble vinyl polymer used in the present invention is prepared directly by a known emulsion polymerization method using the above-mentioned monomers, or a copolymer produced by another polymerization method is used as a liquid medium based on a mechanical emulsion method. It can be produced by fine dispersion.

  As a method using an emulsion polymerization method, there are a method in which various monomers are charged in a batch in the presence of a dispersant and a polymerization initiator, and a method in which polymerization is carried out while continuously supplying monomers. The polymerization at that time is usually performed in a temperature range of 30 to 90 ° C., and polymer particles that are substantially an aqueous dispersion of copolymer particles generally called an emulsion are obtained.

  The aqueous dispersion of copolymer particles obtained by the emulsion polymerization method is excellent in that it is very stable in a small amount of dispersant and can be easily obtained with a very small particle diameter.

  Examples of the dispersant used in the emulsion polymerization method include nonionic surfactants, anionic surfactants, nonionic water-soluble polymers, anionic water-soluble polymers, and the like. Can be selected.

  Specific examples of the nonionic surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether, polyoxyalkylene alkyl ethers, and polyoxyethylene polyoxypropylene alkyl ethers. , Polyoxyethylene styrenated phenyl ether, polyoxyethylene distyrenated phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene oleyl phenyl ether, polyoxyethylene nonyl phenyl ether, oxyethylene / oxypropylene block copolymer, t-octyl Phenoxyethyl polyethoxyethanol, nonylphenoxyethyl polyethoxyethanol and the like, and one of these, It is possible to select two or more kinds.

  Specific examples of the anionic surfactant include, for example, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium alkyldiphenyl ether disulfonate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate, sodium stearate, potassium oleate, Sodium dioctyl sulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, sodium dialkylsulfosuccinate, sodium stearate, sodium oleate, t-octylphenoxy Ethoxypolyethoxyethyl sulfate sodium salt, and the like. It can be-option.

  Nonionic water-soluble polymers include polyvinyl alcohol or derivatives thereof; starch derivatives such as oxidized starch, etherified starch, and phosphate esterified starch; polyvinylpyrrolidone or polyvinylpyrrolidone derivatives such as polyvinylpyrrolidone copolymerized with vinyl acetate; Derivatives Cellulose derivatives such as carboxymethyl cellulose and hydroxymethyl cellulose; polyacrylamide or derivatives thereof; polymethacrylamide or derivatives thereof; gelatin, casein and the like can be mentioned, and one or more of these can be selected.

  Anionic water-soluble polymers include polyalginic acid and its metal salt, carboxymethylcellulose and its metal salt, polyacrylic acid and its metal salt, polyacrylamide partial hydrolyzate and its metal salt, maleic acid copolymer, lignin sulfone Acids and their metal salts and their derivatives, oxyorganic acids and their metal salts, alkylallyl sulfonic acids and their metal salts, polyoxyalkyl allyl ethers, polyol complexes, higher polyhydric alcohol sulfonic acids and their metal salts, gelatin Examples thereof include water-soluble proteins such as glue, metal salts thereof and derivatives thereof, and one or more of these can be selected.

  The amount of the dispersant used is not particularly limited, but is usually 0.02 to 20% by weight, more preferably 0.02 to 10% by weight, and most preferably 0.02 to 5% based on the total weight of the monomers to be copolymerized. % By weight.

  In the present invention, among the above-mentioned dispersants, it is preferable to obtain a water-insoluble vinyl polymer by an aqueous emulsion into which a nonionic surfactant having an HLB value of 13 to 16 is introduced.

  Nonionic surfactant introduction methods include addition to water before polymerization, addition to emulsion, addition at the time of polymerization, addition after polymerization, etc. Addition method, batch addition, divided addition, continuous addition Etc. These introduction methods can be arbitrarily combined and are not particularly limited.

  As the initiator used for copolymerization, a normal radical initiator can be used, for example, hydrogen peroxide; persulfates such as ammonium persulfate, sodium persulfate, potassium persulfate; cumene hydroperoxide, t-butyl. Organic peroxides such as hydroperoxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxybenzoate, lauroyl peroxide; azobisisobutyronitrile, 2,2′- Azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2- (N-phenylamidino) propane] dihydrochloride, 2,2′-azobis {2- [N- (4-chlorophenyl) amidino ] Propane} dihydrochloride, 2,2'-azobis {2- [N- (4-hydroxyphenyl) amidino] pro Dihydrochloride, 2,2′-azobis [2- (N-benzylamidino) propane] dihydrochloride, 2,2′-azobis [2- (N-allylamidino) propane] dihydrochloride, 2, 2′-azobis {2- [N- (2-hydroxyethyl) amidino] propane} dihydrochloride, 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2- Hydroxyethyl] propionamide}, 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) ethyl] propionamide}, 2,2′-azobis [2-methyl-N- [ 2-hydroxyethyl) propionamide], 2,2′-azobis (isobutyramide) dihydrate, and the like; or these and metal ions such as iron ions and sodium sulfoxylate, phor Aldehydes, metabisulfite sodium, sodium bisulfite, L- ascorbic acid, include redox initiators in combination with reducing agents such as Rongalite is able to select one or more of these.

  A common initiator is used in an amount of 0.01 to 20% by weight based on the total weight of monomers to be copolymerized.

  In the present invention, a chain transfer agent may be added when polymerizing the water-insoluble vinyl polymer. Examples of chain transfer agents include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, mercaptoethanol, allyl compounds such as allyl sulfonic acid, methallyl sulfonic acid and soda salts thereof, 1-thioglycerol, and the like. .

  Further, as necessary, as a pH adjuster, sulfuric acid, hydrochloric acid, nitric acid, sodium hydroxide, potassium hydroxide, magnesium sulfate, potassium sulfate, aluminum sulfate, sodium acetate, magnesium acetate, acetic acid lithium, ammonia, triethanolamine, Diethanolamine, monoethanolamine and the like can also be used.

The water-insoluble vinyl polymer forming the polymer particles thus obtained has a minimum film formation temperature (MFT) of 20 ° C. or lower. By forming a water-insoluble vinyl polymer having a minimum film-forming temperature of 20 ° C. or less, polymer fine particles are formed when an ink composition containing the polymer adheres to the recording medium, and a pigment as a coloring material is recorded on the recording medium. Can be fixed. The minimum film formation temperature can be adjusted by blending the monomer composition. The minimum film formation temperature means the minimum temperature required for film formation by combining polymer particles. This minimum film formation temperature can be measured by a temperature gradient plate method as described in Soichi Muroi, “Chemistry of Polymer Latex” (1997) and the like. Specifically, the minimum film formation temperature can be measured as follows, but is not limited thereto. First, an aqueous dispersion of polymer particles is uniformly applied on a PET film so as to have a dry solid content of 5 g / m ² to obtain a measurement sample, and then the measurement sample is commercially available via a silicone release film. The laminator is passed at different temperature levels at a rate of 18 cm / min, and the lowest temperature at which it is considered that a continuous film has been formed is taken as the lowest deposition temperature. Judgment criteria for continuous film formation is that the coating layer is transparent, the coating layer is smooth, and the fallen material from the coating layer obtained by rubbing the surface with a sharp tool is not a discontinuous material, but a continuous film shape. The following three items shall be satisfied. The minimum film-forming temperature can be measured using a commercially available measuring device, for example, “film-forming temperature testing device” (Imoto Seisakusho Co., Ltd.), “TP-801 FT tester” (Tester Sangyo Co., Ltd.) and the like.

  In the present invention, the water-insoluble vinyl polymer forming the polymer particles preferably has a glass transition temperature of −30 ° C. to 100 ° C. The glass transition temperature can be adjusted by blending the monomer composition and can be determined from the DSC curve based on JIS K7121.

  In the present invention, the average particle size of the water-insoluble vinyl polymer needs to be 30 to 70 nm, preferably 35 to 55 nm. If the average particle size of the polymer particles is less than 30 nm, the printing density on plain paper decreases, and problems such as deterioration of clogging recovery and increase in ink deposition occur, and if it exceeds 70 nm, the gloss of the printed surface decreases. However, it is impossible to obtain a high-quality printed matter.

  The particle diameter of the polymer particles is controlled by the amounts of the surfactant and the polymerization initiator used. Increasing the amount of surfactant used decreases the particle size, and decreasing the amount of polymerization initiator decreases the particle size.

  The particle diameter of the polymer particles can be measured by observation with an electron microscope, a Coulter counter, or a light scattering method. For example, with Coulter counter, Coulter counter N4 (manufactured by Coulter), and with light scattering method, particle size analyzer FPAR-1000 (Otsuka Electronics Co., Ltd.), laser particle size analysis system LPA-3000 / 3100 (Otsuka Electronics Co., Ltd.), laser It can be measured with a diffraction particle size distribution analyzer SALD-2000A (Shimadzu Corporation).

<Polymer capable of dispersing pigment in ink composition>
As the polymer that makes it possible to disperse the magenta pigment in the ink composition, a dispersant used in a normal aqueous pigment ink can be suitably used. Preferable examples include synthetic polymers such as polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer, vinyl acetate-acrylic ester copolymer. Polymer, acrylic resin such as acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methyl Styrene-acrylic resin such as styrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinylnaphthalene -Acrylic acid copolymer, vinyl naphthalene -Maleic acid copolymer, and vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid Examples thereof include vinyl acetate copolymers such as copolymers and salts thereof. These can be used alone or in admixture of two or more.

  Among these synthetic polymers, there are copolymers of monomers having hydrophobic groups and monomers having hydrophilic groups, and polymers comprising monomers having both hydrophobic groups and hydrophilic groups in the molecular structure. preferable. The copolymer is not particularly limited to its form, such as a random copolymer or a block copolymer.

  Examples of the salt include salts of diethylamine, ammonia, ethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, triethanolamine, diethanolamine, aminomethylpropanol, morpholine, and the like. Such a salt can be obtained, for example, by a neutralization reaction between a compound for forming a salt (the compounds exemplified above such as diethylamine) and a dispersant composed of an organic substance before forming the salt.

  A natural polymer can also be used as a polymer that enables the magenta pigment to be dispersed in the ink composition. Specific examples thereof include proteins such as glue, gelatin, casein and albumin, natural rubbers such as gum arabic and tragacanth, glucosides such as saponin, alginic acid and propylene glycol alginate, triethanolamine alginate, ammonium alginate and the like. Examples include alginic acid derivatives, cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethyl seleulose, and ethylhydroxycellulose.

  The blending amount of such a polymer is preferably 1 to 100 parts by weight, more preferably 2 to 70 parts by weight with respect to 100 parts by weight of the magenta pigment.

<Magenta pigment>
As the magenta pigment contained in the ink composition according to the present invention, an organic pigment conventionally used in ink compositions for ink jet recording can be used.

  Examples of magenta pigments include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, C.I. I. Pigment violet 19 and the like, preferably C.I. I. Pigment red 122, 202, and 209, C.I. I. Examples thereof include one or a mixture of two or more selected from the group consisting of CI Pigment Violet 19.

  Further, these pigments are preferably contained in an amount of about 0.5 to 15% by weight, more preferably about 1 to 10% by weight, based on the ink.

<Water, other ingredients>
The water contained in the ink composition of the present invention is a main solvent, and it is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled 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.

  The ink composition of 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 Alkanediols (polyhydric alcohols) such as 4-methyl-1,2-pentanediol; Vulcose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol, (Sorbit), maltose Saccharides such as cellobiose, lactose, lactose, sucrose, trehalose, maltotriose; sugar alcohols; peeralonic acids; so-called solid wetting agents such as ureas; 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. From the viewpoint of ensuring appropriate physical property values (viscosity, etc.) of the composition, ensuring printing quality, and reliability, it is preferable that the ink composition contains 10 to 50% by weight.

  In the present invention, it is preferable to contain urea and / or a urea derivative among the above water-soluble organic compounds. By adding urea and / or a urea derivative, ink deposition suppression and clogging recovery when used in an ink jet recording method are further improved.

  Examples of urea and / or urea derivatives include urea, ethyleneurea, biuret, N-methylurea, 1,1-dimethylurea, 1,3-dimethylurea, lactamide, aminoethylpropanediol, and the like. Of these, 1,3-dimethylurea is preferred.

  The amount of urea and / or urea derivative added is preferably 0.5 to 10% by weight based on the total amount of the ink composition.

  The ink composition according to the present invention may further contain various known additives such as pH adjusters, surfactants, antioxidants, ultraviolet absorbers, antiseptic / antifungal agents, and the like, if necessary.

  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.

  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 the nonionic surfactants, acetylene glycol surfactants and acetylene alcohol surfactants are particularly preferable because they are less foamed 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. Examples of commercially available products include Surfynol 104, 82, 465, and 485 manufactured by Air Products, TG, Orphine STG manufactured by Nissin Chemical Co., and Olfin E1010.

  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.

  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 ink composition>
The ink composition according to the present invention can be produced by dispersing and mixing each of the above components by an appropriate method. Preferably, the pigment, polymer dispersant, and water are first used in a suitable dispersing machine (for example, ball mill, sand mill, attritor, roll mill, agitator mill, Henschel mixer, colloid mill, ultrasonic homogenizer, jet mill, ang mill, etc.). Mix to prepare a uniform pigment dispersion, then add separately prepared water-insoluble vinyl polymer, water, water-soluble organic solvent, sugar, pH adjuster, preservative, fungicide, etc. Prepare the solution. After sufficiently stirring, the target ink composition can be obtained by performing filtration in order to remove the coarse particle diameter and foreign matters that cause clogging.

<Inkjet recording method>
The ink jet recording method according to the present invention performs printing by discharging droplets of the ink composition described above and attaching the droplets to a recording medium. By applying the ink composition according to the present invention to the ink jet recording method, the magenta pigment ink has high gloss on glossy paper and high color development on plain paper, and is also capable of recovering clogging and ink deposition. The fixing property can be improved while ensuring the reliability of the ink.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not restrict | limited to these.

<Preparation of water-insoluble vinyl polymer>
Water-insoluble vinyl polymer 1
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 1960 g of ion-exchanged water and 6 g of sodium dodecylbenzenesulfonate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature was kept at 75 ° C., 3 g of ammonium persulfate was added as a polymerization initiator, and after dissolution, 200 g of ion exchange water, 2 g of sodium lauryl sulfate, 22 g of acrylamide, 156 g of styrene, 240 g of butyl acrylate, 30 g of methacrylic acid, 20 g of divinylbenzene An emulsion prepared by adding 5 g of sodium allyl sulfonate and 35 g of polyethylene glycol dimethacrylate under stirring was continuously added dropwise to the reaction solution over 6 hours. After completion of the dropwise addition, aging was performed for 5 hours. After cooling the obtained aqueous emulsion to room temperature, 25 g of polyoxyalkylene alkyl ether, ion-exchanged water and aqueous sodium hydroxide solution were added to adjust the solid content to 15 wt% and pH 8.

  About the obtained aqueous emulsion, when the average particle diameter of the polymer was measured using the particle size analyzer FPAR-1000 (Otsuka Electronics Co., Ltd.), it was about 53 nm.

  Moreover, it was 20 degreeC when the minimum film-forming temperature of the polymer was measured using the film-forming temperature measuring apparatus (Imoto Seisakusho Co., Ltd.).

Water-insoluble vinyl polymer 2
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 2050 g of ion-exchanged water and 11 g of sodium dodecyl diphenyl ether disulfonate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. Internal temperature was kept at 75 ° C., 3 g of sodium persulfate was added as a polymerization initiator, and after dissolution, 200 g of ion-exchanged water, 4 g of sodium dodecylbenzenesulfonate, 10 g of acrylamide, 141 g of styrene, 244 g of butyl acrylate, 5 g of acrylic acid, An emulsion prepared by adding 45 g of hydroxyethyl acrylate and 35 g of polyethylene glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 6 hours. After completion of the dropwise addition, aging was performed for 5 hours. The obtained aqueous emulsion was cooled to room temperature, and then ion-exchanged water and an aqueous sodium hydroxide solution were added to adjust the solid content to 14% by weight and pH 8.

  When the average particle size and the minimum film formation temperature of the obtained aqueous emulsion were measured in the same manner as described above, the average particle size was about 39 nm, and the minimum film formation temperature was 0 ° C. or lower.

Water-insoluble vinyl polymer 3
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 2000 g of ion-exchanged water and 8 g of sodium dodecyl diphenyl ether disulfonate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature was kept at 75 ° C., 3 g of ammonium persulfate was added as a polymerization initiator, and after dissolution, 200 g of ion exchange water, 2 g of sodium lauryl sulfate, 22 g of acrylamide, 156 g of styrene, 240 g of butyl acrylate, 30 g of methacrylic acid, 20 g of divinylbenzene An emulsion prepared by adding 5 g of sodium allyl sulfonate and 35 g of polyethylene glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 6 hours. After completion of the dropwise addition, aging was performed for 5 hours. The obtained aqueous emulsion was cooled to room temperature, and then ion-exchanged water and an aqueous sodium hydroxide solution were added to adjust the solid content to 14% by weight and pH 8.

  With respect to the obtained aqueous emulsion, the average particle size and the minimum film formation temperature of the polymer were measured in the same manner as described above. The average particle size was about 40 nm, and the minimum film formation temperature was 17 ° C.

Water-insoluble vinyl polymer 4
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 2000 g of ion exchange water and 9 g of sodium lauryl sulfate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature was kept at 75 ° C., 3 g of ammonium persulfate was added as a polymerization initiator, and after dissolution, 200 g of ion exchange water, 2 g of sodium lauryl sulfate, 22 g of acrylamide, 156 g of styrene, 240 g of butyl acrylate, 30 g of methacrylic acid, 20 g of divinylbenzene Then, an emulsion prepared by adding 5 g of sodium methallylsulfonate and 35 g of polyethylene glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 6 hours. After completion of the dropwise addition, aging was performed for 5 hours. After cooling the obtained aqueous emulsion to room temperature, 25 g of polyoxyalkylene alkyl ether, ion-exchanged water, and aqueous sodium hydroxide solution were added to adjust the solid content to 14 wt% and pH 8.

  With respect to the obtained aqueous emulsion, the average particle size and the minimum film formation temperature of the polymer were measured in the same manner as described above. The average particle size was about 39 nm, and the minimum film formation temperature was 13 ° C.

Water-insoluble vinyl polymer 5
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 1920 g of ion-exchanged water and 9 g of sodium dodecyl diphenyl ether disulfonate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature is kept at 75 ° C., 3 g of ammonium persulfate is added as a polymerization initiator, and after dissolution, 200 g of ion exchange water, 2 g of sodium lauryl sulfate, 22 g of acrylamide, 156 g of styrene, 240 g of butyl acrylate, 30 g of methacrylic acid, allyl sulfonic acid An emulsion prepared by adding 5 g of soda and 35 g of polyethylene glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 6 hours. After completion of the dropwise addition, aging was performed for 5 hours. The obtained aqueous emulsion was cooled to room temperature, and then ion-exchanged water and an aqueous sodium hydroxide solution were added to adjust the solid content to 15% by weight and pH 8.

  With respect to the obtained aqueous emulsion, the average particle size and the minimum film formation temperature of the polymer were measured in the same manner as described above. The average particle size was about 43 nm, and the minimum film formation temperature was 15 ° C.

Water-insoluble vinyl polymer 6
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 1930 g of ion-exchanged water and 13 g of sodium dodecyl diphenyl ether disulfonate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature was kept at 75 ° C., 9 g of azobisisovityronitrile was added as a polymerization initiator, and after dissolution, 200 g of ion-exchanged water, 2 g of sodium lauryl sulfate, 11 g of acrylamide, 111 g of styrene, 250 g of butyl acrylate, 27 g of methacrylic acid Then, an emulsion prepared by adding 45 g of hydroxyethyl acrylate and 35 g of polyethylene glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 6 hours. After completion of the dropwise addition, aging was performed for 5 hours. The obtained aqueous emulsion was cooled to room temperature, and then ion-exchanged water and an aqueous sodium hydroxide solution were added to adjust the solid content to 15% by weight and pH 8.

  With respect to the obtained aqueous emulsion, the average particle size and the minimum film formation temperature of the polymer were measured in the same manner as described above. The average particle size was about 42 nm, and the minimum film formation temperature was 0 ° C. or lower.

Water-insoluble vinyl polymer 7
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 2000 g of ion-exchanged water and 10 g of sodium lauryl sulfate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature is kept at 75 ° C., 3 g of potassium persulfate is added as a polymerization initiator, and after dissolution, 200 g of ion-exchanged water, 2 g of sodium lauryl sulfate, 22 g of acrylamide, 156 g of styrene, 240 g of butyl acrylate, 30 g of methacrylic acid, methallyl An emulsion prepared by adding 5 g of sodium sulfonate and 35 g of polyethylene glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 6 hours. After completion of the dropwise addition, aging was performed for 5 hours. After cooling the obtained aqueous emulsion to room temperature, 25 g of polyoxyalkylene styrenated alkyl ether, ion-exchanged water, and aqueous sodium hydroxide solution were added to adjust the solid content to 14 wt% and pH 8.

  With respect to the obtained aqueous emulsion, the average particle size and the minimum film formation temperature of the polymer were measured in the same manner as described above. The average particle size was about 42 nm, and the minimum film formation temperature was 13 ° C.

Water-insoluble vinyl polymer 8
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 1890 g of ion-exchanged water and 6 g of sodium dodecylbenzenesulfonate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature was kept at 75 ° C., 3 g of ammonium persulfate was added as a polymerization initiator, and after dissolution, 200 g of ion exchange water, 2 g of sodium lauryl sulfate, 22 g of acrylamide, 107 g of styrene, 288 g of butyl acrylate, 30 g of methacrylic acid, 20 g of divinylbenzene An emulsion prepared by adding 5 g of sodium allyl sulfonate and 35 g of polyethylene glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 6 hours. After completion of the dropwise addition, aging was performed for 5 hours. After cooling the obtained aqueous emulsion to room temperature, 25 g of polyoxyalkylene alkyl ether, ion-exchanged water, and aqueous sodium hydroxide solution were added to adjust the solid content to 14 wt% and pH 8.

  With respect to the obtained aqueous emulsion, the average particle size and the minimum film formation temperature of the polymer were measured in the same manner as described above. The average particle size was about 51 nm, and the minimum film formation temperature was 0 ° C. or lower.

Water-insoluble vinyl polymer 9
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 2000 g of ion-exchanged water and 10 g of sodium lauryl sulfate, and the temperature was raised to 70 ° C. while purging with nitrogen under stirring. The internal temperature is kept at 70 ° C., 3 g of azobisisobutyronitrile is added as a polymerization initiator, and after dissolution, 200 g of ion-exchanged water, 2 g of sodium lauryl sulfate, 10 g of acrylamide, 147 g of methyl methacrylate, 282 g of butyl acrylate, acrylic acid An emulsion prepared by adding 5 g and 35 g of polyethylene glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 6 hours. After completion of the dropwise addition, aging was performed for 5 hours. The resulting aqueous emulsion was cooled to room temperature, and then ion-exchanged water and sodium hydroxide aqueous solution were added to adjust the solid content to 14% by weight and pH 8.

  When the average particle size and the minimum film formation temperature of the obtained aqueous emulsion were measured in the same manner as described above, the average particle size was about 47 nm, and the minimum film formation temperature was 0 ° C. or lower.

Water-insoluble vinyl polymer 10
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 2000 g of ion exchange water and 11 g of sodium lauryl sulfate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature was kept at 75 ° C., 7 g of azobisisobutyronitrile was added as a polymerization initiator, and after dissolution, 200 g of ion-exchanged water, 2 g of sodium lauryl sulfate, 249 g of styrene, 107 g of butyl acrylate, 13 g of divinylbenzene, and hydroxy An emulsion prepared by adding 88 g of ethyl methacrylate under stirring was continuously dropped into the reaction solution over 6 hours. After completion of the dropwise addition, aging was performed for 5 hours. The resulting aqueous emulsion was cooled to room temperature, and then ion-exchanged water and sodium hydroxide aqueous solution were added to adjust the solid content to 14% by weight and pH 8.

  When the average particle size and the minimum film formation temperature of the obtained aqueous emulsion were measured in the same manner as described above, the average particle size was about 40 nm and the minimum film formation temperature was 54 ° C.

Water-insoluble vinyl polymer 11
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 750 g of ion-exchanged water and 0.7 g of sodium dodecyl diphenyl ether disulfonate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature was kept at 75 ° C., 3 g of potassium persulfate was added as a polymerization initiator, and after dissolution, 200 g of ion-exchanged water, 2 g of sodium dodecyl diphenyl ether disulfonate, 9 g of acrylamide, 171 g of styrene, 251 g of butyl acrylate, 15 g of methacrylic acid, Then, an emulsion prepared by adding 5 g of polyethylene glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 6 hours. After completion of the dropwise addition, aging was performed for 5 hours. The obtained aqueous emulsion was cooled to room temperature, and then ion-exchanged water and an aqueous sodium hydroxide solution were added to adjust the solid content to 28% by weight and pH 8.

  When the average particle size and the minimum film formation temperature of the obtained aqueous emulsion were measured in the same manner as described above, the average particle size was about 90 nm and the minimum film formation temperature was 5 ° C.

  The average particle diameter of the obtained aqueous emulsion was about 90 nm. The minimum film formation temperature was 5 ° C.

Water-insoluble vinyl polymer 12
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 2000 g of ion-exchanged water and 10 g of sodium lauryl sulfate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature is kept at 75 ° C., 3 g of potassium persulfate is added as a polymerization initiator, and after dissolution, 200 g of ion exchange water, 2 g of sodium lauryl sulfate, 44 g of acrylamide, 236 g of styrene, 137 g of butyl acrylate, 27 g of methacrylic acid, allyl sulfone An emulsion prepared by adding 5 g of acid soda and 35 g of polyethylene glycol dimethacrylate under stirring was continuously dropped into the reaction solution over 6 hours. After completion of the dropwise addition, aging was performed for 5 hours. The resulting aqueous emulsion was cooled to room temperature, and then ion-exchanged water and sodium hydroxide aqueous solution were added to adjust the solid content to 14% by weight and pH 8.

  The obtained aqueous emulsion was measured for the average particle size and the minimum film formation temperature of the polymer in the same manner as described above. The average particle size was about 45 nm, and the minimum film formation temperature was 49 ° C.

<Preparation of magenta pigment dispersion>
Magenta pigment dispersion 1
Nitrogen replacement of 150 parts by weight of methyl ethyl ketone, 20 parts by weight of styrene, 5 parts by weight of 2-ethylhexyl methacrylate, 15 parts by weight of butyl methacrylate, 10 parts by weight of lauryl methacrylate, 2 parts by weight of methacrylic acid, and 0.3 parts by weight of t-dodecylmethylcaptan The reaction vessel was charged and heated to 70 ° C., and separately prepared 150 parts by weight of styrene, 15 parts by weight of acrylic acid, 50 parts by weight of butyl methacrylate, 1 part by weight of t-dodecyl mercaptan, 20 parts by weight of methyl ethyl ketone, and azobisiso A mixed solution of 1 part by weight of butyronitrile was dropped into a reaction vessel over 4 hours using a dropping funnel to carry out a polymerization reaction. Next, methyl ethyl ketone was added to the reaction vessel to prepare a dispersed polymer solution.

  60 parts by weight of the dispersion polymer solution, magenta pigment [C.I. I. Pigment Red 122, manufactured by Dainippon Ink & Chemicals, Inc.] 6.4 parts by weight, 100 parts by weight of 0.1 mol / L sodium hydroxide aqueous solution, and 30 parts by weight of methyl ethyl ketone were mixed and stirred for 30 minutes with a homogenizer. After that, 300 parts by weight of ion-exchanged water was added, and the mixture was further stirred for 1 hour. Next, the whole amount of methyl ethyl ketone and a part of water were removed using a rotary evaporator, 0.1 mol / L sodium hydroxide was added dropwise to neutralize the solution to a pH of 9, and a 0.3 μm membrane filter ( By filtering through Nippon Millipore Limited, a magenta pigment dispersion 1 having a solid content (the sum of the dispersion polymer and the magenta pigment) of 10% by weight was obtained.

Magenta pigment dispersion 2
20 parts by weight of methyl ethyl ketone, 0.03 part by weight of 2-mercaptoethanol, 30 parts by weight of styrene, 20 parts by weight of benzyl methacrylate, 15 parts by weight of butyl methacrylate, 10 parts by weight of polyethylene glycol monomethacrylate (EO = 15), 15 parts by weight of methacrylic acid Was placed in a reaction vessel sufficiently substituted with nitrogen gas, polymerized under stirring at 75 ° C., and 2,2′-azobis (2,4-dimethyl) dissolved in 40 parts by weight of methyl ethyl ketone per 100 parts by weight of the monomer component. 0.9 parts by weight of valeronitrile was added and aged at 80 ° C. for 1 hour to obtain a polymer solution.

  40 parts by weight of the dispersed polymer solution, magenta pigment [C.I. I. Pigment Violet 19, manufactured by Dainichi Seika Co., Ltd.] 18 parts by weight, 100 parts by weight of 0.1 mol / L sodium hydroxide aqueous solution, and 30 parts by weight of methyl ethyl ketone were mixed and stirred for 30 minutes with a homogenizer. 300 parts by weight of ion exchange water was added, and the mixture was further stirred for 1 hour. Next, the whole amount of methyl ethyl ketone and a part of water were removed using a rotary evaporator, 0.1 mol / L sodium hydroxide was added dropwise to neutralize the solution to a pH of 9, and a 0.3 μm membrane filter ( By filtration through Nippon Millipore Limited, a magenta pigment dispersion 2 having a solid content, the sum of the dispersion polymer and the magenta pigment) of 10% by weight was obtained.

<Preparation of ink composition>
According to the composition shown in Table 1 below, each component was mixed and stirred for 2 hours. Subsequently, each magenta ink of Examples 1 to 10 and Comparative Examples 1 to 4 was prepared by filtration using a membrane filter (trade name) having a pore diameter of about 8 μm (manufactured by Nippon Millipore Limited). In Table 1, the amount of each composition added is% by weight.

Evaluation of Ink Composition (1) Glossiness Printing was performed using an inkjet printer PX-A550 (manufactured by Seiko Epson Corporation). The magenta ink cartridge for this printer was filled with the ink compositions of Examples and Comparative Examples, respectively, and a solid image with gradation was printed at a resolution of 1440 dpi on a recording medium to obtain a recorded matter. As recording media, EPSON photo paper <Glossy> (trade name, manufactured by Seiko Epson Corporation), Canon Professional Photo Paper PR-101 (trade name, manufactured by Canon Inc.), and Kodak Advanced Photo Paper (trade name, Kodak Corporation) 3 types of special paper. 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 same measurement was repeated 5 times, the average value thereof was calculated, and the glossiness was evaluated according to the following criteria.
A: 20 ° gloss is 50 or more B: 20 ° gloss is 40 or more and less than 50 C: 20 ° gloss is less than 40 The results are as shown in Table 2 below.

(2) Print density Xerox P (product name: manufactured by Fuji Xerox Co., Ltd.), Xerox 4024 (product name: Xerox Co. (USA)), recycle cut R-100 (product name: Oji Paper Co., Ltd.) Printing was performed using the same printer as described above. After printing, the recorded matter was allowed to stand in an environment of 24 ° C. for 24 hours, and then the printing density (OD value) of the solid portion was measured using a Gretag densitometer (manufactured by Gretag Macbeth). The average value of the measurement results for each printed matter was calculated and evaluated based on the following criteria.
A: Print density is 1.2 or more B: Print density is 1.0 or more and less than 1.2 C: Print density is 0.9 or more and less than 1.0 D: Print density is less than 0.9 As shown in Table 2.

(3) Fixability For printed matter using EPSON photographic paper <gloss> as the exclusive paper obtained above, the printed portion is rubbed strongly with a finger immediately after printing, and the state of the printed surface is visually confirmed to evaluate the fixability. Went.
The evaluation criteria were as follows.
A: Ink cannot be removed B: Ink can be removed slightly, but fingers are not soiled C: Ink is removed and fingers are soiled The results are as shown in Table 2 below.

(4) Abrasion resistance (line marker resistance)
About the printed matter which used Xerox P as the plain paper obtained above, 1 hour after printing, using yellow aqueous fluorescent pen ZEBRA PEN2 (trade name, manufactured by Zebra Co., Ltd.), the printed part is at a writing pressure of 300 g / 15 mm. The presence or absence of rubbing and dirt was visually confirmed, and the rubbing resistance (line marker property) was evaluated.
The evaluation criteria were as follows.
A: No stain even when rubbing the same part twice B: No dirt after rubbing once, but rubbing when rubbing the same part twice C: Dirt is produced by rubbing once The results are shown in Table 2 below. It was street.

(5) Abrasion resistance (gross change)
For the printed matter using EPSON photographic paper <gloss> as the exclusive paper obtained above, the printed part is lightly rubbed with a finger after 1 hour of printing, and the change in gloss of the printed surface is visually confirmed, whereby the abrasion resistance ( Gross change) was evaluated.
The evaluation criteria were as follows.
A: Traces rubbed with fingers cannot be discriminated and there is no gloss change B: Traces rubbed with fingers can be discriminated, but there is almost no gloss change C: Traces rubbed with fingers can be clearly discriminated and gloss changes The results were as shown in Table 2 below.

(6) Clogging recovery property Using an ink jet printer PX-V600 (manufactured by Seiko Epson Corporation), with the ink cartridge removed, and a position outside the home position (the head is displaced from the position of the cap provided in the printer) And the head is not capped) and left in a 40 ° C. environment for 1 week. After one week, the cleaning operation was repeated until all nozzles ejected again 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 with less than 3 cleaning operations.
B: 3 to 6 cleaning operations are recovered to the same level as the initial stage.
C: Recovered to the same level as the initial stage after 6 or more cleaning operations.
D: Ink was not ejected from all nozzles even when the cleaning operation was repeated. The results were as shown in Table 2 below.

(7) Ink Accumulation Using an inkjet printer PX-V500 (manufactured by Seiko Epson Corporation), 100% dutyless printing was performed on a postcard size recording medium in an environment of 40 ° C. × 20% RH. 500 sheets were continuously printed, and ink deposition was evaluated according to the following criteria.
A: Ink accumulation is less than 1 mm B: Ink accumulation is 1 to 2 mm, and the backside of the postcard to be passed is not soiled by the deposit. C: The backside of the postcard to be passed is soiled by the deposit. It was as shown in.

(8) Storage stability The aluminum packs were left in a 70 ° environment for 1 week with 50 g of the ink compositions of Examples and Comparative Examples. 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 2 below.

Claims (12)

An ink composition comprising at least a magenta pigment, a polymer capable of dispersing the pigment in the ink composition, a water-insoluble vinyl polymer different from the polymer, and water,
The water-insoluble vinyl polymer is a polymer obtained by polymerizing a monomer composition containing [1] an aromatic vinyl monomer and [2] a monomer copolymerizable with the aromatic vinyl monomer. The membrane temperature is below 20 ° C,
The monomer copolymerizable with the aromatic vinyl monomer comprises an unsaturated amide compound;
The water-insoluble vinyl polymer has an average particle size of 30 to 70 nm,
The polymer capable of dispersing the pigment in the ink composition is a styrene-acrylic resin,
The magenta pigment is C.I. I. Pigment red 122, 202, 209, and C.I. I. An ink composition which is one or a mixture of two or more selected from the group consisting of CI Pigment Violet 19 .   The ink composition according to claim 1, wherein the aromatic vinyl monomer is a styrene monomer.   The ink composition according to claim 2, wherein the unsaturated amide compound is contained in an amount of 3 to 8 parts by weight in the monomer composition when the entire monomer composition is 100 parts by weight.   The monomer copolymerizable with the aromatic vinyl monomer further comprises one or more monomers having at least two double bonds polymerizable in at least one molecule. The ink composition according to one item.   The ink composition according to claim 4, wherein the monomer having two or more double bonds polymerizable in at least one molecule is di (meth) acrylate.   The ink composition according to claim 5, wherein the di (meth) acrylate is obtained by an esterification reaction between a compound having an ethylene oxide skeleton and (meth) acrylic acid.   The ink composition according to claim 1, wherein the water-insoluble vinyl polymer has a sulfonic acid group and / or a sulfonic acid group.   The ink composition according to any one of claims 1 to 6, wherein the water-insoluble vinyl polymer is obtained by an aqueous emulsion into which a nonionic surfactant having an HLB value of 13 to 16 is introduced.   The ink composition according to claim 1, further comprising urea and / or a urea derivative.   The ink composition according to claim 9, wherein the urea and / or urea derivative is 1,3-dimethylurea.   An inkjet recording method for performing printing by discharging droplets of an ink composition and attaching the droplets to a recording medium, wherein the inkjet composition uses the ink composition according to any one of claims 1 to 10. Recording method.   A recorded matter recorded by the inkjet recording method according to claim 11.