JP2006124606A - Ink composition for inkjet recording and method for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition for inkjet recording which improves the redispersibility of ink particles sedimenting over a long period of time, and a method for inkjet recording. <P>SOLUTION: The ink composition for inkjet recording comprises dispersion medium and charged particles at least containing a coloring material, in which the charged particles are dispersed in the dispersion medium by a dispersing agent containing a polymer having a crosslinking structure, and the method for inkjet recording comprises a step of flying an ink composition as ink droplets by utilizing an electrostatic field. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ink composition for ink jet recording and an ink jet recording method.

  As an image recording method for forming an image on a recording medium such as paper based on an image data signal, there are an electrophotographic method, a sublimation type and a melt type thermal transfer method, an ink jet method and the like. The electrophotographic system requires a process of forming an electrostatic latent image on a photosensitive drum by charging and exposure, which complicates the system and becomes an expensive apparatus. The thermal transfer method is inexpensive, but uses an ink ribbon, so the running cost is high and waste material is generated. On the other hand, the ink jet system is an inexpensive apparatus and ejects ink only to a required image portion to form an image directly on a recording medium, so that ink can be used efficiently and running cost is low. Furthermore, there is little noise and it is excellent as an image recording method.

Inkjet recording methods include, for example, a method in which ink droplets are ejected by the pressure of steam generated by the heat of a heating element, a method in which ink droplets are ejected by mechanical pressure pulses generated by a piezoelectric element, and an electrostatic field. There is a system (see Patent Document 1 and Patent Document 2) that causes ink droplets containing charged particles to fly. The method of flying ink droplets with steam or mechanical pressure cannot control the flying direction of ink droplets, and causes ink droplets to land accurately on the desired location on the recording medium due to distortion of the ink nozzles or air convection. Is difficult.
On the other hand, the method using an electrostatic field controls the flying direction of the ink droplets by the electrostatic field, so that the ink droplets can be landed accurately at a desired position, and a high-quality image formation (printed material) is created. It is excellent.

  As an ink composition used for inkjet recording using an electrostatic field, an ink composition containing a dispersion medium and charged particles including at least a coloring material is used (see Patent Documents 3 and 4). By changing the color material, the ink composition containing the color material can create four color inks of yellow, magenta, cyan, and black, and can also create special color inks of gold and silver . Therefore, it is useful because a color image formed product (printed product) can be produced. However, the conventional ink composition is difficult to stably discharge for a long time, and the redispersibility of ink particles that settle when the ink is stored for a long time is poor, and improvement has been expected.

US Pat. No. 6,158,844 Japanese Patent No. 3315334 US Pat. No. 5,952,2048 JP-A-8-291267

  An object of the present invention is to discharge stably for a long time and to improve the redispersibility of particles that settle over time.

The present inventor has found that the above object can be achieved by using a polymer dispersant having a crosslinked structure, and has led to the present invention.
That is, the present invention is as follows.
(1) In an inkjet recording ink composition containing a dispersion medium and charged particles containing at least a coloring material, the charged particles are dispersed in the dispersion medium by a dispersant containing a polymer having a crosslinked structure. An ink composition for ink jet recording characterized by the above.
(2) The ink composition for ink jet recording according to (1), wherein the polymer having a crosslinked structure is a graft polymer into which a crosslinked structure is introduced.
(3) The ink composition for ink jet recording according to (1), wherein the polymer having a crosslinked structure is a block polymer into which a crosslinked structure is introduced.
(4) The polymer having the crosslinked structure has a repeating unit having a crosslinked structure in the range of 0.00001 to 30% by mass in the polymer. The ink composition for inkjet recording as described.
(5) An ink jet recording method, wherein an ink droplet is ejected by an ink jet recording method using an electrostatic field, using the ink composition according to any one of (1) to (4).

Hereinafter, the present invention will be described in further detail.
The ink composition of the present invention contains a dispersion medium and charged particles containing at least a coloring material.

[Dispersion medium]
The dispersion medium is preferably a dielectric liquid having a high electrical resistivity, specifically, 10 ¹⁰ Ωcm or more. If a dispersion medium having a low electrical resistivity is used, electrical continuity is generated between adjacent recording electrodes, which is not suitable for this embodiment. Further, the dielectric constant of the dielectric liquid is preferably 5 or less, more preferably 4 or less, and still more preferably 3.5 or less. By setting the relative dielectric constant in such a range, an electric field is effectively applied to charged particles in the dielectric liquid, which is preferable.

  Examples of the dispersion medium used in the present invention include linear or branched aliphatic hydrocarbons, alicyclic hydrocarbons, or aromatic hydrocarbons, halogen substitution products of these hydrocarbons, and silicone oil. Examples include hexane, heptane, octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, toluene, xylene, mesitylene, and the like. Specifically, Isopar C, Isopar E, Isopar G , Isopar H, Isopar L, Isopar M (Isopar: trade name of Exxon), Shellsol 70, Shellsol 71 (Shellsol: trade name of Shell Oil), Amsco OMS, Amsco 460 Solvent (Amsco: Spirits) Trade name), KF-96L (trade name of Shin-Etsu Silicone Co., Ltd.) and the like can be used alone or in combination. The content of the dispersion medium with respect to the entire ink composition is preferably in the range of 20 to 99% by mass. In 20 mass% or more, the particle | grains containing a color material can be disperse | distributed to a dispersion medium, and content of a color material can be satisfied in 99 mass% or less.

[Color material]
As the coloring material used in the present invention, known dyes and pigments can be used, and can be selected according to applications and purposes. For example, it is preferable to use a pigment from the viewpoint of the color tone of the recorded image recorded matter (printed matter) (for example, “Distribution Stabilization and Surface Treatment Technology / Evaluation” issued by the Technical Information Association, December 25, 2001 1) (hereinafter also referred to as “Non-Patent Document 1”). By changing the color material, four color inks of yellow, magenta, cyan, and black can be created. In particular, the use of offset printing inks or pigments used for proofing is preferable because the same color tone as that of offset printed matter can be obtained.

  Examples of pigments for yellow ink include C.I. I. Pigment yellow 1, C.I. I. Monoazo pigments such as CI Pigment Yellow 74; I. Pigment yellow 12, C.I. I. Disazo pigments such as CI Pigment Yellow 17; I. Non-benzidine azo pigments such as CI Pigment Yellow 180; I. Azo lake pigments such as CI Pigment Yellow 100; I. Condensed azo pigments such as CI Pigment Yellow 95; I. Pigment Yellow 115, etc., acidic dye lake pigments, C.I. I. Pigment yellow 18 and other basic dye lake pigments, anthraquinone pigments such as flavantron yellow, isoindolinone yellow 3RLT, C.I. I. Pigment Yellow 139 and other isoindolinone pigments, quinophthalone yellow and other quinophthalone pigments, isoindoline yellow and other isoindoline pigments, C.I. I. Nitroso pigments such as CI Pigment Yellow 153, C.I. I. And metal complex salt azomethine pigments such as CI Pigment Yellow 117.

  Examples of pigments for magenta ink include C.I. I. Monoazo pigments such as CI Pigment Red 3; I. Disazo pigments such as CI Pigment Red 38; I. Pigment red 53: 1 etc. and C.I. I. Azo lake pigments such as CI Pigment Red 57: 1; I. Condensed azo pigments such as CI Pigment Red 144; I. Acidic dye lake pigments such as C.I. Pigment Red 174; I. Basic dye lake pigments such as CI Pigment Red 81; I. Anthraquinone pigments such as CI Pigment Red 177; I. Thioindigo pigments such as CI Pigment Red 88; I. Perinone pigments such as CI Pigment Red 194; I. Perylene pigments such as CI Pigment Red 149; I. Quinacridone pigments such as CI Pigment Red 122; I. Isoindolinone pigments such as CI Pigment Red 180; I. And alizarin lake pigments such as CI Pigment Red 83.

  Examples of the pigment for cyan ink include C.I. Disazo pigments such as CI Pigment Blue 25, C.I. I. Phthalocyanine pigments such as CI Pigment Blue 15; I. Pigment Blue 24, etc., acidic dye lake pigments, C.I. I. Basic dye lake pigments such as CI Pigment Blue 1; I. Anthraquinone pigments such as CI Pigment Blue 60; I. And alkaline blue pigments such as CI Pigment Blue 18.

Examples of the pigment for black ink include organic pigments such as aniline black pigments and iron oxide pigments, and carbon black pigments such as furnace black, lamp black, acetylene black, and channel black.
Furthermore, processed pigments typified by microlith pigments such as Microlith-A, -K, and -T can also be suitably used. Specific examples thereof include Microlith Yellow 4G-A, Micro Resled BP-K, Microlith Blue 4G-T, and Microlith Black CT.
Various pigments can be used as necessary, such as calcium carbonate and titanium oxide pigments for white ink, aluminum powder for silver ink, and copper alloy for gold ink.

Basically, it is preferable to use one kind of pigment for each color, from the viewpoint of simplicity of ink production. However, as a hue adjustment, for example, for black ink, phthalocyanine is mixed with carbon black. Are preferably used in combination of two or more. Alternatively, the pigment may be surface-treated by a known method such as rosin treatment (Non-Patent Document 1).
The pigment content relative to the entire ink composition is preferably in the range of 0.1 to 50% by mass. When the amount is 0.1% by mass or more, the amount of pigment is sufficient, and sufficiently good color development is obtained in the printed matter. When the amount is 50% by mass or less, the particles containing the coloring material can be favorably dispersed in the dispersion medium. More preferably, it is 1-30 mass%.

[Coating agent]
In the present invention, it is preferable that the coloring material such as a pigment is dispersed (particulated) in a state of being coated with a coating agent, rather than directly dispersed (particulated) in a dispersion medium. By covering with a coating agent, it is possible to shield the charge of the color material and to impart desirable charge characteristics. Moreover, the difference in dispersion stability that varies depending on the type of the color material can be canceled, and similar dispersion stability can be imparted. Furthermore, in the present invention, it is preferable to perform inkjet recording on a recording medium and then fix it by a heating means such as a heat roller. At this time, the coating agent is melted by heat and can be fixed efficiently.

  Examples of the coating agent include rosins, phenol resins, rosin-modified phenol resins, alkyd resins, (meth) acrylic polymers, polyurethanes, polyesters, polyethers, polyamides, polyethylenes, polybutadienes, polystyrenes, polyvinyl acetates, polyvinyl alcohols. Acetal-modified products, polycarbonates and the like. Among these, from the viewpoint of ease of particle formation, the mass average molecular weight is in the range of 2,000 to 1,000,000 and the polydispersity (mass average molecular weight / number average molecular weight) is 1.0. Polymers in the range of ~ 5.0 are preferred. Further, from the viewpoint of ease of fixing, a polymer having any one of a softening point, a glass transition point, and a melting point within a range of 40 ° C. to 120 ° C. is preferable.

  In the present invention, the polymer particularly preferably used as the coating agent is a polymer containing at least one of the structural units represented by the following general formulas (1) to (4).

In the formula, X ₁₁ represents an oxygen atom or —N (R ₁₃ ) —. R ₁₁ represents a hydrogen atom or a methyl group, R ₁₂ represents a hydrocarbon group having 1 to 30 carbon atoms, and R ₁₃ represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. R ₂₁ represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. R ₃₁ , R ₃₂ and R ₄₁ each independently represents a divalent hydrocarbon group having 1 to 20 carbon atoms. The hydrocarbon group of R ₁₂ , R ₂₁ , R ₃₁ , R ₃₂ , and R ₄₁ may contain an ether bond, amino group, hydroxy group, or halogen substituent.

  The polymer containing the structural unit represented by the general formula (1) can be obtained by radical polymerization of a corresponding radical polymerizable monomer by a known method. Examples of the radical polymerizable monomer used include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, and (meth) acrylic. Octyl acid, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, (meth) (Meth) acrylic acid esters such as 2-hydroxyethyl acrylate, N-methyl (meth) acrylamide, N-propyl (meth) acrylamide, N-phenyl (meth) acrylamide, N, N-dimethyl (meth) Examples include (meth) acrylamides such as acrylamide.

  The polymer containing the structural unit represented by the general formula (2) can be obtained by radical polymerization of a corresponding radical polymerizable monomer by a known method. Examples of the radical polymerizable monomer used include ethylene, propylene, butadiene, styrene, and 4-methylstyrene.

  The polymer containing the structural unit represented by the general formula (3) can be obtained by dehydrating condensation of a corresponding dicarboxylic acid or acid anhydride and a diol by a known method. Examples of the dicarboxylic acid used include succinic anhydride, adipic acid, sebacic acid, isophthalic acid, terephthalic acid, 1,4-phenylenediacetic acid, diglycolic acid and the like. Examples of the diol used include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, and 2-butene- Examples include 1,4-diol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,4-benzenedimethanol, and diethylene glycol.

  The polymer containing the structural unit represented by the general formula (4) is obtained by dehydrating and condensing a carboxylic acid having a corresponding hydroxy group by a known method, or by using a known ester of a cyclic ester of a carboxylic acid having a corresponding hydroxy group. Is obtained by ring-opening polymerization. Examples of the carboxylic acid having a hydroxy group or a cyclic ester thereof include 6-hydroxyhexanoic acid, 11-hydroxyundecanoic acid, hydroxybenzoic acid, and ε-caprolactone.

  The polymer containing at least one of the structural units represented by the general formulas (1) to (4) may be a homopolymer of the structural units represented by the general formulas (1) to (4). It may be a copolymer (copolymer) with other components. These polymers may be used alone as a coating agent, or may be used in combination of two or more.

  The content of the coating agent with respect to the entire ink composition is preferably in the range of 0.1 to 40% by mass. When the amount is 0.1% by mass or more, the amount of the coating agent is sufficient, and sufficient fixability is obtained. When the amount is 40% by mass or less, particles containing the coloring material and the coating agent can be favorably formed.

[Dispersant]
In the present invention, preferably, the coloring material or a mixture of the coloring material and the coating material is dispersed (particulated) in the dispersion medium. However, in order to stably discharge for a long time, and the redispersibility of the particles that have settled over time. In order to improve the above, a polymer having a crosslinked structure is used as a dispersant. In addition, as long as the effect of the present invention is not impaired, a polymer having no crosslinked structure may be used in combination as a dispersant.
In the present invention, the polymer having a cross-linked structure is a polymer having a cross-linked chain within the same polymer molecule or between polymer molecules, such as a cross-linked chain between the same or different polymer chains of a random polymer, block polymer, or graft polymer. The polymer is not limited as long as it can disperse the coloring material, but it is particularly preferable to use a block polymer having a crosslinked structure or a graft polymer having a crosslinked structure.

When a polymer having a crosslinked structure is used as the dispersant, ink adhesion, that is, piping clogging or head clogging is difficult to occur, and stable ejection can be performed for a long time. In addition, the redispersibility of the ink that has settled over time is improved. The reason why such an effect is obtained is not clear, but is considered as follows.
When an ink jet composition containing at least a coloring material is ejected from an ink jet head, the particle concentration increases due to volatilization of the solvent at the gas-liquid interface typified by the head tip. Similarly, when the ink is stored in the ink tank or in the container for a long period of time, the particle concentration is also increased in the portion where the ink settles and accumulates over time as compared with the dispersed state before the sedimentation. As the particle concentration increases, the density between the particles increases, and the particles become close to or in contact with each other. At this time, in an ink using a polymer having no cross-linked structure as a dispersant, the polymer chains of the dispersant adsorbed on each particle are entangled with each other, and even when stress is applied, it is in a state where it is difficult to loosen. It is guessed. That is, it is an ink composition in which agglomeration and adhesion at the gas-liquid interface such as the head portion is likely to occur, and the redispersibility of the ink that has settled with time is poor. Therefore, by introducing a cross-linked structure into the dispersant polymer chain and making the polymer chains of the dispersant that are structurally adsorbed to each other particle less likely to get entangled, the particles that come into contact are easily loosened, It is considered that the aggregated adhesion to the gas-liquid interface and the redispersibility of the ink that settled with time improved.

  The polymer having a crosslinked structure that can be suitably used in the present invention is a polymer having a two-point crosslinked structure and a multi-point crosslinked structure of three or more points in the polymer structure, but is hardly gelled and has a solubility. From the viewpoint of easily holding the polymer, a polymer having a crosslinked structure having only a two-point crosslinked structure is more preferable.

  The random polymer having a crosslinked structure that can be suitably used in the present invention is a polymer having at least a structural unit represented by the following general formula (5) and general formula (6) and having a mass average molecular weight of 1,000 or more. is there.

In general formulas (5) and (6),
R ₅₁ , R ₅₂ , R ₆₁ , R ₆₂ , R ₆₄ and R ₆₅ may be the same or different and each represents a hydrogen atom or a methyl group.
R ₅₃ represents a hydrogen atom or a hydrocarbon group having 1 to 200 carbon atoms which may have a substituent. In the hydrocarbon group of R ₅₃ , an ether bond, an ester bond, an amide bond, a carbamate bond, an amino group, a hydroxyl group, a halogen substituent, an acidic group, a salt obtained by neutralizing an acidic group, a basic group, or a basic group It may contain an ion-paired salt.
R ₆₃ represents a single bond or a hydrocarbon chain which may have a substituent. R ₆₃ may be a low molecular connecting chain having a molecular weight of 1000 or less, or a polymer connecting chain having a molecular weight of 1000 or more. When R ₆₃ is a polymer linking chain, the mass average molecular weight is preferably 100,000 or less. In the hydrocarbon group of R ₆₃ , an ether bond, ester bond, amide bond, carbamate bond, amino group, hydroxyl group, halogen substituent, acidic group, salt neutralized acidic group, basic group, basic group It may contain an ion-paired salt, a radical polymerizable unsaturated double bond, or the like.
X ₅₁ , X ₆₁ and X ₆₂ may be the same or different and each has a single bond or a total number of atoms consisting of two or more atoms selected from C, H, N, O, S and P of 50. Or less divalent linking group. As for the mass which the structural unit (repeating unit) of General formula (6) makes in a polymer, 0.00001-30 mass% is preferable. When the amount is 0.00001% by mass or more, an effect of suppressing entanglement and interaction between polymer chains is exhibited, and when the amount is 30% by mass or less, solubility in a dispersion medium can be secured. A desirable ratio is 0.01 to 10% by mass.

The polymer having a crosslinked structure containing at least the structural unit represented by the general formula (5) and the structural unit represented by the general formula (6) preferably used in the present invention is a radical corresponding to the general formula (5). Using a known radical polymerization initiator, a polymerizable monomer, a radical polymerizable bifunctional monomer corresponding to the general formula (6), and, if necessary, another radical polymerizable monomer,
It can be obtained by polymerization. Here, the monomer corresponding to the general formula (5) is a monomer represented by the following general formula (5M), and the radical polymerizable bifunctional monomer corresponding to the general formula (6) is the following general formula (6M). It is a radically polymerizable bifunctional monomer represented by

  Each symbol in general formulas (5M) and (6M) has the same meaning as in general formulas (5) and (6).

  Examples of the monomer represented by the general formula (5M) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, Octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate (Meth) acrylic acid esters such as 2-hydroxyethyl (meth) acrylate, and N-methyl (meth) acrylamide, N-propyl (meth) acrylamide, N-phenyl (meth) acrylamide, N, N- (Meth) acrylamides such as dimethyl (meth) acrylamide, styrene, methyl Styrenes such as tylene, chlorostyrene, methoxystyrene, hydrocarbons such as 1-butene, vinyl acetates, vinyl ethers, (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, 2- (meth) Acryloyloxyethyl phthalate, 2- (meth) acryloyloxyethyl succinate, styrene carboxylic acid, maleic acid, itaconic acid, fumaric acid, (meth) acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloyloxyethyl Monomers containing acidic groups such as sulfonic acid, styrene sulfonic acid, ethylene glycol (meth) acrylate phosphate, styrene phosphoric acid, etc., and acidic groups in the monomer are amines, sulfides, phosphines, heterocyclic compounds, etc. Ion-paired monomer, the monomer Monomers obtained by neutralizing the acidic groups of the above by a counter component such as ammonium salt, sulfonium salt, phosphonium salt, vinylamine, allylamine, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) Acrylate, 1- (N, N-dimethylamino) -1,1-dimethylmethyl (meth) acrylate, N, N-dimethylaminohexyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N -Diisopropylaminoethyl (meth) acrylate, N, N-di-n-butylaminoethyl (meth) acrylate, N, N-di-i-butylaminoethyl (meth) acrylate, morpholinoethyl (meth) acrylate, piperidinoethyl ( (Meth) acrylate, 1-pyrrolidinoethyl (Meth) acrylate, N, N-methyl-2-pyrrolidylaminoethyl (meth) acrylate and N, N-methylphenylaminoethyl (meth) acrylate, 2- (N, N-dimethylamino) ethyl (meth) Acrylamide, 2- (N, N-diethylamino) ethyl (meth) acrylamide, 3- (N, N-diethylamino) propyl (meth) acrylamide, 3- (N, N-dimethylamino) propyl (meth) acrylamide, 1- (N, N-dimethylamino) -1,1-dimethylmethyl (meth) acrylamide and 6- (N, N-diethylamino) hexyl (meth) acrylamide, p-vinylaniline, N, N-dimethyl p-vinylbenzylamine , Monomers containing basic groups such as p-dimethylaminostyrene and vinylpyridine , And a monomer in which a basic group in the monomer is neutralized with an acidic group-containing compound, a monomer in which the basic group in the monomer is ionized by a chemical reaction other than a neutralization reaction, polyethylene glycol (meth) acrylate, and polypropylene glycol (Meth) acrylate, glycerol (meth) acrylate, glycidyl (meth) acrylate, 2-isocyanate (meth) acrylate, 2-aminoethyl methacrylate and the like can be mentioned.

  Examples of the radical polymerizable bifunctional monomer represented by the general formula (6M) include ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, allyl acrylate, and bis (acrylic). Roxyethyl) hydroxyethyl isocyanurate, bis (acryloxy neopentyl glycol) adipate, 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, propylene glycol diacrylate, polypropylene glycol Diacrylate, 2-hydroxy-1,3-diacryloxypropane, 2,2-bis [4- (acryloxy) pheny ] Propane, 2,2-bis [4- (acryloxyethoxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy-diethoxy) phenyl] propane, 2,2-bis [4- (acryloxy) Ethoxy polyethoxy) phenyl] propane, hydroxybivalic acid neopentyl glycol diacrylate, 1,4-butanediol diacrylate, dicyclopentanyl diacrylate, dipentaerythritol hexaacrylate, dipentaerythritol monohydroxypentaacrylate, ditrimethylol Propane tetraacrylate, pentaerythritol triacrylate, tetrabromopisphenol A diacrylate, triglycerol diacrylate, trimethylolpropane triacrylate, tris (acrylic) Xylethyl) isocyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, propylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, 2-hydroxy-1,3-dimethacryloxypropane, 2,2-bis [4 (methacryloxy) phenyl ] Propane, 2,2-bis [4- (methacryloxyethoxy) phenyl] propane, 2,2-bis [4- (meth) Acryloxyethoxydiethoxy) phenyl] propane, 2,2-bis [4- (methacryloxyethoxypolyethoxy) phenyl] propane, tetrabromobisphenol A dimethacrylate, dicyclopentanyl dimethacrylate, dipentaerythritol hexamethacrylate, glycerol Dimethacrylate, hydroxypentylglycol dipentadiacrylate, dipentaerythritol monohydroxypentamethacrylate, ditrimethylolpropane tetramethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, triglycerol dimethacrylate, trimethylolpropane trimethacrylate, tris (Methacryloxyethyl) isocyanurate, allyl methacrylate Rate, divinylbenzene, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, diethylene glycol bis allyl carbonate.

  The random polymer having a crosslinked structure that can be suitably used in the present invention includes a polymer having at least one of a hydroxyl group, an amino group, a carboxyl group, and a thiol group, and at least one of an isocyanate group and an epoxy group. Either react with a cross-linking agent having plural or react with a polymer having at least one of isocyanate group and epoxy group with a cross-linking agent having at least one of hydroxyl group, amino group, carboxyl group and thiol group. It can also be obtained.

  As the polymer having a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group, among the monomers represented by the general formula (5M), a hydroxyl group, an amino group, a carboxyl group, a thiol group, The monomer which has an isocyanate group and an epoxy group, and the radically polymerizable monomer shown by General formula (5) which does not contain those functional groups as needed can be obtained using a well-known radical polymerization initiator.

  Among the monomers represented by the general formula (5M), examples of the monomer having a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group include polyethylene glycol (meth) acrylate, polypropylene glycol (meta ) Acrylate, 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, 2- (meth) acryloyloxyethyl phthalate, 2- (meth) acryloyl Examples include oxyethyl succinate, styrene carboxylic acid, maleic acid, itaconic acid, fumaric acid, glycidyl (meth) acrylate, 2-isocyanate (meth) acrylate, and 2-aminoethyl methacrylate.

  Examples of the crosslinking agent having a plurality of hydroxyl groups, amino groups, carboxyl groups, thiol groups, isocyanate groups, and epoxy groups include glycerin polyglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene diglycidyl ether, trimethylolpropane polyglycidyl ether. Sorbitol polyglycidyl ether, bisphenols or polyglycidyl ethers of polyphenols or their hydrogenated products, tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, xylylene diisocyanate, naphthalene diisocyanate, cyclohexanephenylene diisocyanate, isophorone diisocyanate, Hexamethylene diisocyanate , Cyclohexyl diisocyanate, or compounds obtained by blocking them with alcohol or amine, ethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenediamine, propylenediamine, polyethyleneimine, compounds having terminal methylol groups, polyhydric alcohols such as pentaerythritol, bisphenol -Polyphenols, aromatic polycarboxylic acids such as pyromellitic acid, trimellitic acid and phthalic acid, aliphatic polycarboxylic acids such as adipic acid, pyromellitic acid anhydride, benzophenone tetracarboxylic acid anhydride, etc. .

  The random polymer having a crosslinked structure that can be suitably used in the present invention includes a polymer having a carboxyl group, an acid halide group, and an acid anhydride group, and at least one of a hydroxyl group and an amino group. It can also be obtained by reacting a cross-linking agent having a hydroxyl group and an amino group with a cross-linking agent having a plurality of carboxyl groups, acid halide groups, and acid anhydride groups.

  The random polymer having a carboxyl group, a hydroxyl group, and an amino group is as described above, and the random polymer having an acid halide group and an acid anhydride group is an acid among monomers represented by the general formula (5). It is also possible to use a polymer obtained by copolymerization of a radical polysynthetic monomer having a halide group and an acid anhydride group, or by subjecting the carboxyl group of a random polymer having a carboxyl group to a known acid halide reaction and acid anhydride reaction. Can be obtained. Similarly, the crosslinking agent having an acid halide group and an acid anhydride group can be obtained by subjecting the carboxyl group of the crosslinking agent having a carboxyl group to a known acid halide reaction and acid anhydride reaction.

  The random polymer having a crosslinked structure that can be suitably used in the present invention can also be obtained by polymerizing (crosslinking) a polymer having a radical polymerizable group using a known radical polymerization initiator.

  As the polymer having a radical polymerizable group, for example, a radical polymerizable monomer represented by the general formula (5M) and a monomer having a plurality of radical polymerizable groups having different reactivities are used. Can be obtained by polymerization.

  Examples of the monomer having a plurality of radically polymerizable groups having different reactivities include allyl (meth) acrylate and vinyl (meth) acrylate.

  The graft polymer having a crosslinked structure that can be suitably used in the present invention includes a graft polymer having a crosslinked structure in the main chain, a graft polymer having a crosslinked structure in the graft chain that is a side chain, and a main chain and a side chain. Examples thereof include a graft polymer having a crosslinked structure. In the present invention, a graft polymer having a crosslinked structure in the main chain and a graft polymer having a crosslinked structure in the side chain graft chain are particularly preferred. The graft polymer having a crosslinked structure in the main chain has at least a structural unit represented by the following general formula (7) in addition to the structural unit represented by the general formula (5) and the general formula (6), Examples include polymers having a weight average molecular weight of 1,000 or more. Other structural units may be included. The graft polymer having a crosslinked structure in the graft chain has at least a structural unit represented by the general formula (8) in addition to the structural unit represented by the general formula (5), and has a mass average molecular weight of 1, 000 or more polymers. Other structural units such as the structural unit represented by the general formula (7) may be included. The dispersant having a crosslinked structure in both the main chain and the side chain is represented by the following general formula (8) in addition to the structural units represented by the general formula (5) and the general formula (6). A polymer having at least a structural unit and having a mass average molecular weight of 1,000 or more can be mentioned. Other structural units may be included.

In the general formulas (7) and (8), R ₇₁ , R ₇₂ , R ₈₁ and R ₈₂ may be the same or different and each represents a hydrogen atom or a methyl group.
X ₇₁ and X ₈₁ may be the same or different and each has a total number of atoms of 50 or less consisting of a single bond or two or more atoms selected from C, H, N, O, S, and P. A divalent linking group is shown.
G ₁ is a graft chain component, and a polymer component having a mass average molecular weight of 500 or more, containing at least one of the structural units represented by the following general formula (5) and general formulas (9) to (17): Indicates.
G ₂ is a graft chain component having a crosslinked structure, and is represented by the following general formula (5), one or more of the structural units represented by the general formulas (9) to (17), and the general formula (6). And a polymer component having a mass average molecular weight of at least 500 and containing at least a structural unit.

In the general formulas (9) to (17), R ₉₁ , R ₉₂ , R ₁₀₁ , R ₁₀₂ , R ₁₁₁ , R ₁₁₂ , R ₁₂₁ , R ₁₂₂ , R ₁₃₁ , R ₁₃₂ , R ₁₄₁ , R ₁₅₁ , R ₁₆₁ , R ₁₇₁ and R ₁₈₁ each independently represent a divalent hydrocarbon group having 1 to 20 carbon atoms. R ₉₁ , R ₉₂ , R ₁₀₁ , R ₁₀₂ , R ₁₁₁ , R ₁₁₂ , R ₁₂₁ , R ₁₂₂ , R ₁₃₁ , R ₁₃₂ , R ₁₄₁ , R ₁₅₁ , R ₁₆₁ , R ₁₇₁ , R ₁₈₁ hydrocarbon group It may contain an ether bond, an amino group, a hydroxyl group, or a halogen substituent.

  The ratio of the structural unit (repeating unit) of the general formula (6) to the whole polymer is preferably 0.00001 to 30% by mass. When the amount is 0.00001% by mass or more, an effect of suppressing entanglement and interaction between polymer chains is exhibited, and when the amount is 30% by mass or less, solubility in a dispersion medium can be secured. A desirable ratio is 0.01 to 10% by mass.

  The polymer having a cross-linked structure in the main chain that can be suitably used in the present invention is one or a plurality of radical polymerizable monomers corresponding to the general formula (5) and a radical polymerizable second polymer corresponding to the general formula (6). One or a plurality of functional monomers and one or a plurality of macromonomers corresponding to the general formula (7) can be obtained by polymerization using a known radical polymerization initiator. The polymer having a cross-linked structure on the graft chain, which is a side chain that can be suitably used in the present invention, corresponds to one or a plurality of radical polymerizable monomers corresponding to the general formula (5) and the general formula (8). It can obtain by superposing | polymerizing 1 type or multiple types among the macromonomers which have a crosslinked structure to perform using a well-known radical polymerization initiator. The polymer having a crosslinked structure in both the side chain and the main chain that can be suitably used in the present invention corresponds to one or more radical polymerizable monomers corresponding to the general formula (5) and the general formula (6). Can be obtained by polymerizing one or more of the radical polymerizable bifunctional monomers to be used and one or more of the macromonomers corresponding to the general formula (8) using a known radical polymerization initiator. it can. Here, the radical polymerizable monomer corresponding to the general formula (5) is a monomer represented by the following general formula (5M), and the radical polymerizable bifunctional monomer corresponding to the general formula (6) is represented by the following general formula. The macromonomer corresponding to the general formula (7) is a macromonomer represented by the following general formula (7M) and corresponds to the general formula (8). The macromonomer having a crosslinked structure is a macromonomer having a crosslinked structure represented by the following general formula (8M).

  Each symbol in general formulas (5M) to (8M) has the same meaning as in general formulas (5) to (8).

As the macromonomer represented by the general formula (7M), one or more radically polymerizable monomers of the general formula (5M) corresponding to the general formula (5) may be used in the presence of a chain transfer agent as necessary. A polymer having a radical polymerizable functional group at the terminal obtained by polymerization and introducing a radical polymerizable functional group into the terminal of the polymer obtained, and units corresponding to the general formula (9) to the general formula (17) Examples thereof include a polymer having a radical polymerizable functional group at the terminal obtained by introducing a radical polymerizable functional group into the terminal of the polymer chain having a structure.
The macromonomer represented by the general formula (8M) includes one or more radical polymerizable monomers of the general formula (5M) corresponding to the general formula (5) and the following general formula corresponding to the general formula (6). The radically polymerizable bifunctional monomer (6M) and, if necessary, another radically polymerizable monomer are polymerized in the presence of a chain transfer agent as necessary, and the radically polymerizable functional group is obtained at the terminal of the obtained polymer. Examples thereof include polymers having a radical polymerizable functional group at the terminal obtained by introducing.
The mass average molecular weight of the macromonomer represented by the general formula (7M) and the general formula (8M) is in the range of 500 to 500,000, and the polydispersity (mass average molecular weight / number average molecular weight) is Macromonomers that are in the range of 1.0 to 7.0 are preferred.

  In addition, the graft polymer having a crosslinked structure that can be suitably used in the present invention is a hydroxyl group, an amino group, a carboxyl group, or a thiol group in any of the main chain, the side chain, and both the main chain and the side chain. Either a graft polymer having at least one kind is reacted with a cross-linking agent having at least one kind selected from an isocyanate group and an epoxy group, or an isocyanate group in any one of the main chain, the side chain, and the main chain or the side chain. And a graft polymer having at least one of epoxy groups and a crosslinking agent having at least one of hydroxyl group, amino group, carboxyl group and thiol group can be reacted.

  The graft polymer having a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group in the main chain is a hydroxyl group, an amino group, a radical polymerizable monomer represented by the general formula (5M), A radical polymerizable monomer having a carboxyl group, a thiol group, an isocyanate group, and an epoxy group, a radical polymerizable macromonomer represented by the general formula (7M), and, if necessary, a general formula having no functional group (5M ) Can be obtained by polymerization using a known radical polymerization initiator.

  The graft polymer having a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group in the side chain is an amino group, a carboxyl group, or a thiol among the radical polymerizable macromonomers represented by the general formula (7M). It can be obtained by polymerizing a radically polymerizable macromonomer having a group, an isocyanate group and an epoxy group with a radically polymerizable monomer represented by the general formula (5M) using a known radical polymerization initiator.

  Among the radical polymerizable monomers represented by the general formula (5M), examples of the radical polymerizable monomer having a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group include polyethylene glycol (meth) acrylate, Prene glycol (meth) acrylate, 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, 2- (meth) acryloyloxyethyl phthalate, 2- (Meth) acryloyloxyethyl succinate, styrene carboxylic acid, maleic acid, itaconic acid, fumaric acid, glycidyl (meth) acrylate, 2-isocyanate (meth) acrylate, 2-aminoethyl methacrylate, etc. Among the radical polymerizable macromonomers represented by the general formula (7M), the radical polymerizable macromonomer having an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group includes the above monomers at the time of macromonomer synthesis. Polymerized macromonomer is mentioned.

  A monomer having a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group, and at least one of a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group Examples of the crosslinking agent are as described above.

In addition, the graft polymer having a crosslinked structure that can be suitably used in the present invention has a carboxyl group, an acid halide group, and an acid anhydride group in any of the main chain, the side chain, and both the main chain and the side chain. A graft polymer having a hydroxyl group and a cross-linking agent having at least one of amino groups, or a hydroxyl group and an amino group in either the main chain, the side chain, and the main chain or the side chain. It can also be obtained by reacting a graft polymer having a crosslinking agent having a plurality of carboxyl groups, acid halide groups, and acid anhydride groups.

  The graft polymer having a carboxyl group, a hydroxyl group, and an amino group is as described above, and the graft polymer having an acid halide group and an acid anhydride group is an acid among the monomers represented by the general formula (5). Use a graft polymer obtained by copolymerizing a radical polymerization monomer having a halide group and an acid anhydride group, or subjecting the carboxyl group of a graft polymer having a carboxyl group to a known acid halide reaction and acid anhydride reaction. But you can get it.

  In addition, the graft polymer having a crosslinked structure that can be suitably used in the present invention is a known radical polymerization of a graft polymer having a radical polymerizable group in either the main chain, the side chain, or both of the main chain and the side chain. It can also be obtained by polymerizing (crosslinking) using an initiator.

  The graft polymer having a radical polymerizable group in the main chain includes a radical polymerizable monomer having a plurality of radical polymerizable groups having different reactivities, a radical polymerizable monomer represented by the general formula (5M), and a general formula It can be obtained by polymerizing the radically polymerizable macromonomer represented by (7M) with a known radical polymerization initiator.

  The graft polymer having a radically polymerizable group in the side chain requires one or more radically polymerizable monomers represented by the general formula (5M) and a radically polymerizable monomer having a plurality of radically polymerizable groups having different reactivity. And a macromonomer having a radical polymerizable functional group at the terminal obtained by polymerizing in the presence of a chain transfer agent and introducing a radical polymerizable functional group at the terminal of the polymer obtained by the general formula (5M) It can be obtained by copolymerizing the indicated radical polymerizable monomer.

  Examples of the monomer having a plurality of radically polymerizable groups having different reactivities include allyl (meth) acrylate and vinyl (meth) acrylate.

The graft polymer used in the present invention is:
(1) The main chain, the side chain, and both the main chain and the side chain have a crosslinked structure, the main chain part is dissolved in the dispersion medium, and the side chain part (graft chain) is dissolved. (2) The main chain, the side chain, and both the main chain and the side chain have a crosslinked structure, and the main chain part does not dissolve in the dispersion medium, and the side chain part (graft (3) The main chain, the side chain, and both the main chain and the side chain have a crosslinked structure, and the side chain that is dissolved in the dispersion medium and the side that is not dissolved A graft polymer having a chain is particularly preferably used.
“Dissolved in the dispersion medium” means that the polymer composed only of the side chain portion or the main chain portion is dissolved in the dispersion medium. The solubility is preferably 5 g or more, more preferably 10 g or more, and still more preferably 20 g or more.
The phrase “not dissolved in the dispersion medium” means that the polymer composed only of the side chain portion or the main chain portion does not dissolve in the dispersion medium. The solubility is preferably 3 g or less, more preferably 2 g or less, and still more preferably 1 g or less.

  The block polymer having a crosslinked structure that can be suitably used in the present invention is a polymer having two or more types of polymer segments and having a crosslinked structure between one type or two or more types of segments. It is not limited as long as it can be dispersed, but preferably has two or more polymer segments having a mass average molecular weight of 500 or more, and has a crosslinked structure between one or two or more segments. A polymer having a molecular weight of 1,000 or more. The cross-linked structure may be cross-linking within the same polymer, that is, intramolecular cross-linking or intermolecular cross-linking. Particularly preferred is a block polymer having a crosslinked structure in the block polymer represented by the general formula (18) and the general formula (19).

In general formula (18), A, B, C, and D represent polymer segments, and A and B, and C and D are different polymer segments. b ₁ , b ₂ , and b ₃ each indicate that the segments A to D are block-bonded.
The cross-linked structure may be within the same segment, for example, between different segments in a molecule such as between A segment and B segment, between different molecular segments, etc., but is not limited as long as it has a cross-linked structure. .

  The block polymer that can be suitably used in the present invention has at least a structural unit represented by the following general formula (20) and a structural unit represented by the general formula (6), and has a mass average molecular weight of 1,000 or more. Examples include a polymer and a block polymer having at least a structural unit represented by the following general formula (21) and a structural unit represented by the general formula (6) and having a mass average molecular weight of 1,000 or more. The structural unit represented by the general formula (6) is present in each segment or between the segments in the general formula (20) and the general formula (21) and means a crosslinking unit in the same molecule or between molecules. ing.

In the general formulas (20) and (21), R ₂₀₁ , R ₂₀₂ , R ₂₀₄ , R ₂₀₅ , R ₂₁₁ , R ₂₁₂ , R ₂₁₄ , and R ₂₁₅ may be the same or different and are each a hydrogen atom or a methyl group Indicates.
R ₂₀₃ , R ₂₀₆ , R ₂₁₃ , and R _{216 each} represent a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 200 carbon atoms, in which a silicon atom, an ether bond, It may contain an ester bond, amide bond, carbamate bond, halogen group, hydroxyl group, amino group, ammonium group, carboxyl group, sulfonic acid group, phosphoric acid group, or phosphonic acid group.
X ₂₀₁ , X ₂₀₂ , X ₂₁₁ , and X ₂₁₂ may be the same or different and are each a single bond or a total atom composed of two or more atoms selected from C, H, N, O, S, and P A divalent linking group having a number of 50 or less is shown.
b1, b2, and b3 each represent a single bond or a low molecular weight or high molecular weight linking group. When the linking group is a polymer, the mass average molecular weight is preferably 1,000,000 or less. The linking group contains a silicon atom, an ether bond, an ester bond, an amide bond, a carbamate bond, a halogen group, a hydroxyl group, an amino group, an ammonium group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, or a phosphonic acid group. May be.
m, n, r, s, and t mean a polymer and are an integer of 5 or more.

The ratio of the structural unit of the general formula (6) to the whole polymer is preferably 0.00001 to 30% by mass. When the amount is 0.00001% by mass or more, an effect of suppressing entanglement and interaction between polymer chains is exhibited, and when the amount is 30% by mass or less, solubility in a dispersion medium can be secured. A desirable ratio is 0.01 to 10% by mass.

The block polymer having at least the structural unit represented by the general formula (20) and the structural unit represented by the general formula (6) is represented by the general formula (20-1M) corresponding to each of the two segments in the general formula (20). A radical polymerizable monomer represented by the general formula (20-2M) and a radical polymerizable bifunctional monomer corresponding to the general formula (6) using a radical polymerization initiation system. It can be obtained by using a legal method. Further, the block polymer having at least the structural unit represented by the general formula (21) and the structural unit represented by the general formula (6) is represented by the general formula corresponding to each of two types and three segments in the general formula (21). (21-1M), a radically polymerizable monomer represented by the general formula (21-2M) and a radically polymerizable bifunctional monomer corresponding to the general formula (6), using a radical polymerization initiation system, a known living room It can be obtained by using a radical polymerization method. Living radical polymerization methods include iniferter polymerization method, NMP (Nitroxide-Mediated Polymerization) method, ATRP method (Atom Transfer Radical Polymerization) method, RAFT method (Reversible).
(Addition-Fragmentation chain Transfer) method and the like.

  Each symbol in general formulas (20-1M), (20-2M), (21-1M), and (21-2M) has the same meaning as in general formula (20) and general formula (21). is there.

  Examples of the monomer represented by the general formula (20-1M), (20-2M), (21-1M), (21-2M) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, ( (Meth) propyl acrylate, (butyl) (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, dodecyl (meth) acrylate, (Meth) acrylic acid stearyl, (meth) acrylic acid phenyl, (meth) acrylic acid benzyl, (meth) acrylic acid esters such as 2-hydroxyethyl, and N-methyl (meth) acrylamide, N-propyl (meth) acrylamide, N-phenyl (meth) acrylamide, N, N-dimethyl (meth) acryl (Meth) acrylamides such as amides, styrenes such as styrene, methylstyrene, chlorostyrene and methoxystyrene, hydrocarbons such as 1-butene, vinyl acetates, vinyl ethers, (meth) acrylic acid, (meth) 2-carboxyethyl acrylate, 2- (meth) acryloyloxyethyl phthalate, 2- (meth) acryloyloxyethyl succinate, styrene carboxylic acid, maleic acid, itaconic acid, fumaric acid, (meth) acrylamide-2-methyl Monomers containing acidic groups such as propanesulfonic acid, 2- (meth) acryloyloxyethyl sulfonic acid, styrene sulfonic acid, ethylene glycol (meth) acrylate phosphate, styrene phosphoric acid, and the acidic group in the monomer as amines , Sulfides, phosphines A monomer ion-paired with a heterocyclic compound, a monomer obtained by neutralizing an acidic group in the monomer with a counter component such as ammonium salt, sulfonium salt, phosphonium salt, vinylamine, allylamine, N, N-dimethylaminoethyl (Meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, 1- (N, N-dimethylamino) -1,1-dimethylmethyl (meth) acrylate, N, N-dimethylaminohexyl (meth) acrylate N, N-diethylaminoethyl (meth) acrylate, N, N-diisopropylaminoethyl (meth) acrylate, N, N-di-n-butylaminoethyl (meth) acrylate, N, N-di-i-butylamino Ethyl (meth) acrylate, morpholinoethyl (meth) acrylate, Peridinoethyl (meth) acrylate, 1-pyrrolidinoethyl (meth) acrylate, N, N-methyl-2-pyrrolidylaminoethyl (meth) acrylate and N, N-methylphenylaminoethyl (meth) acrylate, 2- (N , N-dimethylamino) ethyl (meth) acrylamide, 2- (N, N-diethylamino) ethyl (meth) acrylamide, 3- (N, N-diethylamino) propyl (meth) acrylamide, 3- (N, N-dimethyl) Amino) propyl (meth) acrylamide, 1- (N, N-dimethylamino) -1,1-dimethylmethyl (meth) acrylamide and 6- (N, N-diethylamino) hexyl (meth) acrylamide, p-vinylaniline, N, N-dimethyl p-vinylbenzylamine, p-dimethylaminostyrene, A monomer containing a basic group such as vinylpyridine, a monomer obtained by neutralizing a basic group in the monomer with an acidic group-containing compound, and a basic group in the monomer was ionized by a chemical reaction other than a neutralization reaction Monomer, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, glycerol (meth) acrylate, glycidyl (meth) acrylate, 2-isocyanate (meth) acrylate, 2-aminoethyl methacrylate, and the like (20- 1M) and (20-2M), and (21-1M) and (21-2M) use different monomers.

  The block polymer having a crosslinked structure that can be suitably used in the present invention is a hydroxyl group, an amino group, or a carboxyl group in the block polymer having at least the structural unit represented by the general formula (20) and the general formula (21). A block polymer having at least one of a group and a thiol group is reacted with a crosslinking agent having at least one of an isocyanate group and an epoxy group, or represented by the general formula (20) and the general formula (21). A block polymer having at least one of an isocyanate group and an epoxy group in a block polymer having at least a structural unit is reacted with a crosslinking agent having at least one of hydroxyl, amino, carboxyl and thiol groups. It can also be obtained.

  The block polymer having a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group in the block polymer having at least the structural unit represented by the general formula (20) and the general formula (21) is generally Among the radical polymerizable monomers represented by the formula (5M), a radical polymerizable monomer having a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group, and, if necessary, a general formula (5M) Among the radical polymerizable monomers represented by the formula (1), a radical polymerizable monomer having no substituent can be synthesized using a radical polymerization initiation system using a known living radical polymerization method. At this time, only the structural unit represented by the general formula (5) having the substituent may form each segment in the general formula (20) and the general formula (21), or may have the substituent. The structural unit represented by the general formula (5) having the above-mentioned substituents, wherein the structural unit represented by the general formula (5) mainly forms each segment in the general formula (20) and the general formula (21). May be partially mixed in the segment.

  Among the radical polymerizable monomers represented by the general formula (5M), examples of the radical polymerizable monomer having a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group include polyethylene glycol (meth) acrylate, Prene glycol (meth) acrylate, 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, 2- (meth) acryloyloxyethyl phthalate, 2- (Meth) acryloyloxyethyl succinate, styrene carboxylic acid, maleic acid, itaconic acid, fumaric acid, glycidyl (meth) acrylate, 2-isocyanate (meth) acrylate, 2-aminoethyl methacrylate, etc. It is.

  A monomer having a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group, and at least one of a hydroxyl group, an amino group, a carboxyl group, a thiol group, an isocyanate group, and an epoxy group Examples of the crosslinking agent are as described above.

  In addition, the block polymer having a crosslinked structure that can be suitably used in the present invention has a carboxyl group, an acid halide group, and an acid anhydride group in any of the main chain, the side chain, and both the main chain and the side chain. A graft polymer having a hydroxyl group and a cross-linking agent having at least one of amino groups, or a hydroxyl group and an amino group in either the main chain, the side chain, and the main chain or the side chain. It can also be obtained by reacting a block polymer having a crosslinking agent having a plurality of carboxyl groups, acid halide groups and acid anhydride groups. Similarly, only the structural unit represented by the general formula (5) having the substituent may form each segment in the general formula (20) and the general formula (21), or does not have the substituent. The structural unit represented by the general formula (5) mainly forms each segment in the general formula (20) and the general formula (21), and the structural unit represented by the general formula (5) having the substituent is Some may be mixed in the segment.

  The block polymer having a carboxyl group, a hydroxyl group, and an amino group is as described above, and the block polymer having an acid halide group and an acid anhydride group is an acid among monomers represented by the general formula (5). Use a block polymer obtained by copolymerizing a radical polysynthetic monomer having a halide group and an acid anhydride group, or subjecting the carboxyl group of the block polymer having a carboxyl group to a known acid halide reaction and acid anhydride reaction. But you can get it.

  The block polymer having a crosslinked structure that can be suitably used in the present invention is a block polymer having a radically polymerizable group in the block polymer having at least the structural unit represented by the general formula (20) and the general formula (21). Can also be obtained by polymerizing (crosslinking) using a known radical polymerization initiator.

  The block polymer having a radical polymerizable group in the block polymer having at least the structural unit represented by the general formula (20) and the general formula (21) is a radical polymerizable having a plurality of radical polymerizable groups having different reactivities. The monomer and the radical polymerizable monomer represented by the general formula (5M) can be synthesized using a radical polymerization initiation system using a known living radical polymerization method. At this time, the structural unit represented by the general formula (5) mainly forms each segment in the general formula (20) and the general formula (21), and the structural unit represented by the general formula (22) in the segment. A form in which is partially mixed is preferable. The proportion of the structural unit represented by the general formula (22) in the polymer is preferably in the range of 0.0001% by mass to 30% by mass.

In general formula (22), R ₂₂₁ and R ₂₂₂ may be the same or different and each represents a hydrogen atom or a methyl group.
R ₂₂₃ has a radically polymerizable group and represents a hydrocarbon group having 1 to 200 carbon atoms that may have a substituent, and in the hydrocarbon group, a silicon atom, an ether bond, an ester bond, It may contain an amide bond, carbamate bond, halogen group, hydroxyl group, amino group, ammonium group, carboxyl group, sulfonic acid group, phosphoric acid group, or phosphonic acid group.
X ₂₂₁ represents a single bond or a divalent linking group having a total number of atoms composed of two or more kinds of atoms selected from C, H, N, O, S and P and having 50 or less total atoms.

  Examples of the monomer having a plurality of radically polymerizable groups having different reactivities include allyl (meth) acrylate and vinyl (meth) acrylate.

In the graft polymer used in the present invention, segments A and C are dissolved in a dispersion medium in the block polymer having a crosslinked structure in the block polymer represented by the general formula (18) and the general formula (19). A block polymer in which the segments B and D are not dissolved in the dispersion medium and a block polymer in which the segment D is dissolved in the dispersion medium and the segment C is not dissolved in the dispersion medium are particularly preferably used.
“Dissolved in the dispersion medium” means that a polymer composed of only one segment is dissolved in the dispersion medium. Specifically, it is more than 5 g with respect to 100 g of the dispersion medium. The solubility is preferably 10 g or more, more preferably 20 g or more.
“Not dissolved in the dispersion medium” means that a polymer composed of only one segment does not dissolve in the dispersion medium. Specifically, 3 g or less, more than 100 g of the dispersion medium. The solubility is preferably 2 g or less, more preferably 1 g or less.

  Specific examples of the graft polymer or block polymer suitably used in the present invention include polymers [BZ-1] to [BZ-88] represented by the following structural formulas.

  In the present invention, in order to obtain an ink composition capable of stable ejection for a long time and having good redispersibility, the weight average molecular weight of the dispersant is in the range of 1,000 to 1,000,000, and A polymer having a polydispersity (weight average molecular weight / number average molecular weight) in the range of 1.0 to 7.0 is preferable.

  The content of the dispersant with respect to the entire ink composition is preferably in the range of 0.01 to 30% by mass. In particular, in this range, which is in the range of 0.1 to 15% by mass, the ink particles can be prevented from agglomerating and fusing, can be stably ejected for a long time, and have good redispersibility. A composition can be provided.

[Charge control agent]
In the present invention, a coloring material (preferably a mixture of a coloring material and a coating agent) is dispersed (particulated) in a dispersion medium using a dispersing agent, but a charge adjusting agent is used in combination to control the charge amount of the particles. More preferably.
Suitable charge control agents include metal salts of organic carboxylic acids such as zirconium naphthenate and zirconium octenoate, ammonium salts of organic carboxylic acids such as tetramethylammonium stearate, sodium dodecylbenzenesulfonate, dioctyl Metal salts of organic sulfonic acids such as magnesium sulfosuccinate, ammonium salts of organic sulfonic acids such as toluenebutyl tetrabutylammonium salt, polymers containing carboxylic acid groups modified with amines of copolymers of styrene and maleic anhydride, etc. Polymers having a carboxylic acid group in the side chain, polymers having a carboxylic acid anion group in the side chain such as a copolymer of stearyl methacrylate and tetramethylammonium methacrylate, side chains such as a copolymer of styrene and vinylpyridine Has a nitrogen atom Rimmer, butyl methacrylate and N- (2-methacryloyloxyethyl) -N, N, polymers having an ammonium group in the side chain of the copolymer of N- trimethylammonium tosylate. Among them, in the present invention, it is preferable to use a polymer charge control agent from the viewpoint of maintaining a stable charge for a long time. The charge applied to the particles may be positively charged or negatively charged.

The content of the charge control agent with respect to the entire ink composition is preferably in the range of 0.0001 to 10% by mass, and more preferably 0.001 to 5% by mass. Within this range, the charge amount of particles necessary for ejection is satisfied, and the charge amount becomes appropriate.

[Other ingredients]
In the present invention, a preservative for preventing corruption, a surfactant for controlling surface tension, and the like can be further contained depending on the purpose.

[Create charged particles]
An ink composition can be prepared by dispersing (particulating) a coloring material and preferably a coating agent using the dispersant of the present invention using the above components. Examples of the dispersion (particulate) method include the following.
1) A colorant and a coating agent are mixed in advance, and then dispersed (granulated) using a dispersant and a dispersion medium, and a charge adjusting agent is added.
2) Disperse (particulate) using a coloring material, a coating agent, a dispersant and a dispersion medium at the same time, and add a charge control agent.
3) Disperse (particulate) using a colorant, a coating agent, a dispersant, a charge control agent and a dispersion medium simultaneously.

  Examples of the apparatus used for mixing and dispersing include a kneader, a dissolver, a mixer, a high-speed disperser, a sand mill, a roll mill, a ball mill, an attritor, and a bead mill.

[Physical properties of ink composition]
The ink composition prepared as described above is recorded on a recording medium by an ink jet recording method. In the present invention, in order to ensure good redispersibility, the following conditions (A) to (D) are satisfied. It is preferable to use an ink composition that satisfies all of the requirements.
(A) The electric conductivity at 20 ° C. of the ink composition is in the range of 10 nS / m to 300 nS / m.
(B) The electric conductivity of the charged particles is 50% or more of the electric conductivity of the ink composition.
(C) The volume average diameter of the charged particles is in the range of 0.2 to 5.0 μm.
(D) The viscosity of the ink composition at 20 ° C. is in the range of 0.5 to 5 mPa · s.

[Inkjet recording apparatus]
The ink composition described above is recorded on a recording medium by an ink jet recording method. In the present invention, it is preferable to use an ink jet recording method utilizing an electrostatic field. An ink jet recording method using an electrostatic field concentrates charged particles of an ink composition to an ejection position by an electrostatic force by applying a voltage between a control electrode and a back electrode on the back of a recording medium, and the recording medium from the ejection position It is a method to fly to. For example, when the charged particles are positive, the voltage applied between the control electrode and the back electrode is such that the control electrode is a positive electrode and the back electrode is a negative electrode. The same effect can be obtained by charging the recording medium instead of applying a voltage to the back electrode.

  As a method of flying ink, for example, there is a method of flying ink from a needle-like tip such as an injection needle. By using the ink composition of the present invention, recording in a short time is possible.

  On the other hand, the ink is circulated in the ink chamber having the ejection opening, and is present in the ejection opening by applying a voltage to the control electrode formed at the periphery of the ejection opening, and the ink guide whose tip is directed to the recording medium side. In the method in which the concentrated ink droplets fly from the front end, the supply of charged particles by the circulation of ink and the meniscus stability at the ejection position can be achieved at the same time, so that recording can be performed stably for a long period of time. Further, in this method, since the portion where the ink is in contact with the outside air is very small with only the discharge opening, the evaporation of the solvent is suppressed and the ink physical properties are stabilized, so that it can be suitably used in the present invention.

A configuration example of an ink jet recording apparatus suitable for applying the ink composition of the present invention is shown below.
First, an outline of an apparatus that performs single-sided four-color printing on a recording medium shown in FIG. 1 will be described.
An ink jet recording apparatus 1 shown in FIG. 1 supplies ink to an ejection head 2 composed of ejection heads 2C, 2M, 2Y, and 2K for four colors for forming a full color image. A head driver 4 for driving the ejection head 2 by an output from an external device such as a computer (not shown) or a RIP, and a position control means 5. Further, the ink jet recording apparatus 1 includes a transport belt 7 stretched around three rollers 6A, 6B, and 6C, a transport belt position detection unit 8 including an optical sensor that can detect the position of the transport belt 7 in the width direction, An electrostatic attraction unit 9 for holding the recording medium P on the conveyance belt, a static elimination unit 10 and a mechanical unit 11 for peeling the recording medium P from the conveyance belt 7 after completion of image formation are provided. Upstream and downstream of the conveying belt 7, the feed roller 12 and the guide 13 that supply the recording medium P from the stocker (not shown) to the conveying belt 7, the ink is fixed to the recording medium P after peeling, and the discharge stocker (not shown). A fixing unit 14 and a guide 15 are arranged to be conveyed. In addition, the inkjet printing apparatus 1 has a recording medium position detecting means 16 at a position facing the ejection head 2 with the conveyance belt 7 interposed therebetween, and further collects the solvent vapor generated from the ink composition. A solvent recovery unit comprising the exhaust fan 17 and the solvent vapor adsorbent 18 is disposed, and the vapor inside the apparatus is discharged outside the apparatus through the recovery unit.

  A known roller can be used as the feed roller 12, and the feed roller 12 is arranged so as to increase the feeding ability to the recording medium. Further, since dirt, paper powder, or the like may adhere on the recording medium P, it is desirable to remove them. The recording medium P supplied by the feed roller is transported to the transport belt 7 through the guide 13. The back surface (preferably metal back surface) of the conveyor belt 7 is installed via a roller 6A. The recording medium transported is electrostatically attracted onto the transport belt by the electrostatic attracting means 9. In FIG. 1, electrostatic adsorption is performed by a scorotron charger connected to a negative high voltage power source. The recording medium P is electrostatically adsorbed without floating on the transport belt 7 by the electrostatic adsorption means 9 and the surface of the recording medium is uniformly charged. Here, the electrostatic attraction means is also used as a charging means for the recording medium, but may be provided separately. The charged recording medium P is transported to the ejection head portion by the transport belt 7, and electrostatic ink jet image formation is performed by superimposing the recording signal voltage with the charging potential as a bias. The recording medium P on which the image has been formed is discharged by the discharging unit 10, peeled off by the transfer belt 7 by the mechanical unit 11, and transferred to the fixing unit. The peeled recording medium P is sent to the image fixing means 14 and fixed. The fixed recording medium P is discharged through a guide 15 to a discharge stocker (not shown). The apparatus also has a means for recovering the solvent vapor generated from the ink composition. The recovery means is composed of the solvent vapor absorbing material 18, and a gas containing solvent vapor in the apparatus is introduced into the adsorbent by the exhaust fan 17, and after the vapor is adsorbed and recovered, it is exhausted outside the apparatus. The apparatus is not limited to the above example, and the number, shape, relative arrangement, charging polarity, and the like of constituent devices such as rollers and chargers can be arbitrarily selected. In the above system, four-color drawing is described. However, a multicolor system may be combined with light color ink or special color ink.

  The ink jet recording apparatus used in the above ink jet printing method includes an ejection head 2 and an ink circulation system 3. The ink circulation system 3 further includes an ink tank, an ink circulation device, an ink concentration control device, an ink temperature management device, and the like. In addition, the ink tank may include a stirring device.

As the ejection head 2, a single channel head, a multi-channel head, or a full line head can be used, and main scanning is performed by the rotation of the transport belt 7.
An ink jet head suitably used in the present invention is an ink jet method in which charged particles in an ink flow path are electrophoresed to increase the ink density near the opening and discharge, and is mainly a recording medium or a recording target. Ink droplets are ejected by electrostatic attraction caused by the counter electrode disposed on the back surface of the medium. Therefore, if the recording medium or the counter electrode does not face the head, or if no voltage is applied to the recording medium or the counter electrode even at the position facing the head, the voltage is accidentally applied to the ejection electrode. Ink droplets are not ejected even when a pressure is applied or vibration is applied, and the inside of the apparatus is not soiled.

  An ejection head suitably used for the ink jet apparatus is shown in FIGS. As shown in FIGS. 2 and 3, the inkjet head 70 includes an electrically insulating substrate 74 that forms the upper wall of the ink flow path 72 where the ink flow Q in one direction is formed, and the ink to the recording medium P. And a plurality of discharge portions 76 that discharge toward the surface. Each of the ejection portions 76 is provided with an ink guide portion 78 that guides the ink droplet G flying from the ink flow path 72 toward the recording medium P, and the substrate 74 has an opening through which the ink guide portion 78 is inserted. 75 is formed, and the ink meniscus 42 is formed between the ink guide portion 78 and the inner wall surface of the opening 75. The gap d between the ink guide portion 78 and the recording medium P is preferably about 200 μm to 1000 μm. Further, the ink guide part 78 is fixed to the support bar part 40 on the lower end side.

  The substrate 74 includes an insulating layer 44 that electrically isolates two discharge electrodes at a predetermined interval, a first discharge electrode 46 formed above the insulating layer 44, and an insulation that covers the first discharge electrode 46. It has a layer 48, a guard electrode 50 formed on the insulating layer 48, and an insulating layer 52 that covers the guard electrode 50. The substrate 74 includes a second ejection electrode 56 formed below the insulating layer 44 and an insulating layer 58 that covers the second ejection electrode 56. The guard electrode 50 is provided in order to prevent an electric field from being affected by the voltage applied to the first ejection electrode 46 and the second ejection electrode 56 in the adjacent ejection section.

Further, the ink jet head 70 constitutes the bottom surface of the ink flow path 72, and the ink flow is generated by the induced voltage that is constantly generated by the pulsed discharge voltage applied to the first discharge electrode 46 and the second discharge electrode 56. A floating conductive plate 62 that moves positively charged ink particles (charged particles) R in the path 72 upward (that is, toward the recording medium side) is provided in an electrically floating state. In addition, a coating film 64 that is electrically insulating is formed on the surface of the floating conductive plate 62 to prevent the physical properties and components of the ink from becoming unstable due to charge injection into the ink. The electric resistance of the insulating coating film is preferably 10 ¹² Ω · cm or more, and more preferably 10 ¹³ Ω · cm or more. In addition, the insulating coating film is desirably resistant to corrosion with respect to ink, and this prevents the floating conductive plate 62 from being corroded by ink. Further, the floating conductive plate 62 is covered with the insulating member 66 from below, and the floating conductive plate 62 is completely electrically insulated by such a configuration.

  There are one or more floating conductive plates 62 per head unit (for example, when there are four heads C, M, Y, and K, the number of floating conductive plates is at least one each, and C and M The floating conductive plate is not shared between the head units.

  As shown in FIG. 3, in order to cause ink to fly from the inkjet head 70 and record on the recording medium P, the ink in the ink flow path 72 is circulated to generate an ink flow Q, and the guard electrode A predetermined voltage (for example, +100 V) is applied to 50. Further, a flying electric field that attracts the positive charged particles R in the ink droplet G that has been guided by the ink guide portion 78 and flew from the opening 75 to the recording medium P is generated by the first ejection electrode 46 and the second ejection electrode. A positive voltage is applied to the first ejection electrode 46, the second ejection electrode 56, and the recording medium P so as to be formed between the recording medium P and the recording medium P (1 kV when the gap d is 500 μm). A potential difference of about ~ 3.0 kV is taken as a guide).

In this state, when a pulse voltage is applied to the first ejection electrode 46 and the second ejection electrode 56 in accordance with the image signal, the ink droplet G having an increased charged particle concentration is ejected from the opening 75 (for example, initial charged particles). When the concentration is 3 to 15%, the charged particle concentration of the ink droplet G is 30% or more).
At that time, the ink droplet G is applied to the first ejection electrode 46 and the second ejection electrode 56 so that the ink droplet G is ejected only when the pulse voltage is applied to both the first ejection electrode 46 and the second ejection electrode 56. Adjust the voltage value.

  In this way, when a pulsed positive voltage is applied, the ink droplet G is guided by the ink guide portion 78 from the opening 75 and flies to adhere to the recording medium P, and the first ejection is applied to the floating conductive plate 62. A positive induced voltage is generated by the positive voltage applied to the electrode 46 and the second ejection electrode 56. Even if the voltage applied to the first ejection electrode 46 and the second ejection electrode 56 is pulsed, this induced voltage is a substantially steady voltage. Therefore, the charged particles R that are positively charged in the ink flow path 72 are subjected to the upward movement force by the electric field formed between the floating conductive plate 62 and the guard electrode 50 and the recording medium P, and The concentration of charged particles R increases near the substrate 74. As shown in FIG. 3, when the number of ejection units (that is, channels for ejecting ink droplets) to be used is large, the number of charged particles necessary for ejection increases, but the first ejection electrode 46 and the second ejection electrode to be used are used. Since the number of 56 increases, the induced voltage induced in the floating conductive plate 62 increases, and the number of charged particles R moving to the recording medium side also increases.

  In the above, an example in which the colored particles are positively charged has been described. However, the colored particles may be negatively charged. In that case, all the above-mentioned charging polarities are reversed.

  In the present invention, it is preferable to fix the ink by an appropriate heating means after discharging the ink onto the recording medium. As the heating means used, a contact-type heating device such as a heat roller, a heat block, or a belt heating, and a non-contact type heating device such as a dryer, an infrared lamp, a visible light lamp, an ultraviolet lamp, or a hot air oven may be used. it can. These heating devices are preferably continuous with and integrated with the ink jet recording apparatus. The temperature of the recording medium at the time of fixing is preferably in the range of 40 ° C. to 200 ° C. for ease of fixing. The fixing time is preferably in the range of 1 microsecond to 20 seconds.

[Replenishment of ink composition]
In the ink jet recording method using an electrostatic field, charged particles in the ink composition are concentrated and discharged. Therefore, when ink is ejected for a long time, the amount of charged particles in the ink composition is reduced, and the electrical conductivity of the ink composition is lowered. Further, the ratio between the electric conductivity of the charged particles and the electric conductivity of the ink composition changes. Further, when discharging, charged particles having a larger diameter tend to be discharged preferentially than charged particles having a smaller diameter, so that the average diameter of the charged particles is reduced. Further, since the solid content in the ink composition changes, the viscosity also changes. Due to these changes in physical property values, as a result, ejection failure occurs, the optical density of recorded images decreases, and ink bleeding occurs. Therefore, by replenishing the ink composition having a higher concentration (higher solid content concentration) than the ink composition initially charged in the ink tank, the reduction of charged particles is prevented, and the electrical conductivity of the ink composition is reduced. The ratio between the electrical conductivity of the charged particles and the electrical conductivity of the ink composition can be kept within a certain range. Also, the average particle diameter and viscosity can be maintained. Further, by maintaining the physical property value of the ink composition within a certain range, the ink discharge is stably and uniformly performed for a long time. The replenishment at this time is preferably performed mechanically or manually, for example, by detecting a physical property value such as the electrical conductivity or optical density of the ink liquid used and calculating the shortage. Further, the amount of the ink composition to be used may be calculated based on the image data, and may be formed mechanically or manually.

[Recording medium]
In the present invention, various recording media can be used depending on the application. For example, if paper, plastic film, metal, and paper on which plastic or metal is laminated or vapor-deposited, a plastic film on which metal is laminated or vapor-deposited, etc., printed matter can be directly obtained by ink jet recording. The shape of the recording medium may be planar such as a sheet shape or three-dimensional such as a cylindrical shape.

[Fixing]
In the present invention, it is preferable to fix the ink by an appropriate heating means after the ink is discharged onto the recording medium. As the heating means to be used, a contact-type heating device such as a heat roller, a heat block, or a belt heating and a non-contact type heating device such as a dryer, an infrared lamp, a visible light lamp, an ultraviolet lamp, or a hot air oven may be used. it can. These heating devices are preferably integrated with an inkjet recording apparatus.

By using the ink composition of the present invention described above, it is possible to stably discharge ink droplets for a long time.
Further, by using the above-described ink jet recording apparatus, a high-quality image recorded matter having no ink bleeding and high image density can be obtained for a long time.

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

<Materials used>
In this example, the following materials were used.

Cyan pigment (coloring material) phthalocyanine pigment C.I. I. Pigment Blue (15: 3) (Toyo Ink Manufacturing Co., Ltd., LIONOL BLUE FG-7350)
・ Coating agent [AP-1]
Dispersant [BZ-26], [BZ-32], [BZ-37], [BZ-40], [BZ-50], [BZ-56], [BZ-57], [BZ-58] , [BZ-61], [BZ-64], [BZ-67], [BZ-68], [BZ-81], [BZ-87], [DZ-1], [DZ-2]
-Charge control agent [CT-1]
・ Dispersion medium Isopar G (manufactured by Exxon Corporation),

The structures of the coating agent [AP-1], the dispersant [DZ-1], [DZ-2], and the charge adjusting agent [CT-1] are shown below.
Dispersant [BZ-26], [BZ-32], [BZ-37], [BZ-40], [BZ-50], [BZ-56], [BZ-57], [BZ-58], The structures of [BZ-61], [BZ-64], [BZ-67], [BZ-68], [BZ-83], and [BZ-87] are as described above.

  In the formula, n and m mean a polymer and are 5 or more)

<Synthesis of AP-1 and CT-1>
The coating agent [AP-1] radically polymerizes styrene, 4-methylstyrene, butyl acrylate, dodecyl methacrylate and 2- (N, N-dimethylamino) ethyl methacrylate using a known polymerization initiator, Furthermore, it was obtained by reacting with methyl tosylate. The mass average molecular weight was 15,000, and the polydispersity (mass average molecular weight / number average molecular weight) was 2.7. The glass transition point (mid point) was 51 ° C., and the softening point by the strain gauge method was 46 ° C.
The charge control agent [CT-1] was obtained by reacting 1-octadecene and maleic anhydride copolymer with 1-hexadecylamine. The weight average molecular weight was 17,000.

<Synthesis of Dispersant [BZ-26]>
The graft polymer dispersant [BZ-26] having a crosslinked structure is a polymer of stearyl methacrylate having a methacryloyl group at its terminal by radically polymerizing stearyl methacrylate in the presence of 2-mercaptopropanol and further reacting with methacrylic anhydride. After obtaining [MM-1] (mass average molecular weight was 6,100), it was obtained by radical copolymerization with styrene and vinylbenzene. The mass average molecular weight was 145,000.

<Synthesis of Dispersant [BZ-32]>
The graft polymer dispersant [BZ-32] having a cross-linked structure is obtained by further adding a hexamethyl methacrylate-containing stearyl methacrylate polymer [MM-1] to a polymer obtained by radical copolymerization of styrene and 2-hydroxyethyl methacrylate. It was obtained by reacting methylene diisocyanate. The weight average molecular weight was 187,000.

<Synthesis of Dispersant [BZ-37]>
The graft polymer dispersant [BZ-37] having a crosslinked structure is a stearyl having a methacryloyl group at the terminal by radically polymerizing stearyl methacrylate and divinylbenzene in the presence of 2-mercaptopropanol and further reacting with methacrylic anhydride. A copolymer of methacrylate and divinylbenzene [MM-2] (mass average molecular weight was 14,000) was obtained and then obtained by radical copolymerization with styrene. The weight average molecular weight was 23,1000.

<Synthesis of dispersant [BZ-40]>
The graft polymer dispersant [BZ-40] having a crosslinked structure was obtained by radical copolymerization of a copolymer of methacryloyl-terminated stearyl methacrylate and divinylbenzene [MM-2] and methyl methacrylate. The weight average molecular weight was 190,000.

<Synthesis of dispersant [BZ-50]>
The graft polymer dispersant [BZ-50] having a crosslinked structure is obtained by radically polymerizing stearyl methacrylate and 1,4-butanediol dimethacrylate in the presence of 2-mercaptopropanol, After obtaining 4-butanediol dimethacrylate copolymer [MM-3] (mass average molecular weight was 18,300), it was obtained by radical copolymerization with styrene. The weight average molecular weight was 167,000.

<Synthesis of Dispersant [BZ-56]>
The graft polymer dispersant [BZ-56] having a crosslinked structure is obtained by radically polymerizing stearyl methacrylate and allyl methacrylate in the presence of 2-mercaptopropanol to obtain a copolymer of stearyl methacrylate and allyl methacrylate having a methacryloyl group at the terminal. The macromonomer [MM-4] into which the crosslinked structure was introduced was obtained by radical polymerization of the unreacted allyl group (the mass average molecular weight was 19,600), and this was further radically copolymerized with styrene. Obtained. The weight average molecular weight was 167,000.

<Synthesis of Dispersant [BZ-57]>
The graft polymer dispersant [BZ-57] having a crosslinked structure was obtained by radical copolymerization of styrene and divinylbenzene with a copolymer [MM-2] of stearyl methacrylate and divinylbenzene having a methacryloyl group at the terminal. The weight average molecular weight was 263,000.

<Synthesis of Dispersant [BZ-58]>
The graft polymer dispersant [BZ-58] having a crosslinked structure is obtained by radically polymerizing styrene and divinylbenzene in the presence of 2-mercaptopropanol, and further reacting with methacrylic anhydride to styrene having a methacryloyl group at the terminal. Divinylbenzene copolymer [MM-5] (mass average molecular weight was 17,000) was obtained, and then obtained by radical copolymerization with stearyl methacrylate. The mass average molecular weight was 132,000.

<Synthesis of dispersant [BZ-61]>
Homopolymer of stearyl methacrylate by polymerizing stearyl methacrylate under nitrogen atmosphere using methyl 2-bromopropionate, CuBr, and N, N, N ', N ", N" -pentamethylenediethylenetriamine as an initiator [HP-1] was obtained. Since the polymer [HP-1] has a bromo group at the end of the main chain, it can be polymerized in the presence of CuBr, N, N, N ′, N ″, N ″ -pentamethylenediethylenetriamine, and further, styrene, and By polymerizing with divinylbenzene, a block polymer [BZ-61] having a crosslinked structure was obtained. The weight average molecular weight was 67,000.

<Synthesis of Dispersant [BZ-64]>
By polymerizing styrene under a nitrogen atmosphere using methyl 2-bromopropionate, CuBr, and N, N, N ′, N ″, N ″ -pentamethylenediethylenetriamine as an initiator, a styrene homopolymer [HP -2]. Since the polymer [HP-2] has a bromo group at the end of the main chain, it can be polymerized in the presence of CuBr, N, N, N ′, N ″, N ″ -pentamethylenediethylenetriamine, and stearyl methacrylate, and Then, by polymerizing with divinylbenzene, a block polymer [BZ-64] having a crosslinked structure was obtained. The mass average molecular weight was 72,000.

<Synthesis of Dispersant [BZ-67]>
A homopolymer [HP-1] of stearyl methacrylate having a bromo group at the end of the main chain is polymerized with methyl methacrylate and divinylbenzene in the presence of CuBr, N, N, N ', N ", N" -pentamethylenediethylenetriamine. As a result, a block polymer [BZ-67] having a crosslinked structure was obtained. The mass average molecular weight was 56,000.

<Synthesis of Dispersant [BZ-68]>
Homopolymer of methyl methacrylate by polymerizing methyl methacrylate under nitrogen atmosphere using methyl 2-bromopropionate, CuBr, and N, N, N ', N ", N" -pentamethylenediethylenetriamine as an initiator [HP-3] was obtained. Since the polymer [HP-3] has a bromo group at the end of the main chain, it can be polymerized in the presence of CuBr, N, N, N ′, N ″, N ″ -pentamethylenediethylenetriamine, and stearyl methacrylate, and Then, by polymerizing with divinylbenzene, a block polymer [BZ-68] having a crosslinked structure was obtained. The weight average molecular weight was 87,000.

<Synthesis of Dispersant [BZ-81]>
Polymerizing styrene homopolymer [HP-2] having bromo group at the end of main chain with stearyl methacrylate and glycidyl methacrylate in the presence of CuBr, N, N, N ', N ", N" -pentamethylenediethylenetriamine Then, after obtaining the block polymer [BP-1], the block polymer [BZ-81] having a crosslinked structure was obtained by reacting with 1,6 hexanediol. The weight average molecular weight was 58,000.

<Synthesis of Dispersant [BZ-87]>
Stearyl methacrylate homopolymer [HP-1] having a bromo group at the end of the main chain
Block polymer [BP-2] was obtained by polymerizing with styrene in the presence of Br, N, N, N ', N ", N" -pentamethylenediethylenetriamine. Since the polymer [BP-2] has a bromo group at the end of the main chain, it can be polymerized in the presence of CuBr, N, N, N ′, N ″, N ″ -pentamethylenediethylenetriamine, and stearyl methacrylate, and Then, by polymerizing with divinylbenzene, a block polymer [BZ-87] having a crosslinked structure was obtained. The mass average molecular weight was 96,000.

<Synthesis of dispersant [DZ-1]>
The graft polymer dispersant [DZ-1] was obtained by radical copolymerization of styrene with a stearyl methacrylate polymer [MM-1] having a methacryloyl group at the terminal. The mass average molecular weight was 61,000.

<Synthesis of Dispersant [DZ-2]>
The block polymer [HP-2] is polymerized with stearyl methacrylate in the presence of CuBr, N, N, N ', N ", N" -pentamethylenediethylenetriamine in the presence of bromo group at the end of the main chain. DZ-2] was obtained. The mass average molecular weight was 56,000.

[Example 1]
10 g of the cyan pigment and 20 g of the coating agent [AP-1] were put into a desktop kneader PBV-0.1 manufactured by Irie Shokai Co., Ltd., the heater temperature was set to 100 ° C., and the mixture was heated and mixed for 2 hours. 30 g of the obtained mixture was coarsely pulverized with a trio-brender manufactured by Trio Science Co., Ltd., and further finely pulverized with a SK-M10 type sample mill manufactured by Kyoritsu Riko Co., Ltd. 30 g of the obtained finely pulverized product was predispersed in a paint shaker manufactured by Toyo Seiki Seisakusho together with 7.5 g of the dispersant [BZ-26], 75 g of Isopar G, and glass beads having a diameter of about 3.0 mm. After removing the glass beads, together with the zirconia ceramic beads having a diameter of about 0.6 mm, the type KDL dynomill manufactured by Shinmaru Enterprises Co., Ltd. was used for 5 hours while maintaining the internal temperature at 25 ° C., followed by 45 ° C. for 5 hours. Dispersion (particle formation) was performed at a rotational speed of 000 rpm. Zirconia ceramic beads were removed from the obtained dispersion, and 316 g of Isopar G and 0.6 g of charge control agent [CT-1] were added to obtain an ink composition [EC-1]. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by HORIBA, Ltd. at a rotation speed of 5000 rpm, and found to be 0.87 μm. The number average particle size was 0.19 μm. When an ink jet recording experiment was performed using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. Further, when the redispersibility test of the obtained ink was performed, a good result was obtained that the redispersion time was 3 minutes 56 seconds. The results are shown in Table 1.

<Inkjet recording experiment method>
The ink composition to be evaluated was filled into the ink tank connected to the head in the ink jet recording apparatus shown in FIGS. Here, a 150 dpi (three-row staggered arrangement with a channel density of 50 dpi), 833 channel head of the type shown in FIG. 2 was used as the ejection head, and a silicon rubber heat roller incorporating a 1 kW heater was used as the fixing means. As the ink temperature control means, a throw-in heater and a stirring blade were provided in the ink tank, the ink temperature was set to 30 ° C., and the temperature was controlled with a thermostat while rotating the stirring blade at 30 rpm. Here, the stirring blade was also used as a stirring means for preventing precipitation and aggregation. In addition, the ink flow path is partially transparent, and the LED light emitting element and the light detecting element are arranged between them, and the ink dilution liquid (Isopar G) or concentrated ink (the solid content concentration of the ink composition is determined by the output signal). The concentration was controlled by charging. A fine coated paper for offset printing was used as a recording medium. After removing dust on the surface of the recording medium by air pump suction, the ejection head is brought close to the recording medium to the image forming position, image data to be recorded is transmitted to the image data calculation control unit, and the recording belt is rotated by rotation of the conveying belt. The ink composition was discharged while sequentially moving the discharge head while transporting the recording medium, and an image was formed with a drawing resolution of 2400 dpi. As the conveyor belt, a metal belt and polyimide film bonded together are used, and a line-shaped marker is placed in the vicinity of one end of the belt along the conveyor direction, and this is optically read by the conveyor belt position detection means. An image was formed by driving the control means. At this time, the distance between the ejection head and the recording medium was kept at 0.5 mm by the output from the optical gap detector. Further, the surface potential of the recording medium was set to −1.5 kV at the time of ejection, and a pulse voltage of +500 V was applied (pulse width 50 μsec) at the time of ejection, and image formation was performed at a driving frequency of 15 kHz. Immediately after image recording, the image was fixed using a heat roller. The temperature of the coated paper at the time of fixing was 90 ° C., and the contact time with the heat roller was 0.3 seconds. In addition, for 10 minutes after the recording was completed, the head was stored in a cover filled with vapor of Isopar G after supplying the head with Isopar G instead of ink for cleaning.

<Redispersibility test method>
Put 1.0 g of the ink composition to be evaluated into a centrifugal sedimentation tube, and use a small high-speed cooling centrifuge (SRX-201 manufactured by Tommy Seiko Co., Ltd.). Allowed to settle. Add 5g of Isopar G to the centrifugal sedimentation tube where the particles have been settled, cover tightly and let it settle on a mix rotor (VMR-5 manufactured by ASONE Co., Ltd.) at room temperature and 80 rpm. The time for complete redispersion was recorded.

[Example 2]
An ink composition [EC-2] was obtained in the same manner as [EC-1] except that [BZ-32] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by HORIBA, Ltd. at a rotation speed of 5000 rpm, and found to be 0.87 μm. The number average particle size was 0.21 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. Further, when the redispersibility test of the obtained ink was performed, a good result was obtained that the redispersion time was 3 minutes 56 seconds. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. The results are shown in Table 1.

Example 3
An ink composition [EC-3] was obtained in the same manner as [EC-1] except that [BZ-37] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by HORIBA, Ltd. at a rotation speed of 5000 rpm, and found to be 0.97 μm. The number average particle size was 0.17 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. Further, when the redispersibility test of the obtained ink was performed, a good result with a redispersion time of 3 minutes and 12 seconds was obtained. The results are shown in Table 1.

Example 4
An ink composition [EC-4] was obtained in the same manner as [EC-1] except that [BZ-40] was used as a dispersant. When the volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by Horiba, Ltd. at a rotation speed of 5000 rpm, it was 1.12 μm. The number average particle size was 0.23 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. Further, when the redispersibility test of the obtained ink was performed, a good result was obtained that the redispersion time was 4 minutes 02 seconds. The results are shown in Table 1.

Example 5
An ink composition [EC-5] was obtained in the same manner as [EC-1] except that [BZ-50] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by HORIBA, Ltd. at a rotation speed of 5000 rpm, and found to be 0.91 μm. The number average particle size was 0.15 μm. When an ink jet recording experiment was performed using the obtained ink, a very clear image without bleeding or density reduction was continuously obtained without the need for maintenance work for one month. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. Further, when the redispersibility test of the obtained ink was performed, a good result with a redispersion time of 3 minutes and 42 seconds was obtained. The results are shown in Table 1.

Example 6
An ink composition [EC-6] was obtained in the same manner as [EC-1] except that [BZ-56] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by HORIBA, Ltd. at a rotation speed of 5000 rpm, and found to be 0.96 μm. The number average particle size was 0.21 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. Further, when the redispersibility test of the obtained ink was performed, a good result was obtained that the redispersion time was 5 minutes and 32 seconds. The results are shown in Table 1.

Example 7
An ink composition [EC-7] was obtained in the same manner as [EC-1] except that [BZ-57] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by HORIBA, Ltd. at a rotation speed of 5000 rpm, and found to be 0.85 μm. The number average particle size was 0.18 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. Further, when the redispersibility test of the obtained ink was performed, a good result was obtained that the redispersion time was 4 minutes 54 seconds. The results are shown in Table 1.

Example 8
An ink composition [EC-8] was obtained in the same manner as [EC-1] except that [BZ-58] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by Horiba, Ltd. at a rotation speed of 5000 rpm, and found to be 1.07 μm. The number average particle size was 0.19 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. Further, when the redispersibility test of the obtained ink was performed, a good result was obtained that the redispersion time was 5 minutes 43 seconds. The results are shown in Table 1.

Example 9
An ink composition [EC-9] was obtained in the same manner as [EC-1] except that [BZ-61] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by HORIBA, Ltd. at a rotation speed of 5000 rpm, and found to be 0.96 μm. The number average particle size was 0.21 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. Further, when the redispersibility test of the obtained ink was performed, a good result was obtained that the redispersion time was 3 minutes and 32 seconds. The results are shown in Table 1.

Example 10
An ink composition [EC-10] was obtained in the same manner as [EC-1] except that [BZ-64] was used as a dispersant. When the volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by Horiba, Ltd. at a rotation speed of 5000 rpm, it was 0.76 μm. The number average particle size was 0.12 μm. When an ink jet recording experiment was performed using the obtained ink, a very clear image without bleeding or density reduction was continuously obtained without the need for maintenance work for one month. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. Further, when the redispersibility test of the obtained ink was performed, a good result was obtained that the redispersion time was 3 minutes 56 seconds. The results are shown in Table 1.

Example 11
An ink composition [EC-11] was obtained in the same manner as [EC-1] except that [BZ-67] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by Horiba, Ltd. at a rotation speed of 5000 rpm, and found to be 0.90 μm. The number average particle size was 0.18 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. Further, when the redispersibility test of the obtained ink was performed, a good result was obtained that the redispersion time was 2 minutes 56 seconds. The results are shown in Table 1.

Example 12
An ink composition [EC-12] was obtained in the same manner as [EC-1] except that [BZ-68] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by HORIBA, Ltd. at a rotation speed of 5000 rpm, and found to be 1.03 μm. The number average particle size was 0.21 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. Further, when the redispersibility test of the obtained ink was performed, a good result with a redispersion time of 4 minutes 22 seconds was obtained. The results are shown in Table 1.

Example 13
An ink composition [EC-13] was obtained in the same manner as [EC-1] except that [BZ-83] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by Horiba, Ltd. at a rotation speed of 5000 rpm, and found to be 0.98 μm. The number average particle size was 0.15 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. When the head was disassembled and confirmed, no ink particles adhered to the ejection port. Further, when the redispersibility test of the obtained ink was performed, a good result was obtained that the redispersion time was 5 minutes 02 seconds. The results are shown in Table 1.

Example 14
An ink composition [EC-15] was obtained in the same manner as [EC-1] except that [BZ-87] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by HORIBA, Ltd. at a rotation speed of 5000 rpm, and found to be 0.96 μm. The number average particle size was 0.17 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. Further, when the redispersibility test of the obtained ink was performed, a good result with a redispersion time of 4 minutes 13 seconds was obtained. The results are shown in Table 1.

[Comparative Example 1]
An ink composition [HC-1] was obtained in the same manner as [EC-1] except that [DZ-1] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by Horiba, Ltd. at a rotation speed of 5000 rpm, and found to be 0.95 μm. The number average particle size was 0.18 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. However, there was a decrease in density in the image when used for 2 months without maintenance work. When the head was disassembled and confirmed, adhesion of ink particles to the ejection port was confirmed. Further, a redispersibility test of the obtained ink was performed, and the redispersion time was 10 minutes 52 seconds, which was not so good. The results are shown in Table 1.

[Comparative Example 2]
An ink composition [HC-2] was obtained in the same manner as [EC-1] except that [DZ-2] was used as a dispersant. The volume average particle diameter of the charged particles was measured with a CAPA-700 manufactured by Horiba, Ltd. at a rotation speed of 5000 rpm, and found to be 0.82 μm. The number average particle size was 0.13 μm. When an ink jet recording experiment was conducted using the obtained ink, a very clear image without ink bleeding and density reduction was continuously obtained without the need for maintenance work for one month. Further, a redispersibility test of the obtained ink was performed, and the redispersion time was 11 minutes and 42 seconds, which was not so good. The results are shown in Table 1.

  Table 1 below summarizes the results of the redispersibility test.

Ink prepared using a dispersant having no cross-linked structure showed a decrease in image density in a two-month inkjet recording test without maintenance work, but using a dispersant containing a polymer having a cross-linked structure. It was not seen in the ink that was made. This is considered to be because the adhesion of ink particles to the head portion was suppressed.
In addition, the redispersion time of an ink prepared using a dispersant containing a polymer having a crosslinked structure was significantly shorter than the redispersion time of an ink prepared using a dispersant having no crosslinked structure. By introducing a cross-linked structure into the dispersant, it was possible to stably discharge for a long period of time, and it was possible to provide an ink composition with good redispersibility of ink particles that settled when the ink was stored for a long period of time.

It is a whole lineblock diagram showing typically an example of an ink jet printer used for the present invention. It is a perspective view which shows the structure of the inkjet head of the inkjet recording device of this invention (In order to make it intelligible, the edge of the guard electrode in each discharge part is not drawn). FIG. 3 is a side sectional view showing a distribution state of charged particles when the number of ejection units of the inkjet head shown in FIG. 2 is large (corresponding to an arrow XX in FIG. 2).

Explanation of symbols

G Injected ink droplet P Recording medium Q Ink flow R Charged particle 1 Inkjet recording apparatus 2 Discharge head 3 Ink circulation system 4 Head driver 5 Position control means 6A to 6C Conveying belt stretching roller 7 Conveying belt 8 Conveying belt position detecting means DESCRIPTION OF SYMBOLS 9 Electrostatic adsorption means 10 Static elimination means 11 Mechanical means 12 Feed roller 13 Guide 14 Image fixing means 15 Guide 16 Recording medium position detection means 17 Exhaust fan 18 Solvent vapor adsorption material 38 Ink guide 40 Support bar part 42 Ink meniscus 44 Insulation Layer 46 First ejection electrode 48 Insulating layer 50 Guard electrode 52 Insulating layer 56 Second ejection electrode 58 Insulating layer 62 Floating conductive plate 64 Coating film 66 Insulating member 70 Ink jet head 72 Ink flow path 74 Substrate 75, 75A, 75B Opening 76 , 76A, 76B Discharge part 78 Discharge part

Claims (5)

  An ink composition for ink jet recording containing a dispersion medium and charged particles containing at least a coloring material, wherein the charged particles are dispersed in the dispersion medium by a dispersant containing a polymer having a crosslinked structure. An ink composition for inkjet recording.   2. The ink composition for ink jet recording according to claim 1, wherein the polymer having a crosslinked structure is a graft polymer into which a crosslinked structure is introduced.   2. The ink composition for ink jet recording according to claim 1, wherein the polymer having a crosslinked structure is a block polymer into which a crosslinked structure is introduced.   The ink for inkjet recording according to any one of claims 1 to 3, wherein the polymer having a crosslinked structure has a repeating unit having a crosslinked structure in a range of 0.00001 to 30% by mass in the polymer. Composition.   An ink-jet recording method, comprising: using the ink composition according to claim 1 to eject ink droplets by an ink-jet recording method utilizing an electrostatic field.

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