JP2006182885A - Method for producing particle of color material, ink composition for ink jet recording and method for ink jet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing particles of color material and ink composition realizing ink composition excellent in dispersing property and storage stability and the particles are not susceptible to adhere on ink jet nozzle of a ink jet recording system in using as an ink composition for ink jet recording. <P>SOLUTION: The invention relates to the method for producing particles containing the color material and the polymer comprising a process dispersing a mixture containing the color material and polymer in a medium at ≥60°C in a wet system. The invention relates to the ink composition containing the particles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing colorant particles, 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 method (see Patent Documents 1 and 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 the electrostatic field controls the flying direction of the ink droplets by the electrostatic field, so that the ink droplets can be accurately landed on a desired position, and a high-quality image formation (printed material) is produced. It is excellent.

  As an ink composition used for ink jet 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 produce four color inks of yellow, magenta, cyan, and black, and can also produce gold or silver spot color inks. . Therefore, it is useful because a color image formed product (printed product) can be produced. However, until now, it has been difficult to stably eject ink droplets in long-time inkjet recording.

  In general, an ink composition used for inkjet recording is obtained by kneading a coloring material and a polymer with heat, and then pulverizing them in a dry manner to obtain particles, adding a dispersion medium and a dispersant to make the particles fine, and It is manufactured by dispersing and further adding a charge control agent to impart charge to the particles. However, the conventional ink composition produced in this way has a problem in that particles adhere to the nozzles (discharge ports) of the ink jet head of the ink jet recording apparatus and clogging is likely to occur. In addition, when stored for a long period of time, the particles settle, do not re-disperse even when stirred, and have a problem that storage stability is poor.

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 provide a method for producing color material particles and an ink composition that can solve the above-mentioned problems. Specifically, the color material particles are used as an ink composition for inkjet recording. To provide colorant particles, a method for producing the same, and an ink composition that are less likely to adhere to the nozzles of an inkjet head of an inkjet recording apparatus and have excellent dispersibility and storage stability when used as a component of It is.

As a result of intensive studies to achieve the above object, the present inventor has found that the above problems can be solved by the following configuration.
(1) A method for producing particles containing a colorant and a polymer, comprising a step of wet-dispersing a mixture containing the colorant and a polymer in a dispersion medium at a temperature of 60 ° C. or higher.
(2) An ink composition for inkjet recording, comprising particles containing a colorant and a polymer produced by the production method according to (1) above.
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 (2).

  According to the production method of the present invention, it is possible to obtain colorant particles that are well coated with a polymer, and it is possible to always stably eject ink droplets in long-term ink jet recording, and there is no ejection failure, which is good. An ink composition for ink jet recording having excellent dispersibility and capable of forming a high quality image can be provided. The particles produced according to the present invention are particularly useful as a component of an ink composition for ink jet recording, but are not limited thereto. For example, in liquid developer for electrophotography, display elements for electronic paper and digital paper, etc. Is also useful.

Hereinafter, the present invention will be described in further detail.
The method for producing particles containing a colorant and a polymer according to the present invention comprises a step of dispersing a mixture containing the colorant and the polymer in a dispersion medium at a temperature of 60 ° C. or more, and the color coated with the polymer. It is characterized by producing material particles (hereinafter also simply referred to as color material particles).
By this step, color material particles coated with a polymer can be obtained, and the ink composition containing such color material particles has excellent ejection stability, good dispersibility, and good drawn images. Can be provided.

  A mixture containing a colorant and a polymer (hereinafter also referred to as a colored mixture) can be prepared, for example, by the following method.

(1) A method in which a coloring material, a polymer, and the like are melt-kneaded using a kneader such as a roll mill, a Banbury mixer, or a kneader at a temperature equal to or higher than the softening point of the polymer, and pulverized after cooling to obtain a colored mixture.
(2) Dissolve the polymer, etc. in the solvent, add ingredients such as coloring materials, and wet disperse with a ball mill, attritor, sand grinder, etc., evaporate the solvent to obtain a colored admixture, or disperse the dispersion A method of pouring into a non-solvent of the polymer and precipitating to obtain a blend, followed by drying to obtain a colored blend.
(3) A water-containing paste (wet cake) such as a coloring material is kneaded with a polymer or a polymer solvent by a flushing method, water is replaced with a polymer or a polymer solution, and then the water and the solvent are dried under reduced pressure. How to get.
Here, the polymer has a function of coating the color material and is generally called a coating agent. The polymer as the coloring material and coating agent will be described later.

  In the production method of the present invention, the colored admixture is pulverized as necessary, and preferably made into a powder having an average volume diameter of 5 μm to 1 mm, and at any stage at a temperature of 60 ° C. or higher. A wet dispersion step is performed.

  As the dispersion medium, those described below can be used, and at least one component constituting the ink composition may be added to the dispersion medium.

  There is no restriction | limiting in particular as a disperser, A commercially available wet disperser can be used. For example, a ball mill, a sand mill, an attritor, etc., and a sealed type is generally used to prevent evaporation of the solvent. Sand mills have a vertical type and a horizontal type, and are dispersed by rotating a shaft on which a disk or a pin is attached at a peripheral speed of 3 to 15 m / s. By arranging several continuous sand mills in series and changing the diameter of the media according to the degree of dispersion, the ink composition can be efficiently produced. Further, when a colorant having a large particle size is dispersed by a continuous sand mill, pre-dispersion is required. In this case, a disperser, a ball mill, a batch sand mill, or the like is used as a pre-dispersing machine.

  Specific examples of horizontal sand mills include Dino Mill, Dino Mill ECM (WAB, Switzerland), Pearl Mill, DCP (Dreis, Germany), Agitator Mill (Necche, Germany), Super Mill (Susmeier, Belgium), Cobol Mill (Switzerland, Freema), spike mill (Inoue Seisakusho), and the like.

In the wet dispersion process, those used as dispersion media such as beads can be used.
For example, various materials such as zirconia, titania, alumina, glass, steel, silicon nitride, which are known as media for ball mills and sand mills, can be used. In accordance with the viscosity of the dispersion, the degree of pre-dispersion, and the like, the material of the media is selected from the viewpoint of the specific gravity of the media, wear resistance, and the like.

  The media diameter is not particularly limited, but is preferably about 0.1 mm to 10 mm in diameter. In general, the larger the media, the wider the particle size distribution, and the smaller the media, the smaller the particle size tends to be dispersed. Further, the filling rate of the media is not particularly limited, but is preferably 50% to 90%. There is a close relationship between the filling rate of media and the dispersion performance, and it is generally known that the dispersion efficiency can be improved if the filling rate can be increased. In the case of a horizontal mill, it is preferable to set the filling rate to 80 to 85% with respect to the vessel capacity because there is no media locking phenomenon at the start-up as compared with the vertical mill.

  The temperature in the step of dispersing at a temperature of 60 ° C. or higher is preferably 60 to 150 ° C., more preferably 60 to 100 ° C. The dispersion time in this step may be appropriately determined depending on the types of raw materials and dispersers, but is preferably 15 minutes to 10 hours, and more preferably 15 minutes to 2 hours. Moreover, it is preferable to set it as the final average volume diameter of a color material particle by this process.

  The method for controlling the liquid temperature of the dispersion is not particularly limited.For example, a jacket is provided around the disperser and cooled with a refrigerant such as cold water, or a heat exchanger is provided on the discharge side of the disperser, and the temperature of the dispersion is controlled. The liquid temperature of the dispersion liquid can be controlled by monitoring and controlling the temperature of the refrigerant according to the change of the dispersion liquid temperature.

In the present invention, the dispersion may be continued at a temperature of 60 ° C. or higher, or a step of dispersing at a temperature lower than 60 ° C. may be included. Preferable is a step of dispersing at a temperature of 60 ° C. or higher after dispersing at a temperature of less than 60 ° C. As a method for increasing the dispersion temperature, the dispersion temperature may be increased at once, or may be increased several times.
Dispersion at a temperature of less than 60 ° C., preferably at −20 to 40 ° C. for 15 minutes to 3 hours, to make the average volume diameter of the colorant particles 0.005 to 1.0 μm, and then disperse at a temperature of 60 ° C. or more The average volume diameter of the colorant particles is preferably 0.2 to 5 μm by the step of performing.

The average volume diameter of the colorant particles finally formed is preferably 0.2 to 5.0 μm, and more preferably 0.5 to 3.0 μm.
The above-described components can be added to the dispersion containing the colorant particles produced by the above method as necessary to obtain an ink composition.

  Hereinafter, each component will be described in detail.

[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 favorably 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, “Technology Information Association,“ Pigment Dispersion Stabilization and Surface Treatment Technology / Evaluation ”, December 25, 2001). Day, first print). By changing the color material, four color inks of yellow, magenta, cyan, and black can be produced. 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. Further, the pigment may be used after being surface-treated by a known method such as rosin treatment (published by Technical Information Association, “Pigment Dispersion Stabilization and Surface Treatment Technology / Evaluation”, December 25, 2001, first printing. reference.).
The content of the coloring material with respect 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 the coloring material is sufficiently secured, 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 well dispersed in the dispersion medium. More preferably, it is 1-30 mass%.

[Coating agent]
In the present invention, by preparing a mixture (color mixture) containing a colorant and a polymer, the colorant is in a form at least partially covered with the polymer, and this is dispersed (particulated) in a dispersion medium. The polymer is also called a coating agent.
By covering the color material with a coating material, it is possible to shield the charge of the color material and to have desirable charge characteristics. Moreover, the difference in dispersion stability that varies depending on the type of color material is canceled, and similar dispersion stability is imparted. Furthermore, in the present invention, it is preferable to perform inkjet recording on a recording medium and then fix the image by a heating means such as a heat roller. At this time, the coating material is melted by heat, which contributes to efficient fixing.

  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 easy particle formation, the weight average molecular weight is in the range of 2,000 to 1,000,000, and the polydispersity (weight average molecular weight / number average molecular weight) is 1.0 to 5 Polymers in the range of 0.0 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 represent 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 sufficiently secured, and better fixability can be obtained, and when the amount is 40% by mass or less, particles containing the colorant and the coating agent can be formed better. it can.

[Dispersant]
In the present invention, a mixture containing a coloring material and a polymer is dispersed (particulated) in a dispersion medium, and it is preferable to use a dispersant in order to control the particle diameter and suppress particle sedimentation.
Suitable dispersants include surfactants typified by sorbitan fatty acid esters such as sorbitan monooleate and polyethylene glycol fatty acid esters such as polyoxyethylene distearate. Further, for example, a copolymer of styrene and maleic acid, and an amine-modified product thereof, a copolymer of styrene and (meth) acrylic compound, a (meth) acrylic polymer, a copolymer of polyethylene and (meth) acrylic compound, rosin, BYK-160, 162, 164, 182 (polyurethane polymer manufactured by Big Chemie), EFKA-401, 402 (acrylic polymer manufactured by EFKA), Solsperse 17000, 24000 (polyester polymer manufactured by Geneca), and the like. In the present invention, from the viewpoint of long-term storage stability of the ink composition, the weight average molecular weight is in the range of 1,000 to 1,000,000 and the polydispersity (weight average molecular weight / number average molecular weight) is Polymers that are in the range of 1.0 to 7.0 are preferred. Furthermore, it is most preferable to use a graft polymer or a block polymer.

  The polymer used particularly preferably in the present invention comprises a polymer component composed of at least one of structural units represented by the following general formulas (5) and (6), and a structural unit represented by the following general formula (7). A graft polymer containing at least a polymer component contained as a graft chain.

In the formula, X ₅₁ represents an oxygen atom or —N (R ₅₃ ) —. R ₅₁ represents a hydrogen atom or a methyl group, R ₅₂ represents a hydrocarbon group having 1 to 10 carbon atoms, and R ₅₃ represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. R ₆₁ represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a halogen atom, a hydroxyl group, or an alkoxy group having 1 to 20 carbon atoms. X ₇₁ represents an oxygen atom or —N (R ₇₃ ) —. R ₇₁ represents a hydrogen atom or a methyl group, R ₇₂ represents a hydrocarbon group having 4 to 30 carbon atoms, and R ₇₃ represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. The hydrocarbon group of R ₅₂ and R ₇₂ may contain an ether bond, an amino group, a hydroxy group, or a halogen substituent.

  The graft polymer is obtained by polymerizing a radical polymerizable monomer corresponding to the general formula (7), preferably in the presence of a chain transfer agent, introducing a polymerizable functional group at the terminal of the obtained polymer, It can be obtained by copolymerizing with a radically polymerizable monomer corresponding to 5) or (6).

  Examples of the radical polymerizable monomer corresponding to the general formula (5) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylic acid. Hexyl (meth) acrylate cyclohexyl, phenyl (meth) acrylate, benzyl (meth) acrylate, (meth) acrylic acid esters of 2-hydroxyethyl (meth) acrylate, and N-methyl (meth) acrylamide And (meth) acrylamides such as N-propyl (meth) acrylamide, N-phenyl (meth) acrylamide, and N, N-dimethyl (meth) acrylamide.

Examples of the radical polymerizable monomer corresponding to the general formula (6) include styrene, 4-methylstyrene, chlorostyrene, methoxystyrene, and the like.
Examples of the radical polymerizable monomer corresponding to the general formula (6) include hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, ( (Meth) stearyl acrylate, and the like.
Specific examples of these graft polymers include polymers represented by the following structural formulas.

  Contains a polymer component containing at least one of the structural units represented by general formulas (5) and (6) and a polymerization component containing at least the structural unit represented by general formula (7) as a graft chain. The graft polymer to be processed may have only the structural unit represented by the general formula (5) and / or (6) and the general formula (7), or may contain other components. A preferred composition ratio between the polymer component containing the graft chain and the other polymer components is 10:90 to 90:10. Within this range, better particle formability is obtained, and a desired particle diameter is easily obtained, which is preferable. These polymers may be used alone as a dispersant, or may be used in combination of two or more.

  The content of the dispersant with respect to the entire ink composition is preferably in the range of 0.01 to 30% by mass. Within this range, better particle formability can be obtained, and a desired particle diameter can be obtained.

[Charge control agent]
In the present invention, a mixture containing a coloring material and a polymer is dispersed (particulated) in a dispersion medium. It is preferable to add a charge adjusting agent in order to control the charge amount of the particles.
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, a sufficient charge amount of particles necessary for ejection is ensured, and the charge amount is moderate.

[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.

[Physical properties of ink composition]
By the above ink composition production method, an ink composition that satisfies the following conditions (A) to (D) and can stably eject ink droplets in long-time inkjet recording can be obtained.
(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 (coloring material particles) is 50% or more of the electric conductivity of the ink composition.
(C) The average volume 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.

The electrical conductivity of the ink composition at 20 ° C. is preferably in the range of 10 nS / m to 300 nS / m. When the electrical conductivity of the ink composition is 10 nS / m or more, ink droplet ejection is good. When the ink composition is 300 nS / m or less, conduction occurs in the head (ejection unit) of the inkjet apparatus, resulting in damage to the head. Absent. More preferably, it is 30 nS / m-200 nS / m.
The electric conductivity of the particles is a value obtained by centrifuging the ink composition, measuring the electric conductivity of the supernatant liquid in which the particles are precipitated, and subtracting the electric conductivity of the ink composition.
In the present invention, the electrical conductivity of the particles is preferably 50% or more of the electrical conductivity of the ink composition. In the ink jet recording method using an electrostatic field, when ink droplets are ejected, the concentration of charged particles occurs. However, in the case of 50% or more, this concentration does not occur, and as a result, when recorded on a recording medium. There is no ink bleeding. More preferably, it is 60% or more.
The charge amount of the particles is preferably in the range of 5 to 200 μC / g. When the charge amount is 5 μC / g or more, the concentration is sufficient, and when it is 200 μC / g or less, the ink is not excessively concentrated and clogging of the ink at the head discharge port can be prevented. More preferably, it is in the range of 10 to 150 μC / g, still more preferably 15 to 100 μC / g.

  The average volume diameter of the particles can be measured, for example, by centrifugal sedimentation using an apparatus such as an ultracentrifugal automatic particle size distribution analyzer CAPA-700 (manufactured by Horiba, Ltd.). The average volume diameter of the charged particles is preferably in the range of 0.2 to 5.0 μm. In the case of 0.2 μm or more, the concentration of the particles is sufficient, and as a result, it is possible to more reliably prevent ink bleeding when recorded on a non-recording medium. Further, when the thickness is 5.0 μm or less, the problem of clogging of the head discharge port is less likely to occur. More preferably, it is 0.5-3.0 micrometers. The particle size distribution is preferably narrow and uniform.

In the present invention, the viscosity of the ink composition is preferably in the range of 0.5 to 5 mPa · s. When the viscosity is 0.5 mPa · s or more, there is no problem that the ink composition leaks from the ink discharge port of the head, and when the viscosity is 5 mPa · s or less, ink droplets are ejected well. It is. More preferably, it is in the range of 0.8 to 4 mPa · s.
The surface tension of the ink composition is preferably in the range of 10 to 70 mN / m. When the surface tension is 10 mN / m or more, there is no problem that the ink composition spills from the ink discharge port of the head, and when the surface tension is 70 mN / m or less, ink droplets are discharged well. . More preferably, it is the range of 15-50 mN / m.

[Inkjet recording apparatus]
The ink composition described above can be 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, ink is circulated in an ink chamber having an ejection opening, and is present in the ejection opening by applying a voltage to a control electrode formed at the periphery of the ejection opening, and an ink guide whose front end faces 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 four-color printing on one side of the 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 adsorption unit 9 for holding the recording medium P on the conveyance belt, a static elimination unit 10 and a mechanical unit 11 for separating the recording medium P from the conveyance belt 7 after completion of image formation are provided. Upstream and downstream of the conveyance belt 7, the recording medium P is fed from a stocker (not shown) to the conveyance belt 7, the ink is fixed to the feed roller 12 and the guide 13, and the peeled recording medium P and conveyed to a paper discharge stocker (not shown). A fixing means 14 and a guide 15 are arranged. The ink jet printing apparatus 1 has a recording medium position detecting means 16 at a position facing the ejection head 2 with the conveying belt 7 interposed therebetween, and further collects 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.

As the feed roller 12, a known roller can be used, 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 to the recording medium P, it is desirable to remove them. The recording medium P supplied by the feed roller is conveyed to the conveying 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 transported recording medium 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 electrostatic adsorbing means 9 electrostatically adsorbs the recording medium 9 on the conveying belt 7 without floating, and uniformly charges the surface of the recording medium. 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 image-formed recording medium P is neutralized by the neutralizing unit 10, peeled off by the conveying belt 7 by the mechanical unit 11, and conveyed 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 concentration near the opening and discharge, and mainly a recording medium or a recording medium rear surface. Ink droplets are ejected by electrostatic attraction caused by the counter electrode disposed on the surface. Therefore, if the recording medium or the counter electrode is not facing the head, or if no voltage is applied to the recording medium or the counter electrode even at a position facing the head, the voltage is improperly applied to the ejection electrode. Ink droplets are not ejected even when applied or when 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 is directed toward the recording medium P. And a plurality of discharge portions 76 for discharging. 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 75 through which the ink guide portion 78 is inserted. 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 first.
The positively charged ink particles (charged particles) R in the ink flow path 72 are directed upward by an induced voltage that is constantly generated by the pulsed discharge voltage applied to the discharge electrode 46 and the second discharge electrode 56 ( That is, a floating conductive plate 62 to be migrated (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 electrical 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 fly ink from the inkjet head 70 and record on the recording medium P, the ink flow Q is generated by circulating the ink in the ink flow path 72, and the guard electrode 50. A predetermined voltage (for example, +100 V) is applied to. 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 56. 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 (when the gap d is 500 μm, 1 kV to 3. (The standard is to form a potential difference of about 0 kV).

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.

  As described above, when a pulsed positive voltage is applied, the ink droplet G is guided by the ink guide 78 from the opening 75 and flies to adhere to the recording medium P, and the floating conductive plate 62 has the first ejection electrode. A positive induced voltage is generated by the positive voltage applied to 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 substrate In the vicinity of 74, the concentration of charged particles R increases. 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 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. For this reason, by reducing the amount of charged particles by replenishing the ink composition having a higher concentration (higher solid content concentration) than the ink composition initially charged in the ink tank, the electrical conductivity of the ink composition 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 can be obtained over a long period of time.

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

[Example 1]
<Materials used>
In Example 1, 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-2]
-Charge control agent [CT-1]
・ Dispersion medium Isopar G (manufactured by Exxon Corporation)

  The structures of the coating agent [AP-1], the dispersant [BZ-2], and the charge control agent [CT-1] are shown below.

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.

Dispersant [BZ-2] is a polymer of stearyl methacrylate having a methacryloyl group at its terminal (mass average molecular weight) by radical polymerization of stearyl methacrylate in the presence of 2-mercaptoethanol and further reacting with methacrylic anhydride. Was obtained by radical polymerization with styrene. The mass average molecular weight was 110,000.
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.

<Preparation of Ink Composition [DC-1]>
Cyan pigment 10g as coloring material and 20g of polymer (coating agent) [AP-1] are put into a table type kneader PBV-0.1 manufactured by Irie Shokai Co., Ltd. did. 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 finely pulverized product obtained was predispersed in a paint shaker manufactured by Toyo Seiki Seisakusho together with 7.5 g of the dispersant [BZ-2], Isopar G112.5 g, and glass beads having a diameter of about 3.0 mm. . After removing the glass beads, dispersed with zirconia ceramic beads with a diameter of about 0.6 mm using a Type KDL dynomill manufactured by Shinmaru Enterprises Co., Ltd. for 2 hours at a rotational speed of 2000 rpm while maintaining the internal temperature at 30 ° C. )did. It was 0.6 micrometer when the average volume diameter of the charged particle was measured by HORIBA, Ltd. CAPA-700. Further, the internal temperature was raised to 65 ° C. and dispersed (granulated) at a rotation speed of 2000 rpm for 1 hour. The zirconia ceramic beads were removed from the obtained dispersion, and 200 g of Isopar G and 0.6 g of the charge control agent [CT-1] were added to obtain an ink composition [DC-1].

The physical properties of the ink composition [DC-1] were as follows.
The electrical conductivity at 20 ° C. of the ink composition was applied using an LCR meter (AG-4431 manufactured by Ando Electric Co., Ltd.) and a liquid electrode (LP-05 type manufactured by Kawaguchi Electric Manufacturing Co., Ltd.). It was 90 nS / m when measured under conditions of a voltage of 5 V and a frequency of 1 kHz. The charged particles were positively charged.
It was 1.2 micrometers when the average volume diameter of the charged particle was measured by HORIBA, Ltd. CAPA-700. The viscosity of the ink composition at 20 ° C. was measured with an E-type viscometer manufactured by Tokyo Keiki Co., Ltd. and found to be 1.4 mPa · s.

<Inkjet recording test>
In the ink jet recording apparatus shown in FIGS. 1 to 3, 100 g of the ink composition [DC-1] was filled in an ink tank connected to the head. Here, a 150 dpi (three-row staggered arrangement with a channel density of 50 dpi) and 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. A2 size 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 at the time of ejection (pulse width 50 μsec), and image recording was performed at a driving frequency of 10 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.
The image recording was performed for one week under the condition that the image area ratio was 15% and 15 sheets of A4 size were recorded per day, and it was examined whether or not particles were attached to the ejection openings of the inkjet head. The results are shown in Table 1.

<Redispersibility test>
The redispersibility test was conducted as follows. 1.0 g of the ink composition [DC-1] is put into a cylindrical 50 ml centrifugal settling tube, and a small high-speed cooling centrifuge (SRX-201 manufactured by Tommy Seiko Co., Ltd.) is used. The particles were allowed to settle under conditions for 2 hours. Add 5g of ISOPAR G to a cylindrical 50ml centrifugal sedimentation tube on which particles have been settled, cover tightly, and shake on a mix rotor (VMR-5 manufactured by ASONE Co., Ltd.) at room temperature and 80rpm. The time for complete redispersion of the sediment was recorded. The results are shown in Table 1.

<Long-term stability test>
The ink composition was allowed to stand at room temperature for 1 month, and the sediment was examined. The results are shown in Table 1.

[Example 2]
The coloring material is C.I. I. Pigment Red 57: 1 manufactured by Toyo Ink Mfg. Co., Ltd., Brilliant Carmine 6B, L.P. R. Ink composition [DM-1] was prepared in the same manner as in Example 1 except that the composition was changed to 6B FG-4213.

Example 3
The coloring material is C.I. I. Pigment Yellow 74 An ink composition [DY-1] was prepared in the same manner as in Example 1 except that the color was changed to Hanza Brilliant Yellow 5GXB manufactured by Clariant Japan.

Example 4
The coloring material is C.I. I. Pigment Black 7 An ink composition [DK-1] was prepared in the same manner as in Example 1 except that carbon black and MA-100 were manufactured by Mitsubishi Chemical Corporation.

[Comparative Example 1]
<Preparation of ink composition [HC-1]>
Cyan pigment 10g and 20g of polymer (coating agent) [AP-1] as a color material are placed in a table type kneader PBV-0.1 manufactured by Irie Shokai Co., Ltd. did. 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 finely pulverized product obtained was predispersed in a paint shaker manufactured by Toyo Seiki Seisakusho together with 7.5 g of the dispersant [BZ-2], Isoper G112.5 g, and glass beads having a diameter of about 3.0 mm. . After removing the glass beads, dispersed with zirconia ceramic beads with a diameter of about 0.6 mm in a Type KDL dyno mill manufactured by Shinmaru Enterprises Co., Ltd. for 30 minutes while maintaining the internal temperature at 30 ° C. (pulverization at 2000 rpm) )did. The zirconia ceramic beads were removed from the obtained dispersion, and 200 g of Isopar G and 0.6 g of the charge adjusting agent [CT-1] were added to obtain an ink composition [HC-1].

The physical properties of the ink composition [HC-1] were as follows.
The electrical conductivity at 20 ° C. of the ink composition was applied using an LCR meter (AG-4431 manufactured by Ando Electric Co., Ltd.) and a liquid electrode (LP-05 type manufactured by Kawaguchi Electric Manufacturing Co., Ltd.). It was 80 nS / m when measured under conditions of a voltage of 5 V and a frequency of 1 kHz. The charged particles were positively charged.
It was 1.0 micrometer when the average volume diameter of the charged particle was measured by HORIBA, Ltd. CAPA-700. The viscosity of the ink composition at 20 ° C. was measured with an E-type viscometer manufactured by Tokyo Keiki Co., Ltd. and found to be 1.4 mPa · s.

[Comparative Example 2]
The coloring material is C.I. I. Pigment Red 57: 1 manufactured by Toyo Ink Mfg. Co., Ltd., Brilliant Carmine 6B, L.P. R. An ink composition [HM-1] was prepared in the same manner as in Comparative Example 1 except that the composition was changed to 6B FG-4213.

[Comparative Example 3]
The coloring material is C.I. I. Pigment Yellow 74 An ink composition [HY-1] was prepared in the same manner as in Comparative Example 1, except that the color was changed to Hanza Brilliant Yellow 5GXB manufactured by Clariant Japan.

[Comparative Example 4]
The coloring material is C.I. I. Pigment Black 7 An ink composition [HK-1] was prepared in the same manner as in Comparative Example 1 except that Mitsubishi Black was changed to carbon black and MA-100.

[Comparative Example 5]
An ink composition was prepared in the same manner as in Example 1, except that dispersion was not performed at an internal temperature of 65 ° C. (1 hour, rotation speed of 2000 rpm).

  The ink composition prepared above was subjected to an inkjet recording test, a redispersibility test, and a long-term stability test in the same manner as in Example 1. The results are shown in Table 1.

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 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 Discharge fan 18 Solvent vapor adsorbent 38 Ink guide 40 Support bar portion 42 Ink meniscus 44 Insulating 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 Inkjet head 72 Ink flow path 74 Substrate 75, 75A, 75B Opening 76, 76A, 76B Discharge unit 78 Discharge unit

Claims (3)

  A method for producing particles containing a colorant and a polymer, comprising a step of wet-dispersing a mixture containing the colorant and a polymer in a dispersion medium at a temperature of 60 ° C. or higher.   An ink composition for ink-jet recording, comprising particles containing a colorant and a polymer produced by the production method according to claim 1.   An ink jet recording method, wherein an ink droplet is ejected by the ink jet recording method using an electrostatic field using the ink composition according to claim 2.

Images