JP2007314651A - Oil-based ink composition for inkjet recording, ink and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil-based ink composition for inkjet recording giving oil-based ink for inkjet recording which maintains low viscosity even in a relatively high pigment content, oil-based ink for inkjet recording containing the composition and an inkjet recording method in which the ink is jetted from a printer head having no heating mechanism. <P>SOLUTION: The oil-based ink composition for inkjet recording contains an organic solvent and a pigment which is an encapsulated-type pigment being surface-treated with a polymer. The oil-based ink for inkjet recording contains the oil-based ink composition for inkjet recording. The inkjet recording method comprises jetting the oil-based ink for inkjet recording from an inkjet printer head having no heating mechanism. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink composition for obtaining an oil-based ink for ink-jet recording having a low viscosity as a recording medium, an oil-based ink for ink-jet recording containing the ink composition, and ink-jet recording using the ink Regarding the method.

  Ink jet recording ink is required to have a low viscosity as compared with general printing ink and the like because ink is ejected from a head orifice of about 20 microns. Printers that use oil-based inks for ink jet recording have a heater in the printer head, and there are printer heads that enable ink jet discharge by reducing viscosity by heating. However, having a heater in the printer head leads to an increase in power consumption, a complicated head structure, and an increase in size. In addition, in order to achieve high image quality, it is necessary to eject fine droplets. For this purpose, since the ink is ejected from a hole having a smaller head orifice diameter, the ink has a lower viscosity. Is required.

  On the other hand, in the water-based ink for ink jet recording used in printers for general consumers, the pigment content in the ink is 3 to 5% by mass. On the other hand, in the offset printing ink or the like, the pigment content is as high as 10 to 20% by mass. A higher pigment content is required to increase the color density of the ink-jet recorded product. However, increasing the pigment content increases the viscosity of the ink, making it difficult to eject from the inkjet head. For this reason, in an inkjet printer for industrial use, a head having a heater is often used as described above.

  When water-based ink for ink-jet recording is used, a cockling phenomenon caused by swelling of fibers by water becomes a problem when printing on a paper medium. In order to suppress this, it is possible to solve the problem by using an oil-based ink for ink jet recording using an organic solvent as a main solvent.

  When preparing such an oil-based ink for ink-jet recording, the ink for ink-jet recording is directly prepared by coexisting a carbon black or an organic pigment in a pigment dispersant and dispersed in an organic solvent (oil), or for ink-jet recording. Generally, a method of preparing an ink composition and then adding various additives to prepare an ink for inkjet recording is generally used.

  An example of oil-based ink for ink-jet recording in which a pigment is dispersed in tripropylene glycol monomethyl ether by the above-described method is shown (for example, see Patent Document 1). However, the oil-based ink described in Patent Document 1 has a low pigment content of about 3 to 5% by mass and a high viscosity of 14 to 250 mPa · s, and requires a heater or the like.

  An example is shown in which a solid pigment preparation treated with a carboxyl group-containing polyacrylic resin is used in an aqueous ink for inkjet recording (see, for example, Patent Document 2). However, it is only intended for use as a water-based ink, and is not suitable for a solvent type because its hydrophilicity is too high.

JP-A-3-240557 Japanese Patent Laid-Open No. 3-153775

  The problem to be solved by the present invention is an oil-based ink composition for ink-jet recording for obtaining an oil-based ink for ink-jet recording that maintains a low viscosity even at a relatively high pigment content, and an oil-based ink for ink-jet recording containing the composition Is to provide.

  Therefore, as a result of intensive studies in view of the above circumstances, the present inventors have produced microcapsule-type composite particles in which the surface of carbon or organic pigment is treated with a resin in water, and by selecting a suitable capsule resin in a solvent. The present inventors have found that the above-described problems in ink-jet recording oil-based inks can be solved, and have completed the present invention.

  That is, the present invention is first a capsule-type pigment in which the pigment (a) is surface-treated with a polymer compound in the oil-based ink composition for inkjet recording containing the pigment (a) and the organic solvent (b). An oil-based ink composition for inkjet recording is provided.

  Secondly, the present invention provides an oil ink for ink jet recording containing the oil ink composition for ink jet recording, and an oil ink set for ink jet recording.

  Furthermore, the present invention provides an ink jet recording method in which the oil-based ink for ink jet recording is ejected from an ink jet printer head having no heating mechanism.

  The oil-based ink for ink-jet recording and the ink set containing the oil-based ink composition for ink-jet recording of the present invention are obtained by using a capsule-type pigment in which carbon black or organic pigment (a) is surface-treated with a polymer compound. Compared with the ink using the dispersion of the above-mentioned dispersant, the pigment occupying the ink has a particularly remarkable effect that the viscosity can be reduced at a higher pigment content.

  Hereinafter, the present invention will be described in detail. The oil-based ink composition for ink-jet recording of the present invention is an oil-based ink composition for ink-jet recording containing a capsule-type pigment in which the pigment (a) is surface-treated with a polymer compound and an organic solvent (b).

  The oil-based ink for ink-jet recording of the present invention and the ink set are required to contain the oil-based ink composition for ink-jet recording containing the capsule-type pigment surface-treated with a polymer compound in a solvent or a solvent in which a binder resin is dissolved. Depending on the condition, it is prepared by dispersing (mixing) together with various additives. It is desirable that the encapsulation treatment be prepared in an aqueous solvent containing water as a main component from an organic solvent in that the hydrophobic interaction can be effectively used in the encapsulation treatment.

  The nucleating agent for forming the capsule-type pigment used in the oil-based ink composition for ink jet recording of the present invention is not particularly limited, and any known and commonly used carbon black or organic pigment can be used. For example, for organic pigments, insoluble azo pigments, soluble azo pigments, indanthrene pigments, phthalocyanine pigments, quinacridone pigments, perylene pigments, isoindolinone pigments, quinophthalone pigments, anthraquinone pigments, diketopyrrolopyrrole And pigments.

  The polymer compound for forming a capsule-type pigment by subjecting the above-described carbon black or organic pigment to a capsule-type pigment is a copolymer of several types of monoethylenically unsaturated monomers, and has an acid value or an amine value. Such a copolymer can be used.

  Monoethylenically unsaturated monomers that give acid value to the copolymer include copolymerizable carbon-carbon double bonds and functional groups that generate free acids such as carboxylic acid, phosphoric acid, boric acid, and sulfonic acid. Can be used in the same molecule. For example, acrylic acid, methacrylic acid, 4-vinylbenzenesulfonic acid, 3-sulfoxyethyl acrylate, 3-sulfoxyethyl methacrylate, 3-sulfoxypropyl acrylate, 3-sulfoxypropyl methacrylate, acid phosphooxyethyl mono (meth) Acrylate, acid phosphooxypropyl mono (meth) acrylate, acid phosphoxypolyoxyalkylene glycol mono (meth) acrylate, and the like can be used.

  The acid value of the above-mentioned copolymer is preferably 30 to 80 (mgKOH / g). Furthermore, 30-60 (mgKOH) is more preferable. When the acid value is too high, when used as a solvent (oil-based) ink, the viscosity becomes too high, which is not preferable. On the other hand, when the acid value is too low, it becomes difficult to disperse the capsule in an aqueous system, which is not preferable. Here, the acid value means the number of mg of potassium hydroxide required to neutralize 1 g of the resin content.

  Examples of the monoethylenically unsaturated monomer that gives an amine value to the copolymer include 2-aminoethyl (meth) acrylate, 2-aminopropyl (meth) acrylate, 3-aminopropyl (meth) acrylate, 2- (methylamino) ethyl acrylate, 2- (methylamino) propyl (meth) acrylate, 2- (ethylamino) ethyl (meth) acrylate, 2- (dimethylamino) ethyl (meth) acrylate, ( Aminoalkyl (meth) acrylic acids such as 3- (dimethylamino) propyl methacrylate), (di) alkylaminoalkyl (meth) acrylic acids; 2-vinylpyridine, 4-vinylpyridine, 4-butenylpyridine, etc. Vinylpyridines are mentioned. Here, (meth) acrylic acid is referred to as (meth) acrylic acid as a general term for acrylic acid and methacrylic acid.

  The amine value of the copolymer is preferably 50 to 100 (mg HCl / g). Furthermore, 50-70 (mgHCl) is more preferable. When the amine value is too high, the viscosity becomes too high when used as a solvent (oil-based) ink, which is not preferable. On the other hand, if the amine value is too low, it is difficult to disperse when the capsule is processed in an aqueous system, which is not preferable. Here, the amine value means the number of mg of hydrogen chloride necessary for neutralizing 1 g of the resin content.

  As a copolymer as a polymer compound to be converted into a capsule type pigment, an ethylenically unsaturated monomer that can be copolymerized with a monomer that gives an acid value or an amine value can be used. Examples of the copolymerizable ethylenically unsaturated monomer include styrene, α-methylstyrene, dimethylstyrene, tert-butylstyrene, chlorostyrene, benzyl (meth) acrylate, phenyl (meth) acrylate, and phenylethyl (meth) ) Acrylate, phenylpropyl (meth) acrylate, phenoxyethyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) ) Acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, dodecyl (meth) acrylate, octadecyl (meth) ) Acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol mono (meth) acrylate, methoxypoly (oxyethyleneoxypropylene) glycol Examples thereof include monoethylenically unsaturated monomers such as mono (meth) acrylate.

  Even if the copolymer used in the present invention is a linear copolymer composed only of polymerized units of monoethylenically unsaturated monomers, various ethylenically unsaturated monomers having various crosslinking properties are used. It may be a copolymer containing a partially cross-linked partly crosslinked part.

  Examples of such ethylenically unsaturated monomers having crosslinkability include glycidyl (meth) acrylate, divinylbenzene, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, and polyethylene glycol di (meth). Examples include poly (meth) acrylates of polyhydric alcohols such as acrylates, poly (oxyethyleneoxypropylene) glycol di (meth) acrylates, and tri (meth) acrylates of alkylene oxide adducts of glycerin.

  The molecular weight of the copolymer in the present invention is not particularly limited. For example, from the viewpoint of film formation, the weight average molecular weight is 5,000 to 100,000. Among these, 5,000 is a low viscosity and easy handling. It is preferable that it is -20,000.

  In the present invention, it is assumed that the reaction rate of each monomer used is substantially the same, and the charging ratio of each monomer is regarded as the content ratio in terms of mass of the polymerization unit of each monomer. The copolymer in the present invention can be synthesized by various known reaction methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. In this case, a known and usual polymerization initiator, chain transfer agent (polymerization degree adjusting agent), surfactant and antifoaming agent can be used in combination.

  As the substance for neutralizing the copolymer, any known and commonly used substances can be used. For example, in the case of an anionic copolymer, an inorganic basic substance such as sodium hydroxide, potassium hydroxide, ammonia, triethylamine, Organic basic substances such as alkanolamines can be used. In the case of a cationic copolymer, inorganic acids such as hydrochloric acid and sulfuric acid, and carboxylic acids such as chloroacetic acid and nitroacetic acid can be mentioned. Of course, the substance for neutralizing these copolymers can also be used in the form of an aqueous solution.

The method for producing a capsule-type pigment used in the oil-based ink composition for ink jet recording of the present invention can be carried out based on, for example, the following methods (1) to (7).
(1) A method for producing an aqueous pigment dispersion in which a pigment is mechanically forcibly dispersed and crosslinked in an aqueous emulsion containing the organic polymer compound.
(2) A method for producing an aqueous pigment dispersion in which the above-described monomers are polymerized and cross-linked using a dispersant in water in the presence of a pigment, and are associated as necessary.
(3) The mixture of the pigment, the organic polymer compound and the organic solvent is gradually phase-inverted from the oil phase to the water phase using water and a basic substance, and then the solvent is removed. A method for producing an aqueous pigment dispersion containing the composite particles, wherein the capsule-type pigment is coated.
(4) After removing the solvent from the homogeneous mixture of the pigment, the organic polymer compound, the basic substance, the organic solvent, and water, adding acid, acidifying and washing the precipitate, the precipitate is combined with the basic substance. A method for producing an aqueous pigment dispersion containing the pigment, wherein the pigment is dispersed in an aqueous medium and the pigment is a capsule-type pigment coated with an organic polymer compound.
(5) Remove the solvent from the homogeneous mixture of the pigment, the organic polymer compound, the basic substance, the organic solvent and water, add an acid, acidify it, wash the precipitate, dry and pulverize the precipitate. A method for producing a capsule-type pigment in which the pigment is coated with an organic polymer compound.
(6) A method for producing capsule-type pigments obtained by drying the aqueous pigment dispersions (1) to (4), removing water, and then pulverizing and drying.
(7) A method for producing a pigment dispersion in which capsule pigments are dispersed in a solvent by distilling off water after the aqueous pigment dispersions (1) to (4) are mixed and stirred in a water-soluble organic solvent. .

  As the drying method in the step of obtaining the powder capsule pigments in (5) and (6) above, known methods such as heat drying, vacuum drying, liquid film drying method, freeze drying and the like can be used. Of these, vacuum drying, freeze drying and the like that suppress resin fusion are preferred. Moreover, the spray-drying method which suppresses dry aggregation can also be utilized.

  In the present invention, it is preferable to include a step of dispersing a mixture comprising a pigment, an organic polymer compound, a substance that neutralizes the organic polymer compound, and water, regardless of which of the capsule pigment production methods described above. This mixture preferably contains a water-soluble organic solvent. More specifically, it is preferable to include a step (dispersing step) of dispersing at least a pigment, an organic polymer compound, a substance that neutralizes the organic polymer compound, a water-soluble organic solvent, and water.

  Dispersing (mixing) a powder (or liquid) capsule-type pigment treated with an aqueous system in a solvent has the following advantages over a method of dispersing a pigment directly in a solvent and using a dispersant. have. (1) The viscosity can be reduced. (2) The pigment surface can be modified with a polymer compound having more ionic functional groups. (3) The dispersion time in the solvent can be shortened.

  In addition, a water-soluble organic solvent can be used in combination in the dispersion step, which can reduce the liquid viscosity in the dispersion step. Examples of water-soluble organic solvents include ketones such as acetone, methyl ethyl ketone, methyl butyl ketone, and methyl isobutyl ketone; methanol, ethanol, 2-propanol, 2-methyl-1-propanol, 1-butanol, 2-methoxyethanol Alcohols such as tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, and the like; amides such as dimethylformamide, N-methylpyrrolidone, and the like. It is preferable to use a compound selected from the group consisting of a ketone and an alcohol having 1 to 5 carbon atoms. These water-soluble organic solvents may be used as an organic polymer compound solution, or may be separately added to the dispersion mixture.

  In the above-described method for producing an aqueous pigment dispersion, it is preferable that pigment / organic polymer compound = 100/10 to 100/100. Optimally, it can be produced using the above-described raw materials so that the non-volatile content of the organic polymer compound is 10 to 65 parts and the aqueous medium is 835 to 890 parts per 100 parts of pigment in terms of mass.

  As a dispersion apparatus that can be used in the dispersion step, apparatuses by various known methods can be used, and are not particularly limited. For example, the dispersion apparatus can be made of steel, stainless steel, zirconia, alumina, silicon nitride, glass, or the like. A method that uses the kinetic energy of a spherical dispersion medium with a diameter of about 0.1 to 10 mm, a method that uses a shearing force by mechanical stirring, a pressure change of a dispersed flow bundle supplied at high speed, a flow path change or a collision It is possible to adopt a dispersion method such as a method using the force generated by

  The capsule-type pigment used in the oil-based ink composition for ink-jet recording of the present invention is an organic polymer compound for exhibiting superior properties in all aspects of dispersion arrival level, required dispersion time, and dispersion stability. It is preferably dispersed in an aqueous medium in the form of particles coated with (that is, the capsule-type pigment described above).

  In order to form such a state, in the state where the pigment is dispersed in the liquid medium containing the organic polymer compound, the pigment surface is coated with the dissolved organic polymer compound as a subsequent step of the dispersion step. It is preferable to incorporate a coating step and a crosslinking step of the polymer compound.

  The step of coating the organic polymer compound in the dissolved state on the pigment surface is preferably a step of precipitating the organic polymer compound dissolved in the alkaline (acidic) aqueous solution by acidifying (alkalizing) the solution. . By this process, the interaction between the pigment and the organic polymer compound can be enhanced by depositing the resin on the pigment surface.

  Examples of the filtration step include a step of filtering the solid content after the resin precipitation step described above with a filter press, a Nutsche type filtration device, a pressure filtration device, or the like. Examples of the redispersion step include a step of adding a basic substance (acidic in the case of a cationic resin) to the solid content obtained by the resin precipitation step and the filtration step and, if necessary, water and additives to obtain a dispersion again. There is. Thereby, the counter ion of the ionic functional group in the organic polymer compound can be changed from that used in the dispersion step.

  As a result, the capsule-type pigment as described above can take a form dispersed in an aqueous dispersion medium, and as an aqueous dispersion, physical properties such as dispersion reach level and dispersion stability, solvent resistance, etc. In terms of suitability for use, more excellent characteristics can be exhibited.

  The capsule-type pigment can also be prepared as a solvent-type dispersion by mixing with a water-soluble organic solvent as an aqueous dispersion. Furthermore, a powdery capsule-type pigment can also be obtained by removing moisture using the drying method as described above and pulverizing. In this case, the capsule type in which the ionic functional groups of the resin on the capsule surface are not in ion pairs (for example, carboxylic acid, amine, etc.) using the method of drying the solid content obtained in the filtration step described above. A pigment can be obtained.

  The powdery (or liquid) capsule-type pigment obtained as described above is dispersed (mixed) in an organic solvent to obtain the oil-based ink composition for inkjet according to the present invention. Examples of organic solvents that can be used include non-polar solvents such as long chain fatty acid esters, vegetable oil esters, higher fatty acids, vegetable oils, hydrocarbons, and higher alcohols. Examples of highly polar solvents include lower alcohols, glycols, glycol ethers, glycol esters, lower alcohol esters, pyrrolidones and the like. When the aqueous dispersion is mixed in a liquid state, it is desirable to use a solvent having high polarity and capable of solubilizing water. When used in inkjet, a high boiling point is desirable in order to suppress drying at the head orifice. Moreover, when dispersing in a nonpolar solvent, it is desirable to use powdery microcapsule type composite particles from which water has been removed. In the case of dispersing (mixing) the capsule-type pigment in these solvents, it is possible to use a dispersant in combination.

  Non-polar solvents include, for example, methyl oleate, ethyl oleate, isopropyl oleate, isobutyl oleate, methyl linoleate, isobutyl linoleate, ethyl linoleate, soy oil methyl, soy oil isobutyl, linseed oil butyl, large Bean oil, linseed oil, castor oil, Nippon Oil Corporation “Nisseki Naphthezol H, No. 0 Solvent H, Isosol 300, Isosol 400, AF-5, AF-6, AF-7”, ExxonMobil “Exxol D80, Exxol D110, Exxol D130, Exxol D140 (all trade names), isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol, isononanoic acid, isomyristic acid, hexadecanoic acid, isopalmitic acid, olein Examples include acids and isostearic acid.

  Examples of highly polar solvents include ethylene glycol, diethylene glycol, glycerin, xylitol, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, Examples include propylene glycol monomethyl ether monoacetate, isopropyl acetate, pyrrolidone, and N-methylpyrrolidone.

  Said solvent can be utilized individually or as a mixed solvent. By using a mixed solvent, it is possible to control the solubility of the binder resin and other additives described later, the evaporation rate of the solvent, and the suitability for the recording medium to be printed (ink fixability, dot spread).

  The solvent used alone or as a mixture is preferably as low as possible in order to obtain a viscosity (20 mPa · s or less) that enables inkjet discharge as an oil-based ink for inkjet recording. Specifically, it is preferable to use a single or mixed solvent having a viscosity at 20 ° C. of 1.5 to 10 mPa · s. If the viscosity of the solvent used alone or in combination is too high, it becomes difficult to add pigments, binder resins, etc., making it difficult to create oil-based inks for ink jet recording, or as the addition amount This is disadvantageous in terms of ink design.

  It is preferable to add a binder resin to the oil-based ink composition for ink-jet recording thus obtained in order to maintain the fixability of the recorded matter. As the binder resin, styrene- (meth) acrylic resin, styrene-maleic acid resin, rosin phenol resin, vinyl acetate resin, urethane resin, polyester resin, epoxy resin, silicone resin, etc. can be used. Insoluble resins are clogged at the head orifice and are difficult to use.

  Additives such as surfactants and wetting agents are added to the oil-based ink composition for ink-jet recording in which the capsule-type pigment is dispersed in the organic solvent thus obtained, and finally the mass. The pigment content is adjusted to 3 to 15% in terms of conversion to obtain an oil-based ink for inkjet recording. In addition, the obtained oil-based ink for ink-jet recording can remove coarse particles and adjust the particle size distribution of dispersed particles by performing ultracentrifugation or filtration with a microfilter, if necessary, such as nozzle clogging. Can be extremely reduced.

  The viscosity at 20 ° C. when the pigment content in the obtained oil-based ink composition for inkjet recording is 10% by mass is preferably 3 to 13 mPa · s. When the pigment content of the oil-based ink composition for ink-jet recording is low, adjustment is made such as adding an ink solvent, adding a binder resin, or adding an additive such as a surfactant when creating an oil-based ink for ink-jet recording. It is difficult to carry out. Moreover, even if the viscosity of the oil-based ink composition for ink-jet recording is high, various additives and the like (solvent, binder resin, surfactant, etc.) are added to obtain an oil-based ink for ink-jet recording with a viscosity capable of ink-jet ejection. Is difficult. The pigment content of 10% by mass of the oil-based ink composition for ink jet recording is a pigment content when the viscosity at 20 ° C. is measured. As an oil-based ink composition for inkjet recording, a higher pigment content is preferable because it can be easily adjusted by adding various additives. The pigment content of the oil-based ink for ink-jet recording is preferably 10 to 30% by mass, and more preferably 10 to 20% by mass because the oil-based ink composition for ink-jet recording can be easily handled.

  As the surfactant, a material having an HLB of about 8 to 17 can be used. For example, alkylbenzene sulfonic acid, polyoxyethylene sorbitan monofatty acid ester, polyoxyethylene oxide monoalkyl ether monophosphate, polyethylene oxide monoalkyl ether, ethylene oxide adduct of acetylene glycol, silicone surfactant, fluorine surfactant Etc.

  The oil-based ink for inkjet recording of the present invention is not particularly limited in terms of the number of ink colors, and is selected from the group consisting of yellow (Y), magenta (M), cyan (C), and black (K). At least one color of oil-based ink. One color or two or more colors may be used.

  In the present invention, by performing ink jet recording on a recording medium, a recorded matter in which a colored image is formed on the recording medium can be obtained.

  The oil-based ink set for ink-jet recording of the present invention can be used in a known and commonly used method for ink-jet recording on a recording medium. Examples of the recording medium at this time include plain paper such as PPC paper, photographic paper (glossy), exclusive paper for ink-jet recording such as photographic paper (silk tone), and coating used for offset printing. A synthetic resin film such as paper or an OHP film may be used. Among these, the oil-based ink set for ink-jet recording of the present invention is effective for improving the color developability of the special paper for ink-jet recording and the coated paper used for offset printing.

  The oil-based ink for ink-jet recording and the ink set containing the oil-based ink composition for ink-jet recording of the present invention are obtained by using a capsule-type pigment in which carbon black or organic pigment (a) is surface-treated with a polymer compound. Compared with the ink using the dispersion of the above-mentioned dispersant, the pigment occupying the non-volatile content in the ink has a particularly remarkable effect that the viscosity can be lowered at a higher pigment content. As a result, the present invention can provide an inkjet recording method in which the oil-based ink for inkjet recording is ejected from an inkjet printer head that does not have a heating mechanism.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following examples and comparative examples, “part” and “%” are both based on mass.

<Synthesis Example 1>
MEK is added to a reaction vessel of an automatic polymerization reaction device (polymerization tester DSL-2AS type, manufactured by Sakai Sangyo Co., Ltd.) having a reaction vessel equipped with a stirring device, a dropping device, a temperature sensor, and a reflux device having a nitrogen introduction device at the top. (2-butanone) 1000 parts were charged and the inside of the reaction vessel was purged with nitrogen while stirring. After raising the temperature inside the reaction vessel to 80 ° C. while maintaining a nitrogen atmosphere, 150 parts of 2-hydroxyethyl methacrylate, 200 parts of styrene, 92.1 parts of methacrylic acid, 370.1 parts of butyl methacrylate, acrylic 1007.8 parts of butyl acid, 30.0 parts of glycidyl methacrylate, 40.0 parts of Blemmer TGL (polymerization degree adjusting agent) and perbutyl (registered trademark) O (polymerization initiator, both manufactured by NOF Corporation) 100. 0 part of the mixture was added dropwise over 4 hours. After completion of the dropwise addition, the reaction was further continued at the same temperature for 7 hours to obtain a MEK solution of a copolymer having an acid value of 60, a weight average molecular weight of 5,900, and a nonvolatile content of 46.32%.

<Preparation Example 1>
In a mixing tank equipped with a cooling jacket, 263 parts of the copolymer obtained in Synthesis Example 1, 30 parts of a 25% aqueous potassium hydroxide solution, water and carbon black Raven (registered trademark) 1255 (manufactured by Columbia Carbon Japan Co., Ltd.) )] 250 parts and 1064 parts of water were charged, stirred and mixed. Here, the amount of each charged is such that the copolymer has a non-volatile content of 50% with respect to the pigment, and the 25% aqueous potassium hydroxide solution has the acid value of the styrene-acrylic copolymer 100% neutralized. Amount.

  The mixed solution was passed through a dispersing device (SC mill SC100 / 32 type, manufactured by Mitsui Mining Co., Ltd.) filled with zirconia beads having a diameter of 0.3 mm, and dispersed for 4 hours by a circulation method. The number of revolutions of the dispersing device was 2700 rpm, and the temperature of the dispersion liquid was kept at 40 ° C. or less through the cooling jacket through cold water. After the dispersion, the dispersion stock solution was extracted from the mixing tank, and then the mixing tank and the dispersion device flow path were washed with 10,000 parts of water, and the diluted dispersion liquid was obtained together with the dispersion stock solution. The diluted dispersion was put into a glass distillation apparatus, and the whole amount of methyl ethyl ketone and a part of water were removed by atmospheric distillation.

  The dispersion from which methyl ethyl ketone was removed was cooled, and then 10% hydrochloric acid was added dropwise with stirring to adjust the pH to 4.5, and then the solid content was filtered with a Nutsche filter and washed with water. The cake was taken in a container and vacuum dried at 50 ° C. and <0.01 mmHg. The obtained solid was pulverized in a mortar to obtain a capsule-type pigment (1).

<Preparation Example 2>
In a mixing tank equipped with a cooling jacket, 142 parts of the copolymer obtained in Synthesis Example 1, 18 parts of a 25% aqueous potassium hydroxide solution, water and Fastogen (registered trademark) Blue TGR [manufactured by Dainippon Ink & Chemicals, Inc. 250 parts, 58 parts of methyl ethyl ketone, and 905 parts of water were charged, stirred and mixed. Here, the amount of each charged is such that the copolymer has a non-volatile content of 30% with respect to the pigment, and the 25% aqueous potassium hydroxide solution has the acid value of the styrene-acrylic copolymer 100% neutralized. Amount.

  The mixed solution was passed through a dispersing device (SC mill SC100 / 32 type, manufactured by Mitsui Mining Co., Ltd.) filled with zirconia beads having a diameter of 0.3 mm, and dispersed for 4 hours by a circulation method. The number of revolutions of the dispersing device was 2700 rpm, and the temperature of the dispersion liquid was kept at 40 ° C. or less through the cooling jacket through cold water. After the dispersion, the dispersion stock solution was extracted from the mixing tank, and then the mixing tank and the dispersion device flow path were washed with 10,000 parts of water, and the diluted dispersion liquid was obtained together with the dispersion stock solution. The diluted dispersion was put into a glass distillation apparatus, and the whole amount of methyl ethyl ketone and a part of water were removed by atmospheric distillation.

  The dispersion from which methyl ethyl ketone was removed was cooled, and then 10% hydrochloric acid was added dropwise with stirring to adjust the pH to 4.5, and then the solid content was filtered with a Nutsche filter and washed with water. The cake was taken in a container and vacuum dried at 50 ° C. and <0.01 mmHg. The obtained solid was pulverized in a mortar to obtain a capsule-type pigment (2).

Example 1
30 parts of the capsule-type pigment (1) prepared in Preparation Example 1 above, 170 parts of dipropylene glycol monomethyl ether, and 200 parts of zirconia beads having a diameter of 0.5 mm were mixed, and a paint conditioner (manufactured by Toyo Seiki Co., Ltd.) Mix for 1 hour. The zirconia beads were removed with a sheet mesh (200 mesh) to obtain an oil-based ink (1) for inkjet recording.

(Example 2)
11.2 parts of capsule type pigment (2) prepared in Preparation Example 1 above, 73.4 parts of methyl soybean oil, 5.8 parts of SOLPERSE (registered trademark) 13940 (manufactured by Nippon Loop Resor Co., Ltd.), Disperbyk (registered trademark) 2100 (produced by Big Chemie Japan Co., Ltd.) 1.0 part, Fineoxocol (registered trademark) 140-N (produced by Nissan Chemical Industries, Ltd.) 4.8 parts, diameter 0.5 mm 96 parts of zirconia beads were mixed and mixed for 1 hour with a paint conditioner (manufactured by Toyo Seiki Co., Ltd.). The zirconia beads were removed with a sheet mesh (200 mesh) to obtain an oil-based ink composition for inkjet recording.

  The oil-based ink composition for ink jet recording obtained as described above was diluted with 21.1 parts of methyl soybean oil to obtain 84.3 parts of oil-based ink composition for ink-jet recording.

(Comparative Example 1)
Carbon black Raven (registered trademark) 1255 (made by Columbia Carbon Japan Co., Ltd.) 20 parts, dipropylene glycol monomethyl ether 170 parts, Disperbyk (registered trademark) 111 (produced by Big Chemie Japan Co., Ltd.), 10 parts in diameter 200 parts of 5 mm zirconia beads were mixed and mixed with a paint conditioner (manufactured by Toyo Seiki Co., Ltd.) for 1 hour. The zirconia beads were removed with a sheet mesh (200 mesh) to obtain an oil-based ink for ink jet recording (3).

(Comparative Example 2)
Carbon black Raven (registered trademark) 1255 (Columbia Carbon Japan Co., Ltd.) 20 parts, dipropylene glycol monomethyl ether 170 parts, Disperbyk (registered trademark) 116 (Bicchemy Japan Co., Ltd.) 10 parts, diameter 0 200 parts of 5 mm zirconia beads were mixed and mixed with a paint conditioner (manufactured by Toyo Seiki Co., Ltd.) for 1 hour. The zirconia beads were removed with a sheet mesh (200 mesh) to obtain an oil-based ink (4) for inkjet recording.

(Comparative Example 3)
Carbon black Raven (registered trademark) 1255 (produced by Columbia Carbon Japan Co., Ltd.) 20 parts, dipropylene glycol monomethyl ether 170 parts, Disperbyk (registered trademark) 185 (produced by Big Chemie Japan Co., Ltd.), 10 parts, diameter 0 200 parts of 5 mm zirconia beads were mixed and mixed with a paint conditioner (manufactured by Toyo Seiki Co., Ltd.) for 1 hour. The zirconia beads were removed with a sheet mesh (200 mesh) to obtain an oil-based ink for ink jet recording (5).

  SOLPERSE (registered trademark) 13940 is a comb-type polyamine pigment dispersant, Disperbyk (registered trademark) 2100 (manufactured by Big Chemie Japan Co., Ltd.) is a pigment synergist, Disperbyk (registered trademark) 111 (manufactured by Big Chemie Japan Co., Ltd.) ) Is a pigment dispersant and a copolymer containing acid groups, Disperbyk (registered trademark) 116 (manufactured by Big Chemie Japan Co., Ltd.) is a pigment dispersant and an acrylic copolymer having an affinity for pigment, Disperbyk (registered trademark) ) 185 (manufactured by Big Chemie Japan Co., Ltd.) is a pigment dispersant and a block copolymer having an affinity for pigment, and Fineoxocol (registered trademark) 140-N (manufactured by Nissan Chemical Industries, Ltd.) is a branched higher alcohol Isomyristyl alcohol as a solvent. The following DPM indicates dipropylene glycol monomethyl ether.

  The volume average particle diameter was measured with a laser Doppler particle size analyzer Microtrac (UPA150 type, manufactured by Leeds & Northrop). The viscosity was measured at a rotational speed of 60 rpm using an R-type viscometer (R-500 type, manufactured by Toki Sangyo Co., Ltd.).

  As can be seen from the comparison between Example 1 and Comparative Examples 1 to 3, the capsule-type pigment treated with acrylic capsule resin and the dispersion with acrylic pigment dispersant take a capsule-type pigment shape. It can be seen that the viscosity is lower. Even when the solvent is non-polar, the capsule-type pigment can be used (Example 2).

The oil-based ink and ink set for ink-jet recording containing the oil-based ink composition for ink-jet recording of the present invention have a higher pigment content than the ink using a dispersion using a conventional dispersant. , Low viscosity can be achieved. Therefore, it can be widely applied to various types of jet ink recording including the possibility of use with a printer head without a heating mechanism.

Claims (9)

An oil-based ink for ink-jet recording comprising a pigment (a) and an organic solvent (b), wherein the pigment (a) is a capsule-type pigment surface-treated with a polymer compound. Ink composition. 2. The oil-based ink composition for ink jet recording according to claim 1, wherein the capsule type pigment (a) is a capsule type pigment surface-treated with a polymer compound in an aqueous medium. The oil-based ink composition for ink jet recording according to claim 1 or 2, wherein the polymer compound is a (meth) acrylic acid copolymer having an acid value of 30 to 60. The ink-jet recording according to any one of claims 1 to 3, wherein the oil-based ink composition for ink-jet recording prepared at 10% by mass of the capsule-type pigment has a viscosity at 20 ° C of 3 to 13 mPa · s. Oil-based ink composition. The oil-based ink composition for ink-jet recording according to any one of claims 1 to 4, wherein the organic solvent (b) has a viscosity at 20 ° C of 1.5 to 10 mPa · s. The oil-based ink composition for inkjet recording according to any one of claims 1 to 5, wherein the organic solvent (b) contains dipropylene glycol monoalkyl ether. An oil-based ink for ink-jet recording, comprising the oil-based ink composition for ink-jet recording according to any one of claims 1 to 6. An oil-based ink set for ink-jet recording, comprising the oil-based ink composition for ink-jet recording according to any one of claims 1 to 6. An ink jet recording method comprising discharging the oil-based ink for ink jet recording according to claim 7 from an ink jet printer head having no heating mechanism.