JP2011016890A - Energy ray-curable inkjet ink composition - Google Patents

Abstract

An energy ray curable inkjet ink composition having excellent storage stability is provided.
An energy ray curable inkjet ink composition comprising at least a phthalocyanine pigment, a polymer compound, and an organic solvent, wherein ions in the energy ray curable inkjet ink composition are phase-shifted into pure water. The total concentration of monovalent cations in the aqueous phase is 20 ppm or less. The energy ray curable inkjet ink composition has excellent storage stability with less generation of precipitates even after long-term storage.
[Selection figure] None

Description

  The present invention relates to an energy beam curable inkjet ink composition containing at least a phthalocyanine pigment and a polymerizable compound, and more particularly to an energy beam curable inkjet ink composition suitably used in an inkjet recording system.

  The ink jet recording method is a recording method in which printing is performed by ejecting liquid ink from a nozzle toward a recording medium by using pressure, heat, electric field or the like as a driving source. Such a recording method has recently been expanding the market because of its low running cost, high image quality, and the ability to print various inks according to the application.

  Conventionally, as an ink composition applied to an ink jet recording method, a water-based ink mainly containing water and a dye / pigment as a solvent as a coloring material and an oil-based ink mainly containing an organic solvent have been used.

For example, a pigment, a polymer compound having a solubility in water and ethanol of less than 3% by mass at 25 ° C., and 30 to 90% by mass of a (poly) alkylene glycol derivative and 1 to 1 of a nitrogen-containing heterocyclic compound as an organic solvent. An oil pigment ink having improved weather resistance and fixability by using an oil pigment ink composition containing 30% by mass has been proposed (for example, Patent Document 1). Further, unlike the water-based dye ink, the oil-based pigment ink as described above is liable to cause ejection failure because the pigment is not dissolved in the ink. Therefore, for the purpose of improving the dispersion stability of the pigment in the organic solvent, it is selected from the group consisting of a pigment, a binder resin, a pigment dispersant, at least one glycol ether acetate, and cyclohexanone and isophorone. An oil-based pigment ink containing at least one organic solvent has been proposed (for example, Patent Document 2).
Further, in recent years, energy ray curable inkjet ink compositions that can reduce the amount of volatile organic solvents and cure the ink by irradiation with energy rays (for example, ultraviolet rays) are attracting attention as environmentally friendly inks.

Japanese Patent Laid-Open No. 2005-60716 JP 2006-56991 A

  By the way, the pigments used in the energy ray curable inkjet ink as described above are roughly classified into inorganic pigments such as titanium oxide and organic pigments such as carbon black, azo series, azomethine series, and phthalocyanine series. When energy ray curable inkjet ink is used as an inkjet ink, a pigment exhibiting each hue of cyan, magenta, yellow, white, and black is selected from these pigments according to desired characteristics, and each pigment is selected. It is used for inkjet printing in the form of an ink set in which an ink tank filled with an energy ray curable inkjet ink prepared by using the ink tank is combined.

  However, when a phthalocyanine pigment is used as the pigment of the energy ray curable ink jet ink as described above, the problem that nozzle clogging frequently occurs when ink is stored for a long period of time and it becomes difficult to discharge by an ink jet printer. .

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an energy ray curable inkjet ink composition having a phthalocyanine-based pigment as a coloring material. An object of the present invention is to provide an energy ray curable ink jet ink composition that is less clogged and can perform stable ink jet printing.

  The present invention is an energy ray curable inkjet ink composition containing at least a phthalocyanine pigment and a polymerizable compound, and when the ions in the energy ray curable inkjet ink composition are phase-inverted into pure water, The total concentration of monovalent cations is 20 ppm or less.

  According to the energy ray curable inkjet ink composition, when the ions in the ink composition are phase-inverted into pure water, the total concentration of monovalent cations in the aqueous phase is 20 ppm or less, so that it can be stored for a long time. The generation of precipitates derived from the phthalocyanine pigment can be suppressed even later. In particular, among monovalent cations, sodium ions and potassium ions are likely to form precipitates, and therefore the total concentration of these ions is preferably 20 ppm or less.

  The specific conductivity of the aqueous phase is preferably 50 μS / cm or less. A low specific conductivity means that when the ions in the ink composition are phase-inverted to pure water, the amount of ions phase-inverted is small. Therefore, if the specific conductivity is 50 μS / cm or less, the content of not only monovalent cations but also other ionic impurities such as anions is small. For this reason, generation | occurrence | production of a precipitate can be suppressed further.

  As described above, according to the present invention, it is possible to provide an energy beam curable inkjet ink composition in which the generation of precipitates derived from phthalocyanine pigments is small. Thereby, even when the ink is stored for a long period of time, it is possible to obtain an ink-jet ink that can be stably ejected with less nozzle clogging.

  First, the development history of the energy ray curable inkjet ink composition of the present embodiment will be described. When the energy ray curable inkjet ink containing a phthalocyanine pigment is stored for a long period of time, the energy ray curable type containing another pigment is used. As a result of investigating the cause of frequent nozzle clogging compared with inkjet ink, solid precipitates different from the phthalocyanine pigment itself adhered to the filter provided in the supply pipe connecting the ink tank and nozzle of the inkjet printer. As a result, it was confirmed that clogging occurred. Since no precipitate was generated in the ink at the time of ink preparation, it was considered that this precipitate was generated by long-term storage of the ink.

  For this reason, as a result of examining the components that can form precipitates in the ink composition, the ionic impurities contained in the phthalocyanine pigment are eluted in the ink by long-term storage, and the salt is generated due to the cause of the precipitates. It was estimated that. That is, in the process of producing a phthalocyanine pigment, first, a crude phthalocyanine pigment is synthesized. During this synthesis, anions such as chlorine ions and nitrate ions derived from raw materials or by-products are unavoidable in the crude phthalocyanine pigment. Mixed in. In addition, the synthesized crude phthalocyanine pigment is generally a lump and is produced as crystals that are not suitable for use as a pigment. For this reason, the pigmentation which adjusts a particle diameter, a crystal structure, a hue, etc. by further processing a crude phthalocyanine pigment is performed. As an industrial method of pigmentation, a salt milling method is generally performed in which a crude phthalocyanine pigment is pulverized with an inorganic salt and then the resulting phthalocyanine pigment is acid extracted. Accordingly, phthalocyanine pigments produced by the salt milling method contain ionic impurities such as alkali metal salts such as sodium and potassium, and alkaline earth metal salts such as calcium and barium.

  When an ink in which a phthalocyanine pigment containing such ionic impurities is dispersed in an organic solvent is stored for a long period of time, it will be taken in from a small amount of moisture contained in the ink components such as polymerizable compounds or in the air in the manufacturing process. It is considered that the ionic impurities as described above are dissolved in the ink due to the generated moisture to form a salt, thereby generating precipitates.

  Furthermore, as a result of detailed analysis of the metal component in the precipitate, the precipitate contained a monovalent alkali metal such as sodium or potassium as the main metal component rather than a divalent alkaline earth metal such as calcium. Therefore, it was considered that the monovalent cation in the inorganic salt mixed in the above-mentioned pigmentation was mainly produced during the long-term storage. Therefore, it can be expected that the generation of precipitates can be suppressed with an ink composition in which at least one of monovalent cations and anions, which are the main factors for generating such precipitates, is reduced.

Based on the above knowledge, the inventors focused on the amount of monovalent cations in the ink composition and studied to reduce the amount of ions, but the energy ray curable inkjet ink composition was Since an organic solvent is used as the dispersion solvent, it is difficult to directly detect the amount of cations in the ink composition. For this reason, as a result of further investigation, if the ions in the ink composition are phase-inverted to pure water containing no ionic component and the total concentration of monovalent cations in the aqueous phase is below a certain value, It was found that depending on the cation concentration, an ink with little generation of precipitates can be obtained even after long-term storage. That is, when the ions in the energy ray curable ink jet ink composition are phase-inverted into pure water, the total concentration of monovalent cations in the aqueous phase is 20 ppm or less, preferably 10 ppm or less, and the ink is used for a long time. Even after storage, the generation of precipitates is suppressed, and an ink having excellent storage stability can be obtained.
In the case where the polymerizable compound contains a water-soluble polymerizable compound, and when the oil-based pigment ink composition is brought into contact with pure water, the water-soluble organic solvent is also phase-inverted in the aqueous phase, By measuring the total concentration of monovalent cations in the aqueous phase containing the water-soluble organic solvent, the amount of monovalent cations in the ink composition can be determined.

  In addition, when the present inventors phase-converted the ions in the energy ray-curable inkjet ink composition to pure water as described above, if the specific conductivity of the aqueous phase is below a certain value, the precipitates We also found that there was little production. That is, since the precipitate is considered to be a salt containing a monovalent cation, the amount of precipitation is also influenced by the amount of anions. Moreover, although there are few precipitates containing bivalent cations, such as calcium, as mentioned above, alkaline earth metal salts, such as calcium, are also contained in the precipitate to some extent. Therefore, in order to suppress the generation of precipitates, it is preferable to reduce divalent cations such as anions and calcium. For this reason, if the content of ionic impurities in the entire ink composition is reduced, the generation of precipitates can be expected to be further suppressed. However, the amount of ions of these ionic substances in the ink affects the specific conductivity. To do. As a result of examination from the above viewpoint, it has been found that when the specific conductivity of the aqueous phase is preferably 50 μS / m or less, more preferably 25 μS / m or less, the generation of precipitates is extremely small.

  In the energy beam curable inkjet ink composition of the present embodiment, the total concentration of monovalent cations in the aqueous phase when the ions in the ink composition are phase-shifted to pure water, and the specific conductivity of the aqueous phase Is adjusted to the above range, it is preferable to use a phthalocyanine pigment, which is considered to be the main cause of the generation of precipitates, having less ionic impurities. In particular, in the range of the content of the phthalocyanine pigment when used as an inkjet ink, the generation of precipitates by using a phthalocyanine pigment having a specific conductivity of 50 μS / m or less, more preferably 25 μS / m or less. Is suppressed. Examples of a method for obtaining such a low specific conductivity phthalocyanine pigment include a method of washing a commercially available phthalocyanine pigment with distilled water or ion-exchanged water. If the phthalocyanine pigment content is high, the total concentration of monovalent cations in the aqueous phase and the specific conductivity of the aqueous phase will increase, so use phthalocyanine pigments with as low specific conductivity as possible. It is preferable to do.

  Next, each component used in the energy beam curable inkjet ink composition of the present embodiment will be specifically described.

  Specific examples of the phthalocyanine pigment used in the present embodiment include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 15: 5, C.I. I. Pigment blue 15: 6. These may be used alone or in combination.

  The content of the phthalocyanine pigment in the ink composition is not particularly limited, but when used as an ink for an ink jet printer, it is preferably 0.1 to 10 parts by mass with respect to the entire ink composition. 1.5-7 parts by mass is more preferable.

  The polymerizable compound has a radical polymerization type and a cationic polymerization type depending on the reaction mechanism, and can be properly used depending on the respective characteristics and purpose of use. Particularly preferred are compounds having an ethylenic double bond.

  Examples of monofunctional (meth) acrylates that can be used for radical polymerization type energy ray curable compounds include methyl, ethyl, propyl, butyl, amyl, 2-ethylhexyl, octyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxy (Meth) acrylate having a substituent such as ethyl, butoxyethyl, phenoxyethyl, nonylphenoxyethyl, glycidyl, dimethylaminoethyl, diethylaminoethyl, isobornyl, dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl, etc. Can be mentioned.

  Examples of the polyfunctional (meth) acrylate include 1.3-butylene glycol, 1.4-butanediol, 1.5-pentanediol, 3-methyl-1.5-pentanediol, and 1.6-hexanediol. , Neopentyl glycol, 1.8-octanediol, 1.9-nonanediol, tricyclodecane dimethanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, etc. Di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of acrylate, tris (2-hydroxyethyl) isocyanurate di (meth) acrylate, neopentyl glycol Di- (meth) acrylate of diol obtained by adding 2 mol of ethylene oxide or propylene oxide to 1 mol of bisphenol A, and obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol of trimethylolpropane Diol or tri (meth) acrylate of triol, Di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of bisphenol A, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (Meth) acrylate, poly (meth) acrylate of dipentaerythritol, ethylene oxide modified phosphoric acid (meth) acrylate, ethylene oxide modified alkyl phosphoric acid (meth) acrylate, etc. Can be mentioned.

  In order to impart excellent curability to the ink composition of the present invention, it is preferable to contain polyurethane (meth) acrylate as the polymerizable compound. The reason why the polymerizable compound containing polyurethane (meth) acrylate exhibits good curability is that the terminal double bond of polyurethane (meth) acrylate is close to the terminal double bond of general (meth) acrylate. It is thought that this is because the urethane bond is easily cleaved. In addition, the wear resistance is improved due to the characteristics of polyurethane.

  Polyurethane (meth) acrylate used for inkjet is low viscosity, or even if the viscosity of polyurethane (meth) acrylate itself is high due to crystallinity, etc., it is easily diluted with (meth) acrylate or organic solvent. It is necessary to reduce the viscosity. For this purpose, it is desirable to use polyurethane (meth) acrylate obtained by reacting polyisocyanate and monohydroxy (meth) acrylate without using polyol such as long-chain polyether and polyester.

  The polyurethane (meth) acrylate is preferably used in the range of 2 to 40% with respect to the total amount of the polymerizable compound in view of the viscosity and curability of the jet ink composition of the present invention.

  As the photopolymerization initiator for radically polymerizable jet ink used in the present invention, any known and conventional one that can cure the polymerizable compound to be used can be used, but as a particularly suitable initiator, a molecular cleavage type can be used. Alternatively, there is a hydrogen abstraction type photopolymerization initiator.

  As a photopolymerization initiator used in the present invention, benzoin isobutyl ether, 2.4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2.4.6-trimethylbenzoyldiphenylphosphine oxide, 6-trimethylbenzoyldiphenylphosphine oxide 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, bis (2,6-dimethoxybenzoyl) -2.4.4-trimethylpentylphosphine oxide, etc. are preferable. In addition to these, molecular cleavage types other than these include 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- ( 4- Sopropylphenyl) -2-hydroxy-2-methylpropan-1-one and 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one may be used in combination, and Benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4′-methyl-diphenyl sulfide, etc., which are hydrogen abstraction type photopolymerization initiators, can be used in combination.

  For the photopolymerization initiator, sensitizers such as trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N.I. An amine that does not cause an addition reaction with the polymerizable component, such as N-dimethylbenzylamine and 4.4′-bis (diethylamino) benzophenone, can also be used in combination. Of course, it is preferable to select and use the photopolymerization initiator and the sensitizer which are excellent in solubility in the polymerizable compound or a composition comprising these and do not inhibit the ultraviolet light transmittance. The photopolymerization initiator and the sensitizer are used in the range of 0.1 to 20% by mass, preferably 7 to 14% by mass, based on the total amount of the polymerizable compounds.

  As the cationic polymerizable compound used in the present invention, various known cationic polymerizable monomers can be used. For example, an epoxy compound, a vinyl ether compound, an oxetane compound, etc. are mentioned.

  Preferred examples of the aromatic epoxide include di- or polyglycidyl ether of bisphenol A or its alkylene oxide adduct, di- or polyglycidyl ether of hydrogenated bisphenol A or its alkylene oxide adduct, and novolak type epoxy resin. .

  Examples of the aliphatic epoxide include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or diglycidyl ether of alkylene glycol such as 1,6-hexanediol diglycidyl ether, diglycidyl or its alkylene oxide adduct di or Polyglycidyl ether of polyhydric alcohol such as triglycidyl ether, diglycidyl ether of polyethylene glycol or its alkylene oxide adduct, diglycidyl ether of polyalkylene glycol such as diglycidyl ether of polypropylene glycol or its alkylene oxide adduct, etc. It is done. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Examples of the vinyl ether compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, and trimethylol. Di- or trivinyl ether compounds such as propane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol monovinyl ether, n-pro Vinyl ether, isopropyl vinyl ether, isopropenyl ether -O- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

  Examples of oxetane compounds include compounds having an oxetane ring, such as 3-hydroxymethyl-3-methyloxetane, 3-hydroxymethyl-3-ethyloxetane, 3-hydroxymethyl-3-propyloxetane, and 3-hydroxymethyl. -3-normal butyl oxetane, 3-hydroxymethyl-3-phenyl oxetane, 3-hydroxymethyl-3-benzyl oxetane, 3-hydroxyethyl-3-methyl oxetane, 3-hydroxyethyl-3-ethyl oxetane, 3-hydroxy Ethyl-3-propyloxetane, 3-hydroxyethyl-3-phenyloxetane, 3-hydroxypropyl-3-methyloxetane, 3-hydroxypropyl-3-ethyloxetane, 3-hydroxypropyl-3-propyloxetane , 3-hydroxypropyl-3-phenyl oxetane, 3-hydroxybutyl-3-methyl oxetane, and the like.

  In the present invention, it contains at least one oxetane compound as a photopolymerizable compound and at least one compound selected from an epoxy compound and a vinyl ether compound from the viewpoint of reactivity, coating film shrinkage, and viscosity adjustment. Is preferred.

  The photocationic polymerization initiator that can be used in the present invention can be used without particular limitation as long as it is a conventionally known compound, and examples thereof include aromatic iodonium complex salts and aromatic sulfonium complex salts. These may be used alone, or two or more may be used in appropriate combination. Moreover, it is preferable to use the addition amount in the range of 0.01-20 weight% with respect to the total weight of an energy-beam curable cationic monomer, especially 0.1-10 weight%.

  Specific examples of the aromatic iodonium include diphenyliodonium, 4-methoxydiphenyliodonium, bis (4-methylphenyl) iodonium, bis (4-tert-butylphenyl) iodonium, bis (dodecylphenyl) iodonium, and the like. Specific examples of the aromatic sulfonium include triphenylsulfonium, diphenyl-4-thiophenoxyphenylsulfonium, bis [4- (diphenylsulfonio) -phenyl] sulfide, bis [4- (di (4- (2 -Hydroxyethyl) phenyl) sulfonio) -phenyl] sulfide, [eta] 5-2,4- (cyclopentagenyl) [1,2,3,4,5,6- [eta]]-(methylethyl) -benzene] -iron (1+) and the like.

Specific examples of the counter anion forming the complex salt include tetrafluoroborate (BF4−), hexafluorophosphate (PF6−), hexafluoroantimonate (SbF6−), hexafluoroarsenate (AsF6−), hexachloroantimonate ( SbCl6-) and the like.
(Anti-gelling agent)
The ink composition of the present invention can contain at least one kind of anti-gelling agent.

  Examples of the gelation inhibitor include phenolic hydroxyl group-containing compounds, quinones, N-oxide compounds, piperidine-1-oxyl free radical compounds, pyrrolidine-1-oxyl free radical compounds, N-nitrosophenylhydroxylamine And compounds selected from the group consisting of cationic dyes.

  Specifically, haloquinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, resorcinol, catechol, t-butylcatechol, hydroquinone monoalkyl ether (for example, hydroquinone monomethyl ether, hydroquinone monobutyl ether), Benzoquinone, 4,4-thiobis (3-methyl-6-tert-butylphenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2,2,6,6-tetramethylpiperidine and its Derivatives, di-t-butyl nitroxide, 2,2,6,6-tetramethylpiperidine-N-oxide and derivatives thereof, piperidine 1-oxyl free radical, 2,2,6,6-tetramethylpiperidine-oxyl free Radical, 4- Xo-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-acetamido-2,2,6 6-tetramethylpiperidine 1-oxyl free radical, 4-maleimido-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-phosphonoxy-2,2,6,6-tetramethylpiperidine 1-oxyl Free radical, 3-carboxy-2,2,5,5-tetramethylpyrrolidine 1-oxyl free radical, N-nitrosophenylhydroxylamine cerium salt, N-nitrosophenylhydroxylamine aluminum salt, crystal violet, methyl violet, Ethyl violet , And Victoria Pure Blue BOH.

  In this embodiment, the ink composition contains a hindered amine compound having a 2,2,6,6-tetramethylpiperidinyl group as an anti-gelling agent. If the hindered amine compound is used as an anti-gelling agent together with a high curing sensitivity polymerizable compound and a photopolymerization initiator, an ink composition having excellent storage stability can be obtained without reducing the curing sensitivity of the ink composition. Obtainable. Specific examples of the anti-gelling agent include bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate and bis (2,2,6) decanedioate. , 6-tetramethyl-1- (octyloxy) -4-piperidinyl) ester, etc. Among these, bis (1 having a 1-hydroxy-2,2,6,6-tetramethylpiperidinyl group is included. -Oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate is preferred. Examples of the anti-gelling agent available on the market include IRGASTAB UV-10 and TINUVIN 123 manufactured by Ciba.

  The amount of the anti-gelling agent in the ink composition is not particularly limited, but is preferably 0.01 to 3% by mass, more preferably 0.05 to 2% by mass with respect to the entire composition. . When the amount of the gelling inhibitor is less than 0.01% by mass, radicals generated during storage cannot be sufficiently captured, and the storage stability tends to decrease. On the other hand, when the amount of the anti-gelling agent is more than 3% by mass, the effect of capturing radicals is saturated and the polymerization reaction at the time of irradiation with energy rays tends to be inhibited.

  The energy ray curable ink composition may further contain other conventionally known gelling agents such as other hindered amine stabilizers, phenolic antioxidants, phosphorus antioxidants, hydroquinone monoalkyl ethers, and the like. . Specific examples of such an antigelling agent include hydroquinone monomethyl ether, hydroquinone, t-butylcatechol, pyrogallol, TINUVIN 111 FDL, TINUVIN 144, TINUVIN 292, TINUVIN XP40, and TINUVIN XP60 manufactured by Ciba. Is mentioned. The amount of the gelation inhibitor in the ink composition is not particularly limited, but is preferably 0.1 to 4% by mass with respect to the entire composition.

  As the pigment dispersant, an ionic or nonionic surfactant or an anionic, cationic or nonionic polymer compound is preferably used. Among these, a polymer compound having a cationic group or an anionic group is more preferable from the viewpoint of dispersion stability, water resistance, squeezing resistance, and the like. Specific examples of the pigment dispersant as described above include SOLPERSE manufactured by Lubrizol, DISPERBYK manufactured by Big Chemie, and EFKA manufactured by Fuka Additives.

  In addition to the phthalocyanine pigment and the polymerizable compound, the energy ray curable inkjet ink composition of the present embodiment includes, as necessary, an organic solvent, a pigment dispersant, a fixing resin, a surfactant, and a surface conditioner. Agent, leveling agent, antifoaming agent, antioxidant, pH adjusting agent, charge imparting agent, bactericidal agent, antiseptic, deodorant, charge adjusting agent, wetting agent, anti-skinning agent, UV absorber, fragrance, pigment derivative For example, a known additive may be blended.

As a method for preparing the energy beam curable inkjet ink composition of the present embodiment, a conventionally known method can be used. The following preparation methods are mentioned as a preferable preparation method.
(How to adjust UV ink)
First, a pigment dispersion is prepared by dispersing a phthalocyanine pigment, a polymer compound (pigment dispersant), a part of a polymerizable compound / polymerization inhibitor, and optionally other optional components. Examples of the disperser include a container drive medium mill such as a ball mill, a centrifugal mill, a planetary ball mill, and a paint shaker; a high-speed rotating mill such as a sand mill; a medium agitation mill such as a stirring tank mill; a disper and the like.

  Next, the remaining polymerizable compound, polymerizable inhibitor, and polymerizable initiator are further added to the obtained pigment dispersion and mixed uniformly using a stirrer. Specific examples of the stirrer include a three-one motor, a magnetic stirrer, a disper, and a homogenizer. Moreover, you may use mixers, such as a line mixer. Furthermore, a dispersing machine such as a bead mill or a high-pressure jet mill may be used for the purpose of further reducing the particles in the ink composition.

  The energy ray curable inkjet ink composition thus prepared preferably has a surface tension of 20 to 40 mN / m (25 ° C.), and has a viscosity of 5 to 40 mPa · s (25 ° C.). Is preferred. When the surface tension and viscosity are set within the above ranges, when used as an ink-jet ink, excellent jetting with little jet bending is obtained, and bleeding when printed on a substrate such as plain paper or matte paper is obtained. Can be suppressed. Moreover, the dispersion average particle diameter of the phthalocyanine pigment in the energy ray curable inkjet ink composition is preferably 20 to 250 nm, and more preferably 100 to 200 nm. When the dispersion average particle diameter is less than 20 nm, the light resistance of the printed matter may be deteriorated because the particles are fine. On the other hand, if the dispersion average particle diameter exceeds 250 nm, the fineness of the printed matter may be lowered. Furthermore, in order to prevent clogging, the maximum dispersed particle diameter is preferably 1,000 nm or less. The surface tension, viscosity, dispersion average particle diameter, and maximum dispersion particle diameter described above can be easily adjusted by changing the type and content of each component.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Hereinafter, “parts” means “parts by mass”. In addition, the apparatus used in the following Example used what was previously wash | cleaned with the pure water in order to exclude the influence of an ionic substance.

<Preparation of phthalocyanine pigment>
A commercially available phthalocyanine pigment (a) (manufactured by Clariant, copper phthalocyanine pigment, HOSTAPERM BLUE P-BFS) was prepared. 100 parts of this phthalocyanine pigment (a) and 500 parts of pure water (ion concentration: 0 ppm, specific conductivity: 0 μS / m) were put into a 1,000 cc plastic disposable cup, and this was added to a room temperature (25 The phthalocyanine pigments (a) to (e) having different numbers of washings were prepared by repeating the washing step of stirring and filtering at 10 [deg.] C. for 10 minutes and sucking and filtering the mixed solution using filter paper (pore size: 1 [mu] m).

  The specific conductivity of each phthalocyanine pigment obtained as described above was measured as follows. Table 1 shows the results.

[Specific conductivity of phthalocyanine pigments]
3 parts of phthalocyanine pigment and 60 parts of pure water (ion concentration: 0 ppm, specific conductivity: 0 μS / m) were put into a 200 cc beaker, and this was put into an oil bath (manufactured by Riko Kagaku Sangyo Co., Ltd., MH-5H). Heated and boiled for 5 minutes. After natural cooling, the solution was filtered using a syringe filter (manufactured by Millipore Corporation, a syringe filter provided with filters of 5 μm, 0.45 μm, and 0.2 μm in order). The filtrate was measured with a compact conductivity meter (manufactured by HORIBA, model B-173), and the specific conductivity obtained was defined as the specific conductivity of the phthalocyanine pigment.

<Preparation of ink>
Example 1
Each component is weighed in a 250 cc plastic bottle at the blending amount shown in Table 2 below, and 100 parts of zirconia beads (diameter: 0.3 mmφ) are added to the bottle and dispersed for 1 hour with a paint conditioner (manufactured by Toyo Seiki Co., Ltd.). Thus, a pigment dispersion (A) was prepared.

  Next, each component was weighed in a 100 cc plastic bottle at the blending amounts shown in Table 3 below, and the solution was stirred with a magnetic stirrer for 30 minutes, followed by suction filtration using a glass filter (manufactured by Kiriyama Seisakusho). Ink was prepared.

(Example 2)
A pigment dispersion (II) was prepared in the same manner as in Example 1 except that the phthalocyanine pigment (d) was used as the pigment in Example 1. An ink was prepared in the same manner as in Example 1 except that this pigment dispersion (II) was used.

(Example 3)
A pigment dispersion (III) was prepared in the same manner as in Example 1, except that the phthalocyanine pigment (c) was used as the pigment in Example 1. An ink was prepared in the same manner as in Example 1 except that this pigment dispersion (III) was used.

(Comparative Example 1)
A pigment dispersion (VI) was prepared in the same manner as in Example 1, except that the phthalocyanine pigment (a) was used as the pigment in Example 1. An ink was prepared in the same manner as in Example 1 except that this pigment dispersion (VI) was used.

(Comparative Example 2)
A pigment dispersion (VII) was prepared in the same manner as in Example 1 except that the phthalocyanine pigment (b) was used as the pigment in Example 1. An ink was prepared in the same manner as in Example 1 except that this pigment dispersion (VII) was used.

  The following evaluation was performed for each ink of the examples and comparative examples prepared as described above.

[Monovalent cation concentration and specific conductivity]
While stirring 34 parts of pure water (ion concentration: 0 ppm, specific conductivity: 0 μS / m) with a magnetic stirrer, 6 parts of ink was slowly dropped into pure water and further stirred at room temperature (25 ° C.) for 30 minutes. . After the solution was filtered using a membrane filter (pore size: 0.65 μm), the concentration of sodium ions in the obtained filtrate (aqueous phase) was measured with a compact sodium ion meter (HORIBA, model C-122). The concentration of each ion was measured with a compact potassium ion meter (HORIBA, model C-131), and each measured value was divided by the ink concentration (0.15) in the solution and converted to 100 parts of ink. The cation concentration was determined. Further, the specific conductivity of the filtrate (aqueous phase) was measured with a compact conductivity meter (HORIBA, model B-173), and the measured value was divided by the ink concentration (0.15) in the solution to obtain ink 100. Specific conductivity when converted to parts was determined.

[Storage stability]
A storage acceleration test was conducted in which the ink was filled in a 30 cc glass bottle and stored in a thermostat at 70 ° C. for one week. After the storage, the presence or absence of precipitates in the ink was visually observed, and the case where no precipitation of precipitates occurred was evaluated as ◯, and the case where precipitates were generated was evaluated as ×.

(Filter permeability)
The ink after storage evaluated based on the storage stability was passed through a filter (pore diameter: 10 μm), and the filter permeability was evaluated according to the following criteria.

○: No filter clogging ×: Filter clogged and ink did not pass through Table 6 shows the types of phthalocyanine pigments used in each Example and Comparative Example and the evaluation results.

  As shown in the above table, when the ions in the ink are phase-shifted to pure water, the total concentration of sodium ions and potassium ions in the aqueous phase is 20 ppm or less, and the specific conductivity of the aqueous phase is 50 μS / m or less. It can be seen that the ink does not generate precipitates and can be ejected stably even after storage. This is presumably because sodium ions and potassium ions, which are monovalent cations that generate precipitates in the ink, are small, and the amount of ionic substances in the entire ink is small.

  On the other hand, it can be seen that the ink of the comparative example containing sodium ions and potassium ions at high concentrations produces precipitates and is inferior in storage stability. For this reason, it can be seen that these inks are clogged even with a large pore size filter after storage. In addition, even when the phthalocyanine pigment is washed and the concentration of sodium ions and potassium ions in the ink is decreased, precipitates are generated when the total concentration exceeds 20 ppm. In addition, even in the conventional ink having improved storage stability, when the total concentration of sodium ions and potassium ions is high, precipitates are similarly generated, indicating that the storage stability is poor.

Claims (3)

  An energy beam curable inkjet ink composition comprising at least a phthalocyanine pigment, a polymerizable compound, a dispersant, and a polymerization initiator, wherein when the ions in the energy beam curable inkjet ink composition are phase-shifted into pure water, An energy ray-curable inkjet ink composition, wherein the total concentration of monovalent cations in the phase is 20 ppm or less.   The energy ray curable inkjet ink composition according to claim 1, wherein the aqueous phase contains one or both of sodium ions and potassium ions as the monovalent cation.   The energy ray-curable inkjet ink composition according to claim 1 or 2, wherein the water phase has a specific conductivity of 50 µS / cm or less.