JP2018123188A - Oily inkjet ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oily inkjet ink that reduces wetting of a nozzle plate, improves image density, and prevents the strike-through phenomenon.SOLUTION: An oily inkjet ink contains a pigment, a water-insoluble resin, a water-soluble resin containing an amino group, a monovalent or bivalent metal salt of an aliphatic monocarboxylic acid, and a nonaqueous solvent.SELECTED DRAWING: None

Description

  The present invention relates to an oil-based inkjet ink.

  The ink jet recording method is a method in which ink jet ink having high fluidity is ejected as droplets from fine nozzles, and an image is recorded on a recording medium placed facing the nozzles, and high speed printing can be performed with low noise. Therefore, it has been spreading rapidly in recent years. As an ink used for such an ink jet recording system, a so-called non-aqueous ink containing a non-aqueous solvent as a main solvent is known. Non-aqueous inks can be classified into solvent ink (solvent ink) whose main solvent is a volatile organic solvent, and oil ink (oil ink) whose main solvent is a low-volatile or nonvolatile organic solvent. The oil-based ink is dried mainly by penetrating into the recording medium.

  Patent Document 1 discloses a non-aqueous pigment ink containing a pigment, a non-aqueous solvent, a non-water-soluble resin, and a water-soluble resin in order to provide an ink capable of suppressing the show-through and achieving a high printing density. An ink using polyethyleneimine as a water-soluble resin has been proposed.

  Patent Document 2 proposes an ink containing a fatty acid or an alkyl phosphate ester and an amine compound as an ink in which wetting to the nozzle plate is suppressed. Patent Document 3 proposes an ink containing an ionic substance such as a quaternary ammonium salt such as tetrabutylammonium bromide as an ink with little adhesion to the nozzle plate.

JP 2014-15491 A JP 2011-052073 A JP 2011-127091 A

  Ink using a water-soluble resin containing an amino group such as polyethyleneimine may cause nozzle plate wetting.

  Accordingly, an object of the present invention is to provide an oil-based inkjet ink that can reduce wetting to a nozzle plate, increase image density, and reduce back-through.

  According to one aspect of the present invention, a pigment, a water-insoluble resin, a water-soluble resin containing an amino group, a monovalent or divalent metal salt of an aliphatic monocarboxylic acid, and a non-aqueous solvent are contained. An oil-based inkjet ink is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the oil-based inkjet ink which can reduce the wetting to a nozzle plate, can raise an image density, and can reduce a back-through can be provided.

  Although one embodiment of the present invention is described below, the present invention is not limited to the following embodiment.

  The oil-based inkjet ink of the embodiment (hereinafter also referred to as “ink” or “oil-based ink”) is a pigment, a water-insoluble resin, a water-soluble resin having an amino group, and an aliphatic monocarboxylic acid. It contains at least a valent or divalent metal salt and a non-aqueous solvent.

  As the pigment, organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, dyed lake pigments, and inorganic pigments can be used. Examples of the azo pigment include a soluble azo lake pigment, an insoluble azo pigment, and a condensed azo pigment. Examples of phthalocyanine pigments include metal phthalocyanine pigments and metal-free phthalocyanine pigments. Polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments. And diketopyrrolopyrrole (DPP). Representative examples of inorganic pigments include carbon black and titanium oxide. These pigments may be used alone or in combination of two or more.

  The content of the pigment in the ink may be usually 0.01 to 20% by mass, preferably 1 to 15% by mass from the viewpoint of printing density and ink viscosity, and 5 to 12% by mass. Is more preferable.

As the water-insoluble resin, the solubility of the resin in water at 23 ° C. is preferably 1 g / 100 g or less, more preferably 0.5 g / 100 g or less, and 0.1 g / 100 g or less. More preferred.
The water-insoluble resin is preferably dispersed or dissolved in a non-aqueous solvent for ink.

Examples of the water-insoluble resin include (meth) acrylic resins, urethane resins, and polyester resins.
The weight average molecular weight of the water-insoluble resin is preferably from 6000 to 80000, and more preferably from 8000 to 50000.

  The weight average molecular weight of the resin is a value in terms of polystyrene by gel permeation (GPC) method. The same applies hereinafter.

  The water-insoluble resin may be either a homopolymer or a copolymer. When the water-insoluble resin is a copolymer, the copolymerization type is not particularly limited. For example, the water-insoluble resin may be a random polymer.

The water-insoluble resin preferably has a functional group having an affinity for a non-aqueous solvent. Thereby, the water-insoluble resin can be dispersed or dissolved in the non-aqueous solvent to improve the ink storage stability.
Examples of the functional group having affinity for the non-aqueous solvent include an alkyl group having 8 or more carbon atoms (more preferably 8 to 22 carbon atoms). Examples of the alkyl group having 8 or more carbon atoms include linear alkyl groups having 12 or more carbon atoms (more preferably 12 to 22 carbon atoms) (for example, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group). Group, octadecyl group, nonadecyl group, icosanyl group, heicosanyl group, docosanyl group, and the like, and a branched alkyl group having 8 or more carbon atoms (more preferably, 8 to 22 carbon atoms) (isooctyl group, 2-ethylhexyl group, Isostearyl group, tert-octyl group, etc.).

The water-insoluble resin preferably has a functional group having affinity for the pigment. As a result, the water-insoluble resin is oriented to the pigment, and the pigment can be provided with dispersibility.
Examples of functional groups having affinity for the pigment include diketone groups (more preferably β-diketone groups), keto acid ester groups (more preferably β-keto acid ester groups), glycidyl groups, aromatic ring-containing groups, and the like. Can be mentioned.
Examples of the diketone group or keto acid ester group include an acetoacetyl group, a propionacetyl group, an acetoacetoxy group, and a propionacetoxy group.
The aromatic ring-containing group preferably has a benzene ring, and examples thereof include a benzyl group and a phenyl group.
A functional group having an affinity for a pigment often has a high affinity for a water-soluble resin. Therefore, the water-insoluble resin is also oriented in the water-soluble resin droplets dispersed in the ink, and can impart dispersibility to the water-soluble resin droplets.

  The ratio between the structural unit containing a functional group having affinity for the non-aqueous solvent and the structural unit containing a functional group having affinity for the pigment is not particularly limited. For example, the mass ratio of the monomer containing a functional group having an affinity for a non-aqueous solvent and the monomer containing a functional group having an affinity for a pigment is preferably 4: 6 to 9.5: 0.5. 5-9: 1 is more preferable, for example, 7: 3 may be sufficient.

Preferred water-insoluble resins include, for example, units having an alkyl group having 8 to 18 carbon atoms and units having a group selected from the group consisting of a diketone group, a ketoester group, a glycidyl group, and a benzyl group. Copolymer, more preferably a copolymer comprising a unit having an alkyl group having 8 to 18 carbon atoms, a unit having a β-diketone group and / or a β-keto ester group, and a unit having a glycidyl group Is mentioned.
A copolymer containing a unit having an alkyl group having 8 to 18 carbon atoms, a unit having a β-diketone group and / or a β-keto ester group, and a unit having a glycidyl group is, for example, from 8 to 8 carbon atoms. Monomer mixture comprising alkyl (meth) acrylate A having 18 alkyl groups, (meth) acrylate B having β-diketone group and / or β-keto ester group, and (meth) acrylate C having glycidyl group Can be obtained by copolymerization.

  Examples of the alkyl (meth) acrylate A having an alkyl group having 8 to 18 carbon atoms include palmityl / stearyl methacrylate (C16 / C18), cetyl acrylate (C16), dodecyl methacrylate (C12), dodecyl acrylate (C12), 2 -Ethylhexyl methacrylate (C8), 2-ethylhexyl acrylate (C8) are mentioned. These can be used alone or in combination of two or more.

  Examples of the (meth) acrylate B having a β-diketone group and / or a β-keto acid ester include (meth) acrylate and (meth) acrylamide having a β-diketone group or a β-keto acid ester group in the ester chain. A preferred example is given. More specifically, acetoacetoxyalkyl (meth) acrylates such as acetoacetoxyethyl (meth) acrylate, acetoacetoxyalkyl (meth) acrylamides such as hexadione (meth) acrylate, acetoacetoxyethyl (meth) acrylamide, and the like can be mentioned. These may be used alone or in combination of two or more.

  Examples of (meth) acrylate C having a glycidyl group include glycidyl (meth) acrylate. These can be used alone or in combination of two or more.

  An alkyl (meth) acrylate A having an alkyl group having 8 to 18 carbon atoms, a (meth) acrylate B having a β-diketone group and / or a β-keto ester group, and a (meth) acrylate C having a glycidyl group, The mixing ratio is preferably 100: 1 to 100: 1 to 50, more preferably 100: 1 to 50: 1 to 10, as a mass ratio.

  Other examples of the water-insoluble resin include, for example, a hydroxyl group-containing carboxylic acid ester, a salt of a long chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a salt of a long chain polyaminoamide and a polar acid ester, High molecular weight unsaturated acid ester, copolymer of vinyl pyrrolidone and long chain alkene, modified polyurethane, modified polyacrylate, polyether ester type anionic activator, polyoxyethylene alkyl phosphate ester, polyester polyamine and the like.

The water-insoluble resin is preferably 0.5 to 10% by mass and more preferably 1 to 5% by mass with respect to the total amount of ink from the viewpoints of ink viscosity and storage stability.
From the viewpoint of pigment dispersibility, the water-insoluble resin is preferably about 0.01 to 1 and more preferably 0.1 to 0.5 with respect to the pigment 1 in terms of mass ratio.

As a water-soluble resin having an amino group, the solubility of the resin in water at 23 ° C. is preferably 5 g / 100 g or more, and more preferably 20 g / 100 g or more.
The water-soluble resin having an amino group has low compatibility with the non-aqueous solvent of the ink and is preferably dispersed in the form of droplets in the non-aqueous solvent of the ink.

The water-soluble resin having an amino group can have a primary amino group, a secondary amino group, a tertiary amino group, or a combination thereof as an amino group.
The water-soluble resin having an amino group preferably has a primary amino group and / or a secondary amino group.
The number average molecular weight of the water-soluble resin having an amino group is preferably 500 or more, and more preferably 600 or more. The number average molecular weight of the water-soluble resin having an amino group is preferably 15000 or less.

  It is considered that the ink containing a water-soluble resin having an amino group contributes to an improvement in image density and a reduction in show-through. The reason for this may be that when a pigment having an acidic group is used, the amino group of the water-soluble resin having an amino group is bonded to the acidic group on the pigment surface. In addition, since the water-soluble resin has low compatibility with the non-aqueous solvent, it may be considered that the pigment is prevented from penetrating into the paper together with the non-aqueous solvent after the ink has landed on the recording medium. .

  Examples of the water-soluble resin having an amino group include polyethyleneimine, polyvinylamine, polyvinylpyridine, and polyvinylpyrrolidone derivatives.

The water-soluble resin having an amino group is preferably polyethyleneimine or a derivative thereof.
Polyethyleneimine has a structure in which ethyleneimine is ring-opening polymerized. Polyethyleneimine has a primary amine, a secondary amine, and a tertiary amine in one molecule, and has a high cation density. Therefore, it is easy to obtain an effect of improving the image density and reducing the show-through.

  As the polyethyleneimine, commercially available products can be used. For example, SP-006, SP-012, SP-018, SP-200 manufactured by Nippon Shokubai Co., Ltd. Lupasol FG, Lupasol G20 Waterfree manufactured by BASF Corp. And Lupasol PR8515.

The water-soluble resin having an amino group is preferably 0.1% by mass or more and more preferably 1% by mass or more with respect to the total amount of ink from the viewpoint of printing density. Further, from the viewpoint of ink viscosity and storage stability, it is preferably 10% by mass or less, more preferably 5% by mass or less, based on the total amount of ink.
From the viewpoint of printing density, the water-soluble resin having an amino group is preferably 0.01 or more and more preferably 0.1 or more with respect to the pigment 1 in terms of mass ratio. Further, from the viewpoint of storage stability, the mass ratio is preferably 1 or less and more preferably 0.5 or less with respect to the pigment 1.
From the viewpoint of printing density, the water-soluble resin having an amino group is preferably 0.05 or more and more preferably 0.2 or more with respect to the water-insoluble resin 1 in terms of mass ratio. From the viewpoint of storage stability, the mass ratio is preferably 2 or less and more preferably 1 or less with respect to the water-insoluble resin 1.

The monovalent or divalent metal salt of the aliphatic monocarboxylic acid will be described.
In oil-based inkjet inks, a water-soluble resin having an amino group can contribute to an improvement in image density and a reduction in show-through. On the other hand, since the water-soluble resin having an amino group is cationic, it has a high affinity with the nozzle plate, and thus the nozzle plate is likely to be wetted.
However, by using a monovalent or divalent metal salt of an aliphatic monocarboxylic acid together with a water-soluble resin having an amino group, the occurrence of nozzle plate wetting can be reduced while improving image density and reducing back-through. Can do.
The reason why the monovalent or divalent metal salt of the aliphatic monocarboxylic acid can reduce the wetting of the nozzle plate is that the monovalent or divalent metal salt of the aliphatic monocarboxylic acid is an amino The affinity between the water-soluble resin having a group and the nozzle plate can be reduced. Further, from the viewpoint of improving the image density, the metal salt is preferably a monovalent or divalent metal salt.
As a method of reducing nozzle plate wetting, there is a method of adding a quaternary ammonium salt such as tetrabutylammonium bromide to the ink. When a quaternary ammonium salt is added, the image density tends to decrease, but when a monovalent or divalent metal salt of an aliphatic monocarboxylic acid is used, image deterioration can be prevented.

In the monovalent or divalent metal salt of the aliphatic monocarboxylic acid, the aliphatic monocarboxylic acid may be a linear or branched aliphatic monocarboxylic acid, and an aliphatic monocarboxylic acid having an alicyclic structure. It may be an acid. The aliphatic monocarboxylic acid is preferably a saturated aliphatic monocarboxylic acid from the viewpoint of the storage stability of the ink.
5-18 are preferable and, as for carbon number of aliphatic monocarboxylic acid, 8-14 are more preferable.

  Examples of the linear aliphatic monocarboxylic acid include octanoic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, and stearic acid, and examples of the aliphatic monocarboxylic acid having a branched chain include 2- Examples include ethylhexanoic acid, isononanoic acid, isododecanoic acid, isomyristic acid, isopalmitic acid, and isostearic acid. Examples of the aliphatic monocarboxylic acid having an alicyclic structure include naphthenic acid. Of these, myristic acid, 2-ethylhexanoic acid, and naphthenic acid are preferable.

In the monovalent or divalent metal salt of the aliphatic monocarboxylic acid, examples of the metal salt include monovalent metals such as Li, Na, K, Rb, Cs, Fr, silver, copper (I), and mercury (I). Salts of divalent metals such as Mg, Ca, Sr, Ba, Ra, zinc (II), manganese (II), cobalt (II), iron (II), copper (II), mercury (II), lead Mention may be made of salts.
Of these, salts of divalent metals are preferred.

  Examples of monovalent or divalent metal salts of aliphatic monocarboxylic acids include zinc 2-ethylhexanoate, cobalt 2-ethylhexanoate, manganese 2-ethylhexanoate, lead 2-ethylhexanoate, 2-ethylhexane. Calcium oxide, barium 2-ethylhexanoate, sodium 2-ethylhexanoate, potassium 2-ethylhexanoate, manganese naphthenate, cobalt naphthenate, lead naphthenate, zinc naphthenate, calcium naphthenate, copper naphthenate, naphthenic acid Examples thereof include iron, barium naphthenate, lithium naphthenate, sodium myristate, and potassium myristate.

The monovalent or divalent metal salt of the aliphatic monocarboxylic acid may be, for example, 50 mass ppm or more with respect to the total amount of the ink. From the viewpoint of improving the image density, 150 mass ppm or more is preferable, and 200 mass ppm or more is preferable. Is more preferable. The monovalent or divalent metal salt of the aliphatic monocarboxylic acid may be, for example, 10000 mass ppm or less with respect to the total amount of the ink, and is preferably 2500 mass ppm or less from the viewpoint of improving the image density, and is preferably 1500 mass ppm or more. Is more preferable.
The monovalent or divalent metal salt of the aliphatic monocarboxylic acid may be, for example, 0.001 or more in terms of mass ratio with respect to the water-soluble resin 1, and is 0.005 or more from the viewpoint of improving image density. It is preferable that it is 0.01 or more. In addition, the monovalent or divalent metal salt of the aliphatic monocarboxylic acid may be, for example, 0.5 or less with respect to the water-soluble resin 1 in terms of mass ratio. From the viewpoint of improving the image density, 0.2. The following is preferable, and 0.1 or less is more preferable.

  As the non-aqueous solvent, any of a non-polar organic solvent and a polar organic solvent can be used. These may be used alone or in combination. In the present invention, as the non-aqueous solvent, it is preferable to use a water-insoluble organic solvent that is not uniformly mixed with the same volume of water at 1 atm.

  Preferable examples of the nonpolar organic solvent include petroleum hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents. Examples of the aliphatic hydrocarbon solvent and the alicyclic hydrocarbon solvent include non-aqueous solvents such as paraffinic, isoparaffinic, and naphthenic solvents, and commercially available products include 0 Solvent L, 0 Solvent M, 0 Solvent H, Cactus normal paraffin N-10, Cactus normal paraffin N-11, Cactus normal paraffin N-12, Cactus normal paraffin N-13, Cactus normal paraffin N-14, Cactus normal paraffin N-15H, Cactus normal paraffin YHNP Cactus normal paraffin SHNP, Isosol 300, Isosol 400, Teclean N-16, Teclean N-20, Teclean N-22, AF Solvent No. 4, AF Solvent No. 5, AF Solvent No. 6, AF Solvent No. 7, Futezol 160, Naphthezol 200, Naphthezol 220 (all trade names manufactured by JX Energy Corporation); Isopar G, Isopar H, Isopar L, Isopar M, Exol D40, Exor D60, Exor D80, Exor D95, Exor D110, Exor D130 (Both are trade names manufactured by TonenGeneral Sekiyu KK) and the like. As the aromatic hydrocarbon solvent, grade alkene L, grade alkene 200P (all are trade names made by JX Energy Co., Ltd.), Solvesso 100, Solvesso 150, Solvesso 200, Solvesso 200ND (all are products made by TonenGeneral Sekiyu KK) Name) etc. can be mentioned preferably. The distillation initial boiling point of the petroleum hydrocarbon solvent is preferably 100 ° C. or higher, more preferably 150 ° C. or higher, and even more preferably 200 ° C. or higher. The distillation initial boiling point can be measured in accordance with JIS K0066 “Method for Distillation Test of Chemical Products”.

  Preferred examples of the polar organic solvent include fatty acid ester solvents, higher alcohol solvents, higher fatty acid solvents and the like. For example, isononyl isononanoate, isodecyl isononanoate, methyl laurate, isopropyl laurate, hexyl laurate, isopropyl myristate, isopropyl palmitate, hexyl palmitate, isooctyl palmitate, isostearyl palmitate, methyl oleate, ethyl oleate , Isopropyl oleate, butyl oleate, hexyl oleate, methyl linoleate, ethyl linoleate, isobutyl linoleate, butyl stearate, hexyl stearate, isooctyl stearate, isopropyl isostearate (, 2-octyldecyl pivalate, large Fatty acid ester having 13 or more, preferably 16 to 30 carbon atoms in one molecule, such as soybean oil methyl, soybean oil isobutyl, tall oil methyl, tall oil isobutyl, etc. Solvent; higher alcohol solvent having 6 or more, preferably 12 to 20 carbon atoms in one molecule, such as isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol, isoeicosyl alcohol, decyltetradecanol; Higher fatty acid solvents such as lauric acid, isomyristic acid, palmitic acid, isopalmitic acid, α-linolenic acid, linoleic acid, oleic acid, isostearic acid and the like having 12 or more, preferably 14 to 20 carbon atoms in one molecule The boiling point of polar organic solvents such as fatty acid ester solvents, higher alcohol solvents and higher fatty acid solvents is preferably 150 ° C. or higher, more preferably 200 ° C. or higher, and 250 ° C. or higher. It is more preferable that the non-aqueous solvent has a boiling point of 250 ° C. or higher. Includes a non-aqueous solvent that does not exhibit a boiling point.

  These non-aqueous solvents may be used alone or in combination of two or more as long as a single phase is formed. Moreover, you may include another organic solvent in the range which can form a single phase with the non-aqueous solvent to be used.

  In addition to the above components, the oil-based ink may contain other additives as long as the effects of the present invention are not impaired. Additives include surfactants (eg, anionic, cationic, amphoteric or nonionic surfactants), antioxidants (eg, dibutylhydroxytoluene, propyl gallate, tocopherol, butylhydroxyanisole, and nordihydrogua Yaletic acid) and the like.

  In the case of an ink jet recording system, the viscosity of the ink varies depending on the nozzle diameter of the ejection head, the ejection environment, and the like, but in general, it is preferably 5 to 30 mPa · s at 23 ° C., preferably 5 to 15 mPa · s. It is more preferable that the pressure is about 10 mPa · s, which is suitable for an inkjet recording apparatus.

  The method for preparing the oil-based ink is not particularly limited, and the oil-based ink can be prepared by mixing a non-aqueous solvent with a pigment and, if necessary, other components.

  The manufacturing method of the printed matter using oil-based inkjet ink is not specifically limited. The method for producing a printed material is preferably, for example, a method including applying the ink of the embodiment to a recording medium by an inkjet recording method. The ink jet recording apparatus to be used may be of any system such as a piezo system, an electrostatic system, or a thermal system. In the case of using an ink jet recording apparatus, for example, the ink of the embodiment may be ejected from an ink jet head based on a digital signal, and the ejected ink droplets may be attached to a recording medium.

  In the present embodiment, the recording medium is not particularly limited, and printing paper such as plain paper, coated paper, special paper, cloth, inorganic sheet, film, OHP sheet, etc., and these are used as a base material and an adhesive layer on the back surface An adhesive sheet or the like provided with can be used. Among these, printing paper such as plain paper and coated paper can be preferably used from the viewpoint of ink permeability.

  Here, the plain paper is paper in which an ink receiving layer, a film layer, and the like are not formed on normal paper. Examples of plain paper include high quality paper, medium quality paper, PPC paper, reprinted paper, recycled paper, and the like. Plain paper is a paper in which ink easily penetrates because paper fibers having a thickness of several μm to several tens of μm form voids of several tens to several hundreds of μm.

  As the coated paper, matte paper, glossy paper, semi-glossy paper or other inkjet coated paper, or so-called coated printing paper can be preferably used. Here, the coated printing paper is a printing paper conventionally used in letterpress printing, offset printing, gravure printing, etc., and has an inorganic pigment such as clay or calcium carbonate on the surface of high-quality paper or medium-quality paper. A printing paper provided with a coating layer by a paint containing a binder such as starch. Coated printing paper can be applied to fine coated paper, high-quality lightweight coated paper, medium-weight lightweight coated paper, high-quality coated paper, medium-quality coated paper, art paper, cast coated paper, etc., depending on the coating amount and coating method. being classified.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[Preparation of water-insoluble resin]
Resin solution a containing water-insoluble resin A was produced as follows.
87.5% by mass of isodecyl isononanoate (manufactured by Higher Alcohol Industry Co., Ltd.) was charged, and heated to 110 ° C. while agitating with nitrogen gas. Next, 16.7% by mass of isodecyl isononanoate in 100.0% by mass of the monomer mixture having the composition shown in Table 1 below, perbutyl O (t-butylperoxy 2-ethylhexanoate (manufactured by NOF Corporation) ) Was mixed 4% by mass, and the resulting mixture was added dropwise over 3 hours. After stirring at 110 ° C. for 1 hour, 0.2% by mass of perbutyl O was added, and further stirred for 1 hour to obtain a resin solution a having a water-insoluble resin A (solid content) of 50% by mass.
The weight average molecular weight (GPC method, standard polystyrene conversion) of the water-insoluble resin A of the obtained resin solution a was 9000 to 12000.

[Preparation of ink]
The mixture shown in Tables 2 and 3 was mixed for 15 minutes with a bead mill (Dynomill KDL-A, manufactured by Shinmaru Enterprises Co., Ltd.) filled with zirconia beads (diameter 0.5 mm) at a filling rate of 85%. By dispersing under conditions, inks of Examples 1 to 10 and Comparative Examples 1 to 6 were produced.

In Tables 2 and 3, the numbers shown for each component indicate “% by mass”. Each component shown in Tables 2 and 3 is as follows.
<Pigment>
・ Carbon black 1: NEROX600, manufactured by Orion Engineered Carbons ・ Carbon black 2: MA8, manufactured by Mitsubishi Chemical Corporation

<Water-insoluble resin>
Resin solution a: Water-insoluble resin A Solid content 50% by mass, the resin solution a
<Water-soluble resin>
Polyethyleneimine: Epomin SP-200, number average molecular weight 10,000, manufactured by Nippon Shokubai Co., Ltd. <Non-aqueous solvent>
-Isodecyl isononanoate: Fatty acid ester solvent, manufactured by Higher Alcohol Industry Co., Ltd.-Isopalmityl alcohol: Lisonol 16SP, higher alcohol solvent, manufactured by Higher Alcohol Industry Co., Ltd.-Naphthenic solvent: Exol D-80, petroleum hydrocarbon Solvent, manufactured by TonenGeneral Sekiyu KK

<Aliphatic monocarboxylic acid metal salt>
・ Hexoate zinc 15%: zinc 2-ethylhexanoate dissolved in mineral spirit (zinc octylate), aliphatic monocarboxylic acid metal salt content 15% by mass, manufactured by Toei Chemical Co., Ltd. ・ Zinc naphthenate 8%: mineral Zinc naphthenate dissolved in spirit, aliphatic monocarboxylic acid metal salt content 8% by mass, manufactured by Toei Kako Co., Ltd. Manganese naphthenate 6%: Manganese naphthenate dissolved in mineral spirit, metal aliphatic monocarboxylic acid Salt content 6% by mass, manufactured by Toei Chemical Co., Ltd./Cobalt naphthenate 8%: Cobalt naphthenate dissolved in mineral spirits, aliphatic monocarboxylic acid metal salt content 8% by mass, manufactured by Toei Chemical Co., Ltd./myristic acid Potassium solution: a solution prepared by dissolving potassium myristate in ethanol to make a 25% by mass solution, Wako Pure Chemical Industrial Co., Ltd., bismuth 2-ethylhexanoate: aliphatic monocarboxylic acid metal salt content 25% by mass, manufactured by Wako Pure Chemical Industries, Ltd.

<Fatty acid>
-Isostearic acid: Isostearic acid, manufactured by Wako Pure Chemical Industries, Ltd. <Amine salt>
-Tetraammonium bromide: Tetraammonium bromide, manufactured by Tokyo Chemical Industry Co., Ltd. <Mineral Spirit>
・ Mineral Spirit: Mineral Spirit, manufactured by JX Energy Corporation

[Evaluation]
The following evaluation was performed using the obtained inks of Examples 1 to 10 and Comparative Examples 1 to 6. The results are shown in Tables 2 and 3.

<Image density and showthrough>
Each of the inks of Examples 1 to 10 and Comparative Examples 1 to 6 was loaded into an inkjet printer (Orifice X9050, manufactured by Riso Kagaku Kogyo Co., Ltd.). A solid image was printed. 24 hours after printing, the OD values of the front and back surfaces of the solid image were measured using an optical densitometer (RD920, manufactured by Macbeth Co.) and evaluated according to the following criteria.
(Surface OD: Image density)
A: 1.18 or more B: 1.15 or more and less than 1.18 C: less than 1.15 (rear surface OD: back-through)
A: Less than 0.20 C: 0.20 or more

<Ink repellency: Wetting on nozzle plate>
For each of Examples 1 to 10 and Comparative Examples 1 to 6, a nozzle plate of an ink jet printer (Orifice X9050, manufactured by Riso Kagaku Kogyo Co., Ltd.) was immersed in ink and allowed to stand in a 60 ° C. environment for 1 day. Thereafter, when the nozzle plate was pulled up, the time until the ink film remaining on the nozzle plate became ink droplets was measured and evaluated according to the following criteria.
A: Less than 10 seconds C: 10 seconds or more

In the oil-based inkjet inks of Examples 1 to 10, the ink repellency of the nozzle plate was excellent, that is, wetting to the nozzle plate was reduced. Moreover, in the oil-based inkjet inks of Examples 1 to 10, it was shown that the surface OD value was high and the image density was high, and the back surface OD value was low and show-through was reduced. .
In contrast, Comparative Examples 1 to 5 in which the monovalent or divalent metal salt of the aliphatic monocarboxylic acid was not used resulted in surface OD (image density) or ink repellency (wetting to the nozzle plate). It was inferior. Specifically, Comparative Examples 1 and 4 in which a metal salt of an aliphatic monocarboxylic acid was not used were inferior in ink repellency (wetting to the nozzle plate). In Comparative Example 2 in which tetrabutylammonium bromide (amine salt) was used instead of a monovalent or divalent metal salt of an aliphatic monocarboxylic acid, and in Comparative Example 3 in which isostearic acid (fatty acid) was used, The surface OD (image density) value was low. Further, Comparative Example 5 in which a trivalent metal salt of a fatty acid was used also had a low surface OD (image density) value.
Comparative Example 6 in which the water-soluble resin having an amino group was not used was inferior to the results of the front surface OD (image density) and the back surface OD (back-through).

Claims (3)

  An oil-based inkjet ink comprising a pigment, a water-insoluble resin, a water-soluble resin containing an amino group, a monovalent or divalent metal salt of an aliphatic monocarboxylic acid, and a non-aqueous solvent.   2. The oil-based inkjet ink according to claim 1, wherein the monovalent or divalent metal salt of the aliphatic monocarboxylic acid is 150 mass ppm to 2500 mass ppm with respect to the total amount of the oil-based inkjet ink.   The oil-based inkjet ink according to claim 1 or 2, wherein the monovalent or divalent metal salt of the aliphatic monocarboxylic acid includes a monovalent or divalent metal salt of myristic acid, 2-ethylhexanoic acid or naphthenic acid. .