JP7341860B2 - Oil-based inkjet ink, method for producing oil-based inkjet ink, and method for producing dispersant - Google Patents

Description

Embodiments of the present invention relate to an oil-based inkjet ink, a method for producing an oil-based inkjet ink, and a method for producing a dispersant.

The inkjet recording method jets highly fluid inkjet ink as droplets from a fine nozzle and records an image on a recording medium placed opposite the nozzle, enabling high-speed printing with low noise. Therefore, it has become rapidly popular in recent years. Inks used in such inkjet recording methods include water-based inks containing water as the main solvent, ultraviolet curable inks (UV inks) containing high amounts of polymerizable monomers as the main component, and ultraviolet curable inks (UV inks) containing high amounts of wax as the main component. So-called non-aqueous inks are known that contain a non-aqueous solvent as a main solvent as well as a hot-melt ink (solid ink). Non-aqueous inks can be classified into solvent inks whose main solvent is a volatile organic solvent and oil-based inks whose main solvent is a low-volatile or non-volatile organic solvent. Solvent ink dries on the recording medium mainly by evaporation of the organic solvent, whereas oil-based ink dries mainly by permeation into the recording medium.

Patent Document 1 discloses a colored resin particle dispersion containing colored resin particles containing a phosphoric acid esterified solid resin and/or a nitric acid esterified solid resin, and an inkjet ink containing the same.
Patent Document 2 discloses a colored resin particle dispersion containing colored resin particles containing a solid resin and a liquid organic compound having an acidic group, and an inkjet ink containing the same.
Patent Document 3 describes an encapsulated pigment containing a urethane compound and a non-aqueous solvent, the urethane compound having a side chain containing a urethane skeleton and a carboxyl group, and is a compound insoluble in the non-aqueous solvent. Oil-based inkjet inks are disclosed.

Japanese Patent Application Publication No. 2015-134850 Japanese Patent Application Publication No. 2015-134852 Japanese Patent Application Publication No. 2018-48293

Aggregates may occur when the ink in the ink path is subjected to an external force, such as when the ink is subjected to sliding motion by a liquid pump.
Embodiments of the present invention aim to provide an oil-based inkjet ink that is less likely to cause aggregates.

One embodiment of the present invention is a pigment, an acidic resin, a low-molecular amine compound, and a group represented by the following general formula (1) and a group represented by the following general formula (2). The present invention relates to an oil-based inkjet ink comprising a dispersant formed by a (meth)acrylic resin containing at least one group and a non-aqueous solvent.

In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a substituent, and R ¹ and R ² may be bonded to each other to form a ring. In general formula (2), R ³ represents a substituent, R ⁴ represents a hydrogen atom or a substituent, and R ³ and R ⁴ may be bonded to each other to form a ring.

（一般式（１）において、Ｒ^１及びＲ^２はそれぞれ独立に水素原子又は置換基を表し、Ｒ^１とＲ^２とは互いに結合して環を形成していてもよい。一般式（２）において、Ｒ^３は置換基を表し、Ｒ^４は水素原子又は置換基を表し、Ｒ^３とＲ^４とは互いに結合して環を形成していてもよい。） Another embodiment of the present invention includes a non-aqueous solvent and at least one group selected from the group consisting of a group represented by the following general formula (1) and a group represented by the following general formula (2). A step of obtaining a water-in-oil emulsion containing a continuous phase containing a (meth)acrylic resin and a dispersed phase containing water, an acidic water-dispersible resin, and a low-molecular amine compound, and removing water from the water-in-oil emulsion. A method for producing an oil-based inkjet ink includes a step of removing the dispersant to obtain a dispersant dispersion, and a step of mixing the dispersant dispersion and a pigment to disperse the pigment.

(In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a substituent, and R ¹ and R ² may be combined with each other to form a ring. General formula (2) , R ³ represents a substituent, R ⁴ represents a hydrogen atom or a substituent, and R ³ and R ⁴ may be bonded to each other to form a ring.)

Another embodiment of the present invention includes a non-aqueous solvent and at least one group selected from the group consisting of a group represented by the following general formula (1) and a group represented by the following general formula (2). A step of obtaining a water-in-oil emulsion containing a continuous phase containing a (meth)acrylic resin and a dispersed phase containing water, an acidic water-dispersible resin, and a low-molecular amine compound, and removing water from the water-in-oil emulsion. The present invention relates to a method for producing a dispersant, including a step of removing the dispersant.

In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a substituent, and R ¹ and R ² may be bonded to each other to form a ring. In general formula (2), R ³ represents a substituent, R ⁴ represents a hydrogen atom or a substituent, and R ³ and R ⁴ may be bonded to each other to form a ring.

According to embodiments of the present invention, it is possible to provide an oil-based inkjet ink that does not easily generate aggregates.

Hereinafter, embodiments of the present invention will be described, but the following embodiments do not limit the present invention.
Hereinafter, oil-based inkjet ink may be referred to as "ink" or "oil-based ink."

The oil-based inkjet ink of one embodiment of the present invention is a group consisting of a pigment, an acidic resin, a low-molecular amine compound, and a group represented by the following general formula (1) and a group represented by the following general formula (2). An oil-based inkjet ink containing a dispersant (hereinafter sometimes simply referred to as "dispersant") formed by a (meth)acrylic resin containing at least one group selected from the following: and a non-aqueous solvent. .

In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a substituent, and R ¹ and R ² may be bonded to each other to form a ring. In general formula (2), R ³ represents a substituent, R ⁴ represents a hydrogen atom or a substituent, and R ³ and R ⁴ may be bonded to each other to form a ring.
Hereinafter, a (meth)acrylic resin containing at least one group selected from the group consisting of a group represented by the following general formula (1) and a group represented by the following general formula (2) will be referred to as "(meth)acrylic resin". Sometimes called acrylic resin A.

In ink, when a compound with a free acidic group exists around the pigment, the cohesive force of the pigment tends to increase, and such ink tends to form aggregates when subjected to external forces such as sliding. Tend. The oil-based inkjet ink of this embodiment uses a dispersant formed by an acidic resin, a low-molecular amine compound, and a (meth)acrylic resin A, so that even when subjected to external forces such as sliding, no aggregates occur. It is possible to create an ink that is less likely to cause Although not bound by any particular theory, the reason for this is that in this dispersant, the basic group of the low-molecular amine compound is bonded to the acidic group of the acidic resin, or At least one group selected from the group consisting of a group represented by It is assumed that this is because it is possible to

Although the method for producing the oil-based inkjet ink of this embodiment is not particularly limited, for example, it can be produced using a method of drying a water-in-oil (W/O) type emulsion in oil, which will be described later.

Oil-based inkjet inks can include pigments.

As the pigment, organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and dyed lake pigments, and inorganic pigments such as carbon black and metal oxides can be used.
Examples of the azo pigment include soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments. Examples of the phthalocyanine pigment include metal phthalocyanine pigments and metal-free phthalocyanine pigments. Examples of polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, and metal complex pigments. and diketopyrrolopyrrole (DPP). Examples of carbon black include furnace carbon black, lamp black, acetylene black, and channel black. Examples of metal oxides include titanium oxide and zinc oxide. These pigments may be used alone or in combination of two or more.
From the viewpoint of being able to obtain printed matter with high chroma, it is preferable that the cyan ink contains copper phthalocyanine blue. The yellow ink preferably contains any one of monoazo yellow, disazo yellow, and benzimidazolone yellow, and more preferably contains disazo yellow. The magenta ink preferably includes any one of Azole Lake Red, Naphthol AS, Benzimidazolone Red, and Quinacridone Magenta, and more preferably includes Azole Lake Red.

The dispersion form of the pigment may be, for example, a form in which colored resin particles containing the pigment and a dispersant are formed and the colored resin particles are dispersed. The colored resin particles containing a pigment and a dispersant may be, for example, a so-called capsule pigment in which a pigment is coated with a dispersant.

The average particle diameter of the pigment is preferably 300 nm or less, more preferably 200 nm or less, from the viewpoint of discharge stability and storage stability.
The content of the pigment is usually 0.01 to 20% by mass based on the total amount of the ink, and preferably 1 to 15% by mass from the viewpoint of image density and ink viscosity.

The oil-based inkjet ink can include an acidic resin, a low-molecular amine compound, and a dispersant formed by (meth)acrylic resin A. This dispersant may be formed using at least an acidic resin, a low molecular weight amine compound, and a (meth)acrylic resin A. In addition to this, other components may be further used.
The dispersant is preferably used in the form of resin particles in the oil-based inkjet ink manufacturing process. For example, when producing a dispersant by a method using an in-oil drying method of a water-in-oil (W/O) emulsion, the dispersant can preferably be produced in the form of resin particles.
In the oil-based inkjet ink, for example, it is preferable that the dispersant and the pigment are contained in the colored resin particles. Examples of such colored resin particles include those in which a pigment is coated with a dispersant.

Acidic resins are not particularly limited, but include, for example, acidic urethane resins, acidic polyester resins, acidic (meth)acrylic resins, acidic urethane (meth)acrylic resins, acidic (meth)acrylic silicone resins, and acidic vinyl chloride. and acidic styrene (meth)acrylic resins. As the acidic resin, from the viewpoint of improving scratch resistance, acidic urethane resins and acidic (meth)acrylic resins are preferred, and acidic urethane resins are more preferred.

Urethane resin has a urethane group. Generally, the urethane group of a urethane resin can be obtained by a reaction between a polyol and a polyisocyanate, but from the viewpoint of storage stability, the acidic urethane resin preferably uses an aliphatic polyisocyanate as the polyisocyanate.

As the acidic urethane resin, an acidic urethane urea resin having a urea group in addition to a urethane group is preferable from the viewpoint of improving scratch resistance. The urethane urea resin is produced by, for example, reacting a urethane prepolymer obtained from a material containing a polyol and a polyisocyanate with water and/or a polyamine compound, thereby combining the isocyanate groups of the urethane prepolymer with water and/or a polyamine compound. can be obtained by reacting to generate a urea group and extending the chain.

Examples of acidic urethane resins include acidic urethane (meth)acrylic resins, which are also included in examples of acidic (meth)acrylic resins.
(Meth)acrylic means containing methacrylic, acrylic, or a combination thereof, and (meth)acrylic resin refers to resins containing methacrylic units, resins containing acrylic units, or resins containing both of these units. means.

The acidic resin may be a resin having an acidic group, or an acidic water-dispersible resin may be used as a raw material in the production of ink. The acidic resin is preferably a resin having an acidic group, and the acidic group is preferably a carboxy group, a sulfo group, a phosphoric acid group, or the like.

The acidic resin is preferably a resin that is solid at 23°C.
From the viewpoint of reducing strike-through and improving image density, the acidic resin should have a solubility of the ink in the non-aqueous solvent of 1 g or less as the amount of resin that can be dissolved in 100 g of the ink non-aqueous solvent at 23°C. It is preferable that there be. Furthermore, since the acidic resin is difficult to dissolve in a non-aqueous solvent, it can also contribute to lowering the viscosity of the ink.

The weight average molecular weight of the acidic resin varies depending on the type of resin, but is preferably, for example, 5,000 to 200,000, more preferably 10,000 to 150,000. For example, the weight average molecular weight of the acidic urethane resin is preferably 5,000 to 50,000, more preferably 10,000 to 30,000. The weight average molecular weight of the acidic (meth)acrylic resin is preferably 10,000 to 200,000, more preferably 30,000 to 150,000.
The weight average molecular weight of the resin is a value determined in terms of standard polystyrene using the GPC method. The same applies to the weight average molecular weight of resins and the like described below.

For example, when producing a dispersant using a method of drying a water-in-oil (W/O) emulsion in oil, it is preferable to use an acidic water-dispersible resin in order to obtain an acidic resin. In the production of ink, the acidic water-dispersible resin is preferably added in the form of a dispersion (oil-in-water (O/W) resin emulsion) that is predispersed in a liquid such as water. When an aqueous dispersion is used, the water contained in the aqueous dispersion is preferably removed during the ink manufacturing process.

The acidic water-dispersible resin may be one in which acidic groups of the resin are present on the particle surface, such as a self-emulsifying resin, or one in which the surface of the resin particle has been surface-treated, such as by attaching an acidic dispersant. good. The acidic resin may be obtained from any of these. The acidic group is typically a carboxy group, a sulfo group, a phosphoric acid group, or the like. Acidic dispersants include anionic surfactants and the like.

The method of synthesizing the acidic urethane resin is not particularly limited. The acidic urethane resin can be obtained, for example, by reacting a polyol and a polyisocyanate.
Examples of the polyol include polytetramethylene glycol, 2,2-dimethylolbutanoic acid, 1,4-butanediol, and diethanolamine. Further, as the polyol, for example, a diol obtained by subjecting a dialkanolamine such as diethanolamine to a Michael addition reaction with a compound having an acryloyloxy group such as acrylic acid may be used. These polyols can be used alone or in combination of two or more. It is preferred that at least one of the polyols used has an acidic group.
As the polyisocyanate, for example, diisocyanates such as hexamethylene diisocyanate can be used. One kind of polyisocyanate can be used alone or two or more kinds can be used in combination.

The acidic urethane urea resin can be obtained, for example, by reacting a polyol and a polyisocyanate to obtain a urethane prepolymer, and then reacting the obtained urethane prepolymer with water and/or a polyamine compound. The polyol and polyisocyanate are as described above. As the polyamine compound, for example, hexanediamine or the like can be used.

The method for synthesizing the acidic (meth)acrylic resin is not particularly limited. For example, it can be obtained by polymerization using one or more monomers such as (meth)acrylic esters such as alkyl (meth)acrylates, and (meth)acrylic acid. It is preferable that at least one of the monomers used to synthesize the acidic (meth)acrylic resin has an acidic group.

A water dispersion of an acidic water-dispersible resin is one in which the resin is dispersed in water such as ion-exchanged water. It is preferable to add A low-molecular amine compound may be added to a commercially available water dispersion of acidic water-dispersible resin.

Commercially available water dispersions of acidic water-dispersible urethane resins include, for example, "WS5984" (trade name), "WS4022" (trade name) manufactured by Mitsui Chemicals, and "Superflex" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. 740” (product name), “Superflex 150H” (product name), “Ucoat UWS-145” (product name) manufactured by Sanyo Chemical Industries, Ltd., “DAOTAN TW-6493” (product name) manufactured by Daicel Allnex Corporation (product name) , "DAOTAN TW-6490" (product name), etc.
Examples of commercially available water dispersions of acidic water-dispersible urethane (meth)acrylic resins include "DAOTAN VTW-1262" (trade name) manufactured by Daicel Allnex Corporation.
Urethane type “WS5984”, “WS4022”, “Superflex 740”, “Superflex 150H”, “Ucoat UWS-145”, “DAOTAN TW-6493”, “DAOTAN TW-6490”, “DAOTAN VTW-1262” The resin is a urethane urea resin having a urea group.
Examples of commercially available water dispersions of acidic water-dispersible (meth)acrylic resins include "Movinyl 6750" (trade name) and "Movinyl 6969D" (trade name) manufactured by Japan Coating Resin Co., Ltd.

As the dispersant, acidic resins can be used alone or in combination of two or more.

As the low molecular weight amine compound, an amine compound with a molecular weight of 1000 or less is preferred, an amine compound with a molecular weight of 700 or less is more preferred, an amine compound with a molecular weight of 400 or less is more preferred, and an amine compound with a molecular weight of 300 or less is even more preferred.
It is preferable that the low molecular weight amine compound does not have repeating units.
The molecular weight of the low-molecular amine compound is determined by the (meth)acrylic resin (( It is preferable that the weight average molecular weight is smaller than the weight average molecular weight of the meth)acrylic resin A).

As the low-molecular amine compound, ammonia, a primary amine compound, a secondary amine compound, a tertiary amine compound, etc. can be used.
Examples of the primary amine compound include monomethylamine, monoethylamine, monobutylamine, and monoethanolamine.
Examples of the secondary amine compound include dimethylamine, diethylamine, dibutylamine, diethanolamine, diisopropanolamine, and methylpropanolamine.
Examples of tertiary amine compounds include trialkylamines such as trialkylamines having an alkyl group having 1 to 4 carbon atoms, exemplified by trimethylamine, triethylamine, dimethylethylamine, etc.; dimethylethanolamine, methyldiethanolamine, triethanolamine; , alkanolamines such as triisopropanolamine; heterocyclic amines such as morpholine compounds such as N-substituted morpholine compounds exemplified by N-alkylmorpholine, and the like.

From the viewpoint of making it difficult to form aggregates over a long period of time, it is preferable that the low molecular weight amine compound has low volatility. From this viewpoint, as the low molecular weight amine compound, alkanolamines such as monoethanolamine, diethanolamine, diisopropanolamine, methylpropanolamine, dimethylethanolamine, methyldiethanolamine, triethanolamine, and triisopropanolamine are preferable.

As the dispersant, one type of low molecular weight amine compound or a combination of two or more types can be used.

A (meth)acrylic resin ((meth)acrylic resin A) containing at least one group selected from the group consisting of a group represented by general formula (1) and a group represented by general formula (2) is , a group represented by general formula (1), a group represented by general formula (2), or both of these. The (meth)acrylic resin A may be, for example, a homopolymer or a copolymer, and is preferably a copolymer.

The weight average molecular weight of the (meth)acrylic resin A is preferably 5,000 or more, more preferably 7,000 or more. The weight average molecular weight of the (meth)acrylic resin A is preferably 50,000 or less, more preferably 30,000 or less.
The weight average molecular weight of the (meth)acrylic resin A is, for example, preferably 5,000 to 50,0000, more preferably 7,000 to 30,000.

The (meth)acrylic resin A is preferably dissolved in the non-aqueous solvent contained in the ink. Specifically, the (meth)acrylic resin A and the non-aqueous solvent contained in the ink are dissolved at 1 atm at 20°C. When mixed in the same volume, it is preferable that they dissolve uniformly without separating into two phases.

(Meth)acrylic resin A preferably contains at least one group selected from the group consisting of a group represented by general formula (1) and a group represented by general formula (2).

In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a substituent, and R ¹ and R ² may be bonded to each other to form a ring.

In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a hydrocarbon group that may have a substituent, or R ¹ and R ² are bonded to each other. It is preferable that the two groups form a ring.

Examples of the hydrocarbon group include aliphatic hydrocarbon groups such as an alkyl group, an alkenyl group, and an alkynyl group, and may be linear or branched. The number of carbon atoms in the hydrocarbon group is preferably 1 to 8, more preferably 1 to 4. The hydrocarbon group is preferably an alkyl group, preferably an alkyl group having 1 to 8 carbon atoms, and more preferably an alkyl group having 1 to 4 carbon atoms. Specific examples of the hydrocarbon group include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, sec-butyl group, and the like. For example, R ¹ and R ² are preferably each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, which may have a substituent. good.

When R ¹ and R ² are bonded to each other to form a ring, the ring is preferably a 3- to 8-membered ring, more preferably a 5- to 7-membered ring, and even more preferably a 4- to 6-membered ring. Examples of the ring formed by bonding R ¹ and R ² to each other include a heterocycle containing a nitrogen atom as a heteroatom, a heterocycle containing a nitrogen atom and an oxygen atom as heteroatoms, and the like. Examples of the ring formed by bonding R ¹ and R ² to each other include morpholine, piperidine, pyrrolidine, etc., which may have a substituent.

In general formula (2), R ³ represents a substituent, R ⁴ represents a hydrogen atom or a substituent, and R ³ and R ⁴ may be bonded to each other to form a ring.

In general formula (2), R ³ represents a hydrocarbon group that may have a substituent, and R ⁴ represents a hydrogen atom or a hydrocarbon group that may have a substituent. Alternatively, R ³ and R ⁴ are preferably bonded to each other to form a ring.

Examples of the hydrocarbon group include aliphatic hydrocarbon groups such as an alkyl group, an alkenyl group, and an alkynyl group, and may be linear or branched. The number of carbon atoms in the hydrocarbon group is preferably 1 to 8, more preferably 1 to 4. The hydrocarbon group is preferably an alkyl group, preferably an alkyl group having 1 to 8 carbon atoms, and more preferably an alkyl group having 1 to 4 carbon atoms. Specific examples of the hydrocarbon group include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, sec-butyl group, and the like. For example, R ³ is preferably an alkyl group having 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, which may have a substituent, and R ⁴ is preferably a hydrogen atom, Alternatively, it may be an alkyl group having 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, which may have a substituent.

When R ³ and R ⁴ are bonded to each other to form a ring, the ring is preferably a 3- to 8-membered ring, more preferably a 5- to 7-membered ring, and even more preferably a 4- to 6-membered ring. Examples of the ring formed by bonding R ³ and R ⁴ to each other include a heterocycle containing a nitrogen atom as a heteroatom, a heterocycle containing a nitrogen atom and an oxygen atom as heteroatoms, and the like. Examples of the ring formed by bonding R ³ and R ⁴ to each other include a pyrrolidone ring which may have a substituent.

The (meth)acrylic resin A contains only one type of group selected from the group consisting of the group represented by general formula (1) and the group represented by general formula (2), or a combination of two or more types. may be included. For example, (meth)acrylic resin A may contain only one type of group represented by general formula (1), or a combination of two or more types. For example, (meth)acrylic resin A may contain only one type of group represented by general formula (2), or a combination of two or more types. For example, (meth)acrylic resin A may include one or more groups represented by general formula (1) and/or one or more groups represented by general formula (2).

(Meth)acrylic resin A preferably has two or more groups selected from the group consisting of a group represented by general formula (1) and a group represented by general formula (2).

The group represented by the general formula (1) and/or the group represented by the general formula (2) is attached to the carbon atom of the main chain of the (meth)acrylic resin A directly or via a divalent linking group. It is preferable that it is bonded, and it is more preferable that it is bonded directly to the carbon atom of the main chain of the (meth)acrylic resin A. Examples of divalent linking groups include alkylene groups, alkynylene groups, alkenylene groups, arylene groups, heteroarylene groups, -O-, carbonyl groups (-(C=O)-), carbonyloxy groups (-(C= Examples thereof include divalent groups such as O)-O-), and groups combining two or more such divalent groups.

The (meth)acrylic resin A preferably has a β-dicarbonyl group and/or an alkyl group, for example, from the viewpoint of improving image density, improving color development, and reducing image strike-through. It is more preferable to have an alkyl group. At least one group selected from the group consisting of a group represented by general formula (1) and a group represented by general formula (2) below, a β-dicarbonyl group, and an alkyl group, for example, two of them At least one group selected from the group consisting of a group represented by general formula (1) and a group represented by general formula (2) below, β- It is preferable that the dicarbonyl group and the alkyl group are contained in different units.

Examples of the β-dicarbonyl group include β-diketone groups such as an acetoacetyl group and a propionacetyl group, and β-keto acid ester groups such as an acetoacetoxy group and a propionacetoxy group. (Meth)acrylic resin A may contain only one type or multiple types of these β-dicarbonyl groups.

The alkyl group is preferably an alkyl group having 8 to 22 carbon atoms, more preferably an alkyl group having 12 to 22 carbon atoms. The alkyl group having 8 to 22 carbon atoms may be linear or branched. Specific examples include octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group, docosyl group, etc. . (Meth)acrylic resin A may contain only one type or multiple types of these alkyl groups.

(Meth)acrylic resin A may contain acidic groups such as sulfo groups and carboxy groups.

(Meth)acrylic resin A is a unit (hereinafter referred to as "unit Ya '') is preferably included.
(Meth)acrylic resin A is, for example, a unit having at least one group selected from the group consisting of a group represented by general formula (1) and a group represented by general formula (2) ("unit Ya ") and a unit having a β-dicarbonyl group (hereinafter sometimes referred to as "unit Yb") and/or a unit having an alkyl group (hereinafter sometimes referred to as "unit Yc"). Preferably, it is more preferable to include a unit Ya, a unit Yb, and a unit Yc.

Examples of the unit (unit Ya) having at least one group selected from the group consisting of the group represented by general formula (1) and the group represented by general formula (2) include (meth)acrylic resin At least one group selected from the group consisting of a group represented by general formula (1) and a group represented by general formula (2) is bonded to the carbon atom of the main chain of A directly or via a linking group. Examples include units that are Examples of such units include a unit represented by the following general formula (3), a unit represented by the following general formula (4), and the like.

In general formula (3), R ¹ and R ² are the same as R ¹ and R ² in general formula (1), respectively, and their preferred ranges are also the same. R ⁵ represents a hydrogen atom or a methyl group. L ¹ represents a divalent linking group or a single bond.
In general formula (4), R ³ and R ⁴ are the same as R ³ and R ⁴ in general formula (2), respectively, and their preferred ranges are also the same. R ⁶ represents a hydrogen atom or a methyl group. L ² represents a divalent linking group or a single bond.
Examples of divalent linking groups include alkylene groups, alkynylene groups, alkenylene groups, arylene groups, heteroarylene groups, -O-, carbonyl groups (-(C=O)-), carbonyloxy groups (-(C= Examples thereof include divalent groups such as O)-O-), and groups combining two or more such divalent groups.

As the unit Ya, for example, a monomer having at least one group selected from the group consisting of a group represented by general formula (1) and a group represented by general formula (2) (hereinafter referred to as "monomer Ya ) can be used.

(Meth)acrylic resin A may contain only one type or two or more types of units Ya. (Meth)acrylic resin A includes, for example, one or more units represented by general formula (3), and/or one or more units represented by general formula (4). may be included.

The unit having a β-dicarbonyl group (unit Yb) may be, for example, an acrylic unit or a methacryl unit.
Examples of the unit Yb include a unit in which a carbonyl group is bonded to a carbon atom in the main chain, and a β-dicarbonyl group is bonded to the carbon atom of the carbonyl group directly or via a linking group.
The unit Yb is preferably a unit derived from (meth)acrylate having a β-dicarbonyl group, a unit derived from (meth)acrylamide having a β-dicarbonyl group, or the like. Examples of (meth)acrylates having a β-dicarbonyl group include a β-diketone group or a β-keto acid ester group (meth) indirectly bonded to the carbonyl (CO) carbon atom of an acryloyl group or a methacryloyl group. ) Acrylate is mentioned as a preferred example. Examples of (meth)acrylamide having a β-dicarbonyl group include a β-diketone group or a β-keto acid ester group (meth) indirectly bonded to the carbonyl (CO) carbon atom of an acryloyl group or a methacryloyl group. ) Acrylamide is mentioned as a preferred example. As the unit Yb, for example, a unit derived from a monomer having a β-dicarbonyl group (hereinafter sometimes referred to as "monomer Yb") described below can be used.
(Meth)acrylic resin A may contain only one type or two or more types of units Yb.

The unit having an alkyl group (unit Yc) may be, for example, an acrylic unit or a methacryl unit having an alkyl group.
An example of the unit Yc is, for example, a unit in which a group represented by -COOR ^e is bonded to a carbon atom in the main chain of the (meth)acrylic resin A, where R ^e is an alkyl group (preferably carbon Examples include units having an alkyl group having 8 to 22 carbon atoms, more preferably 12 to 22 carbon atoms. As the unit Yc, for example, a unit derived from a monomer having an alkyl group (hereinafter sometimes referred to as "monomer Yc") described below can be used.
(Meth)acrylic resin A may contain only one type or two or more types of units Yc.

(Meth)acrylic resin A may contain other units.

The number of units (unit Ya) having at least one group selected from the group consisting of the group represented by general formula (1) and the group represented by general formula (2) is 5 to 30 It is preferably 10 to 25% by mass or more, more preferably 10 to 25% by mass.
The unit having a β-dicarbonyl group (unit Yb) is preferably 5 to 30% by mass, more preferably 10 to 20% by mass, based on the entire polymer.
The unit having an alkyl group (unit Yc) is preferably 40 to 90% by mass, more preferably 50 to 90% by mass, and even more preferably 60 to 80% by mass or more based on the entire polymer.
Here, the entire polymer is based on all units constituting the (meth)acrylic resin A.

(Meth)acrylic resin A is, for example, a monomer (monomer Ya) having at least one group selected from the group consisting of a group represented by general formula (1) and a group represented by general formula (2). It may be a homopolymer obtained by polymerizing a monomer Ya, a copolymer obtained by polymerizing a monomer mixture containing monomer Ya, or a derivative of such a homopolymer or copolymer. The monomer mixture preferably contains monomer Ya, a monomer having a β-dicarbonyl group (monomer Yb) and/or a monomer having an alkyl group (monomer Yc), and monomer Ya, monomer Yb, monomer Yc It is more preferable to include.

As an example of a monomer (monomer Ya) having at least one group selected from the group consisting of a group represented by general formula (1) and a group represented by general formula (2), for example, the following general formula (5 ) and a monomer represented by the following general formula (6).

In general formula (5), R ¹ and R ² are the same as R ¹ and R ² in general formula (1), respectively, and their preferred ranges are also the same. R ⁵ represents a hydrogen atom or a methyl group. L ¹ represents a divalent linking group or a single bond.
In general formula (6), R ³ and R ⁴ are the same as R ³ and R ⁴ in general formula (2), respectively, and their preferred ranges are also the same. R ⁶ represents a hydrogen atom or a methyl group. L ² represents a divalent linking group or a single bond.
Examples of divalent linking groups include alkylene groups, alkynylene groups, alkenylene groups, arylene groups, heteroarylene groups, -O-, carbonyl groups (-(C=O)-), carbonyloxy groups (-(C= Examples thereof include divalent groups such as O)-O-), and groups combining two or more such divalent groups.

Specific examples of the monomer represented by general formula (5) or (6) include dimethylacrylamide, acryloylmorpholine, N-vinyl-2-pyrrolidone, and the like.

The monomer having a β-dicarbonyl group (monomer Yb) is preferably a monomer having an acryloyl group or a methacryloyl group and a β-dicarbonyl group, for example. Preferred examples of the monomer Yb include (meth)acrylate having a β-dicarbonyl group, (meth)acrylamide having a β-dicarbonyl group, and the like. Specific examples of the monomer Yb include acetoacetoxyalkyl (meth)acrylates such as acetoacetoxyethyl (meth)acrylate, hexadione (meth)acrylate, acetoacetoxyalkyl (meth)acrylamides such as acetoacetoxyethyl (meth)acrylamide, etc. Can be mentioned.

The monomer having an alkyl group (monomer Yc) is preferably a monomer having an acryloyl group or a methacryloyl group and an alkyl group, for example. Examples of the monomer Yc include alkyl (meth)acrylates, preferably alkyl (meth)acrylates having an alkyl group having 8 to 22 carbon atoms, and alkyl (meth)acrylates having an alkyl group having 12 to 22 carbon atoms Acrylates are more preferred. Specific examples of the monomer Yc include behenyl (meth)acrylate, lauryl (meth)acrylate (dodecyl (meth)acrylate), and the like.

The monomer mixture may include other monomers.
The blending amount of each monomer in the monomer mixture can be adjusted, for example, so as to provide a preferable ratio of each of the units described above.

These monomers can be polymerized, for example, by known radical polymerization. As the reaction system, solution polymerization or dispersion polymerization is preferably used. During the polymerization reaction, for example, a polymerization initiator, a chain transfer agent, a polymerization inhibitor, a polymerization promoter, a dispersant, etc. can be appropriately added to the reaction system. As the polymerization initiator, for example, t-butylperoxy-2-ethylhexanoate can be used. The polymerization solvent (reaction solvent) used in solution polymerization is not particularly limited, but it is preferably one that can disperse or dissolve the resin obtained by polymerization.

As the dispersant, (meth)acrylic resin A can be used alone or in combination of two or more.

The total amount of the acidic resin and the low-molecular amine compound relative to the total amount of the acidic resin, the low-molecular amine compound, and the (meth)acrylic resin A is preferably 10% by mass or more, more preferably 20% by mass or more, and 30% by mass or more. is even more preferable. On the other hand, the total amount of the acidic resin and the low-molecular amine compound relative to the total amount of the acidic resin, the low-molecular amine compound, and the (meth)acrylic resin A is preferably 90% by mass or less, more preferably 80% by mass or less, and 70% by mass. % or less is more preferable. The total amount of the acidic resin and the low-molecular amine compound relative to the total amount of the acidic resin, the low-molecular amine compound, and the (meth)acrylic resin A is, for example, preferably 10 to 90% by mass, more preferably 20 to 80% by mass, More preferably 30 to 70% by mass.

The amount of (meth)acrylic resin A relative to the total amount of acidic resin, low molecular amine compound, and (meth)acrylic resin A is preferably 10% by mass or more, more preferably 20% by mass or more, and 30% by mass or more. More preferred. On the other hand, the amount of (meth)acrylic resin A relative to the total amount of acidic resin, low molecular weight amine compound, and (meth)acrylic resin A is preferably 90% by mass or less, more preferably 80% by mass or less, and 70% by mass. The following are more preferred. The amount of (meth)acrylic resin A relative to the total amount of acidic resin, low molecular amine compound, and (meth)acrylic resin A is, for example, preferably 10 to 90% by mass, more preferably 20 to 80% by mass, and 30% by mass. More preferably 70% by mass.

The low-molecular amine compound is preferably used in an amount such that the molar ratio (basic group/acidic group) of the basic group of the low-molecular amine compound to the acidic group of the acidic resin is 0.5 to 1.5, and 0. More preferably, the amount is .8 to 1.2. Here, if an acidic water-dispersible resin whose surface has been treated by adhering an acidic resin particle dispersant to the surface of the resin particles is used, the acidic groups of the acidic resin are the acidic groups of the acidic resin particle dispersant. Also included.

The mass ratio of acidic resin to (meth)acrylic resin A (acidic resin: (meth)acrylic resin A) is preferably 10:90 to 90:10, more preferably 20:80 to 80:20, and 30: More preferably, the ratio is 70:30 to 70:30.

The acidic resin is preferably 0.1 to 20% by weight, more preferably 0.1 to 10% by weight, and even more preferably 0.5 to 10% by weight based on the total amount of the ink.

The (meth)acrylic resin A is preferably 0.1 to 10% by mass, more preferably 0.5 to 10% by mass, preferably 1 to 5% by mass, and 1.5 to 5% by mass based on the total amount of the ink. % is more preferred.

From the viewpoint of ensuring the dispersibility of the pigment, the content of the dispersant is 0.1% by mass or more based on the total amount of the ink, as the total amount of the acidic resin, low molecular amine compound, and (meth)acrylic resin A. It is preferably at least 1% by mass, more preferably at least 1% by mass, even more preferably at least 2% by mass. On the other hand, from the viewpoint of ink viscosity and storage stability in high-temperature environments, the content of dispersant is determined as the total amount of acidic resin, low molecular amine compound, and (meth)acrylic resin A based on the total amount of ink. , is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less. The content of the dispersant is preferably, for example, 0.1 to 20% by mass, and 1 to 10% by mass, based on the total amount of the ink, as the total amount of the acidic resin, low molecular amine compound, and (meth)acrylic resin A. More preferably, it is 2 to 8% by mass.

The amount of the dispersant should be such that the total amount of the acidic resin, low molecular amine compound and (meth)acrylic resin A is such that the mass ratio is 0.1 to 5 parts of the dispersant to 1 part of the pigment. The amount is preferably 0.1 to 1, more preferably 0.1 to 1.

As the non-aqueous solvent, both non-polar organic solvents and polar organic solvents can be used in the ink. These may be used alone, or two or more types may be used in combination as long as they form a single phase. In this embodiment, it is preferable to use a water-insoluble organic solvent that does not mix uniformly with the same volume of water at 1 atm and 20° C. as the non-aqueous solvent.

Preferred examples of the nonpolar organic solvent include petroleum hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents.
Examples of aliphatic hydrocarbon solvents and alicyclic hydrocarbon solvents include nonaqueous solvents such as paraffinic, isoparaffinic, and naphthenic solvents. Commercially available products include No. 0 Solvent L, No. 0 Solvent M, No. 0 Solvent H, Cactus Normal Paraffin N-10, Cactus Normal Paraffin N-11, Cactus Normal Paraffin N-12, Cactus Normal Paraffin N-13, and 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, Naftesol 160, Naftesol 200, Naftesol 220 (all manufactured by JXTG Energy Corporation); Isopar G, Isopar H, Isopar L, Isopar M, Exol D40, Exol D60, Exol D80, Exor D95, Exor D110, Exor D130 (all manufactured by ExxonMobil); Moresco White P-40, Moresco White P-60, Moresco White P-70, Moresco White P-80, Moresco White Preferred examples include Moresco White P-100, Moresco White P-120, Moresco White P-150, Moresco White P-200, Moresco White P-260, Moresco White P-350P (all manufactured by MORESCO Co., Ltd.). be able to.
Preferred examples of the aromatic hydrocarbon solvent include Grade Alkene L, Grade Alkene 200P (all manufactured by JXTG Energy Corporation), Solvesso 100, Solvesso 150, Solvesso 200, and Solvesso 200ND (all manufactured by ExxonMobil Corporation). can.
The initial distillation 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 initial boiling point of distillation can be measured according to JIS K0066 "Distillation test method for chemical products".

Preferred examples of the polar organic solvent include fatty acid ester solvents, higher alcohol solvents, and higher fatty acid solvents.
For example, isononyl isononanoate, isodecyl isononanoate, isotridecyl 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-octyl pivalate Fatty acid ester solvents with 13 or more carbon atoms in one molecule, preferably 16 to 30, such as decyl, methyl soybean oil, isobutyl soybean oil, methyl tall oil, and isobutyl tall oil; isomyristyl alcohol, isopalmityl alcohol, stearyl Higher alcohol solvents having 6 or more carbon atoms in one molecule, preferably 12 to 20, such as alcohol, isostearyl alcohol, oleyl alcohol, isoeicosyl alcohol, decyltetradecanol; lauric acid, isomyristic acid, palmitic acid , isopalmitic acid, α-linolenic acid, linoleic acid, oleic acid, isostearic acid, and other higher fatty acid solvents having 12 or more carbon atoms, 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 even more preferably 250°C or higher. preferable. Note that the non-aqueous solvents having a boiling point of 250°C or higher include non-aqueous solvents that do not have a boiling point.

The amount of non-aqueous solvent can be adjusted as appropriate. The non-aqueous solvent is preferably 60% by mass or more, more preferably 70% by mass or more, based on the total amount of the ink. On the other hand, the amount of the nonaqueous solvent is preferably 99% by mass or less, more preferably 95% by mass or less, based on the total amount of the ink. The amount of the non-aqueous solvent is preferably, for example, 60 to 99% by mass, more preferably 70 to 95% by mass, based on the total amount of the ink.

In addition to the above components, the oil-based ink may contain various additives. As additives, nozzle anti-clogging agents, antioxidants, conductivity modifiers, viscosity modifiers, surface tension modifiers, oxygen absorbers, dyes, and the like can be added as appropriate. These types are not particularly limited, and those used in the field can be used.

The amount of water in the ink is preferably 1% by mass or less, more preferably less than 1% by mass, even more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, based on the total amount of the ink.
The total amount of the dispersant and pigment in the ink is preferably 1 to 40% by mass, and 5 to 40% by mass as the total amount of the pigment, acidic resin, low molecular amine compound, and (meth)acrylic resin A based on the total amount of the ink. 30% by mass is more preferred.

The method for producing the above oil-based inkjet ink is not particularly limited. For the production of the above-mentioned oil-based inkjet ink, for example, an in-liquid drying method can be preferably used, and an in-oil drying method of a water-in-oil (W/O) emulsion can be particularly preferably used.

An example of a method for manufacturing an oil-based inkjet ink using a drying method in oil for a water-in-oil emulsion includes, for example, a method that includes manufacturing a dispersant by a method using a drying method in oil for a water-in-oil emulsion. can be mentioned. Such a method includes, for example, a water-in-oil emulsion containing a continuous phase containing a nonaqueous solvent and (meth)acrylic resin A, and a dispersed phase containing water, an acidic water-dispersible resin, and a low-molecular amine compound. (hereinafter sometimes referred to as "Step 1"), and removing water from the water-in-oil emulsion to obtain a dispersion formed by the acidic resin, the low-molecular amine compound, and the (meth)acrylic resin A. A step of obtaining a dispersant dispersion containing a dispersant (hereinafter sometimes referred to as "Step 2") and a step of mixing the dispersant dispersion and a pigment and dispersing the pigment (hereinafter referred to as "Step 3") ). In this method, in step 2, a dispersant dispersion can be obtained as a resin particle dispersion in which the dispersant is dispersed as resin particles. However, the method for producing ink is not limited to this method. The form of the dispersant is also not limited to resin particles.
This method of drying a water-in-oil emulsion in oil does not require the use of volatile organic solvents and is highly safe.

Since the (meth)acrylic resin A has a group represented by the general formula (1) or (2), it is easily oriented at the interface between the water phase and the oil phase, and it is easy to form an emulsion. A method of producing such a water-in-oil (W/O) emulsion using an in-oil drying method is preferable.

As for the non-aqueous solvent, (meth)acrylic resin A, acidic water-dispersible resin, low-molecular amine compound, and pigment, those explained in the description of the components of the ink can be used. For example, as the acidic water-dispersible resin, among the water-dispersible acidic resins explained in the explanation of the components of the ink, acidic water-dispersible (meth)acrylic resins, acidic water-dispersible urethane resins, etc. are preferable. , acidic urethane urea water-dispersible resins are more preferred.
As water, tap water, ion exchange water, deionized water, etc. can be used.

In the water-in-oil emulsion made in step 1, the continuous phase and the dispersed phase may contain other components.

The amount of acidic water-dispersible resin (solid content) is preferably 1 to 60% by mass, more preferably 10 to 50% by mass, and even more preferably 20 to 40% by mass, based on the total amount of the dispersed phase. The amount of acidic water-dispersible resin (solid content) is preferably 0.1 to 30% by mass, more preferably 1 to 20% by mass, and even more preferably 5 to 15% by mass, based on the total amount of the water-in-oil emulsion. .

The amount of acidic water-dispersible resin (solid content) is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 14% by mass or more, based on the total amount of the dispersant dispersion obtained in Step 2. The amount of acidic water-dispersible resin (solid content) is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total amount of the dispersant dispersion obtained in step 2. The amount of acidic water-dispersible resin (solid content) is preferably 5 to 40% by mass, more preferably 10 to 40% by mass, and 14 to 30% by mass based on the total amount of the dispersant dispersion obtained in Step 2. More preferred.

In the water-in-oil emulsion, the amount of the low-molecular amine compound is preferably such that the amount of basic groups thereof falls within the above-mentioned preferred molar range relative to the acidic groups of the acidic water-dispersible resin.
In the water-in-oil emulsion, the amount of water is preferably 40 to 99% by mass, more preferably 50 to 90% by mass, and even more preferably 60 to 80% by mass, based on the total amount of the dispersed phase. The amount of water is preferably 1 to 50% by mass, more preferably 5 to 50% by mass, and even more preferably 10 to 40% by mass, based on the total amount of the water-in-oil emulsion.

In a water-in-oil emulsion, the amount of water is determined so that the amount of acidic water-dispersible resin in the dispersed phase (solid content) is relative to the amount of water, from the viewpoint of maintaining the stability of the water-in-oil emulsion in step 1. The amount is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 35% by mass or more, and even more preferably 40% by mass or more. It is more preferable that On the other hand, the amount of water is preferably such that the amount (solid content) of the acidic water-dispersible resin in the dispersed phase is 80% by mass or less, and 75% by mass or less, based on the amount of water. It is more preferable that In the water-in-oil emulsion, the amount of water is preferably such that, for example, the amount of acidic water-dispersible resin in the dispersed phase (solid content) is 20 to 80% by mass relative to the amount of water. , the amount is preferably 30 to 80% by weight, more preferably 35 to 80% by weight, and even more preferably 40 to 75% by weight.

The entire amount of (meth)acrylic resin A used in the ink may be included in the water-in-oil emulsion obtained in step 1, but only a portion may be added to the water-in-oil emulsion obtained in step 1. The remainder may be mixed together with the pigment and the dispersant dispersion, for example, when the pigment and the dispersant dispersion are mixed in step 3. The (meth)acrylic resin A added in Step 3 and the like may be the same as or different from the (meth)acrylic resin A contained in the water-in-oil emulsion in Step 1.

In the water-in-oil emulsion, the amount of (meth)acrylic resin A is preferably 1 to 60% by mass, more preferably 5 to 50% by mass, and even more preferably 10 to 40% by mass, based on the total amount of the continuous phase. .
In the water-in-oil emulsion, the amount of (meth)acrylic resin A is preferably 1 to 40% by mass, more preferably 5 to 30% by mass, and 10 to 20% by mass based on the total amount of the water-in-oil emulsion. More preferred.

The entire amount of the non-aqueous solvent used in the ink may be included in the water-in-oil emulsion obtained in step 1, but only a portion may be included in the water-in-oil emulsion obtained in step 1, The remainder may be mixed together with the pigment and the dispersant dispersion, for example, in Step 3, when the pigment and the dispersant dispersion are mixed. The non-aqueous solvent added in Step 3 and the like may be the same as or different from the non-aqueous solvent contained in the water-in-oil emulsion in Step 1.

In the water-in-oil emulsion, the amount of the non-aqueous solvent is preferably 40 to 99% by mass, more preferably 50 to 95% by mass, and even more preferably 60 to 90% by mass, based on the total amount of the continuous phase.
In the water-in-oil emulsion, the amount of the non-aqueous solvent is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, based on the total amount of the water-in-oil emulsion.

In step 1, the method for obtaining the water-in-oil emulsion is not particularly limited.
A water-in-oil emulsion can be produced, for example, by mixing and emulsifying components of a dispersed phase and a component of a continuous phase.
From the viewpoint of improving the dispersion stability of the ink and thereby improving the scratch resistance, it is preferable to prepare a continuous phase mixture containing continuous phase components and a dispersed phase mixture containing dispersed phase components separately in advance. . Next, it is preferable that the mixture for the dispersed phase is added to the mixture for the continuous phase and subjected to an emulsification treatment. The emulsification treatment may be performed using, for example, an emulsifier such as an ultrasonic homogenizer. The emulsification treatment may be performed, for example, while adding the dispersed phase mixture to the continuous phase mixture, or after the dispersed phase mixture is added to the continuous phase mixture.

From the viewpoint of reducing the emulsion particle size and thereby improving the dispersion stability and scratch resistance of the obtained ink, for example, in step 1, an acidic water-dispersible resin, a low-molecular amine compound, and A step of obtaining a mixture for a dispersed phase containing water (hereinafter sometimes referred to as "Step a-1") and a step of obtaining a mixture for a continuous phase containing a (meth)acrylic resin A and a non-aqueous solvent (hereinafter referred to as "Step a-1"). (hereinafter sometimes referred to as "Step a-3") and a step of adding the dispersed phase mixture to the continuous phase mixture and emulsifying it (hereinafter sometimes referred to as "Step a-3"). preferable. In step a-1, for example, a dispersed phase mixture can be obtained by mixing an acidic water-dispersible resin, a low-molecular amine compound, water, and other components as necessary. In step a-2, for example, a continuous phase mixture can be obtained by mixing (meth)acrylic resin A, a nonaqueous solvent, and other components as necessary. In step a-3, the dispersed phase mixture obtained in step a-1 is added to the continuous phase mixture obtained in step a-2, and emulsification is performed. In step a-3, the emulsification treatment may be performed, for example, while adding the dispersed phase mixture to the continuous phase mixture, or may be performed, for example, after adding the dispersed phase mixture to the continuous phase mixture. The emulsification treatment may be performed using, for example, an emulsifier such as an ultrasonic homogenizer.

From the perspective of improving production efficiency, water-in-oil emulsions, for example, can be prepared by combining continuous phase components and dispersed phase components at the same time, rather than preparing a continuous phase mixture and a dispersed phase mixture separately in advance. It is preferable to mix and emulsify the resulting mixture using an emulsifying machine or the like.
From the perspective of improving production efficiency, Step 1 is, for example, a step (hereinafter referred to as The process preferably includes a step (hereinafter sometimes referred to as step "b-1") and a step of emulsifying the obtained mixture (hereinafter sometimes referred to as step "b-2"). When the dispersed phase and/or continuous phase contains other components, in step b-1, the other components are added together with the acidic water-dispersible resin, the low molecular weight amine compound, water, (meth)acrylic resin A, and the non-aqueous solvent. may be mixed. In step b-2, the emulsification treatment may be performed using an emulsifier such as an ultrasonic homogenizer.

In step 1, the water-in-oil emulsion has a dispersed phase of 20 to 50% by mass and a continuous phase of 80 to 50% by mass, based on the total amount of the water-in-oil emulsion, as a mass ratio before water is removed. It is preferable.

In step 2, the water in the dispersed phase of the water-in-oil emulsion is removed. As a result, resin particles are formed by the remaining dispersed phase component and the (meth)acrylic resin A as the continuous phase component, and the dispersant is formed by the acidic resin, the low molecular weight amine compound, and the (meth)acrylic resin A. A dispersant dispersion containing this resin particle can be obtained. In this way, in step 2, a dispersant dispersion containing a dispersant and a non-aqueous solvent can be obtained. Further, (meth)acrylic resin A may be further added to the dispersant obtained in Step 2 in Step 3.

As a method for removing water, for example, reduced pressure, heating, bubbling, addition of a moisture absorbent, or a combination thereof can be used. As conditions for the reduced pressure and/or heating, conditions can be adopted such that water is removed but the non-aqueous solvent in the continuous phase remains. For example, an evaporator can be used to reduce the pressure. The heating temperature is preferably 30°C or higher, more preferably 40 to 100°C, and even more preferably 60 to 90°C. For example, it is also preferable to heat at normal pressure. As for bubbling, it is preferable to promote evaporation by bubbling gas into the liquid. Examples of the moisture absorbent include zeolite and the like.

In step 2, the amount of water in the dispersed phase is preferably removed by 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, based on the amount before removal. More preferably, 99% by mass or more is removed.

In the dispersant dispersion obtained in step 2, the amount of solid content of the dispersed phase component of the water-in-oil emulsion relative to the total amount of the dispersant dispersion is preferably 1 to 40% by mass, more preferably 5 to 30% by mass.
In the dispersant dispersion obtained in step 2, the amount of the dispersant is 20 to 60% by mass as the sum of the solid content of the dispersed phase component and the solid content of the continuous phase component of the water-in-oil emulsion. Preferably, 30 to 50% by mass is more preferable.

In step 3, the dispersant dispersion and the pigment are mixed and the pigment is dispersed.
In step 3, the dispersant dispersion and the pigment are mixed, and if necessary, (meth)acrylic resin A and/or a non-aqueous solvent, etc. are mixed together with the dispersant dispersion and the pigment, as described above. You may. The (meth)acrylic resin A added in Step 3 and the like may be the same as or different from the (meth)acrylic resin A contained in the water-in-oil emulsion in Step 1. The non-aqueous solvent added in Step 3 and the like may be the same as or different from the non-aqueous solvent contained in the water-in-oil emulsion in Step 1.
The amount of each material used in step 3 is not particularly limited, but can be appropriately determined taking into consideration the amount of each component in the ink.

In step 3, the pigment may be dispersed, for example, while mixing the dispersant dispersion, the pigment, and (meth)acrylic resin A and/or a non-aqueous solvent, etc. as necessary. This may be carried out after mixing the agent dispersion, the pigment, and, if necessary, the (meth)acrylic resin A and/or the non-aqueous solvent. A bead mill or the like can be used for dispersion.

This oil-based inkjet manufacturing method may further include other steps.
By mixing the dispersant dispersion, the pigment, and (meth)acrylic resin A and/or a non-aqueous solvent as necessary, dispersing the pigment, and performing other steps as necessary, the oil-based Inkjet ink can be obtained. In the oil-based inkjet ink, the pigment and the dispersant may form colored resin particles, and examples of such colored resin particles include those in which the pigment is coated with the dispersant.

The average particle diameter of the colored resin particles in the ink is preferably 50 to 300 nm, more preferably 80 to 200 nm. The average particle diameter of the colored resin particles in the ink is the volume-based average particle diameter determined by a dynamic scattering method. SZ-100" or the like.

The printing method using oil-based inkjet ink is not particularly limited, and may be any method such as a piezo method, an electrostatic method, or a thermal method. When using an inkjet recording apparatus, it is preferable to eject the ink according to this embodiment from an inkjet head based on a digital signal, and to make the ejected ink droplets adhere to a recording medium.

The appropriate viscosity of the oil-based inkjet ink varies depending on the nozzle diameter of the ejection head of the inkjet recording system and the ejection environment, but in general, it is preferably 5 to 30 mPa・s at 23°C, and 5 to 15 mPa・s. More preferably, it is about 10 mPa·s, even more preferably about 10 mPa·s.

In this embodiment, the recording medium is not particularly limited, and may include printing paper such as plain paper, coated paper, and special paper, cloth, inorganic sheet, film, OHP sheet, etc. as a base material with an adhesive layer on the back side. A pressure-sensitive adhesive sheet or the like 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, plain paper is paper on which no ink receiving layer, film layer, etc. are formed. Examples of plain paper include high-quality paper, medium-quality paper, PPC paper, recycled paper, and recycled paper. Plain paper has paper fibers with a thickness of several micrometers to several tens of micrometers forming voids of several tens to hundreds of micrometers, making it easy for ink to penetrate.

Further, as the coated paper, inkjet coated paper such as matte paper, glossy paper, semi-glossy paper, or so-called coated printing paper can be preferably used. Here, coated printing paper is printing paper that has traditionally been used in letterpress printing, offset printing, gravure printing, etc., and is made of high-quality paper or medium-quality paper with inorganic pigments such as clay or calcium carbonate on the surface. , printing paper with a coating layer made of paint containing a binder such as starch. Coated printing paper can be divided into slightly coated paper, high quality lightweight coated paper, medium quality light coated paper, high quality coated paper, medium quality coated paper, art paper, cast coated paper, etc. depending on the amount of paint applied and the coating method. being classified.

A method for producing a dispersant according to one embodiment of the present invention includes a continuous phase containing a nonaqueous solvent and (meth)acrylic resin A, and a dispersed phase containing water, an acidic water-dispersible resin, and a low-molecular amine compound. The process of obtaining a water-in-oil emulsion containing water (hereinafter sometimes referred to as "Step A") and the process of removing water from the water-in-oil emulsion (hereinafter sometimes referred to as "Step B"). A method for producing a dispersant, including:
By this method for producing a dispersant, a dispersant that can be used in the above-mentioned oil-based inkjet ink can be obtained. However, the method for producing the dispersant for oil-based inkjet ink is not limited to this method.

Step A is similar to Step 1 described in the example of the method for producing oil-based inkjet ink described above. In step B, the method of removing water and the amount of water removed are the same as the method of removing water and the amount of water removed in step 2 described in the example of the method for producing oil-based inkjet ink described above. be.

In step B, the water in the dispersed phase of the water-in-oil emulsion is removed, whereby resin particles are formed by the remaining dispersed phase component and the (meth)acrylic resin A as the continuous phase component, and the acidic resin, low A dispersant dispersion containing a molecular amine compound and a dispersant formed by (meth)acrylic resin A as resin particles can be obtained.

The method for producing a dispersant may further include other steps such as adding (meth)acrylic resin A.

Hereinafter, the present invention will be explained in detail with reference to Examples. The invention is not limited to the following examples.
Throughout the following Examples and Comparative Examples, common components are the same unless otherwise specified. Unless otherwise specified, "%" indicates "% by mass."
The amount of each material listed in Tables 1 to 3 is expressed in parts by mass. The amount of each material listed in Tables 4 and 5 is expressed in mass %. The blending amounts of each material in Tables 1 to 5 include the volatile content for materials containing volatile content.

<Ink material>
The raw materials for the inks of Examples and Comparative Examples are shown below.

Copper phthalocyanine blue: Heliogen Blue D7115F (manufactured by BASF)
Azorake Red: Permanent Rubine P-L5b01 (manufactured by Clariant Japan Co., Ltd.)
Carbon black: MOGUL L (manufactured by Cabot Specialty Chemicals)

Urethane urea resin water dispersion 1: Manufactured by the method described below (aqueous dispersion containing acidic urethane urea resin and triethanolamine, 30% active ingredient)
Urethane urea resin water dispersion 2: Manufactured by the method described below (aqueous dispersion containing acidic urethane urea resin and dimethylethanolamine, 30% active ingredient)
Urethane urea resin aqueous dispersion 3: Manufactured by the method described below (aqueous dispersion containing acidic urethane urea resin and triethylamine, 30% active ingredient)

(Meth)acrylic resin aqueous dispersion 1: Manufactured by the method described below (aqueous dispersion containing acidic (meth)acrylic resin and dimethylethanolamine, active ingredient 30%)

Urethane resin aqueous dispersion 1: Manufactured by the method described below (aqueous dispersion containing acidic urethane resin and dimethylethanolamine, 30% active ingredient)

Urethane resin solution 1: Manufactured by the method described below (solution of acidic urethane resin, active ingredient 50%)
Basic urethane urea resin water dispersion 1: Superflex 620 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., water dispersion of basic urethane urea resin, active ingredient 30%)

(Meth)acrylic resin solution a: Manufactured by the method described below ((meth)acrylic resin solution, active ingredient 40%, solvent is fatty acid ester solvent)
(Meth)acrylic resin solution b: Manufactured by the method described below (solution of (meth)acrylic resin, active ingredient 40%, solvent is fatty acid ester solvent)
(Meth)acrylic resin solution c: Manufactured by the method described below ((meth)acrylic resin solution, active ingredient 40%, solvent is fatty acid ester solvent)
(Meth)acrylic resin solution d: Manufactured by the method described below ((meth)acrylic resin solution, active ingredient 40%, solvent is fatty acid ester solvent)
(Meth)acrylic resin solution e: Manufactured by the method described below (solution of (meth)acrylic resin, active ingredient 40%, solvent is petroleum-based hydrocarbon solvent)

Acidic polymer 1: Solsperse 21000 (manufactured by Japan Lubrizol Co., Ltd.) (100% active ingredient)

Fatty acid ester solvent 1: Isopropyl myristate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)
Petroleum-based hydrocarbon solvent 1: Exol D130 (manufactured by ExxonMobil)
Higher alcohol solvent 1: Oleyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

<Production of urethane urea resin water dispersions 1 to 3>
In a four-necked flask, add 767.6 parts by mass of polytetramethylene glycol (manufactured by Mitsubishi Chemical Corporation), 55.5 parts by mass of 2,2-dimethylolbutanoic acid (manufactured by HighChem Corporation), and 1,4-butanediol. (manufactured by Mitsubishi Chemical Corporation) and 203.2 parts by mass of hexamethylene diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) at 80°C in 724.4 parts by mass of methyl ethyl ketone (manufactured by Tokyo Chemical Industry Co., Ltd.). The reaction was allowed to proceed for 6 hours. Thereafter, 21.8 parts by mass of hexanediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) was added thereto. 2000 parts by mass of 50° C. ion-exchanged water was added to this solution, and the pH was further adjusted to 8 with triethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.). Thereafter, methyl ethyl ketone was removed at 50° C. and under reduced pressure. Ion-exchanged water was added thereto to adjust the solid content to 30% by mass to obtain an aqueous dispersion (30% active ingredient) containing an acidic urethane urea resin and triethanolamine as a low molecular weight amine compound. This is referred to as urethane urea resin water dispersion 1.

An acidic urethane urea resin and a low molecular weight amine compound were prepared in the same manner as in the production of urethane urea resin aqueous dispersion 1, except that dimethylethanolamine (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was used instead of triethanolamine. An aqueous dispersion (30% active ingredient) containing dimethylethanolamine was obtained. This is referred to as urethane urea resin water dispersion 2.

Acidic urethane urea resin and triethylamine as a low molecular weight amine compound were prepared in the same manner as in the production of urethane urea resin aqueous dispersion 1, except that triethylamine (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was used instead of triethanolamine. An aqueous dispersion containing (30% active ingredient) was obtained. This is referred to as urethane urea resin water dispersion 3.

<Production of (meth)acrylic resin water dispersion 1>
Monomer mixture A consisting of 95 parts by mass of methyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) and 5 parts by mass of butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to 40 parts by mass of ion-exchanged water with Emulgen 1135S-70 (manufactured by Kao Corporation). , nonionic non-reactive surfactant) and 1.5 parts by mass of Emulsogen EPA073 (manufactured by Clariant Japan Co., Ltd., anionic non-reactive surfactant) are added to an aqueous solution and stirred. An emulsified monomer composition was prepared. Next, 173 parts by mass of ion-exchanged water and 1 part by mass of Emulsogen EPA073 were placed in a four-necked flask, stirred to dissolve, and heated to 73°C. 5% of the above emulsifying monomer composition was added thereto, stirred, and a 3% aqueous solution of potassium persulfate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (hereinafter sometimes referred to as "3% potassium persulfate") was added. 1.3 parts by mass was added to carry out initial polymerization. Thereafter, while maintaining the temperature at 80° C., 5.3 parts by mass of 3% potassium persulfate and the remaining emulsifying monomer composition were added dropwise over 3 hours and 30 minutes to allow the polymerization reaction to proceed. After the dropwise addition was completed, the reaction was carried out for 60 minutes to complete the first stage polymerization. Next, a monomer mixture B consisting of 2.8 parts by mass of methyl methacrylate and 2.4 parts by mass of methacrylic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added simultaneously with 0.87 parts by mass of 3% potassium persulfate to form a second stage. polymerization was started. After completion of the dropwise addition, the pH was adjusted to 8 using dimethylethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.), and the reaction was aged for 1 hour. After that, the temperature was cooled to 50°C and stirring was continued for another hour, and then ion-exchanged water was added to adjust the solid content to 30% by mass, and acidic (meth)acrylic resin and dimethylethanolamine were added as a low molecular weight amine compound. An aqueous dispersion containing 30% of active ingredient was obtained. This is referred to as (meth)acrylic resin water dispersion 1.

<Production of urethane resin solution 1 and urethane resin aqueous dispersion 1>
105.1 parts by mass of diethanolamine (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was placed in a four-necked flask, and the temperature was raised to 110° C. while stirring while blowing nitrogen gas. To this, 72.1 parts by mass of acrylic acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added dropwise over 30 minutes. The mixture was kept at 110° C. for 2 hours to complete the Michael addition reaction, and a liquid diol was obtained. In another four-necked flask, 35.4 parts by mass of the diol solution obtained above and 15.2 parts by mass of propylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as another diol component were charged, and as a tin catalyst. 0.15 parts by mass of dibutyltin dilaurate (manufactured by Tokyo Fine Chemical Co., Ltd.) was added, and the temperature was raised to 78°C while stirring while passing nitrogen gas. Then, a mixture of 67.3 parts by mass of hexamethylene diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) and 118.1 parts by mass of methyl ethyl ketone (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise over 30 minutes. After the dropwise addition, the mixture was reacted for 24 hours under reflux at a temperature of 78° C. to 80° C., and then cooled to obtain a solution of acidic urethane resin with a solid content of 50% by mass. This is referred to as urethane resin solution 1.

80 parts by mass of ion-exchanged water was added to 100 parts by mass of the acidic urethane resin solution (urethane resin solution 1), and the pH was further adjusted to 8 with dimethylethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.). Thereafter, methyl ethyl ketone was removed at 50° C. and under reduced pressure. Ion-exchanged water was added thereto to adjust the solid content to 30% by mass to obtain an aqueous dispersion (active ingredient: 30%) containing an acidic urethane resin and dimethylethanolamine as a low molecular weight amine compound. This is referred to as urethane resin water dispersion 1.

<Production of (meth)acrylic resin solutions a to f>
(Meth)acrylic resin solutions a to f were produced as follows.

Production of (meth)acrylic resin solution a 200 parts by mass of EXEPAL M-OL (manufactured by Kao Corporation, methyl oleate) was charged into a four-neck flask, and the temperature was raised to 110°C while stirring with nitrogen gas aerated. did. Next, while maintaining the temperature at 110°C, 50 parts by mass of behenyl methacrylate (manufactured by NOF Corporation), 20 parts by mass of dodecyl methacrylate (manufactured by Kao Corporation), and 15 parts by mass of acetoacetoxyethyl methacrylate (manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd.) and 100 parts by mass of a monomer mixture containing 15 parts by mass of dimethyl acrylamide (manufactured by KJ Chemicals Co., Ltd.), 50 parts by mass of EXEPAL M-OL, and t-butyl peroxy 2-ethyl O (manufactured by NOF Corporation). Hexanoate) was added dropwise over 3 hours. Thereafter, the mixture was stirred for 1 hour while being kept at 110°C, and then Perbutyl O was added thereto, and further stirred for 1 hour while being kept at 110°C. EXEPAL M-OL was added so that the solid content was 40% by mass to obtain a (meth)acrylic resin solution a.

Production of (meth)acrylic resin solution b The same procedure as in the production of methacrylic resin solution a was carried out, except that 15 parts by mass of N-vinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd.) was used instead of 15 parts by mass of dimethylacrylamide. A (meth)acrylic resin solution b having a solid content of 40% by mass was obtained.

Production of (meth)acrylic resin solution c The solid content A 40% by mass (meth)acrylic resin solution c was obtained.

Production of (meth)acrylic resin solution d Methacrylic resin solution except that 15 parts by mass of M-90G (manufactured by Shin Nakamura Chemical Co., Ltd., methoxypolyethylene glycol #400 methacrylate) was used instead of 15 parts by mass of dimethylacrylamide. A (meth)acrylic resin solution d having a solid content of 40% by mass was obtained in the same manner as in the production of a.

Production of (meth)acrylic resin solution e A solid solution was prepared in the same manner as in the production of methacrylic resin solution a, except that EXOL D130 (manufactured by ExxonMobil, petroleum-based hydrocarbon solvent) was used instead of EXCEPAR M-OL. A 40% by mass (meth)acrylic resin solution e was obtained.

Production of (meth)acrylic resin solution f Same as production of methacrylic resin solution a except that 15 parts by mass of dimethylacrylamide was not used and the amount of acetoacetoxyethyl methacrylate was changed from 15 parts by mass to 30 parts by mass. A (meth)acrylic resin solution f having a solid content of 40% by mass was obtained.

<Manufacture of ink>
Inks of Examples 1 to 11 and Comparative Examples 1 to 4 were produced as follows.

1. Production of dispersant-containing liquids 1 to 8 and 11 to 13 A non-aqueous solvent and a (meth)acrylic resin solution or acidic polymer are mixed in the amounts shown in EM1 to EM9 and EM11 to EM13 in Tables 1 to 3. A mixture for the continuous phase (oil phase) was prepared. Into the thus prepared continuous phase mixture, an aqueous dispersion containing an acidic resin and a low-molecular amine compound ( While dropping urethane urea resin water dispersions 1 to 3, (meth)acrylic resin water dispersion 1, or urethane resin water dispersion 1), an ultrasonic homogenizer "Ultrasonic processor VC-750" was used under ice cooling. (manufactured by Sonics) for 10 minutes to obtain water-in-oil (W/O) emulsions (EM1-9, 11-13).
In EM9, the water phase and oil phase were separated and a water-in-oil emulsion could not be obtained, so the following operations were not performed.
Each of the obtained water-in-oil emulsions (EM1-8, 11-13) was depressurized at a vacuum level of 100 hPa in a water bath at 80°C using a rotary evaporator "RE601" (manufactured by Yamato Chemical Co., Ltd.) to form an emulsion. The emulsion was treated for 1 hour per 100 g to remove water in the emulsion to obtain a dispersant dispersion as a resin particle dispersion with a solid content of 40%. The water removal rate was approximately 100% by mass. Using EM1 to 8 and 11 to 13, the dispersant dispersion obtained by removing water in this way was converted into dispersant-containing liquids 1 to 8 and 11 to 13 (all solid content: 40%) (hereinafter referred to as , may also be referred to as dispersants 1 to 8 and 11 to 13, respectively).

2. Manufacture of dispersant-containing liquid 10 A non-aqueous solvent and (meth)acrylic resin solution a were mixed in the amount shown in ML10 in Table 3. To this, an acidic resin solution (urethane resin solution 1) was added in an amount shown in ML10 in Table 3 to obtain a mixed solution. This mixed solution is designated as ML10. Regarding this ML10, methyl ethyl ketone was removed using a rotary evaporator "RE601" (manufactured by Yamato Chemical Co., Ltd.) in a 60°C water bath at a vacuum level of 100 hPa to remove the dispersant-containing liquid 10 (solid content 40%) ( (Hereinafter, it may also be referred to as Dispersant 10.) was obtained. Note that "amount of water in water-in-oil emulsion" in Tables 2 and 3 indicates the amount of water in mixed liquid ML10 for ML10.

3. Production of ink Pigments were mixed with a dispersant-containing liquid and a nonaqueous solvent in the amounts shown in Tables 4 and 5, and dispersed using a bead mill "Dyno Mill Multi LAB" (manufactured by Shinmaru Enterprises Co., Ltd.). Inks of Examples 1 to 11 and Comparative Examples 1, 3, and 4 were obtained. Note that in Comparative Example 2, the pigments aggregated and it was not possible to obtain an ink, so the following evaluation was not performed for Comparative Example 2.

<Evaluation>
The inks of Examples 1 to 11 and Comparative Examples 1, 3, and 4 obtained as described above were evaluated according to the following evaluation method. The results are shown in Tables 4 and 5.

1. Aggregate Ink was introduced into an inkjet printer "ORPHIS GD9630" (manufactured by Riso Kagaku Kogyo Co., Ltd.), and the ink was allowed to circulate in the ink path for two weeks. 1 ml of ink was taken out from the ink path and observed with an optical microscope, and aggregates were evaluated based on the following evaluation criteria.

(Evaluation criteria)
A: No aggregates observed B: Aggregates observed

2. Storage Stability First, the viscosity of the ink immediately after it was prepared was measured.
Next, the ink was placed in a sealed container and left at 70° C. for 4 weeks. Thereafter, the ink was sampled and the ink viscosity was measured.
The ink viscosity was measured at 23° C. using a rheometer AR-G2 (manufactured by TA Instruments Japan Co., Ltd.) at a cone angle of 2° and a diameter of 40 mm.
From the ink viscosity immediately after preparation and the ink viscosity before and after being left for 4 weeks, the rate of viscosity change was determined by the following formula, and the storage stability was evaluated using the following criteria.
Viscosity change rate (%) = [(ink viscosity after being left for 4 weeks x 100)/(viscosity immediately after preparation)] -100 (%)
(Evaluation criteria)
A: Absolute value of viscosity change rate is less than 5% B: Absolute value of viscosity change rate is 5% or more

3. Scratch Resistance Each ink was loaded into an inkjet printer "ORPHIS GD9630" (manufactured by Riso Kagaku Kogyo Co., Ltd.), and a solid image was printed on plain paper "Riso Paper Multi" (manufactured by Riso Kagaku Kogyo Co., Ltd.). 24 hours after printing, the area containing the solid image on the surface of the printed matter was rubbed with a white cotton cloth 5 times for 5 seconds using a crockmeter ("CM-1" manufactured by Atlas Electric Devices) to measure the image. Surrounding pollution was evaluated using the following criteria.

(Evaluation criteria)
AA: Almost no contamination around the image A: Slight contamination around the image B: Contamination around the image

As shown in each table, no aggregates were observed in the evaluation of aggregates in the inks of each example. On the other hand, Comparative Example 1 in which dispersant 10 not using a low-molecular amine compound was used, selected from the group consisting of a group represented by general formula (1) and a group represented by general formula (2) Comparative Example 3 in which dispersant 11 using acidic polymer 1 instead of (meth)acrylic resin containing at least one group represented by general formula (1) and general formula (2 ) In Comparative Example 4, in which the dispersant 13 using a (meth)acrylic resin that does not contain any of the groups represented by the above was used, aggregates were observed in the evaluation of aggregates.
In Examples 1 to 3 and 6 to 11, in which dispersants 1 to 3 and 6 to 8 in which an acidic urethane urea resin was used as the acidic resin, the scratch resistance was improved.
The inks of Examples 1 to 11 all showed good storage stability.

Claims (6)

pigment and
An acidic resin, a low molecular amine compound, and (meth)acrylic containing at least one group selected from the group consisting of a group represented by the following general formula (1) and a group represented by the following general formula (2). A dispersant formed by a system resin,
Oil-based inkjet ink containing a non-aqueous solvent.

(In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a substituent, and R ¹ and R ² may be combined with each other to form a ring. General formula (2) , R ³ represents a substituent, R ⁴ represents a hydrogen atom or a substituent, and R ³ and R ⁴ may be bonded to each other to form a ring.) The oil-based inkjet ink according to claim 1, wherein the low-molecular amine compound includes an alkanolamine. The oil-based inkjet ink according to claim 1 or 2, wherein the acidic resin includes at least one selected from the group consisting of acidic (meth)acrylic resins and acidic urethane resins. The oil-based inkjet ink according to claim 3, wherein the acidic resin includes an acidic urethane urea resin. A continuum containing a non-aqueous solvent and a (meth)acrylic resin containing at least one group selected from the group consisting of a group represented by the following general formula (1) and a group represented by the following general formula (2). obtaining a water-in-oil emulsion comprising a phase and a dispersed phase containing water, an acidic water-dispersible resin, and a low molecular weight amine compound;
removing water from the water-in-oil emulsion to obtain a dispersant dispersion;
a step of mixing the dispersant dispersion and a pigment and dispersing the pigment;
A method for producing oil-based inkjet ink.

(In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a substituent, and R ¹ and R ² may be combined with each other to form a ring. General formula (2) , R ³ represents a substituent, R ⁴ represents a hydrogen atom or a substituent, and R ³ and R ⁴ may be bonded to each other to form a ring.) A continuum containing a non-aqueous solvent and a (meth)acrylic resin containing at least one group selected from the group consisting of a group represented by the following general formula (1) and a group represented by the following general formula (2). obtaining a water-in-oil emulsion comprising a phase and a dispersed phase containing water, an acidic water-dispersible resin, and a low molecular weight amine compound;
removing water from the water-in-oil emulsion.
A method for producing a dispersant.

(In general formula (1), R ¹ and R ² each independently represent a hydrogen atom or a substituent, and R ¹ and R ² may be combined with each other to form a ring. General formula (2) , R ³ represents a substituent, R ⁴ represents a hydrogen atom or a substituent, and R ³ and R ⁴ may be bonded to each other to form a ring.)